The Role Of TM6SF2 In Lipid Accumulation In Human Vascular Smooth Muscle Cells

Objective: To investigate the expression of transmembrane 6 superfamily 2(TM6SF2)in human vascular smooth muscle cells(VSMCs)and explore the effects of TM6SF2 on oxLDL-induced lipid accumulation in VSMCs and the underlying mechanisms.Methods:(1)The expression of TM6SF2 in cultured VSMCs was analyzed by immunofluorescence staining.In addition,VSMCs were incubated with 0,10,25,50,75?g/ml oxLDL for 24 h or treated with 50?g/ml oxLDL for 0h,12 h,24h,48 h,respectively.Real-time quantitative PCR and Western blot analysis were performed to detect the mRNA and protein levels of TM6SF2 in the cells.(2)VSMCs were transfected with LV-TM6SF2 or TM6SF2 siRNA,followed by treatment with oxLDL/Dil-oxLDL.The lipid accumulation was evaluated by Oil Red O staining,fluorescence microscope and total cholesterol quantitation analysis kit.The expression of lipid uptake receptors,such as Lox-1 and CD36,were examined at both mRNA and protein levels by Real-time quantitative PCR and Western blot,respectively.(3)The expression and distribution of TM6SF2 in human atherosclerotic plaque was detected by immunohistochemical analysis,and the co-localization of VSMCs and TM6SF2 in plaque was examined by immunofluorescence double staining.Results:(1)TM6SF2 mainly localized in the cytoplasm of cultured VSMCs.TM6SF2 mRNA and protein expression was upregulated by oxLDL in VSMCs in a dose-and time-dependent manner.(2)TM6SF2 overexpression by LV-TM6SF2 transfection significantly inhibited cellular oxLDL/Dil-oxLDL-induced lipid accumulation,while TM6SF2 knockdown by TM6SF2 siRNA markedly increased oxLDL/Dil-oxLDL-induced cellular lipid accumulation.Meanwhile,LV-TM6SF2 suppressed the oxLDL-induced upregulation of Lox-1 and CD36 mRNA and protein expression in VSMCs,whereas TM6SF2 siRNA significantly amplified this effect.(3)TM6SF2 was highly expressed in human atherosclerotic plaques,particularly in media.Furthermore,TM6SF2 was co-stained with SM?-actin,a VSMCs marker,in human atherosclerotic plaque.Conclusion: TM6SF2 was expressed in VSMCs,TM6SF2 reduces lipid accumulation in VSMCs involving the downregulation of Lox-1 and CD36 expression.