In response to
cerebral ischemia, neurons activate survival/repair pathways in addition to death cascades. Activation of
cyclic AMP-response-element-binding protein (CREB) is linked to neuroprotection in experimental animal models of
stroke. However, a role of the
mitogen-activated protein kinase/
extracellular signal-regulated kinase kinase (MAPK/ERK or
MEK), an upstream
kinase for CREB, and its relation to CREB phosphorylation in neuroprotection in
cerebral ischemia has not been delineated. Previously, we reported that N-acetyl-O-
methyldopamine (
NAMDA) significantly protected CA1 neurons after transient forebrain
ischemia [J Neurosci 19 (1999b) 87.8]. The current study is to investigate whether
NAMDA-induced neuroprotection occurs via the activation of ERK and its downstream effector, CREB.
NAMDA induced ERK1/2 and CREB phosphorylation with increased survival of HC2S2 hippocampal neurons subjected to
oxygen-
glucose deprivation. These effects were reversed by
U0126, a
MEK kinase inhibitor. Similarly, animals treated with
NAMDA following
ischemia showed increased ERK and CREB phosphorylation in the CA1 subregion of the hippocampus during early reperfusion period with increased number of surviving neurons examined 7 days following
ischemia. The
NAMDA-induced neuroprotection was abolished by
U0126 administered shortly after reperfusion. The results showed that the ERK-CREB signaling pathway might be involved in
NAMDA-induced neuroprotection following transient global
ischemia and imply that the activation of the pathway in neurons may be an effective therapeutic strategy to treat
stroke or other neurological syndromes.