Asbestos Fibers and Interleukin-1 Upregulate the Formation of Reactive Nitrogen Species in Rat Pleural Mesothelial Cells

Abstract

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.

Malondialdehyde (MDA) Superoxide dismutase (SOD) levels - distinguishing parameters betweenbenign malignant pleural effusions

“…The origin of this local oxidative burst is related to the nature of each disease entity. [14] Oxidants have been shown to play an important role in carcinogenesis; serving not only as tumor initiators but also as tumor promoters and regulators of gene expression. [15] In many diseases free radicals play a very important role.…”

Gene Expression Profiles Reveal Increased mClca3 (Gob5) Expression and Mucin Production in a Murine Model of Asbestos-Induced Fibrogenesis

“…21,53,54 The up-regulation of IL-1␤ is noteworthy because it is elevated in rodent inhalation models of asbestos exposure and in cell culture systems. 55,56 IL-1␤ is generally considered an early response cytokine that is produced by many different cell types, but is predominantly synthesized and secreted by macrophages during inflammation whereby it acts on lymphocytes to enhance their capacity to respond to antigens. Transient expression of IL-1␤ in vivo has been causally linked to progressive fibrotic changes, including the presence of myofibroblasts, fibroblast foci, and collagen and fibronectin accumulation.…”

“…11 IL-1␤ also has been implicated in the generation of reactive nitrogen species by chrysotile asbestos fibers, 56 and increases mucin production in human bronchial epithelial cells in vitro. 21 The induction of IL-1␤ concurrent with time points of peak inflammation and the increased production of mucus in this study imply that this cytokine may play an important role in the development of mucus production by chrysotile asbestos fibers.…”

Asbestos inhalation induces reactive nitrogen species and nitrotyrosine formation in the lungs and pleura of the rat.

“…Therefore, it is conceivable that asbestos fibers also may induce cellular injury via mechanisms not based on Fenton chemistry such as by the generation of reactive nitrogen species (RNS), as has been demonstrated in human acute lung injury and experimental models of granulomatous lung inflammation (11,12). Some support for this contention is provided by studies which demonstrated that the addition of either crocidolite or chrysotile fibers to cytokine-stimulated cell cultures upregulated the production of nitric oxide ( · NO) by rat alveolar macrophages (13) as well as by rat parietal pleural mesothelial cells (14). In the latter study, asbestos challenge also generated the formation of the highly reactive nitrogen compound, peroxynitrite anion (ONOO Ϫ ), a finding that was associated with cytotoxic changes within the pleural mesothelial cells (14).…”