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Retinal phototoxicity and the evaluation of the blue light hazard of a new solid-state lighting technology.

ABSTRACT: 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(?) 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.

SUBMITTER: Jaadane I

PROVIDER: S-EPMC7174369 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Retinal phototoxicity and the evaluation of the blue light hazard of a new solid-state lighting technology.

Jaadane Imene I Villalpando Rodriguez Gloria G Boulenguez Pierre P Carré Samuel S Dassieni Irene I Lebon Cecile C Chahory Sabine S Behar-Cohen Francine F Martinsons Christophe C Torriglia Alicia A

Scientific reports 20200421 1

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 ga ...[more]

PMID: 32317708

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Project description:Rhodopsin is a canonical member of class A of the G protein-coupled receptors (GPCRs) that are implicated in many of the drug interventions in humans and are of great pharmaceutical interest. The molecular mechanism of rhodopsin activation remains unknown as atomistic structural information for the active metarhodopsin II state is currently lacking. Solid-state (2)H NMR constitutes a powerful approach to study atomic-level dynamics of membrane proteins. In the present application, we describe how information is obtained about interactions of the retinal cofactor with rhodopsin that change with light activation of the photoreceptor. The retinal methyl groups play an important role in rhodopsin function by directing conformational changes upon transition into the active state. Site-specific (2)H labels have been introduced into the methyl groups of retinal and solid-state (2)H NMR methods applied to obtain order parameters and correlation times that quantify the mobility of the cofactor in the inactive dark state, as well as the cryotrapped metarhodopsin I and metarhodopsin II states. Analysis of the angular-dependent (2)H NMR line shapes for selectively deuterated methyl groups of rhodopsin in aligned membranes enables determination of the average ligand conformation within the binding pocket. The relaxation data suggest that the beta-ionone ring is not expelled from its hydrophobic pocket in the transition from the pre-activated metarhodopsin I to the active metarhodopsin II state. Rather, the major structural changes of the retinal cofactor occur already at the metarhodopsin I state in the activation process. The metarhodopsin I to metarhodopsin II transition involves mainly conformational changes of the protein within the membrane lipid bilayer rather than the ligand. The dynamics of the retinylidene methyl groups upon isomerization are explained by an activation mechanism involving cooperative rearrangements of extracellular loop E2 together with transmembrane helices H5 and H6. These activating movements are triggered by steric clashes of the isomerized all-trans retinal with the beta4 strand of the E2 loop and the side chains of Glu(122) and Trp(265) within the binding pocket. The solid-state (2)H NMR data are discussed with regard to the pathway of the energy flow in the receptor activation mechanism.

Dataset Information

Retinal phototoxicity and the evaluation of the blue light hazard of a new solid-state lighting technology.

Publications

Retinal phototoxicity and the evaluation of the blue light hazard of a new solid-state lighting technology.

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