Visible light affects mitochondrial function and induces neuronal death in retinal cell cultures.
The aim of this study was to provide "proof of principle" for the hypothesis that light would have a detrimental influence on ganglion cells in certain situations, like in glaucoma, by directly impinging on the many mitochondria in their axons within the globe. In this study primary rat retinal cultures and freshly isolated liver mitochondria were exposed to light (400-760 nm; 500-4000 lux) as entering the eye. For culture assessment, 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and 4-[3-(-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetzolio]-1,3-benzene disulfonate (WST-1) reduction assays were used to assess cell and mitochondrial viability, respectively. Furthermore, cultures were stained for reactive oxygen species (ROS), DNA breakdown, numbers of GABA-immunoreactive (IR) cells and caspase-3 content to provide information concerning the effect of light on neuronal survival. Uptake of (3)H-GABA by autoradiography was also used, to assess the effects of light on the energy status of neurons. Light, in an intensity-dependent and trolox-inhibitable manner, reduced cell viability, affected mitochondrial function, increased the number of TUNEL-positive cells, decreased the numbers of GABA-IR neurons and enhanced labelling for ROS. These effects were all exacerbated by the absence of serum. There was also an increased caspase-3 protein content and a reduction of (3)H-GABA uptake in light- compared with dark-treated cultures. These findings support the hypothesis that light can affect mitochondria which could lead to neuronal apoptosis if the energetic status of these neurons is already compromised.
Lascaratos
Gerassimos
G
Nuffield Laboratory of Ophthalmology, University of Oxford, Walton Street, Oxford OX2 6AW, UK.
Ji
Dan
D
Wood
John P M
JP
Osborne
Neville N
NN
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D053148:Caspase 3 / Q000378:metabolism; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D004249:DNA Damage; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005901:Glaucoma / Q000473:pathology; D020287:In Situ Nick-End Labeling; D008930:Mitochondria, Liver / Q000502:physiology / Q000528:radiation effects*; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000528:radiation effects*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D017382:Reactive Oxygen Species; D005680:gamma-Aminobutyric Acid; D053148:Caspase 3