NRF-2/PGC-1α deficiency induces retinal degeneration in mice

Abstract

Purpose : The pathogenesis of dry AMD includes degeneration of the retinal pigment epithelium (RPE), that secondarily leads to loss of rods and cones (photoreceptors). RPE cells are constantly exposed to oxidative stress that could cause damage to cellular proteins, DNA, and lipids and evoke tissue deterioration during the aging process. The ubiquitin-proteasome and the lysosomal/autophagosomal pathways are the two major proteolytic systems that are responsible for removing damaged molecules. NRF-2 (nuclear factor-erythroid 2-related factor-2) and PGC-1α (peroxisome proliferator-activated receptor gamma coactivator-1 alpha) are master transcription factors in the regulation of proteins involved in cellular detoxification. In this study, we examined the role of NRF-2 and PGC-1α in the regulation of RPE cell structure and function by using global double knockout (dKO) mice.

Methods : Light, confocal, and electron microscopy were used to examine microscopic anatomy and age-related RPE degeneration. . Immunohistochemical methods were used to study markers of oxidative stress (4-HNE (4-hydroxynonenal)), endoplasmic reticulum stress (GRP78 (glucose-regulated protein 78) and ATF4 (activating transcription factor 4)), proteasome(ubiquitin), autophagy (p62/SQSTM1(sequestosome 1), Beclin-1 and LC3B (microtubule associated protein 1 light chain 3 beta)) and macrophages (Iba-1) . Micro-MRI imaging was performed to find possible macroscopic differences between the dKO and WT mice.

Results : The NRF-2/PGC-1α dKO mice showed significant age-related RPE degeneration, accumulation of the oxidative stress marker (4-HNE) as well as endoplasmic reticulum stress markers GRP78 and ATF4. Furthermore, levels of protein ubiquitination and autophagy markers p62/SQSTM1, Beclin-1 and LC3B were significantly increased together with Iba-1 (ionized calcium binding adaptor molecule 1) macrophage marker staining. RPE cell size was also increased, suggesting more cell death occurred in the dKO mouse.

Conclusions : The RPE degeneration/phenotype in the NRF-2/PGC-1α dKO mouse replicates key features of dry AMD and thus, may be a valuable model for investigating the mechanism behind development of dry AMD.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.