Phytoglycoprotein inhibits interleukin-1β and interleukin-6 via p38 mitogen-activated protein kinase in lipopolysaccharide-stimulated RAW 264.7 cells

This study was carried out to investigate the anti-inflammatory effects of 30-kDa glycoprotein isolated from Dioscorea batatas Decne (DBD glycoprotein), which consists of carbohydrate content (61%) and protein content (39%) on lipopolysaccharide (LPS, 2 mu g/ml)-stimulated RAW 264.7 cells. We found that DBD glycoprotein (200 mu g/ml) has an inhibitory effect on the production of intracellular hydrogen peroxide (H2O2), on the phosphorylation of p38 mitogen-activated protein (MAP) kinase, on the DNA binding activity of activator protein-1 (AP-1), and on c-Jun and c-Fos protein expression, respectively. In addition, DBD glycoprotein treatment markedly suppressed the interleukin (IL)-1 beta, IL-6, and inducible nitric oxide synthase (iNOS) expression and the production of nitric oxide (NO) in LPS-stimulated RAW 264.7 cells. Interestingly, IL-1 beta, IL-6, and iNOS expression was significantly attenuated by treatment with protein kinase C (PKC) inhibitor (staurosporine) as well as p38 MAP kinase inhibitor (SKF86002) in LPS-stimulated RAW 264.7 cells. On the basis of these results, we assume that DBD glycoprotein has anti-inflammatory potential, which can modulate proinflammatory signal transduction in LPS-stimulated RAW 264.7 cells.