An ethyl acetate fraction derived from Houttuynia cordata extract inhibits the production of inflammatory markers by suppressing NF-kB and MAPK activation in lipopolysaccharide-stimulated RAW 264.7 macrophages

Background: Houttuynia cordata Thunb. (Saururaceae) has been used in traditional medicine for treatment of inflammatory diseases. This study evaluated the anti-inflammatory effects of an ethyl acetate fraction derived from a Houttuynia cordata extract (HCE-EA) on the production of inflammatory mediators and the activation of nuclear factor-kB (NF-kB) and mitogen-activated protein kinases (MAPKs) in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Methods: To measure the effects of HCE-EA on pro-inflammatory cytokine and inflammatory mediator's expression in RAW 264.7 cells, we used the following methods: cell viability assay, Griess reagent assay, enzyme-linked immunosorbent assay, real-time polymerase chain reaction and western blotting analysis. Results: HCE-EA downregulated nitric oxide (NO), prostaglandin E-2 (PGE(2)), tumor necrosis factor-a (TNF-a), and interleukin (IL-6) production in the cells, as well as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression. Furthermore, HCE-EA suppressed nuclear translocation of the NF-kB p65 subunit, which correlated with an inhibitory effect on IkBa (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha) phosphorylation. HCE-EA also attenuated the activation of MAPKs (p38 and JNK). Conclusions: Our results suggest that the anti-inflammatory properties of HCE-EA may stem from the inhibition of pro-inflammatory mediators via suppression of NF-kB and MAPK signaling pathways.