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.

TWIK-related spinal cord K+ (TRESK) channel is abundantly expressed in all primary afferent neurons (PANs) in trigeminal ganglion (TG) and dorsal root ganglion (DRG), mediating background K+ currents and controlling the excitability of PANs. TRESK mutations cause migraine headache but not body pain in humans, suggesting that TG neurons are more vulnerable to TRESK dysfunctions. TRESK knock out (KO) mice exhibit more robust behavioral responses than wild-type controls in mouse models of trigeminal pain, especially headache. We will investigate the mechanisms through which TRESK dysfunction differentially affects TG and DRG neurons. Based on our preliminary finding that changes of endogenous TRESK activity correlate with changes of the excitability of TG neurons during estrous cycles in female mice, we will examine whether estrogen increases migraine susceptibility in women through inhibition of TRESK activity in TG neurons. We will test the hypothesis that frequent migraine attacks reduce TG TRESK currents.

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.

It is unclear what changes in the brain mediate the development of chronic pain from acute pain and how chronic pain may change responses to opioid reward for the altered liability of opioid abuse under chronic pain. Preliminary studies have found that Dnmt3a, a DNA methyltransferase that catalyzes DNA methylation for gene repression, is significantly downregulated in the brain in a time-dependent manner during the development of chronic pain and after repeated opioid treatment. This project will investigate whether Dnmt3a acts as a key protein in the brain for the development of chronic pain, and whether Dnmt3a could be a novel epigenetic target for the development of new drugs and therapeutic options for the treatment of chronic pain while decreasing abuse liability of opioids.

Chronic orofacial pain during Temporomandibular Disorders (TMD) and oral cancer is a significant health problem with scarce non-opioid treatment options. This study aims to validate critical regulators of the balance between protective immunity and immunopathology during chronic inflammatory diseases?tumor necrosis factor alpha superfamily members, LIGHT (TNFSF14) and lymphotoxin-beta (LT?) and their receptors, LT?R and Herpes Virus Entry Mediator (HVEM)?as novel therapeutic targets. The study also seeks to determine whether inhibition of LIGHT and LT? signaling prevents the development and inhibits maintenance of chronic TMD and oral cancer pain via peripheral mechanisms involving plasticity of immune, muscle and tumor cells as well as sensory neurons. The study will define the contribution of LIGHT and LT? signaling to TMD-induced excitability of trigeminal sensory neurons innervating the masseter muscle and joint. New validated therapeutic targets for prevention and treatment of orofacial pain that can be peripherally targeted would reduce side effects of current pain medicates related to drug dependence or tolerance.

Multi-protein complexes have emerged as a mechanism for spatiotemporal specificity and efficiency in the function and regulation of myriad cellular signals. In particular, many ion channels are clustered either with the receptors that modulate them, or with other ion channels whose activities are linked. Often the clustering is mediated by scaffolding proteins, such as the AKAP79/150 protein that is a focus of this research. This research will focus on three different channels critical to nervous function. One is the"M-type" (KCNQ, Kv7) K+ channel that plays fundamental roles in the regulation of excitability in nerve and muscle. It is thought to associate with Gq/11- coupled receptors, protein kinases, calcineurin (CaN), calmodulin (CaM) and phosphoinositides via AKAP79/150. Another channel of focus is TRPV1, a nociceptive channel in sensory neurons that is also thought to be regulated by signaling proteins recruited by AKAP79/150. The third are L-type Ca2+ (CaV1.2) channels that are critical to synaptic plasticity, gene regulation and neuronal firing. This research will probe complexes containing AKAP79/150 and these three channels using"super-resolution" STORM imaging of primary sensory neurons and heterologously-expressed tissue-culture cells, in which individual complexes can be visualized at 10-20 nm resolution with visible light, breaking the diffraction barrier of physics. The researchers hypothesize that AKAP79/150 brings several of these channels together to enable functional coupling, which the researchers will examine by patch-clamp electrophysiology of the neurons. Förster resonance energy transfer (FRET) will also be performed under total internal reflection fluorescence (TIRF) or confocal microscopy, further testing for complexes containing KCNQ, TRPV1 and CaV1.2 channels. Since all three of these channels bind to AKAP79/150, the researchers hypothesize that they co-assemble into complexes in neurons, together with certain G protein-coupled receptors. Furthermore, the researchers hypothesize these complexes to not be static, but rather to be dynamically regulated by other cellular signals, which the researchers will examine using rapid activation of kinases or phosphatases. Several types of mouse colonies of genetically altered AKAP150 knock-out or knock-in mice will be utilized.

Multi-protein complexes have emerged as a mechanism for spatiotemporal specificity and efficiency in the function and regulation of cellular signals. Many ion channels are clustered either with the receptors that modulate them or with other ion channels whose activities are linked. Often, the clustering is mediated by scaffolding proteins, such as AKAP79/150. We will probe complexes containing AKAP79/150 and three different channels critical to nervous function: KCNQ/Kv7, TRPV1, and CaV1.2. We will use"super-resolution" STORM imaging of primary sensory neurons and heterologously expressed tissue-culture cells, in which individual complexes can be visualized at 10–20 nm resolution with visible light. We hypothesize that AKAP79/150 brings several of these channels together to enable functional coupling, which we will examine by patch-clamp electrophysiology of the neurons. Since all three of these channels bind to AKAP79/150, we hypothesize that they co-assemble into complexes in neurons and that they are dynamically regulated by other cellular signals.

This project supports a post-baccalaureate trainee develop skills needed to pursue a career in clinical pain research. The research will use molecular tools to study nerve, joint, muscle, and fascia tissues from individuals with chronic low back pain who had spine surgery. The research will include working with patients, designing clinical studies, and sharing results. 

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.

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.

The primary goal of the PRECISION Human Pain network and its participating centers is to generate comprehensive datasets of molecular signatures and cellular function phenotypes or signatures of various cell types that underlie transmission and processing of pain signals in humans. To maximize the impact of the data generated through this effort, it is vital to standardize and integrate all data generated by the various centers and make these data available in a meaningful way to the larger scientific community. As the Data Coordination and Integration Center, this project will support the network to curate, harmonize, and effectively integrate center-generated datasets as well as provide operational support for the network and conduct educational and outreach efforts.

Chronic pain is maintained, in part, by persistent changes in sensory neurons, including a pathological increase in peptides derived from the neurosecretory protein VGF (non-acronymic). Preliminary findings show that the C-terminal VGF peptide, TLQP-62, contributes to spinal cord neuroplasticity and that TLQP-62 immunoneutralization attenuates established mechanical hypersensitivity in a traumatic nerve injury model of neuropathic pain. This project will test the hypothesis that spinal cord TLQP-62 signaling can be targeted for the development of new chronic pain treatments through immunoneutralization and/or receptor inhibition. It will pursue discovery and validation of TLQP-62-based therapeutic interventions along two parallel lines: identification of TLQP-62 receptor(s) and validation of anti-TLQP-62 antibodies as a potential biological therapeutic option for chronic neuropathic pain conditions.

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.