Ultraviolet radiation-induced oxidative stress in cultured human skin fibroblasts and antioxidant protection

This study was designed to determine whether UVB radiation induces oxidative stress in cultured human skin fibroblasts and, if so, whether the induced oxidative stress can be inhibited by antioxidant supplementation. To answer these questions, the study investigated, on the one hand, the effects of UVB radiation on cell morphology, cell viability, lipid peroxidation and endogenous antioxidant defences, and on the other hand, the effects of dl-α-tocopherol and pycnogenol on UVB radiation-induced cytotoxicity and lipid peroxidation, and the scavenger effect of pycnogenol against superoxide radicals. It was found that UVB radiation of 0.5-2.0 J/cm² resulted in dose-dependent morphological damage in fibroblasts. UVB radiation of 2.0 J/cm² resulted in bleb formation on the surface of the cells. UVB radiation of 0.5-2.0 J/cm² decreased cell viability dose-dependently. Cellular TBARS increased 57% when the cells were exposed to 0.5 J/cm² of UVB radiation. UVB radiation of 0.5-1.5 J/cm² resulted in a decrease in GSH and an increase in GSSG levels. When the cells were exposed to 0.5-2.0 J/cm² of UVB radiation, the activities of glucose 6-phosphate dehydrogenase, superoxide dismutase and thioredoxin reductase decreased with dose responses to UVB, but the activities of glutathione peroxidase and glutathione reductase did not change significantly. When the cells were exposed to 0.5-1.5 J/cm² of UVB radiation, catalase activity did not change significantly, but increased when exposed to 2.0 J/cm² of UVB radiation. When the cells were exposed to 1.5 J/cm² of UVB radiation, the scavenging activity of the cell membranes against free radicals decreased. dl-α-Tocopherol did not reduce UVB radiation-induced cytotoxicity and lipid peroxidation. Pycnogenol reduced UVB radiation-induced cytotoxicity and lipid peroxidation dose-dependently. When pycnogenol was present in the xanthine-xanthine oxidase system at concentrations of 10, 50 and 100 μg/ml, a decrease of about 4%, 58% and 79%, respectively in the intensity of the DMPO-OOH adduct signal was observed. This study thus indicates that UVB radiation induces oxidative stress in cultured human skin fibroblasts, that UVB-induced oxidative injuries are not reduced by dl-a-tocopherol but are reduced by pycnogenol, and that pycnogenol scavenges superoxide radicals in vitro.