Premature graying as a consequence of compromised antioxidant activity in hair bulb melanocytes and their precursors

Irradiation-induced hair graying in mice: an experimental model to evaluate the effectiveness of interventions targeting oxidative stress, DNA damage prevention, and cellular senescence

Hair graying, also known as canities or achromotrichia, is a natural phenomenon associated with aging and is influenced by external factors such as stress, environmental toxicants, and radiation exposure. Understanding the mechanisms underlying hair graying is an ideal approach for developing interventions to prevent or reverse age-related changes in regenerative tissues. Hair graying induced by ionizing radiation (γ-rays or X-rays) has emerged as a valuable experimental model to investigate the molecular pathways involved in this process. In this review, we examine the existing evidence on radiation-induced hair graying, with a particular focus on the potential role of radiation-induced cellular senescence. We explore the current understanding of hair graying in aging, delve into the underlying mechanisms, and highlight the unique advantages of using ionizing-irradiation-induced hair graying as a research model. By elucidating the molecular pathways involved, we aim to deepen our understanding of hair graying and potentially identify novel therapeutic targets to address this age-related phenotypic change.

Putrescine Upregulates Melanogenesis Through Modulation of MITF Transcription Factor in B16F1 Mouse Melanoma Cells

Research background

Ageing is a biochemical, metabolic and genetic physiological phenomenon. The suppression of melanin biosynthesis, evident in the greying of the hair, is a hallmark of ageing resulting from translation failure, reduced enzyme activity and cellular senescence. Putrescine, the smallest member of the polyamine family and an organic chemical, is present in living mammalian cells and plays a crucial role in regulating skin melanogenesis. Therefore, the purpose of this study is to explore the effect of putrescine on the signalling pathways of melanogenesis in melanoma cells.

Experimental approach

Melanin production capacity of putrescine was analysed using a tyrosinase activity assay. To assess the cell viability of B16F1 cells exposed to putrescine, a tetrazolium dye MTT assay was performed. The effect of putrescine on melanin synthesis in the presence of H2O2 was evaluated using various in vitro assays in B16F1 cells. The effect of putrescine on melanin production in B16F1 cells was determined using a specific melanin production assay. Gene expression was analysed using real-time polymerase chain reaction (RT-PCR). Furthermore, the effect of putrescine on the expression of proteins related to melanin production in the cells treated with H2O2 was analysed by immunofluorescence and Western blot analysis.

Results and conclusions

Putrescine increased tyrosinase activity and showed no cytotoxicity in B16F1 cells. In addition, putrescine effectively scavenged H2O2, as shown by the reduction of intracellular H2O2 amounts in 2',7'-dichlorofluorescin diacetate analysis, and promoted melanin production in living cells. The stimulation of melanogenesis by putrescine was attributed to the increased expression of Mitf, Tyr, Trp-1 and Trp-2 genes. Immunofluorescence assays revealed that putrescine enhanced the expression of proteins associated with melanogenesis and upregulated TYR, TRP-1 and TRP-2 via the microphthalmia-associated transcription factor (MITF) and increased the expression of methionine sulfoxide reductases A (MSRA) and B (MSRB) in the cells treated with H2O2, effectively promoting melanogenesis. These results suggest that putrescine can be used to stimulate melanin synthesis.

Novelty and scientific contribution

This is the first study to investigate the effect of putrescine on the signalling pathways of melanogenesis in B16F1 melanoma cells. The results confirm that putrescine can promote melanogenesis through the expression of TYR, TRP-1 and TRP-2 via the MITF in cells treated with H2O2. Putrescine can be used exclusively as a cosmetic product to prevent premature greying of hair.

Investigating the morphology and genetics of scalp and facial hair characteristics for phenotype prediction

Microscopic traits and ultrastructure of hair such as cross-sectional shape, pigmentation, curvature, and internal structure help determine the level of variations between and across human populations. Apart from cosmetics and anthropological applications, such as determining species, somatic origin (body area), and biogeographic ancestry, the evidential value of hair has increased with rapid progression in the area of forensic DNA phenotyping (FDP). Individuals differ in the features of their scalp hair (greying, shape, colour, balding, thickness, and density) and facial hair (eyebrow thickness, monobrow, and beard thickness) features. Scalp and facial hair characteristics are genetically controlled and lead to visible inter-individual variations within and among populations of various ethnic origins. Hence, these characteristics can be exploited and made more inclusive in FDP, thereby leading to more comprehensive, accurate, and robust prediction models for forensic purposes. The present article focuses on understanding the genetics of scalp and facial hair characteristics with the goal to develop a more inclusive approach to better understand hair biology by integrating hair microscopy with genetics for genotype-phenotype correlation research.

NRF2 in the Epidermal Pigmentary System

Melanogenesis is a major part of the environmental responses and tissue development of the integumentary system. The balance between reduction and oxidation (redox) governs pigmentary responses, for which coordination among epidermal resident cells is indispensable. Here, we review the current understanding of melanocyte biology with a particular focus on the "master regulator" of oxidative stress responses (i.e., the Kelch-like erythroid cell-derived protein with cap'n'collar homology-associated protein 1-nuclear factor erythroid-2-related factor 2 system) and the autoimmune pigment disorder vitiligo. Our investigation revealed that the former is essential in pigmentogenesis, whereas the latter results from unbalanced redox homeostasis and/or defective intercellular communication in the interfollicular epidermis (IFE). Finally, we propose a model in which keratinocytes provide a "niche" for differentiated melanocytes and may "imprint" IFE pigmentation.

Focus on the Contribution of Oxidative Stress in Skin Aging

Skin aging is one of the most evident signs of human aging. Modification of the skin during the life span is characterized by fine lines and wrinkling, loss of elasticity and volume, laxity, rough-textured appearance, and pallor. In contrast, photoaged skin is associated with uneven pigmentation (age spot) and is markedly wrinkled. At the cellular and molecular level, it consists of multiple interconnected processes based on biochemical reactions, genetic programs, and occurrence of external stimulation. The principal cellular perturbation in the skin driving senescence is the alteration of oxidative balance. In chronological aging, reactive oxygen species (ROS) are produced mainly through cellular oxidative metabolism during adenosine triphosphate (ATP) generation from glucose and mitochondrial dysfunction, whereas in extrinsic aging, loss of redox equilibrium is caused by environmental factors, such as ultraviolet radiation, pollution, cigarette smoking, and inadequate nutrition. During the aging process, oxidative stress is attributed to both augmented ROS production and reduced levels of enzymatic and non-enzymatic protectors. Apart from the evident appearance of structural change, throughout aging, the skin gradually loses its natural functional characteristics and regenerative potential. With aging, the skin immune system also undergoes functional senescence manifested as a reduced ability to counteract infections and augmented frequency of autoimmune and neoplastic diseases. This review proposes an update on the role of oxidative stress in the appearance of the clinical manifestation of skin aging, as well as of the molecular mechanisms that underline this natural phenomenon sometimes accelerated by external factors.

Modeling human gray hair by irradiation as a valuable tool to study aspects of tissue aging

As one of the earliest and most visible phenomenon of aging, gray hair makes it a unique model system for investigating the mechanism of aging. Ionizing radiation successfully induces gray hair in mice, and also provides a venue to establish an organ-cultured human gray hair model. To establish a suitable organ-cultured human gray HF model by IR, which imitates gray hair in the elderly, and to explore the mechanisms behind the model. By detecting growth parameters, melanotic and senescence markers of the model, we found that the model of 5 Gy accords best with features of elderly gray hair. Then, we investigated the formation mechanisms of the model by RNA-sequencing. We demonstrated that the model of organ-cultured gray HFs after 5 Gy irradiation is closest to the older gray HFs. Moreover, the 5 Gy inhibited the expression of TRP-1, Tyr, Pmel17, and MITF in hair bulbs/ORS of HFs. The 5 Gy also significantly induced ectopically pigmented melanocytes and increased the expression of DNA damage and senescence in HFs. Finally, RNA-seq analysis of the model suggested that IR resulted in cell DNA damage, and the accumulation of oxidative stress in the keratinocytes. Oxidative stress and DNA damage caused cell dysfunction and decreased melanin synthesis in the gray HFs. We found that HFs irradiated at 5 Gy successfully constructed an appropriate aging HF model. This may provide a useful model for cost-effective and predictable treatment strategies to human hair graying and the process of aging.

Hair Graying Regulators Beyond Hair Follicle

Hair graying is an interesting physiological alteration associated with aging and certain diseases. The occurrence is due to depigmentation of the hair caused by depletion and dysfunction of melanocyte stem cells (MeSCs). However, what causes the depletion and dysfunction of MeSCs remains unclear. MeSCs reside in the hair follicle bulge which provides the appropriate niche for the homeostasis of various stem cells within hair follicle including MeSCs. In addition to local signaling from the cells composed of hair follicle, emerging evidences have shown that nerves, adipocytes and immune cells outside of hair follicle per se also play important roles in the regulation of MeSCs. Here, we review the recent studies on different cells in the MeSCs microenvironment beyond the hair follicle per se, discuss their function in regulating hair graying and potentially novel treatments of hair graying.

Analysis of Zinc and Copper Serum Levels in Premature Hair Graying at Young Age

BACKGROUND: Premature canities or premature hair graying is a terminology for early hair graying at an unusual age, with unclear etiology. The pathogenesis of graying is multifactorial such as genetic, environmental, and nutritional factors. The risk factor of premature graying is a deficiency of micronutrient serum such as zinc, copper, and selenium. AIM: The aim of the present study was to examine the role of zinc and copper serum concentrations in premature hair graying as well as the relationship between them. MATERIALS AND METHODS: This study was a cross-sectional recruited 40 consecutive respondents suffering from premature graying and healthy controls, male sex and aged <25 years. The serum samples were collected to detect zinc and copper with atomic absorption spectrophotometry. RESULTS: The mean age of cases was 20.28 ± 1.99 years and controls were 21.25 ± 2.02. Zinc serum concentration was significantly lower in premature hair graying compared with controls (0.48 ± 0.19 vs. 1.92 ± 0.68 ug/dL, p = 0.001) while copper serum concentration was not significantly lower in premature hair gray compared with controls (0.08 ± 0.03 vs. 0.09 ± 0.18 ug/dL, p = 0.706). CONCLUSION: A low zinc serum level may contribute to premature hair graying of college students at Universitas Sumatera Utara.

Melanogenesis markers expression in premature graying of hair- a cross-sectional study

BACKGROUND

Studies on mice and aging human hair follicles provide compelling evidence that graying of hair results from premature differentiation of Melanocyte stem cells (MeSC) in the niche/bulge.

OBJECTIVE

  To analyze whether differentiation of melanocyte stem cells is responsible for premature graying of hair (PGH).

METHODS

  Twenty- five patients of PGH (n=25) attending dermatology department were recruited. Five unpigmented and five pigmented hairs were obtained per patient by separating individual follicles by 1 mm punch biopsies. The hairs were dissected at a distance of 2 mm from the bulb to separate the stem cells (upper segment) (US) from the melanocytes (lower segment) (LS). RNA was extracted from hair follicle segments US and LS, and expression of GP100, Tyrosinase (TYR) and Tyrosinase related protein-1 (TYRP1) genes was quantified using Qiagen one-step RT-PCR kit.

RESULTS

  We found melanogenesis gene expression in both temporary (US) and permanent (LS) segments of unpigmented and pigmented hair follicles. When compared between the US and LS of white hair, the expression of TYR and GP100 was much higher in US than LS, suggestive of melanogenesis in the bulge. Similarly, when compared between white and black US, the expression of all three genes was higher in white US than black US, although not statistically significant.

LIMITATIONS

Low samples size and lack of data pertaining to the expression of genes at protein level are the limitations of current study.

CONCLUSION

Even though this pilot study data yielded key information about the expression of GP100, TYR and TYRP-1 at mRNA level, further studies quantifying the expression of these genes at protein level are needed to provide additional clues to further address the results in detail.

Investigation of the molecular signature of greying hair shafts

OBJECTIVE

Hair greying (i.e. canitie) is a physiological process occurring with the loss of melanin production and deposition within the hair shafts. Many studies reported the oxidation as the main biological process underlying this defect of pigmentation. Even though the overall appearance and biomechanical properties of hairs are reported to be altered with greying, there is a lack of information about molecular modifications occurring in grey hair shafts. The aim of this study was thus to investigate the molecular signature and associated changes occurring in greying hair shafts by confocal Raman microspectroscopy.

METHODS

This study was conducted on pigmented, intermediate (i.e. grey) and unpigmented hairs taken from 29 volunteers. Confocal Raman microspectroscopy measurements were acquired directly on hair shafts.

RESULTS

Automatic classification of Raman spectra revealed 5 groups displaying significant differences. Hence, the analysis of the molecular signature highlighted the existence of 3 sub-groups within grey hair: light, medium and dark intermediate. Among molecular markers altered in the course of greying, this study identified for the first time a gradual modification of lipid conformation (trans/gauche ratio) and protein secondary structure (α-helix/β-sheet ratio), referring respectively to an alteration of barrier function and biomechanical properties of greying hair.

CONCLUSION

This study thus reports for the first time a highly specific molecular signature as well as molecular modifications within grey hair shaft.

In vitro and clinical evaluation of umbilical cord-derived mesenchymal stromal cell-conditioned media for hair regeneration

BACKGROUND

The field of regenerative medicine may present a non-drug, non-steroid, and non-invasive alternative toward addressing male and female pattern hair loss, a global concern.

OBJECTIVE

The aim was to carry out the in vitro and in vivo safety and efficacy evaluation of human umbilical cord-derived mesenchymal stromal cell-conditioned media (MSC-CM) for hair regeneration.

METHODS

Various in vitro parameters were used to estimate the consistency across various batches of MSC-CM. Total protein content was measured by the Biuret method and antioxidant activity by the 2,2-diphenyl-1-picryl hydrazyl (DPPH) assay. Fourier transform infrared spectroscopy (FTIR) analysis was used to determine spectral signatures and biocompatibility was carried out by the Neutral Red Uptake (NRU) and Sulforhodamine B (SRB) assays. In vivo safety and efficacy was evaluated in an experimental pilot study on 15 volunteers.

RESULTS

The in vitro results confirmed stability in the protein content (7 mg/ml), antioxidant activity (49.50%), and FTIR fingerprints of the MSC-CM. In the biocompatibility experiments by both SRB and NRU methods, no IC₅₀ value could be derived at 100% concentration indicating safety at the cellular level. The in vivo results indicated safety with no side effects or adverse reactions, while 86.6% of the subjects experienced a positive effect of hair regeneration.

CONCLUSION

MSC-CM comprises a rich cocktail of physiologically balanced growth factors, cytokines, and beneficial proteins which may explain the bioactivity and mechanism of action in hair regrowth. This may indicate a biocompatible, gentle, and safe regenerative approach to address hair loss.

A Novel Pro-Melanogenic Effect of Standardized Dry Olive Leaf Extract on Primary Human Melanocytes from Lightly Pigmented and Moderately Pigmented Skin

Benolea^® (EFLA^®943) is a standardized dry olive leaf extract (DOLE) considered safe for food consumption and has demonstrated superior pharmaceutical benefits such as antioxidant, anti-obesity, and anti-hypertensive activities. However, there is no study on its effects on melanogenesis yet. Disruption in the sequence of steps in melanogenesis can lead to hypopigmentary disorders which occur due to reduced production or export of pigment melanin in the skin. There is a need for safe and nontoxic therapeutics for the treatment of hypopigmentation disorders. Herein, we studied the effects of DOLE over a concentration range of 10-200 µg/mL on melanin synthesis and melanin secretion in B16F10 mouse melanoma cells and MNT-1 human melanoma cells and validated our results in primary human melanocytes (obtained from lightly pigmented (LP) and moderately pigmented (MP) cells) as well as their cocultures with keratinocytes. The capacity of melanocytes to export melanosomes was also estimated indirectly by the quantitation of melanocyte dendrite lengths and numbers. Our results show that DOLE significantly enhanced levels of extracellular melanin in the absence of effects on intracellular melanin, demonstrating that this plant extract's pro-melanogenic activity is primarily based on its capacity to augment melanin secretion and stimulate melanocyte dendricity. In summary, our preliminary results demonstrate that DOLE may hold promise as a pro-pigmenting agent for vitiligo therapy and gray hair treatment by its exclusive and novel mechanism of functioning as a dendrite elongator. Further studies to elucidate the mechanisms of action of the pro-melanogenic activity and effects of DOLE on melanosome export as well as the last steps of melanogenesis are warranted.

Iron Gall Ink Revisited: A Surfactant-Free Emulsion Technology for Black Hair-Dyeing Formulation

Inspired by the redox reactions in the preparation of the iron gall ink that has been used in Europe since the Middle Ages, we developed a technology for forming the oil-in-water emulsions, without any surfactants and emulsifiers, by homogenizing a mixture of tannic acid, gallic acid, Fe(D-gluconate)2, and natural oil, which are all approved as cosmetic ingredients. Various plant-derived oils, such as argan oil, olive oil, sunflower oil, grape seed oil, hemp seed oil, peppermint oil, rosemary oil, and ylang-ylang oil, were used as an oil phase for the emulsion formation, and all the fabricated emulsions exhibited the capability of black hair-dyeing. This surfactant-free emulsion technology for combining the hair-dyeing capability of Fe3+–tannin complex with the hair-fortifying property of natural oil would have great impact on the hair-cosmetic industry.

Stress-sensing in the human greying hair follicle: Ataxia Telangiectasia Mutated (ATM) depletion in hair bulb melanocytes in canities-prone scalp

Canities (or hair greying) is an age-linked loss of the natural pigment called melanin from hair. While the specific cause(s) underlying the loss of melanogenically-active melanocytes from the anagen hair bulbs of affected human scalp remains unclear, oxidative stress sensing appears to be a key factor involved. In this study, we examined the follicular melanin unit in variably pigmented follicles from the aging human scalp of healthy individuals (22-70 years). Over 20 markers were selected within the following categories: melanocyte-specific, apoptosis, cell cycle, DNA repair/damage, senescence and oxidative stress. As expected, a reduction in melanocyte-specific markers in proportion to the extent of canities was observed. A major finding of our study was the intense and highly specific nuclear expression of Ataxia Telangiectasia Mutated (ATM) protein within melanocytes in anagen hair follicle bulbs. ATM is a serine/threonine protein kinase that is recruited and activated by DNA double-strand breaks and functions as an important sensor of reactive oxygen species (ROS) in human cells. The incidence and expression level of ATM correlated with pigmentary status in canities-affected hair follicles. Moreover, increased staining of the redox-associated markers 8-OHdG, GADD45 and GP-1 were also detected within isolated bulbar melanocytes, although this change was not clearly associated with donor age or canities extent. Surprisingly, we were unable to detect any specific change in the expression of other markers of oxidative stress, senescence or DNA damage/repair in the canities-affected melanocytes compared to surrounding bulbar keratinocytes. By contrast, several markers showed distinct expression of markers for oxidative stress and apoptosis/differentiation in the inner root sheath (IRS) as well as other parts of the hair follicle. Using our in vitro model of primary human scalp hair follicle melanocytes, we showed that ATM expression increased after incubation with the pro-oxidant hydrogen peroxide (H₂O₂). In addition, this ATM increase was prevented by pre-incubation of cells with antioxidants. The relationship between ATM and redox stress sensing was further evidenced as we observed that the inhibition of ATM expression by chemical inhibition promoted the loss of melanocyte viability induced by oxidative stress. Taken together these new findings illustrate the key role of ATM in the protection of human hair follicle melanocytes from oxidative stress/damage within the human scalp hair bulb. In conclusion, these results highlight the remarkable complexity and role of redox sensing in the status of human hair follicle growth, differentiation and pigmentation.

The biology of human hair greying

Hair greying (canities) is one of the earliest, most visible ageing-associated phenomena, whose modulation by genetic, psychoemotional, oxidative, senescence-associated, metabolic and nutritional factors has long attracted skin biologists, dermatologists, and industry. Greying is of profound psychological and commercial relevance in increasingly ageing populations. In addition, the onset and perpetuation of defective melanin production in the human anagen hair follicle pigmentary unit (HFPU) provides a superb model for interrogating the molecular mechanisms of ageing in a complex human mini-organ, and greying-associated defects in bulge melanocyte stem cells (MSCs) represent an intriguing system of neural crest-derived stem cell senescence. Here, we emphasize that human greying invariably begins with the gradual decline in melanogenesis, including reduced tyrosinase activity, defective melanosome transfer and apoptosis of HFPU melanocytes, and is thus a primary event of the anagen hair bulb, not the bulge. Eventually, the bulge MSC pool becomes depleted as well, at which stage greying becomes largely irreversible. There is still no universally accepted model of human hair greying, and the extent of genetic contributions to greying remains unclear. However, oxidative damage likely is a crucial driver of greying via its disruption of HFPU melanocyte survival, MSC maintenance, and of the enzymatic apparatus of melanogenesis itself. While neuroendocrine factors [e.g. alpha melanocyte-stimulating hormone (α-MSH), adrenocorticotropic hormone (ACTH), ß-endorphin, corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH)], and micropthalmia-associated transcription factor (MITF) are well-known regulators of human hair follicle melanocytes and melanogenesis, how exactly these and other factors [e.g. thyroid hormones, hepatocyte growth factor (HGF), P-cadherin, peripheral clock activity] modulate greying requires more detailed study. Other important open questions include how HFPU melanocytes age intrinsically, how psychoemotional stress impacts this process, and how current insights into the gerontobiology of the human HFPU can best be translated into retardation or reversal of greying.

Premature graying of hair: Risk factors, co-morbid conditions, pharmacotherapy and reversal-A systematic review and meta-analysis

Premature graying of hair (PGH) being a very common entity for which pharmacotherapy and reversibility are not properly addressed. Therefore, this systematic review was conducted to address these issues. For this relevant study were selected from various databases including PubMed, EMBASE, OVID, Web of science, Scopus, and Google Scholar till January 20, 2019. Studies which reported risk factors, co-morbid conditions associated with PGH, its pharmacotherapy and reversal were included in the study. Although many risk factors are reported in literature, smoking, vitamin deficiency (B12, folic acid, and B7), mineral deficiency (low serum calcium and serum ferritin) are found to be associated with PGH. Other important risk factors are family history of PGH, obesity, high B.P, lack of exercise, drugs, genetic syndromes, dyslipidemia, thyroid disorders, hyperuricemia, and alteration in liver function. PGH is found to be an important marker of CAD, more so in case of smoker. Among different pharmacotherapeutic management options, low grade recommendation (2A) is given to calcium pantothenate, PABA, calcium pantothenate + PABA combination. Anu-tailam is the only herbal agent evaluated in clinical research settings. Finally, treating the accompanying pathologies led to the reversal of the disease in many cases.

Evaluation of Systemic Oxidative Stress in Patients with Premature Canities and Correlation of Severity of Hair Graying with the Degree of Redox Imbalance

Context:

Premature canities etiopathogenesis is unclear, and approach to its therapy remains arbitrary. Reactive oxygen species generated during melanin biosynthesis in anagen hair bulb have been implicated in melanocyte apoptosis and hair graying. Extraneous factors, namely environmental pollution, stressful lifestyle, may compound the melanogenesis-induced endogenous oxidative stress.

Aims:

We aimed to investigate the role of systemic oxidative stress in causation of premature canities and its correlation with the severity of hair graying.

Settings and Design:

This was a tertiary care hospital-based cross-sectional study.

Materials and Methods:

Consecutive 50 patients with premature hair graying, aged <25 years, and 30 age and sex-matched healthy controls were recruited. Severity of premature canities was graded based on the total number of gray hair on the scalp. Redox status was evaluated in cases and controls, by malondialdehyde (MDA), reduced glutathione (rGSH), and superoxide dismutase (SOD) measurement in serum, by enzyme-linked immunosorbent assay.

Results:

Serum MDA concentration, an oxidative stress marker, was significantly higher (P < 0.01), while serum rGSH and SOD levels, both indicators of antioxidant potential, were significantly lower (P < 0.0001 and P < 0.01 respectively) in premature canities patients compared to controls. A novel observation was the significant correlation of serum MDA rise and serum rGSH decline with increasing severity of hair graying (P < 0.01 and P = 0.01, respectively).

Conclusion:

Systemic redox imbalance is present in premature canities patients, with the severity of hair graying varying in parallel to the degree of oxidative stress. Antioxidants supplementation is likely to yield therapeutic benefit in premature canities.

The Danger of Being Too Sympathetic: Norepinephrine in Alzheimer's Disease and Graying of Hair

Although alterations in the sympathetic nervous system (SNS) with age have been reported, and serious degenerative diseases of the autonomic nervous system such as multiple system atrophy are more likely to strike older people, connections between dysregulated adrenergic receptors and age-associated diseases and phenotypes have not been well studied. Two recent reports suggest that SNS may be more closely connected than previously appreciated. First, low nanomolar concentrations of Alzheimer's disease (AD)-associated Aβ42-amyloid oligomers alter signaling by SNS neurotransmitter norepinephrine (NE) to sufficiently activate kinase GSK3β to hyperphosphorylate tau, a key mediator of neurotoxicity in AD. Connecting beta-amyloid to tau in AD has been a key quest in understanding AD and developing therapeutics. The α₂ adrenergic receptor inhibitory drug idazoxan reduces GSK3β activity and tau phosphorylation in AD mice with improved cognitive function, even in the presence of beta-amyloid deposits. In this study, SNS activation in the brain coupled with problematic Aβ42-amyloid oligomers result in serious consequences that can be ameliorated by reducing SNS signaling. A second example of the detrimental effects of increased SNS signaling is the premature graying of hair in response to stress. Secretion of NE resulting from stress causes differentiation of most hair pigment melanocyte stem cells (MeSCs) into melanocytes, rapidly depleting the hair follicle of pigment-producing cells as mature melanocytes undergo apoptosis and MeSCs are eventually eliminated. Blockade of NE SNS signaling preserves hair coloration in stressed animals. Increased SNS activation has serious apparently irreversible effects on homeostasis in both situations. Although neither report directly addresses aging, given that AD and the loss of hair pigmentation have strong age associations, it is of interest to better understand the role that SNS has in promoting age-associated phenotypes generally and determine if tuning the SNS through drug-mediated attenuation of SNS signaling may be of medical benefit.

Stimulating hair growth via hormesis: Experimental foundations and clinical implications

Numerous agents (approximately 90) are shown to stimulate hair growth in cellular and animal models in a hormetic-like biphasic dose response manner. These hormetic dose responses occur within the framework of direct stimulatory responses as well as in preconditioning experimental protocols. These findings have important implications for experimental and clinical investigations with respect to study design strategies, dose selection and dose spacing along with sample size and statistical power issues. These findings further reflect the general occurrence of hormetic dose responses within the biological and biomedical literature that consistently appear to be independent of biological model, level of biological organization (i.e., cell, organ, and organism), endpoint, inducing agent, potency of the inducing agent, and mechanism.

Therapeutics of premature hair graying: A long journey ahead

Premature graying of hair has major psychosocial and socioeconomic repercussion, as it is considered as a sign of hastily progressing old age, ill health and often leads to loss of self-esteem. Hair is said to gray prematurely when it happens before the age of 20 years in Caucasians, 25 years in Asians, and 30 years in Africans. The hair color chiefly depends on melanin pigment, and fabrication of this pigment takes place in melanosomes through the process of melanogenesis. This complex biochemical pathway (melanogenesis) is further dependent on tyrosinase which acts as fuel.The normal human scalp is subjected to various factors categorized as intrinsic and extrinsic leading to graying of hair. Intrinsic factors comprise of variants responsible for changes at genetic level while extrinsic factors include air pollution, ultraviolet radiation, smoking, and nutrition. It has been proposed that direct or indirect effect of all these factors results in the generation of reactive oxygen species (ROS), thus leading to further damage. Though research has expanded in last few years in terms of microscopic, biochemical (hormonal, enzymatic), and molecular changes happening within hair follicle/shaft, still the exact mechanism leading to premature graying of hair is not well understood. Probable solutions toward this quandary are diet, herbal remedies, and temporary hair colorants. Ironically, the latter one being the most common has various side effects such as allergic reactions, inflammation, and hair loss. The aim of this paper was to review the manifestation and probable future interventions in preventing premature hair graying.

Effects of the selective TrkA agonist gambogic amide on pigmentation and growth of human hair follicles in vitro

The human hair follicle is a neuroendocrine mini-organ that can be used to study aging processes in vitro. Neurotrophins maintain homeostasis in hair biology via the Trk-family of receptors. TrkA, the high affinity receptor for nerve growth factor (NGF), is expressed in hair follicle melanocytes and keratinocytes, where it regulates proliferation, differentiation and apoptosis and may thereby play a role in hair pigmentation and growth. We investigated TrkA expression during the human hair cycle and the effects of a selective high affinity TrkA agonist, Gambogic Amide, on hair pigmentation and hair growth in human hair follicles in vitro. In human scalp skin, TrkA expression was strongest in proliferating melanocytes re-establishing the pigmentary unit in the hair bulb during the early hair growth phase, anagen. During high anagen and in the de-composing pigmentary-unit of the regression phase, catagen, bulb-melanocytes lost TrkA expression and only undifferentiated outer root sheath melanocytes maintained it. In cultured human anagen hair follicles, Gambogic Amide was able to prevent gradual pigment loss, while it stimulated hair shaft elongation. This was achieved by increased melanocyte activation, migration and dendricity, highlighted by distinct c-KIT-expression in melanocyte sub-populations. Our results suggest that Gambogic Amide can maintain hair follicle pigmentation by acting on undifferentiated melanocytes residing in the outer root sheath and making them migrate to establish the pigmentary-unit. This suggests that the selective TrkA agonist Gambogic Amide acts as an anti-hair greying and hair growth promoting molecule in vitro.

Degraded melanocores are incompetent to protect epidermal keratinocytes against UV damage

Melanosomes are membrane-bound intracellular organelles that are uniquely generated by melanocytes (MCs) in the basal layer of human epidermis. Highly pigmented mature melanosomes are transferred from MCs to keratinocytes (KCs), and then positioned in the supra-nuclear region to ensure protection against ultraviolet radiation (UVR). However, the molecular mechanism underlying melanosome (or melanin pigment) transfer remains enigmatic. Emerging evidence shows that exo-/endo-cytosis of the melanosome core (termed melanocore) has been considered as the main transfer manner between MCs and KCs. As KCs in the skin migrate up from the basal layer and undergo terminal differentiation, the melanocores they have taken up from MCs are subjected to degradation. In this study, we isolated individual melanocores from human MCs in culture and then induced their destruction/disruption using a physical approach. The results demonstrate that the ultrastructural integrity of melanocores is essential for their antioxidant and photoprotective properties. In addition, we also show that cathepsin V (CTSV), a lysosomal acid protease, is involved in melanocore degradation in calcium-induced differentiated KCs and is also suppressed in KCs following exposure to UVA or UVB radiation. Thus, our study demonstrates that change in the proportion of melanocores in the intact/undegraded state by CTSV-related degradation in KCs affects photoprotection of the skin.

Association of Epidemiological and Biochemical Factors with Premature Graying of Hair: A Case-Control Study

Background:

Premature hair graying (PHG) is often a matter of great concern for patients as it is viewed as a sign of increasing age, debility, decreasing vigor, and may lead to low self-esteem and psychological morbidity. Its etiopathogenesis is not completely understood but genetic, and various acquired factors have been implicated. The present study was undertaken to evaluate various epidemiological and biochemical variables associated with PHG.

Materials and Methods:

A cross-sectional case–control study was conducted at a tertiary care hospital in North India for 1 year which comprised 120 patients and equal number of controls. Various epidemiological variables were recorded and compared to controls. Serum ferritin, serum calcium, serum Vitamin D, serum Vitamin B12, lipid profile, thyroid profile, and fasting blood sugar were measured and compared among cases and controls.

Results:

Significantly higher proportion of cases had atopic diathesis, sedentary lifestyle, family history, history of smoking, and higher perceived stress values as compared to controls. Hair oiling seemed to protect against premature graying. Significantly, lower levels of serum calcium, ferritin, Vitamin B12, high-density lipoprotein-cholesterol, and high low-density lipoprotein-cholesterol were observed among cases.

Conclusion:

In the light of the present study, further studies with larger sample size are required to establish the definite etiological significance of these variables and formulate various preventive and therapeutic targets to prevent and treat PHG.

Premature Graying of Hair: Review with Updates

Premature graying of hair (PGH) is defined as graying of hair before the age of 20 years in Caucasians and before 30 years in African American population. It can severely affect the self-esteem of an individual. The exact etiopathogenesis remains unknown, although it has been associated with premature aging disorders, atopy, and autoimmune diseases. Patients, who present with PGH, should be assessed for syndromes and metabolism diseases. Hair dyes remain the main modality of the treatment for cosmetic concerns after nutritional supplementation.

Aging in hair follicle stem cells and niche microenvironment

Hair graying and hair loss are prominent and common characteristics of the elderly population. In some individuals these processes can significantly impact their quality of life, leading to depression, anxiety and other serious mental health problems. Accordingly, there has been much interest in understanding the complex physiological changes within the hair follicle in the aging individual. It is now known that hair follicles represent a prototypical stem cell niche, where both micro- and macroenvironmental influences are integrated alongside stem cell-stem cell and stem cell-stem niche interactions to determine hair growth or hair follicle senescence. Recent studies have identified imbalanced stem cell differentiation and altered stem cell activity as important factors during hair loss, indicating new avenues for the development of therapeutic agents to stimulate hair growth. Here, we pull together the latest findings on the hair follicle stem cell niche and the multifactorial interactions underlying the various forms of hair loss.

Deoxyarbutin Possesses a Potent Skin-Lightening Capacity with No Discernible Cytotoxicity against Melanosomes

Safe and effective ingredients capable of removing undesired hyperpigmentation from facial skin are urgently needed for both pharmaceutical and cosmetic purposes. Deoxyarbutin (4-[(tetrahydro-2H-pyran-2-yl) oxy] phenol, D-Arb) is a glucoside derivative of hydroquinone. Here, we investigated the toxicity and efficacy of D-Arb at the sub-cellular level (directly on melanosomes) and skin pigmentation using in vivo and in vitro models to compare with its parent compound hydroquinone (1,4-benzenediol, HQ). At first, we examined the ultrastructural changes of melanosomes in hyperpigmented guinea pig skin induced by 308-nm monochromatic excimer lightand/or treated with HQ and D-Arb using transmission electron microscopy. The results showed that prominent changes in the melanosomal membrane, such as bulb-like structure and even complete rupture of the outer membranes, were found in the skin after topical application of 5% HQ for 10 days. These changes were barely observed in the skin treated with D-Arb. To further clarify whether membrane toxicity of HQ was a direct result of the compound treatment, we also examinedultrastructural changes of individual melanosomes purified from MNT1 human melanoma cells. Similar observations were obtained from the naked melanosome model in vitro. Finally, we determined the effects of melanosomal fractions exposed to HQ or D-Arb on hydroxyl radical generation in the Fenton reaction utilizing an electron spin resonance assay. D-Arb-treated melanosomesexhibit a moderate hydroxyl radical-scavenging activity, whereas HQ-treated melanosomessignificantly generate more hydroxyl free radicals. This study suggests that D-Arb possesses a potent ability in skin lightening and antioxidation with less melanosome cytotoxicity.

Risk Factors for Premature Hair Graying in Young Turkish Adults

BACKGROUND

Premature hair graying (PHG) is a common condition resulting in loss of self-esteem. Studies investigating PHG risk factors for both sexes with a large number of patients are scarce. We sought to investigate the socioclinical risk factors for PHG in young Turkish men and women and the differences between the sexes.

METHODS

A cross-sectional study was conducted in 1,119 participants who answered a survey about PHG and some socioclinical characteristics between February and July 2015. The number of gray hairs, onset age of hair graying, and family history of PHG were asked about, as well as demographic characteristics, anthropometric measures, body mass index, smoking, alcohol consumption, sports life, diet, medical history, educational status, occupation, marital status, monthly income, and Fitzpatrick skin type.

RESULTS

Of 1,119 participants, 315 (28.1%) had PHG and 804 did not. Maternal and paternal PHG, alcohol consumption, presence of chronic disease, educational status, hair loss, perceived stress scale (PSS) score, age, and height were significantly higher in subjects with PHG. Rates of maternal and paternal PHG were high in women with PHG, and the rate of paternal PHG was high in men with PHG. According to the multivariate ordinal regression analysis, PSS score, age, hair loss, and family history of PHG were correlated with the severity of PHG.

CONCLUSION

PHG is closely related to factors causing oxidative stress, such as emotional stress, alcohol consumption, and chronic diseases in genetically predisposed men and women.

Assessment of Oxidative Stress in Patients with Premature Canities

Context:

Premature canities is a common, yet unexplored disorder. Oxidative stress levels have been evaluated within the greying hair follicle but not in the sera of patients with premature canities.

Aims:

To evaluate the oxidative stress parameters in the sera of patients with premature canities.

Settings and Design:

A pilot case-controlled study, conducted in a tertiary care setup in Delhi during November 2011 to December 2012.

Materials and Methods:

Fifty-two self-reporting cases of premature canities (age of onset <20 years) and 30 healthy controls were recruited from outpatient Department of Dermatology. Oxidative stress parameters (serum malonaldehyde (MDA), whole blood reduced glutathione (rGSH) and serum ferric reducing antioxidant potential [FRAP]) were assessed in cases and controls. Mann–Whitney test was used to compare the oxidative stress parameters between the two groups (SPSS version 17.0, SPSS Inc, Chicago, USA; P < 0.05 considered as significant).

Results:

The age and sex distribution of cases and controls was comparable. The mean serum levels of MDA were higher in cases than controls (3.7 ± 1.6 nmol/ml vs. 2.8 ± 1.5 nmol/ml; P = 0.01). The GSH levels were lower in the cases than controls (31.5 ± 8.9 mg/dl vs. 36.6 ± 16.9 mg/dl; P = 0.064). Similarly, the mean FRAP levels were lower in the cases than controls (400 ± 70 nmol/ml vs. 430 ± 80 nmol/ml; P = 0.038).

Conclusions:

Patients with premature canities had a higher level of pro-oxidants and lower levels of antioxidants than controls. This is the first humble attempt to document the oxidative stress parameters in sera of patients with premature canities, further studies with larger sample size are required to reach a definite conclusion.

Vitiligo

Vitiligo is an acquired depigmenting disorder that affects 0.5% to 2% of the world population. Three different forms are classified according to the distribution of lesions; namely non-segmental, segmental and mixed vitiligo. Vitiligo is associated with polymorphisms in genes involved in the immune response and in melanogenesis. However, environmental factors are required for the development of manifest disease. In general, the diagnosis is clinical and no laboratory tests or biopsies are required. Metabolic alterations are central to current concepts in pathophysiology. They induce an increased generation of reactive oxygen species and susceptibility to mild exogenous stimuli in the epidermis. This produces a senescent phenotype of skin cells, leads to the release of innate immune molecules, which trigger autoimmunity, and ultimately causes dysfunction and death of melanocytes. Clinical management aims to halt depigmentation, and to either repigment or depigment the skin, depending on the extent of disease. New therapeutic approaches include stimulation of melanocyte differentiation and proliferation through α-melanocyte-stimulating hormone analogues and through epidermal stem cell engineering. Several questions remain unsolved, including the connection between melanocyte depletion and stem cell exhaustion, the underlying degenerative mechanisms and the biological mediators of cell death. Overall, vitiligo is an excellent model for studying degenerative and autoimmune processes and for testing novel approaches in regenerative medicine. For an illustrated summary of this Primer, visit: http://go.nature.com/vIhFSC.

The melanocyte lineage in development and disease

Melanocyte development provides an excellent model for studying more complex developmental processes. Melanocytes have an apparently simple aetiology, differentiating from the neural crest and migrating through the developing embryo to specific locations within the skin and hair follicles, and to other sites in the body. The study of pigmentation mutations in the mouse provided the initial key to identifying the genes and proteins involved in melanocyte development. In addition, work on chicken has provided important embryological and molecular insights, whereas studies in zebrafish have allowed live imaging as well as genetic and transgenic approaches. This cross-species approach is powerful and, as we review here, has resulted in a detailed understanding of melanocyte development and differentiation, melanocyte stem cells and the role of the melanocyte lineage in diseases such as melanoma.

Summary: This Review discusses melanocyte development and differentiation, melanocyte stem cells, and the role of the melanocyte lineage in diseases such as melanoma.