The role of cell-specific TLR4 in Diabetic Peripheral Neuropathy

摘要 每年发生超过20万例的痛性糖尿病周围神经病变是主要的 令人衰弱的疾病在美国。人们热衷于寻找支撑其发展的机制 之后，因为目前的治疗方法对超过一半的患者都没有缓解作用。西方高脂肪饮食与肥胖 在导致疼痛的糖尿病周围神经病变的神经元过度兴奋中起关键作用。在某些情况下 例如，证据将饮食、糖尿病和肥胖症分开，并了解这些不同的机制 ACTION将在确定可以调节神经元活动的治疗靶点方面发挥分裂作用。外围 感觉神经元表达Toll样受体4(TLR4)，这是一种受体，其激动剂是饮食中的游离脂肪酸， 膳食糖代谢产物(甲基乙二醛)和危险相关分子模式(DAMP)的表达 糖尿病期间(HMGB1)。这表明神经元可以被不同来源的TLR4激动剂直接激活 在糖尿病周围神经病变期间，来源在导致疼痛状态的可塑性中发挥作用。此外， 巨噬细胞紧邻周围感觉神经元，表达TLR4，并释放额外的 使神经元敏感的致痛因子。这项研究将集中在周围神经系统，利用 阐明介导TLR4依赖的DRG激活所需的最小回路的遗传学工具 在饮食诱导/糖尿病神经病理性疼痛形成中的伤害性神经元。 这一建议的一个关键特点是我们将研究TLR4在特定细胞中的生理相关性 体内群体以确定伤害性感受器或巨噬细胞TLR4是否足以发育为 糖尿病神经病理性疼痛。我们将利用cre-lox转基因系统提供细胞特异性 使用新开发的可零再激活的小鼠重新激活TLR4。我们将这些动物与 Nav1.8-cre(感觉神经元)和LysM-cre(巨噬细胞)动物来评估这些特定的种群 因糖尿病、饮食或肥胖而出现神经性疼痛。我们的研究旨在了解 驱动慢性疼痛的机制和将这些分子洞察力推向新的治疗策略 减轻疼痛。为了实现这些目标，我们提出了以下具体目标：1)确定 神经元特异性与巨噬细胞特异性TLR4在神经病理性疼痛发生中的作用 作为细胞特异性TLR4激动剂的饮食成分可诱导敏感化和疼痛状态。 这些研究有望为糖尿病的治疗和预防指明新的治疗途径。 疼痛通过靶向伤害性感受器和巨噬细胞TLR4信号，并确定难以捉摸的机制通过，饮食， 肥胖或糖尿病。

Abstract With an annual occurrence of over 200,000 cases per year, painful diabetic peripheral neuropathy is a leading debilitating disorder in the United States. The mechanisms that underlay its development are highly sought after, because current therapeutics fail to offer relief in over half of patients. A high-fat western diet and obesity play crucial roles in neuronal hyperexcitability that lead to painful diabetic peripheral neuropathy. In certain instances, evidence dissociates diet, diabetes, and obesity, and understanding these disparate mechanisms of action will play a divisive role in identifying therapeutic targets that can modulate neuronal activity. Peripheral sensory neurons express toll-like receptor 4 (TLR4), a receptor whose agonist are dietary free fatty acids, dietary sugar metabolites (methylglyoxal), and danger-associated molecular pattern (DAMPs) expressed during diabetes (HMGB1). This suggests that neurons can be directly activated by TLR4 agonists from various sources to play a role in plasticity leading to painful states during diabetic peripheral neuropathy. Moreover, macrophages are closely situated next to peripheral sensory neurons, express TLR4, and release additional pro-nociceptive factors that sensitize neurons. This study will focus on the peripheral nervous system, utilizing genetic tools to clarify the minimum circuitry necessary to mediate TLR4-dependent activation of DRG nociceptive neurons in developing diet-induced/diabetic neuropathic pain. A key feature of this proposal is that we will study the physiological relevance of TLR4 in specific cell populations in vivo to determine whether nociceptor or macrophage TLR4 is sufficient for the development of diabetic neuropathic pain. We will take advantage of the cre-lox transgenic system offering cell-specific reactivation of TLR4 using newly developed null-reactivatable mice. We have crossed these animals with Nav1.8-cre (sensory neuron) and LysM-cre (macrophage) animals to assess these particular populations in developing neuropathic pain in response to diabetes, diet, or obesity. Our research is aimed at understanding mechanisms driving chronic pain and moving these molecular insights toward new therapeutic strategies for pain alleviation. To accomplish these goals we propose the following specific aims: 1) Determine the role of neuron-specific vs. macrophage-specific TLR4 to develop neuropathic pain and 2) Determine the contribution of dietary components as cell-specific TLR4 agonists to induce sensitization and pain states. These studies will hopefully point to novel therapeutic avenues for the treatment and prevention of diabetic pain by targeting nociceptor and macrophage TLR4 signaling and identify elusive mechanisms through, diet, obesity or diabetes.