SNO-hemoglobin is not essential for red blood cell-dependent hypoxic vasodilation.
The coupling of hemoglobin sensing of physiological oxygen gradients to stimulation of nitric oxide (NO) bioactivity is an established principle of hypoxic blood flow. One mechanism proposed to explain this oxygen-sensing-NO bioactivity linkage postulates an essential role for the conserved Cys93 residue of the hemoglobin beta-chain (betaCys93) and, specifically, for S-nitrosation of betaCys93 to form S-nitrosohemoglobin (SNO-Hb). The SNO-Hb hypothesis, which conceptually links hemoglobin and NO biology, has been debated intensely in recent years. This debate has precluded a consensus on physiological mechanisms and on assessment of the potential role of SNO-Hb in pathology. Here we describe new mouse models that exclusively express either human wild-type hemoglobin or human hemoglobin in which the betaCys93 residue is replaced with alanine to assess the role of SNO-Hb in red blood cell-mediated hypoxic vasodilation. Substitution of this residue, precluding hemoglobin S-nitrosation, did not change total red blood cell S-nitrosothiol abundance but did shift S-nitrosothiol distribution to lower molecular weight species, consistent with the loss of SNO-Hb. Loss of betaCys93 resulted in no deficits in systemic or pulmonary hemodynamics under basal conditions and, notably, did not affect isolated red blood cell-dependent hypoxic vasodilation. These results demonstrate that SNO-Hb is not essential for the physiologic coupling of erythrocyte deoxygenation with increased NO bioactivity in vivo.
Department of Pathology and Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
T Scott
TS
Isbell
Chiao-Wang
CW
Sun
Li-Chen
LC
Wu
Xinjun
X
Teng
Dario A
DA
Vitturi
Billy G
BG
Branch
Christopher G
CG
Kevil
Ning
N
Peng
J Michael
JM
Wyss
Namasivayam
N
Ambalavanan
Lisa
L
Schwiebert
Jinxiang
J
Ren
Kevin M
KM
Pawlik
Matthew B
MB
Renfrow
Rakesh P
RP
Patel
Tim M
TM
Townes
D000818:Animals; D004912:Erythrocytes / Q000473:pathology / Q000502:physiology*; D006439:Hemodynamics; D006454:Hemoglobins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000473:pathology / Q000503:physiopathology*; D051379:Mice; D009566:Nitrates / Q000032:analysis / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D009573:Nitrites / Q000032:analysis / Q000378:metabolism; D015538:Nitrosation; D010100:Oxygen / Q000378:metabolism; D026403:S-Nitrosothiols / Q000032:analysis / Q000378:metabolism; D014664:Vasodilation / Q000502:physiology*
D006454:Hemoglobins; D009566:Nitrates; D009573:Nitrites; D026403:S-Nitrosothiols; C103574:S-nitrosohemoglobin; D009569:Nitric Oxide; D010100:Oxygen