Abstract
Purpose :
Free cholesterol can efflux onto lipid-rich HDL2 particles in the bloodstream from scavenger receptor B1 (SR-B1) on the surface of peripheral cells. SR-B1 has been detected in the retinal pigment epithelium (RPE) of humans and mice. In this work, we investigated if RPE SR-B1 can facilitate free cholesterol efflux from the RPE of Bco2-/- mice.
Methods :
To specifically delete SR-B1 from the RPE of the Bco2-/- mice, we bred the Best-Cre mice and the floxed SR-B1 mice (Srb1f/f) into the Bco2-/- mice and generated the RPE-specific conditional knockout mice of SR-B1 (Best-Cre;Srb1f/f;Bco2-/-). SR-B1 expression was examined by western blot and Immunohistochemistry (IHC). Next, to detect the accumulation of free cholesterol in the RPE, we stained the retinal sections of 6-month-old Best-Cre;Srb1f/f;Bco2-/- mice (Srb1cKO) and Best-Cre;Bco2-/- mice (control) (3 mice/genotype) using filipin, and cholesterol was imaged with a bright-field microscope under excitation of a 365-nm UV light. We also further quantified the contents of free cholesterol in the RPE of these two mice with gas chromatography-mass spectrometry (GC-MS) (3 mice/genotype).
Results :
Western blot and IHC data demonstrate that SR-B1 had been successfully deleted from the RPE of Bco2-/- mice. There was no structural difference between the SR-B1 conditional knockout mice (Srb1cKO) and the control mice. Filipin staining revealed more free cholesterol in the RPE of the retinal sections of the Srb1cKO mice. GC-MS data shows that the accumulation of free cholesterol in the RPE of Srb1cKO mice was increased around 30% relative to the control mice.
Conclusions :
Our results demonstrate that specific deletion of RPE SR-BI can increase the accumulation of free cholesterol in the RPE. This finding may enhance our understanding of the metabolism of local RPE lipids.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.