Abstract: 【Abstract】Objective To investigate the role and mechanism of lysine methyltransferase SET8 mediated damage regulated autophagy modulator 1 (DRAM1) in regulating the apoptosis of vascular smooth muscle cells (VSMCs). Methods VSMCs were cultured in vitro and treated with liposome transfection. The cells were divided into three groups: normal group, SET8-NC group (Transfection of control NS shRNA plasmid), and SET8-shRNA group (Transfection of SET8 shRNA plasmid). MTT colorimetry was used to detect cell proliferation in each group, and apoptosis was detected by in situ end labeling and TUNEL staining, and Western blot was used to detect the protein expression of SET8, DRAM1, B-cell lymphoma / leukemia-2 (Bcelllymphoma2,
Bcl-2), bcl-2 associated X protein (Bcl-2 Associated X protein, Bax) in each group. In order to verify the effect of DRAM1 on the apoptosis of VSMCs, we transfected DRAM1 to make it highly expressed, then divided the cells into three groups: the normal group, the DRAM1-NC group, and the DRAM1 group. The proliferation and apoptosis of each group and the protein expression of DRAM1, Bax and Bcl-2 were detected. Results ①Compared with the normal group and the SET8-NC group, MTT results showed that the proliferation of cells in set8 shRNA group decreased significantly at 12h, 24h, 36h and 48h (F=267.649, P＜0.001; F= 477.534，P＜0.001; F=28.938，P=0.001; F=145.849，P＜0.001), and the TUNEL staining results showed that the apoptosis of the SET8-shRNA group was significantly increased. Western blot results showed that, compared with the normal group and the SET8-NC group, the expression of SET8 and Bcl-2 in the SET8-shRNA group decreased (F=34.247, P=0.001; F=39.218, P＜0.001), and the expression of DRAM1 and Bax increased significantly (F=84.517, P＜0.001; F=15.570, P=0.004). ② Compared with the normal group and the DRAM1-NC group, MTT results showed that the proliferation of cells in DRAM1 group decreased significantly at 12h, 24h, 36h and 48h (F= 347.170, P＜0.001; F=74.621, P＜0.001; F=56.427, P＜0.001; F=393.547, P＜0.001). TUNEL staining showed that the green fluorescent particles in DRAM1 group increased significantly. Western blot results showed that, compared with the normal group and the DRAM1- NC group, the expression of DRAM1 and Bax in the DRAM1 group was increased (F=26.456, P=0.001; F=25.217, P=0.001), and the expression of Bcl- 2 was significantly decreased (F=626.70, P＜0.001). Conclusion The low expression of SET8 can promote the apoptosis of vascular smooth muscle cells. The possible mechanism is that the low expression of SET8 promotes the expression of DRAM1 and promote the expression of apoptotic protein Bax, which in turn causes the apoptosis of vascular smooth muscle cells.

Key words: Vascular smooth muscle cells, Lysine methyltransferase SET8, Damage-regulated autophagy modulator 1, Apoptosis