24 February 2009

Peroxide in the beard

Vladimir Gram, "Newspaper.Ru»Hair turns gray due to the same hydrogen peroxide that unnatural blondes bleach them with.

As it turned out, peroxide deals a double blow: it destroys the pigment in the hair shaft and damages the enzyme through which the pigment is synthesized in the bulb.

For a century and a half, hydrogen peroxide has been one of the best friends of fashionistas around the world. It is with her that all attempts to radically change the color of hair begin: in order to give the hair the right shade, it is first deprived of its natural color. And it does not matter that in the XXI century, discoloration occurs more often in beauty salons, and not at home, as in the Soviet Union of the XX century, or in chemical laboratories, as in France of the XIX century. Peroxide, or hydrogen peroxide, H 2 O 2, no matter what words it is hidden behind, will remain the main means of turning into artificial blondes for a long time.

But, as it turns out, "chemical" peroxide has a much more natural relationship to hair color than "natural" henna and basma. According to scientists from the UK and Germany, led by Karin Schallreiter from the University of Bradford, it is hydrogen peroxide that is responsible for the loss of hair color with age.

First gray, and then white hair is the result of the accumulation of H 2 O 2 in the hair follicles, and it is peroxide that is the main agent of oxidative stress, which leads to the death of melanocyte cells that give our hair color. The work of biochemists and dermatologists is published in the journal of the Federation of American Societies of Experimental Biology (FASEB).

That gray hair is not the coloring of hair in white, but the loss of their natural dark shade, people realized in ancient times. Over time, it also became clear that gray hair is not exclusively a human acquisition and many shaggy mammals also turn gray with age – it's just that wild animals rarely live up to this age in natural conditions. Actually, this is where the progress in the knowledge of the graying process stopped for centuries.

A qualitatively new understanding of gray hair came only with the advent of cell biology and an understanding of the structure and growth of hair at the cellular level. Using a microscope, scientists saw that the bulb from which the hair grows consists mainly of two types of cells – keratinocytes and melanocytes. The task of the first is to build the structure of the hair, that is, to become part of its next lower layer, synthesize as much keratin protein as possible and die, leaving keratin in the hair and allowing new keratinocytes from the next lower layer to do the work.

The purpose of the second is to produce tiny bubbles of pigment – black–brown (eumelanin) or yellow-red (pheomelanin), the combination of which determines all shades of hair color (as well as skin and eyes). These bubbles are then transferred to structural cells and remain in the hair growing from the bulb. Actually, the hair turns gray from the fact that melanocytes stop doing their job – either they become too few, or they stop synthesizing pigment bubbles, or they produce it where it is not necessary.

In 2002, Japanese Amy Nishimura, who was engaged in research on melanoma, a form of skin cancer caused by the uncontrolled growth of those same melanocytes, discovered stem cells in hair follicles that eventually turn into melanocytes. A couple of years later, scientists showed that with age, these stem cells in the bulbs become smaller, and they often differentiate into melanocytes in the wrong place – in a cell niche far from keratinocytes and the focus of hair growth, where there is no way to inject colorful bubbles into growing hair.

Nishimura and her supervisor David Fisher then even found indirect indications that melanocytes eventually die "of their own volition", in the process of apoptosis: as soon as the genes limiting apoptosis were turned off, the mice began to turn gray much faster. However, it remained unclear what was the root cause of death – external signals from "death receptors" on the surface of cells, the results of some internal checks on the integrity of DNA and other vital elements of the cell, or something else.

As Shallreiter and her colleagues have shown by examining human hair follicles, the reason is still the accumulation of hydrogen peroxide.

Using Raman spectroscopy of hair on the heads of living people, scientists tracked the change in the concentration of various substances in the hair rods and bulbs. By old age, the amount of H2O2 in each hair can be measured in milligrams – that is, it makes up a significant fraction of the hair mass.

According to scientists, the accumulation of peroxide begins when the enzyme catalase ceases to cope with its decomposition (by the way, it is this reaction and the oxygen released during it that we owe to the antiseptic properties of peroxide). As a result, a large amount of peroxide, firstly, discolors the hair, and secondly, damages the cells - indiscriminately.

However, there is a third, specific effect on the cells in which the pigment is produced. Simultaneously with catalase, the number of two enzymes – A- and B-methionine sulfoxide reductases, which "release" this amino acid for use in the construction of other proteins, also decreases. In particular, it is used in one of the active centers of tyrosinase, an enzyme that plays a key role in the formation of pigments.

Thus, peroxide strikes a double blow: on the one hand, it destroys an already prepared enzyme, and on the other hand, it interferes with its synthesis.

Scientists have even checked – however, only in vitro, "in vitro", that the artificial introduction of L-methionine stops the processes associated with hair graying. Unlike the black-haired Nishimura, who was interested only in the unexpectedly revealed connection between melanoma and senile gray hair, the blonde Schallreiter hopes for practical application of her discovery.

Portal "Eternal youth" www.vechnayamolodost.ru24.02.2009

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