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The Pan African Medical Journal 2024
Topics: Humans; Clofazimine; Female; Skin Pigmentation; Male; Hyperpigmentation; Leprostatic Agents; Adult; Middle Aged
PubMed: 38737223
DOI: 10.11604/pamj.2024.47.86.42513 -
Pigment Cell & Melanoma Research Mar 2019Ultraviolet radiation (UVR) has numerous effects on skin, including DNA damage, tanning, vitamin D synthesis, carcinogenesis, and immunomodulation. Keratinocytes... (Review)
Review
Ultraviolet radiation (UVR) has numerous effects on skin, including DNA damage, tanning, vitamin D synthesis, carcinogenesis, and immunomodulation. Keratinocytes containing damaged DNA secrete both α-melanocyte-stimulating hormone (α-MSH), which stimulates pigment production by melanocytes, and the opioid β-endorphin, which can trigger addiction-like responses to UVR. The pigmentation (tanning) response is an adaptation that provides some delayed protection against further DNA damage and carcinogenesis, while the opioid response may be an evolutionary adaptation for promoting sun-seeking behavior to prevent vitamin D deficiency. Here, we review the pigmentation response to UVR, driven by melanocytic microphthalmia-associated transcription factor (MITF), and evidence for UVR-induced melanomagenesis and addiction. We also discuss potential applications of a novel approach to generate protective pigmentation in the absence of UVR (sunless tanning) using a topical small-molecule inhibitor of the salt-inducible kinase (SIK) family.
Topics: Animals; Behavior, Addictive; Humans; Melanins; Microphthalmia-Associated Transcription Factor; Skin; Skin Pigmentation; Ultraviolet Rays
PubMed: 30019545
DOI: 10.1111/pcmr.12726 -
Cellular and Molecular Life Sciences :... Mar 2013Melanoblasts are a particular type of cell that displays extensive cellular proliferation during development to contribute to the skin. There are only a few melanoblast... (Review)
Review
Melanoblasts are a particular type of cell that displays extensive cellular proliferation during development to contribute to the skin. There are only a few melanoblast founders, initially located just dorsal to the neural tube, and they sequentially colonize the dermis, epidermis, and hair follicles. In each compartment, melanoblasts are exposed to a wide variety of developmental cues that regulate their expansion. The colonization of the dermis and epidermis by melanoblasts involves substantial proliferation to generate thousands of cells or more from a few founders within a week of development. This review addresses the cellular and molecular events occurring during melanoblast development. We focus on intrinsic and extrinsic factors that control melanoblast proliferation. We also present a robust mathematical model for estimating the doubling-time of dermal and epidermal melanoblasts for all coat color phenotypes from black to white.
Topics: Cell Differentiation; Cell Movement; Cell Proliferation; Humans; Melanocytes; Models, Biological; Neural Crest; Signal Transduction; Skin; Skin Pigmentation
PubMed: 22915137
DOI: 10.1007/s00018-012-1112-4 -
The Journal of Investigative Dermatology Dec 2020Senescent fibroblasts play a role in aging pigmentation. In this study, we found that GDF15 expression levels are increased in UV-irradiated senescent fibroblasts and... (Observational Study)
Observational Study
Senescent fibroblasts play a role in aging pigmentation. In this study, we found that GDF15 expression levels are increased in UV-irradiated senescent fibroblasts and photoaged hyperpigmented skin. To investigate the effects of GDF15 on melanogenesis, normal human melanocytes were cocultured with fibroblasts infected with the GDF15 lentivirus or GDF15 short hairpin RNA. It was found that GDF15 stimulates melanogenesis in melanocytes through MITF/tyrosinase upregulation via β-catenin signaling. The stimulatory action of GDF15 during pigmentation was further confirmed in ex vivo cultured skin and in a reconstituted human skin sample. These results suggest that senescent fibroblast-derived GDF15 stimulates skin pigmentation and may play a role in aging-associated pigmentation.
Topics: Adolescent; Adult; Aged; Biopsy; Cells, Cultured; Cellular Senescence; Child; Coculture Techniques; Fibroblasts; Gene Knockdown Techniques; Growth Differentiation Factor 15; Humans; Melanins; Melanocytes; Melanosis; Middle Aged; Primary Cell Culture; Skin; Skin Aging; Skin Pigmentation; Ultraviolet Rays
PubMed: 32416083
DOI: 10.1016/j.jid.2020.04.016 -
Frontiers in Immunology 2022Post-inflammatory skin hyper- or hypo-pigmentation is a common occurrence with unclear etiology. There is currently no reliable method to predict skin pigmentation...
Post-inflammatory skin hyper- or hypo-pigmentation is a common occurrence with unclear etiology. There is currently no reliable method to predict skin pigmentation outcomes after inflammation. In this study, we analyzed the 5 GEO datasets to screen for inflammatoryrelated genes involved in melanogenesis, and used candidate cytokines to establish different machine learning (LASSO regression, logistic regression and Random Forest) models to predict the pigmentation outcomes of post-inflammatory skin. Further, to further validate those models, we evaluated the role of these candidate cytokines in pigment cells. We found that IL-37, CXCL13, CXCL1, CXCL2 and IL-19 showed high predictive value in predictive models. All models accurately classified skin samples with different melanogenesis-related gene scores in the training and testing sets (AUC>0.7). Meanwhile, we mainly evaluated the effects of IL-37 in pigment cells, and found that it increased the melanin content and expression of melanogenesis-related genes (MITF, TYR, TYRP1 and DCT), also enhanced tyrosinase activity. In addition, CXCL13, CXCL1, CXCL2 and IL-19 could down-regulate the expression of several melanogenesis-related genes. In conclusion, evaluation models basing on machine learning may be valuable in predicting outcomes of post-inflammatory pigmentation abnormalities. IL-37, CXCL1, CXCL2, CXCL13 and IL-19 are involved in regulating post-inflammatory pigmentation abnormalities.
Topics: Melanins; Skin Pigmentation; Monophenol Monooxygenase; Skin; Cytokines
PubMed: 36389813
DOI: 10.3389/fimmu.2022.991594 -
Indian Journal of Dermatology,... 2022
Topics: Dermatology; Humans; Skin; Skin Diseases; Skin Pigmentation
PubMed: 36066307
DOI: 10.25259/IJDVL_750_2022 -
British Journal of Anaesthesia Jan 2023Recent reports highlight potential inaccuracies of pulse oximetry in patients with various degrees of skin pigmentation. We summarise the literature, provide an overview...
Recent reports highlight potential inaccuracies of pulse oximetry in patients with various degrees of skin pigmentation. We summarise the literature, provide an overview of potential clinical implications, and provide insights into how pulse oximetry could be improved to mitigate against such potential shortcomings.
Topics: Humans; Skin Pigmentation; Oximetry; Oxygen
PubMed: 35430087
DOI: 10.1016/j.bja.2022.03.011 -
Pigment Cell & Melanoma Research Jul 2021The primary biological role of human skin pigmentation is as a mediator of penetration of ultraviolet radiation (UVR) into the deep layers of skin and the cutaneous... (Review)
Review
The primary biological role of human skin pigmentation is as a mediator of penetration of ultraviolet radiation (UVR) into the deep layers of skin and the cutaneous circulation. Since the origin of Homo sapiens, dark, protective constitutive pigmentation and strong tanning abilities have been favored under conditions of high UVR and represent the baseline condition for modern humans. The evolution of partly depigmented skin and variable tanning abilities has occurred multiple times in prehistory, as populations have dispersed into environments with lower and more seasonal UVR regimes, with unique complements of genes and cultural practices. The evolution of extremes of dark pigmentation and depigmentation has been rare and occurred only under conditions of extremely high or low environmental UVR, promoted by positive selection on variant pigmentation genes followed by limited gene flow. Over time, the evolution of human skin pigmentation has been influenced by the nature and course of human dispersals and modifications of cultural practices, which have modified the nature and actions of skin pigmentation genes. Throughout most of prehistory and history, the evolution of human skin pigmentation has been a contingent and non-deterministic process.
Topics: Biological Evolution; Culture; Environment; Human Migration; Humans; Selection, Genetic; Sex Characteristics; Skin Pigmentation
PubMed: 33825328
DOI: 10.1111/pcmr.12976 -
Physiological Measurement Jun 2023. Pulse oximetry is a non-invasive optical technique used to measure arterial oxygen saturation (SpO) in a variety of clinical settings and scenarios. Despite being one... (Review)
Review
. Pulse oximetry is a non-invasive optical technique used to measure arterial oxygen saturation (SpO) 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, and are to be addressed.. 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.
Topics: Humans; Skin Pigmentation; Pandemics; COVID-19; Oximetry; Oxygen
PubMed: 37172609
DOI: 10.1088/1361-6579/acd51a -
American Journal of Physiology.... Sep 2019The vitamin D-folate hypothesis has been proposed as an explanation for the evolution of human skin pigmentation. According to this hypothesis, a darkened skin pigment... (Review)
Review
The vitamin D-folate hypothesis has been proposed as an explanation for the evolution of human skin pigmentation. According to this hypothesis, a darkened skin pigment was adapted by early human populations living in equatorial Africa to protect against photodegradation of bioavailable folate by ultraviolet radiation (UVR). As humans moved away from the equator to more northern latitudes and occupied regions of lower UVR exposure and greater seasonal variation, however, depigmentation occurred to allow for adequate biosynthesis of vitamin D. Vitamin D and folate are both recognized for their evolutionary importance in healthy pregnancy and early childhood development. More recently, evidence has emerged demonstrating the importance of both vitamin D and folate in vascular health via their effects in reducing oxidative stress and improving nitric oxide (NO) bioavailability. Thus, populations with darkened skin pigmentation may be at elevated risk of vascular dysfunction and cardiovascular disease in low UVR environments due to hypovitaminosis D; particularly important as darkly-pigmented African-Americans represent an at-risk population for cardiovascular disease. Conversely, lightly pigmented populations in high UVR environments may be at risk of deleterious vascular effects of UVR-induced folate degradation. The focus of this review is to explore the currently available literature regarding the potential role of UVR in vascular health via its differential effects on vitamin D and folate metabolism, as well as the interaction between skin pigmentation, genetics, and environment in modulating the vascular influence of UVR exposure.
Topics: Biological Evolution; Cardiovascular Diseases; Folic Acid; Humans; Skin Pigmentation; Ultraviolet Rays; Vitamin D
PubMed: 31314544
DOI: 10.1152/ajpregu.00136.2019