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Munoz CJ, Lucas D, Muller CR, Martinez J, O'Boyle Q, Pires IS, Palmer AF, Cabrales P. Coadministration of PEGylated apohemoglobin and haptoglobin can limit vascular dysfunction in the microcirculation and prevent acute inflammation. J Appl Physiol (1985) 2024; 137:934-944. [PMID: 39143905 DOI: 10.1152/japplphysiol.00315.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Revised: 07/23/2024] [Accepted: 08/02/2024] [Indexed: 08/16/2024] Open
Abstract
Unfortunately, during pathological conditions resulting in chronic hemolysis cell-free hemoglobin (Hb) is released into the circulation that releases free heme, resulting in several complications. One approach to prevent these toxicities is the administration of supplemental scavenger proteins, haptoglobin (Hp) and hemopexin (Hpx). The goal of this body of work is to objectively measure the levels of vascular reactivity and inflammatory profiles after an infusion of acellular hemoglobin in animals that were given a coadministration of PEGylated human apohemoglobin (PEG-apoHb), a hemopexin (Hpx)-mimetic that can scavenge free heme from hemoglobin, together with human plasma-derived Hp that can scavenge dimerized Hb. Using intravital microscopy, Golden Syrian hamsters instrumented with a dorsal window chamber were used to evaluate the in vivo effects of four experimental groups that were then challenged with a hypovolemic injection (10% of the animal's blood volume) of human Hb (hHb, 5 g/dL). The four experimental groups consisted of: 1) lactated Ringer's solution (control), 2) PEG-apoHb only, 3) Hp only, and 4) PEG-apoHb + Hp. The microvascular hemodynamics (diameter and flow) in arterioles and venules were recorded at baseline, 20 min after treatment, and 20 min after hHb challenge. Systemic parameters (blood pressure and heart rate), blood gases (pH, Pco2, and Po2), blood parameters (Hb concentration and hematocrit), and multiorgan functionality/inflammation were also measured. Our results suggest that coadministration of PEG-apoHb + Hp as a booster before the infusion of acellular hemoglobin significantly prevented vasoconstriction in the microcirculation, significantly increased the number of functional capillaries, and significantly reduced inflammation.NEW & NOTEWORTHY Coadministration of PEGylated human apohemoglobin (PEG-apoHb)-a hemopexin (Hpx) mimetic that can scavenge free heme-and human plasma-derived haptoglobin (Hp) that can scavenge hemoglobin (Hb), reduces microcirculatory dysfunction and cardiac and kidney inflammation in a Hb-challenge model.
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Affiliation(s)
- Carlos J Munoz
- Department of Bioengineering, University of California, San Diego, California, United States
| | - Daniela Lucas
- Department of Bioengineering, University of California, San Diego, California, United States
| | - Cynthia R Muller
- Department of Bioengineering, University of California, San Diego, California, United States
| | - Jacinda Martinez
- Department of Bioengineering, University of California, San Diego, California, United States
| | - Quintin O'Boyle
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, Ohio, United States
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio, United States
| | - Ivan S Pires
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, Ohio, United States
| | - Andre F Palmer
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, Ohio, United States
| | - Pedro Cabrales
- Department of Bioengineering, University of California, San Diego, California, United States
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Munoz CJ, Lucas D, Martinez J, Ricario M, O'Boyle QT, Pires IS, Palmer AF, Cabrales P. Toxic side-effects of diaspirin cross-linked human hemoglobin are attenuated by the apohemoglobin-haptoglobin complex. Biomed Pharmacother 2024; 174:116569. [PMID: 38603886 DOI: 10.1016/j.biopha.2024.116569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 04/01/2024] [Accepted: 04/04/2024] [Indexed: 04/13/2024] Open
Abstract
Alpha-alpha diaspirin-crosslinked human hemoglobin (DCLHb or ααHb) was a promising early generation red blood cell (RBC) substitute. The DCLHb was developed through a collaborative effort between the United States Army and Baxter Healthcare. The core design feature underlying its development was chemical stabilization of the tetrameric structure of hemoglobin (Hb) to prevent Hb intravascular dimerization and extravasation. DCLHb was developed to resuscitate warfighters on the battlefield, who suffered from life-threatening blood loss. However, extensive research revealed toxic side effects associated with the use of DCLHb that contributed to high mortality rates in clinical trials. This study explores whether scavenging Hb and heme via the apohemoglobin-haptoglobin (apoHb-Hp) complex can reduce DCLHb associated toxicity. Awake Golden Syrian hamsters were equipped with a window chamber model to characterize the microcirculation. Each group was first infused with either Lactated Ringer's or apoHb-Hp followed by a hypovolemic infusion of 10% of the animal's blood volume of DCLHb. Our results indicated that animals pretreated with apoHb-Hb exhibited improved microhemodynamics vs the group pretreated with Lactated Ringer's. While systemic acute inflammation was observed regardless of the treatment group, apoHb-Hp pretreatment lessened those effects with a marked reduction in IL-6 levels in the heart and kidneys compared to the control group. Taken together, this study demonstrated that utilizing a Hb and heme scavenger protein complex significantly reduces the microvasculature effects of ααHb, paving the way for improved HBOC formulations. Future apoHb-Hp dose optimization studies may identify a dose that can completely neutralize DCLHb toxicity.
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Affiliation(s)
- Carlos J Munoz
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States
| | - Daniela Lucas
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States
| | - Jacinda Martinez
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States
| | - Mia Ricario
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States
| | - Quintin T O'Boyle
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, United States
| | - Ivan S Pires
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, United States
| | - Andre F Palmer
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, United States
| | - Pedro Cabrales
- Department of Bioengineering, University of California San Diego, La Jolla, CA, United States.
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Lodhi S, Stone JP, Entwistle TR, Fildes JE. The Use of Hemoglobin-Based Oxygen Carriers in Ex Vivo Machine Perfusion of Donor Organs for Transplantation. ASAIO J 2022; 68:461-470. [PMID: 35220355 DOI: 10.1097/mat.0000000000001597] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
There has been significant progress in the development of ex vivo machine perfusion for the nonischemic preservation of donor organs. However, several complications remain, including the logistics of using human blood for graft oxygenation and hemolysis occurring as a result of mechanical technology. Recently, hemoglobin-based oxygen carriers, originally developed for use as blood substitutes, have been studied as an alternative to red blood cell-based perfusates. Although research in this field is somewhat limited, the findings are promising. We offer a brief review of the use of hemoglobin-based oxygen carriers in ex vivo machine perfusion and discuss future directions that will likely have a major impact in progressing oxygen carrier use in clinical practice.
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Affiliation(s)
- Sirat Lodhi
- From the The Ex-Vivo Research Centre, 3F66, Block 3, Alderley Park, Nether Alderley, Cheshire, United Kingdom
- The Ex-Vivo Lab, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
| | - John P Stone
- From the The Ex-Vivo Research Centre, 3F66, Block 3, Alderley Park, Nether Alderley, Cheshire, United Kingdom
- The Ex-Vivo Lab, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
- The Transplant Centre, Manchester Foundation Trust, Manchester, United Kingdom
- Lydia Becker Institute of Immunology and Inflammation, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - Timothy R Entwistle
- From the The Ex-Vivo Research Centre, 3F66, Block 3, Alderley Park, Nether Alderley, Cheshire, United Kingdom
- The Ex-Vivo Lab, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
- The Transplant Centre, Manchester Foundation Trust, Manchester, United Kingdom
- Lydia Becker Institute of Immunology and Inflammation, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
| | - James E Fildes
- From the The Ex-Vivo Research Centre, 3F66, Block 3, Alderley Park, Nether Alderley, Cheshire, United Kingdom
- The Ex-Vivo Lab, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
- The Transplant Centre, Manchester Foundation Trust, Manchester, United Kingdom
- Lydia Becker Institute of Immunology and Inflammation, School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom
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4
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Meegan JE, Bastarache JA, Ware LB. Toxic effects of cell-free hemoglobin on the microvascular endothelium: implications for pulmonary and nonpulmonary organ dysfunction. Am J Physiol Lung Cell Mol Physiol 2021; 321:L429-L439. [PMID: 34009034 DOI: 10.1152/ajplung.00018.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Levels of circulating cell-free hemoglobin are elevated during hemolytic and inflammatory diseases and contribute to organ dysfunction and severity of illness. Though several studies have investigated the contribution of hemoglobin to tissue injury, the precise signaling mechanisms of hemoglobin-mediated endothelial dysfunction in the lung and other organs are not yet completely understood. The purpose of this review is to highlight the knowledge gained thus far and the need for further investigation regarding hemoglobin-mediated endothelial inflammation and injury to develop novel therapeutic strategies targeting the damaging effects of cell-free hemoglobin.
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Affiliation(s)
- Jamie E Meegan
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Julie A Bastarache
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee.,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee.,Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Lorraine B Ware
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee.,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
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Tomasek T, Ware LB, Bastarache JA, Meegan JE. Cell-free hemoglobin-mediated human lung microvascular endothelial barrier dysfunction is not mediated by cell death. Biochem Biophys Res Commun 2021; 556:199-206. [PMID: 33848934 DOI: 10.1016/j.bbrc.2021.03.161] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 03/26/2021] [Accepted: 03/29/2021] [Indexed: 01/14/2023]
Abstract
Circulating cell-free hemoglobin (CFH) contributes to endothelial injury in several inflammatory and hemolytic conditions. We and others have shown that CFH causes increased endothelial permeability, but the precise mechanisms of CFH-mediated endothelial barrier dysfunction are not fully understood. Based on our previous study in a mouse model of sepsis demonstrating that CFH increased apoptosis in the lung, we hypothesized that CFH causes endothelial barrier dysfunction through this cell death mechanism. We first confirmed that CFH causes human lung microvascular barrier dysfunction in vitro that can be prevented by the hemoglobin scavenger, haptoglobin. While CFH caused a small but significant decrease in cell viability measured by the membrane impermeable DNA dye Draq7 in human lung microvascular endothelial cells, CFH did not increase apoptosis as measured by TUNEL staining or Western blot for cleaved caspase-3. Moreover, inhibitors of apoptosis (Z-VAD-FMK), necrosis (IM-54), necroptosis (necrostatin-1), ferroptosis (ferrostatin-1), or autophagy (3-methyladenine) did not prevent CFH-mediated endothelial barrier dysfunction. We conclude that although CFH may cause a modest decrease in cell viability over time, cell death does not contribute to CFH-mediated lung microvascular endothelial barrier dysfunction.
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Affiliation(s)
- Toria Tomasek
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
| | - Lorraine B Ware
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Julie A Bastarache
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jamie E Meegan
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
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Kuck JL, Bastarache JA, Shaver CM, Fessel JP, Dikalov SI, May JM, Ware LB. Ascorbic acid attenuates endothelial permeability triggered by cell-free hemoglobin. Biochem Biophys Res Commun 2018; 495:433-437. [PMID: 29129689 PMCID: PMC5736437 DOI: 10.1016/j.bbrc.2017.11.058] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 11/08/2017] [Indexed: 01/09/2023]
Abstract
BACKGROUND Increased endothelial permeability is central to shock and organ dysfunction in sepsis but therapeutics targeted to known mediators of increased endothelial permeability have been unsuccessful in patient studies. We previously reported that cell-free hemoglobin (CFH) is elevated in the majority of patients with sepsis and is associated with organ dysfunction, poor clinical outcomes and elevated markers of oxidant injury. Others have shown that Vitamin C (ascorbate) may have endothelial protective effects in sepsis. In this study, we tested the hypothesis that high levels of CFH, as seen in the circulation of patients with sepsis, disrupt endothelial barrier integrity. METHODS Human umbilical vein endothelial cells (HUVEC) were grown to confluence and treated with CFH with or without ascorbate. Monolayer permeability was measured by Electric Cell-substrate Impedance Sensing (ECIS) or transfer of 14C-inulin. Viability was measured by trypan blue exclusion. Intracellular ascorbate was measured by HPLC. RESULTS CFH increased permeability in a dose- and time-dependent manner with 1 mg/ml of CFH increasing inulin transfer by 50% without affecting cell viability. CFH (1 mg/ml) also caused a dramatic reduction in intracellular ascorbate in the same time frame (1.4 mM without CFH, 0.23 mM 18 h after 1 mg/ml CFH, p < 0.05). Pre-treatment of HUVECs with ascorbate attenuated CFH induced permeability. CONCLUSIONS CFH increases endothelial permeability in part through depletion of intracellular ascorbate. Supplementation of ascorbate can attenuate increases in permeability mediated by CFH suggesting a possible therapeutic approach in sepsis.
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Affiliation(s)
- Jamie L. Kuck
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | - Julie A. Bastarache
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN
| | - Ciara M. Shaver
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | - Joshua P. Fessel
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN,Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN
| | - Sergey I. Dikalov
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN
| | - James M. May
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | - Lorraine B. Ware
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN,Corresponding author: Lorraine B. Ware, MD, Professor of Medicine and Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, 1161 21st Avenue South, T1218 MCN, Nashville, TN 37232,
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White CW, Hasanally D, Mundt P, Li Y, Xiang B, Klein J, Müller A, Ambrose E, Ravandi A, Arora RC, Lee TW, Hryshko LV, Large S, Tian G, Freed DH. A whole blood–based perfusate provides superior preservation of myocardial function during ex vivo heart perfusion. J Heart Lung Transplant 2015; 34:113-121. [DOI: 10.1016/j.healun.2014.09.021] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 09/04/2014] [Accepted: 09/19/2014] [Indexed: 11/29/2022] Open
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8
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Li T, Zhou R, Yao Y, Yang Q, Zhou C, Wu W, Li Q, You Z, Zhao X, Yang L, Li C, Zhu D, Qiu Y, Luo M, Tan Z, Li H, Chen Y, Gong G, Feng Y, Dian K, Liu J. Angiotensin-converting enzyme inhibitor captopril reverses the adverse cardiovascular effects of polymerized hemoglobin. Antioxid Redox Signal 2014; 21:2095-108. [PMID: 24483164 PMCID: PMC4215427 DOI: 10.1089/ars.2013.5606] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
AIM Cell-free hemoglobin-based oxygen carriers (HBOCs) may increase the risk of myocardial infarction and death. We studied the effect of an angiotensin-converting enzyme (ACE) inhibitor on HBOC-induced adverse cardiovascular outcomes and elucidated the underlying mechanisms. RESULTS With a dog cardiopulmonary bypass model, we demonstrated that a high-dose HBOC (3%, w/v) did not reduce-but aggravated-cardiac ischemia/reperfusion injury. Animals administered a high-dose HBOC experienced coronary artery constriction and depression of cardiac function. Exposure of isolated coronary arteries or human umbilical vein endothelial cells to high-dose HBOC caused impaired endothelium-dependent relaxation, increased endothelial cell necrosis/apoptosis, and elevated NAD(P)H oxidase expression (gp91(phox), p47(phox), p67(phox), and Nox1) and reactive oxygen species (ROS) production. All observed adverse outcomes could be suppressed by the ACE inhibitor captopril (100 μM). Co-incubation with free radical scavenger tempol or NAD(P)H oxidase inhibitor apocynin had no effect on captopril action, suggesting that the positive effects of captopril are ROS- and NAD(P)H oxidase dependent. ACE inhibition by captopril also contributed to these effects. In addition, bioavailable nitrite oxide (NO) reduced by high-dose HBOC was preserved by captopril. Furthermore, HBOC, at concentrations greater than 0.5%, inhibited large conductance Ca(2+)-activated K(+) channel currents in vascular smooth muscle cells in a dose-dependent manner, although captopril failed to improve current activity, providing additional evidence that captopril's effects are mediated by the endothelium, but not by the smooth muscle. INNOVATION AND CONCLUSION Captopril alleviates high-dose HBOC-induced endothelial dysfunction and myocardial toxicity, which is mediated by synergistic depression of NAD(P)H oxidase subunit overproduction and increases in vascular NO bioavailability.
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Affiliation(s)
- Tao Li
- 1 Laboratory of Anesthesiology and Translational Neuroscience Center, West China Hospital, Sichuan University , Chengdu, China
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Adverse effects of hemorrhagic shock resuscitation with stored blood are ameliorated by inhaled nitric oxide in lambs*. Crit Care Med 2013; 41:2492-501. [PMID: 23887236 DOI: 10.1097/ccm.0b013e31828cf456] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
OBJECTIVES Transfusion of stored RBCs is associated with increased morbidity and mortality in trauma patients. Plasma hemoglobin scavenges nitric oxide, which can cause vasoconstriction, induce inflammation, and activate platelets. We hypothesized that transfusion of RBCs stored for prolonged periods would induce adverse effects (pulmonary vasoconstriction, tissue injury, inflammation, and platelet activation) in lambs subjected to severe hemorrhagic shock and that concurrent inhalation of nitric oxide would prevent these adverse effects. DESIGN Animal study. SETTING Research laboratory at the Massachusetts General Hospital, Boston, MA. SUBJECTS Seventeen awake Polypay-breed lambs. INTERVENTIONS Lambs were subjected to 2 hours of hemorrhagic shock by acutely withdrawing 50% of their blood volume. Lambs were resuscitated with autologous RBCs stored for 2 hours or less (fresh) or 39 ± 2 (mean ± SD) days (stored). Stored RBCs were administered with or without breathing nitric oxide (80 ppm) during resuscitation and for 21 hours thereafter. MEASUREMENTS AND MAIN RESULTS We measured hemodynamic and oxygenation variables, markers of tissue injury and inflammation, plasma hemoglobin concentrations, and platelet activation. Peak pulmonary arterial pressure was higher after resuscitation with stored than with fresh RBCs (24 ± 4 vs 14 ± 2 mm Hg, p < 0.001) and correlated with peak plasma hemoglobin concentrations (R = 0.56, p = 0.003). At 21 hours after resuscitation, pulmonary myeloperoxidase activity was higher in lambs resuscitated with stored than with fresh RBCs (11 ± 2 vs 4 ± 1 U/g, p = 0.007). Furthermore, transfusion of stored RBCs increased plasma markers of tissue injury and sensitized platelets to adenosine diphosphate activation. Breathing nitric oxide prevented the pulmonary hypertension and attenuated the pulmonary myeloperoxidase activity, as well as tissue injury and sensitization of platelets to adenosine diphosphate. CONCLUSIONS Our data suggest that resuscitation of lambs from hemorrhagic shock with autologous stored RBCs induces pulmonary hypertension and inflammation, which can be ameliorated by breathing nitric oxide.
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Hai CM. Systems biology of HBOC-induced vasoconstriction. Curr Drug Discov Technol 2012; 9:204-11. [PMID: 21726185 DOI: 10.2174/157016312802650751] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 01/25/2011] [Accepted: 07/01/2011] [Indexed: 01/24/2023]
Abstract
Vasoconstriction is a major adverse effect of HBOCs. The use of a single drug for attenuating HBOC-induced vasoconstriction has been tried with limited success. Since HBOC causes disruptions at multiple levels of organization in the vascular system, a systems approach is helpful to explore avenues to counteract the effects of HBOC at multiple levels by targeting multiple sites in the system. A multi-target approach is especially appropriate for HBOC-induced vasoconstriction, because HBOC disrupts the cascade of amplification by NO-cGMP signaling and protein phosphorylation, ultimately resulting in vasoconstriction. Targeting multiple steps in the cascade may alter the overall gain of amplification, thereby limiting the propagation of disruptive effects through the cascade. As a result, targeting multiple sites may accomplish a relatively high overall efficacy at submaximal drug doses. Identifying targets and doses for developing a multi-target combination HBOC regimen for oxygen therapeutics requires a detailed understanding of the systems biology and phenotypic heterogeneity of the vascular system at multiple layers of organization, which can be accomplished by successive iterations between experimental studies and mathematical modeling at multiple levels of vascular systems and organ systems. Towards this goal, this article addresses the following topics: a) NO-scavenging by HBOC, b) HBOC autoxidation-induced reactive oxygen species generation and endothelial barrier dysfunction, c) NO- cGMP signaling in vascular smooth muscle cells, d) NO and cGMP-dependent regulation of contractile filaments in vascular smooth muscle cells, e) phenotypic heterogeneity of vascular systems, f) systems biology as an approach to developing a multi-target HBOC regimen.
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Affiliation(s)
- Chi-Ming Hai
- Department of Molecular Pharmacology, Physiology & Biotechnology, Brown University, Providence, RI 02912, USA.
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Cabrales P, Rameez S, Palmer AF. Hemoglobin encapsulated poly(ethylene glycol) surface conjugated vesicles attenuate vasoactivity of cell-free hemoglobin. Curr Drug Discov Technol 2012; 9:224-34. [PMID: 22564169 DOI: 10.2174/157016312802650760] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 04/11/2012] [Accepted: 05/01/2012] [Indexed: 12/14/2022]
Abstract
UNLABELLED Widespread clinical use of acellular hemoglobin (Hb)-based O2 carriers (HBOCs) has been hampered by their ability to elicit both vasoconstriction and systemic hypertension. This is primarily due to the ability of acellular Hb to extravasate through the blood vessel wall and scavenge endothelial-derived nitric oxide (NO). Encapsulation of Hb inside the aqueous core of liposomes retards the rates of NO dioxygenation and O2 release, which should reduce or eliminate the vasoactivity of Hb. Our aim is to determine the extent of systemic and microvascular vasoactive responses (hypertension, vasoconstriction and hypoperfusion) after infusion of vesicle encapsulated Hbs, in which the encapsulated Hb is in either the deoxygenated or carbon monoxide (CO) state (HbV and COHbV, respectively). To investigate this hypothesis, we used the hamster window chamber model subjected to two successive hypervolemic infusions of HbV and COHbV solutions (each infusion represents 10% of the animal's calculated blood volume) at Hb concentrations of either 7 or 10 g/dL. The hypervolemic infusion model used in this study has all the regulatory mechanisms responsible for predicting the vasoconstrictive responses of HBOCs. The results of this study demonstrate the absence of vasoconstrictive and hypertensive responses upon single and multiple infusions of HbV and COHbV solutions. The HbV and COHbV solutions increased the plasma O2 carrying capacity. However, COHbV delivered low therapeutic levels of CO without inducing any microcirculatory disturbances. SIGNIFICANCE Vesicles containing Hb can be used as a new therapeutic agent in transfusion medicine to treat anemia and revert hypoperfusion.
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Affiliation(s)
- Pedro Cabrales
- Department of Bioengineering, University of California-San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0412, USA.
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Bucci E. Basic Science Offers a Challenge for Developing Hemoglobin Based Oxygen Carriers into Therapeutic Agents. ACTA ACUST UNITED AC 2011; 39:206-13. [PMID: 21692690 DOI: 10.3109/10731199.2010.538402] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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13
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Zhou Y, Jia Y, Buehler PW, Chen G, Cabrales P, Palmer AF. Synthesis, biophysical properties, and oxygenation potential of variable molecular weight glutaraldehyde-polymerized bovine hemoglobins with low and high oxygen affinity. Biotechnol Prog 2011; 27:1172-84. [PMID: 21584950 DOI: 10.1002/btpr.624] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 03/02/2011] [Indexed: 12/31/2022]
Abstract
In a recent study, ultrahigh molecular weight (Mw ) glutaraldehyde-polymerized bovine hemoglobins (PolybHbs) were synthesized with low O2 affinity and exhibited no vasoactivity and a slight degree of hypertension in a 10% top-load model.(1) In this work, we systematically investigated the effect of varying the glutaraldehyde to hemoglobin (G:Hb) molar ratio on the biophysical properties of PolybHb polymerized in either the low or high O2 affinity state. Our results showed that the Mw of the resulting PolybHbs increased with increasing G:Hb molar ratio. For low O2 affinity PolybHbs, increasing the G:Hb molar ratio reduced the O2 affinity and CO association rate constants in comparison to bovine hemoglobin (bHb). In contrast for high O2 affinity PolybHbs, increasing the G:Hb molar ratio led to increased O2 affinity and significantly increased the CO association rate constants compared to unmodified bHb and low O2 affinity PolybHbs. The methemoglobin level and NO dioxygenation rate constants were insensitive to the G:Hb molar ratio. However, all PolybHbs displayed higher viscosities compared to unmodified bHb and whole blood, which also increased with increasing G:Hb molar ratio. In contrast, the colloid osmotic pressure of PolybHbs decreased with increasing G:Hb molar ratio. To preliminarily evaluate the ability of low and high O2 affinity PolybHbs to potentially oxygenate tissues in vivo, an O2 transport model was used to simulate O2 transport in a hepatic hollow fiber (HF) bioreactor. It was observed that low O2 affinity PolybHbs oxygenated the bioreactor better than high O2 affinity PolybHbs. This result points to the suitability of low O2 affinity PolybHbs for use in tissue engineering and transfusion medicine. Taken together, our results show the quantitative effect of varying the oxygen saturation of bHb and G:Hb molar ratio on the biophysical properties of PolybHbs and their ability to oxygenate a hepatic HF bioreactor. We suggest that the information gained from this study can be used to guide the design of the next generation of hemoglobin-based oxygen carriers (HBOCs) for use in tissue engineering and transfusion medicine applications.
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Affiliation(s)
- Yipin Zhou
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH 43210, USA
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Buehler PW, D'Agnillo F. Toxicological consequences of extracellular hemoglobin: biochemical and physiological perspectives. Antioxid Redox Signal 2010; 12:275-91. [PMID: 19659434 DOI: 10.1089/ars.2009.2799] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Under normal physiology, human red blood cells (RBCs) demonstrate a circulating lifespan of approximately 100-120 days with efficient removal of senescent RBCs taking place via the reticuloendothelial system, spleen, and bone marrow phagocytosis. Within this time frame, hemoglobin (Hb) is effectively protected by efficient RBC enzymatic systems designed to allow for interaction between Hb and diffusible ligands while preventing direct contact between Hb and the external environment. Under normal resting conditions, the concentration of extracellular Hb in circulation is therefore minimal and controlled by specific plasma and cellular (monocyte/macrophage) binding proteins (haptoglobin) and receptors (CD163), respectively. However, during pathological conditions leading to hemolysis, extracellular Hb concentrations exceed normal plasma and cellular binding capacities, allowing Hb to become a biologically relevant vasoactive and redox active protein within the circulation and at extravascular sites. Under conditions of genetic, drug-induced, and autoimmune hemolytic anemias, large quantities of Hb are introduced into the circulation and often lead to acute renal failure and vascular dysfunction. Interestingly, the study of chemically modified Hb for use as oxygen therapeutics has allowed for some basic understanding of extracellular Hb toxicity, particularly in the absence of functional clearance mechanisms and in circulatory antioxidant depleted states.
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Affiliation(s)
- Paul W Buehler
- Laboratory of Biochemistry and Vascular Biology, Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.
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Cabrales P, Sun G, Zhou Y, Harris DR, Tsai AG, Intaglietta M, Palmer AF. Effects of the molecular mass of tense-state polymerized bovine hemoglobin on blood pressure and vasoconstriction. J Appl Physiol (1985) 2009; 107:1548-58. [PMID: 19745190 PMCID: PMC2777796 DOI: 10.1152/japplphysiol.00622.2009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2009] [Accepted: 09/02/2009] [Indexed: 11/22/2022] Open
Abstract
Despite recent advances in the design of hemoglobin (Hb)-based oxygen carriers (HBOCs), vasoconstriction, presumably caused by nitric oxide (NO) scavenging, vessel wall hyperoxygenation, and/or extravasation, has been identified as the principal road block hampering commercial development of HBOCs. This study was designed to analyze systemic and microvascular responses to the molecular mass and plasma concentration of tense (T)-state polymerized bovine Hb (PolybHb) solutions. Experiments were performed using the hamster window chamber model subjected to successive hypervolemic infusions of T-state PolybHb solutions. PolybHb plasma concentrations were evaluated, namely, 0.5, 1.0 and 1.5 g/dl, respectively. Infusion of PolybHb solutions with molecular mass >500 kDa elicited hypertension and vasoconstriction proportional to the plasma concentration and inversely proportional to the PolybHb cross-link density. However, two high-molecular mass PolybHb solutions, PolybHb(40:1)(high) PolybHb(50:1)(high), did not elicit vasoconstriction at all concentrations studied, whereas PolybHb(50:1)(high) only elicited moderate hypertension at the highest concentration studied. In contrast, infusion of PolybHb solutions with molecular mass <500 kDa elicited significant hypertension and vasoconstriction compared with PolybHb solutions with molecular mass >500 kDa that was proportional to the plasma concentration and inversely proportional to the PolybHb cross-link density. We present promising results for highly cross-linked T-state PolybHb solutions with molecular mass >500 kDa [PolybHb(40:1)(high) PolybHb(50:1)(high)], which supports the concept that HBOC size/molecular mass influences its proximity to the vascular endothelium and molecular diffusivity. The hemodynamics of HBOC within the plasma layer surrounding the abluminal side endothelium regulates NO production and consumption, vessel oxygen flux, and extravasation. Although mechanistically attractive, neither of these hypotheses can be directly tested in vivo and will require further investigation.
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Affiliation(s)
- Pedro Cabrales
- La Jolla Bioengineering Institute, 505 Coast Boulevard South, Suite 405, La Jolla, CA 92037, USA.
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Fronticelli C, Koehler RC. Design of recombinant hemoglobins for use in transfusion fluids. Crit Care Clin 2009; 25:357-71, Table of Contents. [PMID: 19341913 DOI: 10.1016/j.ccc.2008.12.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Molecular biology has been applied to the development of hemoglobin-based oxygen carrier (HBOC) proteins that can be expressed in bacteria or yeast. The transformation of the hemoglobin molecule into an HBOC requires a variety of modifications for rendering the acellular molecule of hemoglobin physiologically acceptable when transfused in circulation. Hemoglobins with different oxygen affinities can be obtained by introducing mutations at the heme pocket, the site of oxygen binding, or by introducing surface mutations that stabilize the hemoglobin molecule in the low-oxygen-affinity state. Modification of the size of the heme pocket is also used to hinder nitric oxide depletion and associated vasoconstriction. Introduction of cysteine residues on the hemoglobin surface allows formation of intermolecular bonds and formation of polymeric HBOCs. These polymers of recombinant hemoglobin have the characteristics of molecular size, molecular stability, and oxygen delivery to hypoxic tissue suitable for an HBOC.
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Affiliation(s)
- Clara Fronticelli
- Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Blalock, Baltimore, MD 21287, USA.
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Bucci E. Thermodynamic approach to oxygen delivery in vivo by natural and artificial oxygen carriers. Biophys Chem 2008; 142:1-6. [PMID: 19349106 DOI: 10.1016/j.bpc.2008.12.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Revised: 12/19/2008] [Accepted: 12/19/2008] [Indexed: 11/15/2022]
Abstract
Oxygen is a toxic gas, still indispensable to aerobic life. This paper explores how normal physiology uses the physico-chemical and thermodynamic characteristics of oxygen for transforming a toxic gas into a non toxic indispensable metabolite. Plasma oxygen concentration is in the range of 10(-5) M, insufficient to sustain metabolism. Oxygen carriers, present in blood, release oxygen into plasma, thereby replacing consumed oxygen and buffering PO(2) near their P(50). They are the natural cell-bound carriers, like hemoglobin inside red cells, myoglobin inside myocytes, and artificial cell-free hemoglobin-based oxygen carriers (HBOC) dissolved in plasma. Metabolic oxygen replacement can be defined as cell-bound and cell-free delivery. Cell-bound delivery is retarded by the slow diffusion of oxygen in plasma and interstitial fluids. The 40% hematocrit of normal blood compensates for the delay, coping with the fast oxygen consumption by mitochondria. Facilitated oxygen diffusion by HBOCs corrects for the slow diffusion, making cell-free delivery relatively independent from P(50). At all oxygen affinities, HBOCs produce hyperoxygenations that are compensated by vasoconstrictions. There is a strict direct correlation between the rate of oxygen replacement and hemoglobin content of blood. The free energy loss of the gradient adds a relevant regulation of tissues oxygenation. Oxygen is retained intravascularly by the limited permeability to gases of vessel walls.
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Affiliation(s)
- Enrico Bucci
- Department of Biochemistry and Molecular Biology, University of Maryland Medical School, 108 North Greene St., Baltimore, MD 21201, USA
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Baudin-Creuza V, Chauvierre C, Domingues E, Kiger L, Leclerc L, Vasseur C, Célier C, Marden MC. Octamers and nanoparticles as hemoglobin based blood substitutes. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1448-53. [DOI: 10.1016/j.bbapap.2008.02.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Revised: 02/06/2008] [Accepted: 02/14/2008] [Indexed: 10/22/2022]
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Abstract
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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He X, Azarov I, Jeffers A, Presley T, Richardson J, King SB, Gladwin MT, Kim-Shapiro DB. The potential of Angeli's salt to decrease nitric oxide scavenging by plasma hemoglobin. Free Radic Biol Med 2008; 44:1420-32. [PMID: 18243145 PMCID: PMC2376831 DOI: 10.1016/j.freeradbiomed.2007.12.038] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Revised: 12/21/2007] [Accepted: 12/21/2007] [Indexed: 10/22/2022]
Abstract
Release of hemoglobin from the erythrocyte during intravascular hemolysis contributes to the pathology of a variety of diseased states. This effect is partially due to the enhanced ability of cell-free plasma hemoglobin, which is primarily found in the ferrous, oxygenated state, to scavenge nitric oxide. Oxidation of the cell-free hemoglobin to methemoglobin, which does not effectively scavenge nitric oxide, using inhaled nitric oxide has been shown to be effective in limiting pulmonary and systemic vasoconstriction. However, the ferric heme species may be reduced back to ferrous hemoglobin in plasma and has the potential to drive injurious redox chemistry. We propose that compounds that selectively convert cell-free hemoglobin to ferric, and ideally iron-nitrosylated heme species that do not actively scavenge nitric oxide, would effectively treat intravascular hemolysis. We show here that nitroxyl generated by Angeli's salt (sodium alpha-oxyhyponitrite, Na2N2O3) preferentially reacts with cell-free hemoglobin compared to that encapsulated in the red blood cell under physiologically relevant conditions. Nitroxyl oxidizes oxygenated ferrous hemoglobin to methemoglobin and can convert the methemoglobin to a more stable, less toxic species, iron-nitrosyl hemoglobin. These results support the notion that Angeli's salt or a similar compound could be used to effectively treat conditions associated with intravascular hemolysis.
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Affiliation(s)
- Xiaojun He
- Department of Physics, Wake Forest University, Winston-Salem, NC 27109
| | - Ivan Azarov
- Department of Physics, Wake Forest University, Winston-Salem, NC 27109
| | - Anne Jeffers
- Department of Physics, Wake Forest University, Winston-Salem, NC 27109
| | - Tennille Presley
- Department of Physics, Wake Forest University, Winston-Salem, NC 27109
| | - Jodi Richardson
- Department of Physics, Wake Forest University, Winston-Salem, NC 27109
| | - S. Bruce King
- Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109
| | - Mark T. Gladwin
- Vascular Medicine Branch, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892
- Critical Care Medicine Department, Clinical Center; NIH, Bethesda, MD 20892
| | - Daniel B. Kim-Shapiro
- Vascular Medicine Branch, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892
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Alayash AI, D'Agnillo F, Buehler PW. First-generation blood substitutes: what have we learned? Biochemical and physiological perspectives. Expert Opin Biol Ther 2007; 7:665-75. [PMID: 17477804 DOI: 10.1517/14712598.7.5.665] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Chemically modified or recombinant hemoglobin (Hb)-based oxygen carriers (HBOCs) have been developed as oxygen therapeutics or 'blood substitutes' for use in a variety of clinical settings. Oxidative and nitrosative reactions of acellular Hb can limit the effectiveness and compromise the safety of HBOCs. The reactions between Hb and biologically relevant redox active molecules may also perturb redox sensitive signaling pathways. In recent years, systematic in vitro and in vivo structural and functional evaluation of several HBOCs has been carried out and, in some cases, delineated the 'structural' origin of their toxicity. This enables potential protective strategies against Hb-mediated side reactions to be rationally suggested. Here the authors provide an overview of their research experiences, novel insights into the molecular basis of toxicities of these products and some lessons learned.
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Affiliation(s)
- Abdu I Alayash
- Center for Biologics Evaluation and Research, Food and Drug Administration, Laboratory of Biochemistry and Vascular Biology, Division of Hematology, National Institutes of Health Campus, Bethesda, MD 20892, USA.
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Kim-Shapiro DB, Schechter AN, Gladwin MT. Unraveling the Reactions of Nitric Oxide, Nitrite, and Hemoglobin in Physiology and Therapeutics. Arterioscler Thromb Vasc Biol 2006; 26:697-705. [PMID: 16424350 DOI: 10.1161/01.atv.0000204350.44226.9a] [Citation(s) in RCA: 210] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The ability of oxyhemoglobin to inhibit nitric oxide (NO)-dependent activation of soluble guanylate cyclase and vasodilation provided some of the earliest experimental evidence that NO was the endothelium-derived relaxing factor (EDRF). The chemical behavior of this dioxygenation reaction, producing nearly diffusion limited and irreversible NO scavenging, presents a major paradox in vascular biology: The proximity of large amounts of oxyhemoglobin (10 mmol/L) to the endothelium should severely limit paracrine NO diffusion from endothelium to smooth muscle. However, several physical factors are now known to mitigate NO scavenging by red blood cell encapsulated hemoglobin. These include diffusional boundaries around the erythrocyte and a red blood cell free zone along the endothelium in laminar flowing blood, which reduce reaction rates between NO and red cell hemoglobin by 100- to 600-fold. Beyond these mechanisms that reduce NO scavenging by hemoglobin within the red cell, 2 additional mechanisms have been proposed suggesting that NO can be stored in the red blood cell either as nitrite or as an S-nitrosothiol (S-nitroso-hemoglobin). The latter controversial hypothesis contends that NO is stabilized, transported, and delivered by intra-molecular NO group transfers between the heme iron and beta-93 cysteine to form S-nitroso-hemoglobin (SNO-Hb), followed by hypoxia-dependent delivery of the S-nitrosothiol in a process that links regional oxygen deficits with S-nitrosothiol-mediated vasodilation. Although this model has generated a field of research examining the potential endocrine properties of intravascular NO molecules, including S-nitrosothiols, nitrite, and nitrated lipids, a number of mechanistic elements of the theory have been challenged. Recent data from several groups suggest that the nitrite anion (NO2-) may represent the major intravascular NO storage molecule whose transduction to NO is made possible through an allosterically controlled nitrite reductase reaction with the heme moiety of hemoglobin. As subsequently understood, the hypoxic generation of NO from nitrite is likely to prove important in many aspects of physiology, pathophysiology, and therapeutics.
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Azarov I, Huang KT, Basu S, Gladwin MT, Hogg N, Kim-Shapiro DB. Nitric oxide scavenging by red blood cells as a function of hematocrit and oxygenation. J Biol Chem 2005; 280:39024-32. [PMID: 16186121 DOI: 10.1074/jbc.m509045200] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The reaction rate between nitric oxide and intraerythrocytic hemoglobin plays a major role in nitric oxide bioavailability and modulates homeostatic vascular function. It has previously been demonstrated that the encapsulation of hemoglobin in red blood cells restricts its ability to scavenge nitric oxide. This effect has been attributed to either factors intrinsic to the red blood cell such as a physical membrane barrier or factors external to the red blood cell such as the formation of an unstirred layer around the cell. We have performed measurements of the uptake rate of nitric oxide by red blood cells under oxygenated and deoxygenated conditions at different hematocrit percentages. Our studies include stopped-flow measurements where both the unstirred layer and physical barrier potentially participate, as well as competition experiments where the potential contribution of the unstirred layer is limited. We find that deoxygenated erythrocytes scavenge nitric oxide faster than oxygenated cells and that the rate of nitric oxide scavenging for oxygenated red blood cells increases as the hematocrit is raised from 15% to 50%. Our results 1) confirm the critical biological phenomenon that hemoglobin compartmentalization within the erythrocyte reduces reaction rates with nitric oxide, 2) show that extra-erythocytic diffusional barriers mediate most of this effect, and 3) provide novel evidence that an oxygen-dependent intrinsic property of the red blood cell contributes to this barrier activity, albeit to a lesser extent. These observations may have important physiological implications within the microvasculature and for pathophysiological disruption of nitric oxide homeostasis in diseases.
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Affiliation(s)
- Ivan Azarov
- Department of Physics, School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27109, USA
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