Immunomodulatory activity of purified polysaccharides from Rubus chingii Hu fruits in lymphocytes and its molecular mechanisms

Polysaccharides from Rubus chingii Hu fruits (RFPs) were extracted, purified, characterized and investigated for immunomodulatory activity. Results indicated that RFPs were heteropolysaccharides with molecular weight of 51.7 kDa and contained carbohydrate contents of 96.83%. RFPs with characteristic absorptive peaks of polysaccharide structure and α-configuration were composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, arabinose and fucose with a molecular ratio of 0.08:0.17:0.16:0.48:5.73:1.00:1.79:0.03. RFPs promoted splenocyte proliferation, NO release, cytokine production and intracellular Ca2+ concentration. The mechanism underlying splenocyte activation by RFPs was elucidated by RNA-Seq, in which 2214 differentially expressed genes (DEGs), 2030 GO terms and 92 KEGG pathways were identified. RFPs were further proved to induce a balanced Th1/Th2/Th17 response pattern through MAPK, NF-κB, Jak-STAT and Calcium signaling pathways in splenocytes. These findings provided a fundamental basis for the further application of RFPs as immunomodulators in food and medicine.