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Bringing Nitric Oxide to the Molybdenum World-A Personal Perspective. Molecules 2023; 28:5819. [PMID: 37570788 PMCID: PMC10420851 DOI: 10.3390/molecules28155819] [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: 07/10/2023] [Revised: 07/29/2023] [Accepted: 07/30/2023] [Indexed: 08/13/2023] Open
Abstract
Molybdenum-containing enzymes of the xanthine oxidase (XO) family are well known to catalyse oxygen atom transfer reactions, with the great majority of the characterised enzymes catalysing the insertion of an oxygen atom into the substrate. Although some family members are known to catalyse the "reverse" reaction, the capability to abstract an oxygen atom from the substrate molecule is not generally recognised for these enzymes. Hence, it was with surprise and scepticism that the "molybdenum community" noticed the reports on the mammalian XO capability to catalyse the oxygen atom abstraction of nitrite to form nitric oxide (NO). The lack of precedent for a molybdenum- (or tungsten) containing nitrite reductase on the nitrogen biogeochemical cycle contributed also to the scepticism. It took several kinetic, spectroscopic and mechanistic studies on enzymes of the XO family and also of sulfite oxidase and DMSO reductase families to finally have wide recognition of the molybdoenzymes' ability to form NO from nitrite. Herein, integrated in a collection of "personal views" edited by Professor Ralf Mendel, is an overview of my personal journey on the XO and aldehyde oxidase-catalysed nitrite reduction to NO. The main research findings and the path followed to establish XO and AO as competent nitrite reductases are reviewed. The evidence suggesting that these enzymes are probable players of the mammalian NO metabolism is also discussed.
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Positive feedback loop between dietary nitrate intake and oral health. Nutr Res 2023; 115:1-12. [PMID: 37207592 DOI: 10.1016/j.nutres.2023.04.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 04/12/2023] [Accepted: 04/22/2023] [Indexed: 05/21/2023]
Abstract
Nitrate was once thought to be an inert end-product of endothelial-derived nitric oxide (NO) heme oxidation; however, this view has been radically revised over the past few decades. Following the clarification of the nitrate-nitrite-NO pathway, accumulated evidence has shown that nitrate derived from the diet is a supplementary source of endogenous NO generation, playing important roles in a variety of pathological and physiological conditions. However, the beneficial effects of nitrate are closely related with oral health, and oral dysfunction has an adverse effect on nitrate metabolism and further impacts overall systemic health. Moreover, an interesting positive feedback loop has been identified between dietary nitrate intake and oral health. Dietary nitrate's beneficial effect on oral health may further improve its bioavailability and promote overall systemic well-being. This review aims to provide a detailed description of the functions of dietary nitrate, with an emphasis on the key role oral health plays in nitrate bioavailability. This review also provides recommendations for a new paradigm that includes nitrate therapy in the treatment of oral diseases.
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Therapy for Pulmonary Arterial Hypertension: Glance on Nitric Oxide Pathway. Front Pharmacol 2021; 12:767002. [PMID: 34867394 PMCID: PMC8633825 DOI: 10.3389/fphar.2021.767002] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 10/25/2021] [Indexed: 01/11/2023] Open
Abstract
Pulmonary arterial hypertension (PAH) is a severe disease with a resultant increase of the mean pulmonary arterial pressure, right ventricular hypertrophy and eventual death. Research in recent years has produced various therapeutic options for its clinical management but the high mortality even under treatment remains a big challenge attributed to the complex pathophysiology. Studies from clinical and non-clinical experiments have revealed that the nitric oxide (NO) pathway is one of the key pathways underlying the pathophysiology of PAH. Many of the essential drugs used in the management of PAH act on this pathway highlighting its significant role in PAH. Meanwhile, several novel compounds targeting on NO pathway exhibits great potential to become future therapy medications. Furthermore, the NO pathway is found to interact with other crucial pathways. Understanding such interactions could be helpful in the discovery of new drug that provide better clinical outcomes.
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Innovative Anti-Inflammatory and Pro-resolving Strategies for Pulmonary Hypertension: High Blood Pressure Research Council of Australia Award 2019. Hypertension 2021; 78:1168-1184. [PMID: 34565184 DOI: 10.1161/hypertensionaha.120.14525] [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] [Indexed: 11/16/2022]
Abstract
Pulmonary hypertension is a rare, ostensibly incurable, and etiologically diverse disease with an unacceptably high 5-year mortality rate (≈50%), worse than many cancers. Irrespective of pathogenic origin, dysregulated immune processes underlie pulmonary hypertension pathobiology, particularly pertaining to pulmonary vascular remodeling. As such, a variety of proinflammatory pathways have been mooted as novel therapeutic targets. One such pathway involves the family of innate immune regulators known as inflammasomes. In addition, a new and emerging concept is differentiating between anti-inflammatory approaches versus those that promote pro-resolving pathways. This review will briefly introduce inflammasomes and examine recent literature concerning their role in pulmonary hypertension. Moreover, it will explore the difference between inflammation-suppressing and pro-resolution approaches and how this links to inflammasomes. Finally, we will investigate new avenues for targeting inflammation in pulmonary hypertension via more targeted anti-inflammatory or inflammation resolving strategies.
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Novel Experimental Therapies for Treatment of Pulmonary Arterial Hypertension. J Exp Pharmacol 2021; 13:817-857. [PMID: 34429666 PMCID: PMC8380049 DOI: 10.2147/jep.s236743] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Accepted: 07/07/2021] [Indexed: 12/18/2022] Open
Abstract
Pulmonary arterial hypertension (PAH) is a progressive and devastating disease characterized by pulmonary artery vasoconstriction and vascular remodeling leading to vascular rarefaction with elevation of pulmonary arterial pressures and pulmonary vascular resistance. Often PAH will cause death from right heart failure. Current PAH-targeted therapies improve functional capacity, pulmonary hemodynamics and reduce hospitalization. Nevertheless, today PAH still remains incurable and is often refractory to medical therapy, underscoring the need for further research. Over the last three decades, PAH has evolved from a disease of unknown pathogenesis devoid of effective therapy to a condition whose cellular, genetic and molecular underpinnings are unfolding. This article provides an update on current knowledge and summarizes the progression in recent advances in pharmacological therapy in PAH.
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Preventive effects of nitrate-rich beetroot juice supplementation on monocrotaline-induced pulmonary hypertension in rats. PLoS One 2021; 16:e0249816. [PMID: 33831045 PMCID: PMC8031446 DOI: 10.1371/journal.pone.0249816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 03/26/2021] [Indexed: 11/18/2022] Open
Abstract
Beetroot (Beta vulgaris L.) has a high level of nitrate; therefore, its dietary intake could increase nitric oxide (NO) level in the body, possibly preventing the development of pulmonary hypertension (PH). In this study, we examined the effects of beetroot juice (BJ) supplementation on PH and the contribution of nitrate to such effects using a rat model of monocrotaline (MCT, 60 mg/kg s.c.)-induced PH. Rats were injected subcutaneously with saline or 60 mg/kg MCT and were sacrificed 28 days after the injection. In some rats injected with MCT, BJ was supplemented from the day of MCT injection to the day of sacrifice. First, MCT-induced right ventricular systolic pressure elevation, pulmonary arterial medial thickening and muscularization, and right ventricular hypertrophy were suppressed by supplementation with low-dose BJ (nitrate: 1.3 mmol/L) but not high-dose BJ (nitrate: 4.3 mmol/L). Of the plasma nitrite, nitrate, and their sum (NOx) levels, only the nitrate levels were found to be increased by the high-dose BJ supplementation. Second, in order to clarify the possible involvement of nitrate in the preventive effects of BJ on PH symptoms, the effects of nitrate-rich BJ (nitrate: 0.9 mmol/L) supplementation were compared with those of the nitrate-depleted BJ. While the former exerted preventive effects on PH symptoms, such effects were not observed in rats supplemented with nitrate-depleted BJ. Neither supplementation with nitrate-rich nor nitrate-depleted BJ affected plasma nitrite, nitrate, and NOx levels. These findings suggest that a suitable amount of BJ ingestion, which does not affect systemic NO levels, can prevent the development of PH in a nitrate-dependent manner. Therefore, BJ could be highly useful as a therapy in patients with PH.
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Abstract
Pulmonary arterial hypertension (PAH) is a chronic and progressive disorder
characterized by vascular remodeling of the small pulmonary arteries, resulting
in elevated pulmonary vascular resistance and ultimately, right ventricular
failure. Expanded understanding of PAH pathophysiology as it pertains to the
nitric oxide (NO), prostacyclin (prostaglandin I2) (PGI2)
and endothelin-1 pathways has led to recent advancements in targeted drug
development and substantial improvements in morbidity and mortality. There are
currently several classes of drugs available to target these pathways including
phosphodiesterase-5 inhibitors (PDE5i), soluble guanylate cyclase (sGC)
stimulators, prostacyclin class agents and endothelin receptor antagonists
(ERAs). Combination therapy in PAH, either upfront or sequentially, has become a
widely adopted treatment strategy, allowing for simultaneous targeting of more
than one of these signaling pathways implicated in disease progression. Much of
the current treatment landscape has focused on initial combination therapy with
ambrisentan and tadalafil, an ERA and PDE5I respectively, following results of
the AMBITION study demonstrating combination to be superior to either agent
alone as upfront therapy. Consequently, clinicians often consider combination
therapy with other drugs and drug classes, as deemed clinically appropriate, for
patients with PAH. An alternative regimen that targets the NO and
PGI2 pathways has been adopted by some clinicians as an effective
and sometimes preferred therapeutic combination for PAH. Although there is a
paucity of prospective data, preclinical data and results from secondary data
analysis of clinical studies targeting these pathways may provide novel insights
into this alternative combination as a reasonable, and sometimes preferred,
alternative approach to combination therapy in PAH. This review of preclinical
and clinical data will discuss the current understanding of combination therapy
that simultaneously targets the NO and PGI2 signaling pathways,
highlighting the clinical advantages and theoretical biochemical interplay of
these agents.
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Tracing the path of inhaled nitric oxide: Biological consequences of protein nitrosylation. Pediatr Pulmonol 2021; 56:525-538. [PMID: 33289321 DOI: 10.1002/ppul.25201] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 10/28/2020] [Accepted: 11/29/2020] [Indexed: 12/12/2022]
Abstract
Nitric oxide (NO) is a comprehensive regulator of vascular and airway tone. Endogenous NO produced by nitric oxide synthases regulates multiple signaling cascades, including activation of soluble guanylate cyclase to generate cGMP, relaxing smooth muscle cells. Inhaled NO is an established therapy for pulmonary hypertension in neonates, and has been recently proposed for the treatment of hypoxic respiratory failure and acute respiratory distress syndrome due to COVID-19. In this review, we summarize the effects of endogenous and exogenous NO on protein S-nitrosylation, which is the selective and reversible covalent attachment of a nitrogen monoxide group to the thiol side chain of cysteine. This posttranslational modification targets specific cysteines based on the acid/base sequence of surrounding residues, with significant impacts on protein interactions and function. S-nitrosothiol (SNO) formation is tightly compartmentalized and enzymatically controlled, but also propagated by nonenzymatic transnitrosylation of downstream protein targets. Redox-based nitrosylation and denitrosylation pathways dynamically regulate the equilibrium of SNO-proteins. We review the physiological roles of SNO proteins, including nitrosohemoglobin and autoregulation of blood flow through hypoxic vasodilation, and pathological effects of nitrosylation including inhibition of critical vasodilator enzymes; and discuss the intersection of NO source and dose with redox environment, in determining the effects of protein nitrosylation.
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Bronchopulmonary dysplasia is associated with reduced oral nitrate reductase activity in extremely preterm infants. Redox Biol 2020; 38:101782. [PMID: 33166868 PMCID: PMC7658701 DOI: 10.1016/j.redox.2020.101782] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 10/27/2020] [Accepted: 10/29/2020] [Indexed: 01/08/2023] Open
Abstract
Oral microbiome mediated nitrate reductase (NR) activity regulates nitric oxide (NO) bioavailability and signaling. While deficits in NO-bioavailability impact several morbidities of extreme prematurity including bronchopulmonary dysplasia (BPD), whether oral NR activity is associated with morbidities of prematurity is not known. We characterized NR activity in extremely preterm infants from birth until 34 weeks' post menstrual age (PMA), determined whether changes in the oral microbiome contribute to changes in NR activity, and determined whether changes in NR activity correlated with disease. In this single center prospective cohort study (n = 28), we observed two surprising findings: (1) NR activity unexpectedly peaked at 29 weeks' PMA (p < 0.05) and (2) when infants were stratified for BPD status, infants who developed BPD had significantly less NR activity at 29 weeks' PMA compared to infants who did not develop BPD. Oral microbiota and NR activity may play a role in BPD development in extremely preterm infants, indicating potential for disease prediction and therapeutic targeting.
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Airway nitrite is increased in extremely preterm infants with bronchopulmonary dysplasia. Respir Res 2020; 21:244. [PMID: 32957939 PMCID: PMC7504869 DOI: 10.1186/s12931-020-01508-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 09/13/2020] [Indexed: 11/10/2022] Open
Abstract
RATIONALE Bronchopulmonary dysplasia (BPD) is the most common complication of prematurity and significantly contributes to mortality and morbidity with few predictive biomarkers. Given that nitrites have been implicated in pathways associated with lung disease, we hypothesized that nitrite levels would be altered in the airways of premature infants diagnosed with BPD. METHODS This was a prospective cohort study of extremely low birth infants (< 28 weeks' gestation) at the University of Alabama at Birmingham. Nitrite levels from tracheal aspirates (TAs) were compared between intubated and ventilated infants with BPD and gestation matched full term (FT) controls. TA derived nitrite levels from day one after birth were also compared between preterm infants who did and did not develop BPD. RESULTS Infants with BPD were found to have significantly elevated nitrite levels in their tracheal aspirates compared to gestation matched FT controls (p < 0.05). There was a trend for increased nitrite levels on postnatal day one in infants that developed BPD compared to infants that did not develop BPD (p = 0.05). CONCLUSIONS In conclusion, nitrite levels are significantly increased in airways of infants with BPD. Data from a larger cohort are needed to further support the utility of nitrite for BPD prediction. TRIAL REGISTRATION Not applicable.
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Nutraceuticals in the Treatment of Pulmonary Arterial Hypertension. Int J Mol Sci 2020; 21:E4827. [PMID: 32650586 PMCID: PMC7402298 DOI: 10.3390/ijms21144827] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 06/13/2020] [Accepted: 07/01/2020] [Indexed: 12/11/2022] Open
Abstract
Pulmonary arterial hypertension (PAH) is a severe disease characterized by the loss and obstructive remodeling of the pulmonary arterial wall, causing a rise in pulmonary arterial pressure and pulmonary vascular resistance, which is responsible for right heart failure, functional decline, and death. Although many drugs are available for the treatment of this condition, it continues to be life-threatening, and its long-term treatment is expensive. On the other hand, many natural compounds present in food have beneficial effects on several cardiovascular conditions. Several studies have explored many of the potential beneficial effects of natural plant products on PAH. However, the mechanisms by which natural products, such as nutraceuticals, exert protective and therapeutic effects on PAH are not fully understood. In this review, we analyze the current knowledge on nutraceuticals and their potential use in the protection and treatment of PAH, as well as whether nutraceuticals could enhance the effects of drugs used in PAH through similar mechanisms.
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The Noncanonical Pathway for In Vivo Nitric Oxide Generation: The Nitrate-Nitrite-Nitric Oxide Pathway. Pharmacol Rev 2020; 72:692-766. [DOI: 10.1124/pr.120.019240] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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Mechanisms of the protective effects of nitrate and nitrite in cardiovascular and metabolic diseases. Nitric Oxide 2020; 96:35-43. [PMID: 31954804 DOI: 10.1016/j.niox.2020.01.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/18/2019] [Accepted: 01/13/2020] [Indexed: 12/28/2022]
Abstract
Within the body, NO is produced by nitric oxide synthases via converting l-arginine to citrulline. Additionally, NO is also produced via the NOS-independent nitrate-nitrite-NO pathway. Unlike the classical pathway, the nitrate-nitrite-NO pathway is oxygen independent and viewed as a back-up function to ensure NO generation during ischaemia/hypoxia. Dietary nitrate and nitrite have emerged as substrates for endogenous NO generation and other bioactive nitrogen oxides with promising protective effects on cardiovascular and metabolic function. In brief, inorganic nitrate and nitrite can decrease blood pressure, protect against ischaemia-reperfusion injury, enhance endothelial function, inhibit platelet aggregation, modulate mitochondrial function and improve features of the metabolic syndrome. However, many questions regarding the specific mechanisms of these protective effects on cardiovascular and metabolic diseases remain unclear. In this review, we focus on nitrate/nitrite bioactivation, as well as the potential mechanisms for nitrate/nitrite-mediated effects on cardiovascular and metabolic diseases. Understanding how dietary nitrate and nitrite induce beneficial effect on cardiovascular and metabolic diseases could open up novel therapeutic opportunities in clinical practice.
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Abstract
The introduction of targeted agents into modern cancer therapy pursued the goal of molecularly more specific, and thereby more effective and safer, therapies. Paradoxically, however, several toxicities were brought to greater attention, among these not only cardiac but also vascular toxicities. The latter reach far beyond venous thromboembolism and include a broad spectrum of presentations based on the vascular territories and pathomechanisms involved, including abnormal vascular reactivity, acute thrombosis, or accelerated atherosclerosis. This article provides an overview of the most common presentations and their management strategies.
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Abstract
Significance: Redox homeostasis is finely tuned and governed by distinct intracellular mechanisms. The dysregulation of this either by external or internal events is a fundamental pathophysiologic base for many pulmonary diseases. Recent Advances: Based on recent discoveries, it is increasingly clear that cellular redox state and oxidation of signaling molecules are critical modulators of lung disease and represent a final common pathway that leads to poor respiratory outcomes. Critical Issues: Based on the wide variety of stimuli that alter specific redox signaling pathways, improved understanding of the disease and patient-specific alterations are needed for the development of therapeutic targets. Further Directions: For the full comprehension of redox signaling in pulmonary disease, it is essential to recognize the role of reactive oxygen intermediates in modulating biological responses. This review summarizes current knowledge of redox signaling in pulmonary development and pulmonary vascular disease.
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Nutraceuticals as a potential adjunct therapy toward improving vascular health in CKD. Am J Physiol Regul Integr Comp Physiol 2019; 317:R719-R732. [PMID: 31577157 DOI: 10.1152/ajpregu.00152.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Chronic kidney disease (CKD) is a major public health epidemic and increases risk for developing cardiovascular disease (CVD). Vascular dysfunction is a major independent risk factor toward increased risk for CVD in CKD. Several mechanisms have been postulated to result in vascular dysfunction in CKD, including oxidative stress-mediated inflammation by redox imbalance and reduced nitric oxide (NO) bioavailability and synthesis. Therefore, strategies that decrease oxidative stress and/or increase NO bioactivity may have major clinical implications toward improving vascular health and reducing the burden of CVD in CKD. Nutraceutical therapy in the form of polyphenols, dietary nitrates, or selective mitochondria-targeting therapies has recently been shown to improve vascular function by reducing oxidative stress and/or increasing NO bioavailability and synthesis. This review, therefore, highlights these three emerging nutraceuticals recently implicated in pathophysiological improvement of vascular function in CKD. This review also describes those pathophysiological mechanisms thought to be responsible for the beneficial effects on the vasculature and possible experimental considerations that may exist within human CKD populations. It is clear throughout this review that human-based mechanistic preclinical and health-related clinical studies are lacking regarding whether nutraceuticals do indeed improve vascular function in patients with CKD. As such, a comprehensive, detailed, and fully integrated understanding of nutraceuticals and vasculature function is necessary in patients with CKD. Many opportunities exist for original mechanistic and therapeutic discoveries and investigations on select nutraceuticals and their impact on vascular outcomes in patients with CKD, and these will remain exciting avenues of research in the future.
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Effects of inorganic nitrate in a rat model of monocrotaline-induced pulmonary arterial hypertension. Basic Clin Pharmacol Toxicol 2019; 126:99-109. [PMID: 31429204 DOI: 10.1111/bcpt.13309] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 08/11/2019] [Indexed: 12/27/2022]
Abstract
The nitrate-nitrite-nitric oxide (NO) pathway represents an alternative source of NO generation, which is independent of NO synthase and potentiated by hypoxia. Augmentation of this pathway by dietary nitrate has proven favourable effects in several cardiovascular disease models. However, less is known regarding its potential value in pulmonary arterial hypertension (PAH). The aim of this study was to assess the effects of oral inorganic nitrate administration in monocrotaline (MCT)-induced PAH. Male 12-week-old Wistar rats were injected subcutaneously with monocrotaline (MCT, 60 mg/kg). Nitrate treatment (0.3 or 1 mmol/kg/d; drinking water) commenced on day 12 following the MCT injection and continued for 16 days. Nitrate administration did not attenuate right ventricular (RV) hypertrophy, increased lung weight and up-regulated mRNA expression of brain natriuretic peptide. Plasma nitrate and nitrite levels were significantly increased as well as lung nitrate level, whereas nitrite lung level was decreased following nitrate treatment (1 mmol/kg/d). MCT-induced PAH resulted in an increased MnSOD protein level, which was not observed following nitrate treatment. MCT-associated up-regulation of nNOS in the lung appeared to be dose-dependently prevented by nitrate treatment. Western blot analysis did not reveal any differences in eNOS, iNOS, XO or gp91phox expression in the lungs among the groups. In conclusion, nitrate treatment did not significantly attenuate pathological RV and lung remodelling in the rat MCT model of PAH. The suppression of MnSOD and nNOS expression by nitrate could be interpreted as reduced demand of endogenous antioxidant defence in this model.
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Things We "kNOw" and Do Not "kNOw" about Pulmonary Hypertension. Am J Respir Crit Care Med 2019; 198:151-152. [PMID: 29590535 DOI: 10.1164/rccm.201803-0424ed] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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ITE promotes hypoxia-induced transdifferentiation of human pulmonary arterial endothelial cells possibly by activating transforming growth factor-β/Smads and MAPK/ERK pathways. J Cell Biochem 2019; 120:19567-19577. [PMID: 31297875 DOI: 10.1002/jcb.29264] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 06/13/2019] [Indexed: 01/07/2023]
Abstract
This study aimed to investigate the transdifferentiation of human pulmonary arterial endothelial cells (HPAECs) into smooth muscle like (SM-like) cells under hypoxic conditions and reveal the role of endogenous small molecular compound 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylicacid methyl ester (ITE) in this process. HPAECs were treated by hypoxia and hypoxia + ITE with different durations. The endothelial markers (CD31 and VE-cad) and smooth muscle markers (α-SMA, SM22α, and OPN) were investigated by immunofluorescence double staining, and their expressions, along with the differentiation regulators transforming growth factor-β (TGF-β) ligands and downstream signals including TGF-β1, bone morphogenetic protein (BMP2), BMP9, Samd2/3, ERK, and p38 MAPK, were determined by Western blot analysis. The viability and proliferation of HPAECs were detected by Cell Counting Kit-8 (CCK-8) method and bromodeoxyuridine (BrdU) assays. As a result, hypoxia induced HPAECs transdifferentiation from paving-stone-like into polygonal or spindle cells, whose number increased greatly after additional ITE stimulation for 7 days. Compared with the normoxic HPAECs, the expression of endothelial markers reduced and smooth muscle markers were enhanced with the extension of hypoxia + ITE treatment, and meanwhile the cell viability increased significantly. Hypoxia could promote expression of TGF-β1 protein rather than BMP2 and BMP9, and regulate phosphorylation levels of Samd2/3, ERK and p38 MAPK in different manners. In conclusion, ITE can promote the hypoxia-induced transdifferentiation of HPAECs into SM-like cells via TGF-β/Smads and MAPK/ERK pathways.
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Inhaled nebulized nitrite and nitrate therapy in a canine model of hypoxia-induced pulmonary hypertension. Nitric Oxide 2019; 91:1-14. [PMID: 31299340 DOI: 10.1016/j.niox.2019.07.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 06/17/2019] [Accepted: 07/02/2019] [Indexed: 12/12/2022]
Abstract
Dysfunction in the nitric oxide (NO) signaling pathway can lead to the development of pulmonary hypertension (PH) in mammals. Discovery of an alternative pathway to NO generation involving reduction from nitrate to nitrite and to NO has motivated the evaluation of nitrite as an alternative to inhaled NO for PH. In contrast, inhaled nitrate has not been evaluated to date, and potential benefits include a prolonged half-life and decreased risk of methemoglobinemia. In a canine model of acute hypoxia-induced PH we evaluated the effects of inhaled nitrate to reduce pulmonary arterial pressure (PAP). In a randomized controlled trial, inhaled nitrate was compared to inhaled nitrite and inhaled saline. Exhaled NO, PAP and systemic blood pressures were continuously monitored. Inhaled nitrite significantly decreased PAP and increased exhaled NO. In contrast, inhaled nitrate and inhaled saline did not decrease PAP or increase exhaled NO. Unexpectedly, we found that inhaled nitrite resulted in prolonged (>5 h) exhaled NO release, increase in nitrate venous/arterial levels and a late surge in venous nitrite levels. These findings do not support a therapeutic role for inhaled nitrate in PH but may have therapeutic implications for inhaled nitrite in various disease states.
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Mechanisms impairing blood pressure responses to nitrite and nitrate. Nitric Oxide 2019; 85:35-43. [PMID: 30716418 DOI: 10.1016/j.niox.2019.01.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 12/13/2018] [Accepted: 01/29/2019] [Indexed: 02/07/2023]
Abstract
Hypertension is a multifactorial disease associated with impaired nitric oxide (NO) production and bioavailability. In this respect, restoring NO activity by using nitrite and nitrate has been considered a potential therapeutic strategy to treat hypertension. This possibility is justified by the understanding that both nitrite and nitrate may be recycled back to NO and also promote the generation of other bioactive species. This process involves a complex biological circuit known as the enterosalivary cycle of nitrate, where this anion is actively taken up by the salivary glands and converted to nitrite by nitrate-reducing bacteria in the oral cavity. Nitrite is then ingested and reduced to NO and other nitroso species under the acid conditions of the stomach, whereas reminiscent nitrite that escapes gastric reduction is absorbed systemically and can be converted into NO by nitrite-reductases in tissues. While there is no doubt that nitrite and nitrate exert antihypertensive effects, several agents can impair the blood pressure responses to these anions by disrupting the enterosalivary cycle of nitrate. These agents include dietary and smoking-derived thiocyanate, antiseptic mouthwash, proton pump inhibitors, ascorbate at high concentrations, and xanthine oxidoreductase inhibitors. In this article, we provide an overview of the physiological aspects of nitrite and nitrate bioactivation and the therapeutic potential of these anions in hypertension. We also discuss mechanisms by which agents counteracting the antihypertensive responses to nitrite and nitrate mediate their effects. These critical aspects should be taken into consideration when suggesting nitrate or nitrite-based therapies to patients.
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Nitrite-stimulated Gastric Formation of S-nitrosothiols As An Antihypertensive Therapeutic Strategy. Curr Drug Targets 2019; 20:431-443. [DOI: 10.2174/1389450119666180816120816] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 07/24/2018] [Accepted: 08/07/2018] [Indexed: 12/14/2022]
Abstract
Hypertension is usually associated with deficient nitric oxide (NO) bioavailability, and therefore stimulating NO activity is an important antihypertensive strategy. Recently, many studies have shown that both nitrite and nitrate anions are not simple products of NO metabolism and indeed may be reduced back to NO. While enzymes with nitrite-reductase activity capable of generating NO from nitrite may contribute to antihypertensive effects of nitrite, another mechanism involving the generation of NO-related species in the stomach from nitrite has been validated. Under the acidic conditions of the stomach, nitrite generates NO-related species that form S-nitrosothiols. Conversely, drugs that increase gastric pH may impair the gastric formation of S-nitrosothiols, which may mediate antihypertensive effects of oral nitrite or nitrate. Therefore, it is now becoming clear that promoting gastric formation of S-nitrosothiols may result in effective antihypertensive responses, and this mechanism opens a window of opportunity in the therapy of hypertension. In this review, we discuss the recent studies supporting the gastric generation of S-nitrosothiols as a potential antihypertensive mechanism of oral nitrite. We also highlight some drugs that increase S-nitrosothiols bioavailability, which may also improve the responses to nitrite/nitrate therapy. This new approach may result in increased nitrosation of critical pharmacological receptors and enzymes involved in the pathogenesis of hypertension, which tend to respond less to their activators resulting in lower blood pressure.
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Effects of Beet Juice Supplementation on Monocrotaline-Induced Pulmonary Hypertension in Rats. Am J Hypertens 2019; 32:216-222. [PMID: 30265283 DOI: 10.1093/ajh/hpy144] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 09/27/2018] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Recently, attention has been focused on the cardiovascular protective effects of beet juice (BJ) with high amounts of nitrate. In this study, we examined the effect of BJ supplementation in a rat model of monocrotaline (MCT)-induced pulmonary hypertension (PH). METHODS MCT (60 mg/kg) was subcutaneously administered to rats, and BJ (prepared by dissolving BJ powder at a concentration of 1 g/l or 10 g/l in drinking water) supplementation was started from the day of, 1 week before, and 2 weeks after MCT injection. Saline-injected rats given drinking water were used as controls. RESULTS Low-dose BJ supplementation starting from the day of MCT injection exerted protective effects on the MCT-induced elevation of right ventricular systolic pressure, right ventricular hypertrophy, and pulmonary arterial remodeling, without causing a significant increase in plasma nitrite plus nitrate (NOx) levels. On the other hand, such beneficial effects were not observed with high-dose BJ supplementation, although the NOx levels were slightly higher than those in the low-dose group. In addition, low-dose BJ supplementation starting from 1 week before MCT injection did not improve PH symptoms, as described above. Furthermore, low-dose BJ supplementation starting from 2 weeks after MCT injection was ineffective against functional and morphological alterations in pulmonary circulation associated with MCT-induced PH. CONCLUSIONS Habitual ingestion of a suitable amount of BJ could be a potential option for preventing PH. However, beneficial effects cannot be expected when PH has developed to some degree.
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Sodium nitrite augments lung S-nitrosylation and reverses chronic hypoxic pulmonary hypertension in juvenile rats. Am J Physiol Lung Cell Mol Physiol 2018; 315:L742-L751. [DOI: 10.1152/ajplung.00184.2018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Deficient nitric oxide (NO) signaling plays a critical role in the pathogenesis of chronic neonatal pulmonary hypertension (PHT). Physiological NO signaling is regulated by S-nitrosothiols (SNOs), which act both as a reservoir for NO and as a reversible modulator of protein function. We have previously reported that therapy with inhaled NO (iNO) increased peroxynitrite-mediated nitration in the juvenile rat lung, although having minimal reversing effects on vascular remodeling. We hypothesized that sodium nitrite (NaNO2) would be superior to iNO in enhancing lung SNOs, thereby contributing to reversal of chronic hypoxic PHT. Rat pups were exposed to air or hypoxia (13% O2) from postnatal days 1 to 21. Dose-response prevention studies were conducted from days 1–21 to determine the optimal dose of NaNO2. Animals then received rescue therapy with daily subcutaneous NaNO2 (20 mg/kg), vehicle, or were continuously exposed to iNO (20 ppm) from days 14–21. Chronic PHT secondary to hypoxia was both prevented and reversed by treatment with NaNO2. Rescue NaNO2 increased lung NO and SNO contents to a greater extent than iNO, without causing nitration. Seven lung SNO proteins upregulated by treatment with NaNO2 were identified by multiplex tandem mass tag spectrometry, one of which was leukotriene A4 hydrolase (LTA4H). Rescue therapy with a LTA4H inhibitor, SC57461A (10 mg·kg−1·day−1 sc), partially reversed chronic hypoxic PHT. We conclude that NaNO2 was superior to iNO in increasing tissue NO and SNO generation and reversing chronic PHT, in part via upregulated SNO-LTA4H.
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Putting xanthine oxidoreductase and aldehyde oxidase on the NO metabolism map: Nitrite reduction by molybdoenzymes. Redox Biol 2018; 19:274-289. [PMID: 30196191 PMCID: PMC6129670 DOI: 10.1016/j.redox.2018.08.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Revised: 08/23/2018] [Accepted: 08/28/2018] [Indexed: 02/07/2023] Open
Abstract
Nitric oxide radical (NO) is a signaling molecule involved in several physiological and pathological processes and a new nitrate-nitrite-NO pathway has emerged as a physiological alternative to the "classic" pathway of NO formation from L-arginine. Since the late 1990s, it has become clear that nitrite can be reduced back to NO under hypoxic/anoxic conditions and exert a significant cytoprotective action in vivo under challenging conditions. To reduce nitrite to NO, mammalian cells can use different metalloproteins that are present in cells to perform other functions, including several heme proteins and molybdoenzymes, comprising what we denominated as the "non-dedicated nitrite reductases". Herein, we will review the current knowledge on two of those "non-dedicated nitrite reductases", the molybdoenzymes xanthine oxidoreductase and aldehyde oxidase, discussing the in vitro and in vivo studies to provide the current picture of the role of these enzymes on the NO metabolism in humans.
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Effects of Oral Supplementation With Nitrate-Rich Beetroot Juice in Patients With Pulmonary Arterial Hypertension-Results From BEET-PAH, an Exploratory Randomized, Double-Blind, Placebo-Controlled, Crossover Study. J Card Fail 2018; 24:640-653. [PMID: 30244181 DOI: 10.1016/j.cardfail.2018.09.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 09/06/2018] [Accepted: 09/13/2018] [Indexed: 12/26/2022]
Abstract
BACKGROUND The nitrate-nitrite-nitric oxide (NO) pathway may represent a potential therapeutic target in patients with pulmonary arterial hypertension (PAH). We explored the effects of dietary nitrate supplementation, with the use of nitrate-rich beetroot juice (BRJ), in patients with PAH. METHODS AND RESULTS We prospectively studied 15 patients with PAH in an exploratory randomized, double-blind, placebo-controlled, crossover trial. The patients received nitrate-rich beetroot juice (∼16 mmol nitrate per day) and placebo in 2 treatment periods of 7 days each. The assessments included; exhaled NO and NO flow-independent parameters (alveolar NO and bronchial NO flux), plasma and salivary nitrate and nitrite, biomarkers and metabolites of the NO-system, N-terminal pro-B-type natriuretic peptide, echocardiography, ergospirometry, diffusing capacity of the lung for carbon monoxide, and the 6-minute walk test. Compared with placebo ingestion of BRJ resulted in increases in; fractional exhaled NO at all flow-rates, alveolar NO concentrations and bronchial NO flux, and plasma and salivary levels of nitrate and nitrite. Plasma ornithine levels decreased and indices of relative arginine availability increased after BRJ compared to placebo. A decrease in breathing frequency was observed during ergospirometry after BRJ. A tendency for an improvement in right ventricular function was observed after ingestion of BRJ. In addition a tendency for an increase in the peak power output to peak oxygen consumption ratio (W peak/VO2 peak) was observed, which became significant in patients reaching an increase of plasma nitrite >30% (responders). CONCLUSIONS BRJ administered for 1 week increases pulmonary NO production and the relative arginine bioavailability in patients with PAH, compared with placebo. An increase in the W peak/VO2 peak ratio was observed after BRJ ingestion in plasma nitrite responders. These findings indicate that supplementation with inorganic nitrate increase NO synthase-independent NO production from the nitrate-nitrite-NO pathway.
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Mechanisms underlying blood pressure reduction by dietary inorganic nitrate. Acta Physiol (Oxf) 2018; 224:e13080. [PMID: 29694703 DOI: 10.1111/apha.13080] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 03/28/2018] [Accepted: 04/18/2018] [Indexed: 12/20/2022]
Abstract
Nitric oxide (NO) importantly contributes to cardiovascular homeostasis by regulating blood flow and maintaining endothelial integrity. Conversely, reduced NO bioavailability is a central feature during natural ageing and in many cardiovascular disorders, including hypertension. The inorganic anions nitrate and nitrite are endogenously formed after oxidation of NO synthase (NOS)-derived NO and are also present in our daily diet. Knowledge accumulated over the past two decades has demonstrated that these anions can be recycled back to NO and other bioactive nitrogen oxides via serial reductions that involve oral commensal bacteria and various enzymatic systems. Intake of inorganic nitrate, which is predominantly found in green leafy vegetables and beets, has a variety of favourable cardiovascular effects. As hypertension is a major risk factor of morbidity and mortality worldwide, much attention has been paid to the blood pressure reducing effect of inorganic nitrate. Here, we describe how dietary nitrate, via stimulation of the nitrate-nitrite-NO pathway, affects various organ systems and discuss underlying mechanisms that may contribute to the observed blood pressure-lowering effect.
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Inhaled nebulized sodium nitrite decreases pulmonary artery pressure in β-thalassemia patients with pulmonary hypertension. Nitric Oxide 2018; 76:174-178. [DOI: 10.1016/j.niox.2017.09.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 09/23/2017] [Accepted: 09/26/2017] [Indexed: 01/19/2023]
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Plasma nitrite/nitrate levels: a new biomarker for pulmonary arterial hypertension? Eur Respir J 2018; 48:1265-1267. [PMID: 27799378 DOI: 10.1183/13993003.01542-2016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 08/22/2016] [Indexed: 11/05/2022]
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A Brief Overview of Nitric Oxide and Reactive Oxygen Species Signaling in Hypoxia-Induced Pulmonary Hypertension. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 967:71-81. [PMID: 29047082 DOI: 10.1007/978-3-319-63245-2_6] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Pulmonary hypertension (PH) is characterized by increased vasoconstriction and smooth muscle cell hyperplasia driving pathological vascular remodeling of arterial vessels. In this short review, we discuss the primary source of reactive oxygen species (ROS) and nitric oxide (NO) relevant to PH and the mechanism by which dysregulation of their production contributes to PH. Specifically, hypoxia-induced PH is associated with diminished endothelial nitric oxide synthase (eNOS)-derived NO production and increased production of superoxide (O2•-) through eNOS uncoupling and defective mitochondrial respiration. This drives the inhibition of the NO/soluble guanylate cyclase (sGC) pathway and activation of the transcription factor hypoxia-inducible factor-1α (HIF-1α) with consequential dysregulation of the pulmonary vasculature. Therapeutics aimed at increasing NO or cGMP bioavailabilities are amenable to hypoxia disease-induced PH. Similarly, strategies targeting HIF-1α are now considered. Overall, pulmonary hypertension including hypoxia-induced PH offers unique opportunities for the rational development of therapeutics centered on modulating redox signaling.
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Nitrate, the oral microbiome, and cardiovascular health: a systematic literature review of human and animal studies. Am J Clin Nutr 2018; 107:504-522. [PMID: 29635489 DOI: 10.1093/ajcn/nqx046] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 11/21/2017] [Indexed: 12/25/2022] Open
Abstract
Background Dietary nitrate is an important source of nitric oxide (NO), a molecule critical for cardiovascular health. Nitrate is sequentially reduced to NO through an enterosalivary nitrate-nitrite-NO pathway that involves the oral microbiome. This pathway is considered an important adjunct pathway to the classical l-arginine-NO synthase pathway. Objective The objective of this study was to systematically assess the evidence for dietary nitrate intake and improved cardiovascular health from both human and animal studies. Design A systematic literature search was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines by using key search terms in Medline and EMBASE databases and defined inclusion and exclusion criteria. Results Thirty-seven articles on humans and 14 articles on animals were included from 12,541 screened references. Data on the effects of dietary nitrate on blood pressure, endothelial function, ischemic reperfusion injury, arterial stiffness, platelet function, and cerebral blood flow in both human and animal models were identified. Beneficial effects of nitrate on vascular health have predominantly been observed in healthy human populations, whereas effects in populations at risk of cardiovascular disease are less clear. Few studies have investigated the long-term effects of dietary nitrate on cardiovascular disease clinical endpoints. In animal studies, there is evidence that nitrate improves blood pressure and endothelial function, particularly in animal models with reduced NO bioavailability. Nitrate dose seems to be a critical factor because there is evidence of cross-talk between the 2 pathways of NO production. Conclusions Evidence for a beneficial effect in humans at risk of cardiovascular disease is limited. Furthermore, there is a need to investigate the long-term effects of dietary nitrate on cardiovascular disease clinical endpoints. Further animal studies are required to elucidate the mechanisms behind the observed effects.
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Integrin alpha5beta1 suppresses rBMSCs anoikis and promotes nitric oxide production. Biomed Pharmacother 2018; 99:1-8. [PMID: 29324307 DOI: 10.1016/j.biopha.2018.01.038] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Revised: 12/16/2017] [Accepted: 01/03/2018] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Cell based therapy has been heralded as a novel, promising therapeutic strategy for cardiovascular diseases including pulmonary arterial hypertension (PAH). However, the low survival rate after transplantation due to cell death via anoikis is a major obstacle in stem cell therapy. Cells adhesion via Integrin alpha5beta1 (ITGA5B1) has a tendency to exert higher maximum forces. The present study aimed to evaluate the potential protective effect of ITGA5B1 on rat bone marrow mesenchymal stem cells (rBMSCs) from anoikis. METHODS Mononuclear cells were isolated by density gradient centrifugation with Ficoll, and rBMSCs cell surface markers were evaluated by flow cytometry. Osteogenic and adipocyte differentiation was determined by Alizarin Red S and Oil Red O staining respectively. The expression of Integrin A5 (ITGA5), Integrin B1 (ITGB1), eNOS and actived-caspase-3 mRNA or protein was confirmed by qPCR and western-blot. Cell adhesion, cell viability, anoikis and the migration of rBMSCs were also evaluated. Nitric oxide (NO) production was detected by the greiss assay. RESULTS Co-infected with Integrin A5 and B1 lentivirus to rBMSCs increased ITGA5 and ITGB1 mRNA and protein expression. ITGA5B1 enhanced the cell adhesion, cell viability, cell migration and NO production but reduced the cell anoikis in rBMSCs/ITGA5B1 groups. CONCLUSION Transduction of rat rBMSCs with ITGA5B1 lentivirus could prevent cell anoikis and increase NO production.
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Abstract
BACKGROUND Nitrite has been shown to reduce right ventricle (RV) remodeling in experimental pulmonary hypertension. However, whether this effect is due to a reduction in RV afterload (ie, reduction in pulmonary artery pressure) or a direct effect on the RV itself remains unanswered. We hypothesize that nitrite has direct effects on RV remodeling and studied its effects in mice with pulmonary artery banding (PAB). METHODS AND RESULTS PAB decreased exercise tolerance and reduced RV systolic and diastolic function. Nitrite treatment attenuated the decrease in RV systolic function and improved the RV diastolic function. Nitrite-treated mice with PAB had similar exercise tolerance compared with a control group. PAB induced RV hypertrophy and fibrosis which were associated with increased expression of phospho-Akt. Interestingly, nitrite treatment attenuated PAB-induced RV hypertrophy and reduced the expression of phospho-Akt in RV tissue from mice with PAB. In neonatal rat cardiac fibroblast, nitrite also attenuated hypoxia-induced increase in expression of phospho-Akt. CONCLUSION Our study indicates that nitrite treatment has direct beneficial effects on RV and improves function and attenuates remodeling in RV exposed to chronic pressure overload. These beneficial effects, at least in part, could be due to the inhibition of the phospho-Akt (p-Akt) pathway activation.
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Abstract
Nitric oxide is an endogenous pulmonary vasodilator that is synthesized from L-arginine in pulmonary vascular endothelial cells by nitric oxide synthase and diffuses to adjacent vascular smooth muscle cells where it activates soluble guanylyl cyclase. This enzyme converts GTP to cGMP which activates cGMP dependent protein kinase leading to a series of events that decrease intracellular calcium and reduce vascular muscle tone. Nitric oxide is an important mediator of pulmonary vascular tone and vascular remodeling. A number of studies suggest that the bioavailability of nitric oxide is reduced in patients with pulmonary vascular disease and that augmentation of the nitric oxide/cGMP pathway may be an effective strategy for treatment. Several medications that target nitric oxide/cGMP signaling are now available for the treatment of pulmonary hypertension. This review explores the history of nitiric oxide research, describes the major NO synthetic and signaling pathways and discusses a variety of abnormalities in NO production and metabolism that may contribute to the pathophysiology of pulmonary vascular disease. A summary of the clinical use of presently available medications that target nitric oxide/cGMP signaling in the treatment of pulmonary hypertension is also presented.
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Abstract
Background In this double‐blind randomized placebo‐controlled crossover trial, we investigated whether oral sodium nitrate, when added to existing background medication, reduces exertional ischemia in patients with angina. Methods and Results Seventy patients with stable angina, positive electrocardiogram treadmill test, and either angiographic or functional test evidence of significant ischemic heart disease were randomized to receive oral treatment with either placebo or sodium nitrate (600 mg; 7 mmol) for 7 to 10 days, followed by a 2‐week washout period before crossing over to the other treatment (n=34 placebo‐nitrate, n=36 nitrate‐placebo). At baseline and at the end of each treatment, patients underwent modified Bruce electrocardiogram treadmill test, modified Seattle Questionnaire, and subgroups were investigated with dobutamine stress, echocardiogram, and blood tests. The primary outcome was time to 1 mm ST depression on electrocardiogram treadmill test. Compared with placebo, inorganic nitrate treatment tended to increase the primary outcome exercise time to 1 mm ST segment depression (645.6 [603.1, 688.0] seconds versus 661.2 [6183, 704.0] seconds, P=0.10) and significantly increased total exercise time (744.4 [702.4, 786.4] seconds versus 760.9 [719.5, 802.2] seconds, P=0.04; mean [95% confidence interval]). Nitrate treatment robustly increased plasma nitrate (18.3 [15.2, 21.5] versus 297.6 [218.4, 376.8] μmol/L, P<0.0001) and almost doubled circulating nitrite concentrations (346 [285, 405] versus 552 [398, 706] nmol/L, P=0.003; placebo versus nitrate treatment). Other secondary outcomes were not significantly altered by the intervention. Patients on antacid medication appeared to benefit less from nitrate supplementation. Conclusions Sodium nitrate treatment may confer a modest exercise capacity benefit in patients with chronic angina who are taking other background medication. Clinical Trial Registration URL: https://www.clinicaltrials.gov/. Unique identifier: NCT02078921. EudraCT number: 2012‐000196‐17.
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Blood collection vials and clinically used intravenous fluids contain significant amounts of nitrite. Free Radic Biol Med 2017; 108:533-541. [PMID: 28416347 DOI: 10.1016/j.freeradbiomed.2017.04.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 04/10/2017] [Accepted: 04/12/2017] [Indexed: 12/21/2022]
Abstract
The biology of the inorganic anion nitrite is linked to nitric oxide (NO) as nitrite can be reduced to NO and mediate its biological activities. Thus, studies of nitrite biology require sensitive and selective chemical assays. The acetic and ascorbic acids method is selective for nitrite and measures it in biological matrices. However, one of the pitfalls of nitrite measurements is its ubiquitous presence in sample collection tubes. Here, we showed high levels of nitrite in collection tubes containing EDTA, sodium citrate or sodium heparin and smaller amounts in tubes containing lithium heparin or serum clot activator. We also showed the presence of nitrite in colloid and crystalloid solutions frequently administered to patients and found variable levels of nitrite in 5% albumin, 0.9% sodium chloride, lactated ringer's, and dextrose-plus-sodium chloride solutions. These levels of nitrite varied across lots and manufacturers of the same type of fluid. Because these fluids are administered intravenously to patients (including those in shock), sometimes in large volumes (liters), it is possible that infusions of these nitrite-containing fluids may have clinical implications. A protocol for blood collection free of nitrite contamination was developed and used to examine nitrite levels in whole blood, red blood cells, plasma and urine from normal volunteers. Nitrite measurements were reproducible, had minimal variability, and did not indicate sex-differences. These findings validated a method and protocol for selective nitrite assay in biological fluids free of nitrite contamination which can be applied for study of diseases where dysfunctional NO signaling has been implicated.
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Enterosalivary nitrate metabolism and the microbiome: Intersection of microbial metabolism, nitric oxide and diet in cardiac and pulmonary vascular health. Free Radic Biol Med 2017; 105:48-67. [PMID: 27989792 PMCID: PMC5401802 DOI: 10.1016/j.freeradbiomed.2016.12.015] [Citation(s) in RCA: 102] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 11/18/2016] [Accepted: 12/12/2016] [Indexed: 02/07/2023]
Abstract
Recent insights into the bioactivation and signaling actions of inorganic, dietary nitrate and nitrite now suggest a critical role for the microbiome in the development of cardiac and pulmonary vascular diseases. Once thought to be the inert, end-products of endothelial-derived nitric oxide (NO) heme-oxidation, nitrate and nitrite are now considered major sources of exogenous NO that exhibit enhanced vasoactive signaling activity under conditions of hypoxia and stress. The bioavailability of nitrate and nitrite depend on the enzymatic reduction of nitrate to nitrite by a unique set of bacterial nitrate reductase enzymes possessed by specific bacterial populations in the mammalian mouth and gut. The pathogenesis of pulmonary hypertension (PH), obesity, hypertension and CVD are linked to defects in NO signaling, suggesting a role for commensal oral bacteria to shape the development of PH through the formation of nitrite, NO and other bioactive nitrogen oxides. Oral supplementation with inorganic nitrate or nitrate-containing foods exert pleiotropic, beneficial vascular effects in the setting of inflammation, endothelial dysfunction, ischemia-reperfusion injury and in pre-clinical models of PH, while traditional high-nitrate dietary patterns are associated with beneficial outcomes in hypertension, obesity and CVD. These observations highlight the potential of the microbiome in the development of novel nitrate- and nitrite-based therapeutics for PH, CVD and their risk factors.
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Quercetin Inhibits Pulmonary Arterial Endothelial Cell Transdifferentiation Possibly by Akt and Erk1/2 Pathways. BIOMED RESEARCH INTERNATIONAL 2017; 2017:6147294. [PMID: 28428963 PMCID: PMC5385898 DOI: 10.1155/2017/6147294] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 02/18/2017] [Accepted: 02/23/2017] [Indexed: 12/20/2022]
Abstract
This study aimed to investigate the effects and mechanisms of quercetin on pulmonary arterial endothelial cell (PAEC) transdifferentiation into smooth muscle-like cells. TGF-β1-induced PAEC transdifferentiation models were applied to evaluate the pharmacological actions of quercetin. PAEC proliferation was detected with CCK8 method and BurdU immunocytochemistry. Meanwhile, the identification and transdifferentiation of PAECs were determined by FVIII immunofluorescence staining and α-SMA protein expression. The related mechanism was elucidated based on the levels of Akt and Erk1/2 signal pathways. As a result, quercetin effectively inhibited the TGF-β1-induced proliferation and transdifferentiation of the PAECs and activation of Akt/Erk1/2 cascade in the cells. In conclusion, quercetin is demonstrated to be effective for pulmonary arterial hypertension (PAH) probably by inhibiting endothelial transdifferentiation possibly via modulating Akt and Erk1/2 expressions.
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Functional pharmacological characterization of SER100 in cardiovascular health and disease. Br J Pharmacol 2016; 173:3386-3401. [PMID: 27667485 DOI: 10.1111/bph.13634] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 09/07/2016] [Accepted: 09/15/2016] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND AND PURPOSE SER100 is a selective nociceptin (NOP) receptor agonist with sodium-potassium-sparing aquaretic and anti-natriuretic activity. This study was designed to characterize the functional cardiovascular pharmacology of SER100 in vitro and in vivo, including experimental models of cardiovascular disease. EXPERIMENTAL APPROACH Haemodynamic, ECG parameters and heart rate variability (HRV) were determined using radiotelemetry in healthy, conscious mice. The haemodynamic and vascular effects of SER100 were also evaluated in two models of cardiovascular disease, spontaneously hypertensive rats (SHR) and murine hypoxia-induced pulmonary hypertension (PH). To elucidate mechanisms underlying the pharmacology of SER100, acute blood pressure recordings were performed in anaesthetized mice, and the reactivity of rodent aorta and mesenteric arteries in response to electrical- and agonist-stimulation assessed. KEY RESULTS SER100 caused NOP receptor-dependent reductions in mean arterial blood pressure and heart rate that were independent of NO. The hypotensive and vasorelaxant actions of SER100 were potentiated in SHR compared with Wistar Kyoto. Moreover, SER100 reduced several indices of disease severity in experimental PH. Analysis of HRV indicated that SER100 decreased the low/high frequency ratio, an indicator of sympatho-vagal balance, and in electrically stimulated mouse mesenteric arteries SER100 inhibited sympathetic-induced contractions. CONCLUSIONS AND IMPLICATIONS SER100 exerts a chronic hypotensive and bradycardic effects in rodents, including models of systemic and pulmonary hypertension. SER100 produces its cardiovascular effects, at least in part, by inhibition of cardiac and vascular sympathetic activity. SER100 may represent a novel therapeutic candidate in systemic and pulmonary hypertension.
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Potential Therapeutic Strategies for Hypertension-Exacerbated Cardiotoxicity of Anticancer Drugs. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2016; 2016:8139861. [PMID: 27829985 PMCID: PMC5086499 DOI: 10.1155/2016/8139861] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 09/20/2016] [Indexed: 01/01/2023]
Abstract
Despite their recognized cardiotoxic effects, anthracyclines remain an essential component in many anticancer regimens due to their superior antitumor efficacy. Epidemiologic data revealed that about one-third of cancer patients have hypertension, which is the most common comorbidity in cancer registries. The purpose of this review is to assess whether anthracycline chemotherapy exacerbates cardiotoxicity in patients with hypertension. A link between hypertension comorbidity and anthracycline-induced cardiotoxicity (AIC) was first suggested in 1979. Subsequent preclinical and clinical studies have supported the notion that hypertension is a major risk factor for AIC, along with the cumulative anthracycline dosage. There are several common or overlapping pathological mechanisms in AIC and hypertension, such as oxidative stress. Current evidence supports the utility of cardioprotective modalities as adjunct treatment prior to and during anthracycline chemotherapy. Several promising cardioprotective approaches against AIC pathologies include dexrazoxane, early hypertension management, and dietary supplementation of nitrate with beetroot juice or other medicinal botanical derivatives (e.g., visnagin and Danshen), which have both antihypertensive and anti-AIC properties. Future research is warranted to further elucidate the mechanisms of hypertension and AIC comorbidity and to conduct well-controlled clinical trials for identifying effective clinical strategies to improve long-term prognoses in this subgroup of cancer patients.
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Profiling nitric oxide metabolites in patients with idiopathic pulmonary arterial hypertension. Eur Respir J 2016; 48:1386-1395. [DOI: 10.1183/13993003.00245-2016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 06/22/2016] [Indexed: 11/05/2022]
Abstract
Intact nitric oxide (NO) signalling is critical to maintaining appropriate pulmonary vascular tone. NO bioavailability is reduced in patients with pulmonary arterial hypertension. This study aimed to examine the impact of NO plasma metabolites (NOx) relative to haemodynamic dysfunction and mortality in patients with idiopathic pulmonary arterial hypertension (IPAH).A total of 104 consecutive adult IPAH patients who had undergone genetic counselling when first diagnosed were enrolled in this prospective study.The median concentration of NOx (μmol·L−1) was significantly lower in IPAH patients compared with healthy subjects, and was decreased further in 19 carriers of the bone morphogenetic protein-receptor type-2 (BMPR2) mutation compared to non-carriers. Reduced concentrations of NOx were correlated with mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance (PVR) and cardiac output. Compared with higher baseline NOx concentrations, patients with a NOx concentration of ≤10 μmol·L−1 had a markedly worse survival. After adjustment for clinical features, a BMPR2 mutation and haemodynamics, a lower NOx level remained an increased risk of mortality.Patients with IPAH had lower levels of plasma NOx, which correlated inversely with mPAP, PVR and survival. Plasma NOx may be an important biomarker and prognostic indicator, suggesting that reduced NO synthesis contributes to the pathogenesis of IPAH.
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Oxidative and nitrosative signalling in pulmonary arterial hypertension — Implications for development of novel therapies. Pharmacol Ther 2016; 165:50-62. [DOI: 10.1016/j.pharmthera.2016.05.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Abstract
Since the late 1990s, there has been a steady decline in cancer-related mortality, in part related to the introduction of so-called targeted therapies. Intended to interfere with a specific molecular pathway, these therapies have, paradoxically, led to a number of effects off their intended cancer tissue or molecular targets. The latest examples are tyrosine kinase inhibitors targeting the Philadelphia Chromosome mutation product, which have been associated with progressive atherosclerosis and acute vascular events. In addition, agents designed to interfere with the vascular growth factor signaling pathway have vascular side effects ranging from hypertension to arterial events and cardiomyocyte toxicity. Interestingly, the risk of cardiotoxicity with drugs such as trastuzumab is predicted by preexisting cardiovascular risk factors and disease, posing the question of a vascular component to the pathophysiology. The effect on the coronary circulation has been the leading explanation for the cardiotoxicity of 5-fluorouracil and may be the underlying the mechanism of presentation of apical ballooning syndrome with various chemotherapeutic agents. Classical chemotherapeutic agents such as cisplatin, often used in combination with bleomycin and vinca alkaloids, can lead to vascular events including acute coronary thrombosis and may be associated with an increased long-term cardiovascular risk. This review is intended to provide an update on the evolving spectrum of vascular toxicities with cancer therapeutics, particularly as they pertain to clinical practice, and to the conceptualization of cardiovascular diseases, as well. Vascular toxicity with cancer therapy: the old and the new, an evolving avenue.
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Dietary Nitrate and the Epidemiology of Cardiovascular Disease: Report From a National Heart, Lung, and Blood Institute Workshop. J Am Heart Assoc 2016; 5:e003402. [PMID: 27385425 PMCID: PMC5015377 DOI: 10.1161/jaha.116.003402] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Punicalagin Prevents Hypoxic Pulmonary Hypertension via Anti-Oxidant Effects in Rats. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2016; 44:785-801. [PMID: 27222062 DOI: 10.1142/s0192415x16500439] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Punicalagin (PG), a major bioactive ingredient in pomegranate juice, has been proven to have anti-oxidative stress properties and to exert protective effects on acute lung injuries induced by lipopolysaccharides. This study aimed to investigate the effects of PG treatment on hypoxic pulmonary hypertension (HPH) and the underlying mechanisms responsible for the effects. Rats were exposed to 10% oxygen for 2 wk (8 h/day) to induce the HPH model. PG (5, 15, 45[Formula: see text]mg/kg) was orally administered 10[Formula: see text]min before hypoxia each day. PG treatments at the doses of 15 and 45[Formula: see text]mg/kg/d decreased the mean pulmonary arterial pressure (mPAP) and alleviated right ventricular hypertrophy and vascular remodeling in HPH rats. Meanwhile, PG treatment attenuated the hypoxia-induced endothelial dysfunction of pulmonary artery rings. The beneficial effects of PG treatment were associated with improved nitric oxide (NO)-cGMP signaling and reduced oxidative stress, as evidenced by decreased superoxide generation, gp91[Formula: see text] expression and nitrotyrosine content in the pulmonary arteries. Furthermore, tempol’s scavenging of oxidative stress also increased NO production and attenuated endothelial dysfunction and pulmonary hypertension in HPH rats. Combining tempol and PG did not exert additional beneficial effects compared to tempol alone. Our study indicated for the first time that PG treatment can protect against hypoxia-induced endothelial dysfunction and pulmonary hypertension in rats, which may be induced via its anti-oxidant actions.
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It is rocket science - why dietary nitrate is hard to 'beet'! Part II: further mechanisms and therapeutic potential of the nitrate-nitrite-NO pathway. Br J Clin Pharmacol 2016; 83:140-151. [PMID: 26914827 DOI: 10.1111/bcp.12918] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 02/17/2016] [Indexed: 12/14/2022] Open
Abstract
Dietary nitrate (found in green leafy vegetables such as rocket and in beetroot) is now recognized to be an important source of nitric oxide, via the nitrate-nitrite-NO pathway. Dietary nitrate confers several cardiovascular beneficial effects on blood pressure, platelets, endothelial function, mitochondrial efficiency and exercise. Having described key twists and turns in the elucidation of the pathway and the underlying mechanisms in Part I, we explore the more recent developments which have served to confirm mechanisms, extend our understanding, and discover new properties and potential therapeutic uses of the pathway in Part II. Even the established dependency on low oxygen states for bioactivation of nitrite has recently been challenged. Dietary nitrate appears to be an important component of 'healthy diets', such as the DASH diet to lower blood pressure and the Mediterranean diet, with its potential to lower cardiovascular risk, possibly through beneficial interactions with a range of other constituents. The World Cancer Research Foundation report strong evidence for vegetables including spinach and lettuce (high nitrate-containing) decreasing cancer risk (mouth, pharynx, larynx, oesophagus and stomach), summarized in a 'Nitrate-Cancer Risk Veg-Table'. The European Space Agency recommends that beetroot, lettuce, spinach and rocket (high-nitrate vegetables) are grown to provide food for long-term space missions. Nitrate, an ancient component of rocket fuel, could support sustainable crops for healthy humans.
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Abstract
Patients with pulmonary hypertension (PH) are at high risk for complications in the perioperative setting and often receive vasodilators to control elevated pulmonary artery pressure (PAP). Administration of vasodilators via inhalation is an effective strategy for reducing PAP while avoiding systemic side effects, chiefly hypotension. The prototypical inhaled pulmonary-specific vasodilator, nitric oxide (NO), has a proven track record but is expensive and cumbersome to implement. Alternatives to NO, including prostanoids (such as epoprostenol, iloprost, and treprostinil), NO-donating drugs (sodium nitroprusside, nitroglycerin, and nitrite), and phosphodiesterase inhibitors (milrinone, sildenafil) may be given via inhalation for the purpose of treating elevated PAP. This review will focus on the perioperative therapy of PH using inhaled vasodilators.
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Abstract
Nitric oxide (NO) is generated endogenously by NO synthases to regulate a number of physiological processes including cardiovascular and metabolic functions. A decrease in the production and bioavailability of NO is a hallmark of many major chronic diseases including hypertension, ischaemia-reperfusion injury, atherosclerosis and diabetes. This NO deficiency is mainly caused by dysfunctional NO synthases and increased scavenging of NO by the formation of reactive oxygen species. Inorganic nitrate and nitrite are emerging as substrates for in vivo NO synthase-independent formation of NO bioactivity. These anions are oxidation products of endogenous NO generation and are also present in the diet, with green leafy vegetables having a high nitrate content. The effects of nitrate and nitrite are diverse and include vasodilatation, improved endothelial function, enhanced mitochondrial efficiency and reduced generation of reactive oxygen species. Administration of nitrate or nitrite in animal models of cardiovascular disease shows promising results, and clinical trials are currently ongoing to investigate the therapeutic potential of nitrate and nitrite in hypertension, pulmonary hypertension, peripheral artery disease and myocardial infarction. In addition, the nutritional aspects of the nitrate-nitrite-NO pathway are interesting as diets suggested to protect against cardiovascular disease, such as the Mediterranean diet, are especially high in nitrate. Here, we discuss the potential therapeutic opportunities for nitrate and nitrite in prevention and treatment of cardiovascular and metabolic diseases.
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Abstract
Nitric oxide (NO), a potent vasodilator critical in maintaining vascular homeostasis, can reduce blood pressure in vivo. Loss of constitutive NO generation, for example as a result of endothelial dysfunction, occurs in many pathological conditions, including hypertension, and contributes to disease pathology. Attempts to therapeutically deliver NO via organic nitrates (e.g. glyceryl trinitrate, GTN) to reduce blood pressure in hypertensives have been largely unsuccessful. However, in recent years inorganic (or 'dietary') nitrate has been identified as a potential solution for NO delivery through its sequential chemical reduction via the enterosalivary circuit. With dietary nitrate found in abundance in vegetables this review discusses epidemiological, pre-clinical and clinical data supporting the idea that dietary nitrate could represent a cheap and effective dietary intervention capable of reducing blood pressure and thereby improving cardiovascular health.
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