735 Rescue Potential of 25(OH)D on Skin Exposure to Nitrogen Mustard is a Function of Time and Dose

Nitrogen Mustard (NM) is an alkylating agent known to cause severe blistering and systemic toxicity from cutaneous exposure. Our previous data shows that a single intraperitoneal injection of low dose 25-hydroxyvitamin D3 (25(OH)D) given 1hr after NM exposure rescues mice from pancytopenia and death. However timing of intervention with the appropriate dose of drug in cases of mass exposure either accidental or during warfare is critical to wound repair and survival. In this study we demonstrate that 5ng 25(OH)D administered up to 24hr post NM exposure is able to mediate 100% recovery in mice. Examination of gross wound images and lesion sizes measured up to 20 days demonstrated significant wound resolution with diminishing lesion size, prevention of severe weight loss and death. In contrast failure to intervene before 48 h proved too late at and beyond which there was 60% death between days 6 to 12. If left untreated for 72 to 96 h, all NM-exposed animals showed minimal wound healing, up to 25% loss in body weight that ultimately died or met euthanasia criteria despite intervention at these later time points. Since 48 h seemed to be the critical time at which 25(OH)D had no effect in exposed animals, we tested the effect of two consecutive doses of 5 ng of 25(OH)D at 48 and 72h post NM exposure. Treated animals showed marked improvement of lesion sizes with 100% recovery from mortality. However a 10-fold higher dose (50ng) of 25(OH)D administered at 48 h was not beneficial with only 66% mice surviving. 50 ng of 25(OH)D administered at 72 h resulted in all animals being dead by day 6 with exacerbated skin lesions. Further experiments need to be conducted to ascertain the time limit beyond which rescue from NM mediated toxic death is irreversible, irrespective of repeat doses of intervention. Taken together we propose that there is a finite time within which countermeasures have efficacy in the treatment of NM-induced skin injury.