焦虑诱发的BDNF-CRF脑肠互动在IBS发病机制中作用的研究

As one of common causes of Irritable bowel syndrome (IBS), anxiety maybe triggers abdominal pain/discomfort by inducing brain-gut interaction. Our previous researches demonstrated that excessive brain-derived neurotrophic factor (BDNF) of brain induced by anxiety contributed to visceral hypersensitivity in IBS. However, it is still unknown that how central excessive BDNF lead to peripheral visceral hypersensitivity. As one of the key factors of anxiety reactions, corticotropin releasing factor (CRF), freely through the blood-brain barrier, could interact with BDNF in central and peripheral nervous systems. It suggests that BDNF-CRF participate in IBS brain-gut interaction. This study is designed to clarify the role of BDNF-CRF brain-gut interaction induced by anxiety in the pathogenesis of IBS from the following three aspects: (i) To clarify the abnormal brain-gut interaction in IBS patients using functional magnetic resonance imaging; (ii) To examine BDNF-CRF signaling pathway changes and analyze the relationship of them with anxiety and visceral hypersensitivity in animal models with anxiety and visceral hypersensitivity; (ii) To culture brain and intestinal neurons in vitro respectively, combined with the patch-clamp technique to further validate the mechanism of BDNF-CRF brain-gut interaction. From brain - blood - Intestinal three levels, this study reveal the pathogenesis of IBS induced by anxiety through BDNF-CRF brain-gut interaction. It will provide new insight into finding effective therapeutic targets for IBS patients.

焦虑是肠易激综合征（IBS）的常见病因之一，可诱发脑肠互动异常引起腹痛等症状。我们的前期工作证实，焦虑可诱发脑区脑源性神经营养因子（BDNF）增加，并参与IBS内脏高敏感的发生。然而，中枢BDNF增加如何导致外周肠道高敏感，此研究尚属空白。促肾上腺皮质激素释放因子（CRF）为焦虑反应中的关键因子之一，可自由通过血脑屏障，在中枢与外周可与BDNF交互作用，提示BDNF-CRF参与IBS脑肠互动。本项目旨在阐明焦虑诱发的BDNF-CRF脑肠互动在IBS发病机制中的作用：利用功能性磁共振成像明确IBS患者存在脑肠互动异常；检测焦虑伴内脏高敏动物BDNF-CRF互动信号通路变化；体外分别培养脑、肠神经元，结合膜片钳技术，进一步验证BDNF-CRF脑肠互动的作用机制。本研究从脑-血液-肠道三个层次探讨焦虑诱发的BDNF-CRF脑肠互动在IBS发病中的作用及其分子机制，为寻找IBS的治疗靶点提新思路。

本研究探讨了焦虑诱发的脑源性神经营养因子（BDNF）-促肾上腺皮质激素释放因子（CRF）在肠易激综合征（IBS）内脏高敏感中的作用机制。①利用母婴分离模型模拟IBS患者焦虑和内脏高敏感并存的特点，发现母婴分离大鼠焦虑水平增加，且内脏敏感性增高。分析母婴分离的大鼠焦虑水平和内脏敏感性的相关性发现，焦虑水平与内脏敏感性呈正相关，表明焦虑可以加重内脏高敏感的发生。进一步研究表明，母婴分离大鼠海马区的BDNF蛋白和mRNA的表达水平增高，并且主要是海马CA1、CA3区的BDNF蛋白水平增高，且母婴分离的大鼠焦虑水平与海马区BDNF的蛋白水平、海马区BDNF蛋白水平与内脏高敏感的程度分别呈正相关，表明海马区BDNF参与调节焦虑促进内脏高敏感的作用。②CRF可以下调LS174T细胞中的MUC2，FUT2和TFF3的表达量，导致肠粘膜屏障的组成成分发生改变，对维持肠粘膜屏障功能不利。CRF上调LS174T细胞中的claudin-2的表达，下调occludin和ZO-1的表达，导致细胞间紧密连接蛋白的成分发生改变，对维持肠道上皮屏障的完整性不利。以上表明CRF对肠道杯状细胞分泌产物的分泌以及肠道上皮间紧密连接蛋白的表达的影响是导致肠道屏障功能破坏的原因。③利用细菌代谢产物丁酸刺激肠胶质细胞并进行转录组测序发现，神经营养因子家族成员转录水平上调，特别是BDNF上调了2倍，并且神经营养因子通路显著激活。我们的研究证实：一方面IBS患者焦虑诱发脑部BDNF变化，引起CRF表达改变，CRF通过对肠道杯状细胞分泌产物的分泌以及上皮间紧密连接蛋白的表达的影响，导致肠道屏障功能破坏，从而引发IBS内脏高敏感；另一方面IBS患者肠道菌群代谢产物丁酸可导致肠道胶质细胞BDNF基因数上调，引起IBS内脏高敏感的发生。研究成果具有很强的创新性，为寻找IBS治疗的靶点提供了新的方案。