Study is decoding blue light's mysterious ability to alter body's natural clock

Study is decoding blue light’s mysterious ability to alter body’s natural clock
Arabidopsis thaliana is a small flowering plant that is widely used as a model organism in plant biology.

A study funded by the National Institutes of Health is unraveling the mystery of how blue light from residential and commercial lighting, electronic devices and outdoor lights can throw off-kilter the natural body clock of humans, plants and animals, leading to disease.

Exposure to is on the increase, says chemist Brian D. Zoltowski, Southern Methodist University, Dallas, who leads the study, "Protein : Protein interaction networks in the ."

At the right time of day, blue light is a good thing. It talks to our 24-hour circadian clock, telling our bodies, for example, when to wake up, eat and carry out specific metabolic functions.

In plants, blue light signals them to leaf out, grow, blossom and bloom. In animals, it aids migratory patterns, sleep and wake cycles, regulation of metabolism, as well as mood and the immune system.

But too much blue light—especially at the wrong time—throws biological signaling out of whack.

"As a society, we are using more technology, and there's increasing evidence that artificial light has had a negative consequence on our health," said Zoltowski, an assistant professor in SMU's Department of Chemistry.

"Our study uses physical techniques and chemical approaches to probe an inherently biological problem," he said. "We want to understand the chemical basis for how organisms use light as an environmental cue to regulate growth and development."

Zoltowski's lab was awarded $320,500 from the National Institute of General Medical Sciences of the National Institutes of Health to continue its research on the impact of blue light.

The lab studies a small flowering plant native to Europe and Asia, Arabidopsis thaliana. The flower is a popular model organism in plant biology and genetics, Zoltowski said.

Although signaling pathways differ in organisms such as Arabidopsis when compared to animals, the flower still serves an important research purpose. How the signaling networks are interconnected is similar in both animals and Arabidopsis. That allows researchers to use simpler genetic models to provide insight into how similar networks are controlled in more complicated species like humans.

Understanding the mechanism can lead to targeted drug treatments

In humans, the protein melanopsin absorbs blue light and sends signals to photoreceptor cells in our eyes. In plants and animals, the protein cryptochrome performs similar signaling.

Much is known already about the way blue light and other light wavelengths, such as red and UV light, trigger biological functions through proteins that interact with our circadian clock. But the exact mechanism in that chemical signaling process remains a mystery.

"Light is energy, and that energy can be absorbed by melanopsin proteins that act as a switch that basically activates everything downstream," Zoltowski said.

Study is decoding blue light’s mysterious ability to alter body’s natural clock
An image of Earth’s city lights using data from the Defense Meteorological Satellite Program. Credit: NASA

Melanopsin is a little-understood photoreceptor protein with the singular job of measuring time of day.

When light enters the eye, melanopsin proteins within unique cells in the retina absorb the wavelength as a photon and convert it to energy. That activates cells found only in the eye—called intrinsically photosensitive retinal ganglian cells, of which there are only about 160 in our body. The cells signal the suprachiasmatic nucleus region of the brain.

"We keep a master clock in the suprachiasmatic nucleus—it controls our ," he said. "But we also have other time pieces in our body; think of them as watches, and they keep getting reset by the blue light that strikes the , generating chemical signals."

The switch activates many biological functions, including metabolism, sleep, cancer development, drug addiction and mood disorders, to name a few.

"There's a very small molecule that absorbs the light, acting like a spring, pushing out the protein and changing its shape, sending the signal. We want to understand the energy absorption by the small molecule and what that does biologically."

The answer can lead to new ways to target diabetes, sleep disorders and cancer development, for example.

"If we understand how all these pathways work," he said, "we can design newer, better, more efficacious drugs to help people."

Chemical signal from retina's "atomic clock" synchronizes circadian rhythms

Besides increased reliance on indoors and outdoors, electronic devices also now contribute in a big way to blue light exposure. Endless evening hours on our smartphones and tablets with Candy Crush, Minecraft or Instagram don't really help us relax and go to sleep. Just the opposite, in fact.

The blue glow those devices emit signals our circadian clock that it's daytime, Zoltowski said. Red light, on the other hand, tells us to go to sleep.

Awareness of the problem has prompted lighting manufacturers to develop new lighting strategies and products that transition blue light to red light toward evening and at night, Zoltowski said.

Targeted solutions could neutralize destructive blight in staple crops

In plants, the researchers study how the absence of "true dark" in nature due to artificial light can reduce yields of farm crops and promote crop disease.

For example, fungal systems rely on blue light to proliferate, forming pathogens known as blight in crops resulting in leaves that look chewed on and reducing yields.

"We study fusarium and verticillium," Zoltowski said. "They cause about $3 billion worth of crop damage a year to wheat, corn, soybeans—the staple food crops."

Understanding their ability to infect crops would allow scientists to potentially design small molecules that target and disrupt the fungal system's circadian clock and neutralize their proliferation.

Research to understand how light and clock regulation are coupled

In animals, Zoltowski's lab studies the blue light pathway that signals direction to birds and other animals that migrate. Blue light activates the protein that allows various species to measure the earth's magnetic field for directionality. For example, Monarch butterflies rely on the cryptochrome photoreceptor for their annual migration to Mexico.

"We're interested in how these pathways are regulated in a diverse range of organisms to understand how we can manipulate these pathways to our advantage," he said, "for health consequences and to improve agriculture yields."

The researchers will map the reaction trajectory beginning from the initial absorption of the photon to the point it alters an organism's physiology.

Zoltowski notes that light is just one of a handful of external cues from our environment that trigger biological processes regulating the circadian clock. Others include temperature changes, feeding and metabolites.

Explore further

Circadian clock research may enable designer plants, and cancer and diabetes treatments

More information: "Mechanism-based tuning of a LOV domain photoreceptor." Nature Chemical Biology 5, 827 - 834 (2009) Published online: 30 August 2009 DOI: 10.1038/nchembio.210

"Conformational switching in the fungal light sensor Vivid." Science. 2007 May 18;316(5827):1054-7.

"Structure of full-length Drosophila cryptochrome." Nature. 2011 Nov 13;480(7377):396-9. DOI: 10.1038/nature10618.

Journal information: Nature , Science , Nature Chemical Biology

Citation: Study is decoding blue light's mysterious ability to alter body's natural clock (2014, December 2) retrieved 22 September 2019 from
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Dec 02, 2014
The late Dr. John Nash Ott reported in "Health and Light" (1979) on empirical observations made during his studies of the various effects of light on plants and animals. He claimed that in mammals the circadian rhythym is directly linked to the UV-triggered phototropic activity of chromophores in the epithelial cells of the retina. This activity was very similar to the activity of chloroplasts of plant cells during photosynthesis.
His hypothesis was that the UV triggered chemosynthesis in these cells that was analogous to photosynthesis, and that whatever substance was produced by the chemosysthesis (melatonin?) was conducted directly along the neurons of the optic nerve to the brain.

Dec 02, 2014
In May, 1999, a publicized study strongly suggested that children under two, who slept with a night-light on, had a 34% chance of developing myopia while those who slept in the dark had only a 10% chance. A subsequent study, published a year later found no such correlation. I doubted the second study because published results from the first would surely have influenced survey responses in the second and myopia has certainly become more prevalent as urbanization has increased.
In any case, what this and the myopia study indicate, is that body-clocks matter in health and may be upset by artificial light.

Dec 02, 2014
And this, clearly, explains why as more and more of our existance is under artificial light, life expectancies get longer, and longer, and longer...leftist junk science.

Dec 02, 2014
I wonder what effect all the led street lights are having on people. They just changed the ones in the neighborhood where I live and I'm ready to hang black curtains in my bedroom now. They have a lot bluer and brighter light than the others had.

Dec 03, 2014
I've heard that 5700k 520mn green light spectrum is more efficient at reducing melatonin levels than 6000k 480mn blue light spectrum. Anyone have any thoughts on that?

Also, I get up at 4am, and I can say without hesitation, that I am not awake until an hour after dawn, and getting to sleep by 8pm, is pretty much impossible without absolute exhaustion and perfect conditions like total blackout darkness and silence.

Noise, in my opinion, is just as big a cue as light that it's time to be awake.

Dec 04, 2014
Noise, in my opinion, is just as big a cue as light that it's time to be awake.

That's what I tell my wife when she complains about me snoring.

Dec 09, 2014
Non-24-Hour Sleep-Wake Disorder (Non-24) is a circadian rhythm disorder. Your circadian rhythms are controlled by your master body clock and tell you when to sleep, when to wake, when to eat, among other things.
In most people, the master body clock runs slightly longer than 24 hours. What this means is that rather than cycle on a 24-hour day, most people's natural rhythms actually cycle a bit longer. Whether the cycle runs two minutes or 30 minutes longer, if you have Non-24 these minutes add up day after day, a few one day adding to a few more the next, eventually causing a noticeable change in the times during the day when your body expects to sleep and expects to be awake.
Though Non-24 may appear to be a sleep disorder, it isn't. It's actually a serious, chronic circadian rhythm disorder very common in people who are totally blind, and it can arise at any age.
This demonstrates that interaction of light with the retina is essential to the circadian clock.

Dec 24, 2014
Best think you can do is use a blue light screen protector like a SleepShield. Effectively blocks the blue light and allows you to fall asleep naturally.

Dec 24, 2014
Don't fluorescent lights have a strong "blue light" component to them?

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