News Medical (Austrália)

Study finds stress does whiten hair

Publicado em 22 janeiro 2020

Por Dr. Liji Thomas

In most cases, hair starts to gray in the thirties, and becomes pronounced in the fifties, at which time the head is typically crowned with a thatch of white, gray and perhaps some hair of the original color. A new study published January 2020 in the journal Nature, shows that this process is speeded up significantly by acute stress persisting over a period, or by severe trauma.

Historically, the French queen Marie Antoinette is said to turned gray in one single night, developing a pure white head after she heard of her projected end under the guillotine, when the French Revolution was at its peak in 1793.

Scientists call this phenomenon canities or achromotrichia. The contribution of stress to this graying has been a matter of commonly accepted but not medically proven fact so far. The researchers say, “Our study proved that the phenomenon does indeed occur, and we identified the mechanisms involved. In addition, we discovered a way of interrupting the process of hair color loss due to stress.”

How the study came about

Researcher Thiago Mattar Cunha explains, “We were conducting a study on pain using black C57 mice, a dark-furred laboratory strain. In this model, we administered a substance called resiniferatoxin to activate a receptor expressed by sensory nerve fibers and induce intense pain. Some four weeks after systemic injection of the toxin, a PhD student observed that the animals' fur had turned completely white.”

This was followed up several times but finally it became evident that the gray hair was a consequence of the application of resiniferatoxin. This chemical is sourced from nature, being found abundantly in the resin spurge (Euphorbia resinifera), which is a native Moroccan cactus-like plant.

The study and its findings

The experimental setup for the current study was simple and designed to evaluate just one thing: does the stress of something painful cause the fur to change color? Says Cunha, “"We designed a very simple experiment to see if the phenomenon was dependent on activation of sympathetic nerve fibers.” The sympathetic nervous system is part of the autonomic nervous system from where most of the control of involuntary and visceral action takes place. It is made up of spinal ganglia, or knots of nerve cells, from where fibers branch out to travel all over the country.

The sympathetic system is well known, because it controls the level of epinephrine that directly influences the body. It regulates the well-known “fight or flight” response when the body is faced with a very risky situation, through both epinephrine and cortisol release. Sympathetic stimulation means an increasing heartbeat, a higher blood pressure, faster breathing and a dilated pupil, and other systemic effects.

Sympathetic blockage and preserved hair color

The mice were first administered resiniferatoxin, and then they were treated with guanethidine, a drug that inhibits the neural sympathetic fibers and so can arrest the expression and transmission of sympathetic nerve signals. They found that guanethidine prevented the loss of hair color over the weeks following the induction of stress, by blocking sympathetic inputs following the pain-inducing injection.
Another experiment involved the removal of sympathetic fibers surgically, following the induction of pain. When the sympathetic system was blocked, fur color was preserved.

The researchers concluded that signal transmission through the sympathetic nerve system is a powerful role-player in achromotrichia. Next, they turned their attention to the why of this finding.

Why stress causes graying of hair

Skipping ahead a few years, it was Cunha who, during a scholarship stint at Harward, heard of and later joined a group there which had discovered something similar, partly by a lucky observation. They focused on their new discovery that stress due to pain was speeding up the maturation of the melanocyte stem cells within the bulb of the hair follicle beyond normal limits. Only young cells, which are undifferentiated, produce melanin. As the cell matures, it differentiates and melanin release stops. The researcher explains, “We used various methodologies to show that intense sympathetic activity speeds up differentiation significantly. In our model, therefore, pain accelerated the aging of the stem cells that produce melanin.”

Professor Ya-Chieh Hsu, who leads the group, chimes in: “When we started to study this, I expected that stress was bad for the body - but the detrimental impact of stress that we discovered was beyond what I imagined. After just a few days, all of the pigment-regenerating stem cells were lost. Once they're gone, you can't regenerate pigment anymore. The damage is permanent."

Another researcher, Bing Zhang, describes it as a permanent depletion of stem cells due to acute stress. Thus, instead of the fight-or-flight response benefiting the animal by helping it to survive, it is causing long-term harm to the animal.

Such effects are probably affecting other regions of the body too. Cunha says, “I'm currently working with other researchers on an investigation of the effects of sympathetic activity in other stem cell subpopulations."

Gene expression and hair graying

Using RNA sequencing as a tool, the researchers also examined the processes which enhance the differentiation of melanocyte stem cells, and compared how genes were expressed in mice that were injected with resiniferatoxin and thereafter showed signs of pain, stress and loss of hair color, with the way they were expressed in control mice injected with a placebo.

Their goal was to find genes that were expressed at very different levels after the animal developed stress. They were arrested by one gene that encodes an important enzyme called CDK, or cyclin-dependent kinase, which helps the cell divide.

When a CDK inhibitor was given to the mice after inducing pain, the result was a blockage in the differentiation of melanocyte stem cells, and in color loss. Cunha explains: “This finding shows that CDK participates in the process and could, therefore, be a therapeutic target. It's too soon to know whether it will actually become a target someday in clinical practice, but it's worth exploring further.”

In another experiment, a strong sympathetic stimulus was used. As a result, the scientists found that the nerve fibers to the hair follicle bulbs secreted noradrenaline close to the melanocyte stem cells, causing them to differentiate. Cunha describes the findings: “We showed that melanocyte stem cells express the protein ADRB2 [beta-2 adrenergic receptor], which is activated by noradrenaline, and we discovered that the stem cells differentiate when this receptor is activated by noradrenaline.”

They then repeated the experiment with mice that could not express ADBR2, and thus could not pass on sympathetic signals. These mice remained their original color even after a resiniferatoxin injection was given.

The final test was to treat human melanocytes in culture, which they had taken from the volunteers, with noradrenaline. This mimicked the effects of sympathetic stimulation and produced a rise in the expression of CDK like that which occurred in the whole mice.

About the applications

The researchers are not yet sure whether these findings will be useful for actual aesthetic purposes, such as developing a new drug to preserve the original hair color. They could use CDK inhibitors for this, but they need to look for side effects, and whether these outweigh the benefits. However, they are confident that they have found how and why pain-induced acute stress causes our hair to turn white.

Journal reference:
Zhang, B., Ma, S., Rachmin, I. et al. Hyperactivation of sympathetic nerves drives depletion of melanocyte stem cells. Nature (2020).

Essa notícia também repercutiu nos veículos:
Jammu Links News (Índia) Yahoo! (Reino Unido) Archynetys (EUA) The Federal (Índia) The Week (Índia) online Daily Excelsior (Índia) online The Shillong Times (Índia) online Deccan Herald (Índia) online FarmWeek (Reino Unido) online PressBoltNews (Índia) The Indian Express (Índia) online The National (Reino Unido) online thisisoxfordshire (Reino Unido) Unique Media House (Nigéria) News Archyves UK Swanage & Wareham Voice (Reino Unido) More Radio (Reino Unido) EATG - European AIDS Treatment Group (Bélgica) News Archives Uk (Reino Unido) East Lothain Courier (Reino Unido) Basildon Echo (Reino Unido) Business Standard (Índia) online Science Codex Dunfermline Press (Reino Unido) FR24 News English (EUA) Chochilino Sky News (Reino Unido) (Irlanda) BT Group (Reino Unido) Express & Star (Reino Unido) Evening Express (Reino Unido) online The Irish News (Reino Unido) online Bailiwick Express (Reino Unido) Teller Report The Independent (Reino Unido) online Droitwich Spa Advertiser (Reino Unido) Psychology Today (EUA) online News Archyves UK Get To Info BioTech Times (Índia) Guernsey Press (Reino Unido) Jersey Evening Post (Reino Unido) online USA News (EUA) WhatsVibe (Nigéria) Ardrossan & Saltcoats Herald (Reino Unido) BanburyCake (Reino Unido) Barrhead News (Reino Unido) Barry & DistrictNews (Reino Unido) Brasildon Standard (Reino Unido) Belfast Telegraph (Reino Unido) Bicester Advertiser (Reino Unido) Advertizer (Reino Unido) Border Telegraph (Reino Unido) Borehamwood & Elstree Times (Reino Unido) Daily Echo (Reino Unido) Braintree & Witham Times (Reino Unido) Bridgwater Mercury (Reino Unido) Bridport News (Reino Unido) Burnham & Highbridge Weekly News (Reino Unido) Carrick Herald (Reino Unido) Central Fife Times (Reino Unido) Harrow Times (Reino Unido) Hampshire Chronicle (Reino Unido) East London Guardian Series (Reino Unido) Halesowen News (Reino Unido) Darlington and Stockton Times (Reino Unido) Dorset Echo (Reino Unido) Charg And Ilminster News (Reino Unido) Chelmsford & Mid Essex Times (Reino Unido) The Standard (Reino Unido) The Citizen (Reino Unido) Clacton Gazette (Reino Unido) Clydebank Post (Reino Unido) Coast FM - West Cornwall's (Reino Unido) County Press (Reino Unido) Craven Herald & Pioneer (Reino Unido) Cumnock Chronicle (Reino Unido) Hillingdon & Uxbridge Times (Reino Unido) Ikley Gazette (Reino Unido) Irvine Times (Reino Unido) The Keighley News (Reino Unido) The Kidderminster Shuttle (Reino Unido) online Knutsford Guardian (Reino Unido) Lancashire Telegraph (Reino Unido) The Leader (Reino Unido) Ledbury Reporter (Reino Unido) Leigh Journal (Reino Unido) Love Sport Radio (Reino Unido) Ludlow Advertiser (Reino Unido) Malvern Gazette (Reino Unido) Messenger Newspapers (Reino Unido) North Wales Chronicle (Reino Unido) The Mail (Reino Unido) Ayr Advertiser (Reino Unido) Bracknell News (Reino Unido) Bromsgrove Advertiser (Reino Unido) Denbighshire Free Press (Reino Unido) online Dudley News (Reino Unido) Enfield Independent (Reino Unido) Epping Forest Guardian (Reino Unido) Evesham Jounal (Reino Unido) The Packet (Reino Unido) Free Press (Reino Unido) Gazette & Herald (Reino Unido) The Gazette (Reino Unido) Greenock Telegraph (Reino Unido) Helensburgh Advertiser (Reino Unido) The Herald (Reino Unido) Hereford Times (Reino Unido) Impartial Reporter (Reino Unido) Milford Mercury (Reino Unido) News & Star (Reino Unido) News Shopper (Reino Unido) North Wales Pioneer (Reino Unido) Northwich Guardian (Reino Unido) Oxford Mail (Reino Unido) Peeblesshire News (Reino Unido) Penarth Times (Reino Unido) The Prestwich and Whitefield Guide (Reino Unido) Daily Hunt (Índia) Redditch Advertiser (Reino Unido) Redhill And Reigate Life (Reino Unido) Rhyl Journal (Reino Unido) Richmond and Twickenham Times (Reino Unido) The Romsey Advertiser (Reino Unido) Runcorn and Widnes World (Reino Unido) Salisbury Journal (Reino Unido) Shropshire Star (Reino Unido) Slough Observer (Reino Unido) County Gazette (Reino Unido) Southend Standard (Reino Unido) South Wales Argus (Reino Unido) South Wales Guardian (Reino Unido) St Albans Review (Reino Unido) St Helens Star (Reino Unido) Stourbridge News (Reino Unido) Surrey Comet (Reino Unido) Swindon Advertiser (Reino Unido) Tewkesbury Admag (Reino Unido) The Argus (Reino Unido) The Bolton News (Reino Unido) Fooshya The Gazette (Reino Unido) Daily Times (Paquistão) The Lancaster & Morecambe Citizen (Reino Unido) Tleay (Camboja) The Northern Echo (Reino Unido) The Oldham Times (Reino Unido) Telegraph & Argus (Reino Unido) Westmorland Gazette (Reino Unido) This is Lancashire (Reino Unido) This is Local London (Reino Unido) This is Money (Reino Unido) This is the West Country (Reino Unido) This is Wiltshire (Reino Unido) Thurrock Gazette (Reino Unido) Times & Star (Reino Unido) Barnet Times Series (Reino Unido) Tivyside Advertiser (Reino Unido) Wales Farmer (Reino Unido) Wharfedale Observer (Reino Unido) Whitchurch Herald (Reino Unido) The Whitehaven News (Reino Unido) Wilts and Glos Standard (Reino Unido) Estación Del Siglo (Argentina) Wimbledon Guardian (Reino Unido) The Royal Borough Observer (Reino Unido) Wirral Globe (Reino Unido) online Witney Gazette (Reino Unido) Worcester News (Reino Unido) Yeovil Express (Reino Unido) The Press (Reino Unido) The Andover Advertiser (Reino Unido) Basingstoke Gazette (Reino Unido) Southern Daily Echo (Reino Unido) Dumbarton and Vale Leven (Reino Unido) Ealing Times (Reino Unido) Harwich and Manningtree Standard (Reino Unido) Hexham Courant (Reino Unido) In-Cumbria Magazine (Reino Unido) Wandsworth Times (Reino Unido) Warrington Guardian (Reino Unido) Watford Observer (Reino Unido) Western Telegraph (Reino Unido) Your Local Guardian (Reino Unido) Devdiscourse (Índia) Daily Hunt (Índia) Stem Cell Clinic Oriya News Report Ciencias Medicas News (Argentina) Ansa Latina (Argentina) ItaliaSalute (Itália) Rai News (Itália) Gazzetta del Sud (Itália) online Dagospia (Itália) Corriere della Sera (Itália) Giornale di Brescia (Itália) l'Adige (Itália) online LadyBlitz (Itália) La Stampa (Itália) online Blog Psicologisti (Itália) Tgcom24 (Itália) The Irish News (Reino Unido) online Guernsey News (Reino Unido) InfoSurHoy (EUA) The World News (Reino Unido) Yahoo! (Reino Unido) AOL UK (Reino Unido) Asian Image (Reino Unido) Brentwood Live (Reino Unido) The Bury Times (Reino Unido) online Cotswold Journal (Reino Unido) Powys County Times (Reino Unido) online Gazette Series (Reino Unido) The Herald (Reino Unido) Irish Examiner (Irlanda) online ITV Hub (Reino Unido) Largs & Millport News (Reino Unido) online MSN (Canadá) Stroud News & Journal (Reino Unido) Wiltshire Times (Reino Unido) (França) (França) Yahoo! (França) Epoch Times França Press From Brasil (EUA) Femme Actuelle (França) online La Presse (Canadá) Le Miroir Info Accueil L'Union (França) online MSN (Canadá) NEON (França) online Sciences et Avenir (França) online Pioneer News Chochilino The Economic Times (Índia) Head Topics (Brasil) Yahoo! Lifestyle India (Índia) Indian Express (Índia) The Tribune online (Índia) The Dragon Times The World News (Ucrânia) Top News Wood Trending News 365 AEDaily (Vietnã) Asianet (Índia) Info news Outlook India (Índia) The Telegraph (Reino Unido) The Hans India (Índia) online Tleay (Camboja) Today (Itália) Sky TG24 (Itália) Il Messaggero (Itália) online Lezioni Europa (Itália) PerugiaToday (Itália) Universo Mamma (Itália) Club de Sănătate PS News (Romênia) Albina Romaneasca (Itália) Ce se intampla, Doctore? (Romênia) Digi World (Romênia) Ciencias Medicas News (Argentina) Bloomberg (EUA) News List Jammu Links News (Índia) Canada News (Canadá) Biotech News (Austrália) Giornale di Sicilia (Itália) online Barron's Nestia (Singapura) Jewel 88.5 FM (Canadá) Sansara Nepal BBC Mundo (Reino Unido) IFLScience (Reino Unido) (Alemanha) News18 (Índia) EN24 News Ladders (EUA) (Alemanha) The Harvard Crimson Time 24 News (EUA) PressReader (Canadá) Yahoo Sport France (França) BBC (Reino Unido) Giornale di Sicilia (Itália) online