Abstract
The objective of this study was to investigate the immune-enhancing activity of a high molecular weight fraction (HMF) of Cynanchum wilfordii in RAW 264.7 macrophages and the cyclophosphamide (CYC)-induced mouse model of immunosuppression. To identify the bioactive substances of HMF, a crude polysaccharide (HMFO) was obtained and treated with sodium periodate (an oxidation agent) or digested with protease. In macrophages, HMF treatment enhanced the production of nitric oxide (NO) and cytokines (tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and interleukin 1β (IL-1β)), as well as phagocytic ability. In CYC-immunosuppressed mice, HMF improved relative spleen and thymus weights, natural killer (NK) cell activity, and splenic lymphocyte proliferation. These increases in NO and cytokines were mediated by up-regulation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. Periodate treatment, but not protease treatment, decreased the immune-enhancing activity of HMFO, suggesting that polysaccharides are the active ingredients in C. wilfordii extract.