EPITHELIAL INJURY-INDUCED BY EXPOSURE TO RESIDUAL OIL FLY-ASH PARTICLES - ROLE OF REACTIVE OXYGEN SPECIES

Exposure of animals to airborne particulates is associated with pulmon ary injury and inflammation, In the studies described here, primary cu ltures of rat tracheal epithelial (RTE) cells were exposed to suspensi ons of residual oil fly ash (ROFA), ROFA exposure resulted in progress ive cytotoxicity whereby the amount of lactate dehydrogenase (LDH) rel eased was significantly greater at 24 h than at 6 h after exposure, In a dose-dependent manner, exposure to 5, 10, or 20 mu g/cm(2) of ROFA for 24 h resulted in cytotoxicity and detachment of cells from the col lagen matrix, along with altered permeability of the RTE cell layer, R OFA exposure caused cellular glutathione levels to decrease, producing a condition of oxidative stress in the RTE cells, Treatment of RTE ce lls with buthionine sulfoxamine, an inhibitor of gamma-glutamyl cystei ne synthetase, was found to augment ROFA-induced cytotoxicity, Treatme nt with dimethylthiourea (DMTU) inhibited ROFA-induced LDH release and permeability changes in a dose-dependent manner, Treatment with the n itric oxide synthase inhibitor N-G-monomethyl-D-arginine (D-NMA) for 2 4 h was without effect, In rats intratracheally instilled with ROFA (5 00 mu g/rat), intraperitoneal administration of DMTU (500 mg/kg) signi ficantly ameliorated the degree of pulmonary neutrophilic inflammation present at 24 h, Overall, these in vitro findings suggest that ROFA-i nduced RTE cell injury may be mediated by hydroxyl-radical-like reacti ve oxygen species (i.e., species scavenged by DMTU) that are generated via non-nitric oxide pathways, The delay in induction of maximal RTE cell injury may reflect the time necessary to produce an oxidative bur den by depleting antioxidant defenses such as cellular glutathione.