Therapeutic inhibition of matrix metalloproteinases for the treatment of chronic obstructive pulmonary disease (COPD)

The Purinergic System as a Pharmacological Target for the Treatment of Immune-Mediated Inflammatory Diseases

Immune-mediated inflammatory diseases (IMIDs) encompass a wide range of seemingly unrelated conditions, such as multiple sclerosis, rheumatoid arthritis, psoriasis, inflammatory bowel diseases, asthma, chronic obstructive pulmonary disease, and systemic lupus erythematosus. Despite differing etiologies, these diseases share common inflammatory pathways, which lead to damage in primary target organs and frequently to a plethora of systemic effects as well. The purinergic signaling complex comprising extracellular nucleotides and nucleosides and their receptors, the P2 and P1 purinergic receptors, respectively, as well as catabolic enzymes and nucleoside transporters is a major regulatory system in the body. The purinergic signaling complex can regulate the development and course of IMIDs. Here we provide a comprehensive review on the role of purinergic signaling in controlling immunity, inflammation, and organ function in IMIDs. In addition, we discuss the possible therapeutic applications of drugs acting on purinergic pathways, which have been entering clinical development, to manage patients suffering from IMIDs.

Update on the pathological processes, molecular biology, and clinical utility of N-acetylcysteine in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common and morbid disease characterized by high oxidative stress. Its pathogenesis is complex, and involves excessive oxidative stress (redox imbalance), protease/antiprotease imbalance, inflammation, apoptosis, and autoimmunity. Among these, oxidative stress has a pivotal role in the pathogenesis of COPD by initiating and mediating various redox-sensitive signal transduction pathways and gene expression. The protective physiological mechanisms of the redox balance in the human body, their role in the pathogenesis of COPD, and the clinical correlation between oxidative stress and COPD are reviewed in this paper. N-acetylcysteine (NAC) is a mucolytic agent with both antioxidant and anti-inflammatory properties. This paper also reviews the use of NAC in patients with COPD, especially the dose-dependent properties of NAC, eg, its effects on lung function and the exacerbation rate in patients with the disease. Earlier data from BRONCUS (the Bronchitis Randomized on NAC Cost-Utility Study) did not suggest that NAC was beneficial in patients with COPD, only indicating that it reduced exacerbation in an “inhaled steroid-naïve” subgroup. With regard to the dose-dependent properties of NAC, two recent randomized controlled Chinese trials suggested that high-dose NAC (1,200 mg daily) can reduce exacerbations in patients with COPD, especially in those with an earlier (moderately severe) stage of disease, and also in those who are at high risk of exacerbations. However, there was no significant effect on symptoms or quality of life in patients receiving NAC. Further studies are warranted to investigate the effect of NAC at higher doses in non-Chinese patients with COPD.

Upregulation of gelatinases and epithelial-mesenchymal transition in small airway remodeling associated with chronic exposure to wood smoke

BACKGROUND

Peribronchiolar fibrosis is an important feature of small airway remodeling (SAR) in cigarette smoke-induced COPD. The aim of this study was to investigate the role of gelatinases (MMP9, MMP2) and epithelial-mesenchymal transition (EMT) in SAR related to wood smoke (WS) exposure in a rat model.

METHODS

Forty-eight female Sprague-Dawley rats were randomly divided into the WS group, the cigarette smoke (CS) group and the clean air control group. After 4 to 7 months of smoke exposure, lung tissues were examined with morphometric measurements, immunohistochemistry and Western blotting. Serum MMP9 and TIMP1 concentrations were detected by ELISA. In vitro, primary rat tracheal epithelial cells were stimulated with wood smoke condensate for 7 days.

RESULTS

The COPD-like pathological alterations in rats exposed chronically to WS were similar to those exposed to CS; the area of collagen deposition was significantly increased in the small airway walls of those exposed to WS or CS for 7 months. The expression of gelatinases in rats induced by WS or CS exposure was markedly increased in whole lung tissue, and immunohistochemistry showed that MMP9, MMP2 and TIMP1 were primarily expressed in the airway epithelium. The serum levels of MMP9 and TIMP1 were significantly higher in rats secondary to WS or CS exposure. Few cells that double immunostained for E-cadherin and vimentin were observed in the airway subepithelium of rats exposed to WS for 7 months (only 3 of these 8 rats). In vitro, the expression of MMP9 and MMP2 proteins was upregulated in primary rat tracheal epithelial cells following exposure to wood smoke condensate for 7 days by Western blotting; positive immunofluorescent staining for vimentin and type I collagen was also observed.

CONCLUSIONS

These findings suggest that the upregulation of gelatinases and EMT might play a role in SAR in COPD associated with chronic exposure to wood smoke.

SIRT1 redresses the imbalance of tissue inhibitor of matrix metalloproteinase-1 and matrix metalloproteinase-9 in the development of mouse emphysema and human COPD

Sirtuin1 (SIRT1), a protein/histone deacetylase, protects against the development of pulmonary emphysema. However, the molecular mechanisms underlying this observation remain elusive. The imbalance of tissue inhibitor of matrix metalloproteinases (TIMPs)/matrix metalloproteinases (MMPs) plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD)/emphysema. We hypothesized that SIRT1 protects against emphysema by redressing the imbalance between MMPs and TIMPs. To test this hypothesis, SIRT1-deficient and overexpressing/transgenic mice were exposed to cigarette smoke (CS). The protein level and activity of MMP-9 were increased in lungs of SIRT1-deficient mice exposed to CS compared with wild-type (WT) littermates, and these effects were attenuated by SIRT1 overexpression. SIRT1 deficiency decreased the level of TIMP-1, which was augmented in SIRT1 transgenic mice compared with WT littermates by CS. However, the level of MMP-2, MMP-12, TIMP-2, TIMP-3, or TIMP-4 was not altered by SIRT1 in response to CS exposure. SIRT1 reduction was associated with imbalance of TIMP-1 and MMP-9 in lungs of smokers and COPD patients. Mass spectrometry and immunoprecipitation analyses revealed that TIMP-1 acetylation on specific lysine residues was increased, whereas its interaction with SIRT1 and MMP-9 was reduced in mouse lungs with emphysema, as well as in lungs of smokers and COPD patients. SIRT1 deficiency increased CS-induced TIMP-1 acetylation, and these effects were attenuated by SIRT1 overexpression. These results suggest that SIRT1 protects against COPD/emphysema, in part, via redressing the TIMP-1/MMP-9 imbalance involving TIMP-1 deacetylation. Thus redressing the TIMP-1/MMP-9 imbalance by pharmacological activation of SIRT1 is an attractive approach in the intervention of COPD.

Asthma and COPD - The C/EBP Connection

Asthma and chronic obstructive pulmonary disease (COPD) are the two most prominent chronic inflammatory lung diseases with increasing prevalence. Both diseases are associated with mild or severe remodeling of the airways. In this review, we postulate that the pathologies of asthma and COPD may result from inadequate responses and/or a deregulated balance of a group of cell differentiation regulating factors, the CCAAT/Enhancer Binding Proteins (C/EBPs). In addition, we will argue that the exposure to environmental factors, such as house dust mite and cigarette smoke, changes the response of C/EBPs and are different in diseased cells. These novel insights may lead to a better understanding of the etiology of the diseases and may provide new aspects for therapies.

Grape skin extract reduced pulmonary oxidative response in mice exposed to cigarette smoke

BACKGROUND

Oxidative stress has been implicated in the pathogenesis and progression of chronic obstructive pulmonary disease (COPD), and cigarette smoke (CS) is known to be one of the major sources of oxidants in the lungs. We postulated that acute administration of GSE (grape skin extract) would either reduce or protect the ALI (acute lung inflammation) produced by CS via NO release.

MATERIAL/METHODS

We adopted a nutritional approach by investigating the inflammatory cells, metalloproteinase 9 (MMP-9) activity, and oxidative stress markers (superoxide dismutase - SOD; catalase - CAT; glutathione peroxidase (GPx) activities and malondialdehyde - MDA - levels) that play a role in the development of acute lung inflammation (ALI). Therefore, we tested an orally active antioxidant produced from grape skin manipulation (grape skin extract - GSE), in mice exposed to CS from 6 cigarettes a day for 5 days. In addition, we used a separate group treated with NG-nitro-L-arginine methyl ester (an NO inhibitor) to confirm nitric oxide (NO) involvement in GSE effects.

RESULTS

We showed for the first time that administration of GSE inhibited ALI and oxidative damage induced by CS. This is associated with decreased MMP-9 activity, decreased number of inflammatory cells in the bronchoalveolar lavage fluid, and reduced levels of lipid peroxidation. Our results indicate that beneficial effects of GSE are NO-dependent.

CONCLUSIONS

The study indicates that alteration of the oxidant-antioxidant balance is important in the pathogenesis of CS-induced ALI and suggests lung protective effects of GSE treatment in the mouse.

Update of human and mouse matrix metalloproteinase families

Matrix metalloproteinases (MMPs) are a family of zinc proteases that degrade most of the components of the extracellular matrix (ECM). MMPs also have a number of non-traditional roles in processing factors related to cell growth/proliferation, inflammation and more. There are 23 human MMPs and 23 mouse MMPs, most of which share orthology among most vertebrates; other examples have been found in invertebrates and plants. MMPs are named in order of discovery, but also have been grouped by domain structure or by phylogenetic analysis. MMPs are multi-domain proteins which generally contain a signal sequence; propeptide (which keeps the protein inactive until cleaved); catalytic domain; and a hemopexin-like domain (which provides substrate specificity). MMPs are thought to play a role in many disease states, including arthritis, vascular disease, lung injury, wound repair, cancer and various neurodegenerative disorders. Although there has been much clinical interest in MMP inhibitors (MMPIs), few trials have been successful - often due to the broad nature of inhibition and the complex role of different MMPs in a given disease state.

The identification of beta-hydroxy carboxylic acids as selective MMP-12 inhibitors

A new class of selective MMP-12 inhibitors have been identified via high throughput screening. Crystallization with MMP-12 confirmed the mode of binding and allowed initial optimization to be carried out using classical structure based design.

Therapeutic perspectives in bronchial vascular remodeling in COPD

COPD may be characterized by significant changes in airway mucosal blood vessels, which may contribute to bronchial airway remodeling. The airway wall is more vascularized in COPD patients than in healthy subjects, though this phenomenon is less evident than in asthmatic patients. The vascular mucosal changes in the airways of patients with COPD are strictly linked to the inflammatory processes. The cellular mechanisms responsible for the microvascular changes are still unclear, however, pro-angiogenic factors, such as VEGF, TGF-beta, FGF, and proteolytic enzymes such as MMPs, may play a role. Up to now, the clinical and functional consequences of this phenomenon and the therapeutic approach have been scarcely investigated. Inhaled corticosteroids seem to have positive effects, by reducing the vascular area and growth factor expression. Specific antagonists to VEGF, TGF- beta, FGF, and MMPs could beneficially control chronic airway inflammation and vascular remodeling in COPD as well as slow down the progression of the disease. Several of these growth factor antagonists are being evaluated and some seem to be effective in reducing vascularity, however further studies are required to ascertain whether or not these antagonists may play a role in COPD therapy.

Molecular mechanisms in chronic obstructive pulmonary disease: potential targets for therapy

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory lung disease associated with progressive airflow obstruction. Tobacco smoking is the main risk factor worldwide. In contrast to asthma, antiinflammatory therapies are rather ineffective in improving chronic symptoms and reducing inflammation, lung function decline, and airway remodeling. Specific drugs that are directed against the remodeling and chronic inflammation, thereby preventing lung tissue damage and progressive lung function decline, must be developed. Experimental models and expression studies suggest that anti-vascular endothelial growth factor (VEGF) receptor strategies may be of use in patients with emphysema, whereas anti-HER1-directed strategies may be more useful in patients with pulmonary mucus hypersecretion, as seen in chronic bronchitis and asthma. Growth factors and cytokines including VEGF, fibroblast growth factors, transforming growth factor-beta, tumor necrosis factor-alpha, CXCL1, CXCL8, and CCL2, and signal transduction proteins such as mitogen-activated protein kinase p38 and nuclear factor-kappaB, seem to be important pathogenetic molecules in COPD. Specific antagonists for these proteins may be effective for different inflammatory diseases. However, their efficacy for COPD therapy has not yet been demonstrated. Finally, other drugs such as retinoic acids may provide restoration of lung tissue structure. Such approaches, however, must await the first results of growth factor or cytokine antagonist therapy in chronic lung diseases.

MMPs as therapeutic targets--still a viable option?

Matrix metalloproteinases (MMPs) appear to be ideal drug targets--they are disease-associated, extracellular enzymes with a dependence on zinc for activity. This apparently straightforward target, however, is much more complex than initially realized. Although disease associated, the roles for particular enzymes may be healing rather than harmful making broad-spectrum inhibition unwise; targeting the catalytic zinc with specificity is difficult, since other related proteases as well as non-related proteins can be affected by some chelating groups. While the failure of early-generation MMP inhibitors dampened enthusiasm for this type of drug, there has recently been a wealth of studies examining the basic biology of MMPs which will greatly inform new drug trials in this field.

DNA sequence variations of metalloproteinases: their role in asthma and COPD

Asthma and chronic obstructive pulmonary disease (COPD) are complex genetic diseases that cause considerable morbidity and mortality worldwide. Genetic variability interacting with environmental and ethnic factors is presumed to cause tobacco smoke susceptibility and to influence asthma severity. A disintegrin and metalloproteinase 33 (ADAM33) and matrix metalloproteinase-9 (MMP9) appear to have important roles in asthma and COPD pathogenesis. ADAM33 and MMP9 genetic alterations could possibly contribute to the establishment and progression of these multifactorial diseases, although their association with the clinical phenotypes has not yet been elucidated. However, the occurrence of these alterations does not always result in clear disease, implying that either they are an epiphenomenon or they are in proximity to the true causative alteration. This review summarises the most recent literature dealing with the genetic variations of metalloproteinases and outlines their potential pathogenetic outcome.

Development of Selective Inhibitors and Substrate of Matrix Metalloproteinase-12

Four phosphinic peptide libraries with compounds having the general formula p-Br-Ph-(PO2-CH2)-Xaa'-Yaa'-Zaa'-NH2 have been prepared and screened against 10 matrix metalloproteinases (MMPs). We identified two phosphinic peptides with Ki values of 0.19 and 4.4 nM toward MMP-12 (macrophage elastase) that are more than 2-3 orders of magnitude less potent toward the other MMPs tested. These highly selective MMP-12 inhibitors contain a Glu-Glu motif in their Yaa'-Zaa' positions. Incorporation of this Glu-Glu motif into the sequence of a nonspecific fluorogenic peptide cleaved by MMPs provides a highly selective substrate for MMP-12. A model of one of these inhibitors interacting with MMP-12 suggests that the selectivity observed might be due, in part, to the presence of two unique polar residues in MMP-12, Thr239 and Lys177. These MMP-12-selective inhibitors may have important therapeutic applications to diseases in which MMP-12 has been suggested to play a key role, such as in emphysema, atherosclerosis, and aortic abdominal aneurysm.

Pathology of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is one of the leading causes of death and morbidity worldwide. Despite intensive investigation, its pathology and pathophysiology are not well understood. The hallmarks of the disease are irreversible airflow limitation and chronic inflammation. Small airway obstruction due to progressive inflammation and fibrosis, and the loss of elastic recoil mediated by elastolysis and apoptosis equally contribute to pathologic changes. However, it is debated to what extent the obstruction of large airways leads to altered lung function. Three morphologic entities are described in the literature under one disease; chronic bronchitis, obstructive bronchiolitis and emphysema may appear in the same patient at the same time. The authors review pathologic changes observed in chronic obstructive pulmonary disease, including acute exacerbations and secondary pulmonary hypertension as severe but common complications of the disease. Furthermore, we detail recent scientific evidences for major cellular and molecular inflammatory pathway activation. These mechanisms result in accelerated apoptosis, remodeling and increased proinflammatory cytokine release. Targeting intracellular pathological changes may lead to the discovery of a new generation of drugs that could reduce chronic obstruction before airway irreversibility is established.