Influenza A viruses are a major cause of mortality. Given the potential for future lethal pandemics, effective drugs are needed for the treatment of severe influenza such as that caused by H5N1 viruses. Using mediator lipidomics and bioactive lipid screen, we report that the omega-3 polyunsaturated fatty acid (PUFA)-derived lipid mediator protectin D1 (PD1) markedly attenuated influenza virus replication via RNA export machinery. Production of PD1 was suppressed during severe influenza and PD1 levels inversely correlated with the pathogenicity of H5N1 viruses. Suppression of PD1 was genetically mapped to 12/15-lipoxygenase activity. Importantly, PD1 treatment improved the survival and pathology of severe influenza in mice, even under conditions where known antiviral drugs fail to protect from death. These results identify the endogenous lipid mediator PD1 as an innate suppressor of influenza virus replication that protects against lethal influenza virus infection.

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Phospholipase A 2 hydrolyzes the sn-2 ester bond of glycerophospholipids that produce free fatty acids and lysophospholipids. Cytosolic phospholipase A 2 s (cPLA 2 , group IV) are a subgroup of enzymes that act on the intracellular phospholipid membrane. The best investigated cPLA 2 ␣ (group IVA) is a key enzyme for lipid mediator production in vivo. Here we report cloning and characterization of novel murine cPLA 2 s: cPLA 2 ␦ (group IVD), cPLA 2 ⑀ (group IVE), and cPLA 2 (group IVF), that form a gene cluster with cPLA 2 ␤ (group IVB). The deduced amino acid sequences of cPLA 2 ␦, ⑀, and demonstrated a conserved domain structure of cPLA 2 , i.e. one C2 domain and one lipase domain. The potential catalytic dyad, Ser and Asp, was conserved for these newly cloned cPLA 2 s along with relatively high conservation for the surrounding residues. Transcripts of murine cPLA 2 ␦, ⑀, and appeared to be enriched in certain organs rather than ubiquitous distribution. Major Northern signals for cPLA 2 ␦ were detected in placenta, cPLA 2 ⑀ in thyroid, heart, and skeletal muscle, and cPLA 2 in thyroid. Recombinant proteins expressed in human embryonic kidney 293 cells demonstrated molecular sizes of about 100 kDa by Western blotting and exhibited Ca 2؉ -dependent PLA 2 activities on 1-palmitoyl-2-[ 14 C]arachidonoyl-phosphatidylcholine substrate. In contrast to cPLA 2 ␣, cPLA 2 preferred phosphatidylethanolamine to phosphatidylcholine. Intracellular localization was visualized by green fluorescent-tagged proteins. Each molecule showed specific localization, and cPLA 2 ␦ translocated from the cytosol to the perinuclear region by calcium-ionophore stimulation. We thus discovered these functional novel cPLA 2 genes, which cluster on murine chromosome 2E5.

BackgroundSubarachnoid hemorrhage (SAH) frequently results in several complications, including cerebral vasospasm, associated with high mortality. Although cerebral vasospasm is a major cause of brain damages after SAH, other factors such as inflammatory responses and oxidative stress also contribute to high mortality after SAH. Trehalose is a non-reducing disaccharide in which two glucose units are linked by α,α-1,1-glycosidic bond, and has been shown to induce tolerance to a variety of stressors in numerous organisms. In the present study, we investigated the effect of trehalose on cerebral vasospasm, inflammatory responses, and oxidative stress induced by blood in vitro and in vivo.MethodsEnzyme immunoassay for eicosanoids, pro-inflammatory cytokines, and endothelin-1, and western blotting analysis for cyclooxygenase-2, inducible nitric oxide synthase, and inhibitor of NF-κB were examined in macrophage-like cells treated with hemolysate. After treatment with hemolysate and hydrogen peroxide, the levels of lipid peroxide and amounts of arachidonic acid release were also analyzed. Three hours after the onset of experimental SAH, 18 Japanese White rabbits received an injection of saline, trehalose, or maltose into the cisterna magna. Angiographic and histological analyses of the basilar arteries were performed. In a separate study, the femoral arteries from 60 rats were exposed to fresh autologous blood. At 1, 3, 5, 7, 10, and 20 days after treatment, cryosections prepared from the femoral arteries were histologically analyzed.ResultsWhen cells were treated with hemolysate, trehalose inhibited the production of several inflammatory mediators and degradation of the inhibitor of NF-κB and also suppressed the lipid peroxidation, the reactive oxygen species-induced arachidonic acid release in vitro. In the rabbit model, trehalose produced an inhibitory effect on vasospasm after the onset of experimental SAH, while maltose had only a moderate effect. When the rat femoral arteries exposed to blood were investigated for 20 days, histological analysis revealed that trehalose suppressed vasospasm, inflammatory response, and lipid peroxidation.ConclusionsThese data suggest that trehalose has suppressive effects on several pathological events after SAH, including vasospasm, inflammatory responses, and lipid peroxidation. Trehalose may be a new therapeutic approach for treatment of complications after SAH.

Phosphatidylcholine (PC) is a major constituent of biological membranes and a component of serum lipoproteins and pulmonary surfactants. The PC and other glycerophospholipid compositions of membranes change dynamically through stimulus‐dependent and independent pathways, principally by the action of two different types of enzymes; phospholipase A2 [EC 3.1.1.4] and acyl‐CoA:lysophospholipid acyltransferase [EC 2.3.1.23]. Phospholipase A2 is a key enzyme that catalyzes deacylation of the sn‐2 position of glycerophospholipids. This enzyme is critical in the remodeling of membrane lipids and formation of two subclasses of lipid mediators, fatty acid derivatives and lysophospholipids. Among many different subtypes of phospholipase A2 enzymes, we found that cytosolic phospholipase A2α (cPLA2α) is important in various pathological and physiological responses. Here, we summarize the phenotypes resulting from genetic ablation of cPLA2α, and the properties of newly discovered enzymes in the cPLA2 family. Comprehensive analysis of lipid mediators using liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) is useful for understanding the roles of individual mediators in physiological and pathological processes. iubmb Life, 58: 328‐333, 2006