Ácido gálico e seus ésteres como agentes anti - Helicobacter pylori e sequestradores de oxidantes produzidos por neutrófilos
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Data
2017-06-22
Autores
Wolf, Vanessa Gonçalves [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Helicobacter pylori é um dos principais causadores de gastrite crônica e úlcera péptica, e embora o mecanismo envolvido na inflamação gástrica por esta bactéria não esteja completamente elucidado, sabe-se do importante papel das espécies reativas de oxigênio (EROs) produzidas por polimorfonucleares neutrófilos, que são atraídos e ativados pelo agente da infecção, sem que, entretanto, consigam debelar a mesma, mas que contribuem fortemente para a lesão tecidual e o processo inflamatório crônico. Diante disso, tem aumentado a busca de novas estratégias de tratamento que possam levar à redução do estresse oxidativo gerado no sítio da infecção, com consequente redução do processo inflamatório. Neste sentido, ácido gálico, juntamente com seus ésteres (galato de metila, propila, hexila e octila), foram utilizados neste estudo, com o objetivo de avaliar suas ações como inibidores da liberação de EROs por neutrófilos ativados, bem como seus efeitos antimicrobianos sobre H. pylori. Para a avaliação da atividade antioxidante dessas substâncias foram realizados ensaios livres de células (efeito supressor sobre o radical DPPH e sobre radicais peroxila), e o efeito anti-EROs foi avaliado utilizando neutrófilos isolados de sangue humano estimulados por H. pylori, Zymosan ou PMA, através de ensaio quimiluminescente dependente de luminol ou lucigenina, ensaio com WST-1, ensaio de inibição da produção de HOCl, e o teste do NBT. Ensaio antimicrobiano foi realizado através da técnica de microdiluição em caldo. A presença da cadeia lateral carbônica levou a um significativo aumento na capacidade dos ésteres em inibir a produção de EROs por neutrófilos ativados, quando comparados ao ácido precursor, com destaque para os galatos de hexila e octila, que inibiram em quase 100% a produção de radical ânion superóxido, bem como de todas as EROs do burst oxidativo de forma geral. Galatos de octila e hexila também mostraram-se ser as moléculas com maior atividade antimicrobiana sobre H. pylori, com um valor de CIM de 125 e 250g/mL, respectivamente, ao passo que as demais substâncias apresentaram valor de CIM acima de 1000 g/mL. Os resultados obtidos mostram o grande potencial dos ésteres do ácido gálico quanto à suas atividades anti-H. pylori e anti-EROs, e além disso demonstram a importância da presença de uma cadeia carbônica lateral, conferindo maior hidrofobicidade à molécula, para obter-se a máxima atividade antimicrobiana in vitro e a máxima atividade antioxidante em modelo ex vivo. Assim, os ésteres do ácido gálico apresentam-se como moléculas promissoras no tratamento da infecção por Helicobacter pylori, apresentando ação antimicrobiana sobre o mesmo, bem como na redução do estresse oxidativo gerado no sítio da infecção.
Helicobacter pylori is one of major cause of chronic gastritis and peptic ulcer disease, and although the mechanism involved in gastric inflammation by this bacterium is not fully understood, it is know the important role of reactive oxygen species (ROS) produced by polymorphonuclear neutrophils (PMNs), which are attracted and activated by infection agent, without, however, to be able to overcome the same, but which contribute strongly to the tissue damage and chronic inflammation. Therefore, it has increased the search for new strategies of treatment that can lead to the reduction of the oxidative stress generated at the infection site, with consequent reduction of the inflammatory process. In this sense, gallic acid, together with its esters (methyl, propyl, hexyl and octyl gallate), were used in this study, with the aim of evaluating their actions as inhibitors of ROS release by activated neutrophils, as well as their antimicrobial effects on H. pylori. Cell-free assays (suppressor effect on the DPPH radical and peroxyl radicals) were performed to evaluate the antioxidant activity of these substances, and the anti-EROs effect was evaluated using neutrophils isolated from human blood, stimulated by H. pylori, Zymosan or PMA, through luminol-dependent or lucigenin-dependent chemiluminescent assay, WST-1 assay, inhibition of HOCl production assay, and the NBT assay. Antimicrobial assay was performed by broth microdilution technique. The presence of the carbonic side chain led to a significant increase in the ability of the esters to inhibit the ROS production by activated neutrophils when compared to the precursor acid, especially hexyl and octyl gallates, which inhibited practically 100% of the superoxide anion radical production, as well as all ROS of the oxidative burst in general. Octyl and hexyl gallates were also shown to be the molecules with the highest antimicrobial activity on H. pylori, with a MIC value of 125 and 250 μg/mL, respectively, while the other substances had a MIC value higher than 1000 g/ml. The results show the great potential of the esters of gallic acid for their anti-H. pylori and anti-EROs activities, and furthermore demonstrate the importance of the presence of a lateral carbonic chain, giving greater hydrophobicity to the molecule, to obtain the maximum antimicrobial activity in vitro and the maximum antioxidant activity in an ex vivo model. Thus, esters of gallic acid are promising molecules in the treatment of Helicobacter pylori infection, presenting antimicrobial action on the same, as well as reducing the oxidative stress generated at the site of infection.
Helicobacter pylori is one of major cause of chronic gastritis and peptic ulcer disease, and although the mechanism involved in gastric inflammation by this bacterium is not fully understood, it is know the important role of reactive oxygen species (ROS) produced by polymorphonuclear neutrophils (PMNs), which are attracted and activated by infection agent, without, however, to be able to overcome the same, but which contribute strongly to the tissue damage and chronic inflammation. Therefore, it has increased the search for new strategies of treatment that can lead to the reduction of the oxidative stress generated at the infection site, with consequent reduction of the inflammatory process. In this sense, gallic acid, together with its esters (methyl, propyl, hexyl and octyl gallate), were used in this study, with the aim of evaluating their actions as inhibitors of ROS release by activated neutrophils, as well as their antimicrobial effects on H. pylori. Cell-free assays (suppressor effect on the DPPH radical and peroxyl radicals) were performed to evaluate the antioxidant activity of these substances, and the anti-EROs effect was evaluated using neutrophils isolated from human blood, stimulated by H. pylori, Zymosan or PMA, through luminol-dependent or lucigenin-dependent chemiluminescent assay, WST-1 assay, inhibition of HOCl production assay, and the NBT assay. Antimicrobial assay was performed by broth microdilution technique. The presence of the carbonic side chain led to a significant increase in the ability of the esters to inhibit the ROS production by activated neutrophils when compared to the precursor acid, especially hexyl and octyl gallates, which inhibited practically 100% of the superoxide anion radical production, as well as all ROS of the oxidative burst in general. Octyl and hexyl gallates were also shown to be the molecules with the highest antimicrobial activity on H. pylori, with a MIC value of 125 and 250 μg/mL, respectively, while the other substances had a MIC value higher than 1000 g/ml. The results show the great potential of the esters of gallic acid for their anti-H. pylori and anti-EROs activities, and furthermore demonstrate the importance of the presence of a lateral carbonic chain, giving greater hydrophobicity to the molecule, to obtain the maximum antimicrobial activity in vitro and the maximum antioxidant activity in an ex vivo model. Thus, esters of gallic acid are promising molecules in the treatment of Helicobacter pylori infection, presenting antimicrobial action on the same, as well as reducing the oxidative stress generated at the site of infection.
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Palavras-chave
Helicobacter pylori, Ácido gálico, Alquil galatos, Neutrófilo, Burst oxidativo, NADPH oxidase, Gallic acid, Alkyl gallates, Neutrophil, Oxidative burst