Atractylenolide I (ATL-I) is a bioactive component of Rhizoma Atractylodis macrocephalae. Although increasing evidence shows that ATL-I has an anti-inflammatory effect, the anti-inflammatory molecular mechanism of ATL-I is still unknown. In this study, we investigated the effect of ATL-I on cell viability by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay and the level of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) by enzyme-linked immunosorbent assay (ELISA) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Further, we examined the effect of ATL-I on the activation of nuclear factor-kappaB (NF-κB) and phosphorylation of extracellular signal regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38) by Western blot. We also investigated the effect of ATL-I on the expression of myeloid differentiation protein-2 (MD-2), CD14, complement receptor 3 (CR3), scavenger receptor class A (SR-A), toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88). We found that ATL-I showed no inhibitory effect on cell viability at concentrations ranging from 1 µM to 100 µM and markedly reduced the release of IL-6 and TNF-α at a concentrate-dependent manner. In addition, ATL-I suppressed the activity of nuclear NF-κB and the phosphorylation of ERK1/2 and p38 in LPS-treated RAW264.7 cells. Further analysis showed that ATL-I inhibited the expression of MD-2, CD14, SR-A, TLR4 and MyD88, but the expression of CR3 was unaffected. These data suggest that ATL-I shows an anti-inflammatory effect by inhibiting TNF-α and IL-6 production. The anti-inflammatory effects of ATL-I may be associated with the inhibition of the NF-κB, ERK1/2 and p38 signaling pathways.

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