ASBESTOS CAUSES TRANSLOCATION OF P65 PROTEIN AND INCREASES NF-KAPPA-BDNA-BINDING ACTIVITY IN RAT LUNG EPITHELIAL AND PLEURAL MESOTHELIAL CELLS

The mechanisms of cell signaling and altered gene expression by asbest os, a potent inflammatory, fibrogenic, and carcinogenic agent, are unc lear. Activation of the transcription factor, nuclear factor (NF)-kapp a B, is critical in up-regulating the expression of many genes Linked to inflammation and proliferation, Inhalation models of crocidolite- a nd chrysotile-induced inflammation and asbestosis were used to study t he localization of p65, a protein subunit of the NF-kappa B transcript ion factor, in sham control rats and those exposed to asbestos, In add ition, we investigated, using electrophoretic mobility shift analysis, whether in vitro exposure of rat lung epithelial cells and rat pleura l mesothelial cells to asbestos increased binding of nuclear proteins, including p65, to the NF-kappa B DNA response element. Furthermore, t ranslocation of p65 into the nucleus was determined by confocal micros copy, In comparison with sham animals, striking increases in p65 immun ofluorescence were observed in airway epithelial cells of rats at 5 da ys after inhalation of asbestos, These increases were diminished by 20 days, the time period necessary for development of fibrotic lesions, In contrast, although inter-animal variability was observed, immunorea ctivity for p65 was more dramatic in the interstitial compartment of a sbestos-exposed rat lungs at both 5 and 20 days. Changes in p65 expres sion in pleural mesothelial cells exposed to asbestos in inhalation ex periments were unremarkable, Exposure to asbestos also caused signific ant increases in nuclear protein complexes that bind the NF-kappa B co nsensus DNA sequence in both rat lung epithelial and rat pleural mesot helial cells. Using confocal microscopy, we observed partial nuclear t ranslocation of p65 in rat pleural mesothelial cells exposed to asbest os. This partial response contrasted with the effects of lipopolysacch aride, which caused rapid and complete translocation of p65 from cytop lasm to nucleus. Our studies are the first to show the presence of the NF-kappa B system in lung tissue and evidence of activation in vitro and in vivo after exposure to a potent inflammatory, fibrinogenic, and carcinogenic environmental agent.