Protection against myocardial ischaemia/reperfusion injury by PPAR-alpha activation is related to production of nitric oxide and endothelin-1

Ligands of peroxisome proliferator-activated receptor alpha (PPAR-alpha) have been shown to reduce ischaemia/reperfusion injury. The mechanisms behind this effect are not well known. We hypothesized that activation of PPAR-alpha exerts cardioprotection via a mechanism related to nitric oxide (NO) and endothelin-1 (ET-1). Five groups of anaesthetized open-chest Sprague-Dawley rats were given the PPAR-alpha agonist WY 14643 1 mg/kg (WY; n = 7), dimethyl sulfoxide (DMSO, vehicle for WY; n = 6), the combination of WY and the NO synthase inhibitor N-nitro-L-arginine (L-NNA, 2 mg/kg) (n = 7), L-NNA only (n = 8) or 0.9% sodium chloride (NaCl, vehicle for DMSO and L-NNA; n = 8) i.v. before a 30 min period of coronary artery occlusion followed by 2 h of reperfusion. Infarct size (IS), eNOS and iNOS protein and ET-1 mRNA expression were determined. There were no haemodynamic differences between the groups during the experiment. The IS was 78 +/- 3% of the area at risk in the DMSO group and 77 +/- 2% in the NaCl group (P = NS). WY reduced IS to 56 +/- 3% (P < 0.001 vs. DMSO group). When WY was administered in combination with L-NNA the cardioprotective effect was abolished (IS 73 +/- 3%, P < 0.01 vs. WY 14643). L-NNA did not affect IS per se (78 +/- 2%, P = NS). The expression of eNOS but not iNOS protein in ischaemic myocardium from rats was increased in the group given WY (P < 0.05). ET-1 mRNA levels were lower in the ischaemic myocardium following WY administration. The results suggest that the PPAR-alpha activation protects the rat myocardium against ischaemia/ reperfusion injury via a mechanism related to production of NO, and possibly ET-1.