Ischaemic preconditioning regulates cardiac transcriptome via DNA methylation conferring cardio-protection from ischaemic reperfusion injury.

AIMS: Myocardial ischaemic preconditioning (IPC) increases myocardial ability to withstand ischaemic injury. Myocardial stunning is a reversible dysfunction, while necrosis results in irreversible cell death. The link between IPC, stunning, and necrosis remains unclear. This study aimed to utilize a novel 13.5-min ischaemia-reperfusion (I/R) rat model, distinct from conventional I/R models, to identify transcriptomic changes associated with IPC and investigate the role of DNA methylation in regulating these changes, particularly in relation to myocardial stunning and necrosis. METHODS AND RESULTS: A novel rat model of cardiac I/R injury was used, with IPC induced by two 5-min ischaemia-reperfusion cycles followed by 13.5-min of ischaemia, and a control group undergoing 13.5-min of ischaemia without IPC. Myocardial samples were collected at early (T1) and 4-h (T2) post-reperfusion, representing stunned myocardium in the IPC group and necrosis in the control group. RNA sequencing, DNA methyltransferase (DNMT) activity assay, Chromatin immunoprecipitation (ChIP), and DNA methylation analyses were performed. IPC reprogrammed the cardiac transcriptome, with 53 genes differentially expressed at T1 and 166 at T2, including key regulators of inflammation (Nfkbia), DNA repair (Gadd45b, Parp14), and stress responses (Cebpd, Jun). IPC reduced global DNMT activity, promoting hypomethylation of protective genes like Cebpd, Nfkbia, Gadd45b, Jun, and Aplod1 at T1, while selectively hypermethylating maladaptive genes like Tmem200c and Fgfr4. ChIP assays revealed reduced Dnmt1 binding at Jun and Parp14 promoters, aligning with increased protein levels. CONCLUSION: IPC re-programmes the cardiac transcriptome through dynamic DNA methylation, enhancing myocardial resilience while increasing stunning as an adaptive mechanism to limit necrosis.