Researchers now know why tans only appear after you’ve left the beach

[Aug. 2, 2023: Staff Writer, The Brighter Side of News]

Beachgoers across the world have had the familiar experience of basking in the sun's glory for hours, only to see the true results of their tanning efforts emerge hours or even days later. But what causes this delayed reaction?

A groundbreaking study from Tel Aviv University has shed light on this mystery, revealing the complex ballet of cellular responses that dictates this delay.

The crux of this intricate dance? Our body's cells focus primarily on repairing sun-induced DNA damage, which temporarily takes precedence over the skin-darkening process we commonly know as tanning.

In a recently published article in the Nature Group’s Journal of Investigative Dermatology, a team of researchers led by doctoral student Nadav Elkoshi and Prof. Carmit Levy from Tel Aviv University's Faculty of Medicine unveiled the detailed mechanism behind our body's response to sun exposure.

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The collaborative study also involved experts from Wolfson Medical Center, the Weizmann Institute of Science, the University of California, and Paris-Saclay University.

Nadav Elkoshi delves into the findings, stating, “We have two mechanisms designed to protect the skin from exposure to dangerous UV radiation. Firstly, the mechanism that repairs damaged DNA in skin cells due to radiation. Secondly, the mechanism that ramps up melanin production, darkening the skin to guard against further radiation exposure. Our research indicates that the DNA repair mechanism temporarily puts the brakes on the pigmentation process. It's only after the cells have addressed and repaired the genetic anomalies to the best of their capacity that they shift gears to melanin production."

This theory was put to the test when the research team triggered the DNA repair mechanism in animal models and human skin tissues. Remarkably, a tan developed in both cases without any exposure to UV radiation, solidifying the team's hypothesis.

Delving deeper, Prof. Carmit Levy elaborates on the intricate molecular interactions that underpin this process: “Upon UV radiation from the sun, the cell’s foremost priority is to shield its genetic information from mutations. The DNA repair mechanism assumes control, essentially directing all other cellular systems to pause and allow it to function undisturbed. One system temporarily suspends the other until DNA repair is at its zenith, which typically occurs a few hours post UV exposure. Only then is the green light given to melanin production."

The team's research also touched upon the molecular players in this dance. A prior study by the same group highlighted a protein named MITF, which is triggered during sun exposure and acts as the overseer of these two protective mechanisms.

In their current exploration, another protein named ATM, pivotal in DNA repair, emerged as a key player. It activates one mechanism and concurrently puts the other on standby. This strategic move likely co-opts the components of the pigmentation process to enhance the cell's odds of survival without undergoing radiation-induced mutations.

Unearthing this molecular mechanism is not just an academic triumph. It lays a solid groundwork for further inquiries that could pave the way for innovative treatments. These treatments, as Prof. Levy suggests, could “provide maximum protection of the skin against radiation damage." More ambitiously, understanding these processes might also usher in new methods for skin cancer prevention.

In a world where skin health is paramount, and the risks of sun exposure are ever-present, such revelations stand to have profound implications. For beachgoers and sun-lovers, it's not just about the perfect tan. It's about understanding and harnessing our body's intricate responses for a healthier tomorrow.

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