Deficiency of protein inhibitor of activated STAT3 exacerbates atherosclerosis by modulating VSMC phenotypic switching

Background and aims: Phenotypic switching of vascular smooth muscle cells (VSMCs) plays an essential role in the development of atherosclerosis. Protein inhibitor of activated STAT (Pias) regulates VSMCs phenotype via acting as sumo E3 ligase to promote protein sumoylation. Our previous study indicated that Pias3 expression decreased in atherosclerotic lesions. Therefore, this study aimed to explore the role of Pias3 on VSMCs phenotype switching during atherosclerosis. Methods: ApoE^−/− and ApoE^−/−Pias3^−/− double-deficient mice were fed with high-fat/high-cholesterol diet to induce atherosclerosis. Aorta tissues and primary VSMCs were collected to assess plaque formation and VSMCs phenotype. In vitro, Pias3 was overexpressed in A7r5, a VSMCs cell line, by transfection with Pias3 plasmid. Real-time quantitative PCR, immunoblotting, immunoprecipitation, were used to analyze the effect of Pias3 on VSMCs phenotypic switching. Results: Pias3 deficiency significantly exacerbated atherosclerotic plaque formation and promoted VSMCs phenotypic switching to a synthetic state within lesion. In vitro, overexpressing Pias3 in VSMCs increased the expression of contractile markers (myosin heavy chain 11, calponin 1), while it decreased the level of synthetic marker (vimentin). Additionally, Pias3 overexpression blocked PDGF-BB-induced VSMCs proliferation and migration. Immunoprecipitation and mass spectrometry results showed that Pias3 enhanced sumoylation and ubiquitination of vimentin, and shortened its half-life. Moreover, the ubiquitination level of vimentin was impaired by 2-D08, a sumoylation inhibitor. This suggests that Pias3 might accelerate the ubiquitination-degradation of vimentin by promoting its sumoylation. Conclusions: These results indicate that Pias3 might ameliorate atherosclerosis progression by suppressing VSMCs phenotypic switching and reducing vimentin protein stability.