载脂蛋白A5基因表达调控及其在重症肝炎中抑制LPS/TLR4信号通路的分子机制研究

Previous animal studies found apolipoprotein A5(ApoA5) expression was decreased in severe hepatitis, and increasing ApoA5 expression could decrease the occurrence of lipopolysaccharide(LPS)-induced severe hepatitis by significantly inhibiting the expression of TLR4. However, the cause of decreasing expression of ApoA5 and its molecular mechanism inhibiting LPS/TLR4 signaling are remained unknown in severe hepatitis.. In this project, for revealing the possible mechanism of ApoA5 decreasing in severe hepatitis, we will force on the transcriptional regulation of ApoA5 gene expression as well as gene SNP and DNA methylation and study their influences on protein expression. For investigating the molecular mechanism of ApoA5 in inhibiting LPS-induced TLR4 expression and activation, we will force on the key molecules required for the formation of LPS/TLR4 complexes, and investigate whether ApoA5 could regulate the gene transcription in LPS-induced inflammatory cell model. Additionally, the expression of ApoA5 and the key molecules of LPS/TLR4 complexes will be also evaluated in clinical cohort of severe hepatitis patients, so as to further confirm that the mechanism of ApoA5 action in severe hepatitis is related to TLR4 signaling pathway.. The implementation of this project will help us to reveal new mechanism of severe hepatitis development, and its finding may provide new target for the prevention and treatment of severe hepatitis.

前期动物研究发现，载脂蛋白A5(ApoA5)在重症肝炎发生时表达降低；增加ApoA5水平可降低重症肝炎发生，其机制可能与ApoA5抑制TLR4分子表达有关。但ApoA5在重症肝炎中水平降低的原因及其抑制TLR4表达的机制尚不清楚。. 本项目将首先从基因转录调控、基因SNP和DNA甲基化三个层面，研究影响ApoA5表达的可能机制，揭示重症肝炎中ApoA5低水平表达的机理。其次，通过研究ApoA5对通路上游分子基因转录的调控作用，初步揭示ApoA5在重症肝炎中抑制LPS/TLR4通路的可能机制。最后，通过研究ApoA5与LPS/TLR4通路上游分子在患者体内表达水平，进一步证实ApoA5在重症肝炎中的作用与LPS/TLR4通路有关。. 本项目的实施将有助于阐明重症肝炎病情进展的可能新机制，并为重型肝炎防治提供新的干预靶点。

前期动物研究发现，载脂蛋白A5(ApoA5)在重症肝炎发生时表达降低；增加ApoA5水平可降低重症肝炎发生，其机制可能与ApoA5抑制TLR4分子表达有关。但ApoA5在重症肝炎中水平降低的原因及其抑制TLR4表达的机制尚不清楚。本课题将首先从基因转录调控、基因SNP和DNA甲基化三个层面，研究影响ApoA5表达的可能机制，揭示重症肝炎中ApoA5低水平表达的机理。其次，通过研究ApoA5与LPS/TLR4通路上游分子的结合作用，及ApoA5对通路上游分子基因转录的调控作用，阐明ApoA5在重症肝炎中抑制LPS/TLR4通路的确切机制。最后，通过研究ApoA5与LPS/TLR4通路上游分子在患者体内表达水平，进一步证实ApoA5在重症肝炎中的作用与LPS/TLR4通路有关。. 研究发现，ApoA5基因转录受PPAR调控，ApoA5在慢加急性肝衰竭患者中表达较少可能与PPAR降低有关。ApoA5可调控RAW264.7表面分子CD14 蛋白的表达，而对MD2和LBP分子表达水平无明显影响，提示apoA5可能通过抑制CD14分子的表达来影响LPS与TLR4的结合进而导致TLR4激活受限。ApoA5 SNP位点单核苷酸多态性对慢加急性肝衰竭患者预后无明显影响，但ApoA5-DNA甲基化水平变化可能参与了慢加急性肝衰竭患者的病情进展。外周血apoA5水平与存在内毒素血症慢加急性患者外周PMBC 表面的CD14和TLR4水平呈负相关，且apoA5具有较好的预测伴有内毒素血症的慢加急性肝衰竭临床转归的作用，而在不伴有内毒素血症的慢加急性肝衰竭患者中其预测价值有限。. 本课题的研究发现为深入阐明重症肝炎病情进展的可能新机制，并为重型肝炎防治提供新的思路。