According to this press release, gray hair in aging people is the result of a hydrogen peroxide metabolism gone haywire:
"Not only blondes change their hair color with hydrogen peroxide," said Gerald Weissmann, MD, Editor-in-Chief of The FASEB Journal. "All of our hair cells make a tiny bit of hydrogen peroxide, but as we get older, this little bit becomes a lot. We bleach our hair pigment from within, and our hair turns gray and then white. This research, however, is an important first step to get at the root of the problem, so to speak."
The researchers made this discovery by examining cell cultures of human hair follicles. They found that the build up of hydrogen peroxide was caused by a reduction of an enzyme that breaks up hydrogen peroxide into water and oxygen (catalase). They also discovered that hair follicles could not repair the damage caused by the hydrogen peroxide because of low levels of enzymes that normally serve this function (MSR A and B). Further complicating matters, the high levels of hydrogen peroxide and low levels of MSR A and B, disrupt the formation of an enzyme (tyrosinase) that leads to the production of melanin in hair follicles. Melanin is the pigment responsible for hair color, skin color, and eye color. The researchers speculate that a similar breakdown in the skin could be the root cause of vitiligo.
"As any blue-haired lady will attest, sometimes hair dyes don't quite work as anticipated," Weissmann added. "This study is a prime example of how basic research in biology can benefit us in ways never imagined."
Clearly this guy doesn’t actually know any blue-haired ladies, most of whom are aiming for blue, to get rid of the yellowish color that may remain in gray hair.
But otherwise, I think this is quite cool information to have on this important variant of the pigmentation pathway. Age related-decline in two enzymes. There must be a bit more complication here than that – for example, there is a huge variation among the population of follicles in the time of graying, even on a single person. There’s also variation among hair types – temple versus crown being an obvious example, but also beard versus crown. Not to mention others that I’d rather not mention…
The research does not investigate normal variation, just the metabolic mechanism. I’m curious about other primates. Silverback gorillas are the obvious analogy, but grayish or white pigmentation are by no means uncommon, and this mechanism provides another way besides mere pigment loss to get an age-related reduction in pigmentation.