Effect of environmental particulates on cultured human and bovine endothelium. Cellular injury via an oxidant-dependent pathway

The effects of respirable environmental fibers on cultures of human umbilical vein and bovine pulmonary artery endothelial cell monolayers were studied. Interaction among endothelial cell monolayers and amosite and chrysotile asbestos, attapulgite, fiberglass, or latex beads resulted in rapid phagocytosis of the particulates. A gradient of time-dependent and concentration-dependent endothelial cell injury (measured by specific ⁵¹Cr release) was observed with amosite and attapulgite being markedly toxic. Chrysotile and fiberglass were much les toxic, and latex beads were not significantly injurious at any time or dose examined. Responses of bovine pulmonary artery and human endothelial vein endothelial cells to fiber phagocytosis and fiber-induced injury were similar. In human umbilical cell monolayers, fiber-mediated stimulation of the arachidonate metabolite prostacyclin paralleled endothelial cell injury; i.e. amosite and attapulgite were stimulatory, whereas fiberglass (0-500 μg/ml) and latex beads (10⁹ beads/ml) did not significantly increase prostacyclin generation. Although chrysotile was only weakly cytotoxic, significant stimulation of prostacyclin was observed at the highest dose tested (500 μg/ml). To investigate whether toxic oxygen species may be involved in fiber-induced cytotoxicity, oxidant scavengers or inhibitors were used in injury studies. Both superoxide dismutase (a scavenger of O₂^-) and catalase (an inhibitor of H₂O₂) produced significant protection against fiber-mediated endothelial cell injury. In addition, chelation by deferoxamine of elemental Fe present in the fiber preparations was also protective, suggesting Fe, via the modified Haber-Weiss reaction, may promote hydroxyl radical formation and contribute to endothelial cell injury induced by these particulates. These results suggest that the interaction within the interstitial environment between endothelial cells and occupationally relevant dusts may be important in fiber-mediated inflammatory processes in the lung.