A disturbing new US study has reported that exposure to ‘blue light’ may significantly impact basic cellular functions – resulting in accelerated ageing.
Researchers and health authorities have consistently warned in recent years that exposure to ‘blue light’ before bedtime – notably from increased use of digital devices and artificial lighting in the home – adversely impacts our circadian rhythms and sleep quality.
Meanwhile, the common fruit fly (Drosophila melanogaster) is a widely used and important model organism among scientists because of the many cellular and developmental mechanisms it shares with other animals and humans. Now researchers at Oregon State University (OSU), studying the effects of blue light upon the lives of fruit flies, found it also seriously disturbed some of their basic cellular functions, hence accelerating their ageing process.
Blue light cell damage in brain
A previous fruit fly study at OSU, overseen by Professor Jaga Giebultowicz and led by honours biology graduate Trevor Nash, had reported that ‘daily exposure to blue light may accelerate ageing, even if it doesn’t reach your eyes’.
That study, published in Aging and Mechanisms of Disease, concluded ‘prolonged exposure
to blue light, such as that which emanates from your phone, computer and household fixtures, could be affecting your longevity, even if it’s not shining in your eyes’ – and specifically warned ‘the blue wavelengths produced by light- emitting diodes damage cells in the brain as well as retinas’.
The researchers noted: ‘Light is necessary for life, but prolonged exposure to artificial light is a matter of increasing health concern.
‘Modern 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.’
The research team investigated the effects of light in the model organism (Drosophila melanogaster) and determined that flies maintained in daily cycles of 12 hours blue
LED and 12 hours 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 hours of blue light per day ‘accelerated ageing phenotypes causing damage to retinal cells, brain neurodegeneration, and impaired locomotion’ (for example, the flies’ ability to climb the walls of their enclosures, a common behaviour, was diminished).
The team reported 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’.
They noted 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 ageing’.
They 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.’
Importantly, commented medicalnewstoday.com, the findings ‘suggest a reduced lifespan and brain neurodegeneration, even in mutant flies without eyes.
‘This means that blue light can damage cells and tissues in addition to those specialised for light perception.’
Impact on basic cellular functions
Now the new study from another team of scientists at OSU, also involving Drosophila melanogaster, goes further: it suggests blue light may also impact basic cellular functions, accelerating ageing.
In this study, published in Frontiers in Aging, the researchers reported that ‘chronic blue light leads to accelerated ageing in Drosophila by impairing energy metabolism and neurotransmitter levels’.
First they noted previous studies demonstrating that ‘chronic blue light exposure across lifespan leads to accelerated ageing manifested in reduced lifespan and brain neurodegeneration even in flies with genetically ablated eyes – suggesting blue light can damage cells and tissues not specialised for light perception
‘At the physiological level, blue light exposure impairs mitochondria function in flies, but the metabolic underpinnings of these effects have not been studied.’
Hence for this latest study the authors investigated effects of chronic blue light on metabolic pathways in heads of ‘eyes absent’ mutant flies – in order to focus on extra-retinal tissues.
For their project, the researchers compared the metabolomic profiles of flies kept for 10 or 14 days in constant blue light or constant darkness – including specifically studying the effects of prolonged blue light exposure on the metabolic pathways in the heads of mutant flies without eyes, to see the effect on non-retinal tissues.
Their data analysis revealed ‘significant alterations in the levels of several metabolites suggesting that critical cellular pathways are impacted in blue light-exposed flies.
‘In particular, dramatic metabolic rearrangements are observed in heads of flies kept in blue light for 14 days, including highly elevated levels of succinate but reduced levels of pyruvate and citrate, suggesting impairments in energy production.
‘These flies also show onset of neurodegeneration and our analysis detected significantly reduced levels of several neurotransmitters including glutamate and Gamma- aminobutyric acid (GABA), suggesting blue light disrupts brain homeostasis.
‘Taken together, these data provide novel insights into the mechanisms by which blue light interferes with vital metabolic pathways that are conserved between fly and human cells.’
Reduced energy production in mitochondria
Lead author Jun Yang told medicalnewstoday.com: ‘Our research shows long-time exposure to blue light could cause reduced energy production in mitochondria which is detrimental to cellular health.
‘This is the first research to show that blue light can alter the levels of indispensable metabolites in flies.
‘Those metabolites are compounds that are essential for cell functions – not just in flies but also in mammals.’
He emphasised: ‘These changes suggest cells operate at a suboptimal level, which may cause premature death. Our research is also the first to show that blue light may affect extra-retinal cells that are not specialised in light perception.’
The researchers also detected significantly reduced levels of several neurotransmitters ‘suggesting blue light may disrupt brain homeostasis’.
Yang noted that in daily life, the majority of blue light which humans are exposed to comes from light-emitting diodes (LEDs); and most white LEDs are created by adding yellow fluorescent powder activated by the blue light.
Because of their small size and high brightness, LEDs have become the primary illumination of display screens (phones, laptops, desktops, television) and ambient lights.
Yang summed up: ‘Humans are exposed to LEDs for most of their waking hours. In the model organism used in this research, basic cellular functions, such as energy production in mitochondria, are highly similar to human cells. ‘Therefore, it is possible that excessive use of blue light may have a detrimental effect on human cells that are exposed to it, such as skin, sensory neurons, fat cells, and others.’
But he also added: ‘However, it is still necessary to investigate human cells to find out whether similar changes in the level of metabolites are caused by prolonged exposure to blue light.’
Valuable insights for human research
The scientists in the latest study did, however, note limitations to their research.
Yang told medicalnewstoday.com that the researchers used ‘a fairly strong light’ to understand the mechanism of how blue light impacts the flies, while ‘humans are exposed to less intense light, so cellular damage may be less dramatic’.
Dr Richard Siow, Director of Ageing Research at Kings College London (not involved in this
study) commented: ‘We should treat studies in Drosophila with caution as this model is not directly applicable to humans – for example, differences in sensitivity to light, brain complexity, nutrition, lifestyle, sleep, stress, employment, etc.
‘But it can provide some valuable insights for relevant areas of translational research in humans.’
Jun Yang summed up: ‘Our study suggests avoiding excessive blue light may be a good anti-ageing strategy. This may be achieved by shortening screen time and dimming ambient lights.
‘It is particularly important to use ‘night’ setting, which emits warm light with blue wavelengths filtered out on computer displays and phone screens.’ AMP
What is ‘blue light’?
Blue light is a wavelength of light in the visible spectrum; it has a short wavelength, meaning it produces higher amounts of energy.
Previously, humans were only exposed to blue light during the day from the sun.
However direct human exposure to blue light – for extended periods in our daily lives, night and day – is becoming increasingly common both from artificial lighting and televisions in our homes and due to the increased use of personal electronic devices such as computers and mobile telephones.
Various scientific studies have reported constant exposure to blue light over time could damage retinal cells and cause vision problems such as age-related macular degeneration; it can also contribute to cataracts, eye cancer and growths on the clear covering over the white part of the eye.
Researchers often refer to the ‘blue light effect’ (BLE), reporting that it boosts alertness, helps memory and cognitive function and elevates mood. BLE regulates circadian rhythm, the body’s natural wake and sleep cycle;
and exposure to blue light during daytime hours helps maintain a healthful circadian rhythm.
However, scientists have also reported that blue light ‘fools the brain into thinking it’s daytime’; when that happens, the body stops releasing the natural sleep hormone melatonin – which the body begins releasing a couple of hours before bedtime, as nature’s method for helping humans wind down and prepare to sleep.
Hence scientists refer to ‘blue light addiction’ as the result when blue light suppresses the release of melatonin and disrupts the body’s natural circadian rhythm.
Exposure to blue light wavelengths (peaking at 460nm) stimulates the body’s production of serotonin and dopamine; serotonin is a neurotransmitter that affects mood, appetite, sleep, temperature regulation and some social behaviour.
Scientists also report high levels of blue light exposure can cause an increase in the human stress hormones cortisol and adrenaline – leaving many victims feeling highly stressed, irritable and anxious.
