Glycoprotein isolated from Rhus verniciflua Stokes inhibits inflammation-related protein and nitric oxide production in LPS-stimulated RAW 264.7 cells

Rhus verniciflua Stokes (RVS) has traditionally been used for medical purpose, such as healing of inflammatory diseases in South Korea. Glycoprotein (36 kDa) was isolated from RVS fruit, purified and used to evaluate the inhibitory effect on inflammatory-related proteins and nitric oxide (NO) production in lipopolysaccharide (LPS, 200 ng/ml)-stimulated RAW 264.7 (murine macrophage cell line). Our results were showed that RVS glycoprotein has a strong antioxidative activity against lipid peroxyl radicals in cell-free system, and inhibits NO production in LPS-stimulated RAW 264.7 cells. To elucidate the inhibitory effect of RVS glycoprotein on activities of inflammatory-related proteins, we firstly evaluated the amount of intracellular reactive oxygen species (ROS), and expression of intracellular protein kinase C (PKC), nuclear factor (NF)-kappaB, and activator protein-1 (AP-1). The results in the present study showed that RVS glycoprotein (200 microg/ml) inhibits ROS production and PKCalpha translocation, and down-regulates the expression of NF-kappaB and AP-1. Such upstream signals consequently inhibited the levels of inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 expression. Therefore, we speculate that RVS glycoprotein inhibits the inflammatory-related protein and can act as an anti-inflammatory agent.