Requirement for macrophage elastase for cigarette smoke-induced emphysema in mice

Inhibition of VEGF receptors causes lung cell apoptosis and emphysema

Pulmonary emphysema, a significant global health problem, is characterized by a loss of alveolar structures. Because VEGF is a trophic factor required for the survival of endothelial cells and is abundantly expressed in the lung, we hypothesized that chronic blockade of VEGF receptors could induce alveolar cell apoptosis and emphysema. Chronic treatment of rats with the VEGF receptor blocker SU5416 led to enlargement of the air spaces, indicative of emphysema. The VEGF receptor inhibitor SU5416 induced alveolar septal cell apoptosis but did not inhibit lung cell proliferation. Viewed by angiography, SU5416-treated rat lungs showed a pruning of the pulmonary arterial tree, although we observed no lung infiltration by inflammatory cells or fibrosis. SU5416 treatment led to a decrease in lung expression of VEGF receptor 2 (VEGFR-2), phosphorylated VEGFR-2, and Akt-1 in the complex with VEGFR-2. Treatment with the caspase inhibitor Z-Asp-CH(2)-DCB prevented SU5416-induced septal cell apoptosis and emphysema development. These findings suggest that VEGF receptor signaling is required for maintenance of the alveolar structures and, further, that alveolar septal cell apoptosis contributes to the pathogenesis of emphysema.

Short-term supplementation therapy does not affect elastin degradation in severe alpha(1)-antitrypsin deficiency. The American-Italian AATD Study Group

We evaluated the ability of intravenous supplementation therapy with alpha(1)-antitrypsin (AAT) to reduce the rate of urinary excretion of desmosine (DES), a specific marker of elastin degradation, in eight men and four women with emphysema due to severe, congenital deficiency of AAT (range 17-69 mg/dl). Nine were former cigarette smokers, two were current smokers, and one reported never smoking; their mean age was 54 (SD 12) yr and their mean FEV(1) was 41 (18%) of predicted. Urinary DES was measured by isotope dilution and HPLC. Prior to the start of AAT supplementation, mean DES excretion was 13.0 (5.0) microg/g creatinine, 73% higher than in healthy nonsmokers. During 8 wk of supplementation therapy, mean urinary DES excretion was 13.0 (5.9) microg/g creatinine, unchanged from the baseline period (p = 0.85 by repeated measures ANOVA). We conclude that baseline levels of elastin degradation in emphysematous patients with severe AAT deficiency were abnormally high and that 8 wk of AAT supplementation therapy did not appreciably reduce the rate of elastin degradation. These findings raise the possibilities that protective levels of AAT in the lungs are insufficient or that elastin degradation in the lungs of these subjects is not dependent upon neutrophil elastase at this time.

Evolving concepts in the pathogenesis of chronic obstructive pulmonary disease

It is arguable that more biologic insight has been gained from the study of COPD than from any other pulmonary disorder. A vast knowledge of the biology of extracellular matrix proteins, proteinases, and proteinase inhibitors has largely stemmed from the elastase:anti-elastase hypothesis for the pathogenesis of emphysema. An equally compelling case could be made that interest in, and funding for, COPD research has been woeful, and investigators have made no significant medical breakthroughs in the treatment of this disorder, which, unfortunately, is becoming epidemic worldwide. Indeed, it cannot be argued that physicians have very little treatment to offer to the many patients with COPD. Humankind is rapidly approaching a time when all human genes will be sequenced, and genetic engineering will allow determination of the function of these proteins in vivo. Expression profiling and bioinformatics will allow clinicians to assess the spectrum of genes and proteins regulated in biologic processes, no longer limiting study to naïve candidate genes. These advances will allow investigators to decipher precise pathways of complex diseases, identify genetic and environmental interactions, and ultimately lead to specific (pre)diagnoses and rational treatment. Answers to the question as to why only a subset of smokers develop COPD will enhance the understanding of the disease process. Fortunately, there has been a resurgence of interest in COPD, led largely by the pharmaceutical industry, which has discovered the potential of this unmet need. Consequently, these state-of-the-art scientific techniques are being directly applied to COPD, lending hope for the future. Of even greater importance, the tide seems to be turning on the cigarette industry. Although difficult to imagine, perhaps cigarettes will disappear in this lifetime or at least the next generation won't be fooled by this deadly habit! Well ... the rational therapy thing could work.

Large-scale expression, refolding, and purification of the catalytic domain of human macrophage metalloelastase (MMP-12) in Escherichia coli

We have cloned, overexpressed, and purified the catalytic domain (residues Gly106 to Asn268) of human macrophage metalloelastase (MMP-12) in Escherichia coli. This construct represents a truncated form of the enzyme, lacking the N-terminal propeptide domain and the C-terminal hemopexin-like domain. The overexpressed protein was localized exclusively to insoluble inclusion bodies, in which it was present as both an intact form and an N-terminally truncated form. Inclusion bodies were solubilized in an 8 M guanidine-HCl buffer and purified by gel filtration chromatography under denaturing conditions. Partial refolding of the protein by dialysis into a 3 M urea buffer caused selective degradation of the truncated form of the protein, while the intact catalytic domain was unaffected by proteolysis. An SP-Sepharose chromatography step purified the protein to homogeneity and served also to complete the refolding. The purified protein was homogeneous by mass spectrometry and had an activity similar to that of the recombinant enzyme purified from mammalian cells. The protein was both soluble and monodisperse at a concentration of 9 mg/ml. This purification procedure enables the production of 23 mg of protein per liter of E. coli culture and is amenable to large-scale protein production for structural studies.

Inducible targeting of IL-13 to the adult lung causes matrix metalloproteinase- and cathepsin-dependent emphysema

Cigarette smoke exposure is the major cause of chronic obstructive pulmonary disease (COPD). However, only a minority of smokers develop significant COPD, and patients with asthma or asthma-like airway hyperresponsiveness or eosinophilia experience accelerated loss of lung function after cigarette smoke exposure. Pulmonary inflammation is a characteristic feature of lungs from patients with COPD. Surprisingly, the mediators of this inflammation and their contributions to the pathogenesis and varied natural history of COPD are not well defined. Here we show that IL-13, a critical cytokine in asthma, causes emphysema with enhanced lung volumes and compliance, mucus metaplasia, and inflammation, when inducibly overexpressed in the adult murine lung. MMP-2, -9, -12, -13, and -14 and cathepsins B, S, L, H, and K were induced by IL-13 in this setting. In addition, treatment with MMP or cysteine proteinase antagonists significantly decreased the emphysema and inflammation, but not the mucus in these animals. These studies demonstrate that IL-13 is a potent stimulator of MMP and cathepsin-based proteolytic pathways in the lung. They also demonstrate that IL-13 causes emphysema via a MMP- and cathepsin-dependent mechanism(s) and highlight common mechanisms that may underlie COPD and asthma.

Detection of emphysema in rat lungs by using magnetic resonance measurements of 3He diffusion

Emphysema is a pulmonary disease characterized by alveolar wall destruction, resulting in enlargement of gas exchange spaces without fibrosis. This condition is a part of chronic obstructive pulmonary disease (COPD), which causes 3.5% of deaths worldwide [Anonymous (1990) World Health Stat. Q. Special, 1-51] and contributes greatly to the global burden of disease [Murray, C. J. & Lopez, A. D. (1996) Science 274, 740-743]. Alveolar regeneration has been shown in animal models and could have potential for clinical treatment of early-stage emphysema. However, current techniques for detection of emphysema are not sensitive at the initial stages. Early-stage human panacinar emphysema is modeled in elastase-treated animals. Here, we provide an in vivo imaging method for differentiating normal and emphysematous rat lungs by measuring the apparent diffusion coefficient (ADC) of hyperpolarized (3)He by using magnetic resonance imaging. These data show that the ADC is significantly larger in elastase-treated rats, indicating alveolar expansion. Whereas these rats were clinically asymptomatic, conventional histology confirmed presence of injury. Our results indicate that measurement of the hyperpolarized (3)He ADC can be a valuable research tool and has potential application in the clinical setting.

Hypoxia inhibits amino acid uptake in human lung fibroblasts

Hypoxia and amino acid deprivation downregulate expression of extracellular matrix genes in lung fibroblasts. We examined the effect of hypoxia on amino acid uptake and protein formation in human lung fibroblasts. Low O(2) tension (0% O(2)) suppressed incorporation of [(3)H]proline into type I collagen without affecting [(35)S]methionine labeling of other proteins. Initial decreases in intracellular [(3)H]proline incorporation occurred after 2 h of exposure to 0% O(2), with maximal suppression of intracellular [(3)H]proline levels at 6 h of treatment. Hypoxia significantly inhibited the uptake of radiolabeled proline, 2-aminoisobutyric acid (AIB), and 2-(methylamino)isobutyric acid (methyl-AIB) while inducing minor decreases in leucine transport. Neither cycloheximide nor indomethacin abrogated hypoxia-related suppression of methyl-AIB uptake. Efflux studies demonstrated that hypoxia inhibited methyl-AIB transport in a bidirectional fashion. The downregulation of amino acid transport was not due to a toxic effect; function recovered on return to standard O(2) conditions. Kinetic analysis of AIB transport revealed a 10-fold increase in K(m) accompanied by a small increase in maximal transport velocity among cells exposed to 0% O(2). These data indicate that low O(2) tension regulates the system A transporter by decreasing transporter substrate affinity.

The effect of hyaluronan on elastic fiber injury in vitro and elastase-induced airspace enlargement in vivo

This laboratory has previously described a method of preventing air-space enlargement in experimental pulmonary emphysema using aerosolized hyaluronan (HA). Although it was found that HA preferentially binds to elastic fibers (which undergo breakdown by elastases in emphysema), it remains to be shown that such attachment actually prevents damage to the fibers. In the current study, cell-free radiolabeled extracellular matrices, derived from rat pleural mesothelial cells, were used to test the ability of low molecular weight ( approximately 100 kDa) streptococcal HA to prevent elastolysis. Coating the matrices with HA significantly decreased elastolysis (P<0.05) induced by porcine pancreatic elastase (43%), human neutrophil elastase (53%), and human macrophage metalloelastase (80%). Concomitant in vivo studies examined the ability of an aerosol preparation of the streptococcal HA to prevent experimental emphysema induced by intratracheal administration of porcine pancreatic elastase. As seen with earlier studies involving bovine tracheal HA, a single aerosol exposure significantly decreased elastase-induced airspace enlargement, as measured by the mean linear intercept (107.5 vs 89.6 microm; P < 0. 05). Furthermore, repeated exposure to the HA aerosol for 1 month did not reveal any morphological changes in the lung. The results provide further evidence that aerosolized HA may be an effective means of preventing pulmonary emphysema and perhaps other lung diseases that involve elastic fiber injury.

Regulation of elastinolytic cysteine proteinase activity in normal and cathepsin K-deficient human macrophages

Human macrophages mediate the dissolution of elastic lamina by mobilizing tissue-destructive cysteine proteinases. While macrophage-mediated elastin degradation has been linked to the expression of cathepsins L and S, these cells also express cathepsin K, a new member of the cysteine proteinase family whose elastinolytic potential exceeds that of all known elastases. To determine the relative role of cathepsin K in elastinolysis, monocytes were differentiated under conditions in which they recapitulated a gene expression profile similar to that observed at sites of tissue damage in vivo. After a 12-d culture period, monocyte-derived macrophages (MDMs) expressed cathepsin K in tandem with cathepsins L and S. Though cysteine proteinases are acidophilic and normally confined to the lysosomal network, MDMs secreted cathepsin K extracellularly in concert with cathepsins L and S. Simultaneously, MDMs increased the expression of vacuolar-type H(+)-ATPase components, acidified the pericellular milieu, and maintained extracellular cathepsin K in an active form. MDMs from a cathepsin K-deficient individual, however, retained the ability to express, process, and secrete cathepsins L and S, and displayed normal elastin-degrading activity. Thus, matrix-destructive MDMs exteriorize a complex mix of proteolytic cysteine proteinases, but maintain full elastinolytic potential in the absence of cathepsin K by mobilizing cathepsins L and S.

Semen granulocyte elastase: its relevance for the diagnosis and prognosis of silent genital tract inflammation

Elastase-inhibitor complex was assessed by immunoassay in the seminal plasma of 312 men attending the outpatient infertility clinic. Using receiver operating characteristic (ROC) curve analysis, elastase at the cut-off value of > or =290 ng/ml was shown to be efficient (sensitivity 79.5%, specificity 74.4%) in the detection of genital tract inflammation as defined by leukocytospermia (>1x10(6) leukocytes/ml). The prevalence of increased elastase in 292 infertile men was significantly higher (34%) as compared with that (5%) observed in 20 fertile men (P: = 0.02). Moreover, high elastase concentration (> or =290 ng/ml) was observed in 66 of the 264 men (25%) without leukocytospermia. A significant positive correlation was found between elastase concentration and patient age (r = 0.202, P: < 0.0001) and the number of leukocytes (r = 0.330, P: < 0.0001). A negative correlation was found between elastase concentration and semen volume (r = -0.146, P: = 0.01) and the percentage of spermatozoa with single-stranded DNA (r = -0.194, P: = 0.024), but there was no correlation between elastase and sperm reactive oxygen species production. A higher seminal elastase concentration was significantly associated with tubal damage in female partners (P: < 0.001). After norfloxacine antibiotic therapy, decrease in elastase concentration was observed in 15 (25%) of the 60 treated patients. Tubal damage in the partner negatively affected the response to antibiotic therapy. In conclusion, granulocyte elastase is a reliable screening test for silent genital tract inflammation of the couple. The elastase-inhibitor complex may have a protective effect in reducing sperm DNA denaturation.

Impaired distal airway development in mice lacking elastin

Elastin is a major component of the mammalian lung, predominantly found in the alveoli. Destruction of alveolar elastic fibers is implicated in the pathogenic mechanism of emphysema in adults. These data define a role for elastin in the structure and function of the mature lung, and suggest that elastin is important for alveogenesis. To investigate the role of elastin in lung development, we examined mice lacking elastin (Eln-/-). At birth, the distal air sacs of Eln-/- lungs dilate to form abnormally large cavities. This phenotype appears before the synthesis and deposition of alveolar elastin, a process mediated by myofibroblasts and initiated after postnatal Day 4. Morphometric analyses demonstrate that the perinatal development of terminal airway branches is arrested in Eln-/- mice. The branching defect is accompanied by fewer distal air sacs that are dilated with attenuated tissue septae, a condition reminiscent of emphysema. Elastin expression in the lung parenchyma before alveogenesis is localized to the mesenchyme surrounding the developing airways, supporting a role for elastin in airway branching. Thus, in addition to its role in the structure and function of the mature lung, elastin is essential for pulmonary development and is important for terminal airway branching.

TIMP-2 is required for efficient activation of proMMP-2 in vivo

Matrix metalloproteinases (MMPs) are synthesized as latent proenzymes. A proteolytic cleavage event involving processing of the cysteine-rich N-terminal propeptide is required for their full activation. Previous in vitro studies indicated that activation of proMMP-2 can occur through formation of a trimolecular complex between MMP-14, TIMP-2, and proMMP-2 at the cell surface. Using TIMP-2-deficient mice and cells derived from them, TIMP-2 was shown to be required for efficient proMMP-2 activation both in vivo and in vitro. The requirement for TIMP-2 was not cell-autonomous as exogenously added TIMP-2 could restore activation of proMMP-2 to TIMP-2-deficient cells. Mutant mice were overtly normal, viable, and fertile on the C57BL/6 background, indicating that both TIMP-2 and activated proMMP-2 are dispensable for normal development.

Smoking increases tissue factor expression in atherosclerotic plaques: implications for plaque thrombogenicity

BACKGROUND

Smoking increases the risk of atherothrombotic events. To determine whether smoking influences plaque thrombogenicity, we examined the effect of cigarette smoking and aspirin use on tissue factor (TF) expression in atherosclerotic plaques.

METHODS AND RESULTS

A total of 23 apoE-/- mice were exposed to cigarette smoke with (n=9) or without (n=14) aspirin treatment. Eleven mice who were exposed to filtered room air served as controls. Aortic root plaques of mice exposed to smoke had higher immunoreactivity for TF (14+/-4% versus 6.4+/-3%; P=0.0005), vascular cell adhesion molecule-1 (15+/-4% versus 5+/-2%; P=0.002), and macrophages (16+/-5% versus 6+/-2%; P=0.002) compared with nonsmoking controls. Aspirin treatment attenuated smoking-induced changes in plaque composition. In human plaques obtained by carotid endarterectomy, TF immunoreactivity (8+/-5% versus 2+/-2%; P=0.0002) and activity (P=0. 03) were higher in the plaques from smokers (n=28) than those from nonsmokers (n=28). Aspirin use was associated with reduced TF expression in smokers (9+/-8% versus 3+/-4%; P=0.0017).

CONCLUSIONS

Our results suggest increased plaque TF expression and thrombogenicity as a novel mechanism for the increased risk of atherothrombotic events in smokers. Treatment with aspirin may reduce TF expression.

Gelatinase B (MMP-9) is not essential in the normal kidney and does not influence progression of renal disease in a mouse model of Alport syndrome

Matrix metalloproteinases are matrix degrading enzymes implicated in many biological processes, including development and inflammation. Gelatinase B (gelB; also known as MMP-9) is expressed in the kidney and is hypothesized to be involved in basement membrane remodeling and in preventing pathogenic accumulation of extracellular matrix in the kidney. Inhibition of gelB activity in metanephric organ culture disrupts branching morphogenesis of the ureteric bud, suggesting that gelB plays a role in kidney development in vivo. We studied kidneys of gelB-deficient mice to search for developmental, histological, molecular, ultrastructural, and functional defects. Surprisingly, no differences between gelB-/- and control kidneys were detected, and renal function was normal in gelB mutants. In addition, gelB-/- embryonic kidneys developed normally in organ culture. Gelatinase B-deficient mice were bred with Col4a3-/- mice, a model for Alport syndrome, to determine whether gelB influences the progression of glomerulonephritis. This is an important question, as it has been hypothesized that proteases are involved in damaging Alport glomerular basement membrane. However, the presence or absence of gelB did not affect the rate of progression of renal disease. Thus, gelB does not have a discernible role in the normal kidney and gelB is not involved in the progression of glomerulonephritis in a mouse model of Alport syndrome.

Ciliogenesis and left-right axis defects in forkhead factor HFH-4-null mice

Cilia have been classified as sensory or motile types on the basis of functional and structural characteristics; however, factors important for regulation of assembly of different cilia types are not well understood. Hepatocyte nuclear factor-3/forkhead homologue 4 (HFH-4) is a winged helix/forkhead transcription factor expressed in ciliated cells of the respiratory tract, oviduct, and ependyma in late development through adulthood. Targeted deletion of the Hfh4 gene resulted in defective ciliogenesis in airway epithelial cells and randomized left-right asymmetry so that half the mice had situs inversus. In HFH-4-null mice, classic motile type cilia with a 9 + 2 microtubule ultrastructure were absent in epithelial cells, including those in the airways. In other organs, sensory cilia with a 9 + 0 microtubule pattern, such as those on olfactory neuroepithelial cells, were present. Ultrastructural analysis of mutant cells with absent 9 + 2 cilia demonstrated that defective ciliogenesis was due to abnormal centriole migration and/or apical membrane docking, suggesting that HFH-4 functions to direct basal body positioning or anchoring. Evaluation of wild-type embryos at gestational days 7.0 to 7.5 revealed Hfh4 expression in embryonic node cells that have monocilium, consistent with a function for this factor at the node in early determination of left- right axis. Analysis of the node of HFH-4 mutant embryos revealed that, in contrast to absent airway cilia, node cilia were present. These observations indicate that there are independent regulatory pathways for node ciliogenesis compared with 9 + 2 type ciliogenesis in airways, and support a central role for HFH-4 in ciliogenesis and left-right axis formation.

Targeted gene disruption of matrix metalloproteinase-9 (gelatinase B) suppresses development of experimental abdominal aortic aneurysms

Abdominal aortic aneurysms represent a life-threatening condition characterized by chronic inflammation, destructive remodeling of the extracellular matrix, and increased local expression of matrix metalloproteinases (MMPs). Both 92-kD gelatinase (MMP-9) and macrophage elastase (MMP-12) have been implicated in this disease, but it is not known if either is necessary in aneurysmal degeneration. We show here that transient elastase perfusion of the mouse aorta results in delayed aneurysm development that is temporally associated with transmural mononuclear inflammation, increased local production of several elastolytic MMPs, and progressive destruction of the elastic lamellae. Elastase-induced aneurysmal degeneration was suppressed by treatment with a nonselective MMP inhibitor (doxycycline) and by targeted gene disruption of MMP-9, but not by isolated deficiency of MMP-12. Bone marrow transplantation from wild-type mice prevented the aneurysm-resistant phenotype in MMP-9-deficient animals, and wild-type mice acquired aneurysm resistance after transplantation from MMP-9-deficient donors. These results demonstrate that inflammatory cell expression of MMP-9 plays a critical role in an experimental model of aortic aneurysm disease, suggesting that therapeutic strategies targeting MMP-9 may limit the growth of small abdominal aortic aneurysms.

Differential regulation of type IV collagenases and metalloelastase in murine macrophages by the synthetic bacterial lipopeptide JBT 3002

We determined whether the expression of matrix metalloproteinases (MMP) and tissue inhibitors of MMPs (TIMP) in murine macrophages is regulated by the novel synthetic bacterial lipopeptide JBT 3002. Multilamellar liposomes (MLV) encapsulating JBT 3002 (MLV-JBT 3002) stimulated the production of 72-kDa and 92-kDa (gelatinase A and B) type IV collagenase and inhibited the production of murine metalloelastase (MME) in a dose-dependent manner in murine peritoneal macrophages. MLV-JBT 3002 also induced production of TIMP-1. MLV-JBT 3002 did not induce collagenase production in tumor cells. Priming murine macrophages with interferon-gamma (IFN-gamma) inhibited JBT 3002-stimulated production of both MMP-9 and MMP-2 and further inhibited production of MME by a mechanism involving nitric oxide (NO). This conclusion is based on data showing that IFN-gamma failed to inhibit production of MMP in the presence of L-methyl arginine or in macrophages from inducible nitric oxide synthase knockout mice. These data suggest that JBT 3002 differentially regulates the production of various MMPs and TIMP in macrophages.

Comparison of the structural and inflammatory features of COPD and asthma. Giles F. Filley Lecture

At least three conditions contribute to COPD. (1) Chronic bronchitis (mucous hypersecretion) is an inflammatory condition in which CD8+ T-lymphocytes, neutrophils, and CD68+ monocytes/macrophages predominate. The condition is defined clinically by the presence of chronic cough and recurrent increases in bronchial secretions sufficient to cause expectoration. There is enlargement of mucus-secreting glands and goblet cell hyperplasia, which can occur in the absence of airflow limitation. (2) Adult chronic bronchiolitis (small or peripheral airways disease) is an inflammatory condition of small bronchi and bronchioli in which there are predominantly CD8+ and pigmented macrophages. The functional defect is difficult to detect clinically but may be recognized by sophisticated tests of small airway function. There is mucous metaplasia, enlargement of the mass of bronchiolar smooth muscle, and loss of alveolar attachments. (3) Emphysema is an inflammatory condition of the alveoli in which T-lymphocytes, neutrophils, and pigmented alveolar macrophages are involved, associated with the release of excessive amounts of elastases. It is defined anatomically by permanent, destructive enlargement of airspaces distal to terminal bronchioli without obvious fibrosis. In contrast, asthma is a clinical syndrome characterized by allergic inflammation of bronchi and bronchioli in which CD4+ (helper) T-lymphocytes and eosinophils predominate. There is increased production and release of interleukin (IL)-4 and IL-5, which is referred to as a Th2-type response. There is usually increased tracheobronchial responsiveness to a variety of stimuli, and the condition is usually manifest as variable airflow obstruction. While differences between COPD and asthma have been highlighted, new data are emerging that indicate there may also be similarities.

Impaired endochondral ossification and angiogenesis in mice deficient in membrane-type matrix metalloproteinase I

Membrane-type matrix metalloproteinase I (MT1-MMP)-deficient mice were found to have severe defects in skeletal development and angiogenesis. The craniofacial, axial, and appendicular skeletons were severely affected, leading to a short and domed skull, marked deceleration of postnatal growth, and death by 3 wk of age. Shortening of bones is a consequence of decreased chondrocyte proliferation in the proliferative zone of the growth plates. Defective vascular invasion of cartilage leads to enlargement of hypertrophic zones of growth plates and delayed formation of secondary ossification centers in long bones. In an in vivo corneal angiogenesis assay, null mice did not have angiogenic response to implanted FGF-2, suggesting that the defect in angiogenesis is not restricted to cartilage alone. In tissues from null mice, activation of latent matrix metalloproteinase 2 was deficient, suggesting that MT1-MMP is essential for its activation in vivo.

Monocyte chemoattractant protein 1, interleukin 8, and chronic airways inflammation in COPD

Chronic obstructive pulmonary disease (COPD) is one of the most common causes of death, with cigarette smoking among the main risk factors. Hallmarks of COPD include chronic airflow obstruction and chronic inflammation in the airway walls or alveolar septa. An earlier study reported elevated numbers of macrophages and mast cells within the bronchiolar epithelium in smokers with COPD, compared with smokers without. Since specific chemokines may be involved in this influx, the in situ protein and mRNA expression of monocyte chemoattractant protein 1 (MCP-1) and of interleukin 8 (IL-8) were studied in tumour-free peripheral lung tissue resected for lung cancer of current or ex-smokers with COPD (FEV(1)<75%; n=14) and without COPD (FEV(1)>84; n=14). MCP-1 was expressed by macrophages, T cells, and endothelial and epithelial cells. Its receptor, CCR2, is expressed by macrophages, mast cells, and epithelial cells. IL-8 was found in neutrophils, epithelial cells, and macrophages. In subjects with COPD, semi-quantitative analysis revealed 1.5-fold higher levels of MCP-1 mRNA and IL-8 mRNA and protein in bronchiolar epithelium (p<0.01) and 1.4-fold higher levels of CCR2 in macrophages (p=0.014) than in subjects without COPD. The bronchiolar epithelial MCP-1 mRNA expression correlated with both CCR2 expression on macrophages and mast cells (p<0.05) and the numbers of intra-epithelial macrophages and mast cells (p<0.04). The epithelial IL-8 expression did not correlate with the numbers of neutrophils, macrophages, CD45RO+, CD8+, or mast cells. These data suggest that MCP-1 and CCR2 are involved in the recruitment of macrophages and mast cells into the airway epithelium in COPD.

Upregulation of gelatinases A and B, collagenases 1 and 2, and increased parenchymal cell death in COPD

BACKGROUND

A central feature in the pathogenesis of COPD is the inflammation coexisting with an abnormal protease/antiprotease balance. However, the possible role of different serine and metalloproteinases remains controversial.

PATIENTS AND MEASUREMENTS

We examined the expression of gelatinases A and B (matrix metalloproteinase [MMP]-2 and MMP-9); collagenases 1, 2, and 3 (MMP-1, MMP-8, and MMP-13); as well as the presence of apoptosis in lung tissues of 10 COPD patients and 5 control subjects. In addition, gelatinase-A and gelatinase-B activities were assessed in BAL obtained from eight COPD patients, and from six healthy nonsmokers and six healthy smoker control subjects.

SETTING

Tertiary referral center and university laboratories of biochemistry, and lung cell kinetics.

RESULTS

Immunohistochemical analysis of COPD lungs showed a markedly increased expression of collagenases 1 and 2, and gelatinases A and B, while collagenase 3 was not found. Neutrophils exhibited a positive signal for collagenase 2 and gelatinase B, whereas collagenase 1 and gelatinase A were revealed mainly in macrophages and epithelial cells. BAL gelatin zymography showed a moderate increase of progelatinase-A activity and intense bands corresponding to progelatinase B. In situ end labeling of fragmented DNA displayed foci of positive endothelial cells, although some alveolar epithelial, interstitial, and inflammatory cells also revealed intranuclear staining.

CONCLUSION

These findings suggest that there is an upregulation of collagenase 1 and 2 and gelatinases A and B, and an increase in endothelial and epithelial cell death, which may contribute to the pathogenesis of COPD through the remodeling of airways and alveolar structures.

Smoking and chronic obstructive pulmonary disease

Smoking is overwhelmingly the major cause of chronic bronchitis and emphysema worldwide. Additional risk factors for developing COPD are presented, along with the variables that govern cigarette smoke deposition in the lung. Major paradigms for the pathogenesis of COPD, including the protease-antiprotease and oxidant-antioxidant theories are described, and evidence for impaired reparative mechanisms in the causation of emphysema is noted. A description of the natural history of declining lung function in smokers and in the susceptible subset of smokers that ultimately develop smoking-induced COPD is accompanied by a discussion of the effects of smoking cessation on preservation of lung health. The disordered ventilation and gas-exchange physiology in the cigarette smoke-damaged lung is explained on the basis of the observed morphological changes.

An overview of collagenase-3 expression in malignant tumors and analysis of its potential value as a target in antitumor therapies

Collagenase-3 (MMP-13) is a member of the matrix metalloproteinase family of endopeptidases that is characterized by a potent degrading activity against a wide spectrum of substrates. This enzyme was first detected in breast carcinomas but it is also overexpressed in a variety of malignant tumors including head and neck carcinomas, chondrosarcomas, skin carcinomas, and carcinomas of the female genital tract. Clinical studies have revealed that in all these tumors collagenase-3 expression is associated with invasive and metastatic tumors. Analysis of the molecular mechanisms underlying its marked overexpression in malignant tumors has allowed to identify different cytokines, growth factors and tumor promoters with ability to up-regulate collagenase-3 expression in tumor cells, or in stromal fibroblasts surrounding epithelial tumor cells. The first strategies designed to target this enzyme are being developed, and are mainly directed to prepare synthetic inhibitors with ability to selectively block the collagenase-3 proteolytic activity. Alternatively, inhibitors of the signal transduction pathways mediating the expression of this enzyme by tumor cells may also be useful for collagenase-3 targeting. These studies together with those performed on other enzymes associated with tumor processes may lead to the development of novel therapeutic strategies to control the progression and metastatic capacity of neoplastic cells.

Acute cigarette smoke-induced connective tissue breakdown is mediated by neutrophils and prevented by alpha1-antitrypsin

Recent studies have suggested that macrophage-derived metalloproteases are the critical mediators of cigarette smoke-induced emphysema, in contrast to earlier hypotheses that this process was mediated by neutrophil elastase. To determine whether smoke can acutely induce connective tissue breakdown in the lung and to examine the mediators of this process, we exposed C57-BL/6 mice to whole cigarette smoke and used high-performance liquid chromatography to examine lavage fluid levels of desmosine (DES), a marker of elastin breakdown, and hydroxyproline (HP), a marker of collagen breakdown. Smoke produced a dose-response increase in lavage neutrophils, DES, and HP, but not lavage macrophages (MACs). This effect was evident by 6 h after exposure to two cigarettes. Pretreatment with an antibody against polymorphonuclear leukocytes (PMNs) reduced lavage PMNs to undetectable levels after smoke exposure, did not affect MAC numbers, and prevented increases in lavage DES and HP. Intraperitoneal injection of a commercial human alpha1-antitrypsin (alpha1AT) 24 h before smoke exposure increased serum alpha1AT levels approximately 3-fold and completely abolished smoke-induced connective tissue breakdown as well as the increase in lavage PMNs, again without affecting MAC numbers. We conclude that in this model cigarette smoke can acutely induce connective tissue breakdown and that this effect is mediated by neutrophil-derived serine proteases, most likely neutrophil elastase. Exogenous alpha1AT is protective and appears to inhibit both matrix degradation and PMN influx, suggesting that alpha1AT has anti-inflammatory as well as antiproteolytic effects in this system.

Mechanisms in COPD: differences from asthma

Although considerable progress has been made in understanding the cellular and molecular mechanisms of asthma, much less attention has been paid to COPD. The inflammatory process in COPD is very different from that in asthma, with different inflammatory cells, mediators, inflammatory effects, and response to therapy. Airway inflammation in asthma, characterized by an eosinophilic inflammation affecting all the airways but not lung parenchyma, is linked to airway hyperresponsiveness. In COPD, there is a predominantly neutrophilic inflammation in the airways. Parenchymal destruction is an important irreversible feature and leads to airflow obstruction through dynamic compression. The eosinophilic inflammation in asthma is markedly suppressed by corticosteroids, but they have no appreciable effect on the inflammation in COPD, consistent with a failure of long-term corticosteroids to alter the progression of COPD.

Substance P and neurokinin-1 receptor expression by intrinsic airway neurons in the rat

Tachykinins and their receptors are involved in the amplification of inflammation in the airways. We analyzed the expression of preprotachykinin-A (PPT-A) and neurokinin-1 (NK-1) receptor genes by intrinsic airway neurons in the rat. We also tested the hypothesis that PPT-A-encoded peptides released by these neurons fulfill the requisite role of substance P in immune complex injury of the lungs. We found that ganglion neurons in intact and denervated airways or in primary culture coexpress PPT-A and NK-1 receptor mRNAs and their protein products. Denervated ganglia from tracheal xenografts (nu/nu mice) or syngeneic lung grafts had increased PPT-A mRNA contents, suggesting preganglionic regulation. Formation of immune complexes in the airways induced comparable inflammatory injuries in syngeneic lung grafts, which lack peptidergic sensory fibers, and control lungs. The injury was attenuated in both cases by pretreatment with the NK-1 receptor antagonist LY-306740. We conclude that tachykinins released by ganglia act as a paracrine or autocrine signal in the airways and may contribute to NK-1 receptor-mediated amplification of immune injury in the lungs.

Novel therapy for COPD

The incidence of chronic obstructive pulmonary disease (COPD) is increasing throughout the world. Much less is known about the pathogenesis of COPD than that of asthma and there is little response to current therapy. Most patients with COPD have acquired their lung disease through smoking cigarettes, and the major step in management is to minimise further damage by stopping this habit. A number of therapies are being developed for the treatment of COPD; including new bronchodilators such as tiotropium bromide, agents to block inflammation induced by neutrophils and macrophages, as well as strategies to combat proteases and oxidants. The long-term goal is to provide therapy that retards the accelerated loss of lung function occurring in COPD. Development of novel therapies for COPD requires reliable Phase II decision making before entering large scale Phase III studies. The patient with COPD is often overlooked compared to their asthmatic counterpart, who benefit from an urgent need to identify novel targets and better therapy.

A critical role for neutrophil elastase in experimental bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune skin disease characterized by subepidermal blisters and autoantibodies against 2 hemidesmosome-associated proteins, BP180 and BP230. The immunopathologic features of BP can be reproduced in mice by passive transfer of anti-BP180 antibodies. Lesion formation in this animal model depends upon complement activation and neutrophil recruitment. In the present study, we investigated the role of neutrophil elastase (NE) in antibody-induced blister formation in experimental BP. Abnormally high levels of caseinolytic activity, consistent with NE, were detected in extracts of lesional skin and blister fluid of mice injected with anti-BP180 IgG. The pathogenic anti-BP180 IgG failed to induce subepidermal blistering in NE-null (NE(-/-)) mutant mice. NE(-/-) mice reconstituted with neutrophils from wild-type mice became susceptible to experimental BP. Wild-type mice given NE inhibitors (alpha1-proteinase inhibitor and Me-O-Suc-Ala-Ala-Pro-Val-CH(2)Cl), but not mice given cathepsin G/chymase inhibitors (alpha1-antichymotrypsin or Z-Gly-Leu-Phe-CH(2)Cl), were resistant to the pathogenic activity of anti-BP180 antibodies. Incubation of murine skin with NE induced BP-like epidermal-dermal detachment. Finally, NE cleaved BP180 in vitro and in vivo. These results implicate NE directly in the dermal-epidermal cleavage induced by anti-BP180 antibodies in the experimental BP model.

Effect of cigarette smoking on oral elastase activity in adult periodontitis patients

BACKGROUND

We have previously reported that elastase activity in oral fluids is significantly increased in most adult periodontitis patients. In some patients, however, elastase levels remain low despite the presence of deep periodontal pockets. In this study we explored whether or not smoking is related to the unexpected low elastase values in these patients.

METHODS

We determined what proportion of the periodontitis patients that showed low oral elastase values were smokers. Paraffin-stimulated saliva or oral rinse samples (3 ml of water, 30 second rinse) were assayed for elastase activity by incubating with 1 mM succinyl-alanyl-alanyl-valine-p-nitroanilide for 20 hours at 37 degrees C, and the color formation read with a spectrophotometer. Neutrophil numbers were analyzed by staining the cells in the oral rinse smear samples.

RESULTS

In 2 patient groups, one in Helsinki, Finland (n = 46) and the other in Vancouver, British Columbia (n = 25), 63% and 83%, respectively, of the adult periodontitis patients who had one or more pockets > or =6 mm and had low oral elastase values (increase of optical density <0.5) were smokers. Non-smoking periodontitis patients had elevated neutrophil numbers compared to healthy subjects, while the smoking patients showed no significant change. Next we analyzed elastase levels in stimulated whole saliva in a group of smokers (n = 300) and those who had quit smoking (n = 102). Smokers had significantly lower oral elastase levels than former smokers in both advanced and moderate periodontitis groups. In this subject group, 56% of all smokers with periodontitis (at least one pocket > or =6 mm) had oral elastase values less than 0.5 U while only 31% of those patients who had quit smoking had low values.

CONCLUSIONS

Cigarette smoking leads to lowered elastase and neutrophil levels in the oral cavity. The oral neutrophil elastase assay, therefore, cannot be used to measure the periodontal status of smokers.

Disruption of the klotho gene causes pulmonary emphysema in mice. Defect in maintenance of pulmonary integrity during postnatal life

Homozygous mutant klotho (KL(-/-)) mice exhibit multiple phenotypes resembling human aging. In the present study, we focused on examining the pathology of the lungs of klotho mice and found that it closely resembled pulmonary emphysema in humans both histologically and functionally. Histology of the lung of KL(-/-) mice was indistinguishable from those of wild-type littermates up to 2 wk of age. The first histologic changes appeared at 4 wk of age, showing enlargement of the air spaces accompanied by destruction of the alveolar walls, and progressed gradually with age. In addition to these changes, we observed calcium deposits in type I collagen fibers in alveolar septa and degeneration of type II pneumocytes in 8- to 10-wk-old KL(-/-) mice. Pulmonary function tests revealed prolonged expiration time in KL(-/-) mice, which is comparable with the pathophysiology of pulmonary emphysema. The expression level of messenger RNA for type IV collagen, surfactant protein-A and mitochondrial beta-adenosine triphosphatase was significantly increased in KL(-/-) mice, which may represent a compensatory response to alveolar destruction. Additionally, the heterozygous mutant klotho mice also developed pulmonary emphysema late in life, around 120 wk of age. These findings indicate that klotho gene expression is essential to maintaining pulmonary integrity during postnatal life. The klotho mutant mouse is a useful laboratory animal model for examining the relationship between aging and pulmonary emphysema.

Smoke extract stimulates lung fibroblasts to release neutrophil and monocyte chemotactic activities

Accumulation of monocytes and neutrophils and fibrous distortion of the airway are characteristics of airway disease secondary to smoking. The presence of inflammatory cells and fibrosis correlate, and, therefore, we postulated that lung fibroblasts might release chemotactic activity for neutrophils and monocytes in response to smoke extract. To test this hypothesis, human fetal lung (HFL1) fibroblasts were cultured, and the supernatant fluid was evaluated for neutrophil (NCA) and monocyte (MCA) chemotactic activities with a blind well chamber technique. HFL1 fibroblasts released chemotactic activity in response to smoke extract in a dose- and time-dependent manner (P < 0.05). Checkerboard analysis showed that the activity was predominantly chemotactic. Partial characterization of the released chemotactic activity revealed that the activity was partly heat labile, trypsin sensitive, and ethyl acetate extractable. Lipoxygenase inhibitors and cycloheximide inhibited the release of both NCA and MCA. Molecular-sieve chromatography revealed that NCA and MCA were heterogeneous. NCA was inhibited by anti-human interleukin (IL)-8 and anti-granulocyte colony-stimulating factor antibodies and a leukotriene (LT) B(4)-receptor antagonist. Anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) and anti-monocyte chemoattractant protein (MCP)-1 antibodies and an LTB(4)-receptor antagonist inhibited MCA. Immunoreactive IL-8, granulocyte colony-stimulating factor, GM-CSF, and MCP-1 significantly increased in culture supernatant fluid in response to smoke extract. Finally, smoke extract augmented the expression of mRNAs of IL-8, GM-CSF, and MCP-1. These data demonstrate that lung fibroblasts release NCA and MCA in response to smoke extract and suggest that lung fibroblasts may modulate the inflammatory cell recruitment into the lung.

Effect of high dose inhaled steroid on cells, cytokines, and proteases in induced sputum in chronic obstructive pulmonary disease

Inhaled corticosteroids are widely prescribed for the treatment of stable chronic obstructive pulmonary disease (COPD), despite lack of proven efficacy. Because COPD involves airway inflammation and probable protease-antiprotease imbalance, we examined the effect of high dose fluticasone propionate on markers of activity of both pathogenetic mechanisms. Thirteen patients with COPD were treated with fluticasone propionate (500 microg twice a day) for 4 wk, delivered via MDI and spacer, in a double-blind crossover study. There was no clinical benefit in terms of lung function or symptom scores, and induced sputum inflammatory cells, percentage neutrophils, and IL-8 levels were unchanged. Sputum supernatant elastase activity, matrix metalloproteinase (MMP)-1, MMP-9, and the antiproteases secretory leukoprotease inhibitor (SLPI) and tissue inhibitor of metalloproteinase (TIMP)-1 were similarly unaffected by treatment. These results add to previous evidence that inhaled steroids have no anti-inflammatory action in stable COPD. Furthermore, inhaled steroids do not appear to redress the protease-antiprotease imbalance that is thought to be important in the pathogenesis of airway obstruction.

The macrophage in chronic obstructive pulmonary disease

Macrophages are the predominant defense cell in the normal lung and during conditions associated with chronic inflammation such as COPD. However, the role of the macrophage in the development of COPD has been controversial. Scientific evidence from a variety of sources is emerging that supports a primary role for the macrophage in regulating the inflammatory response and tissue destruction associated with COPD. The role of macrophage proteinases in the development of emphysema, a major component of COPD, will be discussed. Shapiro SD. The macrophage in chronic obstructive pulmonary disease.

Inflammation and repair processes in chronic obstructive pulmonary disease

COPD is characterized by chronic inflammation and injury of both the airways and the parenchymal structures of the lung. These processes are associated with ongoing repair. Whether repair leads to restoration of normal tissue architecture or to altered tissue structure with loss of function depends on complex interrelationships of a variety of interacting mediators. The possibility that repair processes can be modulated by exogenous agents raises the possibility that therapeutic strategies aimed at repair can be effective. Such strategies offer tremendous promise both for slowing the relentlessly progressive natural history which most often characterizes COPD and, possibly, for restoring lung function. Rennard SI. Inflammation and repair processes in chronic obstructive pulmonary disease.

Matrix metalloproteinases in repair

During repair, many different matrix metalloproteinases are produced by multiple cell types residing in various compartments within the wound environment. This diversity of enzymes, coupled with discreet cellular expression, implies that different matrix metalloproteinases serve different functions, acting on a variety of substrates, during wound healing. With few exceptions, however, the actual function and spectrum of functions of matrix metalloproteinases in vivo is not known. Even with the advent of genetically defined animal models, few studies have rigorously addressed the substrates and role of matrix metalloproteinases in wound repair. Before we can understand the role of matrix metalloproteinases in ulceration and disease, we need to determine the function these enzymes serve in normal tissues and repair.

Novel approaches and targets for treatment of chronic obstructive pulmonary disease

There is a driving need to develop new and effective treatments for COPD. Bronchodilators are now the mainstay of symptomatic therapy and a new long-acting anticholinergic bronchodilator, tiotropium bromide, is now in advanced clinical trials as a once daily dry powder inhaler. Several inflammatory mediators are involved in the chronic neutrophilic inflammation that typifies COPD, including leukotriene B(4) and interleukin 8, for which specific receptor antagonists have been developed. Since the inflammatory process in COPD is essentially steroid resistant, new antiinflammatory treatments are needed. Drugs that may be effective include phosphodiesterase 4 inhibitors, NF-kappaB inhibitors, and interleukin 10. Inhibition of proteases is another approach and inhibitors of neutrophil elastase, cathepsins, and matrix metalloproteases are now in clinical development. Supply of endogenous antiproteases, such as alpha(1)-antitrypsin and secretory leukocyte protease inhibitors as recombinant proteins or by gene transfer, is also being explored. In future drugs that may stimulate alveolar repair might be developed, including retinoid receptor agonists and hepatic growth factor. Future directions will include earlier detection of disease, gene profiling to identify which smokers are at risk of COPD, and the development of noninvasive surrogate markers to monitor disease activity in order to monitor new therapies. Identification of genes that confer a risk for COPD in smokers may identify novel targets for drug development. Barnes PJ. Novel approaches and targets for treatment of chronic obstructive pulmonary disease.

Accumulation of matrilysin (MMP-7) and macrophage metalloelastase (MMP-12) in actinic damage

Photodamage is characterized by degradation of collagen and accumulation of abnormal elastin in the superficial dermis and several matrix metalloproteinases have previously been implicated in this process. Using immunohistochemistry and in situ hybridization, we have studied the localization of two elastolytic matrix metalloproteinases, matrilysin (matrix metalloproteinase-7) and human macrophage metalloelastase (matrix metalloproteinase-12) in solar damage. Human macrophage metalloelastase protein was detected in the superficial dermis in areas of elastotic material. Matrix metalloproteinase-7 was seen in the mid-dermis in regions with less damaged elastic fibers and morphologically better preserved collagen as well as in a band-like pattern below basal keratinocytes in eight of 18 solar elastosis. In samples taken from healthy volunteers 3 d after repeated ultraviolet A or ultraviolet B photoprovocation, occasional immunopositive cells for human macrophage metalloelastase (stromal) or matrix metalloproteinase-7 (sweat gland epithelium) were detected. In samples taken 1 d after ultraviolet B exposure, however, basal keratinocytes were matrix metalloproteinase-7 immunopositive, explaining the linear immunostaining below basal keratinocytes noted particularly in ultraviolet B treated 3 d specimens. Upregulation of metalloelastase was also demonstrated in the skin of hairless mice after repeated ultraviolet exposure. In normal skin, no staining for human macrophage metalloelastase or matrix metalloproteinase-7 was observed in association with elastin. The amount of immunoreactivity for the substrates of matrix metalloproteinase-7, versican, and tenascin, was clearly increased in solar elastosis and photoprovocated skin; versican but not tenascin was detected in the same areas as matrix metalloproteinase-7. Our results suggest that both matrix metalloproteinase-7 and -12 may contribute to remodeling of elastotic areas in sun-damaged skin.

Monocyte inflammation augments acrolein-induced Muc5ac expression in mouse lung

Acrolein, an unsaturated aldehyde found in smog and tobacco smoke, can induce airway hyperreactivity, inflammation, and mucus hypersecretion. To determine whether changes in steady-state mucin gene expression (Muc2 and Muc5ac) are associated with inflammatory cell accumulation and neutrophil elastase activity, FVB/N mice were exposed to acrolein (3.0 parts/million; 6 h/day, 5 days/wk for 3 wk). The levels of Muc2 and Muc5ac mRNA were determined by RT-PCR, and the presence of Muc5ac protein was detected by immunohistochemistry. Total and differential cell counts were determined from bronchoalveolar lavage (BAL) fluid, and neutrophil elastase activity was measured in the BAL fluid supernatant. Lung Muc5ac mRNA was increased on days 12 and 19, and Muc5ac protein was detected in mucous granules and on the surface of the epithelium on day 19. Lung Muc2 mRNA was not detected at measurable levels in either control or exposed mice. Acrolein exposure caused a significant and persistent increase in macrophages and a rapid but transient increase in neutrophils in BAL fluid. Recoverable neutrophil elastase activity was not significantly altered at any time after acrolein exposure. To further examine the role of macrophage accumulation in mucin gene expression, additional strains of mice (including a strain genetically deficient in macrophage metalloelastase) were exposed to acrolein for 3 wk, and Muc5ac mRNA levels and macrophage accumulation were measured. The magnitude of macrophage accumulation coincided with increased Muc5ac mRNA levels, indicating that excessive macrophage accumulation augments acrolein-induced Muc5ac synthesis and secretion after repeated exposure. These findings support a role for chronic monocytic inflammation in the pathogenesis of mucus hypersecretion observed in chronic bronchitis.

The pathogenesis of chronic obstructive pulmonary disease

Cigarette smoking is the main risk factor for the development of chronic obstructive pulmonary disease (COPD). An accelerated rate of lung function decline that causes clinically significant COPD, however, is present in only a minority of smokers. In addition to the cumulative amount of cigarettes smoked, other environmental and genetic properties contribute to this variable physiological response. This article reviews the role of airway hyperresponsiveness, mucus hypersecretion, infection, and proteases in the development of COPD.