Dipyridamole with Low-Dose Aspirin Augments the Infarct Size-Limiting Effects of Simvastatin

Statins protect against ischemia-reperfusion injury and limit myocardial infarct size (IS). This effect is dependent on increased generation of adenosine by ecto-5' nucleotidase and downstream activation of cyclooxygenase-2 (COX2). Dipyridamole (DIP) augments the IS-limiting effects of statins by blocking the cellular reuptake of adenosine; whereas aspirin (ASA) attenuates the effect by inhibiting COX2. We studied the effect of acute administration of DIP, ASA and their combination on the IS-limiting effect of simvastatin (SIM). Rats received oral SIM (10 mg/kg/d) or vehicle for 3 days. Rats underwent 30 min of coronary artery occlusion and 4 h reperfusion. After 5 min of ischemia rats received i.v. DIP (5 mg/kg), ASA (20 mg/kg or 2 mg/kg) or DIP+ASA (2 mg/kg) or vehicle alone. Ischemia area at risk (AR) was assessed by blue dye and IS by TTC. Myocardial samples were analyzed for the activation of Akt, ERK 1/2, endothelial nitric oxide synthase (eNOS), and cyclic-AMP-response-element-binding-protein (CREB). SIM limited IS. High- or low-dose ASA alone had no effect on IS. DIP alone or with low-dose ASA significantly reduced IS. Low-dose ASA did not attenuate the SIM effect, whereas high-dose ASA completely blocked the effect. The combination of DIP+low-dose ASA+SIM resulted in the smallest IS. Both SIM and DIP+low-dose ASA augmented Akt phosphorylation and their effect was additive. Both SIM and DIP+low-dose ASA augmented eNOS, ERK 1/2 and CREB phosphorylation. During acute myocardial ischemia, DIP alone or with low-dose ASA limits IS and does not attenuate the IS-limiting effect of SIM as high-dose ASA.