Transcriptional regulation of the intercellular adhesion molecule-1 gene by proinflammatory cytokines in human astrocytes.
Intercellular adhesion molecule-1 (ICAM-1) expression is upregulated by cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interferon-gamma (IFN-gamma) in numerous cell types including the astrocyte, which functions as an immunoregulatory cell within the central nervous system. We investigated the mechanism by which ICAM-1 is transcriptionally regulated by proinflammatory cytokines in human fetal astrocytes. TNF-alpha and IL-1beta enhanced ICAM-1 expression at both the mRNA and protein levels, while IFN-gamma had a modest enhancing effect. However, a synergistic response was noted when IFN-gamma was added with either TNF-alpha or IL-1beta. Using human ICAM-1 deletion constructs and linker scanning mutants, we determined that the NF-kappaB element (-186 bp region) is critical for both TNF-alpha- and IL-1beta-mediated ICAM-1 expression, while the IFN-gamma activation sequence (GAS) element at -75 bp region is important for IFN-gamma stimulation. The synergistic effect between TNF-alpha and IFN-gamma is dependent on both NF-kappaB and GAS elements. Upon TNF-alpha and IL-1beta stimulation, p65 homodimers and p65/p50 heterodimers bind to the NF-kappaB site, and STAT-1alpha homodimers bind to the GAS element upon IFN-gamma stimulation. Transient transfection assays demonstrated that overexpression of the p65 protein transactivated the promoter activity of an ICAM-1 reporter construct, while p50 overexpression inhibited, in a dose-dependent manner, p65-mediated ICAM-1 expression. These data collectively suggest that in human astrocytes, the p65 homodimer is responsible for ICAM-1 upregulation upon TNF-alpha or IL-1beta stimulation, and that IFN-gamma enhancement of ICAM-1 involves activation of STAT-1alpha homodimers.
Lee
S J
SJ
Department of Cell Biology, University of Alabama at Birmingham, 35294-0005, USA.
Park
J Y
JY
Hou
J
J
Benveniste
E N
EN
D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D016207:Cytokines / Q000494:pharmacology*; D005434:Flow Cytometry; D005696:Galactosidases / Q000378:metabolism; D006801:Humans; D007202:Indicators and Reagents; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis* / Q000235:genetics; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D016328:NF-kappa B / Q000378:metabolism; D012313:RNA / Q000302:isolation & purification; D012260:Ribonucleases / Q000378:metabolism; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects*
D016207:Cytokines; D007202:Indicators and Reagents; D007375:Interleukin-1; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D012313:RNA; D007371:Interferon-gamma; D008156:Luciferases; D012260:Ribonucleases; D005696:Galactosidases