Effects of UV wavelength on cell damages caused by UV irradiation in PC12 cells

Ultraviolet (UV) radiations present in sunlight are a major etiologic factor for many skin diseases and induce DNA damage through formation of cyclobutane pyrimidine dimer (CPD). This study was conducted to determine the toxicological effects of different wavelengths (250, 270, 290, and 310 nm) and doses of UV radiation on cell viability, DNA structure, and DNA damage repair mechanisms in a PC12 cell system. For this, we evaluated cell viability and CPD formation. Cell survival rate was markedly decreased 24 h after UV irradiation in a dose-dependent manner at all wavelengths (except at 310 nm). Cell viability increased with increasing wavelength in the following order: 250 < 270 < 290 < 310 nm. UV radiation at 250 nm showed the highest cell killing ability, with a median lethal dose (LD50) of 120 mJ/cm2. The LD50 gradually increased with increase in wavelength. Among the 4 wavelengths tested, the highest LD50 (6000 mJ/cm2) was obtained for 310 nm. CPD formation decreased substantially with increasing wavelength. Among the 4 wavelengths, the proportion of CPD formation was highest at 250 nm and lowest at 310 nm. On the basis of LD50 values for each wavelength, PC12 cells irradiated with UV radiation of 290 nm showed maximum DNA repair ability, whereas those irradiated with the 310-nm radiation did not show any repair ability. Toxicity of UV radiation varied with wavelengths and exposure doses.