High density lipoprotein mediated lipid efflux from retinal pigment epithelial cells in culture

• Published in: British journal of ophthalmology 2006-05, Vol.90 (5), p.616-620
• Main Authors: Ishida, B Y, Duncan, K G, Bailey, K R, Kane, J P, Schwartz, D M
• Format: Article
• Language: English
• Subjects: ABCA1; Adult; age related macular degeneration; Aging; AMD; apoA-I; apoE; apolipoprotein A-I; Apolipoprotein A-I - metabolism; apolipoprotein E; Apolipoproteins; ATP binding cassette transporter A1; Biological and medical sciences; Biological Transport; Bruch’s membrane; C reactive protein; Cells, Cultured; Cholesterol; cholesterol esters; Chromatography, Thin Layer; CRP; DHA; docosahexanoic acid; Epithelial Cells - secretion; HDL; high density lipoprotein; Humans; Laboratory Science - Extended Report; LCAT; LDL; lecithin:cholesterol acyltransferase; lipid; Lipid peroxidation; Lipids; Lipids - analysis; Lipids - secretion; Lipoproteins; Lipoproteins, HDL - metabolism; liquid scintillation counting; low density lipoprotein; LSC; Macular degeneration; Male; Medical sciences; Miscellaneous; Ophthalmology; PBS; phosphate buffered saline; phosphatidyl choline; phosphatidyl ethanolamine; phosphatidyl inosotol; Phosphatidylcholines - analysis; Phosphatidylcholines - secretion; Phosphatidylethanolamines - analysis; Phosphatidylethanolamines - secretion; Phosphatidylinositols - analysis; Phosphatidylinositols - secretion; photoreceptor outer segments; Pigment Epithelium of Eye - metabolism; Pigment Epithelium of Eye - secretion; POS; Radioisotopes; RCT; retinal pigment epithelium; reverse cholesterol transport; Rod Cell Outer Segment - metabolism; RPE; scavenger receptor BI; SR-BI; thin layer chromatography; TLC; triglycerides
• ISSN: 0007-1161; 1468-2079
• DOI: 10.1136/bjo.2005.085076

Backgound/aim: The transport of radiolabelled photoreceptor outer segments (POS) lipids was investigated by cultured retinal pigment epithelial cells (RPE). Phagocytosis of POS by the RPE is essential to maintain the health and function of the photoreceptors in vivo. POS are phagocytised at the apical cell surface of RPE cells. Phagocytised POS lipids may be either recycled to the photoreceptors for reincorporation into new POS or they may be transported to the basolateral surface for efflux into the circulation. Results: The authors have demonstrated that high density lipoprotein (HDL) stimulates efflux of radiolabelled lipids, of POS origin, from the basal surface of RPE cells in culture. Effluxed lipids bind preferentially to HDL species of low and high molecular weight. Effluxed radiolabelled phosphotidyl choline was the major phospholipid bound to HDL, with lesser amounts of phosphatidyl ethanolamine, phosphatidyl inosotol. Effluxed radiolabelled triglycerides, cholesterol, and cholesterol esters also bound to HDL. Lipid free apolipoprotein A-I (apoA-I) and apoA-I containing vesicles also stimulate lipid efflux. Conclusion: The findings suggest a role for HDL and apoA-I in regulating lipid and cholesterol transport from RPE cells that may influence the pathological lipid accumulation associated with age related macular degeneration.