Funded Projects

This project will use a variety of state-of-the-art technologies to generate a comprehensive  gene expression map of human peripheral nerves. The research will enhance understanding about genes involved in various painful conditions associated with nerve damage (neuropathies) resulting from injury or disease. This research will analyze DNA sequences of individual neuronal and non-neuronal cells in human nerve cells (from individuals with and without pain located outside the spinal cord that are involved in pain signal transmission. The findings, together with other imaging and computational approaches, will be used to generate a spatial atlas of the human dorsal root ganglia – a key hub for pain communication between the brain and spinal cord.

Effective treatments are elusive for the majority of patients with neuropathic pain. Reactive oxygen and nitrogen species (ROS/RNS) are involved in neuropathic pain, because they drive mitochondrial dysfunction, cytokine production, and neuronal hyperexcitability; therefore, stimulation of endogenous antioxidants is predicted to simultaneously resolve multiple neuropathic pain mechanisms. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that is a potential therapeutic target because it regulates the expression of a large number of endogenous antioxidant-related genes and can be activated with a single drug. This project will test the hypothesis that Nrf2 activation increases multiple endogenous antioxidants, therefore reversing neuropathic pain behaviors and counteracting neuropathic pain mechanisms that are driven by ROS/RNS and could provide an effective pain therapy, with minimal abuse/addictive potential.

Immune checkpoint proteins regulate the immune system to prevent it from indiscriminately attacking cells. Some cancers activate these immune checkpoints to avoid attack, and drugs that target certain immune checkpoints are approved for cancer treatment. The same pathway may also be involved in pain because immune checkpoint proteins, such as programmed death 1 (PD-1) and the molecule that binds to it (programmed death ligand 1 [PD-L1]), also are found in sensory neurons, microglia, and macrophages. This project will investigate PD-1/PD-L1 in different cell populations to determine their contribution to pain and to the effects of opioids such as morphine. This knowledge may help identify new drugs for pain management that modify immune checkpoint activity.

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.

Neuropilin 1 receptor (NRP1) is a protein receptor that is active in neurons and is hypothesized to be a key mediator of sensory neuron sensitization that can lead to pain. This project will study the cellular mechanisms by which NRP1 leads to sensitization and which cell types—sensory neurons, microglia, or both—are responsible for NRP1’s role in pain. The findings can help validate NRP1 in sensory neurons and the spinal cord as a target to treat pain following nerve injury.

A substantial proportion of Americans seeking emergency care after traumatic stress exposure (TSE) are at a high risk of chronic pain and opioid use/misuse. Physiologic systems involved in the stress response could possibly play a critical role in the development of chronic pain after TSE. FK506-binding protein 51 (FKBP51) is an intracellular protein known to affect glucocorticoid negative feedback inhibition and component of stress response, provides an important non-opioid therapeutic target for such chronic pain. This project will test the hypothesis that functional inhibition of FKBP51 prevents or reduces enduring stress-induced hyperalgesia in a timing, dose, and duration-dependent manner in animal models of single prolonged stress alone and in combination with surgery. This project will also test if FKBP51 inhibition enhances recovery following TSE via reduction in pro-inflammatory responses in peripheral and central tissues. It will also test whether FKBP51 inhibition effects cardiotoxicity or addiction. Completion of these studies will increase understanding of FKBP51 as a novel therapeutic target for the prevention of chronic pain and opioid use/misuse resulting from TSE.

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.

Pain associated with surgery is experienced by millions of patients every year. Although post-surgical pain usually resolves as the surgical site heals, up to half of the patients develop chronic pain after surgery. Opioids remain the mainstay treatment for post-surgical pain which are fraught with serious side-effects and abuse liabilities. The endogenous mechanism that leads to the resolution of post-surgical pain remain unclear, specifically the effects of surgery on the metabolism of sensory neurons and how those changes influence the resolution of post-surgical pain are not known. Preliminary findings suggest that surgical trauma suppresses pyruvate oxidation while increased glutamine catabolism was associated with the resolution of post-surgical pain. This project will test the hypothesis that tissue incision and surgery disrupt the expression of the glutamine transporter ASCT2, which then prevents the resolution of post-incisional pain and aims to validate ASCT2 as a therapeutic target. This project will also employ pharmacological, genetic and animal pain model studies test a novel RNA expression-based strategy to enhance ASCT2 expression in DRG sensory neurons and alleviate postoperative pain in animal model systems. Successful completion of this project would validate ASCT2 as a novel endogenous non-opioid and non-addictive mechanism-based target for the resolution of postoperative pain.

Neuropathic pain is a debilitating affliction present in 26% of diabetic patients, with substantial impact on the quality of life. Despite this significant impact and prevalence, current therapies for painful diabetic neuropathy (PDN) are only partially effective, and the molecular mechanisms underlying neuropathic pain in diabetes are not well understood. Our long-term goal is to elucidate the molecular mechanisms responsible for PDN in order to provide targets for the development of therapeutic agents. Our objective is to identify the molecular cascade linking CXCR4/SDF-1 chemokine signaling to DRG nociceptor hyper-excitability, neuropathic pain, and small fiber degeneration. Our aims will determine: 1) the ion-channel current profile of the nociceptor hyper-excitable state produced by CXCR4/SDF-1 signaling in PDN; 2) the gene expression profile of the nociceptor hyper-excitable state produced by CXCR4/SDF-1 signaling in PDN; and 3) the specific features of nociceptor mitochondrial dysfunction produced by CXCR4/SDF-1 signaling in PDN.

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.

Chronic pancreatitis (CP) and the debilitating pain associated with it remains a common and challenging clinical syndrome that is difficult to treat effectively. Using rodent models of CP, preliminary studies have found that nerve growth factor (NGF) and transforming growth factor beta (TGFb) appear to be acting by the common effector, calcitonin-gene related peptide (CGRP), to induce pain in CP. CGRP is known to mediate pain as a neurotransmitter in the central nervous system, specifically as a potent vasodilator involved in migraine. This project will test the hypothesis that peripheral CGRP is a major mediator of peripheral nociceptive sensitization in CP, and that peripherally restricted anti-CGRP treatment could provide an efficient and sufficient approach for the treatment of pain in pancreatitis

This project will identify molecular characteristics of human sensory neurons and non-neuronal cells from the human dorsal root ganglia. This structure located outside the spinal cord is integrally involved in communicating pain signals to and from the brain. The research will use molecular approaches to characterize tissues obtained from organ donors and in patients who experience chronic pain. The findings will also help generate a connectivity map, or “connectome,” of nerve cell connections between the dorsal root ganglia of the spinal cord and the brain.