Neurotrophins and Neuropeptides in Colon and Bladder Hypersensitivity

描述(申请人提供)：炎症性肠病患者经常出现反映感觉过敏的膀胱过度活动；然而，这种临床综合征的机制尚不清楚。我们实验室和其他实验室的研究表明，结肠炎的动物模型显示出类似的交叉敏感化，导致神经源性膀胱过度活动。背根神经节(DRG)和脊髓初级传入神经元的相互作用可能在结肠-膀胱超敏反应中起作用。本研究的目的是探讨神经营养因子作为初级传入交叉激活和超敏反应的介质在三硝基苯磺酸(TNBS)诱导的大鼠结肠炎后结肠-膀胱敏化中的作用。我们的假设是，结肠炎诱导了DRG传入神经元之间的神经元相互作用，这种相互作用部分是通过增加结肠传入神经元中神经生长因子(NGF)/TrkA受体和相关的信号通路来启动的。这导致脑源性神经营养因子(BDNF)在结肠传入神经元中的表达增加，在膀胱传入神经元中的表达增加。BDNF/TrkB及其相关信号通路的增加导致兴奋性神经递质降钙素基因相关肽(CGRP)在膀胱传入神经元中的诱导，BDNF和CGRP进而导致通道表达改变，部分介导了膀胱传入神经元的超敏反应。具体目标为：1)鉴定结肠炎后结肠传入神经元中神经生长因子/TrkA和导致脊髓背根节中脑源性神经营养因子表达的信号通路(S)；2)鉴定结肠炎后背根节中脑源性神经营养因子/TrkB和导致降钙素基因相关肽和离子通道表达的信号通路(S)；以及3)鉴定神经营养因子和降钙素基因相关肽在调节结肠炎后膀胱高敏感性中的作用，方法是通过膀胱传入神经元的通道活动以及膀胱排尿参数来衡量。这些实验将用一种系统的方法进行，包括通过直接测量信号中间产物以及使用拮抗剂、抗血清和选择性抑制剂来测量神经营养素、神经肽及其受体和信号通路的表达。对炎症中神经控制膀胱和结肠功能的机制的研究将促进对这一综合征的理解，并为更好的控制或治疗提供建议。

DESCRIPTION (provided by applicant): Patients with inflammatory bowel disease often experience overactive bladder reflecting sensory hypersensitivity; however the mechanism underlying this clinical syndrome is not clear. Studies from our laboratory and others indicate that animal models of colitis demonstrate a similar cross-sensitization that leads to neurogenic bladder overactivity. Neuronal interaction at the level of primary afferents in dorsal root ganglia (DRG) and spinal cord likely plays a role in the colon-to-bladder hypersensitivity. The objective of this proposal is to investigate the role of neurotrophins as mediators of primary afferent cross-activation and hypersensitivity in colon-to-bladder sensitization following colitis induced by intracolonic instillation of tri-nitrobenzene sulfonic acid (TNBS) in rat. Our hypothesis is that colitis induces neuronal interaction between afferent neurons in DRG that is initiated, in part, by increases in nerve growth factor (NGF)/TrkA receptor and associated signaling pathways in colonic afferent neurons. This leads to increased expression of brain-derived neurotrophic factor (BDNF) in colonic afferents and increases in BDNF and TrkB in bladder afferent neurons. The increases in BDNF/TrkB and associated signaling pathways lead to subsequent induction of the excitatory neurotransmitter calcitonin gene-related peptide (CGRP) in bladder afferent neurons; BDNF and CGRP, in turn, lead to altered channel expression which mediates in part the hypersensitivity of bladder afferent neurons. The specific aims are: 1) characterization of NGF/TrkA and signaling pathway(s) in colonic afferent neurons that lead to the expression of BDNF in lumbosacral DRG following colitis; 2) characterization of BDNF/TrkB and signaling pathways that lead to the expression of CGRP and ion channel(s) in bladder afferent neurons in DRG following colitis; and 3) characterization of the effects of BDNF and CGRP on the regulation of bladder hypersensitivity as measured by channel activity of bladder afferent neurons as well as bladder micturition parameters following colitis. The experiments will be done with a systematic approach involving measurements of neurotrophins, neuropeptides, and expression of their receptors and signaling pathways by direct measurements of signaling intermediates and use of antagonists, antisera, and selective inhibitors. The investigation of the mechanism underlying neuronal control of bladder and colon function in inflammation will advance understanding of this syndrome as well as suggest approaches for better control or treatment.