Retinal G‐protein‐coupled receptor deletion exacerbates AMD‐like changes via the PINK1–parkin pathway under oxidative stress

Abstract

The intake of high dietary fat has been correlated with the progression of age‐related macular degeneration (AMD), affecting the function of the retinal pigment epithelium through oxidative stress. A high‐fat diet (HFD) can lead to lipid metabolism disorders, excessive production of circulating free fatty acids, and systemic inflammation by aggravating the degree of oxidative stress. Deletion of the retinal G‐protein‐coupled receptor (RGR‐d) has been identified in drusen. In this study, we investigated how the RGR‐d exacerbates AMD‐like changes under oxidative stress, both in vivo and in vitro. Fundus atrophy became evident, at 12 months old, particularly in the RGR‐d + HFD group, and fluorescence angiography revealed narrower retinal vessels and a reduced perfusion area in the peripheral retina. Although rod electroretinography revealed decreasing trends in the a‐ and b‐wave amplitudes in the RGR‐d + HFD group at 12 months, the changes were not statistically significant. Mice in the RGR‐d + HFD group showed a significantly thinner and more fragile retinal morphology than those in the WT + HFD group, with disordered and discontinuous pigment distribution in the RGR‐d + HFD mice. Transmission electron microscopy revealed a thickened Bruch's membrane along the choriocapillaris endothelial cell wall in the RGR‐d + HFD mice, and the outer nuclear layer structure appeared disorganized, with reduced nuclear density. Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated significantly lower levels of 25(OH)‐vitamin D3 metabolites in the RGR‐d + HFD group. Under oxidative stress, RGR‐d localized to the mitochondria and reduced the levels of the PINK1–parkin pathway. RGR‐d mice fed an HFD were used as a new animal model of dry AMD. Under high‐fat‐induced oxidative stress, RGR‐d accumulated in the mitochondria, disrupting normal mitophagy and causing cellular damage, thus exacerbating AMD‐like changes both in vivo and in vitro.

Abstract

Mice on a balanced diet or high‐fat diet were studied. At 12 months, fundus photography, fluorescein angiography, H&E staining, and transmission electron microscopy revealed retinal changes. Electroretinography assessed retinal function. ARPE‐19 cells were transfected with lentivirus carrying human RGR and RGR‐d genes. KEGG pathway analysis linked neurodegenerative signaling pathways to AMD‐like progression. Accumulated RGR‐d protein disrupts mitophagy and causes cellular damage. RGR‐d mice on HFD provide a new model for dry AMD, showing mitochondrial damage and aggravated AMD‐like features.