Role of EP2 and EP4 receptors in airway microvascular leak induced by prostaglandin E2

The severity of NEC is ameliorated by prostaglandin E2 through regulating intestinal microcirculation

Prostaglandin E2 (PGE2) is implicated in intestinal inflammation and intestinal blood flow regulation with a paradoxical effect on the pathogenesis of necrotizing enterocolitis (NEC), which is not yet well understood. In the current study, we found that PGE2, EP4, and COX-2 varied at different distances from the most damaged area in the terminal ileum obtained from human infants with NEC. PGE2 administration alleviated the phenotype of experimental NEC and the intestinal microvascular features in experimental NEC, but this phenomenon was inhibited by eNOS depletion, suggesting that PGE2 promoted intestinal microcirculatory perfusion through eNOS. Furthermore, PGE2 administration increased the VEGF content in MIMECs under TNFα stress and promoted MIMEC proliferation. This response to PGE2 was involved in eNOS phosphorylation and nitric oxide (NO) production and was blocked by the EP4 antagonist in vitro, suggesting that targeting the PGE2-EP4-eNOS axis might be a potential clinical and therapeutic strategy for NEC treatment. The study is reported in accordance with ARRIVE guidelines ( https://arriveguidelines.org ).

Drug repurposing screens to identify potential drugs for chronic kidney disease by targeting prostaglandin E2 receptor

Renal inflammation and fibrosis are significantly correlated with the deterioration of kidney function and result in chronic kidney disease (CKD). However, current therapies only delay disease progression and have limited treatment effects. Hence, the development of innovative therapeutic approaches to mitigate the progression of CKD has become an attractive issue. To date, the incidence of CKD is still increasing, and the biomarkers of the pathophysiologic processes of CKD are not clear. Therefore, the identification of novel therapeutic targets associated with the progression of CKD is an attractive issue. It is a critical necessity to discover new therapeutics as nephroprotective strategies to stop CKD progression. In this research, we focus on targeting a prostaglandin E₂ receptor (EP2) as a nephroprotective strategy for the development of additional anti-inflammatory or antifibrotic strategies for CKD. The in silico study identified that ritodrine, dofetilide, dobutamine, and citalopram are highly related to EP2 from the results of chemical database virtual screening. Furthermore, we found that the above four candidate drugs increased the activation of autophagy in human kidney cells, which also reduced the expression level of fibrosis and NLRP3 inflammasome activation. It is hoped that these findings of the four candidates with anti-NLRP3 inflammasome activation and antifibrotic effects will lead to the development of novel therapies for patients with CKD in the future.

Genome-wide DNA methylation profiling after Ayurveda intervention to bronchial asthmatics identifies differential methylation in several transcription factors with immune process related function

BACKGROUND

The Indian traditional medicinal system, Ayurveda, describes several lifestyle practices, processes and medicines as an intervention to treat asthma. Rasayana therapy is one of them and although these treatment modules show improvement in bronchial asthma, their mechanism of action, particularly the effect on DNA methylation, is largely understudied.

OBJECTIVES

Our study aimed at identifying the contribution of DNA methylation changes in modulating bronchial asthma phenotype upon Ayurveda intervention.

MATERIALS AND METHODS

In this study, genome-wide methylation profiling in peripheral blood DNA of healthy controls and bronchial asthmatics before (BT) and after (AT) Ayurveda treatment was performed using array-based profiling of reference-independent methylation status (aPRIMES) coupled to microarray technique.

RESULTS

We identified 4820 treatment-associated DNA methylation signatures (TADS) and 11,643 asthma-associated DNA methylation signatures (AADS), differentially methylated [FDR (≤0.1) adjusted p-values] in AT and HC groups respectively, compared to BT group. Neurotrophin TRK receptor signaling pathway was significantly enriched for differentially methylated genes in bronchial asthmatics, compared to AT and HC subjects. Additionally, we identified over 100 differentially methylated immune-related genes located in the promoter/5'-UTR regions of TADS and AADS. Various immediate-early response and immune regulatory genes with functions such as transcription factor activity (FOXD1, FOXD2, GATA6, HOXA3, HOXA5, MZF1, NFATC1, NKX2-2, NKX2-3, RUNX1, KLF11), G-protein coupled receptor activity (CXCR4, PTGER4), G-protein coupled receptor binding (UCN), DNA binding (JARID2, EBF2, SOX9), SNARE binding (CAPN10), transmembrane signaling receptor activity (GP1BB), integrin binding (ITGA6), calcium ion binding (PCDHGA12), actin binding (TRPM7, PANX1, TPM1), receptor tyrosine kinase binding (PIK3R2), receptor activity (GDNF), histone methyltransferase activity (MLL5), and catalytic activity (TSTA3) were found to show consistent methylation status between AT and HC group in microarray data.

CONCLUSIONS

Our study reports the DNA methylation-regulated genes in bronchial asthmatics showing improvement in symptoms after Ayurveda intervention. DNA methylation regulation in the identified genes and pathways represents the Ayurveda intervention responsive genes and may be further explored as diagnostic, prognostic, and therapeutic biomarkers for bronchial asthma in peripheral blood.

Antithrombotic and antiplatelet effects of plant-derived compounds: a great utility potential for primary, secondary, and tertiary care in the framework of 3P medicine

Thromboembolism is the third leading vascular disease, with a high annual incidence of 1 to 2 cases per 1000 individuals within the general population. The broader term venous thromboembolism generally refers to deep vein thrombosis, pulmonary embolism, and/or a combination of both. Therefore, thromboembolism can affect both – the central and peripheral veins. Arterial thromboembolism causes systemic ischemia by disturbing blood flow and oxygen supply to organs, tissues, and cells causing, therefore, apoptosis and/or necrosis in the affected tissues. Currently applied antithrombotic drugs used, e.g. to protect affected individuals against ischemic stroke, demonstrate significant limitations. For example, platelet inhibitors possess only moderate efficacy. On the other hand, thrombolytics and anticoagulants significantly increase hemorrhage. Contextually, new approaches are extensively under consideration to develop next-generation antithrombotics with improved efficacy and more personalized and targeted application. To this end, phytochemicals show potent antithrombotic efficacy demonstrated in numerous in vitro, ex vivo, and in vivo models as well as in clinical evaluations conducted on healthy individuals and persons at high risk of thrombotic events, such as pregnant women (primary care), cancer, and COVID-19-affected patients (secondary and tertiary care). Here, we hypothesized that specific antithrombotic and antiplatelet effects of plant-derived compounds might be of great clinical utility in primary, secondary, and tertiary care. To increase the efficacy, precise patient stratification based on predictive diagnostics is essential for targeted protection and treatments tailored to the person in the framework of 3P medicine. Contextually, this paper aims at critical review toward the involvement of specific classes of phytochemicals in antiplatelet and anticoagulation adapted to clinical needs. The paper exemplifies selected plant-derived drugs, plant extracts, and whole plant foods/herbs demonstrating their specific antithrombotic, antiplatelet, and fibrinolytic activities relevant for primary, secondary, and tertiary care. One of the examples considered is antithrombotic and antiplatelet protection specifically relevant for COVID-19-affected patient groups.

Flavonoids: Antiplatelet Effect as Inhibitors of COX-1

Flavonoids are compounds with a benzopyranic structure that exhibits multiple pharmacological activities. They are known for their venotonic activity, but their mechanism of action remains unclear. It is thought that, as this mechanism is mediated by prostaglandins, these compounds may interfere with the arachidonic acid (AA) cascade. These assays are designed to measure the antiplatelet aggregation capacity of quercetin, rutin, diosmetin, diosmin, and hidrosmin, as well as to evaluate a potential structure−activity ratio. In this paper, several studies on platelet aggregation at different concentrations (from 0.33 mM to 1.5 mM) of different flavone compounds are conducted, measuring platelet aggregation by impedance aggregometry, and the cyclooxygenase (COX) activity by metabolites generated, including the activity of the pure recombinant enzyme in the presence of these polyphenols. The results obtained showed that quercetin and diosmetin aglycones have a greater antiplatelet effect and inhibit the COX enzyme activity to a greater extent than their heterosides; however, the fact that greater inhibition of the pure recombinant enzyme was achieved by heterosides suggests that these compounds may have difficulty in crossing biological membranes. In any case, in view of the results obtained, it can be concluded that flavonoids could be useful as coadjuvants in the treatment of cardiovascular pathologies.

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.

Can GPCRs Be Targeted to Control Inflammation in Asthma?

Historically, the drugs used to manage obstructive lung diseases (OLDs), asthma, and chronic obstructive pulmonary disease (COPD) either (1) directly regulate airway contraction by blocking or relaxing airway smooth muscle (ASM) contraction or (2) indirectly regulate ASM contraction by inhibiting the principal cause of ASM contraction/bronchoconstriction and airway inflammation. To date, these tasks have been respectively assigned to two diverse drug types: agonists/antagonists of G protein-coupled receptors (GPCRs) and inhaled or systemic steroids. These two types of drugs "stay in their lane" with respect to their actions and consequently require the addition of the other drug to effectively manage both inflammation and bronchoconstriction in OLDs. Indeed, it has been speculated that safety issues historically associated with beta-agonist use (beta-agonists activate the beta-2-adrenoceptor (β₂AR) on airway smooth muscle (ASM) to provide bronchoprotection/bronchorelaxation) are a function of pro-inflammatory actions of β₂AR agonism. Recently, however, previously unappreciated roles of various GPCRs on ASM contractility and on airway inflammation have been elucidated, raising the possibility that novel GPCR ligands targeting these GPCRs can be developed as anti-inflammatory therapeutics. Moreover, we now know that many GPCRs can be "tuned" and not just turned "off" or "on" to specifically activate the beneficial therapeutic signaling a receptor can transduce while avoiding detrimental signaling. Thus, the fledging field of biased agonism pharmacology has the potential to turn the β₂AR into an anti-inflammatory facilitator in asthma, possibly reducing or eliminating the need for steroids.

microRNA-103a-3p confers protection against lipopolysaccharide-induced sepsis and consequent multiple organ dysfunction syndrome by targeting HMGB1

BACKGROUND

Sepsis and subsequent multiple organ dysfunction syndrome (MODS) have high global incidence and mortality rate, imposing tremendous health burden. microRNAs (miRNAs or miRs) are implicated in the pathogenesis of sepsis and MODS. The aim of this study is to explore the potential mechanisms of miR-103a-3p targeted high mobility group box 1 (HMGB1) involvement in the pathogenesis of sepsis complicated with multiple organ dysfunction syndrome (MODS).

METHODS

A mouse sepsis model was induced by lipopolysaccharide (LPS). Bone marrow-derived macrophages were collected and LPS was used to establish a cellular inflammation model. Targeted binding between miR-103a-3p and HMGB1 was verified by a double luciferase assay and their roles in LPS-induced sepsis were further explored using gain-of-function experiments.

RESULTS

miR-103a-3p was decreased while HMGB1 was increased in sepsis. In LPS-induced mouse sepsis models, the downregulation of HMGB1 was found to result in reductions in NO, TNF-α, IL-1β, IL-6, lung myeloperoxidase activity, pulmonary microvascular albumin leakage, serum alanine aminotransferase, aspartate aminotransferase activity, and lung and liver tissue apoptosis. Additionally, decreased HMGB1 blunted the inflammatory response and increased survival rate of modeled mice. Importantly, HMGB1 was confirmed to a target gene of miR-103a-3p. In cellular inflammation models, miR-103a-3p was found to alleviate LPS-induced sepsis and MODS in vitro by decreasing HMGB1.

CONCLUSIONS

Taken together, our results demonstrated the inhibitory role of miR-103a-3p in sepsis via inhibiting HMGB1 expression.

Stabilization of PTGES by deubiquitinase USP9X promotes metastatic features of lung cancer via PGE2 signaling

Early metastasis and local recurrence are the major causes of mortality and poor prognosis of non-small cell lung cancer (NSCLC). However, the underlying mechanisms of these processes are poorly understood. In this study, we aimed to investigate the roles of the PTGES/PGE2 pathway in lung cancer progression. We found that prostaglandin E synthase (PTGES), a key enzyme for PGE2 synthesis in the arachidonic acid pathway, was highly dysregulated in NSCLC. Dysregulated PTGES was essential for the promotion of tumor migration and metastasis of NSCLC cells. Knockdown of PTGES in lung cancer cells resulted in suppressed cell migration, which was reversed by exogenous PGE2. Consistent with this, PTGES knockdown also reduced the expression of CSC markers, tumor sphere formation, colony forming activity, tumorigenicity, and lung metastasis in vivo. Dysregulated PTGES is mainly attributed to protein stabilization by USP9X, a deubiquitination enzyme. USP9X physically interacted with PTGES and prevented it from proteasome-directed degradation via deubiquitination. Consistent with this, USP9X expression was highly correlated with PTGES expression in NSCLC tumor tissues. Taken together, our results show that the upregulated USP9X-PTGES-PGE2 axis contributes significantly to the metastatic features of NSCLC.

Effect of PM2.5 environmental pollution on rat lung

Particulate matter smaller than 2.5 μm (PM2.5) is a continuing challenge to pulmonary health. Here, we investigated the mechanisms involved in PM2.5 exposure-induced acute lung injury in rats. We analyzed biochemical and morphological changes following a 2-week "real-world" exposure. And then we found that PM2.5 exposure increased the concentrations of total protein, malondialdehyde, hydrogen peroxide, nitric oxide, and soluble elastin in bronchoalveolar lavage fluid, levels of cytokines in blood, and expression of MMP-9 in airways. Further, alveolar macrophage and neutrophil counts increased following PM2.5 exposure, and edema and lung lesions were observed. Our results suggest that PM2.5 exposure can induce oxidative stress and acute inflammatory responses, which can damage the micro-environment and decrease the repair ability of the lung, resulting in tissue damage.

Antipleuritic and Vascular Permeability Inhibition of the Ethyl Acetate-Petroleum Ether Stem Bark Extract of Maerua angolensis DC (Capparaceae) in Murine

Maerua angolensis has been used traditionally in the management of pain, arthritis, and rheumatism in Ghana and Nigeria but no scientific evidence is currently available to give credence to its folkloric use. The aim of this study was therefore to evaluate the anti-inflammatory effects of a stem bark extract of Maerua angolensis DC (MAE) in acute inflammatory models. The effects of MAE (30-300 mg kg⁻¹) on neutrophil infiltration, exudate volume, and endogenous antioxidant enzymes in lung tissues and lung morphology were evaluated with the carrageenan induced pleurisy model in Sprague Dawley rats. The effects of MAE (30-300 mg kg⁻¹) on vascular permeability were also evaluated in the acetic acid induced vascular permeability in ICR mice. MAE significantly reduced neutrophil infiltration, exudate volume, and lung tissue damage in carrageenan induced pleurisy. MAE increased the activities of antioxidant enzymes glutathione, superoxide dismutase, and catalase in lung tissues. The extract was also able to reduce myeloperoxidase activity and lipid peroxidation in lung tissues in carrageenan induced rat pleurisy. Vascular permeability was also attenuated by the extract with marked reduction of Evans blue dye leakage in acetic acid induced permeability assay. The results indicated that Maerua angolensis is effective in ameliorating inflammation induced by carrageenan and acetic acid. It also has the potential of increasing the activity of endogenous antioxidant enzymes.

Pulmonary edema post-adenotonsillectomy in children

Post-adenotonsillectomy pulmonary edema (pATPE) is a life-threatening condition that necessitates immediate clinical intervention. The early diagnosis and detection of the signs of this condition is vital to its treatment and patient outcome. The purpose of this review article is to present epidemiological data on the prevalence of pATPE, and address the mechanisms of development, types, etiology, pathophysiology, and management of pATPE. In order to minimize postoperative intensive care unit admission rates of pATPE, utilization of preoperative clinical assessment, operative/postoperative monitoring tools, and procedural precautions are discussed.

Prolonged activation of cAMP signaling leads to endothelial barrier disruption via transcriptional repression of RRAS

The increase in cAMP levels in endothelial cells triggers cellular signaling to alter vascular permeability. It is generally considered that cAMP signaling stabilizes the endothelial barrier function and reduces permeability. However, previous studies have only examined the permeability shortly after cAMP elevation and thus have only investigated acute responses. Because cAMP is a key regulator of gene expression, elevated cAMP may have a delayed but profound impact on the endothelial permeability by altering the expression of the genes that are vital for the vessel wall stability. The small guanosine triphosphate hydrolase Ras-related protein (R-Ras) stabilizes VE-cadherin clustering and enhances endothelial barrier function, thereby stabilizing the integrity of blood vessel wall. Here we show that cAMP controls endothelial permeability through RRAS gene regulation. The prolonged cAMP elevation transcriptionally repressed RRAS in endothelial cells via a cAMP response element-binding protein (CREB) 3-dependent mechanism and significantly disrupted the adherens junction. These effects resulted in a marked increase of endothelial permeability that was reversed by R-Ras transduction. Furthermore, cAMP elevation in the endothelium by prostaglandin E2 or phosphodiesterase type 4 inhibition caused plasma leakage from intact microvessels in mouse skin. Our study demonstrated that, contrary to the widely accepted notion, cAMP elevation in endothelial cells ultimately increases vascular permeability, and the cAMP-dependent RRAS repression critically contributes to this effect.-Perrot, C. Y., Sawada, J., Komatsu, M. Prolonged activation of cyclic AMP signaling leads to endothelial barrier disruption via transcriptional repression of RRAS.

Maternal exposure to prostaglandin E2 modifies expression of Wnt genes in mouse brain - An autism connection

Prostaglandin E₂ (PGE₂) is a lipid signaling molecule important for brain development and function. Various genetic and environmental factors can influence the level of PGE₂ and increase the risk of developing Autism Spectrum Disorder (ASD). We have previously shown that in neuronal cell lines and mouse brain, PGE₂ can interfere with the Wnt canonical pathway, which is essential during early brain development. Higher levels of PGE₂ increased Wnt-dependent motility and proliferation of neuroectodermal stem cells, and modified the expression of Wnt genes previously linked to autism disorders. We also recently established a cross-talk between these two pathways in the prenatal mouse brain lacking PGE₂ producing enzyme (COX^-/-). The current study complements the published data and reveals that PGE₂ signaling also converges with the Wnt canonical pathway in the developing mouse brain after maternal exposure to PGE₂ at the onset of neurogenesis. We found significant changes in the expression level of Wnt-target genes, Mmp7, Wnt2, and Wnt3a, during prenatal and early postnatal stages. Interestingly, we observed variability in the expression level of these genes between genetically-identical pups within the same pregnancy. Furthermore, we found that all the affected genes have been previously associated with disorders of the central nervous system, including autism. We determined that prenatal exposure to PGE₂ affects the Wnt pathway at the level of β-catenin, the major downstream regulator of Wnt-dependent gene transcription. We discuss how these results add new knowledge into the molecular mechanisms by which PGE₂ may interfere with neuronal development during critical periods.

Prostaglandin E2 Receptor Antagonist with Antimicrobial Activity against Methicillin-Resistant Staphylococcus aureus

Polymicrobial intra-abdominal infections (IAI) involving Candida albicans and Staphylococcus aureus are associated with severe morbidity and mortality (∼80%). Our laboratory discovered that the immunomodulatory eicosanoid prostaglandin E₂ (PGE₂) plays a key role in the lethal inflammatory response during polymicrobial IAI using a mouse model of infection. In studies designed to uncover key PGE₂ biosynthesis/signaling components involved in the response, selective eicosanoid enzyme inhibitors and receptor antagonists were selected and prescreened for antimicrobial activity against C. albicans or S. aureus Unexpectedly, we found that the EP₄ receptor antagonist L-161,982 had direct growth-inhibitory effects on S. aureusin vitro at the physiological concentration required to block the PGE₂ interaction with EP₄ This antimicrobial activity was observed with methicillin-sensitive S. aureus and methicillin-resistant S. aureus (MRSA) strains, with the MIC and minimum bactericidal concentration values for planktonic cells being 50 μg/ml and 100 μg/ml, respectively. In addition, L-161,982 inhibited S. aureus biofilm formation and had activity against preformed mature biofilms. More importantly, treatment of mice with L-161,982 following intraperitoneal inoculation with a lethal dose of MRSA significantly reduced the bioburden and enhanced survival. Furthermore, L-161,982 protected mice against the synergistic lethality induced by coinfection with C. albicans and S. aureus The antimicrobial activity of L-161,982 is independent of EP₄ receptor inhibitory activity; an alternative EP₄ receptor antagonist exerted no antimicrobial or protective effects. Taken together, these findings demonstrate that L-161,982 has potent antimicrobial activity against MRSA and may represent a significant therapeutic alternative in improving the prognosis of mono- or polymicrobial infections involving MRSA.

Mass spectrometry profiling of oxylipins, endocannabinoids, and N-acylethanolamines in human lung lavage fluids reveals responsiveness of prostaglandin E2 and associated lipid metabolites to biodiesel exhaust exposure

The adverse effects of petrodiesel exhaust exposure on the cardiovascular and respiratory systems are well recognized. While biofuels such as rapeseed methyl ester (RME) biodiesel may have ecological advantages, the exhaust generated may cause adverse health effects. In the current study, we investigated the responses of bioactive lipid mediators in human airways after biodiesel exhaust exposure using lipidomic profiling methods. Lipid mediator levels in lung lavage were assessed following 1-h biodiesel exhaust (average particulate matter concentration, 159 μg/m³) or filtered air exposure in 15 healthy individuals in a double-blinded, randomized, controlled, crossover study design. Bronchoscopy was performed 6 h post exposure and lung lavage fluids, i.e., bronchial wash (BW) and bronchoalveolar lavage (BAL), were sequentially collected. Mass spectrometry methods were used to detect a wide array of oxylipins (including eicosanoids), endocannabinoids, N-acylethanolamines, and related lipid metabolites in the collected BW and BAL samples. Six lipids in the human lung lavage samples were altered following biodiesel exhaust exposure, three from BAL samples and three from BW samples. Of these, elevated levels of PGE₂, 12,13-DiHOME, and 13-HODE, all of which were found in BAL samples, reached Bonferroni-corrected significance. This is the first study in humans reporting responses of bioactive lipids following biodiesel exhaust exposure and the most pronounced responses were seen in the more peripheral and alveolar lung compartments, reflected by BAL collection. Since the responsiveness and diagnostic value of a subset of the studied lipid metabolites were established in lavage fluids, we conclude that our mass spectrometry profiling method is useful to assess effects of human exposure to vehicle exhaust.

Role of EP2 and EP4 receptors in airway microvascular leak induced by prostaglandin E2

BACKGROUND AND PURPOSE

Airway microvascular leak (MVL) involves the extravasation of proteins from post-capillary venules into surrounding tissue. MVL is a cardinal sign of inflammation and an important feature of airway inflammatory diseases such as asthma. PGE2, a product of COX-mediated metabolism of arachidonic acid, binds to four receptors, termed EP1–4. PGE2 has a wide variety of effects within the airway, including modulation of inflammation, sensory nerve activation and airway tone. However, the effect of PGE2 on airway MVL and the receptor/s that mediate this have not been described.

EXPERIMENTAL APPROACH

Evans Blue dye was used as a marker of airway MVL, and selective EP receptor agonists and antagonists were used alongside EP receptor-deficient mice to define the receptor subtype involved.

KEY RESULTS

PGE2 induced significant airway MVL in mice and guinea pigs. A significant reduction in PGE2-induced MVL was demonstrated in Ptger2−/− and Ptger4−/− mice and in wild-type mice pretreated simultaneously with EP2 (PF-04418948) and EP4 (ER-819762) receptor antagonists. In a model of allergic asthma, an increase in airway levels of PGE2 was associated with a rise in MVL; this change was absent in Ptger2−/− and Ptger4−/− mice.

CONCLUSIONS AND IMPLICATIONS

PGE2 is a key mediator produced by the lung and has widespread effects according to the EP receptor activated. Airway MVL represents a response to injury and under ‘disease’ conditions is a prominent feature of airway inflammation. The data presented highlight a key role for EP2 and EP4 receptors in MVL induced by PGE2.