PMP22介导“肠上皮-神经单元”稳定性改变参与IBS发病的机制研究

Irritable bowel syndrome (IBS) has been found to involve the ultrastructural disruption and dysfunction of intestinal epithelium-nerve unit. However, the exact mechanism is unclear. Peripheral myelin protein 22 (PMP22), which is expressed on the intestinal epithelial tight junction and enteric glia, has been found to maintain the integrity of myelin of central nerve fibers. Thus we speculate that PMP22 may also play an important role in maintaining the normal function of the intestinal epithelium-nerve unit. We preliminarily found that inflammatory stimuli could induce the down-regulation of intestinal PMP22, and the silence of PMP22 gene by RNA interfere could lead to a significant degradation of intestinal tight junction proteins, indicating that changes of PMP22 may mediate the dysfunction of intestinal barrier and enteric nerves in IBS. This study aims to clarify the specific mechanism of altered PMP22 in modulating intestinal epithelium-nerve unit in IBS and find how this event induce the symptoms of IBS, which is meaningful to find a new target for IBS treatment.

新近研究发现肠易激综合征（IBS）患者存在肠屏障功能、肠神经和胶质细胞，即“肠上皮-神经单元”的超微结构和功能异常，但机制仍未阐明。周围髓鞘蛋白22（PMP22）同时表达于肠上皮紧密连接和肠胶质细胞，已有研究证实PMP22对中枢神经纤维髓鞘完整性起重要支持作用，推测其在肠上皮神经单元的正常功能的维持中同样发挥重要作用。我们前期研究发现炎症刺激可诱导肠道PMP22表达下降，PMP22基因沉默则出现肠上皮紧密连接蛋白的降解，提示PMP22表达改变很可能参与介导了IBS上皮屏障和肠神经功能异常。本课题将通过临床标本检测、细胞实验以及动物实验，使用分子生物学技术，分子克隆技术和转基因技术阐明PMP22表达异常参与介导IBS肠上皮-神经功能的改变，诱发IBS症状的发生，对阐明IBS病理生理机制，寻找IBS治疗新靶点具有重要意义。

本项目研究了周围髓鞘蛋白 22 （peripheral myelin protein 22, PMP22）在正常或炎症状态下对人结肠上皮屏障功能的调节作用。我们发现：1. PMP22是一种紧密连接相关蛋白，并参与人肠上皮细胞紧密连接的形成过程，与其他紧密连接蛋白存在相互作用。2. PMP22在维持上皮紧密连接完整性和正常功能中发挥重要作用，体外敲除PMP22抑制肠上皮紧密连接的建立和维持。3. 进一步的机制研究发现：PMP22通过抑制内吞、蛋白酶体系统介导的蛋白降解稳定上皮紧密连接。PMP22敲除后能够显著降低其他紧密连接蛋白如ZO-1，Occludin，Claudin-1, and Claudin-7的表达，这一过程可能是由于PMP22下调不能正常对抗细胞内吞相关的蛋白内化降解过程所致。4. IBS存在低度炎症反应，是肠上皮损伤的重要机制之一，我们在体外和炎症动物模型中发现炎症因子，尤其是TNF 和 IFN-γ可下调肠上皮与神经胶质细胞表达的PMP22。以上结果表明PMP22表达改变介导了炎症相关的肠上皮-神经单元损伤。因此，PMP22在IBS或IBD等疾病肠屏障损伤的发病过程中可能发挥重要作用。