The Research Of Cultured Rabbit Retinal Pigment Epithelium Cells' Apoptosis Induced By Visible Light

OBJECTIVE: To observe the effect of visible light on apoptosis of cultured rabbit retinal pigment epithelium(RPE)cells.METHODS: Digest and separate RPE cell with two-step enzymic method. Cultured rabbit RPE cells were exposed to cold white light (3652±213)lx in vitro. The duration of exposure was0, 3, 6 and 9 hours respectively(groupⅠⅡⅢand Ⅳ). The culture time after the light exposure was 3, 12, 24 and 72hours respectively each group(Ⅰ3,12,24,72, Ⅱ3,12,24,72, Ⅲ3,12,24,72 and Ⅳ3,12,24,72). Bcl-2 mRNA in site hybridization(ISH) were detected in group Ⅰ3,12,24,72 and Ⅲ3,12,24,72 . Group Ⅲ24 were observed with transmission electron microscope(TEM). All groups were measured with AnnexinV-FITC/PI, labelling and flowcytometry (FCM). Measure of cellcycle in groupⅠ24,Ⅱ24,Ⅲ24 and Ⅳ24 with FCM. RESULTS: After the visible light exposure, apoptotic distinctive change can be observed by TEM. There are some buffy particle in Bcl-2 mRNA positive cell endochylema. Positive rate has no obvious change between group Ⅲ3 and no exposure group. 12hours after exposure or longer, positive cell decrease gradually. Apoptosis and necrosis were found in cultured rabbit RPE cells which were exposed to visible light by FCM. Rate of apoptosis in groupⅡ24 is (11.45±1.78)%,Rate of apoptosis in groupⅢ3 is (5.80±0.77)%,Rate of apoptosis in group Ⅲ24 is(18.49±0.88)%。Rate of necrosis in groupⅡ12 is (1.12±0.56)%,Rate of necrosis in groupⅡ72 is (1.46±0.39)%,Rate of necrosis in group Ⅳ12 is (5.33±1.05)%. The longer the duration of the exposure and the post-exposure period are, the higher the rate of apoptosis and necrosis are. Apoptosis was the main response to shorter (3h and 6h) exposure duration, while necrosis was more pronounced correlated to the prolongation of post-exposure culture (P<0.05), the longer the post-exposure period was, the more apoptotic necrosis were seen. 72 hours after exposure the necrotic percent ages were more pronounced (P<0.05). Measurement of cell circle can display the cell multiplication index decreased and apoptotic rate increased with the prolongation of exposure.CONCLUSIONS: High intensity visible light can cause apoptosis of rabbit RPE cells in vitro. In some time after the exposure, visible light can evoke the defend mechanism of the RPE cells themselves. Visible light increases the proportion of apoptosis and necrosis of rabbit RPE cells in vitro. The extent is related to exposure duration and post-exposure period. It demonstrates that the shorter duration of exposure to light is, the more pronounced apoptotic percentages are observed, otherwise necrosis. Apoptosis can convert into necrosis in some case, which is called apoptotic necrosis. Some intensity visible light can inhibit RPE cells entering into their cell circle in some extent.