PKC-dependent activation of p44/p42 MAPKs during myocardial ischemia-reperfusion in conscious rabbits

Abstract

Using conscious rabbits, we examined the effect of ischemic preconditioning (PC) on p44 and p42 mitogen-activated protein kinases (MAPKs). We found that both isoforms contribute significantly to total MAPK activity in the heart (in-gel kinase assay: p44, 59 ± 1%; p42, 41 ± 1%). Ischemic PC (6 cycles of 4-min occlusion/4-min reperfusion) elicited a pronounced increase in total cellular MAPK activity (+89%). This increase, which occurred exclusively in the nuclear fraction, was contributed by both isoforms (in-gel kinase assay: p44, +97%; p42, +210%) and was accompanied by migration of the two proteins from the cytosolic to the nuclear compartment. In control rabbits, MAPK kinase (MEK)1 and MEK2, direct activators of p44 and p42 MAPKs, were located almost exclusively in the cytosolic fraction. Ischemic PC induced a marked increase in cytosolic MEK activity (+164%), whereas nuclear MEK activity did not change, indicating that MEK-induced activation of MAPKs occurred in the cytosolic compartment. Activation of MAPKs after ischemic PC was completely blocked by the protein kinase C (PKC) inhibitor chelerythrine. Selective overexpression of PKC-ε in adult rabbit cardiomyocytes induced activation of both p44 and p42 MAPKs and reduced lactate dehydrogenase release during simulated ischemia-reperfusion, which was abolished by the MEK inhibitor PD-98059. The results demonstrate that 1) ischemic PC induces a rapid activation of p44 and p42 MAPKs in hearts of conscious rabbits; 2) the mechanism of this phenomenon involves activation of p44 and p42 MAPKs in the cytosol and their subsequent translocation to the nucleus; and 3) it occurs via a PKC-mediated signaling pathway. The in vitro data implicate PKC-ε as the specific isoform responsible for PKC-induced MAPK activation and suggest that p44/p42 MAPKs contribute to PKC-ε-mediated protection against simulated ischemia. The results are compatible with the hypothesis that p44 and p42 MAPKs may play a role in myocardial adaptations to ischemic stress.

H2O2-induced Ca2+overload in NRVM involves ERK1/2 MAP kinases: role for an NHE-1-dependent pathway

“…ERK1/2 are activated during I/R in conscious rabbits (29), and H 2 O 2 and hypoxia activate members of the MAPK family, including p38, c-jun NH 2 -terminal kinase, and ERK1/2 (1,23,31). We have also shown that ERK1/2 are responsible for H 2 O 2 -stimulated NHE-1 activation in NRVM (31) and for NHE-1 phosphorylation in the I/R rat myocardium (26).…”

Signal Pathway Involved in the Development of Hypoxic Preconditioning in Rat Hepatocytes

“…33 Recently, several studies have examined the potential role of MAPKs, including p46/p54 JNK/SAPKs, p42/p44 ERKs, and p38 MAPK in the development of myocardial precondi- tioning. [17][18][19]33,34 In particular, there is evidence that selective enhancement of PKC-activity in cardiac myocytes is coupled with the stimulation of either JNKs and ERKs. 18,19 In preconditioned hepatocytes we have observed that interfering with ERK activation does not affect cytoprotection, whereas SB203580, a specific inhibitor of p38 MAPK 36 completely abolishes the effects of preconditioning.…”

“…One experiment representative of 4. shown that PKC activation is associated with the stimulation of a number of protein kinases, including stress-activated protein kinases (SAPKs), also known as c-Jun N-terminal kinases (JNKs), extracellularly responsive kinases (ERKs), and p38 mitogen-activated protein kinase (p38 MAPK). [17][18][19] Hepatocyte treatment with PD098059 (20 mol /L), a blocker of ERK activation by MAPkinase-Kinase 1 (MEK), did not interfere with preconditioning (Fig. 6).…”

The Mechanism of Heat Shock Activation of ERK Mitogen-activated Protein Kinases in the Interleukin 3-dependent ProB Cell Line BaF3

“…Although this Ras-independent, PKC-dependent mechanism has only been infrequently reported to follow stimulation with a stress factor (50,51), the role of PKC was nevertheless investigated. We have subsequently eliminated participation of PKC in heat shock signaling when a PKC-specific chemical inhibitor, bisindolylmaleimide I, and down-regulation of phorbol ester-sensitive PKC isoforms upon prolonged TPA exposure failed to attenuate consistently heat shock-stimulated ERK MAPK activity (data not shown).…”