Prostaglandin E(2) produced by the lung augments the effector phase of allergic inflammation

Low-dose vanadium pentoxide perturbed lung metabolism associated with inflammation and fibrosis signaling in male animal and in vitro models

Vanadium is available as a dietary supplement and also is known to be toxic if inhaled, yet little information is available concerning the effects of vanadium on mammalian metabolism when concentrations found in food and water. Vanadium pentoxide (V+5) is representative of the most common dietary and environmental exposures, and prior research shows that low-dose V+5 exposure causes oxidative stress measured by glutathione oxidation and protein S-glutathionylation. We examined the metabolic impact of V+5 at relevant dietary and environmental doses (0.01, 0.1, and 1 ppm for 24 h) in human lung fibroblasts (HLFs) and male C57BL/6J mice (0.02, 0.2, and 2 ppm in drinking water for 7 mo). Untargeted metabolomics using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) showed that V+5 induced significant metabolic perturbations in both HLF cells and mouse lungs. We noted 30% of the significantly altered pathways in HLF cells, including pyrimidines and aminosugars, fatty acids, mitochondrial and redox pathways, showed similar dose-dependent patterns in mouse lung tissues. Alterations in lipid metabolism included leukotrienes and prostaglandins involved in inflammatory signaling, which have been associated with the pathogenesis of idiopathic pulmonary fibrosis (IPF) and other disease processes. Elevated hydroxyproline levels and excessive collagen deposition were also present in lungs from V+5-treated mice. Taken together, these results show that oxidative stress from environmental V+5, ingested at low levels, could alter metabolism to contribute to common human lung diseases.NEW & NOTEWORTHY We used relevant dietary and environmental doses of Vanadium pentoxide (V+5) to examine its metabolic impact in vitro and in vivo. Using liquid chromatography-high-resolution mass spectrometry (LC-HRMS), we found significant metabolic perturbations, with similar dose-dependent patterns observed in human lung fibroblasts and male mouse lungs. Alterations in lipid metabolism included inflammatory signaling, elevated hydroxyproline levels, and excessive collagen deposition were present in V+5-treated lungs. Our findings suggest that low levels of V+5 could trigger pulmonary fibrotic signaling.

Prostaglandin regulation of type 2 inflammation: From basic biology to therapeutic interventions

Type 2 immunity is critical for the protective and repair responses that mediate resistance to parasitic helminth infection. This immune response also drives aberrant inflammation during atopic diseases. Prostaglandins are a class of critical lipid mediators that are released during type 2 inflammation and are integral in controlling the initiation, activation, maintenance, effector functions, and resolution of Type 2 inflammation. In this review, we explore the roles of the different prostaglandin family members and the receptors they bind to during allergen‐ and helminth‐induced Type 2 inflammation and the mechanism through which prostaglandins promote or suppress Type 2 inflammation. Furthermore, we discuss the potential role of prostaglandins produced by helminth parasites in the regulation of host–pathogen interactions, and how prostaglandins may regulate the inverse relationship between helminth infection and allergy. Finally, we discuss opportunities to capitalize on our understanding of prostaglandin pathways to develop new therapeutic options for humans experiencing Type 2 inflammatory disorders that have a significant prostaglandin‐driven component including allergic rhinitis and asthma.

Inhibition of microsomal prostaglandin E synthase-1 ameliorates acute lung injury in mice

Background

To examine the effects of BI 1029539 (GS-248), a novel selective human microsomal prostaglandin E synthase-1 (mPGES-1) inhibitor, in experimental models of acute lung injury (ALI) and sepsis in transgenic mice constitutively expressing the mPGES1 (Ptges) humanized allele.

Methods

Series 1: Lipopolysaccharide (LPS)-induced ALI. Mice were randomized to receive vehicle, BI 1029539, or celecoxib. Series 2: Cecal ligation and puncture-induced sepsis. Mice were randomized to receive vehicle or BI 1029539.

Results

Series 1: BI 1029539 or celecoxib reduced LPS-induced lung injury, with reduction in neutrophil influx, protein content, TNF-ɑ, IL-1β and PGE₂ levels in bronchoalveolar lavage (BAL), myeloperoxidase activity, expression of mPGES-1, cyclooxygenase (COX)-2 and intracellular adhesion molecule in lung tissue compared with vehicle-treated mice. Notably, prostacyclin (PGI₂) BAL concentration was only lowered in celecoxib-treated mice. Series 2: BI 1029539 significantly reduced sepsis-induced BAL inflammatory cell recruitment, lung injury score and lung expression of mPGES-1 and inducible nitric oxide synthase. Treatment with BI 1029539 also significantly prolonged survival of mice with severe sepsis. Anti-inflammatory and anti-migratory effect of BI 1029539 was confirmed in peripheral blood leukocytes from healthy volunteers.

Conclusions

BI 1029539 ameliorates leukocyte infiltration and lung injury resulting from both endotoxin-induced and sepsis-induced lung injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03016-9.

Pathophysiological regulation of lung function by the free fatty acid receptor FFA4

Increased prevalence of inflammatory airway diseases including asthma and chronic obstructive pulmonary disease (COPD) together with inadequate disease control by current frontline treatments means that there is a need to define therapeutic targets for these conditions. Here, we investigate a member of the G protein-coupled receptor family, FFA4, that responds to free circulating fatty acids including dietary omega-3 fatty acids found in fish oils. We show that FFA4, although usually associated with metabolic responses linked with food intake, is expressed in the lung where it is coupled to G_q/11 signaling. Activation of FFA4 by drug-like agonists produced relaxation of murine airway smooth muscle mediated at least in part by the release of the prostaglandin E₂ (PGE₂) that subsequently acts on EP₂ prostanoid receptors. In normal mice, activation of FFA4 resulted in a decrease in lung resistance. In acute and chronic ozone models of pollution-mediated inflammation and house dust mite and cigarette smoke-induced inflammatory disease, FFA4 agonists acted to reduce airway resistance, a response that was absent in mice lacking expression of FFA4. The expression profile of FFA4 in human lung was similar to that observed in mice, and the response to FFA4/FFA1 agonists similarly mediated human airway smooth muscle relaxation ex vivo. Our study provides evidence that pharmacological targeting of lung FFA4, and possibly combined activation of FFA4 and FFA1, has in vivo efficacy and might have therapeutic value in the treatment of bronchoconstriction associated with inflammatory airway diseases such as asthma and COPD.

Polymorphisms rs2745557 in PTGS2 and rs2075797 in PTGER2 are associated with the risk of chronic obstructive pulmonary disease development in a Tunisian cohort

We hypothesized that polymorphisms of genes involved in the prostaglandin pathway could be associated with COPD. In this study we explored the involvement of genetic polymorphisms in PTGS2, PTGER2 and PTGER4 genes in the development and severity of COPD and their effects on plasma concentrations of inflammatory/oxidative stress markers. We identified genotypes of PTGS2, PTGER2 and PTGER4 SNPs in a Tunisian cohort including COPD patients (n = 138) and control subjects (n = 216) using PCR-RFLP and PCR TaqMan. Pulmonary function (FEV1 and FVC) were assessed by plethsmography. PGE₂, PGD₂ and cytokine plasma (IL-6, IL-18, TNF-α, TGF-β) concentrations were measured using ELISA and colorimetric standard methods were used to determine oxidative stress concentrations. Genotype frequencies of rs2745557 in PTGS2 and rs2075797 in PTGER2 were different between COPD cases and controls. There was no correlation between these polymorphisms and lung function parameters. For rs2745557, the A allele frequency was higher in COPD cases than in controls. For rs2075797, carriers of the GG genotype were more frequent in the COPD group than in controls. Only rs2745557 in PTGS2 had an effect on PGD₂ and cytokine plasma concentrations. PGD₂ was significantly decreased in COPD patients with the GA or AA genotypes. In contrast, IL-18 and NO plasma concentrations were increased in COPD rs2745557 A allele carriers as compared to homozygous GG subjects. Our findings suggest that rs2745557 in PTGS2 and rs2075797 in PTGER2 are associated with COPD development but not with its severity.

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

Age-Related Dopaminergic Innervation Augments T Helper 2-Type Allergic Inflammation in the Postnatal Lung

Young children are more susceptible to developing allergic asthma than adults. As neural innervation of the peripheral tissue continues to develop after birth, neurons may modulate tissue inflammation in an age-related manner. Here we showed that sympathetic nerves underwent a dopaminergic-to-adrenergic transition during post-natal development of the lung in mice and humans. Dopamine signaled through a specific dopamine receptor (DRD4) to promote T helper 2 (Th2) cell differentiation. The dopamine-DRD4 pathway acted synergistically with the cytokine IL-4 by upregulating IL-2-STAT5 signaling and reducing inhibitory histone trimethylation at Th2 gene loci. In murine models of allergen exposure, the dopamine-DRD4 pathway augmented Th2 inflammation in the lungs of young mice. However, this pathway operated marginally after sympathetic nerves became adrenergic in the adult lung. Taken together, the communication between dopaminergic nerves and CD4⁺ T cells provides an age-related mechanism underlying the susceptibility to allergic inflammation in the early lung.

COX-2 induces T cell accumulation and IFN-γ production during the development of chromium allergy

Chromium (Cr) is commonly added into various metal alloys to improve some mechanical properties such as corrosion resistance, strength, and workability. However, Cr is also known to be a metal allergen for some individuals. Metal allergy is a T cell-mediated disease with symptoms of inflammation and swelling that involve inflammatory cytokines and prostaglandins. Hence, suppressing these inflammation paths by using COX-2 inhibitor might be useful in treating Cr allergy. In this study, mice were used with Cr-induced allergy challenge model. The mice were injected with celecoxib once per day for 7 days one hour after the challenge. Footpad samples were stained with haematoxylin and eosin (H&E), and lymphocytes were isolated from popliteal lymph nodes for the flow cytometric analysis. The results show that both prostaglandin E₂ (PGE₂), a known mediator of inflammation, and cyclooxygenases (COX)-2 have important roles in the development of Cr allergy. Further, COX-2 inhibitor, celecoxib, was effective in relieving swelling and inflammation in Cr-allergic mice concordant with suppression of IFN-γ production by CD8⁺ T cells and T cell accumulation in the lymph nodes. Therefore, the inhibition of COX-2 may be a therapeutic target for Cr allergy, and additional molecules in the PGE₂ signalling pathway may also be an effective therapeutic target for the treatment of metal allergy.

Prostaglandin regulation of T cell biology

Prostaglandins (PG) are pleiotropic bioactive lipids involved in the control of many physiological processes, including key roles in regulating inflammation. This links PG to the modulation of the quality and magnitude of immune responses. T cells, as a core part of the immune system, respond readily to inflammatory cues from their environment, and express a diverse array of PG receptors that contribute to their function and phenotype. Here we put in context our knowledge about how PG affect T cell biology, and review advances that bring light into how specific T cell functions that have been newly discovered are modulated through PG. We will also comment on drugs that target PG metabolism and sensing, their effect on T cell function during disease, and we will finally discuss how we can design new approaches that modulate PG in order to maximize desired therapeutic T cell effects.

miR-155 Modulates Cockroach Allergen- and Oxidative Stress-Induced Cyclooxygenase-2 in Asthma

Exposure to cockroach allergen is a strong risk factor for developing asthma. Asthma has been associated with allergen-induced airway epithelial damage and heightened oxidant stress. In this study, we investigated cockroach allergen-induced oxidative stress in airway epithelium and its underlying mechanisms. We found that cockroach extract (CRE) could induce reactive oxygen species (ROS) production, particularly mitochondrial-derived ROS, in human bronchial epithelial cells. We then used the RT² Profiler PCR array and identified that cyclooxygenase-2 (COX-2) was the most significantly upregulated gene related to CRE-induced oxidative stress. miR-155, predicted to target COX-2, was increased in CRE-treated human bronchial epithelial cells, and was showed to regulate COX-2 expression. Moreover, miR-155 can bind COX-2, induce COX-2 reporter activity, and maintain mRNA stability. Furthermore, CRE-treated miR-155^-/- mice showed reduced levels of ROS and COX-2 expression in lung tissues and PGE₂ in bronchoalveolar lavage fluid compared with wild-type mice. These miR-155^-/- mice also showed reduced lung inflammation and Th2/Th17 cytokines. In contrast, when miR-155^-/- mice were transfected with adeno-associated virus carrying miR-155, the phenotypic changes in CRE-treated miR-155^-/- mice were remarkably reversed, including ROS, COX-2 expression, lung inflammation, and Th2/Th17 cytokines. Importantly, plasma miR-155 levels were elevated in severe asthmatics when compared with nonasthmatics or mild-to-moderate asthmatics. These increased plasma miR-155 levels were also observed in asthmatics with cockroach allergy compared with those without cockroach allergy. Collectively, these findings suggest that COX-2 is a major gene related to cockroach allergen-induced oxidative stress and highlight a novel role of miR-155 in regulating the ROS-COX-2 axis in asthma.

Quantification of membrane transporter proteins in human lung and immortalized cell lines using targeted quantitative proteomic analysis by isotope dilution nanoLC-MS/MS

Information is needed on the expression of transporters in lung to inform drug development and therapeutic decisions. Much of the information currently available is from semiquantitative gene expression or immunometric densitometry studies reported in the literature. NanoLC-MS/MS (MRM mode) isotope dilution targeted quantitative proteomics was used here to quantify twelve selected transporters in fresh human lung membrane fraction samples and in the membrane fraction of selected immortalized human lung epithelial cell line samples. Fractionation was undertaken by homogenization in crude membrane lysis buffer followed by differential centrifugation of the homogenate. In lung membranes we found OATPs to be the most highly expressed transporters of those measured, followed by PEPT2 and ABCs (P-gp & BCRP). SLC22A transporters (OCTs 2 & 3 and OCTN1) were also found to be expressed. OATP2A1, also known as the prostaglandin transporter, was the most highly expressed transporter, being low in two subjects who were at least occasional smokers. One subject, a non-smoker, had an OATP2A1 concentration that was 8.4 times higher than the next nearest concentration, which itself was higher than the concentration of any other transporter. OATP2A1 is known, from gene expression and animal functional studies, to be present in lung. These results inform the understanding of xenobiotic disposition in the lung and show the distinct profile of transporters in lung compared to other tissues.

Prostaglandin E2 Inhibits Group 2 Innate Lymphoid Cell Activation and Allergic Airway Inflammation Through E-Prostanoid 4-Cyclic Adenosine Monophosphate Signaling

Evidence is accumulating that group 2 innate lymphoid cells (ILC2) play an important role in allergic airway inflammation by producing a large amount of type 2 cytokines. But it remains poorly understood how its activities are properly controlled in vivo. Here, we demonstrated that prostaglandin E₂ (PGE₂) had a profound inhibitory effect on IL-33-induced ILC2 expansion and IL-5 and IL-13 production in vitro. This effect was mimicked by PGE₁-alcohol but attenuated by ONO-AE3-208, indicating a selective action through the E-prostanoid 4 (EP4) receptor. In the IL-33-induced asthma model, coadministration of PGE₂ or PGE₁-alcohol resulted in diminished IL-5 and IL-13 production, reduced eosinophilia and alleviated lung pathology. In contrast, EP4-deficient mice displayed an exacerbated inflammatory response in another ILC2-mediated asthma model induced by Alternaria extract. Mechanistic studies demonstrated that the PGE₂-mediated inhibition of ILC2 was dependent on cyclic adenosine monophosphate (cAMP) production. Further downstream, PGE₂-EP4-cAMP signaling led to suppression of GATA3 and ST2 expression, which is known to be critical for ILC2 activation. These findings reveal a novel function of PGE₂ as a negative regulator of ILC2 activation and highlight an endogenous counter-regulatory mechanism for the control of innate allergic inflammatory responses.

Delayed type of allergic skin reaction to Candida albicans in eosinophilic rhinosinusitis cases

OBJECTIVE

Eosinophilic chronic rhinosinusitis (ECRS) is frequently complicated by asthma, and recognized as refractory and persistent rhinosinusitis. However, the detailed pathophysiology of ECRS has not been elucidated yet. In this study, we investigated the association between recurrent ECRS and intradermal testing to multi-antigens including Candida albicans.

METHODS

The subjects were 49 cases of bilateral chronic rhinosinusitis including 24 ECRS cases. They underwent endoscopic sinus surgery and submitted to pathological examination. Prior to surgery, peripheral blood eosinophil count, total and antigen-specific IgE levels (11 categories), and intradermal tests (5 categories) were carried out in all patients. These patients were followed-up for longer than 3 months. We compared the results of preoperative and postoperative clinical examination data between ECRS and non-ECRS (NECRS) cases.

RESULTS

Positive reaction of the delayed type of intradermal testing to C. albicans was significantly more often observed in ECRS than NECRS cases. (P<0.01) Additionally, these positive reaction cases exhibited significantly higher recurrence of nasal polyps and symptoms of ECRS (P<0.05).

CONCLUSION

These results suggest the involvement of (Coombs) type IV allergic reaction to C. albicans in the pathophysiology of ECRS.

Factors Associated with Echinococcosis-Induced Perioperative Anaphylactic Shock

This retrospective case-control study explored the factors associated with anaphylactic shock during surgery for cystic echinococcosis (CE) at the First Affiliated Hospital of Xinjiang Medical University between October 2008 and September 2013. Patients who suffered from anaphylactic shock (n=16) were age-matched 3:1 to patients who did not (n=43). Multivariate analysis suggested that IL-4 levels (odds ratio=1.096; 95% confidence interval=1.015–1.185; P=0.02) and cyst size (odds ratio=3.028, 95% confidence interval=1.259–7.283, P=0.013) were independently associated with CE-induced perioperative anaphylactic shock. Using the receiver operating characteristic (ROC) curves and a cut-off value of 415.7 ng/ml, IL-4 showed an area under the ROC (AUC) of 0.926, sensitivity of 75.0%, and specificity of 97.7%. Using a cut-off value of 7.8 cm, cyst size showed an AUC of 0.828, sensitivity of 81.3%, and specificity of 76.7%. In conclusion, results suggest that levels of IL-4 and cyst size were independently associated with echinococcosis-induced perioperative anaphylactic shock. These results could help identifying patients with echinococcosis at risk of anaphylactic shock in whom appropriate prophylaxis could be undertaken.

Activation of the Prostaglandin E2 receptor EP2 prevents house dust mite-induced airway hyperresponsiveness and inflammation by restraining mast cells' activity

BACKGROUND

Prostaglandin E2 (PGE2 ) has been proposed to exert antiasthmatic effects in patients, to prevent antigen-induced airway pathology in murine models, and to inhibit mast cells (MC) activity in vitro.

OBJECTIVE

To assess in a murine model whether the protective effect of PGE2 may be a consequence of its ability to activate the E-prostanoid (EP)2 receptor on airway MC.

METHODS

Either BALB/c or C57BL/6 mice were exposed intranasally (i.n.) to house dust mite (HDM) aeroallergens. Both strains were given PGE2 locally (0.3 mg/kg), but only BALB/c mice were administered butaprost (EP2 agonist: 0.3 mg/kg), or AH6809 (EP2 antagonist; 2.5 mg/kg) combined with the MC stabilizer sodium cromoglycate (SCG: 25 mg/kg). Airway hyperresponsiveness (AHR) and inflammation, along with lung MC activity, were evaluated. In addition, butaprost's effect was assessed in MC-mediated passive cutaneous anaphylaxis (PCA) in mice challenged with 2,4-dinitrophenol (DNP).

RESULTS

Selective EP2 agonism attenuated aeroallergen-caused AHR and inflammation in HDM-exposed BALB/c mice, and this correlated with a reduced lung MC activity. Accordingly, the blockade of endogenous PGE2 by means of AH6809 worsened airway responsiveness in sensitive BALB/c mice, and such worsening was reversed by SCG. The relevance of MC to PGE2 -EP2 driven protection was further highlighted in MC-dependent PCA, where butaprost fully prevented MC-induced ear swelling. Unlike in BALB/c mice, PGE2 did not protect the airways of HDM-sensitized C57BL/6 animals, a strain in which we showed MC to be irrelevant to aeroallergen-driven AHR and inflammation.

CONCLUSIONS & CLINICAL RELEVANCE

The beneficial effect of both exogenous and endogenous PGE2 in aeroallergen-sensitized mice may be attributable to the activation of the EP2 receptor, which in turn acts as a restrainer of airway MC activity. This opens a path towards the identification of therapeutic targets against asthma along the 'EP2 -MC-airway' axis.

Dietary n-3 long chain polyunsaturated fatty acids in allergy prevention and asthma treatment

The rise in non-communicable diseases, such as allergies, in westernized countries links to changes in lifestyle and diet. N-3 long chain polyunsaturated fatty acids (LCPUFA) present in marine oils facilitate a favorable milieu for immune maturation and may contribute to allergy prevention. N-3 LCPUFA can suppress innate and adaptive immune activation and induce epigenetic changes. Murine studies convincingly show protective effects of fish oil, a source of n-3 LCPUFA, in food allergy and asthma models. Observational studies in human indicate that high dietary intake of n-3 LCPUFA and low intake of n-6 PUFA may protect against the development of allergic disease early in life. High n-6 PUFA intake is also associated with an increased asthma risk while n-3 LCPUFA may be protective and reduce symptoms. The quality of the marine oil used has impact on efficacy of allergy prevention and several observations link in particular n-3 LCPUFA DHA to allergy suppression. Randomized controlled trials indicate that optimal timing, duration and dosage of n-3 LC-PUFA is required to exert an allergy protective effect. Supplementation during early pregnancy and lactation has shown promising results regarding allergy prevention. However these findings should be confirmed in a larger cohort. Although clinical trials in asthma patients reveal no consistent clinical benefits of n-3 LCPUFA supplementation on lung function, it can suppress airway inflammation. Future food-pharma approaches may reveal whether adjunct therapy with dietary n-3 LCPUFA can improve allergy prevention or immunotherapy via support of allergen specific oral tolerance induction or contribute to the efficacy of drug therapy for asthma patients.

Prostaglandins E2 signal mediated by receptor subtype EP2 promotes IgE production in vivo and contributes to asthma development

Prostaglandins E2 (PGE2) has been shown to enhance IgE production by B cells in vitro. The physiological and pathological relevance of this phenomenon and the underlying molecular mechanism, however, remain to be elucidated. B cells from wild type and EP2-deficient mice were compared in culture for their responses to PGE2 in terms of IgE class switching and production. Ovalbumin (OVA)-induced asthma models were used to evaluate the impact of EP2-deficiency on IgE responses and the development of asthma. PGE2 promoted IgE class switching, generation of IgE⁺ cells and secretion of IgE by B cells stimulated with LPS+IL4. These effects were much attenuated as a consequence of EP2 deficiency. Consistent with the in vitro data, EP2-deficient mice showed a markedly suppressed IgE antibody response and developed less pronounced airway inflammation in the OVA-induced asthma model. Mechanistic studies demonstrated that PGE2, in an EP2-depedent manner, enhanced STAT6 activation induced by IL-4, thereby promoting the expression of IgE germline and post switch transcripts and the transcription of activation-induced cytidine deaminase (AID). Collectively, these data support an important regulatory role of the PGE2-EP2-STAT6 signaling pathway in IgE response and allergic diseases.

Human airway smooth muscle cells secrete amphiregulin via bradykinin/COX-2/PGE2, inducing COX-2, CXCL8, and VEGF expression in airway epithelial cells

Human airway smooth muscle cells (HASMC) contribute to asthma pathophysiology through an increased smooth muscle mass and elevated cytokine/chemokine output. Little is known about how HASMC and the airway epithelium interact to regulate chronic airway inflammation and remodeling. Amphiregulin is a member of the family of epidermal growth factor receptor (EGFR) agonists with cell growth and proinflammatory roles and increased expression in the lungs of asthma patients. Here we show that bradykinin (BK) stimulation of HASMC increases amphiregulin secretion in a mechanism dependent on BK-induced COX-2 expression, increased PGE2 output, and the stimulation of HASMC EP2 and EP4 receptors. Conditioned medium from BK treated HASMC induced CXCL8, VEGF, and COX-2 mRNA and protein accumulation in airway epithelial cells, which were blocked by anti-amphiregulin antibodies and amphiregulin siRNA, suggesting a paracrine effect of HASMC-derived amphiregulin on airway epithelial cells. Consistent with this, recombinant amphiregulin induced CXCL8, VEGF, and COX-2 in airway epithelial cells. Finally, we found that conditioned media from amphiregulin-stimulated airway epithelial cells induced amphiregulin expression in HASMC and that this was dependent on airway epithelial cell COX-2 activity. Our study provides evidence of a dynamic axis of interaction between HASMC and epithelial cells that amplifies CXCL8, VEGF, COX-2, and amphiregulin production.

MicroRNA-26a/-26b-COX-2-MIP-2 Loop Regulates Allergic Inflammation and Allergic Inflammation-promoted Enhanced Tumorigenic and Metastatic Potential of Cancer Cells

Cyclooxgenase-2 (COX-2) knock-out mouse experiments showed that COX-2 was necessary for in vivo allergic inflammation, such as passive cutaneous anaphylaxis, passive systemic anaphylaxis, and triphasic cutaneous allergic reaction. TargetScan analysis predicted COX-2 as a target of miR-26a and miR-26b. miR-26a/-26b decreased luciferase activity associated with COX-2-3'-UTR. miR-26a/-26b exerted negative effects on the features of in vitro and in vivo allergic inflammation by targeting COX-2. ChIP assays showed the binding of HDAC3 and SNAIL, but not COX-2, to the promoter sequences of miR-26a and miR-26b. Cytokine array analysis showed that the induction of chemokines, such as MIP-2, in the mouse passive systemic anaphylaxis model occurred in a COX-2-dependent manner. ChIP assays showed the binding of HDAC3 and COX-2 to the promoter sequences of MIP-2. In vitro and in vivo allergic inflammation was accompanied by the increased expression of MIP-2. miR-26a/-26b negatively regulated the expression of MIP-2. Allergic inflammation enhanced the tumorigenic and metastatic potential of cancer cells and induced positive feedback involving cancer cells and stromal cells, such as mast cells, macrophages, and endothelial cells. miR-26a mimic and miR-26b mimic negatively regulated the positive feedback between cancer cells and stromal cells and the positive feedback among stromal cells. miR-26a/-26b negatively regulated the enhanced tumorigenic potential by allergic inflammation. COX-2 was necessary for the enhanced metastatic potential of cancer cells by allergic inflammation. Taken together, our results indicate that the miR26a/-26b-COX-2-MIP-2 loop regulates allergic inflammation and the feedback relationship between allergic inflammation and the enhanced tumorigenic and metastatic potential.

MIG-7 and phosphorylated prohibitin coordinately regulate lung cancer invasion/metastasis

Growth factors and COX-2/PGE2 enhance lung cancer invasion/metastasis via PI3K/Akt and RAS/Raf. Here, we explored their mechanism of action further. We found first that higher levels of migration inducting gene-7 protein (MIG-7) and PHB phosphorylated at threonine 258 (phospho-PHBT258) are positively correlated with advanced stages of human lung cancer in tissue microarray. PGE2 or growth factors such as EGF, HGF and IGF-1 increased complex formation of phospho-PHBT258 with Ras, phospho-AktS473, phospho-Raf-1S338, MEKK1 and IKKα/βS176/180 in the raft domain transiently within 1 hour and MIG-7 in the cytosol 12-24 hours later. Association of phospho-PHBT258 with MEKK1 but not MEKK3 activates IKK/IκB/NF-κB and MEK/ERK to increase cellular COX-2/PGE2 and an E-cadherin suppressor Snail leading to enhancement of epithelial-mesenchymal transition (EMT) and lung cancer migration/invasion. MIG-7, on the other hand, was induced by growth factors and PGE2 via Akt/GSK-3β in a phospho-PHBT258 independent manner. MIG-7 increased two E-cadherin suppressors ZEB-1 and Twist to enhance EMT and cancer migration/invasion. Downregulating phospho-PHBT258 and MIG-7 had an additive effect on attenuating lung cancer invasion/metastasis and prolonging the survival of xenograft mice. Phospho-PHBT258 and MIG-7 may thus play complementary roles in the initiation and sustainment of the effects of growth factors and COX-2/PGE2 on cancer invasion/metastasis.

Gut dysbiosis promotes M2 macrophage polarization and allergic airway inflammation via fungi-induced PGE₂

Although imbalances in gut microbiota composition, or "dysbiosis," are associated with many diseases, the effects of gut dysbiosis on host systemic physiology are less well characterized. We report that gut dysbiosis induced by antibiotic (Abx) treatment promotes allergic airway inflammation by shifting macrophage polarization in the lung toward the alternatively activated M2 phenotype. Adoptive transfer of alveolar macrophages derived from Abx-treated mice was sufficient to increase allergic airway inflammation. Abx treatment resulted in the overgrowth of a commensal fungal Candida species in the gut and increased plasma concentrations of prostaglandin E₂ (PGE₂), which induced M2 macrophage polarization in the lung. Suppression of PGE₂ synthesis by the cyclooxygenase inhibitors aspirin and celecoxib suppressed M2 macrophage polarization and decreased allergic airway inflammatory cell infiltration in Abx-treated mice. Thus, Abx treatment can cause overgrowth of particular fungal species in the gut and promote M2 macrophage activation at distant sites to influence systemic responses including allergic inflammation.

Prostaglandin E₂ suppresses allergic sensitization and lung inflammation by targeting the E prostanoid 2 receptor on T cells

BACKGROUND

Endogenous prostanoids have been suggested to modulate sensitization during experimental allergic asthma, but the specific role of prostaglandin (PG) E₂ or of specific E prostanoid (EP) receptors is not known.

OBJECTIVE

Here we tested the role of EP2 signaling in allergic asthma.

METHODS

Wild-type (WT) and EP2(-/-) mice were subjected to ovalbumin sensitization and acute airway challenge. The PGE2 analog misoprostol was administered during sensitization in both genotypes. In vitro culture of splenocytes and flow-sorted dendritic cells and T cells defined the mechanism by which EP2 exerted its protective effect. Adoptive transfer of WT and EP2(-/-) CD4 T cells was used to validate the importance of EP2 expression on T cells.

RESULTS

Compared with WT mice, EP2(-/-) mice had exaggerated airway inflammation in this model. Splenocytes and lung lymph node cells from sensitized EP2(-/-) mice produced more IL-13 than did WT cells, suggesting increased sensitization. In WT but not EP2(-/-) mice, subcutaneous administration of misoprostol during sensitization inhibited allergic inflammation. PGE₂ decreased cytokine production and inhibited signal transducer and activator of transcription 6 phosphorylation by CD3/CD28-stimulated CD4(+) T cells. Coculture of flow cytometry-sorted splenic CD4(+) T cells and CD11c(+) dendritic cells from WT or EP2(-/-) mice suggested that the increased IL-13 production in EP2(-/-) mice was due to the lack of EP2 specifically on T cells. Adoptive transfer of CD4(+) EP2(-/-) T cells caused greater cytokine production in the lungs of WT mice than did transfer of WT CD4(+) T cells.

CONCLUSION

We conclude that the PGE2-EP2 axis is an important endogenous brake on allergic airway inflammation and primarily targets T cells and that its agonism represents a potential novel therapeutic approach to asthma.

Gene expression of desaturase (FADS1 and FADS2) and Elongase (ELOVL5) enzymes in peripheral blood: association with polyunsaturated fatty acid levels and atopic eczema in 4-year-old children

Background

It is unknown if changes in the gene expression of the desaturase and elongase enzymes are associated with abnormal n-6 long chain polyunsaturated fatty acid (LC-PUFA) levels in children with atopic eczema (AE). We analyzed whether mRNA-expression of genes encoding key enzymes of LC-PUFA synthesis (FADS1, FADS2 and ELOVL5) is associated with circulating LC-PUFA levels and risk of AE in 4-year-old children.

Methods

AE (n=20) and non-AE (n=104) children participating in the Sabadell cohort within the INfancia y Medio Ambiente (INMA) Project were included in the present study. RT-PCR with TaqMan Low-Density Array cards was used to measure the mRNA-expression of FADS1, FADS2 and ELOVL5. LC-PUFA levels were measured by fast gas chromatography in plasma phospholipids. The relationship of gene expression with LC-PUFA levels and enzyme activities was evaluated by Pearson’s rank correlation coefficient, and logistic regression models were used to study its association with risk of developing AE.

Results

Children with AE had lower levels of several n-6 PUFA members, dihomo-γ-linolenic (DGLA) and arachidonic (AA) acids. mRNA-expression levels of FADS1 and 2 strongly correlated with DGLA levels and with D6D activity. FADS2 and ELOVL5 mRNA-expression levels were significantly lower in AE than in non-AE children (-40.30% and -20.36%; respectively), but no differences were found for FADS1.

Conclusions and Significance

Changes in the mRNA-expression levels of FADS1 and 2 directly affect blood DGLA levels and D6D activity. This study suggests that lower mRNA-expressions of FADS2 and ELOVL5 are associated with higher risk of atopic eczema in young children.

Cyclooxygenase-2 in newborn hyperoxic lung injury

Supraphysiological O2 concentrations, mechanical ventilation, and inflammation significantly contribute to the development of bronchopulmonary dysplasia (BPD).Exposure of newborn mice to hyperoxia causes inflammation and impaired alveolarization similar to that seen in infants with BPD.Previously, we demonstrated that pulmonary cyclooxygenase-2 (COX-2) protein expression is increased in hyperoxia-exposed newborn mice.The present studies were designed to define the role of COX-2 in newborn hyperoxic lung injury.We tested the hypothesis that attenuation of COX-2 activity would reduce hyperoxia-induced inflammation and improve alveolarization.Newborn C3H/HeN micewere injected daily with vehicle, aspirin (nonselective COX-2 inhibitor), or celecoxib (selective COX-2 inhibitor) for the first 7 days of life.Additional studies utilized wild-type (C57Bl/6, COX-2(+/+)), heterozygous (COX-2(+/-)), and homozygous (COX-2(-/-)) transgenic mice.Micewere exposed to room air (21% O2) or hyperoxia (85% O2) for 14 days.Aspirin-injected and COX-2(-/-) pups had reduced levels of monocyte chemoattractant protein (MCP-1) in bronchoalveolar lavage fluid (BAL).Both aspirin and celecoxib treatment reduced macrophage numbers in the alveolar walls and air spaces.Aspirin and celecoxib treatment attenuated hyperoxia-induced COX activity, including altered levels of prostaglandin (PG)D2 metabolites.Decreased COX activity, however, did not prevent hyperoxia-induced lung developmental deficits.Our data suggest thatincreased COX-2 activity may contribute to proinflammatory responses, including macrophage chemotaxis, during exposure to hyperoxia.Modulation of COX-2 activity may be a useful therapeutic target to limit hyperoxia-induced inflammation in preterm infants at risk of developing BPD.

Isoflurane regulates atypical type-A γ-aminobutyric acid receptors in alveolar type II epithelial cells

BACKGROUND

Volatile anesthetics act primarily through upregulating the activity of γ-aminobutyric acid type A (GABAA) receptors. They also exhibit antiinflammatory actions in the lung. Rodent alveolar type II (ATII) epithelial cells express GABAA receptors and the inflammatory factor cyclooxygenase-2 (COX-2). The goal of this study was to determine whether human ATII cells also express GABAA receptors and whether volatile anesthetics upregulate GABAA receptor activity, thereby reducing the expression of COX-2 in ATII cells.

METHODS

The expression of GABAA receptor subunits and COX-2 in ATII cells of human lung tissue and in the human ATII cell line A549 was studied with immunostaining and immunoblot analyses. Patch clamp recordings were used to study the functional and pharmacological properties of GABAA receptors in cultured A549 cells.

RESULTS

ATII cells in human lungs and cultured A549 cells expressed GABAA receptor subunits and COX-2. GABA induced currents in A549 cells, with half-maximal effective concentration of 2.5 µM. Isoflurane (0.1-250 µM) enhanced the GABA currents, which were partially inhibited by bicuculline. Treating A549 cells with muscimol or with isoflurane (250 µM) reduced the expression of COX-2, an effect that was attenuated by cotreatment with bicuculline.

CONCLUSIONS

GABAA receptors expressed by human ATII cells differ pharmacologically from those in neurons, exhibiting a higher affinity for GABA and lower sensitivity to bicuculline. Clinically relevant concentrations of isoflurane increased the activity of GABAA receptors and reduced the expression of COX-2 in ATII cells. These findings reveal a novel mechanism that could contribute to the antiinflammatory effect of isoflurane in the human lung.

Prostaglandin E2 deficiency uncovers a dominant role for thromboxane A2 in house dust mite-induced allergic pulmonary inflammation

Prostaglandin E(2) (PGE(2)) is an abundant lipid inflammatory mediator with potent but incompletely understood anti-inflammatory actions in the lung. Deficient PGE(2) generation in the lung predisposes to airway hyperresponsiveness and aspirin intolerance in asthmatic individuals. PGE(2)-deficient ptges(-/-) mice develop exaggerated pulmonary eosinophilia and pulmonary arteriolar smooth-muscle hyperplasia compared with PGE(2)-sufficient controls when challenged intranasally with a house dust mite extract. We now demonstrate that both pulmonary eosinophilia and vascular remodeling in the setting of PGE(2) deficiency depend on thromboxane A(2) and signaling through the T prostanoid (TP) receptor. Deletion of TP receptors from ptges(-/-) mice reduces inflammation, vascular remodeling, cytokine generation, and airway reactivity to wild-type levels, with contributions from TP receptors localized to both hematopoietic cells and tissue. TP receptor signaling ex vivo is controlled heterologously by E prostanoid (EP)(1) and EP(2) receptor-dependent signaling pathways coupling to protein kinases C and A, respectively. TP-dependent up-regulation of intracellular adhesion molecule-1 expression is essential for the effects of PGE(2) deficiency. Thus, PGE(2) controls the strength of TP receptor signaling as a major bronchoprotective mechanism, carrying implications for the pathobiology and therapy of asthma.