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Kazumasa Wakamatsu - One of the best experts on this subject based on the ideXlab platform.

  • Redness Variation in the Eurasian Scops-Owl Otus scops is Due to Pheomelanin But is Not Associated with Variation in the Melanocortin-1 Receptor Gene (MC1R)
    Ardeola, 2019
    Co-Authors: Jesús M. Avilés, Kazumasa Wakamatsu, Alexandre Roulin, Ángel Cruz-miralles, Anne-lyse Ducrest, Céline Simon, Deseada Parejo
    Abstract:

    Melanin-based colorations in birds constitute a paradigm for the study of the molecular basis of phenotypic variation. Variation in the melanocortin-1 receptor (MCR1) gene, a key regulator of melanin synthesis in feather melanocytes, can lead to changes in the production of melanin and hence in feather colour. Here we investigate the proximate mechanisms behind colour plumage polymorphism in the Eurasian Scops-owl Otus scops, a species showing pronounced variation in the degree of redness. Although eumelanin pigment was three times more abundant than Pheomelanin pigments, the degree of plumage redness was more strongly associated with the amount of Pheomelanin than eumelanin pigments. We detected only one synonymous substitution and one non-synonymous substitution in MC1R which were, however, not associated with variation in plumage coloration. Redness variation in Eurasian Scops-Owls is primarily due to variation in Pheomelanin, and to genes or regulatory elements other than MCR1. —Aviles, J.M., Cruz-Miralles, A., Ducrest, A.-L., Simon, C., Roulin, A., Wakamatsu, K. & Parejo, D. (2020). Redness variation in the Eurasian Scops-owl Otus scops is due to Pheomelanin but is not associated with variation in the melanocortin-1 receptor gene (mc1r). Ardeola, 67: 3-13.

  • Males with More Pheomelanin Have a Lower Oxidative Balance in Asian Barn Swallows (Hirundo rustica gutturalis)
    Zoological science, 2018
    Co-Authors: Emi Arai, Kazumasa Wakamatsu, Masaru Hasegawa, Shosuke Ito
    Abstract:

    Pheomelanin-based plumage pigmentation has been suggested to be an honest signal of individual quality to conspecifics. It has been hypothesized that oxidative stress is an important agent linking pheomelanic pigmentation to individual quality. Using the Asian barn swallow Hirundo rustica gutturalis, a wild passerine, we tested whether the Pheomelanin pigmentation in the red throat patch of adult males, a sexually selected trait, is associated with the ratio between reduced and oxidized glutathione (RGSH/GSSG) as an indicator of current oxidative balance during the early breeding season. We found that males with a higher Pheomelanin concentration in their throat feathers had a significantly lower RGSH/GSSG ratio (i.e., higher oxidative stress), but exhibited a better body condition, measured as residual body mass on body size, compared to males with a lower Pheomelanin concentration. The total GSH level was not significantly related to the Pheomelanin concentration. These findings suggest a negative association between the red Pheomelanin pigmentation and oxidative balance during mating and reproductive efforts, which might be mitigated by high-quality males. Further research is needed to understand its actual damage and mitigation mechanism.

  • Acid hydrolysis reveals a low but constant level of Pheomelanin in human black to brown hair.
    Pigment cell & melanoma research, 2017
    Co-Authors: Shosuke Ito, Yukiko Nakanishi, Shiho Miyake, Shoji Maruyama, Itaru Suzuki, Stephane Commo, Kazumasa Wakamatsu
    Abstract:

    We previously reported a constant ratio of the benzothiazole Pheomelanin marker thiazole-2,4,5-tricarboxylic acid (TTCA) to the eumelanin marker pyrrole-2,3,5-tricarboxylic acid (PTCA) in eumelanic, black human hair. A constant level (20%-25%) of benzothiazole-type Pheomelanin was recently demonstrated in human skin with varying concentrations of melanin. Therefore, in this study, we aimed to investigate the origin of Pheomelanin markers in black to brown human hair by developing a method to remove protein components from hair by heating with 6 M HCl at 110°C for 16 hr. For comparison, synthetic melanins were prepared by oxidizing mixtures of varying ratios of dopa and cysteine with tyrosinase. Hair melanins and synthetic melanins were subjected to acid hydrolysis followed by alkaline H2 O2 oxidation. The results show that the hydrolysis leads to decarboxylation of the 5,6-di-hydroxyindole-2-carboxylic acid moiety in eumelanin and the benzothiazole moiety in Pheomelanin and that eumelanic human hair contains 11%-17% benzothiazole-type Pheomelanin.

  • Photodegradation of Eumelanin and Pheomelanin and Its Pathophysiological Implications
    Photochemistry and photobiology, 2017
    Co-Authors: Shosuke Ito, Kazumasa Wakamatsu, Tadeusz Sarna
    Abstract:

    Eumelanin is photoprotective for pigmented tissues while Pheomelanin is phototoxic. In this review, we summarize current understanding of how eumelanin and Pheomelanin structures are modified by ultraviolet A (UVA) and also by visible light and how reactive oxygen species participate in those processes. Alkaline hydrogen peroxide oxidation was employed to characterize eumelanin and benzothiazole-type Pheomelanin, giving pyrrole-2,3,5-tricarboxylic acid (PTCA) and thiazole-2,4,5-tricarboxylic acid (TTCA), respectively. Reductive hydrolysis with hydroiodic acid gives 4-amino-3-hydroxyphenylalanine (4-AHP) from the benzothiazine moiety of Pheomelanin. The results show that the photoaging of eumelanin gives rise to free PTCA (produced by peroxidation in situ) and pyrrole-2,3,4,5-tetracarboxylic acid (PTeCA, produced by cross-linking). The TTCA/4-AHP ratio increases with photoaging, indicating the conversion of benzothiazine to the benzothiazole moiety. Analysis of those markers and their ratios show that both eumelanin and Pheomelanin in human retinal pigment epithelium melanosomes undergo extensive structural modifications due to their lifelong exposure to blue light. Using synthetic melanins, we also found that singlet oxygen, in addition to superoxide anions, is photogenerated and quenched upon UVA irradiation. The (patho)physiological significance of those findings is discussed in relation to the tanning process, to melanomagenesis in the skin and to age-related macular degeneration in the eyes.

  • chemical analysis of constitutive pigmentation of human epidermis reveals constant eumelanin to Pheomelanin ratio
    Pigment Cell & Melanoma Research, 2015
    Co-Authors: Sandra Del Bino, Yukiko Nakanishi, Kazumasa Wakamatsu, Philippe Bastien, Francoise Bernerd
    Abstract:

    Summary The skin constitutive pigmentation is given by the amount of melanin pigment, its relative composition (eu/Pheomelanin) and distribution within the epidermis, and is largely responsible for the sensitivity to UV exposure. Nevertheless, a precise knowledge of melanins in human skin is lacking. We characterized the melanin content of human breast skin samples with variable pigmentations rigorously classified through the Individual Typology Angle (ITA) by image analysis, spectrophotometry after solubilization with Soluene-350 and high-performance liquid chromatography (HPLC) after chemical degradation. ITA and total melanin content were found correlated, ITA and PTCA (degradation product of DHICA melanin), and TTCA (degradation product of benzothiazole-type Pheomelanin) as well but not 4-AHP (degradation product of benzothiazine-type Pheomelanin). Results revealed that human epidermis comprises approximately 74% of eumelanin and 26% Pheomelanin, regardless of the degree of pigmentation. They also confirm the low content of photoprotective eumelanin among lighter skins thereby explaining the higher sensitivity toward UV exposure.

Shosuke Ito - One of the best experts on this subject based on the ideXlab platform.

  • Males with More Pheomelanin Have a Lower Oxidative Balance in Asian Barn Swallows (Hirundo rustica gutturalis)
    Zoological science, 2018
    Co-Authors: Emi Arai, Kazumasa Wakamatsu, Masaru Hasegawa, Shosuke Ito
    Abstract:

    Pheomelanin-based plumage pigmentation has been suggested to be an honest signal of individual quality to conspecifics. It has been hypothesized that oxidative stress is an important agent linking pheomelanic pigmentation to individual quality. Using the Asian barn swallow Hirundo rustica gutturalis, a wild passerine, we tested whether the Pheomelanin pigmentation in the red throat patch of adult males, a sexually selected trait, is associated with the ratio between reduced and oxidized glutathione (RGSH/GSSG) as an indicator of current oxidative balance during the early breeding season. We found that males with a higher Pheomelanin concentration in their throat feathers had a significantly lower RGSH/GSSG ratio (i.e., higher oxidative stress), but exhibited a better body condition, measured as residual body mass on body size, compared to males with a lower Pheomelanin concentration. The total GSH level was not significantly related to the Pheomelanin concentration. These findings suggest a negative association between the red Pheomelanin pigmentation and oxidative balance during mating and reproductive efforts, which might be mitigated by high-quality males. Further research is needed to understand its actual damage and mitigation mechanism.

  • Acid hydrolysis reveals a low but constant level of Pheomelanin in human black to brown hair.
    Pigment cell & melanoma research, 2017
    Co-Authors: Shosuke Ito, Yukiko Nakanishi, Shiho Miyake, Shoji Maruyama, Itaru Suzuki, Stephane Commo, Kazumasa Wakamatsu
    Abstract:

    We previously reported a constant ratio of the benzothiazole Pheomelanin marker thiazole-2,4,5-tricarboxylic acid (TTCA) to the eumelanin marker pyrrole-2,3,5-tricarboxylic acid (PTCA) in eumelanic, black human hair. A constant level (20%-25%) of benzothiazole-type Pheomelanin was recently demonstrated in human skin with varying concentrations of melanin. Therefore, in this study, we aimed to investigate the origin of Pheomelanin markers in black to brown human hair by developing a method to remove protein components from hair by heating with 6 M HCl at 110°C for 16 hr. For comparison, synthetic melanins were prepared by oxidizing mixtures of varying ratios of dopa and cysteine with tyrosinase. Hair melanins and synthetic melanins were subjected to acid hydrolysis followed by alkaline H2 O2 oxidation. The results show that the hydrolysis leads to decarboxylation of the 5,6-di-hydroxyindole-2-carboxylic acid moiety in eumelanin and the benzothiazole moiety in Pheomelanin and that eumelanic human hair contains 11%-17% benzothiazole-type Pheomelanin.

  • Photodegradation of Eumelanin and Pheomelanin and Its Pathophysiological Implications
    Photochemistry and photobiology, 2017
    Co-Authors: Shosuke Ito, Kazumasa Wakamatsu, Tadeusz Sarna
    Abstract:

    Eumelanin is photoprotective for pigmented tissues while Pheomelanin is phototoxic. In this review, we summarize current understanding of how eumelanin and Pheomelanin structures are modified by ultraviolet A (UVA) and also by visible light and how reactive oxygen species participate in those processes. Alkaline hydrogen peroxide oxidation was employed to characterize eumelanin and benzothiazole-type Pheomelanin, giving pyrrole-2,3,5-tricarboxylic acid (PTCA) and thiazole-2,4,5-tricarboxylic acid (TTCA), respectively. Reductive hydrolysis with hydroiodic acid gives 4-amino-3-hydroxyphenylalanine (4-AHP) from the benzothiazine moiety of Pheomelanin. The results show that the photoaging of eumelanin gives rise to free PTCA (produced by peroxidation in situ) and pyrrole-2,3,4,5-tetracarboxylic acid (PTeCA, produced by cross-linking). The TTCA/4-AHP ratio increases with photoaging, indicating the conversion of benzothiazine to the benzothiazole moiety. Analysis of those markers and their ratios show that both eumelanin and Pheomelanin in human retinal pigment epithelium melanosomes undergo extensive structural modifications due to their lifelong exposure to blue light. Using synthetic melanins, we also found that singlet oxygen, in addition to superoxide anions, is photogenerated and quenched upon UVA irradiation. The (patho)physiological significance of those findings is discussed in relation to the tanning process, to melanomagenesis in the skin and to age-related macular degeneration in the eyes.

  • the mouse ruby eye 2d ru2d hps5ru2 d allele inhibits eumelanin but not Pheomelanin synthesis
    Pigment Cell & Melanoma Research, 2013
    Co-Authors: Tomohisa Hirobe, Shosuke Ito, Kazumasa Wakamatsu
    Abstract:

    The novel mutation named ru2(d) /Hps5(ru2-d) , characterized by light-colored coats and ruby-eyes, prohibits differentiation of melanocytes by inhibiting tyrosinase (Tyr) activity, expression of Tyr, Tyr-related protein 1 (Tyrp1), Tyrp2, and Kit. However, it is not known whether the ru2(d) allele affects Pheomelanin synthesis in recessive yellow (e/Mc1r(e) ) or in pheomelanic stage in agouti (A) mice. In this study, effects of the ru2(d) allele on Pheomelanin synthesis were investigated by chemical analysis of melanin present in dorsal hairs of 5-week-old mice from F2 generation between C57BL/10JHir (B10)-co-isogenic ruby-eye 2(d) and B10-congenic recessive yellow or agouti. Eumelanin content was decreased in ruby-eye 2(d) and ruby-eye 2(d) agouti mice, whereas Pheomelanin content in ruby-eye 2(d) recessive yellow and ruby-eye 2(d) agouti mice did not differ from the corresponding Ru2(d) /- mice, suggesting that the ru2(d) allele inhibits eumelanin but not Pheomelanin synthesis.

  • The mouse ruby‐eye 2d (ru2d/Hps5ru2‐d) allele inhibits eumelanin but not Pheomelanin synthesis
    Pigment cell & melanoma research, 2013
    Co-Authors: Tomohisa Hirobe, Shosuke Ito, Kazumasa Wakamatsu
    Abstract:

    The novel mutation named ru2(d) /Hps5(ru2-d) , characterized by light-colored coats and ruby-eyes, prohibits differentiation of melanocytes by inhibiting tyrosinase (Tyr) activity, expression of Tyr, Tyr-related protein 1 (Tyrp1), Tyrp2, and Kit. However, it is not known whether the ru2(d) allele affects Pheomelanin synthesis in recessive yellow (e/Mc1r(e) ) or in pheomelanic stage in agouti (A) mice. In this study, effects of the ru2(d) allele on Pheomelanin synthesis were investigated by chemical analysis of melanin present in dorsal hairs of 5-week-old mice from F2 generation between C57BL/10JHir (B10)-co-isogenic ruby-eye 2(d) and B10-congenic recessive yellow or agouti. Eumelanin content was decreased in ruby-eye 2(d) and ruby-eye 2(d) agouti mice, whereas Pheomelanin content in ruby-eye 2(d) recessive yellow and ruby-eye 2(d) agouti mice did not differ from the corresponding Ru2(d) /- mice, suggesting that the ru2(d) allele inhibits eumelanin but not Pheomelanin synthesis.

Ismael Galvan - One of the best experts on this subject based on the ideXlab platform.

  • impairment of mixed melanin based pigmentation in parrots
    The Journal of Experimental Biology, 2020
    Co-Authors: Ana Carolina De Oliveira Neves, Ismael Galvan, Dirk Van Den Abeele
    Abstract:

    ABSTRACT Parrots and allies (Order Psittaciformes) have evolved an exclusive capacity to synthesize polyene pigments called psittacofulvins at feather follicles, which allows them to produce a striking diversity of pigmentation phenotypes. Melanins are polymers constituting the most abundant pigments in animals, and the sulphurated form (Pheomelanin) produces colors that are similar to those produced by psittacofulvins. However, the differential contribution of these pigments to psittaciform phenotypic diversity has not been investigated. Given the color redundancy, and physiological limitations associated with Pheomelanin synthesis, we hypothesized that the latter would be avoided by psittaciform birds. Here, we tested this using Raman spectroscopy to identify pigments in feathers exhibiting colors suspected of being produced by Pheomelanin (i.e. dull red, yellow, greyish-brown and greenish-brown) in 26 species from the three main lineages of Psittaciformes. We detected the non-sulphurated melanin form (eumelanin) in black, grey and brown plumage patches, and psittacofulvins in red, yellow and green patches, but there was no evidence of Pheomelanin. As natural melanins are assumed to be composed of eumelanin and Pheomelanin in varying ratios, our results represent the first report of impairment of mixed melanin-based pigmentation in animals. Given that psittaciforms also avoid the uptake of circulating carotenoid pigments, these birds seem to have evolved a capacity to avoid functional redundancy between pigments, likely by regulating follicular gene expression. Our study provides the first vibrational characterization of different psittacofulvin-based colors and thus helps to determine the relative polyene chain length in these pigments, which is related to their antireductant protection activity.

  • Differential influence of Slc7a11 expression and body condition on Pheomelanin‐based pigmentation in two Eurasian nuthatch Sitta europaea populations with different predation risk
    Journal of Avian Biology, 2020
    Co-Authors: Ismael Galvan, Juan José Sanz
    Abstract:

    The expression of the gene Slc7a11 promotes the antioxidant capacity of cells by providing them with cysteine that can be used for the synthesis of glutathione (GSH), the most important intracellular antioxidant. In melanocytes, intracellular cysteine can also enter melanosomes and get incorporated in the Pheomelanin pigment synthesis pathway, thus decreasing cysteine availability for GSH synthesis and potentially creating chronic oxidative stress. We thus hypothesized that a mechanism limiting the use of intramelanocytic cysteine for Pheomelanin synthesis in environmental conditions generating oxidative stress may be physiologically advantageous and favored by natural selection. Here we searched for evidence of such a mechanism by comparing the influence of melanocytic Slc7a11 expression on Pheomelanin‐based pigmentation in developing Eurasian nuthatch Sitta europaea nestlings from two populations differing in predation risk, a natural source of oxidative stress. Pheomelanin synthesis and pigmentation tended to increase with Slc7a11 expression in the low‐risk population as expected from the activity of this gene, but decreased with Slc7a11 expression in the high‐risk population. The same was not observed in the expression of five other genes influencing Pheomelanin synthesis without affecting cysteine availability in melanocytes. The influence of body condition on the intensity of Pheomelanin‐based pigmentation also differed between populations, being positive in the low‐risk population and negative in the high‐risk population. The resulting pigmentation of birds was more intense in the high‐risk population. These findings suggest that birds perceiving high predation risk may limit the use of cysteine for Pheomelanin synthesis, which becomes independent of Slc7a11 expression. Some birds may have thus evolved the ability to adjust their pigmentation phenotype to environmental stress.

  • differential influence of slc7a11 expression and body condition on Pheomelanin based pigmentation in two eurasian nuthatch sitta europaea populations with different predation risk
    Journal of Avian Biology, 2020
    Co-Authors: Ismael Galvan, Juan José Sanz
    Abstract:

    The expression of the gene Slc7a11 promotes the antioxidant capacity of cells by providing them with cysteine that can be used for the synthesis of glutathione (GSH), the most important intracellular antioxidant. In melanocytes, intracellular cysteine can also enter melanosomes and get incorporated in the Pheomelanin pigment synthesis pathway, thus decreasing cysteine availability for GSH synthesis and potentially creating chronic oxidative stress. We thus hypothesized that a mechanism limiting the use of intramelanocytic cysteine for Pheomelanin synthesis in environmental conditions generating oxidative stress may be physiologically advantageous and favored by natural selection. Here we searched for evidence of such a mechanism by comparing the influence of melanocytic Slc7a11 expression on Pheomelanin‐based pigmentation in developing Eurasian nuthatch Sitta europaea nestlings from two populations differing in predation risk, a natural source of oxidative stress. Pheomelanin synthesis and pigmentation tended to increase with Slc7a11 expression in the low‐risk population as expected from the activity of this gene, but decreased with Slc7a11 expression in the high‐risk population. The same was not observed in the expression of five other genes influencing Pheomelanin synthesis without affecting cysteine availability in melanocytes. The influence of body condition on the intensity of Pheomelanin‐based pigmentation also differed between populations, being positive in the low‐risk population and negative in the high‐risk population. The resulting pigmentation of birds was more intense in the high‐risk population. These findings suggest that birds perceiving high predation risk may limit the use of cysteine for Pheomelanin synthesis, which becomes independent of Slc7a11 expression. Some birds may have thus evolved the ability to adjust their pigmentation phenotype to environmental stress.

  • juvenile Pheomelanin based plumage coloration has evolved more frequently in carnivorous species
    Ibis, 2020
    Co-Authors: Sol Rodriguezmartinez, Ismael Galvan
    Abstract:

    Distinctive Pheomelanin‐based plumage coloration in juvenile birds has been proposed as a signal of immaturity to avoid aggression by older conspecifics, but recent findings suggest a detoxifying strategy. Pheomelanin synthesis implies the consumption of cysteine, a semi‐essential amino acid that is necessary for the synthesis of the antioxidant glutathione (GSH) but that may be toxic if in excess in the diet. As the nestling stage probably represents a low‐stress period with limited requirement for GSH protection, the synthesis of Pheomelanin in developing birds may help to maintain cysteine homeostasis, particularly in species with a high content of protein in the diet (i.e. carnivores). Here we confirm this hypothesis showing that, among 53 species of Western Palaearctic birds, juvenile Pheomelanin‐based coloration has evolved more frequently in strictly carnivorous species than in species with other diets.

  • Pheomelanin-based coloration is related to individual quality and oxidative stress in blue petrels
    Evolutionary Ecology, 2019
    Co-Authors: Sarah Leclaire, Ismael Galvan, Samuel Perret, Francesco Bonadonna
    Abstract:

    In several species, the rusty color of hair or feathers is due to Pheomelanin pigments, whose adaptive function is unknown. Pheomelanin may be costly because it is phototoxic and its production consumes a key intracellular antioxidant. Pheomelanin-based traits are, however, positively associated with individual quality in several bird species, where they have thus been suggested to have evolved through sexual selection. Here we investigated the signaling potential of the Pheomelanin-based coloration of the crown feathers in the blue petrel. Although this pelagic seabird is nocturnal at the breeding colony and breeds within deep burrows, it might use visual communication when settled on the water during daytime. We tested the correlation between crown color and several fitness-related traits, and we found that higher-quality females displayed less-orange crown than poorer-quality females. This result is inconsistent with an adaptive function of Pheomelanin-based coloration in inter-, or intra-, sexual selection in females. We suggest that it might, however, be in line with a signaling function of eumelanin-based coloration, if inter-individual variations in orange coloration are mainly due to eumelanin-to-Pheomelanin ratio, rather than to Pheomelanin quantity. In contrast to females, we did not find strong evidence for associations between melanin-based coloration and individual quality in males, suggesting sex-specific selective pressures on melanin-based traits in this species.

John D Simon - One of the best experts on this subject based on the ideXlab platform.

  • The Ultraviolet Absorption Coefficient of Melanosomes Decreases with Increasing Pheomelanin Content
    The journal of physical chemistry. B, 2010
    Co-Authors: Dana N Peles, John D Simon
    Abstract:

    Uveal melanosomes from the iridal stroma contain both eumelanin and Pheomelanin, the ratio of which varies with iris color. Herein, we report the absorption coefficient at lambda = 244 nm for individual human iridal stroma melanosomes from dark brown and blue-green irides. The melanosomes are nearly identical in size, but differ in the relative concentration composition, ranging from a eumelanin/Pheomelanin ratio of 14.8:1 (dark brown) to 1.3:1 (blue-green or hazel). The absorption coefficient of the melanosome decreases as its Pheomelanin content increases. The origin of this decrease is attributed to a corresponding decrease in the number of UV-absorbing chromophores, reflecting the different molecular volumes of the monomeric building blocks of the two pigments. In agreement with reported data on synthetic pigments, the absorption coefficient of Pheomelanin is found to be slightly larger than that for eumelanin at lambda = 244 nm (by a factor of 1.2). On the basis of the reported optical properties of synthetic models, this result suggests that the absorption of Pheomelanin is less than eumelanin at wavelengths of biological relevance ( approximately 315-400 nm).

  • the ultraviolet absorption coefficient of melanosomes decreases with increasing Pheomelanin content
    Journal of Physical Chemistry B, 2010
    Co-Authors: Dana N Peles, John D Simon
    Abstract:

    Uveal melanosomes from the iridal stroma contain both eumelanin and Pheomelanin, the ratio of which varies with iris color. Herein, we report the absorption coefficient at λ = 244 nm for individual human iridal stroma melanosomes from dark brown and blue-green irides. The melanosomes are nearly identical in size, but differ in the relative concentration composition, ranging from a eumelanin/Pheomelanin ratio of 14.8:1 (dark brown) to 1.3:1 (blue-green or hazel). The absorption coefficient of the melanosome decreases as its Pheomelanin content increases. The origin of this decrease is attributed to a corresponding decrease in the number of UV-absorbing chromophores, reflecting the different molecular volumes of the monomeric building blocks of the two pigments. In agreement with reported data on synthetic pigments, the absorption coefficient of Pheomelanin is found to be slightly larger than that for eumelanin at λ = 244 nm (by a factor of 1.2). On the basis of the reported optical properties of synthetic ...

  • human iridal stroma melanosomes of varying Pheomelanin contents possess a common eumelanic outer surface
    Journal of Physical Chemistry B, 2009
    Co-Authors: Dana N Peles, Shosuke Ito, Lian Hong, R J Nemanich, John D Simon
    Abstract:

    Uveal melanosomes originating in the iridal stroma contain both black (eumelanin) and red (Pheomelanin) pigment. Recent studies reveal that the eumelanin/Pheomelanin ratio varies with iris color, w...

  • Human iridal stroma melanosomes of varying Pheomelanin contents possess a common eumelanic outer surface.
    The journal of physical chemistry. B, 2009
    Co-Authors: Dana N Peles, Shosuke Ito, Lian Hong, R J Nemanich, John D Simon
    Abstract:

    Uveal melanosomes originating in the iridal stroma contain both black (eumelanin) and red (Pheomelanin) pigment. Recent studies reveal that the eumelanin/Pheomelanin ratio varies with iris color, with lower ratios being observed for lighter color (hazel, blue) irides. This is of great interest because the epidemiology of uveal melanomas also indicates an increased incidence for lighter-colored irides. Herein, we examine human iridal stroma melanosomes from dark brown and blue−green irides, which are characterized by a eumelanin/Pheomelanin ratio of 14.8 and 1.3, respectively. Atomic force microscopy reveals that the melanosomes extracted from these different colored irides have a similar size and overall morphology. Studies of the surface ionization potentials reveal that the surface of these melanosomes is pure eumelanin, despite the significant difference in their overall pigment composition. These data indicate that the Pheomelanin present in the melanosome is encased by eumelanin, providing support fo...

  • The action spectrum for generation of the primary intermediate revealed by ultrafast absorption spectroscopy studies of Pheomelanin.
    Photochemistry and photobiology, 2003
    Co-Authors: John D Simon
    Abstract:

    The observation that fair-skinned individuals are more susceptible to skin cancers is commonly explained by invoking an enhanced photoreactivity of the red melanin, Pheomelanin compared with the black melanin, eumelanin. For the wavelength range from 500 to 1000 nm, pump-probe spectroscopic measurements reveal the photoexcitation of Pheomelanin by UVA light that generates an immediate ( 10 000 fractions of Pheomelanin, indicating that the reactive chromophore has a low MW but is present and its photophysics is similar in the aggregated pigment. The shape of the action spectrum differs from the absorption spectrum of bulk melanin and mass-selected fractions but resembles reported absorption spectrum of benzothiazines, oxidation products of 5-S-cysteinyl-dopa, which are formed along the biosynthetic pathway of Pheomelanin.

Lucia Panzella - One of the best experts on this subject based on the ideXlab platform.

  • Fifty Shades" of Black and Red or How Carboxyl Groups Fine Tune Eumelanin and Pheomelanin Properties.
    International Journal of Molecular Sciences, 2016
    Co-Authors: Raffaella Micillo, Kenzo Koike, Giuseppe Monfrecola, Lucia Panzella, Alessandra Napolitano, Marco D'ischia
    Abstract:

    Recent advances in the chemistry of melanins have begun to disclose a number of important structure-property-function relationships of crucial relevance to the biological role of human pigments, including skin (photo) protection and UV-susceptibility. Even slight variations in the monomer composition of black eumelanins and red Pheomelanins have been shown to determine significant differences in light absorption, antioxidant, paramagnetic and redox behavior, particle morphology, surface properties, metal chelation and resistance to photo-oxidative wear-and-tear. These variations are primarily governed by the extent of decarboxylation at critical branching points of the eumelanin and Pheomelanin pathways, namely the rearrangement of dopachrome to 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA), and the rearrangement of 5-S-cysteinyldopa o-quinoneimine to 1,4-benzothiazine (BTZ) and its 3-carboxylic acid (BTZCA). In eumelanins, the DHICA-to-DHI ratio markedly affects the overall antioxidant and paramagnetic properties of the resulting pigments. In particular, a higher content in DHICA decreases visible light absorption and paramagnetic response relative to DHI-based melanins, but markedly enhances antioxidant properties. In Pheomelanins, likewise, BTZCA-related units, prevalently formed in the presence of zinc ions, appear to confer pronounced visible and ultraviolet A (UVA) absorption features, accounting for light-dependent reactive oxygen species (ROS) production, whereas non-carboxylated benzothiazine intermediates seem to be more effective in inducing ROS production by redox cycling mechanisms in the dark. The possible biological and functional significance of carboxyl retention in the eumelanin and Pheomelanin pathways is discussed.

  • Reverse Engineering Applied to Red Human Hair Pheomelanin Reveals Redox-Buffering as a Pro-Oxidant Mechanism
    Scientific reports, 2015
    Co-Authors: Eunkyoung Kim, Raffaella Micillo, Lucia Panzella, Alessandra Napolitano, William E. Bentley, Gregory F. Payne
    Abstract:

    Pheomelanin has been implicated in the increased susceptibility to UV-induced melanoma for people with light skin and red hair. Recent studies identified a UV-independent pathway to melanoma carcinogenesis and implicated Pheomelanin's pro-oxidant properties that act through the generation of reactive oxygen species and/or the depletion of cellular antioxidants. Here, we applied an electrochemically-based reverse engineering methodology to compare the redox properties of human hair Pheomelanin with model synthetic pigments and natural eumelanin. This methodology exposes the insoluble melanin samples to complex potential (voltage) inputs and measures output response characteristics to assess redox activities. The results demonstrate that both eumelanin and Pheomelanin are redox-active, they can rapidly (sec-min) and repeatedly redox-cycle between oxidized and reduced states, and Pheomelanin possesses a more oxidative redox potential. This study suggests that Pheomelanin's redox-based pro-oxidant activity may contribute to sustaining a chronic oxidative stress condition through a redox-buffering mechanism.

  • Photochemistry of Pheomelanin Building Blocks and Model Chromophores: Excited-State Intra- and Intermolecular Proton Transfer
    2015
    Co-Authors: Amal El Nahhas, Lucia Panzella, Alessandra Napolitano, Torbjörn Pascher, Loredana Leone, Villy Sundström
    Abstract:

    Pheomelanins, the epidermal pigments of red-haired people responsible for their enhanced UV susceptibility, contain 1,4-benzothiazines and 1,3-benzothiazole as main structural components. Despite the major role played in Pheomelanin phototoxicity, the photoreactivity of these species has so far remained unexplored. Static and time-resolved fluorescence spectroscopy was used to identify excited-state reactions of the two main Pheomelanin benzothiazole building blocks, namely, the 6-(2-amino-2-carboxyethyl)-4-hydroxy-1,3-benzothiazole (BT) and the 2-carboxy derivative (BTCA) together with model chromophores lacking some of the ionizable functions. The results show that in aqueous buffer solution the OH at 4-position and the benzothiazole nitrogen atom control the photochemistry of both BT and BTCA via excited-state proton transfer to solvent (ESPT) and excited-state intramolecular proton transfer (ESIPT), while the amino acidic groups of the alanyl chain have a minor influence on the photochemistry. The ESPT and ESIPT produce several different excited-state ionic species with lifetimes ranging from ∼100 ps to ∼3 ns

  • Pheomelanin induced oxidative stress bright and dark chemistry bridging red hair phenotype and melanoma
    Pigment Cell & Melanoma Research, 2014
    Co-Authors: Alessandra Napolitano, Giuseppe Monfrecola, Lucia Panzella, Marco Dischia
    Abstract:

    Summary The complex interplay of genetic and epigenetic factors linking sun exposure to melanoma in the red hair phenotype hinges on the peculiar physical and chemical properties of Pheomelanins and the underlying biosynthetic pathway, which is switched on by the effects of inactivating polymorphisms in the melanocortin 1 receptor gene. In addition to the long recognized UV-dependent pathways of toxicity and cell damage, a UV-independent pro-oxidant state induced by Pheomelanin within the genetically determined background of the red hair phenotype has recently been disclosed. This review provides a detailed discussion of the possible UV-dependent and UV-independent chemical mechanisms underlying Pheomelanin-mediated oxidative stress, with special reference to the oxygen-dependent depletion of glutathione and other cell antioxidants. The new concept of Pheomelanin as a ‘living’ polymer and biocatalyst that may grow by exposure to monomer building blocks and may trigger autooxidative processes is also discussed. As a corollary, treatment of inflammatory skin diseases in RHP patients is briefly commented. Finally, possible concerted strategies for melanoma prevention in the red hair phenotype are proposed.

  • Pheomelanin‐induced oxidative stress: bright and dark chemistry bridging red hair phenotype and melanoma
    Pigment cell & melanoma research, 2014
    Co-Authors: Alessandra Napolitano, Lucia Panzella, Giuseppe Monfrecola, Marco D'ischia
    Abstract:

    The complex interplay of genetic and epigenetic factors linking sun exposure to melanoma in the red hair phenotype hinges on the peculiar physical and chemical properties of Pheomelanins and the underlying biosynthetic pathway, which is switched on by the effects of inactivating polymorphisms in the melanocortin 1 receptor gene. In addition to the long recognized UV-dependent pathways of toxicity and cell damage, a UV-independent pro-oxidant state induced by Pheomelanin within the genetically determined background of the red hair phenotype has recently been disclosed. This review provides a detailed discussion of the possible UV-dependent and UV-independent chemical mechanisms underlying Pheomelanin-mediated oxidative stress, with special reference to the oxygen-dependent depletion of glutathione and other cell antioxidants. The new concept of Pheomelanin as a 'living' polymer and biocatalyst that may grow by exposure to monomer building blocks and may trigger autooxidative processes is also discussed. As a corollary, treatment of inflammatory skin diseases in RHP patients is briefly commented. Finally, possible concerted strategies for melanoma prevention in the red hair phenotype are proposed.