Rationale: Prolonged exposure to 100% O2 causes hyperoxic acute lung injury (HALI), characterized by alveolar epithelial cell injury and death. We previously demonstrated that the murine chitinase-like protein, breast regression protein (BRP)–39 and its human homolog, YKL-40, inhibit cellular apoptosis. However, the regulation and roles of these molecules in hyperoxia have not been addressed.
Objectives: We hypothesized that BRP-39 and YKL-40 (also called chitinase-3–like 1) play important roles in the pathogenesis of HALI.
Methods: We characterized the regulation of BRP-39 during HALI and the responses induced by hyperoxia in wild-type mice, BRP-39–null (−/−) mice, and BRP-39−/− mice in which YKL-40 was overexpressed in respiratory epithelium. We also compared the levels of tracheal aspirate YKL-40 in premature newborns with respiratory failure.
Measurements and Main Results: These studies demonstrate that hyperoxia inhibits BRP-39 in vivo in the murine lung and in vitro in epithelial cells. They also demonstrate that BRP-39−/− mice have exaggerated permeability, protein leak, oxidation, inflammatory, chemokine, and epithelial apoptosis responses, and experience premature death in 100% O2. Lastly, they demonstrate that YKL-40 ameliorates HALI, prolongs survival in 100% O2, and rescues the exaggerated injury response in BRP-39−/− animals. In accord with these findings, the levels of tracheal aspirate YKL-40 were lower in premature infants treated with hyperoxia for respiratory failure who subsequently experienced bronchopulmonary dysplasia or death compared with those that did not experience these complications.
Conclusions: These studies demonstrate that hyperoxia inhibits BRP-39/YKL-40, and that BRP-39 and YKL-40 are critical regulators of oxidant injury, inflammation, and epithelial apoptosis in the murine and human lung.
BRP-39; YKL-40; hyperoxygen; BPD; HALI
Mouse breast regression protein 39 (BRP-39; Chi3l1) and its human homologue YKL-40 are chitinase-like proteins that lack chitinase activity. Although YKL-40 is expressed in exaggerated quantities and correlates with disease activity in asthma and many other disorders, the biological properties of BRP-39/YKL-40 have only been rudimentarily defined. We describe the generation and characterization of BRP-39−/− mice, YKL-40 transgenic mice, and mice that lack BRP-39 and produce YKL-40 only in their pulmonary epithelium. Studies of these mice demonstrated that BRP-39−/− animals have markedly diminished antigen-induced Th2 responses and that epithelial YKL-40 rescues the Th2 responses in these animals. The ability of interleukin13 to induce tissue inflammation and fibrosis was also markedly diminished in the absence of BRP-39. Mechanistic investigations demonstrated that BRP-39 and YKL-40 play an essential role in antigen sensitization and immunoglobulin E induction, stimulate dendritic cell accumulation and activation, and induce alternative macrophage activation. These proteins also inhibit inflammatory cell apoptosis/cell death while inhibiting Fas expression, activating protein kinase B/AKT, and inducing Faim 3. These studies establish novel regulatory roles for BRP-39/YKL-40 in the initiation and effector phases of Th2 inflammation and remodeling and suggest that these proteins are therapeutic targets in Th2- and macrophage-mediated disorders.
BRP-39 and its human homolog YKL-40 have been regarded as a prototype of chitinase-like proteins (CLP) in mammals. Exaggerated levels of YKL-40 protein and/or mRNA have been noted in a number of diseases characterized by inflammation, tissue remodeling, and aberrant cell growth. Asthma is an inflammatory disease characterized by airway hyperresponsiveness and airway remodeling. Recently, the novel regulatory role of BRP-39/YKL-40 in the pathogenesis of asthma has been demonstrated both in human studies and allergic animal models. The levels of YKL-40 are increased in the circulation and lungs from asthmatics where they correlate with disease severity, and CHI3L1 polymorphisms correlate with serum YKL-40 levels, asthma and abnormal lung function. Animal studies using BRP-39 null mutant mice demonstrated that BRP-39 was required for optimal allergen sensitization and Th2 inflammation. These studies suggest the potential use of BRP-39 as a biomarker as well as a therapeutic target for asthma and other allergic diseases. Here, we present an overview of chitin/chitinase biology and summarize recent findings on the role of BRP-39 in the pathogenesis of asthma and allergic responses.
BRP-39; human CHI3L1 protein; asthma; hypersensitivity
While the presence of the chitinase-like molecule YKL40 has been reported in COPD and asthma, its relevance to inflammatory processes elicited by cigarette smoke and common environmental allergens, such as house dust mite (HDM), is not well understood. The objective of the current study was to assess expression and function of BRP-39, the murine equivalent of YKL40 in a murine model of cigarette smoke-induced inflammation and contrast expression and function to a model of HDM-induced allergic airway inflammation.
CD1, C57BL/6, and BALB/c mice were room air- or cigarette smoke-exposed for 4 days in a whole-body exposure system. In separate experiments, BALB/c mice were challenged with HDM extract once a day for 10 days. BRP-39 was assessed by ELISA and immunohistochemistry. IL-13, IL-1R1, IL-18, and BRP-39 knock out (KO) mice were utilized to assess the mechanism and relevance of BRP-39 in cigarette smoke- and HDM-induced airway inflammation.
Cigarette smoke exposure elicited a robust induction of BRP-39 but not the catalytically active chitinase, AMCase, in lung epithelial cells and alveolar macrophages of all mouse strains tested. Both BRP-39 and AMCase were increased in lung tissue after HDM exposure. Examining smoke-exposed IL-1R1, IL-18, and IL-13 deficient mice, BRP-39 induction was found to be IL-1 and not IL-18 or IL-13 dependent, while induction of BRP-39 by HDM was independent of IL-1 and IL-13. Despite the importance of BRP-39 in cellular inflammation in HDM-induced airway inflammation, BRP-39 was found to be redundant for cigarette smoke-induced airway inflammation and the adjuvant properties of cigarette smoke.
These data highlight the contrast between the importance of BRP-39 in HDM- and cigarette smoke-induced inflammation. While functionally important in HDM-induced inflammation, BRP-39 is a biomarker of cigarette smoke induced inflammation which is the byproduct of an IL-1 inflammatory pathway.
The chitinase-like protein YKL-40 was found to be increased in patients with severe asthma and chronic obstructive pulmonary disease (COPD), two disease conditions featuring neutrophilic infiltrates. Based on these studies and a previous report indicating that neutrophils secrete YKL-40, we hypothesized that YKL-40 plays a key role in cystic fibrosis (CF) lung disease, a prototypic neutrophilic disease. The aim of this study was (i) to analyze YKL-40 levels in human and murine CF lung disease and (ii) to investigate whether YKL-40 single-nucleotide polymorphisms (SNPs) modulate CF lung disease severity. YKL-40 protein levels were quantified in serum and sputum supernatants from CF patients and control individuals. Levels of the murine homologue BRP-39 were analyzed in airway fluids from CF-like βENaC-Tg mice. YKL-40SNPs were analyzed in CF patients. YKL-40 levels were increased in sputum supernatants and in serum from CF patients compared to healthy control individuals. Within CF patients, YKL-40 levels were higher in sputum than in serum. BRP-39 levels were increased in airways fluids from βENaC-Tg mice compared to wild-type littermates. In both CF patients and βENaC-Tg mice, YKL-40/BRP-39 airway levels correlated with the severity of pulmonary obstruction. Two YKL-40 SNPs (rs871799 and rs880633) were found to modulate age-adjusted lung function in CF patients. YKL-40/BRP-39 levelsare increased in human and murine CF airway fluids, correlate with pulmonary function and modulate CF lung disease severity genetically. These findings suggest YKL-40 as a potential biomarker in CF lung disease.
The tachykinins, substance P and neurokinin A, present in sensory nerves and inflammatory cells such as macrophages and dendritic cells, are considered as pro-inflammatory agents. Inflammation of the airways and lung parenchyma plays a major role in the pathogenesis of chronic obstructive pulmonary disease (COPD) and increased tachykinin levels are recovered from the airways of COPD patients. The aim of our study was to clarify the involvement of the tachykinin NK1 receptor, the preferential receptor for substance P, in cigarette smoke (CS)-induced pulmonary inflammation and emphysema in a mouse model of COPD.
Tachykinin NK1 receptor knockout (NK1-R-/-) mice and their wild type controls (all in a mixed 129/sv-C57BL/6 background) were subjected to sub acute (4 weeks) or chronic (24 weeks) exposure to air or CS. 24 hours after the last exposure, pulmonary inflammation and development of emphysema were evaluated.
Sub acute and chronic exposure to CS resulted in a substantial accumulation of inflammatory cells in the airways of both WT and NK1-R-/- mice. However, the CS-induced increase in macrophages and dendritic cells was significantly impaired in NK1-R-/- mice, compared to WT controls, and correlated with an attenuated release of MIP-3α/CCL20 and TGF-β1. Chronic exposure to CS resulted in development of pulmonary emphysema in WT mice. NK1-R-/- mice showed already enlarged airspaces upon air-exposure. Upon CS-exposure, the NK1-R-/- mice did not develop additional destruction of the lung parenchyma. Moreover, an impaired production of MMP-12 by alveolar macrophages upon CS-exposure was observed in these KO mice. In a pharmacological validation experiment using the NK1 receptor antagonist RP 67580, we confirmed the protective effect of absence of the NK1 receptor on CS-induced pulmonary inflammation.
These data suggest that the tachykinin NK1 receptor is involved in the accumulation of macrophages and dendritic cells in the airways upon CS-exposure and in the development of smoking-induced emphysema. As both inflammation of the airways and parenchymal destruction are important characteristics of COPD, these findings may have implications in the future treatment of this devastating disease.
Chronic airway inflammation is a cardinal feature of chronic obstructive pulmonary disease (COPD), a destructive cigarette smoke-induced lung disease. Although it is apparent that dendritic cells (DCs) are an important constituent of the chronic inflammatory cell influx found in airways of COPD patients, the functional roles of DCs in the pathogenesis of smoking-induced emphysema are unknown. We postulated that DCs activated by cigarette smoke constituents directly participate in the chronic inflammation that characterizes COPD airways. Concordant with this hypothesis, we observed that incubation of DCs with cigarette smoke extract (CSE), and chronic exposure of mice to cigarette smoke, both augmented the generation of neutrophilic chemokines by immature and lipopolysaccharide (LPS) or CD40L-matured DCs. The generation of interleukin-8 (CXCL8/IL-8) by human DCs conditioned with CSE was suppressed by the anti-oxidant n-acetyl cysteine (NAC), implying the involvement of oxidant sensitive pathways as a primary mechanism involved in the enhanced CXCL8/IL-8 generation. Cigarette smoke extract and nicotine also augment the production of secreted prostaglandin E2 and intracellular cyclo-oxygenase-2 (COX-2) in maturing DCs. Whereas NAC suppressed production of CXCL8 by CSE-conditioned DCs, it augmented production of PGE2 and cellular COX-2 levels in maturing DCs. These studies indicate that the stimulation of DCs by cigarette smoke-induced oxidative stress and nicotine promote the generation of pro-inflammatory responses that promote chronic inflammation in smokers. Certain pharmacologic strategies such as anti-oxidant therapy may be only partially effective in mitigating cigarette smoke-induced pro-inflammatory DC-mediated responses in smokers.
Smoking; dendritic cell; oxidative stress; neutrophil; chemokines; prostaglandins
Previous studies have shown that BrpA plays a major role in acid and oxidative stress tolerance and biofilm formation by Streptococcus mutans. Mutant strains lacking BrpA also display increased autolysis and decreased viability, suggesting a role for BrpA in cell envelope integrity. In this study, we examined the impact of BrpA deficiency on cell envelope stresses induced by envelope-active antimicrobials. Compared to the wild-type strain UA159, the BrpA-deficient mutant (TW14D) was significantly more susceptible to antimicrobial agents, especially lipid II inhibitors. Several genes involved in peptidoglycan synthesis were identified by DNA microarray analysis as downregulated in TW14D. Luciferase reporter gene fusion assays also revealed that expression of brpA is regulated in response to environmental conditions and stresses induced by exposure to subinhibitory concentrations of cell envelope antimicrobials. In a Galleria mellonella (wax worm) model, BrpA deficiency was shown to diminish the virulence of S. mutans OMZ175, which, unlike S. mutans UA159, efficiently kills the worms. Collectively, these results suggest that BrpA plays a role in the regulation of cell envelope integrity and that deficiency of BrpA adversely affects the fitness and diminishes the virulence of OMZ175, a highly invasive strain of S. mutans.
The protease-antiprotease imbalance in the lung plays an important role in the pathogenesis of smoke-induced emphysema. The aim of this study was to characterize the proteolytic responses leading to emphysema formation in the guinea pig smoke exposure model. Guinea pigs were exposed to cigarette smoke for 1, 2, 4, 8 and 12 weeks. Age-matched guinea pigs exposed to room air served as controls. Cigarette smoke induced inflammation after 4 weeks and generated emphysematous changes in the guinea pigs after 12 weeks of smoke exposure. Increased phosphorylation of ERK and JNK MAP kinases was demonstrated post-cigarette smoke exposure. A decrease in elastin and collagen, and the loss of type III collagen were observed in the alveolar wall of smoke-exposed guinea pigs. Interestingly, no change was seen in the expression of collagenolytic matrix metalloproteinases. Furthermore, we observed a three-fold increase in cathepsin K activity in the lungs of smoke-exposed guinea pigs. The significance of this finding was supported by human studies that demonstrate increased expression of cathepsin K in the lungs of patients with emphysema. Elevation of cathepsin K in guinea pig lungs after smoke exposure likely constitutes a critical event leading to the disruption of lung extracellular matrix in this model.
emphysema; proteases; inflammation
Chronic obstructive pulmonary disease (COPD) is a prevalent smoking-related disease for which no disease-altering therapies currently exist. As dysregulated TGF-β signaling associates with lung pathology in patients with COPD and in animal models of lung injury induced by chronic exposure to cigarette smoke (CS), we postulated that inhibiting TGF-β signaling would protect against CS-induced lung injury. We first confirmed that TGF-β signaling was induced in the lungs of mice chronically exposed to CS as well as in COPD patient samples. Importantly, key pathological features of smoking-associated lung disease in patients, e.g., alveolar injury with overt emphysema and airway epithelial hyperplasia with fibrosis, accompanied CS-induced alveolar cell apoptosis caused by enhanced TGF-β signaling in CS-exposed mice. Systemic administration of a TGF-β–specific neutralizing antibody normalized TGF-β signaling and alveolar cell death, conferring improved lung architecture and lung mechanics in CS-exposed mice. Use of losartan, an angiotensin receptor type 1 blocker used widely in the clinic and known to antagonize TGF-β signaling, also improved oxidative stress, inflammation, metalloprotease activation and elastin remodeling. These data support our hypothesis that inhibition of TGF-β signaling through angiotensin receptor blockade can attenuate CS-induced lung injury in an established murine model. More importantly, our findings provide a preclinical platform for the development of other TGF-β–targeted therapies for patients with COPD.
Chronic obstructive pulmonary disease is associated with a chronic inflammatory response of the host to chronic exposure to inhaled toxic gases and particles. Although inflammatory cells of both the innate and adaptive immune system infiltrate the lungs in pulmonary emphysema and form lymphoid follicles around the small airways, the exact role of the acquired immune system in the pathogenesis of emphysema is not known.
In this study, wild type Balb/c mice and immunodeficient scid mice – which lack functional B- and T-cells – were exposed to mainstream cigarette smoke (CS) for 5 weeks or 6 months.
Subacute CS-exposure for 5 weeks significantly increased innate inflammatory cells (neutrophils, macrophages and dendritic cells) in the bronchoalveolar lavage (BAL) fluid of wild type mice and scid mice, which correlated with the CS-induced upregulation of the chemokines Monocyte Chemotactic Protein-1, Macrophage Inflammatory Protein-3α and KC (= mouse Interleukin-8). Chronic CS-exposure for 6 months significantly increased the number of neutrophils, macrophages, dendritic cells, CD4+ and CD8+ T-lymphocytes in BAL fluid and lungs of wild type mice compared to air-exposed littermates, and augmented the size and number of peribronchial lymphoid follicles. In contrast, neither B-lymphocytes, nor T-lymphocytes, nor lymphoid follicles could be discerned in the lungs of air- or CS-exposed scid mice. Importantly, chronic CS-exposure induced pulmonary emphysema in both wild type animals and scid mice, as evidenced by a significant increase in the mean linear intercept and the destructive index of CS-exposed versus air-exposed animals. The CS-induced emphysema was associated with increased mRNA expression of matrix metalloproteinase-12 in the lungs and increased protein levels of Tumor Necrosis Factor-α in the BAL fluid of CS-exposed Balb/c and scid mice compared to air-exposed littermates.
This study suggests that the adaptive immune system is not required per se to develop pulmonary emphysema in response to chronic CS-exposure, since emphysema can be induced in scid mice, which lack lymphoid follicles as well as functional B- and T-cells.
Mouse models of chronic obstructive pulmonary disease (COPD) focus on airway inflammation and lung histology, but their use has been hampered by the lack of pulmonary function data in their assessment. Systemic effects such as muscle dysfunction are also poorly modeled in emphysematous mice. We aimed to develop a cigarette-smoke-induced emphysema mouse model in which serial lung function and muscular dysfunction could be assessed, allowing the disease to be monitored more appropriately. C57Bl6 mice were nose-only exposed to cigarette smoke or filtered air for 3–6 months. Lung function tests were repeated in the same mice after 3 and 6 months of cigarette smoke or air exposure and compared with lung histological changes. Contractile properties of skeletal muscles and muscle histology were also determined at similar time points in separate groups of mice. Serial lung function measurements documented hyperinflation after 3 and 6 months of cigarette smoke exposure, with a significant 31–37% increase in total lung capacity (TLC) and a significant 26–35% increase in compliance (Cchord) when compared with animals exposed to filtered air only (P<0.001 after 3 and after 6 months). These functional changes preceded the changes in mean linear intercept, which became only significant after 6 months of cigarette smoke exposure and which correlated very well with TLC (r=0.74, P=0.004) and Cchord (r=0.79, P=0.001). After 6 months of cigarette smoke exposure, a significant fiber-type shift from IIa to IIx/b was also observed in the soleus muscle (P<0.05), whereas a 20% reduction of force was present at high stimulation frequencies (80 Hz; P=0.09). The extensor digitorum longus (EDL) muscle was not affected by cigarette smoke exposure. These serial pulmonary function variables are sensitive outcomes to detect emphysema progression in a nose-only cigarette-smoke-exposed animal model of COPD. In this model, muscular changes became apparent only after 6 months, particularly in muscles with a mixed fiber-type composition.
Vitamin D can translocate a vitamin D receptor (VDR) from the nucleus to the cell membranes. The meaning of this translocation is not elucidated in terms of a role in pathogenesis of chronic obstructive pulmonary disease (COPD) till now. VDR deficient mice are prone to develop emphysema, suggesting that abnormal function of VDR might influence a generation of COPD. The blood levels of vitamin D have known to be well correlated with that of lung function in patients with COPD, and smoking is the most important risk factor in development of COPD. This study was performed to investigate whether cigarette smoke extracts (CSE) can inhibit the translocation of VDR and whether mitogen activated protein kinases (MAPKs) are involved in this inhibition.
Human alveolar basal epithelial cell line (A549) was used in this study. 1,25-(OH2)D3 and/or MAPKs inhibitors and antioxidants were pre-incubated before stimulation with 10% CSE, and then nucleus and microsomal proteins were extracted for a Western blot of VDR.
Five minutes treatment of 1,25-(OH2)D3 induced translocation of VDR from nucleus to microsomes by a dose-dependent manner. CSE inhibited 1,25-(OH2)D3-induced translocation of VDR in both concentrations of 10% and 20%. All MAPKs inhibitors did not suppress the inhibitory effects of CSE on the 1,25-(OH2)D3-induced translocation of VDR. Quercetin suppressed the inhibitory effects of CSE on the 1,25-(OH2)D3-induced translocation of VDR, but not in n-acetylcysteine.
CSE has an ability to inhibit vitamin D-induced VDR translocation, but MAPKs are not involved in this inhibition.
Vitamin D; Receptors, Calcitriol; Extracelular Signal-Regulated MAP Kinases; Antioxidants; Pulmonary Disease, Chronic Obstructive
Tumor angiogenesis is of paramount importance in solid tumor development. Elevated serum levels of YKL-40, a secreted heparin-binding glycoprotein have been associated with a worse prognosis from a variety of advanced human cancers. Yet the role of YKL-40 activity in these cancers is still missing. Here, we have shown that ectopic expression of YKL-40 in MDA-MB-231 breast cancer cells and HCT-116 colon cancer cells led to larger tumor formation with an extensive angiogenic phenotype than did control cancer cells in mice. Affinity purified recombinant YKL-40 protein promoted vascular endothelial cell angiogenesis in vitro, the effects similar to the activities observed using MDA-MB-231 and HCT-116 cell conditioned medium after transfection with YKL-40. Further, YKL-40 was found to induce the coordination of membrane-bound receptor syndecan-1 and integrin αvβ3 and activate an intracellular signaling cascade including focal adhesion kinase and MAP kinase Erk1/2 in endothelial cells. Also, blockade of YKL-40 using siRNA gene knockdown suppressed tumor angiogenesis in vitro and in vivo. Immunohistochemical analysis of human breast cancer revealed a correlation between YKL-40 expression and blood vessel density. These findings provide novel insights into angiogenic activities and molecular mechanisms of YKL-40 in cancer development.
Matrix metalloproteases (MMPs) are believed to be important in the pathogenesis of cigarette smoke‐induced emphysema, but this hypothesis has only been proved in the mouse and its applicability to other species, particularly humans, is uncertain. The role of MMPs in smoke‐induced small airway remodelling is unknown.
The effects of a dual MMP‐9/MMP‐12 inhibitor, AZ11557272, on the development of anatomical and functional changes of chronic obstructive pulmonary disease (COPD) in guinea pigs exposed daily to cigarette smoke for up to 6 months were examined.
At all times, smoke‐induced increases in lavage inflammatory cells, lavage desmosine (a marker of elastin breakdown) and serum tumour necrosis factor α (TNFα) were completely abolished by AZ11557272. At 6 months there was an increase in lung volumes and airspace size. AZ11557272 returned the pressure‐ volume curve to control levels, decreased smoke‐induced increases in total lung capacity, residual volume and vital capacity by about 70%, and also reversed smoke‐induced airspace enlargement by about 70%. There was a very strong correlation between surface to volume ratio and both lavage desmosine and serum TNFα levels. AZ11557272 protected against smoke‐mediated increases in small airway wall thickness but did not prevent smoke‐induced increases in mean pulmonary artery pressure.
An MMP‐9/MMP‐12 inhibitor can substantially ameliorate morphological emphysema, small airway remodelling and the functional consequences of these lesions in a non‐murine species. These findings strengthen the idea that MMPs are important mediators of the anatomical changes behind COPD in humans, and suggest that MMP‐9 and MMP‐12 may be potential intervention targets.
Cigarette smoke is the major risk factor associated with the development of chronic obstructive pulmonary disease (COPD). Recent studies propose a link between endoplasmic reticulum (ER) stress and emphysema, demonstrated by increased ER stress markers under smoking conditions. Here, we investigate whether cigarette smoke-induced ER stress is cell specific and correlates with acute and chronic cigarette smoke exposure.
Gene and protein expression changes in human primary lung cell cultures following cigarette smoke extract (CSE) exposure were monitored by qPCR and Western blot analysis. Mice and guinea pigs were exposed to cigarette smoke and ER stress markers examined in whole lung homogenates. Inflammatory cells from the bronchoalveolar lavage fluid of 10 days smoke exposed mice were also examined.
Cigarette smoke induced a trend increase in the ER stress response through an activating transcription factor 4 (ATF4) mediated induction of C/EBP homologous protein (CHOP) in primary small airway epithelial cells. Bronchial epithelial cells and macrophages responded similarly to CSE. Wild-type mice and guinea pigs exposed to acute levels of cigarette smoke exhibited increased levels of CHOP but not at significant levels. However, after long-term chronic cigarette smoke exposure, CHOP expression was reduced. Interestingly, inflammatory cells from smoke exposed mice had a significant increase in CHOP/ATF4 expression.
A trend increase in CHOP levels appear in multiple human lung cell types following acute cigarette smoke exposure in vitro. In vivo, inflammatory cells, predominately macrophages, demonstrate significant cigarette smoke-induced ER stress. Early induction of CHOP in cigarette smoke may play a pivotal role in early induction of lung disease, however in vivo long-term cigarette smoke exposure exhibited a reduction in the ER stress response.
COPD; ER stress; cigarette smoke; CHOP
The mutual interactions between reactive oxygen species, airway inflammation, and alveolar cell death play crucial role in the pathogenesis of chronic obstructive pulmonary disease (COPD). In the present study, we investigated the possibility that hydrogen sulfide (H2S) donor sodium hydrosulfide (NaHS) might be a novel option for intervention in COPD.
We used a mouse model of tobacco smoke (TS)-induced emphysema. Mice were injected with H2S donor NaHS (50 μmol/kg in 0.25 ml phosphate buffer saline, intraperitoneally) or vehicle daily before exposed to TS for 1 h/day, 5 days/week for 12 and 24 weeks. We found that NaHS ameliorated TS-induced increase in mean linear intercepts, the thickness of bronchial walls, and the numbers of total cell counts as well as neutrophils, monocytes, and tumor necrosis factor α in bronchial alveolar lavage. Moreover, NaHS reduced increases in right ventricular systolic pressure, the thickness of pulmonary vascular walls, and the ratio of RV/LV+S in TS-exposed mice. Further, TS exposure for 12 and 24 weeks reduced the protein contents of cystathionine γ-lyase (CGL), cystathionine β-synthetase (CBS), nuclear erythroid-related factor 2 (Nrf2), Pser473-Akt, as well as glutathione/oxidized glutathione ratio in the lungs. TS-exposed lungs exhibited large amounts of 8-hydroxyguanine-positive and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells. Treatment with NaHS increased Pser473-Akt and attenuated TS-induced reduction of CGL, CBS, and Nrf2 as well as glutathione/oxidized glutathione ratio in the lungs. NaHS also reduced amounts of 8-hydroxyguanine-positive, terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells and active caspase-3 in TS-exposed lungs. Additionally, knocking-down Akt protein abolished the protective effects of NaHS against TS-induced apoptosis and downregulation of Nrf2, CGL, and CBS in pulmonary artery endothelial cells.
These results indicate that NaHS protects against TS-induced oxidative stress, airway inflammation, and remodeling and ameliorates the development of emphysema and pulmonary hypertension. H2S donors have therapeutic potential for the prevention and treatment of COPD caused by TS. Antioxid. Redox Signal. 15, 2121–2134.
Although inflammation and protease/antiprotease imbalance have been postulated to be critical in cigarette smoke–induced (CS-induced) emphysema, oxidative stress has been suspected to play an important role in chronic obstructive pulmonary diseases. Susceptibility of the lung to oxidative injury, such as that originating from inhalation of CS, depends largely on its upregulation of antioxidant systems. Nuclear factor, erythroid-derived 2, like 2 (Nrf2) is a redox-sensitive basic leucine zipper protein transcription factor that is involved in the regulation of many detoxification and antioxidant genes. Disruption of the Nrf2 gene in mice led to earlier-onset and more extensive CS-induced emphysema than was found in wild-type littermates. Emphysema in Nrf2-deficient mice exposed to CS for 6 months was associated with more pronounced bronchoalveolar inflammation; with enhanced alveolar expression of 8-oxo-7,8-dihydro-2′-deoxyguanosine, a marker of oxidative stress; and with an increased number of apoptotic alveolar septal cells — predominantly endothelial and type II epithelial cells — as compared with wild-type mice. Microarray analysis identified the expression of nearly 50 Nrf2-dependent antioxidant and cytoprotective genes in the lung that may work in concert to counteract CS-induced oxidative stress and inflammation. The responsiveness of the Nrf2 pathway may act as a major determinant of susceptibility to tobacco smoke–induced emphysema by upregulating antioxidant defenses and decreasing lung inflammation and alveolar cell apoptosis.
Several matrix metalloproteinases (MMPs) are involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). In mice, MMP‐12 plays a crucial role in the development of cigarette smoke induced emphysema. A study was undertaken to investigate the role of MMP‐12 in the development of COPD in human smokers.
Induced sputum samples were collected from patients with stable COPD (n = 28), healthy smokers (n = 14), never smokers (n = 20), and former smokers (n = 14). MMP‐12 protein levels in induced sputum were determined by ELISA and compared between the four study groups. MMP‐12 enzymatic activity in induced sputum was evaluated by casein zymography and by cleaving of a fluorescence quenched substrate.
Median (IQR) MMP‐12 levels were significantly higher in COPD patients than in healthy smokers, never smokers, and former smokers (17.5 (7.1–42.1) v 6.7 (3.9–10.4) v 4.2 (2.4–11.3) v 6.1 (4.5–7.6) ng/ml, p = 0.0002). MMP‐12 enzymatic activity was significantly higher in patients with COPD than in controls (4.11 (1.4–8.0) v 0.14 (0.1–0.2) μg/μl, p = 0.0002).
MMP‐12 is markedly increased in induced sputum from patients with stable COPD compared with controls, suggesting a role for MMP‐12 in the development of COPD in smokers.
chronic obstructive pulmonary disease; matrix metalloproteinases; induced sputum; MMP‐12; smoking
Chronic obstructive pulmonary disease (COPD) is characterized by the presence of airflow obstruction and lung destruction with airspace enlargement. In addition to cigarette smoking, respiratory pathogens play a role in pathogenesis, but specific organisms are not always identified. Recent reports demonstrate associations between the detection of Pneumocystis jirovecii DNA in lung specimens or respiratory secretions and the presence of emphysema in COPD patients. Additionally, human immunodeficiency virus-infected individuals who smoke cigarettes develop early emphysema, but a role for P. jirovecii in pathogenesis remains speculative. We developed a new experimental model using immunocompetent mice to test the interaction of cigarette smoke exposure and environmentally acquired Pneumocystis murina infection in vivo. We hypothesized that cigarette smoke and P. murina would interact to cause increases in total lung capacity, airspace enlargement, and pulmonary inflammation. We found that exposure to cigarette smoke significantly increases the lung organism burden of P. murina. Pulmonary infection with P. murina, combined with cigarette smoke exposure, results in changes in pulmonary function and airspace enlargement characteristic of pulmonary emphysema. P. murina and cigarette smoke exposure interact to cause increased lung inflammatory cell accumulation. These findings establish a novel animal model system to explore the role of Pneumocystis species in the pathogenesis of COPD.
Chronic obstructive pulmonary disease/emphysema (COPD/emphysema) is characterized by chronic inflammation and premature lung aging. Anti-aging sirtuin 1 (SIRT1), a NAD+-dependent protein/histone deacetylase, is reduced in lungs of patients with COPD. However, the molecular signals underlying the premature aging in lungs, and whether SIRT1 protects against cellular senescence and various pathophysiological alterations in emphysema, remain unknown. Here, we showed increased cellular senescence in lungs of COPD patients. SIRT1 activation by both genetic overexpression and a selective pharmacological activator, SRT1720, attenuated stress-induced premature cellular senescence and protected against emphysema induced by cigarette smoke and elastase in mice. Ablation of Sirt1 in airway epithelium, but not in myeloid cells, aggravated airspace enlargement, impaired lung function, and reduced exercise tolerance. These effects were due to the ability of SIRT1 to deacetylate the FOXO3 transcription factor, since Foxo3 deficiency diminished the protective effect of SRT1720 on cellular senescence and emphysematous changes. Inhibition of lung inflammation by an NF-κB/IKK2 inhibitor did not have any beneficial effect on emphysema. Thus, SIRT1 protects against emphysema through FOXO3-mediated reduction of cellular senescence, independently of inflammation. Activation of SIRT1 may be an attractive therapeutic strategy in COPD/emphysema.
The chitinase-like proteins YKL-39 (chitinase 3-like-2) and YKL-40 (chitinase 3-like-1) are highly expressed in a number of human cells independent of their origin (mesenchymal, epithelial or haemapoietic). Elevated serum levels of YKL-40 have been associated with a negative outcome in a number of diseases ranging from cancer to inflammation and asthma. YKL-39 expression has been associated with osteoarthritis. However, despite the reported association with disease, the physiological or pathological role of these proteins is still very poorly understood. Although YKL-39 is homologous to the two family 18 chitinases in the human genome, it has been reported to lack any chitinase activity. In the present study, we show that human YKL-39 possesses a chitinase-like fold, but lacks key active-site residues required for catalysis. A glycan screen identified oligomers of N-acetylglucosamine as preferred binding partners. YKL-39 binds chitooligosaccharides and a newly synthesized derivative of the bisdionin chitinase-inhibitor class with micromolar affinity, through a number of conserved tryptophan residues. Strikingly, the chitinase activity of YKL-39 was recovered by reverting two non-conservative substitutions in the active site to those found in the active enzymes, suggesting that YKL-39 is a pseudo-chitinase with retention of chitinase-like ligand-binding properties.
chitinase; chitinase-like proteins; glycan; glycan array; glycobiology; protein structure; lectin; X-ray crystallography
YKL-40 (chitinase-3-like-1) is a member of "mammalian chitinase-like proteins". The protein is expressed in many types of cancer cells and the highest plasma YKL-40 levels have been found in patients with metastatic disease, short recurrence/progression-free intervals, and short overall survival. The aim of the study was to determine the expression of YKL-40 in tumor tissue and plasma in patients with borderline ovarian tumor or epithelial ovarian cancer (OC), and investigate prognostic value of this marker.
YKL-40 protein expression was determined by immunohistochemistry in tissue arrays from 181 borderline tumors and 473 OC. Plasma YKL-40 was determined by ELISA in preoperative samples from 19 patients with borderline tumor and 76 OC patients.
YKL-40 protein expression was found in cancer cells, tumor associated macrophages, neutrophils and mast cells. The tumor cell expression was higher in OC than in borderline tumors (p = 0.001), and associated with FIGO stage (p < 0.0001) and histological subtype (p = 0.0009). Positive YKL-40 expression (≥ 5% staining) was not associated with reduced survival. Plasma YKL-40 was also higher in patients with OC than in patients with borderline tumors (p < 0.0001), and it was positively correlated to serum CA-125 (p < 0.0001) and FIGO stage (p = 0.0001). Univariate Cox analysis of plasma YKL-40 showed association with overall survival (p < 0.0001). Multivariate Cox analysis, including plasma YKL-40, serum CA125, FIGO stage, age and radicality after primary surgery as variables, showed that elevated plasma YKL-40 was associated with a shorter survival (HR = 2.13, 95% CI: 1.40–3.25, p = 0.0004).
YKL-40 in OC tissue and plasma are related to stage and histology, but only plasma YKL-40 is a prognostic biomarker in patients with OC.
Chronic obstructive pulmonary disease (COPD) is a lethal progressive lung disease culminating in permanent airway obstruction and alveolar enlargement. Previous studies suggest CTL involvement in COPD progression; however, their precise role remains unknown. Here, we investigated whether the CTL activation receptor NK cell group 2D (NKG2D) contributes to the development of COPD. Using primary murine lung epithelium isolated from mice chronically exposed to cigarette smoke and cultured epithelial cells exposed to cigarette smoke extract in vitro, we demonstrated induced expression of the NKG2D ligand retinoic acid early transcript 1 (RAET1) as well as NKG2D-mediated cytotoxicity. Furthermore, a genetic model of inducible RAET1 expression on mouse pulmonary epithelial cells yielded a severe emphysematous phenotype characterized by epithelial apoptosis and increased CTL activation, which was reversed by blocking NKG2D activation. We also assessed whether NKG2D ligand expression corresponded with pulmonary disease in human patients by staining airway and peripheral lung tissues from never smokers, smokers with normal lung function, and current and former smokers with COPD. NKG2D ligand expression was independent of NKG2D receptor expression in COPD patients, demonstrating that ligand expression is the limiting factor in CTL activation. These results demonstrate that aberrant, persistent NKG2D ligand expression in the pulmonary epithelium contributes to the development of COPD pathologies.
Chronic obstructive pulmonary disease (COPD) is characterised by chronic inflammation of the airways and progressive destruction of lung parenchyma, a process that in most cases is initiated by cigarette smoking. Several mechanisms are involved in the development of the disease: influx of inflammatory cells into the lung (leading to chronic inflammation of the airways), imbalance between proteolytic and anti-proteolytic activity (resulting in the destruction of healthy lung tissue) and oxidative stress. Recently, an increasing number of data suggest a fourth important mechanism involved in the development of COPD: apoptosis of structural cells in the lung might possibly be an important upstream event in the pathogenesis of COPD. There is an increase in apoptotic alveolar epithelial and endothelial cells in the lungs of COPD patients. Since this is not counterbalanced by an increase in proliferation of these structural cells, the net result is destruction of lung tissue and the development of emphysema. Data from animal models suggest a role for Vascular Endothelial Growth Factor (VEGF) in the induction of apoptosis of structural cells in the lung. Other mediators of apoptosis, such as caspase-3 and ceramide, could be interesting targets to prevent apoptosis and the development of emphysema.
In this review, recent data on the role of apoptosis in COPD from both animal models as well as from studies on human subjects will be discussed. The aim is to provide an up to date summary on the increasing knowledge on the role of apoptosis in COPD and pulmonary emphysema.