Oxidized Lipids Decrease Phagocytic Activity of ARPE‐19 Cells In Vitro

Abstract

Phospholipids, representing 80% of retinal lipids, contain a high level of polyunsaturated fatty acids, which are susceptible to oxidation. It has recently been shown that Folch’ extract of bovine neural retinas reveals moderate photoreactivity by generating reactive oxygen species upon irradiation with blue light. Importantly, the photoreactivity markedly increases upon oxidation of the exctracted lipids. In this work, the phototoxic potential of the Folch’ extract of bovine neural retinas (BRex), subjected to controlled oxidation, is studied in vitro employing a retinal pigment epithelium cell line (ARPE‐19). Multilamellar liposomes prepared from BRex, equilibrated with air, are oxidized in the dark at 37 °C for up to 400 h. The liposomes are then introduced into ARPE‐19 cells by phagocytosis. The impact of BRex at different stages of oxidation on viability and specific phagocytic activity of ARPE‐19 cells exposed to visible light is analyzed. While the oxidized BRex, at the light doses employed, does not induce any measurable killing of the cells, the treatment noticeably decreases their specific phagocytic activity.Practical Applications: Lipid oxidation products are commonly considered as an efficient protein modification factor occurring in the retina. Although possible consequences of oxidation of retinal lipids for the onset and development of age‐related macular degeneration are widely discussed, their potential photoreactivity and possible phototoxicity have not been considered. This is an important issue; taking into account that reactive products of lipid oxidation present in the outer retina, it may be exposed to short‐wavelength visible radiation. If photoreactive, peroxidized retinal lipids may act as acquired endogenous sensitizers increasing the risk of retina photodamage. In this work, the phototoxic potential of the Folch’ extract of bovine neural retinas (BRex), subjected to controlled oxidation, is studied in vitro employing a retinal pigment epithelium cell line (ARPE‐19).Lipids present in the retina are characterized by high level of unsaturation that makes them susceptible to oxidation. When oxidized, retinal lipids become photoreactive under visible light. Treatment of retinal pigment epithelium cells (ARPE‐19) with liposomes prepared from oxidized Folch’ extract of bovine neural retinas followed by irradiation with visible light, reduces phagocytic activity of ARPE‐19 cells.