Effects of nicotinamide on biochemical changes and microblistering induced by sulfur mustard in human skin organ cultures.

Blister formation due to sulfur mustard (HD) exposure was studied in an ex vivo human skin model. Pieces of fresh human skin were exposed to HD vapor and subsequently incubated in medium for 48 hr. During this culture period cellular NAD+ levels and uptake of glucose from the medium decreased relative to the duration of the exposure to HD. In light microscopic sections of skin that were exposed to HD for 6 min. clefts of variable size could be clearly observed between the epidermis and the dermis after a 48-hr culture period. Immunohistochemical staining of collagen type IV demonstrated that separation occurred between the basal membrane and the basal keratinocytes. The described ex vivo human skin model mimicked the in vivo process quite well. Since it was reported that nicotinamide could protect cellular NAD+ levels after HD exposure, HD-treated skin pieces were incubated in medium containing 10 mM nicotinamide. Although this incubation caused an elevation of cellular NAD+ levels and of glucose uptake from the medium compared to control values, it did not result in a substantial reduction of cell death or microblister formation as observed by light microscopy in tissue sections. It was concluded that depletion of cellular NAD+ levels is not the only cause of HD-induced cell death.