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Skin color diversity is the most variable and noticeable phenotypic trait in humans resulting from constitutive pigmentation variability. This paper will review the characterization of skin pigmentation diversity with a focus on the most recent data on the genetic basis of skin pigmentation, and the various methodologies for skin color assessment. Then, melanocyte activity and amount, type and distribution of melanins, which are the main drivers for skin pigmentation, are described. Paracrine regulators of melanocyte microenvironment are also discussed. Skin response to sun exposure is also highly dependent on color diversity. Thus, sensitivity to solar wavelengths is examined in terms of acute effects such as sunburn/erythema or induced-pigmentation but also long-term consequences such as skin cancers, photoageing and pigmentary disorders. More pronounced sun-sensitivity in lighter or darker skin types depending on the detrimental effects and involved wavelengths is reviewed.

As a main part of pigmentation disorders, skin depigmentation diseases such as vitiligo and achromic naevus are very common and get more attention now. The pathogenesis of depigmentation includes melanocyte dysfunction and loss, which are possibly caused by heredity, autoimmunity and oxidative stress. Among them, oxidative stress plays a key role; however, few clinical treatments can deal with oxidative stress. As reported, Cistanche deserticola polysaccharide (CDP) is an effective antioxidant; based on that, we evaluated its role in melanocyte and further revealed the mechanisms. In this study, we found that CDP could promote melanogenesis in human epidermal melanocytes (HEMs) and mouse melanoma B16F10 cells, it also induced pigmentation in zebrafish. Furthermore, CDP could activate mitogen‐activated protein kinase (MAPK) signal pathway, then up‐regulated the expression of microphthalmia‐associated transcription factor (MITF) and downstream genes TYR, TRP1, TRP2 and RAB27A. Otherwise, we found that CDP could attenuate H2O2‐induced cytotoxicity and apoptosis in melanocytes. Further evidence revealed that CDP could enhance NRF2/HO‐1 antioxidant pathway and scavenge intracellular ROS. In summary, CDP can promote melanogenesis and prevent melanocytes from oxidative stress injury, suggesting that CDP helps maintain the normal status of melanocytes. Thus, CDP may be a novel drug for the treatment of depigmentation diseases. Cistanche deserticola polysaccharide (CDP) promotes melanogenesis in human epidermal melanocytes via activating mitogen‐activated protein kinase (MAPK) signal pathway, then up‐regulates the expression of MITF, TYR, TRP1, TRP2, and RAB27A. Otherwise, CDP can attenuate H2O2‐induced oxidative stress in melanocytes via enhancing NRF2/HO‐1 antioxidant pathway and scavenge intracellular ROS.

Reptiles use pterin and carotenoid pigments to produce yellow, orange, and red colors. These conspicuous colors serve a diversity of signaling functions, but their molecular basis remains unresolved. Here, we show that the genomes of sympatric color morphs of the European common wall lizard (Podarcis muralis), which differ in orange and yellow pigmentation and in their ecology and behavior, are virtually undifferentiated. Genetic differences are restricted to two small regulatory regions near genes associated with pterin [sepiapterin reductase (SPR)] and carotenoid [beta-carotene oxygenase 2 (BCO2)] metabolism, demonstrating that a core gene in the housekeeping pathway of pterin biosynthesis has been coopted for bright coloration in reptiles and indicating that these loci exert pleiotropic effects on other aspects of physiology. Pigmentation differences are explained by extremely divergent alleles, and haplotype analysis revealed abundant transspecific allele sharing with other lacertids exhibiting color polymorphisms. The evolution of these conspicuous color ornaments is the result of ancient genetic variation and cross-species hybridization

While natural products and synthetic chemicals are used in functional cosmetics, their potential side effects remain a concern. This has driven the need for safer and more effective agents to treat skin disorders. This has driven the need safer and more effective agents to treat skin disorders. Therefore, the present study aimed to explore the functional properties of Cannabis sativa stem-derived nanoparticles (CSS-NPs) and evaluate their potential as a cosmetic ingredient. Using nanoparticle analysis, CSS-NPs, with a mean diameter of ~120 nm exhibited notable resistance to external stress conditions, including pH fluctuation and enzymatic degradation by DNase, RNase and proteinase K. They also contained 48 distinct biochemical components. In vitro assays revealed that CSS-NPs significantly downregulated the expression of genes and proteins associated with melanin synthesis in mouse B16F10 melanoma cells under α-melanocyte stimulating hormone (α-MSH)-induced hyperpigmentation. These inhibitory effects were mediated by the activation of ERK and Akt signaling pathways. Furthermore, CSS-NPs improved the viability of α-MSH-treated B16F10 cells; this was accompanied by the upregulation of antioxidant-associated enzymes and a decrease in α-MSH-induced reactive oxygen species levels. Collectively, these findings suggested that CSS-NPs carry out a key role in mitigating skin pigmentation and enhancing antioxidant defenses by modulating the ERK/Akt axis during excessive melanin synthesis. Thus, CSS-NPs represent a promising multifunctional cosmetic ingredient with potential in treating pigmentation disorders and protecting skin cells.

Background: Regular exposure to ultraviolet rays is high in India, where most Indians present Fitzpatrick skin phototypes IV and V. Aims: To evaluate the efficacy and compare the effectiveness of two sunscreen products on Indian skin types IV and V with pigmentation irregularities. Methods: A randomized, uncontrolled and investigator-blinded, single-center study enrolled adult men and women (18-45 years) with Fitzpatrick skin phototypes IV (28° < individual typological angle <10°) and V (10° < individual typological angle < −30°) with pigmentary abnormalities seen on the face in adults (actinic lentigines and postinflammatory hyperpigmentation), who did not use sunscreens. Participants were randomized (1:1) to either of the two marketed sunscreen products, Product A (sun protection factor 50 PA+++) or Product B (sun protection factor 19 PA+++), applied twice daily before sun exposure for ≥2 h. Primary objectives aimed at assessing possible improvement in hyperpigmented spots and overall skin appearance after 12 weeks of use. Evaluation of skin radiance and skin color was done by means of L'Oréal color chart and colorimetric measurements (Chromameter®). Results: Among the 230 enrolled participants, 216 (93.91%) completed the study. The clinical assessment of the density of pigmented spots and skin radiance showed significant (P < 0.001) improvement in both groups during all visits. The qualitative (participant perception) and quantitative (Chromameter®) data indicated improvement in pigmentation from Week 0 to Week 12. Both products were well-tolerated. Limitations: The study was conducted over a rather short period of time (12 weeks) at a single location. Conclusions: This is the first study conducted on Indian skin phototypes IV and V under real-life conditions. It demonstrated the effect of regular sunscreen usage in the prevention of certain signs of skin photoaging such as increased pigmentation or pigmentary abnormalities, thus providing support and assistance to clinicians in suggesting the use of efficient sun-screening products to patients.

The oral administration of antioxidants may suppress UV-B-induced skin damage. HITHION YH-15, the extract of Torula yeast ( Cyberlindnera jadinii ), is rich in cysteine-containing peptides such as reduced and oxidized glutathione (GSH and GSSG), γ-glutamylcysteine (γ-Glu-Cys), and cysteinylglycine (Cys-Gly). These four constituents are termed cysteine peptides. In this study, we investigated the protective effects of cysteine peptides against UV-B in a randomized, placebo-controlled, double-blind, parallel-group study. A total of 90 healthy males and females aged 30–59 years were enrolled and randomized into two groups of 45 individuals each (cysteine peptides (48 mg/day) and placebo). Changes in UV-B-induced erythema and pigmentation were compared between groups after 5 weeks of test food intake. The minimal erythema dose (MED) significantly increased (* p  = 0.019) in the cysteine peptides group compared to that in the placebo group, indicating suppression of UV-B-induced erythema. ΔL* value significantly increased (*** p  < 0.0001) in the cysteine peptides group compared to that in the placebo, indicating pigmentation suppression. We demonstrated that oral administration of cysteine peptides suppresses UV-B-induced erythema and pigmentation through multiple mechanisms. Thus, cysteine peptides may find use as nutricosmetics for maintaining skin health and well-being. UMIN Clinical Trials Registry ID: UMIN 000050157.

Loss and absence of melanocytes due to a number of factors is responsible for vitiligo; known to be the commonest disorder of pigmentation. The aim of the current work was to compare the efficacy and safety of excimer light with topical tacrolimus ointment 0.1% versus excimer light with topical bimatoprost gel 0.01% in treatment of facial vitiligo. The study was carried out on 48 patients presented with facial vitiligo. The patients were divided randomly using sealed envelope method into two groups (24 patients each). Group 1 were treated with excimer light plus topical tacrolimus ointment 0.1% and group 2 treated with excimer light plus topical bimatoprost gel 0.01%. Clinical improvement based on the quartile grading scale at the end of treatment did not show any statistically significant difference between groups. The majority of subjects in both groups experienced good to excellent improvement. Only 20.9% of patients in group 1 and 33.3% of subjects in group 2 achieved less than 50% repigmentation ( p  = 0.889). Our study demonstrated that 0.01% topical bimatoprost gel in combination with excimer light is considered safe and effective as treatment of nonsegmental facial vitiligo with comparable results to 0.1% tacrolimus.

Skin pigmentation is a classic example of a polygenic trait that has experienced directional selection in humans. Genome-wide association studies have identified well over a hundred pigmentation-associated loci, and genomic scans in present-day and ancient populations have identified selective sweeps for a small number of light pigmentation-associated alleles in Europeans. It is unclear whether selection has operated on all of the genetic variation associated with skin pigmentation as opposed to just a small number of large-effect variants. Here, we address this question using ancient DNA from 1,158 individuals from West Eurasia covering a period of 40,000 y combined with genome-wide association summary statistics from the UK Biobank. We find a robust signal of directional selection in ancient West Eurasians on 170 skin pigmentation-associated variants ascertained in the UK Biobank. However, we also show that this signal is driven by a limited number of large-effect variants. Consistent with this observation, we find that a polygenic selection test in present-day populations fails to detect selection with the full set of variants. Our data allow us to disentangle the effects of admixture and selection. Most notably, a large-effect variant at SLC24A5 was introduced to Western Europe by migrations of Neolithic farming populations but continued to be under selection post-admixture. This study shows that the response to selection for light skin pigmentation in West Eurasia was driven by a relatively small proportion of the variants that are associated with present-day phenotypic variation.

This is the first attempt to evaluate the impact of four salinity levels on the color parameters, pigments, polyphenols, flavonoids, and antioxidant capacities of four promising A. lividus genotypes. The color parameters, such as the yellowness/blueness (b*) and the chroma (C*); the antioxidant components, such as the polyphenols and flavonoids; and the antioxidant capacities of the leaves were remarkably increased by 39, 1, 5, 10 and 43%, respectively, at 50 mM of NaCl, and by 55, 5, 60, 34, 58 and 82%, respectively, at 100 mM NaCl concentrations. The green tower and SA6 genotypes were identified as tolerant varieties. The total phenolic content (TPC) and the total flavonoid content (TFC) played vital roles in scavenging reactive oxygen species (ROS), and they would be beneficial for the human diet and would serve as good antioxidants for the prevention of aging, and they are also essential to human health. A correlation study revealed the strong antioxidant capacities of the pigments and antioxidant components that were studied. It was revealed that A. lividus could tolerate a certain level of salinity stress without compromising the antioxidant quality of the final product. Taken together, our results suggest that A. lividus could be a promising alternative crop for farmers, especially in saline-prone areas in the tropical and subtropical regions.

Skin color is highly variable in Africans, yet little is known about the underlying molecular mechanism. Here we applied massively parallel reporter assays to screen 1,157 candidate variants influencing skin pigmentation in Africans and identified 165 single-nucleotide polymorphisms showing differential regulatory activities between alleles. We combine Hi-C, genome editing and melanin assays to identify regulatory elements for MFSD12 , HMG20B , OCA2 , MITF , LEF1 , TRPS1 , BLOC1S6 and CYB561A3 that impact melanin levels in vitro and modulate human skin color. We found that independent mutations in an OCA2 enhancer contribute to the evolution of human skin color diversity and detect signals of local adaptation at enhancers of MITF , LEF1 and TRPS1 , which may contribute to the light skin color of Khoesan-speaking populations from Southern Africa. Additionally, we identified CYB561A3 as a novel pigmentation regulator that impacts genes involved in oxidative phosphorylation and melanogenesis. These results provide insights into the mechanisms underlying human skin color diversity and adaptive evolution. Massively parallel reporter assays identify 165 functional variants associated with skin pigmentation in ethnically diverse Africans. Functional characterization of eight variants demonstrates their impact in regulating melanin levels and validates CYB561A3 as a novel gene involved in melanogenesis and pigmentation.