Immunomodulatory effects of an acidic polysaccharide fraction from herbal Gynostemma pentaphyllum tea in RAW264.7 cells
A new acidic polysaccharide (GPTP-3) with a molecular weight of 2.49 × 106 Da was extracted and purified from Gynostemma pentaphyllum tea. Monosaccharide analysis revealed that GPTP-3 mainly comprised mannose (20.4%), glucuronic acid (17.4%), glucose (33.4%), and galactose (21.4%) (parentheses indicate the molar percentages). Immunostimulating assays indicated that GPTP-3 could markedly promote the secretion of NO, TNF-α, IL-1β, and IL-6 in murine macrophage RAW264.7. TLR4 was found to be a recognized target of GPTP-3. Moreover, TLR4-related mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/Akt, including ERK, JNK, p38, and Akt, were rapidly activated by GPTP-3 in RAW264.7 cells. Furthermore, GPTP-3 was found to induce the nuclear translocation of NF-κB subunit p65. All these findings suggest that MAPK, PI3K/Akt, and NF-κB pathways are involved in GPTP-3-induced macrophage activations, and GPTP-3 has the potential to be developed as a functional food with immunomodulatory functions.