2-Mercaptonicotinoyl glycine prevents UV-induced skin darkening and delayed tanning in healthy subjects: A randomized controlled clinical study

BACKGROUND

Chronic nonextreme sun exposure induces two mechanisms of skin pigmentation, causing immediate darkening and delayed tanning. A new molecule, 2-mercaptonicotinoyl glycine (2-MNG), has been shown in vitro to inhibit both immediate darkening and new melanin synthesis via covalent conjugation of the thiol group of 2-MNG to melanin precursors.

OBJECTIVE

To evaluate 2-MNG in preventing both mechanisms in vivo.

METHODS

In a randomized, intra-individual and controlled study, 33 subjects with melanin-rich skin were exposed to UV daylight on designated areas on the back and treated with a cosmetic formula containing 0.5% or 1% 2-MNG alone or 0.5% 2-MNG in association with lipohydroxy acid (LHA, 0.3%) plus Mexoryl-SX (MSX, 1.5%). The respective vehicles were used as controls and 4-n-butyl-resorcinol (4-n-BR, 2.5%) as a positive reference.

RESULTS

2-MNG alone significantly reduced immediate darkening and inhibited new melanin production when compared with vehicle, with higher performance at 1% than at 0.5%. 2-MNG at 0.5% in association with LHA and MSX showed significantly higher performance than 2-MNG 0.5% alone. 2-MNG at 0.5% and 1% showed significantly better performance than 4-n-BR.

CONCLUSIONS

2-MNG inhibited both UV-induced skin pigmentation mechanisms in vivo. The association of 2-MNG with LHA plus MSX showed the highest efficacy on melanin-rich skin with pigmentation induced by UV exposure.

Glucocorticoid hormones in relation to environmental exposure to bisphenols and multiclass pesticides among middle aged-women: Results from hair analysis

Bisphenols and pesticides have been shown to alter circulating glucocorticoids levels in animals, but there is limited human data. Moreover, measurements from biological fluids may not be able to reflect long-term status of non-persistent pollutants and glucocorticoids due to the high variability in their levels. Using hair analysis, we examined the associations between glucocorticoid hormones and environmental exposure to multi-class organic pollutants among a healthy female population aged 25-45 years old. Concentrations of four glucocorticoids, four polychlorinated biphenyl congeners (PCBs), seven polybrominated diphenyl ether congeners (PBDEs), two bisphenols and 140 pesticides and their metabolites were measured in hair samples collected from 196 Chinese women living in urban areas. Due to the low detection frequency of some pollutants, associations were explored only on 54 pollutants, i.e. PCB 180, bisphenol A, bisphenol S and 51 pesticides and their metabolites. Using stability-based Lasso regression, there were associations of cortisol, tetrahydrocortisol, cortisone, and tetrahydrocortisone with 14, 10, 13 and 17 biomarkers of exposure to pollutants, respectively, with bisphenol S, p,p'-dichlorodiphenyldichloroethylene, diethyl phosphate, 3,5,6-trichloro-2-pyridinol, thiamethoxam, imidacloprid, fipronil, tebuconazole, trifluralin, pyraclostrobin and 1-(3,4-dichlorophenyl)-3-methylurea being associated with at least three of the four hormones. There were also associations between cortisone/cortisol molar ratio and pollutants, namely dimethyl phosphate, 3-methyl-4-nitrophenol, carbofuran, λ-cyhalothrin, permethrin, fipronil, flusilazole, prometryn and fenuron. Some of these relationships were confirmed by single-pollutant linear regression analyses. Overall, our results suggest that background level of exposure to bisphenols and currently used pesticides may interfere with the glucocorticoid homeostasis in healthy women.

Association between Environmental Exposure to Multiclass Organic Pollutants and Sex Steroid Hormone Levels in Women of Reproductive Age

Organic pollutant exposure may alter sex steroid hormone levels in both animals and humans, but studies on mixture effects have been lacking and mainly limited to persistent organic pollutants, with few hormones being investigated. Moreover, measurements from a single blood or urine sample may not be able to reflect long-term status. Using hair analysis, here, we evaluated the relationship between multiclass organic pollutants and sex steroid hormones in 196 healthy Chinese women aged 25-45 years. Associations with nine sex steroid hormones, including progesterone, androstenedione (AD), testosterone (T), estrone (E1), and 17β-estradiol (E2), and eight related hormone ratios were explored on 54 pollutants from polychlorinated biphenyl (PCB), pesticide, and bisphenol families using stability-based Lasso regression analysis. Our results showed that each hormone was associated with a mixture of at least 10 examined pollutants. In particular, hair E2 concentration was associated with 19 pollutants, including γ-hexachlorocyclohexane, propoxur, permethrin, fipronil, mecoprop, prochloraz, and carbendazim. There were also associations between pollutants and hormone ratios, with pentachlorophenol, dimethylthiophosphate, 3-phenoxybenzoic acid, and flusilazole being related to both E1/AD and E2/T ratios. Our results suggest that exposure to background levels of pesticides PCB180 and bisphenol S may affect sex steroid hormone homeostasis among women of reproductive age.

Skin microbiome differentiates into distinct cutotypes with unique metabolic functions upon exposure to polycyclic aromatic hydrocarbons

BACKGROUND

The effects of air pollutants, particularly polycyclic aromatic hydrocarbons (PAHs), on the skin microbiome remain poorly understood. Thus, to better understand the interplay between air pollutants, microbiomes, and skin conditions, we applied metagenomics and metabolomics to analyze the effects of PAHs in air pollution on the skin microbiomes of over 120 subjects residing in two cities in China with different levels of air pollution.

RESULTS

The skin microbiomes differentiated into two cutotypes (termed 1 and 2) with distinct taxonomic, functional, resistome, and metabolite compositions as well as skin phenotypes that transcended geography and host factors. High PAH exposure was linked to dry skin and cutotype 2, which was enriched with species with potential biodegradation functions and had reduced correlation network structure integrity. The positive correlations identified between dominant taxa, key functional genes, and metabolites in the arginine biosynthesis pathway in cutotype 1 suggest that arginine from bacteria contributes to the synthesis of filaggrin-derived natural moisturizing factors (NMFs), which provide hydration for the skin, and could explain the normal skin phenotype observed. In contrast, no correlation with the arginine biosynthesis pathway was observed in cutotype 2, which indicates the limited hydration functions of NMFs and explains the observed dry skin phenotype. In addition to dryness, skin associated with cutotype 2 appeared prone to other adverse conditions such as inflammation.

CONCLUSIONS

This study revealed the roles of PAHs in driving skin microbiome differentiation into cutotypes that vary extensively in taxonomy and metabolic functions and may subsequently lead to variations in skin-microbe interactions that affect host skin health. An improved understanding of the roles of microbiomes on skin exposed to air pollutants can aid the development of strategies that harness microbes to prevent undesirable skin conditions. Video Abstract.

Profiling steroid and thyroid hormones with hair analysis in a cohort of women aged 25 to 45 years old

OBJECTIVE

Endogenous hormones regulate numerous physiological processes in humans. Some of them are routinely measured in blood, saliva and/or urine for the diagnosis of disorders. The analysis of fluids may, however, require multiple samples collected at different time points to avoid the high variability in the concentration of some hormones. In contrast, hair analysis has been proposed as an interesting alternative to reveal average hormone levels over a longer period. In this work, we developed and validated an analytical method for analyzing 36 endogenous steroid and thyroid hormones and one pineal hormone in human hair using ultra-performance liquid chromatography (UPLC)-tandem mass spectrometry (MS/MS).

METHODS

Sample preparation involved hair decontamination, pulverization, methanol extraction, and purification with C18-solid phase extraction. Extracts were then divided into two portions, respectively injected into an UPLC-MS/MS system, and analyzed using two different instrumental methods. The method was applied to a healthy female population aged 25-45 years.

RESULTS

The method was validated on supplemented hair samples for the 37 targeted hormones, and its application to the population under study allowed to detect 32 compounds in 2-100% of the samples. Complete reference intervals (2.5-97.5th percentiles) were established for estrone, 17β-estradiol, androstenedione, dehydroepiandrosterone, progesterone, 17α-hydroxyprogesterone, cortisone, cortisol and 3,3',5-triiodo-L-thyronine. Hair cortisone, cortisol, tetrahydrocortisone and tetrahydrocortisol concentrations were highly correlated with each other, with Kendall's τ correlation coefficients ranging from 0.52 to 0.68.

CONCLUSION

Allowing the detection of 32 hormones from different chemical classes, the present method will allow to broaden hormonal profiling for better identifying endocrine disorders.

Relationship between Scalp Histamine Levels and Dandruff within an Indian Population: A confirmation study using LC/MS/MS method

Dandruff is a common and challenging complaint associated with type of scalp, skin and population. Scalp seborrheic dermatitis (SD) is a more severe manifestation of dandruff associated with very severe itching and inflammation. Histamine is an interesting biomarker released in scalp affected by dandruff and SD even though the mechanism is not well understood yet. A monocentre clinical study was conducted to confirm the relationship between dandruff/SD and scalp histamine level in Indian population. Highly sensitive liquid chromatography coupled with mass spectrometry was used for histamine quantification in scalp from samples obtained non-invasively. Results showed that scalps with dandruff and mild to moderate SD had higher histamine levels compared to healthy scalps.

Polycyclic aromatic hydrocarbons regulate the pigmentation pathway and induce DNA damage responses in keratinocytes, a process driven by systemic immunity

BACKGROUND

Urban pollution is correlated with an increased prevalence of skin pigmentation disorders, however the physiological processes underlying this association are unclear.

OBJECTIVES

To delineate the relationship between polycyclic aromatic hydrocarbons (PAHs), a key constituent of atmospheric pollution, and immunity/skin pigmentation pathways.

METHODS

We exposed peripheral blood mononuclear cells (PBMC) to PAHs and performed cytokines/chemokine profiling. We then examined the effect of immune activation on pigmentation by co-culturing PBMC and Benzo(a)pyrene (BaP) with reconstructed human pigmented epidermis (RHPE). To study the mechanism, we treated keratinocytes with conditioned medium from BaP-exposed PBMC and studied DNA damage responses, aryl hydrocarbon receptor (AhR) activation and pro-pigmentation factor, proopiomelanocortin (POMC) secretion.

RESULTS

PAHs induced up-regulation of inflammatory cytokines/chemokine in PBMC. Co-culturing of RHPE with PBMC+BaP resulted in increased melanin content and localization. BaP-conditioned medium significantly increased DNA damage, p53 stabilization, AhR activation and POMC secretion in keratinocytes. We found that IFNγ induced DNA damage, while TNFα and IL-8 potentiated POMC secretion in keratinocytes. Importantly, BaP-conditioned medium-induced DNA damage and POMC secretion is prevented by antioxidants vitamin E, vitamin C and sulforaphane, as well as the prototypical corticosteroid dexamethasone. Finally, vitamin C and sulforaphane enhanced the genome protective and depigmentation effects of dexamethasone, providing proof-of-concept for a combinatorial approach for the prevention and/or correction of PAH-induced pigment spots formation.

CONCLUSION

Our study reveals the importance of systemic immunity in regulating PAH-induced skin pigmentation, and provide a new keratinocyte DNA damage response mechanistic target for the prevention or reversal of pollution-associated skin pigmentation.

Multi-omics analysis to decipher the molecular link between chronic exposure to pollution and human skin dysfunction

Environmental pollution is composed of several factors, namely particulate matter (PM2.5, PM10), ozone and Ultra Violet (UV) rays among others and first and the most exposed tissue to these substances is the skin epidermis. It has been established that several skin disorders such as eczema, acne, lentigines and wrinkles are aggravated by exposure to atmospheric pollution. While pollutants can interact with skin surface, contamination of deep skin by ultrafine particles or Polycyclic aromatic hydrocarbons (PAH) might be explained by their presence in blood and hair cortex. Molecular mechanisms leading to skin dysfunction due to pollution exposure have been poorly explored in humans. In addition to various host skin components, cutaneous microbiome is another target of these environment aggressors and can actively contribute to visible clinical manifestation such as wrinkles and aging. The present study aimed to investigate the association between pollution exposure, skin microbiota, metabolites and skin clinical signs in women from two cities with different pollution levels. Untargeted metabolomics and targeted proteins were analyzed from D-Squame samples from healthy women (n = 67 per city), aged 25-45 years and living for at least 15 years in the Chinese cities of Baoding (used as a model of polluted area) and Dalian (control area with lower level of pollution). Additional samples by swabs were collected from the cheeks from the same population and microbiome was analysed using bacterial 16S rRNA as well as fungal ITS1 amplicon sequencing and metagenomics analysis. The level of exposure to pollution was assessed individually by the analysis of polycyclic aromatic hydrocarbons (PAH) and their metabolites in hair samples collected from each participant. All the participants of the study were assessed for the skin clinical parameters (acne, wrinkles, pigmented spots etc.). Women from the two cities (polluted and less polluted) showed distinct metabolic profiles and alterations in skin microbiome. Profiling data from 350 identified metabolites, 143 microbes and 39 PAH served to characterize biochemical events that correlate with pollution exposure. Finally, using multiblock data analysis methods, we obtained a potential molecular map consisting of multi-omics signatures that correlated with the presence of skin pigmentation dysfunction in individuals living in a polluted environment. Overall, these signatures point towards macromolecular alterations by pollution that could manifest as clinical sign of early skin pigmentation and/or other imperfections.

Human exposure to PCBs, PBDEs and bisphenols revealed by hair analysis: A comparison between two adult female populations in China and France

Humans are exposed to various anthropogenic chemicals in daily life, including endocrine-disrupting chemicals (EDCs). However, there are limited data on chronic, low-level exposure to such contaminants among the general population. Here hair analysis was used to investigate the occurrence of four polychlorinated biphenyls (PCBs), seven polybrominated diphenyl ethers (PBDEs) and two bisphenols (BPs) in 204 Chinese women living in the urban areas of Baoding and Dalian and 311 pregnant French women. All the PCBs and PBDEs tested here were more frequently detected in the hair samples of the French women than in those of the Chinese women. In both cohorts, PCB 180 and BDE 47 were the dominant PCB and PBDE congener, respectively. PCB 180 was found in 82% of the French women and 44% of the Chinese women, while the corresponding values of BDE 47 were 54% and 11%, respectively. A discriminant analysis further demonstrated the difference in PCBs and PBDEs exposure profile between the two cohorts. These results demonstrate that hair analysis is sufficiently sensitive to detect exposure to these pollutants and highlight differences in exposure between populations even at environmental levels. Although BPA and BPS were found in 100% of the hair samples in both cohorts, the French women had significantly higher levels of BPA and BPS than the Chinese women. The median concentrations of BPA were one order of magnitude higher than BPS in both the Chinese (34.9 versus 2.84 pg/mg) and the French women (118 versus 8.01 pg/mg) respectively. Our results suggest that both French and Chinese populations were extensively exposed to BPA and BPS.

Changes of the human skin microbiota upon chronic exposure to polycyclic aromatic hydrocarbon pollutants

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are of environmental and public health concerns and contribute to adverse skin attributes such as premature skin aging and pigmentary disorder. However, little information is available on the potential roles of chronic urban PAH pollutant exposure on the cutaneous microbiota. Given the roles of the skin microbiota have on healthy and undesirable skin phenotypes and the relationships between PAHs and skin properties, we hypothesize that exposure of PAHs may be associated with changes in the cutaneous microbiota. In this study, the skin microbiota of over two hundred Chinese individuals from two cities in China with varying exposure levels of PAHs were characterized by bacterial and fungal amplicon and shotgun metagenomics sequencing.

RESULTS

Skin site and city were strong parameters in changing microbial communities and their assembly processes. Reductions of bacterial-fungal microbial network structural integrity and stability were associated with skin conditions (acne and dandruff). Multivariate analysis revealed associations between abundances of Propionibacterium and Malassezia with host properties and pollutant exposure levels. Shannon diversity increase was correlated to exposure levels of PAHs in a dose-dependent manner. Shotgun metagenomics analysis of samples (n = 32) from individuals of the lowest and highest exposure levels of PAHs further highlighted associations between the PAHs quantified and decrease in abundances of skin commensals and increase in oral bacteria. Functional analysis identified associations between levels of PAHs and abundance of microbial genes of metabolic and other pathways with potential importance in host-microbe interactions as well as degradation of aromatic compounds.

CONCLUSIONS

The results in this study demonstrated the changes in composition and functional capacities of the cutaneous microbiota associated with chronic exposure levels of PAHs. Findings from this study will aid the development of strategies to harness the microbiota in protecting the skin against pollutants. Video Abstract.

Exposure to multiclass pesticides among female adult population in two Chinese cities revealed by hair analysis

The high use of pesticides worldwide and the constant exposure of humans to these toxic-by-design chemicals have drawn the attention on the possible consequences on human health. However, information on the exposure of the general population to pesticides remain very limited in most countries, especially in urban areas. In the present work, hair analysis was conducted to investigate the exposure of 204 urban women living in two Chinese cities (Baoding and Dalian) to 110 pesticides and 30 metabolites of the following families: organochlorines, organophosphates, carbamates, pyrethroids, neonicotinoids, phenylpyrazoles, acid herbicides, urea herbicides and azoles. Results showed that 71 pesticides and 23 metabolites were found in the hair samples, with concentrations ranging up to 1070 pg/mg in hair. In each hair sample, the number of detected chemicals ranged from 25 to 50, demonstrating the cumulative exposure to pesticides among Chinese women in the studied regions. The concentrations of 38 chemicals (e.g., p-nitrophenol, diethyldithiophosphate, λ-cyhalothrin, permethrin, carbendazim and tebuconazole) were significantly different between women in Baoding and Dalian, indicating the regional differences in exposure to pesticide. Using a multiple regression analysis, we found that concentrations of a few dominant pesticides were associated with age, body mass index (BMI), cooking frequency and regions. These results can provide baseline information on exposure of female adult Chinese population to multiple pesticides and support future studies focused on the health effects associated with pesticide exposure.

Exposure to polycyclic aromatic hydrocarbons in women living in the Chinese cities of BaoDing and Dalian revealed by hair analysis

Polycyclic aromatic hydrocarbons (PAH) are produced from incomplete combustion of organic matter and released as environmental contaminants from activities such as transports, wood combustion, coal-fired power plants. In numerous urban areas worldwide, the levels of PAH exposure are considered critical regarding public health issues. The possibility to detect PAH and PAH metabolites biologically incorporated in human hair was demonstrated and proposed as biomarkers of exposure. Nevertheless, the possibility to distinguish different levels of exposure between different populations is still needed to validate the relevance of hair analysis in epidemiological studies. In this work, hair samples were collected from 204 women from two cities in China based on one year Air Quality Index history from governmental data (Baoding as polluted city and Dalian less polluted city). 8 out of the 15 parent PAH and 7 out of the 56 metabolites analyzed in this study were detected in all the samples. The highest concentrations in hair were observed for phenanthrene (4.2 to 889 pg/mg) > fluoranthene (1.05 to 204 pg/mg) > pyrene (3.2 to 124 pg/mg) for parent PAH, and for 9-OH-fluorene (0.04 to 1.78 pg/mg) > 2-OH-naphthalene (0.68 to 811 pg/mg) > 1-OH-anthracene (0.24 to 10.9 pg/mg) for metabolites. 14 parent PAH and 15 metabolites presented a significantly higher concentration in the hair samples collected from Baoding, as compared to Dalian. The median concentration of parent PAH was from 1.5 to 2.8 times higher in the hair of the subjects from Baoding than in subjects from Dalian and that of PAH metabolites was from 1 to 2.3 times higher. The study of inter-chemical associations revealed similarities and differences between the two areas, suggesting common and different sources of exposure depending on PAH respectively. The results confirmed the relevance of hair analysis to identify qualitative and quantitative differences in PAH exposure between populations from different areas. This study is the first one to investigate both parent PAH and their metabolites in a biological matrix.

Frequency of traumatic lesions alleged by victims of assault during police custody

A retrospective study was undertaken to determine the frequency of traumatic lesions found in individuals alleging police brutality during official custody in the département of Hauts-de-Seine, located in the west suburbs of Paris. All medical certificates relating to the examination of 11,653 individuals detained during the year 2004 were analysed. From this population, there were 119 cases where victimized individuals alleged police assault and 245 revealed aggressive police manhandling, as indicated by traces of tight handcuffs. Among the individuals alleging police violence, most of them showed recent traumatic lesions (n=91). The majority of lesions were superficial contusions frequently located in the cervico-cephalic area. All traumatic lesions were compatible with the allegations of police assault. Neurological complications secondary to the application of handcuffs were encountered in less than 2% of the cases. Although no death was recorded in police custody during the period of the study, approximately 5% of the population that had encountered some form of police violence was found to require emergency hospitalization.