Funded Projects

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.

Migraine is the most common neurological disorder. Currently available treatments fail to effectively manage migraine in most patients. Development of new therapeutics has been slow due in large part to a poor understanding of the underlying pathology of migraine. Endogenous proteases, released in the meninges by resident mast cells, have been proposed as a potential driver of migraine pain via an action on protease activated receptor type 2 (PAR2). The central hypothesis is that PAR2 expression in nociceptors that project to the meninges plays a key role in the pathogenesis of migraine pain. The aims are to: 1) use the established PAR2 development pipeline to design new PAR2 antagonists with improved drug-like properties; 2) use pharmacological tools in a novel mouse migraine model to further understand the potential role of PAR2 in migraine; and 3) use mouse genetics to study the cell type–specific role of PAR2 in migraine pain.

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.

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.

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.

The ability to de-risk lead compounds during pre-clinical development with advanced “organoid-on-a-chip” technologies shows promise. Development of microphysiological models of the peripheral nervous system is lagging. The technology described herein allows for 3D growth of high-density axonal fiber tracts, resembling peripheral nerve anatomy. The use of structural and functional analyses should mean drug-induced neural toxicity will manifest in these measurements in ways that mimic clinical neuropathology. The goals of this proposal are to establish our human model using relevant physiological measurements in tissues fabricated from human iPS cells and to validate the model system with a library of compounds, comparing against conventional cell culture models. Validating the peripheral nerve model system with drugs known to induce toxicity via a range of mechanisms will demonstrate the ability of the system to predict various classifications of neuropathy, yielding a high-content assay far more informative than traditional in vitro systems.

Initial studies using positron emission tomography (PET) with [11C] carfentanil, a selective radiotracer for ?-opioid receptor (?OR), have demonstrated that there is a decrease in thalamic µOR availability (non-displaceable binding potential BPND) in the brains of TMD patients during masseteric pain compared to healthy controls. ?-opioid neurotransmission is arguably one of the mechanisms most centrally involved in pain regulation and experience. The main goals of our study are: first, to exploit the ?-opioidergic dysfunction in vivo in TMD patients compared to healthy controls; second, to determine whether 10 daily sessions of non-invasive and precise M1 HD-tDCS have a modulatory effect on clinical and experimental pain measures in TMD patients; and third, to investigate whether repetitive active M1 HD-tDCS induces/reverts ?OR BPND changes in the thalamus and other pain-related regions and whether those changes are correlated with TMD pain measures.

It is increasingly clear that the microbiome influences psychoneurological symptoms, including pain. This project will support clinical research training focused on examining the relationship between the composition and function of the gut microbiome, including the symbiotic bacteria residing in the gut and their functional gene content, and chronic pain among adults with end-stage kidney disease (ESKD). It provides an opportunity for the trainee to expand his skill set as a pain investigator, through experience in implementing and evaluating pain management interventions in adults with ESKD and chronic pain receiving maintenance hemodialysis. The project aims to determine the acceptability of collecting feces and the feasibility of fecal data collection procedure to determine the best strategies for recruiting research participants from multiple dialysis facilities. These steps will allow the exploration of gene content of the gut microbiota and short-chain fatty acids among people with ESKD on maintenance hemodialysis before and after pain management interventions.

Sickle cell disease (SCD) is an inherited hematologic disorder accompanied by severe pain, inflammation, and vascular injury. We propose that nociceptor activation by ongoing hypoxia/reperfusion (H/R) injury leads to the release of neuropeptides by sensory nerves in the skin, stimulating vascular insult and mast cell activation in SCD. In turn, mast cell tryptase activates protease-activated receptor 2 on sensory nerve endings, resulting in exaggerated neuroinflammation, vascular injury, and central sensitization. Our general hypothesis is that neurogenic inflammation contributes to pain in SCD and that cannabinoids provide analgesia by disrupting neurogenic inflammation and nociceptor sensitization. We also hypothesize that EEG and functional MRI can be used to optimize analgesic treatments in SCD. We propose to use transgenic sickle mice, and individual cells involved in evoking pain, to perform this translational study. A proof of principle study in humans will examine the effect of cannabis on pain in sickle patients.

Multiple factors, including inflammation contribute to chronic low back pain. Inflammation is mediated by numerous genes. The study aims to determine how variations in the genes encoding key inflammatory mediators impact the response of patients with chronic low back pain to physical therapy treatment. Gene variations that are known to be linked to inflammation and pain will be tested against their possible association on physical therapy treatment outcomes, to inform clinical decisions on optimal care. This study will support training in clinical research on pain within the context of the HEAL BACPAC Mechanistic Research Center. It will provide resources for a research project relevant to the parent grant and the career development of an individual in the field of pain research. The ability to identify a set of genetic variations and classify patients according to treatment response might enable use of DNA testing as a screening tool for targeted treatments for patients with CLBP.

Identifying optimal chronic low back pain treatments on a patient-specific basis is an important and unresolved challenge. Tailoring interventions according to patient movement characteristics is one option. This research is characterizing patients based on spinal motion during functional tasks and daily activities and will use artificial intelligence to objectively characterize motions of the spine during both clinical assessments and day-to-day life. During clinical assessments, participants will be asked to perform functional tasks while wearing motion sensors. Data collected from the sensors will be used to identify tasks of interest, such as activities of daily living and aberrant/painful motions. An artificial intelligence approach will then interpret data collected continuously during assessment in patients’ homes over a 7-day testing period. Ultimately, this data could be used to help clinicians tailor treatments that are responsive to a patient’s real-world functional impairments.

There are numerous pharmacological and non-pharmacological interventions for chronic low back pain, yet no treatment is universally effective. This award supports an early career physician to develop skills to prepare for a career in clinical pain research in an environment aiming to understand patient characteristics that predict differential responses to pain interventions and thus allow for tailored treatments. This research assesses the impact of mindfulness-based stress reduction on pain interference reported by people with chronic low back pain and explores neurobiological effects of mindfulness-based stress reduction through advanced imaging and clinical assessments.