Studies on nitrosyl hemes in Ni(II)–Fe(II) hybrid hemoglobins

Venkateshrao, Swarnalatha; Venkatesh, Balan; Manoharan, P. T.

doi:10.1016/j.niox.2005.07.001

Cited by 2 publications

(2 citation statements)

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“…(2) The spectrum of fully nitrosylated R-state Hb(II)NO that has NO bound to both α and β heme chains. (3,4) T-state α heme-NO (T-state Hb(II)αNO) and T-state β heme-NO (T-state Hb(II)βNO) spectra obtained from Ni-hybrids with added IHP to stabilize the T-state . (5) The spectrum of a thiyl radical species was obtained by subtracting the EPR spectra of nitrite reacted CPA/NEM treated deoxyHb where no radical intermediate can form from nitrite reacted CPA deoxyHb where the intermediates are stabilized.…”

Section: Methodsmentioning

confidence: 99%

“…(1) The EPR spectrum of R-state β chain heme-NO (R-state Hb(II)βNO) was obtained using semihemoglobin, which is a dimer with one R globin and a β heme 35 where NO is bound to the β heme. ( 2 36 (5) The spectrum of a thiyl radical species was obtained by subtracting the EPR spectra of nitrite reacted CPA/NEM treated deoxyHb where no radical intermediate can form from nitrite reacted CPA deoxyHb where the intermediates are stabilized.…”

Section: Nitrite Preparationmentioning

confidence: 99%

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A New Paramagnetic Intermediate Formed during the Reaction of Nitrite with Deoxyhemoglobin

et al. 2011

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The reduction of nitrite by deoxygenated hemoglobin chains has been implicated in red cell induced vasodilation, although the mechanism for this process has not been established. We have previously demonstrated that the reaction of nitrite with deoxyhemoglobin produces a hybrid intermediate with properties of Hb(II)NO+ and Hb(III)NO that builds up during the reaction retaining potential NO bioactivity. To explain the unexpected stability of this intermediate, which prevents NO release from the Hb(III)NO component, we had implicated the transfer of an electron from the β-93 thiol to NO+ producing •SHb(II)NO. In order to determine if this species is formed and to characterize its properties, we have investigated the electron paramagnetic resonance (EPR) changes taking place during the nitrite reaction. The EPR effects of blocking the thiol group with N-ethyl-maleimide and using carboxypeptidase-A to stabilize the R-quaternary conformation have demonstrated that •SHb(II)NO is formed and that it has the EPR spectrum expected for NO bound to the heme in the β-chain plus that of a thiyl radical. This new NO-related paramagnetic species is in equilibrium with the hybrid intermediate “Hb(II)NO+ ↔ Hb(III)NO” thereby further inhibiting the release of NO from Hb(III)NO. The formation of an NO-related paramagnetic species other than the tightly bound NO in Hb(II)NO was also confirmed by a decrease in the EPR signal by −20°C incubation, which shifts the equilibrium back to the “Hb(II)NO+ ↔ Hb(III)NO” intermediate. This previously unrecognized NO hemoglobin species explains the stability of the intermediates and the buildup of a pool of potentially bioactive NO during nitrite reduction. It also provides a pathway for the formation of β-93 cysteine S-nitrosylated hemoglobin [SNOHb:S-nitrosohemoglobin], which has been shown to induce vasodilation, by a rapid radical-radical reaction of any free NO with the thiyl radical of this new paramagnetic intermediate.

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Section: Methodsmentioning

confidence: 99%

Section: Nitrite Preparationmentioning

confidence: 99%

A New Paramagnetic Intermediate Formed during the Reaction of Nitrite with Deoxyhemoglobin

et al. 2011

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How to Evaluate Blood Substitutes for Endothelial Cell Toxicity

Gaucher

2008

Antioxidants & Redox Signaling

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The most common and widely transplanted tissue worldwide is blood. But concerns about safety and adequacy of blood transfusion have fostered 20 years of research into blood substitutes such as oxygen carriers based on modified hemoglobin (Hb). Chemically modified or genetically engineered Hb developed as oxygen therapeutics are designed to restore blood volume and to correct oxygen deficit due to ischemia in a variety of clinical settings. Uncontrolled oxidative reactions mediated by large amounts of cell-free Hb and their reactions with various oxidant/antioxidant and cell signalling systems emerge as an important pathway of toxicity. Hemoglobin can react with oxygen and NO, leading to the production of reactive oxygen or nitrogen species. Inside the bloodstream, oxidized Hb and ROS/RNS are in direct contact with endothelial cells (EC). Thus, chain reactions may trigger molecular and cellular biology, causing oxidative stress-related pathologies. This editorial presents an overview of interactions between Hb (modified or not) and EC. We also propose a wide range of techniques and methods to assess oxidative stress and inflammation responses of EC after exposure to Hb. This editorial can serve as a guide to evaluate in vitro toxicity of new Hb molecules.

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Studies on nitrosyl hemes in Ni(II)–Fe(II) hybrid hemoglobins

Cited by 2 publications

References 30 publications

A New Paramagnetic Intermediate Formed during the Reaction of Nitrite with Deoxyhemoglobin

A New Paramagnetic Intermediate Formed during the Reaction of Nitrite with Deoxyhemoglobin

How to Evaluate Blood Substitutes for Endothelial Cell Toxicity

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