Endoplasmic Reticulum Stress Induces Apoptosis In The Experimental Retinal Detachment

Objective To investigate endoplasmic reticulum (ER) stress genes (GRP78, GADD153/CHOP) expression at various time points after experimental retinal detachment and to determine whether ER stress-mediated apoptosis pathway becomes activated in the retina after retinal detachment (RD).Methods Experimental retinal detachment models were created in left eyes of Wistar rats by subretinal injection of 10mg/ml sodium hyaluronate. Then, the left eyes of rats were observed at various time points. Histomorphology observation was performed by light microscopy. Apoptosis of retinal cells was detected by TdT-mediated fluorescein-16-dUTP nick-end labelling (TUNEL) assay. GRP78 and GADD153 mRNA level was detected by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). GRP78 and GADD153 protein was detected by Western blot analysis. GRP78 and GADD153 protein distribution in the retinal cells was observed using immunofluorescence by laser scanning confocal fluorescence microscope.Results Histology studies showed depletion and shorten of outer segments, degeneration in photoreceptor cells, bipolar cells, ganglion cells and nerve fiber layer, breakage of Müller cell fibers and so on. Among above, the decrease of number of photoreceptor cells is the most prominent. The apoptosis of photoreceptor cells occurred within 8d after retinal detachment and peaked at 2d-4d (P<0.05). GRP78 and GADD153 mRNA level significantly increased at 1/2d, 1d, 2d and 4d after retinal detachment. The expression of GRP78 protein was presented in all the layers of retina in the RD groups. The expression in RD group at 1/2d, 1d, 2d, 4d, 8d, 16d and 32d after retinal detachment was higher than that in control group (P<0.05). Among them, the expression of GRP78 protein at 8d, 16d and 32d was highest. However, the expression of GADD153 protein was obvious in photoreceptor layers but little in other layers. The expression of GADD153 protein at 1/2d, 1d, 2d and 4d was significantly higher than that in the control group (P<0.05). The trend of expression agreed with the trend of the apoptosis of retinal cells.Conclusion The results show that ER stress genes GRP78, GADD153 are expressed with different level at various time points after retinal detachment. ER stress genes expression associates with the apoptosis of photoreceptor cells. It is evidenced that ER stress-mediated pathway, a new apoptosis pathway, is activated and involved in the apoptosis in the retina after retinal detachment.