title: Defective Autophagy in Diabetic Retinopathy.
abstract: Müller 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).
  
  
  
  Rat retinal Müller 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.
  
  
  
  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.
  
  
  
  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.
authors: Renal Pathophysiology Laboratory Investigation on Diabetes Complications, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
authors: Jacqueline M
authors: JM
authors: Lopes de Faria
authors: Renal Pathophysiology Laboratory Investigation on Diabetes Complications, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
authors: Diego A
authors: DA
authors: Duarte
authors: Renal Pathophysiology Laboratory Investigation on Diabetes Complications, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
authors: Chiara
authors: C
authors: Montemurro
authors: Renal Pathophysiology Laboratory Investigation on Diabetes Complications, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
authors: Alexandros
authors: A
authors: Papadimitriou
authors: Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas, Campinas, Brazil 3Brazilian Biosciences National Laboratory, Brazilian Center for Research in Energy and Materials, Campinas, Brazil.
authors: Sílvio Roberto
authors: SR
authors: Consonni
authors: Renal Pathophysiology Laboratory Investigation on Diabetes Complications, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
authors: José B
authors: JB
authors: Lopes de Faria
mesh_terms: D000818:Animals; D017209:Apoptosis; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental; D003930:Diabetic Retinopathy / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D063928:Ependymoglial Cells / Q000378:metabolism / Q000648:ultrastructure; D005786:Gene Expression Regulation; D005947:Glucose / Q000494:pharmacology; D046529:Microscopy, Electron, Transmission; D018384:Oxidative Stress; D034741:RNA, Small Interfering / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D012160:Retina / Q000378:metabolism* / Q000473:pathology; D000071456:Sequestosome-1 Protein / Q000096:biosynthesis / Q000235:genetics*; D013549:Sweetening Agents / Q000494:pharmacology
chemical_list: D034741:RNA, Small Interfering; D000071456:Sequestosome-1 Protein; C491079:Sqstm1 protein, rat; D013549:Sweetening Agents; D005947:Glucose