Nitroglycerin-induced endothelial dysfunction and tolerance involve adverse phosphorylation and S-Glutathionylation of endothelial nitric oxide synthase: beneficial effects of therapy with the AT1 receptor blocker telmisartan

Promotion of nitric oxide production: mechanisms, strategies, and possibilities

The discovery of nitric oxide (NO) and the role of endothelial cells (ECs) in its production has revolutionized medicine. NO can be produced by isoforms of NO synthases (NOS), including the neuronal (nNOS), inducible (iNOS), and endothelial isoforms (eNOS), and via the non-classical nitrate-nitrite-NO pathway. In particular, endothelium-derived NO, produced by eNOS, is essential for cardiovascular health. Endothelium-derived NO activates soluble guanylate cyclase (sGC) in vascular smooth muscle cells (VSMCs), elevating cyclic GMP (cGMP), causing vasodilation. Over the past four decades, the importance of this pathway in cardiovascular health has fueled the search for strategies to enhance NO bioavailability and/or preserve the outcomes of NO's actions. Currently approved approaches operate in three directions: 1) providing exogenous NO, 2) promoting sGC activity, and 3) preventing degradation of cGMP by inhibiting phosphodiesterase 5 activity. Despite clear benefits, these approaches face challenges such as the development of nitrate tolerance and endothelial dysfunction. This highlights the need for sustainable options that promote endogenous NO production. This review will focus on strategies to promote endogenous NO production. A detailed review of the mechanisms regulating eNOS activity will be first provided, followed by a review of strategies to promote endogenous NO production based on the levels of available preclinical and clinical evidence, and perspectives on future possibilities.

Sodium nitrite induces tolerance in the mouse aorta: Involvement of the renin-angiotensin system, nitric oxide synthase, and reactive oxygen species

Nitrites have emerged as promising therapeutic agents for cardiovascular diseases, alongside nitrates. While chronic use of organic nitrates is well recognized to lead to vascular tolerance, the tolerance associated with nitrite therapy remains incompletely understood. The aim of the present study was to investigate vascular tolerance to sodium nitrite and the underlying molecular mechanisms. Endothelium-denuded aortic rings isolated from male Balb/C mice were incubated with either the EC50 (10-4 mol/L) or EC100 (10-2 mol/L) concentration of sodium nitrite for 15 min to induce tolerance. The EC100 concentration of sodium nitrite induced vascular tolerance. Pre-incubation with captopril and losartan effectively reversed sodium nitrite-induced tolerance. Similarly, pre-incubation with L-NAME and L-arginine prevented sodium nitrite-induced tolerance. Increased levels of reactive oxidative species (ROS) and reduced bioavailability of nitric oxide (NO) were observed in tolerant aortas. Increased superoxide dismutase (SOD) activity and decreased catalase activity were also verified in tolerant aortas. Both captopril and L-NAME prevented the increased levels of ROS observed in tolerant aortas. Furthermore, pre-incubation with catalase effectively prevented sodium nitrite-induced tolerance. Our findings suggest that sodium nitrite induces vascular tolerance through a signaling pathway involving the renin-angiotensin system, nitric oxide synthase, and ROS. This study contributes to the understanding of the interaction between nitrites and vascular tolerance and highlights potential targets to overcome or prevent this phenomenon.

SS-31 alleviated nociceptive responses and restored mitochondrial function in a headache mouse model via Sirt3/Pgc-1α positive feedback loop

Migraine is the second highest cause of disability worldwide, bringing a huge socioeconomic burden. Improving mitochondrial function has promise as an effective treatment strategy for migraine. Szeto-Schiller peptide (SS-31) is a new mitochondria-targeted tetrapeptide molecule that has been shown to suppress the progression of diseases by restoring mitochondrial function, including renal disease, cardiac disease, and neurodegenerative disease. However, whether SS-31 has a therapeutic effect on migraine remains unclear. The aim of this study is to clarify the treatment of SS-31 for headache and its potential mechanisms. Here we used a mouse model induced by repeated dural infusion of inflammatory soup (IS), and examined roles of Sirt3/Pgc-1α positive feedback loop in headache pathogenesis and mitochondrial function. Our results showed that repeated IS infusion impaired mitochondrial function, mitochondrial ultrastructure and mitochondrial homeostasis in the trigeminal nucleus caudalis (TNC). These IS-induced damages in TNC were reversed by SS-31. In addition, IS-induced nociceptive responses were simultaneously alleviated. The effects of SS-31 on mitochondrial function and mitochondrial homeostasis (mainly mitochondrial biogenesis) were attenuated partially by the inhibitor of Sirt3/Pgc-1α. Overexpression of Sirt3/Pgc-1α increased the protein level of each other. These results indicated that SS-31 alleviated nociceptive responses and restored mitochondrial function in an IS-induced headache mouse model via Sirt3/Pgc-1α positive feedback loop. SS-31 has the potential to be an effective drug candidate for headache treatment.

Nitroglycerin: a comprehensive review in cancer therapy

Nitroglycerin (NTG) is a prodrug that has long been used in clinical practice for the treatment of angina pectoris. The biotransformation of NTG and subsequent release of nitric oxide (NO) is responsible for its vasodilatating property. Because of the remarkable ambivalence of NO in cancer disease, either protumorigenic or antitumorigenic (partly dependent on low or high concentrations), harnessing the therapeutic potential of NTG has gain interest to improve standard therapies in oncology. Cancer therapeutic resistance remains the greatest challenge to overcome in order to improve the management of cancer patients. As a NO releasing agent, NTG has been the subject of several preclinical and clinical studies used in combinatorial anticancer therapy. Here, we provide an overview of the use of NTG in cancer therapy in order to foresee new potential therapeutic avenues.

Vascular redox signaling, eNOS uncoupling and endothelial dysfunction in the setting of transportation noise exposure or chronic treatment with organic nitrates

SIGNIFICANCE

Cardiovascular disease and drug-induced health side effects are frequently associated with - or even caused by - an imbalance between the concentrations of reactive oxygen and nitrogen species (RONS) and antioxidants respectively determining the metabolism of these harmful oxidants.

RECENT ADVANCES

According to the "kindling radical" hypothesis, initial formation of RONS may further trigger the additional activation of RONS formation under certain pathological conditions. The present review will specifically focus on a dysfunctional, uncoupled endothelial nitric oxide synthase (eNOS) caused by RONS in the setting of transportation noise exposure or chronic treatment with organic nitrates, especially nitroglycerin. We will further describe the various "redox switches" that are proposed to be involved in the uncoupling process of eNOS.

CRITICAL ISSUES

In particular, the oxidative depletion of tetrahydrobiopterin (BH4), and S-glutathionylation of the eNOS reductase domain will be highlighted as major pathways for eNOS uncoupling upon noise exposure or nitroglycerin treatment. In addition, oxidative disruption of the eNOS dimer, inhibitory phosphorylation of eNOS at threonine or tyrosine residues, redox-triggered accumulation of asymmetric dimethylarginine (ADMA) and L-arginine deficiency will be discussed as alternative mechanisms of eNOS uncoupling.

FUTURE DIRECTIONS

The clinical consequences of eNOS dysfunction due to uncoupling on cardiovascular disease will be summarized also providing a template for future clinical studies on endothelial dysfunction caused by pharmacological or environmental risk factors.

Effectiveness and Tolerability of Trimetazidine 80 Mg Once Daily in Patients with Stable Angina Uncontrolled with Bisoprolol-Based Therapy: The Modus Vivendi Observational Study

Introduction

Modus Vivendi was conducted in routine clinical practice to evaluate the effect of adding trimetazidine 80 mg once daily (TMZ 80 OD) to treat patients with persistent symptoms despite treatment with background antianginal therapies including maximally tolerated bisoprolol.

Methods

This multicenter, prospective, observational, open-label, uncontrolled study recruited adult outpatients with a confirmed diagnosis of stable angina to whom physicians had decided to prescribe TMZ 80 OD. All patients were symptomatic despite treatment, including maximally tolerated doses of bisoprolol. Data on number of angina attacks, use of short-acting nitrates, and quality of life (QoL) were collected at baseline (V1) and at 1-month (V2) and 3-month (V2) follow-up visits. Two sub-analyses assessed efficacy in patients who remained on a stable bisoprolol dose throughout the study, and in patients in whom background antianginal therapy was known.

Results

A total of 1939 patients were recruited (57.2% women). The mean age was 65.6 ± 8.8 years; 73.8% had class II and 26.2% class III angina. At V1, the mean number of angina attacks per week was 6.2 ± 6.5 despite antianginal therapy including maximally tolerated bisoprolol dosage. Following the addition of TMZ 80 OD, this decreased to 3.4 ± 4.2 attacks per week at V2, and 1.6 ± 2.6 at V3 (P < 0.05 at V2 and V3), with concomitant reductions in short-acting nitrate use (P < 0.05). Significant improvements in QoL were observed throughout the study. Subgroup analyses showed that the addition of TMZ 80 OD to guideline-recommended antianginal therapy was associated with significant reductions in the mean number of weekly angina attacks and consumption of short-acting nitrates and improvements in QoL whether patients were treated with maximally tolerated bisoprolol and TMZ 80 OD alone, or maximally tolerated bisoprolol and TMZ 80 OD on top of other antianginal therapies. Treatment was well tolerated.

Conclusion

The study findings support the addition of TMZ 80 OD to bisoprolol with or without other antianginal therapies for patients with persistent angina.

Trial Registration

This study was retrospectively registered under the number ISRCTN29992579.

Delivery of Nitric Oxide in the Cardiovascular System: Implications for Clinical Diagnosis and Therapy

Nitric oxide (NO) is a key molecule in cardiovascular homeostasis and its abnormal delivery is highly associated with the occurrence and development of cardiovascular disease (CVD). The assessment and manipulation of NO delivery is crucial to the diagnosis and therapy of CVD, such as endothelial dysfunction, atherosclerotic progression, pulmonary hypertension, and cardiovascular manifestations of coronavirus (COVID-19). However, due to the low concentration and fast reaction characteristics of NO in the cardiovascular system, clinical applications centered on NO delivery are challenging. In this tutorial review, we first summarized the methods to estimate the in vivo NO delivery process, based on computational modeling and flow-mediated dilation, to assess endothelial function and vulnerability of atherosclerotic plaque. Then, emerging bioimaging technologies that have the potential to experimentally measure arterial NO concentration were discussed, including Raman spectroscopy and electrochemical sensors. In addition to diagnostic methods, therapies aimed at controlling NO delivery to regulate CVD were reviewed, including the NO release platform to treat endothelial dysfunction and atherosclerosis and inhaled NO therapy to treat pulmonary hypertension and COVID-19. Two potential methods to improve the effectiveness of existing NO therapy were also discussed, including the combination of NO release platform and computational modeling, and stem cell therapy, which currently remains at the laboratory stage but has clinical potential for the treatment of CVD.

Telmisartan Loaded Nanofibers Enhance Re-Endothelialization and Inhibit Neointimal Hyperplasia

Stent implantation impairs local endothelial function and may be associated with subsequent adverse cardiovascular events. Telmisartan, an angiotensin II receptor blocker that has unique peroxisome proliferator-activated-receptor-gamma-mediated effects on cardiovascular disease, has been shown to enhance endothelial function and limit neointimal hyperplasia. This study utilized hybrid biodegradable/stent nanofibers to facilitate sustained and local delivery of telmisartan to injured arterial vessels. Telmisartan and poly(d,l)-lactide-co-glycolide (PLGA) (75:25) were dissolved in hexafluoroisopropyl alcohol and electrospun into biodegradable nanofibrous tubes which were coated onto metal stents. By releasing 20% of the loaded telmisartan in 30 days, these hybrid biodegradable/stent telmisartan-loaded nanofibers increased the migration of endothelial progenitor cells in vitro, promoted endothelialization, and reduced intimal hyperplasia. As such, this work provides insights into the use of PLGA nanofibers for treating patients with an increased risk of stent restenosis.

The Role of Nicorandil in the Management of Chronic Coronary Syndromes in the Gulf Region

Chronic coronary syndromes (CCS) and stable angina are a growing clinical burden worldwide. This is of particular concern in the Gulf region given its high prevalence of cardiovascular risk factors, especially diabetes mellitus and smoking. Despite recommendations on the use of first- and second-line anti-anginal medication, management challenges remain. Current guidelines for pharmacologic treatment are not determined by the range of pathophysiological mechanisms of ischaemia and consequent angina, which may occur either in isolation or co-exist. In this article, we highlight the need to improve knowledge of the epidemiology of chronic coronary syndromes in the Middle East and Gulf region, and the need for studies of stratified pharmacologic approaches to improve symptomatic angina and quality of life in the large and growing number of patients with coronary artery disease from this region. We discuss the role of nicorandil, currently recommended as a second-line anti-anginal drug in CCS patients, and suggest that this may be a particularly useful add-on therapy for patients in the Gulf region.

Nitric Oxide Donors as Potential Drugs for the Treatment of Vascular Diseases Due to Endothelium Dysfunction

Endothelial dysfunction and consequent vasoconstriction are a common condition in patients with hypertension and other cardiovascular diseases. Endothelial cells produce and release vasodilator substances that play a pivotal role in normal vascular tone. The mechanisms underlying endothelial dysfunction are multifactorial. However, enhanced reactive oxygen species (ROS) production and consequent vasoconstriction instead of endothelium-derived relaxant generation and consequent vasodilatation contribute to this dysfunction considerably. The main targets of the drugs that are currently used to treat vascular diseases concerning enzyme activities and protein functions that are impaired by endothelial nitric oxide synthase (eNOS) uncoupling and ROS production. Nitric oxide (NO) bioavailability can decrease due to deficient NO production by eNOS and/or NO release to vascular smooth muscle cells, which impairs endothelial function. Considering the NO cellular mechanisms, tackling the issue of eNOS uncoupling could avoid endothelial dysfunction: provision of the enzyme cofactor tetrahydrobiopterin (BH4) should elicit NO release from NO donors, to activate soluble guanylyl cyclase. This should increase cyclic guanosine-monophosphate (cGMP) generation and inhibit phosphodiesterases (especially PDE5) that selectively degrade cGMP. Consequently, protein kinase-G should be activated, and K+ channels should be phosphorylated and activated, which is crucial for cell membrane hyperpolarization and vasodilation and/or inhibition of ROS production. The present review summarizes the current concepts about the vascular cellular mechanisms that underlie endothelial dysfunction and which could be the target of drugs for the treatment of patients with cardiovascular disease.

S-Nitrosylation of Akt by organic nitrate delays revascularization and the recovery of cardiac function in mice following myocardial infarction

The effects of long‐term nitrate therapy are compromised due to protein S‐Nitrosylation, which is mediated by nitric oxide (NO). This study is to determine the role of Akt S‐Nitrosylation in the recovery of heart functions after ischaemia. In recombinant Akt protein and in HEK293 cells, NO donor decreased Akt activity and induced Akt S‐Nitrosylation, but was abolished if Akt protein was mutated by replacing cysteine 296/344 with alanine (Akt‐C296/344A). In endothelial cells, NO induced Akt S‐Nitrosylation, reduced Akt activity and damaged multiple cellular functions including proliferation, migration and tube formation. These alterations were ablated if cells expressed Akt‐C296/344A mutant. In Apoe^−/− mice, nitroglycerine infusion increased both Akt S‐Nitrosylation and infarct size, reduced Akt activity and capillary density, and delayed the recovery of cardiac function in ischaemic hearts, compared with mice infused with vehicle. Importantly, these in vivo effects of nitroglycerine in Apoe^−/− mice were remarkably prevented by adenovirus‐mediated enforced expression of Akt‐C296/344A mutant. In conclusion, long‐term usage of organic nitrate may inactivate Akt to delay ischaemia‐induced revascularization and the recovery of cardiac function through NO‐mediated S‐Nitrosylation.

Evaluation of possible effects of crocin against nitrate tolerance and endothelial dysfunction

Objective(s):

One of the most important problems of taking nitroglycerin is the nitrate tolerance phenomenon and endothelial dysfunction. Oxidative stress is a high-emphasized one of tolerance mechanisms. The possible effect of crocin, one of the anti-oxidant ingredients of saffron, on the nitrate tolerance model was investigated.

Materials and Methods:

In the present study, lipid peroxidation and the level of activated and deactivated forms of eNOS were measured. Animals were administered subcutaneously with 25 mg/kg of nitroglycerin, twice a day for 3 days to induce nitrate tolerance model. For evaluation of crocin effects, 20, 40 and 80 mg/kg/day of this compound were injected intraperitoneally in concomitant with nitroglycerin. In the isolated aorta test, after preparation of aorta rings, different concentrations of acetylcholine, sodium nitroprusside and nitroglycerin were added to the organ bath after inducing contraction by phenylephrine and the responsiveness of tissues was recorded.

Results:

Findings showed that nitroglycerin administration caused a remarkable overproduction of malondialdehyde (MDA) in the cells and crocin treatment significantly decreased the MDA level. In the nitrate tolerance group, the level of activated eNOS decreased and the level of deactivated eNOS increased. Crocin partly alleviated these changes: however, its effects were not remarkable. Nitroglycerin injection for 3 days developed tolerance to nitroglycerin and cross-tolerance to acetylcholine (endothelial dysfunction) and sodium nitroprusside. Crocin failed to influence significantly on the nitrate tolerance.

Conclusion:

Crocin effectiveness is possibly time-dependent; therefore, increasing the duration of treatment with crocin may lead to a significant prevention of nitrate tolerance and endothelial dysfunction.

Renal Effects of Fetal Reprogramming With Pentaerythritol Tetranitrate in Spontaneously Hypertensive Rats

Aims

Current antihypertensive therapies cannot cure hypertension and a life-long medication is necessary. Maternal treatment may represent a promising strategy for hypertension treatment. We have previously shown that maternal treatment of spontaneously hypertensive rats (SHR) with pentaerythritol tetranitrate (PETN) leads to a persistent blood pressure reduction in the female offspring. The underlying mechanisms include improved endothelial function resulting from long-lasting epigenetic changes. In the present study, we address the renal effects of maternal PETN treatment.

Methods and Results

F0 parental SHR were fed with either normal chow or PETN-containing (1 g/kg) chow ad libitum from the time point of mating to the end of lactation period. The F1 offspring received normal chow without PETN from the time point of weaning (at the age of 3 weeks). At the age of 16 weeks, female PETN offspring showed lower blood pressure than the control. No difference was observed in male offspring. All following experiments were performed with kidneys from 16-week-old female offspring. Maternal PETN treatment reduced the mRNA and protein expression of angiotensin-converting enzyme (ACE) and basic fibroblast growth factor (FGF2), resulting from epigenetic modifications found at the proximal promoter regions. The expression levels of mineralocorticoid receptor (MR) and factors in the MR signalling pathway (Rac1 and Sgk1) were also reduced by PETN. Major profibrotic cytokines, including Wnt4, TNF-alpha, TGF-beta, and MMP9, were downregulated by PETN, which was associated with reduced collagen deposition and glomerulus sclerosis in the kidney of PETN offspring. In addition, PETN treatment also decreased the markers of inflammation and immune cell infiltration in the kidneys.

Conclusions

PETN maternal treatment leads to epigenetic changes in the kidney of female SHR offspring. The reduced renal inflammation, alleviated kidney fibrosis, and decreased MR signalling are potential mechanisms contributing to the observed blood pressure-lowering effect.

Oxidative stress and inflammation contribute to traffic noise-induced vascular and cerebral dysfunction via uncoupling of nitric oxide synthases

Environmental pollution and non-chemical stressors such as mental stress or traffic noise exposure are increasingly accepted as health risk factors with substantial contribution to chronic noncommunicable diseases (e.g. cardiovascular, metabolic and mental). Whereas the mechanisms of air pollution-mediated adverse health effects are well characterized, the mechanisms of traffic noise exposure are not completely understood, despite convincing clinical and epidemiological evidence for a significant contribution of environmental noise to overall mortality and disability. The initial mechanism of noise-induced cardiovascular, metabolic and mental disease is well defined by the „noise reaction model“ and consists of neuronal activation involving the hypothalamic-pituitary-adrenal (HPA) axis as well as the sympathetic nervous system, followed by a classical stress response via cortisol and catecholamines. Stress pathways are initiated by noise-induced annoyance and sleep deprivation/fragmentation. This review highlights the down-stream pathophysiology of noise-induced mental stress, which is based on an induction of inflammation and oxidative stress. We highlight the sources of reactive oxygen species (ROS) involved and the known targets for noise-induced oxidative damage. Part of the review emphasizes noise-triggered uncoupling/dysregulation of endothelial and neuronal nitric oxide synthase (eNOS and nNOS) and its central role for vascular dysfunction.

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Exposure to (traffic) noise causes non-auditory (indirect) cardiovascular and cerebral health harms via neuronal activation.

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Noise activates the HPA axis and sympathetic nervous system increasing levels of stress hormones, vasoconstrictors and ROS.

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Noise induces inflammation and stimulates several ROS sources leading to cerebral and cardiovascular oxidative damage.

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Noise leads to eNOS and nNOS uncoupling contributing to cardiometabolic disease and cognitive impairment.

Exogenous NO Therapy for the Treatment and Prevention of Atherosclerosis

Amyl nitrite was introduced in 1867 as the first molecule of a new class of agents for the treatment of angina pectoris. In the following 150 years, the nitric oxide pathway has been the subject of a number of pharmacological approaches, particularly since when this elusive mediator was identified as one of the most important modulators of vascular homeostasis beyond vasomotion, including platelet function, inflammation, and atherogenesis. While having potent antianginal and antiischemic properties, however, nitric oxide donors are also not devoid of side effects, including the induction of tolerance, and, as shown in the last decade, of oxidative stress and endothelial dysfunction. In turn, endothelial dysfunction is itself felt to be involved in all stages of atherogenesis, from the development of fatty streaks to plaque rupture and thrombosis. In the present review, we summarize the agents that act on the nitric oxide pathway, with a particular focus on their potentially beneficial antiatherosclerotic and unwanted pro-atherosclerotic effects.

East Asians Variant Mitochondrial Aldehyde Dehydrogenase 2 Genotype Exacerbates Nitrate Tolerance in Patients With Coronary Spastic Angina

BACKGROUND

Aldehyde dehydrogenase 2 (ALDH2) plays a central role in the biotransformation of glyceryl trinitrate (GTN) or nitroglycerin, which is widely used for the treatment of coronary artery disease (CAD). The deficient variant ALDH2 genotype (ALDH2*2) is prevalent among East Asians. This study examined whether there are differences in nitroglycerine-mediated dilation (NMD) and flow-mediated dilation (FMD) response between wildALDH2*1/*1and variantALDH2*2patients with CAD.

METHODS AND RESULTS

The study subjects comprised 55 coronary spastic angina (CSA) patients, confirmed by coronary angiography and intracoronary injection of acetylcholine (42 men and 13 women, mean age 68.0±9.0 years). They underwent NMD and FMD tests in the morning before and after continuous transdermal GTN administration for 48 h. NMD was lower at baseline inALDH2*2than in theALDH2*1/*1group (P=0.0499) and decreased significantly in both groups (P<0.0001 and P<0.0001, respectively) after GTN, with significantly lower levels in theALDH2*2group (P=0.0002). FMD decreased significantly in bothALDH2*1/*1andALDH2*2groups (P<0.0001and P=0.0002, respectively) after continuous GTN administration, with no significant differences between the 2 groups both before and after GTN.

CONCLUSIONS

Continuous administration of GTN produced endothelial dysfunction as well as nitrate tolerance in bothALDH2*1/1andALDH2*2patients with CSA.ALDH2*2attenuated GTN response and exacerbated GTN tolerance, but not endothelial dysfunction, as compared toALDH2*1/*1in patients with CSA.

Endothelial GLP-1 (Glucagon-Like Peptide-1) Receptor Mediates Cardiovascular Protection by Liraglutide In Mice With Experimental Arterial Hypertension

Supplemental Digital Content is available in the text.

Cardiovascular outcome trials demonstrated that GLP-1 (glucagon-like peptide-1) analogs including liraglutide reduce the risk of cardiovascular events in type 2 diabetes mellitus. Whether GLP-1 analogs reduce the risk for atherosclerosis independent of glycemic control is challenging to elucidate as the GLP-1R (GLP-1 receptor) is expressed on different cell types, including endothelial and immune cells.

Therapeutic Implications of Nitrite in Hypertension

Nitrite, an anion produced from the oxidative breakdown of nitric oxide (NO), has traditionally been viewed as an inert molecule. However, this dogma has been challenged with the findings that nitrite can be readily reduced to NO under pathological conditions, hence representing a physiologically relevant storage reservoir of NO either in the blood or tissues. Nitrite administration has been demonstrated to improve myocardial function in subjects with heart failure and to lower the blood pressure in hypertensive subjects. Thus, extensive amount of work has since been carried out to investigate the therapeutic potential of nitrite in treating cardiovascular diseases, especially hypertension. Studies done on several animal models of hypertension have demonstrated the efficacy of nitrite in preventing and ameliorating the pathological changes associated with the disease. This brief review of the current findings aims to re-evaluate the use of nitrite for the treatment of hypertension and in particular to highlight its role in improving endothelial function.

NADPH oxidases and oxidase crosstalk in cardiovascular diseases: novel therapeutic targets

Reactive oxygen species (ROS)-dependent production of ROS underlies sustained oxidative stress, which has been implicated in the pathogenesis of cardiovascular diseases such as hypertension, aortic aneurysm, hypercholesterolaemia, atherosclerosis, diabetic vascular complications, cardiac ischaemia-reperfusion injury, myocardial infarction, heart failure and cardiac arrhythmias. Interactions between different oxidases or oxidase systems have been intensively investigated for their roles in inducing sustained oxidative stress. In this Review, we discuss the latest data on the pathobiology of each oxidase component, the complex crosstalk between different oxidase components and the consequences of this crosstalk in mediating cardiovascular disease processes, focusing on the central role of particular NADPH oxidase (NOX) isoforms that are activated in specific cardiovascular diseases. An improved understanding of these mechanisms might facilitate the development of novel therapeutic agents targeting these oxidase systems and their interactions, which could be effective in the prevention and treatment of cardiovascular disorders.

Effect of Telmisartan in the Oxidative Stress Components Induced by Ischemia Reperfusion in Rats

The therapeutic effects of telmisartan, an angiotensin II receptor antagonist and a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, have been demonstrated in several disorders. It has antioxidant and immune response modulator properties and has shown promising results in the treatment of an ischemia/reperfusion (I/R) lesion. In this study, a skeletal muscle (right gastrocnemius muscle) I/R lesion was induced in rats and different reperfusion times (1 h, 24 h, 72 h, 7-day, and 14-day subgroups) were assessed. Furthermore, levels of oxidative markers such as enzymatic scavengers (catalase (CAT) and superoxide dismutase (SOD)) and metabolites (nitrates and 8-oxo-deoxyguanosine) were determined. The degree of tissue injury (total lesioned fibers and inflammatory cell count) was also evaluated. We observed an increase in CAT and SOD expression levels under telmisartan treatment, with a decrease in injury and oxidative biomarker levels in the 72 h, 7-day, and 14-day subgroups. Telmisartan reduced oxidative stress and decreased the damage of the I/R lesion.

The Endothelin Receptor Antagonist Macitentan Improves Isosorbide-5-Mononitrate (ISMN) and Isosorbide Dinitrate (ISDN) Induced Endothelial Dysfunction, Oxidative Stress, and Vascular Inflammation

Objective

Organic nitrates such as isosorbide-5-mononitrate (ISMN) and isosorbide dinitrate (ISDN) are used for the treatment of patients with chronic symptomatic stable coronary artery disease and chronic congestive heart failure. Limiting side effects of these nitrovasodilators include nitrate tolerance and/or endothelial dysfunction mediated by oxidative stress. Here, we tested the therapeutic effects of the dual endothelin (ET) receptor antagonist macitentan in ISMN- and ISDN-treated animals.

Methods and Results

Organic nitrates (ISMN, ISDN, and nitroglycerin (GTN)) augmented the oxidative burst and interleukin-6 release in cultured macrophages, whereas macitentan decreased the oxidative burst in isolated human leukocytes. Male C57BL/6j mice were treated with ISMN (75 mg/kg/d) or ISDN (25 mg/kg/d) via s.c. infusion for 7 days and some mice in addition with 30 mg/kg/d of macitentan (gavage, once daily). ISMN and ISDN in vivo therapy caused endothelial dysfunction but no nitrate (or cross-)tolerance to the organic nitrates, respectively. ISMN/ISDN increased blood nitrosative stress, vascular/cardiac oxidative stress via NOX-2 (fluorescence and chemiluminescence methods), ET1 expression, ET receptor signaling, and markers of inflammation (protein and mRNA level). ET receptor signaling blockade by macitentan normalized endothelial function, vascular/cardiac oxidative stress, and inflammatory phenotype in both nitrate therapy groups.

Conclusion

ISMN/ISDN treatment caused activation of the NOX-2/ET receptor signaling axis leading to increased vascular oxidative stress and inflammation as well as endothelial dysfunction. Our study demonstrates for the first time that blockade of ET receptor signaling by the dual endothelin receptor blocker macitentan improves adverse side effects of the organic nitrates ISMN and ISDN.

New Therapeutic Implications of Endothelial Nitric Oxide Synthase (eNOS) Function/Dysfunction in Cardiovascular Disease

The Global Burden of Disease Study identified cardiovascular risk factors as leading causes of global deaths and life years lost. Endothelial dysfunction represents a pathomechanism that is associated with most of these risk factors and stressors, and represents an early (subclinical) marker/predictor of atherosclerosis. Oxidative stress is a trigger of endothelial dysfunction and it is a hall-mark of cardiovascular diseases and of the risk factors/stressors that are responsible for their initiation. Endothelial function is largely based on endothelial nitric oxide synthase (eNOS) function and activity. Likewise, oxidative stress can lead to the loss of eNOS activity or even “uncoupling” of the enzyme by adverse regulation of well-defined “redox switches” in eNOS itself or up-/down-stream signaling molecules. Of note, not only eNOS function and activity in the endothelium are essential for vascular integrity and homeostasis, but also eNOS in perivascular adipose tissue plays an important role for these processes. Accordingly, eNOS protein represents an attractive therapeutic target that, so far, was not pharmacologically exploited. With our present work, we want to provide an overview on recent advances and future therapeutic strategies that could be used to target eNOS activity and function in cardiovascular (and other) diseases, including life style changes and epigenetic modulations. We highlight the redox-regulatory mechanisms in eNOS function and up- and down-stream signaling pathways (e.g., tetrahydrobiopterin metabolism and soluble guanylyl cyclase/cGMP pathway) and their potential pharmacological exploitation.

Sources of Vascular Nitric Oxide and Reactive Oxygen Species and Their Regulation

Nitric oxide (NO) is a small free radical with critical signaling roles in physiology and pathophysiology. The generation of sufficient NO levels to regulate the resistance of the blood vessels and hence the maintenance of adequate blood flow is critical to the healthy performance of the vasculature. A novel paradigm indicates that classical NO synthesis by dedicated NO synthases is supplemented by nitrite reduction pathways under hypoxia. At the same time, reactive oxygen species (ROS), which include superoxide and hydrogen peroxide, are produced in the vascular system for signaling purposes, as effectors of the immune response, or as byproducts of cellular metabolism. NO and ROS can be generated by distinct enzymes or by the same enzyme through alternate reduction and oxidation processes. The latter oxidoreductase systems include NO synthases, molybdopterin enzymes, and hemoglobins, which can form superoxide by reduction of molecular oxygen or NO by reduction of inorganic nitrite. Enzymatic uncoupling, changes in oxygen tension, and the concentration of coenzymes and reductants can modulate the NO/ROS production from these oxidoreductases and determine the redox balance in health and disease. The dysregulation of the mechanisms involved in the generation of NO and ROS is an important cause of cardiovascular disease and target for therapy. In this review we will present the biology of NO and ROS in the cardiovascular system, with special emphasis on their routes of formation and regulation, as well as the therapeutic challenges and opportunities for the management of NO and ROS in cardiovascular disease.

S-Nitrosylation of Prostacyclin Synthase Instigates Nitrate Cross-Tolerance In Vivo

Development of nitrate tolerance is a major drawback to nitrate therapy. Prostacyclin (PGI2) is a powerful vasodilator produced from prostaglandin (PGH2) by prostacyclin synthase (PGIS) in endothelial cells. This study aimed to determine the role of PGIS S-nitrosylation in nitrate tolerance induced by nitroglycerin (GTN). In endothelial cells, GTN increased PGIS S-nitrosylation and disturbed PGH2 metabolism, which were normalized by mutants of PGIS cysteine 231/441 to alanine (C231/441A). Clearance of nitric oxide by carboxy-PTIO or inhibition of S-nitrosylation by N-acetyl-cysteine decreased GTN-induced PGIS S-nitrosylation. Enforced expression of mutated PGIS with C231/441A markedly abolished GTN-induced PGIS S-nitrosylation and nitrate cross-tolerance in Apoe^-/- mice. Inhibition of cyclooxygenase 1 by aspirin, supplementation of PGI2 by beraprost, and inhibition of PGIS S-nitrosylation by N-acetyl-cysteine improved GTN-induced nitrate cross-tolerance in rats. In patients, increased PGIS S-nitrosylation was associated with nitrate tolerance. In conclusion, GTN induces nitrate cross-tolerance through PGIS S-nitrosylation at cysteine 231/441.

Induction of microRNA-199 by Nitric Oxide in Endothelial Cells Is Required for Nitrovasodilator Resistance via Targeting of Prostaglandin I2 Synthase

Background:

Nitrates are widely used to treat coronary artery disease, but their therapeutic value is compromised by nitrate tolerance, because of the dysfunction of prostaglandin I2 synthase (PTGIS). MicroRNAs repress target gene expression and are recognized as important epigenetic regulators of endothelial function. The aim of this study was to determine whether nitrates induce nitrovasodilator resistance via microRNA-dependent repression of PTGIS gene expression.

Methods:

Nitrovasodilator resistance was induced by nitroglycerin (100 mg·kg –1 ·d –1 , 3 days) infusion in Apoe –/– mice. The responses of aortic arteries to nitric oxide donors were assessed in an organ chamber. The expression levels of microRNA-199 (miR-199)a/b were assayed by quantitative reverse transcription polymerase chain reaction or fluorescent in situ hybridization.

Results:

In cultured human umbilical vein endothelial cells, nitric oxide donors induced miR-199a/b endogenous expression and downregulated PTGIS gene expression, both of which were reversed by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt or silence of serum response factor. Evidence from computational and luciferase reporter gene analyses indicates that the seed sequence of 976 to 982 in the 3′-untranslated region of PTGIS mRNA is a target of miR-199a/b. Gain functions of miR-199a/b resulting from chemical mimics or adenovirus-mediated overexpression increased PTGIS mRNA degradation in HEK293 cells and human umbilical vein endothelial cells. Furthermore, nitroglycerin-decreased PTGIS gene expression was prevented by miR-199a/b antagomirs or was mirrored by the enforced expression of miR-199a/b in human umbilical vein endothelial cells. In Apoe –/– mice, nitroglycerin induced the ectopic expression of miR-199a/b in the carotid arterial endothelium, decreased PTGIS gene expression, and instigated nitrovasodilator resistance, all of which were abrogated by miR-199a/b antagomirs or LNA—anti–miR-199. It is important that the effects of miR-199a/b inhibitions were abolished by adenovirus-mediated PTGIS deficiency. Moreover, the enforced expression of miR-199a/b in vivo repressed PTGIS gene expression and impaired the responses of aortic arteries to nitroglycerin/sodium nitroprusside/acetylcholine/cinaciguat/riociguat, whereas the exogenous expression of the PTGIS gene prevented nitrovasodilator resistance in Apoe –/– mice subjected to nitroglycerin infusion or miR-199a/b overexpression. Finally, indomethacin, iloprost, and SQ29548 improved vasorelaxation in nitroglycerin-infused Apoe –/– mice, whereas U51605 induced nitrovasodilator resistance. In humans, the increased expressions of miR-199a/b were closely associated with nitrate tolerance.

Conclusions:

Nitric oxide–induced ectopic expression of miR-199a/b in endothelial cells is required for nitrovasodilator resistance via the repression of PTGIS gene expression. Clinically, miR-199a/b is a novel target for the treatment of nitrate tolerance.

European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed.

Taking up the cudgels for the traditional reactive oxygen and nitrogen species detection assays and their use in the cardiovascular system

Reactive oxygen and nitrogen species (RONS such as H2O2, nitric oxide) confer redox regulation of essential cellular functions (e.g. differentiation, proliferation, migration, apoptosis), initiate and catalyze adaptive stress responses. In contrast, excessive formation of RONS caused by impaired break-down by cellular antioxidant systems and/or insufficient repair of the resulting oxidative damage of biomolecules may lead to appreciable impairment of cellular function and in the worst case to cell death, organ dysfunction and severe disease phenotypes of the entire organism. Therefore, the knowledge of the severity of oxidative stress and tissue specific localization is of great biological and clinical importance. However, at this level of investigation quantitative information may be enough. For the development of specific drugs, the cellular and subcellular localization of the sources of RONS or even the nature of the reactive species may be of great importance, and accordingly, more qualitative information is required. These two different philosophies currently compete with each other and their different needs (also reflected by different detection assays) often lead to controversial discussions within the redox research community. With the present review we want to shed some light on these different philosophies and needs (based on our personal views), but also to defend some of the traditional assays for the detection of RONS that work very well in our hands and to provide some guidelines how to use and interpret the results of these assays. We will also provide an overview on the "new assays" with a brief discussion on their strengths but also weaknesses and limitations.

Redox regulation of cardiovascular inflammation - Immunomodulatory function of mitochondrial and Nox-derived reactive oxygen and nitrogen species

Oxidative stress is a major hallmark of cardiovascular diseases although a causal link was so far not proven by large clinical trials. However, there is a close association between oxidative stress and inflammation and increasing evidence for a causal role of (low-grade) inflammation for the onset and progression of cardiovascular diseases, which may serve as the missing link between oxidative stress and cardiovascular morbidity and mortality. With the present review we would like to highlight the multiple redox regulated pathways in inflammation, discuss the sources of reactive oxygen and nitrogen species that are of interest for these processes and finally discuss the importance of angiotensin II (AT-II) as a trigger of cardiovascular inflammation and the initiation and progression of cardiovascular diseases.

Angiotensin receptor blockers & endothelial dysfunction: Possible correlation & therapeutic implications

The endothelium is one of the most important constituents of vascular homeostasis, which is achieved through continual and balanced production of different relaxing and contractile factors. When there is a pathological disturbance in release of these products, endothelial dysfunction (ED) will probably occur. ED is considered to be the initial step in the development of atherosclerosis. This pathological activation and inadequate functioning of endothelial cells was shown to be to some extent a reversible process, which all together resulted in increased interest in investigation of different beneficial treatment options. To this point, the pharmacological approach, including for example, the use of angiotensin-converting enzyme inhibitors or statins, was clearly shown to be effective in the improvement of ED. One of many critical issues underlying ED represents instability in the balance between nitric oxide and angiotensin II (Ang II) production. Considering that Ang II was confirmed to be important for the development of ED, the aim of this review article was to summarize the findings of up to date clinical studies associated with therapeutic application of angiotensin receptor blockers and improvement in ED. In addition, it was of interest to review the pleiotropic actions of angiotensin receptor blockers linked to the improvement of ED. The prospective, randomized, double-blind, placebo or active-controlled clinical trials were identified and selected for the final evaluation.

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

Cardiovascular diseases are associated with and/or caused by oxidative stress. This concept has been proven by using the approach of genetic deletion of reactive species producing (pro-oxidant) enzymes as well as by the overexpression of reactive species detoxifying (antioxidant) enzymes leading to a marked reduction of reactive oxygen and nitrogen species (RONS) and in parallel to an amelioration of the severity of diseases. Likewise, the development and progression of cardiovascular diseases is aggravated by overexpression of RONS producing enzymes as well as deletion of antioxidant RONS detoxifying enzymes. Thus, the consequences of the interaction (redox crosstalk) of superoxide/hydrogen peroxide produced by mitochondria with other ROS producing enzymes such as NADPH oxidases (Nox) are of outstanding importance and will be discussed including the consequences for endothelial nitric oxide synthase (eNOS) uncoupling as well as the redox regulation of the vascular function/tone in general (soluble guanylyl cyclase, endothelin-1, prostanoid synthesis). Pathways and potential mechanisms leading to this crosstalk will be analysed in detail and highlighted by selected examples from the current literature including hypoxia, angiotensin II-induced hypertension, nitrate tolerance, aging and others. The general concept of redox-based activation of RONS sources via "kindling radicals" and enzyme-specific "redox switches" will be discussed providing evidence that mitochondria represent key players and amplifiers of the burden of oxidative stress.

LINKED ARTICLES

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.

Effect of Shenmai injection on preventing the development of nitroglycerin-induced tolerance in rats

Long-term nitroglycerin (NTG) therapy causes tolerance to its effects attributing to increased oxidative stress and endothelial dysfunction. Shenmai injection (SMI), which is clinically used to treat cardiovascular diseases, consists of two herbal medicines, Ginseng Rubra and Ophiopogonjaponicas, and is reported to have antioxidant effects. The present study was designed to investigate the potential preventive effects of Shenmai injection on development of nitroglycerin-induced tolerance. The present study involves both in vivo and in vitro experiments to investigate nitroglycerin-induced tolerance. We examined the effect of Shenmai injection on the cardiovascular oxidative stress by measuring the serum levels of malondialdehyde (MDA) and superoxide dismutase (SOD). Endothelial dysfunction was determined by an endothelium-dependent vasorelaxation method in aortic rings and NOS activity. Inhibition of the cGMP/cGK-I signalling pathway was determined from released serum levels of cGMP and the protein expression levels of sGC, cGK-I, PDE1A and P-VASP by western blot. Here, we showed that SMI ameliorated the decrease in AV Peak Vel, the attenuation in the vasodilation response to nitroglycerin and endothelial dysfunction. SMI also reduced the cardiovascular oxidative stress by reducing the release of MDA and increasing the activity of SOD. Shenmai injection further ameliorated inhibition of the cGMP/cGK-I signalling pathway triggered by nitroglycerin-induced tolerance through up-regulating the protein expression of sGC, cGK-I, and P-VASP and down- regulating the proteins expression of PDE1A. In vitro studies showed that Shenmai injection could recover the attenuated vasodilation response to nitroglycerin following incubation (of aortic rings) with nitroglycerin via activating the enzymes of sGC and cGK-I. Therefore, we conclude that Shenmai injection could prevent NTG nitroglycerin-induced tolerance at least in part by decreasing the cardiovascular oxidative stress, meliorating the endothelial dysfunction and ameliorating the inhibition of the cGMP/cGK-I signalling pathway. These findings indicate the potential of Shenmai injection (SMI) as a promising medicine for preventing the development of nitroglycerin-induced tolerance.

Alternative Interventions to Prevent Oxidative Damage following Ischemia/Reperfusion

Ischemia/reperfusion (I/R) lesions are a phenomenon that occurs in multiple pathological states and results in a series of events that end in irreparable damage that severely affects the recovery and health of patients. The principal therapeutic approaches include preconditioning, postconditioning, and remote ischemic preconditioning, which when used separately do not have a great impact on patient mortality or prognosis. Oxidative stress is known to contribute to the damage caused by I/R; however, there are no pharmacological approaches to limit or prevent this. Here, we explain the relationship between I/R and the oxidative stress process and describe some pharmacological options that may target oxidative stress-states.

Effects of telmisartan and pioglitazone on high fructose induced metabolic syndrome in rats

Metabolic syndrome (MS) is a cluster of hypertension, insulin resistance, dyslipidaemia, and hyperuricemia. This study was designed to assess the effect of telmisartan and pioglitazone on high fructose induced MS. Thirty-five male albino rats were classified into 5 groups: A, normal diet; B, high-fructose diet (HFD) subdivided into B1 (HFD only), B2 (telmisartan, 5 mg/kg), B3 (pioglitazone, 10 mg/kg), and B4 (telmisartan + pioglitazone). Administration of the drugs was started after the rats had been on HFD for 4 weeks and continued for 4 weeks. Body mass (BM), blood pressure (BP), uric acid (UA), total cholesterol, triglycerides (TG), high-density lipoprotein (HDL-c), low-density lipoprotein (LDL-c), blood urea nitrogen (BUN), creatinine, and nitric oxide (NO) were measured and the levels of fasting glucose and fasting insulin were estimated. Compared with group B1, telmisartan treatment significantly decreased BP, BM, serum glucose, insulin, UA, urea, cholesterol, TGA, and LDL and significantly increased HDL, whereas pioglitazone treatment significantly decreased BP, serum glucose, insulin, UA, urea, creatinine, cholesterol, TGA, and LDL and significantly increased HDL. Co-administration of pioglitazone + telmisartan significantly decreased insulin, urea, and creatinine compared with telmisartan alone. Combined telmisartan + pioglitazone allowed better control of BP, hyperglycaemia, insulin resistance, and the amelioration of BM increase that may be associated with pioglitazone treatment.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

β3 Adrenergic Stimulation Restores Nitric Oxide/Redox Balance and Enhances Endothelial Function in Hyperglycemia

BACKGROUND

Perturbed balance between NO and O2 (•-). (ie, NO/redox imbalance) is central in the pathobiology of diabetes-induced vascular dysfunction. We examined whether stimulation of β3 adrenergic receptors (β3 ARs), coupled to endothelial nitric oxide synthase (eNOS) activation, would re-establish NO/redox balance, relieve oxidative inhibition of the membrane proteins eNOS and Na(+)-K(+) (NK) pump, and improve vascular function in a new animal model of hyperglycemia.

METHODS AND RESULTS

We established hyperglycemia in male White New Zealand rabbits by infusion of S961, a competitive high-affinity peptide inhibitor of the insulin receptor. Hyperglycemia impaired endothelium-dependent vasorelaxation by "uncoupling" of eNOS via glutathionylation (eNOS-GSS) that was dependent on NADPH oxidase activity. Accordingly, NO levels were lower while O2 (•-) levels were higher in hyperglycemic rabbits. Infusion of the β3 AR agonist CL316243 (CL) decreased eNOS-GSS, reduced O2 (•-), restored NO levels, and improved endothelium-dependent relaxation. CL decreased hyperglycemia-induced NADPH oxidase activation as suggested by co-immunoprecipitation experiments, and it increased eNOS co-immunoprecipitation with glutaredoxin-1, which may reflect promotion of eNOS de-glutathionylation by CL. Moreover, CL reversed hyperglycemia-induced glutathionylation of the β1 NK pump subunit that causes NK pump inhibition, and improved K(+)-induced vasorelaxation that reflects enhancement in NK pump activity. Lastly, eNOS-GSS was higher in vessels of diabetic patients and was reduced by CL, suggesting potential significance of the experimental findings in human diabetes.

CONCLUSIONS

β3 AR activation restored NO/redox balance and improved endothelial function in hyperglycemia. β3 AR agonists may confer protection against diabetes-induced vascular dysfunction.

Nanoliposomal Nitroglycerin Exerts Potent Anti-Inflammatory Effects

Nitroglycerin (NTG) markedly enhances nitric oxide (NO) bioavailability. However, its ability to mimic the anti-inflammatory properties of NO remains unknown. Here, we examined whether NTG can suppress endothelial cell (EC) activation during inflammation and developed NTG nanoformulation to simultaneously amplify its anti-inflammatory effects and ameliorate adverse effects associated with high-dose NTG administration. Our findings reveal that NTG significantly inhibits human U937 cell adhesion to NO-deficient human microvascular ECs in vitro through an increase in endothelial NO and decrease in endothelial ICAM-1 clustering, as determined by NO analyzer, microfluorimetry, and immunofluorescence staining. Nanoliposomal NTG (NTG-NL) was formulated by encapsulating NTG within unilamellar lipid vesicles (DPhPC, POPC, Cholesterol, DHPE-Texas Red at molar ratio of 6:2:2:0.2) that were ~155 nm in diameter and readily uptaken by ECs, as determined by dynamic light scattering and quantitative fluorescence microscopy, respectively. More importantly, NTG-NL produced a 70-fold increase in NTG therapeutic efficacy when compared with free NTG while preventing excessive mitochondrial superoxide production associated with high NTG doses. Thus, these findings, which are the first to reveal the superior therapeutic effects of an NTG nanoformulation, provide the rationale for their detailed investigation for potentially superior vascular normalization therapies.

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.

Strategies to increase nitric oxide signalling in cardiovascular disease

Nitric oxide (NO) is a key signalling molecule in the cardiovascular, immune and central nervous systems, and crucial steps in the regulation of NO bioavailability in health and disease are well characterized. Although early approaches to therapeutically modulate NO bioavailability failed in clinical trials, an enhanced understanding of fundamental subcellular signalling has enabled a range of novel therapeutic approaches to be identified. These include the identification of: new pathways for enhancing NO synthase activity; ways to amplify the nitrate-nitrite-NO pathway; novel classes of NO-donating drugs; drugs that limit NO metabolism through effects on reactive oxygen species; and ways to modulate downstream phosphodiesterases and soluble guanylyl cyclases. In this Review, we discuss these latest developments, with a focus on cardiovascular disease.

Comparative effects of Aliskiren and Telmisartan in high fructose diet-induced metabolic syndrome in rats

Fructose is a commonly used sweetener associated with diets that increase the prevalence of metabolic syndrome (MS). Inhibition of the renin-angiotensin system (RAS) has been consistently demonstrated to reduce MS. However, there has been no direct comparison among different pharmacological modes of inhibiting the RAS concerning their effects on MS. This study investigated the effect of aliskiren, a direct renin inhibitor, versus telmisartan, an angiotensin II-receptor blocker, in the treatment of fructose-induced MS in rats. MS was induced by high fructose (FRC) diet feeding for 12 weeks. Oral administrations of telmisartan (TEL, 5 mg/kg), aliskiren (ALS, 30 mg/kg) or vehicle were started in the last 4 weeks. Results showed that administration of either TEL or ALS with FRC diet equally ameliorated the metabolic parameters (glucose level, oral glucose tolerance test, insulin resistance and serum lipids profile), systolic blood pressure and oxidative stress markers (malondialdehyde, nitric oxide, reduced glutathione levels and catalase activity). Additionally, the effects of TEL and ALS were associated with a decrease in body composition index and attenuation of liver index, serum liver enzyme activities and hepatic expressions of inflammatory and fibrotic markers (tumor necrosis factor-α, nuclear factor kappa-B and transforming growth factor-β) with a significant increase in hepatic glucose transporter-2 and peroxisome proliferator-activated receptors-alpha and gamma expressions. The results suggested that, at indicated dosage, ALS has ameliorative effect equal to that of TEL against FRC-induced metabolic and hepatic disorders; implying that drugs which inhibit the RAS, by different mode of inhibition, profoundly affect fructose-induced MS in rats.

Regulation of eNOS enzyme activity by posttranslational modification

The regulation of endothelial NO synthase (eNOS) employs multiple different cellular control mechanisms impinging on level and activity of the enzyme. This review aims at summarizing the current knowledge on the posttranslational modifications of eNOS, including acylation, nitrosylation, phosphorylation, acetylation, glycosylation and glutathionylation. Sites, mediators and impact on enzyme localization and activity of the single modifications will be discussed. Moreover, interdependence, cooperativity and competition between the different posttranslational modifications will be elaborated with special emphasis on the susceptibility of eNOS to metabolic cues.

Candesartan restores pressure-induced vasodilation and prevents skin pressure ulcer formation in diabetic mice

Background

Angiotensin II type 1 receptor (AT1R) blockers have beneficial effects on neurovascular complications in diabetes and in organ’s protection against ischemic episodes. The present study examines whether the AT1R blocker candesartan (1) has a beneficial effect on diabetes-induced alteration of pressure-induced vasodilation (PIV, a cutaneous physiological neurovascular mechanism which could delay the occurrence of tissue ischemia), and (2) could be protective against skin pressure ulcer formation.

Methods

Male Swiss mice aged 5–6 weeks were randomly assigned to four experimental groups. In two groups, diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ, 200 mg.kg⁻¹). After 6 weeks, control and STZ mice received either no treatment or candesartan (1 mg/kg-daily in drinking water) during 2 weeks. At the end of treatment (8 weeks of diabetes duration), C-fiber mediated nociception threshold, endothelium-dependent vasodilation and PIV were assessed. Pressure ulcers (PUs) were then induced by pinching the dorsal skin between two magnetic plates for three hours. Skin ulcer area development was assessed during three days, and histological examination of the depth of the skin lesion was performed at day three.

Results

After 8 weeks of diabetes, the skin neurovascular functions (C-fiber nociception, endothelium-dependent vasodilation and PIV) were markedly altered in STZ-treated mice, but were fully restored by treatment with candesartan. Whereas in diabetes mice exposure of the skin to pressure induced wide and deep necrotic lesions, treatment with candersartan restored their ability to resist to pressure-induced ulceration as efficiently as the control mice.

Conclusion

Candesartan decreases the vulnerability to pressure-induced ulceration and restores skin neurovascular functions in mice with STZ-induced established diabetes.

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.