miR-200a调控p38α信号通路对肠外营养相关肝损害机制研究

Parenteral nutrition-associated liver disease (PNALD) is one of common complications that are induced by parenteral nutrition (PN). Currently, prevention and treatment of PNALD is still very difficult because of the unclear pathogenesis. The previous studies demonstrated that miR-200s were involved in a variety of liver diseases, including liver fibrosis and liver tumor invasion, but the relationship between miR-200s and PNALD has not yet been reported. Our previous studies suggested that changes of miR-200a expression and activation of p38α signaling played an important role the in the PNALD. miRNA target prediction tools analysis showed that p38α was a downstream target of miR-200a. Thus, we proposed a hypothesis that the miR-200a probably participated in the PNALD by regulating p38α signaling pathway. To test this hypothesis, we will explore the roles of miR-200a and p38α signaling in PNALD on the molecular, cellular, tissues and even animals levels with using experiments including dual-luciferase reporter system, Western blot and RNA interference on the base of human liver cell line and rat model of PNALD. Furthermore, the molecular mechanisms for miR-200a regulating p38α signaling pathway will be defined in this study. In a word, this study will be helpful in revealing the mechanism of PNALD and providing new ideas for the prevention and treatment of PNALD from a new perspective miR-200a.

肠外营养相关肝损害（PNALD）是肠外营养常见的并发症，其发病机制不明，临床防治困难。研究证实miR-200家族参与调控肝纤维化、肝肿瘤侵袭等多种肝病发病过程，但迄今尚未报道miR-200家族与PNALD的关系。我们预实验结果提示miR-200a表达改变和p38α信号通路活化在PNALD中起重要作用。靶点预测显示p38α为miR-200a的下游靶基因，那么miR-200a很可能通过调控p38α信号途径影响PNALD发生。为此，我们将通过人肝细胞株和大鼠肠外营养肝损害模型，利用双荧光素酶报告系统、Western blot 及RNA干扰等技术，从分子、细胞、组织和动物整体水平等多方面探讨miR-200a及p38α信号通路活化在PNALD中的具体功能；明确miR-200a调控p38α信号通路的分子机制。本研究将从miR-200a这个新视点为完善PNALD发生机制奠定基础，为临床防治提供新思路。

自上世纪60年代以来，全肠外营养（TPN）已经广泛应用于早产儿以及无法经口喂养婴幼儿的生命支持。这些婴幼儿由于自身缺乏抗氧化防御机制更容易受到TPN导致的氧化应激损害。尽管我们前期研究已经表明氧化应激损伤在TPN相关肝损害（PNALD）的发生中具有重要作用，但具体分子机制还不清楚。我们研究发现miR-200与氧化应激通过交互作用影响肝细胞的氧化应激损害。一方面，H2O2 引起的氧化应激反应导致了miR-200家族表达量显著升高。另一方面，升高的miR-200-3p反过来通过靶向调控p38α影响氧化应激反应。miR-200-3p或p38α基因敲除都可以促进H2O2所导致的肝细胞死亡。与之相反，通过抑制miR-200-3p能够保护肝细胞的氧化损伤。另外，我们还发现p53磷酸化（Ser33）对H2O2诱导的miR-200表达升高起重要作用。H2O2处理肝细胞导致p38α活化，活化的p38α直接磷酸化p53（Ser33），而p53（Ser33）可结合在miR-200启动子上促进其转录水平。综上所述我们研究表明p38/p53/miR-200反馈调控机制在PNALD发生中起重要作用，为PNALD临床干预提供新思路。