Endocytosis of Tight Junctions Caveolin Nitrosylation Dependent Is Improved by Cocoa Via Opioid Receptor on RPE Cells in Diabetic Conditions

Author(s)

Rosales, Mariana Aparecida B. ^[1] ; Silva, Kamila Cristina ^[1] ; Duarte, Diego A. ^[1] ; Rossato, Franco Aparecido ^[2] ; de Faria, Jose B. Lopes ^[1] ; Lopes de Faria, Jacqueline M. ^[1]

Affiliation

^[1] State Univ Campinas UNICAMP, Sch Med Sci, Renal Pathophysiol Lab & Invest Diabet Complicat, Campinas, SP - Brazil

^[2] State Univ Campinas UNICAMP, Sch Med Sci, Dept Clin Pathol, Bioenerget Lab, Campinas, SP - Brazil

• Document type: Journal article
• Source: INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE; v. 55, n. 9, p. 6090-6100, SEP 2014.
• Web of Science Citations: 11

Abstract

PURPOSE. Retinal pigment epithelium cells, along with tight junction (TJ) proteins, constitute the outer blood retinal barrier (BRB). Contradictory findings suggest a role for the outer BRB in the pathogenesis of diabetic retinopathy (DR). The aim of this study was to investigate whether the mechanisms involved in these alterations are sensitive to nitrosative stress, and if cocoa or epicatechin (EC) protects from this damage under diabetic (DM) milieu conditions. METHODS. Cells of a human RPE line (ARPE-19) were exposed to high-glucose (HG) conditions for 24 hours in the presence or absence of cocoa powder containing 0.5% or 60.5% polyphenol (low-polyphenol cocoa {[}LPC] and high-polyphenol cocoa {[}HPC], respectively). RESULTS. Exposure to HG decreased claudin-1 and occludin TJ expressions and increased extracellular matrix accumulation (ECM), whereas levels of TNF-alpha and inducible nitric oxide synthase (iNOS) were upregulated, accompanied by increased nitric oxide levels. This nitrosative stress resulted in S-nitrosylation of caveolin-1 (CAV-1), which in turn increased CAV-1 traffic and its interactions with claudin-1 and occludin. This cascade was inhibited by treatment with HPC or EC through delta-opioid receptor (DOR) binding and stimulation, thereby decreasing TNF-alpha-induced iNOS upregulation and CAV-1 endocytosis. The TJ functions were restored, leading to prevention of paracellular permeability, restoration of resistance of the ARPE-19 monolayer, and decreased ECM accumulation. CONCLUSIONS. The detrimental effects on TJs in ARPE-19 cells exposed to DM milieu occur through a CAV-1 S-nitrosylation-dependent endocytosis mechanism. High-polyphenol cocoa or EC exerts protective effects through DOR stimulation. (AU)

• FAPESP's process: 11/06719-1 - Do green-tea and Tempol (superoxide mimitic) present an beneficial effect in the pathogenesis of diabetic retinopathy? An in vivo study using human retinal pigmented epithelium cells (ARPE-19)
• Grantee: Jacqueline Mendonça Lopes de Faria
• Support Opportunities: Regular Research Grants
• FAPESP's process: 08/57560-0 - Effects of green tea (Camellia sinensis), cocoa and nitric oxide donor on diabetic nephropathy and retinopathy: contribution of the reduction of oxidative stress and inflammation and elevation of nitric oxide
• Grantee: Jose Butori Lopes de Faria
• Support Opportunities: Research Projects - Thematic Grants