Moran John, Pugh Courtney, Brown Nevian, Thomas Ashley, Zhang Shuzhong, McCauley Emily, Cephas Amelia, Shrestha Chandra L, Partida-Sanchez Santiago, Bai Shasha, Bruscia Emanuela, Kopp Benjamin T
bioRxiv. 2024 Nov 8:2024.11.06.622340. doi: 10.1101/2024.11.06.622340.
Cystic fibrosis (CF) is a chronic systemic disease caused by dysfunctional or absent cystic fibrosis transmembrane conductance regulator (CFTR). CFTR is expressed in human immune cells and plays a role in regulating innate immunity both directly and indirectly. Besides CFTR, research indicates that the epithelial sodium channel (ENaC) also contributes to dysfunction in CF airway epithelial cells. However, the impact of non-CFTR ion channel dysfunction on CF immune responses is not yet fully understood. A precise understanding of how CF immune function is regulated by ion channels may allow antibiotic-and mutation-agnostic treatment approaches to chronic bacterial infection and inflammation. Therefore, we hypothesized that ENaC is aberrantly expressed in CF macrophages and directly contributes to impaired phagocytic and inflammatory functions.
ENaC expression was characterized in human immune cells isolated from CF and non-CF blood donors. Monocyte-derived macrophage (MDM) function and bacterial killing was tested in the setting of ENaC modulation.
Baseline expression of ENaC in human CF MDMs, lymphocytes, and granulocytes was increased at both the transcript and protein level relative to non-CF controls and persisted after exposure to bacteria. Inhibition of CFTR in non-CF MDMs resulted in ENaC overexpression.CFTR modulator treatment reduced but did not eliminate ENaC overexpression in CF MDMs. Interestingly, ENaC inhibition with Amiloride increased CFTR expression. Amiloride-treated CF MDMs also showed normalized ROS production, improved autophagy, and decreased pro-inflammatory cytokine production. Finally, results from an ion channel microarray indicated that sodium channel expression in CF MDMs normalized after Amiloride treatment with minimal effect on other ion channels.
ENaC is overexpressed in CF immune cells and is associated with abnormal macrophage function. ENaC modulation in immune cells is a novel potential therapeutic target for infection control in CF, either in combination with CFTR modulators, or as a sole agent for patients not currently eligible for CFTR modulators.
囊性纤维化（CF）是一种由功能失调或缺失的囊性纤维化跨膜传导调节因子（CFTR）引起的慢性全身性疾病。CFTR在人类免疫细胞中表达，直接或间接参与调节固有免疫。除CFTR外，研究表明上皮钠通道（ENaC）也与CF气道上皮细胞功能障碍有关。然而，非CFTR离子通道功能障碍对CF免疫反应的影响尚未完全阐明。精确了解离子通道如何调节CF免疫功能，可能有助于开发针对慢性细菌感染和炎症的、不依赖抗生素和突变类型的治疗方法。因此，我们推测ENaC在CF巨噬细胞中异常表达，并直接导致吞噬和炎症功能受损。
对从CF和非CF献血者分离出的人类免疫细胞中的ENaC表达进行表征。在ENaC调节的情况下测试单核细胞衍生巨噬细胞（MDM）的功能和细菌杀伤能力。
相对于非CF对照，人类CF MDM、淋巴细胞和粒细胞中ENaC的基线表达在转录和蛋白质水平均升高，且在接触细菌后持续存在。非CF MDM中CFTR的抑制导致ENaC过表达。CFTR调节剂治疗可降低但不能消除CF MDM中ENaC的过表达。有趣的是，用氨氯吡咪抑制ENaC可增加CFTR表达。氨氯吡咪处理的CF MDM还显示活性氧生成正常化、自噬改善和促炎细胞因子产生减少。最后，离子通道微阵列的结果表明，氨氯吡咪处理后CF MDM中的钠通道表达正常化，对其他离子通道影响最小。
ENaC在CF免疫细胞中过表达，并与巨噬细胞功能异常有关。免疫细胞中的ENaC调节是CF感染控制的一种新的潜在治疗靶点，可与CFTR调节剂联合使用，或作为目前不符合CFTR调节剂治疗条件的患者的单一治疗药物。
