Selective up-regulation of IκB-α in ischemic penumbra following focal cerebral ischemia

Activation of transcription factor NF-kappa B plays a critical role in immune. inflammatory and cell death responses. In resting cells. NF-kappa-B is sequestrated in the cytoplasm in an inactive form through its association with inhibitory proteins, I kappa B (e.g. I kappa-B-alpha). In response to cell activation, I kappa B is degraded causing release of active NF-kappa B. Active NF-kappa B translocates into the nucleus leading to activation of transcription that may have a profound effect on cell survival, including that after ischemic stroke. Here, using Western blot analysis. we show that immunoreactivity to the major subunit of NF-kappa B, p65, as well as to the inhibitory subunit I kappa B-alpha is equally markedly decreased in the ischemic core after transient middle cerebral and common carotid artery occlusion in rats. In contrast, penumbral regions display no change in p65, and significant increase in I kappa B-alpha immunoreactivity, as compared to non-ischemic areas. In these penumbral regions with elevated I kappa B-alpha immunoreactivity, we find reduced cytosolic and increased nuclear I kappa B-alpha staining of neurons, as determined by immunohistochemistry. Altogether, these results suggest that an altered ratio between activating and inhibitory NF-kappa B pathways mediated through I kappa B-alpha may play an important role in survival of the ischemic penumbra. NeuroReport 11:1529-1533 (C) 2000 Lippincott Williams & Wilkins.