Defective Autophagy in Diabetic Retinopathy

Author(s)

Lopes de Faria, Jacqueline M. ; Duarte, Diego A. ; Montemurro, Chiara ; Papadimitriou, Alexandros ; Consonni, Silvio Roberto ; Lopes de Faria, Jose B.

• Document type: Journal article
• Source: INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE; v. 57, n. 10, p. 4356-4366, AUG 2016.
• Web of Science Citations: 19

Abstract

PURPOSE. Muller cells (MCs) are a major source of VEGF in diabetic retinopathy (DR). Vascular endothelial growth factor is the main therapeutic target for treating DR. This study aimed to investigate whether autophagy is involved in MC response under high glucose (HG). METHODS. Rat retinal Muller cells (rMCs) were exposed to normal or high glucose in and out of presence of pharmacologic inhibitors and activators and small interfering RNA (siRNA) for p62/SQTSM1 for 24 hours. RESULTS. High glucose induces increase of early and late autophagic markers, accumulation of p62/SQTSM1 and endoplasmic reticulum (ER) stress response associated with apoptosis augmentation (P < 0.01). The inhibition of autophagy in HG leads to higher rMC apoptotic rate (P < 0.001). By silencing the p62/SQTSM1, ER stress is ameliorated (p < 0.0001), preventing apoptosis. Retinal MCs in HG treated with rapamycin (mTOR inhibitor) show autophagy machinery activation and reestablishment of cargo degradation, protecting cells from apoptosis (P < 0.0001). Rapamycin improves lysosomal proteolytic activity by improving cathepsin L activity restoring autophagic cargo degradation, and preventing increased VEGF release (P < 0.0001). In experimental model of diabetes, Beclin-1 and p62/SQTSM-1 were found to be marked increased in retinas from diabetic Wystar Kyoto rats compared with control group (P < 0.003) with reduction of cathepsin L activity. CONCLUSIONS. High glucose upregulates autophagy but accumulates p62/SQTSM1 cargo due to lysosomal dysfunction, leading to massive VEGF release and cell death of rMCs. Lysosomal impairment and autophagic dysfunction are early events present in the pathogenesis of diabetic retinopathy (DR). This might be valuable for developing a novel therapeutic strategy to treat DR. (AU)

• FAPESP's process: 13/04331-1 - Possible protective effects of Early Outgrow Cells (EOCs) of diabetic retina from db/db mice: the possible role of SIRT-1 in retina Müller cells
• Grantee: Jacqueline Mendonça Lopes de Faria
• Support Opportunities: Regular Research Grants