Luminol-Enhanced Chemiluminescence After in Vitro Exposures of Rat Alveolar Macrophages to Oil Fly Ash Is Metal Dependent

Epidemiologic studies have associated exposures to air pollution particles with human mortality. Much of this excess mortality is attributed to a respiratory injury. It has been postulated that such injury after particle exposure can result from the capacity of these dusts to catalyze the generation of oxygen-based free radicals. We tested the study hypotheses (1) that oxidant production by rat alveolar macrophages increases with exposures to an emission source air pollution particle (i.e., an oil fly ash), (2) that this elevation in radical generation is dependent on the concentrations of metal associated with the oil fly ash and available to support electron transport, and (3) that increases in the cellular oxidant formation can be simulated by both soluble metal salts and metal complexed to insoluble carboxylate functionalized latex beads. Luminol-enhanced chemiluminescence was measured in reaction mixtures that included rat alveolar macrophages (0.5-1.0 x 106 cells/ml), 0.1 m M luminol, 1% bovine serum albumin, and either oil fly ash, iron sulfate, nickel sulfate, vanadyl sulfate, or latex particles with iron, nickel, and vanadyl cation groups complexed to the surface. In vitro exposure of the cells to the oil fly ash significantly increased chemiluminescence, while inclusion of deferoxamine and hydroxyl radical scavengers diminished the signal. Solutions of metal sulfates similarly elevated chemiluminescence in a dose- and time-dependent manner. Finally, latex beads with complexed iron, nickel, and vanadyl cation groups significantly augmented the signal again in a dose- and time-dependent manner. We conclude that (1) the in vitro generation of oxidants by rat alveolar macrophages increases after exposures to an emission source air pollution particle, (2) these elevations in the production of oxygen-based free radicals after exposure of phagocytes to an air pollution particle can be metal dependent, and (3) solutions of metal sulfates and latex particles with complexed metals similarly augment chemiluminescence by alveolar macrophages.