Inhibition of LPS-induced NO and PGE2 production by asiatic acid via NF-κB inactivation in RAW 264.7 macrophages: Possible involvement of the IKK and MAPK pathways

In the present study, we investigated the effect of asiatic acid (the aglycon of asiaticoside) and asiaticoside isolated from the leaves of Centella asiatica (Umbelliferae) on LPS-induced NO and PGE2 production in RAW 264.7 macrophage cells. Asiatic acid more potently inhibited LPS-induced NO and PGE2 production than asiaticoside. Consistent with these observations, the protein and mRNA expression levels of inducible iNOS and COX-2 enzymes were inhibited by asiatic acid in a concentration-dependent manner. In addition, asiatic acid dose-dependently reduced the production of IL-6, IL-1β and TNF-α in LPS-stimulated RAW 264.7 macrophage cells. Furthermore, asiatic acid inhibited the NF-κB activation induced by LPS, and this was associated with the abrogation of IκB-α degradation and with subsequent decreases in nuclear p65 and p50 protein levels. Moreover, the phosphorylations of IKK, p38, ERK1/2, and JNK in LPS-stimulated RAW 264.7 cells were suppressed by asiatic acid in a dose-dependent manner. These results suggest that the anti-inflammatory properties of asiatic acid might be the results from the inhibition of iNOS, COX-2, IL-6, IL-1β, and TNF-α expressions through the down-regulation of NF-κB activation via suppression of IKK and MAP kinase (p38, ERK1/2, and JNK) phosphorylation in RAW 264.7 cells.