Src and Syk contribute to the anti-inflammatory activities of Achyranthes aspera ethanolic extract

Nuclear factor-kappa B (NF-κB) plays pivotal roles in inflammation. Src and Syk are two tyrosine kinases that act upstream of NF-κB signaling. Although Achyranthes aspera L. (A. aspera) has been used as a traditional medicine to treat fevers and inflammatory ailments and heal wounds, the molecular mechanisms of its anti-inflammatory actions are not yet fully understood.

In this study, we evaluated the anti-inflammatory effect of A. aspera ethanol extract (Aa-EE). To determine the mechanism by which Aa-EE dampens the inflammatory response, nitric oxide (NO) production and the mRNA expression levels of tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) were examined by Griess assay and RT-PCR. Luciferase assays and immunoblotting were also conducted to examine how Aa-EE regulates the NF-κB pathway.

Aa-EE reduced NO production up to 60% without any cytotoxicity. This extract was found to downregulate the mRNA expression levels of inflammatory genes. Aa-EE blocked NF-κB promoter activity induced by both TNF-α and adaptor molecule MyD88 (about 70% and 40%, respectively). Moreover, nuclear translocation of p65 and IκBα phosphorylation were also inhibited. Furthermore, Aa-EE inactivated two upstream signaling molecules, the Src and Syk kinases. In accordance with these data, the kinase activities of Src and Syk were decreased by 50% and 80%, respectively. The anti-inflammatory action of Aa-EE was also confirmed in a gastritis model.

Our data suggest that Aa-EE targets NF-κB to exert its anti-inflammatory properties by suppressing Src and Syk. Therefore, our study raises the possibility that this extract can be developed as a novel natural anti-inflammatory remedy.