The COX-1/COX-2 balance in asthma

Eclipta prostrataImproves DSS-Induced Colitis through Regulation of Inflammatory Response in Intestinal Epithelial Cells

Eclipta prostrata (EP) and its compounds are known to have several pharmacological effects including anti-inflammatory effects. In the present study, we demonstrated that EP improves the dextran sulfate sodium (DSS)-induced colitis symptoms such as body weight loss, colon length shortening and disease activity index. In DSS-induced colitis tissue, EP controls the protein expressions of cyclooxygenase-2 (COX-2) and hypoxia inducible factor-1[Formula: see text] (HIF-1[Formula: see text]). In addition, the release of prostaglandin E2and vascular endothelial growth factor-A were significantly reduced by EP administration. EP also inhibited COX-2 and HIF-1[Formula: see text] expressions in the tumor necrosis factor-[Formula: see text] stimulated HT-29 cells. These inhibitory effects of EP occurred by reducing the phosphorylation of I[Formula: see text]B and the translocation of the nuclear factor-[Formula: see text]B (NF-[Formula: see text]B). Additionally, we found through HPLC analysis that wedelolactone, which is an inhibitor of NF-[Formula: see text]B transcription, was contained in water extract of EP. These results indicate that EP can improve colitis symptoms through the modulation of immune function in intestinal epithelial cells and suggests that EP has the potential therapeutic effect to intestinal inflammation.

COX inhibitors for airway inflammation

INTRODUCTION

The cyclooxygenase (COX) enzyme, which is responsible for the production of prostaglandins (PGs), key mediators of inflammation, may have the potential to become an attractive target for anti-inflammatory therapy. COX catalyzes the conversion of arachidonic acid (AA) into PGs, which play a significant role in disease. PGs are lipid mediators of central importance in the regulation of inflammation and smooth muscle tone. Airway-resident inflammatory cells release PGs: PGD2 and PDF2a amplify smooth muscle contraction and airway inflammation. Following its conversion from membrane phospholipids by phospholipase, AA enters the prostanoid pathway via COX, which catalyzes the conversion of AA to PGH2. PGH2 is then converted to biologically active PGs by cell-specific PG synthases. As COX is the rate limiting step in the PG pathway, the regulation of this enzyme is of critical importance in PG production.

AREAS COVERED

This review addresses the opportunities and challenges of COX inhibitors as therapeutic targets in airway inflammation. The review covers literature from the past 20 years.

EXPERT OPINION

Current literature favors COX inhibitors as potential targets for airway diseases. However, from the information available, it is not clear whether the COX enzyme by itself can serve as a target in drug development for asthma and COPD. Therefore, additional research is required to elucidate the mechanisms of action of COX metabolites before it can be considered as a target.

Clinical, physiological and anti-inflammatory effect of montelukast in patients with cough variant asthma

BACKGROUND

Cough variant asthma (CVA) is a phenotype of asthma presenting solely with coughing, characterized by airway hyperresponsiveness, eosinophilic inflammation and a cough response to bronchodilators. Leukotriene receptor antagonists (LTRAs) are antiasthma medications with anti-inflammatory and bronchodilatory properties. Although LTRAs exert antitussive effects in CVA, the mechanisms involved are unknown.

OBJECTIVES

This study aimed to clarify the antitussive mechanisms of LTRAs in CVA patients.

METHODS

We prospectively observed the effect of montelukast (10 mg) daily for 4 weeks in 23 consecutive nonsmoking adults with anti-inflammatory treatment-naive CVA. We evaluated, before and after treatment, the cough visual analogue scale (VAS), pulmonary function (spirometry and impulse oscillation), methacholine airway responsiveness, cough receptor sensitivity, expressed by the concentration of capsaicin inducing 2 or more (C2) and 5 or more (C5) coughs, sputum eosinophil counts and levels of inflammatory mediators, including cysteinyl leukotrienes, leukotriene B(4), prostaglandin (PG) D(2), PGE(2), PGF(2)(α) and thromboxane B(2). We compared the baseline characteristics of the patients based on the symptomatic response to montelukast, defined as a decrease in the cough VAS of >25% (n = 15) or ≤25% (n = 8).

RESULTS

Montelukast significantly decreased the cough VAS (p = 0.0008), sputum eosinophil count (p = 0.013) and cough sensitivity (C2: p = 0.007; C5: p = 0.039), whereas pulmonary function, airway responsiveness and sputum mediator levels remained unchanged. Multivariate analysis showed that a better response to montelukast was associated solely with younger age (p = 0.032).

CONCLUSION

The antitussive effect of montelukast in CVA may be attributed to the attenuation of eosinophilic inflammation rather than its bronchodilatory properties.

Aspirin and indomethacin reduce lung inflammation of mice exposed to cigarette smoke

Neutrophil accumulation response to cigarette smoke (CS) in humans and animal models is believed to play an important role in pathogenesis of many tobacco-related lung diseases. Here we evaluated the lung anti-inflammatory effect of aspirin and indomethacin in mice exposed to CS. C57BL/6 mice were exposed to four cigarettes per day during 4 days and were treated i.p. with aspirin or indomethacin, administered each day 1h before CS exposure. Twenty four hours after the last exposure, cells and inflammatory mediators were assessed in bronchoalveolar lavage (BAL) fluid and the lungs used for evaluation of lipid peroxidation, p38 mitogen-activated protein kinase (MAPK) phosphorylation and nuclear transcription factor kappaB (NF-kappaB) activation. Exposure to CS resulted in a marked lung neutrophilia. Moreover, the levels of oxidative stress-related lipid peroxidation, prostaglandin E(2) (PGE(2)), interleukin 1beta (IL-1beta), monocyte chemotactic protein 1 (MCP-1), and activated NF-kappaB and p38 MAPK were greatly increased in CS group. Aspirin or indomethacin treatment led to a significant reduction of neutrophil influx, but only aspirin resulted in dramatic decrease of inflammatory mediators. Moreover, both drugs reduced lung p38 MAPK and NF-kappaB activation induced by CS. These results demonstrate that short-term CS exposure has profound airway inflammatory effects counteracted by the anti-inflammatory agents aspirin and indomethacin, probably through COX-dependent and -independent mechanisms.

Setting up a 2D-LC/MS/MS method for the rapid quantitation of the prostanoid metabolites 6-oxo-PGF(1alpha) and TXB2 as markers for hemostasis assessment

6-oxo-PGF(1alpha) and TXB(2) are the metabolites of the prostanglandin PGI(2) and of the thromboxane TXA(2), respectively. PGI(2) and TXA(2) are arachidonic acid-derived compounds which regulate the blood hemostasis. Their quick metabolism leads to the 6-oxo-PGF(1alpha) and TXB(2) metabolites in plasma. In order to study on a large base the external factors influencing the hemostatic conditions, there is a need for a fast and reliable assay for quantitating these metabolites. Some methods have been published for the analysis of the arachidonic acid-derived compounds and some are dealing with mass spectrometry but nonspecifically centered on these specific compounds with a fast and cheap protocol, amenable for large-scale studies. Here we describe an analytical strategy that incorporates a two-dimensional chromatography running coupled to tandem mass spectrometry that minimizes the sample preparation and addresses the presence of the TXB(2) anomers for a robust quantitation measurement. After a protein precipitation, 100 microl of the supernatant (corresponding to 50 microl of the original plasma) was injected in a two-dimensional chromatographic system which operates an on-line clean-up and a subsequent chromatographic separation of the targeted analytes with a limit of quantitation (LOQ) of 22 pg/ml for 6-oxo-PGF(1alpha), and and a LOQ of 25 pg/ml for TXB(2).

Lipid metabolites as regulators of airway smooth muscle function

Compelling evidence identifies airway smooth muscle (ASM) not only as a target but also a cellular source for a diverse range of mediators underlying the processes of airway narrowing and airway hyperresponsiveness in diseases such as asthma. These include the growing family of plasma membrane phospholipid-derived polyunsaturated fatty acids broadly characterised by the prostaglandins, leukotrienes, lipoxins, isoprostanes and lysophospholipids. In this review, we describe the enzymatic and non-enzymatic biosynthetic pathways of these lipid mediators and how these are influenced by drug treatment, oxidative stress and airways disease. Additionally, we outline their cognate receptors, many of which are expressed by ASM. We describe potential deleterious and protective roles for these lipid mediators in airway inflammatory and remodelling processes by describing their effects on diverse functions of ASM in asthma that have the potential to contribute to asthma pathogenesis and symptoms. These functions include contractile tone development, cytokine and extracellular matrix production, and cellular proliferation and migration.

Cyclooxygenase-2 polymorphisms confer susceptibility to sarcoidosis but are not related to prognosis

BACKGROUND

The aim of this multicenter study was to investigate the relationship between single nucleotide polymorphisms (SNPs) of the cyclooxygenase-2 (COX2) gene and susceptibility to sarcoidosis, as well as the relation between these SNPs and the evolution of the disease.

MATERIAL AND METHODS

This multicenter investigation involved seven hospitals in Spain. We used a case-control design followed by a prospective follow-up study. Sarcoid patients were recruited from the participating institutions during outpatient routine visits. Age- and gender-matched control subjects were recruited mainly from among outpatients attending the participating hospitals. Four SNPs in the COX2 gene (COX2.5909 T > G, COX2.8473 T > C, COX2.926 G > C, and COX2.3050 G > C) were genotyped using fluorescent hybridization probes among 131 patients with sarcoidosis (63 males; mean age: 47 +/- 15 years) and 157 healthy controls (83 males; mean age: 50 +/- 16 years). We employed a binomial multiple logistic regression analysis to test the association between the selected SNPs and disease susceptibility. The clinical, functional and radiological prognosis of the sarcoidosis patients was determined after a mean follow-up of 37.4 +/- 30.4 months.

RESULTS

Carriers of the homozygous CC genotype of the COX2.8473 T > C polymorphism had a higher risk of sarcoidosis compared with TT carriers (OR: 3.08; 95% CI: 1.2-7.7; p = 0.035). 84% of patients achieved improvement or complete remission at follow-up. No association between the investigated SNPs and prognosis was seen.

CONCLUSIONS

Our data suggest that the homozygous CC genotype of the COX2.8473 T > C polymorphism may be associated with sarcoidosis susceptibility. No significant association with prognosis was detected.

Randomised aspirin assignment and risk of adult-onset asthma in the Women's Health Study

BACKGROUND

Randomised data in men show a small but significant reduction in the risk of adult-onset asthma among those given aspirin. The results from an observational study in women suggest that frequent use of aspirin decreases the risk of adult-onset asthma, but randomised data in women are lacking. A study was undertaken to test the effect of 100 mg aspirin or placebo on alternate days on the risk of adult-onset asthma in the Women's Health Study.

METHODS

A randomised, double-blind, placebo-controlled clinical trial of aspirin and vitamin E was performed in apparently healthy women with no indication or contraindication to aspirin therapy and no history of asthma at study entry. Female health professionals self-reported an asthma diagnosis on yearly questionnaires.

RESULTS

Among 37 270 women with no reported history of asthma prior to randomisation and during 10 years of follow-up, there were 872 new cases diagnosed with asthma in the aspirin group and 963 in the placebo group (hazard ratio 0.90; 95% CI 0.82 to 0.99; p = 0.027). This apparent 10% lower relative risk of incident adult-onset asthma among those assigned to aspirin was significantly modified by body mass index, with no effect in women with a body mass index of >/=30 kg/m2. The effect of aspirin on adult-onset asthma was not significantly modified by age, smoking status, exercise levels, postmenopausal hormone use or randomised vitamin E assignment.

CONCLUSIONS

In this large randomised clinical trial of apparently healthy adult women, administration of 100 mg aspirin on alternate days reduced the relative risk of a newly reported diagnosis of asthma.

Simultaneous quantification of seven prostanoids using liquid chromatography/tandem mass spectrometry: the effects of arachidonic acid on prostanoid production in mouse bone marrow-derived mast cells

We have developed a method for the simultaneous estimation of the levels of the prostanoids 6-keto prostaglandin (PG) Flalpha, PGB2, PGD2, PGE2, PGF2(alpha), PGJ2, and thromboxane (TX) B2 in blood- or serum-containing medium using liquid chromatography-tandem mass spectrometry. These prostanoids and their deuterium derivatives, which were used as internal standards, were subjected to solid-phase extraction using Empore C18 HD disk cartridges and analyzed in the selected reaction-monitoring mode. A linear response curve starting at 10 pg of prostanoid/tube was observed for each prostanoid. The accuracy of the method was demonstrated with samples containing known amounts of the prostanoids. Furthermore, we used this method to analyze the prostanoids produced in mouse bone marrow-derived mast cells stimulated with arachidonic acid, which resulted in the production of PGD2, PGE2, PGF2alpha, and TXB2. The results suggest that this simultaneous quantification method is useful for the analysis of the production of biomedically important prostanoids.

Role of prostaglandin D2 and E2 terminal synthases in chronic rhinosinusitis

BACKGROUND

Prostaglandin (PG)D(2) and E(2), two major cyclooxygenase (COX) products, are generated by PGD(2) synthase (PGDS) and PGE(2) synthase (PGES), respectively, and appear to mediate airway inflammation.

OBJECTIVE

We sought to determine the role of PGDS and PGES in the pathophysiology of chronic rhinosinusitis (CRS).

METHODS

The study examined the expression of PGDS and PGES in nasal polyps of 22 CRS patients. As controls, uncinate process mucosae were obtained from 12 CRS patients not having nasal polyps and five subjects without sinusitis. Immunohistochemistry and quantitative real-time PCR were used to evaluate the expression.

RESULTS

Both PGDS and PGES were detected in nasal polyps by immunohistochemistry. Significantly greater levels of PGDS mRNA and lesser levels of PGES mRNA were observed in the nasal polyps as compared with uncinate process mucosae, and an inverse correlation between PGDS and PGES expression was observed. Levels of PGDS mRNA in nasal polyps were positively correlated with degree of infiltration by EG2+ eosinophils, whereas the levels of PGES were inversely correlated. Significantly increased levels of PGDS and conversely decreased levels of PGES were observed in asthmatics as compared with non-asthmatics. In addition, PGDS and PGES levels were positively and inversely correlated with the radiological severity of sinusitis, respectively.

CONCLUSIONS

These results suggest that PGDS and PGES display an opposite and important role in the pathophysiology of CRS such as polyp formation, and more specifically, a biased expression of these synthases might contribute to the development of CRS by affecting eosinophilic inflammation.

Aspirin and decreased adult-onset asthma: randomized comparisons from the physicians' health study

RATIONALE

In an observational cohort study, women who self-selected for frequent aspirin use developed less newly diagnosed asthma than women who did not take aspirin.

OBJECTIVE

To explore whether low-dose aspirin decreased the risk of newly diagnosed asthma in a randomized, double-blind, placebo-controlled trial.

METHODS

The Physicians' Health Study randomized 22,071 apparently healthy male physicians, aged 40-84 yr at baseline and tolerant of aspirin, over an 18-wk run-in period, to 325 mg aspirin or placebo on alternate days. The aspirin component was terminated after 4.9 yr due principally to the emergence of a statistically extreme 44% reduction in risk of first myocardial infarction among those randomly assigned to aspirin.

MEASUREMENTS

Physicians could self-report an asthma diagnosis on questionnaires at baseline, 6 mo, and annually thereafter. Asthma was not an a priori endpoint of the trial.

RESULTS

Among 22,040 physicians without reported asthma at randomization, there were 113 new asthma diagnoses in the aspirin group and 145 in the placebo group. The hazard ratio was 0.78 (95% confidence interval, 0.61-1.00; p = 0.045). This apparent 22% lower risk of newly diagnosed asthma among those assigned to aspirin was not modified by baseline characteristics including smoking, body mass index, or age.

CONCLUSIONS

Aspirin reduced the risk of newly diagnosed adult-onset asthma in a large, randomized clinical trial of apparently healthy, aspirin-tolerant men. This result requires replication in randomized trials designed a priori to test this hypothesis; it does not imply that aspirin improves symptoms in patients with asthma.

Induction of cyclooxygenase-2 expression by allergens in lymphocytes from allergic patients

Cyclooxygenase (COX) is a key enzyme in prostaglandin (PG) synthesis. Up-regulation of COX-2 expression is responsible for increased PG release during inflammatory conditions and is thought to be also involved in allergic states. In this study, we demonstrate that in human T, B and natural killer lymphocytes from allergic patients, COX-2 expression became induced upon cell challenge with specific allergens and that this process is presumably IgE dependent and occurs after CD23 receptor ligation. This induction took place at both mRNA and protein levels and was accompanied by PGD2 release. IgE-dependent lymphocyte treatment elicited, in parallel, an activation of the MAPK p38 and extracellular signal-regulated kinase 1/2, an enhancement of calcineurin (CaN) activity, and an increase of the DNA-binding activity of the nuclear factor of activated T cells and of NF-kappaB, with a concomitant decrease in the levels of the cytosolic inhibitor of kappaB, IkappaB. In addition, specific chemical inhibitors of MAPK, such as PD098059 and SB203580, as well as MG-132, an inhibitor of proteasomal activity, abolished allergen-induced COX-2 up-regulation, suggesting that this process is mediated by MAPK and NF-kappaB. However, induction of COX-2 expression was not hampered by the CaN inhibitor cyclosporin A. We also examined the effect of a selective COX-2 inhibitor, NS-398, on cytokine production by human lymphocytes. Treatment with NS-398 severely diminished the IgE-dependently induced production of IL-8 and TNF-alpha. These results underscore the relevant role of lymphocyte COX-2 in allergy and suggest that COX-2 inhibitors may contribute to the improvement of allergic inflammation through the reduction of inflammatory mediator production by human lymphocytes.

Vascular endothelial growth factor induction by prostaglandin E2 in human airway smooth muscle cells is mediated by E prostanoid EP2/EP4 receptors and SP-1 transcription factor binding sites

Prostaglandin E2 (PGE2) can increase endothelial vascular endogrowth factor A (VEGF-A) production but the mechanisms involved are unclear. Here we characterized the transcriptional mechanisms involved in human airway smooth muscle cells (HASMC). PGE2 increased VEGF-A mRNA and protein but not mRNA stability. PGE2 stimulated the activity of a transiently transfected 2068-bp (-2018 to +50) VEGF-A promoter-driven luciferase construct. Functional 5' deletional analysis mapped the PGE2 response element to the 135-bp sequence (-85/+50) of the human VEGF-A promoter. PGE2-induced luciferase activity was reduced in cells transfected with a 135-bp VEGF promoter fragment containing mutated Sp-1 binding sites but not in cells transfected with a construct containing mutated EGR-1 binding sites. Electrophoretic mobility shift assay and chromatin immunoprecipitation assay confirmed binding of Sp-1 to the VEGF promoter. PGE2 increased phosphorylation of Sp-1 and luciferase activity of a transfected Sp-1 reporter construct. PGE receptor agonists EP2 (ONO-AE1 259) and EP4 (ONO-AE1 329) mimicked the effect of PGE2, and reverse transcription-PCR, Western blotting, and flow cytometry confirmed the presence of EP2 and EP4 receptors. VEGF protein release and Sp-1 reporter activity were increased by forskolin and isoproterenol, which increase cytosolic cAMP, and the cAMP analogue, 8-bromoadenosine-3',5'-cyclophosphoric acid. These studies suggest that PGE2 increases VEGF transcriptionally and involves the Sp-1 binding site via a cAMP-dependent mechanism involving EP2 and EP4 receptors.

Cytokines upregulate vascular endothelial growth factor secretion by human airway smooth muscle cells: Role of endogenous prostanoids

Here, we report that vascular endothelial growth factor (VEGF)-A secretion by human airway smooth muscle cells was increased by interleukin 1 beta (IL-1beta) and transforming growth factor beta (TGFbeta). IL-1beta and TGFbeta induced cyclo-oxygenase (COX)-2 protein and increased prostaglandin E(2) (PGE(2)). Both IL-1beta and TGFbeta increased VEGF-A(165) mRNA and VEGF promoter luciferase construct activity, in addition VEGF-A protein was inhibited by actinomycin D suggesting transcriptional regulation. The COX inhibitors indomethacin and NS398 inhibited IL-1beta but not TGFbeta mediated VEGF-A production. Furthermore, the effect of the COX inhibitors was overcome by adding exogenous PGE(2). In conclusion, IL-1beta increases VEGF-A secretion by COX-2 derived PGE(2) production whereas TGFbeta uses COX-independent pathways.

Medications as asthma triggers

Certain medications can generate asthma symptoms, with the potential to cause considerable morbidity. This article focuses on the common drugs that have the potential to cause distinct respiratory reactions in asthmatics: aspirin and other nonsteroidal anti-inflammatory drugs, beta-blockers, and angiotensin-converting enzyme inhibitors. The means by which these medications can trigger asthma vary in terms of acuity of onset, severity, and the mechanisms involved. The general and most practical approach is avoidance and cautious use of these drugs in asthmatics. However, these classes of medications can exert a major role in the management of common and serious diseases. Fortunately, controller therapy for asthma and alternative or more selective medications for the treatment of these conditions are now available.

Aspirin-induced asthma: clinical aspects, pathogenesis and management

Aspirin (acetylsalicylic acid)-induced asthma (AIA) consists of the clinical triad of asthma, chronic rhinosinusitis with nasal polyps, and precipitation of asthma and rhinitis attacks in response to aspirin and other NSAIDs. The prevalence of the syndrome in the adult asthmatic populations is approximately 4-10%. Respiratory disease in these patients may be aggressive and refractory to treatment. The aetiology of AIA is complex and not fully understood, but most evidence points towards an abnormality of arachidonic acid (AA) metabolism. Cyclo-oxygenase (COX), the rate-limiting enzyme in AA metabolism, exists as two main isoforms. COX-1 is the constitutive enzyme responsible for synthesis of protective prostanoids, whereas COX-2 is induced under inflammatory conditions. A number of theories regarding its pathogenesis have been proposed. The shunting hypothesis proposes that inhibition of COX-1 shunts AA metabolism away from production of protective prostanoids and towards cysteinyl leukotriene (cys-LT) biosynthesis, resulting in bronchoconstriction and increased mucus production. The COX-2 hypothesis proposes that aspirin causes a structural change in COX-2 that results in the generation of products of the lipoxygenase pathway. It is speculated that this may result in the formation of mediators that cause respiratory reactions in AIA. Related studies provide evidence for abnormal regulation of the lipoxygenase pathway, demonstrating elevated levels of cys-LTs in urine, sputum and peripheral blood, before and following aspirin challenge in AIA patients. These studies suggest that cys-LTs are continually and aggressively synthesised before exposure to aspirin and, during aspirin-induced reactions, acceleration of synthesis occurs. A genetic polymorphism of the LTC4S gene has been identified consisting of an A to C transversion 444 nucleotides upstream of the first codon, conferring a relative risk of AIA of 3.89. Furthermore, carriers of the C444 allele demonstrate a dramatic rise in urinary LTE(4) following aspirin provocation, and respond better to the cys-LT antagonist pranlukast than A444 homozygotes.AIA patients have an aggressive form of disease, and treatment should include combination therapy with inhaled corticosteroids, beta(2)-adrenoceptor agonists and LT modifiers. Furthermore, recently developed inhibitors of COX-2 may be safer in patients with AIA.

Reduced expression of cyclooxygenase (COX) in idiopathic pulmonary fibrosis and sarcoidosis

AIMS

To test the hypothesis that cyclooxygenase (COX)-1 or COX-2 expression is defective in lungs in idiopathic pulmonary fibrosis (IPF) and to characterize the cellular distribution. IPF is a progressive inflammatory lung disorder with an adverse prognosis. Previous work has shown that prostaglandin E2 (PGE2) regulates collagen deposition and fibroblast proliferation and a defect in COX regulation may contribute to the fibrosis that occurs in IPF.

METHODS

Immunohistochemistry was utilized to determine COX immunoreactivity in lung sections from 25 IPF, six sarcoidosis and 14 control subjects.

RESULTS

COX-1 and COX-2 expression in bronchiolar epithelial cells was significantly lower in IPF and sarcoidosis than in controls. No significant difference was found in COX-2 expression between macrophages in IPF and control sections, but COX-2 was reduced in macrophages in sarcoidosis compared with controls.

CONCLUSIONS

These studies confirm COX-2 loss in bronchial epithelial cells but not macrophages in IPF, and show for the first time reduced constitutive COX-1 expression in epithelial cells and macrophages. Similar abnormalities were observed in sarcoidosis.

Deficient prostaglandin E2 production by bronchial fibroblasts of asthmatic patients, with special reference to aspirin-induced asthma

BACKGROUND

Regulation of prostaglandin synthesis and the activation of human airway fibroblasts associated with the remodeling of the bronchi play an important role in asthma.

OBJECTIVE

We sought to assess the cyclooxygenase pathways in airway fibroblasts of patients with bronchial asthma.

METHODS

Generation of prostaglandin E(2) (PGE(2)) and pros-taglandin D(2) (PGD(2)) by bronchial fibroblasts was measured by means of mass spectrometry in culture supernatants, and cyclooxgenases expression was estimated by means of RT-PCR and immunoblotting. The cells were isolated from 3 groups of subjects: nonasthmatic patients (n = 10), patients with aspirin-tolerant asthma (ATA, n = 9), and patients with aspirin-intolerant asthma (AIA, n = 7).

RESULTS

The cytomix (LPS, 5 square g/mL; IL-1 square, 5 ng/mL; and TNF- square, 10 ng/mL; 18 hours) stimulated the production of prostaglandins. Asthmatic patients were characterized by low capacity to produce PGE(2) after cytomix stimulation. In the nonasthmatic patient group the mean PGE(2) production was 32 +/- 33 ng/mL (35-fold of the basic production), in the ATA group it was 16 +/- 18 ng/mL (16-fold), and in the AIA group it was only 5.3 +/- 3.6 ng/mL (4-fold). The mean concentration of PGD(2) for nonasthmatic patients, patients with ATA, and patients with AIA was 0.18 +/- 0.16 ng/mL (4.7-fold of the basic production), 0.18 +/- 0.14 ng/mL (4.2-fold), and 0.235 +/- 0.19 ng/mL (1.9-fold), respectively. The observed difference was not due to insufficient cyclooxygenase 2 expression because all groups had similar levels of its mRNA and protein. The patients with AIA had low expression levels of cyclooxygenase 1 protein but not of its mRNA. The PGE(2)/PGD(2) concentration ratio increased after cytomix stimulation in all groups but was significantly less in patients with AIA than in patients with ATA.

CONCLUSIONS

Our results point to a deficient PGE(2) production under proinflammatory conditions in asthmatic airways. This could weaken local defensive mechanisms and promote cysteinyl leukotriene overproduction.

Cyclooxygenase (COX) inhibitors induce apoptosis in non-small cell lung cancer through cyclooxygenase independent pathways

Cyclooxygenase (COX) inhibitors are chemopreventive in many tumours but the role of COX inhibition in their effects is contentious. Here we determined if COX inhibitors influenced apoptosis in two non-small cell lung cancer cells one which over expresses COX-2 (MOR-P) and one which expresses neither isoform (H-460). NS398, a selective COX inhibitor, and indomethacin, a non-selective COX inhibitor, were cytotoxic in both cell lines, independently of their COX-2 expression. Furthermore, the cytotoxic concentrations were far greater than the concentrations required to inhibit COX. As indomethacin was more effective we used it in mechanistic studies. Indomethacin induced apoptotic cell death assessed as cytochrome c and apoptotic inducing factor (AIF) release, caspase activation, PARP, lamin B and gelsolin cleavage, chromatin condensation and nuclear fragmentation. The pan-caspase inhibitor, z-VAD, attenuated cell death, and blocked caspase activation, PARP cleavage and nuclear fragmentation without preventing cytochrome c release, suggesting that cytochrome c release is upstream of caspase activation. These observations suggest that COX inhibitors induce apoptosis in non-small lung cancer cells through cytochrome c and AIF release, and subsequent caspase activation, independently of COX-2 expression and prostaglandin production.

Cyclooxygenase-2 expression by nonsteroidal anti-inflammatory drugs in human airway smooth muscle cells: role of peroxisome proliferator-activated receptors

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to modulate cyclooxygenase (COX)-2 expression, but the mechanisms involved are controversial and may be cell specific. We show in this study that indomethacin (Indo), flurbiprofen (Flur), and the selective COX-2 inhibitor NS-398 induced COX-2 expression and markedly enhanced IL-1beta-induced COX-2 expression in human airway smooth muscle (HASM) cells. These effects were not reversed by exogenous PGE(2), suggesting that they are prostanoid-independent. Indeed, PGE(2) also induced and enhanced IL-1beta-induced COX-2 expression. Peroxisome proliferator-activated receptor (PPAR) alpha and PPARgamma (not PPARbeta) were expressed in HASM cells. PPARgamma activators ciglitizone (Cig) and 15-Deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)), but not the PPARalpha activator WY-14643, mimicked the effect of NSAIDs on COX-2 expression. Treatment with Flur, NS-398, Cig, and 15d-PGJ(2) alone, but not Indo and WY-14643, elevated COX activity; however, neither enhanced IL-1beta-induced COX activity. Pretreatment with dexamethasone suppressed COX-2 expression, PGE(2) release, and COX activity induced by NS-398, Cig, IL-1beta, alone or in combination. Unlike IL-1beta, NS-398 and Cig did not cause NF-kappaB (p65) nuclear translocation, nor did they further enhance IL-1beta-induced NF-kappaB translocation, but they stimulated PPARgamma translocation. Indo, NS-398, Flur, and 15d-PGJ(2), but not WY-14643, induced transcriptional activity of a COX-2 reporter construct containing the peroxisome proliferator response element (PPRE) on their own and enhanced the effect of IL-1beta, but had no effect on a COX-2 reporter construct lacking the PPRE. The results suggest that COX-2 expression by NSAIDs is biologically functional, prostanoid-independent, and involves PPARgamma activation, and provide the first direct evidence that the PPRE in the promoter is required for NSAID-induced COX-2 expression.

Neurogenic inflammation of the bladder

Current evidence suggests multiple and redundant pathways through which the nervous system can initiate, amplify, and perpetuate inflammation. Many of the processes initiated by neurogenic inflammation have the capacity to recruit the participation of additional sensory nerves. These observations indicate that effective strategies for prevention or treatment of neurogenic inflammation of the bladder will entail or require intervention at multiple points. It has been observed that pain management in the future will be based on selective intervention tailored to the specific processes modulating pain perception in individual patients. It is exciting to contemplate the same approach to prevention and treatment of neurogenic bladder inflammation.

Bradykinin increases IL-8 generation in airway epithelial cells via COX-2-derived prostanoids

Interleukin (IL)-8, the C-X-C chemokine, is a potent neutrophil chemoattractant that has been implicated in a number of inflammatory airway diseases such as cystic fibrosis. Here we tested the hypothesis that bradykinin, an inflammatory mediator and chloride secretagogue, would increase IL-8 generation in airway epithelial cells through autocrine generation of endogenous prostanoids. Bradykinin increased IL-8 generation in both a non-cystic fibrosis (A549) and cystic fibrosis epithelial cell line (CFTE29) that was inhibited by the nonselective cyclooxygenase (COX) inhibitor indomethacin and the COX-2 selective inhibitor NS-398. COX-2 was the only isoform of COX expressed in both cell lines. Furthermore, the COX substrate arachidonic acid and exogenous prostaglandin E(2) both increased IL-8 release in A549 cells. These results suggest that bradykinin may contribute to neutrophilic inflammation in the airway by generation of IL-8 from airway epithelial cells. The dependence of this response on endogenous production of prostanoids by COX-2 suggests that selective COX-2 inhibitors may have a role in the treatment of airway diseases characterized by neutrophilic inflammation such as cystic fibrosis or chronic obstructive pulmonary disease.

Simultaneous quantification of prostaglandins, isoprostane and thromboxane in cell-cultured medium using gas chromatography-mass spectrometry

We have developed a simultaneous quantification method for prostaglandin (PG) E(2), PGD(2), PGF(2 alpha), 8-epi-PGF(2 alpha), 6-keto-PGF(1 alpha) and thromboxane (TX) B(2). Using [3,3,4,4-(2)H(4)]PGE(2), [3,3,4,4-(2)H(4)]PGD(2), [3,3,4,4-(2)H(4)]8-epi-PGF(2 alpha), [3,3,4,4-(2)H(4)]PGF(2 alpha), [3,3,4,4-(2)H(4)]6-keto-PGF(1 alpha) and [18,18,19,19-(2)H(4)]TXB(2) as internal standards (I.S.), the eicosanoids and their I.S. were simultaneously extracted by solid-phase extraction from cell-cultured medium, derivatized to methyl ester/methoxim/tert.-butyldimethylsilyl ether derivatives and analyzed using gas chromatography-mass spectrometry in the selected ion monitoring mode. The accuracy for the added eicosanoids ranged from 92 to 113%, and coefficients of variation ranged from 0.1 to 12.2%. Increased eicosanoids in RAW264.7 and U937 cells stimulated by lipopolysaccharide were suppressed by NS-398 and indometacin. This simultaneous quantification method can be applied routinely for assaying eicosanoids in vitro.

Decreased antigen-induced eicosanoid release in conjugated linoleic acid-fed guinea pigs

This study investigated the capacity of conjugated linoleic acids (CLA) to reduce ex vivo antigen-induced release of eicosanoids in a type I hypersensitivity model. Guinea pigs were fed a diet containing 0.25% safflower oil (control) or 0.25% CLA [43% trans (t)10, cis (c)12; 41% c9, t11/t9, c11 18:2] for 2 wk before and during sensitization to ovalbumin (OVA). Lungs, tracheas, and bladders were incubated in physiological saline solution (PSS) for 1 h (basal mediator release) and challenged with OVA (0.01 g/l PSS) for 1 h (mediator release in response to antigen). Eicosanoids were quantified by HPLC/tandem mass spectrometry or enzyme immunoassay. CLA feeding resulted in no change in basal release but decreased eicosanoid release from sensitized tissues in response to antigen challenge in the following manner: thromboxane B(2), 6-keto-prostaglandin (PG)F(1alpha), PGF(2alpha), PGD(2), PGE(2) by 57-75% in lung, 45-65% in trachea, and 38-60% in bladder; and leukotriene C(4)/D(4)/E(4) by 87, 90, and 50% in lung, trachea, and bladder, respectively. These data indicate that feeding CLA reduces lipid-derived inflammatory mediators produced by this type I hypersensitivity model.

Cox-2 inhibitors: today and tomorrow

The elucidation of inducible cyclooxygenase (Cox-2) dependent inflammatory pathways led to the development of specific Cox-2 inhibitors, the coxibs. These agents include the currently available celecoxib and rofecoxib and such second-generation agents as parecoxib, valdecoxib, and etoricoxib. The therapeutic advantage of coxibs is founded primarily in their lack of significant gastrointestinal (GI) side effects. Clinical trials have demonstrated the efficacy of coxibs to be completely comparable with traditional nonsteroidal anti-inflammatory drugs (NSAIDs), and pharmacoeconomics suggest favorable cost/benefit ratios with these agents compared with traditional NSAIDs, related to their reduced GI complication profiles and lower indirect costs associated with disability. Although several clinical questions remain (eg, use with low-dose aspirin, risk of thrombosis, myocardial infarction, edema, and hypertension), the emergence and clinical utility of coxibs is likely to continue on the basis of their efficacy and relative GI safety advantage. Although newer, more specific Cox-2 inhibitors may alter the choice, it is likely that this class of anti-inflammatories will become (if they have not already) the drugs of first choice in the treatment of acute pain, chronic pain, and most rheumatic conditions in the 21st century. In addition to the treatment of rheumatic conditions, it is possible that coxibs will also be of clinical utility in protection against malignant transformation and Alzheimer disease.

Expression of PGT in MDCK cell monolayers: polarized apical localization and induction of active PG transport

The PG transporter (PGT) is expressed in subapical vesicles in the kidney collecting duct. To gain insight into the possible function of the PGT in this tubule segment, we tagged rat PGT with green fluorescent protein at the COOH terminus and generated stable PGT-expressing Madin-Darby canine kidney cell lines. When grown on permeable filters, green fluorescent protein-PGT was expressed predominantly at the apical membrane. Although the basal-to-apical transepithelial flux of [(3)H]PGE(2) was little changed by PGT expression, the apical-to-basolateral flux was increased 100-fold compared with wild-type cells. Analysis of driving forces revealed that this flux represents PGT-mediated active transepithelial PGE(2) transport. We propose that endogenous PGT is exocytically inserted into the collecting duct apical membrane, where it could control the concentration of luminal PGs.

Effect of the cyclooxygenase-2 inhibitor celecoxib on bronchial responsiveness and cough reflex sensitivity in asthmatics

Cyclooxygenase (COX), an essential enzyme in the pathway of prostaglandin formation from arachidonic acid, exists in two isoforms. Cyclooxygenase-1 (COX-1) is expressed under normal physiologic conditions, whereas COX-2, the inducible isoform, is associated with inflammation. Recent studies have linked COX-2 induction to the asthmatic inflammatory response, but potentially beneficial results, such as enhanced production of antiinflammatory and bronchoprotective substances, may also occur. The aim of the present study was to investigate the effect of selective COX-2 inhibition on bronchial responsiveness and cough reflex sensitivity. Eight adult subjects with stable asthma underwent spirometry, bronchoprovocation challenge with methacholine, and cough challenge testing with capsaicin, before and after a 7 day course of the COX-2 inhibitor celecoxib (200 mg orally, twice daily) and placebo, in a randomized, double-blind, crossover fashion. No significant changes in pulmonary function, bronchial responsiveness, or cough reflex sensitivity were induced by celecoxib. It appears, therefore, that 1 week of therapy with celecoxib does not significantly affect basal airway tone, nor the afferent airway receptors controlling bronchoconstriction and cough. However, the results of this trial cannot be extrapolated to subjects with severe asthma, or those suffering an asthmatic exacerbation. In such conditions of enhanced inflammatory response, the role of selective COX-2 inhibition remains to be elucidated.

Increased expression of inducible nitric oxide synthase and cyclo-oxygenase-2 in the airway epithelium of asthmatic subjects and regulation by corticosteroid treatment

BACKGROUND

Nitric oxide (NO) and prostanoids are mediators of vascular and bronchial tone that are postulated to be involved in asthma. Increased levels of both are found in asthmatic subjects and are synthesised by enzymes that have cytokine inducible forms: inducible NO synthase (iNOS) and cyclo-oxygenase-2 (COX-2), respectively. We hypothesised that the in vivo expression of iNOS and COX-2 in the airways would be increased in asthma, and that these cytokine inducible enzymes may represent targets for regulation by corticosteroid treatment.

METHODS

Bronchial biopsy specimens were obtained from three groups of subjects: atopic asthmatics treated with beta(2) agonists alone (n=7), atopic asthmatics additionally receiving regular treatment with corticosteroids (n=8), and non-asthmatic control subjects (n=10). Expression of iNOS and COX-2 mRNA and immunoreactive protein was studied using in situ hybridisation and quantitative immunohistochemistry.

RESULTS

Immunoreactivity and the hybridisation signal for iNOS and COX-2 were mainly localised in the airway epithelium. The proportion of epithelium immunostained was significantly greater in the non-steroid treated asthmatic subjects (iNOS 8.6 (1.8)%; COX-2 26.3 (4.6)%) than either the steroid treated asthmatics (iNOS 3.4 (1.0)%, p=0.009; COX-2 13.0 (0.6)%, p=0.0015) or the non-asthmatic controls (iNOS 4.2 (0.9)%, p=0.018; COX-2 11.6 (0.6)%, p=0.0003). Similarly, the hybridisation signal was stronger in the non-steroid treated group of asthmatic subjects than in the other two groups.

CONCLUSIONS

These findings highlight the potential role of the airway epithelium both as a contributor to the inflammatory process in asthma and as a target for inhaled corticosteroid treatment in this disease.

Effect of acetylsalicylic acid on endogenous I kappa B kinase activity in lung epithelial cells

The anti-inflammatory effect of acetylsalicylic acid (ASA) has been thought to be secondary to the inhibition of prostaglandin synthesis. Because doses of ASA necessary to treat chronic inflammatory diseases are much higher than those needed to inhibit prostaglandin synthesis, a prostaglandin-independent pathway has been emerging as the new anti-inflammatory mechanism of ASA. Here, we examined the effect of ASA on the interleukin (IL)-1 beta- and tumor necrosis factor (TNF)-alpha-induced proinflammatory cytokine expression and evaluated whether this effect is closely linked to the nuclear factor (NF)-kappa B/I kappa B-alpha pathway. A high dose of ASA blocked IL-1 beta- and TNF-alpha-induced TNF-alpha and IL-8 expression, respectively. ASA inhibited TNF-alpha-induced activation of NF-kappa B by preventing phosphorylation and subsequent degradation of I kappa B-alpha in a prostanoid-independent manner. TNF-alpha-induced activation of I kappa B kinase was also suppressed by ASA pretreatment. These observations suggest that the anti-inflammatory effect of ASA in lung epithelial cells may be due to suppression of I kappa B kinase activity, which thereby inhibits subsequent phosphorylation and degradation of I kappa B-alpha, activation of NF-kappa B, and proinflammatory cytokine expression in lung epithelial cells.

TGF-beta1 stimulates IL-8 release, COX-2 expression, and PGE(2) release in human airway smooth muscle cells

We have recently shown that endogenous prostanoids are critical in bradykinin-stimulated interleukin (IL)-8 release from human airway smooth muscle (ASM) cells. In this study, we tested the ability of transforming growth factor (TGF)-beta1 to stimulate IL-8 release, cyclooxygenase (COX)-2 expression and PGE(2) generation in cultured human ASM cells and explored the role of COX products and COX-2 induction on IL-8 release. TGF-beta1 stimulated IL-8 release, COX-2 induction, and PGE(2) generation in a concentration- and time-dependent manner. Maximal IL-8 release was achieved with 10 ng/ml of TGF-beta1 after 16 h of incubation, which was inhibited by the transcription inhibitor actinomycin D and the corticosteroid dexamethasone but was not affected by the nonselective COX inhibitor indomethacin and the selective COX-2 inhibitor NS-398 despite their inhibition on TGF-beta1-induced PGE(2) release. These results show for the first time that TGF-beta1 stimulates IL-8 release, COX-2 induction, and PGE(2) generation in human ASM cells and that PGE(2) generation is not critical for TGF-beta1-induced IL-8 release. These findings suggest that TGF-beta1 may play an important role in the pathophysiology of asthma.

General tolerability and use of nonsteroidal anti-inflammatory drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) are generally well tolerated medications but are associated with several adverse effects that may occur as a result of the physiologic effects of inhibition of cyclooxygenase (COX) or for idiosyncratic reasons. Selective COX-1-sparing NSAIDs may be associated with fewer COX-related complications, such as primary gastric injury and bleeding. Adverse effects in other organ systems including liver, skin, and bone may not be diminished with the use of selective COX inhibitors. Prevention of colonic polyps and adenocarcinoma of the colon seems to be mediated by inhibition of the COX-2 isoenzyme.

Induced sputum eicosanoid concentrations in asthma

Further definition of the role of leukotrienes (LT) and prostaglandins (PG) in asthma would be helped by a noninvasive method for assessing airway production. The supernatant from sputum induced with hypertonic saline and dispersed using dithiotrietol has been successfully used to measure other molecular markers of airway inflammation and might be a useful method. We have measured induced sputum supernatant LTC(4)/D(4)/E(4) concentrations using enzyme immunoassay and PGE(2), PGD(2), TXB(2), and PGF(2alpha) using gas chromatography-negative ion chemical ionization-mass spectroscopy in 10 normal subjects and in 26 subjects with asthma of variable severity. Sputum cysteinyl-leukotrienes concentrations were significantly greater in subjects with asthma (median, 9.5 ng/ml) than in normal control subjects (6.4 ng/ml; p < 0.02) and greater in subjects with persistent asthma requiring inhaled corticosteroids (median, 11.4 ng/ml) or studied within 48 h of an acute severe exacerbation of asthma (13 ng/ml) than in subjects with episodic asthma treated with inhaled beta(2)-agonists only (7.2 ng/ml). There were no significant differences in the concentrations of other eicosanoids between groups, although there was a negative correlation between the percentage sputum eosinophil count and sputum PGE(2) concentration (r = -0.48; p < 0.01) in subjects with asthma. We conclude that induced sputum contains high concentrations of eicosanoids and that sputum LTC(4)/D(4)/E(4) concentrations are significantly greater in subjects with asthma than in normal subjects. The inverse relationship between eosinophilic airway inflammation and sputum PGE(2) concentration would be consistent, with the latter having an anti-inflammatory role.

Immunocytochemical localization of cyclo-oxygenase isoforms in cultured human airway structural cells

BACKGROUND

Cyclo-oxygenase (COX) exists as two isoforms, COX-1, the constitutive isoform, and COX-2, which is inducible by cytokines or inflammatory stimuli and may participate in airway inflammation.

OBJECTIVE

To determine the basal distribution of COX isoforms, and their regulation by interleukin-1 beta (IL-1beta), bradykinin (BK) and dexamethasone (Dex) in cultured airway structural cells.

METHODS

We measured COX-1 and COX-2 in cultured human airway smooth muscle (HASM) cells, MRC5 fibroblasts and normal human epithelial cells (NHBE) using immunocytochemical analysis.

RESULTS

The majority of all types of untreated cultured cells expressed COX-1 (75% of HASM, 75% of MRC5 fibroblasts and 72% of NHBE cells). Fibroblasts and smooth muscle cells showed low constitutive COX-2 expression (2 and 8%, respectively) but this was higher in NHBE cells (28%). IL-1beta (24 h incubation) or BK (4 h incubation) had no effect on COX-1 expression in any of the cells studied. In contrast, there was a two- and 1.5-fold rise in the percentage of NHBE cells expressing COX-2; a 7.5- and sixfold rise in the percentage of HASM cells expressing COX-2 and a 33.5- and 20.5-fold increase in the percentage of fibroblasts expressing COX-2 after IL-1beta or BK treatment, respectively. Pretreatment with dexamethasone abolished IL-1beta- and BK-stimulated COX-2 induction in all cells studied.

CONCLUSION

COX-1 is expressed constitutively in human airway fibroblasts, smooth muscle and epithelial cells but epithelial cells also show constitutive expression of COX-2. Both IL-1beta and BK induced COX-2 expression in all cells studied and this induction was blocked by dexamethasone. Immunocytochemical techniques can be successfully used to detect the distribution of COX isoforms in cell cultures.