Nature. Why does stress cause white hair?

For a long time, many stories have linked stress to hoarseness.as early as the spring and Autumn period, there was a legend that Wu Zixu went through Zhaoguan overnight and turned white.it is said that Wu Zixu's father and brother were killed by King Ping of Chu and fled alone.King Ping of Chu hung Wu Zixu's portrait at each city gate and offered a reward of 50000 tons of grain for his head.Wu Zixu was blocked in front of Zhaoguan and was unable to pass through. He was so worried that he could not pass through Zhaoguan. He escaped from investigation and fled to the state of Wu successfully.on January 22, 2020, Harvard University's Hsu Yajie Laboratory (Dr. Zhang Bing as the first author) published the title of hyperactivation of sympathetic nerves drives decomposition of melanocyte stem in the journal Nature The study of cells revealed for the first time the exact mechanism of this phenomenon: stress activates the sympathetic nervous system as part of the fight or flight response, and causes permanent damage to the melanocyte stem cells in hair follicles."everyone has anecdotes to share about how stress affects physical conditions, especially skin and hair, because these are the most obvious tissues we can see in vitro," says co-author Dr. Yajie Xu, who is currently an associate professor of Alvin and esta star in the Department of stem cell and regenerative biology at Harvard University."we want to know if this connection really exists, and if it does, how does stress cause changes in various organizations? Because the color of hair is very obvious, it provides a very good system for us to study this topic."since stress affects the whole body, the author first needs to determine which system in the body affects the color of hair.first of all, the authors suspect that stress can trigger autoimmune attacks against pigment cells.however, when it was found that the immune deficiency mice still had the phenomenon of hair whitening under pressure, the author turned to the research on whether the cortisol hormone could cause the hair whitening phenomenon.however, this is also a wrong direction.although stress increases cortisol hormone levels, it is surprising that when the adrenal glands of experimental mice are removed so that they can no longer produce cortisol hormone, the hair of experimental mice will still turn white under pressure.after systematically excluding various possibilities, the author began to study the sympathetic nervous system, which is responsible for the body's fight or flight response.the sympathetic nerve is linked to each hair follicle on the skin.the authors found that these nerves release a large amount of neurotransmitter norepinephrine, which directly acts on the nearby pigment stem cells.complex sympathetic nerves (green) around pigment stem cells (red). acute pressure induces excessive activation of the sympathetic nervous system and releases a large amount of neurotransmitter norepinephrine. norepinephrine drives the rapid depletion of melanocyte stem cells and makes hair gray. permanent damage in hair follicles, pigment stem cells act as reservoirs of melanocytes. as the hair grows, some pigment stem cells turn into pigment producing cells, which make the hair color. the authors found that norepinephrine released from the sympathetic nerve leads to over activation of stem cells. these stem cells are transformed into pigment producing cells, thus depleting the stem cell stock prematurely. "at the beginning of the study, we had expected that stress would cause damage to the body, but now the effect is far beyond our imagination: in a few days, all the pigment stem cells disappeared. and once disappeared, the hair follicles would not be able to generate pigment. the damage is permanent, "commented Dr. Xu Yajie. Dr. Zhang Bing, the first author of the study, said, "previously, it was generally believed that acute stress, especially combat or flight responses, was a protective mechanism conducive to survival. but we now find that this mechanism directly leads to the permanent depletion of stem cell stocks under acute stress. this discovery reveals the negative effects of this evolutionary protective mechanism. "to solve a basic biological problem}} in order to clarify the relationship between stress and white hair, the author starts from the study of physiological changes in the body, further to determine the role of organ system in the body, and then clarify the interaction between the cells that make up the organ, and finally clarify the regulation mechanism of intracellular molecules. this process requires the use of methods including physiology, neurology, genetics and molecular biology. "because our research needs to be carried out at multiple levels from physiology to cells, we have combined a variety of technologies to solve a fundamental biological problem by cooperating with a number of scientists from different disciplines," said Dr. Zhang Bing. the collaborators include Isaac Chiu, an assistant professor of immunology at Harvard Medical School. His main research area is the interaction between the nervous system and the immune system. Dr Chiu said: "we know that peripheral neurons can effectively regulate organ function, blood vessels and immunity, but little is known about how they regulate stem cells. through this study, we now know that neurons control stem cells and their function, and can explain how they interact at the cellular and molecular levels, which is what links stress to white hair. "these findings are helpful for us to study the extensive effects of stress on various organs and tissues, and point out the direction for finding ways to prevent and reverse the destructive effects of stress. understanding how our bodies change under stress is the first step towards achieving the ultimate treatment. in order to achieve this goal, we still have a long way to go. Clark, S. A. & amp; deppmann, C. D. how the stress of fight or flight turns hair white. Nature 577, 623 – 624 (2020), K. Stress Really Does Make Hair Go Gray Faster. The New York Times.