Epigenetic blockade of SOD2 boosts mitochondria ROS and cytoskeleton remodelling in cardiac fibrosis

AIMS: Mitochondria reactive oxygen species (ROS) play a critical role in the progression of cardiac fibrosis. Nonetheless, the role of mitochondria ROS in cardiac fibroblasts cytoskeletal remodelling and ferroptosis have not been explored. However, little is known about the epigenetic mechanisms through mitochondria ROS, cytoskeletal remodelling and ferroptosis in cardiac fibrosis (CF). METHODS AND RESULTS: Cardiac fibroblast-specific methyl-CpG-binding protein 2 (MeCP2)-deficient mice and wild type mice were treated with Isoprenaline to induce replacement cardiac fibrosis. AAV9 carrying fibroblast-specific POSTN promoter-driven small hairpin RNA targeting superoxide dismutase 2(SOD2), and overexpression of SOD2 were administered to investigate their vital roles in cardiac fibrosis. Biochemical and histological analyses were performed to determine how MeCP2 transcriptional repression of SOD2 through mitochondria ROS, cytoskeletal remodelling and ferroptosis in cardiac fibrosis. The reconstitution of SOD2 in MeCP2-deficient cardiac fibroblasts and mouse hearts was performed to study its effect on mitochondria ROS, cytoskeletal remodelling, ferroptosis and fibrosis. Human heart tissue from patients with atrial fibrillation is used for translational validation. Downregulation of SOD2 in replacement cardiac fibrosis is associated with increased mitochondria ROS, decreased mitochondrial membrane potential (MMP), and enhanced cytoskeletal remodelling. Fibroblasts-specific SOD2 deficiency enhances mitochondrial ROS, decreases MMP, promotes cytoskeletal remodelling and fibroblasts ferroptosis, leading to cardiac fibrosis. Specifically, SOD2 downregulation is associated with elevated CpG 5mC levels. Mechanistically, methyl-CpG binding protein MeCP2 recognizes bond to SOD2 CpG 5mC and recruits H3K27me3, resulting in SOD2 transcriptional repression. MeCP2 knockdown rescues SOD2 inhibition and mitigates cytoskeletal remodelling, ferroptosis and fibrosis. In addition, human atrial fibrillation fibrotic atrial tissue exhibits signs of MeCP2 upregulation, SOD2 inhibition, elevated mitochondria ROS, and ferroptosis. CONCLUSION: We demonstrated a novel epigenetic mechanism through which silencing of SOD2 boosts mitochondria ROS, cytoskeletal remodelling, ferroptosis and promotes cardiac fibrosis. Our findings provide new insights for the development of preventive measures for replacement cardiac fibrosis.