SIRT1对IGF-1诱导的肠上皮细胞间质转化的作用机制及其在肠纤维化中的意义

Intestinal fibrosis is a serious complication of Crohn's disease for which there is no effective treatment. Latest research has confirmed that intestinal epithelial mesenchymal transition (EMT) is a key process influencing intestinal fibrosis. Insulin-like growth factor 1 (IGF-1) is a potent profibrogenic agent involved in intestinal fibrosis. Many studies have shown that type III histone deacetylase SIRT1 reduces EMT in kidney fibrosis, and that the SIRT1 activator resveratrol (RSV) has antifibrotic effects in cultured cells and colitis animal models. However, the effect of RSV on EMT in intestinal epithelial cells has not been reported. Our preliminary data show that IGF-1 induces EMT in intestinal epithelial cells through IGF-1R/MAPK/ERK pathway, and that RSV could restore the expression of E-cadherin inhibited by IGF-1. The present study aims to further explore the mechanism whereby SIRT1 regulates EMT in intestinal epithelial cells induced by IGF-1. We also will examine its relevance in intestinal fibrosis by using intestinal epithelial-specific SIRT1 knockout mice. This study may provide novel insight to prevention and intervention strategies for CD-associated intestinal fibrosis.

肠纤维化是克罗恩病（CD）严重并发症之一。文献提示：上皮间质转化（EMT）是肠纤维化中成纤维细胞的重要来源；胰岛素样生长因子1（IGF-1）是肠纤维化中重要的生长因子；Ⅲ型组蛋白去乙酰化酶SIRT1在肾纤维化中具有抗EMT作用，其激动剂白藜芦醇（RSV）具有抗肠纤维化作用，但其确切机制尚不清楚。我们前期研究发现：IGF-1可通过IGF-1R/MAPK/ERK通路诱导肠上皮细胞EMT，RSV可阻断IGF-1对肠上皮细胞中E-cadherin的下调作用。本课题拟：通过细胞实验和结肠炎动物模型，探讨SIRT1对IGF-1介导的肠上皮细胞EMT的作用及机制，在肠上皮细胞SIRT1特异性敲除小鼠中研究SIRT1对肠纤维化的保护作用，为CD肠纤维化的防治和干预提供新的方法和研究思路。

肝纤维化是肝脏慢性损伤后的一个可逆的适应性修复过程。在缺少有效干预的情况下，肝纤维化可以导致不可逆的肝硬化甚至肝癌。肝星状细胞（hepatic stellate cell，HSC）是肝脏肌成纤维细胞的主要来源，可分泌大量细胞外基质，肝星状细胞的活化是肝纤维化过程中的关键步骤。此外，在肝纤维形成过程受到多种表观遗传机制的调控，主要包括DNA甲基化、组蛋白修饰和调节性非编码RNAs。我们研究发现，小鼠肝纤维化模型的肝脏中及激活的体外培养肝星状细胞中，SRIT1的表达降低，同时HDAC4表达升高。HDAC4在促纤维化因子刺激下结合到SIRT1启动子近端区域，HDAC4介导了H3/H4的去乙酰化，进而促进SIRT1的转录抑制，而HDAC4沉默则恢复SIRT1表达并逆转HSC激活。已知PPARg是HSC活化的抑制因子之一，SIRT1或其激动剂均可去乙酰化PPARg，并增强PPARg转录活性进而抑制HSC活化。我们进一步研究发现，SIRT1可通过去乙酰化EZH2调控PPARγ的转录，EZH2抑制剂或PPARg的活化均能减轻肝星状细胞特异性SIRT1敲除小鼠的肝纤维化。我们的结果表明SIRT1在肝星状细胞表型转化中发挥重要作用。