Daily blue-light exposure shortens lifespan and causes brain neurodegeneration in Drosophila
Light is necessary for life, but prolonged exposure to artificial light is a matter of increasing health concern. Humans are exposed to increased amounts of light in the blue spectrum produced by light-emitting diodes (LEDs), which can interfere with normal sleep cycles. The LED technologies are relatively new; therefore, the long-term effects of exposure to blue light across the lifespan are not understood. We investigated the effects of light in the model organism, Drosophila melanogaster, and determined that flies maintained in daily cycles of 12-h blue LED and 12-h darkness had significantly reduced longevity compared with flies maintained in constant darkness or in white light with blue wavelengths blocked. Exposure of adult flies to 12?h of blue light per day accelerated aging phenotypes causing damage to retinal cells, brain neurodegeneration, and impaired locomotion. We report that brain damage and locomotor impairments do not depend on the degeneration in the retina, as these phenotypes were evident under blue light in flies with genetically ablated eyes. Blue light induces expression of stress-responsive genes in old flies but not in young, suggesting that cumulative light exposure acts as a stressor during aging. We also determined that several known blue-light-sensitive proteins are not acting in pathways mediating detrimental light effects. Our study reveals the unexpected effects of blue light on fly brain and establishes Drosophila as a model in which to investigate long-term effects of blue light at the cellular and organismal level.
Natural light is essential for the entrainment of circadian clocks, which leads to temporal coordination of physiology and behavior. However, emerging evidence suggests that increased exposure to artificial light is a risk factor for sleep and circadian disorders.1,2 With the prevalent use of LED lighting and device displays, humans are subjected to increasing amounts of light in the blue spectrum since commonly used LEDs emit a high fraction of blue light, often peaking at 460?nm (these lights appear white due to the addition of broad-spectrum yellow garnet phosphor).3 Blue light may affect human eyes,4 and recent data suggest that extraocular light may impact human brain physiology.5 However, the consequences of daily exposure to blue-enriched light across the lifespan are not known.
Flies are used extensively to understand the mechanisms of aging in laboratories across the world, but the specifics of light conditions in terms of intensity and spectral composition are usually not provided. Our study suggests that the light used in fly facilities may critically affect experimental outcomes and should be reported in aging studies to facilitate the consistency of the results coming from different labs. Our discovery that lifetime exposure to artificial light may cause extra-retinal damage and reduce longevity in a complex model organism provides a novel opportunity to understand the molecular mechanisms of the increasingly evident harmful side of light.
This was a good scientific method with data for analysis. The results seem to confirm the posit of the article. However is this data relevant to primates or humans.?
Such is the challenge of translating animal studies to humans.