Fletcher A. White, M.S., Ph.D. - US grants

[unreadable] DESCRIPTION (provided by applicant): Inflammatory responses in injured nerves are likely to be key contributing factors in the generation and maintenance of neuropathic pain in inflammatory demyelinating disorders such as Guillain-Barre' Syndrome. Neuropathic pain is a common feature in individuals suffering from the acute phase of Guillain-Barre Syndrome (upwards of 89% of patients) and recovery from the acute phase of Guillain-Barre Syndrome (i.e. remyelination of peripheral axons) does not provide pain relief. In fact, residual neuropathy affecting large- and medium-sized myelinated fibers endures long after the acute attack of Guillain-Barre' syndrome in approximately half of all tested patients. Reported neuropathies include increases in the threshold required for vibration and cold sensation, in addition to neuropathic pain. The positive sensory symptoms of vibration and cold can potentially be explained by delayed remyelination of large and medium diameter fibers. However, the unremitting nature of the neuropathic pain associated with peripheral nerves suggests that factors and/or receptors inherent to the peripheral nerve may be contributing to long-term peripheral sensitization. The aim of this proposal is to examine the cellular and molecular mechanisms underlying the peripheral sensitization by investigating the production of inflammation-associated pro-algesic factors which may directly sensitize sensory nerve fibers and cell bodies. We will determine whether the chronic cutaneous hyperalgesia exhibited by animals subjected to focal nerve demyelination is correlated with the degree of inflammatory response by activated cell types in the peripheral nervous system and the resultant production of the peripherally-derived pro-inflammatory mediators TNFot, IL-1P, and/or MCP-1. In addition, we will identify the cellular sources of cytokine/chemokine production and/or their respective receptors. The cellular sources, inflammatory mediators and their receptors are potential targets for future drug therapies. Verification of the pharmaceutical effects of pro-inflammatory mediators from identified cells may be accomplished by assaying the activation state of the transcription factor, NFvcB, which is central to the regulation of the inflammatory mediators. The combination of this model of an inflammatory demyelinating disease with these techniques offer an unprecedented ability to study the potential influences of cytokine/chemokine(s) on cutaneous hyperalgesia in the rodent. These behavioral, cellular, and biochemical observations will directly advance our fundamental insights into cellular basis of neuropathic pain that accompanies both Guillain-Barre' Syndrome and chronic inflammatory pain processes. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Morphine currently represents the best option for the management of severe pain and chronic pain states. Prolonged use of opiates often produces the need for ever- increasing doses to maintain pain relief, also known as analgesic tolerance. The mechanisms associated with analgesic tolerance are thought to due to morphine- induced cellular adaptations that produce a state of heightened pain or hyperalgesia. Recent studies suggest that opiates acting via the mu-opioid receptor can induce expression of chemokines and their receptors. Previous works from our laboratory demonstrate that some of these same chemokines/receptors have been shown to play central roles in chronic pain states. To uncover evidence of possible links between chronic morophine treatment, chemokine signaling and analgesic tolerance, we propose the hypothesis that opiate-induced chemokine signaling is central to analgesic tolerance. Our specific aims include 1) a characterization of the chronology of cellular/signaling events associated with opiate-induced hyperalgesia 2) explore mechanisms by which morphine induces chemokine/receptor expression in the dorsal root ganglia and 3) examine the cellular/molecular mechanisms by which chronic morphine treatment enhances chemokine signaling. Better understanding of these chemokine/receptor- mediated events may provide the necessary framework for the design of agents that counteract deleterious opiate-induced cellular adaptations and effectively reduce analgesic tolerance. PUBLIC HEALTH RELEVANCE: Morphine is a powerful pain reliever for cancer and non-cancer pain, but also a potent inducer of tolerance. Opiate tolerance refers to a phenomenon in which exposure to a opiate results in the diminution of an analgesic effect (pain relief). Tolerance to the analgesic effect of morphine is a poorly understood phenomenon and can clearly present major management difficulties in some patients. Better understanding of the events associated with the development of tolerance may provide the necessary framework for the design of agents effectively reduce analgesic tolerance.

DESCRIPTION (provided by applicant): Bladder pain syndrome (BPS or interstitial cystitis, IC) patients typically exhibit marked tenderness of pelvic floor musculature and that treatments directed solely at those muscles often resulted in marked improvement of bladder symptoms. This debilitating syndrome of unknown etiology is often postulated, but not proven, to be associated with microbial infection. To better understand the mechanisms that contribute to BPS/IC, we will study an animal model in which pelvic floor muscle injury alone (somatic injury) the degree to which damage- associated molecular patterns (DAMPs) signal through neuronal receptors that recognize pathogen-associated molecular patterns (PAMPs). A potential neurobiological mechanism for the behavioral changes observed with this injury model is the increased nociceptive signaling present in bladder-associated sensory ganglia. To this end, validation of our injury paradigm in the rodent as an experimental representation of BPS/IC provides us with a number of parameters with which to test potential mediators of somatic and visceral hypersensitivity. Furthermore, the outcomes of these proposed experiments may also provide potential therapeutic targets. Taken together, the use of a clinically-relevant animal model will provide us with the unique opportunity to improve PBS/IC diagnostic and treatment paradigms and increase the understanding of the mechanisms underlying the development and maintenance of chronic pelvic pain conditions in women.

Oxaliplatin-associated Chemotherapy-induced Peripheral Neuropathy (CIPN) is a frequent, potentially severe and dose-limiting toxicity of colorectal cancer treatment. The overall incidence of CIPN is estimated to be approximately upwards of 40% in patients. CIPN can persist for months to years beyond chemotherapy completion, causing significant challenges for cancer survivors due to its negative influence on quality of life (QOL). CIPN represents an important challenge because of the lack of treatment that can effectively prevent or mitigate this adverse drug effect. We have identified specific receptor-mediated pathways which contribute to increases in ion current as a potential therapeutic target for the treatment or prevention of CIPN. Noteworthy, several ion channel modulators central to CIPN treatment are FDA-approved drugs used for other disease conditions. This proposal highlights a multidisciplinary research plan that builds upon our preliminary data to explore both the mechanism of CIPN and the degree to which FDA-approved drugs can be repurposed for the treatment or prevention of the condition. In Aim 1, we will examine the influence of platinum-DNA adducts and release of high mobility group box-1 (HMGB1) in rodents following exposure to oxaliplatin. In Aim 2, we will investigate whether the receptor Toll-like receptor (TLR4) is responsible for the development or maintenance of CIPN across time. Finally, in Aim 3, we will conduct a proof of concept assessment of the efficacy of FDA-approved antiepileptic drugs on both neuronal ion currents and CIPN behavioral characteristics. These proposed studies will provide new therapeutic targets which will likely alter the detrimental effects of oxaliplatin on sensory neurons.