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G. Lascaratos, D. Ji, J.P. M. Wood, N.N. Osborne; Light–Induced Retinal Ganglion Cell Apoptosis in Culture Is Attenuated by Certain Antioxidants . Invest. Ophthalmol. Vis. Sci. 2006;47(13):420.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal ganglion cell (RGC) axons in the globe contain many mitochondria and the potential for light to interact with these organelles was investigated on a transformed RGC line (RGC–5 cells) and also on isolated mitochondria. Moreover, selected potential antioxidants were used to determine whether they blunt any toxic influence of light.
Freshly isolated liver mitochondria were incubated for 12–14 hours, in the dark or in the light (400–760nm, intensities of 800 or 4000 lux) with or without different antioxidants. Near confluent cultures of RGC–5 cells were either kept in a dark incubator or transferred to an incubator containing light (generally1000 lux) for 2 days. In some cases the cell culture medium was modified during this period by addition of selected antioxidants or by the removal of serum. Oxidative status of the mitochondria and RGC–5 cells were assessed with the MTT assay and the measurement of mitochondrial dehydrogenase activity (WST–1 assay). In addition RGC–5 cells were stained for the presence of TUNEL–positive nuclei as an indicator of apoptosis and were assessed for the presence of reactive oxygen species (ROS) using 2’,7’–dihydroethidium (DHE).
Both the oxidative status and mitochondrial dehydrogenase activity in isolated mitochondria and RGC–5 cells were reduced by light, in an intensity– dependent manner. Moreover, many more TUNEL–positive RGC–5 cell nuclei were apparent following exposure to light for 2 days than cells maintained in the dark. The numbers of TUNEL–positive cells were exacerbated in cultures lacking serum. Further support for light inducing RGC–5 cell death in culture came from the analysis of the levels of ROS and caspase–3 and Bax proteins. The light–induced toxic effect on the survival of isolated mitochondria and RGC–5 cells was significantly blunted by vitamin E, zinc, metipranolol and nicotinamide but was unaffected by melatonin, manganese, magnesium or propranolol.
These data provide support for the principle that light entering the globe can interact with RGC axon mitochondria to generate ROS. It is proposed that when the RGC is already in a low energetic state, as might occur when IOP is elevated, then light entering the eye is a risk factor to the RGCs.
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