Hypoxic pulmonary vasoconstriction requires connexin 40–mediated endothelial signal conduction
Liming Wang, … , Hermann Kuppe, Wolfgang M. Kuebler
Liming Wang, … , Hermann Kuppe, Wolfgang M. Kuebler
Published October 24, 2012
Citation Information: J Clin Invest. 2012;122(11):4218-4230. https://doi.org/10.1172/JCI59176.
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Hypoxic pulmonary vasoconstriction requires connexin 40–mediated endothelial signal conduction

Abstract

Hypoxic pulmonary vasoconstriction (HPV) is a physiological mechanism by which pulmonary arteries constrict in hypoxic lung areas in order to redirect blood flow to areas with greater oxygen supply. Both oxygen sensing and the contractile response are thought to be intrinsic to pulmonary arterial smooth muscle cells. Here we speculated that the ideal site for oxygen sensing might instead be at the alveolocapillary level, with subsequent retrograde propagation to upstream arterioles via connexin 40 (Cx40) endothelial gap junctions. HPV was largely attenuated by Cx40-specific and nonspecific gap junction uncouplers in the lungs of wild-type mice and in lungs from mice lacking Cx40 (Cx40–/–). In vivo, hypoxemia was more severe in Cx40–/– mice than in wild-type mice. Real-time fluorescence imaging revealed that hypoxia caused endothelial membrane depolarization in alveolar capillaries that propagated to upstream arterioles in wild-type, but not Cx40–/–, mice. Transformation of endothelial depolarization into vasoconstriction involved endothelial voltage-dependent α1G subtype Ca2+ channels, cytosolic phospholipase A2, and epoxyeicosatrienoic acids. Based on these data, we propose that HPV originates at the alveolocapillary level, from which the hypoxic signal is propagated as endothelial membrane depolarization to upstream arterioles in a Cx40-dependent manner.

Authors

Liming Wang, Jun Yin, Hannah T. Nickles, Hannes Ranke, Arata Tabuchi, Julia Hoffmann, Christoph Tabeling, Eduardo Barbosa-Sicard, Marc Chanson, Brenda R. Kwak, Hee-Sup Shin, Songwei Wu, Brant E. Isakson, Martin Witzenrath, Cor de Wit, Ingrid Fleming, Hermann Kuppe, Wolfgang M. Kuebler

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Figure 8

Translocation of endothelial cPLA2 in acute hypoxia.

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Translocation of endothelial cPLA2 in acute hypoxia. (A) Representativ...
(A) Representative merged epifluorescence images showing endothelial cell nuclei in pulmonary arterioles, as stained by HOECHST 33324 (red), and translocated cPLA2, as detected by indirect immunofluorescence (green), in intact lungs of Cx40+/+ mice. Images were obtained at normoxia (21% O2) or after 10 minutes of hypoxia (1 % O2); vessel margins are denoted by dotted lines. Scale bar: 50 μm. Group data (n = 5 lungs each) show cPLA2 translocation as a ratio of cPLA2 immunostaining relative to HOECHST 33324 fluorescence. *P < 0.05 vs. normoxia. (B) Representative merged confocal fluorescence images showing endothelial cell nuclei in cultured PAECs, as stained by HOECHST 33324 (blue), and cPLA2 that had been translocated to the nuclear envelope (arrows) or the cell membrane (arrowheads), as detected by indirect immunofluorescence (green). Images were obtained at normoxia or after 10 minutes of hypoxia; cell margins identified by brightfield microscopy are denoted by dotted lines. Scale bar: 20 μm. Group data show cPLA2 translocation from n = 5 independent experiments. *P < 0.05 vs. normoxia.