Study On The DNA Damage And Repair Of Cell Lines Induced By Ultraviolet Radiation (UV)

Aim: We studied the effects of different waves of ultraviolet radiation (UV) on DNA damage in different cells, and established the model of DNA damage and repair of K562 cell induced by UVC.Methods: 1. The effects of DNA damage in different cells induced by different waves and doses of ultraviolet radiation (UV) were tested by comet assay. 2. The effects of UVC on K562 cell was investigated by MTT test, morphological observation, cell count and comet assay. The cell cycle distribution was detected by the flow cytometer (FCM).Rezults: 1. The mouse hepatocytes primary cultured, mouse hepatoma hepal-6 cells and human leukemia K562 cells were irradiated by UVA,UVB,UVC of 1.2~120J/m~2. The DNA damage of the cells tested by comet assay showed that UVA couldn't induce DNA damage immediately, while UVB and UVC could induce cellular DNA damage in a dose manner, and UVC could induce DNA damage most severely.2. The sensitivities of different cells to UV were different. 10J/m~2UVB and 3.2 J/m~2UVC could induce the mouse hepatocytes DNA damage;3.2J/m~2UVB and 1.2J/m~2UVC could induce hepal-6 cellular DNA damage;for K562 cells, the lowest energys were about 20J/m~2(UVB) and 3.2J/m~2(UVC). The lowest dose of UVC induced human hepatoma SMMC-7721 cellular DNA damage was 10.8J/m~2, and above 16J/m~2UVC could induce DNA damage of h-hepatoma HepG2 cell.3. After irradiated by UVC, the DNA damage of K562 cells represented delayed effect, and it can be repaired during 24h. Cell count and morphological observation showed that the number of K562 cells declined least after incubated 14h, and some cells damaged severely. The results of comet assay showed that the highest damage was appeared after incubated 2-4h.4. When synchronized K562 cells were irradiated by 30J/m~2 UVC, the cells of G2/M phase showed much sensitive than others. The cell cycle distribution was also changed after irradiated. Cells were arrested in G1/S.5. K562 cells were irradiated by low dose UVC, the DNA damage was detected by comet assay after treated 2h but not immediately. The threshold of damage delaylydetected by comet assay was 1.2J/m2.Conclusions: The comet assay results showed that UVA couldn't induce DNA damage immediately, while UVB and UVC could induce cellular DNA damage in a dose manner, and UVC could induce DNA damage most severely. The sensitivities to UV were different in different cells. The cancer cells were more sensitivie to UV, and the sensitivity of cells to UV was related to the proliferation speed. Damage of cell induced by UVC represented delayed effect, and it can be repaired during 24h. K562 cells had heterogeneity responsion, and cells in G2/M were more sensitivie to UV. After irradiated by 30J/m2 UVC, the cell cycle of synchronized K562 cell was arrested in Gl/S. When irradiated by lower dose UVC, DNA damage of K562 cell just appeared in a delayed manner, but not immediately.