Vitronectin adsorption to chrysotile asbestos increases fiber phagocytosisand toxicity for mesothelial cells

Biological modification of asbestos fibers can alter their interaction with target cells. We have shown that vitronectin (VN), a major adhesive protei n in serum, adsorbs to crocidolite asbestos and increases fiber phagocytosi s by mesothelial cells via integrins. Because chrysotile asbestos differs s ignificantly from crocidolite in charge and shape, we asked whether VN woul d also adsorb to chrysotile asbestos and increase its toxicity for mesothel ial cells. We found that VN, either from purified solutions or from serum, adsorbed to chrysotile but at a lower amount per surface area than to croci dolite. Nevertheless, VN coating increased the phagocytosis of chrysotile a s well as of crocidolite asbestos. VN coating of both chrysotile and crocid olite, but not of glass beads, increased intracellular oxidation and apopto sis of mesothelial cells. The additional apoptosis could be blocked by inte grin-ligand blockade with arginine-glycine-aspartic acid peptides, confirmi ng a role for integrins in the fiber-induced toxicity. We conclude that VN increases the phagocytosis of chrysotile as well as of crocidolite asbestos and that phagocytosis is important in fiber-induced toxicity for mesotheli al cells.