HIF2α signaling inhibits adherens junctional disruption in acute lung injury
Haixia Gong, … , Stephen M. Vogel, Asrar B. Malik
Haixia Gong, … , Stephen M. Vogel, Asrar B. Malik
Published January 9, 2015
Citation Information: J Clin Invest. 2015;125(2):652-664. https://doi.org/10.1172/JCI77701.
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Research Article

HIF2α signaling inhibits adherens junctional disruption in acute lung injury

Abstract

Vascular endothelial barrier dysfunction underlies diseases such as acute respiratory distress syndrome (ARDS), characterized by edema and inflammatory cell infiltration. The transcription factor HIF2α is highly expressed in vascular endothelial cells (ECs) and may regulate endothelial barrier function. Here, we analyzed promoter sequences of genes encoding proteins that regulate adherens junction (AJ) integrity and determined that vascular endothelial protein tyrosine phosphatase (VE-PTP) is a HIF2α target. HIF2α-induced VE-PTP expression enhanced dephosphorylation of VE-cadherin, which reduced VE-cadherin endocytosis and thereby augmented AJ integrity and endothelial barrier function. Mice harboring an EC-specific deletion of Hif2a exhibited decreased VE-PTP expression and increased VE-cadherin phosphorylation, resulting in defective AJs. Mice lacking HIF2α in ECs had increased lung vascular permeability and water content, both of which were further exacerbated by endotoxin-mediated injury. Treatment of these mice with Fg4497, a prolyl hydroxylase domain 2 (PHD2) inhibitor, activated HIF2α-mediated transcription in a hypoxia-independent manner. HIF2α activation increased VE-PTP expression, decreased VE-cadherin phosphorylation, promoted AJ integrity, and prevented the loss of endothelial barrier function. These findings demonstrate that HIF2α enhances endothelial barrier integrity, in part through VE-PTP expression and the resultant VE-cadherin dephosphorylation-mediated assembly of AJs. Moreover, activation of HIF2α/VE-PTP signaling via PHD2 inhibition has the potential to prevent the formation of leaky vessels and edema in inflammatory diseases such as ARDS.

Authors

Haixia Gong, Jalees Rehman, Haiyang Tang, Kishore Wary, Manish Mittal, Pallavi Chatturvedi, Youyang Zhao, Yulia A. Komorova, Stephen M. Vogel, Asrar B. Malik

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Figure 1

HIF2α induces VE-PTP expression and enhances the integrity of endothelial AJs.

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HIF2α induces VE-PTP expression and enhances the integrity of endothelia...
(A) HLMVECs were exposed to varying concentrations of O2 for 8 hours. Expression of HIF1α and HIF2α was assessed by WB. (B) Representation of the VEPTP promoter region. HREs are shown by circled numbers, and their sequences are displayed. (C) HLMVECs were exposed to normoxia or 1% O2 for 8 hours. A ChIP assay was performed to amplify the VEPTP and VE-cadherin promoters. (D) 293T cells were transfected with an HIF2α-DPA expression plasmid containing luciferase reporter constructs. Luciferase values were normalized to β-gal values. A schematic representation of corresponding deletion constructs is presented in the right panel. (E) HLMVECs infected with lentiviral HIF2α siRNA/shRNA were exposed to normoxia or 1% O2. Expression of VE-cadherin, VE-PTP, and HIF2α was assessed by WB. (F-G) Quantification of VE-PTP (F) and VE-cadherin (G) protein levels. (H) HLMVECs were exposed to normoxia or 1% O2. Expression of VEPTP and VE-cadherin at the mRNA level was assessed by quantitative PCR. (I) AJ integrity of HLMVECs was examined by VE-cadherin immunostaining using confocal microscopy. Scale bars: 20 μm. n = 3/group (F–H). Blot images were derived from samples run on parallel gels. *P < 0.05; **P < 0.01; ***P < 0.005; ****P < 0.001 by Student’s t test.