The effects of the melatonin on ultraviolet-B irradiated cultured dermal fibroblasts

It has been reported that reactive oxygen species (ROS) and oxygen-derived free radicals are generated by ultraviolet (UV) radiation and various chemi cals and their important roles in cellular damage and apoptosis are being i ncreasingly recognized. Melatonin is a hormone with multiple functions in h umans. produced by the pineal gland and stimulated by beta-adrenergic recep tors. Melatonin has been shown to have photo protection properties. but the re has been little progress toward identifying the specific mechanisms of i ts action. To clarify the role of melatonin as a free radical scavenger, in response to ultraviolet-B (UVB) irradiation. we investigated the effects o f UVB and melatonin on cytotoxicity, lipid peroxidation, terminal deoxynucl eotidyl transferase-mediated digoxigenin-dUTP nick end-labeling (TUNEL) ass ay and alteration of cell cycle in cultured skin fibroblast. Cell survival curves after UVB irradiation showed dose dependent decrement pattern by try pan blue exclusion assay. Only 56% of dermal fibroblasts were survived at 1 40 mJ/cm(2) UVB irradiation. The damage was associated with cell membrane l ipid peroxidation, as shown by accumulation malondialdehyde (MDA). By pre-c ultivation with melatonin (10(-9) M). a significant preventive effect was n oted on the increase in the absolute number of surviving cells (up to 92.5% of cells were survived) and the levels of MDA were markedly decreased. The se finding suggest significant correlation between an increase of lipid per oxide and cell viability. Morphological changes associated with apoptotic c ell death were easily distinguished by TUNEL stain. Quantitative analysis o f DNA content of skin fibroblasts was evaluated by flow cytometric analysis performed after vital staining with propidium iodide. UVB suppresses the G I progression induced pre-GI arrest leading to apoptotic changes of dermal fibroblast and those are blocked by melatonin pre-treatment. The results sh ow the photodynamic effects of UVB that supposes the production of ROS and arrest the cell cycle. Melatonin, which have newly accepted as a potential UV protection properties, is effective membrane peroxidation inhibitor and prevent the pre-GI arrest when present in relevant concentration during UVB irradiation. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.