Pp. Simeonova et Mi. Luster, ASBESTOS INDUCTION OF NUCLEAR TRANSCRIPTION FACTORS AND INTERLEUKIN-8GENE-REGULATION, American journal of respiratory cell and molecular biology, 15(6), 1996, pp. 787-795
Proinflammatory cytokines and chemotactic peptides are strongly implic
ated as mediators of the pathophysiologic responses of asbestosis and
other chronic inflammatory lung diseases. Recent studies in our labora
tory have demonstrated that asbestos fibers stimulate lung epithelial
cells to produce interleukin-8 (IL-8), the major neutrophil chemoattra
ctant in the lung. The mechanisms by which asbestos regulates IL-8 exp
ression were studied using the pulmonary type II-like epithelial cell
line A549. Membrane permeable hydroxyl scavengers inhibited asbestos i
nduced IL-8 expression. Using A549 cells transfected with the -546 IL-
8 construct linked to a chloramphenicol acetyl transferase reporter ge
ne, we have shown that these antioxidants directly inhibited asbestos-
stimulated IL-8 promoter-dependent transcription. Asbestos fibers as w
ell as reactive oxygen species generating systems hypoxanthine-xanthin
e oxidase and hydrogen peroxide stimulated DNA binding activity to the
regulatory elements in the IL-8 promoter, binding sites of nuclear fa
ctor (NF)-kappa B- and NF-IL-6-like transcription factors. Asbestos-in
ducible DNA binding activity was partially inhibited by tetramethylthi
ourea, a hydroxyl radical scavenger. IL-8 secretion was also suppresse
d by staurosporine, an inhibitor of protein kinase C, and by inhibitor
s of tyrosine kinase such as herbimycin A and genistein. The suppressi
on paralleled the effect of these inhibitors on asbestos-induced DNA b
inding to the NF-kappa B- and NF-IL-6-like binding sites of the IL-8 p
romoter. Taken together, the results suggest that asbestos-induced red
ox changes and phosphorylation events, mediated by staurosporine-sensi
tive and tyrosine kinase(s), activate nuclear proteins which recognize
the NF-kappa B/NF-IL-6 binding sites of the IL-8 promoter and contrib
ute to the regulation of IL-8 gene expression.