PAR-2 activation at the time of reperfusion salvages myocardium via an ERK1/2 pathway in in vivo rat hearts

PAR-2 activation at the time of reperfusion salvages myocardium via an ERK1/2 pathway in in vivo rat hearts. Am J Physiol Heart Circ Physiol 293: H2845a??H2852, 2007. First published August 24, 2007; doi:10.1152/ajpheart.00209.2007.a?? Protease-activated receptor-2 (PAR-2) may have proinflammatory effects in some tissues and protective effects in other tissues. The role of PAR-2 in in vivo myocardial ischemia-reperfusion has not yet been determined. This study tested the hypothesis that PAR-2 activation with the PAR-2 agonist peptide SLIGRL (PAR-2 AP) reduces myocardial infarct size when given at reperfusion in vivo, and this cardioprotection involves the ERK1/2 pathway. Anesthetized rats were randomly assigned to the following groups with 30 min of regional ischemia and 3 h reperfusion: 1) control with saline; 2) vehicle (DMSO); 3) PAR-2 AP, 1 mg/kg given intravenously 5 min before reperfusion; 4) scrambled peptide (SP), 1 mg/kg; 5) the ERK1/2 inhibitor PD-98059 (PD), 0.3 mg/kg given 10 min before reperfusion; 6) the phosphatidylinositol 3-kinase inhibitor LY-294002 (LY), 0.3 mg/kg given 10 min before reperfusion; 7) PD PAR-2 AP, 0.3 mg/kg PD given 5 min before PAR-2 AP; 8) LY PAR-2 AP, 0.3 mg/kg LY given 5 min before PAR-2 AP; 9) chelerythrine (Chel) alone, 5 mg/kg given 10 min before reperfusion; and 10) Chel PAR-2 AP, Chel was given 5 min before PAR-2 AP (10 min before reperfusion). Activation of ERK1/2, ERK5, Akt, and the downstream targets of ERK1/2 [P90 RSK and bcl-xl/bcl-2-associated death promoter (BAD)] was determined by Western blot analysis in separate experiments. PAR-2 AP significantly reduced infarct size compared with control (36 2 vs. 53 1 , P 0.05), and SP had no effect on infarct size (53 3 ). PAR-2 AP significantly increased phosphorylation of ERK1/2, p90RSK, and BAD but not Akt or ERK5. Accordingly, the infarct-size sparing effect of PAR-2 AP was abolished by PD (PAR-2 AP, 36 2 vs. PD PAR-2 AP, 50 1 ; P 0.05) and by Chel (Chel PAR-2 AP, 58 2 ) but not by LY (PAR-2 AP, 36 2 vs. LY PAR-2 AP, 38 3 ; P 0.05). Therefore, PAR-2 activation is cardioprotective in the in vivo rat heart ischemia-reperfusion model, and this protection involves the ERK1/2 pathway and PKC.