Immunomodulatory effects of a polysaccharide purified from Lepidium meyenii Walp. on macrophages

A polysaccharide (MP21) was extracted and purified from Lepidium meyenii Walp. using DEAE-52 and Sephacryl (TM) S-500 columns. Its physicochemical properties and macrophage immunomodulatory activity were investigated in vitro. The results indicated that MP21 had an average molecular weight of 3.68 x 10(5) Da and was mainly composed of rhamnose, arabinose and galactose in a molar ratio of 1:4.84:5.34. The conformation of MP21 was between a sphere and random coil, and different treatments could change its conformation and asymmetry. RAW264.7 murine macrophages treated with MP21 could significantly inhibit the proliferation of human hepatocellular carcinoma HepG-2. MP21 could enhance the phagocytic capacity and induce elevated NO, ROS, TNF-alpha, and IL-1 beta secretion in RAW264.7 in a dose dependent manner. MP21 promoted the expression of both iNOS protein and mRNA. The expression of the NF-kappa B p65 protein was also up-regulated by MP21. These results suggest that MP21 could exert cytotoxicity towards HepG-2 by activating macrophages via the NF-kappa B signaling pathway. (C) 2016 Elsevier Ltd. All rights reserved.