The superoxide dismutase (SOD) family is a major antioxidant system, and deficiency of Cu,Zn-superoxide dismutase (SOD1) in mice leads to many different phenotypes that resemble accelerated aging. The purpose of this study was to examine the morphology and physiology of the sensory retina in Sod1 ؊/؊ mice. The amplitudes of the a-and b-waves of electroretinograms elicited by stimuli of different intensity were reduced in senescent Sod1 ؊/؊ mice, and this reduction in amplitude was more pronounced with increasing age. Retinal morphometric analyses showed a reduced number of nuclei in both the inner nuclear cell layer and outer nuclear cell layer. Electron microscopy revealed swollen cells and degenerated mitochondria in the inner nuclear cell and outer nuclear cell layer of senescent Sod1 ؊/؊ mice indicating necrotic cell death. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling revealed no significant differences in the number of apoptotic cells between Sod1 ؊/؊ and wild-type mice, and activated caspase-3 could not be detected in the retina of Sod1 ؊/؊ mice. In addition to the age-related macular degeneration-like phenotypes previously reported, Sod1 ؊/؊ mice also present progressive retinal degeneration. Our results indicate that Sod1 ؊/؊ mice may be a good model system in which to study the mechanism of reactive oxygen species-mediated retinal degeneration. The superoxide dismutase (SOD) family is one of the main antioxidant systems in the body and is made up of the three SOD isoenzymes; Cu,Zn-superoxide dismutase (SOD1) exists in the cytoplasm, SOD2 or Mn-SOD in the mitochondrial matrix, and SOD3 or extracellular SOD in the interstitium of tissues as the secreted form.1 SOD1 catalyzes superoxide radical dismutation and is distributed throughout the body, 1 and among the three isozymes, it is the most abundant in the retina.2 This suggests that SOD1 may be important in protecting the sensory retina from the reactive oxygen species (ROS)-mediated retinal damage.Many models of retinal degeneration have been studied 3,4 ; however, the mechanism of retinal cell deaths in some of these models has still not been determined. Cell death can be either necrotic or apoptotic, and necrotic cell death is characterized by a swelling of the cell membranes and organelles that leads to a disruption of the cell membranes and lysis. These alterations subsequently lead to inflammatory responses. 5 Apoptosis is a process of programmed cell death, and involves an orchestrated series of biochemical events leading to characteristic cell morphology and death. In some models of retinal degeneration, the death of the neurons has been shown to be attributable to apoptosis. 6 -8 SOD1 deficiency (Sod1 Ϫ/Ϫ ) leads to many different phenotypes resembling aging, and the changes are attributable to an elevation of ROS. 9,10 We recently reported that senescent Sod1 Ϫ/Ϫ mice had features of age-related macular degeneration (AMD) including the presence of drusen, choroidal neovascularization, and retinal pigment epithelium d...

PURPOSE. To elucidate the influences of light exposure on the retinal pigment epithelium (RPE) in vivo that may be involved in the pathogenesis of AMD.METHODS. Six-to 7-week-old BALB/c mice were exposed to light at 2000 lux for 3 hours. Flatmount RPE samples were immunostained with anti-ZO-1 antibody for evaluating tight junction, anti-N-cadherin, and anti-b-catenin antibodies for adherens junction, and stained with phalloidin for actin cytoskeleton. The reactive oxygen species (ROS) level was measured using DCFH-DA; Rho-associated coiled-coil forming kinase (ROCK) activity was by ELISA. RESULTS. Light exposure disrupted staining patterns of tight junctions, adherens junctions, and actin cytoskeleton in the RPE, where ROS was elevated. However, NAC treatment avoided the RPE changes, reducing ROS. ROCK activity increased after light exposure was suppressed by NAC, and the structural disruptions were suppressed by Y-27632. The levels of MCP-1, CCL11, and IL-6 increased after light exposure were suppressed by NAC. Light-induced MCP-1 and IL-6 were suppressed by Y-27632. Macrophage recruitment after light exposure was also suppressed either by NAC or Y-27632.CONCLUSIONS. Light exposure induced ROS and Rho/ROCK activation, which caused disruption of cell-cell junctions (tight junctions and adherens junctions) and actin cytoskeleton, the RPE's barrier structure, and induced AMD-associated pathological changes in the RPE-choroid.

Oxidative stress in the retinal pigment epithelium (RPE) is a well-accepted pathogenic change in vision-threatening diseases such as age-related macular degeneration. One source of oxidative stress is excessive light exposure, which causes excessive activation of the visual cycle. Because short wavelength light (blue light) has more energy, it is reported to be more harmful to photoreceptor cells than the other wavelengths of light. However, the biological effect of blue light in the RPE of living animals and the protective effect of a yellow intraocular lens (IOL) material that blocks blue light is still obscure. Therefore, we compared the pathogenic effect in the RPE-choroid complexes of mice exposed to light in a box made of a clear or a yellow IOL material. We measured the level of reactive oxygen species (ROS) using 2', 7'-dichlorodihydrofluorescein diacetate, the mRNA levels of inflammatory cytokines and a macrophage marker by real-time polymerase chain reaction, and the protein level of monocyte chemotactic protein-1 (MCP-1) by ELISA. The ROS level after light exposure was suppressed in the RPE-choroids of light-exposed mice in the yellow IOL material box. In parallel, all the inflammatory cytokines that we measured and a macrophage marker were also suppressed in the RPE-choroids of light-exposed mice in the yellow IOL material box. Therefore, a yellow IOL material suppressed, and thus blue light exacerbated, the increase in the ROS level and inflammatory cytokine expression as well as macrophage recruitment in the RPE-choroid in vivo after light exposure.

SOD1 deficiency causes RGC vulnerability, which may be involved in the underlying condition of NTG.

Choroidal neovascularization (CNV) is a pathogenic process of age-related macular degeneration, a vision-threatening disease. The retinal pigment epithelium and macrophages both influence CNV development. However, the underlying mechanisms remain obscure. Here, we focus on Angptl2 (angiopoietin-like protein 2), a cytokine involved in age-related systemic diseases. Angptl2 was originally identified as an adipocytokine and is also expressed in the eye. Using a laser-induced CNV model, we found that Angptl2 KO mice exhibited suppressed CNV development with reduced macrophage recruitment and inflammatory mediator induction. The mediators monocyte chemotactic protein-1, interleukin-1β (Il-1β), Il-6, matrix metalloprotease-9 (Mmp-9), and transforming growth factor-β1 (Tgf-β1) that were up-regulated during CNV development were all suppressed in the retinal pigment epithelium-choroid of CNV models generated in the Angptl2 KO mice. Bone marrow transplantation using wild-type and KO mice suggested that both bone marrow-derived and host-derived Angptl2 were responsible for macrophage recruitment and CNV development. Peritoneal macrophages derived from Angptl2 KO mice expressed lower levels of the inflammatory mediators. In the wild-type peritoneal macrophages and RAW264.7 cells, Angptl2 induced the mediators via integrins α4 and β2, followed by the downstream activation of NF-κB and ERK. The activation of NF-κB and ERK by Angptl2 also promoted macrophage migration. Therefore, Angptl2 from focal tissue might trigger macrophage recruitment, and that from recruited macrophages might promote expression of inflammatory mediators including Angptl2 in an autocrine and/or paracrine fashion to facilitate CNV development. Angptl2 might therefore represent a multistep regulator of CNV pathogenesis and serve as a new therapeutic target for age-related macular degeneration.