Blockade of sulfur mustard cytotoxicity in human epidermal keratinocytes with the purinergic receptor antagonist suramin

Studies were conducted to determine whether sulfur mustard (HD)-induced cytotoxicity in human epidermal keratinocytes (HEK) could be prevented by the P2 purinergic receptor antagonist suramin. Alamar blue and calcein-AM cytotoxicity assays were conducted 48 h after HD exposure. Short (10-15 min) pre-incubations with 1-5 mM suramin blocked the cytotoxic effect of HD over a narrow HD concentration range (100-150 microM). This protective effect was suramin-concentration dependent and was present if the medium was removed when HD was nearly completely hydrolyzed (60 min post-administration). Thus, suramin was required only during the actual presence of HD to exert its protective effect and not during later events required for the expression of HD-induced cytotoxicity (HD-induced cell death in HEK requires 48-72 h). These results are consistent with the hypothesis that purinergic receptors are involved in the cytotoxic effect of HD. Although suramin possesses a variety of actions unrelated to purinergic receptors, other evidence suggests that HD and suramin interact at the level of P2X receptors. Cysteine residues are primary targets of both HD and suramin. P2X receptors contain a large, cysteine-rich extracellular loop that appears critical for receptor function.