Moderate Autophagy Inhibits Vascular Smooth Muscle Cell Senescence to Stabilize Progressed Atherosclerotic Plaque via the mTORC1/ULK1/ATG13 Signal Pathway

In order to investigate the effects of autophagy induced by rapamycin in the development of atherosclerosis plaque we established murine atherosclerosis model which was induced in ApoE-/- mice by high fat and cholesterol diet (HFD) for 16 weeks. Rapamycin and 3-Methyladenine (MA) were used as autophagy inducer and inhibitor respectively. The plaque areas in aortic artery were detected with HE and Oil Red O staining. Immunohistochemical staining were applied to investigate content of plaque respectively. In contrast to control and 3-MA groups, rapamycin could inhibit atherosclerosis progression. Rapamycin was able to increase collagen content and a-SMA distribution relatively, as well as decrease necrotic core area. Then we used MOVAS and culture with ox-LDL for 72 h to induce smooth muscle-derived foam cell model in vitro. Rapamycin and 3-MA were cultured together respectively. Flow cytometry assay and SA-β-Gal staining experiments were performed to detect survival and senescence of VSMCs. Western blot analysis were utilized to analyze the levels of protein expression. We found that rapamycin could promote ox-LDL-induced VSMCs autophagy survival and alleviate cellular senescence, in comparison to control and 3-MA groups. Western blot analysis showed that rapamycin could upregulate ULK1, ATG13 and downregulate mTORC1 and p53 protein expression.