Src/NF-κB-targeted inhibition of LPS-induced macrophage activation and dextran sodium sulphate-induced colitis by Archidendron clypearia methanol extract

Abstract

Ethnopharmacological relevance: Archidendron clypearia Jack. (Fabaceae) has been traditionally used to treat various inflammatory diseases such as pain in the eyes. However, the antiinflammatory mechanism of A. clypearia has not been fully elucidated. This study examined the anti-inflammatory mechanism of a 95% methanol extract (Ac-ME) of A. clypearia in vitro and in vivo.

Materials and methods: The effect of Ac-ME on the production of inflammatory mediators in RAW264.7 cells and peritoneal macrophages and on symptoms of colitis in mouse induced by dextran sodium sulphate (DSS) was investigated. Molecular mechanisms underlying the inhibitory effects were elucidated by analyzing the activation of transcription factors and their upstream signaling as well as by evaluating the kinase activity of target enzymes in vitro and in vivo.

Results: Ac-ME dose-dependently suppressed the secretion of nitric oxide (NO) and prostaglandin (PG)E₂ from RAW264.7 cells and peritoneal macrophages stimulated by lipopolysaccharide (LPS). Ac-ME clearly reduced mRNA expression of inducible NO synthase (iNOS), cyclooxygenase (COX)-2, and tumor necrosis factor (TNF)-α by the blockade of nuclear factor (NF)-κB activation and its upstream signaling events containing protein tyrosine kinase such as Syk and Src. In agreement with this, Ac-ME directly reduced the kinase activities of Src and Syk as well as the formation of molecular signaling complex including p85. DSS-induced colitis was also remarkably inhibited by this extract through the suppression of Src and IκBα phosphorylation.

Conclusion: Ac-ME displays strong anti-inflammatory activity in vivo by suppressing Src/Syk-mediated NF-κB activation which is linked to its ethno-pharmacological uses as an anti-gastritis remedy. Through preclinical studies, the potential therapeutic application will be tested further.