Anti-inflammatory activity of bark of Dioscorea batatas DECNE through the inhibition of iNOS and COX-2 expressions in RAW264.7 cells via NF-κB and ERK1/2 inactivation

We identified a bioactive herbal medicine with anti-inflammatory activity from an ethanol extract derived from the bark of Dioscorea batatas DECNE (BDB) in RAW264.7 cells. We examined the effects of BDB on nitric oxide (NO) and prostaglandin E-2 (PGE(2)) production in LPS-induced RAW264.7 cells. BDB consistently inhibited both NO and PGE2 production in a dose-dependent manner, with an IC50 of 87-71 mu g/ml, respectively. The reduction of NO and PGE2 production were accompanied by a reduction in iNOS and COX-2 protein expression, as evaluated by Western blotting. To evaluate the action mode of BDB and its ability to inhibit iNOS and COX-2 protein expression, we assessed the effects of BDB on nuclear factor-kappa B (NF-kappa B) DNA-binding activity, NF-kappa B-dependent reporter gene activity, inhibitory factor-kappa B (I kappa B) phosphorylation and degradation, and p65 nuclear translocation. BDB suppressed DNA-binding activity and reporter gene activity as well as translocation of the NF-kappa B p65 subunit. BDB also down-regulated I kappa B kinase (IKK), thus inhibiting LPS-induced both phosphorylation and the degradation of I kappa B alpha. In addition, BDB also inhibited the LPS-induced activation of ERK1/2. (C) 2010 Elsevier Ltd. All rights reserved.