Toll-like receptor (TLR)9 ligand CpG-oligodeoxynucleotide (CpG-ODN) exerts preconditioning in myocardial ischemia/reperfusion. We hypothesized a postconditioning effect of CpG-ODN in a murine closed-chest model of myocardial infarction.

C57BL/6 (12 weeks, male, WT) mice were instrumented at the left anterior descending artery, then allowed 5d of recovery before 30 min ischemia. Treatments comprised: 1) PBS: 250 μl phosphate buffer solution intraperitoneally 5 min before reperfusion and 2) IPC (ischemic postconditioning): 3 twenty-second reperfusion and occlusion episodes at the end of ischemia 3) CpG-ODN: 1668 thioate 0.2 μmol/kg BW intraperitoneally 5 min before reperfusion. Infarct size was assessed via triphenyltetrazolium chloride (TTC) staining after 2 and 24 h reperfusion. Myocardial mRNA-expression of cytokines was measured using real-time PCR after 2 h reperfusion. Phosphatidylinositol-3 kinase (PI3K)-inhibitor wortmannin was injected intraperitoneally in WT 15 min before postconditioning and PBS in each group. Cardiac function in WT was assessed with a left-ventricular pressure-volume catheter at 24 h reperfusion.

Following 30 min ischemia and 2 h reperfusion, infarct size was diminished by 90% in WT postconditioned with CpG-ODN (2.4 ± 1.55 IS/AAR%) and IPC (1.98 ± 1.03 IS/AAR%) compared to PBS mice (23.2 ± 3.97 IS/AAR%). Infarct size increased following 24 h reperfusion but the differences remained robust. Expression of TNF-α and IL-10 was increased in CpG-ODN. Wortmannin abolished the postconditioning effect of CpG-ODN and IPC. Ejection fraction and preload-recruitable stroke work were significantly greater in CpG-ODN mice.

CpG-ODN confers postconditioning via activation of TLR9. Cardiac function is preserved following CpG-ODN postconditioning. The PI3K -inhibitor wortmannin attenuates CpG-ODN postconditioning.