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Investigations on the role of hemoglobin in sulfide metabolism by intact human red blood cells

Investigations on the role of hemoglobin in sulfide metabolism by intact human red blood cells
Investigations on the role of hemoglobin in sulfide metabolism by intact human red blood cells

In addition to their role as oxygen transporters, red blood cells (RBCs) contribute to cardiovascular homeostasis by regulating nitric oxide (NO) metabolism via interaction of hemoglobin (Hb) with nitrite and NO itself. RBCs were proposed to also participate in sulfide metabolism. Although Hb is known to react with sulfide, sulfide metabolism by intact RBCs has not been characterized so far. Therefore we explored the role of Hb in sulfide metabolism in intact human RBCs. We find that upon exposure of washed RBCs to sulfide, no changes in oxy/deoxyhemoglobin (oxy/deoxyHb) are observed by UV-vis and EPR spectroscopy. However, sulfide reacts with methemoglobin (metHb), forming a methemoglobin-sulfide (metHb-SH) complex. Moreover, while metHb-SH is stable in cell-free systems even in the presence of biologically relevant thiols, it gradually decomposes to produce oxyHb, inorganic polysulfides and thiosulfate in intact cells, as detected by EPR and mass spectrometry. Taken together, our results demonstrate that under physiological conditions RBCs are able to metabolize sulfide via intermediate formation of a metHb-SH complex, which subsequently decomposes to oxyHb. We speculate that decomposition of metHb-SH is preceded by an inner-sphere electron transfer, forming reduced Hb (which binds oxygen to form oxyHb) and thiyl radical (a process we here define as "reductive sulfhydration"), which upon release, gives rise to the oxidized products, thiosulfate and polysulfides. Thus, not only is metHb an efficient scavenger and regulator of sulfide in blood, intracellular sulfide itself may play a role in keeping Hb in the reduced oxygen-binding form and, therefore, be involved in RBC physiology and function.

Journal Article
0006-2952
163-173
Bianco, Christopher L.
cabb8305-5084-4f2e-a877-00ce4314ac07
Savitsky, Anton
8ffccd3e-e2a6-4f00-bef6-4860180565fe
Feelisch, Martin
8c1b9965-8614-4e85-b2c6-458a2e17eafd
Cortese-Krott, Miriam M.
7dc9b44c-847c-4196-8866-a3cc0c1dc357
Bianco, Christopher L.
cabb8305-5084-4f2e-a877-00ce4314ac07
Savitsky, Anton
8ffccd3e-e2a6-4f00-bef6-4860180565fe
Feelisch, Martin
8c1b9965-8614-4e85-b2c6-458a2e17eafd
Cortese-Krott, Miriam M.
7dc9b44c-847c-4196-8866-a3cc0c1dc357

Bianco, Christopher L., Savitsky, Anton, Feelisch, Martin and Cortese-Krott, Miriam M. (2018) Investigations on the role of hemoglobin in sulfide metabolism by intact human red blood cells. Biochemical Pharmacology, 149, 163-173. (doi:10.1016/j.bcp.2018.01.045).

Record type: Article

Abstract

In addition to their role as oxygen transporters, red blood cells (RBCs) contribute to cardiovascular homeostasis by regulating nitric oxide (NO) metabolism via interaction of hemoglobin (Hb) with nitrite and NO itself. RBCs were proposed to also participate in sulfide metabolism. Although Hb is known to react with sulfide, sulfide metabolism by intact RBCs has not been characterized so far. Therefore we explored the role of Hb in sulfide metabolism in intact human RBCs. We find that upon exposure of washed RBCs to sulfide, no changes in oxy/deoxyhemoglobin (oxy/deoxyHb) are observed by UV-vis and EPR spectroscopy. However, sulfide reacts with methemoglobin (metHb), forming a methemoglobin-sulfide (metHb-SH) complex. Moreover, while metHb-SH is stable in cell-free systems even in the presence of biologically relevant thiols, it gradually decomposes to produce oxyHb, inorganic polysulfides and thiosulfate in intact cells, as detected by EPR and mass spectrometry. Taken together, our results demonstrate that under physiological conditions RBCs are able to metabolize sulfide via intermediate formation of a metHb-SH complex, which subsequently decomposes to oxyHb. We speculate that decomposition of metHb-SH is preceded by an inner-sphere electron transfer, forming reduced Hb (which binds oxygen to form oxyHb) and thiyl radical (a process we here define as "reductive sulfhydration"), which upon release, gives rise to the oxidized products, thiosulfate and polysulfides. Thus, not only is metHb an efficient scavenger and regulator of sulfide in blood, intracellular sulfide itself may play a role in keeping Hb in the reduced oxygen-binding form and, therefore, be involved in RBC physiology and function.

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More information

Accepted/In Press date: 26 January 2018
e-pub ahead of print date: 31 January 2018
Published date: March 2018
Additional Information: Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.
Keywords: Journal Article

Identifiers

Local EPrints ID: 418769
URI: http://eprints.soton.ac.uk/id/eprint/418769
ISSN: 0006-2952
PURE UUID: 65edc395-b9aa-4a81-9944-7912cbb385fe
ORCID for Martin Feelisch: ORCID iD orcid.org/0000-0003-2320-1158

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Date deposited: 21 Mar 2018 17:30
Last modified: 17 Dec 2019 01:39

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