Adenosine A(1) receptor induced delayed preconditioning in rabbits - Induction of p38 mitogen-activated protein kinase activation and Hsp27 phosphorylation via a tyrosine kinase- and protein kinase C-dependent mechanism

Transient adenosine A(1) receptor (A(1)R) activation in rabbits induces del ayed preconditioning against myocardial infarction 24 to 72 hours later. Th e cellular mechanisms downstream of A(1)R mediating this delayed cardioprot ection have not been elucidated. This study examined the role of protein ki nase C (PKC) and tyrosine kinases (TKs) in the signaling cascade mediating A(1)R-induced late preconditioning in rabbits. The small heat shock protein Hsp27 has been shown to confer cytoskeletal protection when in the phospho rylated state. We therefore also evaluated the potential role of the p38 mi togen-activated protein kinase (p38 MAPK) and Hsp27 as distal mediators of A(1)R-induced delayed preconditioning, Pharmacological preconditioning of r abbits with the selective A(1) agonist 2-chloro-N-6-cyclopentyladenosine (C CPA; 100 mu g/kg) significantly reduced myocardial infarct size compared wi th control animals, after 30-minute regional ischemia/2-hour reperfusion in vivo 24 hours later (23.7+/-3.1 versus 43.0+/-4.1%; P<0.05). This delayed protection was abrogated by prior inhibition of either PKC with chelerythri ne chloride (5 mg/kg) or of TKs with lavendustin A (1.3 mg/kg), suggesting that both PKC and TK are crucial for the development of delayed preconditio ning after A(1) receptor activation in the rabbit. Myocardial tissue extrac ts obtained 24 hours after CCPA treatment were analyzed for p38 MAPK cataly tic activity using an in vitro kinase assay. This showed an almost 7-fold i ncrease in p38 MAPK activity in myocardial samples pretreated with CCPA com pared with control hearts. Two-dimensional gel electrophoresis revealed an increase in the phosphorylated isoforms of Hsp27 in hearts pretreated with CCPA compared with control hearts. Prior inhibition of either PKC or TK pre vented the CCPA-induced increase in p38 MAPK activity and phosphorylation o f Hsp27. This study identifies new components of the signaling mechanism of A(1)R-induced delayed preconditioning. Our results suggest an important ro le for both PKC and TK as mediators of late preconditioning against infarct ion after A(1)R activation and, although correlative, point to the p38 MAPK /Hsp27 pathway as a potential distal effector of this protection.