NFAT5-dependent transcriptional stress control of endothelial cells prevents maladaptive remodeling of pulmonary arterioles in the hypoxic lung
AimsChronic hypoxia causes detrimental structural alterations in the lung, which are partially dependent on stress responses of the endothelium. In this context, we revealed that hypoxia-exposed murine lung endothelial cells (MLEC) activate nuclear factor of activated T-cells 5 (NFAT5) - a transcription factor that adjusts the cellular transcriptome to cope with multiple environmental stressors. Here, we studied the functional relevance of NFAT5 for the control of hypoxia-induced transcription in MLEC. Methods and ResultsTargeted ablation of Nfat5 in endothelial cells did not evoke phenotypic abnormalities in normoxia-exposed mice. However, MLEC in Nfat5-deficient mice up-regulated energy- and protein-metabolism-associated gene expression under normobaric hypoxia (10% O2) for seven days as evidenced by microarray- and scRNA-seq-based analyses. Moreover, loss of NFAT5 boosted the expression and release of platelet-derived growth factor B (Pdgfb) - a HIF1-regulated driver of vascular smooth muscle cell (VSMC) growth - in capillary MLEC of hypoxia-exposed mice, which was accompanied by exaggerated coverage of distal pulmonary arterioles by VSMC, increased pulmonary vascular resistance and impaired right ventricular functions. In vitro, knockout of Nfat5 in cultured MLEC stimulated Pdgfb expression and release after exposure to hypoxia and amplified binding of HIF1 in the Pdgfb promoter region. ConclusionCollectively, our study identifies NFAT5 as a protective transcription factor required to rapidly adjust the transcriptome of MLEC to hypoxia. Specifically, NFAT5 restricts HIF1-mediated Pdgfb expression and consequently limits muscularization and resistance of pulmonary arterioles. HighlightsO_LIHypoxia stimulates the transcriptional activity of NFAT5 in MLEC. C_LIO_LILoss of NFAT5 in hypoxia-exposed MLEC results in EC subtype-specific maladaption of growth factor-, energy- and protein-metabolism-associated gene expression. C_LIO_LISpecifically, NFAT5-deficient capillary lung EC unleash HIF1-regulated Pdgfb expression and release, which results in excessive coverage of pulmonary arterioles by VSMC. C_LIO_LINFAT5-dependent control of early stress responses of capillary MLEC is required to limit the increase in pulmonary vascular resistance and impairment of right ventricular functions. C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=166 SRC="FIGDIR/small/563022v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@c9be61org.highwire.dtl.DTLVardef@f1d7cforg.highwire.dtl.DTLVardef@18f795forg.highwire.dtl.DTLVardef@695601_HPS_FORMAT_FIGEXP M_FIG C_FIG