Recent studies suggest that
ischemia activates Src and members of the
mitogen-activated
protein (MAP)
kinase superfamily and their downstream effectors, including
big MAP kinase 1 (BMK1) and
p90 ribosomal S6 kinase (p90RSK). It has also been reported that
adenosine is released during
ischemia and involved in triggering the protective mechanism of ischemic preconditioning. To assess the roles of Src and
adenosine in
ischemia-induced MAP
kinases activation, we utilized the Src inhibitor PP2 (4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]
pyrimidine) and the
adenosine receptor antagonist 8-(p-sulfophenyl)
theophylline (SPT) in perfused guinea pig hearts. PP2 (1 microm) inhibited
ischemia-induced Src, BMK1 and JNK activation but not JAK2 and p38 activation. SPT inhibited
ischemia-mediated p38 and JNK activation. These results demonstrate that
Src family kinase and
adenosine regulate MAP
kinases by parallel pathways. Preconditioning significantly improved both recovery of developed pressure and dp/dt in isolated guinea pig hearts. Since the protective effect of preconditioning was blocked by PP2 (1 microm) and SPT (50 microm), we next investigated the regulation of Src, MAP
kinases and p90RSK during preconditioning. The activity and time course of ERK1/2 was not changed, but p90RSK activation by reperfusion was completely inhibited by preconditioning. In contrast, the activation by
ischemia of Src, BMK1, p38 and JNK was significantly faster in preconditioned hearts. Maximal BMK1 activation by
ischemia was also significantly enhanced by preconditioning. These data suggest important roles for
Src family kinases and
adenosine in mediating preconditioning, and suggest specific roles for individual MAP
kinases in preconditioning.