Respirable Particulate Interactions with the Lecithin Component of Pulmonary Surfactant.
Keane-M; Wallace-W; Seerha-M; Hill-C; Vallyathan-V; Raghootama-P; Mike-P
NIOSH 1990 Sep:231-244
Studies on the effects of lecithin on the in-vitro cytotoxicity of respirable quartz (14808607) and aluminosilicate dusts were summarized. Dispersions of lecithin in physiological saline were used as a surrogate pulmonary surfactant. Quartz and kaolin (1332587) dusts when coated with lecithin at concentrations up to 90 milligrams per gram showed sharply reduced cytotoxicity, measured by erythrocyte hemolysis and release of lactate-dehydrogenase by pulmonary macrophages. When lecithin coated quartz particles were treated with phospholipase-A2 (PLA2) the degree of cytotoxicity returned to essentially the control value at relatively low PLA2 concentrations. The particle surfaces were almost depleted of lecithin and lysophatidylcholine (lysolecithin), a lecithin hydrolysis product, by PLA2. Treating lecithin coated kaolin particles with PLA2 had little effect on cytotoxicity except at relatively high PLA2 concentrations. Significant quantities of lecithin and lysolecithin were left on the surface. Fourier transform infrared spectra of lecithin adsorbed on the surfaces of quartz and kaolin when compared with spectra of pure lecithin indicated that quartz had formed an adduct with the trimethylamine moiety of lecithin and kaolin had formed an adduct with the phosphate moiety. Plots of the pH dependence of quartz and kaolin induced hemolysis showed positive slopes between pHs 5 and 7. This was taken as evidence that a charge dependent mechanism was involved quartz or kaolin induced hemolysis. The authors conclude that the surface toxicity of quartz and kaolin dusts can be eliminated by coating them with lecithin. Lecithin coated quartz is readily retoxified by PLA2. Both quartz and kaolin appear to have acidic surface groups that are involved in hemolysis and which may associate with the charged trimethylamine group in lecithin.
NIOSH-Author; In-vitro-studies; Phospholipids; Surface-properties; Cytotoxic-effects; Chemical-structure; Acidity; Mineral-dusts;
Proceedings of the VIIth International Pneumoconioses Conference