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Premont RT, Reynolds JD, Zhang R, Stamler JS. Role of Nitric Oxide Carried by Hemoglobin in Cardiovascular Physiology: Developments on a Three-Gas Respiratory Cycle. Circ Res 2019; 126:129-158. [PMID: 31590598 DOI: 10.1161/circresaha.119.315626] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
A continuous supply of oxygen is essential for the survival of multicellular organisms. The understanding of how this supply is regulated in the microvasculature has evolved from viewing erythrocytes (red blood cells [RBCs]) as passive carriers of oxygen to recognizing the complex interplay between Hb (hemoglobin) and oxygen, carbon dioxide, and nitric oxide-the three-gas respiratory cycle-that insures adequate oxygen and nutrient delivery to meet local metabolic demand. In this context, it is blood flow and not blood oxygen content that is the main driver of tissue oxygenation by RBCs. Herein, we review the lines of experimentation that led to this understanding of RBC function; from the foundational understanding of allosteric regulation of oxygen binding in Hb in the stereochemical model of Perutz, to blood flow autoregulation (hypoxic vasodilation governing oxygen delivery) observed by Guyton, to current understanding that centers on S-nitrosylation of Hb (ie, S-nitrosohemoglobin; SNO-Hb) as a purveyor of oxygen-dependent vasodilatory activity. Notably, hypoxic vasodilation is recapitulated by native S-nitrosothiol (SNO)-replete RBCs and by SNO-Hb itself, whereby SNO is released from Hb and RBCs during deoxygenation, in proportion to the degree of Hb deoxygenation, to regulate vessels directly. In addition, we discuss how dysregulation of this system through genetic mutation in Hb or through disease is a common factor in oxygenation pathologies resulting from microcirculatory impairment, including sickle cell disease, ischemic heart disease, and heart failure. We then conclude by identifying potential therapeutic interventions to correct deficits in RBC-mediated vasodilation to improve oxygen delivery-steps toward effective microvasculature-targeted therapies. To the extent that diseases of the heart, lungs, and blood are associated with impaired tissue oxygenation, the development of new therapies based on the three-gas respiratory system have the potential to improve the well-being of millions of patients.
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Affiliation(s)
- Richard T Premont
- From the Institute for Transformative Molecular Medicine (R.T.P., J.D.R., R.Z., J.S.S.), Case Western Reserve University School of Medicine, OH.,Harrington Discovery Institute (R.T.P., J.D.R., J.S.S.), University Hospitals Cleveland Medical Center, OH
| | - James D Reynolds
- From the Institute for Transformative Molecular Medicine (R.T.P., J.D.R., R.Z., J.S.S.), Case Western Reserve University School of Medicine, OH.,Department of Anesthesiology and Perioperative Medicine (J.D.R.), Case Western Reserve University School of Medicine, OH.,Harrington Discovery Institute (R.T.P., J.D.R., J.S.S.), University Hospitals Cleveland Medical Center, OH
| | - Rongli Zhang
- From the Institute for Transformative Molecular Medicine (R.T.P., J.D.R., R.Z., J.S.S.), Case Western Reserve University School of Medicine, OH.,Department of Medicine, Cardiovascular Research Institute (R.Z., J.S.S.), Case Western Reserve University School of Medicine, OH
| | - Jonathan S Stamler
- From the Institute for Transformative Molecular Medicine (R.T.P., J.D.R., R.Z., J.S.S.), Case Western Reserve University School of Medicine, OH.,Department of Medicine, Cardiovascular Research Institute (R.Z., J.S.S.), Case Western Reserve University School of Medicine, OH.,Harrington Discovery Institute (R.T.P., J.D.R., J.S.S.), University Hospitals Cleveland Medical Center, OH
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Miura T, Nishinaka T, Terada T, Yonezawa K. Vasodilatory effect of nitroglycerin in Japanese subjects with different aldehyde dehydrogenase 2 (ALDH2) genotypes. Chem Biol Interact 2017; 276:40-45. [PMID: 28342890 DOI: 10.1016/j.cbi.2017.03.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2016] [Revised: 01/31/2017] [Accepted: 03/19/2017] [Indexed: 11/28/2022]
Abstract
The functional genetic polymorphism of aldehyde dehydrogenase 2 (ALDH2) influences the enzymatic activities of its wild type (Glu504 encoded by ALDH2*1) and mutant type (Lys504 encoded by ALDH2*2) proteins. The enzymatic activities of mutant-type ALDH2 are limited compared with those of the wild type. ALDH2 has been suggested as a critical factor for nitroglycerin-mediated vasodilation by some human studies and in vitro studies. Currently, there is no research on direct observations of the vasodilatory effect of nitroglycerin sublingual tablets, which is the generally used dosage form. In the present study, the contribution of ALDH2 to the vasodilatory effect of nitroglycerin sublingual tablets was investigated among three genotype groups (ALDH2*1/*1, ALDH2*1/*2, and ALDH2*2/*2) in Japanese. The results by direct assessments of in vivo nitroglycerin-mediated dilation showed no apparent difference in vasodilation among all genotypes of ALDH2. Furthermore, to analyze the effect of other factors (age and flow-mediated dilation), multiple regression analysis and Pearson's correlation coefficient analysis were carried out. These analyses also indicated that the genotypes of ALDH2 were not related to the degree of vasodilation. These results suggest the existence of other predominant pathway(s) for nitroglycerin biotransformation, at least with regard to clinical nitroglycerin (e.g., a sublingual tablet) in Japanese subjects.
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Affiliation(s)
- Takeshi Miura
- Laboratory of Biochemistry, Faculty of Pharmacy, Osaka Ohtani University, 3-11-1 Nishikiori-kita, Tondabayashi, Osaka 584-8540, Japan; Pharmaceutical Education Support Center, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Koshien, 9-Bancho, Nishinomiya, Hyogo 663-8179, Japan.
| | - Toru Nishinaka
- Laboratory of Biochemistry, Faculty of Pharmacy, Osaka Ohtani University, 3-11-1 Nishikiori-kita, Tondabayashi, Osaka 584-8540, Japan
| | - Tomoyuki Terada
- Laboratory of Biochemistry, Faculty of Pharmacy, Osaka Ohtani University, 3-11-1 Nishikiori-kita, Tondabayashi, Osaka 584-8540, Japan
| | - Kazuya Yonezawa
- Department of Clinical Research, National Hospital Organization Hakodate Hospital, 18-16, Kawahara, Hakodate, Hokkaido 041-8512, Japan
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3
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Burnstock G. Blood cells: an historical account of the roles of purinergic signalling. Purinergic Signal 2015; 11:411-34. [PMID: 26260710 PMCID: PMC4648797 DOI: 10.1007/s11302-015-9462-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 07/23/2015] [Indexed: 12/17/2022] Open
Abstract
The involvement of purinergic signalling in the physiology of erythrocytes, platelets and leukocytes was recognised early. The release of ATP and the expression of purinoceptors and ectonucleotidases on erythrocytes in health and disease are reviewed. The release of ATP and ADP from platelets and the expression and roles of P1, P2Y(1), P2Y(12) and P2X1 receptors on platelets are described. P2Y(1) and P2X(1) receptors mediate changes in platelet shape, while P2Y(12) receptors mediate platelet aggregation. The changes in the role of purinergic signalling in a variety of disease conditions are considered. The successful use of P2Y(12) receptor antagonists, such as clopidogrel and ticagrelor, for the treatment of thrombosis, myocardial infarction and stroke is discussed.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK.
- Department of Pharmacology and Therapeutics, The University of Melbourne, Melbourne, Australia.
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Daiber A, Münzel T. Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress. Antioxid Redox Signal 2015; 23:899-942. [PMID: 26261901 PMCID: PMC4752190 DOI: 10.1089/ars.2015.6376] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Organic nitrates, such as nitroglycerin (GTN), isosorbide-5-mononitrate and isosorbide dinitrate, and pentaerithrityl tetranitrate (PETN), when given acutely, have potent vasodilator effects improving symptoms in patients with acute and chronic congestive heart failure, stable coronary artery disease, acute coronary syndromes, or arterial hypertension. The mechanisms underlying vasodilation include the release of •NO or a related compound in response to intracellular bioactivation (for GTN, the mitochondrial aldehyde dehydrogenase [ALDH-2]) and activation of the enzyme, soluble guanylyl cyclase. Increasing cyclic guanosine-3',-5'-monophosphate (cGMP) levels lead to an activation of the cGMP-dependent kinase I, thereby causing the relaxation of the vascular smooth muscle by decreasing intracellular calcium concentrations. The hemodynamic and anti-ischemic effects of organic nitrates are rapidly lost upon long-term (low-dose) administration due to the rapid development of tolerance and endothelial dysfunction, which is in most cases linked to increased intracellular oxidative stress. Enzymatic sources of reactive oxygen species under nitrate therapy include mitochondria, NADPH oxidases, and an uncoupled •NO synthase. Acute high-dose challenges with organic nitrates cause a similar loss of potency (tachyphylaxis), but with distinct pathomechanism. The differences among organic nitrates are highlighted regarding their potency to induce oxidative stress and subsequent tolerance and endothelial dysfunction. We also address pleiotropic effects of organic nitrates, for example, their capacity to stimulate antioxidant pathways like those demonstrated for PETN, all of which may prevent adverse effects in response to long-term therapy. Based on these considerations, we will discuss and present some preclinical data on how the nitrate of the future should be designed.
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Affiliation(s)
- Andreas Daiber
- The 2nd Medical Clinic, Medical Center of the Johannes Gutenberg University , Mainz, Germany
| | - Thomas Münzel
- The 2nd Medical Clinic, Medical Center of the Johannes Gutenberg University , Mainz, Germany
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Seabra AB, Ouellet M, Antonic M, Chrétien MN, English AM. Catalysis of nitrite generation from nitroglycerin by glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Nitric Oxide 2013; 35:116-22. [PMID: 24064205 DOI: 10.1016/j.niox.2013.09.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 09/12/2013] [Accepted: 09/13/2013] [Indexed: 01/11/2023]
Abstract
Vascular relaxation to nitroglycerin (glyceryl trinitrate; GTN) requires its bioactivation by mechanisms that remain controversial. We report here that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the release of nitrite from GTN. In assays containing dithiothreitol (DTT) and NAD(+), the GTN reductase activity of purified GAPDH produces nitrite and 1,2-GDN as the major products. A vmax of 2.6nmolmin(-)(1)mg(-)(1) was measured for nitrite production by GAPDH from rabbit muscle and a GTN KM of 1.2mM. Reductive denitration of GTN in the absence of DTT results in dose- and time-dependent inhibition of GAPDH dehydrogenase activity. Disulfiram, a thiol-modifying drug, inhibits both the dehydrogenase and GTN reductase activity of GAPDH, while DTT or tris(2-carboxyethyl)phosphine reverse the GTN-induced inhibition. Incubation of intact human erythrocytes or hemolysates with 2mM GTN for 60min results in 50% inhibition of GAPDH's dehydrogenase activity, indicating that GTN is taken up by these cells and that the dehydrogenase is a target of GTN. Thus, erythrocyte GAPDH may contribute to GTN bioactivation.
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Affiliation(s)
- Amedea B Seabra
- Department of Chemistry and Biochemistry, Concordia University, Montreal, QC H4B 1R6, Canada
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Kallakunta VM, Slama-Schwok A, Mutus B. Protein disulfide isomerase may facilitate the efflux of nitrite derived S-nitrosothiols from red blood cells. Redox Biol 2013; 1:373-80. [PMID: 24024174 PMCID: PMC3757710 DOI: 10.1016/j.redox.2013.07.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 07/08/2013] [Accepted: 07/09/2013] [Indexed: 12/26/2022] Open
Abstract
Protein disulfide isomerase (PDI) is an abundant protein primarily found in the endoplasmic reticulum and also secreted into the blood by a variety of vascular cells. The evidence obtained here, suggests that PDI could directly participate in the efflux of NO+ from red blood cells (RBC). PDI was detected both in RBC membranes and in the cytosol. PDI was S-nitrosylated when RBCs were exposed to nitrite under ∼50% oxygen saturation but not under ∼100% oxygen saturation. Furthermore, it was observed that hemoglobin (Hb) could promote PDI S-nitrosylation in the presence of ∼600 nM nitrite. In addition, three lines of evidence were obtained for PDI–Hb interactions: (1) Hb co-immunoprecipitated with PDI; (2) Hb quenched the intrinsic PDI fluorescence in a saturable manner; and (3) Hb–Fe(II)–NO absorption spectrum decreased in a [PDI]-dependent manner. Finally, PDI was detected on the surface RBC under ∼100% oxygen saturation and released as soluble under ∼50% oxygen saturation. The soluble PDI detected under ∼50% oxygen saturation was S-nitrosylated. Based on these data it is proposed that PDI is taken up by RBC and forms a complex with Hb. Hb–Fe(II)–NO that is formed from nitrite reduction under ∼50% O2, then transfers NO+ to either Hb–Cys β93 or directly to PDI resulting in S-nitroso-PDI which transverses the RBC membrane and attaches to the RBC surface. When RBCs enter tissues the S-nitroso-PDI is released from the RBC-surface into the blood where its NO+ is transferred into the endothelium thereby inducing vasodilation, suggesting local oxygen-dependent dynamic interplays between nitrite, NO and S-nitrosylation. Red blood cells (RBC) contain protein disulfide isomerase (PDI) that can associate with hemoglobin. Formation of S-nitroso-PDI is an oxygen- and Hb-dependent process. S-nitroso-PDI associates with RBC surface in an oxygen dependent manner that facilitates its release under hypoxia.
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Key Words
- BCA, bicinchoninic acid
- EDTA, ethylenediaminetetraacetic acid
- Hb, hemoglobin
- Hypoxic vasodilation
- NOx, nitric oxide related species
- NP-40, nonyl phenoxypolyethoxylethanol
- Nitrite reductase
- PDI, protein disulfide isomerase
- PMSF, penylmethylsulfenylfluoride
- Protein disulfide isomerase
- RBC, red blood cells
- Red blood cells
- S-nitroso-protein disulfide isomerase
- S-nitrosohemoglobin
- SDS-PAGE, sodium dodecyl sulfate, poly acrylamide gel electrophoresis
- SNO, S-nitrosothiol
- SNO-Hb, S-nitrosohemoglobin
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7
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Overcoming matrix effects in the chemiluminescence determination of extracellular adenosine triphosphate in erythrocyte suspensions. Anal Biochem 2013; 436:66-8. [PMID: 23376575 DOI: 10.1016/j.ab.2013.01.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Revised: 12/12/2012] [Accepted: 01/23/2013] [Indexed: 11/20/2022]
Abstract
As erythrocyte-derived extracellular adenosine triphosphate (ATP) gains recognition as a key vasodilator, its accurate determination is critical. Erythrocytes' high hemoglobin content can act as an inner filter when measuring ATP concentrations by chemiluminescence. We evaluated two approaches to correct for this matrix effect: addition of cell-free hemoglobin to the ATP standards and standard addition of ATP to erythrocyte suspensions. In addition, we reduced sample hematocrit to minimize the absorbance. We conclude that extracellular ATP should be determined in erythrocyte suspensions at 0.06 to 0.004% hematocrit. This gives robust signals without matrix effects and requires only microliters of blood.
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Abstract
Several apparent paradoxes are evident when one compares mathematical predictions from models of nitric oxide (NO) diffusion and convection in vasculature structures with experimental measurements of NO (or related metabolites) in animal and human studies. Values for NO predicted from mathematical models are generally much lower than in vivo NO values reported in the literature for experiments, specifically with NO microelectrodes positioned at perivascular locations next to different sizes of blood vessels in the microcirculation and NO electrodes inserted into a wide range of tissues supplied by the microcirculation of each specific organ system under investigation. There continues to be uncertainty about the roles of NO scavenging by hemoglobin versus a storage function that may conserve NO, and other signaling targets for NO need to be considered. This review describes model predictions and relevant experimental data with respect to several signaling pathways in the microcirculation that involve NO.
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Omar SA, Artime E, Webb AJ. A comparison of organic and inorganic nitrates/nitrites. Nitric Oxide 2012; 26:229-40. [PMID: 22491087 DOI: 10.1016/j.niox.2012.03.008] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 02/15/2012] [Accepted: 03/22/2012] [Indexed: 11/19/2022]
Abstract
Although both organic and inorganic nitrates/nitrites mediate their principal effects via nitric oxide, there are many important differences. Inorganic nitrate and nitrite have simple ionic structures and are produced endogenously and are present in the diet, whereas their organic counterparts are far more complex, and, with the exception of ethyl nitrite, are all medicinally synthesised products. These chemical differences underlie the differences in pharmacokinetic properties allowing for different modalities of administration, particularly of organic nitrates, due to the differences in their bioavailability and metabolic profiles. Whilst the enterosalivary circulation is a key pathway for orally ingested inorganic nitrate, preventing an abrupt effect or toxic levels of nitrite and prolonging the effects, this is not used by organic nitrates. The pharmacodynamic differences are even greater; while organic nitrates have potent acute effects causing vasodilation, inorganic nitrite's effects are more subtle and dependent on certain conditions. However, in chronic use, organic nitrates are considerably limited by the development of tolerance and endothelial dysfunction, whereas inorganic nitrate/nitrite may compensate for diminished endothelial function, and tolerance has not been reported. Also, while inorganic nitrate/nitrite has important cytoprotective effects against ischaemia-reperfusion injury, continuous use of organic nitrates may increase injury. While there are concerns that inorganic nitrate/nitrite may induce carcinogenesis, direct evidence of this in humans is lacking. While organic nitrates may continue to dominate the therapeutic arena, this may well change with the increasing recognition of their limitations, and ongoing discovery of beneficial effects and specific advantages of inorganic nitrate/nitrite.
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Affiliation(s)
- Sami A Omar
- King's College London British Heart Foundation Centre, Cardiovascular Division, Department of Clinical Pharmacology, London, UK
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Rieckeheer E, Schwinger RHG, Bloch W, Brixius K. Hawthorn special extract WS® 1442 increases red blood cell NO-formation without altering red blood cell deformability. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2011; 19:20-24. [PMID: 21899992 DOI: 10.1016/j.phymed.2011.08.059] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Accepted: 08/08/2011] [Indexed: 05/31/2023]
Abstract
UNLABELLED WS(®) 1442 is a special extract of hawthorn leaves with flowers used for the treatment of mild cardiac failure. The activation of endothelial nitric oxide synthase (eNOS) has been shown to contribute to its vasodilating properties. Quite recently it has been demonstrated that red blood cells (RBCs) express a functional NO-synthase (rbcNOS) and rbcNOS activation has been associated with increased RBC deformability. The aim of the present study was to determine whether WS(®) 1442 is able to activate rbcNOS, to induce NO-formation in RBC and to alter RBC-deformability. Blood from healthy volunteers was incubated with WS(®) 1442 (25-100 μg/ml) for up to 30 min. RbcNOS activation was detected by immunohistochemical staining of phosphorylated rbcNOS and NO-formation was examined by diaminofluorescein (DAF) fluorescence. RBC deformability was measured by a laser assisted optical rotational cell analyzer. Serine 1177 of RbcNOS (rbcNOS Ser(1177)) was time- and concentration-dependently phosphorylated by WS(®) 1442. Rates of rbcNOS Ser(1177) phosphorylation were up to 149% higher in RBCs treated with WS(®) 1442 in comparison to control (DMSO 0.05%). WS(®) 1442 induced a time-dependent increase in NO-formation in RBCs which reached its maximum after 5 min. An increase in shear stress (0.3-50 Pa) caused an increase in RBC deformability. WS(®) 1442 did not change either basal or maximal RBC-deformability or shear stress sensitivity of RBC at normoxia. CONCLUSION WS(®) 1442 activates rbcNOS and causes NO-formation in RBCs. WS(®) 1442-dependent NO-formation however does not affect RBC-deformability at normoxia.
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Affiliation(s)
- Eva Rieckeheer
- Department of Molecular and Cellular Sport Medicine, Institute for Circulation Research and Sport Medicine, German Sports University Cologne, Cologne, Germany
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11
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Wagner MCE. The therapeutic potential of adenosine triphosphate as an immune modulator in the treatment of HIV/AIDS: a combination approach with HAART. Curr HIV Res 2011; 9:209-22. [PMID: 21675943 PMCID: PMC3343418 DOI: 10.2174/157016211796320289] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 04/27/2011] [Accepted: 06/08/2011] [Indexed: 12/11/2022]
Abstract
Extracellular adenosine triphosphate (eATP) is a potent molecule that has the capacity to modulate various aspects of cell functions including gene expression. This element of modulation is essential to the role of ATP as a therapeutic agent. The hypothesis presented is that ATP can have an important impact on the treatment of HIV infection. This is supported in part by published research, although a much greater role for ATP is suggested than prior authors ever thought possible. ATP has the ability to enhance the immune system and could thus improve the host's own defense mechanisms to eradicate the virus-infected cells and restore normal immune function. This could provide effective therapy when used in conjunction with highly active antiretroviral therapies (HAART) to eliminate the latently infected cells. The key lies in applying ATP through the methodology described. This article presents a strategy for using ATP therapeutically along with background evidence to substantiate the importance of using ATP in the treatment of HIV infection.
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Bardai GK, Hales BF, Sunahara GI. Developmental toxicity of glyceryl trinitrate in quail embryos. ACTA ACUST UNITED AC 2011; 91:230-40. [PMID: 21472843 DOI: 10.1002/bdra.20801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 02/02/2011] [Accepted: 02/04/2011] [Indexed: 11/08/2022]
Abstract
BACKGROUND Although glyceryl trinitrate (GTN) is used extensively to treat angina and heart failure, little is known about its effects on the conceptus during organogenesis. The goal of these studies was to investigate the effects of GTN in a model organism, the quail (Coturnix coturnix japonica) embryo. METHODS To identify the effects of GTN on quail embryo development, fertilized quail eggs (n = 10-12 eggs/group) were injected with GTN (0, 4.4, 44, or 440 μM) at Hamburger-Hamilton (HH) stage 0, 9, or 19 and examined 7 days later. Next, HH 9 embryos were injected with GTN (0, 0.88, 4.4, 8.8, 44, 88, and 440 μM, in 20 μL per egg) and examined 24-hours, 48-hours, or 72-hours postinjection. Finally, the developing eye on one side was exposed to GTN (44 μM) ex ovo and the tissue was probed for the presence of nitrated proteins. RESULTS In ovo GTN exposure induced a dose-dependent increase in the number of malformed viable quail embryos with a maximal effect in HH 9 embryos. Microphthalmia, craniofacial, heart, and neural tube defects were elevated in GTN-exposed embryos. An increase in nitrated proteins was observed in the developing eye region of embryos exposed ex ovo to GTN. CONCLUSIONS GTN treatment induced a variety of malformations in quail embryos. The presence of nitrated proteins suggests that organic nitrates, such as GTN, generate reactive nitrogen species. We hypothesize that GTN perturbations in the redox status of the embryo may underlie its developmental toxicity.
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Affiliation(s)
- Ghalib K Bardai
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
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Patel RP, Hogg N, Kim-Shapiro DB. The potential role of the red blood cell in nitrite-dependent regulation of blood flow. Cardiovasc Res 2010; 89:507-15. [PMID: 20952416 DOI: 10.1093/cvr/cvq323] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Nitrite was once thought to have little physiological relevance. However, nitrite is now being increasingly recognized as a therapeutic or possibly even physiological precursor of nitric oxide (NO) that is utilized when needed to increase blood flow. It is likely that different mechanisms for nitrite bioconversion occur in different tissues, but in the vascular system, there is evidence that erythrocyte haemoglobin (Hb) is responsible for the oxygen-dependent reduction of nitrite to modulate blood flow. Here, we review the complex chemical interactions of Hb and nitrite and discuss evidence supporting its role in vasodilation. We also discuss ongoing work focused on defining the precise mechanisms for export of NO activity from red blood cells and of other pathways that may mediate nitrite-dependent vasodilation.
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Affiliation(s)
- Rakesh P Patel
- Department of Pathology and Center for Free Radical Biology, University of Alabama, Birmingham, AL 35294, USA
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14
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Gilchrist M, Shore AC, Benjamin N. Inorganic nitrate and nitrite and control of blood pressure. Cardiovasc Res 2010; 89:492-8. [PMID: 20884639 DOI: 10.1093/cvr/cvq309] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Continual nitric oxide (NO) synthesis is important in the regulation of vascular tone and thus blood pressure. Whereas classically NO is provided by the enzymatic oxidation of l-arginine via endothelial NO synthase, it is now clear that NO can also be generated in mammals from the reduction of nitrite and nitrate. Thus inorganic nitrate derived either from NO oxidation or from dietary sources may be an important storage form of reactive nitrogen oxides which can be reduced back to nitrite and NO when physiologically required or in pathological conditions. The very short half-life of NO and the ready availability of stored nitrite and nitrate make for a very sensitive and responsive blood pressure control system. This review will examine processes by which these storage forms are produced and how augmentation of dietary nitrate intake may have a beneficial effect on blood pressure and other vascular function in humans.
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Affiliation(s)
- Mark Gilchrist
- Diabetes and Vascular Medicine, Institute of Biomedical and Clinical Science, Peninsula College of Medicine and Dentistry, University of Exeter, Barrack Road, Exeter EX2 5AX, UK.
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15
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Daiber A, Münzel T, Gori T. Organic nitrates and nitrate tolerance--state of the art and future developments. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2010; 60:177-227. [PMID: 21081219 DOI: 10.1016/b978-0-12-385061-4.00007-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The hemodynamic and antiischemic effects of nitroglycerin (GTN) are lost upon chronic administration due to the rapid development of nitrate tolerance. The mechanism of this phenomenon has puzzled several generations of scientists, but recent findings have led to novel hypotheses. The formation of reactive oxygen and nitrogen species in the mitochondria and the subsequent inhibition of the nitrate-bioactivating enzyme mitochondrial aldehyde dehydrogenase (ALDH-2) appear to play a central role, at least for GTN, that is, bioactivated by ALDH-2. Importantly, these findings provide the opportunity to reconcile the two "traditional" hypotheses of nitrate tolerance, that is, the one postulating a decreased bioactivation and the concurrent one suggesting a role of oxidative stress. Furthermore, recent animal and human experimental studies suggest that the organic nitrates are not a homogeneous group but demonstrate a broad diversity with regard to induction of vascular dysfunction, oxidative stress, and other side effects. In the past, attempts to avoid nitrate-induced side effects have focused on administration schedules that would allow a "nitrate-free interval"; in the future, the role of co-therapies with antioxidant compounds and of activation of endogeneous protective pathways such as the heme oxygenase 1 (HO-1) will need to be explored. However, the development of new nitrates, for example, tolerance-free aminoalkyl nitrates or combination of nitrate groups with established cardiovascular drugs like ACE inhibitors or AT(1)-receptor blockers (hybrid molecules) may be of great clinical interest.
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Affiliation(s)
- Andreas Daiber
- II. Medizinische Klinik, Labor für Molekulare Kardiologie und Abteilung für Kardiologie und Angiologie, Universitätsmedizin der Johannes-Gutenberg-Universität, Mainz, Germany
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