Effects of bevacizumab on endoplasmic reticulum stress in hypoxic retinal pigment epithelial cells

PURPOSE To investigate the effects of bevacizumab on endoplasmic reticulum (ER) stress in human retinal pigment epithelial (RPE) cells cultured under hypoxic conditions. METHODS RPE cells (ARPE-19) were cultured under hypoxic conditions (1% O2) with or without bevacizumab (0.3125 mg/mL) for 24 and 48 h. Cell viability was measured by a PrestoBlue assay. The expression of vascular endothelial growth factor (VEGF), binding protein/glucose-regulated protein 78 (BiP/GRP78), and C/EBP homologous protein-10 (CHOP) mRNA was measured by quantitative real-time polymerase chain reaction (qRT-PCR). BiP/GRP78 and CHOP protein levels in the cells were assessed by western blot. VEGF protein in the media was quantified by enzyme-linked immunosorbent assay (ELISA). RESULTS Under hypoxic conditions, cell viability decreased and mRNA and protein levels of VEGF, BiP/GRP78, and CHOP increased compared to those under normoxic conditions. Bevacizumab improved cell viability and reduced the expression of VEGF mRNA under hypoxic conditions. Bevacizumab also reduced the expression of both mRNA and protein of two ER stress indicators, BiP/GRP78 and CHOP, under hypoxic conditions. CONCLUSIONS Bevacizumab mitigated ER stress in human RPE cells cultured under hypoxic conditions. This effect may be involved in the improved cell viability and reduction of VEGF expression after bevacizumab treatment of hypoxic RPE cells in vitro. However, the effects of bevacizumab on RPE cells under experimental conditions are unlikely to be clinically equivalent to those in the human eye.