Regular dipyridamole therapy produces sustained protection against cardiac ischemia-reperfusion injury: is it time to revisit PARIS?

BACKGROUND: Increased activated Akt and eNOS expression coincide with this persistent cardioprotection. Emergent coronary reperfusion therapies are rarely carried out before considerable myocardial injury has occurred. Moreover, reperfusion after prolonged ischemia produces paradoxical ischemia-reperfusion injury, attenuating the efficacy of reperfusion therapies. This has provided impetus for identifying chronic therapies to protect against ischemia-reperfusion injury in those at risk. We previously found that regular dipyridamole therapy produces a chronic preconditioning-like effect mediated through adenosine A1 receptors. METHODS: To determine how long this chronic preconditioning effect of dipyridamole remains present after discontinuing therapy, guinea pigs received 4 mg/kg/day in their water for 6 weeks. Ischemia-reperfusion was performed at 0, 2, 3, and 4 days after dipyridamole discontinuation (0 day, 2 days, 3 days and 4 days; n=8 per group). Left ventricular developed pressure (LVDP), end-diastolic pressure (LVEDP), coronary flow (CF), infarct size, and western blot analyses for Akt and endothelial nitric oxide synthase (eNOS) were studied. RESULTS: After ischemia-reperfusion, 0 day, 2 days and 3 days, but not 4 days, had significantly higher LVDP and lower LVEDP compared to control. Myocardial infarct size was significantly reduced at 0 day, 2 days and 3 days, but not 4 days, compared to control. Western blot analyses demonstrated upregulation of phospho-Akt and phospho-eNOS expression at 0 day, 2 days, and 3 days, but not 4 days. CONCLUSIONS: A chronic preconditioning-like cardioprotection by regular dipyridamole treatment persists for 3 days after discontinuing therapy. Increased activated Akt and eNOS expression may play a role in this persistent cardioprotection