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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.

SUBMITTER: Weber J

PROVIDER: S-EPMC7605532 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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

Weber Jonas J Rajan Suhasini S Schremmer Christian C Chao Yu-Kai YK Krasteva-Christ Gabriela G Kannler Martina M Yildirim Ali Önder AÖ Brosien Monika M Schredelseker Johann J Weissmann Norbert N Grimm Christian C Gudermann Thomas T Dietrich Alexander A

JCI insight 20201015 20

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 th ...[more]

PMID: 32931478

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Project description:Background: Dysregulation of TRPV4-mediated signaling has been associated with inflammation and tissue fibrosis, both of which are key features in the pathophysiology of lymphatic system diseases; however, the expression and functional roles of lymphatic TRPV4 channels remain largely unexplored. Methods: We generated a single-cell RNA sequencing dataset from microdissected mouse collecting lymphatic vessels to characterize the expression of Trpv4. Using a novel Trpv4fx/fx mouse strain and the Cre-lines Prox1-CreERT2 and LysM-Cre we assessed the role of TRPV4 channels in lymphatic endothelial cells (LECs) and peri-lymphatic myeloid cells, respectively. Confocal microscopy and extensive functional experimentation on isolated and pressurized lymphatics, including measurements of intracellular calcium activity, were employed to validate our scRNAseq findings and to elucidate the underlying mechanisms. Clinical significance was assessed using biopsies from breast cancer-related lymphedema (BCRL) patients. Results: We characterized the single-cell transcriptome of collecting lymphatic vessels and surrounding tissues. Trpv4 was highly enriched in LECs and in a subset of Lyve1+ macrophages displaying a tissue-resident profile. In clinical samples, BCRL was associated with increased infiltration of macrophages co-expressing LYVE1 and TRPV4. Pharmacological activation of TRPV4 channels led to contractile dysregulation in isolated collecting lymphatics. The response was multi-phasic, including initial vasospasm and subsequent vasodilation and inhibition of contractions, which was associated with the activation of thromboxane A2 receptors (TXA2Rs) in lymphatic muscle cells (LMCs) by secreted prostanoids from TRPV4+ myeloid cells, and increased nitric oxide (and perhaps other vasodilatory prostanoids) from LECs. The TXA2R-mediated vasospasm resulted from increased mobilization of calcium from intracellular stores through IP3 receptors and store-operated calcium entry. Conclusions: Our results uncovered a novel mechanism of lymphatic contractile dysregulation mediated by the crosstalk between TRPV4-expressing myeloid cells, including LYVE1+ macrophages, and LMCs or LECs. These findings highlight potentially important roles of TRPV4 channels in lymphatic dysfunction associated with inflammation, including secondary lymphedema.

Dataset Information

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

Publications

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

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