Modification of cytosolic free calcium concentrations in human keratinocytes after sulfur mustard exposure

Exposure of confluent cultures of human skin keratinocytes to sulfur mustard (SM) induced an immediate and irreversible rise in internal free Ca(2+) levels that was independent of external Ca(2+) concentrations. The response was rapid, beginning within 1min after addition of SM to the cells, and sensitive, with significant effects observed at 100 mum. The rise in [Ca(2+)](INT) was unaffected by zero external Ca(2+) but was blocked by prior incubation with thapsigargin. The sensitivity to and irreversibility of the effects of SM on Ca(2+) levels was paralleled by cellular toxicity as assessed using three different cell viability assays. In addition, the time course of the onset of irreversible toxicity in our cultures coincides with the time course of effects on [Ca(2+)](INT). SM was also found to displace specifically bound ATP from purinergic (P(2)) receptors. These results suggest that therapies aimed at protecting internal stores of Ca(2+) from disruption by SM, perhaps at P(2) receptors, may provide substantial benefit in protecting human skin cells from the toxic effects of this vesicant.