Funded Projects

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.

Osteoarthritis (OA) is the most common form of arthritis and a leading cause of pain and disability. Current challenges of managing OA are that there is no OA disease-modifying drug available, there are few effective treatment strategies, and there is an over-reliance on the use of opioids to manage OA-related joint pain. This project aims to validate vascular endothelial growth factor receptors 1 and 2 (VEGFR 1 receptor = Flt1) and (VEGFR 2 receptor = Flk1) as novel therapeutic targets for OA. This is based on a hypothesis that blocking these two specific receptors of VEGF will inhibit cartilage tissue degeneration and alleviate pain symptoms. This study will test the role of VEGFR-1 and -2 in multiple OA animal models using multiple available VEGF inhibitor molecules. The findings from these studies will develop a rationale for future clinical trials to target VEGFR-1 and -2 for OA patients and develop a novel non-addictive treatment for both joint pain and OA pathology.

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.

Activation of immune cells (microglia) in the central nervous system and neuroinflammation have emerged as key drivers of neuropathic pain. These processes can be triggered by release of ATP, the compound that provides energy to many biochemical reactions. The source and mechanism of ATP release are poorly understood but could be targets of novel treatment approaches for neuropathic pain. This project will use genetic, pharmacological, and electrophysiological approaches to determine whether a large pore channel called Swell 1 that spans the cell membrane is the source of ATP release and resulting neuropathic pain and thus could be a treatment target.

Myofascial pain syndrome is a prevalent and debilitating condition and can aggravate other conditions such as sickle cell disease. This project will use total body imaging using positron emission tomography/computed tomography (TB-PET/CT) to identify and monitor this pain syndrome and potential treatments over time. The research will use TB-PET/CT to assess myofascial tissue effects of chronic low back pain and sickle cell disease pain. The first phase of the project will assess health changes observed by TB-PET/CT imaging in painful and non-painful myofascial tissues compared to healthy myofascial tissue. The second phase of the research will be a randomized, controlled longitudinal interventional study to evaluate the effectiveness of acupuncture on myofascial pain syndrome, using TB-PET/CT imaging to assess changes.

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.

This project will establish a rapid research pipeline for linking plant-derived compounds to nociception (pain) and to G Protein-Coupled Receptors (GPCRs) and ion channels in the druggable human genome. As more than 80% of these membrane proteins are conserved in the C. elegans nematodes, the study will screen for compounds and genes affecting nociception as well as to identify novel ligand-receptor pairs using this model organism. The study will test which understudied GPCRs and ion channels are involved in nociception as well as attraction or repulsion behaviors. This research has the potential to reveal novel ligand-receptor pairs that could serve as new entry points for improved or alternative pain treatments.

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.

Oral cancers are painful and often require use of opioid medications to manage pain. However, the effectiveness of opioids often wanes quickly, and many patients require higher doses because they develop tolerance to these medications. This project will study the potential value of blocking epidermal growth-factor receptors interacting with peripheral nerves to treat oral cancer pain. The findings will advance understanding of the molecular mechanisms underlying oral cancer pain and provide a rationale for repurposing epidermal growth-factor receptor blockers, which is already approved for head and neck cancer treatment for treating oral cancer and associated pain.

Many non-opioid drugs target G Protein-Coupled Receptors (GPCRs), a family of proteins involved in many pathophysiological processes including pain, fail during clinical trials for unknown reasons. A recent study found GPCRs not only function at the surface of nerve cells but also within a cell compartment called the endosome, where their sustained activity drives pain. This study will build upon this finding and test whether the clinical failure of drugs targeting plasma membrane GPCRs is related to their inability to target and engage endomsomal GPCRs (eGPCRs). This study will use stimulus-responsive nanoparticles (NP) to encapsulate non-opioid drugs and selectively target eGPCR dyads to investigate how eGCPRs generate and regulate sustained pain signals in neuronal subcellular compartments. This study will also validate eGCPRs as therapeutic targets for treatment of chronic inflammatory, neuropathic and cancer pain. Using NPs to deliver non-opioid drugs, individually or in combinations, directly into specific compartments in nerve cells could be a potential strategy for new pain therapies.

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.

An important component of neuropathic pain is spontaneous or ongoing pain, such as burning pain or intermittent paroxysms of sharp and shooting pain, which may result from abnormal spontaneous activity in sensory nerves. However, due to technical limitations, spontaneous activity in sensory neurons in vivo has not been well studied. Using in vivo imaging in genetically-modified mice, preliminary findings identified spontaneously-firing clusters of neurons formed within the dorsal root ganglia (DRG) after traumatic nerve injury that exhibits increased spontaneous pain behaviors. Furthermore, preliminary evidence has been collected that cluster firing may be related to abnormal sympathetic sprouting in the sensory ganglia. This project will test the hypothesis that cluster firing is triggered by abnormal sympathetic inputs to sensory neurons, and that it underpins spontaneous paroxysmal pain in neuropathic pain models. Findings from this project will identify potential novel therapeutic targets for the treatment of neuropathic pain.