TRPV4 channels are essential for alveolar epithelial barrier function as protection from lung edema
Jonas Weber, … , Thomas Gudermann, Alexander Dietrich
Jonas Weber, … , Thomas Gudermann, Alexander Dietrich
Published September 15, 2020
Citation Information: JCI Insight. 2020;5(20):e134464. https://doi.org/10.1172/jci.insight.134464.
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Research Article Cell biology Pulmonology

TRPV4 channels are essential for alveolar epithelial barrier function as protection from lung edema

Abstract

Ischemia/reperfusion-induced edema (IRE), one of the most significant causes of mortality after lung transplantation, can be mimicked ex vivo in isolated perfused mouse lungs (IPL). Transient receptor potential vanilloid 4 (TRPV4) is a nonselective cation channel studied in endothelium; however, its role in the lung epithelium remains elusive. Here, we show enhanced IRE in TRPV4-deficient (TRPV4–/–) IPL compared with that of WT controls, indicating a protective role of TRPV4 in maintenance of the alveolar epithelial barrier. By immunohistochemistry, mRNA profiling, and electrophysiological characterization, we detected TRPV4 in bronchial epithelium, alveolar epithelial type I (ATI), and alveolar epithelial type II (ATII) cells. Genetic ablation of TRPV4 resulted in reduced expression of the water-conducting aquaporin-5 (AQP-5) channel in ATI cells. Migration of TRPV4–/– ATI cells was reduced, and cell barrier function was impaired. Analysis of isolated primary TRPV4–/– ATII cells revealed a reduced expression of surfactant protein C, and the TRPV4 activator GSK1016790A induced increases in current densities only in WT ATII cells. Moreover, TRPV4–/– lungs of adult mice developed significantly larger mean chord lengths and altered lung function compared with WT lungs. Therefore, our data illustrate essential functions of TRPV4 channels in alveolar epithelial cells and in protection from edema formation.

Authors

Jonas Weber, Suhasini Rajan, Christian Schremmer, Yu-Kai Chao, Gabriela Krasteva-Christ, Martina Kannler, Ali Önder Yildirim, Monika Brosien, Johann Schredelseker, Norbert Weissmann, Christian Grimm, Thomas Gudermann, Alexander Dietrich

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Figure 5

Nuclear localization of nuclear factor of activated T cells in and migration and adhesion of TRPV4-deficient and WT ATI cells.

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Nuclear localization of nuclear factor of activated T cells in and migra...
Representative Western blot analysis of AQP-5 expression in WT and TRPV4–/– ATII cells differentiated to ATI cells (A) and summary of AQP-5 expression in these cells (B). Representative Western blot analysis of podoplanin expression — another ATI cell marker — in WT and TRPV4–/– ATII cells differentiated to ATI cells (C) and summary of podoplanin expression in these cells (D). Representative Western blot analysis of nuclear NFATc1 localization in WT and TRPV4–/– ATI cells (E) and summary of nuclear factor of activated T cells (NFAT) localization in these cells (F). Lamin B1 served as loading control. Representative images of a migration assay after removing inserts (scale bar: 200 μm) (G). Summary of remaining gap values normalized to initial values quantified in migration assays of TRPV4–/– and WT ATI cells after releasing inserts at 0, 1, 3, 5, 8, 12, and 24 hours (H). Electrical cell resistance was quantified with an ECIS device for WT and TRPV4–/– ATI cells for 160 hours. (I). Data represent mean ± SEM from at least 3 independent cell preparations of 5 mice each. Significance between means was analyzed using 2-tailed unpaired Student’s t test; *P < 0.05, ***P < 0.001.