Vivianne Tawfik, MD, PhD is a board certified Anesthesiologist and Pain Medicine physician who specializes in the treatment of complex chronic pain disorders including chronic post-operative pain, complex regional pain syndrome and peripheral nerve injury.

She obtained her MD and PhD in Neuroscience, with a focus on basic pain mechanisms, at Dartmouth Medical School before joining the Stanford Department of Anesthesiology, Perioperative & Pain Medicine as an anesthesiology resident in the Fellowship in Anesthesia Research and Medicine (FARM) program, of which she now serves as the Director. After completion of her subspecialty fellowship training in Pain Medicine, Dr. Tawfik joined the faculty at Stanford and continues to research the immune contribution to persistent pain while treating patients suffering from chronic pain.

She enjoys science, sushi and snowboarding in her free time.

Clinical Focus

  • Pain Medicine
  • Pain Management

Academic Appointments

Administrative Appointments

  • Vice-Chair for Research- Basic Science, Department of Anesthesiology, Perioperative & Pain Medicine (2022 - Present)
  • Director, Fellowship in Anesthesia Research & Medicine (FARM), Department of Anesthesiology, Perioperative & Pain Medicine (2018 - Present)
  • Assistant Director, Fellowship in Anesthesia Research & Medicine (FARM), Department of Anesthesiology, Perioperative and Pain Medicine (2015 - 2018)

Honors & Awards

  • Award in Pain, Rita Allen Foundation (2019-2022)

Professional Education

  • Board Certification: American Board of Anesthesiology, Pain Management (2015)
  • Fellowship, Stanford Hospital and Clinics, Pain Medicine (2015)
  • Fellowship, Stanford Hospital and Clinics, Research (2014)
  • Board Certification: American Board of Anesthesiology, Anesthesiology (2014)
  • Residency, Stanford Hospital and Clinics, Anesthesiology (2013)
  • M.D./Ph.D., Dartmouth Medical School, Pharmacology/Neuroscience (2009)
  • Internship: Dartmouth Hitchcock Medical Center (2010) NH

Current Research and Scholarly Interests

My overall research interest is to understand how the immune system interacts with the nervous system after injury to promote the transition from acute to chronic pain. In my clinical practice I care for patients with persistent pain that often occurs after minor trauma such as fracture or surgery. Using basic science approaches including whole system immune phenotyping with mass cytometry and genetic manipulation of peripheral and central immune cells, we seek to dissect the temporal and tissue-specific contribution of these cells to either promotion or inhibition of healing.

Clinical Trials

  • [18F]FTC-146 PET/MRI in Healthy Volunteers and in CRPS and Sciatica Not Recruiting

    Chronic pain can result from injured or inflamed nerves, as occurs in people suffering from sciatica and CRPS. These nerve injuries or regions of nerve irritation are often the cause of pain in these conditions, but the current diagnostic tools are limited in pinpointing the area of origin. Several studies have implicated involvement of sigma-1 receptors in the generation and perpetuation of chronic pain conditions, others are investigating anti sigma-1 receptor drugs for the treatment of chronic pain. Using the sigma-1 receptor (S1R) detector and experimental radiotracer \[18F\]FTC-146 and positron emission tomography/magnetic resonance imaging (PET/MRI) scanner, the researchers may potentially identify the source of pain generation in patients suffering from complex regional pain syndrome (CRPS) and chronic sciatica. The ultimate goal is to assist in the optimization of pain treatment regimens using an \[18F\]FTC-146 PET/MRI scan. The study is not designed to induce any physiological/pharmacological effect.

    Stanford is currently not accepting patients for this trial. For more information, please contact Sandip Biswal, MD, 650-725-8018.

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  • Use of PET/MR Imaging in Chronic Pain Not Recruiting

    The investigators are studying the ability of PET/MR imaging (using the PET tracer \[18F\]FDG) to objectively identify and characterize pain generators in patients suffering from chronic pain.

    Stanford is currently not accepting patients for this trial.

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2023-24 Courses

Stanford Advisees

Graduate and Fellowship Programs

All Publications

  • Repopulated spinal cord microglia exhibit a unique transcriptome and contribute to pain resolution. Cell reports Donovan, L. J., Bridges, C. M., Nippert, A. R., Wang, M., Wu, S., Forman, T. E., Haight, E. S., Huck, N. A., Bond, S. F., Jordan, C. E., Gardner, A. M., Nair, R. V., Tawfik, V. L. 2024; 43 (2): 113683


    Microglia are implicated as primarily detrimental in pain models; however, they exist across a continuum of states that contribute to homeostasis or pathology depending on timing and context. To clarify the specific contribution of microglia to pain progression, we take advantage of a temporally controlled transgenic approach to transiently deplete microglia. Unexpectedly, we observe complete resolution of pain coinciding with microglial repopulation rather than depletion. We find that repopulated mouse spinal cord microglia are morphologically distinct from control microglia and exhibit a unique transcriptome. Repopulated microglia from males and females express overlapping networks of genes related to phagocytosis and response to stress. We intersect the identified mouse genes with a single-nuclei microglial dataset from human spinal cord to identify human-relevant genes that may ultimately promote pain resolution after injury. This work presents a comprehensive approach to gene discovery in pain and provides datasets for the development of future microglial-targeted therapeutics.

    View details for DOI 10.1016/j.celrep.2024.113683

    View details for PubMedID 38261512

  • The Anesthesiology Physician-Scientist Pipeline: Current Status and Recommendations for Future Growth-An Initiative of the Anesthesia Research Council. Anesthesia and analgesia Emala, C. W., Tawfik, V. L., Lane-Fall, M. B., Toledo, P., Wong, C. A., Vavilala, M. S., Fleisher, L. A., Wood, M. 2023; 137 (4): 728-742


    The limited number and diversity of resident physicians pursuing careers as physician-scientists in medicine has been a concern for many decades. The Anesthesia Research Council aimed to address the status of the anesthesiology physician-scientist pipeline, benchmarked against other medical specialties, and to develop strategic recommendations to sustain and expand the number and diversity of anesthesiology physician-scientists. The working group analyzed data from the Association of American Medical Colleges and the National Resident Matching Program to characterize the diversity and number of research-oriented residents from US and international allopathic medical schools entering 11 medical specialties from 2009 to 2019. Two surveys were developed to assess the research culture of anesthesiology departments. National Institutes of Health (NIH) funding information awarded to anesthesiology physician-scientists and departments was collected from NIH RePORTER and the Blue Ridge Medical Institute. Anesthesiology ranked eighth to tenth place of 11 medical specialties in the percent of "research-oriented" entering residents, defined as those with advanced degrees (Master's or PhDs) in addition to the MD degree or having published at least 3 research publications before residency. Anesthesiology ranked eighth of 11 specialties in the percent of entering residents who were women but ranked fourth of 11 specialties in the percent of entering residents who self-identified as belonging to an underrepresented group in medicine. There has been a 72% increase in both the total NIH funding awarded to anesthesiology departments and the number of NIH K-series mentored training grants (eg, K08 and K23) awarded to anesthesiology physician-scientists between 2015 and 2020. Recommendations for expanding the size and diversity of the anesthesiology physician-scientist pipeline included (1) developing strategies to increase the number of research intensive anesthesiology departments; (2) unifying the diverse programs among academic anesthesiology foundations and societies that seek to grow research in the specialty; (3) adjusting American Society of Anesthesiologists metrics of success to include the number of anesthesiology physician-scientists with extramural research support; (4) increasing the number of mentored awards from Foundation of Anesthesia Education and Research (FAER) and International Anesthesia Research Society (IARS); (5) supporting an organized and concerted effort to inform research-oriented medical students of the diverse research opportunities within anesthesiology should include the specialty being represented at the annual meetings of Medical Scientist Training Program (MSTP) students and the American Physician Scientist Association, as well as in institutional MSTP programs. The medical specialty of anesthesiology is defined by new discoveries and contributions to perioperative medicine which will only be sustained by a robust pipeline of anesthesiology physician-scientists.

    View details for DOI 10.1213/ANE.0000000000006520

    View details for PubMedID 37712462

  • Temporal contribution of myeloid-lineage TLR4 to the transition to chronic pain: A focus on sex differences. The Journal of neuroscience : the official journal of the Society for Neuroscience Huck, N. A., Siliezar-Doyle, J., Haight, E. S., Ishida, R., Forman, T. E., Wu, S., Shen, H., Takemura, Y., Clark, J. D., Tawfik, V. L. 2021


    Complex regional pain syndrome (CRPS) is a chronic pain disorder with a clear acute-to-chronic transition. Preclinical studies demonstrate that toll-like receptor 4 (TLR4), expressed by myeloid-lineage cells, astrocytes, and neurons, mediates a sex-dependent transition to chronic pain; however, evidence is lacking on which exact TLR4-expressing cells are responsible. We used complementary pharmacologic and transgenic approaches in mice to more specifically manipulate myeloid-lineage TLR4 and outline its contribution to the transition from acute-to-chronic CRPS based on three key variables: location (peripheral vs. central), timing (prevention vs. treatment), and sex (male vs. female). We demonstrate that systemic TLR4 antagonism is more effective at improving chronic allodynia trajectory when administered at the time of injury (early) in the tibial fracture model of CRPS in both sexes. In order to clarify the contribution of myeloid-lineage cells peripherally (macrophages) or centrally (microglia), we rigorously characterize a novel spatiotemporal transgenic mouse line, Cx3CR1-CreERT2-eYFP;TLR4fl/fl (TLR4 cKO) to specifically knock-out TLR4 only in microglia and no other myeloid-lineage cells. Using this transgenic mouse, we find that early TLR4 cKO results in profound improvement in chronic, but not acute, allodynia in males, with a significant but less robust effect in females. In contrast, late TLR4 cKO results in partial improvement in allodynia in both sexes, suggesting that downstream cellular or molecular TLR4-independent events may have already been triggered. Overall, we find that the contribution of TLR4 is time- and microglia-dependent in both sexes; however, females also rely on peripheral myeloid-lineage (or other TLR4 expressing) cells to trigger chronic pain.Significance statementThe contribution of myeloid cell TLR4 to sex-specific pain progression remains controversial. We used complementary pharmacologic and transgenic approaches to specifically manipulate TLR4 based on three key variables: location (peripheral vs. central), timing (prevention vs. treatment), and sex (male vs. female). We discovered that microglial TLR4 contributes to early pain progression in males, and to a lesser extent in females. We further found that maintenance of chronic pain likely occurs through myeloid TLR4-independent mechanisms in both sexes. Altogether we define a more nuanced contribution of this receptor to the acute-to-chronic pain transition in a mouse model of complex regional pain syndrome.

    View details for DOI 10.1523/JNEUROSCI.1940-20.2021

    View details for PubMedID 33846230

  • Microglial Modulation as a Target for Chronic Pain: From the Bench to the Bedside and Back. Anesthesia and analgesia Haight, E. S., Forman, T. E., Cordonnier, S. A., James, M. L., Tawfik, V. L. 2019; 128 (4): 737–46


    With a widespread opioid epidemic and profound biopsychosocial implications, chronic pain is a multifaceted public health issue requiring urgent attention. The treatment of chronic pain is particularly important to anesthesiologists given our unique role as perioperative physicians and pain medicine specialists. The present review details the recent shift from a neuronal theory of chronic pain to one that includes complex neuron-glia interactions. In particular, we highlight microglia, the myeloid-lineage cells of the central nervous system, as initiators of a postinjury neuroimmune response that contributes to the acute to chronic pain transition. We discuss ever-advancing preclinical studies, wherein significant success has been made through pharmacologic and genetic modulation of microglia, and we emphasize where these approaches have made the transition to the clinical realm. Furthermore, we highlight the most current, novel efforts to visualize glial activation in vivo using positron emission tomography and improve the diagnosis of chronic pain through radiotracer binding of specific targets, like the 18 kDa translocator protein in microglia and myeloid-lineage cells. Our rapidly advancing knowledge about microglia and their involvement in pain suggests that the era of glial-targeted therapeutics is just beginning so long as we refocus our attention on optimizing preclinical studies using a clinically informed approach, before translation.

    View details for PubMedID 30883419

  • Longitudinal TSPO-PET imaging of peripheral and central myeloid cells in a mouse model of complex regional pain syndrome. Pain Cropper, H. C., Johnson, E. M., Haight, E. n., Cordonnier, S. A., Chaney, A. M., Forman, T. E., Biswal, A. n., Stevens, M. Y., James, M. L., Tawfik, V. L. 2019


    Complex regional pain syndrome (CRPS) is a severely disabling disease characterized by pain, temperature changes, motor dysfunction and edema that most often occurs as an atypical response to a minor surgery or fracture. Inflammation involving activation and recruitment of innate immune cells, including both peripheral and central myeloid cells (i.e. macrophages and microglia, respectively), is a key feature of CRPS. However, the exact role and time-course of these cellular processes relative to the known acute and chronic phases of the disease are not fully understood. Positron emission tomography (PET) of translocator protein-18kDa (TSPO) is a method for non-invasively tracking these activated innate immune cells. Here, we reveal the temporal dynamics of peripheral and central inflammatory responses over 20 weeks in a tibial fracture/casting mouse model of CRPS through longitudinal TSPO-PET using [F]GE-180. PET tracer uptake quantification in the tibia revealed increased peripheral inflammation as early as 2 days post-fracture and lasting 7 weeks. Centralized inflammation was detected in the spinal cord and brain of fractured mice at 7 and 21 days post-injury. Spinal cord tissue immunofluorescent staining revealed TSPO expression in microglia (CD11b+) at 7 days, but was restricted mainly to endothelial cells (PECAM1+) at baseline and 7 weeks. Our data suggest early and persistent peripheral myeloid cell activation, and transient central microglial activation are limited to the acute phase of CRPS. Moreover, we show that TSPO-PET can be used to noninvasively monitor the spatiotemporal dynamics of myeloid cell activation in CRPS progression with potential to inform disease phase-specific therapeutics.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

    View details for PubMedID 31095093

  • Comprehensive overview of the anesthesiology research landscape: A machine Learning Analysis of 737 NIH-funded anesthesiology primary Investigator's publication trends. Heliyon Ghanem, M., Espinosa, C., Chung, P., Reincke, M., Harrison, N., Phongpreecha, T., Shome, S., Saarunya, G., Berson, E., James, T., Xie, F., Shu, C. H., Hazra, D., Mataraso, S., Kim, Y., Seong, D., Chakraborty, D., Studer, M., Xue, L., Marić, I., Chang, A. L., Tjoa, E., Gaudillière, B., Tawfik, V. L., Mackey, S., Aghaeepour, N. 2024; 10 (7): e29050


    Anesthesiology plays a crucial role in perioperative care, critical care, and pain management, impacting patient experiences and clinical outcomes. However, our understanding of the anesthesiology research landscape is limited. Accordingly, we initiated a data-driven analysis through topic modeling to uncover research trends, enabling informed decision-making and fostering progress within the field.The easyPubMed R package was used to collect 32,300 PubMed abstracts spanning from 2000 to 2022. These abstracts were authored by 737 Anesthesiology Principal Investigators (PIs) who were recipients of National Institute of Health (NIH) funding from 2010 to 2022. Abstracts were preprocessed, vectorized, and analyzed with the state-of-the-art BERTopic algorithm to identify pillar topics and trending subtopics within anesthesiology research. Temporal trends were assessed using the Mann-Kendall test.The publishing journals with most abstracts in this dataset were Anesthesia & Analgesia 1133, Anesthesiology 992, and Pain 671. Eight pillar topics were identified and categorized as basic or clinical sciences based on a hierarchical clustering analysis. Amongst the pillar topics, "Cells & Proteomics" had both the highest annual and total number of abstracts. Interestingly, there was an overall upward trend for all topics spanning the years 2000-2022. However, when focusing on the period from 2015 to 2022, topics "Cells & Proteomics" and "Pulmonology" exhibit a downward trajectory. Additionally, various subtopics were identified, with notable increasing trends in "Aneurysms", "Covid 19 Pandemic", and "Artificial intelligence & Machine Learning".Our work offers a comprehensive analysis of the anesthesiology research landscape by providing insights into pillar topics, and trending subtopics. These findings contribute to a better understanding of anesthesiology research and can guide future directions.

    View details for DOI 10.1016/j.heliyon.2024.e29050

    View details for PubMedID 38623206

    View details for PubMedCentralID PMC11016610

  • In Response. Anesthesia and analgesia Emala, C. W., Tawfik, V. L., Lane-Fall, M. B., Toledo, P., Wong, C. A., Vavilala, M. S., Fleisher, L. A., Wood, M. 2024; 138 (4): e16-e17

    View details for DOI 10.1213/ANE.0000000000006899

    View details for PubMedID 38489801

  • Astrocytes: Dual Roles in Chronic Pain and Memory Formation. Anesthesiology Tawfik, V. L. 2024; 140 (3): 358-360

    View details for DOI 10.1097/ALN.0000000000004832

    View details for PubMedID 38349757

  • Impact of Adding Carpal Tunnel Release or Trigger Finger Release to Carpometacarpal Arthroplasty on Postoperative Complications". Plastic and reconstructive surgery Trinh, P., Luan, A., Tawfik, V. L., Sheckter, C., Rochlin, D., Fox, P., Curtin, C. 2023


    BACKGROUND: This study assessed whether adding trigger finger or carpal tunnel release at the time of thumb carpometacarpal (CMC) arthroplasty would increase postoperative opioid use, readmissions, complications, and development of CRPS.METHODS: Using the IBM MarketScan Research Databases from 2012 to 2016, we identified a two groups of CMC arthroplasty patients. The "CMC only" group only had a CMC arthroplasty on the day of operation. The "multiple procedures" group had a CMC arthroplasty and concurrent carpal tunnel and / or trigger finger release. Between the two groups, we compared persistent opioid use, 30-day readmissions, 30-day complications, and diagnosis of complex regional pain syndrome (CRPS).RESULTS: The CMC only group consisted of 18,010 patients. The multiple procedures group consisted of 4,064 patients. These patients received a CMC arthroplasty and a carpal tunnel release (74%), a trigger finger release (20%), or both (6%). CMC only patients had lower rates of persistent opioid use compared to patients who underwent multiple procedures (16% vs 18%). Readmission rates were also lower for CMC only patients (3% vs 4%). CMC only patients had decreased odds of persistent opioid use (OR=0.85; 95% CI, 0.75-0.97, p=0.013) and readmissions (OR=0.80; 95% CI, 0.67-0.96, p=0.016). The most common reason for readmission was pain (16%).CONCLUSIONS: Adding another procedure to a CMC arthroplasty slightly increases the odds of adverse outcomes such as persistent opioid use and readmission. Patients and providers should weigh the efficiency of doing these procedures concurrently against the risk of performing multiple procedures at once.CLINICAL QUESTION / LEVEL OF EVIDENCE: Risk, II.

    View details for DOI 10.1097/PRS.0000000000010144

    View details for PubMedID 36728633

  • Clinical Assessments of Fracture Healing and Basic Science Correlates: Is There Room for Convergence? Current osteoporosis reports Lopas, L. A., Shen, H., Zhang, N., Jang, Y., Tawfik, V. L., Goodman, S. B., Natoli, R. M. 2022


    PURPOSE OF REVIEW: The purpose of this review is to summarize the clinical and basic science methods used to assess fracture healing and propose a framework to improve the translational possibilities.RECENT FINDINGS: Mainstays of fracture healing assessment include clinical examination, various imaging modalities, and assessment of function. Pre-clinical studies have yielded insight into biomechanical progression as well as the genetic, molecular, and cellular processes of fracture healing. Efforts are emerging to identify early markers to predict impaired healing and possibly early intervention to alter these processes. Despite of the differences in clinical and preclinical research, opportunities exist to unify and improve the translational efforts between these arenas to develop and optimize our ability to assess and predict fracture healing, thereby improving the clinical care of these patients.

    View details for DOI 10.1007/s11914-022-00770-7

    View details for PubMedID 36534307

  • Successful epidural fibrin glue patch to treat intracranial hypotension in a patient with bacteraemia and malignancy. BJA open Gupta, A., Madriz, V. C., Carroll, I. R., Tawfik, V. L. 2022; 4: 100091


    Cerebrospinal fluid leaks after diagnostic lumbar puncture are often treated using an epidural blood patch; however, there are situations in which this may not be a desirable or safe option. We describe a case of a 55-yr-old male who developed a cerebrospinal fluid leak with intracranial hypotension and subdural haematoma after multiple diagnostic lumbar punctures who also had Klebsiella bacteraemia, malignancy, and low platelets. Given concern about bacterial and malignant seeding of the epidural space, we considered several options including a patch with banked blood or neurosurgical intervention. To treat impending brain herniation, we opted to perform an epidural patch using fibrin glue. The fibrin patch is an absorbable surgical sealing patch that is placed on wound tissue. In this case, it was used to close the assumed dural tear, which resulted in a good outcome for the patient without need for neurosurgical intervention.

    View details for DOI 10.1016/j.bjao.2022.100091

    View details for PubMedID 37588781

    View details for PubMedCentralID PMC10430854

  • Sex-distinct microglial activation and myeloid cell infiltration in the spinal cord after painful peripheral injury. Neurobiology of pain (Cambridge, Mass.) Huck, N. A., Donovan, L. J., Shen, H., Jordan, C. E., Muwanga, G. P., Bridges, C. M., Forman, T. E., Cordonnier, S. A., Haight, E. S., Dale-Huang, F., Takemura, Y., Tawfik, V. L. 2022; 12: 100106


    Chronic pain is a common and often debilitating problem that affects 100 million Americans. A better understanding of pain's molecular mechanisms is necessary for developing safe and effective therapeutics. Microglial activation has been implicated as a mediator of chronic pain in numerous preclinical studies; unfortunately, translational efforts using known glial modulators have largely failed, perhaps at least in part due to poor specificity of the compounds pursued, or an incomplete understanding of microglial reactivity. In order to achieve a more granular understanding of the role of microglia in chronic pain as a means of optimizing translational efforts, we utilized a clinically-informed mouse model of complex regional pain syndrome (CRPS), and monitored microglial activation throughout pain progression. We discovered that while both males and females exhibit spinal cord microglial activation as evidenced by increases in Iba1, activation is attenuated and delayed in females. We further evaluated the expression of the newly identified microglia-specific marker, TMEM119, and identified two distinct populations in the spinal cord parenchyma after peripheral injury: TMEM119+microglia and TMEM119- infiltrating myeloid lineage cells, which are comprised of Ly6G+neutrophils and Ly6G- macrophages/monocytes. Neurons are sensitized by inflammatory mediators released in the CNS after injury; however, the cellular source of these cytokines remains somewhat unclear. Using multiplex in situ hybridization in combination with immunohistochemistry, we demonstrate that spinal cord TMEM119+microglia are the cellular source of cytokines IL6 and IL1beta after peripheral injury. Taken together, these data have important implications for translational studies: 1) microglia remain a viable analgesic target for males and females, so long as duration after injury is considered; 2) the analgesic properties of microglial modulators are likely at least in part related to their suppression of microglial-released cytokines, and 3) a limited number of neutrophils and macrophages/monocytes infiltrate the spinal cord after peripheral injury but have unknown impact on pain persistence or resolution. Further studies to uncover glial-targeted therapeutic interventions will need to consider sex, timing after injury, and the exact target population of interest to have the specificity necessary for translation.

    View details for DOI 10.1016/j.ynpai.2022.100106

    View details for PubMedID 36531615

  • The Tibial Fracture-Pin Model: A Clinically Relevant Mouse Model of Orthopedic Injury. Journal of visualized experiments : JoVE Muwanga, G. P., Siliezar-Doyle, J., Ortiz, A. A., Kaslow, J., Haight, E. S., Tawfik, V. L. 2022


    The tibial fracture-pin model is a mouse model of orthopedic trauma and surgery that recapitulates the complex muscle, bone, nerve, and connective tissue damage that manifests with this type of injury in humans. This model was developed because previous models of orthopedic trauma did not include simultaneous injury to multiple tissue types (bone, muscle, nerves) and were not truly representative of human complex orthopedic trauma. The authors therefore modified previous models of orthopedic trauma and developed the tibial fracture-pin model. This modified fracture model consists of a unilateral open tibial fracture with intramedullary nail (IMN) internal fixation and simultaneous tibialis anterior (TA) muscle injury, resulting in mechanical allodynia that lasts up to 5 weeks post injury. This series of protocols outlines the detailed steps to perform the clinically relevant orthopedic trauma tibial fracture-pin model, followed by a modified hot plate assay to examine nociceptive changes after orthopedic injury. Taken together, these detailed, reproducible protocols will allow pain researchers to expand their toolkit for studying orthopedic trauma-induced pain.

    View details for DOI 10.3791/63590

    View details for PubMedID 35969043

  • Migraine and peripheral pain models show differential alterations in neuronal complexity. Headache Bertels, Z., Mangutov, E., Conway, C., Siegersma, K., Asif, S., Shah, P., Huck, N., Tawfik, V., Pradhan, A. A. 2022


    OBJECTIVE: Our laboratory has recently shown that there is a decrease in neuronal complexity in head pain processing regions in mouse models of chronic migraine-associate pain and aura. Importantly, restoration of this neuronal complexity corresponds with anti-migraine effects of known and experimental pharmacotherapies. The objective of the current study was to expand this work and examine other brain regions involved with pain or emotional processing. We also investigated the generalizability of our findings by analyzing neuronal cytoarchitectural changes in a model of complex regional pain syndrome (CRPS), a peripheral pain disorder.METHODS: We used the nitroglycerin (NTG) model of chronic migraine-associated pain in which mice receive 10 mg/kg NTG every other day for 9days. Cortical spreading depression (CSD), a physiological corelate of migraine aura, was evoked in anesthetized mice using KCl. CRPS was induced by tibial fracture followed by casting. Neuronal cytoarchitecture was visualized with Golgi stain and analyzed with Simple Neurite Tracer.RESULTS: In the NTG model, we previously showed decreased neuronal complexity in the trigeminal nucleus caudalis (TNC) and periaqueductal grey (PAG). In contrast, we found increased neuronal complexity in the thalamus and no change in the amygdala or caudate putamen in this study. Following CSD, we observed decreased neuronal complexity in the PAG, in line with decreases in the somatosensory cortex and TNC reported with this model previously. In the CRPS model there was decreased neuronal complexity in the hippocampus, as reported by others; increased complexity in the PAG, and no change within the somatosensory cortex.CONCLUSIONS: Collectively these results demonstrate that alterations in neuronal complexity are a feature of both chronic migraine and chronic CRPS. However, each type of pain presents a unique cytoarchitectural signature which may provide insight on how these pain states differentially transition from acute to chronic conditions.

    View details for DOI 10.1111/head.14352

    View details for PubMedID 35676889

  • Mechanical Conflict-Avoidance Assay to Measure Pain Behavior in Mice. Journal of visualized experiments : JoVE Gaffney, C. M., Muwanga, G., Shen, H., Tawfik, V. L., Shepherd, A. J. 2022


    Pain comprises of both sensory (nociceptive) and affective (unpleasant) dimensions. In preclinical models, pain has traditionally been assessed using reflexive tests that allow inferences regarding pain's nociceptive component but provide little information about the affective or motivational component of pain. Developing tests that capture these components of pain are therefore translationally important. Hence, researchers need to use non-reflexive behavioral assays to study pain perception at that level. Mechanical conflict-avoidance (MCA) is an established voluntary non-reflexive behavior assay, for studying motivational responses to a noxious mechanical stimulus in a 3 chamber paradigm. A change in a mouse's location preference, when faced with competing noxious stimuli, is used to infer the perceived unpleasantness of bright light versus tactile stimulation of the paws. This protocol outlines a modified version of the MCA assay which pain researchers can use to understand affective-motivational responses in a variety of mouse pain models. Though not specifically described here, our example MCA data use the intraplantar complete Freund's adjuvant (CFA), spared nerve injury (SNI), and a fracture/casting model as pain models to illustrate the MCA procedure.

    View details for DOI 10.3791/63454

    View details for PubMedID 35253785

  • Morphine Tolerance and Reward is Regulated by Aldehyde Dehydrogenase-2 in Mice Zambelli, V., Salgado, J. S., Heifets, B. D., Tawfik, V., Gross, E. R. LIPPINCOTT WILLIAMS & WILKINS. 2021: 626-627
  • Neurovascular, muscle, and skin changes on [18F]FDG PET/MRI in complex regional pain syndrome of the foot: A Prospective Clinical Study. Pain medicine (Malden, Mass.) Yoon, D., Xu, Y., Cipriano, P. W., Alam, I. S., Mari Aparici, C. A., Tawfik, V. L., Curtin, C. M., Carroll, I. R., Biswal, S. 2021


    The goal of this study is to demonstrate the feasibility of simultaneous [18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) and magnetic resonance imaging (MRI) for non-invasive visualization of muscular, neurovascular, and skin changes secondary to complex regional pain syndrome (CRPS).Seven adult patients with CRPS of the foot and seven healthy adult controls participated in our [18F]FDG PET/MRI study.All participants received whole-body PET/MRI scans one hour after the injection of 370MBq [18F]FDG. Resulting PET/MRI images were reviewed by two radiologists. Metabolic and anatomic abnormalities identified, were grouped into muscular, neurovascular, and skin lesions. The [18F]FDG uptake of each lesion was compared with that of corresponding areas in controls using a Mann-Whitney U-test.On PET images, muscular abnormalities were found in five patients, neurovascular abnormalities in four patients, and skin abnormalities in two patients. However, on MRI images, no muscular abnormalities were detected. Neurovascular abnormalities and skin abnormalities in the affected limb were identified on MRI in one and two patients, respectively. The difference in [18F]FDG uptake between the patients and the controls was significant in muscle (p = 0.018) and neurovascular bundle (p = 0.0005).The increased uptake of [18F]FDG in the symptomatic areas likely reflects the increased metabolism due to the inflammatory response causing pain. Therefore, our approach combining metabolic [18F]FDG PET and anatomic MR imaging may offer non-invasive monitoring of the distribution and progression of inflammatory changes associated with CRPS.

    View details for DOI 10.1093/pm/pnab315

    View details for PubMedID 34718774

  • Characteristics of Patients With Complex Limb Pain Evaluated Through an Interdisciplinary Approach Utilizing Magnetic Resonance Neurography Frontiers in Pain Research Johnson, E. M., Yoon, D., Biswal, S., Curtin, C., Fox, P., Wilson, T. J., Carroll, I., Lutz, A., Tawfik, V. 2021
  • The Neuroimmunology of Chronic Pain: From Rodents to Humans. The Journal of neuroscience : the official journal of the Society for Neuroscience Grace, P. M., Tawfik, V. L., Svensson, C. I., Burton, M. D., Loggia, M. L., Hutchinson, M. R. 2020


    Chronic pain, encompassing conditions, such as low back pain, arthritis, persistent post-surgical pain, fibromyalgia, and neuropathic pain disorders, is highly prevalent but remains poorly treated. The vast majority of therapeutics are directed solely at neurons, despite the fact that signaling between immune cells, glia, and neurons is now recognized as indispensable for the initiation and maintenance of chronic pain. This review highlights recent advances in understanding fundamental neuroimmune signaling mechanisms and novel therapeutic targets in rodent models of chronic pain. We further discuss new technological developments to study, diagnose, and quantify neuroimmune contributions to chronic pain in patient populations.

    View details for DOI 10.1523/JNEUROSCI.1650-20.2020

    View details for PubMedID 33239404

  • Of mice, microglia, and (wo)men: a case series and mechanistic investigation of hydroxychloroquine for complex regional pain syndrome. Pain reports Haight, E. S., Johnson, E. M., Carroll, I. R., Tawfik, V. L. 2020; 5 (5): e841


    Introduction: Complex regional pain syndrome (CRPS) is a condition that occurs after minor trauma characterized by sensory, trophic, and motor changes. Although preclinical studies have demonstrated that CRPS may be driven in part by autoinflammation, clinical use of immune-modulating drugs in CRPS is limited. Hydroxychloroquine (HCQ) is a disease-modifying antirheumatic drug used to treat malaria and autoimmune disorders that may provide benefit in CRPS.Objectives: To describe the use of HCQ in patients with refractory CRPS and investigate possible mechanisms of benefit in a mouse model of CRPS.Methods: We initiated HCQ therapy in 7 female patients with refractory CRPS undergoing treatment at the Stanford Pain Management Center. We subsequently undertook studies in the mouse tibial fracture-casting model of CRPS to identify mechanisms underlying symptom reduction. We evaluated behavior using mechanical allodynia and spinal cord autoinflammation by immunohistochemistry and enzyme-linked immunosorbent assay.Results: We treated 7 female patients with chronic, refractory CRPS with HCQ 200 mg twice daily for 2 months, followed by 200 mg daily thereafter. Two patients stopped HCQ secondary to lack of response or side effects. Overall, HCQ significantly improved average numerical rating scale pain from 6.8 ± 1.1 before HCQ to 3.8 ± 1.9 after HCQ treatment. In the tibial fracture-casting mouse model of CRPS, we observed reductions in allodynia, paw edema, and warmth following daily HCQ treatment starting at 3 weeks after injury. Spinal cord dorsal horn microglial activation and cytokine levels were also reduced by HCQ treatment.Conclusion: Together, these preclinical and clinical results suggest that HCQ may benefit patients with CRPS at least in part by modulating autoinflammation and support further investigation into the use of HCQ for CRPS.

    View details for DOI 10.1097/PR9.0000000000000841

    View details for PubMedID 33490839

  • A Guide to Understanding "State-of-the-Art" Basic Research Techniques in Anesthesiology. Anesthesia and analgesia Obal, D., Wu, S., McKinstry-Wu, A., Tawfik, V. L. 2020


    Perioperative medicine is changing from a "protocol-based" approach to a progressively personalized care model. New molecular techniques and comprehensive perioperative medical records allow for detection of patient-specific phenotypes that may better explain, or even predict, a patient's response to perioperative stress and anesthetic care. Basic science technology has significantly evolved in recent years with the advent of powerful approaches that have translational relevance. It is incumbent on us as a primarily clinical specialty to have an in-depth understanding of rapidly evolving underlying basic science techniques to incorporate such approaches into our own research, critically interpret the literature, and improve future anesthesia patient care. This review focuses on 3 important and most likely practice-changing basic science techniques: next-generation sequencing (NGS), clustered regularly interspaced short palindromic repeat (CRISPR) modulations, and inducible pluripotent stem cells (iPSCs). Each technique will be described, potential advantages and limitations discussed, open questions and challenges addressed, and future developments outlined. We hope to provide insight for practicing physicians when confronted with basic science articles and encourage investigators to apply "state-of-the-art" technology to their future experiments.

    View details for DOI 10.1213/ANE.0000000000004801

    View details for PubMedID 32371742

  • 18F-FDG PET/MRI of patients with chronic pain alters management. Cipriano, P., Yoon, D., Carroll, I., Curtin, C., Tawfik, V., Xu, Y., Biswal, S. SOC NUCLEAR MEDICINE INC. 2020
  • Modeling Complex Orthopedic Trauma in Rodents: Bone, Muscle and Nerve Injury and Healing. Frontiers in pharmacology Shen, H., Gardner, A. M., Vyas, J., Ishida, R., Tawfik, V. L. 2020; 11: 620485


    Orthopedic injury can occur from a variety of causes including motor vehicle collision, battlefield injuries or even falls from standing. Persistent limb pain is common after orthopedic injury or surgery and presents a unique challenge, as the initiating event may result in polytrauma to bone, muscle, and peripheral nerves. It is imperative that we understand the tissue-specific and multicellular response to this unique type of injury in order to best develop targeted treatments that improve healing and regeneration. In this Mini Review we will first discuss current rodent models of orthopedic trauma/complex orthotrauma. In the second section, we will focus on bone-specific outcomes including imaging modalities, biomechanical testing and immunostaining for markers of bone healing/turnover. In the third section, we will discuss muscle-related pathology including outcome measures of fibrosis, muscle regeneration and tensile strength measurements. In the fourth section, we will discuss nervous system-related pathology including outcome measures of pain-like responses, both reflexive and non-reflexive. In all sections we will consider parallels between preclinical outcome measures and the functional and mechanistic findings of the human condition.

    View details for DOI 10.3389/fphar.2020.620485

    View details for PubMedID 33597884

  • Systematic Immunophenotyping Reveals Sex-Specific Responses After Painful Injury in Mice. Frontiers in immunology Tawfik, V. L., Huck, N. A., Baca, Q. J., Ganio, E. A., Haight, E. S., Culos, A. n., Ghaemi, S. n., Phongpreecha, T. n., Angst, M. S., Clark, J. D., Aghaeepour, N. n., Gaudilliere, B. n. 2020; 11: 1652


    Many diseases display unequal prevalence between sexes. The sex-specific immune response to both injury and persistent pain remains underexplored and would inform treatment paradigms. We utilized high-dimensional mass cytometry to perform a comprehensive analysis of phenotypic and functional immune system differences between male and female mice after orthopedic injury. Multivariate modeling of innate and adaptive immune cell responses after injury using an elastic net algorithm, a regularized regression method, revealed sex-specific divergence at 12 h and 7 days after injury with a stronger immune response to injury in females. At 12 h, females upregulated STAT3 signaling in neutrophils but downregulated STAT1 and STAT6 signals in T regulatory cells, suggesting a lack of engagement of immune suppression pathways by females. Furthermore, at 7 days females upregulated MAPK pathways (p38, ERK, NFkB) in CD4T memory cells, setting up a possible heightened immune memory of painful injury. Taken together, our findings provide the first comprehensive and functional analysis of sex-differences in the immune response to painful injury.

    View details for DOI 10.3389/fimmu.2020.01652

    View details for PubMedID 32849569

    View details for PubMedCentralID PMC7403191

  • Longitudinal translocator protein-18 kDa-positron emission tomography imaging of peripheral and central myeloid cells in a mouse model of complex regional pain syndrome PAIN Cropper, H. C., Johnson, E. M., Haight, E. S., Cordonnier, S. A., Chaney, A. M., Forman, T. E., Biswal, A., Stevens, M. Y., James, M. L., Tawfik, V. L. 2019; 160 (9): 2136–48
  • Predictors of post-anaesthesiology residency research productivity: preliminary report. British journal of anaesthesia Haight, E. S., Chen, F., Tanaka, P., Brock-Utne, J. G., Macario, A., Sun, E. C., Tawfik, V. L. 2019

    View details for DOI 10.1016/j.bja.2019.07.018

    View details for PubMedID 31474349

  • Cell-specific overexpression of COMT in dopaminergic neurons of Parkinson's disease. Brain : a journal of neurology Kuzumaki, N., Suda, Y., Iwasawa, C., Narita, M., Sone, T., Watanabe, M., Maekawa, A., Matsumoto, T., Akamatsu, W., Igarashi, K., Tamura, H., Takeshima, H., Tawfik, V. L., Ushijima, T., Hattori, N., Okano, H., Narita, M. 2019; 142 (6): 1675–89


    The mechanism by which dopaminergic neurons are selectively affected in Parkinson's disease is not fully understood. In this study, we found a dramatic increase in the expression of catechol-O-methyltransferase (COMT), along with a lower level of DNA methylation, in induced pluripotent stem cell-derived dopaminergic neurons from patients with parkin (PARK2) gene mutations compared to those from healthy controls. In addition, a significant increase in the expression of COMT was found in dopaminergic neurons of isogenic PARK2 induced pluripotent stem cell lines that mimicked loss of function of PARK2 by CRISPR Cas9 technology. In dopamine transporter (DAT)-Cre mice, overexpression of COMT, specifically in dopaminergic neurons of the substantia nigra, produced cataleptic behaviours associated with impaired motor coordination. These findings suggest that upregulation of COMT, likely resulting from DNA hypomethylation, in dopaminergic neurons may contribute to the initial stage of neuronal dysfunction in Parkinson's disease.

    View details for DOI 10.1093/brain/awz084

    View details for PubMedID 31135049

  • 18F-FDG PET/MRI of patients with chronic pain alters management. Cipriano, P., Yoon, D., Carroll, I., Curtin, C., Tawfik, V., Xu, Y., Biswal, S. SOC NUCLEAR MEDICINE INC. 2019
  • Musculoskeletal changes on [18F]FDG PET/MRI from complex regional pain syndrome in foot Yoon, D., Xu, Y., Cipriano, P., Tawfik, V., Curtin, C., Carroll, I., Biswal, S. SOC NUCLEAR MEDICINE INC. 2019
  • Morphine Exacerbates Postfracture Nociceptive Sensitization, Functional Impairment, and Microglial Activation in Mice ANESTHESIOLOGY Li, W., Irvine, K., Sahbaie, P., Guo, T., Shi, X., Tawfik, V. L., Kingery, W. S., Clark, J. 2019; 130 (2): 292–308
  • Angiotensin receptor blockade mimics the effect of exercise on recovery after orthopaedic trauma by decreasing pain and improving muscle regeneration. The Journal of physiology Tawfik, V. L., Quarta, M. n., Paine, P. n., Forman, T. E., Pajarinen, J. n., Takemura, Y. n., Goodman, S. B., Rando, T. A., Clark, J. D. 2019


    Our tibial fracture orthopaedic injury model in mice recapitulates the major manifestations of complex trauma including nociceptive sensitization, bone fracture, muscle fibrosis and muscle fibre loss. Delayed exercise after complex orthopaedic trauma results in decreased muscle fibrosis and improved pain Losartan, an angiotensin-receptor blocker with antifibrotic abilities, recapitulates the effect of exercise on post-injury recovery and may provide an enhanced recovery option for those who are unable to exercise after injury ABSTRACT: Chronic pain and disability after limb injury are major public health problems. Early mobilization after injury improves functional outcomes for patients but when and how to implement rehabilitation strategies remains a clinical challenge. Additionally, whether the beneficial effects of exercise can be reproduced using pharmacological tools remains unknown and may benefit patients who are unable to exercise due to immobilization. We developed a murine model of orthopaedic trauma combining tibia fracture and pin fixation with muscle damage. Behavioral measures included mechanical nociceptive thresholds and distances run on exercise wheels. Bone healing was quantified using microCT scanning, and muscle fibre size distribution and fibrosis were followed using immunohistochemistry. We found that the model provided robust mechanical allodynia, fibrosis and a shift to smaller average muscle fibre size lasting up to 5 weeks from injury. We also observed that allowing "late" (weeks 1-2) rather than "early" (weeks 0-1) exercise after injury resulted in greater overall running activity and greater reversal of allodynia. In parallel, the late running paradigm was associated with reduced muscle fibrosis, earlier increase in muscle fibre diameter and a short-term benefit in reducing callus volume. Providing the anti-fibrotic angiotensin receptor blocker losartan to mice in drinking water reduced both allodynia and muscle fibrosis. Combining losartan and late exercise provided no additional benefit. We conclude that early healing after orthopaedic trauma must be allowed prior to the initiation of exercise to achieve optimal pain, functional and physiological outcomes and that losartan is a viable candidate for translational studies. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1113/JP278991

    View details for PubMedID 31784993

  • Chronic Pain Management in the Elderly. Anesthesiology clinics Schwan, J. n., Sclafani, J. n., Tawfik, V. L. 2019; 37 (3): 547–60


    Chronic pain is extremely prevalent in older adults and is associated with significant morbidity, including limited mobility, social isolation, and depressed mood. Pain is defined by a biopsychosocial model highlighting the importance of a multidisciplinary approach to treatment, including multimodal medications, selected interventions, physical therapy and rehabilitation, and psychological treatments. In this narrative review, the authors highlight the use of these approaches in older adults with specific attention paid to considerations unique to aging, including alterations in drug metabolism, avoidance of polypharmacy, and physiologic changes predisposing to painful conditions.

    View details for DOI 10.1016/j.anclin.2019.04.012

    View details for PubMedID 31337484

  • Morphine Exacerbates Postfracture Nociceptive Sensitization, Functional Impairment, and Microglial Activation in Mice. Anesthesiology Li, W., Irvine, K., Sahbaie, P., Guo, T., Shi, X., Tawfik, V. L., Kingery, W. S., Clark, J. D. 2018


    WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Emerging evidence suggests that opioid use immediately after surgery and trauma may worsen outcomes. In these studies, the authors aimed to determine whether morphine administered for a clinically relevant time period (7 days) in a tibia fracture orthopedic surgery model had adverse effects on postoperative recovery.METHODS: Mice were given morphine twice daily for 7 days after unilateral tibial fracture and intramedullary pin fixation to model orthopedic surgery and limb trauma. Mechanical allodynia, limb-specific weight bearing, gait changes, memory, and anxiety were measured after injury. In addition, spinal cord gene expression changes as well as glial activation were measured. Finally, the authors assessed the effects of a selective Toll-like receptor 4 antagonist, TAK-242, on nociceptive and functional changes after injury.RESULTS: Tibial fracture caused several weeks of mechanical nociceptive sensitization (F(1, 216) = 573.38, P < 0.001, fracture + vehicle vs. sham + vehicle, n = 10 per group), and this change was exacerbated by the perioperative administration of morphine (F(1, 216) = 71.61, P < 0.001, fracture + morphine vs. fracture + vehicle, n = 10 per group). In additional testing, injured limb weight bearing, gait, and object location memory were worse in morphine-treated fracture mice than in untreated fracture mice. Postfracture expression levels of several genes previously associated with opioid-induced hyperalgesia, including brain-derived neurotrophic factor and prodynorphin, were unchanged, but neuroinflammation involving Toll-like receptor 4 receptor-expressing microglia was observed (6.8 ± 1.5 [mean ± SD] cells per high-power field for fracture + vehicle vs. 12 ± 2.8 fracture + morphine, P < 0.001, n = 8 per /group). Treatment with a Toll-like receptor 4 antagonist TAK242 improved nociceptive sensitization for about 2 weeks in morphine-treated fracture mice (F(1, 198) = 73.36, P < 0.001, fracture + morphine + TAK242 vs. fracture + morphine, n = 10 per group).CONCLUSIONS: Morphine treatment beginning at the time of injury impairs nociceptive recovery and other outcomes. Measures preventing glial activation through Toll-like receptor 4 signaling may reduce the adverse consequences of postoperative opioid administration.

    View details for PubMedID 30418215

  • Autoinflammatory and autoimmune contributions to complex regional pain syndrome MOLECULAR PAIN Clark, J., Tawfik, V. L., Tajerian, M., Kingery, W. S. 2018; 14
  • [EXPRESS] Autoinflammatory and Autoimmune Contributions to Complex Regional Pain Syndrome. Molecular pain Clark, J. D., Tawfik, V., Tajerian, M., Kingery, W. 2018: 1744806918799127


    Complex regional pain syndrome (CRPS) is a highly enigmatic syndrome typically developing after injury or surgery to a limb. Severe pain and disability are common amongst those with chronic forms of this condition. Accumulating evidence suggests that CRPS may involve both autoinflammatory and autoimmune components. In this review article evidence for dysfunction of both the innate and adaptive immune systems in CPRS is presented. Findings from human studies in which cytokines and other inflammatory mediators were measured in the skin of affected limbs is discussed. Additional results from studies of mediator levels in animal models are evaluated in this context. Similarly, the evidence from human, animal and translational studies of the production of autoantibodies and the potential targets of those antibodies is reviewed. Compelling evidence of autoinflammation in skin and muscle of the affected limb has been collected from CRPS patients and laboratory animals. Cytokines including IL-1beta, IL-6, TNFalpha and others are reliably identified during the acute phases of the syndrome. More recently, autoimmune contributions have been suggested by the discovery of self-directed pain-promoting IgG and IgM antibodies in CRPS patients and model animals. Both the autoimmune and autoinflammatory components of CRPS appear to be regulated by neuropeptide containing peripheral nerve fibers and the sympathetic nervous system. While CRPS displays a complex neuroimmunological pathogenesis, therapeutic interventions could be designed targeting autoinflammation, autoimmunity or the neural support for these phenomena.

    View details for PubMedID 30124090

  • Functional Divergence of Delta and Mu Opioid Receptor Organization in CNS Pain Circuits NEURON Wang, D., Tawfik, V. L., Corder, G., Low, S. A., Francois, A., Basbaum, A. I., Scherrer, G. 2018; 98 (1): 90-+


    Cellular interactions between delta and mu opioid receptors (DORs and MORs), including heteromerization, are thought to regulate opioid analgesia. However, the identity of the nociceptive neurons in which such interactions could occur in vivo remains elusive. Here we show that DOR-MOR co-expression is limited to small populations of excitatory interneurons and projection neurons in the spinal cord dorsal horn and unexpectedly predominates in ventral horn motor circuits. Similarly, DOR-MOR co-expression is rare in parabrachial, amygdalar, and cortical brain regions processing nociceptive information. We further demonstrate that in the discrete DOR-MOR co-expressing nociceptive neurons, the two receptors internalize and function independently. Finally, conditional knockout experiments revealed that DORs selectively regulate mechanical pain by controlling the excitability of somatostatin-positive dorsal horn interneurons. Collectively, our results illuminate the functional organization of DORs and MORs in CNS pain circuits and reappraise the importance of DOR-MOR cellular interactions for developing novel opioid analgesics.

    View details for PubMedID 29576387

    View details for PubMedCentralID PMC5896237

  • Activation of ventral tegmental area dopaminergic neurons reverses pathological allodynia resulting from nerve injury or bone cancer MOLECULAR PAIN Watanabe, M., Narita, M., Hamada, Y., Yamashita, A., Tamura, H., Ikegami, D., Kondo, T., Shinzato, T., Shimizu, T., Fukuchi, Y., Muto, A., Okano, H., Yamanaka, A., Tawfik, V. L., Kuzumaki, N., Navratilova, E., Porreca, F., Narita, M. 2018; 14: 1744806918756406


    Chronic pain induced by nerve damage due to trauma or invasion of cancer to the bone elicits severe ongoing pain as well as hyperalgesia and allodynia likely reflecting adaptive changes within central circuits that amplify nociceptive signals. The present study explored the possible contribution of the mesolimbic dopaminergic circuit in promoting allodynia related to neuropathic and cancer pain. Mice with ligation of the sciatic nerve or treated with intrafemoral osteosarcoma cells showed allodynia to a thermal stimulus applied to the paw on the injured side. Patch clamp electrophysiology revealed that the intrinsic neuronal excitability of ventral tegmental area (VTA) dopamine neurons projecting to the nucleus accumbens (N.Acc.) was significantly reduced in those mice. We used tyrosine hydroxylase (TH)-cre mice that were microinjected with adeno-associated virus (AAV) to express channelrhodopsin-2 (ChR2) to allow optogenetic stimulation of VTA dopaminergic neurons in the VTA or in their N.Acc. terminals. Optogenetic activation of these cells produced a significant but transient anti-allodynic effect in nerve injured or tumor-bearing mice without increasing response thresholds to thermal stimulation in sham-operated animals. Suppressed activity of mesolimbic dopaminergic neurons is likely to contribute to decreased inhibition of N.Acc. output neurons and to neuropathic or cancer pain-induced allodynia suggesting strategies for modulation of pathological pain states.

    View details for PubMedID 29357732

  • Successful treatment of chronic knee pain following localization by a sigma-1 receptor radioligand and PET/MRI: a case report JOURNAL OF PAIN RESEARCH Cipriano, P., Lee, S., Yoon, D., Shen, B., Tawfik, V., Curtin, C., Dragoo, J. L., James, M., Mccurdy, C., Chin, F., Biswal, S. 2018; 11: 2353–56


    The ability to accurately diagnose and objectively localize pain generators in chronic pain sufferers remains a major clinical challenge since assessment relies on subjective patient complaints and relatively non-specific diagnostic tools. Developments in clinical molecular imaging, including advances in imaging technology and radiotracer design, have afforded the opportunity to identify tissues involved in pain generation based on their pro-nociceptive condition. The sigma-1 receptor (S1R) is a pro-nociceptive receptor upregulated in painful, inflamed tissues, and it can be imaged using the highly specific radioligand 18F-FTC-146 with PET.A 50-year-old woman with a 7-year history of refractory, left-knee pain of unknown origin was referred to our pain management team. Over the past several years, she had undergone multiple treatments, including a lateral retinacular release, radiofrequency ablation of a peripheral nerve, and physical therapy. While certain treatments provided partial relief, her pain would inevitably return to its original state. Using simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) with the novel radiotracer 18F-FTC-146, imaging showed increased focal uptake of 18F-FTC-146 in the intercondylar notch, corresponding to an irregular but equivocal lesion identified in the simultaneously acquired MRI. These imaging results prompted surgical removal of the lesion, which upon resection was identified as an inflamed, intraarticular synovial lipoma. Removal of the lesion relieved the patient's pain, and to date the pain has not recurred.We present a case of chronic, debilitating knee pain that resolved with surgery following identification of the pathology with a novel clinical molecular imaging approach that detects chronic pain generators at the molecular and cellular level. This approach has the potential to identify and localize pain-associated pathology in a variety of chronic pain syndromes.

    View details for PubMedID 30349360

  • Loss of mu opioid receptor signaling in nociceptors, but not microglia, abrogates morphine tolerance without disrupting analgesia NATURE MEDICINE Corder, G., Tawfik, V. L., Wang, D., Sypek, E. I., Low, S. A., Dickinson, J. R., Sotoudeh, C., Clark, J. D., Barres, B. A., Bohlen, C. J., Scherrer, G. 2017; 23 (2): 164-173


    Opioid pain medications have detrimental side effects including analgesic tolerance and opioid-induced hyperalgesia (OIH). Tolerance and OIH counteract opioid analgesia and drive dose escalation. The cell types and receptors on which opioids act to initiate these maladaptive processes remain disputed, which has prevented the development of therapies to maximize and sustain opioid analgesic efficacy. We found that μ opioid receptors (MORs) expressed by primary afferent nociceptors initiate tolerance and OIH development. RNA sequencing and histological analysis revealed that MORs are expressed by nociceptors, but not by spinal microglia. Deletion of MORs specifically in nociceptors eliminated morphine tolerance, OIH and pronociceptive synaptic long-term potentiation without altering antinociception. Furthermore, we found that co-administration of methylnaltrexone bromide, a peripherally restricted MOR antagonist, was sufficient to abrogate morphine tolerance and OIH without diminishing antinociception in perioperative and chronic pain models. Collectively, our data support the idea that opioid agonists can be combined with peripheral MOR antagonists to limit analgesic tolerance and OIH.

    View details for DOI 10.1038/nm.4262

    View details for PubMedID 28092666

  • Complex management of a patient with refractory primary erythromelalgia lacking a SCN9A mutation JOURNAL OF PAIN RESEARCH Low, S. A., Robbins, W., Tawfik, V. L. 2017; 10: 973-977


    A 41-year-old woman presented with burning and erythema in her extremities triggered by warmth and activity, which was relieved by applying ice. Extensive workup was consistent with adult-onset primary erythromelalgia (EM). Several pharmacological treatments were tried including local anesthetics, capsaicin, ziconotide, and dantrolene, all providing 24-48 hours of relief followed by symptom flare. Interventional therapies, including peripheral and sympathetic ganglion blocks, also failed. Thus far, clonidine and ketamine have been the only effective agents for our patient. Genetic testing was negative for an EM-associated mutation in the SCN9A gene, encoding the NaV1.7 sodium channel, suggesting a mutation in an alternate gene.

    View details for DOI 10.2147/JPR.S129661

    View details for Web of Science ID 000400133100003

    View details for PubMedCentralID PMC5414616

  • (118) Physical and psychological predictors of dysfunction in complex regional pain syndrome (CRPS): a Collaborative Health Outcomes Information Registry (CHOIR) study. journal of pain Adelus, M., Sturgeon, J., RICO, T., Tawfik, V., Mackey, S. 2016; 17 (4S): S5-?

    View details for DOI 10.1016/j.jpain.2016.01.021

    View details for PubMedID 28162531

  • (218) Characterization of patients with complex regional pain syndrome (CRPS) in a tertiary care pain management setting: A Collaborative Health Outcomes Information Registry (CHOIR) study. journal of pain Adelus, M., Sturgeon, J., RICO, T., Tawfik, V., Mackey, S. 2016; 17 (4S): S30-?

    View details for DOI 10.1016/j.jpain.2016.01.122

    View details for PubMedID 28162448

  • Electrical Synapses High-speed Communication in the Maintenance of Neuropathic Pain ANESTHESIOLOGY Tawfik, V. L., Flood, P. 2016; 124 (1): 13-15

    View details for Web of Science ID 000366461300005

    View details for PubMedID 26566281

  • Input- and Cell-Type-Specific Endocannabinoid-Dependent LTD in the Striatum. Cell reports Wu, Y., Kim, J., Tawfik, V. L., Lalchandani, R. R., Scherrer, G., Ding, J. B. 2015; 10 (1): 75-87


    Changes in basal ganglia plasticity at the corticostriatal and thalamostriatal levels are required for motor learning. Endocannabinoid-dependent long-term depression (eCB-LTD) is known to be a dominant form of synaptic plasticity expressed at these glutamatergic inputs; however, whether eCB-LTD can be induced at all inputs on all striatal neurons is still debatable. Using region-specific Cre mouse lines combined with optogenetic techniques, we directly investigated and distinguished between corticostriatal and thalamostriatal projections. We found that eCB-LTD was successfully induced at corticostriatal synapses, independent of postsynaptic striatal spiny projection neuron (SPN) subtype. Conversely, eCB-LTD was only nominally present at thalamostriatal synapses. This dichotomy was attributable to the minimal expression of cannabinoid type 1 (CB1) receptors on thalamostriatal terminals. Furthermore, coactivation of dopamine receptors on SPNs during LTD induction re-established SPN-subtype-dependent eCB-LTD. Altogether, our findings lay the groundwork for understanding corticostriatal and thalamostriatal synaptic plasticity and for striatal eCB-LTD in motor learning.

    View details for DOI 10.1016/j.celrep.2014.12.005

    View details for PubMedID 25543142

    View details for PubMedCentralID PMC4286501

  • In vivo techniques to investigate the internalization profile of opioid receptors. Methods in molecular biology (Clifton, N.J.) Pradhan, A. A., Tawfik, V. L., Tipton, A. F., Scherrer, G. 2015; 1230: 87-104


    G-protein-coupled receptors (GPCRs) regulate a remarkable diversity of biological functions, and are thus often targeted for drug therapies. Receptor internalization is commonly observed following agonist binding and activation. Receptor trafficking events have been well characterized in cell systems, but the in vivo significance of GPCR internalization is still poorly understood. To address this issue, we have developed an innovative knock-in mouse model, where an opioid receptor is directly visible in vivo. These knockin mice express functional fluorescent delta opioid receptors (DOR-eGFP) in place of the endogenous receptor, and these receptors are expressed at physiological levels within their native environment. DOR-eGFP mice have proven to be an extraordinary tool in studying receptor neuroanatomy, real-time receptor trafficking in live neurons, and in vivo receptor internalization. We have used this animal model to determine the relationship between receptor trafficking in neurons and receptor function at a behavioral level. Here, we describe in detail the construction and characterization of this knockin mouse. We also outline how to use these mice to examine the behavioral consequences of agonist-specific trafficking at the delta opioid receptor. These techniques are potentially applicable to any GPCR, and highlight the powerful nature of this imaging tool.

    View details for DOI 10.1007/978-1-4939-1708-2_7

    View details for PubMedID 25293318

  • Delta Opioid Receptors Presynaptically Regulate Cutaneous Mechanosensory Neuron Input to the Spinal Cord Dorsal Horn NEURON Bardoni, R., Tawfik, V. L., Wang, D., Francois, A., Solorzano, C., Shuster, S. A., Choudhury, P., Betelli, C., Cassidy, C., Smith, K., de Nooij, J. C., Mennicken, F., O'Donnell, D., Kieffer, B. L., Woodbury, C. J., Basbaum, A. I., MacDermott, A. B., Scherrer, G. 2014; 81 (6): 1312-1327


    Cutaneous mechanosensory neurons detect mechanical stimuli that generate touch and pain sensation. Although opioids are generally associated only with the control of pain, here we report that the opioid system in fact broadly regulates cutaneous mechanosensation, including touch. This function is predominantly subserved by the delta opioid receptor (DOR), which is expressed by myelinated mechanoreceptors that form Meissner corpuscles, Merkel cell-neurite complexes, and circumferential hair follicle endings. These afferents also include a small population of CGRP-expressing myelinated nociceptors that we now identify as the somatosensory neurons that coexpress mu and delta opioid receptors. We further demonstrate that DOR activation at the central terminals of myelinated mechanoreceptors depresses synaptic input to the spinal dorsal horn, via the inhibition of voltage-gated calcium channels. Collectively our results uncover a molecular mechanism by which opioids modulate cutaneous mechanosensation and provide a rationale for targeting DOR to alleviate injury-induced mechanical hypersensitivity.

    View details for DOI 10.1016/j.neuron.2014.01.044

    View details for Web of Science ID 000333326000012

    View details for PubMedID 24583022

  • Perioperative interventions to reduce chronic postsurgical pain. Journal of reconstructive microsurgery Carroll, I., Hah, J., Mackey, S., Ottestad, E., Kong, J. T., Lahidji, S., Tawfik, V., Younger, J., Curtin, C. 2013; 29 (4): 213-222


    Approximately 10% of patients following a variety of surgeries develop chronic postsurgical pain. Reducing chronic postoperative pain is especially important to reconstructive surgeons because common operations such as breast and limb reconstruction have even higher risk for developing chronic postsurgical pain. Animal studies of posttraumatic nerve injury pain demonstrate that there is a critical time frame before and immediately after nerve injury in which specific interventions can reduce the incidence and intensity of chronic neuropathic pain behaviors-so called "preventative analgesia." In animal models, perineural local anesthetic, systemic intravenous local anesthetic, perineural clonidine, systemic gabapentin, systemic tricyclic antidepressants, and minocycline have each been shown to reduce pain behaviors days to weeks after treatment. The translation of this work to humans also suggests that brief perioperative interventions may protect patients from developing new chronic postsurgical pain. Recent clinical trial data show that there is an opportunity during the perioperative period to dramatically reduce the incidence and severity of chronic postsurgical pain. The surgeon, working with the anesthesiologist, has the ability to modify both early and chronic postoperative pain by implementing an evidence-based preventative analgesia plan.

    View details for DOI 10.1055/s-0032-1329921

    View details for PubMedID 23463498

  • Perioperative Interventions to Reduce Chronic Postsurgical Pain JOURNAL OF RECONSTRUCTIVE MICROSURGERY Carroll, I., Hah, J., Mackey, S., Ottestad, E., Kong, J. T., Lahidji, S., Tawfik, V., Younger, J., Curtin, C. 2013; 29 (4): 213-222


    Approximately 10% of patients following a variety of surgeries develop chronic postsurgical pain. Reducing chronic postoperative pain is especially important to reconstructive surgeons because common operations such as breast and limb reconstruction have even higher risk for developing chronic postsurgical pain. Animal studies of posttraumatic nerve injury pain demonstrate that there is a critical time frame before and immediately after nerve injury in which specific interventions can reduce the incidence and intensity of chronic neuropathic pain behaviors-so called "preventative analgesia." In animal models, perineural local anesthetic, systemic intravenous local anesthetic, perineural clonidine, systemic gabapentin, systemic tricyclic antidepressants, and minocycline have each been shown to reduce pain behaviors days to weeks after treatment. The translation of this work to humans also suggests that brief perioperative interventions may protect patients from developing new chronic postsurgical pain. Recent clinical trial data show that there is an opportunity during the perioperative period to dramatically reduce the incidence and severity of chronic postsurgical pain. The surgeon, working with the anesthesiologist, has the ability to modify both early and chronic postoperative pain by implementing an evidence-based preventative analgesia plan.

    View details for DOI 10.1055/s-0032-1329921

    View details for Web of Science ID 000317597000001

    View details for PubMedID 23463498

  • Deep Brain Stimulation Results in Local Glutamate and Adenosine Release: Investigation Into the Role of Astrocytes NEUROSURGERY Tawfik, V. L., Chang, S., Hitti, F. L., Roberts, D. W., Leiter, J. C., Jovanovic, S., Lee, K. H. 2010; 67 (2): 367-375


    Several neurological disorders are treated with deep brain stimulation; however, the mechanism underlying its ability to abolish oscillatory phenomena associated with diseases as diverse as Parkinson's disease and epilepsy remain largely unknown.To investigate the role of specific neurotransmitters in deep brain stimulation and determine the role of non-neuronal cells in its mechanism of action.We used the ferret thalamic slice preparation in vitro, which exhibits spontaneous spindle oscillations, to determine the effect of high-frequency stimulation on neurotransmitter release. We then performed experiments using an in vitro astrocyte culture to investigate the role of glial transmitter release in high-frequency stimulation-mediated abolishment of spindle oscillations.In this series of experiments, we demonstrated that glutamate and adenosine release in ferret slices was able to abolish spontaneous spindle oscillations. The glutamate release was still evoked in the presence of the Na channel blocker tetrodotoxin, but was eliminated with the vesicular H-ATPase inhibitor bafilomycin and the calcium chelator 2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetrakis acetoxymethyl ester. Furthermore, electrical stimulation of purified primary astrocytic cultures was able to evoke intracellular calcium transients and glutamate release, and bath application of 2-bis (2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetrakis acetoxymethyl ester inhibited glutamate release in this setting.Vesicular astrocytic neurotransmitter release may be an important mechanism by which deep brain stimulation is able to achieve clinical benefits.

    View details for DOI 10.1227/01.NEU.0000371988.73620.4C

    View details for Web of Science ID 000280105800032

    View details for PubMedID 20644423

    View details for PubMedCentralID PMC2919357

  • The Role of Astrocytes in the Modulation of Pain SYNAPTIC PLASTICITY IN PAIN Tawfik, V. L., DeLeo, J. A., Malcangio, M. 2009: 387-402
  • Propentofylline-induced astrocyte modulation leads to alterations in glial glutamate promoter activation following spinal nerve transection NEUROSCIENCE Tawfik, V. L., Regan, M. R., Haenggeli, C., Lacroix-Fralish, M. L., Nutile-McMenemy, N., Perez, N., Rothstein, J. D., DeLeo, J. A. 2008; 152 (4): 1086-1092


    We have previously shown that the atypical methylxanthine, propentofylline, reduces mechanical allodynia after peripheral nerve transection in a rodent model of neuropathy. In the present study, we sought to determine whether propentofylline-induced glial modulation alters spinal glutamate transporters, glutamate transporter-1 (GLT-1) and glutamate-aspartate transporter (GLAST) in vivo, which may contribute to reduced behavioral hypersensitivity after nerve injury. In order to specifically examine the expression of the spinal glutamate transporters, a novel line of double transgenic GLT-1-enhanced green fluorescent protein (eGFP)/GLAST-Discosoma Red (DsRed) promoter mice was used. Adult mice received propentofylline (10 mg/kg) or saline via i.p. injection starting 1 h prior to L5-spinal nerve transection and then daily for 12 days. Mice receiving saline exhibited punctate expression of both eGFP (GLT-1 promoter activation) and DsRed (GLAST promoter activation) in the dorsal horn of the spinal cord, which was decreased ipsilateral to nerve injury on day 12. Propentofylline administration reinstated promoter activation on the injured side as evidenced by an equal number of eGFP (GLT-1) and DsRed (GLAST) puncta in both dorsal horns. As demonstrated in previous studies, propentofylline induced a concomitant reversal of L5 spinal nerve transection-induced expression of glial fibrillary acidic protein (GFAP). The ability of propentofylline to alter glial glutamate transporters highlights the importance of controlling aberrant glial activation in neuropathic pain and suggests one possible mechanism for the anti-allodynic action of this drug.

    View details for DOI 10.1016/j.neuroscience.2008.01.065

    View details for Web of Science ID 000255152800022

    View details for PubMedID 18358622

    View details for PubMedCentralID PMC2423012

  • Neuregulin 1 is a pronociceptive cytokine that is regulated by progesterone in the spinal cord: Implications for sex specific pain modulation EUROPEAN JOURNAL OF PAIN LaCroix-Fralish, M. L., Tawfik, V. L., Nutile-McMenemy, N., DeLeo, J. A. 2008; 12 (1): 94-103


    Sex differences in the magnitude of response to thermal and tactile stimuli have been demonstrated in both clinical and animal studies. Females typically display lower threshold responses to painful stimuli as compared to males. We have previously observed sexually dimorphic expression of the growth factor, neuregulin 1 (NRG1) following L5 nerve root ligation (LR) in male and female rats. In the present study, we sought to determine which gonadal hormones were involved in regulating NRG1 expression following L5 nerve root ligation. We observed that expression of NRG1 mRNA and the neuregulin receptors, ErbB2 and ErbB4 in the lumbar spinal cord was facilitated by the presence of progesterone in female rats following L5 nerve root ligation. An increase in NRG1 protein and NRG1 immunoreactivity was also observed in the ipsilateral spinal cord of progesterone treated female rats as compared to ovariectomized female rats and male rats at day 14 following LR. NRG1 immunoreactivity was equally colocalized with either the astrocytic marker, GFAP, and with NeuN labeled neurons 14days following L5 nerve root ligation. Intrathecal administration of recombinant NRG1-beta1 protein significantly decreased the hindpaw tactile withdrawal threshold in male rats, ovariectomized female rats, and progesterone treated female rats. These results demonstrate a role for progesterone-dependent regulation of glial and/or neuronal neuregulin 1 in female rats in mediating sex differences in nociception. Furthermore, our results suggest that NRG1 may be involved in central sensitization during the maintenance phase, but not in the initiation of persistent pain in female rats.

    View details for DOI 10.1016/j.ejpain.2007.03.010

    View details for Web of Science ID 000251934200012

    View details for PubMedID 17459743

  • Intracranial self-stimulation of the dorsal raphe sensitizes psychostimulant locomotion BEHAVIORAL NEUROSCIENCE Boye, S. M., Grant, R. J., Tawfik, V. L. 2007; 121 (3): 550-558


    The authors hypothesized that repeated rewarding electrical stimulation of the dorsal raphe can produce behavioral sensitization to psychostimulants. Groups of male rats were implanted with a stimulation electrode and preexposed to brain stimulation at parameters set to equate rewarding effectiveness across rats. Control groups were implanted with an electrode but never stimulated, or not implanted at all. Twenty-four hours after the 12th self-stimulation session, all groups were challenged with amphetamine (0.5 mg/kg, ip), nicotine (0.2 mg/kg, sc), or saline, and locomotor activity was measured for 1 hr. Locomotor responses to amphetamine and to nicotine were significantly greater in rats preexposed to brain stimulation. These findings suggest at least partial overlap of underlying substrates. ((c) 2007 APA, all rights reserved).

    View details for DOI 10.1037/0735-7044.121.3.550

    View details for Web of Science ID 000247359300011

    View details for PubMedID 17592946

  • Efficacy of propentofylline, a glial modulating agent, on existing mechanical allodynia following peripheral nerve injury BRAIN BEHAVIOR AND IMMUNITY Tawfik, V. L., Nutile-McMenemy, N., LaCroix-Fralish, M. L., DeLeo, J. A. 2007; 21 (2): 238-246


    Increasing evidence points to a role for spinal neuroimmune dysregulation (glial cell activation and cytokine expression) in the pathogenesis of chronic pain. Suppression of astrocytic and microglial activation with the methylxanthine derivative, propentofylline, pre-emptively attenuates the development of nerve injury-induced allodynia. Currently, we investigated the ability of systemic propentofylline to reverse existing, long-term allodynia after nerve injury--a clinically relevant paradigm. Rats received L5 spinal nerve transection or sham surgery and the development of mechanical allodynia was assessed daily for 2 weeks, at which time injured rats exhibited robust responses to non-noxious von Frey filaments. On days 14-27, rats received either saline or 101 mg/kg propentofylline by intraperitoneal (i.p.) injection. On day 28 or 42 (after a 14-day drug washout period), lumbar spinal cord sections were processed for assessment of astrocytic glial fibrillary acidic protein (GFAP) and microglial OX-42 (antibody against CR3/CD11b). Propentofylline treatment to nerve injured rats resulted in significant reversal of allodynia that lasted throughout the 14-day washout period. Spinal microglial activation was observed at days 28 and 42 post-injury at the protein level, in the absence of mRNA level changes. Less robust increases in GFAP immunoreactivity were observed at days 28 and 42 post-transection. Interestingly, propentofylline treatment suppressed microglial activation at both time points in this paradigm. Taken together, our results highlight the clinical potential of the glial modulating agent, propentofylline, for the treatment of neuropathic pain as well as a role for microglia in the long-term maintenance of allodynia.

    View details for DOI 10.1016/j.bbi.2006.07.001

    View details for Web of Science ID 000243896100014

    View details for PubMedID 16949251

  • Induction of astrocyte differentiation by propentofylline increases glutamate transporter expression in vitro: Heterogeneity of the quiescent phenotype GLIA Tawfik, V. L., LaCroix-Fralish, M. L., Bercury, K. K., Nutile-McMenemy, N., Harris, B. T., DeLeo, J. A. 2006; 54 (3): 193-203


    Reactive astrocytes display decreased glutamate transporters, such as GLT-1, and as a result synaptic glutamate clearance is impaired. In addition, these activated astrocytes are immunocompetent and release algesic mediators that can sensitize neurons in the spinal cord. Currently, we evaluated the effect of propentofylline (PPF), an experimental antiallodynic agent, on the phenotype and glutamate transporter expression of astrocytes. Primary astrocyte cultures, which represent an activated phenotype with a polygonal morphology and low GLT-1 expression, were treated for 3 or 7 days with 10, 100, or 1,000 microM PPF or dibutyryl-cAMP (db-cAMP), a known inducer of GLT-1 expression. PPF dose-dependently induced astrocytes to display a mature phenotype, with elongated processes and a stellate shape, as well as increased GLT-1 and GLAST immunoreactivity, similar to that seen with db-cAMP. Real time RT-PCR and Western blot analysis clearly demonstrated that PPF caused a potent dose-dependent induction of GLT-1 and GLAST mRNA and protein in these astrocytes. Importantly, the observed increase in glutamate transporters was found to have a functional effect, with significantly enhanced glutamate uptake in astrocytes treated with 100 or 1,000 microM PPF that was sensitive to dihydrokainate inhibition, suggesting it is GLT-1 mediated. Finally, the effect of PPF on lipopolysaccharide-induced chemokine release was investigated. Interestingly, PPF was able to dampen both MCP-1 (CCL2) and MIP-2 (CXCL2) release from astrocytes while db-cAMP significantly enhanced this chemokine expression. These findings suggest that PPF is capable of differentiating astrocytes to a homeostatic, mature phenotype, competent for glutamate clearance and distinct from that induced by db-cAMP.

    View details for DOI 10.1002/glia.20365

    View details for Web of Science ID 000239351600005

    View details for PubMedID 16819765

  • Differential spinal cord gene expression in rodent models of radicular and neuropathic pain ANESTHESIOLOGY LaCroix-Fralish, M. L., Tawfik, V. L., Tanga, F. Y., Spratt, K. F., DeLeo, J. A. 2006; 104 (6): 1283-1292


    Neuropathic pain and radicular low back pain both have a major impact on human health worldwide. Microarray gene analysis on central nervous system tissues holds great promise for discovering novel targets for persistent pain modulation.Rat models of lumbar radiculopathy (L5 nerve root ligation) and neuropathy (L5 spinal nerve transection) were used for these studies. The authors measured mechanical allodynia followed by analysis of global gene expression in the lumbar spinal cord at two time points (7 days and 14 days) after surgery using the Affymetrix RAE230A GeneChip(R) (Santa Clara, CA). The expression patterns of several genes of interest were subsequently confirmed using real-time reverse transcriptase polymerase chain reaction.The authors observed similarly robust mechanical allodynia in both models. Second, they observed significant differences in lumbar spinal cord gene expression across chronic pain models. There was little overlap between genes altered in each injury model, suggesting that the site and type of injury produce distinct spinal mechanisms mediating the observed mechanical allodynia. The authors further confirmed a subset of the genes using reverse transcriptase polymerase chain reaction and identified several genes as either neuropathy-associated genes or radiculopathy-associated genes.These two models of persistent pain produce similar allodynic outcomes but produce differential gene expression. These results suggest that diverging mechanisms lead to a common behavioral outcome in these pain models. Furthermore, these distinct pathophysiologic mechanisms in neuropathic versus radicular pain may implicate unique drug therapies for these types of chronic pain syndromes.

    View details for Web of Science ID 000237869500024

    View details for PubMedID 16732101

  • The tetrapartite synapse: Path to CNS sensitization and chronic pain PAIN de Leo, J. A., Tawfik, V. L., LaCroix-Fralish, M. L. 2006; 122 (1-2): 17-21

    View details for DOI 10.1016/j.pain.2006.02.034

    View details for Web of Science ID 000237549100007

    View details for PubMedID 16564626

  • Progesterone mediates gonadal hormone differences in tactile and thermal hypersensitivity following L5 nerve root ligation in female rats NEUROSCIENCE Lacroix-Fralish, M. L., Tawfik, V. L., Nutile-McMenemy, N., DeLeo, J. A. 2006; 138 (2): 601-608


    Sex differences in the magnitude of response to thermal and tactile stimuli have been demonstrated in both clinical and animal studies. Female rats typically display lower thresholds to painful stimuli and display more robust responses following nerve injury as compared with males. There is a body of evidence implicating the sex hormones in mediating this sex difference. In the present study, we sought to determine which gonadal hormones were involved in mediating the observed female hypersensitivity in female rats both prior to and following experimental nerve root injury using a chronic hormone replacement paradigm. Female rats were ovariectomized and hormone pellets containing 17beta-estradiol, progesterone (P), 17beta-estradiol+progesterone or placebo were implanted s.c. Our results demonstrate that only the group of female rats that received progesterone alone maintained the hypersensitive phenotype following ovariectomy, compared with gonadally intact male rats. This result was observed both in response to thermal stimuli in non-injured female rats and to thermal and tactile stimuli following L5 nerve root ligation, a model of low back pain associated with lumbar radiculopathy. Postmortem analysis of serum gonadal hormone concentrations demonstrates that the hormonal manipulations were successful and the exogenous hormones were similar to physiological levels observed in the sham-ovariectomized controls. Taken together, these results demonstrate the critical role for progesterone in mediating enhanced female tactile and thermal hypersensitivity following L5 nerve root ligation.

    View details for DOI 10.1016/j.neuroscience.2005.11.048

    View details for Web of Science ID 000236046100021

    View details for PubMedID 16413124

  • Sex differences in lumbar spinal cord gene expression following experimental lumbar radiculopathy JOURNAL OF MOLECULAR NEUROSCIENCE LaCroix-Fralish, M. L., Tawfik, V. L., Spratt, K. F., DeLeo, J. A. 2006; 30 (3): 283-295


    Considerable evidence indicates that there are sex-related differences in clinical and experimental pain sensitivity. In the present study, we sought to determine what genes were expressed in the spinal cord in a sexually dimorphic manner. We first analyzed global gene expression in the lumbar spinal cord of uninjured male and female rats using the Affymetrix RAE230A GeneChip platform in order to identify genes that are selectively expressed in male and female rats at a basal level. We subsequently analyzed global gene expression in the lumbar spinal cord of male and female rats at two time points (7 days and 14 d) following a rodent model of lumbar radiculopathy (L5 nerve root ligation) in order to determine what genes were regulated in a sexually dimorphic manner following nerve root injury. We utilized a linear regression analysis method to identify genes that were significantly different from the corresponding sham surgical controls. The expression patterns of several genes of interest were subsequently confirmed using RT-PCR. Our findings demonstrate significant differences in lumbar spinal cord gene expression in both uninjured and injured (L5 nerve root ligation) male and female rats. Further confirmation of a subset of the genes identified Neuregulin 1 and its high affinity receptor, ErbB4, Tachykinin 1, and Metabotropic glutamate receptor 6 as female specific genes upregulated following L5 nerve root injury. These findings provide several target genes for further study that may elucidate the neurochemical mechanisms underlying sex differences in pain sensitivity and lead to improved treatments for chronic pain syndromes.

    View details for DOI 10.1385/JMN/30:03:283

    View details for Web of Science ID 000243782200004

    View details for PubMedID 17401154

  • Differential regulation of neuregulin 1 expression by progesterone in astrocytes and neurons NEURON GLIA BIOLOGY LaCroix-Fralish, M. L., Tawfik, V. L., Nutile-McMenemy, N., Harris, B. T., DeLeo, J. A. 2006; 2: 227-234


    Glial-neuronal interactions are crucial processes in neuromodulation and synaptic plasticity. The neuregulin 1 family of growth and differentiation factors have been implicated as bidirectional signaling molecules that are involved in mediating some of these interactions. We have shown previously that neuregulin 1 expression is regulated by the gonadal hormones progesterone and 17beta-estradiol in the CNS, which might represent a novel, indirect mechanism of the neuromodulatory actions of these gonadal hormones. In the present study, we sought to determine the effects of progesterone and 17beta-estradiol on neuregulin 1 expression in rat cortical astrocytes and neurons in vitro. We observed that progesterone increased the expression of neuregulin 1 mRNA and protein in a dose-dependent manner in cultured astrocytes, which was blocked by the progesterone receptor antagonist RU-486. In contrast, 17beta-estradiol did not increase either neuregulin 1 mRNA or protein in astrocytes. We observed no effect of either progesterone or 17beta-estradiol on neuregulin 1 mRNA and protein in rat cortical neurons in vitro. Finally, we observed that treatment of cortical neurons with recombinant NRG1-beta1 caused PSD-95 to localize in puncta similar to that observed following treatment with astrocyte-conditioned medium. These results demonstrate that progesterone regulates neuregulin 1 expression, principally in astrocytes. This might represent a novel mechanism of progesterone-mediated modulation of neurotransmission through the regulation of astrocyte-derived neuregulin 1.

    View details for DOI 10.1017/S1740925X07000385

    View details for Web of Science ID 000248510100002

    View details for PubMedID 18049715

    View details for PubMedCentralID PMC2099160

  • Safety issues concerning the medical use of cannabis and cannabinoids. Pain research & management Ware, M. A., Tawfik, V. L. 2005; 10: 31A-7A


    Safety issues are a major barrier to the use of cannabis and cannabinoid medications for clinical purposes. Information on the safety of herbal cannabis may be derived from studies of recreational cannabis use, but cannabis exposure and effects may differ widely between medical and recreational cannabis users. Standardized, quality-controlled cannabinoid products are available in Canada, and safety profiles of approved medications are available through the Canadian formulary. In the present article, the evidence behind major safety issues related to cannabis use is summarized, with the aim of promoting informed dialogue between physicians and patients in whom cannabinoid therapy is being considered. Caution is advised in interpreting these data, because clinical experience with cannabinoid use is in the early stages. There is a need for long-term safety monitoring of patients using cannabinoids for a wide variety of conditions, to further guide therapeutic decisions and public policy.

    View details for PubMedID 16237480

  • Transcriptional and translational regulation of glial activation by morphine in a rodent model of neuropathic pain JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS Tawfik, V. L., Lacroix-Fralish, M. L., Nutile-McMeneny, N., DeLeo, J. A. 2005; 313 (3): 1239-1247


    Glial cells function in maintenance of homeostasis as well as in pathophysiology. In this study, we determined the time course of spinal glial cell activation during the development of morphine analgesic tolerance in an L5 spinal nerve transection rodent model of neuropathic pain. We also sought to assess whether the method of morphine administration affected neuroimmune activation at the levels of transcription and translation. Rats received L5 spinal nerve transection or no surgery on day 0. On day 6 post-transection, osmotic minipumps were implanted to deliver saline or morphine s.c. (1 or 10 mg/kg) or i.t. (5 or 20 nmol/h). Mechanical allodynia developed immediately after spinal nerve transection; this hypersensitivity was reversed with both low- and high-dose morphine by either route. Tolerance to antiallodynia developed after 3 days of i.t. morphine and after 6 days of s.c. morphine, indicating hastened tolerance following i.t. delivery. Analysis of mRNA revealed that s.c. morphine treatment did not lead to increases in glial activation markers. In contrast, i.t. morphine caused a biphasic alteration in glial fibrillary acidic protein (GFAP) and integrin alpha M mRNA. Protein levels for GFAP were elevated after s.c. and i.t. administration of morphine; however, induction was further enhanced in the latter group. Here, we show for the first time that there is differential recruitment of transcriptional and translational mechanisms of glial activation by systemic and i.t. morphine. Furthermore, we suggest that enhanced neuroimmune activation after i.t. dosing contributes to the hastened development of analgesic tolerance seen in these animals.

    View details for DOI 10.1124/jpet.104.082420

    View details for Web of Science ID 000229203200033

    View details for PubMedID 15743926

  • The organizational and activational effects of sex hormones on tactile and thermal hypersensitivity following lumbar nerve root injury in male and female rats PAIN Lacroix-Fralish, M. L., Tawfik, V. L., DeLeo, J. A. 2005; 114 (1-2): 71-80


    Considerable evidence exists for sex differences in human pain sensitivity. Women typically report a higher incidence of various painful conditions and report that the conditions are more painful when compared to men. In the present study, we sought to determine whether sex differences in pain sensitivity are observed using a lumbar radiculopathy model of low back pain in the rat and whether removal or alteration of gonadal hormones at specific timepoints can modulate these sex differences. Pubertal and adult male and female Sprague-Dawley rats were castrated 2 or 6 weeks prior to L5 nerve root injury to determine the activational hormonal effects. In a separate study, neonatal male and female Sprague-Dawley rats were either castrated or injected with testosterone, respectively, on postnatal day one to determine the organizational effects of gonadal hormones on L5 nerve root injury-induced behavioral hypersensitivity. Our results demonstrate that there was a statistically significant sex difference in the magnitude of mechanical allodynia and thermal hyperalgesia following experimentally induced radiculopathy in the rat: females demonstrated decreased thresholds to tactile and thermal stimuli as compared to males. Furthermore, the enhanced female hypersensitivity was reversed in pubertal and adult animals ovariectomized 6 weeks, but not 2 weeks prior to L5 nerve root injury. Our results demonstrate that the activational effects of gonadal hormones mediate the enhanced female tactile and thermal hypersensitivity following L5 nerve root injury. These results suggest that manipulation of gonadal hormones may be a potential source for novel therapies for chronic pain in women.

    View details for DOI 10.1016/j.pain.2004.12.006

    View details for Web of Science ID 000227683500010

    View details for PubMedID 15733633

    View details for PubMedCentralID PMC1361499

  • Neupoimmune activation and neuroinflammation in chronic pain and opioid tolerance/hyperalgesia NEUROSCIENTIST DeLeo, J. A., Tanga, F. Y., Tawfik, V. L. 2004; 10 (1): 40-52


    One area that has emerged as a promising therapeutic target for the treatment and prevention of chronic pain and opioid tolerance/hyperalgesia is the modulation of the central nervous system (CNS) immunological response that ensues following injury or opioid administration. Broadly defined, central neuroimmune activation involves the activation of cells that interface with the peripheral nervous system and blood. Activation of these cells, as well as parenchymal microglia and astrocytes by injury, opioids, and other stressors, leads to subsequent production of cytokines, cellular adhesion molecules, chemokines, and the expression of surface antigens that enhance a CNS immune cascade. This response can lead to the production of numerous pain mediators that can sensitize and lower the threshold of neuronal firing: the pathologic correlate to central sensitization and chronic pain states. CNS innate immunity and Toll-like receptors, in particular, may be vital players in this orchestrated immune response and may hold the answers to what initiates this complex cascade. The challenge remains in the careful perturbation of injury/opioid-induced neuroimmune activation to down-regulate this process without inhibiting beneficial CNS autoimmunity that subserves neuronal protection following injury.

    View details for DOI 10.1177/1073858403259950

    View details for Web of Science ID 000188233400013

    View details for PubMedID 14987447

  • Neuroimmune activation and neuroinflammation in chronic pain and opioid tolerance/hyperalgesia. Neuroscientist DeLeo, J. A., Tanga, F. Y., Tawfik, V. L. 2004; 10 (1): 40-52