Abstract: Objective To investigate the effects and mechanism of BMAL1 on H2O2-induced H9C2 cardiomyocyte injury. Methods BMAL1 stable overexpression H9C2 cell lines were established. The experiments were divided into two parts. Part one：cells were divided into control group, H2O2 group (0.2 mmol/L H2O2 treatment for 24 h), BMAL1 overexpression group (BMAL1 stable overexpression cells, BMAL1-OE) and BMAL1 overexpression+H2O2 group (BMAL1 stable overexpression cells + 0.2 mmol/L H2O2 treatment for 24 h, BMAL1-OE+H2O2). Part two: there were H2O2 group, BMAL1-OE+H 2O2 group, BMAL1 overexpression+NRF2 inhibition+H2O2 group (NRF2 inhibitor 2 μmol/L ML385 pretreatment BMAL1 stable overexpression cells for 24 h, and 0.2 mmol/L H2O2 treatment for 24 h, BMAL1-OE+ML385+H2O2) and BMAL1-OE+HO-1 inhibition+H 2O2 group (HO-1 inhibitor 5 μmol/L Znpp pre-treatment BMAL1 stable overexpression cells for 24 h, and 0.2 mmol/L H2O2 treatment for 24 h, BMAL1-OE+Znpp+H2O2). CCK-8 was used to detect cell viability. Hydroxylamine method was used to detect SOD activity. TBA method was used to detect MDA content. Western blot assay was used to determine the protein expression of BMAL1, NRF2 and HO-1. Results (1) Experiment one. Compared with control group, the BMAL1 mRNA expression was increased in the BMAL1-OE group, the cell viability and the SOD activity of cell supernatant were decreased in H2O2 group, the MDA content was increased, and the expression levels of BMAL1, NRF2 and HO-1 protein were decreased (P＜0.05). Compared with H2O2 group, the cell viability and the SOD activity of cell supernatant were increased in BMAL1-OE+H2O2 group, the MDA content was decreased and the expression levels of BMAL1, NRF2 and HO-1 protein were increased (P＜0.05). (2) Experiment two. Compared with BMAL1-OE+H2O2 group, the cell viabilities and the SOD activity of cell supernatant were both decreased in BMAL1-OE+ML385+H2O2 group and BMAL1-OE+Znpp+H2O2 group, the MDA contents were increased (P＜0.05). Conclusion BMAL1 may up-regulate the NRF2/HO-1 signal axis, thereby reducing H2O2-induced cardiomyocyte oxidative stress injury in rat cardiomyocytes.

Key words: myocytes, cardiac, hydrogen peroxide, oxidative stress, ARNTL transcription factors, NF-E2-related factor 2, heme oxygenase-1, rhythm gene BMAL1