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Background. Persistent asthma is characterized by airway remodeling. Whereas we have previously shown that neither β2-agonists nor corticosteroids inhibit extracellular matrix (ECM) protein release from airway smooth muscle (ASM) cells, the effect of their combination is unknown and this forms the rationale for the present study. Methods. ASM cells from people with and without asthma were stimulated with TGFβ1 (1 ng/ml) with or without budesonide (10-8 M) and formoterol (10-10 and 10-8 M), and fibronectin expression and IL-6 release were measured by ELISA. Bronchial rings from nonasthmatic individuals were incubated with TGFβ1 (1 ng/ml) with or without the drugs, and fibronectin expression was measured using immunohistochemistry. Results. Budesonide stimulated fibronectin deposition, in the presence or absence of TGFβ1, and this was partially reversed by formoterol (10-8> M) in both asthmatic and nonasthmatic cells. Budesonide and formoterol in combination failed to inhibit TGFβ-induced fibronectin in either cell type. A similar pattern of expression of fibronectin was seen in bronchial rings. TGFβ1-induced IL-6 release was inhibited by the combination of drugs. Conclusion. Current combination asthma therapies are unable to prevent or reverse remodeling events regulated by ASM cells. [ABSTRACT FROM AUTHOR]

Hyperplasia of airway smooth muscle (ASM) within the bronchial wall of asthmatic patients has been well documented and is likely due to increased muscle proliferation. We have shown that ASM cells obtained from asthmatic patients proliferate faster than those obtained from non-asthmatic patients. In ASM from non-asthmatics, mitogens act via dual signaling pathways (both ERK- and PI 3-kinase-dependent) to control growth. In this study we are the first to examine whether dual pathways control the enhanced proliferation of ASM from asthmatics. When cells were incubated with 0.1% or 1% FBS, ERK activation was significantly greater in cells from asthmatic subjects (P < 0.05). In contrast, when cells were stimulated with 10% FBS, ERK activity was significantly greater in the non-asthmatic cells. However, cell proliferation in asthmatic cells was still significantly higher in cells stimulated by both 1% and 10% FBS. Pharmacological inhibition revealed that although dual proliferative pathways control ASM growth in cells from non-asthmatics stimulated with 10% FBS to an equal extent ([3H]-thymidine incorporation reduced to 57.2 ± 6.9% by the PI 3-kinase inhibitor LY294002 and 57.8 ± 1.1% by the ERK-pathway inhibitor U0126); in asthmatics, the presence of a strong proliferative stimulus (10% FBS) reduces ERK activation resulting in a shift to the PI 3-kinase pathway. The underlying mechanism appears to be upregulation of an endogenous MAPK inhibitor—MKP-1—that constrains ERK signaling in asthmatic cells under strong mitogenic stimulation. This study suggests that the PI 3-kinase pathway may be an attractive target for reversing hyperplasia in asthma. J. Cell. Physiol. 216: 673–679, 2008, © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Increased levels of IL-6 are documented in asthma, but its contribution to the pathology is unknown. Asthma is characterized by airway wall thickening due to increased extracellular matrix deposition, inflammation, angiogenesis, and airway smooth muscle (ASM) mass. IL-6 binds to a specific membrane-bound receptor, IL-6 receptor-α (mIL-6Rα, and subsequently to the signaling protein gp130. Alternatively, IL-6 can bind to soluble IL-6 recpetor-s (sIL-6Rα) to stimulate membrane receptor-deficient cells, a process called trans-signaling. We discovered that primary human ASM cells do not express mIL-6Rα and, therefore, investigated the effect of IL-6 trans-signaling on the pro-remodeling phenotype of ASM. ASM required sIL-6Rα to activate signal transducer and activator 3, with no differences observed between cells from asthmatic subjects compared with controls. Further analysis revealed that IL-6 alone or with sIL-6Rα did not induce release of matrix-stimulating factors (including connective tissue growth factor, fibronectin, or integrins) and had no effect on mast cell adhesion to ASM or ASM proliferation. However, in the presence of sIL-6Rα, IL-6 increased eotaxin and VEGF release and may thereby contribute to local inflammation and vessel expansion in airway walls of asthmatic subjects. As levels of sIL-6Rα are increased in asthma, this demonstration of IL-6 trans-signaling in ASM has relevance to the development of airway remodeling. [ABSTRACT FROM AUTHOR]

Human airway smooth muscle (ASM) plays an immunomodulatory role in asthma. Recently, IL-17A has become of increasing interest in asthma, being found at elevated levels in asthmatic airways and emerging as playing an important role in airway neutrophilia. IL-17A predominantly exerts its neutrophil orchestrating role indirectly via the induction of cytokines by resident airway structural cells. Here, we perform an in vitro study to show that although IL-17A did not induce secretion of the CXC chemokine IL-8 from ASM cells, IL-17A significantly potentiates TNF-α-induced IL-8 protein secretion and gene expression in a concentration- and time-dependent manner (P < 0.05). Levels of IL-8 protein produced after 24 h of incubation with TNF-α were enhanced 2.7-fold in the presence of IL-17A, and conditioned media significantly enhanced neutrophil chemotaxis in vitro. As IL-17A had no effect on the activity of NF-κB, a key transcriptional regulator of IL-8 gene expression, we then examined whether IL-17A acts at the posttranscriptional level. We found that IL-17A significantly augmented TNF-α-induced IL-8 mRNA stability. Interestingly, this enhanced stability occurred via a p38 MAPK-dependent pathway. The decay of IL-8 mRNA transcripts proceeded at a significantly faster rate when cells were pretreated with the p38 MAPK inhibitor SB-203580 (-0.05763 ± 0.01964, t1/2 = 12.0 h), compared with vehicle (-0.0 1030 ± 0.007963, t1/2 = 67.3 h) [results are expressed as decay constant (means ± SE) and half-life (t1/2 in h): P < 0.051. Collectively, these results demonstrate that IL-17A amplifies the synthetic function of ASM cells, acting via a p38 MAPK-dependent posttranscriptional pathway to augment TNF-α-induced secretion of the potent neutrophil chemoattractant IL-8 from ASM cells. [ABSTRACT FROM AUTHOR]

Airway remodeling describes the structural changes that occur in the asthmatic airway that include airway smooth muscle hyperplasia, increases in vascularity due to angiogenesis, and thickening of the basement membrane. Our aim in this study was to examine the effect of transforming growth factor-β on the release of connective tissue growth factor and vascular endothelial growth factor from human airway smooth muscle cells derived from asthmatic and nonasthmatic patients. In addition we studied the immunohistochemical localization of these cytokines in the extracellular matrix after stimulating bronchial rings with transforming growth factor-β. Connective tissue growth factor and vascular endothelial growth factor were released from both cell types and colocalized in the surrounding extracellular matrix. Prostaglandin E2 inhibited the increase in connective tissue growth factor mRNA but augmented the release of vascular endothelial growth factor. Matrix metalloproteinase-2 decreased the amount of connective tissue growth factor and vascular endothelial growth factor, but not fibronectin deposited in the extracellular matrix. This report provides the first evidence that connective tissue growth factor may anchor vascular endothelial growth factor to the extracellular matrix and that this deposition is decreased by matrix metalloproteinase-2 and prostaglandin E2. This relationship has the potential to contribute to the changes that constitute airway remodeling, therefore providing a novel focus for therapeutic intervention in asthma. [ABSTRACT FROM AUTHOR]

The protease-activated receptor-2 (PAR-2) is present on human airway smooth muscle (ASM) cells and can be activated by mast cell tryptase, trypsin, or an activating peptide (AP). Trypsin induced significant increases in PGE[sub 2] release from human ASM cells after 6 and 24 h and also induced cyclooxygenase (COX)-2 mRNA expression and COX-2 protein. Tryptase and the PAR-2 AP did not alter PGE[sub 2] release or COX-2 protein levels, suggesting a lack of PAR-2 involvement. When we compared results in asthmatic and nonasthmatic muscle cells, both trypsin and bradykinin induced less PGE[sub 2] from asthmatic ASM cells, and bradykinin induced significantly less COX-2 mRNA in asthmatic cells. Significantly less PGE[sub 2] was released from proliferating ASM cells from asthmatic patients. In conclusion, trypsin induces PGE[sub 2] release and COX-2 in human ASM cells, which is unlikely to be via PAR-2 activation. In addition, ASM cells from asthmatic patients produce significantly less PGE[sub 2] and COX-2 compared with nonasthmatic cells. These findings may contribute to the increase in muscle mass evident in asthmatic airways. [ABSTRACT FROM AUTHOR]