Nitrate Tolerance Research Articles

Effect of calcitonin gene-related peptide antagonist on the cardiovascular events, mortality, and prostaglandin E2 production by nitrate-induced tolerant rats with acute myocardial infarction.

BackgroundAnti-ischemic effects of NO releasing by nitroglycerin (NTG) and the release of calcitonin gene-related peptide (CGRP) are involved in the decrease of vascular remodeling in different cardiovascular diseases. Using a nitrate-free period is still generally required to prevent nitrate tolerance and should be used as the first-line option to maintain adequate symptom control and on an individual basis. Personalized anti-ischemic concerns require the urgent change of paradigm from interventional measures to predictive, preventive, and personalized treatment with organic nitrates and its combination with drugs that may improve prognosis and drugs that can be added for patients who remain symptomatic despite therapy with the other classes of agents. The purpose of this study was to evaluate the influence of human calcitonin gene-related peptide antagonist (CGRP8-37) on cardiohemodynamic events, prostaglandin E2 (PGE2) plasma concentration, the severity of ventricular arrhythmias, and mortality occurring during acute myocardial infarction (AMI) in NTG-tolerant and nontolerant rats.MethodsIn the pilot study of efficacy of calcitonin gene-related peptide antagonist (CGRP8-37), 58 male Wistar rats were included. All procedures were performed according to protocols approved by the General Animal Care and Use Committee. Adult male rats underwent surgery to induce AMI by ligating the left anterior descending coronary artery or SHAM. ECG was used to confirm myocardial ischemia. In each experiment, a rat was maintained under anesthesia for the duration of the experiment. At the end of the experiment, the rat was killed by an overdose of pentobarbital. All animals in accordance with the received pharmacological agent were randomized into three groups: I—received only NTG, 50 mg/kg daily, s.c. injections b.i.d. 3 days prior to AMI; II—received NTG by the same dose, route, and frequency of administration + CGRP antagonist (CGRP8-37), 10 μg/kg two times daily by a similar period of administration; and III—served as control (C) group without preliminary tolerance to NTG.ResultsSubcutaneous injections of NTG (50 mg/kg) 30 min prior to AMI in NTG-tolerant animals (group I) and in NTG-tolerant rats + CGRP antagonist (group II) caused minor changes in blood pressure and heart period that was accompanied before NTG s.c. administration with blunted baroreflex sensitivity in response to i.v. administration of sodium nitroprusside in these groups of rats (0.66 ± 0.05 and 0.56 ± 0.04 ms/mmHg, P < 0.05, respectively) in comparison to C (group III) animals (0.9 ± 0.1 ms/mmHg). AMI 1 h duration was associated with a high incidence of ventricular arrhythmia and significant mortality in group I (70 %) and especially in group II (90 %) animals at 72 h after reperfusion as compared with group III rats (56 %), that correlated to a decrease of PGE2 plasma content in group II (2.2 ± 0.4 ng/ml, P < 0.001) and group I (3.6 ± 0.2 ng/ml, P < 0.01) vs. control group of rats (4.8 ± 0.3 ng/ml).ConclusionsCGRP could be involved in the mechanism of nitrate tolerance via the inhibition of release of the potent vasodilator CGRP leading to exacerbation of acute myocardial ischemia. The influence of CGRP antagonist could enhance this condition.

Crosstalk of mitochondria with NADPH oxidase via reactive oxygen and nitrogen species signalling and its role for vascular function.

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Developing New Organic Nitrates for Treating Hypertension: A Review

Nitric oxide (NO) is one of the most important vasodilator molecules produced by endothelium and presents plenty of cardiovascular actions. It has already been established that deficiency in NO/cGMP signaling pathway is involved in pathophysiological mechanisms of many cardiovascular diseases. In this context, the use of NOreleasing drugs appears to be an effective alternative to replace the deficient endogenous NO and mimic the role of this molecule in the body. Organic nitrates represent the oldest class of NO donors that have been clinically applied. Considering that tolerance can occur when these drugs are used chronically, the search for new compounds of this class with lower tolerance potential is increasing. Here we briefly discuss the mechanisms involved in nitrate tolerance and highlight some achievements from our group in the development of new organic nitrates and their preclinical application in cardiovascular disorders.

Aldehyde dehydrogenase 2 protects human umbilical vein endothelial cells against oxidative damage and increases endothelial nitric oxide production to reverse nitroglycerin tolerance.

Medical nitroglycerin (glyceryl trinitrate, GTN) use is limited principally by tolerance typified by a decrease in nitric oxide (NO) produced by biotransformation. Such tolerance may lead to endothelial dysfunction by inducing oxidative stress. In vivo studies have demonstrated that aldehyde dehydrogenase 2 (ALDH2) plays important roles in GTN biotransformation and tolerance. Thus, modification of ALDH2 expression represents a potentially effective strategy to prevent and reverse GTN tolerance and endothelial dysfunction. In this study, a eukaryotic expression vector containing the ALDH2 gene was introduced into human umbilical vein endothelial cells (HUVECs) by liposome-mediated transfection. An indirect immunofluorescence assay showed that ALDH2 expression increased 24 h after transfection. Moreover, real-time polymerase chain reaction and western blotting revealed significantly higher ALDH2 mRNA and protein expression in the gene-transfected group than in the two control groups. GTN tolerance was induced by treating HUVECs with 10 mM GTN for 16 h + 10 min, which significantly decreased NO levels in control cells, but not in those transfected with ALDH2. Overexpression of ALDH2 increased cell survival against GTN-induced cytotoxicity and conferred protection from oxidative damage resulting from nitrate tolerance, accompanied by decreased production of intracellular reactive oxygen species and reduced expression of heme oxygenase 1. Furthermore, ALDH2 overexpression promoted Akt phosphorylation under GTN tolerance conditions. ALDH2 gene transfection can reverse and prevent tolerance to GTN through its bioactivation and protect against oxidative damage, preventing the development of endothelial dysfunction.

Effects of Exogenous Polyamines on Nitrate Tolerance in Cucumber

Effects of Exogenous Polyamines on Nitrate Tolerance in Cucumber

Deterioration in Hemodynamics Reaction, Baroreflex Sensitivity, Sympathetic Nerve Activity and Redox State of Thoracic Aorta in the Experimental Model of Nitrate Tolerance and Its Pharmacological Correction

Continuous treatment with organic nitrates causes nitrate tolerance and provides evidence for a relationship between mitochondrial complex 1 activity and mitochondrial aldehyde dehydrogenase-2 (ALDH-2) with disturbances of the hemodynamics reaction during nitroglycerin (NTG) tolerance (NTGT). The purpose of this study was the evaluation of efficacy of original oxidized form NAD-containing drug, NADCIN&reg, on hemodynamic reactions, baroreflex sensitivity (BRS) and reflex control of splanchnic sympathetic nerve activity (SSNA), level of redox-potential, activity of ALDH-2 and superoxide anion generation in aortic tissue in rat model of NTGT. Five groups (7 - 9 each) of male Wistar rats, including control, acute i.v. NTG (150 mcg/kg) administration, NTG tolerance NTGT treatment with NADCIN&reg 8 mg/kg and methylene blue (MB, 2.5 mg/kg) were used. NTGT in rats was accompanied with the greatly attenuation of hemodynamics reaction, BRS, the decreasing of the ability to reflex control of SSNA without pronounce overexpression of endothelin-1 in vessels (aorta). In NTGT rats i.v. NTG along induced less hypotensive reactions and alterations in heart period vs single NTG treated group, more expressively decreased BRS (-34%) and reflex control of SSNA (-18%). NADCIN&reg significantly inhibits tolerance-inducing properties of the prolonged nitroglycerin infusion (max decrease of blood pressure response to nitroglycerin injection, % of normal controls: NTGT 51.2%, NADCIN&reg 91.6%, MB 55.8%). NADCIN&reg in NTGT rats after NTG i.v. administration increased reduced BRS (+37.8%, p &reg of NTGT rats restores hemodynamics changes, BRS and SSNA throughout the increasing of redox-potential NAD/NADH and cessates the NTGT developing.

Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress

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. Antioxid. Redox Signal. 23, 899–942.

Pentaerythritol Tetranitrate Targeting Myocardial Reactive Oxygen Species Production Improves Left Ventricular Remodeling and Function in Rats With Ischemic Heart Failure.

Reduced nitric oxide bioavailability contributes to progression of cardiac dysfunction and remodeling in ischemic heart failure. Clinical use of organic nitrates as nitric oxide donors is limited by development of nitrate tolerance and reactive oxygen species formation. We investigated the effects of long-term therapy with pentaerythritol tetranitrate (PETN), an organic nitrate devoid of tolerance, in rats with congestive heart failure after extensive myocardial infarction. Seven days after coronary artery ligation, rats were randomly allocated to treatment with PETN (80 mg/kg BID) or placebo for 9 weeks. Long-term PETN therapy prevented the progressive left ventricular dilatation and improved left ventricular contractile function and relaxation in rats with congestive heart failure. Mitochondrial superoxide anion production was markedly increased in the failing left ventricular myocardium and nearly normalized by PETN treatment. Gene set enrichment analysis revealed that PETN beneficially modulated the dysregulation of mitochondrial genes involved in energy metabolism, paralleled by prevention of uncoupling protein-3, thioredoxin-2, and superoxide dismutase-2 downregulation. Moreover, PETN provided a remarkable protective effect against reactive fibrosis in chronically failing hearts. Mechanistically, induction of heme oxygenase-1 by PETN prevented mitochondrial superoxide generation, NOX4 upregulation, and ensuing formation of extracellular matrix proteins in fibroblasts from failing hearts. In summary, PETN targeting reactive oxygen species generation prevented the changes of mitochondrial antioxidant enzymes and progressive fibrotic remodeling, leading to amelioration of cardiac functional performance. Therefore, PETN might be a promising therapeutic option in the treatment of ischemic heart diseases involving oxidative stress and impairment in nitric oxide bioactivity.

Effect of soluble guanylyl cyclase activator and stimulator therapy on nitroglycerin-induced nitrate tolerance in rats

article Chronic nitroglycerin (GTN) anti-ischemic therapy induces side effects such as nitrate tolerance and endothelial dysfunction. Both phenomena could be based on a desensitization/oxidation of the soluble guanylyl cyclase (sGC). Therefore, the present study aims at investigating the effects of the therapy with the sGC activator BAY 60-2770 and the sGC stimulator BAY 41-8543 on side effects induced by chronic nitroglycerin treatment. Male Wistar rats were treated with nitroglycerin (100 mg/kg/d for 3.5 days, s.c. in ethanol) and BAY 60-2770 (0.5 or 2.5 mg/kg/d) or BAY 41-8543 (1 and 5 mg/kg/d) for 6 days. Therapy with BAY 60-2770 but not with BAY 41-8543 improved nitroglycerin-triggered endothelial dysfunction and nitrate tolerance, corrected the decrease in aortic nitric oxide levels, improved the cGMP dependent activation of protein kinase I in aortic tissue and reduced vascular, cardiac and whole blood oxidative stress (fluorescence and chemiluminescence assays; 3- nitrotyrosine staining). In contrast to BAY 41-8543, the vasodilator potency of BAY 60-2770 was not impaired in isolated aortic ring segments from nitrate tolerant rats. sGC activator therapy improves partially the adverse effects of nitroglycerin therapy whereas sGC stimulation has only minor beneficial effects pointing to a

The nitric oxide donor pentaerythritol tetranitrate reduces platelet activation in congestive heart failure.

BackgroundPlatelet activation associated with endothelial dysfunction and impaired endogenous platelet inhibition is part of the cardiovascular phenotype of congestive heart failure (CHF) and contributes to the increased risk for thromboembolic complications. Pentaerythritol tetranitrate (PETN) has been shown to release nitric oxide without development of nitrate tolerance. We investigated the effect of chronic PETN treatment on platelet activation and aggregation in an experimental CHF model.Methods and ResultsChronic ischemic heart failure was induced in male Wistar rats by coronary artery ligation. Starting 7 days thereafter, rats were randomised to placebo or PETN (80 mg/kg twice daily). After 9 weeks, activation of circulating platelets was determined measuring platelet bound fibrinogen, which requires activated glycoprotein IIb/IIIa on the platelet surface. Binding was quantified by flow-cytometry using a FITC-labelled anti-fibrinogen antibody. Platelet-bound fibrinogen was significantly increased in CHF-Placebo (mean fluorescence intensity: Sham 88±4, CHF-Placebo 104±6, p<0.05) and reduced following treatment with PETN (89±7, p<0.05 vs. CHF-Placebo). Maximal and final ADP-induced aggregation was significantly enhanced in CHF-Placebo vs. Sham-operated animals and normalized / decreased following chronic PETN treatment. Moreover, platelet adhesion was significantly reduced (number of adherent platelets: control: 85.6±5.5, PETN: 40±3.3; p<0.001) and VASP phosphorylation significantly enhanced following in vitro PETN treatment.ConclusionChronic NO supplementation using PETN reduces platelet activation in CHF rats. Thus, PETN may constitute a useful approach to prevent thromboembolic complications in CHF.

Effect of soluble guanylyl cyclase activator and stimulator therapy on nitroglycerin-induced nitrate tolerance in rats

Chronic nitroglycerin (GTN) anti-ischemic therapy induces side effects such as nitrate tolerance and endothelial dysfunction. Both phenomena could be based on a desensitization/oxidation of the soluble guanylyl cyclase (sGC). Therefore, the present study aims at investigating the effects of the therapy with the sGC activator BAY 60-2770 and the sGC stimulator BAY 41-8543 on side effects induced by chronic nitroglycerin treatment. Male Wistar rats were treated with nitroglycerin (100mg/kg/d for 3.5days, s.c. in ethanol) and BAY 60-2770 (0.5 or 2.5mg/kg/d) or BAY 41-8543 (1 and 5mg/kg/d) for 6days. Therapy with BAY 60-2770 but not with BAY 41-8543 improved nitroglycerin-triggered endothelial dysfunction and nitrate tolerance, corrected the decrease in aortic nitric oxide levels, improved the cGMP dependent activation of protein kinase I in aortic tissue and reduced vascular, cardiac and whole blood oxidative stress (fluorescence and chemiluminescence assays; 3-nitrotyrosine staining). In contrast to BAY 41-8543, the vasodilator potency of BAY 60-2770 was not impaired in isolated aortic ring segments from nitrate tolerant rats. sGC activator therapy improves partially the adverse effects of nitroglycerin therapy whereas sGC stimulation has only minor beneficial effects pointing to a nitroglycerin-dependent sGC oxidation/inactivation mechanism contributing to nitrate tolerance.

Increased Role for Large Conductance, Calcium‐Activated K Channels (BKCa) in Endothelium‐Dependent Relaxation of Nitrate Tolerant Mesenteric Arteries

Prolonged exposure to nitroglycerin (NTG) leads to tolerance and impaired endothelium‐dependent vasodilation. Causes of endothelial dysfunction in nitrate tolerant arteries are well studied, but little is known about mechanisms that underlie the responses to endothelium‐derived mediators in nitrate tolerant blood vessels. Here we evaluated the role of BKCa in acetylcholine (ACh)‐induced relaxation of isolated mesenteric arterial rings from rats treated with or without application of transdermal NTG patches (0.6 mg/hr) for 3 days. Nitrate tolerance was confirmed by the impaired relaxation response to NTG (1 nM – 100 μM) observed in rings from rats treated with NTG patches (pD2= 5.6 + 0.1 vs 4.9 + 0.1, Emax= 86 + 7 vs 53 + 5% relaxation; control vs treated, respectively). ACh‐induced (1 nM – 3 μM) relaxation was also impaired in tolerant rings (pD2= 7.1+ 0.1 vs 6.5 + 0.1; control vs tolerant, respectively) Incubation with nitro‐l‐arginine (30 μM) or indomethacin (10 μM) had no effect on the response to ACh in control or tolerant arteries, consistent with the release of a non‐NO, non‐prostanoid endothelium‐derived mediator in both control and tolerant arteries. ACh‐induced relaxation was unaffected by the selective BKCa‐blocker, iberiotoxin (IBT), in control rings, but was nearly abolished in tolerant rings (Emax = 78 ± 9 vs 8 + 8% relaxation; without vs with IBT, respectively). Protein expression of BKCa β‐subunits was increased by 50% in nitrate tolerant arteries, while BKCa α‐subunit expression was unchanged. The data provide evidence that nitrate tolerance unmasks a pivotal role for BKCa in the smooth muscle relaxation evoked by a non‐NO, non‐prostanoid endothelium‐derived mediator in mesenteric arteries.

The Role of DNA Damage in the Pathogenesis of Nitrate Tolerance

Organic nitrates act as endothelium-independent vasodilators of blood vessels. For these reasons, nitroglycerin (GTN) is one of the most widely used anti-ischemic drugs. The chronic efficacy of nitrates is blunted because of the development of nitrate tolerance and endothelial dysfunction. Recent data indicate that GTN induced reactive oxygen and nitrogen species (RONS) formation accounts for both phenomena. In 2005, Andreassi demonstrated that organic nitrate therapy increased DNA damage (Mol. Med. 2005). This report indicates our lack of understanding of molecular mechanism contributing to nitrate tolerance development. Following this initial trend, we conducted our experiments with the cell culture system using Ea.hy 926 cells. After GTN treatment we detected presence of oxidative DNA damage and DNA strand breaks in response to GTN. We proceeded with investigations on the animal model. After 3 days of continuous GTN treatment, as a correlate of clinical nitrate tolerance in patients, presence of the endothelial dysfunction and nitrate tolerance was confirmed. Additionally, we were able to detect increased cardiac RONS formation. With the help of immuno staining of the aortic tissue we found substantial elevation in the levels of 8-oxo-guanine and O6-methyl-guanine. Currently, it is still enigmatic whether noted increase in DNA damage during treatment with GTN is simply due to the accumulation of DNA damage under nitrate-induced oxidative stress or due to a more complex mechanisms such as inhibition of DNA repair machinery. In order to elucidate exact mechanism of action for GTN-induced DNA damage further investigations will be conducted on mice with impaired DNA repair machinery.

Nitroglycerin‐induced tolerance in rat conduit artery and vein

Clinical use of nitroglycerin (GTN) is limited because its long‐term therapy results in the development of nitrate tolerance. The etiology of nitrate tolerance is controversial and poorly understood. This study aimed to investigate the mechanisms of GTN‐induced tolerance and to compare them in aorta and vena cava from GTN tolerant rats. In vivo tolerance for GTN was induced by 3 days treatment with GTN (150 mg/kg/day). We evaluated the maximum relaxing effect (ME) and the potency (pD2) induced by GNT in aorta and vena cava from tolerant and control rats. The endothelial NOS3 and soluble guanylyl‐cyclase (sGC) protein expression was accessed by Western Blot. The procedures are according to the Ethics Committee. Differences were considered significant for P&lt;0.05. GTN treatment reduced the pD2 of GTN from 14.3±0.8, n=6 to 12.8±0.6, n=6, whereas ME was not different between control and tolerant rat aorta. In vena cava, ME was lower in tolerant rats (35.2 ± 2.5%, n= 6, P&lt;0.05) as compared to control rats (73.1 ± 5.7%, n=6). sGC expression was similar in aorta and vein from control and tolerant rats. However, NOS3 expression was higher in aortas from tolerant (1.08 ± 0.06 n= 6, P&lt;0.05) than in control animals (0.66 ± 0.04, n=7). Similarly, NOS3 expression was higher in veins from tolerant (1.08 ± 0.06 n= 6, P&lt;0.05) than in control animals (0.66 ± 0, 04, n= 7). Therefore, GTN‐induced tolerance in rat aorta and vein involves NOS3 but not sGC.

Molecular cloning and functional analysis of spinach SoSMT2 in response to excess nitrate stress

Plant sterols are important multifunctional lipids, which are involved in determining membrane properties. Sterol C24 methyltransferase2 (SMT2) governs the pattern of phytosterols synthesized in higher plants. In this study, the spinach sterol C24 methyltransferase2 (SoSMT2) cDNA was cloned by RT-PCR and RACE-PCR. The full length of SoSMT2 consists of 1614bp, including a 278bp 5′-untranslated region (UTR), a 1086bp open reading frame (ORF), and a 250bp 3′-UTR. The SoSMT2 gene encodes a polypeptide of 361 amino acid residues with a predicted molecular mass of 40.47kDa. RT-PCR analysis indicated that the expression of SoSMT2 was induced by excess nitrate in the root and shoot of spinach. The transcript level of SoSMT2 was decreased by NaCl treatment. In contrast, dehydration, and H2O2 treatment increased the transcript levels of SoSMT2. To examine the biological roles of SoSMT2 in stress responses, transgenic Arabidopsis plants that constitutively overexpress SoSMT2 under the control of cauliflower mosaic virus 35S promoter were generated. The germination rate of transgenic seeds was higher than wild type (WT) in MS medium supplemented with 160mM nitrate. When seedlings were transferred to MS liquid medium with 160mM nitrate for 0, 8, 24 and 48h, the transgenic plants showed lower levels of MDA and H2O2 contents, compared with WT plants. Additionally, transgenic plants had relatively higher SOD, CAT and POD activities and soluble sugar contents than WT plants under nitrate stress with the increasing of treatment time. These data suggest that SoSMT2 is involved in nitrate tolerance in spinach.

Vasorelaxing effects of the soluble guanylyl cyclase activator BAY 60-2770 in nitrate-tolerant monkey and canine coronary arteries.

Nitrate tolerance is an important problem in the treatment of ischemic heart diseases. The present study investigated whether or not a soluble guanylyl cyclase (sGC) activator can be used as a coronary vasodilator under nitrate-tolerant conditions. Helically cut strips of endothelium-denuded monkey and canine coronary arteries were suspended in organ chambers for isometric tension recording. Nitrate tolerance was induced by a 1-h treatment with nitroglycerin (0.1mM) followed by 1-h washout of the agent. Control strips were not exposed previously to nitroglycerin, but otherwise were treated identically. The relaxant response to nitroglycerin was dramatically impaired by previous exposure to the drug for 1h in either monkey or canine coronary arteries, indicating the development of nitrate tolerance. In contrast, development of nitrate tolerance did not affect the relaxant potency and efficacy of the sGC activator BAY 60-2770 in either the monkey or canine coronary arteries. These findings suggest that it may be possible to use sGC activators as substitute drugs for nitroglycerin if tolerance is developed during the treatment of ischemic heart diseases.

Reversion of nitrate tolerance in rat aorta rings by freeze-dried red wine.

Chronically administered organic nitrates induce nitrate tolerance and endothelial dysfunction, which limit their therapeutic use. eNOS uncoupling, ROS over-production, aldehyde dehydrogenase-2 as well as superoxide dismutase (SOD) oxidative inhibition, and cGMP desensitization are thought to play an important role. Natural polyphenols are effective antioxidants, which might counteract the mechanisms leading to nitrate tolerance. The aim of this work was to verify whether freeze-dried (dealcoholized) red wine (FDRW) was able to revert glyceryl trinitrate (GTN) tolerance and endothelial dysfunction induced in rat aorta rings with either GTN or diethyldithiocarbamate (DETCA), an irreversible inhibitor of Cu/Zn SOD. GTN induced a concentration-dependent relaxation of rings pre-contracted with phenylephrine. GTN spasmolysis was significantly reduced in rings pre-incubated with either GTN or DETCA. FDRW, at 2.8 µg of gallic acid equivalents (GAE)/mL concentration, was able to revert partially, though significantly, GTN-induced tolerance but not tolerance and endothelial dysfunction induced by DETCA. This work provides the first evidence in vitro that red wine components, at concentrations comparable to those achieved in human blood after moderate consumption of red wine, revert tolerance to nitrates with a mechanism possibly mediated by SOD.

Effect of Transdermal Nitroglycerin on Insulin Resistance in Healthy Young Men

Objective: There are evidences indicating transdermal nitroglycerin changes the sensitivity of peripheral tissues to the hypoglycemic effect of insulin. In this study we determined effect of continuous application of transdermal nitroglycerin patches in healthy volunteers on development of tolerance to the hypotensive effect of nitroglycerin and hypoglycemic effect of insulin. Materials and methods: The effect of transdermal application of nitroglycerin, as NO donor was studied during 24 hours on blood insulin and glucose level and on blood pressure in healthy, young volunteers. Patches of 0.2 mg/ hour nitroglycerine were administered to young healthy volunteers along 24 hours and Venous blood samples were taken early before and 24 hours after the nitroglycerin. Serum was separated and free zed (-80°C) for insulin and glucose determination. Blood pressure also was determined in 6 hours intervals. Results: Before nitroglycerin patches application mean serum insulin level determined level 9.53 ± 4.37 and after nitroglycerin were 9.18 ± μU/ml which is statistically significant (P>0.05). Fasting blood glucose levels were increased by 6.63 ± 1.9 mg/dl determined 24 hours after nitroglycerine application in comparison with before treatment. The changes observed in blood glucose levels also were statistically significant (P<0.001). Insulin resistance calculated by Homa formula was 1.445 before treatment and 1.540 after nitroglycerin treatment. Conclusion: Transdermal nitroglycerin by doses of 0.2 mg/h causing blood glucose level changes more than change of insulin level indicating change in tissue sensitivity to insulin. The present work was therefore concerned with the possibility that nitrate tolerance impairs the sensitivity of tissues to the hypoglycemic effect of insulin.

Recent developments in vascular biology.

The field of vascular biology has transformed dramatically in recent years as new research has elucidated complex roles of novel proteins, stem/progenitor/hematopoietic cells, and miRNAs as well as redox signaling in vascular development, vascular tone regulation and disease in preclinical models and clinical settings. Review of this body of work highlights seminal findings and new developments that emphasize and illuminate underlying principles and historical connections. In the 1980s, there was the frenzied search for the identity of the Endothelium-Derived Relaxing Factor (EDRF; ie, NO).1,2 In the 1990s, the elucidation of myriad EDHFs (hyperpolarizing factors, eg, H2O2, K+, arachidonic acid metabolites) expanded endothelial cell complexity beyond NO.3–5 In the 2000s, the endothelial cell generation and overall cardiovascular effects of H2S were hotly pursued.6,7 In the 2010s, the role of the perivascular adipose tissue (PVAT) derived relaxing and contractile factors in vascular regulation under physiological and disease promoting conditions (eg, diet-induced obesity, metabolic syndrome) has emerged as a new integrative vascular issue of import because of the obesity epidemic.8 Critically important mechanisms continue to be sources of interest and renewed research. Indeed, the panoply of endothelium-derived factors that regulate vascular tone continues to grow, and identifying new ones will only enhance our understanding of the diverse factors that regulate vascular tone and blood flow in context-dependent ways. As elucidated in the article by Zhang et al, entitled “H2O2-induced dilation in human coronary arterioles: role of protein kinase G dimerization and large-conductance Ca2+-activated K+ channel activation,” redox-mediated VSMC K+-channel opening ultimately leads to relaxation and dilation in coronary blood vessels.9 Similarly, PPAR-γ stimulated Regulatory G-protein S 5 (RGS5)-control of Protein Kinase C-mediated opening of calcium-activated …

Maternal treatment of spontaneously hypertensive rats with pentaerythritol tetranitrate reduces blood pressure in female offspring.

Pentaerythritol tetranitrate is devoid of nitrate tolerance and shows no reproductive or developmental toxicity in animal studies. Recently, pentaerythritol tetranitrate has been demonstrated to reduce the risk of intrauterine growth restriction and the risk of preterm birth in women with abnormal placental perfusion. This study was conducted to test the perinatal programming effect of pentaerythritol tetranitrate in spontaneously hypertensive rats, a rat model of genetic hypertension. Parental spontaneously hypertensive rats were treated with pentaerythritol tetranitrate (50 mg/kg per day) during pregnancy and lactation periods; the offspring received standard chow without pentaerythritol tetranitrate after weaning. Maternal treatment with pentaerythritol tetranitrate had no effect on blood pressure in male offspring. In the female offspring, however, a persistent reduction in blood pressure was observed at 6 and 8 months. This long-lasting effect was accompanied by an upregulation of endothelial nitric oxide synthase, mitochondrial superoxide dismutase, glutathione peroxidase 1, and heme oxygenase 1 in the aorta of 8-month-old female offspring, which was likely to result from epigenetic changes (enhanced histone 3 lysine 27 acetylation and histone 3 lysine 4 trimethylation) and transcriptional activation (enhanced binding of DNA-directed RNA polymerase II to the transcription start site of the genes). In organ chamber experiments, the endothelium-dependent, nitric oxide-mediated vasodilation to acetylcholine was enhanced in aorta from female offspring of the pentaerythritol tetranitrate-treated parental spontaneously hypertensive rats. In conclusion, maternal pentaerythritol tetranitrate treatment leads to epigenetic modifications, gene expression changes, an improvement of endothelial function and a persistent blood pressure reduction in the female offspring.