Cigarette smoking extract induces mitochondrial dysfunction and apoptosis in HUVECs via the Sirt1-SHH axis

Introduction Cigarette smoking extract (CSE) can cause endothelial cell (EC) dysfunction, and then promote the occurrence and development of atherosclerosis. However, the molecular mechanisms underlying CSE-induced EC dysfunction are unknown. Sirt1, as a deacetylase, is involved in various biological processes of ECs. Therefore, this study investigated whether CSE induces apoptosis and mitochondrial dysfunction in human umbilical vein endothelial cells (HUVECs) via Sirt1-dependent mechanisms. Methods HUVEC activity was assessed using MTT and crystal violet staining following treatment with different concentrations of CSE. Lentiviral transfection technology was used to generate HUVECs overexpressing Sirt1. Apoptosis was detected by Tunnel staining. MitoTracker™ Deep Red FM and JC-1 were used to assess mitochondrial structure and membrane potential. ELISA was used to detect the expression of superoxide dismutase (SOD) and malondialdehyde (MDA). qPCR was used to determine mRNA expression. Atherosclerosis was evaluated by oil red O staining in ApoE-KO mice after cigarette smoke exposure. Results CSE decreased Sirt1 and sonic hedgehog (SHH) expression, leading to mitochondrial dysfunction and apoptosis in HUVECs. Overexpressing Sirt1 or activating the SHH signaling pathway attenuated CSE-induced apoptosis and mitochondrial dysfunction. However, inhibiting the SHH signaling axis attenuated the protective effect of Sirt1 overexpression on CSE-induced apoptosis and mitochondrial dysfunction. In vivo studies also showed that cigarette smoke exacerbated atherosclerosis in ApoE-KO mice, downregulating Sirt1, SHH, and Gli1 expression in the aorta. Additionally, cigarette smoke increased Bax expression and decreased Bcl-2 expression in ApoE-KO mice aortas. Discussions Smoking can affect all stages of the atherosclerosis process, and the specific mechanism remains unclear. This study confirms that CSE can induce mitochondrial dysfunction and apoptosis of HUVECs by reducing Sirt1 expression and inhibiting SHH signaling activation. These findings provide new insights into the prevention and treatment of smoking-induced atherosclerosis.