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Pulmonary fibrosis and emphysema are chronic lung diseases characterized by a progressive decline in lung function, resulting in significant morbidity and mortality. A hallmark of these diseases is recurrent or persistent alveolar epithelial injury, typically caused by common environmental exposures such as cigarette smoke. We propose that critical determinants of the outcome of the injury-repair processes that result in fibrosis versus emphysema are mesenchymal cell fate and associated extracellular matrix dynamics. In this review, we explore the concept that regulation of mesenchymal cells under the influence of soluble factors, in particular transforming growth factor-β1, and the extracellular matrix determine the divergent tissue remodeling responses seen in pulmonary fibrosis and emphysema.

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., ACE degrades the collagen-derived matrikine, acetylate proline–glycine–proline, to limit pulmonary inflammation and promote repair.

Myofibroblasts are effector cells in fibrotic disorders that synthesize and remodel the extracellular matrix (ECM). This study investigated the role of the Src kinase pathway in myofibroblast activation in vitro and fibrogenesis in vivo. The profibrotic cytokine, transforming growth factor β1 (TGF-β1), induced rapid activation of Src kinase, which led to myofibroblast differentiation of human lung fibroblasts. The Src kinase inhibitor AZD0530 (saracatinib) blocked TGF-β1-induced Src kinase activation in a dose-dependent manner. Inhibition of Src kinase significantly reduced α-smooth muscle actin (α-SMA) expression, a marker of myofibroblast differentiation, in TGF-β1-treated lung fibroblasts. In addition, the induced expression of collagen and fibronectin and three-dimensional collagen gel contraction were also significantly inhibited in AZD0530-treated fibroblasts. The therapeutic efficiency of Src kinase inhibition in vivo was tested in the bleomycin murine lung fibrosis model. Src kinase activation and collagen accumulation were significantly reduced in the lungs of AZD0530-treated mice when compared with controls. Furthermore, the total fibrotic area and expression of α-SMA and ECM proteins were significantly decreased in lungs of AZD0530-treated mice. These results indicate that Src kinase promotes myofibroblast differentiation and activation of lung fibroblasts. Additionally, these studies provide proof-of-concept for targeting the noncanonical TGF-β signaling pathway involving Src kinase as an effective therapeutic strategy for lung fibrosis.

Chemoattractant properties of matrix proteins, like collagen and elastin, for neutrophils and monocytes in vitro have long been recognized. This activity often resides in fragments of these proteins. These peptides may play a role in diseases of the lung matrix, such as chronic obstructive pulmonary disease. Recent advances include the elucidation of the structure of chemotactic collagen fragments and the demonstration that their activity may reside in a structural relatedness to CXC chemokines. Collagen and elastin fragments have been demonstrated to have a role in in vivo lung pathophysiology and have been quantified in patients with chronic lung diseases where they may activate autoimmune pathways. Elucidation of these pathways may provide novel biomarkers and therapeutic targets for chronic lung diseases.

Chronic neutrophilic inflammation is a manifestation of a variety of lung diseases including cystic fibrosis (CF). There is increasing evidence that fragments of extracellular matrix proteins, such as collagen and elastin, play an important role in inflammatory cell recruitment to the lung in animal models of airway inflammation. Unfortunately, the association of these peptides with human disease and the identification of therapeutic targets directed toward these inflammatory pathways have remained elusive. In this study, we demonstrate that a novel extracellular matrix-derived neutrophil chemoattractant, proline-glycine-proline (PGP), acts through CXC receptors 1 and 2 on neutrophils, similar to N-acetylated proline-glycine-proline (N-α-PGP). We describe the specific multistep proteolytic pathway involved in PGP generation from collagen, involving matrix metalloproteases 8 and 9 and prolyl endopeptidase, a serine protease for which we identify a novel role in inflammation. PGP generation correlates closely with airway neutrophil counts after administration of proteases in vivo. Using CF as a model, we show that CF sputum has elevated levels of PGP peptides and that PGP levels decline during the course of CF inpatient therapy for acute pulmonary exacerbation, pointing to its role as a novel biomarker for this disease. Finally, we demonstrate that CF secretions are capable of generating PGP from collagen ex vivo and that this generation is significantly attenuated by the use of inhibitors directed toward matrix metalloprotease 8, matrix metalloprotease 9, or prolyl endopeptidase. These experiments highlight unique protease interactions with structural proteins regulating innate immunity and support a role for these peptides as novel biomarkers and therapeutic targets for chronic, neutrophilic lung diseases.

Acute renal failure in critically ill patients is a growing clinical problem. Options for renal replacement therapy in these patients use convective and diffusive clearance and may be intermittent, as in classic hemodialysis, or continuous. New ways of delivering dialysis in the intensive care unit, such as sustained low-efficiency dialysis, are also under development. It may be that renal replacement therapy needs to be tailored to the needs of each individual patient. Current and future research studies should provide the answers to many of these questions.

ARDS is a disease process that is characterized by diffuse inflammation in the lung parenchyma. The involvement of inflammatory mediators in ARDS has been the subject of intense investigation,12 and oxidant-mediated tissue injury is likely to be important in the pathogenesis of ARDS.3 In response to various inflammatory stimuli, lung endothelial cells, alveolar cells, and airway epithelial cells, as well as activated alveolar macrophages, produce both nitric oxide and superoxide, which may react to form peroxynitrite, which can nitrate and oxidize key amino acids in various lung proteins, such as surfactant protein A, and inhibit their functions. The nitration and oxidation of a variety of crucial proteins present in the alveolar space have been shown to be associated with diminished function in vitro and also have been identified ex vivo in proteins sampled from patients with acute lung injury (ALI)/ARDS. Various enzymes and low-molecular-weight scavengers that are present in the lung tissue and alveolar lining fluid decreased the concentration of these toxic species. The purpose of this brief chapter is to review the results from various studies demonstrating increased levels of reactive oxygen-nitrogen intermediates in the alveolar spaces of patients with ALI/ARDS.

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).

Study objectives A high incidence of nocturnal cardiacrhythm disturbances among patients with obstructive sleep apnea (OSA)syndrome has been described in some reports, but not in others. Wewished to examine the prevalence of significant cardiac rhythmdisturbance in patients with established moderate to severe OSAsyndrome and , in particular, to assess the impact of nasal continuouspositive airway pressure (nCPAP) therapy. Design and setting A prospective study of consecutive eligible patients ina dedicated sleep disorders unit of a university teachinghospital. Measurements and results Holter monitoringwas performed for 18 h in 45 patients with previously diagnosed, OSA syndrome (mean [SD] apnea/hypopnea frequency [AHI] of 50[23]/h) and repeated within 2 to 3 days after institution of n, CPAPtherapy. Investigators were blinded to the patients’ treatmentsduring data analysis. Thirty-five patients were found to have somecardiac rhythm disturbance, but only 8 had pathologically significantdisturbances (ventricular tachycardia or fibrillation, complexventricular ectopy, new-onset supraventricular tachycardia other thansinus tachycardia, pauses of > 2 s, and second- or third-degree heartblock). Significant rhythm disturbances occurred only during thenighttime, and there was a significant correlation between OSA severityand the severity of rhythm disturbance (p = 0.04, r = 0.301). No significant correlation was found between, OSA severity and any other anthropometric parameter measured. n, CPAPtherapy resulted in abolition of rhythm disturbance in seven of theseeight patients; the eighth patient was found to have coexistingsevere aortic valve disease requiring valve replacement. Conclusion The data indicate that OSA syndrome predisposesto clinically significant cardiac rhythm disturbances that can besuccessfully controlled by n, CPAP therapy.

Prolyl endopeptidase (PE), a protease that cleaves after proline residues in oligopeptides, is highly active in brain and degrades neuropeptides in vitro. We have recently demonstrated that PE, in concert with MMP's, can generate PGP (proline-glycine-proline), a novel, neutrophil chemoattractant, from collagen. In this study, we demonstrate that human peripheral blood neutrophils contain PE, which is constitutively active, and can generate PGP de novo from collagen after activation with LPS. This novel, pro-inflammatory role for PE raises the possibility of a self-sustaining pathway of neutrophilic inflammation and may provide biomarkers and therapeutic targets for diseases caused by chronic, neutrophilic inflammation.

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.

Purpose of review Long-term oxygen treatment is one of the few interventions that improve survival in chronic obstructive pulmonary disease and it is widely used even though published evidence supporting the use of this treatment in chronic obstructive pulmonary disease is scanty. In addition, some studies do not demonstrate a mortality benefit for long-term oxygen treatment in this disease. It is important that long-term oxygen treatment be administered only to those patients who will benefit and in a manner that maximizes its efficacy. New studies are urgently needed to address these questions. Recent findings The published evidence for and against the use of long-term oxygen treatment in chronic obstructive pulmonary disease is summarized and problems with current guidelines and important areas for future research are discussed. Summary Future research will address the optimal timing and duration of oxygen therapy during rest, exercise and sleep, ways of identifying chronic obstructive pulmonary disease patients who are most likely to benefit and ways of improving patient compliance, all of which may have a profound effect on clinical practice.

Surfactant protein A (SP-A) and alveolar macrophages are essential components of lung innate immunity. Alveolar macrophages phagocytose and kill pathogens by the production of reactive oxygen and nitrogen species. In particular, peroxynitrite, the reaction product of superoxide and nitric oxide, appears to have potent antimicrobial effects. SP-A stimulates alveolar macrophages to phagocytose and kill pathogens and is important in host defense. However, SP-A has diverse effects on both innate and adaptive immunity, and may stimulate or inhibit immune function. SP-A appears to mediate toxic or protective effects depending on the immune status of the lung. In contrast to mouse or rat cells, it has been difficult to demonstrate nitric oxide production by human macrophages. We have recently demonstrated that human macrophages produce nitric oxide and use it to kill Klebsiella pneumoniae. SP-A either stimulates or inhibits this process, depending on the activation state of the macrophage. Given its diverse effects on immune function, SP-A may prove to be an effective therapy for both infectious and inflammatory diseases of the lung.

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.

Measurements of the B coefficients of viscosity in the Jones–Dole equation ηr= 1 +Ac½+Bc are reported for the alkali-metal chlorides in the propan-1-ol–water system at 25 and 35 °C; they extend to 85%(w/w) propanol for Cs+Cl– to 70%(w/w) propanol for Na+Cl– and K+Cl– and 30%(w/w) propanol for Li+Cl–. Photoelectric timing and high-precision density measurements were used in determining the relative viscosities, ηr, of the solutions. Conductivity measurements of intermediate precision gave values of the limiting equivalent conductivities of the electrolytes for use in the calculation of A, above. To 50% alcohol, the equivalent conductances of the ions could be established accurately using transport numbers from another investigation. To 30% alcohol the Jones–Dole equation was obeyed by all the electrolytes except Li+Cl–, where an additional term Dc2, with small positive values of D, was required. For mixtures containing 50%(w/w) alcohol or more, the Jones–Dole equation was of the correct form to represent the ηr, but the values of A required were larger than the theoretical ones; the conductivity measurements indicated that the electrolytes were associated in these mixtures. The values of the ion-pair dissociation constants, determined from the conductivity measurements, were about those expected from Bjerrum theory; they were used to calculate the degree of dissociation α of the ion pairs. Values of Bi, referring to the free ions, were obtained by fitting the ηr to the equation ηr= 1 +A(αc)½+Biαc+Bp(1 –α)c in which Bp is the corresponding coefficient for the ion pairs. Values of the partial molal volumes of the electrolytes at infinite dilution in the various solvent mixtures were obtained from the density measurements. The densities and viscosities of the mixtures are recorded.

The molar contributions of the electrolyte Δµ⊖≠3, Δtext-decoration:overlineH⊖≠3 and Δtext-decoration:overlineS⊖≠3 to the activation parameters for viscous flow of the ternary systems propan-1-ol-water–electrolyte are analysed in terms of the new approach given in the first part of this series. The thermodynamic activation parameters for the binary solvent system are first briefly discussed. The excess enthalpy for the transition state is calculated and resolved into the corresponding partial molar enthalpies; these functions are compared with the corresponding ground-state functions. The thermodynamics and quasi-thermodynamics are consistent with the retention of an aqueous structure as propanol is added to water, up to a volume fraction ϕ2 of ca. 0.25, followed by a breakdown to a structure of lower order. The mean entropy of activation Δtext-decoration:overlineS≠12 passes through a maximum at ϕ2 of ca. 0.25 and is taken as a measure of the extent to which the transition-state mixtures are in turn broken down with respect to the ground state. Minima in Δµ⊖≠3 near ϕ2≈ 0.25 are observed for all the salts at both temperatures. In solvents having an aqueous type of structure, coordination of the ions is incomplete in the ground state but increases in the less strongly bonded transition state; the increase in coordination is a maximum and Δµ⊖≠3 a minimum when the transition-state mixed solvent is most broken up with respect to the ground-state solvent. The minima are least pronounced and at lowest ϕ2 for the chloride of the strongly coordinating Li+. For ϕ2 > 0.25 the Δµ⊖≠3 increase to the values characteristic of typical non-aqueous solvents, in which ground-state coordination is complete and formation of the transition state is characterised by breaking rather than making ion–solvent bonds. The enthalpies of transfer of the electrolytes in the transition state, ΔH⊖′t, are related to the thermodynamics of the transition-state solvent by the theory of de Valera, Feakins and Waghorne. Though crude, the approach shows why the minima in Δtext-decoration:overlineH⊖≠3, unlike those in Δµ⊖≠3, occur at widely different ϕ2 for different electrolytes, and demonstrates the power of considering the special properties of the solvent in the transition state.