Inhibitory Effect of Sirtuin6 on EndMT by Regulating Oxidative Stress and Autophagy in Coxsackievirus B3-Induced Cardiac Endothelial Cells.

OBJECTIVE: Sirtuin 6 (Sirt6) plays a critical role in cardiovascular pathophysiology, yet its involvement in viral myocarditis (VMC) remains poorly understood. This study aimed to investigate the role of Sirt6 in coxsackievirus B3 (CVB3)-induced endothelial-to-mesenchymal transition (EndMT) and its underlying molecular mechanisms. METHODS: A model of CVB3-infected mouse cardiac endothelial cells (MCECs) was established. EndMT markers and Sirt6 expression were detected by WB/IF and qRT-PCR. Lentivirus-mediated Sirt6 knockdown or overexpression was performed to examine its impact on EndMT. Apoptosis and apoptosis-related proteins were analyzed by flow cytometry and WB. Proteomic analysis was further conducted on Sirt6-knockdown MCECs and their controls. Based on the results, oxidative stress and autophagy were assessed in CVB3-induced EndMT, and the influence of altered Sirt6 expression on these indicators was evaluated. RESULTS: Sirt6 expression was significantly downregulated in CVB3-induced EndMT. Sirt6 knockdown promoted EndMT, as manifested by decreased vascular endothelial cadherin (VE-cad) and increased α-smooth muscle actin (α-SMA) expression. It also exacerbated apoptosis, accompanied by upregulation of pro-apoptotic Bax, downregulation of anti-apoptotic Bcl-2, and an increase in Caspase-3 expression. Sirt6 overexpression partially reversed these changes. Proteomic analysis indicated that Sirt6 was involved in inflammatory signaling, apoptotic cascades, redox homeostasis, and metabolic pathways. CVB3 infection markedly elevated intracellular oxidative stress (increased ROS and MDA levels, decreased SOD activity) and suppressed autophagy (reduced LC3B-II and Beclin-1, elevated p62). These CVB3‑induced effects were aggravated by Sirt6 knockdown but attenuated by Sirt6 overexpression. CONCLUSION: This study reveals that Sirt6 inhibits CVB3-induced EndMT by regulating oxidative stress and autophagy. These findings provide experimental evidence for elucidating the pathological mechanisms of VMC and suggest Sirt6 as a potential therapeutic target.