Contribution of human pulmonary macrophage-derived cytokines to asbestos-induced lung inflammation and fibrosis

There have been reports on the induction of production of tumor necrosis factor (TNF) alpha and interleukin (IL) 1 beta in macrophages by fibrogenic dusts, such as those from asbestos, man-made fibers and mineral particles, suggesting that release of TNF-alpha and IL-1 beta from alveolar macrophages may be relevant to in vivo findings of inflammation and fibrotic lung disease in animals and humans. This evidence suggests that some cytokines related to inflammation and fibroblast cell growth may become useful biochemical markers for assessment of fiber-induced biological effects. However, the relationships of other cytokines and fibers have not been sufficiently clarified because of the paucity of immunoassay tools for quantitative analysis in animals. The aim of the current work has been to define the role of cytokines as markers for the assessment of asbestos fiber-induced lung inflammation and fibrosis in vitro using human pulmonary macrophages and various human immunoassay kits. Normal human pulmonary macrophages (h-PAM) were collected by fiberoptic bronchoscopy, and specimens containing >85% viable and >90% pure cells were used. Nonadherent cells were removed by preincubation for 2 h; after that the h-PAM cells were incubated with UICC standard reference samples of 3 types of asbestos (crocidolite, amosite, and chrysotile) in 10% fetal calf serum containing RPMI-1640 medium at 37 degrees C, in a CO2 incubator. At the end of incubation, supernatant medium and cells plates with adherent were frozen immediately at -80 degrees C. Macrophage-derived cytokines were measured in culture medium and sonicated cell solution by enzyme-linked immunosorbent assay. TNF-alpha reached a maximum at 6 h and IL-1 beta, IL-8, and growth-regulated peptide (GRO alpha) tended to increase time-dependently up to 24 h after incubation with asbestos. TNF-alpha macrophage inflammatory protein (MIP-1 alpha), IL-8, and GRO-alpha increased dose-dependently from 30 to 200 mu g/ml asbestos. Fibroblast growth factor (FGF) basic, platelet-derived growth factor (PDGF). and transforming growth factor (TGF) beta 1 and -beta 2, which are found within macrophage cells, did not show marked changes on incubation with asbestos. Contents of cytokines relative to fibers in culture medium were higher than those of intracellular contents except for IL-1 beta. Following incubation with the 3 kinds of asbestos at a concentration of 100 mu g/ml, the degree of induction of cytokines was greatest with crocidolite, followed by amosite, then chrysotile. These results suggest that macrophage-derived MIP-1 alpha, IL-8, and GRO alpha may be more useful biochemical markers than PDGF, TGF-beta 1, and -beta 2, and FGF for the assessment of fiber-induced lung inflammation and subsequent fibrosis.