同型半胱氨酸通过下调胰岛素诱导因子1mRNA表达增加巨噬细胞胆固醇合成

Homocysteine Increases the Cholesterol Synthesis in Macrophages Through Down-Regulating the Expression of Insulin-Induced Gene 1

目的探讨同型半胱氨酸对THP-1巨噬细胞胆固醇合成的直接影响及其可能的作用靶位。方法佛波酯诱导体外培养的THP-1单核细胞分化为巨噬细胞,逆转录聚合酶链反应检测5mmol/L同型半胱氨酸作用于巨噬细胞0、4、8、18h及24h后胰岛素诱导因子1mRNA和3-羟基-3甲基戊二酰辅酶A还原酶mRNA的表达。酶比色法检测细胞内总胆固醇水平。结果细胞内总胆固醇水平随同型半胱氨酸作用时间的延长而增加,18h和24h组细胞内总胆固醇水平与0h组比较明显增加(P<0.01)。同型半胱氨酸呈时间依赖性降低胰岛素诱导因子1mRNA的表达,8、18、24h组与0h组比较,差异有显著性(P<0.05和P<0.01)。3-羟基-3甲基戊二酰辅酶A还原酶mRNA表达水平随同型半胱氨酸作用时间的延长而增加,18h和24h组3-羟基-3甲基戊二酰辅酶A还原酶mRNA表达水平与0h组比较,明显增加(P<0.01)。结论同型半胱氨酸诱导巨噬细胞内脂质堆积、进而形成泡沫细胞的一个可能机制是下调胰岛素诱导因子1表达、进而上调3-羟基-3甲基戊二酰辅酶A还原酶表达导致巨噬细胞内胆固醇合成异常增加。

Aim To investigate the effects of homocysteine（Hcy）on cholesterol synthesis in THP-1 macrophages and its potential target loci.Methods The macrophages were induced by phorbol 12-myristate 13-acetate（PMA）from THP-1 mononuclear cells,and treated by 5 mmol/L Hcy for 0 h,4 h,8 h,18 h and 24 h respectively.The mRNA expression of insulin-induced gene 1（Insigl）and 3-hydroxy-3-methylglutaryl coenzyme A reductase（HMGCR）were determined by reverse transcription polymerase chain reaction（RT-PCR）.Intracellular total cholesterol levels were examined by enzymatic colorimetric assay.Results Intracellular total cholesterol level increased significantly compared with the 0 h group at 18 h and 24 h（P0.01）after Hcy-treatment.The expression of Insigl mRNA demonstrated a time-dependent down-regulation after Hcy-treatment,8 h,18 h and 24 h groups had significant lower Insigl mRNA level vs 0h group（P0.05 and P0.01）.The HMGCR mRNA expression showed obvious upregulation at 18 h and 24 h compared with the 0 h group（P0.01）.Conclusion A potential mechanism for Hcy-induced lipid accumulation in macrophage and foam cell formation may go through the following way：Hcy down-regulates the expression of Insigl,and sequentially up-regulates the HMGCR expression,which eventually increases the cholesterol synthesis in THP-1 macrophages.