Human keratinocyte growth inhibition by ultraviolet B and the protective effect of vitamin E.

OBJECTIVE

To investigate the survival and cell cycle of HaCaT keratinocytes following UVB irradiation at various dosages, and observe the effect of vitamin E(Vit E) on the growth behavior of the cells in this condition.

METHODS AND RESULTS

MTT assay and flow cytometry were employed to analyze the cell survival ratio and changes in cell growth behavior in various phases of the cell cycle. It was found that for a given length of time of cell incubation following UVB irradiation, the survival ratio of HaCaT keratinocytes decreased gradually as the irradiation dose increased; at a fixed UVB irradiation dose, prolonged incubation of the cells following the irradiation resulted in decreased cell survival ratio, which, however, began to increase when the minimum ratio was reached, with the exception of the cells subjected to irradiation for 15 min. As indicated by cell cycle analysis, the proliferation indexes of the cells [(S+G2)/(G1+S+G2)] subjected to irradiation for less than 5 min increased gradually as the cell incubation time was prolonged, and contrary results occurred in cells receiving UVB irradiation for longer time. Obvious protective effect of Vit E on the cells was observed against UVB irradiation-induced cell growth inhibition, with optimal dose of Vit E of 40 microg/ml.

CONCLUSION

UVB irradiation for no less than 5 min can inhibit HaCaT human keratinocyte growth, and the effect is antagonized by Vit E administration.