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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]

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]