Potential Role of NUR77 in the Aging Retinal Pigment Epithelium and Age-Related Macular Degeneration

The underlying mechanisms associated with age-related changes in the morphology and function of retinal pigmented epithelial (RPE) cells are poorly understood. The aging RPE progresses through several structural changes including loss of melanin granules, accumulation of lipofuscin, and cytoskeletal changes, among others. Extracellular to it, there is also thickening of Bruch's membrane and changes in the integrity of the choroid. Recent studies have revealed that aging also affects the metabolic ecosystem of the RPE. Aged mitochondria exhibit decreased rates of oxidative phosphorylation, increased reactive oxygen species generation, and increased number of mitochondrial mutations relative to baseline. These changes are also found in age-related macular degeneration (AMD), a late-onset vision-impairing disease, in which the RPE is particularly vulnerable. The orphan nuclear receptor NR4A1/NUR77 is an early response gene and regulator of various cellular processes during development, aging, and disease. Previously we observed decreased levels of Nur77/NUR77 in both mouse and human RPE as a function of age. Current knowledge of the function of this receptor in the RPE is limited. Herein, we discuss the putative roles of NUR77 in the RPE during aging and disease.