Inhibition of LPS-induced iNOS, COX-2 and cytokines expression by poncirin through the NF-κB inactivation in RAW 264.7 macrophage cells

We previously reported that poncirin, a flavanone glycoside isolated from the EtOAc extract of the dried immature fruits of Poncirus trifoliata, is an anti-inflammatory compound that inhibits PGE₂ and IL-6 production. The present work was undertaken to investigate the molecular actions of poncirin in RAW 264.7 macrophage cell line. Poncirin reduced lipopolysaccharide (LPS)-induced protein levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and the mRNA expressions of iNOS, COX-2, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in a concentration- dependent manner, as determined by Western blotting and RT-PCR, respectively. Furthermore, poncirin inhibited the LPS-induced DNA binding activity of nuclear factor-κB (NF-κB). Moreover, this effect was accompanied by a parallel reduction in IκB-α degradation and phosphorylation that in by nuclear translocations of p50 and p65 NF-βB subunits. Taken together, our data indicate that anti-inflammatory properties of poncirin might be the result from the inhibition iNOS, COX-2, TNF-α and IL-6 expression via the down-regulation of NF-κB binding activity.