TRPV1通道在诱发肠道炎症反射中的作用及其机制研究

Intestinal inflammation reflex is a kind of vago-vagal reflex. It is important for the maintenance of the immunological homeostasis in the intestine. Although there are lots of data about the efferent pathway about this reflex, the afferent mechanism is unknown. We recently found that SNP, the donor of nitric oxide, selectively excited vagal afferents in the mesenteric nerve fiber bundle originating in the intestine. It was caused by the S-nitrosylation of the transient receptor potential V1 (TRPV1) channel. We hypothesized that during intestinal local inflammation, upregulation of the iNOS, expression in macrophages, results in increased levels of NO, which in turn modifies TRPV1 on vagal afferent ending by S-nitrosylation. This might be the mechanism of the initiation of intestinal inflammation reflex. In this project, we will test this hypothesis using bioelectrical and molecular method. Three kinds of animal models of gastrointestinal inflammation, including acetic acid induced ulcers in stomach, colitis caused by dextransulfatesodium (DSS) and trinitro-benzene-sulfonic acid (TNBS), will be used to test the effect of the intestine inflammation reflex initiated by the S-nitrosylation of TRPV1. This study will provide new data about the afferent pathway of the intestinal inflammation reflex, and provide a clue for a new potential target for the pharmacological treatment of gastrointestinal inflammatory disease.

肠道炎症反射是一种迷走-迷走长反射，在肠道免疫稳态维持中发挥重要作用，该机制的异常容易诱发胃肠道慢性炎症，但其传入末梢的诱发机制尚不清楚，影响了对肠道免疫稳态维持和肠道炎性疾病发生发展的深入了解。我们发现，一氧化氮（NO）选择性兴奋小肠的迷走传入纤维，该作用与V1型瞬时受体电位（TRPV1）通道巯基亚硝酸化有关，因此我们推测，肠道局部炎症上调巨噬细胞内诱导型NO合酶（iNOS）表达，释放NO，引起局部迷走传入末梢上的TRPV1巯基亚硝酸化，从而兴奋迷走传入纤维，诱发肠道炎症反射。我们将利用电生理学、分子生物学、免疫组织化学等方法，从分子、细胞和整体水平研究TRPV1巯基亚硝酸化在肠道炎症反射诱发中的作用，以及对胃肠慢性炎症的影响。该课题将揭示肠道炎症反射的诱发机制，进一步了解胃肠免疫稳态维持机理，阐明炎症反射在胃肠道慢性炎症发生发展过程中的作用，为胃肠炎症的治疗提供新的思路和靶点。

研究背景：一氧化氮（nitric oxide, NO)能够促进胃溃疡的愈合，迷走神经传入纤维能够感受肠道局部的炎性因子，诱发抗炎反应。然后，目前尚无关于NO是否能够兴奋迷走神经传入纤维，从而诱发抗炎反射的报道。.研究方法：NO促进酸诱发小鼠胃溃疡的作用用溃疡面面积、组织学观察和髓过氧化物酶(myeloperoxidase,MPO)活性检验。记录并分析小鼠离体空肠传入神经放电活动。小鼠结状神经节（odose ganglion, NG）和脊髓背根神经节（dorsal root ganglion, DRG)神经元的电活动采用全细胞膜片钳模式记录分析。.主要结果：腹腔注射硝普纳（sodium nitroprusside, SNP)，一种NO供体，能够降低酸导致的溃疡面积，减少胃黏膜局部炎症细胞浸润，降低MPO。迷走神经切断后，该作用消失。SNP剂量依赖性的促进空肠传入神经的放电活动，该作用被事先应用蛋白质巯基亚硝基化保护剂 N-ethylmaleimide和TRPV1阻断剂capsazepine，或者TRPV1基因敲除，或者隔下迷走神经切断所逆转。全细胞膜片钳记录技术发现，SNP引起结状神经节细胞去极化，促进辣椒素（TRPV1激动剂）诱发的内向离子流，这些作用也可以被N-ethylmaleimide阻断；相反，SNP引起DRG神经元的超极化。.结论与意义：NO的供体SNP缓解酸造成的胃溃疡，该作用是通过兴奋迷走神经传入纤维实现的，蛋白质巯基亚硝酸化和TRPV1在其中发挥了重要作用。SNP对迷走和交感神经传入纤维的电活动发挥了相反的作用。我们的结果解释了一种迷走神经兴奋的新机制，同时也是一种新的抗炎症神经反射通路。