Biphasic role of nuclear factor-kappa B on cell survival and COX-2 expression in SOD1 Tg astrocytes after oxygen glucose deprivation.
In cytoplasm, nuclear factor-kappaB (NF-kappaB) is associated with the inhibitory protein, IkappaBalpha. On activation by H2O2, IkappaBalpha is phosphorylated and degraded, exposing the nuclear localization signals on the NF-kappaB heterodimer. Cyclooxygenase-2 (COX-2), which mediates prostaglandin synthesis during inflammation, is induced by oxidative stress mediated by NF-kappaB. We investigated whether the NF-kappaB 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-IkappaBalpha was highly expressed after oxygen-glucose deprivation (OGD) and 2 h of reperfusion, concomitant with the decrease in IkappaBalpha. The NF-kappaB 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-kappaB 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-kappaB small interfering RNAs in SOD1 Tg astrocytes aggravated cell death and increased COX-2 expression. These results suggest that the NF-kappaB signaling pathway induced COX-2 expression and promoted cell death in WTs after OGD injury; however, NF-kappaB activation protected cells and decreased COX-2 expression in SOD1 Tg astrocytes. This biphasic role of NF-kappaB might be coordinately regulated by reactive oxygen species levels in astrocytes, thereby functioning as a regulator of cell death/survival.
Lee
Yong-Sun
YS
Department of Neurosurgery, Department of Neurology and Neurological Sciences, and Program in Neurosciences, Stanford University School of Medicine, Stanford, California 94305-5487, USA.
Song
Yun Seon
YS
Giffard
Rona G
RG
Chan
Pak H
PH
D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000235:genetics; D000818:Animals; D001253:Astrocytes / Q000201:enzymology*; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D015687:Cell Hypoxia; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000096:biosynthesis* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics; D005947:Glucose / Q000172:deficiency* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D020672:I-kappa B Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D000072000:NF-KappaB Inhibitor alpha; D052002:NF-kappa B p50 Subunit / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D015424:Reperfusion; D013482:Superoxide Dismutase / Q000096:biosynthesis* / Q000235:genetics; D000072105:Superoxide Dismutase-1
D020672:I-kappa B Proteins; D052002:NF-kappa B p50 Subunit; C000606205:Nfkbia protein, mouse; D016877:Oxidants; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D000072000:NF-KappaB Inhibitor alpha; D006861:Hydrogen Peroxide; D051546:Cyclooxygenase 2; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D005947:Glucose