Achyranthes japonica exhibits anti-inflammatory effect via NF-κB suppression and HO-1 induction in macrophages

Ethnopharmacological relevance: The roots of Achyranthes japonica Nakai have been used in traditional herbal medicine for the treatment of edema and arthritis in Korea. Aim of the study: In this study, we investigated the molecular mechanism responsible for anti-inflammatory effects of the aqueous extract of A. japonica roots (AJ) in LPS-stimulated macrophages. Materials and methods: Nitric oxide (NO) production and as inducible nitric oxide synthase (iNOS) expression were examined in TG-elicited peritoneal macrophages and RAW 264.7 cells. Cell viability was monitored by MTT assay. Protein and mRNA expressions were determined by Western blotting and RT-PCR, respectively. The activity of NF-kappa B and Nrf2 were examined by EMSA, immunocytochemistry or reporter assay. Results: AJ inhibited LPS-induced NO secretion as well as iNOS expression, without affecting cell viability. Furthermore, AJ suppressed LPS-induced NF-kappa B activation, degradation of I kappa B-alpha, phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38. Further study demonstrated that AJ induced heme oxygenase-1 (HO-1) gene expression via nuclear translocation and transactivation of Nrf2. In addition, the inhibitory effects of AJ on iNOS expression were abrogated by small interfering RNA-mediated knock-down of HO-1. Conclusions: These results suggest that AJ suppresses LPS-induced NO production and iNOS expression in macrophages through the inhibition of I kappa B/NF-kappa B and MAPK as well as the Nrf2-mediated HO-1 induction. These findings provide the scientific rationale for anti-inflammatory therapeutic use of A. japonica roots. (C) 2012 Elsevier Ireland Ltd. All rights reserved.