Figure 1.

Removal of pyrimidine dimers from UVB-irradiated human skin through photoreactivation. (a–d) Human buttock skin was left untreated (a), UVB-irradiated (1 MED) (b), UVB-irradiated and subsequently treated with photolyase-containing liposomes followed by a 30-min exposure to photoreactivating light (c), or UVB-irradiated and subsequently exposed to photoreactivating light for 30 min and then treated topically with photolyase-containing liposomes (d). The presence of cyclobutane pyrimidine dimers was assessed 22.5 h after photoreactivation by immunofluorescence microscopy with mAb H3 as described in Materials and Methods. Data represent one of seven essentially identical experiments. (e) Dose response of photoreactivation-induced dimer removal from UVB-irradiated human skin. To assess the dose response between photoreactivation and dimer removal, human buttock skin was either left unirradiated (A) or exposed to 2 MED of UVB radiation and subsequently left untreated (B), UVB-irradiated and treated with photolyase-containing liposomes plus photoreactivating light for 1 min (C), 5 min (D), or 30 min (E). The presence of dimers in these skin areas was assessed immediately after photoreactivation in triplicates and quantified by immunfluorescence microscopy with mAb H3 as described in Materials and Methods. Data are given as histograms of specific fluorescence in arbitrary units (a. u.) as described (16) versus skin area and represent mean values ± SD of three experiments.