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Abstract

This report reviews our experimental work on cultured retinal pigment epithelial (RPE) cells, fed native or UV-irradiated photoreceptor outer segments (POS). We showed that significantly more lipofuscin (LF) was formed in cells cultured in 40% oxygen than in cells cultured in 8% oxygen, indicating an involvement of oxidative mechanisms in LF formation. The antioxidants alpha-tocopherol, lycopene, zeaxanthin and lutein significantly reduced LF formation. RPE cells high in melanin content exhibited significantly less formation of LF than cells low in or devoid of melanin, suggesting that melanin acts as an effective antioxidant. The phagocytic capacity of LF-loaded RPE cells was significantly reduced compared to that of unloaded control cells, indicating that LF-loaded RPE cells may be unable to serve the photoreceptors sufficiently regarding phagocytosis of shed outer segment tips. Blue light irradiation destabilized lysosomal membranes in LF-loaded RPE cells and significantly reduced the viability of such cells compared to unloaded, irradiated control cells. These results may be of significance in relation to the development of age-related macular degeneration (AMD).

Physiological effects of formulation containing tannase-converted green tea extract on skin care: physical stability, collagenase, elastase, and tyrosinase activities

“…In addition, antioxidants inhibit pigmentation by various mechanisms including scavenging of ROS and reactive nitrogen species, 40 and reduction of o -quinones or other intermediates in melanin biosynthesis, thus delaying oxidative polymerization 41 . α-Tocopherol, an antioxidant, is usually known to inhibit melanin formation by suppressing oxidative polymerization of phenylalanines 42 . Therefore, polyphenolic compounds are partially responsible for the efficacy of substances used as whitening agents in skin-care products.…”

Studying melanin and lipofuscin in RPE cell culture models

“…Over the past two and a half decades there have been a plethora of studies reporting that repeated phagocytosis of isolated photoreceptor outer segments leads to the progressive accumulation of autofluorescent granules within cultured primary RPE cells and RPE cell lines (Boulton et al, 1989; Guha et al, 2013; Kaemmerer et al, 2007; Lei et al, 2013; Nilsson et al, 2003; Thampi et al, 2012; Wihlmark et al, 1996). The first such report was by Boulton and colleagues who fed cultured primary human RPE cells purified bovine rod outer segments daily for up to 3 months (Boulton et al, 1989).…”

Idebenone Prevents Oxidative Stress, Cell Death and Senescence of Retinal Pigment Epithelium Cells by Stabilizing BAX/Bcl-2 Ratio

“…In this context, it is of importance that RPE cells are highly susceptible to oxidative stress [5]. One reason for this is that RPE cells contain numerous intracellular photoreactive compounds, including lipofuscin, melanin, and others, absorbing especially in the blue spectral range and thereby promoting the formation of oxygen radicals [6]. In addition, numerous oxygen radical-producing enzymes as well as the high content of fatty acids and the high metabolism rate of the RPE cells contribute to a metabolic imbalance and to an oxidized status [7].…”