Neutrophil chemotactic activity of sputum from patients with COPD: role of interleukin 8 and leukotriene B4

Interleukin-26 in antibacterial host defense of human lungs. Effects on neutrophil mobilization

RATIONALE

The role of the presumed Th17 cytokine IL-26 in antibacterial host defense of the lungs is not known.

OBJECTIVES

To characterize the role of IL-26 in antibacterial host defense of human lungs.

METHODS

Intrabronchial exposure of healthy volunteers to endotoxin and vehicle was performed during bronchoscopy and bronchoalveolar lavage (BAL) samples were harvested. Intracellular IL-26 was detected using immunocytochemistry and immunocytofluorescence. This IL-26 was also detected using flow cytometry, as was its receptor complex. Cytokines and phosphorylated signal transducer and activator of transcription (STAT) 1 plus STAT3 were quantified using ELISA. Gene expression was analyzed by real-time polymerase chain reaction and neutrophil migration was assessed in vitro.

MEASUREMENTS AND MAIN RESULTS

Extracellular IL-26 was detected in BAL samples without prior exposure in vivo and was markedly increased after endotoxin exposure. Alveolar macrophages displayed gene expression for, contained, and released IL-26. Th and cytotoxic T cells also contained IL-26. In the BAL samples, IL-26 concentrations and innate effector cells displayed a correlation. Recombinant IL-26 potentiated neutrophil chemotaxis induced by IL-8 and fMLP but decreased chemokinesis for neutrophils. Myeloperoxidase in conditioned media from neutrophils was decreased. The IL-26 receptor complex was detected in neutrophils and IL-26 decreased phosphorylated STAT3 in these cells. In BAL and bronchial epithelial cells, IL-26 increased gene expression of the IL-26 receptor complex and STAT1 plus STAT3. Finally, IL-26 increased the release of neutrophil-mobilizing cytokines in BAL but not in epithelial cells.

CONCLUSIONS

This study implies that alveolar macrophages produce IL-26, which stimulates receptors on neutrophils and focuses their mobilization toward bacteria and accumulated immune cells in human lungs.

Discovery of 2-[5-(4-Fluorophenylcarbamoyl)pyridin-2-ylsulfanylmethyl]phenylboronic Acid (SX-517): Noncompetitive Boronic Acid Antagonist of CXCR1 and CXCR2

The G protein-coupled chemokine receptors CXCR1 and CXCR2 play key roles in inflammatory diseases and carcinogenesis. In inflammation, they activate and recruit polymorphonuclear cells (PMNs) through binding of the chemokines CXCL1 (CXCR1) and CXCL8 (CXCR1 and CXCR2). Structure-activity studies that examined the effect of a novel series of S-substituted 6-mercapto-N-phenyl-nicotinamides on CXCL1-stimulated Ca(2+) flux in whole human PMNs led to the discovery of 2-[5-(4-fluorophenylcarbamoyl)pyridin-2-ylsulfanylmethyl]phenylboronic acid (SX-517), a potent noncompetitive boronic acid CXCR1/2 antagonist. SX-517 inhibited CXCL1-induced Ca(2+) flux (IC50 = 38 nM) in human PMNs but had no effect on the Ca(2+) flux induced by C5a, fMLF, or PAF. In recombinant HEK293 cells that stably expressed CXCR2, SX-517 antagonized CXCL8-induced [(35)S]GTPγS binding (IC50 = 60 nM) and ERK1/2 phosphorylation. Inhibition was noncompetitive, with SX-517 unable to compete the binding of [(125)I]-CXCL8 to CXCR2 membranes. SX-517 (0.2 mg/kg iv) significantly inhibited inflammation in an in vivo murine model. SX-517 is the first reported boronic acid chemokine antagonist and represents a novel pharmacophore for CXCR1/2 antagonism.

Cytokine inhibition in the treatment of COPD

Cytokines play an important part in many pathobiological processes of chronic obstructive pulmonary disease (COPD), including the chronic inflammatory process, emphysema, and altered innate immune response. Proinflammatory cytokines of potential importance include tumor necrosis factor (TNF)-α, interferon-γ, interleukin (IL)-1β, IL-6, IL-17, IL-18, IL-32, and thymic stromal lymphopoietin (TSLP), and growth factors such as transforming growth factor-β. The current objectives of COPD treatment are to reduce symptoms, and to prevent and reduce the number of exacerbations. While current treatments achieve these goals to a certain extent, preventing the decline in lung function is not currently achievable. In addition, reversal of corticosteroid insensitivity and control of the fibrotic process while reducing the emphysematous process could also be controlled by specific cytokines. The abnormal pathobiological process of COPD may contribute to these fundamental characteristics of COPD, and therefore targeting cytokines involved may be a fruitful endeavor. Although there has been much work that has implicated various cytokines as potentially playing an important role in COPD, there have been very few studies that have examined the effect of specific cytokine blockade in COPD. The two largest studies that have been reported in the literature involve the use of blocking antibody to TNFα and CXCL8 (IL-8), and neither has provided benefit. Blocking the actions of CXCL8 through its CXCR2 receptor blockade was not successful either. Studies of antibodies against IL-17, IL-18, IL-1β, and TSLP are currently either being undertaken or planned. There is a need to carefully phenotype COPD and discover good biomarkers of drug efficacy for each specific target. Specific groups of COPD patients should be targeted with specific anticytokine therapy if there is evidence of high expression of that cytokine and there are features of the clinical expression of COPD that will respond.

Role of leukotriene A4 hydrolase aminopeptidase in the pathogenesis of emphysema

The leukotriene A4 hydrolase (LTA4H) is a bifunctional enzyme with epoxy hydrolase and aminopeptidase activities. We hypothesize that the LTA4H aminopeptidase activity alleviates neutrophilic inflammation, which contributes to cigarette smoke (CS)-induced emphysema by clearing proline-glycine-proline (PGP), a triamino acid chemokine known to induce chemotaxis of neutrophils. To investigate the biological contributions made by the LTA4H aminopeptidase activity in CS-induced emphysema, we exposed wild-type mice to CS over 5 mo while treating them with a vehicle or a pharmaceutical agent (4MDM) that selectively augments the LTA4H aminopeptidase without affecting the bioproduction of leukotriene B4. Emphysematous phenotypes were assessed by premortem lung physiology with a small animal ventilator and by postmortem histologic morphometry. CS exposure acidified the airspaces and induced localization of the LTA4H protein into the nuclei of the epithelial cells. This resulted in accumulation of PGP in the airspaces by suppressing the LTA4H aminopeptidase activity. When the LTA4H aminopeptidase activity was selectively augmented by 4MDM, the levels of PGP in the bronchoalveolar lavage fluid and infiltration of neutrophils into the lungs were significantly reduced without affecting the levels of leukotriene B4. This protected murine lungs from CS-induced emphysematous alveolar remodeling. In conclusion, CS exposure promotes the development of CS-induced emphysema by suppressing the enzymatic activities of the LTA4H aminopeptidase in lung tissues and accumulating PGP and neutrophils in the airspaces. However, restoring the leukotriene A4 aminopeptidase activity with a pharmaceutical agent protected murine lungs from developing CS-induced emphysema.

Inhibition of LPS-induced airway neutrophilic inflammation in healthy volunteers with an oral CXCR2 antagonist

Background

Inhaled lipopolysaccharide (LPS) induces a dose-dependent, acute neutrophilic response in the airways of healthy volunteers that can be quantified in induced sputum. Chemokines, such as CXCL1 and CXCL8, play an important role in neutrophilic inflammation in the lung through the activation of CXCR2 and small molecule antagonists of these receptors have now been developed. We investigated the effect of AZD8309, a CXCR2 antagonist, compared with placebo on LPS-induced inflammation measured in sputum of healthy volunteers.

Methods

Twenty healthy subjects were randomized in a double-blind placebo-controlled, cross-over study. AZD8309 (300 mg) or placebo was dosed twice daily orally for 3 days prior to challenge with inhaled LPS and induced sputum was collected 6 h later.

Results

Treatment with AZD8309 showed a mean 77% reduction in total sputum cells (p < 0.001) and 79% reduction in sputum neutrophils (p < 0.05) compared with placebo after LPS challenge. There was also a reduction in neutrophil elastase activity (p < 0.05) and CXCL1 (p < 0.05) and trends for reductions in sputum macrophages (47%), leukotriene B₄ (39%) and CXCL8 (52%).

Conclusions

AZD8309 inhibited LPS-induced inflammation measured in induced sputum of normal volunteers, indicating that this treatment may be useful in the treatment of neutrophilic diseases of the airways, such as COPD, severe asthma and cystic fibrosis.

Trial registration

NCT00860821.

Cellular and molecular mechanisms of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is associated with chronic inflammation affecting predominantly lung parenchyma and peripheral airways and results in largely irreversible and progressive airflow limitation. This inflammation is characterized by increased numbers of alveolar macrophages, neutrophils, and T lymphocytes, which are recruited from the circulation. Oxidative stress plays a key role in driving this inflammation. The pulmonary inflammation may enhance the development and growth of lung cancer. The peripheral inflammation extends into the circulation, resulting in systemic inflammation with the same inflammatory proteins. Systemic inflammation may worsen comorbidities. Treatment of pulmonary inflammation may therefore have beneficial effects.

New drug therapies for COPD

Clinical trials with new drugs for chronic obstructive pulmonary disease (COPD) have been performed. Viruses exacerbate COPD and bacteria may play a part in severe COPD; therefore, antibiotic and antiviral approaches have a sound rationale. Antiinflammatory approaches have been studied. Advances in understanding the molecular basis of other processes have resulted in novel drugs to target reactive oxidant species, mucus, proteases, fibrosis, cachexia, and muscle wasting, and accelerated aging. Studies with monoclonal antibodies have been disappointing, highlighting the tendency for infections and malignancies during treatment. Promising future directions are lung regeneration with retinoids and stem cells.

Recent developments in microfluidics-based chemotaxis studies

Microfluidic devices can better control cellular microenvironments compared to conventional cell migration assays. Over the past few years, microfluidics-based chemotaxis studies showed a rapid growth. New strategies were developed to explore cell migration in manipulated chemical gradients. In addition to expanding the use of microfluidic devices for a broader range of cell types, microfluidic devices were used to study cell migration and chemotaxis in complex environments. Furthermore, high-throughput microfluidic chemotaxis devices and integrated microfluidic chemotaxis systems were developed for medical and commercial applications. In this article, we review recent developments in microfluidics-based chemotaxis studies and discuss the new trends in this field observed over the past few years.

Corticosteroid insensitivity is reversed by formoterol via phosphoinositide-3-kinase inhibition

BACKGROUND AND PURPOSE

Patients with chronic obstructive pulmonary disease (COPD) show a poor response to corticosteroids, which has been linked to oxidative stress. Here we show that the long-acting β(2) -agonist formoterol (FM) reversed corticosteroid insensitivity under oxidative stress via inhibition of phosphoinositide-3-kinase (PI3K) signalling.

EXPERIMENTAL APPROACH

Responsiveness to corticosteroids dexamethasone (Dex), budesonide (Bud) and fluticasone propionate (FP) was determined, as IC(50) values on TNF-α-induced interleukin 8 release, in U937 monocytic cell line treated with hydrogen peroxide (H(2) O(2) ) or peripheral blood mononuclear cells (PBMCs) from patients with COPD or severe asthma.

KEY RESULTS

PBMCs from severe asthma and COPD were less sensitive to Dex compared with those from healthy subjects. Both FM (10(-9)  M) and salmeterol (SM, 10(-8)  M) reversed Dex insensitivity in severe asthma, but only FM restored Dex sensitivity in COPD. Although H(2) O(2) exposure decreased steroid sensitivity in U937 cells, FM restored responsiveness to Bud and FP while the effects of SM were weaker. Additionally, FM, but not SM, partially inhibited H(2) O(2) -induced PI3Kδ-dependent (PKB) phosphorylation. H(2) O(2) decreased SM-induced cAMP production in U937 cells, but did not significantly affect the response to FM. The reduction of SM effects by H(2) O(2) was reversed by pretreatment with LY294002, a PI3K inhibitor, or IC87114, a PI3Kδ inhibitor.

CONCLUSION AND IMPLICATIONS

FM reversed oxidative stress-induced corticosteroid insensitivity and decreased β(2) adrenoceptor-dependent cAMP production via inhibition of PI3Kδ signalling. FM will be more effective than SM, when combined with corticosteroids, for the treatment of respiratory diseases under conditions of high oxidative stress, such as in COPD.

Cytokines in chronic respiratory diseases

Cytokines are small, secreted proteins that control immune responses. Within the lung, they can control host responses to injuries or infection, resulting in clearance of the insult, repair of lung tissue, and return to homeostasis. Problems can arise when this response is over exuberant and/or cytokine production becomes dysregulated. In such cases, chronic and repeated inflammatory reactions and cytokine production can be established, leading to airway remodeling and fibrosis with unintended, maladaptive consequences. In this report, we describe the cytokines and molecular mechanisms behind the pathology observed in three major chronic diseases of the lung: asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis. Overlapping mechanisms are presented as potential sites for therapeutic intervention.

Cigarette smoke-induced collagen destruction; key to chronic neutrophilic airway inflammation?

Background

Cigarette smoking induces inflammatory responses in all smokers and is the major risk factor for lung disease such as chronic obstructive pulmonary disease (COPD). In this progressive disease, chronic inflammation in the lung contributes to lung tissue destruction leading to the formation of chemotactic collagen fragments such as N-acetylated Proline-Glycine-Proline (N-ac-PGP). The generation of this tripeptide is mediated by a multistep pathway involving matrix metalloproteases (MMPs) 8 and 9 and prolyl endopeptidase (PE). Here we investigated whether cigarette smoke extract (CSE) stimulates human PMNs to breakdown whole matrix collagen leading to the generation of the chemotactic collagen fragment N-ac-PGP.

Methodology/Principal Findings

Incubating PMNs with CSE led to the release of chemo-attractant CXCL8 and proteases MMP8 and MMP9. PMNs constitutively expressed PE activity as well as PE protein. Incubating CSE-primed PMNs with collagen resulted in collagen breakdown and in N-ac-PGP generation. Incubation of PMNs with the tripeptide N-ac-PGP resulted in the release of CXCL8, MMP8 and MMP9. Moreover, we tested whether PMNs from COPD patients are different from PMNs from healthy donors. Here we show that the intracellular basal PE activity of PMNs from COPD patients increased 25-fold compared to PMNs from healthy donors. Immunohistological staining of human lung tissue for PE showed that besides neutrophils, macrophages and epithelial cells express PE.

Conclusions

This study indicates that neutrophils activated by cigarette smoke extract can breakdown collagen into N-ac-PGP and that this collagen fragment itself can activate neutrophils, which may lead in vivo to a self-propagating cycle of neutrophil infiltration, chronic inflammation and lung emphysema. MMP-, PE- or PGP-inhibitors can serve as an attractive therapeutic target and may open new avenues towards effective treatment of COPD.

Increased neutrophil migration in smokers with or without chronic obstructive pulmonary disease

BACKGROUND AND OBJECTIVE

The number of airway neutrophils is increased in chronic obstructive pulmonary disease (COPD), and this may have a central pathophysiological role in the disease. In addition, activation of neutrophils increases their migration into sites of injury. We hypothesize that circulating neutrophils are activated in smokers.

METHODS

Peripheral blood neutrophils were isolated from healthy non-smokers (n = 15), and smokers with (n = 15) or without COPD (n = 15), who were matched with regard to cumulative tobacco exposure, and chemotactic responses to N-formyl-methionyl-leucyl-phenylalanine (fMLP), interleukin-8 (IL-8, CXCL8) and leukotriene B(4) (LTB(4)) were assessed using the ChemoTx System (Neuro Probe Inc., Gaithersburg, MD, USA). Serum tumour necrosis factor-α (TNF-α) concentrations were measured by ELISA. Surface expression of the neutrophil activation marker, CD11b, was measured by flow cytometry.

RESULTS

The chemotactic response to CXCL8 was increased in smokers with or without COPD (P < 0.05). Migration towards LTB(4) was increased in smokers without COPD compared with non-smokers (P < 0.05), whereas there was no difference in fMLP-induced chemotaxis between the groups. There was a correlation between serum TNF-α levels and migration induced by IL-8 (Rho = 0.442; P = 0.038) and LTB(4) (Rho = 0.428; P = 0.044) in the smokers. Furthermore, there was a tendency towards higher CD11b expression in the COPD group (P = 0.057).

CONCLUSIONS

Chemotaxis of circulating neutrophils towards CXCL8, and partly towards LTB(4), is increased in smokers, indicating a systemic influence of smoking on cell activation, irrespective of the presence of airflow limitation. The relationship between TNF-α and chemotactic response suggests that TNF-α is involved in neutrophil activation, resulting in enhanced migration.

The neutrophilic inflammatory phenotype is associated with systemic inflammation in asthma

BACKGROUND

The role of systemic inflammation in asthma is unclear. The aim of this study was to compare systemic inflammation in subjects with stable asthma, categorized by airway inflammatory phenotype, with healthy control subjects.

METHODS

Adults with stable asthma (n = 152) and healthy control subjects (n = 83) underwent hypertonic saline challenge and sputum induction. Differential leukocyte counts were performed on selected sputum. Plasma high-sensitivity C-reactive protein (CRP), IL-6, and tumor necrosis factor-α levels and sputum IL-8 and neutrophil elastase levels were determined by enzyme-linked immunosorbent assay. Sputum IL-8 receptor α (IL-8RA) and IL-8 receptor β (IL-8RB) messenger RNA expression were determined by real-time polymerase chain reaction.

RESULTS

Subjects with asthma were classified as having nonneutrophilic asthma or neutrophilic asthma. The asthma (neutrophilic) group had increased systemic inflammation compared with the asthma (nonneutrophilic) and healthy control groups, with median (interquartile range) CRP levels of 5.0 (1.6-9.2), 1.8 (0.9-5.3), and 1.8 (0.8-4.1) mg/L (P = .011), respectively, and IL-6 levels of 2.1 (1.5-3.1), 1.4 (1.0-2.1), and 1.1 (0.8-1.5) pg/mL (P < .001), respectively. The proportion of subjects with elevated CRP and IL-6 levels was also higher in the asthma (neutrophilic) group. Sputum IL-8 and neutrophil elastase protein and IL-8RA and IL-8RB gene expression were significantly increased in the asthma (neutrophilic) group. In multiple regression analysis of subjects with asthma, sex, BMI, statin use, and percent sputum neutrophils were significant predictors of log(10)CRP. Sex, BMI, and %FEV(1) were significant predictors of log(10)IL-6.

CONCLUSIONS

Systemic inflammation is increased in patients with asthma with neutrophilic airway inflammation and associated with worse clinical outcomes. Systemic inflammation may contribute to the pathophysiology of neutrophilic asthma.

RAGE and tobacco smoke: insights into modeling chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a progressive condition characterized by chronic airway inflammation and airspace remodeling, leading to airflow limitation that is not completely reversible. Smoking is the leading risk factor for compromised lung function stemming from COPD pathogenesis. First- and second-hand cigarette smoke contain thousands of constituents, including several carcinogens and cytotoxic chemicals that orchestrate chronic lung inflammation and destructive alveolar remodeling. Receptors for advanced glycation end-products (RAGE) are multi-ligand cell surface receptors primarily expressed by diverse lung cells. RAGE expression increases following cigarette smoke exposure and expression is elevated in the lungs of patients with COPD. RAGE is responsible in part for inducing pro-inflammatory signaling pathways that culminate in expression and secretion of several cytokines, chemokines, enzymes, and other mediators. In the current review, new transgenic mouse models that conditionally over-express RAGE in pulmonary epithelium are discussed. When RAGE is over-expressed throughout embryogenesis, apoptosis in the peripheral lung causes severe lung hypoplasia. Interestingly, apoptosis in RAGE transgenic mice occurs via conserved apoptotic pathways also known to function in advanced stages of COPD. RAGE over-expression in the adult lung models features of COPD including pronounced inflammation and loss of parenchymal tissue. Understanding the biological contributions of RAGE during cigarette smoke-induced inflammation may provide critically important insight into the pathology of COPD.

Effect of incremental exercise on airway and systemic inflammation in patients with COPD

Airway and systemic inflammation are features of chronic obstructive pulmonary disease (COPD), and there is growing interest in clarifying the inflammatory processes. Strenuous exercise induces an intensified systemic inflammatory response in patients with COPD, but no study has investigated the airway inflammatory and anti-inflammatory responses to exercise. Twenty steroid-naïve, ex-smokers with diagnosed COPD (forced expired volume in 1 s = 66 ± 12%) underwent baseline collection of venous blood and induced sputum followed by an incremental exercise test to symptom limitation 48 h later. Additional venous blood samples were collected following exercise at 0, 2, and 24 h, while induced sputum was collected 2 and 24 h after exercise. Sputum and blood samples were analyzed for differential cell count, CD4+and CD8+T lymphocytes (serum only), interleukin (IL)-6, IL-8, IL-10, chemokine (C-C motif) ligand 5 (CCL5), and high sensitivity C-reactive protein (serum only). There was an increase in the number of sputum eosinophils (cells/gram, P = 0.012) and a reduction in sputum IL-6 ( P = 0.01) 24 h postexercise. Sputum IL-8 and CCL5 were also persistently decreased after exercise ( P = 0.0098 and P = 0.0012, respectively), but sputum IL-10 did not change. There was a decrease in serum eosinophils 2 h after exercise ( P = 0.0014) and a reduction in serum CCL5 immediately following and 2 h postexercise ( P < 0.0001). Both serum eosinophils and CCL5 returned to baseline levels within 24 h. An acute bout of exercise resulted in a significant increase in the number of sputum eosinophils, which may be mediated by serum CCL5. However, there was also a reduction in sputum proinflammatory cytokines, suggesting some anti-inflammatory effect of exercise in the lungs of steroid-naïve patients with COPD.

Neutrophil activation in severe, early-onset COPD patients versus healthy non-smoker subjects in vitro: effects of antioxidant therapy

BACKGROUND

Neutrophils and oxidative stress have been implicated in the pathogenesis of COPD. Severe, early-onset COPD is characterized by a rapid decline in the lung function at an early age; however, nothing is known about neutrophil activation in COPD patients.

OBJECTIVES

The aim of this study was to evaluate peripheral blood neutrophil activation in severe, early-onset COPD patients versus healthy non-smokers and the effect of N-acetyl-L-cysteine (NAC) on neutrophil activation in vitro.

METHODS

Neutrophils were isolated from 15 severe, early-onset COPD patients and 15 age-matched healthy subjects and stimulated with N-formyl-Met-Leu-Phe (fMLP) in the presence or absence of NAC (10 μM to 10 mM). Neutrophil chemotaxis, elastase release, reactive oxygen species (ROS), intracellular thiols and apoptosis were measured by Boyden chamber, spectrofluorometry, CMFDA and H2DCF-DA dyes and by annexin V-FITC, respectively.

RESULTS

Chemotaxis of peripheral blood neutrophils from COPD patients in response to fMLP was 30% more increased than that observed in healthy subjects. Elastase release in response to fMLP was 2-fold higher in neutrophils from COPD patients versus healthy subjects. Intracellular thiol levels were 30% lower in COPD and ROS was approximately 30% higher in COPD versus healthy neutrophils. Spontaneous apoptosis showed no differences in both groups of patients and fMLP-induced apoptosis was higher in COPD. Pre-treatment with the antioxidant NAC effectively attenuated neutrophil chemotaxis, elastase release and ROS as well as effectively increased thiol levels in COPD.

CONCLUSIONS

Neutrophils in severe, early-onset COPD patients are highly activated and this is alleviated by NAC in vitro.

A study of the effect of proinflammatory cytokines on the epithelial cells of smokers, with or without COPD

INTRODUCTION

Cigarette smoke is the main cause of inflammation in COPD. The mechanisms that differentiate smokers who develop COPD are diverse. In this study, we analyzed the presence of cytokines in the respiratory secretions of smokers with or without COPD and the secretory properties of the differentiated bronchial epithelium obtained from the individuals themselves after exposure to tobacco smoke.

MATERIAL AND METHODS

Twenty-seven smokers were studied, 12 of whom had COPD that had not been previously treated with steroids. In 11, samples were obtained by means of induced sputum, and the remaining samples were collected from bronchial aspiration after bronchoscopy. Concentrations of IL-8, IL-13 and TNFα in the supernatant were determined. The results obtained were compared between individuals with and without COPD, and we studied their relationship with the severity of COPD as expressed by the degree of obstruction, dyspnea, presence of hypersecretion and intensity of smoking. Bronchial epithelial cell cultures were obtained by air-liquid interface in 4 smokers. The samples were exposed to increasing concentrations of cigarette smoke (5-20%) and the epithelial mRNA expressions of MUC5AC, IL8 and TNFα were determined.

RESULTS

COPD patients had significantly higher values of IL-8 than healthy smokers (41 [22] vs. 21 [12] pM). The values of IL-8 correlated significantly with the severity of the obstruction (r=0.6; p<0.05), dyspnea (r=0.45; p<0.05) and the presence of hypersecretion. There was no relationship between cytokines and the intensity or duration of the tobacco habit. Cigarette smoke produced a dose-dependent increase in the expression of RNAm for Muc5AC, IL8 and TNFα.

CONCLUSIONS

There are differences in cytokine production (fundamentally IL8) between smokers and smokers with COPD which could be explained by the direct action of cigarette smoke on epithelial cells.

Targeting of a common receptor shared by CXCL8 and N-Ac-PGP as a therapeutic strategy to alleviate chronic neutrophilic lung diseases

Persistent neutrophilia is implicated in the pathology of several chronic lung diseases and consequently targeting the signals that drive the recruitment of these cells offers a plausible therapeutic strategy. The tripeptide Pro-Gly-Pro (PGP) is a neutrophil chemoattractant derived from extracellular matrix collagen and implicated in diseases such as COPD and cystic fibrosis. It was anticipated that PGP exerts its chemoatactic activity by mimicking key sequences found within classical neutrophil chemokines, such as CXCL8, and binding their receptors, CXCR1/2. Recently, however, the role of CXCR1/2 as the receptors for PGP has been questioned. In this issue of European Journal of Pharmacology, three studies address this controversy and demonstrate CXCR1/2 to be a common receptor for CXCL8 and PGP. Accordingly, these studies demonstrate the therapeutic potential of targeting this shared receptor to simultaneously alleviate neutrophilic inflammation driven by multiple neutrophil chemoattractants.

N-acetylated Proline-Glycine-Proline induced G-protein dependent chemotaxis of neutrophils is independent of CXCL8 release

Chronic inflammation in lung diseases contributes to lung tissue destruction leading to the formation of chemotactic collagen fragments such as N-acetylated Proline-Glycine-Proline (N-ac-PGP). In this study, we investigated in more detail the mechanism of action of N-ac-PGP in neutrophilic inflammation. N-ac-PGP was chemotactic for human neutrophils via pertussis toxin sensitive G protein-coupled receptors in vitro and directly activated this cell type, which led to cytosolic calcium mobilization and release of CXCL8. Furthermore, using a selective CXCR2 antagonist confirmed that N-ac-PGP-induced neutrophil chemotaxis is mediated through CXCR2 activation. To determine whether N-ac-PGP was solely responsible for the migration and activation of human neutrophils in vitro and not the released CXCL8 upon stimulation with N-ac-PGP, an antibody directed against CXCL8 was used. Performing chemotaxis and calcium influx assays in the presence of this antibody did not alter the effects of N-ac-PGP whereas effects of CXCL8 were attenuated. These experiments indicate that N-ac-PGP, in addition to the direct induction of chemotaxis, also directly activates neutrophils to release CXCL8. In vivo, this may lead in the long term to a self-maintaining situation enhanced by both N-ac-PGP and CXCL8, leading to a further increase in neutrophil infiltration and chronic inflammation.

Inhibition of granulocyte migration by tiotropium bromide

STUDY OBJECTIVES

Neutrophil influx into the airways is an important mechanism in the pathophysiology of the inflammatory process in the airways of patients with chronic obstructive pulmonary disease (COPD). Previously it was shown that anticholinergic drugs reduce the release of non-neuronal paracrine mediators, which modulate inflammation in the airways. On this basis, we investigated the ability of the long-acting anticholinergic tiotropium bromide to inhibit a) alveolar macrophage (AM)-mediated chemotaxis of neutrophils, and b) cellular release of reactive oxygen species (ROS).

METHOD

AM and neutrophils were collected from 71 COPD patients. Nanomolar concentrations of tiotropium bromide were tested in AM cultured up to 20 h with LPS (1 μg/ml). AM supernatant was tested for TNFα, IL8, IL6, LTB4, GM-CSF, MIPα/β and ROS. It was further used in a 96-well chemotaxis chamber to stimulate the migration of fluorescence labelled neutrophils. Control stimulants consisted of acetylcholine (ACh), carbachol, muscarine or oxotremorine and in part PMA (phorbol myristate acetate, 0.1 μg/ml). Potential contribution of M1-3-receptors was ascertained by a) analysis of mRNA transcription by RT-PCR, and b) co-incubation with selective M-receptor inhibitors.

RESULTS

Supernatant from AM stimulated with LPS induced neutrophilic migration which could be reduced by tiotropium in a dose dependent manner: 22.1 ± 10.2 (3 nM), 26.5 ± 18,4 (30 nM), and 37.8 ± 24.0 (300 nM, p < 0.001 compared to non-LPS activated AM). Concomitantly TNFα release of stimulated AM dropped by 19.2 ± 7.2% of control (p = 0.001). Tiotropium bromide did not affect cellular IL8, IL6, LTB4, GM-CSF and MIPα/β release in this setting. Tiotropium (30 nM) reduced ROS release of LPS stimulated AM by 36.1 ± 15.2% (p = 0.002) and in carbachol stimulated AM by 46.2 ± 30.2 (p < 0.001). M3R gene expression dominated over M2R and M1R. Chemotaxis inhibitory effect of tiotropium bromide was mainly driven by M3R inhibition.

CONCLUSION

Our data confirm that inhibiting muscarinic cholinergic receptors with tiotropium bromide reduces TNFα mediated chemotactic properties and ROS release of human AM, and thus may contribute to lessen cellular inflammation.

Current concepts on oxidative/carbonyl stress, inflammation and epigenetics in pathogenesis of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a global health problem. The current therapies for COPD are poorly effective and the mainstays of pharmacotherapy are bronchodilators. A better understanding of the pathobiology of COPD is critical for the development of novel therapies. In the present review, we have discussed the roles of oxidative/aldehyde stress, inflammation/immunity, and chromatin remodeling in the pathogenesis of COPD. An imbalance of oxidants/antioxidants caused by cigarette smoke and other pollutants/biomass fuels plays an important role in the pathogenesis of COPD by regulating redox-sensitive transcription factors (e.g., NF-κB), autophagy and unfolded protein response leading to chronic lung inflammatory response. Cigarette smoke also activates canonical/alternative NF-κB pathways and their upstream kinases leading to sustained inflammatory response in lungs. Recently, epigenetic regulation has been shown to be critical for the development of COPD because the expression/activity of enzymes that regulate these epigenetic modifications have been reported to be abnormal in airways of COPD patients. Hence, the significant advances made in understanding the pathophysiology of COPD as described herein will identify novel therapeutic targets for intervention in COPD.

Antioxidant and anti-inflammatory effects of resveratrol in airway disease

Respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are a significant and increasing global health problem. These diseases are characterized by airway inflammation, which develops in response to various stimuli. In asthma, inflammation is driven by exposure to a variety of triggers, including allergens and viruses, which activate components of both the innate and acquired immune responses. In COPD, exposure to cigarette smoke is the primary stimulus of airway inflammation. Activation of airway inflammatory cells leads to the release of excessive quantities of reactive oxygen species (ROS), resulting in oxidative stress. Antioxidants provide protection against the damaging effects of oxidative stress and thus may be useful in the management of inflammatory airways disease. Resveratrol, a polyphenol that demonstrates both antioxidative and anti-inflammatory functions, has been shown to improve outcomes in a variety of diseases, in particular, in cancer. We review the evidence for a protective role of resveratrol in respiratory disease. Mechanisms of resveratrol action that may be relevant to respiratory disease are described. We conclude that resveratrol has potential as a therapeutic agent in respiratory disease, which should be further investigated.

Medicine. Neutrophils find smoke attractive

The altered activity of a neutrophil enzyme promotes the type of persistent lung inflammation seen in chronic pulmonary disease and cystic fibrosis.

Decreased apoptosis of pulmonary PMN in COPD patients with community-acquired pneumonia

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) predisposes for the acquisition of community-acquired pneumonia (CAP).

OBJECTIVE/METHODS

To assess clinically and scientifically suggested disorders in innate immune response during acute phrase and resolution CAP (T2), we evaluated peripheral and pulmonary polymorphnuclear neutrophils (PMN), recovered by induced sputum, from CAP patients with and without COPD with regard to cell activation, interleukin-8 (CXCL-8) and CXCL-8 receptor expression, and apoptosis rate.

RESULTS

At T1, COPD patients displayed significantly lower pulmonary PMN apoptosis rates, while total cell count, the amount of macrophages, and vital and necrotic neutrophils in sputum samples were similar between study groups. At T2, there were no differences between study groups or between pulmonary and peripheral compartment. While under systemic steroid treatment apoptosis rates of peripheral and pulmonary PMN at T1 were slightly decreased, there were no significant differences in intrapulmonary CXCL-8 levels. Regarding cell activation, no significant differences could be seen, neither in comparing study groups nor in pulmonary to peripheral PMN.

CONCLUSION

Elucidating the pathology of suspected disorder in innate immune response, we found decreased apoptosis rates of pulmonary neutrophils in COPD at the peak of CAP indicating an increased inflammatory response, which is independent from anti-apoptotic cytokines such as CXCL-8, severity of disease and isolation of bacteria from sputum cultures.

Role of LTB₄ in the pathogenesis of elastase-induced murine pulmonary emphysema

Exaggerated levels of the leukotriene B₄ (LTB₄) frequently coexist at sites of inflammation and tissue remodeling. Therefore, we hypothesize that the LTB₄ pathway plays an important role in the pathogenesis of neutrophilic inflammation that contributes to pulmonary emphysema. In this study, significant levels of LTB₄ were detected in human lung tissues with emphysema compared with lungs without emphysema (9,497 ± 2,839 vs. 4,142 ± 1,173 pg/ml, n = 9 vs. 10, P = 0.04). To further determine the biological role of LTB₄ in the pathogenesis of emphysema, we compared the lungs of wild-type (WT) and LTA₄ hydrolase-/- mice (LTB₄ deficient, LTA₄H-/-) exposed to intranasal elastase or vehicle control. We found that intranasal elastase induced accumulation of LTB₄ in the lungs and caused progressively worsening emphysema between 14 and 28 days after elastase exposure in WT mice but not in LTA₄H-/- mice. Premortem physiology documented increased lung compliance in elastase-exposed WT mice compared with elastase-exposed LTA₄H-/- mice as measured by Flexivent (0.058 ± 0.005 vs. 0.041 ± 0.002 ml/cmH₂O pressure). Postmortem morphometry documented increased total lung volume and alveolar sizes in elastase-exposed WT mice compared with elastase-exposed LTA₄H-/- mice as measured by volume displacement and alveolar chord length assessment. Furthermore, elastase-exposed LTA₄H-/- mice were found to have significantly delayed influx of the CD45(high)CD11b(high)Ly6G(high) leukocytes compatible with neutrophils compared with elastase-exposed WT mice. Mechanistic insights to these phenotypes were provided by demonstrating protection from elastase-induced murine emphysema with neutrophil depletion in the elastase-exposed WT mice and by demonstrating time-dependent modulation of cysteinyl leukotriene biosynthesis in the elastase-exposed LTA₄H-/- mice compared with elastase-exposed WT mice. Together, these findings demonstrated that LTB₄ played an important role in promoting the pathogenesis of pulmonary emphysema associated with neutrophilic pulmonary inflammation.

Neutrophilic Cells in Sputum of Allergic Asthmatic Children

Airway inflammation is regarded as a central feature of asthma and is mostly sustained by eosinophilic infiltrate. Recent studies have shown that a co-activation of eosinophil- and neutrophil-dependent inflammatory mechanisms might explain why some asthmatics do not respond to conventional asthma therapy. The aim of our study is to determine whether neutrophilic inflammation was involved in 55 allergic children with mild-moderate persistent asthma and the relationship with the response to steroid treatment. Before the sputum analysis, all children underwent spirometry with the reversibility test, and were divided into two groups on the basis of the response (such as >12% of baseline FEV1): group 1 positive and group 2 negative. Eosinophil cationic protein concentrations were measured by radioimmunoassay and neutrophyl myeloperoxidase (MPO) concentrations were measured by an MPO-EIA. Ten healthy children of comparable ages served as control group. Total IgE, FEV1 and FEV/FVC values were similar in both groups. The sputum macrophage count was higher in controls than in allergic asthmatics, but there was no difference between groups 1 and 2 (59.6% vs 18.3% and 17%; p≤ 0.005). Sputum neutrophils were significantly higher in group 2 both vs controls (62% vs 34%; p≤ 0.005) and vs group 1 (62% vs 37%; p≤ 0.005). Our data suggest that neutrophils are involved in airway allergic inflammation in mild-moderate persistent childhood asthma and a high neutrophil count in sputum may be related to a lower responsiveness to inhaled corticosteroids.

Developments in drugs for the treatment of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) affects more than 600 million adults worldwide and accounts for 3 million deaths annually. Approximately 50% of the cases are directly attributable to cigarette smoking; the rest are accounted for by different risk factors, including childhood infections, genetic defects, environmental pollution and biomass exposure. The mainstay of current drug treatment is bronchodilation. Anti-inflammatory drugs are reserved for patients with moderate-to-severe disease. In this article, we will review the current paradigm of COPD pathogenesis and discuss some promising molecular targets that may be modified in the future to improve health outcomes of patients with COPD.

Overview of novel therapeutic targets for asthma and chronic obstructive pulmonary disease

Obstructive lung diseases, in particular asthma and chronic obstructive pulmonary disease, are a worldwide health problem that is increasing in incidence. While significant progress has been made in the control of symptoms, further advances must be made in modifying the clinical situation in terms of disease progression. Numerous pathogenetic studies have demonstrated that inflammatory responses play a crucial role in the development of chronic lung obstruction, while current molecular findings have provided a myriad of new and promising therapeutic targets. The aim of this article is to provide an overview of clinically and pharmacologically relevant targets for asthma and chronic obstructive pulmonary diseases, considering currently investigated therapeutic approaches.

Pathogenesis of inflammation and repair in advanced COPD

Chronic obstructive pulmonary disease is characterized by an abnormal persistent inflammatory response to noxious environmental stimuli, most commonly cigarette smoke. Although cigarette smoking elicits airway inflammation in all of those who smoke, persistent inflammation and clinically significant COPD occurs in only a minority of smokers. The pathogenesis of COPD involves the recruitment and regulation of neutrophils, macrophages, and lymphocytes to the lung, as well as the induction of oxidative stress, all of which result in lung parenchymal destruction and airway remodeling. Recent research has generated a greater understanding of the mechanisms responsible for COPD development, including new concepts in T cell biology and the increasing recognition that the processes governing lung cell apoptosis are upregulated. We are also starting to understand the reasons for continued inflammation even after smoking cessation, which accelerates the rate of lung function decline in COPD. Herein we review our current knowledge of the inflammatory pathways involved in COPD pathogenesis, as well as newer concepts that have begun to unfold in recent years.

Signal transduction pathways linking the activation of alveolar macrophages with the recruitment of neutrophils to lungs in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major and increasing global health problem. It is predicted by the World Health Organization to become the third most common cause of death and the fifth most common cause of disability in the world by 2020. COPD is a complex inflammatory disease involving several types of inflammatory cells and multiple inflammatory mediators. Although abnormal numbers of inflammatory cells such as macrophages, dendritic cells, neutrophils, and T lymphocytes have been documented in COPD, the relationship between these cell types and the sequence of their appearance and persistence is largely unknown. Alveolar macrophages have been identified as one of the major cell types that plays a key role in orchestrating the inflammatory events associated with the pathophysiology of COPD. One of the major functions of macrophages is the secretion of chemotactic factors and this function is markedly increased on exposure to cigarette smoke (CS). This enhanced release of chemoattractants results in increased lung neutrophil infiltration, which is thought to be a key event in the development of COPD. The molecular basis for this amplified inflammatory response is not very clear, but it could be due to an alteration in signal transduction pathways within the macrophage. Based on existing literature, an attempt has been made to create a comprehensive review of the signal transduction pathways that link the activation of macrophages with the increased recruitment of neutrophils into the airways. Some of the major stimuli that activate macrophages and cause them to secrete chemotactic factors have been identified as CS, wood smoke, ozone, bacterial endotoxin, and proinflammatory cytokines such as interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha. These stimuli seem to activate mainly redox-sensitive transcription factors such as nuclear factor (NF)-kappa B and activator protein (AP)-1, both of which play a major role in the synthesis and secretion of chemotactic factors such as IL-8 and leukotriene B(4) (LTB(4)). The pathways involved in the synthesis and secretion of other factors such as macrophage chemotactic protein-1 (MCP-1) and growth-related oncogene-alpha (Gro-alpha) have also been reviewed.

Nicotinamide glycolates antagonize CXCR2 activity through an intracellular mechanism

The chemokine receptors CXCR1/2 are involved in a variety of inflammatory diseases, including chronic obstructive pulmonary disease. Several classes of allosteric small-molecule CXCR1/2 antagonists have been developed. The data presented here describe the cellular pharmacology of the acid and ester forms of the nicotinamide glycolate pharmacophore, a potent antagonist of CXCR2 signaling by the chemokines CXCL1 and CXCL8. Ester forms of the nicotinamide glycolate antagonized CXCL1-stimulated chemotaxis (IC(50) = 42 nM) and calcium flux (IC(50) = 48 nM) in human neutrophils, but they were inactive in cell-free assays of (125)I-CXCL8/CXCR2 binding and CXCL1-stimulated guanosine 5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS) exchange. Acid forms of the nicotinamide glycolate were inactive in whole-cell assays of chemotaxis and calcium flux, but they inhibited (125)I-CXCL8/CXCR2 binding and CXCL1-stimulated [(35)S]GTPgammaS exchange. The (3)H ester was internalized by neutrophils and rapidly converted to the (3)H acid in a concentrative process. The (3)H acid was not internalized by neutrophils but was sufficient alone to inhibit CXCL1-stimulated calcium flux in neutrophils that were permeabilized by electroporation to permit its direct access to the cell interior. Neutrophil efflux of the acid was probenecid-sensitive, consistent with an organic acid transporter. These data support a mechanism wherein the nicotinamide glycolate ester serves as a lipophilic precursor that efficiently translocates into the intracellular neutrophil space to liberate the active acid form of the pharmacophore, which then acts at an intracellular site. Rapid inactivation by plasma esterases precluded use in vivo, but the mechanism elucidated provided insight for new nicotinamide pharmacophore classes with therapeutic potential.

New drugs for exacerbations of chronic obstructive pulmonary disease

Tobacco smoking is the dominant risk factor for chronic obstructive pulmonary disease (COPD), but viral and bacterial infections are the major causes of exacerbations in later stages of disease. Reactive oxygen species (ROS), pathogen-associated molecular patterns (PAMPs), and damage-associated molecular patterns (DAMPs) activate families of pattern recognition receptors (PRRs) that include the toll-like receptors (TLRs). This understanding has led to the hypothesis that COPD is an archetypal disease of innate immunity. COPD is characterised by abnormal response to injury, with altered barrier function of the respiratory tract, an acute phase reaction, and excessive activation of macrophages, neutrophils, and fibroblasts in the lung. The activated non-specific immune system then mediates the processes of inflammation and repair, fibrosis, and proteolysis. COPD is also associated with corticosteroid resistance, abnormal macrophage and T-cell populations in the airway, autoinflammation and autoimmunity, aberrant fibrosis, accelerated ageing, systemic and concomitant disease, and defective regeneration. Such concepts have been used to generate a range of molecular targets, and clinical trials are taking place to identify effective drugs for the prevention and treatment of COPD exacerbations.

N-alpha-PGP and PGP, potential biomarkers and therapeutic targets for COPD

Background

Chronic obstructive pulmonary disease (COPD) is a common respiratory disorder for which new diagnostic and therapeutic approaches are required. Hallmarks of COPD are matrix destruction and neutrophilic airway inflammation in the lung. We have previously described two tri-peptides, N-α-PGP and PGP, which are collagen fragments and neutrophil chemoattractants. In this study, we investigate if N-α-PGP and PGP are biomarkers and potential therapeutic targets for COPD.

Methods

Induced sputum samples from COPD patients, healthy controls and asthmatics were examined for levels of N-α-PGP and PGP using mass spectrometry and for the ability to generate PGP de novo from collagen. Proteases important in PGP generation in the lung were identified by the use of specific inhibitors in the PGP generation assay and by instillation of proteases into mouse lungs. Serum levels of PGP were compared between COPD patients and controls.

Results

N-α-PGP was detected in most COPD sputum samples but in no asthmatics or controls. PGP was detected in a few controls and in all COPD sputum samples, where it correlated with levels of myeloperoxidase. COPD sputum samples had the ability to generate N-α-PGP and PGP de novo from collagen. PGP generation by COPD sputum was blocked by inhibitors of matrix metalloproteases (MMP's) 1 and 9 and prolyl endopeptidase. MMP's 1 and 9 and prolyl endopeptidase acted synergistically to generate PGP in vivo when instilled into mouse lungs. Serum levels of PGP were also significantly higher in COPD patients than in controls

Conclusion

N-α-PGP and PGP may represent novel diagnostic tests and biomarkers for COPD. Inhibition of this pathway may provide novel therapies for COPD directed at the chronic, neutrophilic, airway inflammation which underlies disease progression.

Leukotriene B4 contributes to exhaled breath condensate and sputum neutrophil chemotaxis in COPD

BACKGROUND

Neutrophils have been implicated in the pathogenesis of COPD. Several chemoattractants for neutrophils have been measured in samples of exhaled breath condensate (EBC) and induced sputum (IS) from patients with COPD. The aims of this study were to compare EBC and IS supernatant neutrophil chemotactic activity (NCA) from ex-smoking subjects with COPD and healthy ex-smokers, and to assess the contribution of leukotriene B(4) (LTB(4)) to this activity.

METHODS

Thirty-four subjects with COPD were compared to 24 control subjects. EBC and IS chemotactic activity for neutrophils was assessed by using Boyden microchambers. The chemotactic index was used to evaluate cell migration. LTB(4) was measured by a specific enzyme immunoassay. The contribution of LTB(4) to EBC and sputum neutrophil chemotaxis was assessed by an LTB(4) receptor antagonist (U-75302; Cayman Chemical Company; Ann Arbor, MI).

RESULTS

EBC and IS samples from both COPD patients and healthy subjects displayed significant NCA, but this activity was raised in COPD patients compared to healthy subjects. The chemotactic activity contained in sputum, however, failed to correlate with that in EBC. In COPD patients, there was a significant correlation between EBC NCA and sputum neutrophil counts. LTB(4) levels were raised in EBC samples, but not in sputum samples, from COPD subjects compared to those from healthy subjects. LTB(4) receptor antagonist concentrations (2.5 x 10(-4) mol/L) reduced by 44.6% and by 44.4%, respectively, the chemotactic activity contained in the EBC and sputum samples.

CONCLUSIONS

EBC and IS from COPD patients have a raised NCA to which LTB(4) contributes.

Role of T-lymphocytes and pro-inflammatory mediators in the pathogenesis of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the US and a major worldwide healthcare problem. The pathophysiologic mechanisms that drive development and progression of this disease are complex and only poorly understood. While tobacco smoking is the primary risk factor, other disease processes also appear to play a role. Components of the innate immune system (eg, macrophages and neutrophils) have long been believed to be important in the development of COPD. More recent evidence also suggests involvement of the adaptive immune system in pathogenesis of this disease. Here we will review the literature supporting the participation of T-cells in the development of COPD, and comment on the potential antigenic stimuli that may account for these responses. We will further explore the prospective contributions of T-cell derived mediators that could contribute to the inflammation, alveolar wall destruction, and small airway fibrosis of advanced COPD. A better understanding of these complex immune processes will lead to new insights that could result in improved preventative and/or treatment strategies.

Modeling the role of homologous receptor desensitization in cell gradient sensing

G-protein-coupled chemoattractant receptors signal transiently upon ligand binding to effect cell orientation and motility but then are rapidly desensitized. The importance of desensitization has been unclear, because mutated nondesensitizable receptors mediate efficient chemotaxis. We hypothesized that homologous receptor desensitization is required for cellular navigation in fields of competing attractants. Modeling of receptor-mediated orientation shows that desensitization allows integration of attractant signals. Cells expressing normal receptors are predicted to 1) orient preferentially to distant gradients; 2) seek an intermediate position between balanced agonist sources; 3) and can be repositioned between chemoattractant-defined microenvironmental domains by modest changes in receptor number. In contrast, in the absence of desensitization, orientation is dominated by local agonist sources, precluding continued navigation. Furthermore, cell orientation in competing ligand gradients depends on the relative kinetic rates of receptor desensitization and recycling. We propose that homologous receptor desensitization is critical for cellular navigation in complex chemoattractant fields.

Potential role of leukotriene modifiers in the treatment of chronic obstructive pulmonary disease

Abstract Chronic obstructive pulmonary disease (COPD) is characterized by progressive, irreversible airflow limitation coupled with an abnormal inflammatory process. It is associated with high morbidity and mortality. Leukotriene modifiers, approved by the United States Food and Drug Administration as treatment for asthma and allergic rhinitis, may also alleviate the abnormal inflammatory response seen in patients with COPD. To explore the outcomes of research in this area, we conducted a literature search from 1950-2007, using the PubMed database. We found no published studies that provided conclusive evidence that the available leukotriene modifiers benefit patients with COPD. However, data do suggest that leukotriene modifiers may offer benefits to patients with COPD, including effects that pertain to airflow limitation, neutrophil and lymphocyte chemotaxis, and neutrophil longevity. Added to conventional treatment, these agents appear to reduce symptoms, improve objective measures of disease, and control inflammation. Further studies are needed to determine the precise role of leukotriene modifiers in the treatment of COPD.

Phosphorylation of serine 271 on 5-lipoxygenase and its role in nuclear export

The enzyme 5-lipoxygenase (5-LO) initiates the biosynthesis of leukotrienes, inflammatory mediators involved in immune diseases and defense. The subcellular localization of 5-LO is regulated, with nuclear import commonly leading to increased leukotriene production. We report here that 5-LO is constitutively phosphorylated on Ser-271 in transfected NIH 3T3 cells. This residue is nested in a classical nuclear export sequence, and phosphorylated Ser-271 5-LO was exclusively found in the nucleus by immunofluorescence and by fractionation techniques. Mutation of Ser-271 to Ala allowed nuclear export of 5-LO that was blocked by the specific nuclear export inhibitor leptomycin b, suggesting that phosphorylation of Ser-271 serves to interfere with exportin-1-mediated nuclear export. Consistent with previous reports that purified 5-LO can be phosphorylated on Ser-271 in vitro by MAPK-activated protein kinase 2, the nuclear export of 5-LO was increased by either treatment with the p38 inhibitor SB 203,580 or co-expression of a kinase-deficient p38 MAPK. Nuclear export of 5-LO can also be induced by KN-93, an inhibitor of Ca2+/calmodulin-dependent kinase II, and the effects of SB 203,580 plus KN-93 are additive. Finally, HeLa cells, which lack nuclear 5-LO, also lack constitutive phosphorylation of Ser-271. Taken together, these results indicate that the phosphorylation of Ser-271 serves to inhibit the nuclear export of 5-LO. This action works in concert with nuclear import, which is regulated by phosphorylation on Ser-523, to determine the subcellular distribution of 5-LO, which in turn regulates leukotriene biosynthesis.

Induction of lung emphysema is prevented by L-arginine-threonine-arginine

In patients with chronic obstructive pulmonary disease (COPD), an inflammatory process is ongoing in the lungs, with concomitant damage of the alveolar structures and loss of airway function. In this inflammatory process, extracellular matrix degradation is observed. During this lung matrix degradation, small peptide fragments consisting of proline and glycine repeats generated from collagen fibers are liberated from the matrix by matrix metalloproteinases. Chemotactic activities of these collagen-derived peptides such as N-acetyl-proline-glycine-proline (PGP) via CXCR1 and CXCR2 have been reported. We show here that PGP induces neutrophil migration in vivo, which is dose dependent. Moreover, PGP is involved in the development of emphysema-like changes in the airways. The complementary peptide, L-arginine-threonine-arginine (RTR), has been shown to bind to PGP sequences and inhibit neutrophil infiltration. We show that RTR impedes both PGP- and interleukin-8-induced chemotaxis in vitro. In vivo, RTR prevents both migration and activation of neutrophils induced by PGP. Furthermore, RTR completely inhibits PGP-induced lung emphysema, assessed by changes in alveolar enlargement and right ventricular hypertrophy. In conclusion, these data indicate that collagen breakdown products, especially PGP, are important in the pathogenesis of COPD and that PGP antagonism via RTR ameliorates lung emphysema.