Department of Pulmonary Medicine, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.
Laboratory for Immune Cell Systems, RIKEN Center for Integrative Medical Sciences, Yokohama, Japan.
Allergy. 2021 Sep;76(9):2785-2796. doi: 10.1111/all.14836. Epub 2021 Apr 25.
Tiotropium bromide, a long-acting muscarinic antagonist, reduces the frequency of exacerbation in patients with moderate to severe asthma, but its underlying mechanism is not clear. Asthma exacerbations are associated with exposure to external stimuli, and group 2 innate lymphoid cells (ILC2s) are considered to be involved in the pathophysiology of asthma exacerbation. We investigated whether tiotropium modulates airway inflammation through ILC2 functions.
Mice were administered papain intranasally to induce innate-type airway inflammation with or without tiotropium pretreatment, and bronchoalveolar lavage fluids (BALF) and lung tissues were collected. Lung-derived ILC2s and bone marrow-derived basophils were stimulated in vitro with IL-33 in the presence or absence of tiotropium. Muscarinic M3 receptor (M3R) expression on immune cells was assessed by RNA sequence.
Papain induced airway eosinophilic inflammation, and tiotropium reduced the numbers of eosinophils in BALF. The concentrations of IL-4, IL-5, and IL-13, and the numbers of ILC2s in BALF were also reduced by tiotropium treatment. However, tiotropium did not affect IL-33-induced IL-5 and IL-13 production from ILC2s, suggesting that tiotropium regulates ILC2s indirectly. Gene-expression analysis showed that basophils predominantly expressed M3R mRNA among murine immune cells. Tiotropium reduced IL-4 production from basophils derived from mouse bone marrow and human basophils after stimulation with IL-33.
These findings suggest that tiotropium attenuates ILC2-dependent airway inflammation by suppressing IL-4 production from basophils and, subsequently, regulating ILC2 activation. The inhibitory effects of long-acting muscarinic antagonists on the innate response may contribute to reducing asthma exacerbation.
噻托溴铵是一种长效毒蕈碱拮抗剂，可降低中重度哮喘患者的恶化频率，但其潜在机制尚不清楚。哮喘恶化与暴露于外部刺激有关，2 型固有淋巴细胞（ILC2）被认为与哮喘恶化的病理生理学有关。我们研究了噻托溴铵是否通过 ILC2 功能调节气道炎症。
通过鼻内给予木瓜蛋白酶诱导小鼠发生固有型气道炎症，并在给予或不给予噻托溴铵预处理的情况下收集支气管肺泡灌洗液（BALF）和肺组织。在存在或不存在噻托溴铵的情况下，用 IL-33 体外刺激肺源性 ILC2 和骨髓源性嗜碱性粒细胞。通过 RNA 测序评估免疫细胞上的毒蕈碱 M3 受体（M3R）表达。
木瓜蛋白酶诱导气道嗜酸性粒细胞炎症，噻托溴铵减少 BALF 中的嗜酸性粒细胞数量。IL-4、IL-5 和 IL-13 的浓度以及 BALF 中的 ILC2 数量也因噻托溴铵治疗而降低。然而，噻托溴铵并不影响 IL-33 诱导的 ILC2 产生的 IL-5 和 IL-13，表明噻托溴铵间接调节 ILC2。基因表达分析表明，在鼠免疫细胞中，嗜碱性粒细胞主要表达 M3R mRNA。噻托溴铵减少了骨髓来源的小鼠嗜碱性粒细胞和人类嗜碱性粒细胞在受到 IL-33 刺激后产生的 IL-4。
这些发现表明，噻托溴铵通过抑制嗜碱性粒细胞产生 IL-4 并随后调节 ILC2 激活来减轻 ILC2 依赖性气道炎症。长效毒蕈碱拮抗剂对先天反应的抑制作用可能有助于减少哮喘恶化。
