UVA RADIATION-INDUCED OXIDATIVE DAMAGE TO LIPIDS AND PROTEINS IN-VITRO AND IN HUMAN SKIN FIBROBLASTS IS DEPENDENT ON IRON AND SINGLET OXYGEN

This study describes the damage that occurs to lipids and proteins tha t have been irradiated in vitro or in human skin fibroblasts with phys iological doses of UVA radiation. Thiobarbituric acid-reactive species were formed from phosphatidylcholine after UVA radiation in vitro. By using iron chelators, this process was shown to involve iron. Ferric iron associated with potential physiological chelators was reduced by UVA radiation, but iron within ferritin was not. By enhancing the half life-time with deuterium oxide or by using scavengers, singlet oxygen was also shown to be involved in the UVA radiation-dependent peroxida tion of phosphatidylcholine. UVA radiation-generated singlet oxygen re acted with phosphatidylcholine to form lipid hydroperoxides, and the b reakdown of these hydroperoxides to thiobarbituric acid-reactive speci es was dependent on iron. We have shown that iron and singlet oxygen a re also involved in the UVA radiation-dependent formation of thiobarbi turic acid-reactive species in human skin fibroblasts, and we propose that a similar concerted effect of iron and singlet oxygen is involved in UVA radiation-dependent damage to fibroblast lipids. Sulphydryl gr oups of bovine serum albumin and human gamma-globulin were oxidised up on WA irradiation in vitro. The use of scavengers and deuterium oxide showed that WA radiation-dependent sulphydryl oxidation was dependent on singlet oxygen. By adding or chelating iron, UVA radiation-dependen t oxidation of sulphydryl groups of bovine serum albumin and human gam ma-globulin was shown to be iron-dependent. The use of catalase and hy droxyl radical scavengers demonstrated that hydrogen peroxide, but not the hydroxyl radical, was involved. The oxidation of sulphydryl group s of proteins in human skin fibroblasts that occurs as a result of WA irradiation was also shown to involve iron, singlet oxygen, and hydrog en peroxide. We conclude that iron, singlet oxygen, and hydrogen perox ide are important redox active species involved in the deleterious eff ects of UVA radiation on lipids and proteins of human skin cells.