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As várias facetas dos antioxidantes e a sua influência na saúde e desenvolvimento do cancro
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As espécies reativas de oxigénio são produzidas por células vivas como subproduto metabólico celular normal. Sob condições de stress, as células irão produzir vários subprodutos e os organismos vivos irão desenvolver uma série de mecanismos de resposta para se adaptarem à exposição do subproduto, bem como utilizá-lo como veículo de sinalização. As espécies reativas de oxigénio desencadeiam o stress oxidativo num mecanismo de feedback envolvendo muitos processos biológicos, como apoptose, necrose e autofagia. Várias evidências têm sugerido que as espécies reativas de oxigénio desempenham um papel crítico como moléculas de sinalização em todo o caminho da morte celular e uma produção elevada deste subproduto pode destruir a estrutura dos organelos e biomoléculas, o que leva à resposta inflamatória, que é um mecanismo para o desenvolvimento do cancro. As células desenvolveram um sistema equilibrado para neutralizar as espécies reativas de oxigénio, ou seja, sistemas antioxidantes que consistem em antioxidantes enzimáticos, bem como antioxidantes não enzimáticos que reduzem, em conjunto, o estado oxidativo.
Os antioxidantes são essenciais para prevenir a formação e suprimir as atividades das espécies reativas oxigénio. Acredita-se que os antioxidantes são capazes de prevenir e tratar vários tipos de doenças malignas e, atualmente, os compostos antioxidantes naturais têm sido consumidos para prevenir e tratar diferentes tipos de cancro. Compostos fenóis extraídos de plantas medicinais abriram uma nova perspetiva no que diz respeito à prevenção e tratamento de cancros por possuírem características antioxidantes, entretanto, alguns estudos publicados recentemente revelaram que compostos antioxidantes não indicam propriedades anti tumorais absolutas. Alguns deles são úteis na iniciação e progressão do cancro.
O PubMed foi consultado para identificar e analisar artigos publicados entre 1999 e 2021, adotando algumas palavras-chave (tanto em português como em inglês), como por exemplo: “espécies reativas de oxigénio”, “cancro”, “antioxidantes” e “stress oxidativo”, para encontrar artigos sobre este tópico. Desta pesquisa resultou a consulta de cerca de 110 artigos, dos quais 42 foram selecionados para integrar este trabalho. Numa análise extensa, com base em critérios de aceitação e exclusão, foram selecionados artigos que incluíam estudos que correlacionavam a associação entre o uso de antioxidantes e o cancro. Este trabalho permitiu-nos concluir que, em conjunto, os antioxidantes demonstram uma natureza dupla em relação ao cancro.
Reactive oxygen species are produced by living cells as a normal cellular metabolic byproduct. Under excessive stress conditions, cells will produce numerous byproducts, and the living organisms eventually evolve series of response mechanisms to adapt to the byproduct exposure as well as utilize it as the signaling device. Reactive oxygen species would trigger oxidative stress in a feedback mechanism involving many biological processes, such as apoptosis, necrosis and autophagy. Growing evidence have suggested that reactive oxygen species play a critical role as the signaling molecules throughout the entire cell death pathway and an overwhelming production of this byproduct can destroy organelle’s structure and biomolecules, which lead to inflammatory response that is a mechanism for the development of cancer. Cells have evolved a balanced system to neutralize the reactive oxygen species, namely antioxidant systems that consist of enzymatic antioxidants as well as the non-enzymatic antioxidants which collectively reduce oxidative state. Antioxidants are essential in preventing the formation and suppressing the activities of reactive oxygen species. Antioxidants are believed to prevent and treat various types of malignancies and, currently, natural antioxidant compounds have been generally consumed to prevent and treat different kinds of cancers. Phenolic compounds extracted from medicinal plants have opened a new prospect with respect to the prevention and treatment of cancers due to having antioxidant characteristics, however, some recently published studies have revealed that antioxidant compounds do not indicate absolute anti-tumor properties. Some of them are helpful in cancer initiation and progression. PubMed was consulted to identify and analyze articles published between 1999 and 2021, adopting some keywords (both in Portuguese and in English) such as, for example: “reactive oxygen species”, “cancer”, “antioxidants” and “oxidative stress”, to find articles about this topic. From this research resulted the consultation of about 110 articles, of which 42 were selected to integrate this work. In an extensive analysis, based on acceptance and exclusion criteria, articles were selected that included studies that dealt with the association between the use of antioxidants and cancer. This work allowed us to conclude that taken together, antioxidants demonstrate a two-faced nature towards cancer.
Reactive oxygen species are produced by living cells as a normal cellular metabolic byproduct. Under excessive stress conditions, cells will produce numerous byproducts, and the living organisms eventually evolve series of response mechanisms to adapt to the byproduct exposure as well as utilize it as the signaling device. Reactive oxygen species would trigger oxidative stress in a feedback mechanism involving many biological processes, such as apoptosis, necrosis and autophagy. Growing evidence have suggested that reactive oxygen species play a critical role as the signaling molecules throughout the entire cell death pathway and an overwhelming production of this byproduct can destroy organelle’s structure and biomolecules, which lead to inflammatory response that is a mechanism for the development of cancer. Cells have evolved a balanced system to neutralize the reactive oxygen species, namely antioxidant systems that consist of enzymatic antioxidants as well as the non-enzymatic antioxidants which collectively reduce oxidative state. Antioxidants are essential in preventing the formation and suppressing the activities of reactive oxygen species. Antioxidants are believed to prevent and treat various types of malignancies and, currently, natural antioxidant compounds have been generally consumed to prevent and treat different kinds of cancers. Phenolic compounds extracted from medicinal plants have opened a new prospect with respect to the prevention and treatment of cancers due to having antioxidant characteristics, however, some recently published studies have revealed that antioxidant compounds do not indicate absolute anti-tumor properties. Some of them are helpful in cancer initiation and progression. PubMed was consulted to identify and analyze articles published between 1999 and 2021, adopting some keywords (both in Portuguese and in English) such as, for example: “reactive oxygen species”, “cancer”, “antioxidants” and “oxidative stress”, to find articles about this topic. From this research resulted the consultation of about 110 articles, of which 42 were selected to integrate this work. In an extensive analysis, based on acceptance and exclusion criteria, articles were selected that included studies that dealt with the association between the use of antioxidants and cancer. This work allowed us to conclude that taken together, antioxidants demonstrate a two-faced nature towards cancer.
Descrição
Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, 2021, Universidade de Lisboa, Faculdade de Farmácia.
Palavras-chave
Antioxidantes Cancro Stress oxidativo Espécies reativas de oxigénio Mestrado integrado - 2021