Retinal Pigment Epithelium in Human Donor Eyes Contains Higher Levels of Bisretinoids Including A2E in Periphery than Macula

Abstract

Purpose With age, human retinal pigment epithelium (RPE) accumulates bisretinoid fluorophores that may impact cellular function and contribute to age-related macular degeneration (AMD). Bisretinoids are comprised of a central pyridinium, dihydropyridinium, or cyclohexadiene ring. The pyridinium bisretinoid A2E has been extensively studied, and its quantity in the macula has been questioned. Age-changes and distributions of other bisretinoids are not well characterized. We measured levels of three bisretinoids and oxidized A2E in macula and periphery in human donor eyes of different ages. Methods Eyes ( N = 139 donors, 61 women and 78 men, aged 40–80 years) were dissected into 8 mm diameter macular and temporal periphery punches. Using liquid chromatography – electrospray ionization – mass spectrometry (LC-ESI-MS) and an authentic synthesized standard, we quantified A2E (ng). Using LC-ESI-MS and a 50-eye-extract of A2E, we semiquantified A2E and 3 other compounds (eye extract equivalent units [EEEUs): A2-glycerophosphoethanolamine (A2GPE), dihydropyridine phosphatidyl ethanolamine (A2DHPE), and monofuranA2E (MFA2E). Results A2E quantities in ng and EEEUs were highly correlated ( r = 0.97, P < 0.001). From 262 eyes, 5 to 9-fold higher levels were observed in the peripheral retina than in the macula for all assayed compounds. A2E, A2DHPE, and MFA2E increased with age, whereas A2GPE remained unaffected. No significant right-left or male-female differences were detected. Conclusions Significantly higher levels were observed in the periphery than in the macula for all assayed compounds signifying biologic differences between these regions. Levels of oxidized A2E parallel native A2E and not the distribution of retinal illuminance. Data will assist with the interpretion of clinical trial outcomes of agents targeting bisretinoid-related pathways.

Causal Influence of Plasma Metabolites on Age-Related Macular Degeneration: A Mendelian Randomization Study.

“…Research involving the quanti cation of mixed extracts from the macula and surrounding retinal areas has investigated the relationship between lipofuscin accumulation and age in the retinal pigment epithelium. Notably, A2-Glycerophosphoethanolamine, a type of retinoid acid, showed a 7.1-fold increase in these areas, although the increase was not statistically signi cant [37]. This implies that A2-Glycerophosphoethanolamine, despite being a retinoid acid, may not contribute to lipofuscin accumulation [38]].…”

Fluorescence Lifetime Imaging of Human Retinal Pigment Epithelium in Pentosan Polysulfate Toxicity Using Adaptive Optics Scanning Light Ophthalmoscopy

“…The work by Ami et al in hyperspectral autofluorescence imaging suggest at least 3 independent fluorophores in the RPE. 43 It is possible that prolonged lifetimes in PPS toxicity is attributable to increased melanolipofuscin, which is known to increase with age and in AMD 44 but is not obtainable in an exogenous form. Prolonged lifetimes in AMD RPE cells have also been hypothesized to be associated with increased oxidative stress.…”

Prolonged Lifetimes of Histologic Autofluorescence in Ectopic Retinal Pigment Epithelium in Age-Related Macular Degeneration

“…A recent study by Kotnala et al. 45 identified and quantified four bis-retinoids in the RPE. Whereas N-retinyl-N-retinylidene ethanolamine (A2E), dihydropyridine phosphatidyl ethanolamine (A2DHPE), and monofuranA2E (MFA2E) was more abundant in eyes >60 years than eyes <60 years, A2-glycerophosphoethanolamine (A2GPE) did not show this difference, and all 4 were more abundant in peripheral retina than in the macula.…”