Cell biological and biochemical study on the mechanism and oxidative regulation of photoaging

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Since the biochemical changes associated with the photoaging process are not fully understood, the theory that accumulated photo-oxidative cellular injury contributes significantly to the photoaging process in skin still remains open to debate.In the present study, we have demonstrated that SOD activity was increased by repeated UVB irradiation and gradually returned to the control levels but unaffected by UVA irradiation. The SOD activity, which has been reported to decrease after acute actinic injury, is induced by repeated exposures to UVB presumably in response to the chronic photo-oxidative stress, however, continual cumulative stress may overwhelm the capacity of this system with resultant photoaging symptoms. We have also investigated the alteration of main disaccharide units of GAGs from hairless mice skin after chronic and repeated UV radiation using high performance liquid chromatography by our newly developed method. We found that the total amount of main disaccharide units … More increased by UVA irradiation at 36th week. Concerning the changes in the disaccharide composition after 36 weeks'repeated exposure, DELTADi-HA (HA) decreased and DELTADi-4S (DS) increased in the order of control, UVA- and UVB- irradiated group. These results, for the first time, demonstrate the precise alterations of GAGs both in total amount and composition confirming the previous histochemical findings. We have also developed the three-dimensional culture system supplemented with L-ascorbic acid 2-phosphate (Asc 2-P) using dermal fibroblasts. The addition of Asc 2-P rendered fibroblasts to the organization of the dermis-like three-dimensional structure in vitro without any pretreatments of plastic dish. Multilayred fibroblasts surrounded by extracellular matrices were readily observed and the amounts of both main disaccharide units and hydroxyproline are significantly increased and, furthermore, the composition revealed more similar to that of dermis when compared with monolayr culture system. Using this culture system, it should be possible to investigate the biochemical changes of collagen produced by dermal fibroblasts obtained from photoaged skin. Less