Cigarette Smoke Disturbs The Survival Of Cd8(+) Tc/Tregs Partially Through Muscarinic Receptors-Dependent Mechanisms In Chronic Obstructive Pulmonary Disease

BackgroundCD8(+) 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.MethodsCirculating 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.ResultsWhile 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.ConclusionThe 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.