Why is there too much screen time disrupting sleep?

Washington DC: Now, we all know that spending too much time watching screens – computers, phones, iPads – wreaks havoc on sleep. But do you know why? The researchers said how some cells in the eye treated ambient light and reset our internal clocks, the daily cycles of physiological processes known as circadian rhythm.

When these cells are exposed to artificial light late at night, our internal clocks can get confused, resulting in a host of health problems. The study, conducted by researchers at the Salk Institute, was published in the journal Cell Reports.

The findings could contribute to the development of new treatments for migraine headaches, insomnia, jet lag and circadian rhythm disorders, related to cognitive dysfunction, cancer, obesity, resistance to the disease. insulin, metabolic syndrome and more.

"We are continually exposed to artificial light, whether it is time spent in front of a screen, spending the day indoors or staying awake late at night," said Professor Satchin Panda of Salk , lead author of the study. "This lifestyle disrupts our circadian rhythms and has adverse health consequences."

The back of our eyes contains a sensory membrane called retina, whose innermost layer contains a tiny subpopulation of light-sensitive cells that function like pixels in a digital camera. When these cells are exposed to continuous light, a protein called melanopsin continually regenerates within them, signaling ambient light levels directly to the brain to regulate consciousness, sleep, and alertness. Melanopsin plays a vital role in the synchronization of our internal clock after 10 minutes of illumination and removes the hormone melatonin, responsible for regulating sleep, under the effect of a bright light .

"Compared to other light-sensing cells in the eye, melanopsin cells react as long as light lasts, even a few more seconds," said Ludovic Mure, first author from Journal. "It's essential because our circadian clocks are designed to respond only to prolonged illumination."

In this new work, Salk researchers used molecular tools to activate the production of melanopsin in retinal cells in mice. They discovered that some of these cells were able to maintain bright responses when they were exposed to long repeated light pulses, while others became insensitive.

Clbadical wisdom dictates that proteins called arrestins, which stop the activity of certain receptors, stop photosensitive response of the cells within seconds of the lights being turned on. The researchers were surprised to find that arrestins were in fact necessary for melanopsin to continue to respond to prolonged illumination.

In mice lacking one or the other version of the arrestin protein (beta arrestin 1 and beta arrestin 2), retinal cells producing melanopsin failed. maintain their sensitivity to light under prolonged lighting. It turns out that the reason is that stopin helps melanopsin to regenerate in retinal cells.

"Our study suggests that both arrestines perform the regeneration of melanopsin in a particular way," said Panda. "One artery does its conventional job of stopping the response, and the other helps the melanopsin protein to reload its co-factor for retinal light detection." When these two steps are performed in rapid succession, the cell appears to react in permanence in the light. " [19659004] By better understanding the interactions of melanopsin in the body and how the eyes react to light, Panda hopes to find new targets to counter biased circadian rhythms due to, for example, artificial lighting. Previously, the Panda research team had discovered that chemicals called opsinamides could block the activity of melanopsin in mice without affecting their vision, thus providing a potential therapeutic track to fight against. hypersensitivity to light experienced by migraine sufferers. .