Selenium protects primary human keratinocytes from apoptosis induced by exposure to ultraviolet radiation

The generation of reactive oxygen species has been implicated in ultraviolet radiation (UVR)-induced skin damage. In mice, increasing dietary selenium intake protects skin from UVR-induced DNA damage and photocarcinogenesis. We sought to determine whether selenium supplementation could protect keratinocytes from apoptosis resulting from exposure to broadband (TL20W/12) UVR. Unirradiated cultures contained 6.5+/-1% apoptotic cells; the maximum percentage of apoptotic cells (34+/-5%) was seen 16 h after UVR of 600 J/m(2). Under these conditions cell death from necrosis was 15+/-2.5% of the total cells. A 24-h preincubation with sodium selenite (10 nm-1 mum) or selenomethionine (50 nm-1 mum) protected cultured human keratinocytes from UVR-induced apoptosis. In primary keratinocytes the greatest reduction in apoptosis was found with 100 nm of either selenium compound (71% reduction in the numbers of total apoptotic cells; P<0.01). Supplementation with 100-200 nm selenite or selenomethionine prevented UVR-induced apoptosis, but did not decrease the levels of UVR-induced p53, as measured by Western blotting. Collectively, this data suggests that selenium prevents UVR-induced cell death by inhibiting p53-independent cell death pathways.