Augmentation by eosinophils of gelatinase activity in the airway mucosa: comparative effects as a putative mediator of epithelial injury

Implications for matrix metalloproteinases as modulators of pediatric lung disease

Matrix metalloproteinases (MMPs) are a large family (>20) of cation-dependent proteinases believed to be important modulators of normal human lung development and potentially harmful mediators of lung damage. Little is known about MMP production and secretion by the lung during childhood or how alterations in MMP levels may be involved in lung damage. We examined endotracheal aspirates from children (<19 years) without lung disease for the presence of MMP activity. Only gelatinase activity was detectable, and inhibitor profiles suggest they represented one or more MMPs. Comparison of gelatinase activity, MMP expression, and MMP activity in children without pulmonary disease with children who required mechanical ventilation for respiratory failure show: 1) gelatinase activity was approximately five- to sixfold higher in respiratory failure; 2) MMP-7, MMP-8, and MMP-9 concentrations and MMP-8 and MMP-9 activities were markedly elevated in respiratory failure; and 3) MMP-7, MMP-8, and MMP-9 levels were significantly correlated in children with lung disease. These studies provide compelling evidence that specific MMPs are present in the diseased lung and may participate in the pathogenesis of pediatric respiratory failure.

Metalloproteinase and growth factor interactions: do they play a role in pulmonary fibrosis?

Chronic lung disease due to interstitial fibrosis can be a consequence of acute lung injury and inflammation. The inflammatory response is mediated through the migration of inflammatory cells, actions of proinflammatory cytokines, and the secretion of matrix-degrading proteinases. After the initial inflammatory insult, successful healing of the lung may occur, or alternatively, dysregulated tissue repair can result in scarring and fibrosis. On the basis of recent insights into the mechanisms underlying acute lung injury and its long-term consequences, data suggest that proteinases, such as the matrix metalloproteinases (MMPs), may not only be involved in the breakdown and remodeling that occurs during the injury but may also cause the release of growth factors and cytokines known to influence growth and differentiation of target cells within the lung. Through the release of and activation of fibrosis-promoting cytokines and growth factors such as transforming growth factor-beta1, tumor necrosis factor-alpha, and insulin-like growth factors by MMPs, we propose that these metalloproteinases may be integral to the initiation and progression of pulmonary fibrosis.

Antihistamines in late-phase clinical development for allergic disease

Allergic rhinitis (AR) is a global health concern and shares a high comorbidity with asthma. Recent research suggests that different allergic diseases, such as AR, asthma, allergic conjunctivitis and chronic idiopathic urticaria (CIU), are evoked by common pathological mechanisms characterised by the release of histamine and other inflammatory mediators. Although H(1) receptor antagonists are the mainstay of therapy for allergic disease, the unacceptably high incidence of anticholinergic and CNS-related side effects of first-generation H(1) antagonists led to the search for improved second-generation H(1) antagonists. While many of these agents were largely devoid of CNS side effects, their tendency for drug-drug interactions (e.g., terfenadine and astemizole) resulted in an increased incidence of cardiotoxicity. Furthermore, second-generation H(1) antagonists exhibited weak anti-inflammatory properties and had no effect on nasal congestion. These observations emphasised the need for newer anti-allergic agents with a broader spectrum of activity and an improved safety profile. Among the newer H(1) antagonists currently in clinical development, desloratadine and mizolastine are the most widely studied. Both have a rapid onset of action, and desloratadine has demonstrated clinical efficacy in AR, CIU and seasonal asthma. Desloratadine has several advantages over other H(1) antagonists in that it has proven decongestant activity, a sparing effect on the use of bronchodilators (beta(2)-agonists) and a low potential for drug interactions. The broad anti-inflammatory properties of desloratadine and mizolastine, which distinguish these agents from other H(1) antagonists in clinical development (e.g., norastemizole and levocetirizine), suggest they may have a more profound impact on the underlying disease in patients suffering from different forms of allergy. The lack of clinical efficacy and safety data on rupatadine and HSR-609, both novel H(1) antagonists, precludes an accurate assessment of their potential for treating allergic disease. Epinastine and efletirizine are being developed exclusively for topical application and are unlikely to play a significant role in the management of allergic diseases as a whole.

Role of gelatinases MMP-2 and MMP-9 in tissue remodeling following acute lung injury

Acute lung injury is characterized by a severe disruption of alveolo-capillary structures and includes a variety of changes in lung cell populations. Evidence suggests the occurrence of rupture of the basement membranes and interstitial matrix remodeling during acute lung injury. The dynamic equilibrium of the extracellular matrix (ECM) under physiological conditions is a consequence of the balance between the regulation of synthesis and degradation of ECM components. Matrix metalloproteinases (MMPs) represent a group of enzymes involved in the degradation of most of the components of the ECM and therefore participate in tissue remodeling associated with pathological situations such as acute lung injury. MMP activity is regulated by proteolytic activation of the latent secreted proenzyme and by interaction with specific tissue inhibitors of metalloproteinases. This review details our knowledge of the involvement of MMPs, namely MMP-2 and MMP-9, in acute lung injury and acute respiratory distress syndrome.

Inhibition of gelatinase activity in human airway epithelial cells and fibroblasts by dexamethasone and beclomethasone

The effects of dexamethasone and beclomethasone on gelatinase activity released from lung epithelial cells (A549, NCI-H292 and Calu-3 cell lines and NHBE primary cultures) and human lung fibroblasts (HLF) were investigated. All cells spontaneously released gelatin-degrading activity but the amounts were unaffected by treatment with glucocorticoids. Phorbol myristate acetate (PMA) increased the amount of gelatinase activity in conditioned media prepared from all cell types examined. In epithelial cells, PMA induced the expression of gelatinase B, whereas in HLF the increased gelatinase activity resulted from increased activation of gelatinase A. Dexamethasone and beclomethasone produced concentration-dependent inhibition of PMA-induced gelatinase activity in HLF and epithelial cell lines. In the epithelial cell lines, the inhibition of activity was associated with an attenuation of enzyme induction by PMA. In contrast, primary cultures of human bronchial epithelial cells were unresponsive to dexamethasone at concentrations that were maximally effective at inhibiting gelatinase activity induced in other cells.

Cigarette smoke potentiates house dust mite allergen-induced increase in the permeability of human bronchial epithelial cells in vitro

Although studies have suggested that exposure to cigarette smoke (CS) may be associated with the development of atopy, the mechanisms underlying this are not clearly understood. It has been suggested that CS impairs the barrier function of the airway epithelium, leading to increased access of allergens such as those of the house dust mite (HDM) Dermatophagoides pteronyssinus (Der p) to antigen-presenting cells, with subsequent allergic sensitization. In order to test this hypothesis, we established primary explant cultures of human bronchial epithelial cells (HBEC) in cell culture inserts, and exposed these for 20 min, 1 h, 3 h, and 6 h to CS or air in the absence or presence of 300 ng/ml Der p, and then further incubated the cultures over a period of 24 h. The HBEC cultures were assessed for changes in permeability as measured by changes in: (1) electrical resistance (ER); and (2) passage of 14C-labeled bovine serum albumin (14C-BSA) and Der p allergens across the HBEC cultures. We also assessed the effects of protease inhibitors and the antioxidant glutathione (GSH) in this experimental system. Damage to HBEC cultures was assessed by the release of [51Cr]sodium chromate from prelabeled cells, and by release of lactate dehydrogenase (LDH). Twenty minutes of exposure to CS as compared with exposure to air did not significantly alter either the ER or passage of 14C-BSA across the HBEC cultures. In contrast, incubation with Der p led to a significant increase in the permeability of HBEC cultures, an effect that was enhanced by exposure to CS but was abrogated by the specific protease inhibitors and GSH. Passage of Der p was also increased by exposure to CS. Exposure of HBEC cultures to CS led to a significant release of 51Cr and LDH from these cells as compared with cells exposed to air. This effect was augmented further when HBEC cultures were incubated with Der p. Exposure of HBEC cultures for 1 h, 3 h, and 6 h to CS led to a markedly significant dose- and time-dependent increase in the permeability of these cells. These results suggest that exposure to CS significantly enhances Der p-induced decreases in electrical resistance and the increased passage across HBEC cultures of 14C-BSA and of the Der p allergen itself.

Contribution of 92 kDa gelatinase/type IV collagenase in bronchial inflammation during status asthmaticus

In order to assess inflammatory features related to severe asthma as compared with mild asthma, we investigated the secretion of 92 kDa gelatinase matrix metalloproteinase (MMP-9) in bronchial lavages of six patients undergoing mechanical ventilation (MV) for status asthmaticus (SA) and in six patients with mild asthma. Ten healthy nonventilated patients and four patients under MV without preexisting respiratory disease were also investigated. Patients with SA were characterized by prominent neutrophilic inflammation (82 +/- 4% versus 10% in mild asthma). On the basis of enzymatic and immunological analysis, results showed an acute 10- to 160-fold increase of 92 kDa gelatinase (MMP-9) concentration in epithelial lining fluid (ELF) from patients with SA, together with activated forms (46 and 26 kDa) of stromelysin-1 matrix metalloproteinase (MMP-3) and detectable concentration of free metallogelatinolytic activity (1-5 micrograms gelatin hydrolyzed/48 h/ml ELF). Concomitant elevated level of tissue inhibitor of metalloproteinase-1 (TIMP-1) was shown only in patients with SA, thus counterbalancing, at least partially, excess of activated 92 kDa gelatinase. Acutely enhanced albumin levels were only observed in patients with SA; in addition, 92 kDa gelatinase and albumin levels were significantly and positively correlated (r = 0.96, p < 0.0001), suggesting that 92 kDa gelatinase may account for increased bronchial permeability in patients with SA. Several arguments support that 92 kDa gelatinase during SA originates both from numerous activated chemoattracted neutrophils and from activated bronchial epithelial cells in response to in situ lung injury. The fact that no relevant change in ELF, albumin, MMP-9, MMP-3, TIMP-1, or laminin degradation products was observed during mild asthma, strongly supports that the mechanism of airway inflammation in SA is quite distinct from that observed in mild asthma.

Inhibition of Matrix Metalloproteinases Prevents Allergen-Induced Airway Inflammation in a Murine Model of Asthma

Although matrix metalloproteinases (MMPs) have been reported to play crucial roles in the migration of inflammatory cells through basement membrane components in vitro, the role of MMPs in the in vivo accumulation of the cells to the site of inflammation in bronchial asthma is still obscure. In this study, we investigated the role of MMPs in the pathogenesis of bronchial asthma, using a murine model of allergic asthma. In this model, we observed the increase of the release of MMP-2 and MMP-9 in bronchoalveolar lavage fluids after Ag inhalation in the mice sensitized with OVA, which was accompanied by the infiltration of lymphocytes and eosinophils. Administration of tissue inhibitor of metalloproteinase-2 to airways inhibited the Ag-induced infiltration of lymphocytes and eosinophils to airway wall and lumen, reduced Ag-induced airway hyperresponsiveness, and increased the numbers of eosinophils and lymphocytes in peripheral blood. The inhibition of cellular infiltration to airway lumen was observed also with tissue inhibitor of metalloproteinase-1 and a synthetic matrix metalloproteinase inhibitor. These data suggest that MMPs, especially MMP-2 and MMP-9, are crucial for the infiltration of inflammatory cells and the induction of airway hyperresponsiveness, which are pathophysiologic features of bronchial asthma, and further raise the possibility of the inhibition of MMPs as a therapeutic strategy of bronchial asthma.

Class specific inhibition of house dust mite proteinases which cleave cell adhesion, induce cell death and which increase the permeability of lung epithelium

1. House dust mite (HDM) allergens with cysteine and serine proteinase activity are risk factors for allergic sensitization and asthma. A simple method to fractionate proteinase activity from HDM faecal pellets into cysteine and serine class activity is described. 2. Both proteinase fractions increased the permeability of epithelial cell monolayers. The effects of the serine proteinase fraction were inhibited by 4-(2-aminoethyl)-benzenesulphonyl fluoride hydrochloride (AEBSF) and soybean trypsin inhibitor (SBTI). The effects of the cysteine proteinase fraction could be inhibited by E-64. No reciprocity of action was found. 3. Treatment of epithelial monolayers with either proteinase fraction caused breakdown of tight junctions (TJs). AEBSF inhibited TJ breakdown caused by the serine proteinase fraction, whereas E-64 inhibited the cysteine proteinase fraction. 4. Agarose gel electrophoresis revealed that the proteinases induced DNA cleavage which was inhibited by the matrix metalloproteinase inhibitor BB-250. Compound E-64 inhibited DNA fragmentation caused by the cysteine proteinase fraction, but was without effect on the serine proteinase fraction. Staining of proteinase-treated cells with annexin V (AV) and propidium iodide (PI) revealed a diversity of cellular responses. Some cells stained only with AV indicating early apoptosis, whilst others were dead and stained with both AV and PI. 5. HDM proteinases exert profound effects on epithelial cells which will promote allergic sensitization; namely disruption of intercellular adhesion, increased paracellular permeability and initiation of cell death. Attenuation of these actions by proteinase inhibitors leads to the conclusion that compounds designed to be selective for the HDM enzymes may represent a novel therapy for asthma.