Tanning Ability Research Articles

Molecular Basis of MC1R Activation: Mutation-Induced Alterations in Structural Dynamics.

The MC1R protein is a receptor found in melanocytes that plays a role in melanin synthesis. Mutations in this protein can impact hair color, skin tone, tanning ability, and increase the risk of skin cancer. The MC1R protein is activated by the alpha-melanocyte-stimulating hormone (α-MSH). Previous studies have shown that mutations affect the interaction between MC1R and α-MSH; however, the mechanism behind this process is poorly understood. Our study aims to shed light on this mechanism using molecular dynamics (MD) simulations to analyze the Asp84Glu and Asp294His variants. We simulated both the wild-type (WT) protein and the mutants with and without ligand. Our results reveal that mutations induce unique conformations during state transitions, hindering the switch between active and inactive states and decreasing cellular levels of cAMP. Interestingly, Asp294His showed increased ligand affinity but decreased protein activity, highlighting that tighter binding does not always lead to increased activation. Our study provides insights into the molecular mechanisms underlying the impact of MC1R mutations on protein activity.

Weakened tanning ability is an important mechanism for evolutionary skin lightening in East Asians

The evolution of light-skin pigmentation among Eurasians is considered as an adaptation to the high-latitude environments. East Asians are ideal populations for studying skin color evolution because of the complex environment of East Asia. Here, we report a strong selection signal for the pigmentation gene phenylalanine hydroxylase (PAH) in light-skinned Han Chinese individuals. The intron mutation rs10778203 in PAH is enriched in East Asians and is significantly associated with skin color of the back of the hand in Han Chinese males (P < 0.05). In vitro luciferase and transcription factor binding assays show that the ancestral allele of rs10778203 could bind to SMAD2 and has a significant enhancer activity for PAH. However, the derived T allele (the major allele in East Asians) of rs10778203 decreases the binding activity of transcription factors and enhancer activity. Meanwhile, the derived T allele of rs10778203 shows a weaker ultraviolet radiation response in A375 cells and zebrafish embryos. Furthermore, rs10778203 decreases melanin production in transgenic zebrafish embryos after ultraviolet B (UVB) treatment. Collectively, PAH is a potential pigmentation gene that regulates skin tanning ability. Natural selection has enriched the adaptive allele, resulting in weakened tanning ability in East Asians, suggesting a unique genetic mechanism for evolutionary skin lightening in East Asians.

Tanning with Pomegranate Peel Tannin

By-products of pomegranate juice enterprises are evaluated as a “green” raw material for many industries. In this study, pomegranate peels which are well known with high polyphenolic content were evaluated as a potential source of tanning agent for leather industry. For this purpose, firstly pomegranate peels were extracted in Koch extractor at 70°C for 8 hours. In order to determine the tanning ability, 30% of ground pomegranate peel powder (containing 7.2% of active tannin matter) was used in the tanning process and pomegranate peel tanned leather was evaluated in terms of increases in thickness and shrinkage temperature, color change and mechanical properties. The application of pomegranate peel tannin in the tanning process provided that an acceptable shrinkage temperature (68.5°C) and mechanical properties for vegetable tanned leathers. The results revealed that the tannin obtained from pomegranate peel has a remarkable tanning effect and can be used in the tanning process. Thus, it is concluded that pomegranate peels can be evaluated as a new source of tannin for leather industry.

Quantitative Assessment of Ultraviolet-Induced Erythema and Tanning Responses in the Han Chinese Population

Ultraviolet radiation (UVR) can induce erythema and tanning responses with strong diversity within and between populations, but there were no precise method for evaluating the variation in these responses. In this study, we assessed the time course of ultraviolet (UV)-induced responses based on the erythema index (EI) and melanin index (MI) over 14 consecutive days in a pilot cohort study (N = 31). From safety evaluations, we found that no skin blisters occurred at a UV dosage of 45 mJ/cm2, but there were significant skin reactions. Regardless of UV dosage, the measurements and variances of EI peaked on day 1 after UV irradiation, and those of MI peaked on day 7. Dose–response curves, including erythema dose–response (EDR) and melanin dose–response (MDR), could measure UV-induced phenotypes sensitively but more laboriously. As an alternative, we directly represented the UV-induced erythema and tanning responses using the erythema increment (ΔE) and melanin increment (ΔM). We found that ΔE and ΔM at 45 mJ/cm2 significantly correlated with erythema dose–response (EDR) (R2 > 0.9) and melanin dose–response (MDR) (R2 > 0.9), respectively. Therefore, ΔE and ΔM on day 1 and day 7 after UV irradiation at a dosage of 45 mJ/cm2 might be ideal alternative measures for assessing individual erythema and tanning responses. Then, a second cohort (N = 664) was recruited to validate the UV-induced phenotypes, and, as expected, the results of the two cohorts were in agreement. Therefore, we developed a simplified and precise method to quantify the UV-induced erythema response and tanning ability for the Han Chinese population.

SPECTROPHOTOMETRIC DETERMINATION OF THE TANNIDITY OF LIGNOSULFONATES IN THE PRODUCTION OF REAGENT SYSTEMS FOR OILFIELD CHEMISTRY

The article is devoted to the issue of quantitative determination of the main qualitative indicator of lignosulfonates - a product of processing of vegetable wood raw materials. For a number of reasons of various nature, the quality of lignosulfonates has declined sharply over the past decades. The consequence was the need for additional operations to modify the lignosulfonate matrix in the technological cycles of obtaining reagent systems for oilfield chemistry, in the case of supplies of lignosulfonate with a low tannidity index. The tannidity index characterizes the inhibitory or tanning ability of reagent systems based on lignosulfonate and is quantitatively determined by the content of OH-phenolic functional groups in the composition of the lignosulfonate macromolecule (20-30 monomer units). The paper presents a comparative study of the results of determining the tannidity index of lignosulfonates of various methods of obtaining by adsorption on collagen and spectrophotometric method with ammonium molybdate. The results of the determinations were processed by the method of mathematical statistics and it was found that the variances of the results of experimental studies are homogeneous and belong to one general population according to the Fisher criterion. Based on the results of the work carried out, it can be considered mathematically justified to replace the long-term collagen method with a spectrophotometric express method for determining tannidity with ammonium molybdate at a wavelength of 400 nm and calculating the quantitative content of OH-phenolic groups. The determination of the values of the confidence intervals of the analytical methods under study shows a relatively high accuracy of the spectrophotometric method compared to the collagen method, which is characterized by overestimated results. Recommendations were issued on the inclusion of a spectrophotometric method for determining the tannidity of the process of obtaining reagent systems as an input control operation of raw materials. For citation: Teptereva G.A., Rolnik L.Z., Pugachev N.V., Zhuravleva A.A., Lukmanova I.F. Spectrophotometric determination of the tannidity of lignosulfonates in the production of reagent systems for oilfield chemistry. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 23-30. DOI: 10.6060/ivkkt.20236606.6797.

TANNING EFFECT OF POMEGRANATE PEEL AND OLIVE LEAF TANNIN COMBINATION

Agro-industrial wastes possess highly-valuable bioactive compounds. Recently, they have been taken into account as an alternative source that can be used as raw material for various industries. Such an approach can help to reduce both production cost and pollution load. In this study, the usability of pomegranate peels and olive leaves, defined to be agricultural and industrial residues, as a combined tanning agent in leather industry was investigated. For this purpose, first of all pomegranate peels and olive leaves were extracted for determining their tannin contents and then they were used in tanning process for evaluation their combined tanning ability. Shrinkage temperature (76.5 °C) resulted from this combination tanning and the mechanical properties of the tanned leather revealed that pomegranate peels and olive leaves can be evaluated as an alternative, satisfying combination of tanning material for leather industry.

Genetic adaptation of skin pigmentation in highland Tibetans

Strong ultraviolet (UV) radiation at high altitude imposes a serious selective pressure, which may induce skin pigmentation adaptation of indigenous populations. We conducted skin pigmentation phenotyping and genome-wide analysis of Tibetans in order to understand the underlying mechanism of adaptation to UV radiation. We observe that Tibetans have darker baseline skin color compared with lowland Han Chinese, as well as an improved tanning ability, suggesting a two-level adaptation to boost their melanin production. A genome-wide search for the responsible genes identifies GNPAT showing strong signals of positive selection in Tibetans. An enhancer mutation (rs75356281) located in GNPAT intron 2 is enriched in Tibetans (58%) but rare in other world populations (0 to 18%). The adaptive allele of rs75356281 is associated with darker skin in Tibetans and, under UVB treatment, it displays higher enhancer activities compared with the wild-type allele in invitro luciferase assays. Transcriptome analyses of gene-edited cells clearly show that with UVB treatment, the adaptive variant of GNPAT promotes melanin synthesis, likely through the interactions of CAT and ACAA1 in peroxisomes with other pigmentation genes, and they act synergistically, leading to an improved tanning ability in Tibetans for UV protection.

The Skin We Live in: Pigmentation Traits and Tanning Behaviour in British Young Adults, an Observational and Genetically-Informed Study.

Skin cancer incidence has been increasing worldwide, representing a particularly high burden for populations of European ancestry. Outdoor and indoor tanning using ultraviolet (UV) radiation devices are major risk factors for skin cancer. While tanning behaviours can be modified by targeted interventions to reduce skin cancer rates, there is insufficient evidence on the motivations for tanning preferences and their relationship with pigmentation phenotypes. The present observational and genetically-informed study investigates motives for tanning and the role that pigmentation phenotypes play on outdoor and indoor tanning behaviour in British young adults. This study included 3722 participants from the Avon Longitudinal Study of Parents and Children in South West England, with data on pigmentation features, tanning ability and preferences, and SNP genotypes. Liking to tan and outdoor tanning were strongly influenced by pigmentary traits and tanning ability. However, the association of these phenotypes with UV indoor tanning was weaker. Our results provide evidence to support the implementation of skin cancer preventative interventions that consider individual biological characteristics and motives for undergoing outdoor and indoor tanning.

A UVB-responsive common variant at chromosome band 7p21.1 confers tanning response and melanoma risk via regulation of the aryl hydrocarbon receptor, AHR

Genome-wide association studies (GWASs) have identified a melanoma-associated locus on chromosome band 7p21.1 with rs117132860 as the lead SNP and a secondary independent signal marked by rs73069846. rs117132860 is also associated with tanning ability and cutaneous squamous cell carcinoma (cSCC). Because ultraviolet radiation (UVR) is a key environmental exposure for all three traits, we investigated the mechanisms by which this locus contributes to melanoma risk, focusing on cellular response to UVR. Fine-mapping of melanoma GWASs identified four independent sets of candidate causal variants. A GWAS region-focused Capture-C study of primary melanocytes identified physical interactions between two causal sets and the promoter of the aryl hydrocarbon receptor (AHR). Subsequent chromatin state annotation, eQTL, and luciferase assays identified rs117132860 as a functional variant and reinforced AHR as a likely causal gene. Because AHR plays critical roles in cellular response to dioxin and UVR, we explored links between this SNP and AHR expression after both 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and ultraviolet B (UVB) exposure. Allele-specific AHR binding to rs117132860-G was enhanced following both, consistent with predicted weakened AHR binding to the risk/poor-tanning rs117132860-A allele, and allele-preferential AHR expression driven from the protective rs117132860-G allele was observed following UVB exposure. Small deletions surrounding rs117132860 introduced via CRISPR abrogates AHR binding, reduces melanocyte cell growth, and prolongs growth arrest following UVB exposure. These data suggest AHR is a melanoma susceptibility gene at the 7p21.1 risk locus and rs117132860 is a functional variant within a UVB-responsive element, leading to allelic AHR expression and altering melanocyte growth phenotypes upon exposure.

The use of negative control outcomes in Mendelian randomization to detect potential population stratification.

A key assumption of Mendelian randomization (MR) analysis is that there is no association between the genetic variants used as instruments and the outcome other than through the exposure of interest. One way in which this assumption can be violated is through population stratification, which can introduce confounding of the relationship between the genetic variants and the outcome and so induce an association between them. Negative control outcomes are increasingly used to detect unobserved confounding in observational epidemiological studies. Here we consider the use of negative control outcomes in MR studies to detect confounding of the genetic variants and the exposure or outcome. As a negative control outcome in an MR study, we propose the use of phenotypes which are determined before the exposure and outcome but which are likely to be subject to the same confounding as the exposure or outcome of interest. We illustrate our method with a two-sample MR analysis of a preselected set of exposures on self-reported tanning ability and hair colour. Our results show that, of the 33 exposures considered, genome-wide association studies (GWAS) of adiposity and education-related traits are likely to be subject to population stratification that is not controlled for through adjustment, and so any MR study including these traits may be subject to bias that cannot be identified through standard pleiotropy robust methods. Negative control outcomes should therefore be used regularly in MR studies to detect potential population stratification in the data used.

Influence of microwave on chromium complex composition in tanning liquor

Since microwave irradiation could promote hydrolysis and olation of chromium tanning liquor, but the influence of microwave on chromium complex component in the liquor was still unknown. Chromium sulphate solution (0% basicity) and 33% basicity chromium tanning liquor were subjected microwave (MW) and water bath (WB) heating, and the samples without any warming were regarded as control. Ion exchange chromatography (IEC) and gel filtration chromatography (GFC) were used to measure the charge composition and molecular size of chromium complexes in each sample. FT-IR was used to characterize the structure of chromium complexes in each composition separated by IEC. Moreover, the chromium tanning liquor after warming was used in hide powder tanning trials to illustrate whether microwave would affect its tanning ability. The results show there are more high positive charge and large molecular size complexes in chromium tanning liquor after warming but the phenomena are more significant in MW samples compared with WB due to non-thermal effect of microwave. In addition, microwave has more powerful effect on 33% basicity chromium tanning liquor hydrolysis and olation to generate larger molecular size complexes. In FT-IR results, the combination pattern between chromium and ligands are changed after warming but there is no difference between WB and MW. The chromium exhaustion and thermal stability of hide powder tanned with chromium tanning liquor after microwave irradiation are both higher. It could conclude that both thermal and non-thermal effects of microwave promote the process together, and the non-thermal effect leads to more high positive charge and large molecular size complexes and has stronger influence on high polarity system. In short, this work would provide theoretical basis for applying microwave in tanning agent modification and chrome tanning process further.Graphical abstract

MC1R Variation in a New Mexico Population.

The Melanocortin 1 Receptor (MC1R) contributes to pigmentation, an important risk factor for developing melanoma. Evaluating SNPs in MC1R and association with race/ethnicity, skin type, and perceived cancer risk in a New Mexico (NM) population will elucidate the role of MC1R in a multicultural population. We genotyped MC1R in 191 NMs attending a primary care clinic in Albuquerque. We obtained individuals' self-identified race/ethnicity, skin type, and perceived cancer risk. We defined genetic risk as carriage of any one or more of the nine most common SNPs in MC1R. We found that one MC1R SNP, R163Q (rs885479), was identified in 47.6% of self-identified Hispanics and 12.9% of non-Hispanic whites (NHW), making Hispanics at higher "genetic risk" (as defined by carrying one of the MC1R common variants). When we deleted R163Q from analyses, Hispanics were no longer at higher genetic risk (33.3%) compared with NHW (48.3%), consistent with melanoma rates, tanning ability, and lower perceived risk. Hispanics had a perceived risk significantly lower than NHW and a nonsignificant better tanning ability than NHW. The R163Q variant in MC1R may not be a risk factor for melanoma among NM Hispanics. This suggestion points to the need to carefully interpret genetic risk factors among specific populations. Genetic risk cannot be extrapolated from Northern European populations directly to non-European populations.

Vegetable tannin composition and its association with the leather tanning effect

The increasing environmentally friendly approach of using renewable materials has led to vegetable tannins having an important role as tanning agents in the leather industry. Tannins are complex phenolic structures, and the literature shows that a considerable amount of chemical parameters measured through analytical techniques can be associated with their tanning ability. In the present study, five types of vegetable tannins highly used in the tanning industry were chosen for the evaluation of some of their relevant chemical parameters and the correlation with their cross-sectional penetration in the hide. Black wattle (Acacia mearnsii), quebracho (Schinopsis lorentzii), chestnut (Castanea sativa), tara (Caesalpinia spinosa), and myrobalan (Terminalia chebula) were tested. The chemical properties of the total tannin polyphenols, non-tannin polyphenols, insoluble solids, soluble solids, total solids, total phenols, non-tannin polyphenols:total phenols ratio, and residual tanning float concentration were measured and associated with the leather cross-sectional penetration results. The statistical Mann–Whitney-U test showed that the insoluble solids, non-tannin polyphenols, soluble solids, and total tannin polyphenol percentages distinguished the groups of tannins that crossed the hide from those that did not well. Hence, since the analysis of insoluble solids is the simplest and the most direct among them, it would be recommended to use this parameter to define a cutoff to distinguish the performance of tannins for leather application.

Cells to Surgery Quiz: May 2019

Cells to Surgery Quiz: May 2019

Preclinical signs of Parkinson's disease: A possible association of Parkinson's disease with skin and hair features

Parkinson’s disease (PD) is a neurodegenerative disorder, characterized by loss of dopaminergic neuromelanin containing neurons in the substantia nigra. Peripheral melanin, found in skin and hair, and neuromelanin appear to have some characteristics in common and share the same precursor for their synthesis; therefore, skin and hair features could be associated with PD. We hypothesize that earlier age at onset of hair greying, greater tendency to sunburn, difficulty tanning and dysregulation of sebum production are more common among PD patients due to genetically determined lower constitutive amounts of melanin and accumulation of α-synuclein in the skin, which leads to disrupted synthesis of peripheral melanin and dysregulated sebum secretion. In order to test this hypothesis 32 PD patients and 35 age and gender matched PD-unaffected individuals were included in a pilot study. The median of age at onset of hair greying was 30% lower in the PD group compared to the control group (35 and 50 years, respectively, p = 0.002). Age at onset of hair greying ≤ 41 years predicted the development of PD with 71.0% sensitivity and 70.6% specificity (area under curve = 0.725, 95% confidence interval = 0.601–0.850, p = 0.002). Significant differences were found when comparing skin types between PD patients and the control group (p < 0.001): dry (n = 14, 43.8%) and oily (n = 9, 28.1%) skin types were the most prevalent among individuals with PD, whereas the majority of control subjects reported having normal skin (n = 24, 68.6%). Differences in tanning ability were also found between the groups (p = 0.035): the majority of individuals in the control group (n = 24, 68.6%) and only 12 (37.5%) PD patients reported being able to tan easily. PD patients were also more likely to burn often in comparison to control subjects (n = 21, 65.6% vs n = 10, 28.6%, p = 0.001). Our results support the hypothesis that PD is associated with earlier age at onset of hair greying, greater tendency to sunburn, difficulty tanning and non-normal skin type; however these ideas should be evaluated in a large prospective study in order to draw final conclusions. If such work supports our hypothesis, skin and hair features could be included in a risk-score model to identify individuals at high risk of PD in order to diagnose patients prior to the manifestation of motor symptoms and initiate potential neuroprotective treatment when neuronal loss is minimal.

Host Characteristics and Risk of Incident Melanoma by Breslow Thickness.

Several host characteristics, including pigmentary traits (hair color, sunburn susceptibility and tanning ability), number of common nevi (moles), and family history of melanoma, have been associated with risk of melanoma. We prospectively examined the associations between host characteristics and risk of incident melanoma by Breslow thickness (≤1 mm, thin melanoma; or >1 mm, "thicker melanoma") based on the Nurses' Health Study (NHS, n = 86,380 women), NHS II (n = 104,100 women), and Health Professionals Follow-up Study (HPFS, n = 46,934 men). During 22-30 years' follow-up, a total of 1,813 incident melanoma cases were identified with information on Breslow thickness, 1,392 (76.8%) of which had thin melanoma. No significant differences were observed for thin and thicker melanoma in associations with hair color, sunburn susceptibility, and tanning ability. However, we found significant differences for the association with family history of melanoma, with a higher risk estimate for thicker melanoma [HR = 2.55; 95% confidence interval (CI): 1.91-3.42] than thin melanoma (HR = 1.59; 95% CI: 1.21-2.08; P heterogeneity = 0.02). Interestingly, women and men displayed differential associations between nevi count and risk of melanoma by Breslow thickness, with the association appearing stronger for thicker melanoma than thin melanoma in men (P heterogeneity = 0.01), but not in women. Individuals with family history of melanoma may be more likely to develop thicker melanoma. Men with high number of common nevi may tend to develop thicker melanoma, which was not found for women. The findings further stress the risk of thicker melanoma for individuals with a family history of melanoma and men with a high nevi count.

Melanoma - role of the environment and genetics.

Melanoma rates have increased in populations that are mainly European. The main etiologic factor is ultraviolet radiation, from the sun as well as artificial tanning devices. Host factors such as skin color, number of nevi, hair and eye color and tanning ability are critical factors in modifying an individual's response to the sun. Genetic factors interact with host factors and environmental factors to increase risk. This review summarizes our current knowledge of environment and genetics on melanoma risk and on gene-environment interaction.

Genome-wide association study in 176,678 Europeans reveals genetic loci for tanning response to sun exposure

The skin’s tendency to sunburn rather than tan is a major risk factor for skin cancer. Here we report a large genome-wide association study of ease of skin tanning in 176,678 subjects of European ancestry. We identify significant association with tanning ability at 20 loci. We confirm previously identified associations at six of these loci, and report 14 novel loci, of which ten have never been associated with pigmentation-related phenotypes. Our results also suggest that variants at the AHR/AGR3 locus, previously associated with cutaneous malignant melanoma the underlying mechanism of which is poorly understood, might act on disease risk through modulation of tanning ability.

Risk Stratification for Melanoma: Models Derived and Validated in a Purpose-Designed Prospective Cohort.

Risk stratification can improve the efficacy and cost-efficiency of screening programs for early detection of cancer. We sought to derive a risk stratification tool for melanoma that was suitable for the general population using only self-reported information. We used melanoma risk factor information collected at baseline from QSKIN, a prospective cohort study of Queensland adults age 40 to 69 years at recruitment (n = 41 954). We examined two separate outcomes: 1) invasive melanomas and 2) all melanomas (invasive + in situ) obtained through data linkage to the cancer registry. We used stepwise Cox proportional hazards modeling to derive the risk models in a randomly selected two-thirds sample of the data set and assessed model performance in the remaining one-third validation sample. After a median follow-up of 3.4 years, 655 (1.6%) participants developed melanoma (257 invasive, 398 in situ). The prediction model for invasive melanoma included seven terms. At baseline, the strongest predictors of invasive melanoma were age, sex, tanning ability, number of moles at age 21 years, and number of skin lesions treated destructively. The model for "all melanomas" (ie, invasive and in situ) included five additional terms. Discrimination in the validation data set was high for both models (C-index = 0.69, 95% confidence interval [CI] = 0.62 to 0.76, and C-index = 0.72, 95% CI = 0.69 to 0.75, respectively), and calibration was acceptable. Such a tool could be used to target surveillance activities to those at highest predicted risk of developing melanoma over a median duration of 3.4 years.

Cell signalling: Red alert about lipid's role in skin cancer.

Some versions of the MC1R protein are associated with red hair and an increased risk of developing a skin cancer called melanoma. It emerges that a lipid that binds MC1R might provide a target to reduce this risk. See Letter p.399 People with red hair, fair skin and poor tanning ability have a higher risk of developing melanoma. They often carry variants of the melanocortin-1 receptor (MC1R), which has a reduced capacity to induce pigmentation compared with the more common MCR1 forms. Rutao Cui and colleagues show how a modification called protein palmitoylation increases the ability of variant MCR1 to induce pigmentation in mice, and this is linked to reduced melanoma development. These findings may point to strategies for melanoma prevention, although it remains to be seen whether such an approach is practical.