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In cytoplasm, nuclear factor-κB (NF-κB) is associated with the inhibitory protein, IκBα. On activation by H2O2, IκBα is phosphorylated and degraded, exposing the nuclear localization signals on the NF-κB heterodimer. Cyclooxygenase-2 (COX-2), which mediates prostaglandin synthesis during inflammation, is induced by oxidative stress mediated by NF-κB. We investigated whether the NF-κB signaling pathway affected cell death and COX-2 expression after hypoxia-induced oxidative stress in wild-type (WT) and copper/zinc-superoxide dismutase transgenic (SOD1 Tg) astrocytes. In WT astrocytes, phospho-IκBα was highly expressed after oxygen–glucose deprivation (OGD) and 2 h of reperfusion, concomitant with the decrease in IκBα. The NF-κB p50 level increased similarly in WT and SOD1 Tg astrocytes (1.2-/1.4-fold) after OGD. Electrophoretic mobility shift assay showed higher DNA-binding activity of NF-κB p50 in WT than in SOD1 Tg astrocytes 6 h after 4 h of OGD. The COX-2 level was induced by 2.7- and 1.3-fold after OGD in WT and SOD1 Tg astrocytes, and an antioxidant protected both groups against OGD injury. Superoxide dismutase transgenic cells were 23% more protective against OGD injury than WTs when assessed by lactate dehydrogenase release. However, transfection of NF-κB small interfering RNAs in SOD1 Tg astrocytes aggravated cell death and increased COX-2 expression. These results suggest that the NF-κB signaling pathway induced COX-2 expression and promoted cell death in WTs after OGD injury; however, NF-κB activation protected cells and decreased COX-2 expression in SOD1 Tg astrocytes. This biphasic role of NF-κB might be coordinately regulated by reactive oxygen species levels in astrocytes, thereby functioning as a regulator of cell death/survival.Journal of Cerebral Blood Flow & Metabolism (2006) 26, 1076–1088. doi:10.1038/sj.jcbfm.9600261; published online 14 December 2005 [ABSTRACT FROM AUTHOR]

Heat shock protein (Hsp)70 can suppress both necrosis and apoptosis induced by various injuries in vivo and in vitro. However, the relative importance of different functions and binding partners of Hsp70 in ischemic protection is unknown. To explore this question, we tested the ability of Hsp70-K71E, an adenosine triphosphate (ATP)ase-deficient point mutant, and Hsp70-381–640, a deletion mutant lacking the ATPase domain and encoding the carboxyl-terminal portion, to protect against ischemia-like injury in vivo and in vitro. Heat shock protein 70-wild type (-WT), -K71E, -381–640, and control vector plasmid LXSN were expressed in primary murine astrocyte cultures. Astrocytes overexpressing Hsp70-WT, -K71E, or -381–640 were all significantly protected from 4 h combined oxygen–glucose deprivation and 24 h reperfusion when assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay or propidium iodide staining and cell counting (P<0.05). Brains of rats were transfected with plasmids encoding Hsp70-WT, -K71E, -381–640, or LXSN 24 h before 2 h middle cerebral artery occlusion followed by 24 h reperfusion. Animals that overexpressed either of the mutant proteins or Hsp70-WT had significantly better neurological scores and smaller infarcts than control animals. Protection by both mutants was associated with reduced protein aggregation, as assessed by ubiquitin immunohistochemistry and reduced nuclear translocation of apoptosis-inducing factor. The results show that the carboxyl-terminal portion of Hsp70 is sufficient for neuroprotection. This indicates that neither the ability to fold denatured proteins nor interactions with cochaperones or other proteins that bind the amino-terminal half of Hsp70 are essential to ischemic protection.Journal of Cerebral Blood Flow & Metabolism (2006) 26, 937–950. doi:10.1038/sj.jcbfm.9600246; published online 16 November 2005 [ABSTRACT FROM AUTHOR]