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Halocynthia aurantium, an edible ascidian species, has not been studied scientifically, even though tunicates and ascidians are well-known to contain several unique and biologically active materials. The current study investigated the fatty acid profiles of the H. aurantium tunic and its immune-regulatory effects on RAW264.7 macrophage cells. Results of the fatty acid profile analysis showed a difference in ratios, depending on the fatty acids being analysed, including those of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA). In particular, omega-3 fatty acids, such as eicosatrienoic acid n-3 (ETA n-3), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), were much higher than omega-6 fatty acids. Moreover, the H. aurantium tunic fatty acids, significantly and dose-dependently, increased the NO and prostaglandin E2 (PGE2) production in RAW264.7 cells, for immune-enhancement without cytotoxicity. In addition, these fatty acids regulated the transcription of immune-associated genes, including iNOS, IL-1β, IL-6, COX-2, and TNF-α. These actions were activated and deactivated via Mitogen-activated protein kinase (MAPK)and NF-κB signaling, to regulate the immune responses. Conversely, the H. aurantium tunic fatty acids effectively suppressed the inflammatory cytokine expressions, including iNOS, IL-1β, IL-6, COX-2, and TNF-α, in LPS-stimulated RAW264.7 cells. Productions of COX-2 and PGE2, which are key biomarkers for inflammation, were also significantly reduced. These results elucidated the immune-enhancement and anti-inflammatory mechanisms of the H. aurantium tunic fatty acids in macrophage cells. Moreover, the H. aurantium tunic might be a potential fatty acid source for immune-modulation.

Fatty acids extracted from the Halocynthia aurantium gonad (HAGF) were shown to be primarily composed of the highest concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) at 41% and 17% of total fatty acids, respectively. In the present study, HAGF were examined for their immunostimulant and anti-inflammatory effects on RAW264.7 macrophage cells. HAGF were found to significantly boost nitric oxide (NO) production and increase the levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin-1β (IL-1β), IL-6, and tumor necrosis factor (TNF)-α expression in a dose-dependent manner. Moreover, the phosphorylation of c-Jun N-terminal kinase/stress-activated protein kinase (JNK), extracellular signal-regulated kinase (ERK), p38, and nuclear factor κB (NF-κB) p65 was up-regulated by the stimulation of RAW264.7 cells with HAGF. When lipopolysaccharide (LPS)—stimulated the macrophages, they also exhibited anti-inflammatory activity via decreasing NO production and immune-related gene expression, Cluster of differentiation (CD) 86 expression, and protein levels in the NF-κB and mitogen-activated protein kinases (MAPK) signaling pathways. Overall, these results indicate that HAGF exert immune-modulatory effects in macrophages.