Inhibitory effect of 30-kDa phytoglycoprotein on expression of TNF-alpha and COX-2 via activation of PKCalpha and ERK 1/2 in LPS-stimulated RAW 264.7 cells.

A 30-kDa DBD glycoprotein, which consists of carbohydrate content (61%) and protein content (39%), is a naturally occurring phytoglycoprotein found in Dioscorea batatas Decne (DBD). In the present study, we investigated the anti-inflammatory potentials of the DBD glycoprotein on lipopolysaccharide (LPS, 2 microg/ml)-induced pro-inflammatory signal transduction cascade in murine macrophage cell line (RAW 264.7 cells). Our results showed that the DBD glycoprotein significantly inhibits the translocation of protein kinase C alpha (PKCalpha) to membrane and the phosphorylation of extracellular signal-regulated kinase (ERK) in LPS-stimulated RAW 264.7 cells. We also found that the DBD glycoprotein (200 microg/ml) has suppressive effects on the DNA binding activities of nuclear factor-kappa B (NF-kappaB), on the expression of p50, p65, tumor necrosis factor (TNF)-alpha, and cyclooxygenase (COX)-2, and on the production of superoxide anion radical [see text] in LPS-stimulated RAW 264.7 cells. Interestingly, the expression of TNF-alpha and COX-2 was significantly blocked by treatment with PKC inhibitor (Staurosporine) as well as ERK1/2 inhibitors (PD98059). Collectively, we assume that the DBD glycoprotein has anti-inflammatory potential, which can modulate pro-inflammatory signal transduction cascade in LPS-stimulated RAW 264.7 cells.