Oxidative Stress and Dysfunctional Intracellular Traffic Linked to an Unhealthy Diet Results in Impaired Cargo Transport in the Retinal Pigment Epithelium (RPE)

Abstract

Scope: Oxidative stress and dysregulated intracellular trafficking are associated with an unhealthy diet which underlies pathology. Here, these effects on photoreceptor outer segment (POS) trafficking in the retinal pigment epithelium (RPE), a major pathway of disease underlying irreversible sight-loss, are studied.

Methods and results: POS trafficking is studied in ARPE-19 cells using an algorithm-based quantification of confocal-immunofluorescence data supported by ultrastructural studies. It is shown that although POS are tightly regulated and trafficked via Rab5, Rab7 vesicles, LAMP1/2 lysosomes and LC3b-autophagosomes, there is also a considerable degree of variation and flexibility in this process. Treatment with H₂ O₂ and bafilomycin A¹ reveals that oxidative stress and dysregulated autophagy target intracellular compartments and trafficking in strikingly different ways. These effects appear limited to POS-containing vesicles, suggesting a cargo-specific effect.

Conclusion: The findings offer insights into how RPE cells cope with stress, and how mechanisms influencing POS transport/degradation can have different outcomes in the senescent retina. These shed new light on cellular processes underlying retinopathies such as age-related macular degeneration. The discoveries reveal how diet and nutrition can cause fundamental alterations at a cellular level, thus contributing to a better understanding of the diet-disease axis.

Keywords: cargo trafficking; oxidative stress; phagosome and autophagy-lysosomal pathways; retinal pigment epithelium.