Role of apoptosis in the pathogenesis of COPD and pulmonary emphysema

Carbon nanoparticles induce ceramide- and lipid raft-dependent signalling in lung epithelial cells: a target for a preventive strategy against environmentally-induced lung inflammation

Background

Particulate air pollution in lung epithelial cells induces pathogenic endpoints like proliferation, apoptosis, and pro-inflammatory reactions. The activation of the epidermal growth factor receptor (EGFR) is a key event responsible for signalling events involving mitogen activated protein kinases specific for these endpoints. The molecular events leading to receptor activation however are not well understood. These events are relevant for the toxicological evaluation of inhalable particles as well as for potential preventive strategies in situations when particulate air pollution cannot be avoided. The current study therefore had the objective to elucidate membrane-coupled events leading to EGFR activation and the subsequent signalling cascade in lung epithelial cells. Furthermore, we aimed to identify the molecular target of ectoine, a biophysical active substance which we described to prevent carbon nanoparticle-induced lung inflammation.

Methods

Membrane signalling events were investigated in isolated lipid rafts from lung epithelial cells with regard to lipid and protein content of the signalling platforms. Using positive and negative intervention approaches, lipid raft changes, subsequent signalling events, and lung inflammation were investigated in vitro in lung epithelial cells (RLE-6TN) and in vivo in exposed animals.

Results

Carbon nanoparticle treatment specifically led to an accumulation of ceramides in lipid rafts. Detailed analyses demonstrated a causal link of ceramides and subsequent EGFR activation coupled with a loss of the receptor in the lipid raft fractions. In vitro and in vivo investigations demonstrate the relevance of these events for carbon nanoparticle-induced lung inflammation. Moreover, the compatible solute ectoine was able to prevent ceramide-mediated EGFR phosphorylation and subsequent signalling as well as lung inflammation in vivo.

Conclusion

The data identify a so far unknown event in pro-inflammatory signalling and contribute to the understanding of particle cell interaction and therefore to risk identification and risk assessment of inhalable xenobiotics. Moreover, as this cellular reaction can be prevented by the well tolerated substance ectoine, a molecular preventive strategy for susceptible persons against airway inflammation is proposed.

Intraperitoneal injection of cigarette smoke extract induced emphysema, and injury of cardiac and skeletal muscles in BALB/C mice

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a chronic, progressive, airway disease. In order to recognize mechanisms of COPD, various types of COPD animal models have been established, and the pathogenesis are different. The present study was designed to establish a COPD animal model by intraperitoneal injection of cigarette smoke extract (CSE) in BALB/C mice.

METHODS

Mice were injected intraperitoneally with PBS/CSE and sacrificed at day 28. Pulmonary function, pathology of lung tissue, morphology of hearts and skeletal muscle, leukocytes count and antioxidant activity of bronchoalveolar lavage fluid (BALF), pulmonary parenchymal apoptosis index (AI), expression of cleaved caspase-3, expression of MMP-2 and MMP-9 mRNA, and activity of MMP-2 and MMP-9 in lung tissue were measured.

RESULTS

Intraperitoneal injection of CSE induced pulmonary parenchymal destruction, pulmonary function reduction, leukocytes count, injury of cardiac and peripheral muscles, and increased pulmonary parenchymal AI, cleaved caspase-3 protein, expression of MMP-2 and MMP-9 mRNA, activity of MMP-2 and MMP-9 protein in lung tissue, and suppressed antioxidant activity in BALF (P < 0.05).

CONCLUSIONS

Intraperitoneal injection of CSE produced emphysema, pulmonary parenchymal apoptosis, and injury of cardiac and skeletal muscles in mice. All pathobiologically relevant mechanisms in this model are shared with the COPD patients.

Histone deacetylase (HDAC) 1 controls the expression of beta defensin 1 in human lung epithelial cells

Deregulation of the expression human beta defensin 1 (DEFB1), an antimicrobial peptide, has been implicated in the pathogenesis of COPD and asthma. Since the molecular mechanisms that regulate DEFB1 gene expression are widely unknown, the epigenetic processes involved in the regulation of the constitutive expression of DEFB1 in lung epithelial cells (A549) were investigated. The data demonstrate that histone deacetylases (HDACs) participate in the regulation of DEFB1 gene expression. Inhibition of the class I HDACs, HDACs 1-3, increases DEFB1 gene expression in A549 cells. Chromatin immunoprecipitation (ChIP) assays revealed that the inhibition of the class I HDACs also results in modifications of the chromatin at the DEFB1 promoter. Histone modifications, histone H3 acetylation and H3K4 trimethylation, that are associated with transcriptional activation, were found to increase after inhibition of HDACs 1-3. Finally, RNAi knockdown experiments identified HDAC1 as the sole HDAC responsible for maintaining the constitutive level of DEFB1 transcription. Taken together, our data reveal epigenetic mechanisms which are the basis of the maintenance of the constitutive gene expression of human beta defensin 1.

Beraprost sodium attenuates cigarette smoke extract-induced apoptosis in vascular endothelial cells

Apoptosis is now widely recognized as an important part of chronic obstructive pulmonary disease (COPD) pathogenesis. Our previous study demonstrated that a prostacyclin (PGI(2)) analogue (beraprost sodium, BPS) prevented cigarette smoke extract (CSE) induced apoptosis of the pulmonary endothelium in rats. So we determined to clarify the apoptosis of vascular endothelial cells in COPD patient and the role of prostacyclin in the protection against apoptosis in vascular endothelial cells induced by CSE. Surgical specimens were obtained from 12 patients with COPD and 10 controls, and the level of apoptosis, prostacyclin synthase (PGI(2)S) expression and 6-keto-PGF1α (a stable metabolite of PGI(2)) were detected. The apoptotic index (AI), caspase-3 activity, expression of caspase-3 and 6-keto-PGF1α were examined in human umbilical vein endothelial cells (HUVECs) under exposure to varied concentrations of CSE for 24 h as well as under exposure to 2.5 % CSE for varied durations. Then, HUVECs under 2.5 % CSE were exposed to varied concentrations of BPS for 24 h and observed the alteration and the level of cAMP. Increased AI, decreased expression of PGI(2)S and 6-keto-PGF1α, were found in the lungs of patients with COPD compared with controls. Moreover, CSE induced apoptosis in means of both dose-dependent and time-dependent manners, and reduced the level of 6-keto-PGF1α in HUVECs. And with the treatment of BPS, an enhanced level of cAMP and decreased apoptosis were detected. The deficiency of PGI(2) critically contributes to the COPD-associated endothelial dysfunction and apoptosis. And BPS protects against the apoptosis in the vascular endothelial cells induced by CSE.

The role of small heat-shock protein αB-crystalline (HspB5) in COPD pathogenesis

Background

αB-crystallin (HspB5) is a chaperone whose role as a marker of innate immunity activation as well as its therapeutic potential have recently been investigated in several inflammatory diseases: multiple sclerosis, myocardial ischemia, and Guillain–Barré syndrome.

Aim

The aim of this study is to determine the role of αB-crystallin in chronic obstructive pulmonary disease (COPD) pathogenesis and inflammation.

Materials

Plasma levels of αB-crystallin were studied in 163 patients: 52 healthy non-COPD smokers; 20 COPD smokers in Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages I–II; 43 COPD smokers in GOLD stages III-IV. Forty-eight patients were diagnosed with acute inflammatory respiratory disease. The plasma levels of αB-crystallin antibodies were determined by an enzyme-linked immunosorbent assay (Calbiochem), and were confirmed with Western blotting. Tissue expression of the protein was compared in three different groups of patients: COPD smokers, COPD nonsmokers, and in patients with age-related emphysema.

Results

The mean level of anti-αB-crystallin antibodies in non-COPD smokers was 0.291nm. In COPD smokers it was 0.352 nm and, in patients with inflammatory lung diseases, 0.433 nm. There was a statistically significant difference between COPD smokers and healthy non-COPD smokers (P = 0.010). The same could be observed comparing the group of patients with acute inflammation and non-COPD healthy smokers (P = 0.007). There was no statistically significant difference between patients with mild/moderate inflammation and those with severe COPD. Tissue detection of the protein showed that it was significantly overexpressed in COPD smokers in comparison to COPD nonsmokers and was only slightly expressed in patients with age-related emphysema.

Conclusion

αB-crystallin is increased in patients with inflammatory lung diseases. Though unspecific, it could be used in a panel of markers discerning COPD smokers from healthy nonsmokers. As αB-crystallin is a regulator of innate immunity and a therapeutic anti-inflammatory agent, its exact role in COPD pathogenesis and therapy should be explored further.

Salubrinal protects against cigarette smoke extract-induced HBEpC apoptosis likely via regulating the activity of PERK-eIF2α signaling pathway

BACKGROUND AND AIMS

Endoplasmic reticulum (ER) stress plays an important role in cigarette smoke extract (CSE)-induced apoptotic cell death, which is an important pathogenic factor of chronic obstructive pulmonary disease (COPD). The aim of this study was to explore the role of the PERK-eIF2 pathway in CSE-induced human bronchial epithelial (HBE) cell apoptosis and to evaluate the protective effects and possible mechanism of salubrinal (Sal) on CSE-induced HBE cell apoptosis.

METHODS

Normal human bronchial epithelial cells (HBEpC) were cultured and then treated with CSE alone or together with Sal or preincubated with or without PERK siRNA. Expressions of p-PERK/PERK, p-eIF2α/eIF2α, and caspase 3 and 4 were detected with PCR, Western blot, and immunofluorescence. Apoptosis was detected using AnnexinV-PI flow cytometry.

RESULTS

CSE induced apoptotic cell death and caused a dynamic change in PERK-eIF2α pathway activity following the course of CSE exposure. The knockdown of PERK suppressed the expression of both PERK and p-eIF2a and caused a great increase in cell apoptosis. Sal could eliminate the effects of PERK knockdown, protecting the cells against the CSE insult, and this protection was accomplished through maintaining the homeostasis of PERK- eIF2α pathway.

CONCLUSIONS

PERK-eIF2α pathway mediates the CSE-induced HBE cell apoptosis. The intactness of PERK-eIF2α pathway is crucial for HBE cell survival under CSE insult. Sal can protect against CSE-induced HBE cell apoptosis, and this effect is likely achieved through maintaining the homeostasis of PERK- eIF2α pathway.

Ceramide expression and cell homeostasis in chronic obstructive pulmonary disease

BACKGROUND

Increased expression of ceramide has been detected in emphysema. Ceramide promotes autophagy and apoptosis, which concur with cellular homeostasis.

OBJECTIVES

To determine whether ceramide expression is associated with the development of chronic obstructive pulmonary disease (COPD) and with altered cellular homeostasis in lung parenchyma.

METHODS

We studied 10 subjects with severe COPD, 13 with mild/moderate COPD, 11 with idiopathic pulmonary fibrosis (IPF), 12 non-COPD smokers, and 11 nonsmoking controls. The immunoreactivity for ceramide along with markers of autophagy (LC3B), apoptosis (cleaved caspase-3), and cell proliferation (MIB1) was quantified in alveolar walls.

RESULTS

Ceramide expression was increased in COPD patients compared with control smokers and was related to the impairment of gas exchange but not to the degree of airflow limitation. In COPD, an important activation of apoptosis and autophagy pathways was observed, particularly in patients with severe disease, that was not counterbalanced by cell proliferation. Upregulation of ceramide was observed even in subjects with IPF in whom activation of apoptosis and autophagy was negligible and cell proliferation was instead the most prominent feature.

CONCLUSIONS

Ceramide expression, which is increased in COPD and even more so in IPF, appears to be neither specific nor related to COPD severity, probably representing a broader marker of lung damage. In contrast, apoptosis and autophagy are characteristics of the COPD pathology, particularly in its most severe stage.

Longitudinal study of spatially heterogeneous emphysema progression in current smokers with chronic obstructive pulmonary disease

BACKGROUND

Cigarette smoke is the main risk factor for emphysema, which is a key pathology in chronic obstructive pulmonary disease (COPD). Low attenuation areas (LAA) in computed tomography (CT) images reflect emphysema, and the cumulative size distribution of LAA clusters follows a power law characterized by the exponent D. This property of LAA clusters can be explained by model simulation, where mechanical force breaks alveolar walls causing local heterogeneous lung tissue destruction. However, a longitudinal CT study has not investigated whether continuous smoking causes the spatially heterogeneous progression of emphysema.

METHODS

We measured annual changes in ratios of LAA (LAA%), D and numbers of LAA clusters (LAN) in CT images acquired at intervals of ≥ 3 years from 22 current and 31 former smokers with COPD to assess emphysema progression. We constructed model simulations using CT images to morphologically interpret changes in current smokers.

RESULTS

D was decreased in current and former smokers, whereas LAA% and LAN were increased only in current smokers. The annual changes in LAA%, D, and LAN were greater in current, than in former smokers (1.03 vs. 0.37%, p=0.008; -0.045 vs. -0.01, p=0.004; 13.9 vs. 1.1, p=0.007, respectively). When LAA% increased in model simulations, the coalescence of neighboring LAA clusters decreased D, but the combination of changes in D and LAN in current smokers could not be explained by the homogeneous emphysema progression model despite cluster coalescence. Conversely, a model in which LAAs heterogeneously increased and LAA clusters merged somewhat in relatively advanced emphysematous regions could reflect actual changes.

CONCLUSIONS

Susceptibility to parenchymal destruction induced by continuous smoking is not uniform over the lung, but might be higher in local regions of relatively advanced emphysema. These could result in the spatially heterogeneous progression of emphysema in current smokers.

Potential significance of telocytes in the pathogenesis of lung diseases

Multiple cells play critical roles in the pathogenesis of lung diseases, even though the exact mechanisms are still not clear. Telocytes are characterized by telopodes, which are thin and long prolongations, and a small amount of cytoplasm rich with mitochondria, as shown by immune-positive staining against CD34, c-kit and vimentin. Telocytes have been found in many organs of mammals, including the trachea and lung. This report summarizes the latest findings associated with telocytes, with a special focus on the lung, and demonstrates that telocytes exist in the smooth muscle layer under cartilage and bronchiole in the lung, and also in the interstitial space of alveoli. Telocytes have a mediate connection with epithelial cells and direct connection with smooth muscle cells both in blood vessels and bronchiole in the lung. Telocytes also have a close relationship with other cell types, such as immune cells and stem cells. Telopodes appear with dichotomous branching and alternation of podom and podomer, forming a 3D network structure with complex homo- and hetero-cellular junctions. All characteristics of telocytes in lung tissue indicate that telocytes may play a potential, but important, role in the pathogenesis of lung diseases.

Effect of cigarette smoke exposure and structural modifications on the α-1 Antitrypsin interaction with caspases

α-1 Antitrypsin (A1AT) is a serpin with a major protective effect against cigarette smoke-induced emphysema development, and patients with mutations of the A1AT gene display a markedly increased risk for developing emphysema. We reported that A1AT protects lung endothelial cells from apoptosis and inhibits caspase-3 activity. It is not clear if cigarette smoking or A1AT mutations alter the caspase-3 inhibitory activity of A1AT and if this serpin alters the function of other caspases. We tested the hypothesis that the caspase-3 inhibitory activity of A1AT is impaired by cigarette smoking and that the A1AT RCL, the key antiprotease domain of the serpin, is required for its interaction with the caspase. We examined the caspase-3 inhibitory activity of human A1AT purified from plasma of actively smoking and nonsmoking individuals, either affected or unaffected with chronic obstructive pulmonary disease. We also tested the caspase inhibitory activity of two mutant forms of A1AT, the recombinant human piZZ and the RCL-deleted (RCL-null) A1AT forms. A1AT purified from the blood of active smokers exhibited marked attenuation in its caspase-3 inhibitory activity, independent of disease status. In vitro exposure of the normal (MM) form of A1AT to cigarette smoke extract reduced its ability to interact with caspase-3, measured by isothermal titration calorimetry, as did the deletion of the RCL, but not the ZZ point mutation. In cell-free assays A1AT was capable of inhibiting all executioner caspases, -3, -7 and especially -6, but not the initiator or inflammatory caspases. The inhibitory effect of A1AT against caspase-6 was tested in vivo, where overexpression of both human MM and ZZ-A1AT via adeno-associated virus transduction significantly protected against apoptosis and against airspace damage induced by intratracheal instillation of caspase-6 in mice. These data indicate a specific inhibitory effect of A1AT on executioner caspases, which is profoundly attenuated by active exposure to cigarette smoking and is dependent on the protein RCL, but is not affected by the PiZZ mutation.

Deregulated Stat3 signaling dissociates pulmonary inflammation from emphysema in gp130 mutant mice

Interleukin (IL)-6 is a potent immunomodulatory cytokine that is associated with emphysema, a major component of chronic obstructive pulmonary disease (COPD). IL-6 signaling via the gp130 coreceptor is coupled to multiple signaling pathways, especially the latent transcription factor signal transducer and activator of transcription (Stat)3. However, the pathological role of endogenous gp130-dependent Stat3 activation in emphysema is ill defined. To elucidate the role of the IL-6/gp130/Stat3 signaling axis in the cellular and molecular pathogenesis of emphysema, we employed a genetic complementation strategy using emphysematous gp130F/F mice displaying hyperactivation of endogenous Stat3 that were interbred with mice to impede Stat3 activity. Resected human lung tissue from patients with COPD and COPD-free individuals was also evaluated by immunohistochemistry. Genetic reduction of Stat3 hyperactivity in gp130F/F: Stat3 −/+ mice prevented lung inflammation and excessive protease activity; however, emphysema still developed. In support of these findings, Stat3 activation levels in human lung tissue correlated with the extent of pulmonary inflammation but not airflow obstruction in COPD. Furthermore, COPD lung tissue displayed increased levels of IL-6 and apoptotic alveolar cells, supporting our previous observation that increased endogenous IL-6 expression in the lungs of gp130F/F mice contributes to emphysema by promoting alveolar cell apoptosis. Collectively, our data suggest that IL-6 promotes emphysema via upregulation of Stat3-independent apoptosis, whereas IL-6 induction of lung inflammation occurs via Stat3. We propose that while discrete targeting of Stat3 may alleviate pulmonary inflammation, global targeting of IL-6 potentially represents a therapeutically advantageous approach to combat COPD phenotypes where emphysema predominates.

Piclamilast inhibits the pro-apoptotic and anti-proliferative responses of A549 cells exposed to H(2)O(2) via mechanisms involving AP-1 activation

AIMS

Reactive oxygen species (ROS) are involved in the pathogenesis of many inflammatory diseases such as chronic obstructive pulmonary disease (COPD). They can alter the expression of genes involved in cellular damage by activating transcription factors, including the NF-κB and the activator protein 1 (AP-1). Phosphodiesterase type 4 (PDE4) inhibitors have anti-inflammatory and antioxidant effects, as described in in vivo and in vitro COPD models. This study analysed the effects of piclamilast, a selective PDE4 inhibitor, on modulating the global gene expression profile in A549 cells exposed to H(2)O(2).

MAIN METHODS

Changes in gene expression were analysed using high-density Affymetrix microarrays and validated by RT-PCR. Cell proliferation was studied using BrdU incorporation. Apoptosis was assessed by flow cytometry using annexin V-fluorescein isothiocyanate. C-Jun phosphorylation and AP-1 activation were determined by ELISA and luciferase assay, respectively.

KEY FINDINGS

Our results indicate that H(2)O(2) modified the expression of several genes related to apoptosis, cell cycle control and cell signalling, including IL8, FAS, HIG2, CXCL2, CDKN25 and JUNB. Piclamilast pre-treatment significantly inhibited the changes in 23 genes via mechanisms involving AP-1 activation and c-Jun phosphorylation at Ser63. Functional experiments confirmed our results, suggesting new targets related to the antioxidant properties of PDE4 inhibitors.

SIGNIFICANCE

This is the first study to demonstrate antioxidant effects of a selective PDE4 inhibitor at the global gene expression level, and the results support the importance of AP-1 as a key regulator of the expression of genes involved in the inflammatory response of epithelial cells to oxidative damage.

Imbalance of apoptosis and cell proliferation contributes to the development and persistence of emphysema

BACKGROUND

We postulate that in adults there is an established lung structure maintenance program and that lung alveolar septal cells are undergoing both continuous apoptosis and proliferation. Whereas lung cell apoptosis has been recognized in human emphysema, little is known about cell proliferation.

METHODS

Using a novel rat model of emphysema, induced by intratracheal instillation of cigarette smoke extract (CSE), we investigated the dynamics of emphysematous lung destruction. Emphysematous lung destruction was determined by measuring mean linear intercept and destructive index. Lung injury and repair were assessed by immunohistochemistry and Western blot analysis for active caspase-3 and proliferating cell nuclear antigen (PCNA) after 4, 8, and 12 weeks of CSE instillations.

RESULTS

The emphysematous lung tissue destruction was present at 4 weeks of CSE treatment and progressed to 8 weeks. Spontaneous repair began at 12 weeks. Treatment with a peroxisome proliferator activated receptor (PPAR)α+γ agonist or granulocyte and macrophage-colony stimulating factor (GM-CSF) for 4 weeks prevented the progression of emphysematous lung destruction and decreased the number of caspase-3-positive cells.

CONCLUSION

Apoptosis and cell proliferation occur in this new model of emphysema. Treatment with a PPARα+γ agonist or GM-CSF can inhibit the progression of emphysematous alveolar septal destruction by decreasing alveolar cell apoptosis.

Genetic ablation of the aryl hydrocarbon receptor causes cigarette smoke-induced mitochondrial dysfunction and apoptosis

Cigarette smoke is the primary risk factor for chronic obstructive pulmonary disease (COPD). Alterations in the balance between apoptosis and proliferation are involved in the etiology of COPD. Fibroblasts and epithelial cells are sensitive to the oxidative properties of cigarette smoke, and whose loss may precipitate the development of COPD. Fibroblasts express the aryl hydrocarbon receptor (AhR), a transcription factor that attenuates pulmonary inflammation and may also regulate apoptosis. We hypothesized the AhR would prevent apoptosis caused by cigarette smoke. Using genetically deleted in vitro AhR expression models and an established method of cigarette smoke exposure, we report that AhR expression regulates fibroblasts proliferation and prevents morphological features of apoptosis, including membrane blebbing and chromatin condensation caused by cigarette smoke extract (CSE). Absence of AhR expression results in cleavage of PARP, lamin, and caspase-3. Mitochondrial dysfunction, including cytochrome c release, was associated with loss of AhR expression, indicating activation of the intrinsic apoptotic cascade. Heightened sensitivity of AhR-deficient fibroblasts was not the result of alterations in GSH, Nrf2, or HO-1 expression. Instead, AhR(-/-) cells had significantly less MnSOD and CuZn-SOD expression, enzymes that protects against oxidative stress. The ability of the AhR to suppress apoptosis was not restricted to fibroblasts, as siRNA-mediated knockdown of the AhR in lung epithelial cells also increased sensitivity to smoke-induced apoptosis. Collectively, these results suggest that cigarette smoke induced loss of lung structural support (i.e. fibroblasts, epithelial cells) caused by aberrations in AhR expression may explain why some smokers develop lung diseases such as COPD.

The role of endoplasmic reticulum stress in emphysema results from cigarette smoke exposure

Apoptosis is of considerable importance in the pathogenesis of emphysema, and recent studies show that endoplasmic reticulum (ER) stress is involved in emphysema. In our research, we investigated the role of protein kinase RNA (PKR)-like ER kinase (PERK)/ eukaryotic initiation factor 2 alpha (eIF2α) pathway, the CCAAT enhancer-binding protein-homologous protein (CHOP) expression, caspase-12 activation and apoptosis in emphysema results from cigarette smoke (CS) exposure. Expression of phosphorylated-PERK (p-PERK), phospholated-eIF2α (p-eIF2α),CHOP and caspase-12 as well as the apoptosis rate are remarkably increased in rats after exposure to 2 months CS compared with control rats, significantly elevated in rats exposed to 4 months CS over rats exposed only to 2 months CS, and slightly decreased in ex-smoking rats in contrast to rats exposed to 4 months CS. Taken together, our results show that CS induces ER stress in lung epithelial cells, which may subsequently lead to lung injury in rats, and this might be a novel target for protection of pulmonary epithelial cells from ER stress injury in emphysema.

HIV and chronic obstructive pulmonary disease: is it worse and why?

Smoking-related diseases, such as chronic obstructive pulmonary disease (COPD), are of particular concern in the HIV-infected population. Smoking rates are high in this population, and long-term exposure to cigarette smoke in the setting of HIV infection may increase the number of complications seen. Before the era of combination antiretroviral therapy, HIV-infected persons were noted to have an accelerated form of COPD, with significant emphysematous disease seen in individuals less than 40 years old. Unlike many of the AIDS-defining opportunistic infections, HIV-associated COPD may be more common in the current era of HIV because it is frequently reported in patients without a history of AIDS-related pulmonary complications and because many aging HIV-infected individuals have had a longer exposure to smoking and HIV. In this review, we document the epidemiology of HIV-associated COPD before and after the institution of combination antiretroviral therapy, review data suggesting that COPD is accelerated in those with HIV, and discuss possible mechanisms of HIV-associated COPD, including an increased susceptibility to chronic, latent infections; an aberrant inflammatory response; altered oxidant-antioxidant balance; increased apoptosis associated with HIV; and the effects of antiretroviral therapy.

Molecular and cellular mechanism of lung injuries due to exposure to sulfur mustard: a review

Sulfur mustard (SM), a potent chemical weapon agent, was used by Iraqi forces against Iranian in the Iraq-Iran war (1981-1989). Chronic obstructive pulmonary disease (COPD) is a late toxic pulmonary consequence after SM exposure. The COPD observed in these patients is unique (described as Mustard Lung) and to some extent different from COPD resulted from other well-known causes. Several mechanisms have been hypothesized to contribute to the pathogenesis of COPD including oxidative stress, disruption of the balance between apoptosis and replenishment, proteinase-antiproteinase imbalance and inflammation. However, it is not obvious which of these pathways are relevant to the pathogenesis of mustard lung. In this paper, we reviewed studies addressing the pathogenicity of mustard lung, and reduced some recent ambiguities in this field. There is ample evidence in favor of crucial role of both oxidative stress and apoptosis as two known mechanisms that are more involved in pathogenesis of mustard lung comparing to COPD. However, according to available evidences there are no such considerable data supporting neither proteolytic activity nor inflammation mechanism as the main underlying pathogenesis in Mustard Lung.

New insights into the immunology of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a heterogeneous syndrome associated with abnormal inflammatory immune responses of the lung to noxious particles and gases. Cigarette smoke activates innate immune cells such as epithelial cells and macrophages by triggering pattern recognition receptors, either directly or indirectly via the release of damage-associated molecular patterns from stressed or dying cells. Activated dendritic cells induce adaptive immune responses encompassing T helper (Th1 and Th17) CD4+ T cells, CD8+ cytotoxicity, and B-cell responses, which lead to the development of lymphoid follicles on chronic inflammation. Viral and bacterial infections not only cause acute exacerbations of COPD, but also amplify and perpetuate chronic inflammation in stable COPD via pathogen-associated molecular patterns. We discuss the role of autoimmunity (autoantibodies), remodelling, extracellular matrix-derived fragments, impaired innate lung defences, oxidative stress, hypoxia, and dysregulation of microRNAs in the persistence of the pulmonary inflammation despite smoking cessation.

Pathogenic triad in COPD: oxidative stress, protease-antiprotease imbalance, and inflammation

Patients with chronic obstructive pulmonary disease (COPD) exhibit dominant features of chronic bronchitis, emphysema, and/or asthma, with a common phenotype of airflow obstruction. COPD pulmonary physiology reflects the sum of pathological changes in COPD, which can occur in large central airways, small peripheral airways, and the lung parenchyma. Quantitative or high-resolution computed tomography is used as a surrogate measure for assessment of disease progression. Different biological or molecular markers have been reported that reflect the mechanistic or pathogenic triad of inflammation, proteases, and oxidants and correspond to the different aspects of COPD histopathology. Similar to the pathogenic triad markers, genetic variations or polymorphisms have also been linked to COPD-associated inflammation, protease–antiprotease imbalance, and oxidative stress. Furthermore, in recent years, there have been reports identifying aging-associated mechanistic markers as downstream consequences of the pathogenic triad in the lungs from COPD patients. For this review, the authors have limited their discussion to a review of mechanistic markers and genetic variations and their association with COPD histopathology and disease status.

Increased expression of beta-defensin 1 (DEFB1) in chronic obstructive pulmonary disease

On-going airway inflammation is characteristic for the pathophysiology of chronic obstructive pulmonary disease (COPD). However, the key factors determining the decrease in lung function, an important clinical parameter of COPD, are not clear. Genome-wide linkage analyses provide evidence for significant linkage to airway obstruction susceptibility loci on chromosome 8p23, the location of the human defensin gene cluster. Moreover, a genetic variation in the defensin beta 1 (DEFB1) gene was found to be associated with COPD. Therefore, we hypothesized that DEFB1 is differently regulated and expressed in human lungs during COPD progression. Gene expression of DEFB1 was assessed in bronchial epithelium and BAL fluid cells of healthy controls and patients with COPD and using bisulfite sequencing and ChIP analysis, the epigenetic control of DEFB1 mRNA expression was investigated. We can demonstrate that DEFB1 mRNA expression was significantly increased in bronchopulmonary specimen of patients with COPD (n = 34) vs. healthy controls (n = 10) (p<0.0001). Furthermore, a significant correlation could be detected between DEFB1 and functional parameters such as FEV₁ (p = 0.0024) and the FEV₁/VC ratio (p = 0.0005). Upregulation of DEFB1 mRNA was paralleled by changes in HDAC1-3, HDAC5 and HDAC8 mRNA expression. Whereas bisulfite sequencing revealed no differences in the methylation state of DEFB1 promoter between patients with COPD and controls, ChIP analysis showed that enhanced DEFB1 mRNA expression was associated with the establishment of an active histone code. Thus, expression of human DEFB1 is upregulated and related to the decrease in pulmonary function in patients with COPD.

Effect of cigarette smoke and dexamethasone on Hsp72 system of alveolar epithelial cells

Smoking is the leading risk factor of chronic obstructive pulmonary disease (COPD) and lung cancer. Corticosteroids are abundantly used in these patients; however, the interaction of smoking and steroid treatment is not fully understood. Heat shock proteins (Hsps) play a central role in the maintenance of cell integrity, apoptosis and cellular steroid action. To better understand cigarette smoke-steroid interaction, we examined the effect of cigarette smoke extract (CSE) and/or dexamethasone (DEX) on changes of intracellular heat shock protein-72 (Hsp72) in lung cells. Alveolar epithelial cells (A549) were exposed to increasing doses (0; 0.1; 1; and 10 μM/μl) of DEX in the medium in the absence(C) and presence of CSE. Apoptosis, necrosis, Hsp72 messenger-ribonucleic acid (mRNA) and protein expression of cells were measured, and the role of Hsp72 on steroid effect examined. CSE reduced the number of viable cells by significantly increasing the number of apoptotic and necrotic cells. DEX dose-dependently decreased the ratio of apoptosis when CSE was administered, without change in necrosis. CSE - DEX co-treatment dose-dependently increased Hsp72 mRNA and protein expression, with the highest level measured in CSE + DEX (10) cells, while significantly lower levels were noted in all respective C groups. Pretreatment with Hsp72 silencing RNA confirmed that increased survival observed following DEX administration in CSE-treated cells was mainly mediated via the Hsp72 system. CSE significantly decreases cell survival by inducing apoptosis and necrosis. DEX significantly increases Hsp72 mRNA and protein expression only in the presence of CSE resulting in increased cellular protection and survival. DEX exerts its cell protective effects by decreasing apoptotic cell death via the Hsp72 system in CSE-treated alveolar epithelial cells.

Therapeutic effect of lecithinized superoxide dismutase on pulmonary emphysema

No medication exists that clearly improves the mortality of chronic obstructive pulmonary disease (COPD). Oxidative molecules, in particular superoxide anions, play important roles in the COPD-associated abnormal inflammatory response and pulmonary emphysema, which arises because of an imbalance in proteases and antiproteases and increased apoptosis. Superoxide dismutase (SOD) catalyzes the dismutation of superoxide anions. Lecithinized human Cu/Zn- SOD (PC-SOD) has overcome a number of the clinical limitations of SOD, including low tissue affinity and low stability in plasma. In this study, we examine the effect of PC-SOD on elastase-induced pulmonary emphysema, an animal model of COPD. The severity of the pulmonary inflammatory response and emphysema in mice was assessed by various criteria, such as the number of leukocytes in the bronchoalveolar lavage fluid and the enlargement of airspace. Not only intravenous administration but also inhalation of PC-SOD suppressed elastase-induced pulmonary inflammation, emphysema, and dysfunction. Inhalation of PC-SOD suppressed the elastase-induced increase in the pulmonary level of superoxide anions and apoptosis. Inhalation of PC-SOD also suppressed elastase-induced activation of proteases and decreased in the level of antiproteases and expression of proinflammatory cytokines and chemokines. We also found that inhalation of PC-SOD suppressed cigarette smoke-induced pulmonary inflammation. The results suggest that PC-SOD protects against pulmonary emphysema by decreasing the pulmonary level of superoxide anions, resulting in the inhibition of inflammation and apoptosis and amelioration of the protease/antiprotease imbalance. We propose that inhalation of PC-SOD would be therapeutically beneficial for COPD.

Critical role of CFTR-dependent lipid rafts in cigarette smoke-induced lung epithelial injury

Apoptosis of lung epithelial and endothelial cells by exposure to cigarette smoke (CS) severely damages the lung tissue, leading to the pathogenesis of emphysema, but the underlying mechanisms are poorly understood. We have recently established a direct correlation between decreased lipid raft CFTR expression and emphysema progression through increased ceramide accumulation. In the present work, we investigated the role of membrane CFTR in regulating apoptosis and autophagy responses to CS exposure. We report a constitutive and CS-induced increase in the number of TUNEL-positive apoptotic cells in Cftr(-/-) murine lungs compared with Cftr(+/+) murine lungs that also correlated with a concurrent increase in the expression of ceramide, NF-κB, CD95/Fas, lipid raft proteins, and zonula occludens (ZO)-1/2 (P < 0.001). We also verified that stable wild-type CFTR expression in CFBE41o(-) cells controls constitutively elevated caspase-3/7 activity (-1.6-fold, P < 0.001). Our data suggest that membrane CFTR regulates ceramide-enriched lipid raft signaling platforms required for the induction of Fas-mediated apoptotic signaling. In addition, lack of membrane CFTR also modulates autophagy, as demonstrated by the significant increase in constitutive (P < 0.001) and CSE-induced (P < 0.005) perinuclear accumulation of green fluorescent protein-microtubule-associated protein 1 light chain-3 (LC3) in the absence of membrane CFTR (CFBE41o(-) cells). The significant constitutive and CS-induced increase (P < 0.05) in p62 and LC3β expression in CFTR-deficient cells and mice corroborates these findings and suggest a defective autophagy response in the absence of membrane CFTR. Our data demonstrate the critical role of membrane-localized CFTR in regulating apoptotic and autophagic responses in CS-induced lung injury that may be involved in the pathogenesis of severe emphysema.

CT emphysema predicts thoracic aortic calcification in smokers with and without COPD

COPD patients are at increased risk for cardiovascular morbidity and mortality independent of smoking habits. Recent studies suggest CT emphysema is an independent predictor of cardiovascular risk as evidenced by its association with arterial stiffness and impaired endothelial function. We examined the relationship between demographics, lung function, CT emphysema and airway wall thickness and thoracic aortic calcification, another marker of cardiovascular risk, in the National Lung Screening Trial. We hypothesized that CT emphysema would be independently associated with thoracic aortic calcification. Two hundred forty current and former smokers were enrolled. After CT examination, we recorded subjects' demographics and they performed spirometry. Subjects were classified into COPD and non-COPD subgroups. CT emphysema was quantified as a percentage of lung volume and measurements of the right upper lobe airway were performed using standard methods and expressed as wall area (%). Total calcification scores for the thoracic aorta were computed using TeraRecon image analysis. Univariate and multivariate analyses were performed to determine the associations between calcium score and subject characteristics. Subjects with COPD were older, more often male, heavier smokers and had more CT emphysema and greater aortic calcification than those without COPD. Calcium score was associated with age, pack-years, CT emphysema, wall area%, and lung function on univariate testing but only with age and CT emphysema on multivariate analysis. We conclude that CT emphysema is independently associated with thoracic calcification and thus may be used to assess cardiovascular risk in smokers with and without COPD.

Nitrative stress in inflammatory lung diseases

Since the discovery of nitric oxide (NO), an intracellular signal transmitter, the role of NO has been investigated in various organs. In the respiratory system, NO derived from the constitutive type of NO synthase (cNOS, NOS1, NOS3) induces bronchodilation and pulmonary vasodilatation to maintain homeostasis. In contrast, the roles of excessive NO derived from the inducible type of NOS (iNOS, NOS2) in airway and lung inflammation in inflammatory lung diseases including bronchial asthma and chronic obstructive pulmonary disease (COPD) are controversial. In these inflammatory lung diseases, excessive nitrosative stress has also been observed. In asthma, some reports have shown that nitrosative stress causes airway inflammation, airway hyperresponsiveness, and airway remodeling, which are the features of asthma, whereas others have demonstrated the anti-inflammatory role of NO derived from NOS2. In the case of refractory asthma, more nitrosative stress has been reported to be observed in such airways compared with that in well-controlled asthmatics. In COPD, reactive nitrogen species (RNS), which are NO and NO-related molecules including nitrogen dioxide and peroxynitrite, cause lung inflammation, oxidative stress, activation of matrix metalloproteinase, and inactivation of antiprotease, which are involved in the pathophysiology of the disease. In the present paper, we review the physiological and pathophysiological effects of NO and NO-related molecules in the respiratory system and in inflammatory lung diseases.

Short-term exposure of mice to cigarette smoke and/or residual oil fly ash produces proximal airspace enlargements and airway epithelium remodeling

Chronic obstructive pulmonary disease (COPD) is associated with inflammatory cell reactions, tissue destruction and lung remodeling. Many signaling pathways for these phenomena are still to be identified. We developed a mouse model of COPD to evaluate some pathophysiological mechanisms acting during the initial stage of the disease. Forty-seven 6- to 8-week-old female C57/BL6 mice (approximately 22 g) were exposed for 2 months to cigarette smoke and/or residual oil fly ash (ROFA), a concentrate of air pollution. We measured lung mechanics, airspace enlargement, airway wall thickness, epithelial cell profile, elastic and collagen fiber deposition, and by immunohistochemistry transforming growth factor-β1 (TGF-β1), macrophage elastase (MMP12), neutrophils and macrophages. We observed regional airspace enlargements near terminal bronchioles associated with the exposure to smoke or ROFA. There were also increases in airway resistance and thickening of airway walls in animals exposed to smoke. In the epithelium, we noted a decrease in the ciliated cell area of animals exposed to smoke and an increase in the total cell area associated with exposure to both smoke and ROFA. There was also an increase in the expression of TGF-β1 both in the airways and parenchyma of animals exposed to smoke. However, we could not detect inflammatory cell recruitment, increases in MMP12 or elastic and collagen fiber deposition. After 2 months of exposure to cigarette smoke and/or ROFA, mice developed regional airspace enlargements and airway epithelium remodeling, although no inflammation or increases in fiber deposition were detected. Some of these phenomena may have been mediated by TGF-β1.

Cigarette smoke targets glutaredoxin 1, increasing s-glutathionylation and epithelial cell death

It is established that cigarette smoke (CS) causes irreversible oxidations in lung epithelial cells, and can lead to their death. However, its impact on reversible and physiologically relevant redox-dependent protein modifications remains to be investigated. Glutathione is an important antioxidant against inhaled reactive oxygen species as a direct scavenger, but it can also covalently bind protein thiols upon mild oxidative stress to protect them against irreversible oxidation. This posttranslational modification, known as S-glutathionylation, can be reversed under physiological conditions by the enzyme, glutaredoxin 1 (Grx1). The aim of this study was to investigate if CS modifies Grx1, and if this impacts on protein S-glutathionylation and epithelial cell death. Upon exposure of alveolar epithelial cells to CS extract (CSE), a decrease in Grx1 mRNA and protein expression was observed, in conjunction with decreased activity and increased protein S-glutathionylation. Using mass spectrometry, irreversible oxidation of recombinant Grx1 by CSE and acrolein was demonstrated, which was associated with attenuated enzyme activity. Furthermore, carbonylation of Grx1 in epithelial cells after exposure to CSE was shown. Overexpression of Grx1 attenuated CSE-induced increases in protein S-glutathionylation and increased survival. Conversely, primary tracheal epithelial cells of mice lacking Grx1 were more sensitive to CS-induced cell death, with corresponding increases in protein S-glutathionylation. These results show that CS can modulate Grx1, not only at the expression level, but can also directly modify Grx1 itself, decreasing its activity. These findings demonstrate a role for the Grx1/S-glutathionylation redox system in CS-induced lung epithelial cell death.

Oxidative DNA damage in lung tissue from patients with COPD is clustered in functionally significant sequences

Lung tissue from COPD patients displays oxidative DNA damage. The present study determined whether oxidative DNA damage was randomly distributed or whether it was localized in specific sequences in either the nuclear or mitochondrial genomes. The DNA damage-specific histone, gamma-H2AX, was detected immunohistochemically in alveolar wall cells in lung tissue from COPD patients but not control subjects. A PCR-based method was used to search for oxidized purine base products in selected 200 bp sequences in promoters and coding regions of the VEGF, TGF-β1, HO-1, Egr1, and β-actin genes while quantitative Southern blot analysis was used to detect oxidative damage to the mitochondrial genome in lung tissue from control subjects and COPD patients. Among the nuclear genes examined, oxidative damage was detected in only 1 sequence in lung tissue from COPD patients: the hypoxic response element (HRE) of the VEGF promoter. The content of VEGF mRNA also was reduced in COPD lung tissue. Mitochondrial DNA content was unaltered in COPD lung tissue, but there was a substantial increase in mitochondrial DNA strand breaks and/or abasic sites. These findings show that oxidative DNA damage in COPD lungs is prominent in the HRE of the VEGF promoter and in the mitochondrial genome and raise the intriguing possibility that genome and sequence-specific oxidative DNA damage could contribute to transcriptional dysregulation and cell fate decisions in COPD.

Lung injury after cigarette smoking is particle related

The specific component responsible and the mechanistic pathway for increased human morbidity and mortality after cigarette smoking are yet to be delineated. We propose that 1) injury and disease following cigarette smoking are associated with exposure to and retention of particles produced during smoking and 2) the biological effects of particles associated with cigarette smoking share a single mechanism of injury with all particles. Smoking one cigarette exposes the human respiratory tract to between 15,000 and 40,000 μg particulate matter; this is a carbonaceous product of an incomplete combustion. There are numerous human exposures to other particles, and these vary widely in composition, absolute magnitude, and size of the particle. Individuals exposed to all these particles share a common clinical presentation with a loss of pulmonary function, increased bronchial hyperresponsiveness, pathologic changes of emphysema and fibrosis, and comorbidities, including cardiovascular disease, cerebrovascular disease, peripheral vascular disease, and cancers. Mechanistically, all particle exposures produce an oxidative stress, which is associated with a series of reactions, including an activation of kinase cascades and transcription factors, release of inflammatory mediators, and apoptosis. If disease associated with cigarette smoking is recognized to be particle related, then certain aspects of the clinical presentation can be predicted; this would include worsening of pulmonary function and progression of pathological changes and comorbidity (eg, emphysema and carcinogenesis) after smoking cessation since the particle is retained in the lung and the exposure continues.

Involvement of type II pneumocytes in the pathogenesis of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality, but the cellular and molecular mechanisms are still not fully understood. Type II pneumocytes are identified as the synthesizing cells of the alveolar surfactant, which has important properties in maintaining alveolar and airway stability. Lung surfactant can reduce the surface tension and prevent alveolar collapse and the airway walls collapse. Pulmonary surfactant components play important roles in normal lung function and inflammation in the lung. Surfactant has furthermore been shown to modulate the process of innate host defense, including suppression of cytokine secretion and transcription factor activation, in the inflammatory network of COPD. Abnormalities of lung surfactant might be one of the mechanisms leading to increased airway resistance in COPD. The increased expression of Granzyme A and B was found in lung tissues of patients with COPD and type II pneumocytes was proposed to be involved in the pathogenesis of COPD. These novel findings provide new sights into the role of the type II pneumocytes in the pathogenesis of COPD.

Interleukin-6 promotes pulmonary emphysema associated with apoptosis in mice

The IL-6 cytokine family, which signals via the shared gp130 coreceptor, is linked with the pathogenesis of emphysema. However, the definitive mechanisms by which these cytokines cause emphysema remain ill-defined. We took an in vivo genetic complementation approach to identify the specific IL-6 cytokine family members and gp130-regulated cellular processes that cause emphysema. We used gp130(F/F) mice homozygous for a subtle knock-in mutation in gp130 that deregulates intracellular signaling by the IL-6 cytokine family. The gp130(F/F) mice spontaneously develop emphysema by age 6 months. Within the IL-6 cytokine family, only IL-6 was significantly up-regulated in the lungs of gp130(F/F) mice, and the genetic targeting of IL-6 in gp130(F/F) mice (gp130(F/F):IL-6(-/-)) prevented emphysema. By contrast, the genetic ablation of receptor signaling via IL-11, which like IL-6 signals via a gp130 homodimer and uses the same signaling machinery, failed to ameliorate emphysema in gp130(F/F) mice. Among the disease-associated processes examined, emphysema strongly correlated with elevated alveolar cell apoptosis. Acute (4-day) exposure to cigarette smoke (CS) further augmented the expression of IL-6 in lungs of gp130(F/F) mice, and subchronic (6-week) exposure to CS exacerbated emphysematous and apoptotic changes in the lungs of gp130(F/F) but not gp130(F/F): IL-6(-/-) mice. IL-6 is the main causative agent of IL-6 cytokine family-induced emphysema, and operates to induce apoptosis in the lung. We propose that the discrete targeting of IL-6 signaling may provide an effective therapeutic strategy against human lung disease.

A causal model of chronic obstructive pulmonary disease (COPD) risk

Research on the etiology of chronic pulmonary disease (COPD), an irreversible degenerative lung disease affecting 15% to 20% of smokers, has blossomed over the past half-century. Profound new insights have emerged from a combination of in vitro and -omics studies on affected lung cell populations (including cytotoxic CD8(+) T lymphocytes, regulatory CD4(+) helper T cells, dendritic cells, alveolar macrophages and neutrophils, alveolar and bronchiolar epithelial cells, goblet cells, and fibroblasts) and extracellular matrix components (especially, elastin and collagen fibers); in vivo studies on wild-type and genetically engineered mice and other rodents; clinical investigation of cell- and molecular-level changes in asymptomatic smokers and COPD patients; genetic studies of susceptible and rapidly-progressing phenotypes (both human and animal); biomarker studies of enzyme and protein degradation products in induced sputum, bronchiolar lavage, urine, and blood; and epidemiological and clinical investigations of the time course of disease progression. To this rich mix of data, we add a relatively simple in silico computational model that incorporates recent insights into COPD disease causation and progression. Our model explains irreversible degeneration of lung tissue as resulting from a cascade of positive feedback loops: a macrophage inflammation loop, a neutrophil inflammation loop, and an alveolar epithelial cell apoptosis loop. Unrepaired damage results in clinical symptoms. The resulting model illustrates how to simplify and make more understandable the main aspects of the very complex dynamics of COPD initiation and progression, as well as how to predict the effects on risk of interventions that affect specific biological responses.

Impairment of phagocytosis of apoptotic cells and its role in chronic airway diseases

Phagocytosis of dying cells is a complex and dynamic process coordinated by the interaction of many surface molecules, adaptors, and chemotactic molecules, and it is controlled at multiple levels. This well regulated clearance process is of utmost importance for the development and homeostasis of organisms because defective or inefficient phagocytosis may contribute to human pathologies. In this review we discuss recent advances in the knowledge of the molecular interactions involved in recognition and clearance of apoptotic cells and how derangement of these processes can contribute to the pathogenesis of chronic airway diseases such as chronic obstructive pulmonary disease, cystic fibrosis and asthma. We will briefly consider how different types of macrophages are implicated in chronic airway diseases. Finally, we will address possible therapeutic strategies, such as the use of macrolide antibiotics and statins, for modulating apoptotic cell clearance.

Structure-function relations in an elastase-induced mouse model of emphysema

Emphysema is a progressive disease characterized by the destruction of peripheral airspaces and subsequent decline in lung function. However, the relation between structure and function during disease progression is not well understood. The objective of this study was to assess the time course of the structural, mechanical, and remodeling properties of the lung in mice after elastolytic injury. At 2, 7, and 21 days after treatment with porcine pancreatic elastase, respiratory impedance, the constituents of lung extracellular matrix, and histological sections of the lung were evaluated. In the control group, no changes were observed in the structural or functional properties, whereas, in the treatment group, the respiratory compliance and its variability significantly increased by Day 21 (P < 0.001), and the difference in parameters decreased with increasing positive end-expiratory pressure. The heterogeneity of airspace structure gradually increased over time. Conversely, the relative amounts of elastin and type I collagen exhibited a peak (P < 0.01) at Day 2, but returned to baseline levels by Day 21. Structure-function relations manifested themselves in strong correlations between compliance parameters and both mean size and heterogeneity of airspace structure (r(2) > 0.9). Similar relations were also obtained in a network model of the parenchyma in which destruction was based on the notion that mechanical forces contribute to alveolar wall rupture. We conclude that, in a mouse model of emphysema, progressive decline in lung function is sensitive to the development of airspace heterogeneity governed by local, mechanical, force-induced failure of remodeled collagen.

Dual function inhibitors of relevance to chronic obstructive pulmonary disease

The general strategy and rationale underlying the design of COPD therapeutics that possess protease inhibitory activity and are also capable of releasing a species that attenuates inflammation by inhibiting caspase-1, are described. The synthesis and in vitro biochemical evaluation of a dual function molecule that sequentially inhibits HNE and caspase-1 in a time-dependent manner is reported.

[Role of inflammation in the etiopathogenesis of COPD]

Inflammation is one of the first immune system responses to any type of aggression. As with any type of aggression, the lesion produced by inhalation of tobacco smoke prompts an innate inflammatory response. Subsequently, this lesion is stimulated by the release of various chemical factors that enhance the inflammatory response and, finally--depending on the type of aggression--acquired immunity is activated, which, mediated by lymphocyte participation, serves to establish a physical barrier against the propagation of the lesion and to aid repair of the damaged pulmonary tissue. However, the balance between inflammation and repair is not always maintained, as is the case in chronic obstructive pulmonary disease (COPD), in which marked changes appear in the architecture of the airways, alveolar spaces and pulmonary arteries, forming the structural background of the functional changes characteristic of this disease. COPD is basically a pulmonary disease but data are available on the existence of associated systemic inflammation. The origins of this systemic inflammation are unclear: some information indicates that tobacco smoke is a direct origin common to local and systemic inflammation, while other data point to primary pulmonary inflammation that secondarily produces systemic involvement. The present review describes the main mechanisms involved in both pulmonary and systemic inflammation in COPD.

Current perspectives of oxidative stress and its measurement in chronic obstructive pulmonary disease

Cigarette smoking, the principal aetiology of chronic obstructive pulmonary disease (COPD) in the developed countries, delivers and generates oxidative stress within the lungs. This imbalance of oxidant burden and antioxidant capacity has been implicated as an important contributing factor in the pathogenesis of COPD. Oxidative processes and free radical generation orchestrate the inflammation, mucous gland hyperplasia, and apoptosis of the airway lining epithelium which characterises COPD. Pivotal oxidative stress/pro-inflammatory molecules include reactive oxygen species such as the superoxides and hydroxyl radicals, pro-inflammatory cytokines including leukotrienes, interleukins, tumour necrosis factor alpha, and activated transcriptional factors such as nuclear factor kappa-B and activator protein 1. The lung has a large reserve of antioxidant agents such as glutathione and superoxide dismutase to counter oxidants. However, smoking also causes the depletion of antioxidants, which further contributes to oxidative tissue damage. The downregulation of antioxidant pathways has also been associated with acute exacerbations of COPD. The delivery of redox-protective antioxidants may have preventative and therapeutic potential of COPD. Although these observations have yet to translate into common clinical practice, preliminary clinical trials and studies of animal models have shown that interventions to counter this oxidative imbalance may have potential to better manage COPD. There is, thus, a need for the ability to monitor such interventions and exhaled breath condensate is rapidly emerging as a novel and noninvasive approach in the sampling of airway epithelial lining fluid which could be used for repeated analysis of oxidative stress and inflammation in the lungs.

MicroRNA expression in induced sputum of smokers and patients with chronic obstructive pulmonary disease

RATIONALE

Chronic obstructive pulmonary disease (COPD) is characterized by progressive inflammation in the airways and lungs combined with disturbed homeostatic functions of pulmonary cells. MicroRNAs (miRNAs) have the ability to regulate these processes by interfering with gene transcription and translation.

OBJECTIVES

We aimed to identify miRNA expression in induced sputum and examined whether the expression of miRNAs differed between patients with COPD and subjects without airflow limitation.

METHODS

Expression of 627 miRNAs was evaluated in induced sputum supernatant of 32 subjects by stem-loop reverse transcription-quantitative polymerase chain reaction. Differentially expressed miRNAs were validated in an independent replication cohort of 41 subjects. Enrichment of miRNA target genes was identified by in silico analysis. Protein expression of target genes was determined by ELISA.

MEASUREMENTS AND MAIN RESULTS

Thirty-four miRNAs were differentially expressed between never-smokers and current smokers without airflow limitation in the screening cohort. Eight miRNAs were expressed at a significantly lower level in current-smoking patients with COPD compared with never-smokers without airflow limitation. Reduced expression of let-7c and miR-125b in patients with COPD compared with healthy subjects was confirmed in the validation cohort. Target genes of let-7c were significantly enriched in the sputum of patients with severe COPD. The concentration of tumor necrosis factor receptor type II (TNFR-II, implicated in COPD pathogenesis and a predicted target gene of let-7c) was inversely correlated with the sputum levels of let-7c .

CONCLUSIONS

let-7c is significantly reduced in the sputum of currently smoking patients with COPD and is associated with increased expression of TNFR-II.