An SMU 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 interfere with the natural body clocks of humans, plants and animals – and the negative consequences it can bring.
Exposure to blue light is on the increase, says SMU chemist Brian Zoltowski, who leads the study, “Protein : Protein interaction networks in the circadian clock.”
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 the Department of Chemistry in SMU’s Dedman College of Humanities and Sciences.
“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. They are studying a small flowering plant native to Europe and Asia, Arabidopsis thaliana – a popular model organism in plant biology and genetics, Zoltowski says.
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.
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.
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 circadian rhythms,” 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 master clock, 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.”
Written by Margaret Allen