Funded Projects

Masticatory and spontaneous pain associated with temporomandibular joint disorders (TMJD) is a significant contributor to orofacial pain, and current treatments for TMJD pain are unsatisfactory. Pain-related transient receptor potential (TRP) channels, expressed by trigeminal ganglion (TG) sensory neurons, have been implicated in both acute and chronic pain and represent possible targets for anti-pain strategies. Using bite force metrics, we found TMJ inflammation-induced masticatory pain to be significantly, but not fully, reversed in Trpv4 knockout mice, suggesting the residual pain might be mediated by other pain-TRPs. Our gene expression studies demonstrated that TRPV1 and TRPA1 were up-regulated in the TG in response to TMJ inflammation in a Trpv4-dependent manner. We hypothesize that TRPV1 and TRPA1, like TRPV4, contribute to TMJ pain. Our specific aims will examine the contribution of TRPV1, TRPV4, and TRPA1 to pathogenesis of TMJD pathologic pain including assessment of the role of neurogenic inflammation.

This project focuses on identifying and validating a new central analgesic circuit in the brain, based on a highly innovative hypothesis that the strong analgesic effects of general anesthesia (GA) are in part carried out by GA-mediated activation of the endogenous analgesic circuits. Preliminary discovery studies found that a subset of GABAergic neurons located in the central amygdala (CeA) become strongly activated and express high levels of the immediate early gene Fos under GA (hereafter referred to as CeAGA neurons). Furthermore, activation of these neurons exert profound pain-suppressing effects in an acute pain model and a chronic orofacial neuropathic pain model in mice. Based on these exciting preliminary findings, this project will identify and validate CeAGA neurons’ analgesic functions utilizing multiple mouse pain models. Identification of these shared common pathways that need to be suppressed by specific subtypes of CeAGA analgesic neurons will be highly critical for developing precise CeAGA-targeted therapies to treat chronic pain.

Common chronic pain syndromes such as fibromyalgia, temporomandibular disorder, and low back pain, are significant health conditions for which safe and effective treatments are needed. Previous studies have identified the adrenergic receptor beta-3 (Adrb3) as a novel target for chronic pain, but past attempts to block this receptor have not worked. This project aims to identify and develop new molecules to attach selectively and block Adrb3 without entering the brain and spinal cord. The research will test these molecules in rodent animal models to determine their ability to block pain without significant side effects.

A complex network of different nerve cell subtypes connects to joints in different ways throughout body regions, such as the knee and the temporomandibular joint (TMJ) that connects the lower jaw and skull. This project aims to identify disease-specific pain symptoms using clinically relevant rat models of TMJ and knee osteoarthritis – and compare findings with disease-specific pain symptoms in human patients with the same conditions. This research may lead to a better understanding of how different nerve cell subtypes contribute to joint pain as well as how these nerve cell subtypes change with age and disease.

Despite the need for non-opioid treatments for chronic pain, few alternative treatment approaches exist. Transcutaneous auricular neurostimulation (tAN) is a safe and effective treatment for pain during opioid withdrawal; however, researchers do not understand how tAN reduces pain, which limits its clinical use. A better understanding of how tAN affects neurophysiological processes to provide pain relief would likely expand tAN development and use. This interdisciplinary project will conduct research in both healthy adults and those with chronic pain to explain the neurochemical and neurophysiological mechanisms for tAN-based pain relief, and also help optimize treatments and their use.

This project aims to validate Peptidase Inhibitor 16 (PI16) as a novel target for the treatment of chronic pain using mouse models and tissues of human patients with neuropathy. PI16 was identified as a novel regulator of chronic pain in preclinical bench studies. PI16 is a small molecule that has not been studied in the context of pain. Mice that are deficient for PI16 function are protected against mechanical allodynia (tactile pain from light touch) in spared nerve injury (SNI) and paclitaxel models of neuropathic pain. PI16 is only detectable in fibroblasts around peripheral nerves (perineurium), and in the meninges of dorsal root ganglia (DRG), spinal cord, and brain, but not in neurons, glia or leukocytes. PI16 levels in perineurial and DRG meningeal fibroblasts increase during neuropathic pain. Increased PI16 secretion by DRG meningeal and perineurial fibroblasts may promote chronic pain by increasing blood nerve barrier (BNB) permeability and leukocyte trafficking into nerve and DRG.

Pain caused by degenerative joint diseases such as osteoarthritis (OA) is a major public health challenge that significantly affects quality of life for millions of Americans. There are no therapies available that offer pain relief and reverse the course of OA.  This project will use state-of-the-art technologies to create a neuronal connectivity and molecular map of the mouse knee joint, which will help identify molecular signatures that can be targeted for therapy. The research will include animals of different ages and of both sexes and test joint effects after exercise, in animals with OA, and after gene therapy that delivers an experimental OA medication directly to the joint.

Debilitating neuropathic pain occurs in 40 percent to 70 percent of people who suffer from spinal cord injury (SCI). There are no distinguishing characteristics to identify who will develop neuropathic pain. The objective of this research is to develop a biomarker signature prognostic of SCI-induced neuropathic pain (NP). The aims of the project are to (1) identify autoantibodies in plasma samples from acute SCI patients to CNS autoantigens and determine the relationship between autoantibodies levels to the development of NP, (2) identify the autoantibody combination with maximal prognostic accuracy for the development of NP at six months after SCI, and (3) develop and optimize an assay to simultaneously measure several autoantibodies and independently validate the prognostic efficacy for NP using plasma samples collected prospectively. Establishing a panel will refine the prognostic value of these autoantibodies as biomarkers to detect who are vulnerable to NP and may be used to for development of nonaddictive pain therapeutics.

For patients with neuropathic pain refractory to therapy using small molecules, modulation of specific neural structures in the central or peripheral nervous system can provide effective alternative treatments. While current Food and Drug Administration–approved devices for dorsal root ganglion (DRG) stimulation are safe and effective, there have been an unfortunate number of adverse events associated with pulse generator infections and lead migration. The research team will develop a wireless, millimeter-sized nerve stimulator that can be delivered through the vasculature and stimulate the DRG to alleviate symptoms of neuropathic pain and the associated minimally invasive delivery method. This endovascular nerve stimulation (EVNS) system depends on development and integration of key novel technologies into an endovascular stent. The magnetoelectric transducers and electronic circuits will convert wireless power and data into stimulus patterns that can trigger neural activity in the DRG via miniature electrodes. After chronic demonstration of safety and functionality in large animal models, the team will prepare for regulatory discussions with the FDA. If successful, the EVNS will provide a technology platform for treating other neuropathic pain syndromes. 

Chronic pain severely reduces the quality of life and ability to work for millions of Americans. Because misuse of opioids for chronic pain treatment contributes to opioid addiction and opioid overdose, there is an urgent need to study novel non-opioid mechanisms, targets, and treatment strategies for chronic pain. Many ion channels control the flow of electrical signals in peripheral sensory neurons and are thus key targets for understanding and treating chronic pain. This project will conduct detailed studies to identify major ion channel-related molecular activities, targets, and treatment strategies for chronic pain. In particular, this research will explore the role of a specific ion channel (lysosomal mechanosensitive ion channel, orTmem63A) in neuropathic pain resulting from nerve injury.

Validation of novel pain targets is a critical step toward the development of new non-addictive therapeutic agents for chronic pain management. Recent findings suggest that nerve injury-induced concurrent upregulation of the calcium channel alpha-2delta-1 subunit (CaValpha-2-delta-1) and thrombospondin-4 (TSP4) proteins in sensory and spinal cord neurons contributes to neuropathic pain development. Specifically, induction of aberrant excitatory synapse formation and sensitization of neurotransmission in spinal cord underlies this process; accordingly, a target site has been identified in the TSP4 that plays a critical role in mediating these pathological changes upon interaction with the CaValpha-2-delta-1 protein. This project will validate this novel target site in TSP4 for development of non-addictive pain medications, utilizing multidisciplinary approaches to investigate if blocking and genetic deletion of the target site can block or prevent the development of chronic pain state, aberrant excitatory synapse formation, and spinal cord neuron sensitization after injury in multiple rodent neuropathic pain models.

Persistent pain states arising from inflammatory conditions, such as in arthritis, diabetes, HIV, and chemotherapy, exhibit a common feature in the release of damage-associated molecular pattern molecules, which can activate toll-like receptor-4 (TLR4). Previous studies suggest that TLR4 is critical in mediating the transition from acute to persistent pain. TLR4 as well as other inflammatory receptors localize to lipid raft microdomains on the plasma membrane. We have found that the secreted apoA-I binding protein (AIBP) accelerates cholesterol removal, disrupts lipid rafts, prevents TLR4 dimerization, and inhibits microglia inflammatory responses. We propose that AIBP targets cholesterol removal to lipid rafts harboring activated TLR4. The aims of this proposal are to: 1) determine whether AIBP targets lipid rafts harboring activated TLR4; 2) test whether AIBP reduces glial activation and neuroinflammation in mouse models of neuropathic pain; and 3) identify the origin and function of endogenous AIBP in the spinal cord.

Natural products, which are substances found in nature and made by living organisms, have been used in the past as good sources for developing new medications. Natural products isolated from marine bacteria that attach to the pain-signaling protein sigma-2 receptor (also known as transmembrane protein 97 [TMEM97]), may serve as a starting point to create new, non-opioid pain medications. This project will use chemistry and biology approaches to refine such natural products as a treatment for neuropathic pain.