The polysaccharide from Aralia continentalis Kitagawa enhances immune responses via activating the MAPKs and NF-κB signaling pathways in RAW 264.7 macrophages

Polysaccharides derived from Aralia continentalis Kitagawa possess excellent biological properties, such as anti-tumor, antioxidant, antibacterial, lipid-lowering, and anti-inflammatory. However, the immunomodulatory effects of these polysaccharides on macrophages and their underlying mechanisms remain largely unexplored due to their complex molecular structure. The study isolated and characterized a pure polysaccharide, namely WACP(S)-A3-b from Aralia continentalis Kitagawa to investigate its impact on RAW 264.7 cell activation. The structural analysis of WACP(S)-A3-b revealed an average molecular weight of 40.1 kDa with a pectin-like structure composed of HG and RG-I domains, primarily composed of galacturonic acid, rhamnose, galactose, fucose, and arabinose at molar ratios of 55.56: 19.60: 10.29: 7.85: 6.69; NMR found that WACP(S)-A3-b contains α-1,4-GalpA, α-1,2-Rhap, α-1,2,4-Rhap, and t-α-GalpA. Further results demonstrated that the immunomodulatory activity of WACP(S)-A3-b could enhance the production of nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α), and promote the expression of interleukin-1beta (IL-1β). Additionally, WACP(S)-A3-b could activate MAPKs and NF-κB signaling pathways, thereby enhancing the ability of RAW 264.7 macrophages to release cytokines. The study isolated and purified the Aralia continentalis Kitagawa stem polysaccharide, clarified the basic structure of the polysaccharide, and explored the mechanism of immune activity, which provided a theoretical basis for the structure–activity relationship of the polysaccharide.