Anti-inflammatory action of methanol extract of Carthamus tinctorius involves in heme oxygenase-1 induction

Ethnopharmacological relevance: The methanol extracts of Carthamus tinctorius (MEC) have long been used in traditional medicine as anti-inflammatory agent, however, the molecular mechanism by which MEC shows anti-inflammatory action is not investigated. Aim of the study: Induction of heme oxygenase-1 (HO-1) by many medicinal herbs has been reported excellent anti-inflammatory action. Thus, the aim of the study is to explore whether anti-inflammatory action of MEC is related with HO-1 induction in RAW 264.7 cells. Materials and methods: The present study was designed to investigate as to MEC induces HO-1 expression so that it reduces inflammation by suppression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in cells activated with lipopolysaccharide (LPS). Results: Expression of HO-1 protein by MEC in macrophages was increased in a concentration- and time-dependent manner. Treatment with MEC significantly inhibited upregulation of both iNOS and COX-2 in LPS-activated macrophages and consequently reduced production of NO and PGE(2), respectively. The reduced expression of iNOS and COX-2 by MEC was reversed by siHO-1 RNA transfection. In addition, NF-E2-related factor (Nrf2) was translocated from cytosol to nucleus by MEC. The binding of NF-kappa B as well as NF-kappa B luciferase activity was also significantly diminished by MEC. Finally, tumor necrosis factor (TNF)-alpha-mediated VCAM-1 expression in endothelial cell was significantly inhibited by MEC. Conclusions: The present results show that MEC induces HO-1 expression via Nrf2 translocation and inhibits NF-kappa B activity, which may be responsible for anti-inflammatory action. Therefore, we propose that anti-inflammatory action of MEC involves at least HO-1 induction. (C) 2010 Elsevier Ireland Ltd. All rights reserved.