β-glucan suppresses LPS-stimulated NO production through the down-regulation of iNOS expression and NFκB transactivation in RAW 264.7 macrophages

The antioxidant and anti-inflammatory protective effects of β-glucan from barley on RAW 264.7 murine macrophage cells induced by lipopolysaccharide (LPS) were examined. The RAW 264.7 murine macrophages were preincubated with various concentrations (0-200 μg/mL) of β-glucan and stimulated with LPS to induce oxidative stress and inflammation. The β-glucan treatments were found to reduce thiobarbituric acid-reactive substance (TBARS) accumulation, and enhance glutathione levels and the activities of antioxidative enzymes, including superoxide dismutase (SOD), catalase, glutathione reductase, and glutathione peroxidase (GSH-px) in the LPS-stimulated macrophages as compared to the LPS-only treated cells. Nitric oxide (NO) production was significantly suppressed in a dose-dependent manner (p<0.05) with an IC₅₀ of 104 μg/mL. Further treatment with β-glucan at 200 μg/mL suppressed NO production to 2% of the LPS-control, and suppressed the levels of inducible nitric oxide synthase (iNOS) protein and mRNA in a dose-dependent manner. The specific DNA binding activity of nuclear factor κB (NFκB) was significantly suppressed by β-glucan treatment with an IC₅₀ of 220 μg/mL in a dose-dependent manner. Finally, barley β-glucan ameliorates NO production and iNOS expression through the down-regulation of NFκB activity, which may be mediated by attenuated oxidative stress in RAW 264.7 macrophages.