热休克转录因子2调控线粒体自噬在溃疡性结肠炎中的作用机制研究

The etiology of Ulcerative colitis (UC) is not clear. According to the report,NLRP3 inflammasome plays an important role in the occurrence of UC. Mitophagy might reduce reactive oxygen species(ROS) produced by the mitochondria pathway,thus inhibiting the activation of NLRP3 inflammasome and the inflammatory reaction. Our preliminary studies have shown that the heat shock transcription factor 2 (HSF2) was highly expressed in UC and positively correlated to the disease activity of UC, HSF2 might inhibit the activation of NLRP3 and HSF2 could promote autophagy in vitro,but the mechanism is not clear.So we make a plan to find out this correlation by three steps. Firstly, to observe the differences and correlations between HSF2 and mitophagy-ROS-NLRP3 inflammasome in intestinal mucosa of UC patients who are in different disease activity in clinic; then to study the influences of HSF2 on mitophagy and ROS , the effects of it on the activation of NLRP3 inflammasome in vitro. Finally, to investigate the influences and correlations of mitophagy, ROS and inflammation in DSS-colitis mucosa of HSF2 overexpression or knockout mice. The project aimed to clarify the mechanism that HSF2 inhibits the mucosal inflammation of UC, provide a theoretical basis for new therapeutic targets of UC.

溃疡性结肠炎（UC）发病机制不清，据报道，NLRP3炎症小体在UC发生、发展中起重要作用；线粒体自噬可减少线粒体产生的活性氧（ROS）从而抑制NLRP3炎症小体的激活及炎症反应。我们前期研究显示热休克转录因子2（HSF2）在UC中高表达并与疾病严重度呈正相关；体外实验显示HSF2抑制NLRP3炎症小体激活，促进肠上皮细胞自噬，但具体机制不清。故提出假设：HSF2促进线粒体自噬而降低ROS，进而抑制NLRP3炎症小体激活及UC粘膜炎症。项目拟通过三方面观察：①临床：轻、中、重度UC肠粘膜HSF2与线粒体自噬-ROS-NLRP3炎症小体表达的相关性；②细胞：HSF2对线粒体自噬和ROS的影响及在NLRP3炎症小体激活中的作用；③动物：HSF2基因过表达和敲除对DSS小鼠肠粘膜线粒体自噬、ROS和炎症的影响及相关性。旨在阐明HSF2抑制UC肠粘膜炎症的作用机制，为寻找UC新治疗靶点提供理论依据。

炎症性肠病(Inflammatory bowel disease,IBD)是一种慢性非特异性肠道炎症性疾病，它包括溃疡性结肠炎(Ulcerative colitis,UC)和克罗恩病(Crohn’s disease,CD)，尤以UC多见。UC以反复发作的腹泻、黏液脓血便伴腹痛为主要表现。在我国，随着经济水平的不断提高，UC发病率及患病率快速增高。UC发病机制不清，尤其是炎症调控机制复杂，这是导致UC诊疗困难的重要原因，也是一个复杂的科学问题。课题组前期发现热休克转录因子2（HSF2）是UC活动期差异表达的蛋白质并与UC严重度呈正相关，并可抑制IL-1β水平，提示HSF2参与调控UC肠粘膜组织炎症反应。本项目进一步探索HSF2在UC肠上皮细胞中通过线粒体自噬调控NLRP3炎症小体激活程度的作用和机制。.在本研究中，目前有如下发现：.临床水平：UC患者肠上皮细胞受损线粒体数量、线粒体自噬水平及结肠组织ROS含量均升高，且与UC严重程度及HSF2水平正相关，其中，PARL/PINK/Parkin信号通路在UC肠上皮细胞线粒体自噬方面可能发挥重要作用。.动物水平：hsf2可以通过促进DSS诱导的小鼠结肠炎模型肠上皮细胞线粒体自噬，减少受损线粒体数量，降低小鼠肠粘膜组织内ROS水平，抑制NLRP3炎症小体激活程度，降低肠粘膜组织内IL-1β及IL-18水平，最终减轻小鼠肠道炎症反应。.细胞水平：在Caco-2细胞中，HSF2可以提高肠上皮细胞线粒体自噬水平，减少受损线粒体数量，降低细胞内ROS，抑制NLRP3炎症小体激活程度及IL-1β与IL-18分泌量。提示在Caco-2细胞中，HSF2可能通过促进细胞线粒体自噬，发挥抗炎作用。.本研究为明确HSF2在UC肠上皮细胞中调控炎症反应的具体机制提供了一定的理论基础，具有较好的学术价值和运用价值。