Delivery of a hydrophobic small molecule LXR agonist via sHDL nanoparticles in a preclinical model of dry AMD

Abstract

Purpose : AMD is a blinding disorder characterized by the accumulation of lipids beneath the Bruch’s membrane (drusen) and the invasion of immune cells into the retina. Activating the Liver X receptor (LXR) pathway can promote efflux of cholesterol from atherosclerotic plaques and inhibit pro-inflammatory cytokine production. Here, we evaluated the delivery of the hydrophobic LXR agonist (T0) complexed within a synthetic HDL (sHDL) molecule via intravitreal treatment (IVT) in a dry AMD animal model.

Methods : Mice or rats were injected with sodium iodate (NaIO₃, 40mg/kg) via the femoral vein. Either vehicle (PBS or DMSO) or drug (sHDL, T0, or sHDL-T0) was given via IVT immediately before NaIO₃ injection. A subset of animals were treated with vehicle or drug only. Retina and eye cups containing RPE/Choroid were collected for qRT-PCR and Western blotting. In vivo OCT and ex vivo histology were performed to assess retinal thickness and photoreceptor viability. Retinal immune cell invasion was assessed via flow cytometry. Human iPSC-RPE cells grown on trans-well inserts were used to determine cholesterol efflux.

Results : T0-sHDL or T0 alone significantly increased expression of both Abca1 and Abcg1 in retina and RPE/choroid. Cholesterol efflux studies in iPSC-RPE cells showed significant increase in both apical and basolateral directions with basal efflux being 3.5-4.7 fold higher than apical efflux. We saw significant decreases in IL-6, Tnfα, Nlrp3, and Nf-κb expression via qRT-PCR. Flow cytometry showed sHDL-T0 induced a significant decrease in microglia and macrophage activity (CD45, Ly6C, IBA1) in retinas from NaIO₃ treated animals. OCT analysis did not show any difference in retinal thickness at 7-days post NaIO₃ treatment. We also did not detect any differences between vehicle or drug treated eyes at days 1-5 post NaIO₃ administration.

Conclusions : Activating the LXR pathway enhances expression of cholesterol transporters in the retina/RPE while significantly increasing basal transport of cholesterol in human iPSC-RPE cells. We found significant decreases in pro-inflammatory signaling and immune cell activation in the NaIO₃ model of dry AMD after T0-sHDL treatment. Severe and rapid degeneration associated with NaIO₃ treatment prevented our ability to detect any neuroprotection in animals treated with the LXR agonist.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.