Reduced glucocorticoid receptor binding affinity in blood lymphocytes and monocytes of COPD patients

Background: COPD patients have limited therapeutic response to glucocorticoids. Molecular mechanisms of steroid resistance include defective glucocorticoid receptor (GR) binding and translocation into the nucleus. Whether GR binding capacity varies among different types of immune cells is currently unknown. Aim: The aim of the study was to determine the GR binding affinity in blood lymphocytes and monocytes of COPD patients. Methods: The study population consisted of 24 smokers with COPD, 24 healthy smokers (HS) and 21 healthy non-smokers (HNS). One hundred µL aliquots of blood were incubated with FITC-conjugated dexamethasone (FITC-Dex; 10-6 M) for 60 min at 37°C. As controls, another tube was prepared adding 10-5 M nonconjugated Dex 10 minutes before FITC-Dex. Cells were washed twice and stained with primary monoclonal antibodies to CD3, CD4, CD25, CD127, CD8, CD19, CD56, CD14, CD45 for 20 min. Erythrocytes were lysed and Dex binding was assessed by flow cytometry. Results: There were no significant differences in the percentage of CD3+, CD3+CD4+, CD4+CD25+CD127-, CD3+CD8+, CD3-CD56+, CD3+CD56+, CD19+, CD14+ cells expressing FITC-Dex between COPD smokers and HS. However mean fluorescence intensity (MFI) of FITC-Dex by those cells was significantly lower in blood of smokers with COPD compared with HS. HNS had significantly higher MFI of FITC-Dex in the same cells than HS. Patients with COPD had a positive correlation of FITC-Dex MFI between different lymphocyte subpopulations, as well as between monocytes and lymphocyte subtypes. Conclusion: Reduction of GR binding in lymphocyte subpopulations and monocytes is independently affected by COPD and smoking.