Funded Projects

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.

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.

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.

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.

Chronic post-traumatic headache (PTH) is highly debilitating, poorly understood, and difficult to treat. This project aims to identify proteins located in the membrane of certain neurons that are critical for the development, maintenance, and/or resolution of PTH. These proteins may be targets for novel treatment approaches that are nonaddictive and have minimal side effects.

Neuropathic pain conditions are difficult to treat, and novel non-narcotic analgesics are desperately needed. The G protein-coupled receptor 160 (GPR160) has emerged as a novel target for analgesic development, as GPR160 in the spinal cord may play a role in the transition from acute to chronic pain. Cocaine- and Amphetamine-Regulated transcript peptide (CARTp) was identified as a ligand for GPR160. Blocking endogenous CARTp signaling in the spinal cord attenuates neuropathic pain, whereas intrathecal injection of CARTp evokes painful hypersensitivity in rodents through GPR160-dependent extracellular signal-regulated kinase (ERK) and cyclic AMP response element-binding pathways (CREB). This project will isolate and biochemically characterize GPR160 and establish methods for biochemical characterization of GPR160 interaction with CARTp activator. Researchers will miniaturize and optimize biochemical assay and scale up protein production for future high throughput biochemical screening to identify potent inhibitors of GPR160 activation. These studies are critical for defining the molecular mechanism of CARTp/GPR160 interactions and initiating large-scale screens for new inhibitors to develop novel therapeutics.

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.

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.

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.

Neuropathic pain conditions are exceedingly difficult to treat, and novel non-opioid analgesics are desperately needed. Receptomic and unbiased transcriptomic approaches recently identified the orphan G-protein coupled receptor (oGPCR), GPR160, as a major oGPCR whose transcript is significantly increased in the dorsal horn of the spinal cord (DH-SC) ipsilateral to nerve injury, in a model of traumatic nerve-injury induced neuropathic pain caused by constriction of the sciatic nerve in rats (CCI). De-orphanization of GPR160 led to the identification of cocaine- and amphetamine-regulated transcript peptide (CARTp) as a ligand which activates pathways crucial to persistent pain sensitization. This project will test the hypothesis that CARTp/GPR160 signaling in the spinal cord is essential for the development and maintenance of neuropathic pain states. It will also validate GPR160 as a non-opioid receptor target for therapeutic intervention in neuropathic pain, and characterize GPR160 coupling and downstream molecular signaling pathways underlying chronic neuropathic pain.

Epidural/spinal administration of analgesics such as opioids, ziconotide and local anesthetics have profound efficacy in some of the most intractable pain conditions such as severe neuropathic pain after failed back surgery, cancer pain and post-operative pain after major abdominal/thoracic surgeries. Contulakin G (CGX) is a snail venom derived peptide that has homology with mammalian neurotensin and was shown to be safe in humans in preliminary studies. A small pilot study demonstrated CGX?s analgesic effect in some patients with spinal cord injury-associated pain. Preliminary findings from mechanistic studies in rodents identified neurotensin receptor 2 (NTSR2) as the mediator for analgesic effects of CGX. This project aims to validate spinal NTSR2 as an analgesic target utilizing three species (rat, mice and human), and two pain models (neuropathic pain and post-surgical pain). The project will utilize pharmacological and gene editing tools such as CRISPR-Cas9 and will include assessment of both sensory and affective measures of pain. A two-site parallel confirmation study is designed based on multisite clinical trials to further authenticate spinal NTSR2 as an analgesic target. Successful completion of this project could lead to the development of a non-opioid spinal analgesic that has high translational potential.