Reactive oxygen species (ROS) activate members of the
Src kinase and
mitogen-activated protein kinase superfamily, including big
mitogen-activated protein kinase 1 (BMK1) and
extracellular signal-regulated kinases (ERK1/2). A potentially important downstream effector of ERK1/2 is
p90 ribosomal S6 kinase (p90RSK), which plays an important role in cell growth through the activation of several
transcription factors, as well as the
Na(+)/H(+) exchanger. Previously, we showed that Src regulates BMK1 via a redox-sensitive signaling pathway. Because ROS are generated during
ischemia and reperfusion after
ischemia, we assessed the effects of these stimuli (H(2)O(2),
ischemia, and reperfusion) in the activation of ERK1/2, p90RSK, Src, and BMK1 in perfused guinea pig hearts. H(2)O(2) (100 micromol/L) significantly activated all
kinases.
Ischemia alone stimulated p90RSK, Src, and BMK1 but not ERK1/2. These results suggest that p90RSK activation through
ischemia occurs via a pathway other than ERK1/2. A role of Src in
ischemia-mediated BMK1 activation was demonstrated through inhibition with the Src inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]
pyrimidine. Reperfusion after
ischemia stimulated both p90RSK and ERK1/2. In contrast, although ROS increase during reperfusion after
ischemia, the activities of both BMK1 and its upstream regulator, Src, were markedly attenuated by reperfusion after
ischemia. The activation of
C-terminal Src kinase during
ischemia but not during reperfusion suggests that the attenuation of Src and BMK1 activity by reperfusion was not regulated by
C-terminal Src kinase activity. The
antioxidant N-2-mercaptopropionylglycine completely inhibited ERK1/2 and p90RSK activation by reperfusion but only partially inhibited
ischemia-induced Src and BMK1 activation. 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-independent pathway.