Mast cell-derived prostaglandin D2 limits the subcutaneous absorption of honey bee venom in mice.

Mast cells play pivotal roles in innate host defenses against venom. Activated mast cells release large amounts of prostaglandin D2 (PGD2). However, the role of PGD2 in such host defense remains unclear. We found that c-kit-dependent and c-kit-independent mast cell-specific hematopoietic prostaglandin D synthase (H-pgds) deficiency significantly exacerbated honey bee venom (BV)-induced hypothermia and increased mortality rates in mice. BV absorption via postcapillary venules in the skin was accelerated upon endothelial barrier disruption resulting in increased plasma venom concentrations. These results suggest that mast cell-derived PGD2 may enhance host defense against BV and save lives by inhibiting BV absorption into circulation.

Deficiency of interleukin-19 exacerbates acute lung injury induced by intratracheal treatment of hydrochloric acid.

Interleukin (IL-19) belongs to the IL-10 family of cytokines and plays diverse roles in inflammation, cell development, viral responses, and lipid metabolism. Acute lung injury (ALI) is a severe respiratory condition associated with various diseases, including severe pneumonia, sepsis, and trauma, lacking established treatments. However, the role of IL-19 in acute inflammation of the lungs is unknown. We reported the impact of IL-19 functional deficiency in mice crossed with an ALI model using HCl. Lungs damages, neutrophil infiltration, and pulmonary edema induced by HCl were significantly worse in IL-19 knockout (KO) mice than in wild-type (WT) mice. mRNA expression levels of C-X-C motif chemokine ligand 1 (CXCL1) and IL-6 in the lungs were significantly higher in IL-19 KO mice than in WT mice. Little apoptosis was detected in lung injury in WT mice, whereas apoptosis was observed in exacerbated area of lung injury in IL-19 KO mice. These results are the first to show that IL-19 is involved in acute inflammation of the lungs, suggesting a novel molecular mechanism in acute respiratory failures. If it can be shown that neutrophils have IL-19 receptors and that IL-19 acts directly on them, it would be a novel drug target.

Prostaglandin F2α receptor antagonist attenuates LPS-induced systemic inflammatory response in mice.

Although it is known that prostaglandin (PG) F2α level is elevated in the plasma of patients with sepsis, the roles of PGF2α is still unknown. We aimed to clarify the roles of PGF2α in the regulation of lipopolysaccharide (LPS)-induced systemic inflammation. At 24 hours after LPS administration, neutrophil infiltration in peritoneal cavity, the mRNA expression of pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin (IL)-1ß, IL-6, and macrophage inflammatory protein-2, and tissue damages in lung, liver, and kidney were all increased. Inhibition of FP receptors significantly decreased LPS-induced neutrophil infiltration and lowered the mRNA expression of the pro-inflammatory cytokines. At 6 hour after LPS administration, the level of anti-inflammatory cytokine, IL-10 in peritoneal lavage fluid was higher than that in naïve mice. Inhibition of FP receptors in these mice increased IL-10 level further. Stimulation of isolated peritoneal neutrophils by LPS increased the gene expression of IL-10, which was further increased by AL8810 treatment. Administration of an anti-IL-10 antibody antagonized the AL8810-decreased mRNA expression of pro-inflammatory cytokines and tissue damages. These results indicate that inhibition of FP receptors by AL8810 attenuated LPS-induced systemic inflammation in mice via enhanced IL-10 production.

Inhibition of Prostaglandin F2α Receptors Exaggerates HCl-Induced Lung Inflammation in Mice.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are severe respiratory disorders that are caused by aspiration, sepsis, trauma, and pneumonia. A clinical feature of ALI/ARDS is the acute onset of severe hypoxemia, and the mortality rate, which is estimated at 38-50%, remains high. Although prostaglandins (PGs) are detected in the bronchoalveolar lavage fluid of patients with ALI/ARDS, the role of PGF2α in ALI remains unclear. We aimed to clarify the role of PGF2α/PGF2α receptor (FP) signaling in acid-induced ALI using an FP receptor antagonist, AL8810. Intratracheal injection of hydrochloric acid (HCl) increased neutrophil migration into the lungs, leading to respiratory dysfunction. Pre-administration of AL8810 further increased these features. Moreover, pre-treatment with AL8810 enhanced the HCl-induced expression of pro-inflammatory cytokines and neutrophil migratory factors in the lungs. Administration of HCl decreased the gene expression of lung surfactant proteins, which was further reduced by co-administration of AL8810. Administration of AL8810 also increased lung edema and reduced mRNA expression of epithelial sodium channel in the lungs, indicating that AL8810 reduced fluid clearance. Furthermore, AL8810 also increased lipopolysaccharide-induced expression of adhesion molecules such as intracellular adhesion molecule-1 and E-selectin in human umbilical vein endothelial cells. These results indicate that inhibition of FP receptors by AL8810 exacerbated HCl-induced ALI.

Epithelial cell-derived prostaglandin D2 inhibits chronic allergic lung inflammation in mice.

The precise role of prostaglandin D (PGD)2 in allergic lung inflammation remains controversial. Here, we aimed to clarify the role of PGD2 in chronic allergic lung inflammation using hematopoietic PGD synthase (H-PGDS)-deficient mice. Repeated intranasal administration of ovalbumin (OVA) resulted in eosinophilic infiltration and mucin production in the lungs of wild type (WT) mice, leading to respiratory dysfunction. H-PGDS deficiency exacerbated these effects, which were accompanied by increased mRNA expression of TNF-α and eosinophil chemoattractants. The bronchial epithelium expressed both H-PGDS and TNF-α in the inflamed WT lung, and H-PGDS deficiency increased TNF-α expression further. In cultured bronchial tissue of WT mice, treatment with LPS elevated mRNA expression of TNF-α and eosinophil chemoattractants. H-PGDS deficiency promoted the expression of these factors, which was inhibited by treatment with PGD2 receptor, D prostanoid (DP) receptor agonist, or PGD2 metabolite 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2). Treatment with TNF-α receptor antibody inhibited eosinophil chemoattractant expression. In vivo, administration of DP agonist or 15d-PGJ2 inhibited OVA-induced allergic lung inflammation. Bronchial epithelial cell-derived PGD2 attenuated lung eosinophilic infiltration with chronic allergic inflammation; these phenomena are at least partly attributed to the inhibition of TNF-α production via DP activation or 15-deoxy-Δ12,14-PGJ2 signaling.-Maehara, T., Nakamura, T., Maeda, S., Aritake, K., Nakamura, M., Murata, T. Epithelial cell-derived prostaglandin D2 inhibits chronic allergic lung inflammation in mice.

Hematopoietic prostaglandin D synthase-derived prostaglandin D2 ameliorates adjuvant-induced joint inflammation in mice.

Although prostaglandins (PGs) are known to be involved in the progression of arthritis, the role of PGD2 remains unclear. In this study, we evaluated the role of PGD2 in joint inflammation using genetically modified mice. Injection of complete Freund's adjuvant (CFA) increased the production of PGD2 and induced paw swelling and cartilage erosion in wild-type (WT) mice. These phenomena were accompanied with an increase in the mRNA levels of TNF-α, IL-6, IL-1ß, and matrix-degrading metalloproteinase-9. Knockdown of hematopoietic PGD synthase (H-PGDS) abolished the PGD2 production and exacerbated all of the arthritic manifestations in the inflamed paw. Immunostaining revealed that infiltrating macrophages strongly expressed H-PGDS in the CFA-injected paw. Morphologic studies revealed vascular hyperpermeability and angiogenesis in the inflamed WT paw. H-PGDS deficiency was accelerated, whereas daily administration of a PGD2 receptor D prostanoid (DP) agonist attenuated the CFA-induced hyperpermeability and angiogenesis. We further confirmed that DP deficiency exacerbated, whereas the administration of the DP agonist improved, the CFA-induced arthritic manifestations. The findings demonstrate that H-PGDS-derived PGD2 ameliorates joint inflammation by attenuating vascular permeability and subsequent angiogenesis and indicates the therapeutic potential of a DP agonist for arthritis.-Tsubosaka, Y., Maehara, T., Imai, D., Nakamura, T., Kobayashi, K., Nagata, N., Fujii, W., Murata, T. Hematopoietic prostaglandin D synthase-derived prostaglandin D2 ameliorates adjuvant-induced joint inflammation in mice.

Profile of uterine flush lipid mediators in cows with subclinical endometritis: pilot study.

Subclinical endometritis affects reproductive outcomes and causes economic losses in dairy cows, thus, it is important to understand disease progression mechanisms and develop diagnostic procedures for better disease management. We measured the levels of 146 lipid mediators in uterine flush samples using lipid chromatography-mass spectrometry. We detected 25 lipid mediators in the uterine flush of both the control and subclinical endometritis cows; 15 of the 25 lipid mediators were AA-derived metabolites. Among the AA-derived metabolites, cyclooxygenase (COX)-generated mediators were the most abundant. Specifically, levels of 11ß-13,14-dihydro-15-keto prostaglandin (PG) F2α, PGE2, PGA2, 13-hydroxyoctadecadienoic acid, and PGD1 were elevated in all the cows with subclinical endometritis. This study may provide new insights for the management of subclinical bovine endometritis.

Leukotriene C4 synthase is a novel PPARγ target gene, and leukotriene C4 and D4 activate adipogenesis through cysteinyl LT1 receptors in adipocytes.

Leukotriene (LT) C4 synthase (LTC4S) catalyzes the conversion from LTA4 to LTC4, which is a proinflammatory lipid mediator in asthma and other inflammatory diseases. LTC4 is metabolized to LTD4 and LTE4, all of which are known as cysteinyl (Cys) LTs and exert physiological functions through CysLT receptors. LTC4S is expressed in adipocytes. However, the function of CysLTs and the regulatory mechanism in adipocytes remain unclear. In this study, we investigated the expression of LTC4S and production of CysLTs in murine adipocyte 3T3-L1 cells and their underlying regulatory mechanisms. Expression of LTC4S and production of LTC4 and CysLTs increased during adipogenesis, whereas siRNA-mediated suppression of LTC4S expression repressed adipogenesis by reducing adipogenic gene expression. The CysLT1 receptor, one of the two LTC4 receptors, was expressed in adipocytes. LTC4 and LTD4 increased the intracellular triglyceride levels and adipogenic gene expression, and their enhancement was suppressed by co-treatment with pranlukast, a CysLT1 receptor antagonist. Moreover, the expression profiles of LTC4S gene/protein during adipogenesis resembled those of peroxisome proliferator-activated receptor (PPAR) γ. LTC4S expression was further upregulated by treatment with troglitazone, a PPARγ agonist. Promoter-luciferase and chromatin immunoprecipitation assays showed that PPARγ directly bound to the PPAR response element of the LTC4S gene promoter in adipocytes. These results indicate that the LTC4S gene expression was enhanced by PPARγ, and LTC4 and LTD4 activated adipogenesis through CysLT1 receptors in 3T3-L1 cells. Thus, LTC4S and CysLT1 receptors are novel potential targets for the treatment of obesity.

Protection of 6-OHDA neurotoxicity by PGF2α through FP-ERK-Nrf2 signaling in SH-SY5Y cells.

6-Hydroxydopamine (6-OHDA) is a neurotoxin that destroy dopaminergic neurons and widely used to establish animal models of Parkinson's disease. Prostaglandins (PGs) are involved in various cellular processes, including the damage and repair of neuronal cells. However, the function of PGF2α in neuronal cells remains unclear. In this study, we investigated the effects of PGF2α against 6-OHDA-mediated toxicity in human neuroblastoma SH-SY5Y cells and elucidated its underlying molecular mechanism. When the cells were treated with 6-OHDA (50 µM) for 6 h, the expression levels of PGF2α synthetic enzymes; cyclooxygenase-2 and aldo-keto reductase 1C3 as PGF2α synthase were enhanced in an incubation-time-dependent manner. In addition, the production of PGF2α was increased in 6-OHDA-treated cells. Fluprostenol, a PGF2α receptor (FP) agonist (500 nM), suppressed 6-OHDA-induced cell death by decreasing the production of reactive oxygen species (ROS) and increasing the expression of the anti-oxidant genes. These fluprostenol-mediated effects were inhibited by co-treatment with AL8810, an FP receptor antagonist (1 µM) or transfection with FP siRNA (20 nM). Moreover, 6-OHDA-induced phosphorylation of extracellular signal-regulated kinase (ERK), a member of the mitogen-activated protein kinase family, was inhibited by co-incubation with AL8810. Furthermore, fluprostenol itself enhanced ERK phosphorylation and further elevated the 6-OHDA-induced phosphorylation of ERK. In addition, 6-OHDA induced nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), activating anti-oxidant gene expression, was repressed by co-culturing with AL8810. These results indicate that PGF2α suppressed 6-OHDA-induced neuronal cell death by enhancing anti-oxidant gene expression via the FP receptor-ERK-Nrf2 signaling. Thus, FP receptor is a potential target for inhibition of ROS-mediated neuronal cell death.

Contribution of FP receptors in M1 macrophage polarization via IL-10-regulated nuclear translocation of NF-κB p65.

Macrophages are the effector immune cells with plasticity to differentiate as M1 (classically activated) and M2 (alternatively activated) phenotypes. Prostaglandins (PGs) have various important roles and are involved in the regulation of macrophage activation. However, the role of PGF2α in macrophage activation remains unclear. We investigated the role of PGF2α receptor (FP)-mediated signaling in the M1 macrophage polarization using murine macrophage RAW264.7 cells. Stimulation with lipopolysaccharide (LPS) + interferon (IFN)-γ increased the mRNA expression of the M1 macrophage markers such as inducible nitric oxide synthase, tumor necrosis factor-α, and CD11c. Pre-treatment with AL8810, an FP receptor antagonist, further enhanced the expression of these genes. In contrast, treatment with fluprostenol, an FP receptor agonist, decreased the LPS + IFN-γ-induced expression of M1 markers. LPS-induced M1 macrophage polarization was dependent on the activation of NF-κB p65. Treatment with IκB kinase ß inhibitor reduced AL8810-induced mRNA expression of the M1 markers. Stimulation with LPS + IFN-γ increased the expression of IL-10. Pre-treatment with AL8810 lowered LPS + IFN-γ-induced IL-10 expression, and further enhanced LPS + IFN-γ-stimulated nuclear translocation of NF-κB p65. In contrast, co-treatment with IL-10 reversed AL8810-induced nuclear translocation of NF-κB p65. These results indicate that the FP receptor signaling was involved in the control of M1 polarization of macrophages via IL-10-regulated nuclear translocation of NF-κB p65.