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Endothelial cell α-globin and its molecular chaperone α-hemoglobin–stabilizing protein regulate arteriolar contractility
Christophe Lechauve, … , Brant E. Isakson, Mitchell J. Weiss
Christophe Lechauve, … , Brant E. Isakson, Mitchell J. Weiss
Published October 8, 2018
Citation Information: J Clin Invest. 2018;128(11):5073-5082. https://doi.org/10.1172/JCI99933.
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Research Article Hematology Vascular biology

Endothelial cell α-globin and its molecular chaperone α-hemoglobin–stabilizing protein regulate arteriolar contractility

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Abstract

Arteriolar endothelial cell–expressed (EC-expressed) α-globin binds endothelial NOS (eNOS) and degrades its enzymatic product, NO, via dioxygenation, thereby lessening the vasodilatory effects of NO on nearby vascular smooth muscle. Although this reaction potentially affects vascular physiology, the mechanisms that regulate α-globin expression and dioxygenase activity in ECs are unknown. Without β-globin, α-globin is unstable and cytotoxic, particularly in its oxidized form, which is generated by dioxygenation and recycled via endogenous reductases. We show that the molecular chaperone α-hemoglobin–stabilizing protein (AHSP) promotes arteriolar α-globin expression in vivo and facilitates its reduction by eNOS. In Ahsp−/− mice, EC α-globin was decreased by 70%. Ahsp−/− and Hba1−/− mice exhibited similar evidence of increased vascular NO signaling, including arteriolar dilation, blunted α1-adrenergic vasoconstriction, and reduced blood pressure. Purified α-globin bound eNOS or AHSP, but not both together. In ECs in culture, eNOS or AHSP enhanced α-globin expression posttranscriptionally. However, only AHSP prevented oxidized α-globin precipitation in solution. Finally, eNOS reduced AHSP-bound α-globin approximately 6-fold faster than did the major erythrocyte hemoglobin reductases (cytochrome B5 reductase plus cytochrome B5). Our data support a model whereby redox-sensitive shuttling of EC α-globin between AHSP and eNOS regulates EC NO degradation and vascular tone.

Authors

Christophe Lechauve, Joshua T. Butcher, Abdullah Freiwan, Lauren A. Biwer, Julia M. Keith, Miranda E. Good, Hans Ackerman, Heather S. Tillman, Laurent Kiger, Brant E. Isakson, Mitchell J. Weiss

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Figure 3

Ahsp or Hba1 gene disruption causes steady-state TDA dilation in vivo.

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Ahsp or Hba1 gene disruption causes steady-state TDA dilation in vivo.
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(A) TDAs and veins in situ. Scale bars: 5 mm. (B) Electron micrographs of TDA cross sections from 24-week-old mice. Scale bars: 20 μm. (C) Histomorphometric analysis of randomly sampled TDA cross sections from WT control mice (n = 5, 15 random measurements), Ahsp−/− mice (n = 5, 13 random measurements), and Hba1−/− mice (n = 4, 5 random measurements). **P < 0.01 and ***P < 0.005, by unpaired t test.

Copyright © 2021 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)

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