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Hair: Stress really makes you gray

Suspicion confirmed: stress actually makes our hair turn gray. Researchers have now discovered evidence of this widespread assumption in experiments with mice. Accordingly, the activation of the sympathetic nervous system responsible for stress reactions leads to changes in the pigment-forming cells in the hair follicle. The visible consequence: loss of color. But there may be a remedy, as the team reports in the specialist magazine "Nature".

Whether blond curls or dark hair: at some point every hair begins to turn gray. At first it is mostly just individual strands, but over time, more and more hair loses its former color. Because with increasing age, the body produces less melanin. Different variants of this color pigment usually give our hair its characteristic color.

How early the graying process begins is a matter of disposition. A few years ago, for example, researchers discovered a gene for premature graying. But external influences such as stress should also be able to promote graying. According to legend, the French Queen Marie Antoinette even went gray overnight when she learned of her impending execution. “It is a common belief that stress makes hair pale. So far, however, there has been no scientific evidence of this, ”explains Thiago Cunha from Harvard Medical School in Boston.

Suddenly gray: Stress literally pulled the color out of the fur of the mouse below. Her relaxed fellow (above) has remained black. © William A. Goncalves

Gray mice

So does the psychological stress really cause gray hair? Cunha and his colleagues around first author Bing Zhang from Harvard University in Cambridge have now established that this phenomenon actually exists - and what mechanisms it is based on. The starting point of their work was a chance discovery: in experiments with mice, the researchers observed that some of the previously black rodents suddenly got light fur. The exciting thing: These animals had been deliberately inflicted pain in the experiment, they had suffered acute stress.

“We wanted to investigate whether the color loss was related to the pain-induced stress,” reports Cunha. To do this, he and his colleagues prevented the transmission of signals via the sympathetic nervous system. This part of the autonomic nervous system is responsible, among other things, for our reaction to stress and danger. It controls the so-called fight-or-flight reaction and, for example, triggers the release of stress hormones that make our heart beat faster.

Effect on melanocytes

The results revealed that if this influence was inhibited with the help of medication or the removal of sympathetic nerve fibers, the mice actually did not turn gray after the stressful ordeal. "These and other experiments suggested that the sympathetic nervous system is involved in the loss of pigment in the hair and that pain in this case acts as a powerful stressor," summarizes Cunha.

But how exactly do the signals conveyed by this system turn the hair gray? The scientists finally found an answer to this, too. They found that acute stress affects the melanocytes in the hair follicle. “These pigment-producing cells are as undifferentiated as stem cells at a young age, but they mature with increasing age. When this process is complete, they stop producing melanin and migrate, ”explains Cunha.

Accelerated aging

Specifically, it was shown: In the event of physical or psychological stress, sympathetic nerve fibers that end in the hair follicle release more norepinephrine. The melanocyte stem cells in turn have a receptor for this messenger substance - if it is activated, they begin to differentiate.

A strong activation of the sympathetic nervous system accelerates the natural aging process of the pigment-producing cells in the hair. If they are lost, there is no more color supply. "The damage is permanent," says co-author Ya-Chieh Hsu from Harvard University.

Antidote in sight?

But there is good news: this stress effect can possibly be prevented. In search of a potential antidote, Cunha and his colleagues investigated how stress changes the gene expression in cells. Particularly noticeable was a section of DNA that contained the building instructions for a protein called CDK - this protein plays an important role in regulating the cell cycle. As the scientists report, the activity of the CDK gene increased due to stress.

But what would happen if this protein were blocked? To find out, the team repeated the pain experiment with the mice, this time giving them a CDK inhibitor. And indeed: unlike before, there was no premature differentiation of the melanocyte stem cells and the rodents retained their dark coat color.

Other tissues in view

Further experiments with human melanocytes confirmed that a very similar mechanism takes place in humans. "This suggests that CDK could be a point of attack for therapies against graying," states Cunha. Whether such a product will be available in pharmacies in the future remains to be seen, however. First, more research is needed.

All in all, the current study underpins the lasting consequences stress can have on our body and our health. The fact that this type of exposure affects pigment-producing stem cells in the hair follicle means, according to the researchers, that other tissues and organs could be similarly affected. “We assume that other systems in the organism show comparable reactions to intense stress. We are currently investigating the effect of sympathetic activity on other stem cell subpopulations, ”conclude Cunha and his colleagues. (Nature, 2020; doi: 10.1038 / s41586-020-1935-3)

Source: Nature Press / Harvard University / Fundacao de Amparo à Pesquisa do Estado de Sao Paulo

January 23, 2020

- Daniela Albat