Pepducins as a potential treatment strategy for asthma and COPD.

Current therapies to treat asthma and other airway diseases primarily include anti-inflammatory agents and bronchodilators. Anti-inflammatory agents target trafficking and resident immunocytes and structural cells, while bronchodilators act to prevent or reverse shortening of airway smooth muscle (ASM), the pivotal tissue regulating bronchomotor tone. Advances in our understanding of the biology of G protein-coupled receptors (GPCRs) and biased agonism offers unique opportunities to modulate GPCR function that include the use of pepducins and allosteric modulators. Recent evidence suggests that small molecule inhibitors of Gα q as well as pepducins targeting G q -coupled receptors can broadly inhibit contractile agonist-induced ASM function. Given these advances, new therapeutic approaches can be leveraged to diminish the global rise in morbidity and mortality associated with asthma and chronic obstructive pulmonary disease

Laminin α4 contributes to airway remodeling and inflammation in asthma

Airway inflammation and remodeling are characteristic features of asthma, both contributing to airway hyperresponsiveness (AHR) and lung function limitation. Airway smooth muscle (ASM) accumulation and extracellular matrix deposition are characteristic features of airway remodeling, which may contribute to persistent AHR. Laminins containing the α2 chain contribute to characteristics of ASM remodeling in vitro and AHR in animal models of asthma. The role of other laminin chains, including the laminin α4 and α5 chains, which contribute to leukocyte migration in other diseases, is currently unknown. The aim of the current study was to investigate the role of these laminin chains in ASM function and in AHR, remodeling and inflammation in asthma. Expression of both laminin α4 and α5 was observed in the human and mouse ASM bundle. In vitro, laminin α4 was found to promote a pro-proliferative, pro-contractile and pro-fibrotic ASM cell phenotype. In line, treatment with laminin α4 and α5 function-blocking antibodies reduced allergen-induced increases in ASM mass in a mouse model of allergen-induced asthma. Moreover, eosinophilic inflammation was reduced by the laminin α4 function-blocking antibody as well. Using airway biopsies from healthy subjects and asthmatic patients, we found inverse correlations between ASM α4 chain expression and lung function and AHR, whereas eosinophil numbers correlated positively with expression of laminin α4 in the ASM bundle. This study for the first time indicates a prominent role for laminin α4 in ASM function and in inflammation, AHR and remodeling in asthma, whereas the role of laminin α5 is more subtle

Inflammation and remodelling in experimental models of COPD - Mechanisms and therapeutic perspectives

Chronic obstructive pulmonary disease (COPD), primarily caused by smoking, is characterized by a progressive decline of lung function. Pulmonary inflammation in this disease leads to the development of structural abnormalities, including emphysema and airway remodelling, which contribute to the airflow limitation. This thesis explores novel mechanisms involved in the pathophysiology of COPD. Using chronic intranasal instillation of lipopolysaccharide (LPS) in guinea pigs, a new animal model of COPD was developed. Using this model, we demonstrated that inhalation of the long-acting anticholinergic bronchodilator, tiotropium, inhibits the development of airway inflammation and remodelling. These results suggest a major role for endogenous acetylcholine in the pathophysiology of COPD and reveal potential mechanisms underlying the non-bronchodilator effects of tiotropium, as found recently in a large clinical trial. In addition, we demonstrated increased pulmonary activity of the enzyme arginase in our COPD model. Inhalation of a specific arginase inhibitor reduced airway inflammation, remodelling and right ventricular hypertrophy, indicating for the first time that increased arginase activity contributes to the pathophysiology of COPD as well. Since increased airway smooth muscle (ASM) mass is a feature of airway remodelling in COPD, our in vitro studies focused on molecular mechanisms of ASM cell proliferation and pro-inflammatory cytokine release. Exposure of ASM to cigarette smoke extract (CSE) or LPS in vitro induced a proliferative ASM phenotype, in a mitogen-activated protein kinase (MAPK)-dependent manner. Furthermore, TGF-β-activated kinase 1 (TAK1) was identified as a key mediator of growth factor-induced MAPK signalling as well as of CSE-induced MAPK and NF-κB signalling, resulting in ASM phenotypic modulation and pro-inflammatory cytokine production, respectively. To summarize, within the framework of this thesis we developed new in vitro and in vivo models for COPD and used these to identify novel mechanisms of inflammation and remodelling in this disease.

Arginase and pulmonary diseases

Recent studies have indicated that arginase, which converts l-arginine into l-ornithine and urea, may play an important role in the pathogenesis of various pulmonary disorders. In asthma, chronic obstructive pulmonary disease (COPD) and cystic fibrosis, increased arginase activity in the airways may contribute to obstruction and hyperresponsiveness of the airways by inducing a reduction in the production of bronchodilatory nitric oxide (NO) that results from its competition with constitutive (cNOS) and inducible (iNOS) NO synthases for their common substrate. In addition, reduced l-arginine availability to iNOS induced by arginase may result in the synthesis of both NO and the superoxide anion by this enzyme, thereby enhancing the production of peroxynitrite, which has procontractile and pro-inflammatory actions. Increased synthesis of l-ornithine by arginase may also contribute to airway remodelling in these diseases. l-Ornithine is a precursor of polyamines and l-proline, and these metabolic products may promote cell proliferation and collagen production, respectively. Increased arginase activity may also be involved in other fibrotic disorders of the lung, including idiopathic pulmonary fibrosis. Finally, through its action of inducing reduced levels of vasodilating NO, increased arginase activity has been associated with primary and secondary forms of pulmonary hypertension. Drugs targeting the arginase pathway could have therapeutic potential in these diseases

TAK1 plays a major role in growth factor-induced phenotypic modulation of airway smooth muscle

Pera T, Sami R, Zaagsma J, Meurs H. TAK1 plays a major role in growth factor-induced phenotypic modulation of airway smooth muscle. Am J Physiol Lung Cell Mol Physiol 301: L822-L828, 2011. First published August 26, 2011; doi:10.1152/ajplung.00017.2011.-Increased airway smooth muscle (ASM) mass is a major feature of airway remodeling in asthma and chronic obstructive pulmonary disease. Growth factors induce a proliferative ASM phenotype, characterized by an increased proliferative state and a decreased contractile protein expression, reducing contractility of the muscle. Transforming growth factor-beta-activated kinase 1 (TAK1), a mitogen-activated protein kinase kinase kinase, is a key enzyme in proinflammatory signaling in various cell types; however, its function in ASM is unknown. The aim of this study was to investigate the role of TAK1 in growth factor-induced phenotypic modulation of ASM. Using bovine tracheal smooth muscle (BTSM) strips and cells, as well as human tracheal smooth muscle cells, we investigated the role of TAK1 in growth factor-induced proliferation and hypocontractility. Platelet-derived growth factor- (PDGF; 10 ng/ml) and fetal bovine serum (5%)-induced increases in DNA synthesis and cell number in bovine and human cells were significantly inhibited by pretreatment with the specific TAK1 inhibitor LL-Z-1640-2 (5Z-7-oxozeaenol; 100 nM). PDGF-induced DNA synthesis and extracellular signal-regulated kinase-1/2 phosphorylation in BTSM cells were strongly inhibited by both LL-Z-1640-2 pretreatment and transfection of dominant-negative TAK1. In addition, LL-Z-1640-2 inhibited PDGF-induced reduction of BTSM contractility and smooth muscle alpha-actin expression. The data indicate that TAK1 plays a major role in growth factor-induced phenotypic modulation of ASM

Cigarette smoke and lipopolysaccharide induce a proliferative airway smooth muscle phenotype

Abstract Background A major feature of chronic obstructive pulmonary disease (COPD) is airway remodelling, which includes an increased airway smooth muscle (ASM) mass. The mechanisms underlying ASM remodelling in COPD are currently unknown. We hypothesized that cigarette smoke (CS) and/or lipopolysaccharide (LPS), a major constituent of CS, organic dust and gram-negative bacteria, that may be involved in recurrent airway infections and exacerbations in COPD patients, would induce phenotype changes of ASM. Methods To this aim, using cultured bovine tracheal smooth muscle (BTSM) cells and tissue, we investigated the direct effects of CS extract (CSE) and LPS on ASM proliferation and contractility. Results Both CSE and LPS induced a profound and concentration-dependent increase in DNA synthesis in BTSM cells. CSE and LPS also induced a significant increase in BTSM cell number, which was associated with increased cyclin D1 expression and dependent on activation of ERK 1/2 and p38 MAP kinase. Consistent with a shift to a more proliferative phenotype, prolonged treatment of BTSM strips with CSE or LPS significantly decreased maximal methacholine- and KCl-induced contraction. Conclusions Direct exposure of ASM to CSE or LPS causes the induction of a proliferative, hypocontractile ASM phenotype, which may be involved in airway remodelling in COPD.</p

Role for TAK1 in cigarette smoke-induced proinflammatory signaling and IL-8 release by human airway smooth muscle cells

Pera T, Atmaj C, van der Vegt M, Halayko AJ, Zaagsma J, Meurs H. Role for TAK1 in cigarette smoke-induced proinflammatory signaling and IL-8 release by human airway smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 303: L272-L278, 2012. First published April 20, 2012; doi:10.1152/ajplung.00291.2011.-Chronic obstructive pulmonary disease (COPD) is an inflammatory disease, characterized by a progressive decline in lung function. Airway smooth muscle (ASM) mass may be increased in COPD, contributing to airflow limitation and proinflammatory cytokine production. Cigarette smoke (CS), the major risk factor of COPD, causes ASM cell proliferation, as well as interleukin-8 (IL-8)-induced neutrophilia. In various cell types, transforming growth factor-beta-activated kinase 1 (TAK1) plays a crucial role in MAP kinase and NF-kappa B activation, as well as IL-8 release induced by IL-1 beta, TNF-alpha, and lipopolysaccharide. The role of TAK1 in CS-induced IL-8 release is not known. The aim of this study was to investigate the role of TAK1 in CS-induced NF-kappa B and MAP kinase signaling and IL-8 release by human ASM cells. Stimulation of these cells with CS extract (CSE) increased IL-8 release and ERK-1/2 phosphorylation, as well as I kappa-B alpha degradation and p65 NF-kappa B subunit phosphorylation. CSE-induced ERK-1/2 phosphorylation and I kappa-B alpha degradation were both inhibited by pretreatment with the specific TAK1 inhibitor LL-Z-1640-2 (5Z-7-oxozeaenol; 100 nM). Similarly, expression of dominant-negative TAK1 inhibited CSE-induced ERK-1/2 phosphorylation. In addition, inhibitors of TAK1 and the NF-kappa B (SC-514; 50 mu M) and ERK-1/2 (U-0126; 3 mu M) signaling inhibited the CSE-induced IL-8 release by ASM cells. These data indicate that TAK1 plays a major role in CSE-induced ERK-1/2 and NF-kappa B signaling and in IL-8 release by human ASM cells. Furthermore, they identify TAK1 as a novel target for the inhibition of CS-induced inflammatory responses involved in the development and progression of COPD

Pharmacology of airway smooth muscle proliferation

Airway smooth muscle thickening is a pathological feature that contributes significantly to airflow limitation and airway hyperresponsiveness in asthma. Ongoing research efforts aimed at identifying the mechanisms responsible for the increased airway smooth muscle mass have indicated that hyperplasia of airway smooth muscle, due in part to airway myocyte proliferation, is likely a major factor. Airway smooth muscle proliferation has been studied extensively in culture and in animal models of asthma, and these studies have revealed that a variety of receptors and mediators contributes to this response. This review aims to provide an overview of the receptors and mediators that control airway smooth muscle cell proliferation, with emphasis on the intracellular signalling mechanisms involved. (C) 2008 Elsevier B.V. All rights reserved