Residual oil fly ash induces cytotoxicity and mucin secretion by guinea pig tracheal epithelial cells via an oxidant-mediated mechanism

Inhalation of ambient air particulate matter (PM) is associated with pulmon ary injury and inflammation. Using primary cultures of guinea pig tracheal epithelial (GPTE) cells as an in vitro model of airway epithelium, we exami ned effects of exposure to suspensions of six different emission and ambien t air PM samples: residual oil fly ash (ROFA) from an electrical power plan t; fly ash from a domestic oil burning furnace (DOFA); ambient air dust fro m St. Louis (STL), Ottawa (OT), and Washington, DC (WDC); and volcanic ash from the eruption of Mount Saint Helens (MSH) in 1980. Effects of these par ticulates on cell viability (assessed via LDH assay), secretion of mucin (m easured by a monoclonal antibody-based ELISA), and steady-state mRNA levels of the mucin gene MUC2 were determined. ROFA was the most toxic of the dus ts tested, as it significantly increased LDH release following a 24-h incub ation with 50 mu g/cm(2) ROFA. ROFA also enhanced MUC2 mRNA after 4-h expos ure, and mucin secretion after 8 h. ROFA-induced mucin secretion and cytoto xicity were attenuated by the oxidant scavenger, dimethylthiourea (DMTU). R OFA exposure also depleted cells of glutathione (GSH). Relatedly, depletion of intracellular GSH by treatment of the cells with buthionine sulfoxamine (BSO) also provoked mucin secretion, as well as enhancing the secretory ef fect of ROFA when the two agents were added together. L-NMA, the nitric oxi de synthase (NOS) inhibitor, did not affect ROFA-induced mucin secretion. O f the soluble transition metals in ROFA (nickel, iron, vanadium), only vana dium individually, or combinations of the metals containing vanadium, provo ked secretion. The results suggest ROFA enhances mucin secretion and genera tes toxicity in vitro to airway epithelium via a mechanism(s) involving gen eration of oxidant stress, perhaps related to depletion of cellular antioxi dant capacity. Deleterious effects of inhalation of ROFA in the respiratory tract in vivo may relate to these cellular responses. Vanadium, a componen t of ROFA, may be important in generating these reactions. (C) 2000 Academi c Press.