Ischaemic and pharmacological preconditioning is associated with attenuation of p38 MAPK activation during sustained ischaemia and reperfusion

The stress kinase, p38 mitogen activated protein kinase (p38 MAPK), is known to be activated by both ischaemia and reperfusion. Whether this activation is beneficial or deleterious is still a matter of debate. The aims of this study were to (i) evaluate the activation pattern of p38 MAPK during a multi-cycle preconditioning protocol, during sustained (index) ischaemia and during reperfusion (ii) use transient beta-adrenergic stimulation to mimic ischaemic preconditioning and to study its effects on p38 MAPK activation and (iii) re-evaluate the effects of p38 MAPK blockade by SB 203580 on cardioprotection elicited by ischaernic preconditioning as well as by beta-adrenergic preconditioning. The isolated perfused working rat heart was subjected to a preconditioning protocol of 3 X 5 min global ischaemia or 5 min isoproterenol (10(-7) M) followed by 5min washout. All hearts were then subjected to 25min global ischaemia and 30min reperfusion during which time mechanical function was monitored. Hearts were freeze-clamped at different time intervals for subsequent analysis of p38 MAPK activation using Western blotting and a p38 MAPK phospho-antibody (Thr 180/Tyr 182). The results showed that p38 MAPK was activated transiently during a multi-cycle ischaernic preconditioning protocol and this was associated with attenuation of its kinase activity during both sustained ischaemia and reperfusion when compared with non-preconditioned hearts. beta-adrenergic preconditioning induced a similar pattern of attenuated p38 MAPK activation during sustained ischaemia and reperfusion. In all cases attenuation of p38 MAPK activation during ischaemia and reperfusion was associated with improved mechanical recovery during reperfusion. Using SB 203580 it was shown that p38 MAPK activation was not required as a trigger for ischaemic preconditioning, whereas it was a prerequisite for beta-adrenergic preconditioning. Conclusions: Attenuation of p38 MAPK activation during sustained ischaemia and reperfusion is always associated with improved functional recovery during reperfusion, indicating that activation of this kinase is detrimental to the ischaemic heart.