Time-course Phosphorylation of the Mitogen Activated Protein (MAP) Kinase Group of Signalling Proteins and Related Molecules Following Middle Cerebral Artery Occlusion (MCAO) in Rats

Recovery from the debilitating effects of ischaemic stroke is variable and unpredictable. To maximize patient recovery, a greater understanding of the molecular mechanisms involved in regulating both apoptosis and the repair processes affecting neuronal protection, particularly in the penumbra region, is desirable. We have previously shown, in human subjects, the increased expression of several growth factors soon after stroke, together with appearance of tyrosine phosphorylated proteins, in particular mitogen activated protein (MAP) kinase (ERK1/2). In this paper, we demonstrate a relatively short-lasting (< 12 h), but substantial increase in expression of phosphorylated proteins, in particular, p-JNK (phosphorylated c-Jun N-terminal kinase) and p-ERK1/2 in both the grey matter penumbra and infarcted tissue of rats, following permanent middle cerebral artery occlusion. p-ERK1/2 was associated with neurones and endothelial cells in the vicinity of the infarct while p-JNK was mainly expressed in neurones. Expression of both p-MEK3/6 and p-p38 MAP kinase was also increased in neurones and astroglia, within 1 h of infarction, p-p38 remaining elevated and associated with neurones and in particular with astroglia in the penumbra region for > 4 days. Evidence suggests that short-term activation of these proteins may be detrimental to neuronal survival, while their transient nature makes them unlikely to support angiogenesis, revascularization and reperfusion over a period of days and weeks. On the other hand, short-medium-term up-regulation of neuronal p-JNK, p-c-Jun, p-Stat-1 and p-p38 might be a factor in the regulation of apoptosis. Therapeutic manipulation of phosphorylation/activation of these and other important signalling intermediates might form the basis of an appropriate treatment to maximize revascularization and neuronal protection after ischaemic stroke.