NOV 27, 2018 6:03 PM PST

Why Screens can Interfere With Sleep

WRITTEN BY: Carmen Leitch

Most of us spend a lot of time looking at some type of screen, whether it’s a laptop, a phone, or another device. For some people, that time adds up to many hours, which is thought to be disruptive to sleep. Researchers at the Salk Institute have now discovered that specific cells in the eye can sense ambient light. These cells also help regulate our daily cycle, which is known as the circadian rhythm. When artificial light stimulates these cells long into the evening hours, the cells become confused, which can have a disruptive ripple effect on our physiology. This work has been published in Cell Reports, and could help researchers that are working on therapeutics for disorders including obesity, insulin resistance, cancer, and metabolic diseases, which have all been linked to problems with circadian rhythm.

From left: Salk scientists Ludovic Mure and Satchin Panda uncover how certain retinal cells respond to artificial illumination. / Credit: Salk Institute

"We are continuously exposed to artificial light, whether from screen time, spending the day indoors or staying awake late at night," said the senior author of the report, Salk Professor Satchin Panda. "This lifestyle causes disruptions to our circadian rhythms and has deleterious consequences on health."

The retina sits at the back of our eyes and is made up of layers of cells. One of those layers contains a small group of cells that are sensitive to light. When they’re exposed continuously to light, a protein called melanopsin is constantly produced in those cells, which sends information about light levels to the brain so it can control sleep, alertness, and consciousness. Melanopsin can suppress a hormone called melatonin, which regulates sleep, and can synchronize the internal clock after only ten minutes of light exposure.

Melanopsin-producing cells can rapidly respond to light, and work to reset our daily clocks on the basis of those light levels. "Compared to other light-sensing cells in the eye, melanopsin cells respond as long as the light lasts, or even a few seconds longer," noted the first author of the report, Ludovic Mure, staff scientist. "That's critical because our circadian clocks are designed to respond only to prolonged illumination."

For the study, the scientists used a mouse model to stimulate the production of melanopsin in the mouse retina. Some cells could sustain their response to light while other cells had become desensitized and stopped responding.

Arrestins are molecules that can halt the activity of some receptors. It had been suggested that arrestins can stop the light response after only seconds, but the researchers found instead that melanopsin needed arrestins to maintain their response to prolonged light.

When mice were engineered to lack either type of arrestin protein, the retina cells that generate melanopsin could not continue their response to sustained light. In the retina, arrestin was helping melanopsin to regenerate.

"Our study suggests the two arrestins accomplish regeneration of melanopsin in a peculiar way. One arrestin does its conventional job of arresting the response, and the other helps the melanopsin protein reload its retinal light-sensing co-factor. When these two steps are done in quick succession, the cell appears to respond continuously to light," explained Panda.

The researchers plan to continue this work and hope to learn how to manipulate melanopsin to treat insomnia and other problems with the internal clock.

 

Sources: AAAS/Eurekalert! Via Salk Institute, Cell Reports

About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
MAR 15, 2020
Microbiology
MAR 15, 2020
A Second Person Has Been Cured of HIV
New research has suggested that after long-term follow-up, HIV is no longer detectable in a patient that was previously ...
MAR 22, 2020
Cell & Molecular Biology
MAR 22, 2020
Capturing Images of Firing Neurons
Our bodies run on electricity. Neurons send rapidly fired electrical signals through the brain and limbs constantly, ena ...
MAR 23, 2020
Cell & Molecular Biology
MAR 23, 2020
How a Father's Diet Can Impact the Health of His Offspring
When fathers consume a diet high in fat or low in protein it can increase the risk of metabolic disorders like diabetes ...
APR 02, 2020
Immunology
APR 02, 2020
Transforming T Cells into Powerful Memory Cells That Target Cancer
New cancer treatments are now based on harnessing the power of the human body’s own immune cells to get the job do ...
APR 13, 2020
Immunology
APR 13, 2020
Macrophages: An Origin Story
Macrophages are well-known defense cells of the immune system, responsible for utilizing the cellular breakdown process ...
APR 21, 2020
Cell & Molecular Biology
APR 21, 2020
Virtual Cell Provides a Close Look at Gene Expression During Development
Living organisms start out as one cell, and its genetic programs allow it to divide many times over, to give rise to the ...
Loading Comments...