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Background: CD8+ T cells (Cytotoxic T cells, Tc) are known to play a critical role in the pathogenesis of smoking related airway inflammation including chronic obstructive pulmonary disease (COPD). However, how cigarette smoke directly impacts systematic CD8+ T cell and regulatory T cell (Treg) subsets, especially by modulating muscarinic acetylcholine receptors (MRs), has yet to be well elucidated. Methods: Circulating CD8+ Tc/Tregs in healthy nonsmokers (n = 15), healthy smokers (n = 15) and COPD patients (n = 18) were evaluated by flow cytometry after incubating with anti-CD3, anti-CD8, anti-CD25, anti-Foxp3 antibodies. Peripheral blood T cells (PBT cells) from healthy nonsmokers were cultured in the presence of cigarette smoke extract (CSE) alone or combined with MRs agonist/antagonist for 5 days. Proliferation and apoptosis were evaluated by flow cytometry using Ki-67/Annexin-V antibodies to measure the effects of CSE on the survival of CD8+ Tc/Tregs. Results: While COPD patients have elevated circulating percentage of CD8+ T cells, healthy smokers have higher frequency of CD8+ Tregs. Elevated percentages of CD8+ T cells correlated inversely with declined FEV1 in COPD. CSE promoted the proliferation and inhibited the apoptosis of CD8+ T cells, while facilitated both the proliferation and apoptosis of CD8+ Tregs. Notably, the effects of CSE on CD8+ Tc/Tregs can be mostly simulated or attenuated by muscarine and atropine, the MR agonist and antagonist, respectively. However, neither muscarine nor atropine influenced the apoptosis of CD8+ Tregs. Conclusion: The results imply that cigarette smoking likely facilitates a proinflammatory state in smokers, which is partially mediated by MR dysfunction. The MR antagonist may be a beneficial drug candidate for cigarette smoke-induced chronic airway inflammation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]