Prostaglandin E2 mediates IL-1beta-related fibroblast mitogenic effects in acute lung injury through differential utilization of prostanoid receptors

Implications of xenobiotic-response element(s) and aryl hydrocarbon receptor in health and diseases

The effect of air pollution on public health is severely detrimental. In humans; the physiological response against pollutants is mainly elicited via the activation of aryl hydrocarbon receptor (AhR). It acts as a prime sensor of xenobiotic chemicals, also functioning as a transcription factor regulating a variety of gene expressions. Along with AhR, another pivotal element of the pollution stress pathway is Xenobiotic Response Elements (XREs). XRE, as studied are some conserved sequences in the DNA, responsible for the physiological response against pollutants. XRE is present at the upstream of the inducible target genes of AhR and it regulates the function of the AhR. XRE(s) are highly conserved in species as it has only eight specific sequences found so far in humans, mice, and rats. Inhalation of toxicants like dioxins, gaseous industrial effluents, and smoke from burning fuel and tobacco leads to predominant damage to the lungs. However, scientists are exploring the involvement of AhR in chronic diseases for example chronic obstructive pulmonary disease (COPD) and also other lethal diseases like lung cancer. In this review, we summarise what is known at this time about the roles played by the XRE and AhR in our molecular systems that have a defined control in the normal maintenance of homeostasis as well as dysfunctions.

Prostaglandin E2 (PGE2) and Roflumilast Involvement in IPF Progression

The ECM propagates processes in idiopathic pulmonary fibrosis (IPF), leading to progressive lung scarring. We established an IPF-conditioned matrix (IPF-CM) system as a platform for testing drug candidates. Here, we tested the involvement of a PGE2 and PDE4 inhibitor, Roflumilast, in the IPF-CM system. Primary normal/IPF tissue-derived human lung fibroblasts (N/IPF-HLFs) were cultured on Matrigel and then removed to create the IPF-CM. N-HLFs were exposed to the IPF-CM/N-CM with/without PGE2 (1 nM) and Roflumilast (1 µM) for 24 h. The effect of the IPF-CM on cell phenotype and pro-fibrotic gene expression was tested. In addition, electronic records of 107 patients with up to 15-year follow-up were retrospectively reviewed. Patients were defined as slow/rapid progressors using forced vital capacity (FVC) annual decline. Medication exposure was examined. N-HLFs cultured on IPF-CM were arranged in large aggregates as a result of increased proliferation, migration and differentiation. A PGE2 and Roflumilast combination blocked the large aggregate formation induced by the IPF-CM (p < 0.001) as well as cell migration, proliferation, and pro-fibrotic gene expression. A review of patient records showed that significantly more slow-progressing patients were exposed to NSAIDs (p = 0.003). PGE2/PDE4 signaling may be involved in IPF progression. These findings should be further studied.

Extracellular stimulation of lung fibroblasts with arachidonic acid increases interleukin 11 expression through p38 and ERK signaling

Interleukin-11 (IL-11) is a pleiotropic cytokine that regulates proliferation and motility of cancer cells. Fibroblasts reside in the cancer microenvironment and are the primary source of IL-11. Activated fibroblasts, including cancer-associated fibroblasts that produce IL-11, contribute to the development and progression of cancer, and induce fibrosis associated with cancer. Changes in fatty acid composition or its metabolites, and an increase in free fatty acids have been observed in cancer. The effect of deregulated fatty acids on the development and progression of cancer is not fully understood yet. In the present study, we investigated the effects of fatty acids on mRNA expression and secretion of IL-11 in lung fibroblasts. Among the eight fatty acids added exogenously, arachidonic acid (AA) increased mRNA expression and secretion of IL-11 in lung fibroblasts in a dose-dependent manner. AA-induced upregulation of IL-11 was dependent on the activation of the p38 or ERK MAPK signaling pathways. Furthermore, prostaglandin E2, associated with elevated cyclooxygenase-2 expression, participated in the upregulation of IL-11 via its specific receptor in an autocrine/paracrine manner. These results suggest that AA may mediate IL-11 upregulation in lung fibroblasts in the cancer microenvironment, accompanied by unbalanced fatty acid composition.

Immunotherapy strategies and prospects for acute lung injury: Focus on immune cells and cytokines

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a disastrous condition, which can be caused by a wide range of diseases, such as pneumonia, sepsis, traumas, and the most recent, COVID-19. Even though we have gained an improved understanding of acute lung injury/acute respiratory distress syndrome pathogenesis and treatment mechanism, there is still no effective treatment for acute lung injury/acute respiratory distress syndrome, which is partly responsible for the unacceptable mortality rate. In the pathogenesis of acute lung injury, the inflammatory storm is the main pathological feature. More and more evidences show that immune cells and cytokines secreted by immune cells play an irreplaceable role in the pathogenesis of acute lung injury. Therefore, here we mainly reviewed the role of various immune cells in acute lung injury from the perspective of immunotherapy, and elaborated the crosstalk of immune cells and cytokines, aiming to provide novel ideas and targets for the treatment of acute lung injury.

Aryl Hydrocarbon Receptor in Oxidative Stress as a Double Agent and Its Biological and Therapeutic Significance

The aryl hydrocarbon receptor (AhR) has long been implicated in the induction of a battery of genes involved in the metabolism of xenobiotics and endogenous compounds. AhR is a ligand-activated transcription factor necessary for the launch of transcriptional responses important in health and disease. In past decades, evidence has accumulated that AhR is associated with the cellular response to oxidative stress, and this property of AhR must be taken into account during investigations into a mechanism of action of xenobiotics that is able to activate AhR or that is susceptible to metabolic activation by enzymes encoded by the genes that are under the control of AhR. In this review, we examine various mechanisms by which AhR takes part in the oxidative-stress response, including antioxidant and prooxidant enzymes and cytochrome P450. We also show that AhR, as a participant in the redox balance and as a modulator of redox signals, is being increasingly studied as a target for a new class of therapeutic compounds and as an explanation for the pathogenesis of some disorders.

IL-1β Promotes Expansion of IL-33+ Lung Epithelial Stem Cells Following RSV Infection During Infancy

Respiratory syncytial virus (RSV)-induced immunopathogenesis and disease severity in neonatal mice and human infants have been related to elevated pulmonary IL-33. Thus, targeting IL-33 has been suggested as a potential therapy for respiratory viral infections. Yet, the regulatory mechanisms on IL-33 during early life remain unclear. Here, using a neonatal mouse model of RSV, we demonstrate that IL-1β positively regulates but is not required for RSV-induced expression of pulmonary IL-33 in neonatal mice early after the initial infection. Exogenous IL-1β upregulates RSV-induced IL-33 expression by promoting the proliferation of IL-33pos lung epithelial stem/progenitor cells (EpiSPC). These cells are exclusively detected in RSV-infected neonatal rather than adult mice, partially explaining the IL-1β-independent IL-33 expression in RSV-infected adult mice. Furthermore, IL-1β aggravates IL-33 mediated Th2 biased immunopathogenesis upon reinfection. Collectively, our study demonstrates that IL-1β exacerbates IL-33 mediated RSV immunopathogenesis by promoting the proliferation of IL-33pos EpiSPC in early life.

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 PGF_2α in ALI remains unclear. We aimed to clarify the role of PGF_2α/PGF_2α 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.

Cyclooxgenase-2 is induced by SARS-CoV-2 infection but does not affect viral entry or replication

Identifying drugs that regulate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and its symptoms has been a pressing area of investigation during the coronavirus disease 2019 (COVID-19) pandemic. Nonsteroidal anti-inflammatory drugs (NSAIDs), which are frequently used for the relief of pain and inflammation, could modulate both SARS-CoV-2 infection and the host response to the virus. NSAIDs inhibit the enzymes cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), which mediate the production of prostaglandins (PGs). PGE2, one of the most abundant PGs, has diverse biological roles in homeostasis and inflammatory responses. Previous studies have shown that NSAID treatment or inhibition of PGE2 receptor signaling leads to upregulation of angiotensin-converting enzyme 2 (ACE2), the cell entry receptor for SARS-CoV-2, thus raising concerns that NSAIDs could increase susceptibility to infection. COX/PGE2 signaling has also been shown to regulate the replication of many viruses, but it is not yet known whether it plays a role in SARS-CoV-2 replication. The purpose of this study was to dissect the effect of NSAIDs on COVID-19 in terms of SARS-CoV-2 entry and replication. We found that SARS-CoV-2 infection induced COX-2 upregulation in diverse human cell culture and mouse systems. However, suppression of COX-2/PGE2 signaling by two commonly used NSAIDs, ibuprofen and meloxicam, had no effect on ACE2 expression, viral entry, or viral replication. Our findings suggest that COX-2 signaling driven by SARS-CoV-2 may instead play a role in regulating the lung inflammation and injury observed in COVID-19 patients.

Current perspectives on the role of interleukin-1 signalling in the pathogenesis of asthma and COPD

Asthma and chronic obstructive pulmonary disease (COPD) cause significant morbidity and mortality worldwide. In the context of disease pathogenesis, both asthma and COPD involve chronic inflammation of the lung and are characterised by the abnormal release of inflammatory cytokines, dysregulated immune cell activity and remodelling of the airways. To date, current treatments still only manage symptoms and do not reverse the primary disease processes. In recent work, interleukin (IL)-1α and IL-1β have been suggested to play important roles in both asthma and COPD. In this review, we summarise overwhelming pre-clinical evidence for dysregulated signalling of IL-1α and IL-1β contributing to disease pathogenesis and discuss the paradox of IL-1 therapeutic studies in asthma and COPD. This is particularly important given recent completed and ongoing clinical trials with IL-1 biologics that have had varying degrees of failure and success as therapeutics for disease modification in asthma and COPD.

Activated Human Lung Fibroblasts Produce Extracellular Vesicles with Antifibrotic Prostaglandins

The differentiation of interstitial lung fibroblasts into contractile myofibroblasts that proliferate and secrete excessive extracellular matrix is critical for the pathogenesis of pulmonary fibrosis. Certain lipid signaling molecules, such as prostaglandins (PGs), can inhibit myofibroblast differentiation. However, the sources and delivery mechanisms of endogenous PGs are undefined. Activated primary human lung fibroblasts (HLFs) produce PGs such as PGE₂. We report that activation of primary HLFs with IL-1β inhibited transforming growth factor β-induced myofibroblast differentiation in both the IL-1β-treated cells themselves (autocrine signal) and adjacent naive HLFs in cocultures (paracrine signal). Additionally, we demonstrate for the first time that at least some of the antifibrotic effect of activated fibroblasts on nearby naive fibroblasts is carried by exosomes and other extracellular vesicles that contain several PGs, including high levels of the antifibrotic PGE₂. Thus, activated fibroblasts communicate with surrounding cells to limit myofibroblast differentiation and maintain homeostasis. This work opens the way for future research into extracellular vesicle-mediated intercellular signaling in the lung and may inform the development of novel therapies for fibrotic lung diseases.

Beneficial role of bioactive lipids in the pathobiology, prevention, and management of HBV, HCV and alcoholic hepatitis, NAFLD, and liver cirrhosis: A review

It has been suggested that hepatitis B virus (HBV)- and hepatitis C virus (HCV)-induced hepatic damage and cirrhosis and associated hypoalbuminemia, non-alcoholic fatty liver disease (NAFLD), and alcoholic fatty liver disease (AFLD) are due to an imbalance between pro-inflammatory and anti-inflammatory bioactive lipids. Increased tumour necrosis factor (TNF)-α production induced by HBV and HCV leads to a polyunsaturated fatty acid (PUFA) deficiency and hypoalbuminemia. Albumin mobilizes PUFAs from the liver and other tissues and thus may aid in enhancing the formation of anti-inflammatory lipoxins, resolvins, protectins, maresins and prostaglandin E1 (PGE1) and suppressing the production of pro-inflammatory PGE2. As PUFAs exert anti-viral and anti-bacterial effects, the presence of adequate levels of PUFAs could inactivate HCV and HBV and prevent spontaneous bacterial peritonitis observed in cirrhosis. PUFAs, PGE1, lipoxins, resolvins, protectins, and maresins suppress TNF-α and other pro-inflammatory cytokines, exert cytoprotective effects, and modulate stem cell proliferation and differentiation to promote recovery following hepatitis, NAFLD and AFLD. Based on this evidence, it is proposed that the administration of albumin in conjunction with PUFAs and their anti-inflammatory products could be beneficial for the prevention of and recovery from NAFLD, hepatitis and cirrhosis of the liver. NAFLD is common in obesity, type 2 diabetes mellitus, and metabolic syndrome, suggesting that even these diseases could be due to alterations in the metabolism of PUFAs and other bioactive lipids. Hence, PUFAs and co-factors needed for their metabolism and albumin may be of benefit in the prevention and management of HBV, HCV, alcoholic hepatitis and NAFLD, and liver cirrhosis.

Lipids - two sides of the same coin in lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive extracellular matrix deposition in the lung parenchyma leading to the destruction of lung structure, respiratory failure and premature death. Recent studies revealed that the pathogenesis of IPF is associated with alterations in the synthesis and the activity of lipids, lipid regulating proteins and cell membrane lipid transporters and receptors in different lung cells. Furthermore, deregulated lipid metabolism was found to contribute to the profibrotic phenotypes of lung fibroblasts and alveolar epithelial cells. Consequently, several pharmacological agents, targeting lipids, lipid mediators, and lipoprotein receptors, was successfully tested in the animal models of lung fibrosis and entered early phase clinical trials. In this review, we highlight new therapeutic options to counteract disturbed lipid hemostasis in the maladaptive lung remodeling.

Baicalin Down-Regulates IL-1β-Stimulated Extracellular Matrix Production in Nasal Fibroblasts

Purpose

Baicalin, a Chinese herbal medicine, has anti-fibrotic and anti-inflammatory effects. The aims of present study were to investigate the effects of baicalin on the myofibroblast differentiation, extracellular matrix production, migration, and collagen contraction of interleukin (IL)-1β-stimulated nasal fibroblasts and to determine the molecular mechanism of baicalin in nasal fibroblasts.

Methods

Nasal fibroblasts were isolated from the inferior turbinate of patients. Baicalin was used to treat IL-1β-stimulated nasal fibroblasts. To evaluate cytotoxicity, a 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl-tetrazolium bromide assay was used. The expression levels of α-smooth muscle actin (SMA), fibronectin, phospho-mitogen-activated protein kinase (p-MAPK), p-Akt, p-p50, p-p65, and p-IκBα were measured by western blotting, reverse transcription-polymerase chain reaction (RT—PCR),or immunofluorescence staining. Fibroblast migration was analyzed with scratch assays and transwell migration assays. Total collagen was evaluated with the Sircol collagen assay. Contractile activity was measured with a collagen gel contraction assay.

Results

Baicalin (0–50 μM) had no significant cytotoxic effects in nasal fibroblasts. The expression of α–SMA and fibronectin were significantly down-regulated in baicalin-treated nasal fibroblasts. Migration, collagen production, and contraction of IL-1β-stimulated nasal fibroblasts were significantly inhibited by baicalin treatment. Baicalin also significantly down-regulated p-MAPK, p-Akt, p-p50, p-p65, and p-IκBα in IL-1β-stimulated nasal fibroblasts.

Conclusions

We showed that baicalin down-regulated myofibroblast differentiation, extracellular matrix production, migration, and collagen contraction via the MAPK and Akt/ NF-κB pathways in IL-1β-stimulated nasal fibroblasts.

Increased lethality and defective pulmonary clearance of Streptococcus pneumoniae in microsomal prostaglandin E synthase-1-knockout mice

The production of prostaglandin E2 (PGE2) increases dramatically during pneumococcal pneumonia, and this lipid mediator impairs alveolar macrophage (AM)-mediated innate immune responses. Microsomal prostaglandin E synthase-1 (mPGES-1) is a key enzyme involved in the synthesis of PGE2, and its expression is enhanced during bacterial infections. Genetic deletion of mPGES-1 in mice results in diminished PGE2 production and elevated levels of other prostaglandins after infection. Since PGE2 plays an important immunoregulatory role during bacterial pneumonia we assessed the impact of mPGES-1 deletion in the host defense against pneumococcal pneumonia in vivo and in AMs in vitro. Wild-type (WT) and mPGES-1 knockout (KO) mice were challenged with Streptococcus pneumoniae via the intratracheal route. Compared with WT animals, we observed reduced survival and increased lung and spleen bacterial burdens in mPGES-1 KO mice 24 and 48 h after S. pneumoniae infection. While we found modest differences between WT and mPGES-1 KO mice in pulmonary cytokines, AMs from mPGES-1 KO mice exhibited defective killing of ingested bacteria in vitro that was associated with diminished inducible nitric oxide synthase expression and reduced nitric oxide (NO) synthesis. Treatment of AMs from mPGES-1 KO mice with an NO donor restored bacterial killing in vitro. These results suggest that mPGES-1 plays a critical role in bacterial pneumonia and that genetic ablation of this enzyme results in diminished pulmonary host defense in vivo and in vitro. These results suggest that specific inhibition of PGE2 synthesis by targeting mPGES-1 may weaken host defense against bacterial infections.

Elastase modifies bleomycin-induced pulmonary fibrosis in mice

Pulmonary fibrosis (PF) is characterized by excessive accumulation of collagen in the lungs. Emphysema is characterized by loss of the extracellular matrix (ECM) and alveolar enlargement. We studied the co-participation of elastase-induced mild emphysema in bleomycin-induced PF in mice by analyzing oxidative stress, inflammation and lung histology. C57BL/6 mice were divided into four groups: control; bleomycin (0.1U/mouse); elastase (using porcine pancreatic elastase (PPE)+bleomycin (3U/mouse 14 days before 0.1U/mouse of bleomycin; PPE+B); elastase (3U/mouse). Mice were humanely sacrificed 7, 14 and 21 days after treatment with bleomycin or vehicle. PF was observed 14 days and 21 days after bleomycin treatment but was observed after 14 days only in the PPE+B group. In the PPE+B group at 21 days, we observed many alveoli and alveolar septa with few PF areas. We also observed marked and progressive increases of collagens 7, 14 and 21 days after bleomycin treatment whereas, in the PPE+B group, collagen deposition was observed only at 14 days. There was a reduction in activities of the antioxidant enzymes superoxide dismutase (p<0.05), catalase (p<0.01) and glutathione peroxidase (p<0.01) parallel with an increase in nitrite (p<0.01) 21 days after bleomycin treatment compared with the control group. These endpoints were also reduced (p<0.05, p<0.05 and p<0.01, respectively) and increased (p<0.01) in the PPE+B group at 21 days compared with the control group. Interleukin (IL)-1β expression was upregulated (p<0.01) whereas IL-6 was downregulated (p<0.05) in the PPE+B group at 21 days compared with the control group. PF and emphysema did not coexist in our model of lung disease and despite increased levels of oxidative stress and inflammatory markers after combined stimulus (elastase and bleomycin) overall histology was improved to that of the nearest control group.

Physiopathologic mechanisms involved in mare endometrosis

Endometrosis is a degenerative chronic process, characterized by paramount fibrosis development in mare endometrium. This condition is one of the major causes of subfertility/infertility in mares. As in other organs, fibrosis might be a pathologic sequel of many chronic inflammatory diseases. However, aetiology and physiopathologic mechanisms involved in endometrial fibrosis are still controversial. This review presents new hypotheses based on our newest data. As the first line of innate immune defence, systemic neutrophils arrive in the uterus at mating or in the presence of pathogens. A novel paradigm is that neutrophils cast out their DNA in response to infectious stimuli and form neutrophil extracellular traps (NETs). We have shown that bacterial strains of Streptococcus zooepidemicus, Escherichia coli or Staphylococcus capitis, known to cause endometritis in mares were able to induce NETs release in vitro by equine PMN to different extents. An intriguing dilemma is the dual action of NETs. While NETs play a desirable role fighting micro-organisms in mare uterus, they may also contribute to endometrial fibrosis. A long-term in vitro exposure of mare endometrium explants to NETs components (myeloperoxidase, elastase and cathepsin G) up-regulated fibrosis markers TGFβ and Tissue inhibitor of metalloproteinase (TIMP-1). Also, pro-fibrotic cytokines regulated collagen deposition and fibrosis. Changes in expression of connective tissue growth factor (CTGF), interleukins (IL)1-α, IL-1β, IL-6 and receptors in endometrium with different degrees of fibrosis and/or inflammation were observed. A putative role of CTGF, IL and NETs components in endometrosis development should be considered. Additionally, we speculate that in sustained endometritis in mares, prostaglandins may not only cause early luteolysis or early pregnancy loss, but may also be related to endometrial fibrosis pathogenesis by stimulating collagen deposition.

PGE2 reduces MMP-14 and increases plasminogen activator inhibitor-1 in cardiac fibroblasts

Prostaglandin E2 (PGE2) is elevated during cardiac injury and we have previously shown that mice lacking the PGE2 EP4 receptor display dilated cardiomyopathy (DCM) with increased expression of the membrane type matrix metalloproteinase, MMP-14. We thus hypothesized that PGE2 regulates expression of MMP-14 and also affects fibroblast migration. Primary cultures of neonatal rat ventricular fibroblasts (NVFs) were used to test the effects of PGE2. Gene and protein expression was assessed by real time RT-PCR and Western blot, MMP activity was determined by zymography and migration of NVF was assessed by motility in a transwell system. PGE2 reduced expression of MMP-14 and these effects were antagonized by an EP4 antagonist. An EP4 agonist mimicked the effect of PGE2. PGE2 also increased mRNA and protein levels of plasminogen activator inhibitor-1 (PAI-1), an inhibitor of MMP activation. However, PGE2-stimulation of PAI-1 was mediated by the EP1/EP3 receptor and not EP4. Migration of NVF was assessed by motility in a transwell system. Treatment of NVFs with PGE2 reduced the number of cells migrating toward 10% FCS. Treatment with the EP2 agonist also reduced migration but did not affect MMP-14 expression or PAI-1. Our results suggest that PGE2 utilizes different receptors and mechanisms to ultimately decrease MMP expression and NVF migration.

Inhibitory effects of prostaglandin E2 on collagen synthesis and cell proliferation in human stellate cells from pancreatic head adenocarcinoma

BACKGROUND

Several studies have described an increased cyclooxygenase-2 (COX-2) expression in pancreatic cancer, but the role of COX-2 in tumour development and progression is not clear. The aim of the present study was to examine expression of COX-2 in cancer cells and stromal cells in pancreatic cancer specimens, and to explore the role of PGE2 in pancreatic stellate cell proliferation and collagen synthesis.

METHODS

Immunohistochemistry and immunofluorescence was performed on slides from whole sections of tissue blocks using antibodies against COX-2 and α-smooth muscle actin (αSMA). Pancreatic stellate cells (PSC) were isolated from surgically resected tumour tissue by the outgrowth method. Cells were used between passages 4 and 8. Collagen synthesis was determined by [(3)H]-proline incorporation, or by enzyme immunoassay measurement of collagen C-peptide. DNA synthesis was measured by incorporation of [(3)H]-thymidine in DNA. Cyclic AMP (cAMP) was determined by radioimmunoassay. Collagen 1A1 mRNA was determined by RT-qPCR.

RESULTS

Immunohistochemistry staining showed COX-2 in pancreatic carcinoma cells, but not in stromal cells. All tumours showed positive staining for αSMA in the fibrotic stroma. Cultured PSC expressed COX-2, which could be further induced by interleukin-1β (IL-1β), epidermal growth factor (EGF), thrombin, and PGE2, but not by transforming growth factor-β1 (TGFβ). Indirect coculture with the adenocarcinoma cell line BxPC-3, but not HPAFII or Panc-1, induced COX-2 expression in PSC. Treatment of PSC with PGE2 strongly stimulated cAMP accumulation, mediated by EP2 receptors, and also stimulated phosphorylation of extracellular signal-regulated kinase (ERK). Treatment of PSC with PGE2 or forskolin suppressed both TGFβ-stimulated collagen synthesis and PDGF-stimulated DNA synthesis.

CONCLUSIONS

The present results show that COX-2 is mainly produced in carcinoma cells and suggest that the cancer cells are the main source of PGE2 in pancreatic tumours. PGE2 exerts a suppressive effect on proliferation and fibrogenesis in pancreatic stellate cells. These effects of PGE2 are mediated by the cAMP pathway and suggest a role of EP2 receptors.

Interaction of apoptotic cells with macrophages upregulates COX-2/PGE2 and HGF expression via a positive feedback loop

Recognition of apoptotic cells by macrophages is crucial for resolution of inflammation, immune tolerance, and tissue repair. Cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE₂) and hepatocyte growth factor (HGF) play important roles in the tissue repair process. We investigated the characteristics of macrophage COX-2 and PGE₂ expression mediated by apoptotic cells and then determined how macrophages exposed to apoptotic cells in vitro and in vivo orchestrate the interaction between COX-2/PGE₂ and HGF signaling pathways. Exposure of RAW 264.7 cells and primary peritoneal macrophages to apoptotic cells resulted in induction of COX-2 and PGE₂. The COX-2 inhibitor NS-398 suppressed apoptotic cell-induced PGE₂ production. Both NS-398 and COX-2-siRNA, as well as the PGE₂ receptor EP2 antagonist, blocked HGF expression in response to apoptotic cells. In addition, the HGF receptor antagonist suppressed increases in COX-2 and PGE₂ induction. The in vivo relevance of the interaction between the COX-2/PGE₂ and HGF pathways through a positive feedback loop was shown in cultured alveolar macrophages following in vivo exposure of bleomycin-stimulated lungs to apoptotic cells. Our results demonstrate that upregulation of the COX-2/PGE₂ and HGF in macrophages following exposure to apoptotic cells represents a mechanism for mediating the anti-inflammatory and antifibrotic consequences of apoptotic cell recognition.

Role of interleukin-1β in radiation-enhancement of MDA-MB-231 breast cancer cell invasion

The ability of radiation to increase the invasiveness of cancer cells is associated with the inflammatory response, which is induced in almost all irradiated patients. For breast cancer patients, elevated plasma levels of the inflammatory cytokine interleukin-1β (IL1β) persisted for a few weeks after completion of radiotherapy. The aim of this study was to determine whether IL1β is involved in the enhancement of breast cancer cell invasion induced by radiation. The role of IL1β was assessed with invasion chambers where irradiated fibroblasts were used as chemoattractant for the MDA-MB-231 breast cancer cells plated in the upper compartment. The ability of IL1β to stimulate the expression of cyclooxygenase-2 (COX-2) and biosynthesis of the prostaglandin E2 (PGE2) in MDA-MB-231 cells were also determined. Our results show that radiation-enhancement of MDA-MB-231 cell invasion was prevented with an anti-IL1β antibody. The production of IL1β was increased in irradiated fibroblasts, while the invasiveness of the MDA-MB-231 cells not exposed to irradiated fibroblasts was favored by adding this cytokine. Furthermore, addition of the COX-2 inhibitor NS-398 prevented the stimulation of cancer cell invasion induced either by irradiated fibroblasts or IL1β. We propose that the effect of IL1β on the invasiveness of the MDA-MB-231 cells involves elevation of matrix metalloproteinase-9 (MMP-9) production, induction of COX-2 expression and PGE2 biosynthesis. In conclusion, this study supports the involvement of IL1β in the radiation-enhancement of breast cancer cell invasion.

Coordinated induction of cyclooxygenase-2/prostaglandin E2 and hepatocyte growth factor by apoptotic cells prevents lung fibrosis

Apoptotic cell instillation after bleomycin induces persistent HGF production and protects from pulmonary fibrosis, but the underlying mechanism remains unclear. We investigated immediate and prolonged effects of in vivo instillation of apoptotic cells into bleomycin-stimulated mouse lungs (2 days old) on COX-2 expression in lung tissue and alveolar macrophages and PGE2 production in BALF. Furthermore, functional interaction between these molecules and HGF, following apoptotic cell instillation in a bleomycin-induced lung fibrosis model, was assessed. Apoptotic cell instillation results in enhanced immediate and prolonged expression of COX-2 and PGE2 when compared with those from bleomycin-only-treated mice. Coadministration of the COX-2-selective inhibitor NS398 or the selective PGE2R EP2 inhibitor AH6809 inhibited the increase in HGF production. Inhibition of HGF signaling using PHA-665752 inhibited increases in COX-2 and PGE2. Long-term inhibition of COX-2, PGE2, or HGF reversed the reduction of TGF-β, apoptotic and MPO activities, protein levels, and hydroxyproline contents. Up-regulation of COX-2/PGE2 and HGF through a positive-feedback loop may be an important mechanism whereby apoptotic cell instillation exerts the net results of anti-inflammatory, antiapoptotic, and antifibrotic action.

The role of prostaglandin E2 in human vascular inflammation

Prostaglandins (PG) are the product of a cascade of enzymes such as cyclooxygenases and PG synthases. Among PG, PGE2 is produced by 3 isoforms of PGE synthase (PGES) and through activation of its cognate receptors (EP1-4), this PG is involved in the pathophysiology of vascular diseases. Some anti-inflammatory drugs (e.g. glucocorticoids, nonsteroidal anti-inflammatory drugs) interfere with its metabolism or effects. Vascular cells can initiate many of the responses associated with inflammation. In human vascular tissue, PGE2 is involved in many physiological processes, such as increasing vascular permeability, cell proliferation, cell migration and control of vascular smooth muscle tone. PGE2 has been shown to contribute to the pathogenesis of atherosclerosis, abdominal aortic aneurysm but also in physiologic/adaptive processes such as angiogenesis. Understanding the roles of PGE2 and its cognate receptors in vascular diseases could help to identify diagnostic and prognostic biomarkers. In addition, from these recent studies new promising therapeutic approaches like mPGES-1 inhibition and/or EP4-antagonism should be investigated.

Ulinastatin suppresses lipopolysaccharide-induced prostaglandin E2 synthesis and nitric oxide production through the downregulation of nuclear factor‑κB in BV2 mouse microglial cells

Ulinastatin is an intrinsic serine-protease urinary trypsin inhibitor that can be extracted and purified from human urine. Urinary trypsin inhibitors are widely used to treat patients with acute inflammatory disorders, such as shock and pancreatitis. However, although the anti-inflammatory activities of urinary trypsin inhibitors have been investigated, the mechanisms underlying their actions are not yet fully understood. In the present study, we evaluated the effect of ulinastatin on lipopolysaccharide (LPS)-induced inflammation in relation with nuclear factor-κB (NF-κB) activation using BV2 mouse microglial cells. To accomplish this, we performed a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, reverse transcription-polymerase chain reaction (RT-PCR), western blot analysis, electrophoretic mobility gel shift assay (EMSA), prostaglandin E(2) (PGE(2)) immunoassay and nitric oxide (NO) detection. The results demonstrated that ulinastatin suppressed PGE2 synthesis and NO production by inhibiting the LPS-induced mRNA and protein expression of cyclooxygenase-2 (COX-2) and inducible NO synthase (iNOS) in BV2 mouse microglial cells. Ulinastatin suppressed the activation of NF-κB in the nucleus. These findings demonstrate that ulinastatin exerts analgesic and anti-inflammatory effects that possibly occur via the suppression of COX-2 and iNOS expression through the downregulation of NF-κB activity.

The fibroproliferative response in acute respiratory distress syndrome: mechanisms and clinical significance

Acute respiratory distress syndrome (ARDS) continues to be a major healthcare problem, affecting >190,000 people in the USA annually, with a mortality of 27-45%, depending on the severity of the illness and comorbidities. Despite advances in clinical care, particularly lung protective strategies of mechanical ventilation, most survivors experience impaired health-related quality of life for years after the acute illness. While most patients survive the acute illness, a subset of ARDS survivors develops a fibroproliferative response characterised by fibroblast accumulation and deposition of collagen and other extracellular matrix components in the lung. Historically, the development of severe fibroproliferative lung disease has been associated with a poor prognosis with high mortality and/or prolonged ventilator dependence. More recent studies also support a relationship between the magnitude of the fibroproliferative response and long-term health-related quality of life. The factors that determine which patients develop fibroproliferative ARDS and the cellular mechanisms responsible for this pathological response are not well understood. This article reviews our current understanding of the contribution of pulmonary dysfunction to mortality and to quality of life in survivors of ARDS, the mechanisms driving pathological fibroproliferation and potential therapeutic approaches to prevent or attenuate fibroproliferative lung disease.

FAK-related nonkinase is a multifunctional negative regulator of pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease whose underlying molecular mechanisms are largely unknown. Herein, we show that focal adhesion kinase-related nonkinase (FRNK) plays a key role in limiting the development of lung fibrosis. Loss of FRNK function in vivo leads to increased lung fibrosis in an experimental mouse model. The increase in lung fibrosis is confirmed at the histological, biochemical, and physiological levels. Concordantly, loss of FRNK function results in increased fibroblast migration and myofibroblast differentiation and activation of signaling proteins that drive these phenotypes. FRNK-deficient murine lung fibroblasts also have an increased capacity to produce and contract matrix proteins. Restoration of FRNK expression in vivo and in vitro reverses these profibrotic phenotypes. These data demonstrate the multiple antifibrotic actions of FRNK. More important, FRNK expression is down-regulated in human IPF, and down-regulation of FRNK in normal human lung fibroblasts recapitulates the profibrotic phenotype seen in FRNK-deficient cells. The effect of loss and gain of FRNK in the experimental model, when taken together with its down-regulation in human IPF, suggests that FRNK acts as an endogenous negative regulator of lung fibrosis by repressing multiple profibrotic responses.

Lipids and eicosanoids in fibrosis: emerging targets for therapy

PURPOSE OF REVIEW

Lipid mediators including the lysophospholipids, sphingolipids and eicosanoids have long been implicated in inflammation, cancer and numerous other diseases. Over the last decade, new research suggests a role for these mediators in fibrosis.

RECENT FINDINGS

Recent developments in the study of fibrotic mediators have centered on lysophospholipids and eicosanoids. New research is evaluating metabolic-profiling strategies to quantitatively measure lipid mediators in human plasma. Lysophosphatidic acid receptor antagonists are currently under development with early phase trials scheduled for idiopathic pulmonary fibrosis and scleroderma dermal fibrosis. Eicosanoids have long been implicated in maintaining tissue homeostasis, and the balance of profibrotic and antifibrotic effects has drawn attention in recent years. Targeting the prostanoids, specifically PGE2 and PGI2, as well as the leukotrienes is now being considered for antifibrotic therapies.

SUMMARY

Lipid mediators have significant roles in many disease processes. Significant research now suggests a critical role for these mediators in the pathogenesis of fibrosis. Targeting these mediators is a promising area of drug discovery.

Prostaglandin E2 induces stromal cell-derived factor-1 expression in prostate stromal cells by activating protein kinase A and transcription factor Sp1

Recent reports indicate prostaglandin E2 (PGE2) can modulate tumor environment and promote angiogenesis through induction of stromal cell-derived factor 1 (SDF-1) production. We investigated the mechanism of PGE2-induced SDF-1 regulation in human prostate stromal cell and analyzed the effects in a stromal-epithelial interaction model. PGE2 stimulation increased SDF-1 expression in the prostate stromal cell lines WPMY-1 and NAF. We revealed signaling through the PGE2 receptor EP3 and activation of protein kinase A (PKA) are required. The EP3 agonist sulprostone and the cAMP analog forskolin mimicked and the EP3 siRNA, antagonist L798106 and the PKA inhibitor H89 abrogated the effect of PGE2 on SDF-1 expression. SDF-1 promoter truncation experiments demonstrated a 254 bp (from nt -219 to nt +34) SDF-1 proximal promoter fragment containing 5 putative transcription factor Sp1 binding motifs is sufficient for PGE2 induction. CHIP assays confirmed binding and PGE2 induced recruitment of Sp1 to the SDF-1 promoter. Sp1 motif mutation identified Sp1 motifs -140/-133 and -9/+1 as the crucial elements responsible for PGE2 induction. Moreover, SDF-1 was up- or down-regulated by Sp1 over-expression or knock-down. We also demonstrate stimulation of migration of prostate cancer cell lines PC3 and DU145 with conditioned media collected from WPMY-1 or NAF cells stimulated with PGE2 and blockade of enhanced migration by a SDF-1 neutralizing antibody. In conclusion, we provide evidence for a paracrine prostate stromal-epithelial interaction induced by upregulation of expression of SDF-1 by PGE2. Our research provides new insights into the mechanism promoting metastasis of prostate carcinoma via stromal-epithelial interaction.

Immunomodulatory effects of Liriope platyphylla water extract on lipopolysaccharide-activated mouse macrophage

The tuber of Liriope platyphylla Wang et Tang (Liliaceae), also known as Liriopis tuber, is famous in Oriental medicine owing to its tonic, antitussive, expectorant and anti-asthmatic properties. In the present study, the effects of Liriopis tuber water extract (LP) on proinflammatory mediators secreted from lipopolysaccharide (LPS)-induced cultured RAW 264.7 mouse macrophages were investigated. Nitric oxide (NO), prostaglandin E2 (PGE2) and intracellular calcium release were measured after 24 h incubation. Various cytokines and nuclear transcription factors (NF-&#954;B and CREB) of LPS-induced RAW 264.7 were measured by a multiplex bead array assay based on xMAP technology. LP (up to 200 &#956;g/mL) significantly decreased levels of nitric oxide (NO), interleukin (IL)-6, IL-10, IL-12p40, interferon-inducible protein-10, keratinocyte-derived chemokine, monocyte chemotactic protein-1, vascular endothelial growth factor, granulocyte macrophage-colony stimulating factor, platelet derived growth factor, PGE2, intracellular calcium, NF-&#954;B and CREB in LPS-induced RAW 264.7 cells (p &lt; 0.05). The results suggest that LP has immunomodulatory activity to reduce excessive immune reactions during the activation of macrophages by LPS. Further studies are needed to verify the precise mechanism regulating immunomodulatory activities of LP.

Role of the Arylhydrocarbon Receptor (AhR) in the Pathology of Asthma and COPD

The dioxins and dioxin-like compounds in cigarette smoke and environmental pollutants modulate immunological responses. These environmental toxicants are known to cause lung cancer but have also recently been implicated in allergic and inflammatory diseases such as bronchitis, asthma, and chronic obstructive pulmonary disease (COPD). In a novel pathway of this response, the activation of a nuclear receptor, arylhydrocarbon receptor (AhR), mediates the effects of these toxins through the arachidonic acid cascade, cell differentiation, cell-cell adhesion interactions, cytokine expression, and mucin production that are implicated in the pathogenesis and exacerbation of asthma/COPD. We have previously reported that human bronchial epithelial cells express AhR, and AhR activation induces mucin production through reactive oxygen species. This review discusses the role of AhR in asthma and COPD, focusing in particular on inflammatory and resident cells in the lung. We describe the important impact that AhR activation may have on the inflammation phase in the pathology of asthma and COPD. In addition, crosstalk of AhR signaling with other ligand-activated transcription factors such as peroxisome proliferator-activated receptors (PPARs) has been well documented.

Anti-inflammatory effect of myristicin on RAW 264.7 macrophages stimulated with polyinosinic-polycytidylic acid

Myristicin (1-allyl-5-methoxy-3,4-methylenedioxybenzene) is an active aromatic compound found in nutmeg (the seed of Myristica fragrans), carrot, basil,cinnamon, and parsley. Myristicin has been known to have anti-cholinergic, antibacterial,and hepatoprotective effects, however, the effects of myristicin on virus-stimulated macrophages are not fully reported. In this study, the anti-inflammatory effect of myristicin on double-stranded RNA (dsRNA)-stimulated macrophages was examined. Myristicin did not reduce the cell viability of RAW 264.7 mouse macrophages at concentrations of up to 50 μM. Myristicin significantly inhibited the production of calcium, nitric oxide (NO),interleukin (IL)-6, IL-10, interferon inducible protein-10, monocyte chemotactic protein(MCP)-1, MCP-3, granulocyte-macrophage colony-stimulating factor, macrophage inflammatory protein (MIP)-1α, MIP-1β, and leukemia inhibitory factor in dsRNA[polyinosinic-polycytidylic acid]-induced RAW 264.7 cells (P < 0.05). In conclusion,myristicin has anti-inflammatory properties related with its inhibition of NO, cytokines,chemokines, and growth factors in dsRNA-stimulated macrophages via the calcium pathway.

Immunostimulatory effects of gold nanorod and silica-coated gold nanorod on RAW 264.7 mouse macrophages

In this study, we have investigated immunostimulatory effects of gold nanorod (Au) and silica-coated gold nanorod (SiAu) concerned with inflammatory mediators such as calcium (Ca), hydrogen peroxide, nitric oxide (NO), various cytokines, prostaglandin E2 (PGE2), transcription factors, and immune response gene in RAW 264.7 mouse macrophages. Both Au and SiAu significantly increased the release of Ca, hydrogen peroxide, NO, IL-1α, IL-1β, IL-6, IL-10, IP-10, MCP-1, MCP-3, TNF-α, RANTES, G-CSF, GM-CSF, LIF, MIP-2, VEGF, and PGE2 with enhancing expression of STAT1, STAT3, c-Fos, and COX-2 mRNA in RAW 264.7 cells. The results suggest that Au and SiAu have immunostimulatory properties to strengthen immune reactions via calcium-transcription factors pathway in macrophage.

Ginger phenylpropanoids inhibit IL-1beta and prostanoid secretion and disrupt arachidonate-phospholipid remodeling by targeting phospholipases A2

The rhizome of ginger (Zingiber officinale) is employed in Asian traditional medicine to treat mild forms of rheumatoid arthritis and fever. We have profiled ginger constituents for robust effects on proinflammatory signaling and cytokine expression in a validated assay using human whole blood. Independent of the stimulus used (LPS, PMA, anti-CD28 Ab, anti-CD3 Ab, and thapsigargin), ginger constituents potently and specifically inhibited IL-1β expression in monocytes/macrophages. Both the calcium-independent phospholipase A(2) (iPLA(2))-triggered maturation and the cytosolic phospholipase A(2) (cPLA(2))-dependent secretion of IL-1β from isolated human monocytes were inhibited. In a fluorescence-coupled PLA(2) assay, most major ginger phenylpropanoids directly inhibited i/cPLA(2) from U937 macrophages, but not hog pancreas secretory phospholipase A(2). The effects of the ginger constituents were additive and the potency comparable to the mechanism-based inhibitor bromoenol lactone for iPLA(2) and methyl arachidonyl fluorophosphonate for cPLA(2), with 10-gingerol/-shogaol being most effective. Furthermore, a ginger extract (2 μg/ml) and 10-shogaol (2 μM) potently inhibited the release of PGE(2) and thromboxane B2 (>50%) and partially also leukotriene B(4) in LPS-stimulated macrophages. Intriguingly, the total cellular arachidonic acid was increased 2- to 3-fold in U937 cells under all experimental conditions. Our data show that the concurrent inhibition of iPLA(2) and prostanoid production causes an accumulation of free intracellular arachidonic acid by disrupting the phospholipid deacylation-reacylation cycle. The inhibition of i/cPLA(2), the resulting attenuation of IL-1β secretion, and the simultaneous inhibition of prostanoid production by common ginger phenylpropanoids uncover a new anti-inflammatory molecular mechanism of dietary ginger that may be exploited therapeutically.

Profiling target genes of FGF18 in the postnatal mouse lung: possible relevance for alveolar development

Better understanding alveolarization mechanisms could help improve prevention and treatment of diseases characterized by reduced alveolar number. Although signaling through fibroblast growth factor (FGF) receptors is essential for alveolarization, involved ligands are unidentified. FGF18, the expression of which peaks coincidentally with alveolar septation, is likely to be involved. Herein, a mouse model with inducible, lung-targeted FGF18 transgene was used to advance the onset of FGF18 expression peak, and genome-wide expression changes were determined by comparison with littermate controls. Quantitative RT-PCR was used to confirm expression changes of selected up- and downregulated genes and to determine their expression profiles in the course of lung postnatal development. This allowed identifying so-far unknown target genes of the factor, among which a number are known to be involved in alveolarization. The major target was adrenomedullin, a promoter of lung angiogenesis and alveolar development, whose transcript was increased 6.9-fold. Other genes involved in angiogenesis presented marked expression increases, including Wnt2 and cullin2. Although it appeared to favor cell migration notably through enhanced expression of Snai1/2, FGF18 also induced various changes consistent with prevention of epithelial-mesenchymal transition. Together with antifibrotic effects driven by induction of E prostanoid receptor 2 and repression of numerous myofibroblast markers, this could prevent alveolar septation-driving mechanisms from becoming excessive and deleterious. Last, FGF18 up- or downregulated genes of extracellular matrix components and epithelial cell markers previously shown to be up- or downregulated during alveolarization. These findings therefore argue for an involvement of FGF18 in the control of various developmental events during the alveolar stage.

Radiation-enhancement of MDA-MB-231 breast cancer cell invasion prevented by a cyclooxygenase-2 inhibitor

BACKGROUND

Recent evidences support that radiation can promote the invasion of cancer cells. As interactions between cancer cells and surrounding stromal cells can have an important role in tumour progression, we determined whether an irradiation to fibroblasts can enhance the invasiveness of breast cancer cells. The role of cyclooxygenase-2 (COX-2), an inflammatory enzyme frequently induced by radiotherapy, was investigated.

METHODS

Irradiated 3T3 fibroblasts were plated in the lower compartment of invasion chambers and used as chemoattractant for non-irradiated human breast cancer cell MDA-MB-231, which are oestrogen receptor negative (ER(-)) and the oestrogen receptor positive (ER(+)) MCF-7 cells. Stimulation of COX-2 expression in irradiated 3T3 cells was measured by a semi-quantitative qPCR and western blot. Capacity of the major product of COX-2, the prostaglandin E2 (PGE(2)), to stimulate the production of the matrix metalloproteinase-2 (MMP-2) and cancer cell invasion were assessed with a zymography gel and invasion chambers.

RESULTS

Irradiation (5 Gy) of 3T3 fibroblasts increased COX-2 expression and enhanced by 5.8-fold the invasiveness of non-irradiated MDA-MB-231 cells, while their migration was not modified. Addition of the COX-2 inhibitor NS-398 completely prevented radiation-enhancement of cancer cell invasion. Further supporting the potential role of COX-2, addition of PGE(2) has increased cancer cell invasion and release of MMP-2 from the MDA-MB-231 cells. This effect of radiation was dependant on the expression of membrane type 1 (MT1)-MMP, which is required to activate the MMP-2, but was not associated with the ER status. Although irradiated fibroblasts stimulated the invasiveness of MDA-MB-231 ER(-) cells, no enhancement was measured with the ER(+) cell line MCF-7.

CONCLUSIONS

Radiation-enhancement of breast cancer cell invasion induced by irradiated 3T3 fibroblasts is not dependant on the ER status, but rather the expression of MT1-MMP. This adverse effect of radiation can be prevented by a specific COX-2 inhibitor.

Role of the arylhydrocarbon receptor in lung disease

Ubiquitous environmental contaminants such as dioxins have long been implicated in cellular toxicity, but only recently have various biological effects been linked to immune regulation. These plentiful noxious agents exert their effects through the arylhydrocarbon receptor (AhR) recognized as a ligand-activated transcription factor. AhR activation mediates gene alteration, cell-cell adhesion interaction, cytokine expression, and mucin production, which are involved in the induction of cancer or inflammation. We have reported that human bronchial epithelial cells express AhR, and AhR activation induces mucin production through reactive oxygen species. This review discusses the role of AhR in lung disease, focusing in particular on airway epithelial cells. In addition, although it is not yet clear how the activation of AhR modifies carcinogenesis or airway inflammation, we mention a potent therapeutic target for AhR activation in the prevention/treatment of lung cancer, allergic asthma, and chronic obstructive pulmonary disease.

Prostaglandin E2 increases cardiac fibroblast proliferation and increases cyclin D expression via EP1 receptor

PGE(2) affects growth of many cell types. Thus, we hypothesized that PGE(2) would stimulate growth of cardiac fibroblasts. To test our hypothesis we used neonatal rat ventricular fibroblasts (NVF). RT-PCR demonstrated the presence of all 4 PGE(2) receptor (EPs) mRNAs in NVF. Using flow cytometry, we found that PGE(2) decreased the percentage of cells in G0/G1 and increased the number of cells in S phase. PGE(2) also increased expression of cyclin D3, a known regulator of the cell cycle and this effect was mimicked by the EP1/EP3 agonist sulprostone. Next, we found that treatment of NVF with PGE(2) increased phosphorylation of p42/44 MAPK and Akt and that PGE(2)-stimulation of cyclin D3 was antagonized with both a MEK inhibitor and a PI3 kinase inhibitor. In conclusion, PGE(2) stimulates cardiac fibroblast proliferation via EP1 and/or EP3, p42/44 MAPK and Akt-regulation of cyclin D3. These results may be relevant to cardiac fibrosis.

Prostaglandin E2 and the pathogenesis of pulmonary fibrosis

Prostaglandin (PG)E(2) is a bioactive eicosanoid that regulates many biologically important processes in part due to its ability to signal through four distinct G-protein-coupled receptors with differential signaling activity and unique expression patterns in different cell types. Although PGE(2) has been linked to malignancy in many organs, it is believed to play a beneficial role in the setting of fibrotic lung disease. This is in part due to the ability of PGE(2) to limit many of the pathobiologic features of lung fibroblasts and myofibroblasts, including the ability of PGE(2) to limit fibroblast proliferation, migration, collagen secretion, and, as originally reported in the Journal by us in 2003, the ability to limit transforming growth factor (TGF)-β-induced myofibroblast differentiation. In the setting of lung fibrosis, PGE(2) production and signaling is often diminished. In the last 8 years, significant advances have been made to better understand the dysregulation of PGE(2) production and signaling in the setting of lung fibrosis. We also have a clearer picture of how PGE(2) inhibits myofibroblast differentiation and the receptor signaling pathways that can influence fibroblast proliferation. This review highlights these recent advances and offers new insights into the potential ways that PGE(2) and its downstream signals can be regulated for therapeutic benefit in a disease that has no validated treatment options.

Involvement of the constitutive prostaglandin E synthase cPGES/p23 in expression of an initial prostaglandin E2 inactivating enzyme, 15-PGDH

We previously showed that cytosolic prostaglandin (PG) E synthase (cPGES/p23) which isomerizes PGH(2) to PGE(2), is essential for fetal mouse development. Embryonic fibroblasts derived from cPGES/p23 knockout mice generated higher amounts of PGE(2) in culture supernatants than wild-type-derived cells. In order to elucidate this apparent conflict that absence of PGE(2) synthetic enzyme caused facilitation of PGE(2) biosynthesis, we examined expression of the PGE(2) degrading enzyme in embryonic fibroblasts. We report here that embryonic fibroblasts deficient in cPGES/p23 decreased the expression of the PGE(2) degrading enzyme, 15-hydroxyprostaglandin dehydrogenase (15-PGDH), which catalyzes the inactivating conversion of the PGE(2) 15-OH to a 15-keto group, compared with that of wild-type. In addition, rat fibroblastic 3Y1 cells harboring cPGES/p23 siRNA exhibited lower 15-PGDH expression than mock-transfected cells. Furthermore, forcible expression of cPGES/p23 in 3Y1 cells resulted in facilitation of 15-PGDH promoter activity. These results suggest that the PGE(2)-inactivating pathway is controlled by the PGE(2) biosynthetic enzyme, cPGES/p23.

Arylhydrocarbon receptor (AhR) activation in airway epithelial cells induces MUC5AC via reactive oxygen species (ROS) production

The dioxins and dioxin-like compounds in cigarette smoke regulate various immunological responses via the arylhydrocarbon receptor (AhR). These environmental toxicants are known to cause bronchitis, asthma, chronic obstructive pulmonary disease (COPD), and lung cancer. Recent studies have demonstrated that AhR activation upregulates the expression of mucin 5AC, oligomeric mucus/gel-forming (MUC5AC) in the airway epithelial cell line. However, the mechanism for the production of mucin has not been clarified. In this study, we investigated the role and pathway of AhR in airway epithelial cells by using selective agonists and antagonists. After stimulation with or without benzopyrene (B[a]P), an AhR agonist, MUC5AC expression was measured by real-time RT-PCR. The mechanism of AhR-induced MUC5AC expression in airway epithelial cells was studied in terms of the production of cytokine and reactive oxygen species (ROS). Treatment with B[a]P increased ROS generation in NCI-H₂₉₂ cells. Furthermore, B[a]P-induced MUC5AC upregulation and mucin production were inhibited by AhR siRNA or the use of an antioxidative agent. These results suggest that the AhR-induced increase of mucin production is partially mediated by ROS generation. An antioxidant therapy approach may help to cure AhR-induced mucus hypersecretory diseases.

Cytokine-dependent balance of mitogenic effects in primary human lung fibroblasts related to cyclic AMP signaling and phosphodiesterase 4 inhibition

Interleukin-1beta (IL-1beta) and basic fibroblast growth factor (bFGF) are important regulators of proliferation, and their expression is increased in lungs of patients with asthma, idiopathic pulmonary fibrosis (IPF), or chronic obstructive pulmonary disease (COPD). We investigated the effect of IL-1beta and bFGF on proliferation of human lung fibroblasts and the role of COX-2, PGE(2), and cAMP in this process. Furthermore, the effect of phosphodiesterase (PDE) 3 and 4 inhibition was analyzed. In primary human lung fibroblasts low concentrations of IL-1beta (<10 pg/ml) potentiated the bFGF-induced DNA synthesis, whereas higher concentrations revealed antiproliferative effects. Higher concentrations of IL-1beta-induced COX-2 mRNA and protein associated with an increase in PGE(2) and cAMP, and all of these parameters were potentiated by bFGF. The PDE4 inhibitor piclamilast concentration-dependently reduced proliferation by a partial G1 arrest. The PDE3 inhibitor motapizone was inactive by itself but enhanced the effect of the PDE4 inhibitor. This study demonstrates that bFGF and IL-1beta act in concert to fine-tune lung fibroblast proliferation resulting in amplification or reduction. The antiproliferative effect of IL-1beta is likely attributed to the induction of COX-2, which is further potentiated by bFGF, and the subsequent generation of PGE(2) and cAMP. Inhibition of PDE4 inhibition (rather than PDE3) may diminish proliferation of human lung fibroblasts and therefore could be useful in the therapy of pathological remodeling in lung diseases.

Anti-inflammatory and analgesic effects of the aqueous extract of corni fructus in murine RAW 264.7 macrophage cells

Corni fructus is the fruit of Cornus officinalis Sieb. et Zucc, which is classified into the dogwood family of Cornaceae. Corni fructus has antineoplastic, antioxidative, and antidiabetic effects, but its anti-inflammatory and analgesic effects are unknown. Here, we investigated the anti-inflammatory and analgesic effects of an aqueous extract of corni fructus using murine RAW 264.7 macrophage cells. For this study, we used the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, western blot analysis, prostaglandin (PG) E(2) immunoassay, and nitric oxide (NO) detection. In addition, the analgesic effect of corni fructus was assessed by the acetic acid-induced writhing response in mice. The aqueous extract of corni fructus suppressed PGE(2) synthesis and NO production by inhibiting the lipopolysaccharide-induced expression of cyclooxygenase (COX)-2 and inducible NO synthase (iNOS) in murine RAW 264.7 macrophage cells. The extract also suppressed increases in nuclear factor-kappaB (NF-kappaB) levels in the nucleus. In vivo study showed that the extract suppressed the acetic acid-induced writhing response in mice. The aqueous extract of corni fructus exerts anti-inflammatory and analgesic effects by suppressing COX-2 and iNOS expression through the down-regulation of NF-kappaB binding activity.

Prostaglandin E2 is activated by airway injury and regulates fibroblast cytoskeletal dynamics

OBJECTIVES/HYPOTHESIS

To characterize the activation of cyclooxygenase (COX)-2/prostaglandin (PG) E2 signaling during airway mucosal repair and its subsequent role during the wound healing process.

STUDY DESIGN

Prospective animal study.

METHODS

The subglottis was approached via cricothyroidotomy. Sham airways were closed, and wounded airways were subjected to laser injury and closed. Subglottic tissue was harvested at 12 hours, 24 hours, 48 hours, and 72 hours postinjury. Secretions were collected preoperatively and at time of sacrifice. Inflammatory gene expression was analyzed using quantitative reverse transcriptase polymerase chain reaction. Subglottic/tracheal explants were exposed to exogenous IL-1beta in the presence or absence of COX inhibitors. Explant-produced PGE2 levels were assayed using enzyme linked immunoassays. Human airway fibroblast migration and collagen contraction were assayed in the presence or absence of prostaglandin E2.

RESULTS

Laser injury triggers a rapid, dose-dependent increase in mucosal IL-1beta and COX-2 gene expression, with an anatomical distribution proportional to the distance from the site of injury. Gene upregulation correlates with dose-dependent increases in PGE2 mucosal secretion levels. Ex vivo analysis indicates IL-1beta is responsible for the activation of the COX-2 / PGE2 pathway. Prostaglandin E2 differentially inhibits airway fibroblast migration and contraction in a specific, dose-dependent manner.

CONCLUSIONS

PGE2 is activated during mucosal inflammation and acts to decrease fibroplastic activity in the mucosal wound bed. During subglottic stenosis (SGS) development, the levels of PGE2 generated in response to injury may be insufficient to blunt the intrinsically fibroplastic phenotype of SGS fibroblasts, resulting in excessive scarring.

Prostaglandins compromise basal forebrain cholinergic neuron differentiation and survival: action at EP1/3 receptors results in AIF-induced death

Activated microglia produce a factor or cocktail of factors that promotes cholinergic neuronal differentiation of undifferentiated precursors in the embryonic basal forebrain (BF) in vitro. To determine whether microglial prostaglandins mediate this action, microglia were stimulated in the presence of the cyclooxygenase inhibitor ibuprofen, and microglial conditioned medium (CM) was used to culture rat BF precursors at embryonic day 15. Choline acetyltransferase (ChAT) activity served as a measure of cholinergic differentiation. While inhibition of prostaglandin biosynthesis did not affect the ability of microglial CM to promote ChAT activity, treatment of microglia with prostaglandin E2 (PGE2) inhibited it. Agonists of E prostanoid receptors EP2 (butaprost) and EP1/3 (sulprostone) mimicked PGE2, while misoprostol (E1-4) actually enhanced the action of CM. PGE2 added directly to BF cultures together with microglial CM also inhibited ChAT activity. While BF cultures expressed all four prostanoid receptors, direct addition of sulprostone but not butaprost mimicked PGE2, suggesting that PGE2 engaged EP1/3 receptors in the BF. Neither PKA inhibition by H89 nor cAMP induction by forskolin or dibutyrl-cAMP altered the action of sulprostone. Sulprostone severely compromised ChAT activity, dendrite number, axonal length and axonal branching, but caspase inhibition did not restore these. However, sulprostone resulted in increased staining intensity and nuclear translocation of apoptosis-inducing factor (AIF) suggesting caspase-independent cell death. We have found that PGE2 action at microglial EP2 receptors inhibits the microglial production of the cholinergic differentiating cocktail, while action at neuronal EP3 receptors has a deleterious effect on cholinergic neurons causing neurite retraction and cell death.