1alpha,25-dihydroxyvitamin D3 and a variety of its natural metabolites transcriptionally repress nuclear-factor-kappaB-mediated interleukin-8 gene expression.
Regulation of interleukin-8 (IL-8) gene transcription occurs mainly through the sequences -94 to -71 of the 5'-flanking region of the IL-8 gene, involving the transcription factors nuclear factor for interleukin-6 (NF-IL-6) and nuclear factor kappaB (NF-kappaB). The human melanoma cell line A3 was derived from G-361 cells by stable transfection with an IL-8 promoter-luciferase construct containing these sequences. 1alpha,25-Dihydroxyvitamin D3 (calcitriol) repressed IL-8 promoter activity induced by tumor necrosis factor-alpha (TNF-alpha) by 50%, compared to 30% inhibition using dexamethasone, an effect consistent with its effect on TNF-alpha-induced IL-8 release and IL-8 mRNA levels. A variety of vitamin D metabolites caused the same repressive effect on IL-8 promoter activation as calcitriol. However, only those metabolites which were able to transactivate a classical vitamin D response element had the ability to repress IL-8 promoter activation, suggesting that this repression is mediated via vitamin D receptor (VDR). Furthermore, overexpression of VDR in the parental G-361 cell line enhanced the repressive effect of calcitriol on activation of the IL-8 promoter by either TNF-alpha stimulation or overexpression of the NF-kappaB subunit p65. Electrophoretic mobility shift assays using nuclear extracts from A3 cells showed that calcitriol decreased the abundance of nuclear factors bound to the NF-kappaB binding site of the IL-8 promoter and this reduced binding of NF-kappaB proteins presumably contributes to its inhibitory action.
Harant
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Novartis Research Institute, Vienna, Austria. hanna.harant@pharma.novartis.com
Andrew
P J
PJ
Reddy
G S
GS
Foglar
E
E
Lindley
I J
IJ
D001665:Binding Sites; D015152:Blotting, Northern; D002117:Calcitriol / Q000378:metabolism / Q000494:pharmacology*; D002135:Calcium-Binding Proteins; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics* / Q000378:metabolism; D008562:Membrane Glycoproteins; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000378:metabolism; D050863:Synaptotagmin I; D050857:Synaptotagmins; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D002135:Calcium-Binding Proteins; D016209:Interleukin-8; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D050863:Synaptotagmin I; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D050857:Synaptotagmins; D003907:Dexamethasone; D002117:Calcitriol