Interleukin-13-dependent expression of matrix metalloproteinase-12 is required for the development of airway eosinophilia in mice

Airway proteomics reveals broad residual anti-inflammatory effects of prednisolone in mepolizumab-treated asthma

BACKGROUND

Mepolizumab is an anti-IL-5 mAb treatment for severe eosinophilic asthma that reduces asthma exacerbations. Residual airway inflammation with mepolizumab therapy may lead to persistent exacerbations. Oral corticosteroids remain the main treatment for these residual exacerbations.

OBJECTIVE

Our study aimed to explore the corticosteroid responsiveness of airway inflammation after mepolizumab treatment to find potentially treatable inflammatory mechanisms beyond the IL-5 pathway.

METHODS

The MAPLE trial was a multicenter, randomized, double-blind, placebo-controlled, crossover study of 2 weeks of high-dose oral prednisolone treatment at stable state in 27 patients treated with mepolizumab for severe eosinophilic asthma. We analyzed paired sputum (n = 16) and plasma (n = 25) samples from the MAPLE trial using high-throughput Olink proteomics. We analyzed additional sputum proteins using ELISA.

RESULTS

In patients receiving mepolizumab, prednisolone significantly downregulated sputum proteins related to type 2 inflammation and chemotaxis including IL-4, IL-5, IL-13, CCL24, CCL26, EDN, CCL17, CCL22, OX40 receptor, FCER2, and the ST2 receptor. Prednisolone also downregulated cell adhesion molecules, prostaglandin synthases, mast cell tryptases, MMP1, MMP12, and neuroimmune mediators. Neutrophilic pathways were upregulated. Type 2 proteins were also downregulated in plasma, combined with IL-12, IFN-γ, and IP-10. IL-10 and amphiregulin were upregulated.

CONCLUSIONS

At stable state, prednisolone has broad anti-inflammatory effects on top of mepolizumab. These effects are heterogeneous and may be clinically relevant in residual exacerbations.

Roles of Inflammatory Biomarkers in Exhaled Breath Condensates in Respiratory Clinical Fields

BACKGROUND

Exhaled condensates contain inflammatory biomarkers; however, their roles in the clinical field have been under-investigated.

METHODS

We prospectively enrolled subjects admitted to pulmonology clinics. We collected exhaled breath condensates (EBC) and analysed the levels of six and 12 biomarkers using conventional and multiplex enzyme-linked immunosorbent assay, respectively.

RESULTS

Among the 123 subjects, healthy controls constituted the largest group (81 participants; 65.9%), followed by the preserved ratio impaired spirometry group (21 patients; 17.1%) and the chronic obstructive pulmonary disease (COPD) group (21 patients; 17.1%). In COPD patients, platelet derived growth factor-AA exhibited strong positive correlations with COPD assessment test (ρ=0.5926, p=0.0423) and COPD-specific version of St. George's Respiratory Questionnaire (SGRQ-C) score (total, ρ=0.6725, p=0.0166; activity, ρ=0.7176, p=0.0086; and impacts, ρ=0.6151, p=0.0333). Granzyme B showed strong positive correlations with SGRQ-C score (symptoms, ρ=0.6078, p=0.0360; and impacts, ρ=0.6007, p=0.0389). Interleukin 6 exhibited a strong positive correlation with SGRQ-C score (activity, ρ=0.4671, p=0.0378). The absolute serum eosinophil and basophil counts showed positive correlations with pro-collagen I alpha 1 (ρ=0.6735, p=0.0164 and ρ=0.6295, p=0.0283, respectively). In healthy subjects, forced expiratory volume in 1 second (FEV1)/forced vital capacity demonstrated significant correlation with CC chemokine ligand 3 (CCL3)/macrophage inflammatory protein 1 alpha (ρ=0.3897 and p=0.0068). FEV1 exhibited significant correlation with CCL11/eotaxin (ρ=0.4445 and p=0.0017).

CONCLUSION

Inflammatory biomarkers in EBC might be useful to predict quality of life concerning respiratory symptoms and serologic markers. Further studies are needed.

IL-4 and IL-13: Regulators and Effectors of Wound Repair

Type 2 immunity mediates protective responses to helminths and pathological responses to allergens, but it also has broad roles in the maintenance of tissue integrity, including wound repair. Type 2 cytokines are known to promote fibrosis, an overzealous repair response, but their contribution to healthy wound repair is less well understood. This review discusses the evidence that the canonical type 2 cytokines, IL-4 and IL-13, are integral to the tissue repair process through two main pathways. First, essential for the progression of effective tissue repair, IL-4 and IL-13 suppress the initial inflammatory response to injury. Second, these cytokines regulate how the extracellular matrix is modified, broken down, and rebuilt for effective repair. IL-4 and/or IL-13 amplifies multiple aspects of the tissue repair response, but many of these pathways are highly redundant and can be induced by other signals. Therefore, the exact contribution of IL-4Rα signaling remains difficult to unravel.

Potential targeted therapy based on deep insight into the relationship between the pulmonary microbiota and immune regulation in lung fibrosis

Pulmonary fibrosis is an irreversible disease, and its mechanism is unclear. The lung is a vital organ connecting the respiratory tract and the outside world. The changes in lung microbiota affect the progress of lung fibrosis. The latest research showed that lung microbiota differs in healthy people, including idiopathic pulmonary fibrosis (IPF) and acute exacerbation-idiopathic pulmonary fibrosis (AE-IPF). How to regulate the lung microbiota and whether the potential regulatory mechanism can become a necessary targeted treatment of IPF are unclear. Some studies showed that immune response and lung microbiota balance and maintain lung homeostasis. However, unbalanced lung homeostasis stimulates the immune response. The subsequent biological effects are closely related to lung fibrosis. Core fucosylation (CF), a significant protein functional modification, affects the lung microbiota. CF regulates immune protein modifications by regulating key inflammatory factors and signaling pathways generated after immune response. The treatment of immune regulation, such as antibiotic treatment, vitamin D supplementation, and exosome micro-RNAs, has achieved an initial effect in clearing the inflammatory storm induced by an immune response. Based on the above, the highlight of this review is clarifying the relationship between pulmonary microbiota and immune regulation and identifying the correlation between the two, the impact on pulmonary fibrosis, and potential therapeutic targets.

Mmp12 Is Upregulated by in utero Second-Hand Smoke Exposures and Is a Key Factor Contributing to Aggravated Lung Responses in Adult Emphysema, Asthma, and Lung Cancer Mouse Models

Matrix metalloproteinase-12 (Mmp12) is upregulated by cigarette smoke (CS) and plays a critical role in extracellular matrix remodeling, a key mechanism involved in physiological repair processes, and in the pathogenesis of emphysema, asthma, and lung cancer. While cigarette smoking is associated with the development of chronic obstructive pulmonary diseases (COPD) and lung cancer, in utero exposures to CS and second-hand smoke (SHS) are associated with asthma development in the offspring. SHS is an indoor air pollutant that causes known adverse health effects; however, the mechanisms by which in utero SHS exposures predispose to adult lung diseases, including COPD, asthma, and lung cancer, are poorly understood. In this study, we tested the hypothesis that in utero SHS exposure aggravates adult-induced emphysema, asthma, and lung cancer.

Methods: Pregnant BALB/c mice were exposed from gestational days 6–19 to either 3 or 10mg/m³ of SHS or filtered air. At 10, 11, 16, or 17weeks of age, female offspring were treated with either saline for controls, elastase to induce emphysema, house-dust mite (HDM) to initiate asthma, or urethane to promote lung cancer. At sacrifice, specific disease-related lung responses including lung function, inflammation, gene, and protein expression were assessed.

Results: In the elastase-induced emphysema model, in utero SHS-exposed mice had significantly enlarged airspaces and up-regulated expression of Mmp12 (10.3-fold compared to air-elastase controls). In the HDM-induced asthma model, in utero exposures to SHS produced eosinophilic lung inflammation and potentiated Mmp12 gene expression (5.7-fold compared to air-HDM controls). In the lung cancer model, in utero exposures to SHS significantly increased the number of intrapulmonary metastases at 58weeks of age and up-regulated Mmp12 (9.3-fold compared to air-urethane controls). In all lung disease models, Mmp12 upregulation was supported at the protein level.

Conclusion: Our findings revealed that in utero SHS exposures exacerbate lung responses to adult-induced emphysema, asthma, and lung cancer. Our data show that MMP12 is up-regulated at the gene and protein levels in three distinct adult lung disease models following in utero SHS exposures, suggesting that MMP12 is central to in utero SHS-aggravated lung responses.

Alteration of lung tissues proteins in birch pollen induced asthma mice before and after SCIT

Subcutaneous immunotherapy (SCIT) is a classic form of allergen-specific immunotherapy that is used to treat birch pollen induced allergic asthma. To investigate the underlying molecular mechanisms of SCIT, we aimed to profile lung samples to explore changes in the differential proteome before and after SCIT in mice with allergic asthma. Fresh lungs were collected from three groups of female BALB/c mice: 1) control mice, 2) birch pollen-induced allergic mice, and 3) birch pollen-induced allergic mice with SCIT. Tandem mass tag (TMT) labelling coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyze the lung proteome in the mice. Ingenuity pathway analysis (IPA) and Gene Ontology (GO) classification analysis were applied to identify differentially expressed proteins (DEPs) and crucial pathways. The screened DEPs were validated by immunohistochemistry analysis. A total of 317 proteins were upregulated and 184 proteins were downregulated in the asthma group compared to those of the control group. In contrast, 639 DEPs (163 upregulated and 456 downregulated proteins) were identified after SCIT in comparison with those of the asthma group. Among the 639 DEPs, 277 proteins returned to similar levels as those of the relative non-asthma condition. Bioinformatic analysis revealed that the 277 proteins played a significant role in the leukocyte extravasation signaling pathway. The leukocyte extravasation signaling pathway and related DEPs were of crucial importance in birch pollen SCIT.

Macrophages in Lung Injury, Repair, and Fibrosis

Fibrosis progression in the lung commonly results in impaired functional gas exchange, respiratory failure, or even death. In addition to the aberrant activation and differentiation of lung fibroblasts, persistent alveolar injury and incomplete repair are the driving factors of lung fibrotic response. Macrophages are activated and polarized in response to lipopolysaccharide- or bleomycin-induced lung injury. The classically activated macrophage (M1) and alternatively activated macrophage (M2) have been extensively investigated in lung injury, repair, and fibrosis. In the present review, we summarized the current data on monocyte-derived macrophages that are recruited to the lung, as well as alveolar resident macrophages and their polarization, pyroptosis, and phagocytosis in acute lung injury (ALI). Additionally, we described how macrophages interact with lung epithelial cells during lung repair. Finally, we emphasized the role of macrophage polarization in the pulmonary fibrotic response, and elucidated the potential benefits of targeting macrophage in alleviating pulmonary fibrosis.

Revisiting matrix metalloproteinase 12: its role in pathophysiology of asthma and related pulmonary diseases

PURPOSE OF REVIEW

Matrix metalloproteinases (MMPs) are a family of over 20 zinc-dependent proteases with different biological and pathological activities, and many have been implicated in several diseases. Although nonselective MMP inhibitors are known to induce serious side-effects, targeting individual MMPs may offer a safer therapeutic potential for several diseases. Hence, we provide a concise overview on MMP-12, given its association with pulmonary diseases, including asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis, and other progressive pulmonary fibrosis (PPF), which may also occur in coronavirus disease 2019.

RECENT FINDINGS

In asthma, COPD, and PPF, increased MMP-12 levels have been associated with inflammation and/or structural changes within the lungs and negatively correlated with functional parameters. Increased pulmonary MMP-12 levels and MMP-12 gene expression have been related to disease severity in asthma and COPD. Targeting MMP-12 showed potential in animal models of pulmonary diseases but human data are still very scarce.

SUMMARY

Although there may be a potential role of MMP-12 in asthma, COPD and PPF, several pathophysiological aspects await elucidation. Targeting MMP-12 may provide further insights into MMP-12 related mechanisms and how this translates into clinical outcomes; this warrants further research.

Eosinophil-derived IL-13 promotes emphysema

The inflammatory responses in chronic airway diseases leading to emphysema are not fully defined. We hypothesised that lung eosinophilia contributes to airspace enlargement in a mouse model and to emphysema in patients with chronic obstructive pulmonary disease (COPD).A transgenic mouse model of chronic type 2 pulmonary inflammation (I5/hE2) was used to examine eosinophil-dependent mechanisms leading to airspace enlargement. Human sputum samples were collected for translational studies examining eosinophilia and matrix metalloprotease (MMP)-12 levels in patients with chronic airways disease.Airspace enlargement was identified in I5/hE2 mice and was dependent on eosinophils. Examination of I5/hE2 bronchoalveolar lavage identified elevated MMP-12, a mediator of emphysema. We showed, in vitro, that eosinophil-derived interleukin (IL)-13 promoted alveolar macrophage MMP-12 production. Airspace enlargement in I5/hE2 mice was dependent on MMP-12 and eosinophil-derived IL-4/13. Consistent with this, MMP-12 was elevated in patients with sputum eosinophilia and computed tomography evidence of emphysema, and also negatively correlated with forced expiratory volume in 1 s.A mouse model of chronic type 2 pulmonary inflammation exhibited airspace enlargement dependent on MMP-12 and eosinophil-derived IL-4/13. In chronic airways disease patients, lung eosinophilia was associated with elevated MMP-12 levels, which was a predictor of emphysema. These findings suggest an underappreciated mechanism by which eosinophils contribute to the pathologies associated with asthma and COPD.

Matrix metalloproteinase-12 as an endogenous resolution promoting factor following myocardial infarction

Following myocardial infarction (MI), timely resolution of inflammation promotes wound healing and scar formation while limiting excessive tissue damage. Resolution promoting factors (RPFs) are agents that blunt leukocyte trafficking and inflammation, promote necrotic and apoptotic cell clearance, and stimulate scar formation. Previously identified RPFs include mediators derived from lipids (resolvins, lipoxins, protectins, and maresins), proteins (glucocorticoids, annexin A1, galectin 1, and melanocortins), or gases (CO, H₂S, and NO). Matrix metalloproteinase-12 (MMP-12; macrophage elastase) has shown promising RPF qualities in a variety of disease states. We review here the evidence that MMP-12 may serve as a novel RPF with potential therapeutic efficacy in the setting of MI.

Merkel cell polyomavirus and Langerhans cell neoplasm

BACKGROUND

The relationship between various external agents such as pollen, food, and infectious agents and human sensitivity exists and is variable depending upon individual's health conditions. For example, we believe that the pathogenetic potential of the Merkel cell polyomavirus (MCPyV), the resident virus in skin, is variable and depends from the degree of individual's reactivity. MCPyV as well as Epstein-Barr virus, which are normally connected with humans under the form of subclinical infection, are thought to be involved at various degrees in several neoplastic and inflammatory diseases. In this review, we cover two types of Langerhans cell neoplasms, the Langerhans cell sarcoma (LCS) and Langerhans cell histiocytosis (LCH), represented as either neoplastic or inflammatory diseases caused by MCPyV.

METHODS

We meta-analyzed both our previous analyses, composed of quantitative PCR for MCPyV-DNA, proteomics, immunohistochemistry which construct IL-17 endocrine model and interleukin-1 (IL-1) activation loop model, and other groups' data.

RESULTS

We have shown that there were subgroups associated with the MCPyV as a causal agent in these two different neoplasms. Comparatively, LCS, distinct from the LCH, is a neoplastic lesion (or sarcoma) without presence of inflammatory granuloma frequently observed in the elderly. LCH is a proliferative disease of Langerhans-like abnormal cells which carry mutations of genes involved in the RAS/MAPK signaling pathway. We found that MCPyV may be involved in the development of LCH.

CONCLUSION

We hypothesized that a subgroup of LCS developed according the same mechanism involved in Merkel cell carcinoma pathogenesis. We proposed LCH developed from an inflammatory process that was sustained due to gene mutations. We hypothesized that MCPyV infection triggered an IL-1 activation loop that lies beneath the pathogenesis of LCH and propose a new triple-factor model.

Recruited Monocytes and Type 2 Immunity Promote Lung Regeneration following Pneumonectomy

To investigate the role of immune cells in lung regeneration, we used a unilateral pneumonectomy model that promotes the formation of new alveoli in the remaining lobes. Immunofluorescence and single-cell RNA sequencing found CD115+ and CCR2+ monocytes and M2-like macrophages accumulating in the lung during the peak of type 2 alveolar epithelial stem cell (AEC2) proliferation. Genetic loss of function in mice and adoptive transfer studies revealed that bone marrow-derived macrophages (BMDMs) traffic to the lung through a CCL2-CCR2 chemokine axis and are required for optimal lung regeneration, along with Il4ra-expressing leukocytes. Our data suggest that these cells modulate AEC2 proliferation and differentiation. Finally, we provide evidence that group 2 innate lymphoid cells are a source of IL-13, which promotes lung regeneration. Together, our data highlight the potential for immunomodulatory therapies to stimulate alveologenesis in adults.

IL-17A receptor expression differs between subclasses of Langerhans cell histiocytosis, which might settle the IL-17A controversy

Langerhans cell histiocytosis (LCH) is a lymphoproliferative disorder consisting of abnormal Langerhans cell-like cells and other lymphoid cells. LCH presents as either a multisystem LCH (LCH-MS) or a single-system LCH (LCH-SS). Currently, neither the pathogeneses nor the factors that define these disease subclasses have been elucidated. The interleukin (IL)-17A autocrine LCH model and IL-17A-targeted therapies have been proposed and have engendered much controversy. Those authors showed high serum IL-17A levels in LCH and argued that serum IL-17A-dependent fusion activities in vitro, rather than serum IL-17A levels, correlated with LCH severity (i.e. the IL-17A paradox). In contrast, others could not confirm the IL-17A autocrine model. So began the controversy on IL-17A, which still continues. We approached the IL-17A controversy and the IL-17A paradox from a new perspective in considering the expression levels of IL-17A receptor (IL-17RA). We detected higher levels of IL-17RA protein expression in LCH-MS (n = 10) as compared to LCH-SS (n = 9) (P = 0.041) by immunofluorescence. We reconfirmed these data by re-analyzing GSE16395 mRNA data. We found that serum levels of IL-17A were higher in LCH (n = 38) as compared to controls (n = 20) (P = 0.005) with no significant difference between LCH subclasses. We propose an IL-17A endocrine model and stress that changes in IL-17RA expression levels are important for defining LCH subclasses. We hypothesize that these IL-17RA data could clarify the IL-17A controversy and the IL-17A paradox. As a potential treatment of LCH-MS, we indicate the possibility of an IL-17RA-targeted therapy.

MiR-375 is downregulated in epithelial cells after IL-13 stimulation and regulates an IL-13-induced epithelial transcriptome

Interleukin 13 (IL-13)-induced epithelial gene and protein expression changes are central to the pathogenesis of multiple allergic diseases. Herein, using human esophageal squamous and bronchial columnar epithelial cells, we identified microRNAs (miRNAs) that were differentially regulated after IL-13 stimulation. Among the IL-13-regulated miRNAs, miR-375 showed a conserved pattern of downregulation. Furthermore, miR-375 was downregulated in the lung of IL-13 lung transgenic mice. We subsequently analyzed miR-375 levels in a human disease characterized by IL-13 overproduction--the allergic disorder eosinophilic esophagitis (EE)--and observed downregulation of miR-375 in EE patient samples compared with control patients. MiR-375 expression levels reflected disease activity, normalized with remission, and inversely correlated with the degree of allergic inflammation. Using a lentiviral strategy and whole-transcriptome analysis in epithelial cells, miR-375 overexpression was sufficient to markedly modify IL-13-associated immunoinflammatory pathways in epithelial cells in vitro, further substantiating interactions between miR-375 and IL-13. Taken together, our results support a key role of miRNAs, particularly miR-375, in regulating and fine-tuning IL-13-mediated responses.

Alternatively activated macrophages and airway disease

Macrophages are the most abundant immune cell population in normal lung tissue and serve critical roles in innate and adaptive immune responses as well as the development of inflammatory airway disease. Studies in a mouse model of chronic obstructive lung disease and translational studies of humans with asthma and COPD have shown that a special subset of macrophages is required for disease progression. This subset is activated by an alternative pathway that depends on production of IL-4 and IL-13, in contrast to the classic pathway driven by interferon-γ. Recent and unexpected results indicate that alternatively activated macrophages (AAMs) can also become a major source of IL-13 production and, thereby, drive the increased mucus production and airway hyperreactivity that is characteristic of airway disease. Although the normal and abnormal functions of AAMs are still being defined, it is already apparent that markers of this immune cell subset can be useful to guide stratification and treatment of patients with chronic airway diseases. Here, we review basic and clinical research studies that highlight the importance of AAMs in the pathogenesis of asthma, COPD, and other chronic airway diseases.

Differential expression and function of breast regression protein 39 (BRP-39) in murine models of subacute cigarette smoke exposure and allergic airway inflammation

Background

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.

Methods

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.

Results

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.

Conclusions

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.

Transcriptomic analysis reveals a mechanism for a prefibrotic phenotype in STAT1 knockout mice during severe acute respiratory syndrome coronavirus infection

Severe acute respiratory syndrome coronavirus (SARS-CoV) infection can cause the development of severe end-stage lung disease characterized by acute respiratory distress syndrome (ARDS) and pulmonary fibrosis. The mechanisms by which pulmonary lesions and fibrosis are generated during SARS-CoV infection are not known. Using high-throughput mRNA profiling, we examined the transcriptional response of wild-type (WT), type I interferon receptor knockout (IFNAR1-/-), and STAT1 knockout (STAT1-/-) mice infected with a recombinant mouse-adapted SARS-CoV (rMA15) to better understand the contribution of specific gene expression changes to disease progression. Despite a deletion of the type I interferon receptor, strong expression of interferon-stimulated genes was observed in the lungs of IFNAR1-/- mice, contributing to clearance of the virus. In contrast, STAT1-/- mice exhibited a defect in the expression of interferon-stimulated genes and were unable to clear the infection, resulting in a lethal outcome. STAT1-/- mice exhibited dysregulation of T-cell and macrophage differentiation, leading to a TH2-biased immune response and the development of alternatively activated macrophages that mediate a profibrotic environment within the lung. We propose that a combination of impaired viral clearance and T-cell/macrophage dysregulation causes the formation of prefibrotic lesions in the lungs of rMA15-infected STAT1-/- mice.

Proinflammatory role for let-7 microRNAS in experimental asthma

MicroRNAs (miRNAs) are short, non-coding RNAs that target and silence protein coding genes through 3'-UTR elements. Evidence increasingly assigns an immunosuppressive role for miRNAs in immunity, but relatively few miRNAs have been studied, and an overall understanding of the importance of these regulatory transcripts in complex in vivo systems is lacking. Here we have applied multiple technologies to globally analyze miRNA expression and function in allergic lung disease, an experimental model of asthma. Deep sequencing and microarray analyses of the mouse lung short RNAome revealed numerous extant and novel miRNAs and other transcript classes. Similar to mRNAs, lung miRNA expression changed dynamically during the transition from the naive to the allergic state, suggesting numerous functional relationships. A possible role for miRNA editing in altering the lung mRNA target repertoire was also identified. Multiple members of the highly conserved let-7 miRNA family were the most abundant lung miRNAs, and we confirmed in vitro that interleukin 13 (IL-13), a cytokine essential for expression for allergic lung disease, is regulated by mmu-let-7a. However, inhibition of let-7 miRNAs in vivo using a locked nucleic acid profoundly inhibited production of allergic cytokines and the disease phenotype. Our findings thus reveal unexpected complexity in the miRNAome underlying allergic lung disease and demonstrate a proinflammatory role for let-7 miRNAs.

Matrix metalloproteinase-12 is a therapeutic target for asthma in children and young adults

BACKGROUND

Matrix metalloproteinase (MMP)-12-mediated pathologic degradation of the extracellular matrix and the subsequent repair cycles influence the airway changes in patients with asthma and chronic obstructive pulmonary disease (COPD). The common serine variant at codon 357 of the MMP12 gene (rs652438) is associated with clinical manifestations consistent with more aggressive matrix degradation in other tissues.

OBJECTIVE

We sought to explore the hypothesis that MMP12 represents a novel therapeutic target in asthma.

METHODS

The role of the rs652438 variant on clinical phenotype was explored in young asthmatic patients and patients with COPD. Candidate MMP-12 inhibitors were identified on the basis of potency and selectivity against a panel of other MMPs. The role of MMP-12-specific inhibition was tested in vitro, as well as in animal models of allergic airway inflammation.

RESULTS

The odds ratio for having greater asthma severity was 2.00 (95% CI, 1.24-3.24; P = .004) when comparing asthmatic patients with at least 1 copy of the serine variant with those with none. The carrier frequency for the variant increased in line with asthma treatment step (P = .000). The presence of the variant nearly doubled the odds in favor of asthmatic exacerbations (odds ratio, 1.90; 95% CI, 1.19-3.04; P = .008) over the previous 6 months. The serine variant was also associated with increased disease severity in patients with COPD (P = .016). Prior administration of an MMP-12-specific inhibitor attenuated the early airway response and completely blocked the late airway response with subsequent Ascaris suum challenge in sheep.

CONCLUSION

Studies on human participants with asthma and COPD show that the risk MMP12 gene variant is associated with disease severity. In allergen-sensitized sheep pharmacologic inhibition of MMP12 downregulates both early and late airway responses in response to allergic stimuli.

New immune pathways from chronic post-viral lung disease

To better understand the immunopathogenesis of chronic inflammatory lung disease, we established a mouse model of disease that develops after respiratory viral infection. The disease that develops in this model is similar to chronic obstructive lung disease in humans. Using this model we have characterized two distinct phases in the chronic disease process. The first phase appears at three weeks after viral infection and depends on type I interferon‐dependent expression and then subsequent activation of the high‐affinity IgE receptor (FcɛRI) on conventional lung dendritic cells, which in turn recruit IL‐13‐producing CD4⁺ T cells to the lower airways. The second phase becomes maximal at seven weeks after infection and depends on invariant natural killer T (iNKT) cells and lung macrophages. Cellular cross‐talk relies on interactions between the semi‐invariant Vα14Jα18 T‐cell receptor on lung iNKT cells and CD1d on macrophages as well as iNKT cell‐derived IL‐13 and IL‐13 receptor on macrophages. These interactions drive macrophages to a pattern of alternative activation and overproduction of IL‐13. This innate immune axis is also activated in patients with chronic obstructive lung disease, as evidenced by increased numbers of iNKT cells and IL‐13‐producing alternatively activated macrophages marked by chitinase 1 production. Together the findings identify two new immune pathways responsible for early and late phases of chronic inflammatory lung disease in experimental and clinical settings. These findings extend our understanding of the complex mechanisms that underlie chronic obstructive lung disease and provide useful targets for diagnosis and therapy of this common disorder.

Matrix metalloproteinase 12-deficiency augments extracellular matrix degrading metalloproteinases and attenuates IL-13-dependent fibrosis

Infection with the parasitic helminth Schistosoma mansoni causes significant liver fibrosis and extracellular matrix (ECM) remodeling. Matrix metalloproteinases (MMP) are important regulators of the ECM by regulating cellular inflammation, extracellular matrix deposition, and tissue reorganization. MMP12 is a macrophage-secreted elastase that is highly induced in the liver and lung in response to S. mansoni eggs, confirmed by both DNA microarray and real-time PCR analysis. However, the function of MMP12 in chronic helminth-induced inflammation and fibrosis is unclear. In this study, we reveal that MMP12 acts as a potent inducer of inflammation and fibrosis after infection with the helminth parasite S. mansoni. Surprisingly, the reduction in liver and lung fibrosis in MMP12-deficient mice was not associated with significant changes in cytokine, chemokine, TGF-beta1, or tissue inhibitors of matrix metalloproteinase expression. Instead, we observed marked increases in MMP2 and MMP13 expression, suggesting that Mmp12 was promoting fibrosis by limiting the expression of specific ECM-degrading MMPs. Interestingly, like MMP12, MMP13 expression was highly dependent on IL-13 and type II-IL-4 receptor signaling. However, in contrast to MMP12, expression of MMP13 was significantly suppressed by the endogenous IL-13 decoy receptor, IL-13Ralpha2. In the absence of MMP12, expression of IL-13Ralpha2 was significantly reduced, providing a possible explanation for the increased IL-13-driven MMP13 activity and reduced fibrosis. As such, these data suggest important counter-regulatory roles between MMP12 and ECM-degrading enzymes like MMP2, MMP9, and MMP13 in Th2 cytokine-driven fibrosis.

Effect of a matrix metalloproteinase-12 inhibitor, S-1, on allergic airway disease phenotypes in mice

OBJECTIVE

Matrix metalloproteinase-12 (MMP-12) has been reported to play an important role in chronic airway inflammatory diseases, but its detailed role in allergic airway disease is not well known. In this study, we investigated the expressions of MMP-12 and the effect of S-1, an MMP-12 inhibitor, in a mouse model of allergic airway inflammation.

MATERIALS AND METHODS

The expressions and activity of MMP-12 were measured by RT-PCR western blot and zymography, respectively. The locations in the airways of MMP-12 and elastin fiber were histologically studied. The mice were orally administered with S-1 during the period of antigen challenge. Bronchoalveolar lavage fluid (BALF) cells were counted, and the activity of MMP-12 in BALF was measured by zymography after the treatment with S-1.

RESULTS

The allergen challenge model resulted in increased eosinophil number in BALF and damage to elastin fiber. Upregulation of MMP-12 was also found in the airways of challenged mice. The increased eosinophil number in the BALF after antigen challenge was inhibited by S-1.

CONCLUSION

These findings suggest that MMP-12 may play an important role in the eosinophil infiltration of the allergic airway.

Identification of an orally efficacious matrix metalloprotease 12 inhibitor for potential treatment of asthma

MMP-12 plays a significant role in airway inflammation and remodeling. Increased expression and production of MMP-12 have been observed in the lungs of asthmatic patients. Compound 27 was identified as a potent and selective MMP-12 inhibitor possessing good physicochemical properties. In pharmacological studies, the compound was orally efficacious in an MMP-12 induced ear-swelling inflammation model in the mouse with a good dose response. This compound also exhibited oral efficacy in a naturally Ascaris-sensitized sheep asthma model showing significant inhibition of the late phase response to allergen challenge. This compound has been considered for further development as a treatment therapy for asthma.

Immune pathways for translating viral infection into chronic airway disease

To better understand the immune basis for chronic inflammatory lung disease, we analyzed a mouse model of lung disease that develops after respiratory viral infection. The disease that develops in this model is similar to asthma and chronic obstructive pulmonary disease (COPD) in humans and is manifested after the inciting virus has been cleared to trace levels. The model thereby mimics the relationship of paramyxoviral infection to the development of childhood asthma in humans. When the acute lung disease appears in this model (at 3 weeks after viral inoculation), it depends on an immune axis that is initiated by expression and activation of the high-affinity IgE receptor (FcvarepsilonRI) on conventional lung dendritic cells (cDCs) to recruit interleukin (IL)-13-producing CD4(+) T cells to the lower airways. However, when the chronic lung disease develops fully (at 7 weeks after inoculation), it is driven instead by an innate immune axis that relies on invariant natural killer T (iNKT) cells that are programmed to activate macrophages to produce IL-13. The interaction between iNKT cells and macrophages depends on contact between the semi-invariant Valpha14Jalpha18-TCR on lung iNKT cells and the oligomorphic MHC-like protein CD1d on macrophages as well as NKT cell production of IL-13 that binds to the IL-13 receptor (IL-13R) on the macrophage. This innate immune axis is also activated in the lungs of humans with severe asthma or COPD based on detection of increased numbers of iNKT cells and alternatively activated IL-13-producing macrophages in the lung. Together, the findings identify an adaptive immune response that mediates acute disease and an innate immune response that drives chronic inflammatory lung disease in experimental and clinical settings.

Matrix metalloproteinase 12 silencing: a therapeutic approach to treat pathological lung tissue remodeling?

Among the large matrix metalloproteinases (MMPs) family, MMP-12, also referred to as macrophage elastase, plays a significant role in chronic pulmonary pathologies characterized by an intense tissue remodeling such as asthma and COPD. This review will summarize knowledge about MMP-12 structure, functions and mechanisms of activation and regulation, including potential MMP-12 modulation by microRNA. As MMP-12 is involved in many tissue remodeling diseases, efforts have been made to develop specific synthetic inhibitors. However, at this time, very few chemical inhibitors have proved to be efficient and specific to a particular MMP. The relevance of silencing MMP-12 by RNA interference is highlighted. The specificity of this approach using siRNA or shRNA and the strategies to deliver these molecules in the lung are discussed.

Gene expression profiling identifies MMP-12 and ADAMDEC1 as potential pathogenic mediators of pulmonary sarcoidosis

RATIONALE

Little is known about the genetic regulation of granulomatous inflammation in sarcoidosis.

OBJECTIVES

To determine if tissue gene array analysis would identify novel genes engaged in inflammation and lung remodeling in patients with sarcoidosis.

METHODS

Gene expression analysis was performed on tissues obtained from patients with sarcoidosis at the time of diagnosis (untreated) (n = 6) compared with normal lung tissue (n = 6). Expression of select genes was further confirmed in lung tissue from a second series of patients with sarcoidosis and disease-free control subjects (n = 11 per group) by semi-quantitative RT-PCR. Interactive gene networks were identified in patients with sarcoidosis using Ingenuity Pathway Analysis (Ingenuity Systems, Inc., Redwood, CA) software. The expression of proteins corresponding to selected overexpressed genes was determined using fluorokine multiplex analysis, and immunohistochemistry. Selected genes and proteins were then analyzed in bronchoalveolar lavage fluid in an independent series of patients with sarcoidosis (n = 36) and control subjects (n = 12).

MEASUREMENTS AND MAIN RESULTS

A gene network engaged in Th1-type responses was most significantly overexpressed in the sarcoidosis lung tissues, including genes not previously reported in the context of sarcoidosis (e.g., IL-7). MMP-12 and ADAMDEC1 transcripts were most highly expressed (> 25-fold) in sarcoidosis lung tissues, corresponding with increased protein expression by immunohistochemistry. MMP-12 and ADAMDEC1 gene and protein expression were increased in bronchoalveolar lavage samples from patients with sarcoidosis, correlating with disease severity.

CONCLUSIONS

Tissue gene expression analyses provide novel insights into the pathogenesis of pulmonary sarcoidosis. MMP-12 and ADAMDEC1 emerge as likely mediators of lung damage and/or remodeling and may serve as markers of disease activity.

Real-time assessment of inflammation and treatment response in a mouse model of allergic airway inflammation

Eosinophils are multifunctional leukocytes that degrade and remodel tissue extracellular matrix through production of proteolytic enzymes, release of proinflammatory factors to initiate and propagate inflammatory responses, and direct activation of mucus secretion and smooth muscle cell constriction. Thus, eosinophils are central effector cells during allergic airway inflammation and an important clinical therapeutic target. Here we describe the use of an injectable MMP-targeted optical sensor that specifically and quantitatively resolves eosinophil activity in the lungs of mice with experimental allergic airway inflammation. Through the use of real-time molecular imaging methods, we report the visualization of eosinophil responses in vivo and at different scales. Eosinophil responses were seen at single-cell resolution in conducting airways using near-infrared fluorescence fiberoptic bronchoscopy, in lung parenchyma using intravital microscopy, and in the whole body using fluorescence-mediated molecular tomography. Using these real-time imaging methods, we confirmed the immunosuppressive effects of the glucocorticoid drug dexamethasone in the mouse model of allergic airway inflammation and identified a viridin-derived prodrug that potently inhibited the accumulation and enzyme activity of eosinophils in the lungs. The combination of sensitive enzyme-targeted sensors with noninvasive molecular imaging approaches permitted evaluation of airway inflammation severity and was used as a model to rapidly screen for new drug effects. Both fluorescence-mediated tomography and fiberoptic bronchoscopy techniques have the potential to be translated into the clinic.

Persistent activation of an innate immune response translates respiratory viral infection into chronic lung disease

To understand the pathogenesis of chronic inflammatory disease, we analyzed an experimental mouse model of chronic lung disease with pathology that resembles asthma and chronic obstructive pulmonary disease (COPD) in humans. In this model, chronic lung disease develops after an infection with a common type of respiratory virus is cleared to only trace levels of noninfectious virus. Chronic inflammatory disease is generally thought to depend on an altered adaptive immune response. However, here we find that this type of disease arises independently of an adaptive immune response and is driven instead by interleukin-13 produced by macrophages that have been stimulated by CD1d-dependent T cell receptor-invariant natural killer T (NKT) cells. This innate immune axis is also activated in the lungs of humans with chronic airway disease due to asthma or COPD. These findings provide new insight into the pathogenesis of chronic inflammatory disease with the discovery that the transition from respiratory viral infection into chronic lung disease requires persistent activation of a previously undescribed NKT cell-macrophage innate immune axis.

IL-13Ralpha2 and IL-10 coordinately suppress airway inflammation, airway-hyperreactivity, and fibrosis in mice

Development of persistent Th2 responses in asthma and chronic helminth infections are a major health concern. IL-10 has been identified as a critical regulator of Th2 immunity, but mechanisms for controlling Th2 effector function remain unclear. IL-10 also has paradoxical effects on Th2-associated pathology, with IL-10 deficiency resulting in increased Th2-driven inflammation but also reduced airway hyperreactivity (AHR), mucus hypersecretion, and fibrosis. We demonstrate that increased IL-13 receptor alpha 2 (IL-13Ralpha2) expression is responsible for the reduced AHR, mucus production, and fibrosis in BALB/c IL-10(-/-) mice. Using models of allergic asthma and chronic helminth infection, we demonstrate that IL-10 and IL-13Ralpha2 coordinately suppress Th2-mediated inflammation and pathology, respectively. Although IL-10 was identified as the dominant antiinflammatory mediator, studies with double IL-10/IL-13Ralpha2-deficient mice illustrate an indispensable role for IL-13Ralpha2 in the suppression of AHR, mucus production, and fibrosis. Thus, IL-10 and IL-13Ralpha2 are both required to control chronic Th2-driven pathological responses.

Over-expression and refolding of isotopically labeled recombinant catalytic domain of human macrophage elastase (MMP-12) for NMR studies

Human macrophage elastase (MMP-12) plays an important role in inflammatory processes and is involved in a number of physiological or pathological situations, such as conversion of plasminogen into angiostatin, allergic airway inflammation, vascular remodeling or alteration, as well as emphysema, and has been justified as a novel drug target. Here, we report the over-expression in Escherichia coil, purification and refolding of MMP-12 catalytic domain for NMR studies. The primary sequence of expressed protein was identified by means of MALDI-TOF MS, and was confirmed by the MALDI-TOF MS data of trypsin-digested peptides. A significantly optimized protocol has been worked out to prepare 15N and/or 13C-labeled MMP-12 catalytic domain, and the yield of the purified protein is estimated to 10-12 mg from 0.5L of M9 minimal media. Finally, the 15N-1H HSQC spectrum of uniformly 15N-labeled MMP-12 catalytic domain indicates the presence of well-ordered and properly folded protein in a monomeric form.

Increase in the expression of matrix metalloproteinase-12 in the airways of rats with allergic bronchial asthma

Although an involvement of matrix metalloproteinase (MMP)-12 in the development of chronic obstructive pulmonary disease (COPD) and airway inflammation has been suggested, its detailed role in the airways is not well known now. In the present study, the changes in the expression and localization of MMP-12 in airways of repeatedly antigen-challenged rats were investigated to show an association of MMP-12 with allergic bronchial asthma. Rats sensitized by dinitrophenylated Ascaris antigen were 3 times repeatedly challenged with aerosolized antigen solution to induce an asthmatic reaction. Twenty-four hours after the last antigen challenge, marked airway inflammation and bronchial smooth muscle hyperresponsiveness were observed. In this animal model of allergic bronchial asthma, a significant increase in the expression/activity of MMP-12 was found: the peak was observed at 12 h after the last antigen challenge. Furthermore, mRNA expression of MMP-12 was also increased at the early phase (1-3 h) after the last antigen challenge. Immunohistochemical studies revealed that MMP-12 was mainly expressed in airway epithelia and alveolar macrophages. These findings suggest that MMP-12 is upregulated after the induction of asthmatic reaction. MMP-12 might be a new target for the therapy against allergic bronchial asthma.

Uteroglobin-related protein 1 expression suppresses allergic airway inflammation in mice

RATIONALE

Uteroglobin-related protein (UGRP) 1, which is highly expressed in the epithelial cells of the airways, has been suggested to play a role in lung inflammation.

OBJECTIVES

The aim of study was to understand the effect of overexpressed UGRP1 on lung inflammation in a mouse model of allergic airway inflammation.

METHODS

Ovalbumin-sensitized and -challenged mice, a model for allergic airway inflammation, were used in conjunction with recombinant adenovirus expressing UGRP1.

MEASUREMENTS AND MAIN RESULTS

We demonstrated that intranasal administration of adeno-UGRP1 successfully delivered UGRP1 to the epithelial cells of airways and markedly reduced the number of infiltrating inflammatory cells, particularly eosinophils, in lung tissue as well as the level of proinflammatory cytokines such as interleukin (IL)-4, IL-5, and IL-13 in bronchoalveolar lavage fluids. The healed phase of inflammation was clearly seen in the peripheral areas of adeno-UGRP1-treated mouse lungs.

CONCLUSION

These results demonstrate that UGRP1 can suppress inflammation in the mouse model of allergic airway inflammation. Based on this result, we propose UGRP1 as a novel therapeutic candidate for treating lung inflammation such as is found in asthma.

What targets have knockouts revealed in asthma?

There have been numerous studies of mice rendered genetically deficient of various genes in the context of allergic inflammatory airway disease. These studies have provided invaluable information about basic immune processes, but have also been considered to be useful in predicting novel pharmacological targets. In this review, the effect of a wide range of individual knockouts (KO) on the development of asthma-like pathologies in mice is compiled and considered. How the results of these studies compare with effects of agents that interfere with the function of each gene product, where known, is also described. Finally, a personal view of the utility of these studies in drug development is presented.

Allergic airway inflammation

Several genes, including ADAM33, DPP10, PHF11, GPRA, and TIM-1, have been implicated in the pathogenesis and susceptibility to atopy and asthma. Advances have been made in defining the mechanism for the control of allergic airway inflammation in response to inhaled antigens. There is growing evidence that associates asthma with a systemic propensity for allergic type 2 T-cell cytokines. Disordered coagulation and fibrinolysis could also exacerbate asthma symptoms. Major emphasis on immunotherapy for asthma during the past decade has been to direct the immune response to a type 1 response. Recent literature supports the pivotal role of plasmacytoid dendritic cells and allergen-specific T-regulatory cells in the development of tolerance to allergens. In this review article, we discuss the current information on the pathogenesis of allergic airway inflammation and potential allergen immunotherapies, which could be beneficial in the treatment of airway inflammation, allergy, and asthma.

Suppression of allergic inflammation by the prostaglandin E receptor subtype EP3

Prostaglandins, including PGD(2) and PGE(2), are produced during allergic reactions. Although PGD(2) is an important mediator of allergic responses, aspirin-like drugs that inhibit prostaglandin synthesis are generally ineffective in allergic disorders, suggesting that another prostaglandin-mediated pathway prevents the development of allergic reactions. Here we show that such a pathway may be mediated by PGE(2) acting at the prostaglandin E receptor EP3. Mice lacking EP3 developed allergic inflammation that was much more pronounced than that in wild-type mice or mice deficient in other prostaglandin E receptor subtypes. Conversely, an EP3-selective agonist suppressed the inflammation. This suppression was effective when the agonist was administered 3 h after antigen challenge and was associated with inhibition of allergy-related gene expression. Thus, the PGE(2)-EP3 pathway is an important negative modulator of allergic reactions.

Interleukin-4 and dexamethasone counterregulate extracellular matrix remodelling and phagocytosis in type-2 macrophages

Alternatively activated macrophages (Mphi2) are induced by Th2 cytokines and by glucocorticoids (GC), and can be distinguished from classically activated effector macrophages (Mphi1) on the basis of their anti-inflammatory properties. In addition, Mphi2 are involved in Th2/Th1 skewing, enhance antigen uptake and processing and support tissue remodelling and healing. In order to elucidate the heterogeneity of Mphi2 population systematically, we analysed a number of genes involved in extracellular matrix (ECM) remodelling, inflammation and phagocytosis in Mphi2 populations generated with interleukin-4 (IL-4) or GC. Using real-time polymerase chain reaction, we demonstrated that the ECM component, tenascin-C, is stimulated by IL-4, whereas it is suppressed by dexamethasone. The ECM remodelling enzymes--MMP-1 and MMP-12--and tissue transglutaminase (TG) showed a similar regulation pattern. FXIIIa, another putative Mphi2-associated TG, was synergistically regulated by IL-4 and GC. Enzyme-linked immunosorbent assay analysis revealed that the production of Mphi2-associated chemokines, AMAC-1, MCP-4 or TARC, was induced by IL-4 and was modulated by GC. Phagocytosis of opsonized and non-opsonized particles was stimulated by GC, whereas IL-4 had only a modulatory effect, what may be partially explained by the expression pattern of hMARCO, a scavenger receptor for non-opsonized particles, that was strongly and selectively induced by GC. In conclusion, stimulation of Mphi with IL-4 and GC regulate antagonistically the expression of ECM remodelling-related molecules and phagocytosis of opsonized and non-opsonized particles.

A protective role for the A1 adenosine receptor in adenosine-dependent pulmonary injury

Adenosine is a signaling nucleoside that has been implicated in the regulation of asthma and chronic obstructive pulmonary disease. Adenosine signaling can serve both pro- and anti-inflammatory functions in tissues and cells. In this study we examined the contribution of A(1) adenosine receptor (A(1)AR) signaling to the pulmonary inflammation and injury seen in adenosine deaminase-deficient (ADA-deficient) mice, which exhibit elevated adenosine levels. Experiments revealed that transcript levels for the A(1)AR were elevated in the lungs of ADA-deficient mice, in which expression was localized predominantly to alveolar macrophages. Genetic removal of the A(1)AR from ADA-deficient mice resulted in enhanced pulmonary inflammation along with increased mucus metaplasia and alveolar destruction. These changes were associated with the exaggerated expression of the Th2 cytokines IL-4 and IL-13 in the lungs, together with increased expression of chemokines and matrix metalloproteinases. These findings demonstrate that the A(1)AR plays an anti-inflammatory and/or protective role in the pulmonary phenotype seen in ADA-deficient mice, which suggests that A(1)AR signaling may serve to regulate the severity of pulmonary inflammation and remodeling seen in chronic lung diseases by controlling the levels of important mediators of pulmonary inflammation and damage.

Local IL-13 gene transfer prior to immune-complex arthritis inhibits chondrocyte death and matrix-metalloproteinase-mediated cartilage matrix degradation despite enhanced joint inflammation

During immune-complex-mediated arthritis (ICA), severe cartilage destruction is mediated by Fcgamma receptors (FcgammaRs) (mainly FcgammaRI), cytokines (e.g. IL-1), and enzymes (matrix metalloproteinases (MMPs)). IL-13, a T helper 2 (Th2) cytokine abundantly found in synovial fluid of patients with rheumatoid arthritis, has been shown to reduce joint inflammation and bone destruction during experimental arthritis. However, the effect on severe cartilage destruction has not been studied in detail. We have now investigated the role of IL-13 in chondrocyte death and MMP-mediated cartilage damage during ICA. IL-13 was locally overexpressed in knee joints after injection of an adenovirus encoding IL-13 (AxCAhIL-13), 1 day before the onset of arthritis; injection of AxCANI (an empty adenoviral construct) was used as a control. IL-13 significantly increased the amount of inflammatory cells in the synovial lining and the joint cavity, by 30% to 60% at day 3 after the onset of ICA. Despite the enhanced inflammatory response, chondrocyte death was diminished by two-thirds at days 3 and 7. The mRNA level of FcgammaRI, a receptor shown to be crucial in the induction of chondrocyte death, was significantly down-regulated in synovium. Furthermore, MMP-mediated cartilage damage, measured as neoepitope (VDIPEN) expression using immunolocalization, was halved. In contrast, mRNA levels of MMP-3, -9, -12, and -13 were significantly higher and IL-1 protein, which induces production of latent MMPs, was increased fivefold by IL-13. This study demonstrates that IL-13 overexpression during ICA diminished both chondrocyte death and MMP-mediated VDIPEN expression, even though joint inflammation was enhanced.

Human bronchial epithelial cells express and secrete MMP-12

Matrix metalloproteinases (MMPs) degrade extracellular matrix proteins, which may be responsible for enlargement of alveoli in chronic obstructive pulmonary disease (COPD) and remodeling of pulmonary tissue associated with chronic asthma. Here, we provide novel evidence that MMP-12 is expressed and secreted by normal human bronchial epithelial cell cultures (NHBECs) and reveal the regulation of MMP-12 gene expression by tumor necrosis factor-alpha (TNF-alpha), epidermal growth factor (EGF), and interferon gamma (IFN-gamma). Reverse transcription-polymerase chain reaction analyses demonstrated MMP-12 mRNA presence in unstimulated differentiated NHBEC cultures. Cultures stimulated independently with EGF or IFN-gamma failed to alter MMP-12 mRNA abundance, while TNF-alpha, TNF-alpha+EGF, or TNF-alpha+IFN-gamma elicited relatively early (6 h) peak increases in MMP-12 mRNA levels. Western blot analyses specifically indicated the presence of MMP-12 in differentiated NHBEC-conditioned media. These findings indicate that the bronchial epithelium may be an important source of elastolytic activity in COPD and tissue remodeling in chronic asthma.

Crystal structures of novel non-peptidic, non-zinc chelating inhibitors bound to MMP-12

Human macrophage elastase (MMP-12) plays an important role in inflammatory processes and has been implicated in diseases such as emphysema and chronic obstructive pulmonary disease (COPD). It is therefore an attractive target for therapeutic agents. As part of a structure-based drug design programme to find new inhibitors of MMP-12, the crystal structures of the MMP-12 catalytic domain (residues 106-268) complexed to three different non-peptidic small molecule inhibitors have been determined. The structures reveal that all three ligands bind in the S1' pocket but show varying degrees of interaction with the Zn atom. The structures of the complexes with inhibitors CP-271485 and PF-00356231 reveal that their central morpholinone and thiophene rings, respectively, sit over the Zn atom at a distance of approximately 5A, locating the inhibitors halfway down the S1' pocket. In both of these structures, an acetohydroxamate anion, an artefact of the crystallisation solution, chelates the zinc atom. By contrast, the acetohydroxamate anion is displaced by the ligand in the structure of MMP-12 complexed to PD-0359601 (Bayer), a potent zinc chelating N-substituted biaryl butyric acid, used as a reference compound for crystallisation. Although a racemate was used for the crystallisation, the S enantiomer only is bound in the crystal. Important hydrophobic interactions between the inhibitors and residues from the S1' pocket are observed in all of the structures. The relative selectivity displayed by these ligands for MMP-12 over other MMP family members is discussed.