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Richard H. Funk, Ulrike Schumann, Marius Ader, Lilla Knels, Cora Roehlecke; Oxidative Stress In Photoreceptors After Blue Light Exposure And Rescue By Wide-range Long-wavelength Light. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2567.
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Exposure of the retina to shorter wavelengths of light can lead to oxidative stress and severe damage in photoreceptors. In the present study, we focused on the effects of blue light irradiation on retinal explant cultures and possible rescue of wide-range long-wavelength light on photoreceptor morphology as well as metabolic function.
Murine retinal explant cultures were exposed to visible blue light (405 nm) as well as wide-range long-wavelength light (670 - 1250 nm). Live-dead kit was used to determine the viability of retinal (photoreceptor) cells. ROS production in the retinas was determined by dihydroethidium and CM-H2DCFDA, respectively. Mitochondrial membrane potential was estimated by JC-1 staining. The presence of the stress related proteins nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox)-2 and 4-hydroxy-2-nonenal (4-HNE) was assessed by immunohistochemistry. Morphological alterations of photoreceptor outer segments were studied by live imaging microscopy, transmission and scanning electron microscopy.
Already after 30 min of blue light exposure, live retinal explants displayed an increase in ROS production in photoreceptor cells; 3 h of blue light exposure caused a disorganization of the normally neatly stacked outer segments of living photoreceptors. Additionally, breaks in the cell membrane that surrounds the outer segments were observed. The outer segments appeared tortuous, and the lamellar structures became disrupted. Nox-2, a protein within the cell membrane and a major source for ROS, and 4-HNE (produced by lipid peroxidation after oxidative stress), were increased in the outer segments. Wide-range long-wavelength light exposure protected photoreceptors by reducing stress induced cell death.
In vitro blue light irradiation elicited very early morphological and metabolic changes that can lead to photoreceptor apoptosis. The molecular mechanisms of mitochondrial rescue by wide-range long-wavelength light are under investigation.
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