Objective: To investigate the relationship between beta(2)-adrenoceptor (beta(2)-AR) expression in inflammatory cells and airflow limitation in patients with chronic obstructive pulmonary disease (COPD).
Methods: According to the severity of COPD, 37 patients with stable COPD were divided into three groups. Samples of peripheral blood and induced sputum were collected from 37 COPD patients, 11 of II grade, 12 of grade III, and 14 of grade IV. Counting and classification of white blood cells in the peripheral blood and induced sputum were made. Radioligand binding assay was used to detect the maximum binding capacity (Bmax) reflecting the density, and balance dissociation constant (Kd) reflecting the affinity of beta(2)-AR in the peripheral blood mononuclear cells (PBMC) from both kinds of specimens. Thirteen normal smokers were used as control group.
Results: No significant differences were found in peripheral blood leukocyte count, classification and induced sputum cell count among the 3 COPD groups and control group, but the neutrophil cell count levels of induced sputum of the COPD groups were all significantly higher than that of the control group (all P = 0.00). For the control, and COPD grade II, III, and IV groups, the Bmax levels of PBMC beta(2)-AR were (106 +/- 52), (156 +/- 72), (135 +/- 57) and (123 +/- 58) fmol/mg respectively (F = 1.45, P = 0.24); the Kd levels of PBMC beta(2)-AR were (548 +/- 267), (343 +/- 144), (297 +/- 150), and (375 +/- 95) pmol/L respectively (F = 4.84, P = 0.01); the Bmax levels of beta(2)-AR of induced sputum cells were (126 +/- 46), (116 +/- 54), (106 +/- 36), and (76 +/- 30) respectively (F = 3.46, P = 0.02); and the Kd levels of beta(2)-AR of induced sputum cells were (570 +/- 290), (405 +/- 197), (404 +/- 139), and (347 +/- 123) respectively (F = 2.97, P = 0.04). There was a positive correlation between the forced expiratory volume in one second in percentage of predicted and density of beta(2)-AR in induced sputum cells from the COPD patients (r = 0.43, P = 0.01). There was a positive correlation between the Bmax of beta(2)-AR in PBMC and induced sputum cells (r = 0.40, P = 0.02).
Conclusions: The expression of beta(2)-AR in PBMC and induced sputum cells from COPD patients is down-regulated with progression of the disease. The expression of beta(2)-AR in the induced sputum cells changes more significantly than that in the PBMC. The expression of beta(2)-AR in inflammatory cells in the airway may play a more important role in the COPD progress.