Cigarette Smoking Promotes Inflammation in Patients with COPD by Affecting the Polarization and Survival of Th/Tregs through Up-Regulation of Muscarinic Receptor 3 and 5 Expression

BACKGROUND: CD4(+) T cells in the lung are involved in the pathogenesis of chronic obstructive pulmonary disease (COPD), although CD4(+) T cell subsets and the direct effect of smoking on these cells, especially the expression of MRs, have not been comprehensively examined. METHODS: First, circulating CD4(+) T cell subsets in healthy nonsmokers, patients with SCOPD and patients with AECOPD were evaluated by flow cytometry. Then, differentiation experiments were carried out using RT-PCR, and Ki-67/Annexin V antibodies were used to measure proliferation and apoptosis. We also explored the impact of CSE on the differentiation and survival of CD4(+)Th/Tregs and examined the expression of MRs in healthy nonsmokers and patients with SCOPD. RESULTS: We found the percentages of circulating Th1 and Th17 cells were increased in patients with AECOPD, while the percentage of Th2 cells was decreased in patients with SCOPD. The percentages of Th10 cells were decreased in both patients with SCOPD and patients with AECOPD, while the percentages of Tregs were increased. In addition, the percentages of CD4(+)α-7(+) T cells were decreased in patients with SCOPD and patients with AECOPD. However, only the decrease observed in patients with AECOPD was significant. In vitro studies also revealed MR expression affected the polarization of T cells, with different CD4(+) T cell subtypes acquiring different MR expression profiles. The addition of CSE facilitated CD4(+) T cell polarization towards pro-inflammatory subsets (Th1 and Th17) and affected the survival of CD4(+) T cells and Treg cells by up-regulating the expression of MR3 and 5, resulting in an imbalance of CD4(+) T cell subsets. CONCLUSIONS: Our findings suggest an imbalance of circulating CD4(+) T cell subsets is involved in COPD pathogenesis in smokers. Cigarette smoking may contribute to this imbalance by affecting the polarization and survival of Th/Tregs through the up-regulation of MR3 and MR5.