Role of kinin receptors in skin pigmentation

Previous studies have shown that all kinin system is constitutively expressed in the normal and inflamed skin, with a potential role in both physiological and pathological processes. However, the understanding regarding the involvement of the kinin system in skin pigmentation and pigmentation disorders remains incomplete. In this context, the present study was designed to determine the role of kinins in the Monobenzone (MBZ)-induced vitiligo-like model. Our findings showed that MBZ induces higher local skin depigmentation in kinin receptors knockout mice (KOB1R, KOB2R and KOB1B2R) than in wild type (WT). Remarkably, lower levels of melanin content and reduced ROS generation were detected in KOB1R and KOB2R mice treated with MBZ. In addition, both KOB1R and KOB2R show increased dermal cell infiltrate in vitiligo-like skin, when compared to WT-MBZ. Additionally, lack of B1R was associated with greater skin accumulation of IL-4, IL-6, and IL-17 by MBZ, while KOB1B2R presented lower levels of TNF and IL-1. Of note, the absence of both kinin B1 and B2 receptors demonstrates a protective effect by preventing the increase in polymorphonuclear and mononuclear cell infiltrations, as well as inflammatory cytokine levels induced by MBZ. In addition, in vitro assays confirm that B1R and B2R agonists increase intracellular melanin synthesis, while bradykinin significantly enhanced extracellular melanin levels and proliferation of B16F10 cells. Our findings highlight that the lack of kinin receptors caused more severe depigmentation in the skin, as well as genetic deletion of both B1/B2 receptors seems to be linked with changes in levels of constitutive melanin levels, suggesting the involvement of kinin system in crucial skin pigmentation pathways.

Determining factors of pulse oximetry accuracy: a literature review

OBJECTIVE

Identify and reach consensus on the variables that affect the measurement of oxygen saturation using pulse oximetry.

METHODS

We applied inclusion and exclusion criteria to select relevant studies in databases such as Ebsco and PubMed. The search strategies, carried out until December 2023, focused on publications that addressed the technology of pulse oximeters and variables that influence their accuracy. We assessed the risk of bias of the included studies and used standardized methods for synthesis of results.

RESULTS

23 studies were included. The synthesis of the results highlighted that equipment with tetrapolar technology showed greater precision in oxygen saturation measurements. Increased skin pigmentation, hemoglobinopathies and high skin temperatures can lead to an overestimation of SpO2, while factors such as low perfusion, cold skin temperature, nail polish or tattoos, hypoxemia, anemia and high altitude training, they may underestimate it. On the other hand, motion artifacts, light pollution, frequency >150 beats per minute, electromagnetic interference and location of the sensor can cause distortion of the photoplethymography signal.

CONCLUSIONS

The synthesis of the results highlighted that skin pigmentation and light interference can lead to an overestimation of SpO2, while other factors such as low perfusion and altitude tend to underestimate it. The studies presented variability and heterogeneity in their designs, evidencing limitations in the consistency and precision of the evidence. Despite these limitations, the results underscore the importance of considering multiple variables when interpreting pulse oximetry measurements to ensure their reliability. The findings have significant implications for clinical practice and future research.

Racial effects on masimo pulse oximetry: impact of low perfusion index

PURPOSE

 Evaluate the SpO2-SaO2 difference between Black and White volunteer subjects having a low perfusion index (Pi) compared to those having a normal Pi.

METHODS

 The Pi data were abstracted from electronic files collected on 7183 paired SpO2-SaO2 samples (3201 Black and 3982 White) from a recently reported desaturation study of 75 subjects (39 Black and 36 White) where SaO2 values were sequentially decreased from 100 to 70%. The Pi values from that dataset were divided into two groups (Pi ≤ 1 or Pi > 1) for analysis. A Pi value ≤ 1 was considered "low perfusion" and a Pi value > 1 was considered "normal perfusion". Statistical calculations included values of bias (mean difference of SpO2-SaO2), precision (standard deviation of the difference), and accuracy (root-mean-square error [ARMS]). During conditions of low perfusion (Pi ≤ 1, range [0.1 to 1]), overall bias and precision were + 0.48% ± 1.59%, while bias and precision were + 0.19 ± 1.53%, and + 0.91 ± 1.57%, for Black and White subjects, respectively.

RESULTS

 During normal perfusion (Pi > 1, range [1 to 12]), overall bias and precision were + 0.18% ± 1.34%, while bias and precision were -0.26 ± 1.37%, and - 0.12 ± 1.31%, for Black and White subjects, respectively. ARMS was 1.37% in all subjects with normal perfusion and 1.64% in all subjects with low perfusion.

CONCLUSION

 Masimo SET® pulse oximeters with RD SET® sensors are accurate for individuals of both Black and White races when Pi is normal, as well as during conditions when Pi is low. The ARMS for all conditions studied is well within FDA standards. This study was conducted in healthy volunteers during well-controlled laboratory desaturations, and results could vary under certain challenging clinical conditions.

The performance of 11 fingertip pulse oximeters during hypoxemia in healthy human participants with varied, quantified skin pigment

BACKGROUND

Fingertip pulse oximeters are widely available, inexpensive, and commonly used to make clinical decisions in many settings. Device performance is largely unregulated and poorly characterised, especially in people with dark skin pigmentation.

METHODS

Eleven popular fingertip pulse oximeters were evaluated using the US Food and Drug Administration (FDA) Guidance (2013) and International Organization for Standardization Standards (ISO, 2017) in 34 healthy humans with diverse skin pigmentation utilising a controlled desaturation study with arterial oxygen saturation (SaO 2) plateaus between 70% and 100%. Skin pigmentation was assessed subjectively using a perceived Fitzpatrick Scale (pFP) and objectively using the individual typology angle (ITA) via spectrophotometry at nine anatomical sites.

FINDINGS

Five of 11 devices had a root mean square error (ARMS) > 3%, falling outside the acceptable FDA performance range. Nine devices demonstrated worse performance in participants in the darkest skin pigmentation category compared with those in the lightest category. A commonly used subjective skin colour scale frequently miscategorised participants as being darkly pigmented when compared to objective quantification of skin pigment by ITA.

INTERPRETATION

Fingertip pulse oximeters have variable performance, frequently not meeting regulatory requirements for clinical use, and occasionally contradicting claims made by manufacturers. Most devices showed a trend toward worse performance in participants with darker skin pigment. Regulatory standards do not adequately account for the impact of skin pigmentation on device performance. We recommend that the pFP and other non-standardised subjective skin colour scales should no longer be used for defining diversity of skin pigmentation. Reliable methods for characterising skin pigmentation to improve diversity and equitable performance of pulse oximeters are needed.

FUNDING

This study was conducted as part of the Open Oximetry Project funded by the Gordon and Betty Moore Foundation, Patrick J McGovern Foundation, and Robert Wood Johnson Foundation. The UCSF Hypoxia Research Laboratory receives funding from multiple industry sponsors to test the sponsors' devices for the purposes of product development and regulatory performance testing. Data in this paper do not include sponsor's study devices. All data were collected from devices procured by the Hypoxia Research Laboratory for the purposes of independent research. No company provided any direct funding for this study, participated in study design or analysis, or was involved in analysing data or writing the manuscript. None of the authors own stock or equity interests in any pulse oximeter companies. Dr Ellis Monk's time utilised for data analysis, reviewing and editing was funded by grant number: DP2MH132941.

Skin Pigmentation Impacts the Clinical Diagnosis of Wound Infection: Imaging of Bacterial Burden to Overcome Diagnostic Limitations

Underrepresentation of diverse skin tones in medical education and providers' implicit racial bias drives inequities in wound care, such as disproportionally poor outcomes for Black patients. Diagnostic indicators (e.g., erythema) can present differently depending on skin pigmentation. This post hoc analysis of 350 chronic wounds from a prospective 14-site clinical trial aimed to determine how the perception of clinical signs and symptoms of infection (CSS) differs by patient skin tone and if fluorescence-imaging can offer a more objective diagnostic solution. Participants were grouped by skin tone (low, medium, high) as measured by the Fitzpatrick Skin Phototype Classification (FSPC) scale. CSS and total bacterial load (TBL) were compared across FSPC groups, along with sensitivity to detect TBL >104 CFU/g using CSS alone and combined with fluorescence-imaging. Erythema was reported less often with increasing FSPC score (p = 0.05), from 13.4% (low), to 7.2% (medium), to 2.3% (high), despite comparable bacterial loads (median = 1.8 × 106 CFU/g). CSS sensitivity in the high group (2.9%) was 4.8-fold to 8.4-fold lower than the low (p = 0.003) and medium groups (p = 0.04). Fluorescence-imaging significantly improved the detection of high bacterial load in each group, peaking in the high group at 12-fold over CSS alone. These findings underscore the threat of pervasive racialized health inequities in wound care, where missed diagnosis of pathogenic bacteria and infection could delay treatment, increasing the risk of complications and poor outcomes. Fluorescence-imaging is poised to fill this gap, at least in part, serving as a more objective and equitable indicator of wound bacteria. Clinicaltrials.gov #NCT03540004 registered 16-05-2018.

A review of the current policies and guidance regarding Apgar scoring and the detection of jaundice and cyanosis concerning Black, Asian and ethnic minority neonates

BACKGROUND

Ethnic inequalities in maternal and neonatal health in the UK are well documented. Concerns exist regarding the use of skin colour in neonatal assessments. Healthcare professionals should be trained to recognise symptoms of diverse skin tones, and comprehensive, and inclusive guidance is necessary for the safe assessment of all infants. Disparities in healthcare provision have been emphasised during the COVID-19 pandemic, and additional research is needed to determine whether such policies adequately address ethnic minority neonates.

METHODS

A desktop search included searches of guidance produced for the United Kingdom (UK). Further searches of the Cochrane and World Health Organization (WHO) were used to identify any international guidance applicable in the UK context.

RESULTS

Several policies and one training resource used descriptors 'pink,' 'pale,' 'pallor,' and 'blue' about neonatal skin and mucous membrane colour. No policies provided specific guidance on how these colour descriptors may appear in neonates with different skin pigmentation. Only the NICE guidance and HEE e-learning resource acknowledged the challenges of assessing jaundice in infants with diverse skin tones, while another guideline noted differences in the accuracy of bilirubin measurements for the assessment of jaundice. Three policies and one training resource advised against relying on visual observation of skin colour when diagnosing neonatal conditions. The training resource included images of ethnic minority neonates, although most images included white infants.

CONCLUSIONS

Inadequate consideration of ethnicity in UK policy and training perpetuates disparities, leading to inaccurate assessments. A review is needed for inclusivity in neonatal care, regardless of skin pigmentation.

Methylanthranilate, a Food Fragrance Attenuates Skin Pigmentation through Downregulation of Melanogenic Enzymes by cAMP Suppression

Methyl anthranilate (MA) is a botanical fragrance used in food flavoring with unexplored potential in anti-pigment cosmetics. MA dose-dependently reduced melanin content without affecting cell viability, inhibited dendrite elongation and melanosome transfer in the co-culture system of human melanoma cells (MNT-1) and human keratinocyte cell line (HaCaT), and downregulated melanogenic genes, including tyrosinase, tyrosinase-related protein 1 and 2 (TRP-1, TRP-2). Additionally, MA decreased cyclic adenosine monophosphate (cAMP) production and exhibited a significant anti-pigmentary effect in Melanoderm™. These results suggest that MA is a promising anti-pigmentary agent for replacing or complementing existing anti-pigmentary cosmetics.

What influences the inclusion of skin tone diversity when teaching skin assessment? Findings from a survey

BACKGROUND

Understanding the variances in visual skin changes across all skin tones is important in clinical care. However, the experiences of those teaching skin assessment to pre- and post-registrant nurses are unknown.

AIMS

To determine the barriers and facilitators experienced in teaching skin assessment across a range of skin tones to pre- and post-registrant nurses.

METHODS

A cross-sectional, mixed-methods online survey was undertaken throughout February and March 2023 based on the Theoretical Domains Framework of behaviour change.

FINDINGS

In this self-selecting sample, most participants were aware of why it was important to include all skin tones when teaching skin assessment and were professionally motivated to include this in their practice. However, resources and support are needed to overcome an unconscious bias in teaching skin tone diversity, resulting in a lack of availability of good quality photographs and educator confidence in their own skills. Educators not considering skin tone when selecting patient cases and relying on people with dark skin tones to highlight where practice is not inclusive may also lead to insufficient exposure for students.

CONCLUSION

There is some awareness of the importance of including diverse skin tones in teaching, but further education and resources are needed.

Assessment of skin pigmentation-related bias in pulse oximetry readings among adults

PURPOSE

Recent reports that pulse oximeters may overestimate oxygen saturation in individuals with darker skin pigmentation have prompted concerns from regulatory authorities regarding racial bias. We investigated the performance of TruSignal SpO2 sensors (GE Healthcare, Helsinki, Finland) in adults with varying skin pigmentation.

METHODS

A retrospective study was conducted using a set of pooled assessments of SpO2/SaO2 measurements from nine studies to assess bias, accuracy (Arms), and precision of TruSignal sensors in healthy adults under induced hypoxia. Subgroup analyses were performed based on oxygen saturation levels (band 1, ≥ 70 and ≤ 80%; band 2, > 80 and ≤ 90%; band 3, > 90 and ≤ 100%).

RESULTS

Of the 10,800 data points from 131 individuals, 8,202 (75.9%) and 2,598 (24.1%) were assigned to the light and dark pigment groups, respectively. Bias was 0.14% overall and less than 1% across oxygenation bands. The difference in bias between dark and light pigment groups was statistically significant at the low oxygenation band with SpO2 ≥ 70 and ≤ 80% (+ 0.58% and + 0.30% respectively; p = 0.0035). Throughout the saturation range, Arms was 1.64% in the light and 1.71% in the dark pigment group, within device specifications and regulatory requirements. Oxygenation was the dominating factor in stepwise ANOVA modeling. The mixed model also showed that bias was strongly affected by the oxygenation range.

CONCLUSION

TruSignal sensors demonstrated higher bias at lower oxygen saturation, with less than 0.5% difference between pigment groups. These findings raise new questions, such as ways to improve pulse oximetry measurements during challenging clinical conditions, including low perfusion.

Light-specific wavelengths differentially affect the exploration rate, opercular beat, skin color change, opsin transcripts, and the oxi-redox system of the longsnout seahorse Hippocampus reidi

Light is a strong stimulus for the sensory and endocrine systems. The opsins constitute a large family of proteins that can respond to specific light wavelengths. Hippocampus reidi is a near-threatened seahorse that has a diverse color pattern and sexual dimorphism. Over the years, H. reidi's unique characteristics, coupled with its high demand and over-exploitation for the aquarium trade, have raised concerns about its conservation, primarily due to their significant impact on wild populations. Here, we characterized chromatophore types in juvenile and adult H. reidi in captivity, and the effects of specific light wavelengths with the same irradiance (1.20 mW/cm2) on color change, growth, and survival rate. The xanthophores and melanophores were the major components of H. reidi pigmentation with differences in density and distribution between life stages and sexes. In the eye and skin of juveniles, the yellow (585 nm) wavelength induced a substantial increase in melanin levels compared to the individuals kept under white light (WL), blue (442 nm), or red (650 nm) wavelengths. In addition, blue and yellow wavelengths led to a higher juvenile mortality rate in comparison to the other treatments. Adult seahorses showed a rhythmic color change over 24 h, the highest reflectance values were obtained in the light phase, representing a daytime skin lightening for individuals under WL, blue and yellow wavelength, with changes in the acrophase. The yellow wavelength was more effective on juvenile seahorse pigmentation, while the blue wavelength exerted a stronger effect on the regulation of adult physiological color change. Dramatic changes in the opsin mRNA levels were life stage-dependent, which may infer ontogenetic opsin functions throughout seahorses' development. Exposure to specific wavelengths differentially affected the opsins mRNA levels in the skin and eyes of juveniles. In the juveniles, skin transcripts of visual (rh1, rh2, and lws) and non-visual opsins (opn3 and opn4x) were higher in individuals under yellow light. While in the juvenile's eyes, only rh1 and rh2 had increased transcripts influenced by yellow light; the lws and opn3 mRNA levels were higher in juveniles' eyes under WL. Prolonged exposure to yellow wavelength stimulates a robust increase in the antioxidant enzymes sod1 and sod2 mRNA levels. Our findings indicate that changes in the visible light spectrum alter physiological processes at different stages of life in H. reidi and may serve as the basis for a broader discussion about the implications of artificial light for aquatic species in captivity.

Involvement of miR-495 in the skin pigmentation of rainbow trout (Oncorhynchus mykiss) through the regulation of mc1r

MicroRNAs (miRNAs) play crucial roles in skin pigmentation in animals. Rainbow trout (Oncorhynchus mykiss) is a key economic fish species worldwide, and skin color directly affects its economic value. However, the functions of miRNAs in rainbow trout skin pigmentation remain largely unknown. Herein, we overexpressed and silenced miR-495 in vitro and in vivo to investigate its functions. The analysis of spatial and temporal expression patterns suggested that miR-495 is a potential regulator during the process of skin pigmentation. In vitro, mc1r was validated as a direct target for miR-495 by dual-luciferase reporter assay, and overexpression of miR-495 significantly inhibited mc1r expression; in contrast, mc1r and its downstream gene mitf levels were markedly upregulated by decreased miR-495. In vivo, overexpressed miR-495 by injecting agomiR-495 led to a substantial decrease in the expression of mc1r and mitf in dorsal skin and liver, while the opposite results were obtained after miR-495 silencing by antagomiR-495. These findings suggested that miR-495 can target mc1r to regulate rainbow trout skin pigmentation, which provide a potential basis for using miRNAs as target drugs to treat pigmentation disorders and melanoma.

Natural tyrosinase enzyme inhibitors: A path from melanin to melanoma and its reported pharmacological activities

The skin containing melanin pigment acts as a protective barrier and counteracts the UVR and other environmental stressors to maintain or restore disrupted cutaneous homeostasis. The production of melanin pigment is dependent on tyrosine levels. L-tyrosine and L-dihydroxyphenylalanine (L-DOPA) can serve both as a substrates and intermediates of melanin synthetic pathway and as inducers and positive regulators of melanogenesis. The biosynthesis of melanin is stimulated upon exposure to UVR, which can also stimulate local production of hormonal factors, which can stimulate melanoma development by altering the chemical properties of eu- and pheomelanin. The process of melanogenesis can be altered by several pathways. One involves activation of POMC, with the production of POMC peptides including MSH and ACTH, which increase intracellular cAMP levels, which activates the MITF, and helps to stimulate tyrosinase (TYR) expression and activity. Defects in OCA1 to 4 affects melanogenic activity via posttranslational modifications resulting in proteasomal degradation and reducing pigmentation. Further, altering, the MITF factor, helps to regulate the expression of MRGE in melanoma, and helps to increase the TYR glycosylation in ER. CRH stimulates POMC peptides that regulate melanogenesis and also by itself can stimulate melanogenesis. The POMC, P53, ACTH, MSH, MC1R, MITF, and 6-BH4 are found to be important regulators for pigmentation. Melanogenesis can affect melanoma behaviour and inhibit immune responses. Therefore, we reviewed natural products that would alter melanin production. Our special focus was on targeting melanin synthesis and TYR enzyme activity to inhibit melanogenesis as an adjuvant therapy of melanotic melanoma. Furthermore, this review also outlines the current updated pharmacological studies targeting the TYR enzyme from natural sources and its consequential effects on melanin production.

Differences in Body Weight According to Skin Color and Sex in Mexican Adults

OBJECTIVES

1) To analyze the differences in body weight according to skin color in Mexican adults. 2) Identify mediator variables that could explain possible differences in body weight according to skin color.

METHODS

A nationally representative survey of Mexican adults was analyzed (n = 12,021). People with obesity were identified (body mass index, BMI > 30) based on self-reported weight and height. Skin color was measured by self-report using a chromatic scale. The mediator variables were socioeconomic level, height, neighborhood public services, public safety, and discrimination based on skin color.

RESULTS

Compared to white-skinned women, brown-skinned women had higher BMI and a higher probability of being obese. These differences in weight by skin color are related to the lower level of education and more discrimination experiences of brown-skinned women. In men, there were no differences in weight according to skin color.

CONCLUSIONS

In Mexican women (but not in men), darker skin color was associated with a higher probability of being obese, and the examined social factors partially explained this disparity.

Mitigating skin tone bias in linear array in vivo photoacoustic imaging with short-lag spatial coherence beamforming

Photoacoustic (PA) imaging has the potential to deliver non-invasive diagnostic information. However, skin tone differences bias PA target visualization, as the elevated optical absorption of melanated skin decreases optical fluence within the imaging plane and increases the presence of acoustic clutter. This paper demonstrates that short-lag spatial coherence (SLSC) beamforming mitigates this bias. PA data from the forearm of 18 volunteers were acquired with 750-, 810-, and 870-nm wavelengths. Skin tones ranging from light to dark were objectively quantified using the individual typology angle (ITA° ). The signal-to-noise ratio (SNR) of the radial artery (RA) and surrounding clutter were measured. Clutter was minimal (e.g., -16 dB relative to the RA) with lighter skin tones and increased to -8 dB with darker tones, which compromised RA visualization in conventional PA images. SLSC beamforming achieved a median SNR improvement of 3.8 dB, resulting in better RA visualization for all skin tones.

Skin pigmentation as landmark for arteriovenous fistula cannulation in hemodialysis

BACKGROUND

The cannulation of the arteriovenous fistula (AVF) for hemodialysis (HD) has traditionally depended on the nurse's tactile sensation, which has been associated with suboptimal needle placement and detrimental effects on vascular access (VA) longevity. While the introduction of ultrasound (US) has proven beneficial in mapping the AVF outflow vein and assisting in cannulation planning, aneurysmal deformations remain a common occurrence resulting from various factors, including inadequate cannulation techniques. Within this context, the utilization of skin pigmentation as a clinical landmark has emerged as a potential approach to enhance cannulation planning in HD.

METHODS

A prospective longitudinal study was undertaken to investigate the correlation between the occurrence of venous morphological deformations and the cannulation technique guided by skin pigmentation after a 2-month period of implementation.

RESULTS

Thirty patients were enrolled in the study with 433 cannulations being described within the first 2 months of AVF use. The overall rate of cannulation-related adverse events was 21.9%. Comparative analysis demonstrated a statistically significant relationship (p < 0.001) between aneurysmal deformation and non-compliance with the proposed cannulation technique, resulting in cannulation outside the designated points. Non-compliance was primarily attributed to nurse's decision (57.1%).

CONCLUSION

The integration of US mapping of the AVF outflow vein and the utilization of skin pigmentation as a guiding tool have shown promising results in enhancing cannulation planning over time. Consistent adherence to a cannulation technique other than the area technique has been found to reduce the risk of AVF morphological deformation. These findings underscore the potential benefits of incorporating skin pigmentation as a clinical landmark in cannulation practices, highlighting its ability to impact positively cannulation outcomes.

ASIP gene polymorphism associated with black coat and skin colour in Murrah buffalo

The melanogenesis pathway regulates pigmentation through the synergic action of various genes. We are interested in analysing the genetic variations in the ASIP which determine eumelanin production in the dermis layer. In the present study, the ASIP gene was characterized in buffalo and 268 genetically unrelated buffaloes belonging to 10 different populations were genotyped for the non-synonymous SNP (c.292C>T) identified in the exon 3 region of the gene using Tetra-ARMS-PCR. The TT genotype occurred at a higher rate in Murrah, followed by Nili Ravi, Tripura, and Paralakhemundi (42.63%, 19.30%, 3.45%, and 3.33%). These results convey the association of the black coat colour of Murrah with the ASIP gene TT genotype and the lighter shades of black coat (brown and greyish-black) colour phenotype in other breeds with the CC genotype. This article is protected by copyright. All rights reserved.

A review of the effect of skin pigmentation on pulse oximeter accuracy

Pulse oximetry is a non-invasive optical technique used to measure arterial oxygen saturation (SpO2) in a variety of clinical settings and scenarios. Despite being one the most significant technological advances in health monitoring over the last few decades, there have been reports on its various limitations. Recently due to the Covid-19 pandemic, questions about pulse oximeter technology and its accuracy when used in people with different skin pigmentation have resurfaced. This review presents an introduction to the technique of pulse oximetry including its basic principle of operation, technology, and limitations, with a more in depth focus on skin pigmentation. Relevant literature relating to the performance and accuracy of pulse oximeters in populations with different skin pigmentation are evaluated. The majority of the evidence suggests that the accuracy of pulse oximetry differs in subjects of different skin pigmentations to a level that requires particular attention, with decreased accuracy in patients with dark skin. Some recommendations, both from the literature and contributions from the authors, suggest how future work could address these inaccuracies to potentially improve clinical outcomes. These include the objective quantification of skin pigmentation to replace currently used qualitative methods, and computational modelling for predicting calibration algorithms based on skin colour.

miR-330 targeting BCO2 is involved in carotenoid metabolism to regulate skin pigmentation in rainbow trout (Oncorhynchus mykiss)

BACKGROUND

MicroRNAs (miRNAs) play a critical role in regulating skin pigmentation. As a key economic trait, skin color directly affects the market value of rainbow trout (Oncorhynchus mykiss), however, the regulatory mechanism of most miRNAs in fish skin color is still unclear.

RESULTS

In this study, the full-length cDNA sequence of β-carotene oxygenase 2 (BCO2, a key regulator of carotenoid metabolism) from the rainbow trout was obtained using rapid-amplification of cDNA ends (RACE) technology, and qRT-PCR was used to investigate the differential expression of miR-330 and BCO2 in 14 developmental stages and 13 tissues between wild-type rainbow trout (WTrt) and yellow mutant rainbow trout (YMrt). Additionally, the function of miR-330 was verified by overexpression and silencing in vitro and in vivo. The results showed that the complete cDNA sequence of BCO2 was 2057 bp with a 1707 bp ORF, encoding a 568 amino acid protein having a molecular weight of 64.07 kD. Sequence alignment revealed that higher conservation of BCO2 protein amongst fishes than amongst other vertebrates, which was further confirmed by phylogenetic analysis. The analysis of spatial and temporal expression patterns suggested that BCO2 and miR-330 were abundantly expressed from fertilized-stage to multi-cell as well as in the dorsal and ventral skin of WTrt and YMrt, and their expression patterns were opposite in most of the same periods and tissues. In vitro, luciferase reporter assay confirmed that BCO2 was a direct target of miR-330, and transfection of miR-330 mimics into rainbow trout liver cells resulted in a decrease in the expression of BCO2; conversely, miR-330 inhibitor had the opposite effect to the miR-330 mimics. In vivo, miR-330 agomir significantly decreased BCO2 expression in dorsal skin, tail fin, and liver. Furthermore, overexpression of miR-330 could suppress cell proliferation and induce apoptosis.

CONCLUSION

Our results showed that miR-330 is involved in the regulation of skin pigmentation in rainbow trout by targeting BCO2 and shows its promise as a potential molecular target to assist the selection of rainbow trout with better skin color patterns.

The role of single nucleotide variant rs3819817 of the Histidine Ammonia-Lyase gene and 25-Hydroxyvitamin D on bone mineral density, adiposity markers, and skin pigmentation, in Mexican population

PURPOSE

Vitamin D (VD) deficiency and osteoporosis have become a global public health problem. A variant in the Histidine Ammonia-Lyase (HAL) gene has been associated with VD levels and bone mineral density (BMD). However, whether this variant has an influence on VD levels and BMD in Mexican adults remain unclear.

METHODS

This cross-sectional analysis included 1,905 adults participating in the Health Worker Cohort Study and 164 indigenous postmenopausal women from the Metabolic Analysis in an Indigenous Sample (MAIS) cohort. The rs3819817 variant was genotyped by TaqMan probe assay. Total 25 hydroxyvitamin D levels were measured by DiaSorin Liaison. BMD at the different sites was assessed through dual-energy X-ray absorptiometry. Linear and logistic regression models were performed to evaluate the associations of interest.

RESULTS

The prevalence of VD deficiency was 41%, showing differences between sexes. Obesity and skin pigmentation were associated with lower levels of VD in males and females. rs3819817-T allele was associated with low levels of 25-hydroxyvitamin D, VD deficiency, and hip and femoral neck BMD values (g/cm²). We found two interactions with VD levels, one between adiposity and rs3819817-T allele (P = 0.017) and another between skin pigmentation and rs3819817-T allele (P = 0.019). In indigenous postmenopausal women, we observed higher VD levels in the southern region compared to the northern region (P < 0.001); however, we did not observe differences by genotype.

CONCLUSION

Our findings confirm that the genetic variant rs3819817 has an essential function in VD levels and BMD and suggests a role in skin pigmentation in the Mexican population.

Oculocutaneous albinism: epidemiology, genetics, skin manifestation, and psychosocial issues

Oculocutaneous albinism (OCA) is a group of rare, inherited disorders associated with reduced melanin biosynthesis. Clinical manifestations of the eight known subtypes of OCA include hypopigmented skin, eyes, and hair and ocular manifestations, such as decreased visual acuity and nystagmus. OCA affects people globally but is most prevalent in African countries. Individuals with oculocutaneous albinism lack UV protection and are prone to skin damage and skin cancers. For many African albino individuals, there are significant challenges in seeking treatment for skin cancer and preventing sun damage due to psychosocial factors and poor education. This review summarizes the current understanding of the epidemiology, genetics, and clinical manifestations of OCA. We also discuss the medical and psychosocial challenges that affect individuals with OCA and the current landscape of albinism treatment modalities. The extent of the psychosocial challenges needs to be better understood and additional educational interventions may improve quality of life for people with albinism.

The cutaneous effects of blue light from electronic devices: a systematic review with health hazard identification

The biologic effects of visible light, particularly blue light, on the skin at doses and irradiances representative of sunlight have been established. Recent research studies investigated the effects of blue light (BL) from electronic screen devices; however, it is unclear if the evidence can be generalized to real life. The aim of this systematic review was to evaluate available evidence regarding clinical effects of BL emitted from electronic devices on human skin using the framework established by the Office of Health Assessment and Translation (OHAT). A systematic literature search was conducted by two librarians in Ovid MEDLINE, Embase.com, and Web of Science for relevant articles published from 1946 to March 2022. In vitro and in vivo studies that investigated the effects of BL from electronic devices on skin were included. From the 87 articles gathered from database searches and 1 article identified from citation search, only 9 met the inclusion criteria (6 in vitro and 3 in vivo studies). Human and animal literature with the highest level of evidence ratings were considered with mechanistic data to form one of five human hazard identifications for each outcome category using the OHAT protocol: (1) known, (2) presumed, (3) suspected, (4) not classifiable, or (5) not identified to be a hazard to humans. Literature-based evidence integration did not identify exposure to BL from electronic devices as a hazard to skin pigmentation, redness, yellowness, or melasma exacerbation. Exposure to BL from electronic devices was not classified as a skin photoaging hazard. Low confidence in representative exposure characterization drove high OHAT risk-of-bias ratings for the majority of included studies. While these conclusions hold true for the limited existing data, a larger number of future studies with high-confidence evidence are needed to verify and strengthen hazard identification conclusions.

The accuracy of pulse oximetry in measuring oxygen saturation by levels of skin pigmentation: a systematic review and meta-analysis

BACKGROUND

During the COVID-19 pandemic, there have been concerns regarding potential bias in pulse oximetry measurements for people with high levels of skin pigmentation. We systematically reviewed the effects of skin pigmentation on the accuracy of oxygen saturation measurement by pulse oximetry (SpO2) compared with the gold standard SaO2 measured by CO-oximetry.

METHODS

We searched Ovid MEDLINE, Ovid Embase, EBSCO CINAHL, ClinicalTrials.gov, and WHO International Clinical Trials Registry Platform (up to December 2021) for studies with SpO2-SaO2 comparisons and measuring the impact of skin pigmentation or ethnicity on pulse oximetry accuracy. We performed meta-analyses for mean bias (the primary outcome in this review) and its standard deviations (SDs) across studies included for each subgroup of skin pigmentation and ethnicity and used these pooled mean biases and SDs to calculate accuracy root-mean-square (Arms) and 95% limits of agreement. The review was registered with the Open Science Framework ( https://osf.io/gm7ty ).

RESULTS

We included 32 studies (6505 participants): 15 measured skin pigmentation and 22 referred to ethnicity. Compared with standard SaO2 measurement, pulse oximetry probably overestimates oxygen saturation in people with the high level of skin pigmentation (pooled mean bias 1.11%; 95% confidence interval 0.29 to 1.93%) and people described as Black/African American (1.52%; 0.95 to 2.09%) (moderate- and low-certainty evidence). The bias of pulse oximetry measurements for people with other levels of skin pigmentation or those from other ethnic groups is either more uncertain or suggests no overestimation. Whilst the extent of mean bias is small or negligible for all subgroups evaluated, the associated imprecision is unacceptably large (pooled SDs > 1%). When the extent of measurement bias and precision is considered jointly, pulse oximetry measurements for all the subgroups appear acceptably accurate (with Arms < 4%).

CONCLUSIONS

Pulse oximetry may overestimate oxygen saturation in people with high levels of skin pigmentation and people whose ethnicity is reported as Black/African American, compared with SaO2. The extent of overestimation may be small in hospital settings but unknown in community settings. REVIEW PROTOCOL REGISTRATION: https://osf.io/gm7ty.

MiR-382 Functions on the Regulation of Melanogenesis via Targeting dct in Rainbow Trout (Oncorhynchus mykiss)

MicroRNAs (miRNAs) are a class of endogenous small noncoding RNAs that are involved in a diverse collection of biological processes as important post-transcriptional regulators. However, little is known about the molecular regulatory mechanism of miRNAs in fish skin pigmentation. In this study, we first confirmed that dopachrome tautomerase (dct), a key gene of melanogenesis, is a target of miR-382 in rainbow trout (Oncorhynchus mykiss) using luciferase reporter assay. The analysis of different developmental stages and tissue expression patterns between wild-type and yellow mutant rainbow trout suggested that miR-382 is a potential regulator during the process of skin pigmentation. In vitro, miR-382 mimics in rainbow trout primary liver cells significantly downregulated dct expression and resulted in decreased expression of key melanogenic genes including tyrosine-related protein 1 (tyrp1) and premelanosome protein (pmel), whereas the expression level of dct was markedly increased after transfected with miR-382 inhibitor. In vivo, overexpression of miR-382 by injection of miR-382 agomir significantly depressed the expression of dct in dorsal skin, tail fin, and liver and then reduced the expression levels of tyrp1 and pmel. Furthermore, transfection of miR-382 mimics inhibited cell proliferation and induced apoptosis. Taken together, our results identified a functional role of miR-382 in rainbow trout skin pigmentation through targeting dct, which facilitate understanding the regulatory mechanism of rainbow trout skin color at the post-transcriptional level and provide a theoretical basis for molecular breeding with skin color as the target trait.

Exploring the Role and Mechanism of Adipose Derived Mesenchymal Stem Cells on Reversal of Pigmentation Model Effects

Interventions for extrinsic aging can be implemented, but these must address photoaging, which is the primary cause of extrinsic aging. Pigmentation due to photoaging depends on the duration and intensity of sun exposure. This study investigated the relationship between adipose-derived mesenchymal stem cells (ASCs) and photoaging pigmentation, and the underlying mechanism of action by establishing a photoaging pigmentation model using various treatments and exposure options in a guinea pigs. The energy dose of each UVB irradiation was 120 mJ/cm² and the total dose of irradiation was 360 mJ/cm². After successfully establishing the photoaging model, ASCs (1×10⁶) in an balanced salt solution (0.9 ml), balanced salt solution (0.9 ml), and bFGF (9 μg) mixed with an balanced salt solution (0.9 ml) were injected intradermally in ten guinea pigs. ELISA, macroscopic skin and histological observations, and Masson-Fontana staining were done. At 2 and 4 weeks post-injection, noticeable changes were observed. Guinea pigs receiving ASCs injections displayed significantly lower visible skin scores while the melanin content continued to decrease. Somewhat improved histopathological morphology, including epidermal thinning, dermal thickening, and little inflammatory cell infiltration was observed immediately after and up to 4 weeks of ASCs injection. Melanocortin 1 receptor (MC1R) and alpha-melanocyte test hormone (alpha-MSH) levels reduced significantly, and basic fibroblast growth factor (bFGF) levels increased significantly immediately after and up to 4 weeks of ASCs injection. The MC1R and alpha-MSH levels reduced significantly immediately after and up to 4 weeks of bFGF injection. Briefly, intradermal ASCs injection can notably eliminate pigmentation in a guinea pig photoaging pigmentation model. This may be related to the fact that bFGF secreted by ASCs lowers MC1R and alpha-MSH levels, blocks the cAMP signalling pathway, and inhibits melanin synthesis. This finding may present new options for treating photoaging pigmentation.Level of Evidence: N/A.

CLEC12B is a melanocytic gene regulating the color of the skin

Pigmentation of the human skin is a complex process regulated by many genes. However, only a few have a profound impact on melanogenesis. Transcriptome analysis of pigmented skin compared to vitiligo skin devoid of melanocytes, allowed us to unravel CLEC12B as a melanocytic gene. We demonstrated that CLEC12B, a C-type lectin receptor, is highly expressed in melanocytes, and that its expression is decreased in dark skin compared to white skin. CLEC12B directly recruits and activates SHP-1 and SHP-2 through its ITIM domain and promotes CREB degradation, leading to downregulation of the downstream MITF pathway. CLEC12B ultimately controls melanin production and pigmentation in vitro and in a model of reconstructed human epidermis. The identification of CLEC12B in melanocyte demonstrates that C-type lectin receptors exert function beyond immunity and inflammation. It also provides insights in the understanding of the melanocyte biology and regulation of melanogenesis.

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.

Biological and socioeconomic factors as moderator in relationship between leisure-time physical activity and cardiometabolic risk in adolescents from southern Brazil

BACKGROUND

Given the important repercussions that sociodemographic factors can have on physical activity, especially in the field of leisure, and cardiometabolic risk, it seems relevant to analyze the implications of these variables on the relationship between physical activity in leisure time (LTPA) and cardiometabolic risk. In this sense, the present study aims to verify the moderating role of biologic and socioeconomic factors in the relationship between LTPA and cardiometabolic risk in adolescents in southern Brazil.

METHODS

Cross-sectional study that included 1596 adolescents selected at random (58.2% girls), aged between 10 and 17 years. LTPA, biological and socioeconomic factors were assessed using a self-reported questionnaire and the cardiometabolic risk score (total cholesterol/HDL-c ratio, triglycerides, fasting glucose, systolic blood pressure, and waist circumference, considering the participant's age and sex) was included as an outcome. Associations and moderations were tested by multiple linear regression models.

RESULTS

It was observed a positive interaction of LTPA and sex (p = 0.048) and LTPA and school system (p = 0.037), and negative interaction of LTPA and skin color (p = 0.040), indicating that these factors were moderators in the relationship between LTPA and clustered cardiometabolic risk score (cMetS) in adolescents. A reduction in cardiometabolic risk was observed according to the increase in weekly minutes of LTPA among boys, non-white adolescents, and students from municipal schools.

CONCLUSIONS

The association between LTPA and cardiometabolic risk was moderated by sex, skin color, and school system in adolescents from southern Brazil.

Exon-1 skipping and intron-1 retaining by alternative splicing of the c-KIT gene encodes a novel splice variant in the skin of Merino sheep (Ovis aries)

c-KIT, a type III receptor protein tyrosine kinase, plays an essential role in melanocyte development, migration, and survival. Mutations within the c-KIT gene are previously shown to cause the white coat color phenotypes in pigs, mice, goats, and humans. However, up so far, the splicing isoform(s), genomic architecture of c-KIT have not been characterized well in merino sheep. Reverse transcriptase (RT)-PCR analysis with molecular prediction identified two basic splice variants: Transcript Variant-1, 2 for 12 bp insertion coding sequences (CDS) corresponding to the four amino acids 'GNSK', respectively. Using 5' RACE, here we report for the first time a novel c-KIT 'Transcript Variant-3' from the skin of merino sheep by comparative genome analyses at exon(1)-intron(1)-exon(2) boundaries. In contrast, a single product of 795 bp was characterized by 3' RACE. We also demonstrated that the c-KIT gene expression at the transcript level is not mediated via an intron-9 splicing event. Overall, beyond what was observed in other mammals, our data provide novel insights into the molecular structure of the c-KIT gene in sheep.

Multiple bilateral hip fractures in a patient with dyskeratosis congenita caused by a novel mutation in the PARN gene

We report a case of a young male patient with clinical signs of dyskeratosis congenita who presented with multiple bilateral low-traumatic hip fractures. Whole exome sequencing (WES) showed a previously unreported mutation in the poly(A)-specific ribonuclease (PARN) gene. Zoledronic acid 5 mg over 3 years was effective at preventing further fractures. A male patient was referred to our clinic at age 24 due to multiple bilateral hip fractures. At the time of admission, the patient's height was 160 cm and weight 40 kg; bone mineral density (BMD) at the lumbar spine was normal (L1-L4 0.0 Z-score). The patient was found to have abnormal skin pigmentation, hyperkeratosis of palms and soles, nail dystrophy, and signs of bone marrow failure (BMF). Bone fragility first presented at 5 years old with a wrist fracture, followed by multiple bilateral low-traumatic hip fractures without falls from 14 to 24 years. WES showed a previously unreported mutation (NM_002582.3: c.1652delA; p.His551fs) in the poly(A)-specific ribonuclease (PARN) gene. Flow fish telomere measurement result was 5.9 (reference range 8.0-12.6), which is consistent with the DC diagnosis. Permanent fixation with internal metal rods and zoledronic acid 5 mg over 3 years was effective at preventing further fractures over 4 years of follow-up. Additionally, BMF did not progress over 4 years of observation. DC associated with PARN gene mutations might predispose to low-traumatic multiple hip fractures in adolescents and young adults. Treatment with zoledronic acid in this case was effective and safe at preventing further fractures.

Violet-blue light exposure of the skin: is there need for protection?

Advocates of skin protection against blue light express concern about exposure to indoor lighting and electronic screens as well as natural outdoor exposure. However, the nature of adverse effects in skin is unclear and the doses to induce effects are unknown. We aimed to reveal whether there is a scientific basis for promoting skin protection against violet-blue light (400-500 nm, VBL). Based on published literature, we determined the time to reach a threshold dose that induced a biological response in human skin. In the absence of an action spectrum for effects on skin, we used a hand held probe with a defined spectral response and measurements of the unweighted exposure between 400 and 500 nm to estimate the exposure by a selection of artificial light sources and solar light. For comparison, an outdoor threshold erythemally weighted UV dose was set to 1 SED (standard erythema dose). Outdoor, weighted irradiances were obtained using a radiative transfer model. Induction of pigmentation in human skin tissue was the only consistently reported endpoint after VBL exposure of about 65 Jcm^-2. This threshold dose was reached in 0.5 to 20 months of exposure to indoor lighting sources. In comparison, specialised medical sources reached this dose in 0.5 min to 45 h. The time outdoors to reach 1 SED was shorter than the time to reach a VBL threshold dose throughout all seasons. Skin protection against VBL is superfluous for exposures to domestic lighting sources or screens and for solar radiation; however, it may be advantageous for patients suffering from photosensitive diseases or taking photosensitising medication.

The Arp2/3 complex is crucial for colonisation of the mouse skin by melanoblasts

The Arp2/3 complex is essential for the assembly of branched filamentous actin, but its role in physiology and development is surprisingly little understood. Melanoblasts deriving from the neural crest migrate along the developing embryo and traverse the dermis to reach the epidermis, colonising the skin and eventually homing within the hair follicles. We have previously established that Rac1 and Cdc42 direct melanoblast migration in vivo We hypothesised that the Arp2/3 complex might be the main downstream effector of these small GTPases. Arp3 depletion in the melanocyte lineage results in severe pigmentation defects in dorsal and ventral regions of the mouse skin. Arp3 null melanoblasts demonstrate proliferation and migration defects and fail to elongate as their wild-type counterparts. Conditional deletion of Arp3 in primary melanocytes causes improper proliferation, spreading, migration and adhesion to extracellular matrix. Collectively, our results suggest that the Arp2/3 complex is absolutely indispensable in the melanocyte lineage in mouse development, and indicate a significant role in developmental processes that require tight regulation of actin-mediated motility.

Constitutive melanin density is associated with prevalent and short-term, but not long-term, incident fracture risk in older Caucasian adults

Higher cutaneous melanin reduces vitamin D3 production. This may increase fracture risk. We found that cutaneous melanin density was associated with prevalent and short-term, but not long-term, incident fracture risk in older Caucasian adults. Melanin density either acts as a surrogate marker or its relationship with fracture changes with time.

INTRODUCTION

Higher cutaneous melanin reduces vitamin D3 production. This may impact lifetime vitamin D status and increase fracture risk. This study aimed to describe the relationship between spectrophotometrically determined constitutive melanin density, prevalent and incident fractures in a cohort of exclusively older Caucasian adults.

METHODS

1072 community-dwelling adults aged 50-80 years had constitutive melanin density quantified using spectrophotometry. Participants were followed up at 2.5 (n = 879), 5 (n = 767), and 10 (n = 571) years after the baseline assessment. Prevalence and number of symptomatic fractures were assessed by questionnaire.

RESULTS

Higher melanin density was independently associated with greater prevalence of any fracture (RR 1.08, p = 0.03), vertebral fracture (RR 1.41, p = 0.04) and major fracture (RR 1.12, p = 0.04) and the number of fractures (RR 1.09, p = 0.04) and vertebral fractures (RR 1.47, p = 0.04) in cross-sectional analysis. At the 2.5-year follow-up, higher melanin density was associated with incident fractures (RR 1.42, p = 0.01) and major fractures (RR 1.81, p = 0.01) and the number of incident fractures (RR 1.39, p = 0.02) and major fractures (RR 2.14, p = 0.01). The relationship between melanin density and incident fracture attenuated as the duration of follow-up increased and was not significant at the 5- or 10-year follow-up.

CONCLUSIONS

Constitutive melanin density was associated with prevalent and short-term, but not long-term, incident fracture risk in older Caucasian adults. This suggests melanin density either acts as a surrogate marker for an unmeasured fracture risk factor or the relationship between melanin density and fracture changes with time.

Distribution of variants in multiple vitamin D-related loci (DHCR7/NADSYN1, GC, CYP2R1, CYP11A1, CYP24A1, VDR, RXRα and RXRγ) vary between European, East-Asian and Sub-Saharan African-ancestry populations

BACKGROUND

The frequency of vitamin D-associated gene variants appear to reflect changes in long-term ultraviolet B radiation (UVB) environment, indicating interactions exist between the primary determinant of vitamin D status, UVB exposure and genetic disposition. Such interactions could have health implications, where UVB could modulate the impact of vitamin D genetic variants identified as disease risk factors. However, the current understanding of how vitamin D variants differ between populations from disparate UVB environments is limited, with previous work examining a small pool of variants and restricted populations only.

METHODS

Genotypic data for 46 variants within multiple vitamin D-related loci (DHCR7/NADSYN1, GC, CYP2R1, CYP11A1, CYP27A1, CYP24A1, VDR, RXRα and RXRγ) was collated from 60 sample sets (2633 subjects) with European, East Asian and Sub-Saharan African origin via the NCBI 1000 Genomes Browser and ALFRED (Allele Frequency Database), with the aim to examine for patterns in the distribution of vitamin D-associated variants across these geographic areas.

RESULTS

The frequency of all examined genetic variants differed between populations of European, East Asian and Sub-Saharan African ancestry. Changes in the distribution of variants in CYP2R1, CYP11A1, CYP24A1, RXRα and RXRγ genes between these populations are novel findings which have not been previously reported. The distribution of several variants reflected changes in the UVB environment of the population's ancestry. However, multiple variants displayed population-specific patterns in frequency that appears not to relate to UVB changes.

CONCLUSIONS

The reported population differences in vitamin D-related variants provides insight into the extent by which activity of the vitamin D system can differ between cohorts due to genetic variance, with potential consequences for future dietary recommendations and disease outcomes.

Regional cerebral oximetry is consistent across self-reported racial groups and predicts 30-day mortality in cardiac surgery: a retrospective analysis

Darker skin pigmentation appears to cause underestimation of regional oxygen saturation (rSO₂) for certain cerebral oximetry devices. This presents a risk of triggering unindicated interventions and may limit its utility for predicting adverse outcomes. Our goal was to quantify the impact of self-reported race on oximetry measurements during cardiac surgery and elucidate whether race has a mediating role in the association of rSO₂ with mortality. Data was extracted from our department's data warehouse for adult patients who underwent on-pump cardiac surgery between June 2014 and June 2018. Intraoperative rSO₂ was recorded every 15 s throughout all cases. After grouping patients by self-reported race, multiple linear regression modeling was utilized to assess the association between race and mean pre-bypass rSO₂ while controlling for various perioperative variables. The role of mean pre-bypass rSO₂ for predicting 30-day mortality was evaluated via multiple logistic regression, and the threshold for rSO₂ was selected by maximizing F1 score. There were 4267 patients included. Compared to Caucasian patients, the unadjusted difference in mean pre-bypass rSO₂ was - 0.6% (95% CI - 1.3 to 0.04) for African American patients, - 1.8% (- 2.7 to - 0.9) for Asian patients, 0.1% (- 0.8 to 1.0) for Hispanic patients, - 1.6% (- 3.0 to - 0.4) for Indian/South Asian patients, and - 1.4% (- 3.7 to 0.9) for Pacific Islander patients. After adjusting for perioperative variables, differences in rSO₂ readings less than 2% were observed between racial groups. Mean pre-bypass rSO₂ under 63% was an independent predictor of higher 30-day mortality risk (OR: 2.86, CI 1.39 to 5.53, p = 0.003), and the interaction variable between rSO₂ and race was not statistically significant (p = 0.299). Cerebral oximetry measurements are more consistent across racial groups than previously reported, supporting its utility for intraoperative monitoring and risk stratification. Pre-intervention rSO₂ is associated with increased 30-day mortality at a higher threshold than previously reported and was not significantly impacted by self-reported race.

[Complications of cosmetic piercings and tattoos in the head and neck region]

Piercings and tattoos have gained popularity across all cultural environments during the past century, and one in ten Europeans are now pierced. While tattoos are often restricted to the rest of the body, piercings are common at facial sites such as ears, nose, lips, and tongue. Complications following piercings are not uncommon. Infections can rapidly spread across the auricular cartilage and require antibiotic and often surgical treatment. Mild trauma (i.e., piercing the earlobe) can lead to excessive scar formation due to fibroblast proliferation. Keloids have a particularly high rate of recurrence and are therefore difficult to treat. Due to recent developments in the field of permanent makeup, tattooing techniques are also increasingly applied in the head and neck region. Here, complications such as infection or allergic reactions can occur. Topical medication or laser procedures are the usual therapeutic options.

Structure-function relationships of K+-dependent Na+/Ca2+ exchangers (NCKX)

K⁺-dependent Na⁺/Ca²⁺ exchanger proteins (NCKX1-5) of the SLC24 gene family play important roles in a wide range of biological processes including but not limited to rod and cone photoreceptor vision, olfaction, enamel formation and skin pigmentation. NCKX proteins are also widely expressed throughout the brain and NCKX2 and NCKX4 knockouts in mice have specific phenotypes. Here we review our work on structure-function relationships of NCKX proteins. We discuss membrane topology, domains critical to transport function, and residues critical to cation binding and transport function, all in the context of crystal structures that were obtained for the archaeal Na⁺/Ca²⁺ exchanger NCX_Mj.

High SLC7A11 expression in normal skin of melanoma patients

BACKGROUND

Melanoma is one of the highest metastatic cancers and its incidence is rapidly increasing. A great effort has been devoted to determine gene mutations and expression profiles in melanoma cells, but less attention has been given to the possible influence of melanin synthesis in melanocytes on melanomagenesis. SLC7A11 encodes the cystine/glutamate antiporter xCT and its expression increases the antioxidant capacity of cells by providing cysteine that may be used for glutathione (GSH) synthesis. Melanocytes, however, can also use cysteine for pheomelanin synthesis and pigmentation. Therefore, pheomelanin synthesis may lead to chronic oxidative stress. Possible consequences of this for melanomagenesis have never been explored.

METHODS

We quantified the expression of SLC7A11 and other genes that are involved in the synthesis of pheomelanin but do not regulate the transport of cysteine from the extracellular medium to the cytosol (CTNS, MC1R, ASIP and SLC45A2) in non-tumorous skin of 45 patients of cutaneous melanoma and 50 healthy individuals. We controlled for the effects of Fitzpatrick skin type, age, gender, body mass, frequency of sun exposure and sunburns and number of melanocytic nevi, as well as for the intrinsic antioxidant capacity as given by the expression of the gene NFE2L2.

RESULTS

The expression of SLC7A11, but not of the other genes, was significantly higher in melanoma patients than in healthy individuals. This was independent of phenotypic factors and antioxidant capacity, thus supporting an effect of pheomelanin-induced oxidative stress on melanomagenesis.

CONCLUSION

Our findings indicate that SLC7A11 downregulation in normal epidermal melanocytes may represent a preventive treatment against melanoma.

Skin lightening products' violations in Europe: An analysis of the rapid alert system for dangerous non-food products 2005-2018

BACKGROUND

Skin lightening products containing dangerous levels of chemicals pose a serious health concern for consumers. However, to date, the extent of these products in Europe has not been extensively studied. The aim of this study was to determine whether harmful skin lightening products are available for sale in Europe and what violations exist regarding their composition.

MATERIALS AND METHODS

We queried the Rapex database, which is the Rapid Alert System for dangerous non-food products among 31 European countries, to identify skin lightening cosmetics reported between 2005 and 2018, and presented a detailed summary of these notifications.

RESULTS

In the years 2005-2018, of all violations regarding cosmetics, 26.3% concerned skin lightening products. In the database, 266 reports on skin lightening products were identified. Most of the notifications came from Germany (17.29%), France (17.29%), Portugal (15.41%), and the United Kingdom (11.65%). The majority of the registered products originated from non-European countries, mainly the Côte d'Ivoire (29.70%). The major reason for the violation was the content of hydroquinone, mercury, or clobetasol propionate.

CONCLUSIONS

Hazardous skin lightening products that are not in line with European cosmetics legislation are available on the European market. Most of the products are imported. The main risk associated with these products is the content of hydroquinone, mercury, and clobetasol propionate. It is important to bear in mind that this study focuses on the Rapex system and other sources of information may exist. Based on our findings, a more comprehensive evaluation by international authorities is justified.

The Evolutionary History of Human Skin Pigmentation

Skin pigmentation is a complex, conspicuous, highly variable human trait that exhibits a remarkable correlation with latitude. The evolutionary history and genetic basis of skin color variation has been the subject of intense research in the last years. This article reviews the major hypotheses explaining skin color diversity and explores the implications of recent findings about the genes associated with skin pigmentation for understanding the evolutionary forces that have shaped the current patterns of skin color variation. A major aspect of these findings is that the genetic basis of skin color is less simple than previously thought and that geographic variation in skin pigmentation was influenced by the concerted action of different types of natural selection, rather than just by selective sweeps in a few key genes.

Meta-analysis of GWA studies provides new insights on the genetic architecture of skin pigmentation in recently admixed populations

BACKGROUND

Association studies in recently admixed populations are extremely useful to identify the genetic architecture of pigmentation, due to their high genotypic and phenotypic variation. However, to date only four Genome-Wide Association Studies (GWAS) have been carried out in these populations.

RESULTS

We present a GWAS of skin pigmentation in an admixed sample from Cuba (N = 762). Additionally, we conducted a meta-analysis including the Cuban sample, and admixed samples from Cape Verde, Puerto Rico and African-Americans from San Francisco. This meta-analysis is one of the largest efforts so far to characterize the genetic basis of skin pigmentation in admixed populations (N = 2,104). We identified five genome-wide significant regions in the meta-analysis, and explored if the markers observed in these regions are associated with the expression of relevant pigmentary genes in human melanocyte cultures. In three of the regions identified in the meta-analysis (SLC24A5, SLC45A2, and GRM5/TYR), the association seems to be driven by non-synonymous variants (rs1426654, rs16891982, and rs1042602, respectively). The rs16891982 polymorphism is strongly associated with the expression of the SLC45A2 gene. In the GRM5/TYR region, in addition to the rs1042602 non-synonymous SNP located on the TYR gene, variants located in the nearby GRM5 gene have an independent effect on pigmentation, possibly through regulation of gene expression of the TYR gene. We also replicated an association recently described near the MFSD12 gene on chromosome 19 (lead variant rs112332856). Additionally, our analyses support the presence of multiple signals in the OCA2/HERC2/APBA2 region on chromosome 15. A clear causal candidate is the HERC2 intronic variant rs12913832, which has a profound influence on OCA2 expression. This variant has pleiotropic effects on eye, hair, and skin pigmentation. However, conditional and haplotype-based analyses indicate the presence of other variants with independent effects on melanin levels in OCA2 and APBA2. Finally, a follow-up of genome-wide signals identified in a recent GWAS for tanning response indicates that there is a substantial overlap in the genetic factors influencing skin pigmentation and tanning response.

CONCLUSIONS

Our meta-analysis of skin pigmentation GWAS in recently admixed populations provides new insights about the genetic architecture of this complex trait.

A systematic review of global legal regulations on the permissible level of heavy metals in cosmetics with particular emphasis on skin lightening products

BACKGROUND

There is an urgent need to address the safety problems caused by the use of skin lightening cosmetics. Evidence suggests that some of them may contain heavy metals.

OBJECTIVES

We conducted a systematic review of global legal regulations regarding the permissible level of mercury, lead, arsenic, and cadmium in cosmetic products, with particular emphasis on skin lightening preparations.

METHODS

The systematic search of documents was a two-stage process. First, official websites of 17 regional organizations and subsequently regulations for countries with a population over 100 million were searched.

RESULTS

Fifteen legislative acts, encompassing more than 67·2% of the global population were reviewed. Regulations were identified for 44/59 high income countries, 16/55 upper middle income countries, 9/45 lower income countries, 0/34 low income countries. The median adult literacy rate was 91·4% and 64·2% in countries with and without regulations, respectively. The use of mercury, lead, arsenic, and cadmium has been banned in 67, 67, 65, and 65 out of 69 countries, respectively.

CONCLUSIONS

While regulations exist in most of the high income countries, in low income countries there is a lack of similar standards. In most countries for which these legal regulations have been identified, restrictions on the permissible level of heavy metals are strict. There is a need for enforcement of existing rules, and rigorous assessment of the effectiveness of these regulations.

A disadvantageous effect of adsorption of barium by melanin on transforming activity

At present, beneficial effects of melanin and harmful effects of barium have been reported. However, little is known about the adsorption of barium, and even less is known about the biological significance of adsorption of barium by melanin. In this study, we showed that there was a strong correlation between the digitalized level of skin pigmentation and barium level in murine skin compared to the correlations between skin pigmentation level and levels of homologous elements of barium (magnesium, calcium and strontium). The concentration of subcutaneously injected barium in skin with a high level of pigmentation was higher than that in skin with a low level of pigmentation. Our cell-free experiment using the Langmuir isotherm for adsorption of barium in synthetic melanin also provided direct evidence of adsorption of barium by melanin. We then investigated the biological significance of melanin-mediated barium adsorption. We found barium-mediated increase in transforming activity in pigmented melanocytes (melan-a) but not in unpigmented melanocytes (melan-c) after confirming that the barium level in melan-a melanocytes was 3.4-fold higher than that in melan-c melanocytes after culture of 5 μM barium for 24 h. Taken together, our results not only indicate adsorption of barium by melanin in mice, cells and cell-free systems but also suggest a disadvantageous effect of adsorption of barium by melanin on transforming activity in cultured cells.

Video-based heart rate monitoring across a range of skin pigmentations during an acute hypoxic challenge

The robust monitoring of heart rate from the video-photoplethysmogram (video-PPG) during challenging conditions requires new analysis techniques. The work reported here extends current research in this area by applying a motion tolerant algorithm to extract high quality video-PPGs from a cohort of subjects undergoing marked heart rate changes during a hypoxic challenge, and exhibiting a full range of skin pigmentation types. High uptimes in reported video-based heart rate (HRvid) were targeted, while retaining high accuracy in the results. Ten healthy volunteers were studied during a double desaturation hypoxic challenge. Video-PPGs were generated from the acquired video image stream and processed to generate heart rate. HRvid was compared to the pulse rate posted by a reference pulse oximeter device (HRp). Agreement between video-based heart rate and that provided by the pulse oximeter was as follows: Bias = - 0.21 bpm, RMSD = 2.15 bpm, least squares fit gradient = 1.00 (Pearson R = 0.99, p < 0.0001), with a 98.78% reporting uptime. The difference between the HRvid and HRp exceeded 5 and 10 bpm, for 3.59 and 0.35% of the reporting time respectively, and at no point did these differences exceed 25 bpm. Excellent agreement was found between the HRvid and HRp in a study covering the whole range of skin pigmentation types (Fitzpatrick scales I-VI), using standard room lighting and with moderate subject motion. Although promising, further work should include a larger cohort with multiple subjects per Fitzpatrick class combined with a more rigorous motion and lighting protocol.

Senescent fibroblasts drive ageing pigmentation: ​A potential therapeutic target for senile lentigo

Cutaneous ageing is an important extrinsic process that modifies the pigmentary system. Because cellular senescence is a fundamental ageing mechanism, we examined the role of senescent cells in ageing pigmentation.

Methods: Biopsies obtained from senile lentigo and perilesional normal skin were assayed for a marker of cellular senescence, p16^INK4A. To determine the secretory phenotypes of senescent fibroblasts, we performed microarray, RNA sequencing and methylation array analyses in senile lentigo and senescent fibroblasts. To further investigate the impact of senescent cells on ageing-related pigmentation, an intervention that targeted senescent cells using radiofrequency was performed.

Results:In vivo, senescent fibroblasts accumulated at the sites of age-related pigmentation. Phenotype switching of the cells resulted in the repression of stromal-derived factor 1 (SDF1) by promoter methylation. SDF1 induced melanocyte differentiation via stromal-epithelial interactions, ultimately driving skin pigmentation. Furthermore, the elimination of senescent fibroblasts from pigmented skin using radiofrequency was accompanied by skin lightening, rendering it a potential target for treatment.

Conclusion: Aged pigmented skin contains an increasing proportion of senescent fibroblasts. Cells with phenotype switching exhibited a loss of SDF1, which stimulates the melanogenic process and thereby contributes to aging pigmentation. These data may promote the development of new therapeutic paradigms, such as a stroma-targeting therapy for pigmentary disorders.

Constitutive melanin density is associated with higher 25-hydroxyvitamin D and potentially total body BMD in older Caucasian adults via increased sun tolerance and exposure

Greater skin pigmentation reduces dose equivalent cutaneous vitamin D3 production, potentially impacting lifetime vitamin D status and fracture risk. We show that melanin density was positively associated with 25-hydroxyvitamin D and total body bone mineral density. These relationships were partially explained by greater sun exposure due to more permissive skin phenotype.

INTRODUCTION

Higher cutaneous melanin reduces vitamin D3 production. This may impact lifetime vitamin D status and increase fracture risk. This study aimed to describe the relationship between spectrophotometrically determined constitutive melanin density, osteoporotic risk factors and potential intermediaries in a cohort of exclusively older Caucasian adults.

METHODS

One thousand seventy-two community-dwelling adults aged 50-80 years had constitutive melanin density quantified using spectrophotometry. Sun exposure, skin phenotype, non-melanoma skin cancer (NMSC) prevalence and smoking status were assessed by questionnaire. Bone mineral density (BMD), falls risk, physical activity and 25-hydroxyvitamin D were measured using DXA, the short form Physiological Profile Assessment, pedometer and radioimmunoassay, respectively.

RESULTS

Higher melanin density was independently associated with greater ability to tan (RR = 1.27, p < 0.001), less propensity to sunburn (RR = 0.92, p < 0.001), fewer lifetime sunburns (RR = 0.94, p = 0.01), current smoking (RR = 1.41, p < 0.001), female sex (RR = 1.24, p < 0.001) and less photodamage (RR = 0.98, p = 0.01). The associations between melanin density and sun exposure (RR = 1.05-1.11, p < 0.001-0.01), sun protection behaviours (RR = 0.89, p < 0.001) and NMSC prevalence (RR = 0.75, p = 0.001) were no longer significant after taking into account skin phenotype and sun exposure, respectively. 25-Hydroxyvitamin D was strongly associated with higher melanin density (β = 1.71-2.05, p = 0.001). The association between melanin density and total body BMD (β = 0.007, p = 0.04) became non-significant after adjustment for 25-hydroxyvitamin D. There was no association between melanin density and physical activity, falls risk or BMD at other sites.

CONCLUSIONS

Our data support a model of higher constitutive melanin density underpinning a less photosensitive skin phenotype, permitting greater sun exposure with fewer sequelae and yielding higher 25-hydroxyvitamin D and, potentially, total body BMD.

Dyskeratosis congenita with a novel genetic variant in the DKC1 gene: a case report

Background

Dyskeratosis congenita (DC) is a rare genetic disorder of bone marrow failure inherited in an X-linked, autosomal dominant or autosomal recessive pattern. It has a wide array of clinical features and patients may be cared for by many medical sub specialties. The typical clinical features consist of lacy reticular skin pigmentation, nail dystrophy and oral leukoplakia. As the disease advances, patients may develop progressive bone marrow failure, pulmonary fibrosis, oesophageal stenosis, urethral stenosis, liver cirrhosis as well as haematological and solid malignancies. Several genes have been implicated in the pathogenesis of dyskeratosis congenita, with the dyskerin pseudouridine synthase 1 (DKC1) gene mutations being the X-linked recessive gene.

Case presentation

Herein, we report a 31-year-old male with history of recurrent febrile episodes who was found to have reticulate skin pigmentation interspersed with hypopigmented macules involving the face, neck and extremities, hyperkeratosis of palms and soles, nail dystrophy, leukoplakia of the tongue, premature graying of hair, watery eyes and dental caries. Several of his male relatives, including two maternal uncles and three maternal cousins were affected with a similar type of disease condition. Pedigree analysis suggested a possible X-linked pattern of inheritance. Genetic testing in the proband showed a novel hemizygous, non-synonymous likely pathogenic variant [NM_001363.4: c.1054A > G: p.Thr352Ala] in the PUA domain of the DKC1 gene. Quantitative polymerase chain reaction for relative telomere length measurements performed in the proband showed that he had very short telomeres [0.38, compared to a control median of 0.71 (range 0.44–1.19)], which is consistent with the DC diagnosis. Co-segregation analysis of the novel mutation and telomere length measurements in the extended family members could not be performed as they were unwilling to provide consent for testing.

Conclusions

The novel variant detected in the DKC1 gene adds further to the existing scientific literature on the genotype-phenotype correlation of DC, and has important implications for the clinical and molecular characterization of the disease.

Replacement of Arg with Nle and modified D-Phe in the core sequence of MSHs, Ac-His-D-Phe-Arg-Trp-NH2, leads to hMC1R selectivity and pigmentation

Melanoma skin cancer is the fastest growing cancer in the US [1]. A great need exists for improved formulations and mechanisms to prevent and protect human skin from cancers and other skin damage caused by sunlight exposure. Current efforts to prevent UV damage to human skin, which in many cases leads to melanoma and other skin cancers. The primordial melanocortin-1 receptor (MC1R) is involved in regulating skin pigmentation and hair color, which is a natural prevention from UV damage. The endogenous melanocortin agonists induce pigmentation and share a core pharmacophore sequence "His-Phe-Arg-Trp", and it was found that substitution of the Phe by D-Phe results in increasing melanocortin receptor potency. To improve the melanocortin 1 receptor (MC1R) selectivity a series of tetra-peptides with the moiety of Ac-Xaa-Yaa-Nle-Trp-NH2, and structural modifications to reduce electrostatic ligand-receptor interactions have been designed and synthesized. It is discovered that the tetrapeptide Ac-His-D-Phe(4-CF3)-Nle-Trp-NH2 resulted in a potent and selective hMC1R agonist at the hMC1R (EC50: 10 nM). Lizard anolis carolinensis pigmentation study shows very high potency in vivo. NMR studies revealed a reversed β turn structure which led to the potency and selectivity towards the hMC1R.