Inflammatory gene transcription in human astrocytes exposed to hypoxia: roles of the nuclear factor-kappaB and autocrine stimulation.
Mechanisms of hypoxia-induced activation of nuclear factor-kappaB (NF-kappaB) and inflammatory genes were investigated in fetal human astrocytes in culture. Astrocytes were subjected to interleukin-1beta (IL-1beta; 50-100 u/ml; 4-24 h), or to a 4-h hypoxia (<2% O2) followed by a 4-24-h reoxygenation. NF-kappaB binding and transcriptional activity increased up to 10-fold in astrocytes exposed to IL-1beta, and up to 3-fold in astrocytes subjected to hypoxia followed by reoxygenation. Both IL-1beta- mRNAs and proteins hypoxia-induced NF-kappaB activation were blocked by the proteasome inhibitor, MG-132. MG-132 inhibited IL-1beta-induced up-regulation of IL-1beta and IL-8 mRNA and protein but increased hypoxia-stimulated expression/release of IL-1beta and IL-8. IL-1 receptor antagonist (IL-1Ra) blocked both hypoxic astrocyte-conditioned media-induced NF-kappaB activation and the expression/release of IL-1beta and IL-8. Astrocytes subjected to hypoxia in the presence of IL-1Ra failed to activate NF-kappaB, but expressed elevated levels of IL-1beta and IL-8. The data suggest that hypoxia/reoxygenation-induced up-regulation of IL-1beta and IL-8 in human astrocytes has two components, a NF-kappaB independent up-regulation during hypoxia, followed by amplification through autocrine IL-1beta-induced NF-kappaB activation during reoxygenation.
Stanimirovic
D
D
Cellular Neurobiology Group, Institute for Biological Sciences, National Research Council of Canada, Montreal Road Campus, Bldg. M-54, K1A 0R6, Ottawa, ON, Canada. danica.stanimirovic@nrc.ca
Zhang
W
W
Howlett
C
C
Lemieux
P
P
Smith
C
C
D001253:Astrocytes / Q000166:cytology / Q000502:physiology*; D019898:Autocrine Communication / Q000276:immunology*; D015687:Cell Hypoxia / Q000276:immunology; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D017931:DNA Primers; D005333:Fetus / Q000166:cytology; D015870:Gene Expression / Q000187:drug effects / Q000276:immunology; D006801:Humans; D002534:Hypoxia, Brain / Q000276:immunology*; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000235:genetics; D016209:Interleukin-8 / Q000235:genetics; D007976:Leupeptins / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D016328:NF-kappa B / Q000235:genetics* / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D012795:Sialoglycoproteins / Q000494:pharmacology; D014158:Transcription, Genetic / Q000276:immunology*
D015853:Cysteine Proteinase Inhibitors; D017931:DNA Primers; C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D016209:Interleukin-8; D007976:Leupeptins; D009097:Multienzyme Complexes; D016328:NF-kappa B; D012795:Sialoglycoproteins; D008156:Luciferases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde