METTL3-mediated MSRB3 m6A modification accelerates hypoxia-induced cardiomyocyte ferroptosis by inhibiting mitochondrial oxidative phosphorylation

Objective: Cardiomyocyte death is a complex biological process involving the interaction of many factors and signaling pathways. In chronic sustained hypoxic environments, cardiomyocytes may die due to insufficient energy supply and increased production of Reactive Oxygen Species (ROS). Myocardial injury caused by chronic sustained hypoxia is a challenging issue with an underlying molecular mechanism that is yet to be clarified. Methionine sulfoxide reductase B3 (MSRB3) protects cells from oxidative damage by catalyzing the stereospecific reduction of methionine-R-sulfoxide residues and reducing intracellular ROS, thus inhibiting cell death. This study aimed to evaluate the role of MSRB3 in regulating chronic sustained hypoxia-induced myocardial injury.

Methods: Human AC16 cardiomyocytes under hypoxia for 48 h were used for in vitro experiments. Ferroptosis was evaluated using flow cytometry and Western blotting. Mitochondrial Oxidative Phosphorylation (OXPHOS) was evaluated by measuring the oxygen consumption rate. A murine model of chronic sustained hypoxia-induced myocardial injury was used to assess the effects of MSRB3 on cardiac dysfunction (evaluated via echocardiography) in vivo. Mitochondrial function was evaluated using DHE staining and biochemical analyses. METTL3-mediated N⁶-methyladenosine (m⁶A) modification of MSRB3 was evaluated using MeRIP-PCR, a dual-luciferase reporter assay, and RIP-PCR.

Results: MSRB3 modulates OXPHOS, thereby affecting cell viability and mitochondrial function in cardiomyocytes while mitigating chronic sustained hypoxia-induced Ferroptosis. Further investigations demonstrated that chronic sustained hypoxia suppresses MSRB3 expression by promoting METTL3-induced m⁶A modification of MSRB3. Both in vivo and in vitro experiments highlighted the influence of MSRB3 m⁶A modification and OXPHOS on chronic sustained hypoxia-induced myocardial injury. Notably, treatment with STM2457 inhibited MSRB3 m⁶A modification, leading to increased MSRB3 expression, which boosted the OXPHOS process, improving cardiomyocyte viability and mitochondrial function under chronic sustained hypoxia conditions, and alleviated cardiac dysfunction and myocardial injury in mice with chronic sustained hypoxia.

Conclusion: Our results suggest that MSRB3 plays a critical role in chronic sustained hypoxia-induced cardiomyocyte Ferroptosis through mitochondrial OXPHOS modulation.

Chronic sustained hypoxia; Ferroptosis; Methionine sulfoxide reductase B3; Mitochondrial dysfunction; Oxidative phosphorylation.