Combination of ebselen and hydrocortisone substantially reduces nitrogen mustard-induced cutaneous injury

The purpose of the present study was to investigate the vesicant countermeasure effects of hydrocortisone (HC) and ebselen (EB-1), administered as monotherapy or as a combination treatment. The mouse ear vesicant model (MEVM) was utilized and test doses of HC (0.016, 0.023, 0.031, 0.047, 0.063, 0.125 or 0.250 mg/ear), EB-1 (0.125, 0.187, 0.250, 0.375 or 0.500 mg/ear) or the combination of HC + EB-1 were topically applied at 15 min, 4 h and 8 h after nitrogen mustard exposure. Ear punch biopsies were obtained 24 h after mechlorethamine (HN2) exposure. Compared to control ears, ear tissues exposed topically to HN2 (0.500 µmol/ear) presented with an increase in ear thickness, vesication, TUNEL fluorescence and expression of matrix metalloproteinase 9 (MMP-9) and inducible nitric oxide synthase (iNOS). In contrast, HN2 exposed ears treated topically with EB-1 showed a significant decrease in morphometric thickness and vesication vs. HN2 alone. Ear tissues exposed to HN2 and then treated with HC also demonstrated reductions in morphometric thickness and vesication. Combination treatment of HC + EB-1 was found to be the most effective at reducing HN2-induced ear edema and vesication. The combination also dramatically decreased HN2-mediated cutaneous expression of iNOS and MMP-9 and decreased HN2-induced TUNEL staining. Taken together, our study demonstrates that the combination of HC + EB-1 is an efficacious countermeasure to HN2.