Funded Projects

Chronic pain results in long-term changes throughout the central nervous system. These include abnormal structure and function of the frontal cortex region of the brain, which relays pain messages and also the common pain-related conditions depression, anxiety, and cognitive impairment. Peripheral nerve injury results in widespread and long-lasting changes to DNA in the frontal cortex. DNA methylation, in which chemical tags are attached to DNA, is one way the body controls the activity of genes over time. This control occurs via proteins that recognize tagged DNA, and some of these proteins do not work properly in the frontal cortex many months after nerve injury. These changes occur after nerve injury and are linked to mechanical sensitivity. This project will determine this DNA-binding protein is a good target for finding new medications for chronic pain. 

Routine treatment of pain with prescription opioid medications may evolve into opioid use disorder, addiction, and potentially overdose. New, non-opioid molecular targets for pain are needed as a key element of responding to the opioid and overdose crisis. Ion channels are molecular gateways that convert electrical signals into physiological responses, and many have been implicated in transmitting pain signals. The ion channel Kir6.1/KCNJ8 has been linked to the control of postoperative and cancer pain. Studies in animal models show that low levels of this ion channel are evident after an injury. This research will identify compounds that can open the Kir6.1/KCNJ8 channel as potential treatment strategy for pain.

The cannabis plant contains many active compounds known collectively as cannabinoids that have been shown to possess analgesic and anti-inflammatory properties. These compounds exert their biological activity, in part, through the cannabinoid receptor. The cannabinoid receptor is a member of a class of proteins known as G-protein coupled receptors (GPCRs). This study will test whether a GPCR with unknown biological function, called Gpr149, has a role in the activity of cannabinoids. The study will identify and characterize Gpr149 expression in mouse cells, and deeply characterize the action of minor cannabinoids, endocannabinoids and products of inflammation to modulate Gpr149. This research will provide insight into the analgesic and anti-inflammatory action of minor cannabinoids and into the role of Gpr149 in nociception and the sensitization of nociceptors to inflammatory mediators.

G-protein coupled receptor 3 (GPR3) is an orphan receptor present in the central nervous system (CNS) that plays important role in many normal physiological functions and is involved in a variety of pathological conditions. Although the brain chemical that activates this receptor has not been identified, work with GPR3 knockout mice has identified GPR3 as a novel drug target for several Central Nervous System (CNS) mediated diseases including neuropathic pain. However, despite the emerging behavioral implications of the GPR3 system, little is known about how GPR3 affects behavior due to the lack of potent and selective chemical probes that allow scientists to examine functioning of the receptor. Recently, two cannabinoid chemicals present in the cannabis plant were discovered as affecting GPR3. This study will modify the chemical structure of these compounds to increase their potency and selectivity so that they may be used as pharmacological tools to investigate the role of GPR3 in modulating pain. In addition, this project focuses on identifying new compounds that show promise for development into therapeutics for the treatment of pain.

Endometriosis is an often-painful disorder in which uterine tissue grows outside the uterus. Treatment of endometriosis-associated pain involves use of opioids in many women. This project aims to study a culprit gene thought to be involved with the disorder (capillary morphogenesis gene or CMG2) as a target for new, nonopioid pain medications. The research will also clarify how CMG2 s affects endometriosis-associated pain to test the effects of new medications for endometriosis pain.

Severe tissue injury generates central sensitization. Latent sensitization (LS) is a silent form of central sensitization that persists after tissue has healed and overt signs of hyperalgesia have resolved. Pain remission during LS is likely maintained by tonic opioid receptor activity. The opioid receptor inverse agonist, naloxone, can reinstate experimental pain when delivered one week after the resolution of secondary hyperalgesia following first degree thermal injury. Our aims are to test: 1) the hypothesis that burn or surgery triggers LS and long-term opioid analgesia in humans; 2) the hypothesis that mu-opioid receptor (MOR) constitutive activity (MORCA) receptors by opioid peptides maintains endogenous analgesia and restricts LS to a state of pain remission; 3) the extent to which MORs inhibit neural activity in the DH and synaptic strength in presynaptic terminals of primary afferent nociceptors during LS; and 4) whether MORs inhibit spinal NMDA receptor subunits to block pain during LS.

Opioids affect the body by attaching to certain types of receptors that attach to G-proteins (particularly, a subtype called G-alpha). Opioids vary in their ability to provide pain relief as well as in their ability to require more drug to provide a response, known as tolerance. This project will explore the potential of various G-alpha subunits to increase or decrease opioid receptor signaling. The research findings will lay the groundwork for tailoring G-alpha related opioid effects to provide more pain relief while being less addictive.

Mismanagement of orofacial chronic pain, such as temporomandibular joint and muscle disorders (TMJD) and oral cancer, substantially contributes to opioid overuse; overdose-related deaths; and cardiovascular, renal, and neurological complications at epidemic proportions. The current paradigm implies that orofacial conditions could trigger maladaptation of the immune system and plasticity supporting persistent inflammation, which influences the development and maintenance of orofacial chronic pain. LIGHT (TNFSF14) and Lymphotoxin-beta (LT?), members of the tumor necrosis factor superfamily, provide a balance between protective immunity and immunopathology during chronic inflammatory diseases. This project will test the hypothesis that targeting LIGHT and LT? signaling could prevent the development and inhibit the maintenance of chronic pain produced by TMJD and oral cancer, via peripheral mechanisms involving plasticity of immune, stromal, and tumor cells, as well as sensory neurons. The proposed research is significant as it advances our understanding of mechanisms regulating the development and maintenance of orofacial pain and offers new therapeutic targets and an immunotherapeutic approach for preventing and blocking chronic pain during TMJD and oral cancer.

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.

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.

Interstitial cystitis/bladder pain syndrome is a debilitating disease affecting many women. Opioid-based pain management is a common feature of current treatment approaches but is associated with the risk of addiction. The causes of this disorder remain unknown, and no effective treatments are available. This project will provide new insights using genetic, medication-based and other approaches in a mouse model, along with single-cell gene expression studies conducted with cells from mice and human patients who have this condition. The analyses will help provide targeted, safe, and effective treatment approaches for individuals with interstitial cystitis/bladder pain syndrome.

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.

Using neural tissues from pain patients, this project will investigate mechanisms of neuronal and/or immune dysfunction driving chronic pain. The researchers will use spatial transcriptomics on human dorsal root ganglion (DRG) and spinal cord tissues to examine the cellular expression profile for these targets using the 10X Genomics Visium technology. The use of tissues from control surgical patients and organ donors as well as surgical patients with neuropathic pain will enable validation of expression of these targets in human tissue as well as indication of their potential involvement in neuropathic pain. This collaborative effort will use DRGs removed from pain-phenotyped patients during neurological surgery, as well as lumbar DRGs and spinal cord from organ donors. This study will map the spatial transcriptomes at approximately single cell resolution in the human DRG and spinal cord.