Intratracheal injection of crocidolite asbestos depresses the secretion of tumor necrosis factor by pleural leukocytes in vitro

Asbestos fibers and interleukin-1 upregulate the formation of reactive nitrogen species in rat pleural mesothelial cells

Nitric oxide radical (.NO) and peroxynitrite anion (ONOO-) have been implicated in lung inflammation and may be important in pleural injury. The present study was undertaken to determine the effects of asbestos exposure and cytokine stimulation on .NO and ONOO- production by rat pleural mesothelial cells. Accordingly, rat parietal pleural mesothelial cells were cultured for 2 to 72 h with or without 50 ng/ml of recombinant interleukin-1beta (IL-1beta) in the presence (1.05 to 8.4 microg/cm2) or absence of crocidolite or chrysotile asbestos fibers. The effects of asbestos were compared with those of carbonyl iron, a nonfibrogenic particulate. Mesothelial cell messenger RNA (mRNA) expression of the inducible form of .NO synthase (iNOS), assessed with the reverse transcription-polymerase chain reaction (RT-PCR), increased progressively from 2 to 12 h in IL-1beta-containing cultures. Nitrite (NO2-), the stable oxidation product of .NO in mesothelial cell conditioned medium, was assayed through the Griess reaction. Both types of asbestos fibers (chrysotile > crocidolite) upregulated the formation of NO2- in mesothelial cells costimulated with IL-1beta in a concentration-dependent and time-dependent fashion. In contrast, carbonyl iron did not upregulate NO2- formation in IL-1beta-stimulated cells. Both types of asbestos fibers also induced iNOS protein expression and the formation of nitrotyrosine in mesothelial cells and greatly induced the formation of nitrate (NO3-), a surrogate marker of ONOO- formation, in IL-1beta-stimulated cells. However, the effects of chrysotile were notably greater than those of crocidolite. These findings may have significance for the induction of pleural injury by asbestos fibers.

Production of interleukin 1 by rat pleural leucocytes in culture after intratracheal instillation of crocidolite asbestos

This study was undertaken to investigate the production of interleukin 1 (IL-1) by pleural leucocytes in culture and to evaluate the influence of intratracheal instillation of crocidolite asbestos on this production. Normal pleural leucocytes spontaneously released IL-1 in culture and stimulation with lipopolysaccharide (LPS) dramatically increased production. Intratracheal instillation with crocidolite asbestos induced recruitment of pleural leucocytes in the longer term and changed IL-1 production by the leucocytes. Reduced production of IL-1 was found by one day after instillation of asbestos and this was correlated with the dose of asbestos. With increasing time after instillation, however, release of IL-1 by pleural leucocytes gradually recovered to normal until, one month after asbestos injection, the leucocytes produced augmented IL-1 in culture compared with control pleural leucocytes. Our data show that pleural leucocytes possess the potential to produce IL-1 in vitro and this capability is altered by intratracheal instillation of crocidolite asbestos. This may be relevant to development of pleural diseases associated with inhalation of asbestos.