Abnormal pro-gly-pro pathway and airway neutrophilia in pediatric cystic fibrosis.

BACKGROUND: Proline-glycine-proline (PGP) is a bioactive fragment of collagen generated by the action of matrix metalloproteinase-9 (MMP-9) and prolylendopeptidase (PE), and capable of eliciting neutrophil chemotaxis and epithelial remodelling. PGP is normally then degraded by leukotriene A4 hydrolase (LTA4H) to limit inflammation and remodelling. This study hypothesized that early and persistent airway neutrophilia in Cystic Fibrosis (CF) may relate to abnormalities in the PGP pathway and sought to understand underlying mechanisms. METHODS: Broncho-alveolar lavage (BAL) fluid was obtained from 38 CF (9 newborns and 29 older children) and 24 non-CF children. BAL cell differentials and levels of PGP, MMP-9, PE and LTA4H were assessed. RESULTS: Whilst PGP was present in all but one of the older CF children tested, it was absent in non-CF controls and the vast majority of CF newborns. BAL levels of MMP-9 and PE were elevated in older children with CF relative to CF newborns and non-CF controls, correlating with airway neutrophilia and supportive of PGP generation. Furthermore, despite extracellular LTA4H commonly being greatly elevated concomitantly with inflammation to promote PGP degradation, this was not the case in CF children, potentially owing to degradation by neutrophil elastase. CONCLUSIONS: A striking imbalance between PGP-generating and -degrading enzymes enables PGP accumulation in CF children from early life and potentially supports airway neutrophilia.

Vaporized E-Cigarette Liquids Induce Ion Transport Dysfunction in Airway Epithelia.

Cigarette smoking is associated with chronic obstructive pulmonary disease and chronic bronchitis. Acquired ion transport abnormalities, including cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction, caused by cigarette smoking have been proposed as potential mechanisms for mucus obstruction in chronic bronchitis. Although e-cigarette use is popular and perceived to be safe, whether it harms the airways via mechanisms altering ion transport remains unclear. In the present study, we sought to determine if e-cigarette vapor, like cigarette smoke, has the potential to induce acquired CFTR dysfunction, and to what degree. Electrophysiological methods demonstrated reduced chloride transport caused by vaporized e-cigarette liquid or vegetable glycerin at various exposures (30 min, 57.2% and 14.4% respectively, vs. control; P < 0.0001), but not by unvaporized liquid (60 min, 17.6% vs. untreated), indicating that thermal degradation of these products is required to induce the observed defects. We also observed reduced ATP-dependent responses (-10.8 ± 3.0 vs. -18.8 ± 5.1 µA/cm2 control) and epithelial sodium channel activity (95.8% reduction) in primary human bronchial epithelial cells after 5 minutes, suggesting that exposures dramatically inhibit epithelial ion transport beyond CFTR, even without diminished transepithelial resistance or cytotoxicity. Vaporizing e-cigarette liquid produced reactive aldehydes, including acrolein (shown to induce acquired CFTR dysfunction), as quantified by mass spectrometry, demonstrating that respiratory toxicants in cigarette smoke can also be found in e-cigarette vapor (30 min air, 224.5 ± 15.99; unvaporized liquid, 284.8 ± 35.03; vapor, 54,468 ± 3,908 ng/ml; P < 0.0001). E-cigarettes can induce ion channel dysfunction in airway epithelial cells, partly through acrolein production. These findings indicate a heretofore unknown toxicity of e-cigarette use known to be associated with chronic bronchitis onset and progression, as well as with chronic obstructive pulmonary disease severity.

An extracellular matrix fragment drives epithelial remodeling and airway hyperresponsiveness.

It is anticipated that bioactive fragments of the extracellular matrix (matrikines) can influence the development and progression of chronic diseases. The enzyme leukotriene A4 hydrolase (LTA4H) mediates opposing proinflammatory and anti-inflammatory activities, through the generation of leukotriene B4 (LTB4) and degradation of proneutrophilic matrikine Pro-Gly-Pro (PGP), respectively. We show that abrogation of LTB4 signaling ameliorated inflammation and airway hyperresponsiveness (AHR) in a murine asthma model, yet global loss of LTA4H exacerbated AHR, despite the absence of LTB4 This exacerbated AHR was attributable to a neutrophil-independent capacity of PGP to promote pathological airway epithelial remodeling. Thus, we demonstrate a disconnect between airway inflammation and AHR and the ability of a matrikine to promote an epithelial remodeling phenotype that negatively affects lung function. Subsequently, we show that substantial quantities of PGP are detectable in the sputum of moderate-severe asthmatics in two distinct cohorts of patients. These studies have implications for our understanding of remodeling phenotypes in asthma and may rationalize the failure of LTA4H inhibitors in the clinic.

The neutrophil chemoattractant peptide proline-glycine-proline is associated with acute respiratory distress syndrome.

Acute respiratory distress syndrome (ARDS) is characterized by unrelenting polymorphonuclear neutrophil (PMN) inflammation and vascular permeability. The matrikine proline-glycine-proline (PGP) and acetylated PGP (Ac-PGP) have been shown to induce PMN inflammation and endothelial permeability in vitro and in vivo. In this study, we investigated the presence and role of airway PGP peptides in acute lung injury (ALI)/ARDS. Pseudomonas aeruginosa-derived lipopolysaccharide (LPS) was instilled intratracheally in mice to induce ALI, and increased Ac-PGP with neutrophil inflammation was noted. The PGP inhibitory peptide, arginine-threonine-arginine (RTR), was administered (it) 30 min before or 6 h after LPS injection. Lung injury was evaluated by detecting neutrophil infiltration and permeability changes in the lung. Pre- and posttreatment with RTR significantly inhibited LPS-induced ALI by attenuating lung neutrophil infiltration, pulmonary permeability, and parenchymal inflammation. To evaluate the role of PGP levels in ARDS, minibronchoalveolar lavage was collected from nine ARDS, four cardiogenic edema, and five nonlung disease ventilated patients. PGP levels were measured and correlated with Acute Physiology and Chronic Health Evaluation (APACHE) score, PaO2 to FIO2 (P/F), and ventilator days. PGP levels in subjects with ARDS were significantly higher than cardiogenic edema and nonlung disease ventilated patients. Preliminary examination in both ARDS and non-ARDS populations demonstrated PGP levels significantly correlated with P/F ratio, APACHE score, and duration on ventilator. These results demonstrate an increased burden of PGP peptides in ARDS and suggest the need for future studies in ARDS cohorts to examine correlation with key clinical parameters.

Macrophage Rac2 Is Required to Reduce the Severity of Cigarette Smoke-induced Pneumonia.

RATIONALE: Cigarette smoking is prevalent in the United States and is the leading cause of preventable diseases. A prominent complication of smoking is an increase in lower respiratory tract infections (LRTIs). Although LRTIs are known to be increased in subjects that smoke, the mechanism(s) by which this occurs is poorly understood. OBJECTIVES: Determine how cigarette smoke (CS) reduces reactive oxygen species (ROS) production by the phagocytic NOX2 (NADPH oxidase 2), which is essential for innate immunity in lung macrophages. METHODS: NOX2-derived ROS and Rac2 (Ras-related C3 botulinum toxin substrate 2) activity were determined in BAL cells from wild-type and Rac2-/- mice exposed to CS or cadmium and in BAL cells from subjects that smoke. Host defense to respiratory pathogens was analyzed in mice infected with Streptococcus pneumoniae. MEASUREMENTS AND MAIN RESULTS: NOX2-derived ROS in BAL cells was reduced in mice exposed to CS via inhibition of the small GTPase Rac2. These mice had greater bacterial burden and increased mortality compared with air-exposed mice. BAL fluid from CS-exposed mice had increased levels of cadmium, which mediated the effect on Rac2. Similar observations were seen in human subjects that smoke. To support the importance of Rac2 in the macrophage immune response, overexpression of constitutively active Rac2 by lentiviral administration increased NOX2-derived ROS, decreased bacterial burden in lung tissue, and increased survival compared with CS-exposed control mice. CONCLUSIONS: These observations suggest that therapies to maintain Rac2 activity in lung macrophages restore host defense against respiratory pathogens and diminish the prevalence of LRTIs in subjects that smoke.

Angiotensin-converting enzyme defines matrikine-regulated inflammation and fibrosis.

The neutrophil chemoattractant proline-glycine-proline (PGP) is generated from collagen by matrix metalloproteinase-8/9 (MMP-8/9) and prolyl endopeptidase (PE), and it is concomitantly degraded by extracellular leukotriene A4 hydrolase (LTA4H) to limit neutrophilia. Components of cigarette smoke can acetylate PGP, yielding a species (AcPGP) that is resistant to LTA4H-mediated degradation and can, thus, support a sustained neutrophilia. In this study, we sought to elucidate if an antiinflammatory system existed to degrade AcPGP that is analogous to the PGP-LTA4H axis. We demonstrate that AcPGP is degraded through a previously unidentified action of the enzyme angiotensin-converting enzyme (ACE). Pulmonary ACE is elevated during episodes of acute inflammation, as a consequence of enhanced vascular permeability, to ensure the efficient degradation of AcPGP. Conversely, we suggest that this pathway is aberrant in chronic obstructive pulmonary disease (COPD) enabling the accumulation of AcPGP. Consequently, we identify a potentially novel protective role for AcPGP in limiting pulmonary fibrosis and suggest the pathogenic function attributed to ACE in idiopathic pulmonary fibrosis (IPF) to be a consequence of overzealous AcPGP degradation. Thus, AcPGP seemingly has very divergent roles: it is pathogenic in its capacity to drive neutrophilic inflammation and matrix degradation in the context of COPD, but it is protective in its capacity to limit fibrosis in IPF.

Doxycycline improves clinical outcomes during cystic fibrosis exacerbations.

Matrix metalloprotease-9 (MMP-9) plays a role in progression of cystic fibrosis, and doxycycline can reduce MMP-9 in vitro Here, we explore the effect of doxycycline during cystic fibrosis exacerbation treatment on MMP-9 related readouts and clinical end-points.This randomised, double-blind, placebo-controlled study enrolled hospitalised patients with cystic fibrosis undergoing exacerbation. In total, 20 participants were given doxycycline and 19 participants were given placebo over an 8-day period during hospitalisation. Biospecimens were collected at the beginning and the end of the study period. Primary end-points were total MMP-9 levels in the sputum and safety/tolerability. Secondary end-points included change in lung function, time to next exacerbation, and markers of MMP-9-related protease activity (active MMP-9 and TIMP-1). Nonparametric testing was used for within-group and between-group analyses.Doxycycline was well tolerated, with no treatment discontinuations or serious adverse events. Doxycycline reduced total sputum MMP-9 levels by 63.2% (p<0.05), and was also associated with a 56.5% reduction in active MMP-9 levels (p<0.05), a 1.6-fold increase in sputum TIMP-1 (p<0.05), improvement in forced expiratory volume in 1 s (p<0.05), and an increase in time to next exacerbation (p<0.01).Adjunctive use of doxycycline improved dysregulated MMP-9 levels in sputum, along with biomarkers consistent with a reduced proteolytic pulmonary environment. Improvement in clinical outcome measures suggests an important therapeutic benefit of doxycycline for individuals with cystic fibrosis.

The development of novel LTA4H modulators to selectively target LTB4 generation.

The pro-inflammatory mediator leukotriene B4 (LTB4) is implicated in the pathologies of an array of diseases and thus represents an attractive therapeutic target. The enzyme leukotriene A4 hydrolase (LTA4H) catalyses the distal step in LTB4 synthesis and hence inhibitors of this enzyme have been actively pursued. Despite potent LTA4H inhibitors entering clinical trials all have failed to show efficacy. We recently identified a secondary anti-inflammatory role for LTA4H in degrading the neutrophil chemoattractant Pro-Gly-Pro (PGP) and rationalized that the failure of conventional LTA4H inhibitors may be that they inadvertently prevented PGP degradation. We demonstrate that these inhibitors do indeed fail to discriminate between the dual activities of LTA4H, and enable PGP accumulation in mice. Accordingly, we have developed novel compounds that potently inhibit LTB4 generation whilst leaving PGP degradation unperturbed. These novel compounds could represent a safer and superior class of LTA4H inhibitors for translation into the clinic.

The Cystic Fibrosis Transmembrane Conductance Regulator Potentiator Ivacaftor Augments Mucociliary Clearance Abrogating Cystic Fibrosis Transmembrane Conductance Regulator Inhibition by Cigarette Smoke.

Acquired cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction may contribute to chronic obstructive pulmonary disease pathogenesis and is a potential therapeutic target. We sought to determine the acute effects of cigarette smoke on ion transport and the mucociliary transport apparatus, their mechanistic basis, and whether deleterious effects could be reversed with the CFTR potentiator ivacaftor (VX-770). Primary human bronchial epithelial (HBE) cells and human bronchi were exposed to cigarette smoke extract (CSE) and/or ivacaftor. CFTR function and expression were measured in Ussing chambers and by surface biotinylation. CSE-derived acrolein modifications on CFTR were determined by mass spectroscopic analysis of purified protein, and the functional microanatomy of the airway epithelia was measured by 1-µm resolution optical coherence tomography. CSE reduced CFTR-dependent current in HBE cells (P < 0.05) and human bronchi (P < 0.05) within minutes of exposure. The mechanism involved CSE-induced reduction of CFTR gating, decreasing CFTR open-channel probability by approximately 75% immediately after exposure (P < 0.05), whereas surface CFTR expression was partially reduced with chronic exposure, but was stable acutely. CSE treatment of purified CFTR resulted in acrolein modifications on lysine and cysteine residues that likely disrupt CFTR gating. In primary HBE cells, CSE reduced airway surface liquid depth (P < 0.05) and ciliary beat frequency (P < 0.05) within 60 minutes that was restored by coadministration with ivacaftor (P < 0.005). Cigarette smoking transmits acute reductions in CFTR activity, adversely affecting the airway surface. These effects are reversible by a CFTR potentiator in vitro, representing a potential therapeutic strategy in patients with chronic obstructive pulmonary disease with chronic bronchitis.

Tristetraprolin Down-Regulation Contributes to Persistent TNF-Alpha Expression Induced by Cigarette Smoke Extract through a Post-Transcriptional Mechanism.

RATIONALE: Tumor necrosis factor-alpha (TNF-α) is a potent pro-inflammatory mediator and its expression is up-regulated in chronic obstructive pulmonary disease (COPD). Tristetraprolin (TTP) is implicated in regulation of TNF-α expression; however, whether TTP is involved in cigarette smoke-induced TNF-α expression has not been determined. METHODS: TTP expression was examined by western blot analysis in murine alveolar macrophages and alveolar epithelial cells challenged without or with cigarette smoke extract (CSE). TNF-α mRNA stability, and the decay of TNF-α mRNA, were determined by real-time quantitative RT-PCR. TNF-α protein levels were examined at the same time in these cells. To identify the molecular mechanism involved, a construct expressing the human beta-globin reporter mRNA containing the TNF-α 3'-untranslated region was generated to characterize the TTP targeted site within TNF-α mRNA. RESULTS: CSE induced TTP down-regulation in alveolar macrophages and alveolar epithelial cells. Reduced TTP expression resulted in significantly increased TNF-α mRNA stability. Importantly, increased TNF-α mRNA stability due to impaired TTP function resulted in significantly increased TNF-α levels in these cells. Forced TTP expression abrogated the increased TNF-α mRNA stability and expression induced by CSE. By using the globin reporter construct containing TNF-α mRNA 3'-untranslated region, the data indicate that TTP directly targets the adenine- and uridine-rich region (ARE) of TNF-α mRNA and negatively regulates TNF-α expression at the post-transcriptional level. CONCLUSION: The data demonstrate that cigarette smoke exposure reduces TTP expression and impairs TTP function, resulting in significantly increased TNF-α mRNA stability and excessive TNF-α expression in alveolar macrophages and epithelial cells. The data suggest that TTP is a novel post-transcriptional regulator and limits excessive TNF-α expression and inflammatory response induced by cigarette smoke.

Matrikines are key regulators in modulating the amplitude of lung inflammation in acute pulmonary infection.

Bioactive matrix fragments (matrikines) have been identified in a myriad of disorders, but their impact on the evolution of airway inflammation has not been demonstrated. We recently described a pathway where the matrikine and neutrophil chemoattractant proline-glycine-proline (PGP) could be degraded by the enzyme leukotriene A4 hydrolase (LTA4H). LTA4H classically functions in the generation of pro-inflammatory leukotriene B4, thus LTA4H exhibits opposing pro- and anti-inflammatory activities. The physiological significance of this secondary anti-inflammatory activity remains unknown. Here we show, using readily resolving pulmonary inflammation models, that loss of this secondary activity leads to more pronounced and sustained inflammation and illness owing to PGP accumulation. PGP elicits an exacerbated neutrophilic inflammation and protease imbalance that further degrades the extracellular matrix, generating fragments that perpetuate inflammation. This highlights a critical role for the secondary anti-inflammatory activity of LTA4H and thus has consequences for the generation of global LTA4H inhibitors currently being developed.

The matrikine N-α-PGP couples extracellular matrix fragmentation to endothelial permeability.

The compartmentalization and transport of proteins and solutes across the endothelium is a critical biologic function altered during inflammation and disease, leading to pathology in multiple disorders. The impact of tissue damage and subsequent extracellular matrix (ECM) fragmentation in regulating this process is unknown. We demonstrate that the collagen-derived matrikine acetylated proline-glycine-proline (N-α-PGP) serves as a critical regulator of endothelial permeability. N-α-PGP activates human endothelial cells via CXC-chemokine receptor 2 (CXCR2), triggering monolayer permeability through a discrete intracellular signaling pathway. In vivo, N-α-PGP induces local vascular leak after subcutaneous administration and pulmonary vascular permeability after systemic administration. Furthermore, neutralization of N-α-PGP attenuates lipopolysaccharide-induced lung leak. Finally, we demonstrate that plasma from patients with acute respiratory distress syndrome (ARDS) induces VE-cadherin phosphorylation in human endothelial cells, and this activation is attenuated by N-α-PGP blockade with a concomitant improvement in endothelial monolayer impedance. These results identify N-α-PGP as a novel ECM-derived matrikine regulating paracellular permeability during inflammatory disease and demonstrate the potential to target this ligand in various disorders characterized by excessive matrix turnover and vascular leak such as ARDS.

A Potential Role for Acrolein in Neutrophil-Mediated Chronic Inflammation.

Neutrophils (PMNs) are key mediators of inflammatory processes throughout the body. In this study, we investigated the role of acrolein, a highly reactive aldehyde that is ubiquitously present in the environment and produced endogenously at sites of inflammation, in mediating PMN-mediated degradation of collagen facilitating proline-glycine-proline (PGP) production. We treated peripheral blood neutrophils with acrolein and analyzed cell supernatants and lysates for matrix metalloproteinase-9 (MMP-9) and prolyl endopeptidase (PE), assessed their ability to break down collagen and release PGP, and assayed for the presence of leukotriene A4 hydrolase (LTA4H) and its ability to degrade PGP. Acrolein treatment induced elevated production and functionality of collagen-degrading enzymes and generation of PGP fragments. Meanwhile, LTA4H levels and triaminopeptidase activity declined with increasing concentrations of acrolein thereby sparing PGP from enzymatic destruction. These findings suggest that acrolein exacerbates the acute inflammatory response mediated by neutrophils and sets the stage for chronic pulmonary and systemic inflammation.

A Randomized, Placebo-controlled Trial of Roflumilast. Effect on Proline-Glycine-Proline and Neutrophilic Inflammation in Chronic Obstructive Pulmonary Disease.

RATIONALE: Roflumilast is a therapeutic agent in the treatment of chronic obstructive pulmonary disease (COPD). It has antiinflammatory effects; however, it is not known whether it can affect a biologic pathway implicated in COPD pathogenesis and progression. The self-propagating acetyl-proline-glycine-proline (AcPGP) pathway is a novel means of neutrophilic inflammation that is pathologic in the development of COPD. AcPGP is produced by extracellular matrix collagen breakdown with prolyl endopeptidase and leukotriene A4 hydrolase serving as the enzymes responsible for its production and degradation, respectively. OBJECTIVES: We hypothesized that roflumilast would decrease AcPGP, halting the feed-forward cycle of inflammation. METHODS: We conducted a single-center, placebo-controlled, randomized study investigating 12 weeks of roflumilast treatment added to current therapy in moderate-to-severe COPD with chronic bronchitis. Subjects underwent sputum and blood analyses, pulmonary function testing, exercise tolerance, and quality-of-life assessment at 0, 4, and 12 weeks. MEASUREMENTS AND MAIN RESULTS: Twenty-seven patients were enrolled in the intention-to-treat analysis. Roflumilast treatment decreased sputum AcPGP by more than 50% (P < 0.01) and prolyl endopeptidase by 46% (P = 0.02), without significant improvement in leukotriene A4 hydrolase activity compared with placebo. Roflumilast also reduces other inflammatory markers. There were no significant changes in lung function, quality of life, or exercise tolerance between roflumilast- and placebo-treated groups. CONCLUSIONS: Roflumilast reduces pulmonary inflammation through decreasing prolyl endopeptidase activity and AcPGP. As expected for lower AcPGP levels, markers of neutrophilic inflammation are blunted. Inhibiting this self-propagating pathway lessens the overall inflammatory burden, which may alter the natural history of COPD, including the risk of exacerbation. Clinical trial registered with www.clinicaltrials.gov (NCT 01572948).

Innate immune cell-produced IL-17 sustains inflammation in bullous pemphigoid.

Bullous pemphigoid (BP) is an autoimmune skin disease characterized by the binding of autoantibodies to components of the hemidesmosome structure, resulting in an inflammatory response and subepidermal blister formation. To investigate the role of immune orientation in the inflammatory processes associated with disease progression, blister fluid, serum, and biopsy specimens were collected from 31 consecutive BP patients. Blister fluids displayed high levels of IL-6, IL-17, IL-22, and IL-23, whereas transforming growth factor-ß was increased in BP sera. However, neither immunocytochemistry on a trans-differentiation model of IL-17-producing peripheral blood mononuclear cells nor immunohistochemistry on BP biopsy specimens could demonstrate the presence of T helper type 17 lymphocytes. Instead, innate immune cells, especially neutrophils, produced IL-17 at the skin lesional site. Of note, superpotent topical corticosteroid application quickly and markedly reduced both IL-17 expression and clinical signs of BP. Consistently, IL-17 upregulated matrix-metalloprotease-9 and neutrophil elastase expression, two proteases involved in blister formation, thereof further demonstrating its role in the progress of BP. Finally, IL-17-induced matrix degradation, originated from neutrophil activation, initiated the formation of an amplification loop of the inflammatory response that could represent the underlying phenomenon leading to the maintenance and even disease extent. Thus, our results could open new therapeutic strategies for BP patients.

Targeting prolyl endopeptidase with valproic acid as a potential modulator of neutrophilic inflammation.

A novel neutrophil chemoattractant derived from collagen, proline-glycine-proline (PGP), has been recently characterized in chronic obstructive pulmonary disease (COPD). This peptide is derived via the proteolytic activity of matrix metalloproteases (MMP's)-8/9 and PE, enzymes produced by neutrophils and present in COPD serum and sputum. Valproic acid (VPA) is an inhibitor of PE and could possibly have an effect on the severity of chronic inflammation. Here the interaction site of VPA to PE and the resulting effect on the secondary structure of PE is investigated. Also, the potential inhibition of PGP-generation by VPA was examined in vitro and in vivo to improve our understanding of the biological role of VPA. UV-visible, fluorescence spectroscopy, CD and NMR were used to determine kinetic information and structural interactions between VPA and PE. In vitro, PGP generation was significantly inhibited by VPA. In vivo, VPA significantly reduced cigarette-smoke induced neutrophil influx. Investigating the molecular interaction between VPA and PE showed that VPA modified the secondary structure of PE, making substrate binding at the catalytic side of PE impossible. Revealing the molecular interaction VPA to PE may lead to a better understanding of the involvement of PE and PGP in inflammatory conditions. In addition, the model of VPA interaction with PE suggests that PE inhibitors have a great potential to serve as therapeutics in inflammatory disorders.

An aberrant leukotriene A4 hydrolase-proline-glycine-proline pathway in the pathogenesis of chronic obstructive pulmonary disease.

RATIONALE: Chronic neutrophilic inflammation is a hallmark in the pathogenesis of chronic obstructive pulmonary disease (COPD) and persists after cigarette smoking has stopped. Mechanisms involved in this ongoing inflammatory response have not been delineated. OBJECTIVES: We investigated changes to the leukotriene A4 hydrolase (LTA4H)-proline-glycine-proline (PGP) pathway and chronic inflammation in the development of COPD. METHODS: A/J mice were exposed to air or cigarette smoke for 22 weeks followed by bronchoalveolar lavage and lung and cardiac tissue analysis. Two human cohorts were used to analyze changes to the LTA4H-PGP pathway in never smokers, control smokers, COPD smokers, and COPD former smokers. PGP/AcPGP and LTA4H aminopeptidase activity were detected by mass spectroscopy, LTA4H amounts were detected by ELISA, and acrolein was detected by Western blot. MEASUREMENTS AND MAIN RESULTS: Mice exposed to cigarette smoke developed emphysema with increased PGP, neutrophilic inflammation, and selective inhibition of LTA4H aminopeptidase, which ordinarily degrades PGP. We recapitulated these findings in smokers with and without COPD. PGP and AcPGP are closely associated with cigarette smoke use. Once chronic inflammation is established, changes to LTA4H aminopeptidase remain, even in the absence of ongoing cigarette use. Acrolein modifies LTA4H and inhibits aminopeptidase activity to the same extent as cigarette smoke. CONCLUSIONS: These results demonstrate a novel pathway of aberrant regulation of PGP/AcPGP, suggesting this inflammatory pathway may be intimately involved in disease progression in the absence of ongoing cigarette smoke exposure. We highlight a mechanism by which acrolein potentiates neutrophilic inflammation through selective inhibition of LTA4H aminopeptidase activity. Clinical trial registered with www.clinicaltrials.gov (NCT 00292552).

Collagen degradation and neutrophilic infiltration: a vicious circle in inflammatory bowel disease.

OBJECTIVE: Proline-glycine-proline (PGP) has been shown to have chemotactic effects on neutrophils via CXCR2 in several lung diseases. PGP is derived from collagen by the combined action of matrix metalloproteinase (MMP) 8 and/or MMP9 and prolyl endopeptidase (PE). We investigated the role of PGP in inflammatory bowel disease (IBD). DESIGN: In intestinal tissue from patients with IBD and mice with dextran sodium sulfate (DSS)-induced colitis, MMP8, MMP9 and PE were evaluated by ELISA, immunoblot and immunohistochemistry. Peripheral blood polymorphonuclear cell (PMN) supernatants were also analysed accordingly and incubated with collagen to assess PGP generation ex vivo. PGP levels were measured by mass spectrometry, and PGP neutralisation was achieved with a PGP antagonist and PGP antibodies. RESULTS: In the intestine of patients with IBD, MMP8 and MMP9 levels were elevated, while PE was expressed at similar levels to control tissue. PGP levels were increased in intestinal tissue of patients with IBD. Similar results were obtained in intestine from DSS-treated mice. PMN supernatants from patients with IBD were far more capable of generating PGP from collagen ex vivo than healthy controls. Furthermore, PGP neutralisation during DSS-induced colitis led to a significant reduction in neutrophil infiltration in the intestine. CONCLUSIONS: The proteolytic cascade that generates PGP from collagen, as well as the tripeptide itself, is present in the intestine of patients with IBD and mice with DSS-induced colitis. PGP neutralisation in DSS-treated mice showed the importance of PGP-guided neutrophilic infiltration in the intestine and indicates a vicious circle in neutrophilic inflammation in IBD.

Sputum PGP is reduced by azithromycin treatment in patients with COPD and correlates with exacerbations.

RATIONALE: Proline-glycine-proline (PGP), a neutrophil chemoattractant derived from the enzymatic breakdown of collagen, is elevated in sputum of patients with chronic obstructive pulmonary disease (COPD) and may contribute to disease progression. Whether sputum levels of PGP respond to therapy for COPD or predict outcomes is unknown. OBJECTIVES: We conducted a study ancillary to a multicenter trial of the efficacy of azithromycin treatment for 1 year in preventing COPD exacerbations to test whether sputum levels of PGP were altered by treatment or associated with exacerbation frequency. METHODS: We collected remnant sputa from trial participants and assayed them in a blinded fashion for PGP, myeloperoxidase and matrix metalloproteinase (MMP)-9 and for the ability to generate PGP from collagen ex vivo. Once the parent trial was unblinded, the results were correlated with use of azithromycin or placebo and exacerbations in participants. RESULTS: Azithromycin treatment significantly reduced sputum levels of PGP and myeloperoxidase in patients with COPD, particularly with increased duration of therapy. We found no difference in sputum MMP-9 or PGP generation between participants taking azithromycin or placebo. Sputum PGP levels were highest around the time of an exacerbation and declined with successful treatment. CONCLUSIONS: These data support a role for PGP in the airway and parenchymal neutrophilic inflammation that drives COPD progression and exacerbations, and provide new information on the anti-inflammatory properties of macrolides. PGP may have potential as a target for novel anti-inflammatory therapies in COPD and as a biomarker for clinical trials.

Cigarette smoke induces systemic defects in cystic fibrosis transmembrane conductance regulator function.

RATIONALE: Several extrapulmonary disorders have been linked to cigarette smoking. Smoking is reported to cause cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction in the airway, and is also associated with pancreatitis, male infertility, and cachexia, features characteristic of cystic fibrosis and suggestive of an etiological role for CFTR. OBJECTIVES: To study the effect of cigarette smoke on extrapulmonary CFTR function. METHODS: Demographics, spirometry, exercise tolerance, symptom questionnaires, CFTR genetics, and sweat chloride analysis were obtained in smokers with and without chronic obstructive pulmonary disease (COPD). CFTR activity was measured by nasal potential difference in mice and by Ussing chamber electrophysiology in vitro. Serum acrolein levels were estimated with mass spectroscopy. MEASUREMENTS AND MAIN RESULTS: Healthy smokers (29.45 ± 13.90 mEq), smokers with COPD (31.89 ± 13.9 mEq), and former smokers with COPD (25.07 ± 10.92 mEq) had elevated sweat chloride levels compared with normal control subjects (14.5 ± 7.77 mEq), indicating reduced CFTR activity in a nonrespiratory organ. Intestinal current measurements also demonstrated a 65% decrease in CFTR function in smokers compared with never smokers. CFTR activity was decreased by 68% in normal human bronchial epithelial cells exposed to plasma from smokers, suggesting that one or more circulating agents could confer CFTR dysfunction. Cigarette smoke-exposed mice had decreased CFTR activity in intestinal epithelium (84.3 and 45%, after 5 and 17 wk, respectively). Acrolein, a component of cigarette smoke, was higher in smokers, blocked CFTR by inhibiting channel gating, and was attenuated by antioxidant N-acetylcysteine, a known scavenger of acrolein. CONCLUSIONS: Smoking causes systemic CFTR dysfunction. Acrolein present in cigarette smoke mediates CFTR defects in extrapulmonary tissues in smokers.