Division of Experimental Pathology, Department of Pathology, National Institute of Medical Sciences and Nutrition Salvador Zubirán, México City, Mexico.
Department of Bronchial Hyperreactivity, National Institute of Respiratory Diseases (Mexico), Mexico City, Mexico.
Front Immunol. 2021 Feb 18;11:581911. doi: 10.3389/fimmu.2020.581911. eCollection 2020.
The cholinergic system is present in both bacteria and mammals and regulates inflammation during bacterial respiratory infections through neuronal and non-neuronal production of acetylcholine (ACh) and its receptors. However, the presence of this system during the immunopathogenesis of pulmonary tuberculosis (TB) and in its causative agent () has not been studied. Therefore, we used an experimental model of progressive pulmonary TB in BALB/c mice to quantify pulmonary ACh using high-performance liquid chromatography during the course of the disease. In addition, we performed immunohistochemistry in lung tissue to determine the cellular expression of cholinergic system components, and then administered nicotinic receptor (nAChR) antagonists to validate their effect on lung bacterial burden, inflammation, and pro-inflammatory cytokines. Finally, we subjected cultures to colorimetric analysis to reveal the production of ACh and the effect of ACh and nAChR antagonists on growth. Our results show high concentrations of ACh and expression of its synthesizing enzyme choline acetyltransferase (ChAT) during early infection in lung epithelial cells and macrophages. During late progressive TB, lung ACh upregulation was even higher and coincided with ChAT and α7 nAChR subunit expression in immune cells. Moreover, the administration of nAChR antagonists increased pro-inflammatory cytokines, reduced bacillary loads and synergized with antibiotic therapy in multidrug resistant TB. Finally, studies revealed that the bacteria is capable of producing nanomolar concentrations of ACh in liquid culture. In addition, the administration of ACh and nicotinic antagonists to cultures induced or inhibited bacterial proliferation, respectively. These results suggest that possesses a cholinergic system and upregulates the lung non-neuronal cholinergic system, particularly during late progressive TB. The upregulation of the cholinergic system during infection could aid both bacterial growth and immunomodulation within the lung to favor disease progression. Furthermore, the therapeutic efficacy of modulating this system suggests that it could be a target for treating the disease.
胆碱能系统存在于细菌和哺乳动物中，通过神经元和非神经元产生乙酰胆碱（ACh）及其受体来调节细菌呼吸道感染中的炎症。然而，在肺结核（TB）的免疫发病机制及其病原体 （）中，该系统的存在尚未得到研究。因此，我们使用 BALB/c 小鼠进行的进行性肺结核实验模型，在疾病过程中使用高效液相色谱法来量化肺部中的 ACh。此外，我们对肺组织进行了免疫组织化学染色，以确定胆碱能系统成分的细胞表达，然后给予烟碱型乙酰胆碱受体（nAChR）拮抗剂，以验证其对肺部细菌负荷，炎症和促炎细胞因子的影响。最后，我们对 进行比色分析，以揭示 ACh 的产生及其对 生长的影响。
我们的研究结果显示，在肺部上皮细胞和巨噬细胞中，早期感染时 ACh 浓度较高，并且表达其合成酶胆碱乙酰转移酶（ChAT）。在晚期进行性 TB 中，肺部 ACh 的上调甚至更高，并且与免疫细胞中的 ChAT 和α7 nAChR 亚基表达一致。此外，nAChR 拮抗剂的给药增加了促炎细胞因子，降低了细菌负荷，并与耐多药 TB 的抗生素治疗协同作用。最后， 研究表明，该细菌能够在液体培养中产生纳摩尔浓度的 ACh。此外，将 ACh 和烟碱拮抗剂施用于 培养物分别诱导或抑制细菌增殖。
这些结果表明， 具有胆碱能系统，并上调肺部非神经元胆碱能系统，特别是在晚期进行性 TB 中。感染过程中胆碱能系统的上调可能有助于细菌的生长和肺部的免疫调节，从而有利于疾病的进展。此外，调节该系统的治疗效果表明，它可能是治疗该疾病的靶标。
