Sustained activation of p42/p44 mitogen-activated protein kinase during recovery from simulated ischaemia mediates adaptive cytoprotection in cardiomyocytes
A. Punn et al., Sustained activation of p42/p44 mitogen-activated protein kinase during recovery from simulated ischaemia mediates adaptive cytoprotection in cardiomyocytes, BIOCHEM J, 350, 2000, pp. 891-899
Delayed cytoprotection (preconditioning) occurs 24 h after sublethal simula
ted ischaemia and reperfusion (SI/R) in neonatal rat ventricular cardiomyoc
ytes, SI/R was used to investigate the role of activation of mitogen-activa
ted protein kinases (MAPKs), stress-activated protein kinases (SAPKs) and p
hosphoinositide 3-kinase-dependent protein kinase B (PKB)/Akt in cytoprotec
tion. SI resulted in transient dual (Thr/Tyr) phosphorylation of p42/p44-MA
PK and p38-MAPK, weak phosphorylation of p46/p54-SAPK, but no phosphorylati
on of PKB. 'Reperfusion' caused further transient phosphorylation of p38-MA
PK, but sustained phosphorylation of p42/p44-MAPK (lasting 4 h) and of Ser(
473) of PKB (lasting 2 h). Furthermore, SI/R (24h) induced delayed protecti
on against lethal SI, as determined by an increase in cell viability {biore
duction of MTT [3-(4, 5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromid
e]} and a decrease in cell injury (release of creatine kinase). Both protec
tion and phosphorylation of p42/p44-MAPK were blocked by the MEK-1/2 (MAPK/
Erk kinase-1/2) inhibitor PD98059 (50 mu M) when given during SI/R, but not
when given during SI alone. The p38-MAPK inhibitor SB203580 (10 mu M) bloc
ked the p38-MAPK-dependent phosphorylation of activating transcription fact
or 2 in vitro, and the phosphoinositide 3-kinase inhibitor wortmannin (100
nM) blocked PKB phosphorylation on Ser(473). However, neither SB203580 nor
wortmannin had any effect on delayed protection. Therefore sustained activa
tion of p42/p44-MAPK during simulated 'reperfusion' following sublethal SI
mediates preconditioning in cardiomyocytes independently of transient activ
ation of p38-MAPK or sustained activation of PKB.