Age-Related Changes in the Retinal Pigment Epithelium (RPE)

Abstract

BackgroundAge-related changes in the retina are often accompanied by visual impairment but their mechanistic details remain poorly understood.MethodologyProteomic studies were pursued toward a better molecular understanding of retinal pigment epithelium (RPE) aging mechanisms. RPE cells were isolated from young adults (3–4 month-old) and old (24–25 month-old) F344BN rats, and separated into subcellular fractions containing apical microvilli (MV) and RPE cell bodies (CB) lacking their apical microvilli. Proteins were extracted in detergent, separated by SDS-PAGE, digested in situ with trypsin and analyzed by LC MS/MS. Select proteins detected in young and old rat RPE were further studied using immunofluorescence and Western blot analysis.Principal FindingsA total of 356 proteins were identified in RPE MV from young and 378 in RPE MV from old rats, 48% of which were common to each age group. A total of 897 proteins were identified in RPE CB from young rats and 675 in old CB, 56% of which were common to each age group. Several of the identified proteins, including proteins involved in response to oxidative stress, displayed both quantitative and qualitative changes in overall abundance during RPE aging. Numerous proteins were identified for the first time in the RPE. One such protein, collectrin, was localized to the apical membrane of apical brush border of proximal tubules where it likely regulates several amino acid transporters. Elsewhere, collectrin is involved in pancreatic β cell proliferation and insulin secretion. In the RPE, collectrin expression was significantly modulated during RPE aging. Another age-regulated, newly described protein was DJ-1, a protein extensively studied in brain where oxidative stress-related functions have been described.Conclusions/SignificanceThe data presented here reveals specific changes in the RPE during aging, providing the first protein database of RPE aging, which will facilitate future studies of age-related retinal diseases.

Oxidative Stress Regulation by DJ-1 in the Retinal Pigment Epithelium

“…We also reported immunolocalization of DJ-1 protein in both young and aged rat RPE cells [7]. Here we extend our initial observations of DJ-1 expression and further discuss DJ-1 function in the RPE cells.…”

Effect of aging and lifestyle on photoreceptors and retinal pigment epithelium: cross-sectional study in a healthy Danish population

“…Exposure to reactive oxygen species may affect the health of photoreceptors and the Bruch’s membrane [24]. RPE isolated from young and old rats share only ~50% of their protein expression and the differences concern mostly proteins involved in pathways of oxidative stress such as catalase, glutathione peroxidase, and superoxidate dismutase [25]. Chen et al found that exposure to oxidized photoreceptor outer segments induced the multinucleation process in the RPE cells [23], and that age-related RPE multinucleation was more profound in central retina.…”

Loss of DJ-1 elicits retinal abnormalities, visual dysfunction, and increased oxidative stress in mice

“…Antibodies used included PARK7 (TA301239, Origene, Rockville, MD, 1:750), red/green opsin (AB5405, Millipore, Billerica, MA, 1:200), ribeye (CtBP2, 612044, BD Transduction, 1:500), ezrin (MS-661-P0, Thermo Scientific, Rockford, IL, 1:100), tyrosine hydroxylase (TH) (MAB318, Millipore, 1:400), 8-oxoguanine (MAB3560, Millipore, 1:300), and Nrf2 (sc-13032, Santa Cruz Biotechnology, Santa Cruz, CA, 1:100). For DJ-1 staining, sections were processed and labeled as previously described (Gu et al, 2012). …”

“…We initially reported the identification of DJ-1 peptides in both young and aged retinal pigment epithelium (RPE) lysates using a proteomic approach (Gu et al, 2012). Further studies showed that DJ-1 expression is higher in older eyes, suggesting a correlation between DJ-1 levels of expression and oxidative stress in the retina.…”