Downregulation of FOXO6 alleviates hypoxia-induced apoptosis and oxidative stress in cardiomyocytes by enhancing Nrf2 activation via upregulation of SIRT6

Forkhead box protein O6 (FOXO6) has been recently identified as a novel regulator of oxidative stress in multiple pathological processes. However, whether FOXO6 participates in the regulation of oxidative stress of myocardial infarction is unclear. The present study was performed to evaluate the potential role of FOXO6 in regulating hypoxia-induced apoptosis and oxidative stress in cardiomyocytes in vitro. Our results demonstrated that FOXO6 expression was highly elevated in cardiomyocytes exposed to hypoxia. Downregulation of FOXO6 expression by the siRNA-mediated gene knockdown in hypoxia-exposed cardiomyocytes increased cell viability, while repressing apoptosis and reactive oxygen species (ROS) production. In contrast, overexpression of FOXO6 enhanced the sensitivity of cardiomyocytes to hypoxia-induced injury. Further, in-depth research revealed that knockdown of FOXO6 promoted the expression of sirtuin6 (SIRT6) and enhanced the activation of nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant signaling. Moreover, SIRT6 inhibition markedly blocked the FOXO6 knockdown-induced promotion effect on Nrf2 activation. In addition, Nrf2 inhibition partially reversed the FOXO6 knockdown-mediated protective effect against hypoxia-induced cardiomyocyte injury. Taken together, the findings of our study demonstrate that knockdown of FOXO6 is capable of protecting cardiomyocytes from hypoxia-induced apoptosis and oxidative stress by enhancing Nrf2 activation via upregulation of SIRT6. Our study highlights a potential role of FOXO6 in myocardial infarction and suggests it as an attractive target for cardioprotection.