Cellular stress response in human Müller cells (MIO-M1) after bevacizumab treatment

Bevacizumab, an anti-vascular endothelial growth factor (VEGF) agent, is widely used in the treatment of retinal vascular diseases. However, due to the essential role Müller cell derived-VEGF plays in the maintenance of retinal neurons and glial cells, cell viability is likely to be affected by VEGF inhibition. We therefore evaluated the effect of bevacizumab-induced VEGF inhibition on Müller cells (MIO-M1) in vitro. MIO-M1 cells were cultured for 12 or 24 h in media containing bevacizumab at 0.25 or 0.5 mg/mL. Controls were cultured in medium only. Cell viability was determined with the trypan blue exclusion test and MTT assay. Caspase-3, beclin-1, glial fibrillary acidic protein (GFAP) and vimentin content were quantified by immunohistochemistry. Gene expression was evaluated by real-time quantitative PCR. Treatment with bevacizumab did not reduce MIO-M1 cell viability, but increased metabolic activity at 24 h (0.5 mg/mL) and induced apoptosis and autophagy, as shown by the increased caspase-3 levels at 12 h (0.25 and 0.5 mg/mL) and the increased beclin levels at 24 h (0.5 mg/mL). Caspase-3 mRNA was upregulated at 12 h and downregulated at 24 h in cells treated with bevacizumab at 0.25 mg/mL. Bevacizumab treatment was also associated with structural protein abnormalities, with decreased GFAP and vimentin content and upregulated GFAP and vimentin mRNA expression. Although bevacizumab did not significantly affect MIO-M1 cell viability, it led to metabolic and molecular changes (apoptosis, autophagy and structural abnormalities) suggestive of significant cellular toxicity.