Effects of iron nitrosylation on sickle cell hemoglobin solubility.
One mechanism by which nitric oxide (NO) has been proposed to benefit patients with sickle cell disease is by reducing intracellular polymerization of sickle hemoglobin (HbS). In this study we have examined the ability of nitric oxide to inhibit polymerization by measuring the solubilizing effect of iron nitrosyl sickle hemoglobin (HbS-NO). Electron paramagnetic resonance spectroscopy was used to confirm that, as found in vivo, the primary type of NO ligation produced in our partially saturated NO samples is pentacoordinate alpha-nitrosyl. Linear dichroism spectroscopy and delay time measurements were used to confirm polymerization. Based on sedimentation studies we found that, although fully ligated (100% tetranitrosyl) HbS is very soluble, the physiologically relevant, partially ligated species do not provide a significant solubilizing effect. The average solubilizing effect of 26% NO saturation was 0.045; much less than the 0.15 calculated for the effect of 26% oxygen saturation. Given the small amounts of NO-ligated hemoglobin achievable through any kind of NO therapy, we conclude that NO therapy does not benefit patients through any direct solubilizing effect.
Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109, USA.
Xiuli
X
Xu
Virginia L
VL
Lockamy
Kejing
K
Chen
Zhi
Z
Huang
Howard
H
Shields
S Bruce
SB
King
Samir K
SK
Ballas
James S
JS
Nichols
Mark T
MT
Gladwin
Constance T
CT
Noguchi
Alan N
AN
Schechter
Daniel B
DB
Kim-Shapiro
D004578:Electron Spin Resonance Spectroscopy; D006451:Hemoglobin, Sickle / Q000378:metabolism*; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism*; D009569:Nitric Oxide / Q000737:chemistry* / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D013053:Spectrophotometry; D013057:Spectrum Analysis; D013997:Time Factors; D014466:Ultraviolet Rays
D006451:Hemoglobin, Sickle; D006454:Hemoglobins; D009569:Nitric Oxide; D007501:Iron; D009584:Nitrogen