Expression of nonmuscle cofilin-1 and steroid responsiveness in severe asthma.

BACKGROUND: Glucocorticoids are the mainstay of asthma therapy; however, a proportion of patients with asthma has a severe form of the disease that fails to respond to therapy. Understanding the molecular mechanisms behind glucocorticoid-insensitive asthma is therefore of clinical importance. Evidence in glucocorticoid-unresponsive Henrietta Lack (HeLa) cells indicated that cofilin-1 could act as an inhibitor of glucocorticoid function. OBJECTIVE: To determine whether cofilin-1 expression is abnormally expressed in cells from patients with severe glucocorticoid-insensitive asthma and examine the effect of cofilin-1 overexpression on glucocorticoid function. METHODS: Peripheral blood CD4(+) T cells were purified from 16 subjects with severe glucocorticoid-insensitive asthma and 16 subjects with mild glucocorticoid-sensitive asthma, and cofilin-1 expression was determined by quantitative real-time RT-PCR and Western blotting. The effect of dexamethasone on cofilin-1 expression was determined in Jurkat T cells, and the effect of cofilin-1 overexpression on anti-CD3/CD28-stimulated IL-2 release was measured. RESULTS: Peripheral blood CD4(+) T cells from subjects with severe glucocorticoid-insensitive asthma are less responsive to dexamethasone than cells from subjects with mild glucocorticoid-sensitive asthma. Cells from these patients express significantly (P < .05) higher levels of cofilin-1 than cells from subjects with mild asthma. Dexamethasone did not affect cofilin-1 expression in Jurkat T cells. Functionally, dexamethasone suppression of anti-CD3/CD28-stimulated IL-2 was attenuated in Jurkat cells overexpressing cofilin-1. CONCLUSION: These results suggest that increased cofilin-1 expression may be important in the regulation of glucocorticoid sensitivity in peripheral blood lymphocytes of patients with severe treatment-insensitive asthma. CLINICAL IMPLICATIONS: Understanding the mechanisms of enhanced cofilin-1 expression may lead to the development of new therapies for severe treatment-insensitive asthma.

Latent adenoviral infection induces production of growth factors relevant to airway remodeling in COPD.

Previous studies showed an association between latent adenoviral infection with expression of the adenoviral E1A gene and chronic obstructive pulmonary disease (COPD). The present study focuses on how the adenoviral E1A gene could alter expression of growth factors by human bronchial epithelial (HBE) cells. The data show that connective tissue growth factor (CTGF) and transforming growth factor (TGF)-beta 1 mRNA and protein expression were upregulated in E1A-positive HBE cells. Upregulation of CTGF in this in vitro model was independent of TGF-beta secreted into the growth medium. Comparison of E1A-positive with E1A-negative HBE cells showed that both expressed cytokeratin but only E1A-positive cells expressed the mesenchymal markers vimentin and alpha-smooth muscle actin. We conclude that latent infection of epithelial cells by adenovirus E1A could contribute to airway remodeling in COPD by the viral E1A gene, inducing TGF-beta 1 and CTGF expression and shifting cells to a more mesenchymal phenotype.

GM-CSF increases airway smooth muscle cell connective tissue expression by inducing TGF-beta receptors.

Fibrosis around the smooth muscle of asthmatic airway walls leads to irreversible airway obstruction. Bronchial epithelial cells release granulocyte/macrophage colony-stimulating factor (GM-CSF) in asthmatics and are in close proximity to airway smooth muscle cells (ASMC). The findings in this study demonstrate that GM-CSF induces confluent, prolonged, serum-deprived cultures of ASMC to increase expression of collagen I and fibronectin. GM-CSF also induced ASMC to increase the expression of transforming growth factor (TGF)-beta receptors type I, II, and III (TbetaR-I, TbetaR-II, TbetaR-III), but had no detectable effect on the release of TGF-beta1 by the same ASMC. The presence of GM-CSF also induced the association of TGF-beta1 with TbetaR-III, which enhances binding of TGF-beta1 to TbetaR-II. The induction of TbetaRs was parallel to the increased induction of phosphorylated Smad2 (pSmad2) and connective tissue growth factor (CTGF), indicative of TGF-beta-mediated connective tissue synthesis. Dexamethasone decreased GM-CSF-induced TbetaR-I, TbetaR-II, TbetaR-III, pSmad2, CTGF, collagen I, and fibronectin. In conclusion, GM-CSF increases the responsiveness of ASMC to TGF-beta1-mediated connective tissue expression by induction of TbetaRs, which is inhibited by corticosteroids.