Effect of hypoxia on sunburn cell formation and inflammation induced by ultraviolet radiation

Oxygen intermediates are responsible for a number of ultraviolet (UV) radiation effects. To test the hypothesis that UV-induced formation of sunburn cells and skin edema (ear swelling) result from oxidative damage, we examined the effect of hypoxia tissue responses to UV in the mouse ear. Hypoxia resulting from vascular occlusion by ear clamping, either before or after UVB exposure, decreased formation of sunburn cells. Ear clamping alone caused significant ear swelling, which was enhanced when combined with UVB exposure. Using topical 8-methoxypsoralen + UVA (PUVA), increased sunburn cells were observed when ears were clamped for 10 min prior to UVA exposure, but not following exposure. Ear swelling caused by PUVA was also enhanced when ears were clamped during exposure. These results suggest that induction of sunburn cells by UVB is dependent on oxygen, and that UVB and PUVA induce sunburn cell formation by distinct mechanisms.