结肠粘膜慢性炎症过程中DRG内BKCa/TRPA1互作稳态失调参与IBS内脏高敏感形成的机制研究

The persistent low-grade mucosal inflammation in the gastrointestinal tract after acute inflammation is crucial in the pathogenesis of post-infectious or inflammatory irritable bowel syndrome (PI-IBS). Visceral hypersensitivity is the core mechanism for IBS symptoms, in which facilitation of spinal afferent nociception to noxious stimuli in the gut may be the most important pathway. However, the underlying mechanisms are not fully elucidated. Recent studies suggested that the large conductance calcium-activated potassium channel (BKCa) and transient receptor potential ankyrin-1 (TRPA1) might be functionally correlated on the cell membrane of dorsal root ganglion (DRG) neurons. Our preliminary studies in rats with visceral hypersensitivity induced by chronic colonic mucosal inflammation showed that TRPA1 expression in DRG was increased while BKCa expression decreased, suggesting a possible interaction between TRPA1 and BKCa in spinal pathway, and that this interaction might play a role in the development of visceral hypersensitivity. This project intends to explore: ① How BKCa interacts with TRPA1 under physiological condition; ② How the homeostasis of this interaction is changed during chronic colonic mucosal inflammation and whether this change play a role in the pathogenesis of visceral hypersensitivity. This study will shed new light on the mechanisms for visceral hypersensitivity related to PI-IBS and may offer novel targets for IBS treatment.

持续存在的消化道粘膜低度炎症是IBS（特别是PI-IBS）发病的主要病生基础，而内脏高敏感是IBS症状产生的核心机制。脊髓传入神经通路神经元兴奋性增高所致感觉易化是内脏伤害性感受异常的最关键动因，但其机制未明。新近研究提示，脊髓传入神经DRG神经元细胞膜BKCa K+通道与瞬时受体电位TRPA1之间可能存在功能上的相互影响；本课题组预实验发现，结肠粘膜慢性炎症诱发内脏高敏感动物模型DRG内BKCa表达下调，而TRPA1表达上调。提示DRG内BKCa与TRPA1之间可能存在表达及功能的互作（interactions），该互作可能参与脊髓传入神经炎性内脏痛调控机制。本项目拟阐明①生理状态下脊髓传入神经BKCa/TRPA1互作机制；②结肠粘膜慢性炎症状态下，BKCa/TRPA1互作稳态改变及其在内脏高敏感形成中的作用。本研究对探明慢性炎症状态下IBS相关内脏高敏感发病机制具有较重要意义。

内脏高敏感是肠易激综合征（IBS）症状产生的核心机制，脊髓传入神经通路感受伤害性刺激的神经元兴奋性增高导致的感觉易化是内脏伤害性感受异常的最关键机制，但其详细机制尚未完全阐明。大电导Ca2+激活K+通道（BKCa）和瞬时受体电位离子通道（TRPA1）均参与脊髓传入神经通路躯体痛或内脏痛调控机制。本课题组的预实验研究发现，结肠粘膜慢性炎症诱发的内脏高敏感（结直肠扩张诱发的腹肌收缩反应易化）动物模型中，脊髓背根神经元（DRG）中BKCa表达下调，而TRPA1表达上调。但是内脏高敏感状态下DRG中BKCa与TRPA1表达及功能互作稳态发生了怎样的改变，这一改变是否为脊髓传入神经通路介导内脏高敏感反应的关键机制，这些科学问题尚不清楚。本项目通过对正常动物与慢性水应激模型（WAS）致肠粘膜炎症而诱发内脏高敏感反应模型动物的研究，结合神经药理、电生理以及神经分子生物学技术，研究脊髓传入神经BKCa/TRPA1互作的细节，以及WAS致内脏高敏感反应进程中BKCa/TRPA1互作稳态的异常改变。项目取得了如下有重要理论和临床价值的原创性研究成果：①WAS可增强大鼠的腹肌收缩反应（VMR）；②BKCa参与降低WAS引起的内脏高敏感反应，TRPA1参与升高WAS引起的内脏高敏感反应，提示BKCa和TRPA1对内脏感觉发挥相反的作用；③WAS大鼠结肠和DRG处TRPA1受体表达增加，而BKCa表达下降，该变化可能共同参与内脏高敏感的形成；④在TRPA1基因敲除小鼠WAS造模后不再出现BKCa mRNA改变，提示WAS模型鼠BKCa的作用改变可能依赖于TRPA1。综上，本课题组首次对BKCa/TRPA1互作稳态失调参与内脏高敏感形成的机制展开探索性研究，对于阐明IBS病理生理机制、探寻有效治疗的新思路和新靶标具有较重要理论指导价值。