title: Angeli's salt counteracts the vasoactive effects of elevated plasma hemoglobin.
abstract: Plasma hemoglobin (Hb) released during intravascular hemolysis has been associated with numerous deleterious effects that may stem from increased nitric oxide (NO) scavenging, but has also been associated with reactive oxygen species generation and platelet activation. Therapies that convert plasma oxyHb to metHb, or metHb to iron-nitrosyl Hb, could be beneficial because these species do not scavenge NO. In this study, we investigated the effects of Angeli's salt (AS; sodium α-oxyhyponitrite, Na2N2O3), a nitroxyl (HNO) and nitrite (NO2(-)) donor, on plasma Hb oxidation and formation of iron-nitrosyl Hb from metHb and on the vasoactivity of plasma Hb. We hypothesized that AS could ameliorate hemolysis-associated pathology via its preferential reactivity with plasma Hb, as opposed to red-cell-encapsulated Hb, and through its intrinsic vasodilatory activity. To test this hypothesis, we infused (n=3 per group) (1) cell-free Hb and AS, (2) cell-free Hb+0.9% NaCl, (3) AS+3% albumin, and (4) 3% albumin+0.9% NaCl (colloid controls for Hb and AS, respectively) in a canine model. Co-infusion of AS and cell-free Hb led to preferential conversion of plasma Hb to metHb, but the extent of conversion was lower than anticipated based on the in vivo concentration of AS relative to plasma Hb. This lower metHb yield was probably due to reactions of nitroxyl-derived AS with plasma components such as thiol-containing compounds. From a physiological and therapeutic standpoint, the infusion of Hb alone led to significant increases in mean arterial pressure (p=0.03) and systemic vascular resistance index (p=0.01) compared to controls. Infusion of AS alone led to significant decreases in these parameters and co-infusion of AS along with Hb had an additive effect in reversing the effects of Hb alone on the systemic circulation. Interestingly, in the pulmonary system, the decrease in pressure when AS was added to Hb was significantly less than would have been expected compared to the effects of Hb and AS alone, suggesting that inactivation of scavenging with AS reduced the direct vasodilatory effects of AS on the vasculature. We also found that AS reduced platelet activation when administered to whole blood in vitro. These data suggest that AS-like compounds could serve as therapeutic agents to counteract the negative vasoconstrictive consequences of hemolysis that occur in hemolytic anemias, transfusion of stored blood, and other diseases. Increases in metHb in the red blood cell, the potential of AS for neurotoxicity, and hypotension would need to be carefully monitored in a clinical trial.
authors.affiliation: Critical Care Medicine Department, National Institutes of Health, Bethesda, MD 20892, USA. Electronic address: ssolomon@cc.nih.gov.
authors.forename: Steven B
authors.initials: SB
authors.lastname: Solomon
authors.affiliation: Department of Physics.
authors.forename: Landon
authors.initials: L
authors.lastname: Bellavia
authors.affiliation: Critical Care Medicine Department, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Sweeney
authors.affiliation: Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Barbora
authors.initials: B
authors.lastname: Piknova
authors.affiliation: Department of Physics.
authors.forename: Andreas
authors.initials: A
authors.lastname: Perlegas
authors.affiliation: Department of Physics; Translational Science Center, Wake Forest University, Winston-Salem, NC 27109, USA.
authors.forename: Christine C
authors.initials: CC
authors.lastname: Helms
authors.affiliation: Critical Care Medicine Department, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Gabriela A
authors.initials: GA
authors.lastname: Ferreyra
authors.affiliation: Department of Chemistry.
authors.forename: S
authors.initials: S
authors.lastname: Bruce King
authors.affiliation: Vascular Medicine Institute; Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
authors.forename: Nicolaas J H
authors.initials: NJ
authors.lastname: Raat
authors.affiliation: Critical Care Medicine Department, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Kern
authors.affiliation: Critical Care Medicine Department, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Junfeng
authors.initials: J
authors.lastname: Sun
authors.affiliation: Department of Biochemistry, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
authors.forename: Linda C
authors.initials: LC
authors.lastname: McPhail
authors.affiliation: Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Alan N
authors.initials: AN
authors.lastname: Schechter
authors.affiliation: Critical Care Medicine Department, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Natanson
authors.affiliation: Vascular Medicine Institute; Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
authors.forename: Mark T
authors.initials: MT
authors.lastname: Gladwin
authors.affiliation: Department of Physics; Translational Science Center, Wake Forest University, Winston-Salem, NC 27109, USA. Electronic address: shapiro@wfu.edu.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Kim-Shapiro
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D004912:Erythrocytes / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D007962:Leukocytes / Q000187:drug effects; D008706:Methemoglobin / Q000378:metabolism*; D009573:Nitrites / Q000494:pharmacology*; D010084:Oxidation-Reduction; D011651:Pulmonary Artery / Q000187:drug effects / Q000503:physiopathology; D014661:Vasoconstriction; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D009573:Nitrites; D014665:Vasodilator Agents; C021229:oxyhyponitrite; D008706:Methemoglobin
keywords: Angeli's salt; Cell-free hemoglobin; Free radicals; Methemoglobin; Nitroxyl