Myocardial ischemia/reperfusion is associated with inflammation, apoptosis and necrosis. During this process, c‐jun N‐terminal kinase is activated in cardiac myocytes resulting in apoptosis.

This study investigates the effects of AS601245, a nonpeptide ATP competitive JNK inhibitor, on infarct size caused by myocardial ischemia/reperfusion in anaesthetized rats. The left descending coronary artery of anaesthetized rats was occluded for 30 min and then reperfused for 3 h. AS601245 was administered 5 min before the end of the ischemia period as an i.v. bolus (1.5, 4.5 or 15 mg kg⁻¹ i.v.) followed by continuous i.v. infusion (18, 55 and 183 μg kg⁻¹ min⁻¹, respectively) during reperfusion. Controls received saline only. 3‐Aminobenzamide, a poly(ADP‐ribose) polymerase inhibitor, was used as reference compound at 10 mg kg⁻¹ i.v. bolus plus 0.17 mg kg⁻¹ min⁻¹ continuous infusion.

AS601245 significantly reduced infarct size at 4.5 mg kg⁻¹ (−44%; P<0.001) and 15 mg kg⁻¹ i.v. (−40.3%; P<0.001) similarly to 3‐aminobenzamide (−44.2%; P<0.001). This protective effect was obtained without affecting hemodinamics or reducing ST‐segment displacement.

The beneficial effects on infarct size correlated well with the reduction of c‐jun phosphorylation (−85%; P<0.001 versus control) and of TUNEL‐positive cells (−82.1%; P<0.001) in post‐ischemic cardiomyocytes. No change in the phosphorylation state of p38 MAPK and ERK in post‐ischemic heart was observed in the presence of AS601245 in comparison to the vehicle‐treated group.

These results demonstrate that blocking the JNK pathway may represent a novel therapeutic approach for treating myocardial ischemia/reperfusion‐induced cardiomyocyte death.