Targeting the ALKBH5-NLRP3 positive feedback loop alleviates cardiomyocyte pyroptosis after myocardial infarction

Several studies have associated the epitranscriptomic RNA modification of N6-methyladenosine (m⁶A) with cardiovascular diseases; however, how m⁶A modification affects cardiomyocyte pyroptosis after myocardial infarction (MI) remains unknown. Here, we showed that AlkB homolog 5 (ALKBH5), an m⁶A demethylase, is crucial in cardiomyocyte pyroptosis after MI. We used MI rat and mouse models, a cell hypoxia model of rat primary cardiomyocytes (RCMs), and rat embryonic ventricle cell line (H9c2) to explore the functional role of m⁶A modification and ALKBH5 in the heart and cardiomyocytes. Using plasmids and small interfering RNAs, the expressions of ALKBH5 and NOD-like receptor family pyrin domain-containing 3 (NLRP3) were determined to study their functions in regulating cardiomyocyte m⁶A and pyroptosis, respectively. We characterized the role of ALKBH5, which exhibited elevated expression in the ischemic heart tissue of rats and mice and hypoxic cardiomyocytes (RCMs and H9c2 cells). ALKBH5 knockdown alleviated hypoxia-induced H9c2 cell pyroptosis by inhibiting NLRP3 inflammasome activation, whereas ALKBH5 overexpression had the opposite effect. NLRP3 knockdown alleviated hypoxia-induced H9c2 cardiomyocyte pyroptosis by inhibiting ALKBH5 expression, whereas NLRP3 overexpression had the opposite effect. Mechanistically, ALKBH5 mediated m⁶A modification of NLRP3 mRNA in an IGF2BP2-dependent manner, and NLRP3, as a nuclear transcription factor, regulated the ALKBH5 transcription process. Targeting the ALKBH5-NLRP3 loop with the small-molecule inhibitors alleviated cardiomyocyte pyroptosis. Our results highlight that ALKBH5-NLRP3 forms a positive feedback loop that promotes cardiomyocyte pyroptosis after MI. Therefore, inhibiting the ALKBH5-NLRP3 loop is a potential strategy for treating cardiovascular diseases.