miR-125b甲基化在同型半胱氨酸促进血管平滑肌细胞增殖中的作用

Role of homocysteine to promote the vascular smooth muscle cell proliferation by MiR-125b methylation

目的探讨同型半胱氨酸(homocysteine,Hcy)促进血管平滑肌细胞增殖中miR-125b甲基化的作用。方法原代培养人脐静脉平滑肌细胞(VSMCs),并分为空白对照组(0μmol·L-1Hcy),不同浓度Hcy干预组(50、100、200及500μmol·L-1Hcy),以荧光定量PCR(qRT-PCR)法检测miR-125b的表达变化;利用miR-125b前体和抑制剂转染VSMCs后MTT法检测细胞增殖活性;生物信息学分析miR-125b启动子区Cp G岛分布情况,巢式降落式甲基特异性PCR(nt-MSP)法检测miR-125b甲基化状态的变化;并利用DNA甲基化酶抑制剂5-氮杂胞苷(AZC)干预细胞后再次检测miR-125b的表达。结果与对照组相比,100,200及500μmol·L-1Hcy可使miR-125b的表达水平降低,差异有显著性(P<0.01);miR-125b前体可以抑制VSMCs增殖,而miR-125b抑制剂可以促进VSMCs增殖(P<0.01);以miR-125b基因上游3 700 bp作为研究对象,生物信息学分析发现miR-125b启动子区含有一个长度为792bp(1881-2672区域)的CpG岛,且在Hcy干预下miR-125b的甲基化水平增强(P<0.01);而用AZC干预后,发现miR-125b表达上调,差异有显著性(P<0.05)。结论 Hcy可能通过下调miR-125b表达从而促进VSMCs增殖,可能通过上调miR-125b基因甲基化水平从而下调miR-125b表达。

Aim To investigate the role of miR-125 b and its DNA methylation in homocysteine ( Hcy )-in-duced vascular smooth muscle cells( VSMCs) prolifera-tion. Methods VSMCs were stimulated with 0,50, 100, 200, 500 μmol · L-1 Hcy respectively. Then qRT-PCR was used to detect the mRNA levels of miR-125b,and nested-touchdown methylation-specific PCR ( ntMS-PCR) was used to detect the methylation levels of miR-125b. VSMCs were transfected with miR-125b precursor or the inhibitor of miR-125b ,then 3-(4,5-dimethylthiazol-2-yl)-2-5-diphenyl tetrazolium bromide ( MTT ) assay was used to reflect the proliferation of VSMCs. The distribution of CpG islands of miR-125b promoter region was analyzed by bioinformatics meth-ods. VSMCs were stimulated with 100 μmol·L-1 Hcy and transfected with or without DNA methylation inhib-itors 5-nitrogen impurity cytidine ( AZC) , then the ex-pression of miR-125b was detected by qRT-PCR. Re-sults The mRNA levels of miR-125 b were decreased in 100,200,500 μmol·L-1 Hcy group compared with 0 μmol·L-1 Hcy group. The precursor of miR-125b could inhibit the proliferation activity and the inhibitor of miR-125 b could increase the proliferation activity of VSMCs cells. Bioinformatics analysis indicated that MiR-125 b promoter region had a CpG island whose length was 792 bp ( 1881-2672 ) . The miR-125 b pro-moter region methylation levels increased after Hcy in-tervention ( P <0. 01 ) . The expression level of miR-125 b increased after AZC intervention ( P <0. 05 ) . Conclusions ① Hcy promotes vascular smooth mus-cle cell proliferation maybe by down-regulating the ex-pression of miR-125b. ② Hcy down-regulates the ex-pression of miR-125 maybe by up-regulating the methy-lation levels of miR-125b promoter region.