Inhaled long-acting ß2 agonists enhance glucocorticoid receptor nuclear translocation and efficacy in sputum macrophages in COPD.

ABSTRACT

BACKGROUND: Combination inhaled therapy with long-acting ß2 agonists (LABAs) and corticosteroids is beneficial in treating asthma and chronic obstructive pulmonary disease (COPD). OBJECTIVE: In asthma, LABAs enhance glucocorticoid receptor (GR) nuclear translocation in the presence of corticosteroids. Whether this biological mechanism occurs in COPD, a relatively corticosteroid-resistant disease, is uncertain. METHODS: Eight patients with mild/moderate COPD participated in a double-blind, placebo-controlled, crossover study and inhaled single doses of fluticasone propionate (FP) 100 µg, FP 500 µg, salmeterol xinafoate (SLM) 50 µg, and combination FP 100 µg + SLM 50 µg. One hour postinhalation, sputum was induced, nuclear proteins isolated from purified macrophages, and levels of activated nuclear GR quantified by using a GR-glucocorticoid response element ELISA-based assay. RESULTS: Nuclear GR significantly increased after the inhalation of FP 500 µg (P < .01), but not after the inhalation of FP 100 µg or SLM 50 µg, compared with placebo. Interestingly, SLM in combination with FP 100 µg increased nuclear GR levels equivalent to those of FP 500 µg alone. This was significantly greater than either FP 100 µg (P < .05) or SLM 50 µg (P < .01) alone. In vitro in a human macrophage cell line, SLM (10(-8) mol/L) enhanced FP (10(-9) mol/L)-induced mitogen-activated protein kinase phosphatase-1 mRNA (5.8 ± 0.6 vs 8.4 ± 1.1 × 10(-6) copies, P < .05) and 2 × glucocorticoid response element-luciferase reporter gene activity (250.1 ± 15.6 vs 103.1 ± 23.6-fold induction, P < .001). Addition of SLM (10(-9) mol/L) to FP (10(-11) mol/L) significantly enhanced FP-mediated suppression of IL-1ß-induced CXCL8 (P < .05). CONCLUSIONS: Addition of SLM 50 µg to FP 100 µg enhanced GR nuclear translocation equivalent to that seen with a 5-fold higher dose of FP in sputum macrophages from patients with COPD. This may account for the superior clinical effects of combination LABA/corticosteroid treatment compared with either as monotherapy observed in COPD.