Objective  To investigate whether hesperetin (Hes) alleviates doxorubicin (DOX)-induced cardiomyocytotoxicity by reducing oxidative stress via regulating silent information regulator 1 (SIRT1)/nuclear transcription factor E2-related factor 2 (NRF2) signaling in H9c2 cells.

  Methods  H9c2 cells were treated with DOX to establish the cardiotoxicity model and were randomly assigned to four groups, a control group (Control) and three treatment groups, receiving respectively DOX (the DOX group), Hes+DOX (the DOX+Hes group), and Hes+SIRT1 inhibitor EX527+DOX (the DOX+Hes+EX527 group). Cellular morphology was observed by the light microscope. Cell viability was evaluated by CCK-8. DOX-induced apoptosis in H9c2 cells was examined by flow cytometry. The levels of reactive oxygen species (ROS) in the H9c2 cells of the four groups were determied with 2'-7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining. The activities of lactate dehydrogenase (LDH), superoxide dismutase (SOD), catalase (CAT), and SIRT1 as well as the malondialdehyde (MDA) content were measured using ELISA kits. The expressions of cleaved caspase-3, cytochrome c, SIRT1, Ac-FOXO1, NRF2, and heme oxygenase 1 (HO-1) were determined by Western blot.

  Results  Compared with the Control group, the DOX group showed swollen cellular morphology, decreased cell density and viability, and increased LDH activity in the medium (P<0.01); both apoptosis and the expression of cleaved caspase-3 and cytochrome c increased (P<0.01); the activities of CAT and SOD decreased while the contents of MDA and ROS increased (P<0.01); the expression of SIRT1, NRF2, and HO-1 decreased, the activity of SIRT1 decreased, and the expression of Ac-FOXO1 increased (P<0.01). Compared with the DOX group, the DOX+Hes group showed improved cellular morphology, increased cell density and viability, and decreased LDH activity in the medium (P<0.01); the apoptosis and the expression of cleaved caspase-3 and cytochrome c decreased (P<0.01); the activities of CAT and SOD increased while the levels of MDA and ROS decreased (P<0.01); the expression of SIRT1, NRF2, and HO-1 increased, the activity of SIRT1 increased, and the expression of Ac-FOXO1 decreased (P<0.01). Comparison of the findings for the DOX+Hes group and the DOX+Hes+EX527 group showed that EX527 could block the protective effects of Hes against DOX-induced cell injury, oxidative stress, and SIRT1/NRF2 signaling.

  Conclusion  Hes inhibits oxidative stress and apoptosis via regulating SIRT1/NRF2 signaling, thereby reducing DOX-induced cardiotoxicity in H9c2 cells.