肺炎衣原体对SR-A1和CD36表达的影响及相关信号机制研究

摘要

目的:探讨肺炎衣原体(Cpn)对THP-1源性巨噬细胞A1型清道夫受体(SR-A1)和B类清道夫受体CD36表达的影响及c-jun氨基端激酶(JNK)信号通路在其中的调控作用.方法:THP-1单核细胞诱导分化为巨噬细胞后随机分为四组:对照组、Cpn组、Cpn+SP600125(JNK特异性抑制剂)组、SP600125组.运用油红O染色观察细胞浆内脂滴的变化,用酶荧光学法检测细胞内胆固醇酯含量的变化,分别用逆转录聚合酶链反应法(RT-PCR)和免疫印迹法(Western blot)检测各组SR-A1、CD36 mRNA和蛋白表达.结果:SP600125能呈浓度依赖性的抑制Cpn诱导的泡沫细胞形成和SR-A1表达上调,但对Cpn诱导的CD36的表达无明显影响.结论:Cpn可通过JNK信号通路上调SR-A1表达,而Cpn对CD36表达无明显影响.%Objective:To investigate the effects of Chlamydia pneumoniae(Cpn) on SR-A1 and CD36 expression in THP-1-derived macrophages and role of c-Jun NH_2-terminal signal transduction pathway in the process.Methods:Cpn was propagated in Hep-2 cells.THP-1 monocytes were induced into macrophages by 160 nmol/L phorbol myristate acetate(PMA)for 48h,and were randomly allocated into four groups to be incubated continually: control group;Cpn infection group;Cpn and SP600125(a JNK inhibiter)group and SP600125 group.Lipid droplets in cytoplasm were observed by oil red O staining.The contents of intracellular cholesterol ester were detected by enzyme-fluorescence.The expression of SR-A1 and CD36mRNA and protein were determined by RT-PCR and Western blot, respectively. Results:THP-1-derived macrophages infected with Cpn resulted in large accumulation of lipid droplets and foam cell formation when co-cultured with LDL.Meanwhile,the expression of SR-A1 mRNA and protein were up-regulated by Cpn infection (P<0.05).However,the expressions of CD36 mRNA and protein in THP-1-derived macrophages infected with Cpn were unchanged.Moreover,the up-regulation of SR-A1 and foam cell formation induced by Cpn could be restrained by the JNK inhibiter SP600125 in a dose-dependent manner,and SP600125 had little impact on the expression of CD36 in THP-1-derived macrophages infected with Cpn.Conclusion:The up-regulation of SR-A1 but not CD36 expression is involved in mechanisms of Cpn inducing foam cell formation.And Chlamydia pneumoniae up-regulates the expression of SR-A1 via the JNK signal transduction pathway.This may be a novel mechanism for the foam cell formation induced by Cpn.