Polyacetylenes Impair the Expression of Inducible Nitric Oxide Synthas by Abrogating the Nuclear Translocation of NF-κB and Stat1 in Rat Primary Astrocytes

The effects of polyacetylenes on the activity of inducible nitric oxide synthase (iNOS) induced by lipopolysaccharide/interferon-γ (LPS/IFN-γ) in rat primary astrocytes were investigated. The mechanisms underlying how polyacetylenes confer their effects on INOS activity were also elucidated. Five polyaceylenes differentially abrogated the LPS/IFN-γ-mediated induction of 1NOS as determined by nitrite accumulation in the culture medium. Falcarindiol and panaxynol inhibited the activity of iNOS by about 80-90%. Panaxydol showed medial inhibition on the activity of iNOS, whereas panaxynone and panaxytriol only exerted marginal effects on iNOS expression. Polyacetlenes attenuated the expression of 1NOS in a concentration- and time-dependent manner. The inhibitory effects of polyacetylenes were attributable to decreases in iNOS protein. The detailed inhibitory mechanisms of falcarindiol were further investigated. Electrophoretic mobility shift assay showed that treatment with 50 μM falcarindiol for 30 mill decreased LPS/IFN-γ-induced nuclear factor-κB (NF-κB) activation by 42.8±9.4%. Immunofluorescence staining further confirmed this conclusion. Furthermore, falcarindiol also modulated the nuclear translocation of signal transducer and activator of transcription 1 (Stati) in a time-dependent manner. Fifty tM of falcarindiol diminished the nuclear translocation of Stati by 22.5±5.7, 33.6±5.9, and 20.7±3.5% after 1, 2, and 3 h of treatment, respectively. The present study demonstrates that polyacetylenes attenuate the activation of NF-KB and Stati, thereby leading to the suppression of iNOS expression.