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Melanossomas e tráfego de vesículas na pigmentação da pele e cabelo: estratégias no controlo da pigmentação
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Resumo(s)
A nossa imagem assume um papel fundamental na forma como somos percepcionados, constituindo a primeira impressão que causamos nos outros. Neste contexto, o aspeto da pele e do cabelo faz parte da identidade de cada um e influencia a autoestima, tendo por isso um grande impacto social.
A unidade melano-epidérmica está presente na pele e consiste num complexo funcional de melanócitos e queratinócitos que, em associação, são responsáveis pela sua pigmentação. No interior dos melanócitos existem organelos específicos destas células denominados melanossomas, onde se dá a síntese e o armazenamento do pigmento biológico do ser humano – a melanina. Após a sua maturação, os melanossomas são transportados dos melanócitos para os queratinócitos, onde os grânulos de melanina vão formar um “escudo” protetor junto do núcleo celular, impedindo que agressões externas (como a radiação ultravioleta) atinjam o núcleo e provoquem danos no DNA. Consequentemente, a presença de melanina nos queratinócitos provoca também a pigmentação dos tecidos.
Todas estas etapas necessárias à pigmentação dos tecidos necessitam da intervenção de diversos agentes autócrinos e parácrinos com a capacidade de regular os acontecimentos em resposta a estímulos externos ou internos. Estes moduladores são muitas vezes selecionados como alvos terapêuticos para combater algumas anomalias do processo.
Apesar da síntese de melanina se processar de forma semelhante na pele e no cabelo, os sistemas melanogénicos epidérmicos e foliculares apresentam algumas diferenças. Esta monografia aborda várias etapas do processo de pigmentação da pele e do cabelo, bem como a forma como estas são reguladas por alguns fatores.
As alterações da pigmentação da pele e do cabelo no Homem, quer fisiológicas, quer patológicas serão ainda revistas nesta monografia, incluindo as que poderão estar relacionadas com a toma de certos medicamentos.
Our image assumes a fundamental part in the way we are perceived, being the basis of the first impression we cause on other people. Each individual’s identity is influenced by skin and hair appearance and this has a huge social impact on account of its role on everyone’s self-esteem. The pigmentation process relies on the Epidermal-Melanin Unit, which is a functional complex composed by melanocytes and keratinocytes that work together in order to lead to skin pigmentation. There are specific organelles inside melanocytes, the melanosomes, responsible for the synthesis and storage of the biological human pigment – melanin. After the maturation process, melanosomes are transported from melanocytes to keratinocytes, where melanin granules will form a protector “shield” around the nucleus with the aim to prevent any damage caused by external threats (such as UV radiation). Consequently, the presence of melanin in keratinocytes is also responsible for tissue pigmentation. All these stages of skin and hair pigmentation need the intervention of many autocrin and paracrin agents which possess the ability to regulate the responses to external or internal stimuli. Although melanogenesis takes a similar path in hair and skin, the epidermal and follicular melanogenic systems differ from each other. This review focuses on the steps involved in the skin and hair pigmentation process, as well as the agents able to regulate several stages of this phenomenon. This work also reports some physiological and pathological pigmentation changes, including the ones associated to particular medications.
Our image assumes a fundamental part in the way we are perceived, being the basis of the first impression we cause on other people. Each individual’s identity is influenced by skin and hair appearance and this has a huge social impact on account of its role on everyone’s self-esteem. The pigmentation process relies on the Epidermal-Melanin Unit, which is a functional complex composed by melanocytes and keratinocytes that work together in order to lead to skin pigmentation. There are specific organelles inside melanocytes, the melanosomes, responsible for the synthesis and storage of the biological human pigment – melanin. After the maturation process, melanosomes are transported from melanocytes to keratinocytes, where melanin granules will form a protector “shield” around the nucleus with the aim to prevent any damage caused by external threats (such as UV radiation). Consequently, the presence of melanin in keratinocytes is also responsible for tissue pigmentation. All these stages of skin and hair pigmentation need the intervention of many autocrin and paracrin agents which possess the ability to regulate the responses to external or internal stimuli. Although melanogenesis takes a similar path in hair and skin, the epidermal and follicular melanogenic systems differ from each other. This review focuses on the steps involved in the skin and hair pigmentation process, as well as the agents able to regulate several stages of this phenomenon. This work also reports some physiological and pathological pigmentation changes, including the ones associated to particular medications.
Descrição
Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, 2020, Universidade de Lisboa, Faculdade de Farmácia.
Palavras-chave
Melanogénese Melanossomas Pigmentação Regulação Envelhecimento Mestrado integrado - 2020