Role of mitochondrial DNA in human retinal pigment epithelium cells apoptosis induced by blue light

Objective

To research the role of mitochondrial DNA mediate the cultured human retinal pigment epithelium (hRPE) cell apoptosis induced by blue light and the relationship with time.

Methods

Established the blue light damage model of cultured hRPE cells in vitro with light emitting diode (LED) blue light density of (4.0±0.5)mW/cm² adjusted by FL-1D blue light illumination meter, and the illumination time was set as 0, 0.5, 1, 2, 4, 6, 12 and 24 hours, then the cells were grouped according to the illumination time.Immunofluorescence were used to identify the cells; the expressions of caspase-3, cleaved caspase-3, caspase-9, cleaved caspase-9, bax and bcl-2 were detected with Western blot.Quantitative PCR was used to detect the copy number of mitochondrial DNA and PCR was used to detect mitochondrial DNA 4977bp common deletion.

Results

Immunofluorescence results showed that the RPE65 protein was expressed in the cytoplasm.The expressions of bax were upregulated after illumination for 1 hour, cleaved caspase-3 were upregulated after illumination for 2 hours, caspase-3, caspase-9, cleaved caspase-9 were upregulated after illumination for 4 hours, while the expression of bcl-2 was downregulated after illuminated for 2 hours, with significant differences compared to the normal control group (all at P<0.05). The copy number of mitochondrial DNA in 0.5, 1, 2, 4, 6, 12 and 24 hours groups was downregulated, with significant differences compared to the normal control group (all at P<0.05). The expressions of 4977bp common deletion in 0.5, 1, 2, 4, 6, 12 and 24 hours groups were increased, with significant differences compared with the normal control group (all at P<0.05).

Conclusions

Blue light can cause cell apoptosis, especially mitochondrial apoptosis, in hRPE probably motivated by mitochondrial DNA damage.