RESUMO
Stem cell-based disease modeling is an emerging technology for the mechanistic study and therapeutic screening of complex ocular pathologies. In this issue of Cell Stem Cell, Saini et al. (2017) show that iPSC-derived RPE cells from age-related macular degeneration patients express increased levels of pro-inflammatory factors that can be normalized by the anti-aging drug nicotinamide.
Assuntos
Degeneração Macular/metabolismo , Corioide/citologia , Corioide/metabolismo , Serina Peptidase 1 de Requerimento de Alta Temperatura A/metabolismo , Humanos , Lisossomos/efeitos dos fármacos , Lisossomos/metabolismo , Degeneração Macular/tratamento farmacológico , Niacinamida/farmacologia , Niacinamida/uso terapêutico , Estresse Oxidativo/efeitos dos fármacos , Proteínas/metabolismo , Epitélio Pigmentado da Retina/efeitos dos fármacos , Epitélio Pigmentado da Retina/metabolismo , Transtornos da Visão/metabolismo , Transtornos da Visão/fisiopatologiaRESUMO
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-α 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 δ-opioid receptor (DOR) binding and stimulation, thereby decreasing TNF-α-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.