STIMULATION OF STRESS-REGULATED MITOGEN-ACTIVATED PROTEIN-KINASES (STRESS-ACTIVATED PROTEIN-KINASES C-JUN N-TERMINAL KINASES AND P38-MITOGEN-ACTIVATED PROTEIN-KINASES) IN PERFUSED RAT HEARTS BY OXIDATIVE AND OTHER STRESSES

''Stress regulated'' mitogen-activated protein kinases (SR-MAPKs) comp rise the stress activated protein kinases (SAPKs)/c-Jun N-terminal kin ases (JNKs) and the p38-MAPKs. In the perfused heart, ischemia/reperfu sion activates SR-MAPKs. Although the agent(s) directly responsible is unclear, reactive oxygen species are generated during ischemia/reperf usion. We have assessed the ability of oxidative stress (as exemplifie d by H2O2) to activate SR-MAPKs in the perfused heart and compared it with the effect of ischemia/reperfusion. H2O2 activated both SAPKs/JNK s and p38-MAPK. Maximal activation by H2O2 in both cases was observed at 0.5 mM. Whereas activation of p38-MAPK by H2O2 was comparable to th at of ischemia and ischemia/reperfusion, activation of the SAPKs/JNKs was less than that of ischemia/reperfusion. As with ischemia/reperfusi on, there was minimal activation of the ERK MAPK subfamily by H2O2. MA PK-activated protein kinase 2 (MAPKAPK2), a downstream substrate of p3 8-MAPKs, was activated by H2O2 to a similar extent as with ischemia or ischemia/reperfusion. In all instances, activation of MAPKAPK2 in per fused hearts was inhibited by SB203580, an inhibitor of p38-MAPKs. Per fusion of hearts at high aortic pressure (20 kilopascals) also activat ed the SR-MAPKs and MAPKAPK2. Free radical trapping agents (dimethyl s ulfoxide and N-t-butyl-alpha-phenyl nitrone) inhibited the activation of SR-MAPKs and MAPKAPK2 by ischemia/reperfusion. These data are consi stent with a role for reactive oxygen species in the activation of SR- MAPKs during ischemia/reperfusion.