RESUMO
Branched-chain amino acids (BCAA) are essential for maintaining intestinal mucosal integrity. However, only a few studies have explored the role of BCAA in the modulation of intestinal inflammation. In this study, we investigated in vitro effects of BCAA on the inflammatory response induced by lipopolysaccharide (LPS) (1 µg/mL) in Caco-2 cells. Caco-2 cells were assigned to six groups: control without BCAA (CTL0), normal BCAA (CTL; 0.8 mM leucine, 0.8 mM isoleucine, and 0.8 mM valine); leucine (LEU; 2 mM leucine), isoleucine (ISO; 2 mM isoleucine), valine (VAL; 2 mM valine), and high BCAA (LIV; 2 mM leucine, 2 mM isoleucine, and 2 mM valine). BCAA was added to the culture medium 24 h before LPS stimulation. Our results indicated that BCAA supplementation did not impair cell viability. The amino acids leucine and isoleucine attenuated the synthesis of IL-8 and JNK and NF-kB phosphorylation induced by LPS. Furthermore, neither BCAA supplementation nor LPS treatment modulated the activity of glutathione peroxidase or the intracellular reduced glutathione/oxidized glutathione ratio. Therefore, leucine and isoleucine exert anti-inflammatory effects in Caco-2 cells exposed to LPS by modulating JNK and NF-kB phosphorylation and IL-8 production. Further in vivo studies are required to validate these findings and gather valuable information for potential therapeutic or dietary interventions.
RESUMO
Introdução: A inflamação é um fator presente na fisiopatologia de doenças, e, o intestino, órgão susceptível a disfunções e à disbiose, que está em constante exposição a microrganismos, pode estar associado a este processo. Por outro lado, aminoácidos de cadeia ramificada (ACR) podem apresentar efeitos anti-inflamatórios em linhagem celular intestinal. Objetivo: Investigar os efeitos da suplementação de ACR, in vitro, na modulação da resposta inflamatória e do estresse oxidativo induzida por LPS em modelo de células intestinais Caco-2. Métodos: As culturas de células foram distribuídas em seis grupos, sendo: dois grupos controle - controle com meio Dulbecco's Modified Eagle's Medium sem ACR (CTL0) e com ACR (CTL) - e quatro grupos suplementados - grupo leucina (LEU), grupo isoleucina (ISO), grupo valina (VAL) e associação de ACR (LIV). Foi adotado um protocolo de pré-tratamento, com os ACR e o LPS. A viabilidade celular foi avaliada pelo ensaio de redução do MTT (brometo de [3-(4,5-dimetiltiazol-2yl 2,5-difenil tetrazolium]). A análise de proteínas (mTOR, AKT, AMPK, NF-kB, TAK-1 e JNK) foi feita por Western Blotting. A dosagem de citocina IL-8 no sobrenadante de cultura celular foi realizada por meio do kit Multiplex para imunoensaio. Foram avaliados componentes do sistema antioxidante relacionado à glutationa (GSH, GSSG e GPx) por meio de kit comercial. Os resultados foram expressos como média ± erro padrão. Resultados: No teste de viabilidade celular por MTT, verificou-se que os grupos tratados com ACR e LPS não apresentaram comprometimento da viabilidade celular em relação ao grupo CTL sem LPS. Os grupos CTL0, CTL, VAL e LIV, quando estimulados com LPS, apresentaram maior capacidade de síntese, in vitro, de IL-8, bem como maior fosforilação das proteínas JNK e NF-kB em relação aos seus respectivos grupos sem LPS. A suplementação. Todavia, as células estimuladas com LPS e suplementadas com leucina e isoleucina apresentaram capacidade de síntese, in vitro, de IL-8 e fosforilação das proteínas JNK e NF-kB que não diferiram significativamente das células suplementadas com esses aminoácidos e não estimuladas com LPS. A ausência de ACR (grupo CTL0) e a suplementação desses aminoácidos, in vitro, em células intestinais Caco-2, tratadas com ou sem LPS, não induziram alteração da atividade da enzima GPx e da razão intracelular GSH/GSSG. Conclusões: Os aminoácidos leucina e isoleucina apresentaram potencial efeito anti-inflamatório nas células Caco-2 por meio da modulação da fosforilação das proteínas JNK e NF-kB, cujo fato está associado à modulação da síntese, in vitro, de IL-8, a qual está envolvida na resposta inflamatória no intestino.
Introduction: Inflammation is a factor present in the pathophysiology of diseases, and the intestine, an organ susceptible to dysfunction and dysbiosis, which is constantly exposed to microorganisms, may be associated with this process. On the other hand, branched-chain amino acids (BCAAs) may have anti-inflammatory effects on intestinal cell lines. Objective: To investigate the effects of ACR supplementation, in vitro, on the modulation of inflammatory response and oxidative stress induced by LPS in a model of intestinal Caco-2 cells. Methods: The cell cultures were divided into six groups, as follows: two control groups - control with Dulbecco's Modified Eagle's Medium without ACR (CTL0) and with ACR (CTL) - and four supplemented groups - leucine group (LEU), isoleucine group (ISO), valine group (VAL) and ACR association (LIV). A pre-treatment protocol was adopted, with ACR and LPS. Cell viability was assessed by MTT reduction assay ([3-(4,5-dimethylthiazol-2yl 2,5-diphenyl tetrazolium] bromide)) Protein analysis (mTOR, AKT, AMPK, NF-kB, TAK -1 and JNK) was performed by Western Blotting. The dosage of cytokine IL-8 in the cell culture supernatant was performed using the Multiplex kit for immunoassay. Components of the antioxidant system related to glutathione (GSH, GSSG, and GPx) were evaluated by commercial kit. The results were expressed as mean ± standard error. Results: In the cell viability test by MTT, it was verified that the groups treated with ACR and LPS did not show impairment of cell viability compared to the CTL group without LPS. The CTL0, CTL, VAL, and LIV groups, when stimulated with LPS, showed a greater capacity for in vitro synthesis of IL-8, as well as greater phosphorylation of JNK and NF-kB proteins in relation to their respective groups without LPS. However, cells stimulated with LPS and supplemented with leucine and isoleucine showed in vitro synthesis capacity of IL-8 and phosphorylation of JNK and NF-kB proteins that did not differ significantly from cells supplemented with these amino acids and not stimulated with LPS. The absence of ACR (CTL0 group) and the supplementation of these amino acids, in vitro, in intestinal Caco-2 cells, treated with or without LPS, did not induce changes in the activity of the GPx enzyme and the intracellular GSH/GSSG ratio. Conclusions: The amino acids leucine and isoleucine had a potential anti-inflammatory effect on Caco-2 cells by modulating the phosphorylation of JNK and NF-kB proteins, which fact is associated with the modulation of the in vitro synthesis of IL-8, which is involved in the inflammatory response in the gut.
