Immune enhancement effects of neutral lipids, glycolipids, phospholipids from Halocynthia aurantium tunic on RAW264.7 macrophages

The fractionated lipids of Halocynthia aurantium (Pyuridae) have been demonstrated to possess anti-inflammatory properties, but their modulatory properties have not been studied. This study aimed at estimating the immune enhancing effects of fractionated lipids from H. aurantium tunic on macrophage cells. The tunic of H. aurantium was used to isolate total lipids, which were then subsequently separated into neutral lipids, glycolipids, and phospholipids. RAW264.7 cells were stimulated with different concentrations (0.5, 1.0, 2.0, and 4.0%) of each fractionated lipid. The cytotoxicity, the production of NO, the expression of immune-associated genes, and signaling pathways were performed. The neutral lipids and glycolipids significantly stimulated the production of NO and the expression of IL-1β , IL-6 , TNF-α and COX-2 in a dose-dependent manner, while phospholipids ineffectively induced NO production and mRNA expression. Furthermore, it was found that both the neutral and glycolipids increased NF-κB p-65, p38, ERK1/2 and JNK phosphorylation, suggesting that these lipids may enhance immunity by activating the NF-κB and MAPK signaling pathways. In addition, H. aurantium lipids-induced TNF-α expression was also decreased by blocking the MAPK or NF-κB signaling pathways. These results suggest that the neutral lipids and glycolipids from H. aurantium tunic have potential as a source of immune-enhancement materials.