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Fight-or-Flight Nerves Make Mice Go Gray

They say that Marie Antoinette’s hair turned white the night before she lost her head to the guillotine. But can stress really have such a dramatic effect on hair color? A new study in mice concludes that it can and credits overactive nerves with stripping the color from the animals’ locks—and possibly ours.

他们说玛丽·安托瓦内特被送上断头台的前一天晚上，她的头发变白了。但压力真的会对头发颜色产生如此显著的影响吗?在老鼠身上进行的一项新研究得出结论认为，过度活跃的神经会使动物的锁眼(也可能是我们的)褪掉颜色。

Researchers at Harvard’s Stem Cell Institute were interested in the stress and hair color issue. So they decided¹ to take a closer look at those stem cells that give rise to melanocytes—the cells that pump pigments² into each hair follicle. The stem cells were an obvious target ...

哈佛干细胞研究所的研究人员对压力和头发颜色问题很感兴趣。因此，他们决定进一步研究那些产生黑色素细胞的干细胞——这些细胞将色素注入每个毛囊。干细胞是一个明显的目标…

“Because changes in the stem cell population translate to changes in hair color, which are very visible and easy to identify.”

“因为干细胞群的变化转化为头发颜色的变化，这是非常明显的，很容易识别。”

Ya-Chieh Hsu, the study’s senior author.

这项研究的资深作者徐雅芝说。

To start, she and her colleagues subjected mice to some rodent-sized stressors—like having their cage tilted³, their bedding dampened or their lights left on all night.

首先，她和同事让老鼠承受一些啮齿类动物大小的压力——比如把笼子倾斜，床上用品弄湿，或者整晚开着灯。

“So what did we find? We found that stress indeed leads to premature⁴ hair graying in mice. But it took a long time for us to actually narrow down how it occurs.”

“我们发现了什么?”我们发现压力确实会导致老鼠的头发过早变白。但我们花了很长时间才真正缩小它是如何发生的。”

First, they thought it could be the immune system attacking the melanocyte stem cell population.

首先，他们认为可能是免疫系统攻击黑素细胞干细胞群。

“However, mice lacking immune cells still show premature hair graying under stress.”

“然而，缺乏免疫细胞的老鼠在压力下仍然表现出过早变白的毛发。”

Then they thought the key factor could be cortisol, the quintessential stress hormone⁵.

然后他们认为关键因素可能是皮质醇，一种典型的应激激素。

“But when we removed the adrenal glands⁶ from the mice so they cannot produce cortisol-like hormones⁷, their hair still turned gray under stress.”

“但是，当我们从老鼠身上摘除肾上腺，使它们不能产生类皮质激素时，老鼠的头发在压力下仍然会变白。”

That’s when they turned their attention to the sympathetic nervous system, which orchestrates the body’s overall reaction to stress, including the classic fight-or-flight response. Those nerves reach out to our muscles, organs and, yes, even our hair.

这时，他们将注意力转向交感神经系统，该系统负责协调身体对压力的整体反应，包括经典的“战或逃”反应。这些神经延伸到我们的肌肉、器官，是的，甚至我们的头发。

“The nerve terminals wrap around each hair follicle like a ribbon.”

“神经末梢像丝带一样缠绕着每个毛囊。”

And when Hsu and her team cut those connections, the stem cells were spared, and the animals kept their shiny black coat even in the face of minor⁸ discomfort⁹. The findings appear in the journal Nature.

当Hsu和她的团队切断这些连接时，干细胞得以保留，动物们即使面对轻微的不适也能保持它们闪亮的黑色皮毛。研究结果发表在《自然》杂志上。

It’s unclear whether the same sympathetic nerves make us gray as we age. But the results provide hope that we may someday be able to fight to hold onto our natural hair color—and avoid that monthly flight to the hairdresser.

目前还不清楚是否相同的交感神经会使我们变老。但研究结果为我们提供了希望，也许有一天我们能够努力保持我们的自然发色，避免每月去一次理发店。