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 2

TRPV4 and aquaporin-5 expression in mouse lungs.

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TRPV4 and aquaporin-5 expression in mouse lungs. (A) GFP staining (green...
(A) GFP staining (green) by fluorescence-coupled GFP-specific antibodies in lung cryosections of TRPV4EGFP reporter mice reveals expression of TRPV4 in cells of the lung endothelium (EN) as well as in the bronchial (BE) and alveolar epithelium (AE). Nuclei staining was performed with Hoechst dye (blue). Scale bar: 10 μm (right); 20 μm (middle); 50 μm (left). (B) Lung cryosections from TRPV4EGFP– reporter mice were stained with fluorescence-coupled antisera directed against GFP and aquaporin-5 (AQP-5). Confocal images were obtained after excitation at 488 nm (for EGFP, left top, green) or after excitation at 561 nm (for AQP-5, left bottom, red). Both images were merged (right). Nuclei staining was performed with Hoechst dye (blue). A, alveolus; B, bronchus; V, vasculature. The inset shows the bottom boxed region in at higher magnification. Scale bar: 10 μm (inset); 20 μm. (C) TRPV4 mRNA quantification in lung cells using NanoString technology. ATII, alveolar type II cells; EC, endothelial cells; PASMC, precapillary arterial smooth muscle cells; pmLF, primary murine lung fibroblasts. Data represent mean ± SEM from at least 3 independent cell isolations.