Institute of Clinical Microbiology and Hygiene, University Hospital Regensburg and University of Regensburg, 93053 Regensburg, Germany.
Institute of Orthodontics, University Hospital Regensburg and University of Regensburg, 93053 Regensburg, Germany.
Cells. 2023 Dec 11;12(24):2816. doi: 10.3390/cells12242816.
Inflamed and infected tissues can display increased local sodium (Na) levels, which can have various effects on immune cells. In macrophages, high salt (HS) leads to a Na/Ca-exchanger 1 (NCX1)-dependent increase in intracellular Na levels. This results in augmented osmoprotective signaling and enhanced proinflammatory activation, such as enhanced expression of type 2 nitric oxide synthase and antimicrobial function. In this study, the role of elevated intracellular Na levels in macrophages was investigated. Therefore, the Na/K-ATPase (NKA) was pharmacologically inhibited with two cardiac glycosides (CGs), ouabain (OUA) and digoxin (DIG), to raise intracellular Na without increasing extracellular Na levels. Exposure to HS conditions and treatment with both inhibitors resulted in intracellular Na accumulation and subsequent phosphorylation of p38/MAPK. The CGs had different effects on intracellular Ca and K compared to HS stimulation. Moreover, the osmoprotective transcription factor nuclear factor of activated T cells 5 (NFAT5) was not upregulated on RNA and protein levels upon OUA and DIG treatment. Accordingly, OUA and DIG did not boost nitric oxide (NO) production and showed heterogeneous effects toward eliminating intracellular bacteria. While HS environments cause hypertonic stress and ionic perturbations, cardiac glycosides only induce the latter. Cotreatment of macrophages with OUA and non-ionic osmolyte mannitol (MAN) partially mimicked the HS-boosted antimicrobial macrophage activity. These findings suggest that intracellular Na accumulation and hypertonic stress are required but not sufficient to mimic boosted macrophage function induced by increased extracellular sodium availability.
发炎和感染的组织会显示出局部钠离子（Na）水平升高，这会对免疫细胞产生各种影响。在巨噬细胞中，高盐（HS）导致钠/钙交换器 1（NCX1）依赖性的细胞内 Na 水平增加。这导致增强的渗透保护信号和增强的促炎激活，例如增强的 2 型一氧化氮合酶和抗菌功能的表达。在这项研究中，研究了升高的细胞内 Na 水平在巨噬细胞中的作用。因此，通过两种心脏糖苷（CGs），哇巴因（OUA）和地高辛（DIG）药理学抑制钠/钾-ATP 酶（NKA），在不增加细胞外 Na 水平的情况下提高细胞内 Na 水平。暴露于 HS 条件下并用两种抑制剂处理会导致细胞内 Na 积累和随后的 p38/MAPK 磷酸化。CGs 对细胞内 Ca 和 K 的影响与 HS 刺激不同。此外，CG 处理不会上调 RNA 和蛋白质水平的核因子活化 T 细胞 5（NFAT5）的渗透保护转录因子。因此，OUA 和 DIG 不会促进一氧化氮（NO）的产生，并且对消除细胞内细菌表现出不同的作用。虽然 HS 环境会导致高渗应激和离子紊乱，但心脏糖苷仅会引起后者。用 OUA 和非离子渗透剂甘露醇（MAN）共同处理巨噬细胞可部分模拟 HS 增强的抗菌巨噬细胞活性。这些发现表明，细胞内 Na 积累和高渗应激是模拟由细胞外钠离子增加引起的增强的巨噬细胞功能所必需的，但不是充分的。
