NEUTROPHIL AND ASBESTOS FIBER-INDUCED CYTOTOXICITY IN CULTURED HUMAN MESOTHELIAL AND BRONCHIAL EPITHELIAL-CELLS

This study investigates reactive oxygen species generation and oxidant -related cytotoxicity induced by amosite asbestos fibers and polymorph onuclear leucocytes (PMNs) in human mesothelial cells and human bronch ial epithelial cells in vitro. Transformed human pleural mesothelial c ells (MET 5A) and bronchial epithelial cells (BEAS 2B) were treated wi th amosite (2 mu g/cm(2)) for 48 h. After 24 h of incubation, the cell s were exposed for 1 h to nonactivated or amosite (50 mu g) activated PMNs, washed, and incubated for another 23 h. Reactive oxygen species generation by the PMNs and the target cells was measured by chemilumin escence. Cell injury was assessed by cellular adenine nucleotide deple tion, extracellular release of nucleotides, and lactate dehydrogenase (LDH). Amosite-activated (but also to a lesser degree nonactivated) PM Ns released substantial amounts of reactive oxygen metabolites, wherea s the chemiluminescence of amosite-exposed mesothelial cells and epith elial cells did not differ from the background. Amosite treatment (48 h) of the target cells did not change intracellular adenine nucleotide s (ATP, ADP, AMP) or nucleotide catabolite products (xanthine, hypoxan thine, and uric acid). When the target cells were exposed to nonactiva ted PMNs, significant adenine nucleotide depletion and nucleotide cata bolite accumulation was observed in mesothelial cells only. In separat e experiments, when the target cells were exposed to amosite-activated PMNs, the target cell injury was further potentiated compared with th e amosite treatment alone or exposure to nonactivated PMNs. In conclus ion, this study suggests the importance of inflammatory cell-derived f ree radicals in the development of amosite-induced mesothelial cell in jury.