Neurotrophins and Neuropeptides in Colon and Bladder Hypersensitivity

描述（由申请人提供）：炎症性肠病患者经常出现膀胱过度活动，反映感觉过敏；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化，导致神经源性膀胱过度活动。在背根神经节（DRG）和脊髓初级传入事件水平上的神经元相互作用可能在结肠-膀胱超敏反应中起作用。本研究旨在探讨神经营养因子在大鼠结肠内灌注三硝基苯磺酸（TNBS）致结肠炎后结肠-膀胱致敏过程中作为原发性传入神经交叉激活和超敏反应介质的作用。我们的假设是，结肠炎诱导DRG传入神经元之间的神经元相互作用，部分是由结肠传入神经元中神经生长因子(NGF)/TrkA受体和相关信号通路的增加引起的。这导致结肠传入神经中脑源性神经营养因子（BDNF）的表达增加，膀胱传入神经元中BDNF和TrkB的表达增加。BDNF/TrkB和相关信号通路的增加导致膀胱传入神经元中兴奋性神经递质降钙素基因相关肽（CGRP）的随后诱导；BDNF和CGRP反过来导致通道表达改变，从而部分介导膀胱传入神经元的超敏反应。具体目的是：1)结肠传入神经元中导致BDNF在结肠炎后腰骶DRG中表达的NGF/TrkA和信号通路的表征；2)结肠炎后DRG膀胱传入神经元中导致CGRP和离子通道表达的BDNF/TrkB及信号通路的表征；3) BDNF和CGRP对结肠炎后膀胱传入神经元通道活性和膀胱排尿参数调节膀胱超敏反应的作用。实验将采用系统的方法进行，包括通过直接测量信号中间体和使用拮抗剂、抗血清和选择性抑制剂来测量神经营养因子、神经肽及其受体的表达和信号通路。研究炎症中神经元控制膀胱和结肠功能的机制将促进对这种综合征的理解，并为更好的控制或治疗提供方法。

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.