scholarly journals Peer Review #1 of "Ultrastructural alterations in the retinal pigment epithelium and photoreceptors of a Stargardt patient and three Stargardt mouse models: indication for the central role of RPE melanin in oxidative stress (v0.2)"

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5215 ◽  
Author(s):  
Tatjana Taubitz ◽  
Alexander V. Tschulakow ◽  
Marina Tikhonovich ◽  
Barbara Illing ◽  
Yuan Fang ◽  
...  

Background Stargardt disease (SD) is characterized by the accumulation of the age-pigment lipofuscin in the retinal pigment epithelium (RPE) and subsequent neuroretinal degeneration. The disease leads to vision loss early in life. Here, we investigate age-dependent ultrastructural changes in three SD mouse models: albino Abca4-/- and pigmented Abca4-/- and Abca4-/-.Rdh8-/- mice. Since we found indications for oxidative stress primarily in albino SD mice, we tested RPE melanin for its antioxidative capabilities. Methods SD mouse eyes were investigated by light, fluorescence and electron microscopy and were compared to the respective albino and pigmented wild type mice and to a human donor SD eye. To confirm the role of RPE melanin in scavenging oxidative stress, melanin from S. officinalis as a standard and porcine RPE were tested for their capability to quench superoxide anions. Results Histological alterations indicative of oxidative stress and/or lysosomal dysfunction were present in albino Abca4-/- and Abca4-/-.Rdh8-/- mice. Retinal damage, such as inner segment rupture and pyknotic or free photoreceptor nuclei in the subretinal space and RPE vacuolization were exclusively found in albino Abca4-/- mice. Shortened and disorganized photoreceptor outer segments and dead RPE cells were found in albino Abca4-/- and Abca4-/-.Rdh8-/- mice, with earlier onset in albino Abca4-/- mice. Undegraded phagosomes and lipofuscin accumulation were present in the RPE of all three SD strains, but numbers were highest in Abca4-/-.Rdh8-/- mice. Lipofuscin morphology differed between SD strains: (melano-)lipofuscin granules in pigmented Abca4-/- mice had a homogenous electron density and sharp demarcations, while lipofuscin in albino Abca4-/- mice had a flocculent electron density and often lacked a surrounding membrane, indicating loss of lysosomal integrity. Young Abca4-/-.Rdh8-/- mice showed (melano-)lipofuscin granules with homogenous electron density, while in aged animals granules with flocculent electron density predominated. Both strains of pigmented SD mice had melanolipofuscin clusters as found in the human SD eye. Like melanin from S. officinalis, porcine RPE melanin can also quench superoxide anions. Discussion The presented pathologies in albino Abca4-/- and Abca4-/-.Rdh8-/- mice suggest oxidative stress and/or lysosomal dysfunction within the RPE. Since albino Abca4-/- mice have the earliest onset and severest damage and as absence of melanin and also melanin turnover with age are known to diminish RPEs anti-oxidative properties, we assume that RPE melanin plays a role in SD related damages. A lack of pathology in pigmented Abca4-/- mice due to lower stress levels as compared to the Abca4-/-.Rdh8-/- mice underlines this hypothesis. It is also supported by the finding that RPE melanin can quench superoxide anions. We therefore suppose that RPE melanin is important in retinal health and we discuss its role as an oxidative stress scavenger.


Antioxidants ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 838 ◽  
Author(s):  
Patricia Fernandez-Robredo ◽  
Jorge González-Zamora ◽  
Sergio Recalde ◽  
Valentina Bilbao-Malavé ◽  
Jaione Bezunartea ◽  
...  

Diabetic retinopathy is a vision-threatening microvascular complication of diabetes and is one of the leading causes of blindness. Oxidative stress and inflammation play a major role in its pathogenesis, and new therapies counteracting these contributors could be of great interest. In the current study, we investigated the role of vitamin D against oxidative stress and inflammation in human retinal pigment epithelium (RPE) and human retinal endothelial cell lines. We demonstrate that vitamin D effectively counteracts the oxidative stress induced by hydrogen peroxide (H2O2). In addition, the increased levels of proinflammatory proteins such as Interleukin (IL)-6, IL-8, Monocyte chemoattractant protein (MCP)-1, Interferon (IFN)-γ, and tumor necrosis factor (TNF)-α triggered by lipopolysaccharide (LPS) exposure were significantly decreased by vitamin D addition. Interestingly, the increased IL-18 only decreased by vitamin D addition in endothelial cells but not in RPE cells, suggesting a main antiangiogenic role under inflammatory conditions. Moreover, H2O2 and LPS induced the alteration and morphological damage of tight junctions in adult retinal pigment epithelium (ARPE-19) cells that were restored under oxidative and inflammatory conditions by the addition of vitamin D to the media. In conclusion, our data suggest that vitamin D could protect the retina by enhancing antioxidant defense and through exhibiting anti-inflammatory properties.


Redox Biology ◽  
2020 ◽  
Vol 37 ◽  
pp. 101623 ◽  
Author(s):  
Mala Upadhyay ◽  
Caroline Milliner ◽  
Brent A. Bell ◽  
Vera L. Bonilha

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