炎症反应过度失控是ALI发病的关键环节。肝X受体（LXRs）参与ALI发病但机制不明。课题组前期研究表明，LPS诱导的ALI大鼠肺部LXRα/β表达下降。LXRs激动剂预处理降低大鼠肺部P65 NF-κB表达，减轻LPS诱导的ALI。生物信息学分析和预试验显示E3泛素化连接酶SOCS1是LXRs的潜在靶基因。因此，我们提出“LXRs靶向SOCS1泛素化降解NF-κB抑制ALI发生”假说。本项目首先观察LXRs对P65 NF-κB泛素化降解作用；通过观察LXRs对SOCS1表达和基因启动子活性影响，鉴定SOCS1为LXRs靶基因；沉默SOCS1，观察LXRs对P65 NF-κB多聚泛素化水平、炎症反应和ALI的影响，明确SOCS1在LXRs泛素化降解P65 NF-κB和减轻ALI中的作用。本项目有望深化LXRs抗炎机制认识，阐明SOCS1在LXRs减轻ALI中的作用，为ALI防治提供新靶点。

Uncontrolled excessive inflammatory responses are critical to the pathogenesis of ALI. Studies have shown that LXRs are involved in the pathogenesis of acute lung injury, but the detail mechanism was still unknown. Our previous studies have shown that expressions of LXRα/β were decreased in lung tissues of rats after LPS-induced acute lung injury. Pretreatment with LXRs agonist significantly reduced LPS-induced p65 NF-κB expression in lung tissues of rats and acute lung injury. SOCS1 plays critical roles in degradation of p65 NF-κB via the ubiquitin-proteasome pathway. Bioinformatics and pre-test have shown that SOCS1 is a potential target gene of LXRs. Therefore, we proposed that LXRs attenuated acute lung inflammation and injury through SOCS1-mediated degradation of NF-κB via the ubiquitin-proteasome pathway. We will firstly observe the role of LXRs on degradation of p65 NF-κB via the ubiquitin-proteasome pathway. To confirm that SOCS1 is a direct target of LXRs, we will observe the impact of LXRs on SOCS1 expression and SOCS1 gene promoter dual luciferase reporter gene system. To further clarify the relationship between SOCS1 and LXRs on inflammation and acute lung injury, we will silence or overexpress SOCS1 and then observe the impact of LXRs on degradation of p65 NF-κB, inflammatory cytokines expression and acute lung injury. Thus, the present study will reveal a novel mechanism on LXRs in the pathogenesis of acute lung injury and provide new targets and avenues for the treatment of acute lung injury.

肝X受体具有抗炎活性，但机制不明。课题组前期研究表明，LPS诱导的ALI大鼠肺部LXRα/β表达下降。LXRs激动剂预处理降低大鼠肺部P65 NF-κB表达，减轻LPS诱导的ALI。生物信息学分析和预试验显示E3泛素化连接酶SOCS1是LXRs的潜在靶基因。因此，我们提出“LXRs靶向SOCS1泛素化降解NF-κB抑制炎症反应发生”假说。本项目首先观察LXRs对P65 NF-κB泛素化降解作用，结果表明，LXRs激动剂T0901317预处理不影响LPS诱导的p65 mRNA表达但抑制p65蛋白表达。当亚胺环己酮 (CHX)抑制p65蛋白的产生后，T0901317能够明显促进p65蛋白的降解。当MG132抑制蛋白酶体泛素化降解途径后，T0901317明显促进p65 NF-κB的泛素化但不影响p65 NF-κB的蛋白水平。综上结果表明，T0901317通过促进p65 NF-κB的泛素化和泛素化降解抑制p65蛋白的产生。另外，T0901317促进LPS诱导的SOCS1基因和蛋白的表达，当沉默SOCS1，我们发现T0901317诱导的p65 NF-κB泛素化和泛素化降解和抑炎活性明显被抑制。这些结果表明，SOCS1介导LXRs泛素化降解NF-κB抑制炎症反应发生。本项目研究成果进一步完善了LXRs抗炎的新认识，为后续以LXRs为靶点开发新抗炎药物奠定理论和应用基础。