LXRs抑炎新机制：miR-33/MAPK1/TTP通路介导的炎症因子mRNA降解

It is well established that liver X receptors (LXRs) could inhibit the expression of multiple inflammatory genes and down-regulate the inflammatory response, but the exact mechanism has not been fully elucidated. AREs-mediated mRNA decay regulats the expression of many inflammatory mediators makes this pathway a likely target for the suppression of inflammatory cytokine. Based on this common law, we therefore hypothesized that LXRs may be involved in post-transcriptional regulation of inflammatory cytokines by mRNA degradation, thereby inhibiting the expression of inflammatory cytokine. LPS-stimulated macrophages as a model of inflammation is used in this study. we use actinomycin D to terminate transcription, and then observe the effect of LXRs on inflammatory cytokine mRNA decay. To test the hypothesis that LXRs target MAPK1/TTP-dominated circuit by regulating the miR-33 expression, we investigate the role of LXRs in inflammatory cytokine mRNA decay, TTP activity and MAPK1 expression separately after specific blocking of TTP,MAPK1 or miR-33. The study will deepen the understanding of the molecular mechanisms of LXRs on inflammatory response, explore new ideas for multi-target, broad-spectrum anti-inflammatory approach to systemic inflammatory response syndrome and other acute and chronic inflammatory diseases therapy, provide new target for the development of anti-inflammatory drugs.

研究表明LXRs能广谱抑制炎症因子表达，负性调节炎症反应，但其确切机制尚未完全阐明。AREs介导的mRNA降解是炎症因子mRNA代谢的一个共有方式，活化该途径能同时抑制多种炎症因子的表达。基于二者有广泛抑制炎症因子表达的共性，因此我们推测LXRs可能参与转录后调节炎症因子mRNA的降解，进而抑制炎症因子的表达。本课题拟以脂多糖诱导巨噬细胞建立炎症模型，通过放线菌素D终止转录，观察LXRs对转录后炎症因子mRNA降解的影响；通过特异性的TTP、MAPK1或miR-33阻断处理，分别观察LXRs对炎症因子mRNA降解、TTP活性、MAPK1表达的影响，证实LXRs通过miR-33靶向MAPK1/TTP降解炎症因子mRNA的假说。本课题将深化LXRs调节炎症反应分子机制的认识，为多靶点广谱抗炎治疗全身炎症反应综合征等急慢性炎症性疾病开拓新思路，为抗炎药物开发提供新靶点。

肝x受体具有抗炎活性，但机制尚未完全阐明。本项目以脂多糖诱导巨噬细胞建立炎症模型，观察肝x受体能否在转录后水平调节炎症因子表达，并探讨其可能机制。我们首次发现：肝x受体活化能够促进IL-1β， IL-6和TNFα mRNA的降解，降低相关炎症因子的表达；肝x受体活化通过影响TNFα 3'-UTR与RNA结合蛋白的结合活性，从而失稳TNFα mRNA；肝x受体活化能够促进锌指蛋白36（TTP）基因和蛋白的表达，并且TTP小RNA干扰能够逆转肝x受体活化诱导的炎症因子mRNA降解；肝x受体活化能够明显抑制p-ERK1/2（MAPK3/1）和p-p38 MAPK蛋白的表达；肝x受体活化能够提高miR-33的表达，逆转LPS诱导的miR-33下调。另外，miR-33抑制剂能够阻断肝x受体对p-ERK1/2（MAPK3/1）的抑制作用；miR-33抑制剂能够阻断肝x受体活化对TTP的上调，并且肝x受体活化引起的IL-1β，IL-6和TNFα mRNA降解可以被miR-33抑制剂逆转。上述结果证实了肝x受体可能通过miR-33/MAPK1/TTP通路降解炎症因子mRNA的假说。本项目进一步拓展了肝x受体抗炎机制的新认识，为后续以肝x受体为靶点开发新抗炎药物奠定理论和应用基础。