Inhibition by 1′-acetoxychavicol acetate of lipopolysaccharide- and interferon-γ-induced nitric oxide production through suppression of inducible nitric oxide synthase gene expression in RAW264 cells

Although nitric oxide (NO) is an important biological mediator, excessive production in inflammation is thought to be a causative factor of cellular injury and cancer in the long term. In the present study the effects of 1'-acetoxychavicoI acetate (ACA), which has anticarcinogenic properties, on NO production in murine macrophage cell line RAW264 cells stimulated with lipopolysaccharide or interferon-gamma were examined. ACA suppressed NO production dose dependently with an IC50 of 160 ng/ml (680 nM), The decrease in NO production was shown to parallel reduced expression of iNOS mRNA and protein. The influence of ACA on transcription factors, such as NF-kappa B, AP-1 and Stat1, which are involved in expression of the iNOS gene was assessed. ACA was found to suppress degradation of I kappa B, an NF-kappa B inhibitory factor, and consequently inhibit NF-kappa B activation. Activation of AP-1 and Stat1 was also blocked by ACA treatment. Thus we demonstrate that ACA exerts potent inhibitory effects on NO production, apparently mediated by modulation of activation of several transcription factors. This could contribute to the anticarcinogenic properties of ACA.