Methanol extracts of Xanthium sibiricum roots inhibit inflammatory responses via the inhibition of nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) in murine macrophages

Ethnopharmacological relevance: Xanthium sibiricum has been used as a traditional Chinese medicine for the treatment of appendicitis, bronchitis, arthritis, and other inflammatory ailments. However, its pharmacological activity related to an anti-inflammatory effect remain unknown. This present study aims to investigate the anti-inflammatory effect of methanol extracts of X. sibiricum roots (MXS), and to further determine its underlying mechanism of action in order to assess the medicinal value of X sibiricum roots. Materials and methods: To assess the anti-inflammatory activity of MXS in lipopolysaccharides (LPS)-stimulated RAW 264.7 macrophages, the production of nitric oxide (NO) was measured using the Griess reagent system. The levels of pro-inflammatory cytokines and mediators were quantified using an Enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR). Subsequently, immunoblotting analyses were employed to detect inflammatory mediators as well as to elucidate the underlying regulatory mechanisms suppressed by MXS. Results: MXS inhibited LPS-stimulated NO production and inducible nitric oxide synthase (iNOS) expression in RAW 264.7 macrophages within the non-cytotoxic concentration range (50-400 mu g/ml). In addition, mRNA and protein levels of pro-inflammatory cytokines such as interleukin (IL)-6, IL-1 beta, and tumor necrosis factor (TNF)-alpha were significantly suppressed by MXS at the concentration of 400 mu g/ml. Furthermore, MXS (200 mu g/ml) clearly reduced the phosphorylation levels of the inhibitor of kappa B alpha (I kappa B alpha) and signal transducer and activator of transcription 3 (STAT3), without affecting changes in the phosphorylation levels of mitogen-activated protein kinases (MAPKs). When five major components (betulin, betulinic acid, beta-sitosterol, stigmasterol, and scopoletin) of MXS were separately investigated, stigmasterol and beta-sitosterol seemed to play major inhibitory roles in the LPS-induced production of inflammatory mediators such as NO, IL-6, and TNF-alpha. Conclusion: Our results demonstrate that MXS has an anti-inflammatory property in LPS-stimulated RAW 264.7 macrophages, and its anti-inflammatory activity is exerted by the regulation of nuclear factor-kappa B (NF-kappa B) and STAT3 signaling pathways. (c) 2015 Elsevier Ireland Ltd. All rights reserved.