Neuronal Activation of NF-κB Contributes to Cell Death in Cerebral Ischemia

The transcription factor NF-κB is a key regulator of inflammation and cell survival. NF-κB is activated by cerebral ischemia in neurons and glia, but its function is controversial. To inhibit NF-κB selectively in neurons and glial cells, we have generated transgenic mice that express the IκBα superrepressor (IκBα mutated at serine-32 and serine-36, IκBα-SR) under transcriptional control of the neuron-specific enolase (NSE) and the glial fibrillary acidic protein (GFAP) promoter, respectively. In primary cortical neurons of NSE-IκBα-SR mice, NF-κB activity was partially inhibited. To assess NF-κB activity in vivo after permanent middle cerebral artery occlusion (MCAO), we measured the expression of NF-κB target genes by real-time polymerase chain reaction (PCR). The induction of c-myc and transforming growth factor-β2 by cerebral ischemia was inhibited by neuronal expression of IκBα-SR, whereas induction of GFAP by MCAO was reduced by astrocytic expression of IκBα-SR. Neuronal, but not astrocytic, expression of the NF-κB inhibitor reduced both infarct size and cell death 48 hours after permanent MCAO. In summary, the data show that NF-κB is activated in neurons and astrocytes during cerebral ischemia and that NF-κB activation in neurons contributes to the ischemic damage.