The Protective Role of Melanin Against UV Damage in Human Skin†

Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
Photochemistry and Photobiology (Impact Factor: 2.27). 05/2008; 84(3):539-49. DOI: 10.1111/j.1751-1097.2007.00226.x
Source: PubMed

ABSTRACT Human skin is repeatedly exposed to UVR that influences the function and survival of many cell types and is regarded as the main causative factor in the induction of skin cancer. It has been traditionally believed that skin pigmentation is the most important photoprotective factor, as melanin, besides functioning as a broadband UV absorbent, has antioxidant and radical scavenging properties. Besides, many epidemiological studies have shown a lower incidence for skin cancer in individuals with darker skin compared to those with fair skin. Skin pigmentation is of great cultural and cosmetic importance, yet the role of melanin in photoprotection is still controversial. This article outlines the major acute and chronic effects of UVR on human skin, the properties of melanin, the regulation of pigmentation and its effect on skin cancer prevention.

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    • "Photoprotection of the skin is apparently one of the most important biological functions of melanin pigments. Subjects with white skin are approximately 70 times more likely to develop skin cancer than subjects with black skin, suggesting that higher levels of constitutive pigmentation decrease susceptibility to the deleterious effects of ultraviolet radiation (UVR) (Brenner and Hearing, 2008; Coelho et al., 2009). Usually, black skin and Asian skin contain higher levels of melanin than fair skin (Tadokoro et al., 2003). "
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    ABSTRACT: During the past decade, melanins and melanogenesis have attracted growing interest for a broad range of biomedical and technological applications. The burst of polydopamine-based multifunctional coatings in materials science is just one example, and the list may be expanded to include melanin thin films for organic electronics and bioelectronics, drug delivery systems, functional nanoparticles and biointerfaces, sunscreens, environmental remediation devices. Despite considerable advances, applied research on melanins and melanogenesis is still far from being mature. A closer intersectoral interaction between research centers is essential to raise the interests and increase the awareness of the biomedical, biomaterials science and hi-tech sectors of the manifold opportunities offered by pigment cells and related metabolic pathways. Starting from a survey of biological roles and functions, the present review aims at providing an interdisciplinary perspective of melanin pigments and related pathway with a view to showing how it is possible to translate current knowledge about physical and chemical properties and control mechanisms into new bioinspired solutions for biomedical, dermocosmetic, and technological applications.
    Pigment Cell & Melanoma Research 09/2015; 28(5):520-544. DOI:10.1111/pcmr.12393 · 4.62 Impact Factor
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    • "Molecular hydrogen might scavenge toxic ROS that are believed to play an important role in diverse skin diseases. A lower incidence found for ROS-mediated skin diseases in individuals with darker skin [5] could be due to beneficial effects of melanin-driven hydrogen. It seems that the production and pooling of molecular hydrogen by eumelanin should be considered as a novel element of skin defense system that interact with toxic agents to eliminate their deleterious effect. "
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    ABSTRACT: Molecular hydrogen (H2, dihydrogen) has been recognized as a unique cell protectant. Dihydrogen protects tissues against oxidative injuries by selectively reducing reactive oxygen species (ROS). It seems that melanin, natural pigment of skin and hair, might produce endogenous hydrogen. The protective role of skin melanin (eumelanin) could be due to its capacity for molecular hydrogen production. An effective pooling of dihydrogen by eumelanin should be considered as a novel element of skin defense system against oxidative stress-related disorders. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Medical Hypotheses 04/2015; 85(2). DOI:10.1016/j.mehy.2015.04.014 · 1.07 Impact Factor
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    • "The current preliminary screening of the medicinal properties of the extracts was focused on their ability to protect human cells and skin explants against ultraviolet B (UVB)induced damage. Although low levels of UVR have several beneficial effects, such as the formation of melanin and vitamin D3 (Brenner and Hearing, 2008; Reichrath and Rass, 2014), high dosage of radiation may hamper normal skin function. "
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    ABSTRACT: Medicinal plants have been traditionally used to address and treat a variety of pathologies including skin diseases. Six medicinal herbs, grown in Jordan, were evaluated for their ability to reduce UVB-induced skin damage, a major contributor to erythema, skin aging and cancer formation. Ethanolic, acetonic and aqueous extracts were prepared from the stems and leaves of the plants. Human keratinocyte HaCaT cells were incubated without or with the different extracts for 24 hr, exposed to UVB irradiation and taken for viability and apoptosis assessment by resazurin and caspase-3 determinations, respectively. Selected extracts were further evaluated by the DCFDA method (ROS production measurement) and on pig and human skin explants. From the 18 extracts screened, only Citrillus colocynthis extracts showed significant protective properties against UVB-induced apoptosis. UV protective activity was found in the water extracts of both stem and leaf preparations of the plant. UV protection was independent of ROS production. Importantly, Citrillus colocynthis extracts were also able to attenuate the photodamage in both ex vivo skin models used in this study. Therefore, the current preliminary screening indicates that Jordanian medicinal plants might be valuable sources for novel skin care compounds. This study also suggests that Citrillus colocynthis extracts exhibit significant photoprotection properties and may attenuate the deleterious effects of UVB radiation.
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