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.