Interleukin-8 gene expression in human bronchial epithelial cells.
The capacity of cells of the human bronchial epithelium to express the gene for interleukin-8 (IL-8) was evaluated in bronchial epithelium derived cell lines, HS-24 and BET-1A, using tumor necrosis factor-alpha (TNF) as a model inflammatory stimulus. As in other epithelium, TNF markedly increased the level of the 1.8-kilobase IL-8 mRNA transcripts in both bronchial epithelial cell lines. In HS-24 cells, nuclear run-on analyses showed the IL-8 gene transcription rate was dramatically increased, more than 30-fold, after TNF stimulation. The half-life of IL-8 mRNA transcripts in these cells was approximately 40 min and did not change after TNF stimulation, suggesting that TNF up-regulated IL-8 gene expression mainly at the transcriptional level. DNase I hypersensitivity site mapping of chromatin DNA in resting HS-24 cells demonstrated two hypersensitivity sites within 400 base pairs (bp) 5' to exon I and one site within exon I. However, after TNF stimulation, the exon I hypersensitivity site disappeared and a new site approximately 120 bp 5' to exon I emerged. Consistent with these observations, transfection studies with HS-24 cells using fusion genes composed of the 5'-flanking sequences of the IL-8 gene and a luciferase reporter gene demonstrated potent promoter activity in a 174-bp segment (-130 to +44 relative to the transcription start site), which also exhibited a response to TNF, while a segment from -112 to +44 showed very low promoter activity and no response to TNF. Thus, human bronchial epithelial cells can express the IL-8 gene, with expression in response to the inflammatory mediator TNF regulated mainly at the transcriptional level, and with elements within the 5'-flanking region of the gene that are directly or indirectly modulated by the TNF signal.
Nakamura
H
H
Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892.
Yoshimura
K
K
Jaffe
H A
HA
Crystal
R G
RG
D001980:Bronchi / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D002634:Chemotaxis, Leukocyte; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics*; D008156:Luciferases / Q000235:genetics; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation
D016209:Interleukin-8; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D008156:Luciferases