Interactions of Silica and Asbestos with Macrophages
Crystalline silica is highly toxic for macrophages. This appears to be due to the capacity of silica particles to disrupt the membranes around the secondary lysosomes in which the ingested silica particles lie. Silica interacts with natural membranes, producing cytolysis, and with liposomes consisting of phosphatidyl-choline and cholesterol. This reaction appears to be due to hydrogen bonding of silicic acid groups on the surface of the particles with quaternary and phosphate ester groups of phospholipids. Chrysotile asbestos stimulates macrophages to secrete hydrolytic enzymes, which are probably involved in the inflammatory responses to these particles. Chrysotile is also membrane active, and this appears to be due, at least in part, to interactions of surface magnesium groups with sialic acid groups of membrane glycoproteins or glycolipids. Experiments are quoted suggesting that macrophages interacting with sublethal amounts of silica secrete a factor or factors increasing proliferation of and collagen synthesis by fibroblasts.
KeywordsCholesterol Permeability Quartz Magnesium Silicate
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