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Proceedings. Biological Sciences Aug 2015Colour, derived primarily from melanin and/or carotenoid pigments, is integral to many aspects of behaviour in living vertebrates, including social signalling, sexual... (Review)
Review
Colour, derived primarily from melanin and/or carotenoid pigments, is integral to many aspects of behaviour in living vertebrates, including social signalling, sexual display and crypsis. Thus, identifying biochromes in extinct animals can shed light on the acquisition and evolution of these biological traits. Both eumelanin and melanin-containing cellular organelles (melanosomes) are preserved in fossils, but recognizing traces of ancient melanin-based coloration is fraught with interpretative ambiguity, especially when observations are based on morphological evidence alone. Assigning microbodies (or, more often reported, their 'mouldic impressions') as melanosome traces without adequately excluding a bacterial origin is also problematic because microbes are pervasive and intimately involved in organismal degradation. Additionally, some forms synthesize melanin. In this review, we survey both vertebrate and microbial melanization, and explore the conflicts influencing assessment of microbodies preserved in association with ancient animal soft tissues. We discuss the types of data used to interpret fossil melanosomes and evaluate whether these are sufficient for definitive diagnosis. Finally, we outline an integrated morphological and geochemical approach for detecting endogenous pigment remains and associated microstructures in multimillion-year-old fossils.
Topics: Animals; Biological Evolution; Fossils; Melanins; Melanosomes; Microbodies; Pigmentation; Vertebrates
PubMed: 26290071
DOI: 10.1098/rspb.2015.0614 -
International Journal of Molecular... Apr 2016The regulation of melanin production is important for managing skin darkness and hyperpigmentary disorders. Numerous anti-melanogenic agents that target tyrosinase... (Review)
Review
The regulation of melanin production is important for managing skin darkness and hyperpigmentary disorders. Numerous anti-melanogenic agents that target tyrosinase activity/stability, melanosome maturation/transfer, or melanogenesis-related signaling pathways have been developed. As a rate-limiting enzyme in melanogenesis, tyrosinase has been the most attractive target, but tyrosinase-targeted treatments still pose serious potential risks, indicating the necessity of developing lower-risk anti-melanogenic agents. Sugars are ubiquitous natural compounds found in humans and other organisms. Here, we review the recent advances in research on the roles of sugars and sugar-related agents in melanogenesis and in the development of sugar-based anti-melanogenic agents. The proposed mechanisms of action of these agents include: (a) (natural sugars) disturbing proper melanosome maturation by inducing osmotic stress and inhibiting the PI3 kinase pathway and (b) (sugar derivatives) inhibiting tyrosinase maturation by blocking N-glycosylation. Finally, we propose an alternative strategy for developing anti-melanogenic sugars that theoretically reduce melanosomal pH by inhibiting a sucrose transporter and reduce tyrosinase activity by inhibiting copper incorporation into an active site. These studies provide evidence of the utility of sugar-based anti-melanogenic agents in managing skin darkness and curing pigmentary disorders and suggest a future direction for the development of physiologically favorable anti-melanogenic agents.
Topics: Animals; Antigens, Neoplasm; Carbohydrates; Humans; Melanins; Membrane Transport Proteins; Skin Pigmentation
PubMed: 27092497
DOI: 10.3390/ijms17040583 -
Molecules (Basel, Switzerland) Aug 2017Melanin, the compound primarily responsible in humans for hair, eye and skin pigmentation, is produced by melanocytes through a complicated process called melanogenesis... (Review)
Review
Melanin, the compound primarily responsible in humans for hair, eye and skin pigmentation, is produced by melanocytes through a complicated process called melanogenesis that is catalyzed by tyrosinase and other tyrosinase-related proteins. The abnormal loss of melanin causes dermatological problems such as vitiligo. Hence the regulation of melanogenesis and tyrosinase activity is very important for treating hypopigmentary disorders. Many melanogenesis stimulators have been discovered during the past decade. This article reviews recent advances in research on extracts and active ingredients of plants, synthesized compounds with stimulating effect on melanin synthesis and tyrosinase activity, as well as their influence on the expression of related proteins and possible signaling pathways for the design and development of novel anti-vitiligo agents.
Topics: Animals; Enzyme Activators; Humans; Melanins; Monophenol Monooxygenase; Plant Extracts; Vitiligo
PubMed: 28777326
DOI: 10.3390/molecules22081303 -
Frontiers of Neurology and Neuroscience 2021During the last decade, optogenetic-based circuit mapping has become one of the most common approaches to systems neuroscience, and amassing studies have expanded our... (Review)
Review
During the last decade, optogenetic-based circuit mapping has become one of the most common approaches to systems neuroscience, and amassing studies have expanded our understanding of brain structures causally involved in the regulation of sleep-wake cycles. Recent imaging technologies enable the functional mapping of cellular activity, from population down to single-cell resolution, across a broad repertoire of behaviors and physiological processes, including sleep-wake states. This chapter summarizes experimental evidence implicating hypocretins/orexins, melanin-concentrating hormone, and inhibitory neurons from the lateral hypothalamus (LH) in forming an intricate network involved in regulating sleep and metabolism, including feeding behaviors. It further confirms the dual sleep-metabolic functions of LH cells, and sheds light on a possible mechanism underlying brain plasticity during sleep and metabolic disorders.
Topics: Animals; Feeding Behavior; Humans; Hypothalamic Area, Lateral; Hypothalamic Hormones; Melanins; Nerve Net; Neurons; Orexins; Pituitary Hormones; Sleep
PubMed: 34052816
DOI: 10.1159/000514966 -
Sheng Wu Gong Cheng Xue Bao = Chinese... Sep 2019Melanogenesis is a biosynthetic pathway to produce melanin pigment in melanocyte, involving a series of intricate enzymatic and chemical catalyzed reactions.... (Review)
Review
Melanogenesis is a biosynthetic pathway to produce melanin pigment in melanocyte, involving a series of intricate enzymatic and chemical catalyzed reactions. Melanogenesis involves five signaling pathways that converge on microphthalmia-associated transcription factor. In addition, many cytokines, involved in the regulation of melanogenesis, play an important role in the development, proliferation, differentiation and migration of melanocytes. Polyoxometalate can be used as a potential inhibitor of melanin production. Hence, this paper reviews the signaling pathways of melanogenesis and their regulatory mechanism, to apply polyoxometalates in the melanin production pathway, and briefly introduces the regulatory factors of related pathways.
Topics: Cell Differentiation; Melanins; Melanocytes; Microphthalmia-Associated Transcription Factor; Signal Transduction
PubMed: 31559745
DOI: 10.13345/j.cjb.190084 -
FEBS Open Bio Apr 2019Melanin-producing and are highly invasive and can suppress or escape the immune system of the host. Since non-melanin-producing strains do not affect the immune...
Melanin-producing and are highly invasive and can suppress or escape the immune system of the host. Since non-melanin-producing strains do not affect the immune system, melanin may play a role in immune system suppression. Artificial melanin synthesized using conventional methods is insoluble, making structural and functional analysis of this chemical difficult. In this study, we describe a melanin solubilization method based on polymerization of homogentisic acid (solubilizing component) and an equivalent amount of L-DOPA in the presence of laccase. In addition, we investigated the effect of melanin on the immune system. Homogentisic acid and L-DOPA mixed melanin (HALD), the synthetic solubilized melanin, did not exert a cytotoxic effect on mouse macrophages. HALD suppressed cytokine and reactive oxygen species production by macrophages when they were stimulated by fungal components. HALD also suppressed the phagocytosis of fungal components by macrophages. These results suggest that HALD can suppress the function of macrophages without causing cytotoxicity.
Topics: Animals; Biochemistry; Homogentisic Acid; Laccase; Levodopa; Macrophages; Male; Melanins; Mice; Mice, Inbred C57BL; Polymerization; Solubility
PubMed: 30984552
DOI: 10.1002/2211-5463.12615 -
ELife Dec 2021The brilliant iridescent plumage of birds creates some of the most stunning color displays known in the natural world. Iridescent plumage colors are produced by...
The brilliant iridescent plumage of birds creates some of the most stunning color displays known in the natural world. Iridescent plumage colors are produced by nanostructures in feathers and have evolved in diverse birds. The building blocks of these structures-melanosomes (melanin-filled organelles)-come in a variety of forms, yet how these different forms contribute to color production across birds remains unclear. Here, we leverage evolutionary analyses, optical simulations, and reflectance spectrophotometry to uncover general principles that govern the production of brilliant iridescence. We find that a key feature that unites all melanosome forms in brilliant iridescent structures is thin melanin layers. Birds have achieved this in multiple ways: by decreasing the size of the melanosome directly, by hollowing out the interior, or by flattening the melanosome into a platelet. The evolution of thin melanin layers unlocks color-producing possibilities, more than doubling the range of colors that can be produced with a thick melanin layer and simultaneously increasing brightness. We discuss the implications of these findings for the evolution of iridescent structures in birds and propose two evolutionary paths to brilliant iridescence.
Topics: Animals; Biological Evolution; Birds; Color; Feathers; Iridescence; Melanins; Melanosomes; Microscopy, Electron, Transmission
PubMed: 34930526
DOI: 10.7554/eLife.71179 -
Journal of the American Chemical Society Mar 2021Melanin is a ubiquitous natural pigment found in a diverse array of organisms. Allomelanin is a class of nitrogen-free melanin often found in fungi. Herein, we find...
Melanin is a ubiquitous natural pigment found in a diverse array of organisms. Allomelanin is a class of nitrogen-free melanin often found in fungi. Herein, we find artificial allomelanin analogues exhibit high intrinsic microporosity and describe an approach for further increasing and tuning that porosity. Notably, the synthetic method involves an oxidative polymerization of 1,8-DHN in water, negating the need for multiple complex templating steps and avoiding expensive or complex chemical precursors. The well-defined morphologies of these nanomaterials were elucidated by a combination of electron microscopy and scattering methods, yielding to high-resolution 3D reconstruction based on small-angle X-ray scattering (SAXS) results. Synthetic allomelanin nanoparticles exhibit high BET areas, up to 860 m/g, and are capable of ammonia capture up to 17.0 mmol/g at 1 bar. In addition, these nanomaterials can adsorb nerve agent simulants in solution and as a coating on fabrics with high breathability where they prevent breakthrough. We also confirmed that naturally derived fungal melanin can adsorb nerve gas simulants in solution efficiently despite lower porosity than synthetic analogues. Our approach inspires further analysis of yet to be discovered biological materials of this class where melanins with intrinsic microporosity may be linked to evolutionary advantages in relevant organisms and may in turn inspire the design of new high surface area materials.
Topics: Adsorption; Biopolymers; Fungi; Melanins; Nanoparticles; Naphthols; Paraoxon; Porosity; Scattering, Small Angle; X-Ray Diffraction
PubMed: 33673734
DOI: 10.1021/jacs.1c00748 -
International Journal of Molecular... Apr 2016Melanins are the ubiquitous pigments distributed in nature. They are one of the main pigments responsible for colors in living cells. Birds are among the most diverse... (Review)
Review
Melanins are the ubiquitous pigments distributed in nature. They are one of the main pigments responsible for colors in living cells. Birds are among the most diverse animals regarding melanin-based coloration, especially in the plumage, although they also pigment bare parts of the integument. This review is devoted to the main characteristics of bird melanins, including updated views of the formation and nature of melanin granules, whose interest has been raised in the last years for inferring the color of extinct birds and non-avian theropod dinosaurs using resistant fossil feathers. The molecular structure of the two main types of melanin, eumelanin and pheomelanin, and the environmental and genetic factors that regulate avian melanogenesis are also presented, establishing the main relationship between them. Finally, the special functions of melanin in bird feathers are also discussed, emphasizing the aspects more closely related to these animals, such as honest signaling, and the factors that may drive the evolution of pheomelanin and pheomelanin-based color traits, an issue for which birds have been pioneer study models.
Topics: Amino Acid Sequence; Animals; Biological Evolution; Birds; Body Temperature Regulation; Environment; Gene Expression Regulation; Melanins; Signal Transduction
PubMed: 27070583
DOI: 10.3390/ijms17040520 -
Journal of Neuroscience Research Jan 2019Albinism, typically characterized by decreased melanin synthesis, is associated with significant visual deficits owing to developmental changes during neurosensory... (Review)
Review
Albinism, typically characterized by decreased melanin synthesis, is associated with significant visual deficits owing to developmental changes during neurosensory retina development. All albinism is caused by genetic mutations in a group of diverse genes including enzymes, transporters, G-protein coupled receptor. Interestingly, these genes are not expressed in the neurosensory retina. Further, regardless of cause of albinism, all forms of albinism have the same retinal pathology, the extent of which is variable. In this review, we explore the possibility that this similarity in retinal phenotype is because all forms of albinism funnel through the same final common pathway. There are currently seven known genes linked to the seven forms of ocular cutaneous albinism. These types of albinism are the most common, and result in changes to all pigmented tissues (hair, skin, eyes). We will discuss the incidence and mechanism, where known, to develop a picture as to how the mutations cause albinism. Next, we will examine the one form of albinism which causes tissue-specific pathology, ocular albinism, where the eye exhibits the retinal albinism phenotype despite near normal melanin synthesis. We will discuss a potential way to treat the disease and restore normal retinal development. Finally, we will briefly discuss the possibility that this same pathway may intersect with the most common cause of permanent vision loss in the elderly.
Topics: Albinism, Ocular; Eye Proteins; Humans; Melanins; Membrane Glycoproteins; Mutation; Pigmentation; Retina; Retinal Pigment Epithelium
PubMed: 29761529
DOI: 10.1002/jnr.24246