Funded Projects

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.

Debilitating pain is the most common complication of sickle cell disease (SCD), but there is significant variability in pain expression in these patients. Currently, there is no plasma biomarker that can prognosticate which patients are likely to experience pain. The overall goal of this proposed research is to develop a biomarker that prognosticates the clinical expression of pain in SCD. Project aims are to (1) derive the inflammatory index for pain by identifying inflammatory and immune regulatory gene probe sets that will distinguish healthy controls, patients with SCD in baseline health, and patients with SCD in acute pain and (2) determine whether co-expressed genes from patients with SCD correlate with clinical pain data. Subsequent aims are to (1) determine the clinically meaningful changes of the index in patients with SCD and (2) investigate the preliminary clinical validity of the index as a prognostic biomarker for pain in patients with SCD.

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.

Masticatory and spontaneous pain associated with temporomandibular joint disorders (TMJD) is a significant contributor to orofacial pain, and current treatments for TMJD pain are unsatisfactory. Pain-related transient receptor potential (TRP) channels, expressed by trigeminal ganglion (TG) sensory neurons, have been implicated in both acute and chronic pain and represent possible targets for anti-pain strategies. Using bite force metrics, we found TMJ inflammation-induced masticatory pain to be significantly, but not fully, reversed in Trpv4 knockout mice, suggesting the residual pain might be mediated by other pain-TRPs. Our gene expression studies demonstrated that TRPV1 and TRPA1 were up-regulated in the TG in response to TMJ inflammation in a Trpv4-dependent manner. We hypothesize that TRPV1 and TRPA1, like TRPV4, contribute to TMJ pain. Our specific aims will examine the contribution of TRPV1, TRPV4, and TRPA1 to pathogenesis of TMJD pathologic pain including assessment of the role of neurogenic inflammation.

An International Cooperative Biodiversity Group with an interdisciplinary leadership team of physicians, pharmacologists, evolutionary biologists, and chemists will discover and develop therapeutic agents produced by Brazilian symbiotic bacteria. The team will target three therapeutic areas: 1) infectious fungal pathogens, 2) Chagas disease and leishmaniasis, and 3) cancers of the blood. All three areas represent major threats to human health that need to be addressed with new therapeutic agents. Internationally, invasive fungal diseases kill more people than malaria or TB, while Chagas disease imposes a special burden on Brazil, killing as many Brazilians as TB. Leishmaniasis has now passed Chagas disease in the Brazilian population. Despite major improvements in cancer chemotherapy, cancer is projected to result in 8 million deaths internationally this year (13% of all deaths, WHO) and an estimated 13 million per year by 2030.

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.

Spinal cord injury (SCI) impairs sensory transmission leading to chronic, debilitating neuropathic pain. While our understanding of the molecular basis underlying the development of chronic pain has improved, the available therapeutics provide limited relief. In the lab, we have shown the timing of exercise is critical to meaningful sensory recovery. Early administration of a sustained locomotor exercise program in spinal cord–injured rats prevents the development of neuropathic pain, while delaying similar locomotor training until pain was established was ineffective at ameliorating it. The time elapsed since the injury occurred also indicates the degree of inflammation in the dorsal horn. We have previously shown that chronic SCI and the development of neuropathic pain correspond with robust increases in microglial activation and the levels of pro-inflammatory cytokines. This proposal seeks to lengthen the therapeutic window where rehabilitative exercise can successfully suppress neuropathic pain by pharmacologically reducing inflammation in dorsal root ganglia.

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.

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.

Effective treatments are elusive for the majority of patients with neuropathic pain. Reactive oxygen and nitrogen species (ROS/RNS) are involved in neuropathic pain, because they drive mitochondrial dysfunction, cytokine production, and neuronal hyperexcitability; therefore, stimulation of endogenous antioxidants is predicted to simultaneously resolve multiple neuropathic pain mechanisms. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that is a potential therapeutic target because it regulates the expression of a large number of endogenous antioxidant-related genes and can be activated with a single drug. This project will test the hypothesis that Nrf2 activation increases multiple endogenous antioxidants, therefore reversing neuropathic pain behaviors and counteracting neuropathic pain mechanisms that are driven by ROS/RNS and could provide an effective pain therapy, with minimal abuse/addictive potential.

Neuropathic corneal pain (NCP) causes patients to have severe discomfort and a compromised quality of life (QoL). The lack of signs observed by standard examination has resulted in misdiagnosis as dry eye disease (DED). An optical biopsy using laser in vivo confocal microscopy (IVCM) revealed that microneuromas (bulbs at the ends of severed nerves caused by buildup of molecular constituents) are present in NCP but not DED and may serve as a biomarker for NCP. The aims are to (1) use a database of more than 2,000 DED/NCP subjects and more than 500,000 IVCM images to confirm that the presence of microneuromas is an appropriate biomarker for NCP, (2) provide biological validation of microneuromas, (3) develop a validated artificial intelligence (AI) program for automated identification of microneuromas, and (4) establish the clinical utility of microneuromas observed by IVCM as a biomarker for NCP in a prospective, multicenter study.

The Philippine Mollusk Symbiont International Cooperative Biodiversity Group harnesses the vast biodiversity of the Philippines to discover new drugs to treat bacterial infections, parasitic infections, pain, and other neurological conditions and cancer, all of which are serious health problems in both the Philippines and the United States. The Republic of the Philippines represents a unique nexus of exceptional biodiversity, dense human population with pressing societal needs, consequent urgent need for conservation, and government commitment to education and technology to harness national human and natural resources for a sustainable future. Mollusks are one of the most diverse groups of marine animals, and their associated bacteria represent an unexplored trove of chemical diversity. Researchers will use an increasing understanding of the interactions between mollusk symbionts and their hosts to discover the most novel and useful molecules. The project will document and describe Philippine mollusk biodiversity and support training and infrastructure that provide the foundation for conservation of Philippine biodiversity.

Debilitating neuropathic pain occurs in 40 percent to 70 percent of people who suffer from spinal cord injury (SCI). There are no distinguishing characteristics to identify who will develop neuropathic pain. The objective of this research is to develop a biomarker signature prognostic of SCI-induced neuropathic pain (NP). The aims of the project are to (1) identify autoantibodies in plasma samples from acute SCI patients to CNS autoantigens and determine the relationship between autoantibodies levels to the development of NP, (2) identify the autoantibody combination with maximal prognostic accuracy for the development of NP at six months after SCI, and (3) develop and optimize an assay to simultaneously measure several autoantibodies and independently validate the prognostic efficacy for NP using plasma samples collected prospectively. Establishing a panel will refine the prognostic value of these autoantibodies as biomarkers to detect who are vulnerable to NP and may be used to for development of nonaddictive pain therapeutics.