Reactions of Deoxy-, Oxy-, and Methemoglobin with Nitrogen Monoxide

Herold, Susanna; Röck, Gabriele

doi:10.1074/jbc.m210275200

Cited by 94 publications

(62 citation statements)

References 73 publications

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“…The oxygen-linked formation of SNO-Hb appears to follow several pathways (29) and may be driven by formation of nitrosating species, such as NO x , which can be generated when NO slowly dissociates from NO-heme complexes and interacts with O 2 . At NO to Hb ratios similar to those of Fig.…”

Section: Discussionmentioning

confidence: 99%

The case of the missing NO– hemoglobin: Spectral changes suggestive of heme redox reactions reflect changes in NO– heme geometry

Fago

Crumbliss

Peterson

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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When low levels of gaseous nitric oxide (NO) are equilibrated with deoxygenated Hb, all NO added can be accounted for in terms of hexacoordinate and pentacoordinate forms of NO-Hb, despite recent reports on NO disappearance from heme groups to form nitroxyl anions or S-nitrosated Hb at low ratios of NO to Hb. We demonstrate that a fraction of the spectral signature of fully nitrosylated (largely hexacoordinate) Hb disappears as the pentacoordinate state forms and reappears when pentacoordinate NO-Hb is reconverted to the hexacoordinate condition. We show that the spectral changes associated with these reversible shifts in NO-heme geometry can be remarkably well approximated as variations in the contributions from fully nitrosylated Hb and oxidized Hb (MetHb). As a result, increases in the level of pentacoordinate NO-Hb that occur at low NO to Hb ratios can be misinterpreted as increases in MetHb levels associated with NOdependent heme oxidation. Conversely, any decrease in levels of pentacoordinate NO-Hb can be misinterpreted as a disappearance of MetHb associated with NO-dependent heme reduction. Transitions between pentacoordinate and hexacoordinate forms of NO-Hb with spectral changes suggestive of changes in levels of heme-bound NO are sensitive to the protein's quaternary conformation and can be brought about by alterations in anion levels or the degree of heme saturation with either O 2 or NO. O rganic phosphates and low pH, which stabilize the lowaffinity T-state of Hb, bring about differences in the interactions of Hb and NO that differ from those observed at high pH, where Hb's R-state conformation is favored (1-6). The literature is less clear about differences resulting from variations in levels of heme ligation with NO, a ligand with extremely high affinity for ferrous heme (7-9).A direct influence of the NO to Hb ratio on NO interactions with Hb was suggested by Gow and Stamler (10), who hypothesized that the NO-Hb level is significantly depleted at low NO to Hb ratios by redox-driven formation of MetHb and the nitroxyl ion (NO Ϫ ) in the absence of oxygen and by formation of S-nitrosated Hb (SNO-Hb) at the expense of NO-Hb in the presence of oxygen. In support of these concepts, these authors reported changes in the NO-Hb spectrum seemingly coupled with changes in MetHb and SNO-Hb levels.To explore the interactions of deoxy Hb with low to saturating levels of NO, we sought to quantitatively account for all NO introduced into large-volume tonometers containing deoxy Hb. The data obtained argue against the hypothesis of redoxmediated depletion of NO-Hb at low ratios of NO to Hb (10) and show instead that NO is bound stoichiometrically to deoxy Hb from low to high degrees of heme nitrosylation. Here we present an alternative view of the reactions of NO and deoxy Hb at varied NO to Hb ratios (supported by electronic absorption and EPR spectroscopies) that is based on iron coordination shifts between hexacoordinate and pentacoordinate forms of NO-Hb rather than on redox-or oxygen-linked alterations of N...

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Section: Discussionmentioning

confidence: 99%

The case of the missing NO– hemoglobin: Spectral changes suggestive of heme redox reactions reflect changes in NO– heme geometry

Fago

Crumbliss

Peterson

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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“…Nitrogen monoxide (Linde) was passed through a NaOH solution and a column of NaOH pellets before use to remove higher nitrogen oxides. Nitrogen monoxide solutions were prepared as described previously (33). Peroxynitrite was prepared from KO 2 and gaseous nitrogen monoxide according to Koppenol et al (34) and stored in small aliquots at Ϫ80°C.…”

Section: Methodsmentioning

confidence: 99%

Reactivity Studies of the Fe(III) and Fe(II)NO Forms of Human Neuroglobin Reveal a Potential Role against Oxidative Stress

Herold¹,

Fago

Weber

et al. 2004

Journal of Biological Chemistry

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248

304

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Neuroglobin, recently discovered in the brain and in the retina of vertebrates, belongs to the class of hexacoordinate globins, in which the distal histidine coordinates the iron center in both the Fe(II) and Fe(III) forms. As for most other hexacoordinate globins, the physiological function of neuroglobin is still unclear, but seems to be related to neuronal survival following acute hypoxia. In this study, we have addressed the question whether human neuroglobin could act as a scavenger of toxic species, such as nitrogen monoxide, peroxynitrite, and hydrogen peroxide, which are generated at high levels in the brain during hypoxia; we have also investigated the kinetics of the reactions of its Fe(III) (metNGB) and Fe(II)NO forms with several reagents. Binding of cyanide or NO ⅐ to metNGB follows bi-exponential kinetics, showing the existence of two different protein conformations. In the presence of excess NO ⅐ , metNGB is converted into NGBFe(II)NO by reductive nitrosylation, in analogy to the reactions of NO ⅐ with metmyoglobin and methemoglobin. The Fe(II)NO form of neuroglobin is oxidized to metNGB by peroxynitrite and dioxygen, two reactions that also take place in hemoglobin, albeit at lower rates. In contrast to myoglobin and hemoglobin, metNGB unexpectedly does not generate the cytotoxic ferryl form of the protein upon addition of either peroxynitrite or hydrogen peroxide. Taken together, our data indicate that human neuroglobin may be an efficient scavenger of reactive oxidizing species and thus may play a role in the cellular defense against oxidative stress.

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“…Hb also sustains S-nitrosylation at two cysteine residues conserved in all mammals and birds. Biochemical and mutational analyses (␤93Cys3Ala) indicate that S-nitrosohemoglobin (SNO-Hb) is formed upon oxygenation of Hb [FeNO] by means of heme-to-Cys NO transfer (13)(14)(15) and by transnitrosylative transfer from low-mass S-nitrosothiols (SNOs) (16,17). SNO-Hb is very stable in the oxygenated (or R) structure and thus cannot effectively dilate blood vessels (5,10,18).…”

Section: S-nitrosothiol (Sno)-deficient Rbcs Produce Impaired Vasodilmentioning

confidence: 99%

A nitric oxide processing defect of red blood cells created by hypoxia: Deficiency of S-nitrosohemoglobin in pulmonary hypertension

McMahon

Ahearn

Moya

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

118

138

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The mechanism by which hypoxia [low partial pressure of O2 (pO2)] elicits signaling to regulate pulmonary arterial pressure is incompletely understood. We considered the possibility that, in addition to its effects on smooth muscle, hypoxia may influence pulmonary vascular tone through an effect on RBCs. We report that exposure of native RBCs to sustained hypoxia is accompanied by a buildup of heme iron-nitrosyl (FeNO) species that are deficient in pO 2-governed intramolecular transfer of NO to cysteine thiol, yielding a deficiency in the vasodilator S-nitrosohemoglobin (SNO-Hb). hemoglobin ͉ red blood cell vasodilation ͉ S-nitrosylation I n the systemic microcirculation, blood flow is regulated by physiological O 2 gradients that couple the O 2 content of blood to regulated vasodilation and vasoconstriction (1-3). Blood flow is thereby matched to tissue O 2 demand. An analogous mechanism operates in the lungs, where O 2 uptake (ventilation) is optimized through regulated vasodilation and vasoconstriction (perfusion). Blood flow is thereby matched to alveolar ventilation (2). Because it is Hb O 2 saturation, not the partial pressure of O 2 (pO 2 ), that is coupled to blood flow in vivo (1, 3) it has been deduced that RBCs may serve as O 2 sensors within the integrated vascular system. In support of this idea, it has been shown recently that RBCs can act as O 2 -responsive transducers of vasodilator and vasoconstrictor activity (4-10), at least partly by modulating the availability of [6][7][8]10,11). According to these studies, RBCs release NO bioactivity under hypoxia and sequester it at hyperoxia. The release of NO bioactivity would facilitate hypoxic vasodilation in peripheral tissues and oppose hypoxic pulmonary vasoconstriction (HPV) in the lungs. S-nitrosothiol (SNO)-deficientThe mechanism by which NO bioactivity escapes from RBCs is incompletely understood. It is generally accepted that the rapid reaction of NO with the hemes of Hb produces a heme-iron nitrosyl adduct (Hb [FeNO]) that exhibits no vasodilator activity (4,7,12). Hb also sustains S-nitrosylation at two cysteine residues conserved in all mammals and birds. Biochemical and mutational analyses (␤93Cys3Ala) indicate that S-nitrosohemoglobin (SNO-Hb) is formed upon oxygenation of Hb [FeNO] by means of heme-to-Cys NO transfer (13-15) and by transnitrosylative transfer from low-mass S-nitrosothiols (SNOs) (16,17). SNO-Hb is very stable in the oxygenated (or R) structure and thus cannot effectively dilate blood vessels (5, 10, 18). However, upon deoxygenation [or with change in the spin state of the hemes (3)], the vasodilator potency of SNO-Hb is markedly potentiated (5,16,18). Crystal structures and molecular models show that the ␤-Cys NO gains solvent access in the deoxygenated (or T) state (3, 19). Solvent-exposed NO can exchange with acceptor thiols within the N-terminal cytoplasmic domain of the RBC membrane anion exchange protein (AE1; band 3) (4, 15). Transnitrosylation of AE1 by SNO-Hb involves a direct protein-protein interaction. The st...

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Reactions of Deoxy-, Oxy-, and Methemoglobin with Nitrogen Monoxide

Cited by 94 publications

References 73 publications

The case of the missing NO– hemoglobin: Spectral changes suggestive of heme redox reactions reflect changes in NO– heme geometry

The case of the missing NO– hemoglobin: Spectral changes suggestive of heme redox reactions reflect changes in NO– heme geometry

Reactivity Studies of the Fe(III) and Fe(II)NO Forms of Human Neuroglobin Reveal a Potential Role against Oxidative Stress

A nitric oxide processing defect of red blood cells created by hypoxia: Deficiency of S-nitrosohemoglobin in pulmonary hypertension

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