SULFUR MUSTARD INDUCES APOPTOSIS AND NECROSIS IN ENDOTHELIAL-CELLS

Sulfur Mustard (SM) is a vesicant or blistering chemical warfare agent , for which there still is no effective therapy. Endothelial cells are one of the major cellular targets for SM. The mechanism of endothelia l cell death during SM injury is poorly understood. We studied the eff ect of exposure of endothelial cells to 0-1000 mu M SM over the time c ourse of 2-24 hr to determine the role of apoptotic and necrotic patte rns of cell death in endothelial injury induced by SM. SM concentratio ns less than or equal to 250 mu M induced exclusively apoptosis which was observed after 5 hr in 30% of endothelial cells. Exposure to SM co ncentrations greater than or equal to 500 mu M caused apoptosis and ne crosis to the same extent in 60-85% of all cells after 5 to 6 hr. Necr osis was accompanied by a significant (similar to 509) depletion of in tracellular ATP, while in apoptotic cells ATP remained at the level si milar to healthy cells. Interestingly, disruption of the long actin fi lament stress fibers and rounding of cells preceded other features of apoptosis-DNA fragmentation, membrane budding, and apoptotic body form ation. In apoptotic cells, microfilaments formed constricted perinucle ar bands, which were not observed in necrotic cells. Pretreatment with 50 mM N-acetyl-L-cysteine (NAC), a sulfhydryl donor and antioxidant, nearly eliminated the apoptotic features of cell death but did not pre vent necrosis in response to SM. NAC pretreatment alone induced reorga nization of actin filaments into an enhanced network of long stress fi bers instead of a dominant cortical band of actin. NAC pretreatment pr evented loss of cell adherence and cell rounding following exposure to 250 mu M SM. The effect of NAC on cytoskeletal organization and its a bility to eliminate SRI-induced apoptosis suggests that actin filament organization may be an important element in cellular susceptibility t o apoptotic stimuli. (C) 1996 Academic Press, Inc.