ALKBH5 alleviates hypoxia postconditioning injury in aged cardiomyocytes by regulating STAT3

Ischemic postconditioning (I/Post) reduces ischemia/reperfusion (I/R) injury by activating endogenous cardioprotection mechanisms, such as the JAK/STAT3 and PI3K/Akt pathways, which offer a traditional approach to myocardial protection. According to the previous study, cardioprotection by I/Post may lost in aged mice, and in our previous research, hypoxic postconditioning (H/Post) lacked a protective effect in senescent cardiomyocytes, which was associated with low expression of long noncoding RNA (lncRNA) H19. The N6-methyladenosine (m 6 A) modification is a dynamic and reversible process that has been confirmed plays a role in cardiovascular diseases. However, the mechanisms of m 6 A modification in myocardial I/Post remains to be explored. Neonatal cardiomyocytes were isolated from 2-day-old Sprague Dawley rats and senescence was induced by D-galactose, followed by stimulation of hypoxia-reoxygenation (H/R) and H/Post. Hypoxic injury was evaluated by cell viability and the Bcl-2/Bax protein ratio. Total m 6 A levels were measured using a colorimetric m 6 A RNA Methylation Quantification Kit and the m 6 A modified and differentially expressed mRNA was determined by methylated RNA immunoprecipitation (MeRIP). We found that H/Post increased m 6 A methylation and decreased RNA mA demethylase alkB homolog 5 (ALKBH5) expression in aged cardiomyocytes. Furthermore, ALKBH5 knockdown exacerbated injury following H/Post in senescent cardiomyocytes. Additionally, ALKBH5 regulated STAT3 expression by mediating its m 6 A modification and lncRNA H19/miR-124-3p. ALKBH5 also alleviated the H/Post injury induced by the low expression of STAT3 in aged cardiomyocytes.