Long-Acting RXR Agonism Preserves Retinal Function and Modulates Inflammation in Diabetic Retinopathy.

Abstract

Diabetic retinopathy (DR) is a leading cause of vision loss and is associated with reduced nuclear retinoid X receptor (RXR) activity. Retinal explants exposed to high glucose showed downregulation of RXR, peroxisome proliferator-activated receptor (PPAR), and liver X receptor-β and their lipid metabolism targets (Abca1, Scd1, and Acox1). Supplementation with the RXR agonist UAB126 restored nuclear receptor signaling and preferentially activated RXR/PPAR heterodimers. We evaluated UAB126 microparticles (UAB126-MP), a sustained-release RXR agonist formulation, for pharmacokinetic, molecular, and functional effects in db/db mouse retinas. A single intravitreal injection of UAB126-MP provided extended drug exposure for up to 6 months and increased retinal RXRα expression. Functionally, UAB126-MP preserved scotopic and photopic electroretinographic responses at 2 months and sustained cone photoreceptor function at 6 months. However, it did not reduce acellular capillaries. At 6 months, immunostaining and flow cytometry revealed decreased retinal macrophage/microglial infiltration and reduced CD45-positive myeloid cells and monocytes. These findings indicate that RXR agonism supports neuronal protection and immune modulation but does not prevent vasodegeneration, suggesting primarily neuroprotective and anti-inflammatory actions. Collectively, UAB126-MP confers durable retinal protection through nuclear receptor-mediated pathways, underscoring its potential as a long-acting therapeutic strategy for DR. High glucose exposure of retinal explants reduces expression of nuclear receptors retinoid X receptor (RXR), peroxisome proliferator-activated receptor, and liver X receptor-β, and treatment with UAB126 increases the formation of RXR-peroxisome proliferator-activated receptor heterodimers. Sustained release of UAB126-loaded microparticles enables intravitreal drug delivery for up to 6 months. Intravitreal UAB126 microparticles injection in diabetic mice confers long-term neuroprotection and anti-inflammatory benefits. RXR-targeted therapy represents a promising approach strategy for managing diabetic retinopathy.