Purchase this article with an account.
Jason Miller, Feriel Presswalla, Qitao Zhang, David N Zacks, Debra A Thompson; Measuring and Modulating Lipid Handling Pathways in the RPE: Implications for Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4032.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Lipid handling by the RPE is predicted to influence the deposition of extracellular lipid-rich drusen and reticular pseudodrusen (RSD) that are hallmarks of dry age-related macular degeneration (AMD). The RPE’s balance between storing, degrading, or secreting lipid is not well defined. Further, whether this balance can be pharmacologically manipulated, with the goal of diminishing drusen accummulation, is also unknown. In this study, primary human RPE cultures with or without photoreceptor outer segment (POS) feedings were monitored for lipid droplet accumulation, ketogenesis, and secretion of key drusen components in the presence or absence of inducers of the catabolic autophagy pathway.
Apical versus basolateral secretion was measured on mature cultures of polarized primary human fetal RPE maintained on Transwells, cultured in various serum-free media formulations with and without lipid supplementation. POS challenge was used to isolate the effect of phagocytosis on lipid balance. The buildup and dissipation of lipid droplets and ketone bodies were tracked by anti-ADRP immunocytochemistry and a fluorometric beta-hydroxybutyrate assay, respectively. Secretion of apolipoproteins E and B (APOE/APOB) were evaluated by western blot. Cholesterol secretion was measured by a fluorometric assay. Autophagy inducers were mTor independent and selected from a previously performed screen.
Primary human fetal RPE cultures constitutively secrete APOE in approximately equal quantities apically and basolaterally, along with unesterified cholesterol largely apically, consistent with the known compositional differences of drusen and RSD from human AMD samples. A POS bolus delivered apically to mimic photoreceptor shedding triggers a transient rise in lipid droplets, then ketone bodies, and finally APOE secretion. The influence of POS on cholesterol and APOB secretion is under evaluation. The effect of basolaterally supplied lipid (to mimic choroid-derived lipid) on lipid balance is also under evaluation. Preliminary data demonstrates that autophagy inducers alter the RPE culture’s lipid secretory profile.
The balance of lipid storage, degradation, and secretion in RPE changes with POS exposure and possibly with basolateral lipid exposure. This balance can be manipulated by altering autophagy, with implications for lessening drusen and RSD burden in AMD.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
This PDF is available to Subscribers Only