Antioxidant and anti-inflammatory activities of Radix Isatidis polysaccharide in murine alveolar macrophages

Radix Isatidis is an official herbal medicine for treatment of infection and inflammation in China. In this study, a novel heteropolysaccharide (RIWP) was isolated from R. Isatidis through DEAE Sepharose Fast Flow column and Sepharose CL-6B column. RIWP had a molecular weight of 57 kDa and was mainly composed of glucose, galactose and arabinose with a relative molar ratio of 2.0:1.1:1.0. The cytoprotective, antioxidant and anti-inflammatory properties of RIWP in lipopolysaccharide (LPS) stimulated murine alveolar macrophages were first reported here. Pretreatment with RIWP was found to potently prolong cell survival and repress the generation of reactive oxygen species (ROS) and lipid peroxidation after LPS-stimulation in murine alveolar macrophages. Furthermore antioxidant status was significantly deteriorated in the LPS-treated alveolar macrophages, such as low superoxide dismutase (SOD) activity and G-SH content, which was effectively restored by RIWP supplementation. More importantly, RIWP significantly suppressed LPS-induced increase in nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production in murine alveolar macrophages. Additionally RIWP recovered mitochondrial membrane potential to normal conditions. All above response to LPS stimulation behaved in a concentration-dependent manner. This study provided evidences that RIWP appears to have the potential to prevent inflammatory disease in lung.