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To elucidate the biological effects of blocking fluorescent light on the retina using specific blocking materials.Seven- to 8-week-old BALB/c mice were divided into three groups and placed in one of the three boxes: one blocked ultraviolet and violet wavelengths of light (violet blockade), one blocked ultraviolet, violet, blue and some other visible wavelengths (blue-plus blockade), and one allowed most visible light to pass through (control). They were then exposed to a white fluorescent lamp for 1 h at 5.65E-05 mW/cm(2) /s. After treatment, the electroretinogram, retinal outer nuclear layer thickness and retinal outer segment length were measured. In addition, retinal apoptotic cells were quantified by TdT-mediated dUTP nick-end labelling assay and c-Fos messenger RNA, and protein levels were measured by real-time reverse-transcription polymerase chain reaction and immunoblot analyses, respectively.The blue-plus blockade group retained a significantly better electroretinogram response following light exposure than the control or violet blockade groups. The blue-plus blockade group also exhibited greater outer nuclear layer thickness and greater outer-segment length, and fewer apoptotic cells after light exposure than the other groups. The c-Fos messenger RNA and protein levels were substantially reduced in the blue-plus blockade group and reduced to a lesser extent in the violet blockade group.The blockade of blue plus additional visible wavelengths of light was most effective in protecting the retina from light-induced damage. The blockade of violet light alone was also effective in reducing intracellular molecular responses, but these effects were not sufficient for attenuating retinal degeneration.

Background Anti-vascular endothelial growth factor (VEGF) drugs and/or photodynamic therapy (PDT) constitute current treatments targeting pathological vascular tissues in tumors and age-related macular degeneration. Concern that PDT might induce VEGF and exacerbate the disease has led us to current practice of using anti-VEGF drugs with PDT simultaneously. However, the underlying molecular mechanisms of these therapies are not well understood. Methods We assessed VEGF levels after PDT of normal mouse retinal tissue, using a laser duration that did not cause obvious tissue damage. To determine the role of PDT-induced VEGF and its downstream signaling, we intravitreally injected a VEGF inhibitor, VEGFR1 Fc, or a PI3K/Akt inhibitor, LY294002, immediately after PDT. Then, histological and biochemical changes of the retinal tissue were analyzed by immunohistochemistry and immunoblot analyses, respectively. Results At both the mRNA and protein levels, VEGF was upregulated immediately and transiently after PDT. VEGF suppression after PDT resulted in apoptotic destruction of the photoreceptor cell layer in only the irradiated area during PDT. Under these conditions, activation of the anti-apoptotic molecule Akt was suppressed in the irradiated area, and levels of the pro-apoptotic protein BAX were increased. Intravitreal injection of a PI3K/Akt inhibitor immediately after PDT increased BAX levels and photoreceptor cell apoptosis. Conclusion Cytotoxic stress caused by PDT, at levels that do not cause overt tissue damage, induces VEGF and activates Akt to rescue the neural tissue, suppressing BAX. Thus, the immediate and transient induction of VEGF after PDT is neuroprotective.

Light damage to the retina accelerates retinal degeneration in human diseases and rodent models. Recently, the polyphenolic phytoalexin resveratrol has been shown to exert various bioactivities in addition to its classical antioxidant property. In the present study, we investigated the effect of resveratrol on light-induced retinal degeneration together with its underlying molecular mechanisms. BALB/c mice with light exposure (5000-lux white light for 3 hours) were orally pretreated with resveratrol at a dose of 50 mg/kg for 5 days. Retinal damage was evaluated by TdT-mediated dUTP nick-end labeling, outer nuclear layer morphometry, and electroretinography. Administration of resveratrol to mice with light exposure led to a significant suppression of light-induced pathological parameters, including TdT-mediated dUTP nick-end labeling-positive retinal cells, outer nuclear layer thinning, and electroretinography changes. To clarify the underlying molecular mechanisms, the nuclear translocation of activator protein−1 subunit c-fos was evaluated by enzyme-linked immunosorbent assay, and the retinal activity of sirtuin 1 was measured by deacetylase fluorometric assay. Retinal activator protein-1 activation, up-regulated following light exposure, was significantly reduced by application of resveratrol. In parallel, retinal sirtuin 1 activity, reduced in animals with light damage, was significantly augmented by resveratrol treatment. Our data suggest the potential use of resveratrol as a therapeutic agent to prevent retinal degeneration related to light damage.

The process of aging involves the accumulating changes in the microenvironment that lead to cell senescence or apoptosis, and subsequent tissue or organ dysfunction. Multiple extrinsic and intrinsic events that cause DNA instability are associated with aging. Cells containing unstable DNA are biologically vulnerable, and if the DNA damage is too great for the cell to repair, it becomes senescent or dies by apoptosis. Thus, the cell’s capacity to repair its DNA determines the progress of aging, at least in part. Here, we focus on the sirtuins, the mammalian homologs of the yeast life-span-extending molecule, Sir2. Among the sirtuin family proteins in mammals, the one most similar to yeast Sir2 is SIRT1, which is involved in multiple pathways, including the repair of DNA double-strand breaks. Although the role of SIRT1 in mammalian longevity is not clear, it is expressed throughout the retina, where it may suppress aging. In fact, a mutant mouse model of retinal degeneration shows an abnormal subcellular localization of SIRT1 protein and accelerated retinal cell apoptosis. Further analyses are required to elucidate the mechanism of DNA damage and repair, including the contributions of the sirtuins, in the aged or diseased retinas, which will help us understand the mechanisms of retinal aging.

Aims/hypothesis: Diabetic retinopathy is a progressive neuro-degenerative disease, but the underlying mechanism is still obscure. Here, we focused on oxidative stress in the retina, and analysed its influence on retinal neurodegeneration, using an antioxidant, lutein. Methods: C57BL/6 mice with streptozotocin-induced diabetes were constantly fed either a lutein-supplemented diet or a control diet from the onset of diabetes, and their metabolic data were recorded. In 1-month-diabetic mice, reactive oxygen species (ROS) in the retina were measured using dihydroethidium and visual function was evaluated by electroretinograms. Levels of activated extracellular signal-regulated kinase (ERK), synaptophysin and brain-derived neurotrophic factor (BDNF) were also measured by immunoblotting in the retina of 1-month-diabetic mice. In the retinal sections of 4-month-diabetic mice, histological changes, cleaved caspase-3 and TUNEL staining were analysed. Results: Lutein did not affect the metabolic status of the diabetic mice, but it prevented ROS generation in the retina and the visual impairment induced by diabetes. ERK activation, the subsequent synaptophysin reduction, and the BDNF depletion in the diabetic retina were all prevented by lutein. Later, in 4-month-diabetic mice, a decrease in the thickness of the inner plexiform and nuclear layers, and ganglion cell number, together with increase in cleaved caspase-3- and TUNEL-positive cells, were avoided in the retina of lutein-fed mice. Conclusions/interpretation: The results indicated that local oxidative stress that has a neurodegenerative influence in the diabetic retina is prevented by constant intake of a lutein-supplemented diet. The antioxidant, lutein may be a potential therapeutic approach to protect visual function in diabetes.