Effects of selected arginine analogues on sulphur mustard toxicity in human and hairless guinea pig skin keratinocytes

The toxicity of sulphur mustard (HD) was characterized in first passage cul tures of human neonatal foreskin keratinocytes and then several arginine an alogues were investigated to ascertain their efficacies in protecting again st HD toxicity in this system. D-and L-nitroarginine methyl ester (D/L-NAME ), L-phosphoarginine, and L-nitroarginine were all found to confer concentr ation-related protective effects against HD in confluent cultures. L-NAME w as used to further characterize this protection and was only effective in c ultures that were not actively proliferating. This compound was also found to be efficacious when added to the cultures up to several hours after HD e xposure, although its continued presence was required in order for protecti on to be effective. The protective effects of L-thiocitrulline (L-TC) against HD toxicity were also assessed. This arginine analogue was extremely potent in preventing HD toxicity in actively proliferating just-confluent, and postconfluent cultu res in a concentration-dependent fashion (0.1-15 mM), with little HD toxici ty apparent at high L-TC concentrations. Protection was prophylactic in nat ure, with L-TC having almost maximal effect when added to the cultures only 1 min prior to HD culture exposure. Efficacy then declined rapidly so that no protection was evident when L-TC was added 30 min post-HD. The effects of this drug were persistent, with no decrease in protective efficacy up to 4 days after HD exposure, even when L-TC was removed from the cultures. L- TC did not protect against the antimitotic effects of HD; while L-TC-protec ted cells were subcultured successfully, they displayed no clonogenic activ ity. Although L-TC is closely related structurally to protective nitroargin ine derivatives, the characteristics of L-TC protection against HD were mar kedly different and suggest that they exert their protective activities at different sites. Administration of L-NAME and L-TC by a variety of routes d id not result in consistent protection against topical vapor challenges of HD in hairless guinea pigs. However, both compounds were effective in preve nting the toxicity of HD in primary cultures of hairless guinea pig skin ke ratinocytes, indicating that species differences were not likely to be resp onsible for the poor efficacy of these compounds in vivo. (C) 2000 Academic Press.