RESUMO
Ageing and alteration of the functions of the retinal pigment epithelium (RPE) are at the origin of lost of vision seen in age-related macular degeneration (AMD). The RPE is known to be vulnerable to high-energy blue light. The white light-emitting diodes (LED) commercially available have relatively high content of blue light, a feature that suggest that they could be deleterious for this retinal cell layer. The aim of our study was to investigate the effects of "white LED" exposure on RPE. For this, commercially available white LEDs were used for exposure experiments on Wistar rats. Immunohistochemical stain on RPE flat mount, transmission electron microscopy and Western blot were used to exam the RPE. LED-induced RPE damage was evaluated by studying oxidative stress, stress response pathways and cell death pathways as well as the integrity of the outer blood-retinal barrier (BRB). We show that white LED light caused structural alterations leading to the disruption of the outer blood-retinal barrier. We observed an increase in oxidized molecules, disturbance of basal autophagy and cell death by necrosis. We conclude that white LEDs induced strong damages in rat RPE characterized by the breakdown of the BRB and the induction of necrotic cell death.
Assuntos
Barreira Hematorretiniana/efeitos da radiação , Proteínas do Olho/genética , Luz/efeitos adversos , Proteína Quinase C/genética , Epitélio Pigmentado da Retina/efeitos da radiação , Animais , Autofagia/genética , Autofagia/efeitos da radiação , Barreira Hematorretiniana/metabolismo , Proteínas do Olho/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Iluminação/efeitos adversos , Masculino , Necrose/etiologia , Necrose/genética , Necrose/metabolismo , Necrose/patologia , Estresse Oxidativo/efeitos da radiação , Proteína Quinase C/antagonistas & inibidores , Proteína Quinase C/metabolismo , Ratos , Ratos Wistar , Epitélio Pigmentado da Retina/metabolismo , Epitélio Pigmentado da Retina/patologia , Técnicas de Cultura de TecidosRESUMO
Exposure Limit Values (ELV) for artificial lighting were defined in order to prevent light-induced damage to the retina. The evaluation of the lighting devices include the correction of their spectra by the B(λ) function or blue light hazard function, representing the relative spectral sensitivity of the human eye to the blue light. This weighting function peaks between 435 and 440 nm. In this study we evaluate a new generation of light emitting diode (LED), the GaN-on-GaN (gallium nitride on gallium nitride) LED, that present an emission peak in the purple part of the spectrum. Wistar rats were exposed to GaN-on-GaN and conventional diodes at different retinal doses (from 2.2 to 0.5 J/cm2). We show that GaN-on-GaN diodes are more toxic than conventional LED for the rat neural retina and the rat retinal pigment epithelium, indicating that the BLH (blue light hazard) weighting is not adapted to this type of diodes. One of the reasons of this increased toxicity is the effects of shorter wavelengths on mitochondria polarization. We also show that the threshold of phototoxic retinal dose in the rat (fixed at 11 J/cm2, BLH weighted) is overestimated, suggesting that the values used for regulations, calculated in primates using the same methods than in rats, should be revised.
Assuntos
Gálio/química , Luz/efeitos adversos , Substâncias Luminescentes/química , Mitocôndrias/efeitos da radiação , Epitélio Pigmentado da Retina/efeitos da radiação , Animais , Biomarcadores/metabolismo , Cor , Relação Dose-Resposta à Radiação , Expressão Gênica/efeitos da radiação , Proteína Glial Fibrilar Ácida/genética , Proteína Glial Fibrilar Ácida/metabolismo , Humanos , Iluminação , Masculino , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Estresse Oxidativo , Primatas , Radiometria , Ratos , Ratos Wistar , Epitélio Pigmentado da Retina/metabolismo , Epitélio Pigmentado da Retina/patologia , Especificidade da Espécie , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismoRESUMO
Spectra of "white LEDs" are characterized by an intense emission in the blue region of the visible spectrum, absent in daylight spectra. This blue component and the high intensity of emission are the main sources of concern about the health risks of LEDs with respect to their toxicity to the eye and the retina. The aim of our study was to elucidate the role of blue light from LEDs in retinal damage. Commercially available white LEDs and four different blue LEDs (507, 473, 467, and 449nm) were used for exposure experiments on Wistar rats. Immunohistochemical stain, transmission electron microscopy, and Western blot were used to exam the retinas. We evaluated LED-induced retinal cell damage by studying oxidative stress, stress response pathways, and the identification of cell death pathways. LED light caused a state of suffering of the retina with oxidative damage and retinal injury. We observed a loss of photoreceptors and the activation of caspase-independent apoptosis, necroptosis, and necrosis. A wavelength dependence of the effects was observed. Phototoxicity of LEDs on the retina is characterized by a strong damage of photoreceptors and by the induction of necrosis.