Nitiric oxide (NO) and eicosanoids function as crucial immune mediators in insects. This study focuses on cross-talkbetween two immune mediators in term of humoral immune response in Spodoptera exigua. Up-regulation of eight differentanti-microbial peptides (AMP) was observed against bacterial challenge. In contrast, injection of E. coli along with L-NAMEsignificantly down regulation the AMP production whereas D-NAME was not effective. The injection of E. coli withdexamethasone or SNAP also decreased AMP production whereas arachidonic acid (AA) compensated the dexamethasoneeffects. RNA inerferece against SeNOS showed the down-regulation of defensin mRNA level, whereas dsNOS injectionswith AA reversed the gene regulation.

As the immune reactions in human white blood cells of certain substances from insects to defend it when invaded by immune blood cells is increased. We experiment with changes in the total number of blood cells through the blood cells which increases and decreases, as well as to observe whether the immune response through any route is to evaluate what happens. Hemocyte population was analyzed in the last instar larvae of Spodoptera exigua. Granulocyte and plasmatocyte were predominant (>75%) types of hemocytes, whereas spherulocyte, prohemocyte, and oenocytoid hemocytes were observed in small densities (5~10%). Total hemocyte counts (THCs) were varied among different ages (day1-day5) of the last instar, in which day 3 larvae (L5D3) had the maximal density. Upon bacterial challenge to L5D3 larvae, THC was further enhanced within 2 h and then decreased to background level. This rapid THC increase in response to bacterial challenge was inhibited by injection with dexamethasone (1 ㎍ per larva). However, the addition of arachidonic acid reversed the inhibitory activity of dexamethasone and allowed the larvae to increase THC. This THC increase was mediated by cyclooxygenase products, but not by lipoxygenase products.

Monoamines have been known to mediate cellular immune responses such as hemocyte nodulation and phagocytosis in some insects. Eicosanoids also mediate the cellular immune reactions responsible for clearing bacterial infection from hemolymph circulation in various insects. In this study, we investigated a functional relationship of both mediators in expressing hemocyte nodulation and phagocytosis of fifth instar larvae of the beet armyworm, Spodoptera exigua. Addition of octopamine or serotonin along with bacteria enhanced hemocyte nodulation and phagocytosis of S. exigua larvae. Phentolamine (octopamine inhibitor) and ketanserin (serotonin inhibitor) suppressed hemocyte nodulation and phagocytosis of S. exigua in response to a bacterial challenge. Each inhibitory effect of both monoamine inhibitors was recovered by addition of either octopamine or serotonin, suggesting their independent signaling pathways. Both inhibitor effects were also recovered by addition of arachidonic acid (a precursor of eicosanoid biosynthesis). Furthermore, the stimulatory effects of monoamines on the cellular immune responses were prevented by addition of dexamethasone (a specific phospholipase A2). However, the inhibitory effect of dexamethasone was not recovered by excess amounts of monoamines. These results suggest that monoamines mediate hemocyte nodulation and phagocytosis through a downstream eicosanoid signal pathway in S. exigua.

Background : While the anti-inflammatory effects of 20 (S)-ginsenoside Rg3 (Rg3) have been studied, it remains unclear how Rg3 regulates lipid metabolism in inflammatory macrophages. Thus, in this study, we characterized some eicosanoids related to the anti-inflammatory effects of 20 (S)-ginsenoside Rg3 in murine macrophages. Methods and Results : UPLC-MS/MS was used to profile various eicosanoids from RAW264.7 cells treated with lipopolysaccharide (LPS) and Rg3. The profiling data were statistically analyzed by principal component analysis, hierarchical clustering analysis and analysis of variance. The anti-inflammatory effect of Rg3 was validated by assessing the levels of nitric oxide, tumor necrosis factor-α, and interleukin-6 in the activated macrophages treated with Rg3. A total of 69 eicosanoids were analyzed in RAW264.7 cells. Principal component and hierarchical cluster analyses differentiated control cells from cells treated with LPS, Rg3, or LPS + Rg3 for 12 or 24 h. Furthermore, some differentially regulated compounds were found between macrophages treated with LPS for 24 h and those treated with LPS + Rg3 for 24 h. Conclusion : Rg3 alters eicosanoid metabolism in activated macrophages treated with LPS. Furthermore, we identified several eicosanoids correlated with the anti-inflammatory activity of Rg3.