RESUMEN

Melanosomes have been considered crucial targets in melanoma treatments. In this study we explored the role of melanosomes in photodynamic therapy (PDT), employing the synthetic Zn(II) phthalocyanine Pc13, a potent photosensitizer that promotes melanoma cell death after irradiation. Phototoxic action is mediated by reactive oxygen species increase. The internalization mechanism of Pc13 and its consequent subcellular localization were evaluated in melanotic B16-F0 cells. Pharmacological inhibitors of dynamin or caveolae, but not of clathrin, decreased Pc13 cellular uptake and phototoxicity. Similar results were obtained when cells over-expressed dominant negative mutants of dynamin-2 and caveolin-1, indicating that Pc13 is internalized by caveolae-mediated endocytosis. Confocal microscopy analysis revealed that Pc13 targets melanosomes and damage of these structures after irradiation was demonstrated by transmission electron microscopy. Treatment of pigmented B16-F0 and WM35 melanoma cells with the melanin synthesis inhibitor phenylthiourea for 48 h led to cell depigmentation and enhanced cell death after irradiation, whereas a 3-h period of inhibition did not modify melanin content but produced a marked reduction of Pc13 phototoxicity, together with a decrease of oxidative melanin synthesis intermediates. In contrast, the effect of Pc13 in amelanotic A375 cells was not altered by phenylthiourea treatment. These results provide evidence that melanosomes have a dual role in the efficacy of PDT. While melanin antagonizes the phototoxic action of Pc13, the release of cytotoxic synthetic intermediates to cytosol after irradiation and melanosome damage is conducive to the phototoxic response. Based on these findings, we demonstrate that melanosome-targeted PDT could be an effective approach for melanoma treatment.

Asunto(s)

Dermatitis Fototóxica , Melanoma , Caveolina 1/metabolismo , Caveolina 1/farmacología , Caveolina 1/uso terapéutico , Endocitosis , Humanos , Indoles/química , Isoindoles , Melaninas/metabolismo , Melanoma/tratamiento farmacológico , Melanoma/metabolismo , Melanosomas/metabolismo , Melanosomas/ultraestructura , Feniltiourea/metabolismo , Feniltiourea/farmacología , Feniltiourea/uso terapéutico

RESUMEN

Melanin is a heteropolymer formed by the polymerization of phenolic and indolic compounds. It occurs in organisms across all biological kingdoms and has a range different of functions, thus indicating its important evolutionary role. The presence of melanin offers several protective advantages, including against ultraviolet radiation, traumatic damage, oxidative stress, extreme temperatures, and pressure. For many species of fungi, melanin also participates directly in the process of virulence and pathogenicity. These organisms can synthesize melanin in two main ways: using a substrate of endogenous origin, involving 1,8-dihydroxynaphthalene (DHN); alternatively, in an exogenous manner with the addition of L-3, 4-dihydroxyphenylalanine (L-DOPA or levodopa). As melanin is an amorphous and complex substance, its study requires expensive and inaccessible technologies and analyses are often difficult to perform with conventional biochemical techniques. As such, details about its chemical structure are not yet fully understood, particularly for nematophagous fungi that remain poorly studied. Thus, this review presents an overview of the different types of melanin, with an emphasis on fungi, and discusses the role of melanin in the biology and ecology of nematophagous fungi.

Asunto(s)

Hongos/metabolismo , Melaninas/metabolismo , Hongos/patogenicidad , Lacasa/metabolismo , Levodopa/química , Levodopa/metabolismo , Melaninas/química , Monofenol Monooxigenasa/metabolismo , Naftoles/química , Naftoles/metabolismo , Sintasas Poliquetidas/metabolismo

RESUMEN

Histology and electron microscopic studies of the dorsal skin of the Fringe-toed lizard, Acanthodactylus orientalis Angel, 1936, showed three types of dermal chromatophores: xanthophores, iridophores and melanophores. These pigment cells were observed in vertical combination, with an uppermost layer of xanthophores, an intermediate layer of iridophores and a basal layer of melanophores. The ultrastructure of the melanophore is characterized by oval nucleus and numerous pigment granules, the melanosomes of different stages that remain scattered in the cytoplasm. The chromatophores of this species contain significant information of anatomical similarity with lower as well as higher vertebrates. They can help to better understand the inter relationships between vertebrate pigment cells and their role in skin dysfunctions.

Asunto(s)

Animales , Cromatóforos/ultraestructura , Lagartos/anatomía & histología , Células Epiteliales/ultraestructura

RESUMEN

Histology and electron microscopic studies of the dorsal skin of the Fringe-toed lizard, Acanthodactylus orientalis Angel, 1936, showed three types of dermal chromatophores: xanthophores, iridophores and melanophores. These pigment cells were observed in vertical combination, with an uppermost layer of xanthophores, an intermediate layer of iridophores and a basal layer of melanophores. The ultrastructure of the melanophore is characterized by oval nucleus and numerous pigment granules, the melanosomes of different stages that remain scattered in the cytoplasm. The chromatophores of this species contain significant information of anatomical similarity with lower as well as higher vertebrates. They can help to better understand the inter relationships between vertebrate pigment cells and their role in skin dysfunctions.(AU)

Asunto(s)

Animales , Lagartos/anatomía & histología , Cromatóforos/ultraestructura , Células Epiteliales/ultraestructura

RESUMEN

Os autores propõem a análise da classificação clínica da pele, considerando a evolução do homem dentro de diferentes locais geográficos no planeta. Estudos histológicos sugerem ser a origem do homem única, tendo como base a quantidade de melanócitos, que é semelhante nos diferentes tipos de pele, variando apenas nas características dos melanossomos. Verifica-se que a diferença entre a melanina da epiderme de um caucasoide e de um negroide se encontra, de fato, nas características dos melanossomos. Relatam, também, as várias tentativas de classificar os tipos de pele, mostrando que até hoje não existe uma classificação plenamente satisfatória.

RESUMEN

FUNDAMENTOS - Melasma é hipermelanose comum caracterizada por máculas acastanhadas em áreas fotoexpostas, cuja fisiopatogenia não é totalmente esclarecida. OBJETIVOS - Caracterizar e comparar morfologica e funcionalmente os melanócitos da epiderme sã com os da pele afetada por melasma. MÉTODOS - Avaliaram-se 12 pacientes portadores de melasma facial, sendo realizadas biópsias da pele lesada e pele sã adjacente. Os cortes foram corados por hematoxilina-eosina, Fontana-Masson, marcados pelo Melan-A e submetidos à microscopia eletrônica. A quantificação epidérmica de melanina e melanócitos foi estimada a partir de análise citomorfométrica digital. RESULTADOS - Todas as pacientes eram mulheres com média de idade 41,3±2,8 anos. Ao Fontana-Masson evidenciou-se importante aumento da melanina epidérmica na pele lesada em relação à pele sã. A marcação pelo Melan-A demonstrou melanócitos maiores com dendritos proeminentes na pele lesada. Observou-se maior densidade de melanina epidérmica na pele lesada, e a análise digital do número de melanócitos da epiderme não demonstrou diferença significativa entre pele lesada e sã. À microscopia eletrônica, observaram-se número aumentado de melanossomas maduros nos ceratinócitos e melanócitos com organelas citoplasmáticas proeminentes na pele lesada. CONCLUSÕES - Melanogênese aumentada na epiderme com melasma em relação à epiderme normal adjacente.

---

BACKGROUND - Melasma is a common hypermelanosis characterized by symmetric brownish macules on photoexposed areas, most frequently on the face of women. Its pathophysiology is still unknown. OBJECTIVES - To morphologically and functionally characterize and compare melanocytes of normal skin and of melasma. METHODS - Twelve patients with facial melasma were assessed and biopsies of lesions and adjacent healthy skin were performed. The slices were stained with hematoxylin-eosin and Fontana-Masson, immunohistochemically marked for Melan-A and evaluated by electronic microscopy. Quantification of epidermal melanin and melanocytes was estimated by digital cytomorphometric analysis. RESULTS - All patients were female, mean age of 41.3±2.8 years. The Fontana-Masson staining showed an important increase in epidermal melanin as compared to normal skin. The Melan-A staining demonstrated larger and intensely marked melanocytes and more prominent dendrites in the damaged skin. Greater epidermal melanin density was observed in melasma lesions and the digital analysis of number of epidermal melanocytes did not show a significant difference between damaged and normal skin. Electronic microscopy analysis revealed an increased number of mature melanosomes in keratinocytes and melanocytes, with marked cytoplasmic organelles in melasma skin. CONCLUSIONS - Melanogenesis is increased on melasma epidermis as compared to adjacent normal skin.