Hydrogen peroxide mediates UV-induced impairment of antigen presentation in a murine epidermal-derived dendritic cell line.

Ultraviolet-B (290-320 nm) radiation is known to impair the antigen-presenting cell (APC) function of Langerhans cells (LC), skin-specific members of the dendritic cell (DC) family. We sought to address mechanisms of this effect, focusing on the role played by hydrogen peroxide. For this purpose, we used a newly established murine DC line, XS52, which resembles epidermal LC in several respects. The APC capacity of XS52 cells, using two different CD4+ T cell clones as responders, was inhibited significantly (> 50%) by exposure to UV radiation (unfiltered FS20 sunlamps) at relatively small fluences (50-100 J/m2). Ultraviolet radiation also inhibited growth factor-dependent proliferation of XS52 cells. On the other hand, cell surface phenotype was relatively well preserved after irradiation; expression levels of B7-1 and B7-2 were reduced slightly, while other molecules (e.g. Ia, CD54, CD11a and CD18) were not affected. With respect to the role played by hydrogen peroxide, pretreatment with purified catalase (900 U/ mL) prevented UV-induced inhibition of APC function. Short-term exposure to 3 mM H2O2 or t-butyl H2O2 mimicked UV radiation by inhibiting APC function. Finally, intrinsic catalase activity was substantially lower in XS52 cells compared with Pam 212 keratinocytes. These results indicate that the generation of hydrogen peroxide alone is sufficient to produce some, but not all, of the deleterious effects of UV radiation on DC derived from the skin.