Sensitivity to glucocorticosteroids and heterogeneity of in vitro cell response in patients with chronic obstructive pulmonary disease

Abstract

Inhaled corticosteroids are widely used for the treatment of chronic obstructive pulmonary disease (COPD), but their efficacy significantly varies between patients. The aim of the study was to establish approaches to reveal steroid-sensitive and steroid-resistant patients with COPD using the blood and lung cells. Methods. Forty five patients with COPD undergoing bronchoscopy were recruited for the study of cytokine secretion by alveolar macrophages under the influence of glucocorticoids. Alveolar macrophages isolated from bronchoalveolar lavage fluid were cultured with lipopolysaccharide (LPS) and different concentrations of dexamethasone (0.01 – 1000 nM) for 24 h. Then, supernatants were removed and analyzed for concentrations of interleukin 6 (IL-6), IL-8 and tumor necrosis factor α (TNF-α). Binding of the glucocorticoid with its receptors was investigated in 24 patients with COPD, 20 healthy smokers and 20 healthy non-smokers. Blood cells were cultured with fluorescein isothiocyanate (FITC)-labelled dexamethasone and monoclonal antibodies against surface antigens of lymphocyte and monocyte populations. Fluorescence intensity of FITC-labelled dexamethasone was analyzed in blood cells using flow cytometry. Results. Dexamethasone significantly inhibited IL-6, IL-8, and TNF-α production in alveolar macrophages in a dose dependent manner. The maximal inhibition of cytokine production was observed at dexamethasone concentration of 100 nM, and the maximal cell response variability was found at 10 nM. IL-8 was less sensitive to the corticosteroid compared to IL-6 and TNF-α. Dexamethasone at any concentration failed to reach >50% inhibition of LPS-induced production of IL-8, IL-6 and TNF-α in alveolar macrophages of 40.0%; 11.1% and 8.9% of COPD patients, respectively. The fluorescence intensity of FITC-labelled dexamethasone in blood lymphocytes and monocytes was lower in smokers with COPD compared to healthy smokers and healthy non-smokers. The binding of dexamethasone with its receptors in the blood cells was higher in healthy non-smokers compared to healthy smokers. Conclusion. In vitro response of alveolar macrophages to glucocorticoids in COPD patients is characterized by significant inter-individual variability. The weak corticosteroid-related inhibition of IL-8 production can contribute to neutrophilic inflammation in COPD. The capacity of glucocorticoid receptors to bind with their ligands in blood lymphocytes and monocytes is decreased in COPD patients.