Differential regulation of p90 ribosomal S6 kinase and big mitogen-activated protein kinase 1 by ischemia/reperfusion and oxidative stress in perfused guinea pig hearts

Reactive oxygen species (ROS) activate members of the Src kinase and mitoge n-activated protein kinase superfamily, including big mitogen-activated pro tein kinase 1 (BMK1) and extracellular signal-regulated kinases (ERK1/2), A potentially important downstream effector of ERK1/2 is p90 ribosomal S6 ki nase (p90RSK), which plays an important role in cell growth through the act ivation of several transcription factors, as well as the Na+/H+ exchanger. Previously, we showed that Src regulates BMK1 via a redox-sensitive signali ng pathway. Because ROS are generated during ischemia and reperfusion after ischemia, we assessed the effects of these stimuli (H2O2, ischemia, and re perfusion) in the activation of ERK 1/2, p90RSK, Src, and BMK1 in perfused guinea pig hearts. H2O2 (100 mu mol/L) significantly activated all kinases, Ischemia alone stimulated p90RSK, Src. and BMK1 but not ERK1/2, These resu lts suggest that p90RSK activation through ischemia occurs via a pathway ot her than ERK1/2, A role of Src in ischemia-mediated BMK1 activation was dem onstrated through inhibition with the Src inhibitor 4-amino-5-(4-chlorophen yl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine. Reperfusion after ischemia stimul ated both p90RSK and ERK1/2. In contrast, although ROS increase during repe rfusion after ischemia, the activities of both BMK1 and its upstream regula tor, Src, were markedly attenuated by reperfusion after ischemia. The activ ation of C-terminal Src kinase during ischemia but not during reperfusion s uggests that the attenuation of Src and BMK1 activity by reperfusion was no t regulated by C-terminal Src kinase activity. The antioxidant N-2-mercapto propionylglycine completely inhibited ERK1/2 and p90RSK activation by reper fusion but only partially inhibited ischemia-induced Src and BMK1 activatio n. The present study is the first to show the coregulation of Src and BMK1 by reperfusion after ischemia, which we propose to occur via a novel, ROS-i ndependent pathway.