Department of Radiation Oncology, Shands Cancer Center, University of Florida, Gainesville, Florida, United States of America.
Pediatric Pulmonary Division, Massachusetts General Hospital for Children, Boston, Massachusetts, United States of America.
PLoS One. 2024 Jul 25;19(7):e0307809. doi: 10.1371/journal.pone.0307809. eCollection 2024.
The airway epithelium plays a pivotal role in regulating mucosal immunity and inflammation. Epithelial barrier function, homeostasis of luminal fluid, and mucociliary clearance are major components of mucosal defense mechanisms. The epithelial sodium channel (ENaC) is one of the key players in controlling airway fluid volume and composition, and characteristic cytokines cause ENaC and barrier dysfunctions following pulmonary infections or allergic reactions. Given the limited understanding of the requisite duration and magnitude of cytokines to affect ENaC and barrier function, available treatment options for restoring normal ENaC activity are limited. Previous studies have demonstrated that distinct amino acids can modulate epithelial ion channel activities and barrier function in intestines and airways. Here, we have investigated the time- and concentration-dependent effect of representative cytokines for Th1- (IFN-γ and TNF-α), Th2- (IL-4 and IL-13), and Treg-mediated (TGF-β1) immune responses on ENaC activity and barrier function in human bronchial epithelial cells. When cells were exposed to Th1 and Treg cytokines, ENaC activity decreased gradually while barrier function remained largely unaffected. In contrast, Th2 cytokines had an immediate and profound inhibitory effect on ENaC activity that was subsequently followed by epithelial barrier disruption. These functional changes were associated with decreased membrane protein expression of α-, β-, and γ-ENaC, and decreased mRNA levels of β- and γ-ENaC. A proprietary blend of amino acids was developed based on their ability to prevent Th2 cytokine-induced ENaC dysfunction. Exposure to the select amino acids reversed the inhibitory effect of IL-13 on ENaC activity by increasing mRNA levels of β- and γ-ENaC, and protein expression of γ-ENaC. This study indicates the beneficial effect of select amino acids on ENaC activity in an in vitro setting of Th2-mediated inflammation suggesting these amino acids as a novel therapeutic approach for correcting this condition.
气道上皮在调节黏膜免疫和炎症方面起着关键作用。上皮屏障功能、管腔液的动态平衡和黏液纤毛清除是黏膜防御机制的主要组成部分。上皮钠通道（ENaC）是控制气道液体积和成分的关键因素之一，特征性细胞因子导致 ENaC 和屏障功能障碍，发生于肺部感染或过敏反应后。鉴于对影响 ENaC 和屏障功能所需的细胞因子持续时间和幅度的了解有限，恢复正常 ENaC 活性的可用治疗选择有限。先前的研究表明，不同的氨基酸可以调节肠道和气道中的上皮离子通道活性和屏障功能。在这里，我们研究了代表 Th1（IFN-γ 和 TNF-α）、Th2（IL-4 和 IL-13）和 Treg 介导（TGF-β1）免疫反应的细胞因子对人支气管上皮细胞中 ENaC 活性和屏障功能的时间和浓度依赖性影响。当细胞暴露于 Th1 和 Treg 细胞因子时，ENaC 活性逐渐降低，而屏障功能基本不受影响。相比之下，Th2 细胞因子对 ENaC 活性有立即和深远的抑制作用，随后上皮屏障破坏。这些功能变化与α-、β-和γ-ENaC 的膜蛋白表达减少以及β-和γ-ENaC 的 mRNA 水平降低有关。根据它们预防 Th2 细胞因子诱导的 ENaC 功能障碍的能力，开发了一种专有氨基酸混合物。暴露于选择的氨基酸通过增加β-和γ-ENaC 的 mRNA 水平和γ-ENaC 的蛋白表达，逆转了 IL-13 对 ENaC 活性的抑制作用。这项研究表明，在 Th2 介导的炎症的体外环境中，选择的氨基酸对 ENaC 活性有有益的影响，表明这些氨基酸是纠正这种情况的一种新的治疗方法。
