STAT3 Up-Regulates The Transcription Of Autophagy Gene ATG7 To Mediate Angiotensin Ⅱ-induced Proliferation Of Vascular Smooth Muscle Cells

Purpose To investigate whether signal transducer and activator of transcription 3 mediate angiotensin Ⅱ to induce the proliferation of vascular smooth muscle cells by up-regulating the transcription of autophagy-specific gene ATG7.Methods Cultured Human aortic smooth muscle cells(HASMCs)and human embryonic kidney 293 cells(HEK 293 cells),hereinafter referred to as 293 cells,in vitro.(1)The liposome transfection technique was used to silence or overexpress the STAT3 gene in HASMCs,respectively.And the liposome transfection technique was used to transfect the p CMV-m Cherry-GFP-LC3 B plasmid,Western Blot to detect the expression of autophagy marker proteins LC3Ⅱ,p62,ATG7,as well as fluorescence confocal microscopy to detect the number of autophagosomes and autophagolysosomes.(2)Western Blot to detect the expression of proliferation-specific protein nuclear antigen(PCNA)protein,the level of PCNA m RNA was detected by RT-PCR,and the proliferation rates of HASMCs was detected by CCK8;(3)The combination of ATG7 and STAT3 was verified by detecting the luminescence of the dual luciferase reporter.Results(1)Ang Ⅱ could induce autophagy in HASMCs.The number of autophagosome and autophagosolysosome in HASMCs were increased(P<0.01),and the protein level of autophagy specific proteins LC3-Ⅱand ATG7 were increased,while p62 protein was decreased(P<0.05,P<0.01).At the same time,PCNA is increased in both protein and m RNA levels(P<0.05).(2)Silencing or overexpressing of STAT3 could inhibited or promoted the autophagy induced by AngⅡin HASMCs(P<0.05,P<0.01),respectively,and the number of autophagosome and autophagosolysosome in HASMCs were decreased or increased,respectively(P<0.01).(3)The test results of dual luciferase reporter showed that STAT3 could up-regulate the promoter activity of ATG7 gene in a concentration-dependent manner.In addition,STAT3 may have binding sites with ATG7 gene at 1760～1815 of the ATG7 promoter(P<0.05).Conclusions 1.Ang Ⅱ-induced autophagy may be one of the mechanisms promoting the proliferation of HASMCs.2.STAT3 mediates AngⅡ-induced autophagy of HASMCs via up-regulating autophagyspecific gene ATG7 transcription.