Funded Projects

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.

The development of non-addictive pain therapeutics can help counter opioid addiction and benefit patients, including those who suffer from neuropathic pain, in particular diabetic neuropathic pain (DNP). This project’s goal is to develop a safe, efficacious, and non-addictive small-molecule drug that activates Kv7 voltage-gated potassium channels to address overactive neuronal activity in DNP. Researchers will discover Kv7 activators that favor Kv7 isoforms altered in DNP and found in dorsal root ganglia, decrease off-target side effects observed with the use of earlier non-biased Kv7 activators, and optimize the absorption, distribution, metabolism, excretion, and toxicity profiles of these activators. This screening paradigm is intended to establish a clinic-ready, well-tolerated, and widely effective product to treat neuropathic pain.

Dorsal root ganglion (DRG) neuronal hyperexcitability is central to the pathology of neuropathic pain and is a target for local anesthetics, even though the efficacy of local anesthetic patches has been mixed. The coordinated movement of ion channels, especially voltage-dependent sodium channels, from intracellular pools to the sites of nerve injury has been suggested to be an underlying cause of electrogenesis and ectopic firing in neuropathic pain conditions. Recent studies identified Magi1 as a scaffold protein responsible for sodium channel targeting and membrane stabilization in DRG neurons. This project will determine whether reducing the expression Magi1 could disrupt intracellular trafficking of sodium channels in DRG neurons under neuropathic injury conditions, and could therefore serve as a potential therapeutic target for neuropathic pain.

The research team developed an in vitro multi-component joint on a chip (microJoint), in which engineered osteochondral complexes, synovium, and adipose tissues were integrated. This study will introduce sensory innervation into the microJoint and a neuron-containing microfluidic ally will be developed to innervate the microJoint. The osteoarthritis (OA) model will be created in the Neu-microJoint system. The research team will assess activation and/or sensitization of nociceptive afferents with electrophysiology, as well as neurite outgrowth. They will mechanically insult the Neu-microJoint and assess the emergence of “pain” in response to prolonged mechanical stress. Researchers will assess the impact of drugs used clinically for management of OA on OA models and will then use “omic” approaches to identify new biomarkers and therapeutic targets. Researchers will assess the impact of opioids—which they hypothesize will increase the rate of joint degeneration and potentiate the release of pain-producing mediators—on neural activity in the presence and absence of joint injury, as well as the integrity of all joint elements.

Researchers will develop multi-organ, microphysiological systems (MPSs) based on human induced pluripotent stem cell-derived midbrain-fated dopamine (DA)/gamma-aminobutyric acid neurons on a three-dimensional platform that incorporates microglia, blood–brain barrier (BBB), and liver metabolism. RNA sequencing and metabolomics analyses will complement the primary DA release measure to identify novel mechanisms contributing to chronic opioid-induced plasticity in DA responsiveness. The chronic pain-relevant aspect of the model will be realized by examination of aversive kappa-mediated opioid effects on DA transmission in addition to commonly abused mu opioid receptor agonists, and by incorporation of inflammatory-mediating microglia. Incorporation of BBB and liver metabolism modules into the microphysiologic system platform will permit screening of drugs. Throughput will be increased by integration of online sensors for online detection of DA and other analytes. Researchers will use a curated set of 100 chemical genomics probes.

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.

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 will design and test optimized temporal patterns of stimulation to improve the efficacy of commercially available spinal cord stimulation (SCS) systems to treat chronic neuropathic pain. Researchers will build upon a validated biophysical model of the effects of SCS on sensory signal processing in neurons within the dorsal horn of the spinal cord to better understand how to improve the electrical stimulus patterns applied to the spinal cord. They will use sensitivity analyses to determine the robustness of stimulation patterns to variations in electrode positioning, selectivity of stimulation, and biophysical properties of the dorsal horn neural network. Researchers will demonstrate improvements from these new stimulus patterns by 1) measuring their effects on pain-related behavioral outcomes in a rat model of chronic neuropathic pain and by 2) quantifying the effects of optimized temporal patterns on spinal cord neuron activity. The outcome will be mechanistically derived and validated stimulus patterns that are significantly more efficacious than the phenomenologically derived standard of care patterns; these patterns could be implemented with either a software update or minor hardware modifications to existing SCS products.

The goal of this project is to generate data and reagents that help uncover critical functions of the poorly characterized members of ion channels. It focuses on co-perturbation of ion channel genes and their interacting genetic components as opposed to singly altering ion channel genes in mouse models. This approach will validate our proteomics approaches in the most definitive manner: in vivo. We see in vivo exploration as an essential step to evaluate ion channel function. Our major aims include mapping ion channel interactions and complexes using a high-throughput proteomics platform at UCSF. These data will be interrogated using integrative approaches established by the Monarch Initiative, where biochemical interactions will be validated and prioritized for further study. Another major aim is function-centric: We use mouse models for elucidation of human disease mechanisms, where we embrace a genetic interaction scheme to uncover ion channel redundancy and polygenic effects.

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.

This study aims to address critical gaps and unmet therapeutic needs of chronic low back pain (CLBP) patients using a next-generation deep brain stimulation (DBS) device with directional steering capability to engage networks known to mediate the affective component of CLBP. Researchers will utilize patient-specific probabilistic tractography to target the subgenual cingulate cortex (SCC) to engage the major fiber pathways mediating the affective component of chronic pain. The objective is to conduct an exploratory first-in-human clinical trial of SCC DBS for treatment of medically refractory CLBP. The research team aims to: (1) assess the preliminary efficacy of DBS of SCC in treatment of medically refractory CLBP; (2) demonstrate the safety and feasibility of SCC DBS for CLBP; and (3) develop diffusion tensor imaging–based blueprints of response to SCC DBS for CLBP.

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.