Role of G proteins and modulation of p38 MAPK activation in the protectionby nitric oxide against ischemia-reoxygenation injury

Protein kinase C (PKC)-mediated regulation of the mitogen-activated protein kinases (MAPK) may play a role in the protection afforded by ischemic prec onditioning (PC). Nitric oxide (NO) can influence MAPK activation via inter action with PKC or farnesylation of low-molecular-weight (LMWT) G proteins. However, we have recently reported the mechanism of NO-induced cardioprote ction to be a PKC-independent process. Therefore, we investigated the role of LMWT G proteins and MAPK signaling in NO-induced cardioprotection agains t simulated ischemia-reoxygenation (SI-R) injury. Neonatal rat cardiomyocyt es treated for 90 min with the NO donor S-nitroso-N-acetyl-L,L-penicillamin e (SNAP) 1 mM were protected against 6 h of SI (hypoxic conditions at 37 de greesC with 20 mM lactate, 16 mM KCl at pH 6:2) and 24 h reoxygenation unde r normal culture conditions. NO-induced protection was blocked by the G pro tein inhibitor alpha -hydroxyfarnesylphosphonic acid (alpha HFP) 10 muM. We studied the time course of p42/44 and p38 MAPK dual-phosphorylation hourly during SI using phosphospecific antibodies. p38 was phospholylated during SI and the peak phosphorylation was significantly delayed by SNAP pretreatm ent. The p38 inhibitor SB203580 1 muM, given during SI, protected against i njury. Thus the delay in peak p38 activation may contribute to, rather than be the effect of, NO-induced cardioprotection. We have shown that p38 beta does not contribute to the total p38 signal in our extracts. Thus there is no detectable beta isoform. We conclude that the main isoform present in t hese cells and thought to be responsible for the observed phenomenon, is th e a isoform. (C) 2001 Academic Press.