Abstract
Purpose :
We have previously shown that hindered phenol compounds have potent cytoprotective activity against oxidized low-density lipoprotein-induced death of retinal pigment epithelial cells (RPE) in vitro. The goal of this work was to determine the ocular pharmacokinetics (PK) as well as the therapeutic effect of a sustained-release solid lipid nanoparticle (SLN) formulation of the hindered phenol pentamethyl-6-chromanol (PMC) in two mouse models, in which characteristics of AMD are induced by aging and high fat diet.
Methods :
PMC-loaded SLNs (SLN:PMC) were prepared by high-shear homogenization and delivered by periocular injection.For the PK study, total PMC in cornea/lens, retina, and RPE/choroid was determined by LC/MS analysis at 24 hours post-injection. For the efficacy study, 12-month-old wildtype C57BL/6J and APOE4-TR mice were fed with high fat diets (HFD) and treated weekly with SLN:PMC or empty SLN for five to six months. The eyes were then subjected to transmission electron microscopic analysis, or the RPE/choroid complex were used for gene expression analysis by semi-quantitative real-time PCR.
Results :
A single periocular injection of PMC (969 ng in 5 ul) either as SLN:PMC or free drug achieved therapeutic levels of total PMC (~100 ng/tissue, 17 uM) in both the retina and RPE/choroid complex at 24 hours (n = 3-4 eyes/group). Five to six months of HFD in aged C57BL/6J and APOE4-TR mice resulted in significant sub-retinal deposits of drusen-like material, thickening and sometimes disruption of the Bruch’s membrane, and frequent signs of RPE degeneration. Weekly treatment with SLN:PMC (1 mM of PMC) resulted in reduction of sub-retinal deposits, preservation of the normal morphology of the Bruch’s membrane and RPE. Analysis of gene expression of the RPE/choroid did not reveal any significant changes to genes that are involved in RPE function comparing aged C57BL/6J mice with and without HFD and comparing HFD fed C57BL/6J mice without and without PMC treatment.
Conclusions :
We have developed a sustained release SLN:PMC formulation which upon periocular injection achieved therapeutic levels of PMC in the back of the eye in the mouse. Preliminary experiments based on ultrastructural analysis suggested that SLN:PMC treatment was effective in reducing dry AMD-like pathologies in mouse models. These data support SLN:PMC as a potential therapeutic formulation for dry AMD.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.