The polysaccharide from Camellia oleifera fruit shell enhances immune responses via activating MAPKs and NF-κB signaling pathways in RAW264.7 macrophages

BACKGROUND: Macrophage plays an important role in innate immune responses by secreting immune molecules and phagocytosis. Camellia oleifera fruit shell, accounting for approximately 60% weight of the single C. oleifera fruit, is rich in polysaccharides and has several biological activities such as anti-oxidation, lipid regulation and anticancer. However, the immunomodulatory activity of the polysaccharide from C. oleifera fruit shells (CPS) has not been reported. OBJECTIVE: This study aimed to investigate the immunomodulatory activities and mechanisms of CPS in RAW264.7 macrophages. METHODS: The Methyl Thiazolyl Tetrazolium (MTT) method was used to evaluate the effect of CPS on the cell viability of RAW264.7 macrophages, and cell morphology was pictured using microscope. The production of immune-related molecules, including nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor α (TNFα), interleukin (IL)-1β and IL-6, was detected by Griess assay and enzyme-linked immunosorbent assay (ELISA). The protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2) and the phosphorylation level of mitogen-activated protein kinases (MAPKs) were analyzed through western blotting. The mRNA levels of related genes were tested using reverse transcription-polymerase chain reaction (RT-PCR). The nuclear translocation of nuclear factor-kappa B (NF-κB) was detected using immunofluorescence technology. RESULTS: The results indicated that CPS treatment stimulated the production of NO and PGE2 and significantly enhanced the protein expression of iNOS and COX2 with little effect on the cell morphology and viability. Also, the secretion and mRNA levels of TNFα were increased by the treatment of CPS. In addition, CPS treatment markedly upregulated the phosphorylation level of MAPKs including Extracellular Signal Regulated Kinase (ERK), P38, and c-Jun N-terminal Kinase (JNK) at different time points and caused the activation and nuclear translocation of NF-κB. CONCLUSION: Our data implied that CPS exerts immunomodulatory activities by activating MAPKs and NF-κB signaling pathways in RAW264.7 macrophages.