Nitric oxide in blood. The nitrosative-oxidative disequilibrium hypothesis on the pathogenesis of cardiovascular disease

Insight into the Pro-inflammatory and Profibrotic Role of Macrophage in Heart Failure With Preserved Ejection Fraction

The prevalence of heart failure (HF) with preserved ejection fraction (HFpEF) is higher than that of HF with reduced/midrange ejection fraction (HFrEF/HFmrEF). However, no evidence-based guidelines for managing HFpEF have been generated. The current body of knowledge indicates that fibrosis and inflammation are important components of the cardiac remodeling process in HFpEF. In addition, macrophages potentially play an important role in pro-inflammatory and profibrotic processes in HFpEF patients, whereas HFpEF comorbidities could be a driving force for systemic microvascular inflammation and endothelial dysfunction. Under such circumstances, macrophages reportedly contribute to inflammation and fibrosis through 3 phases namely, inflammation, repair, and resolution. Signal transduction pathway-targeted therapies using animal experiments have generated important discoveries and breakthroughs for understanding the underlying mechanisms of HFpEF. However, only a handful of studies have reported promising results using human trials. Further investigations are therefore needed to elucidate the exact mechanisms underlying HFpEF and immune-pathogenesis of cardiac fibrosis.

Bridelia ferruginea inhibits key carbohydrate digesting enzyme and intestinal glucose absorption and modulates glucose metabolism in diabetic rats

The antidiabetic potentials of the dichloromethene, ethyl acetate, butanol and aqueous fractions of Bridelia ferruginea leaves were investigated using in vitro, ex vivo and in vivo models. In vitro and ex vivo antidiabetic activities revealed the butanol (BFBF) to be the most active of the fractions, and thus selected for in vivo study. Diabetes was induced using the fructose-streptozotocin model. Treatments with BFBF significantly reduced blood glucose level and improved glucose tolerance, serum insulin level and sensitivity as well as suppressed hyperlipidaemia and serum nephropathy markers. Histopathological analysis revealed the ability of BFBF to protect and regenerate pancreatic β-cells. BFBF significantly elevated glutathione level, catalase and superoxide dismutase activities, while depleting MDA level in serums and kidney of diabetic rats. Phenols, steroids, terpenoids, aliphatic and aromatic compounds were identified in the fractions following GC-MS analysis. Overall, results from this study propose that BFBF possess potent antidiabetic activity.

Dysregulation of stress systems and nitric oxide signaling underlies neuronal dysfunction in Alzheimer's disease

Stress is a multimodal response involving the coordination of numerous body systems in order to maximize the chance of survival. However, long term activation of the stress response results in neuronal oxidative stress via reactive oxygen and nitrogen species generation, contributing to the development of depression. Stress-induced depression shares a high comorbidity with other neurological conditions including Alzheimer's disease (AD) and dementia, often appearing as one of the earliest observable symptoms in these diseases. Furthermore, stress and/or depression appear to exacerbate cognitive impairment in the context of AD associated with dysfunctional catecholaminergic signaling. Given there are a number of homologous pathways involved in the pathophysiology of depression and AD, this article will highlight the mechanisms by which stress-induced perturbations in oxidative stress, and particularly NO signaling, contribute to neurodegeneration.

The Inflammatory Response to Ventricular Assist Devices

The therapeutic use of ventricular assist devices (VADs) for end-stage heart failure (HF) patients who are ineligible for transplant has increased steadily in the last decade. In parallel, improvements in VAD design have reduced device size, cost, and device-related complications. These complications include infection and thrombosis which share underpinning contribution from the inflammatory response and remain common risks from VAD implantation. An added and underappreciated difficulty in designing a VAD that supports heart function and aids the repair of damaged myocardium is that different types of HF are accompanied by different inflammatory profiles that can affect the response to the implanted device. Circulating inflammatory markers and changes in leukocyte phenotypes receive much attention as biomarkers for mortality and disease progression. However, they are seldom used to monitor progress during and outcomes from VAD therapy or during the design phase for new devices. Even the partial reversal of heart damage associated with heart failure is a desirable outcome from VAD use. Therefore, improved understanding of the interplay between VADs and the recipient's inflammatory response would potentially increase their uptake, improve patient lives, and fuel research related to other blood-contacting medical devices. Here we provide a review of what is currently known about inflammation in heart failure and how this inflammatory profile is altered in heart failure patients receiving VAD therapy.

Circulating levels of perfluoroalkyl substances and left ventricular geometry of the heart in the elderly

AIMS

Some persistent organic pollutants (POPs) such as hexachlorobenzene (HCB) and some polychlorinated biphenyls (PCBs) have been shown to interfere with myocardial function and geometry. We therefore investigated if also another group of POPs: per- and polyfluoroalkyl substances (PFASs) were associated with alterations in left ventricular geometry.

METHODS

801 subjects aged 70 years were investigated in a cross-sectional study within the scope of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study. Eight PFASs were detected in >75% of participants´ plasma by ultra-performance liquid chromatograph/tandem mass spectrometry. Left ventricular geometry was determined by echocardiography. Multivariable linear regression was used to investigate the associations between PFASs and left ventricular geometry of the heart after exclusion of subjects with previous myocardial infarction (n = 72).

RESULTS

When adjusting for multiple comparisons, none of the eight PFASs evaluated were significantly related to left ventricular mass. However, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA) were related to relative wall thickness (RWT) in a negative fashion (p < 0.0021). Besides being inversely related to RWT, PFNA was also positively related to left ventricular end-diastolic volume (LVEDD) (p < 0.0021). These analyses were adjusted for traditional cardiovascular risk factors.

CONCLUSION

In this cross-sectional study, several of the PFASs evaluated, especially PFNA, were related to myocardial geometry: a reduction in relative wall thickness and an increase in left ventricular diameter following adjustment for traditional cardiovascular risk factors, suggesting a role for PFASs in cardiac remodeling.

Tadalafil: Protective Action against the Development of Multiple Organ Failure Syndrome

Introduction

Multiple organ failure syndrome (MOFS) is a pathology associated to unspecified and severe trauma, characterized by elevated morbidity and mortality. The complex inflammatory MOFS-related reactions generate important ischemia-reperfusion responses in the induction of this syndrome. Nitric oxide elevation, through the activation of cyclic guanosine monophosphate (cGMP), has the potential of counteracting the typical systemic vasoconstriction, and platelet-induced hypercoagulation. Tadalafil would possibly act protectively by reducing cGMP degradation with consequent diffuse vasodilatation, besides reduction of platelet-induced hypercoagulation, thus, preventing multiple organ failure syndrome development.

Methods

The experimental protocol was previously approved by an institution animal research committee. Experimental MOFS was induced through the stereotaxic micro-neurosurgical bilateral anterior hypothalamic lesions model. Groups of 10 Wistar rats were divided into:

a) Non-operated control;

b) Operated control group;

c) 2 hours after tadalafil-treated operated group;

d) 4 hours after tadalafil-treated operated group;

e) 8 hours after post-treated operated group. The animals were sacrificed 24 hours after the neurosurgical procedure and submitted to histopathologic examination of five organs: brain, lungs, stomach, kidneys, and liver.

Results

The electrolytic hypothalamic lesions resulted in a full picture of MOFS with disseminated multiple-organs lesions, provoked primarily by diffusely spread micro-thrombi. The treatment with tadalafil 2 hours after the micro-neurosurgical lesions reduced the experimental MOFS lesions development, in a highly significant level (P<0.01) of 58.75%. The treatment with tadalafil, 4 hours after the micro-neurosurgically-induced MOFS lesions, also reduced in 49.71%, in a highly significant level (P<0.01). Finally, the treatment with tadalafil 8 hours after the neurosurgical procedure resulted in a statistically significant reduction of 30.50% (P<0.05) of the experimentally-induced MOFS gravity scores.

Conclusion

The phosphodiesterase 5 inhibitor, tadalafil, in the doses and timing utilized, showed to protect against the experimentally-induced MOFS.

T786C Mutation in the Endothelial Nitric Oxide Synthase Gene in Patients With Primary Osteonecrosis

Mutations in the T786C endothelial nitric oxide synthase gene (eNOS) are associated with osteonecrosis and Prinzmetal's angina. Nitric oxide is necessary for bone health and ameliorates Prinzmetal's angina. This study compared mutations of T786C eNOS in 146 patients with primary osteonecrosis, 114 patients with Prinzmetal's angina, and 83 normal control subjects. Patients with osteonecrosis had more mutant eNOS alleles than control subjects (42% vs 22%, respectively; P<.0001) but had the same number of mutant alleles as patients with Prinzmetal's angina (42% vs 41%, respectively; P=.7), who in turn had more mutant eNOS alleles than control subjects (41% vs 22%, respectively; P=.0001). Of 146 patients with primary osteonecrosis, 65 (45%) had none of the 5 thrombophilias (Factor V Leiden heterozygosity, high levels of Factors VIII and XI, anticardiolipin antibody immunoglobulin M, and homocysteine) that otherwise distinguished patients with osteonecrosis from control subjects (P<.05). No associations were found between eNOS hetero-homozygosity and the 5 major thrombophilias in primary osteonecrosis. Of the 65 patients who had osteonecrosis but no major thrombophilias, for 41 (28% of the total sample of 146), eNOS hetero-homozygosity was the only abnormality. Normalization of nitric oxide levels with l-arginine 9 g/d or l-citrulline 800 mg/d, both of which relieve vasospastic angina in Prinzmetal's angina, which has the same eNOS genotype as primary osteonecrosis, may slow or stop the progression of osteonecrosis. Placebo-controlled trials of patients with primary osteonecrosis who are hetero-homozygous for the T786C eNOS mutation and have no major thrombophilias are needed to assess the safety and efficacy of this treatment. [Orthopedics. 2017; 40(5):e898-e903.].

Moderate Treadmill Exercise Training Improves Cardiovascular and Nitrergic Response and Resistance to Trypanosoma cruzi Infection in Mice

There is evidence suggesting that exercise training (ET) acts as a factor toward resistance to Trypanosoma cruzi infection. However, the effects of mean arterial pressure (MAP), heart rate (HR), and nitric oxide (NO) during the acute phase of infection has not been elucidated yet. Swiss mice were randomly assigned into four groups: sedentary control (SC, n = 30), trained control (TC, n = 30), sedentary infected (SI, n = 30), and trained infected (TI, n = 30). ET was performed on the treadmill for 9 weeks. After training, the mice were infected with 5 × 10³ trypomastigotes of T. cruzi (Y strain) or PBS. We observed resting bradycardia and improved performance in trained animals compared with sedentary ones. On the 20th day post-infection (DPI), we found a decrease in HR in SI animals compared to TI animals (699.73 ± 42.37 vs. 742.11 ± 25.35 bpm, respectively, P < 0.05). We also observed increased production of NO in cardiac tissue on the 20th DPI in the SI group, normalized in TI group (20.73 ± 2.74 vs. 6.51 ± 1.19 μM, respectively). Plasma pro-inflammatory cytokines (IL-12, TNF-α, IFN-γ,) and MCP-1 were increased in SI animals, but decreased in TI animals. The increase in parasitemia on the 15th and 17th DPI in the SI group was attenuated in the TI group. Our results suggest that previous ET plays a preventive role in resistance to T. cruzi infection, modulating cardiovascular aspects, inflammatory reaction, and NO levels of infected mice.

The role of inflammation and cell death in the pathogenesis, progression and treatment of heart failure

Chronic inflammation underlies a variety of seemingly unrelated conditions including coronary artery disease. The interest in exploring the role of inflammation in heart failure (CHF) arises from earlier observations that circulating pro-inflammatory biomarker levels are elevated in patients with both ischaemic and non-ischaemic cardiomyopathies and correlate with severity of disease and prognosis (McMurray et al. in Eur Heart J 33:1787-1847, 2012; Mosterd and Hoes in Heart 93:1137-1146, 2007; Owan et al. in New Engl J Med 355:251-259, 2006). In acute decompensated HF, pro-inflammatory biomarker levels have been associated with mortality and readmission rates (Cowie et al. in Heart 83:505-510, 2000). Similar to neurohormonal activation and inflammation, production of pro-inflammatory cytokines is a response to stress in an attempt to restore cellular function. However, sustained expression and exposure to cytokines can lead to left ventricular dysfunction, negative inotropic effects, altered cardiac metabolism, myocardial remodelling and HF progression. However, it is unclear whether elevated levels of pro-inflammatory biomarkers, such as high-sensitivity C-reactive protein, signify an ongoing inflammatory process that leads to HF progression, or are merely markers of advanced disease. Beta-blockers, renin-angiotensin-aldosterone axis antagonists, statins and immunosuppressants have been found to decrease the levels of cytokines in small clinical studies of patients with HF (Hobbs et al. in Heart J 28:1128-1134, 2007). However, 'immunomodulatory' approaches applied in the RECOVER, RENAISSANCE, ATTACH, IMAC and ACCLAIM double-blind, placebo-controlled studies had neutral or negative effects on outcomes of patients with HF. In the present review, we focus on the role of inflammation in pathogenesis and progression of the HF, the value of pro-inflammatory cytokines as biomarkers and the potential therapeutic applications of immunomodulation in HF patients.

Diabetes and Kidney Disease: Role of Oxidative Stress

Intrarenal oxidative stress plays a critical role in the initiation and progression of diabetic kidney disease (DKD). Enhanced oxidative stress results from overproduction of reactive oxygen species (ROS) in the context of concomitant, insufficient antioxidant pathways. Renal ROS production in diabetes is predominantly mediated by various NADPH oxidases (NOXs), but a defective antioxidant system as well as mitochondrial dysfunction may also contribute. Recent Advances: Effective agents targeting the source of ROS generation hold the promise to rescue the kidney from oxidative damage and prevent subsequent progression of DKD. Critical Issues and Future Directions: In the present review, we summarize and critically analyze molecular and cellular mechanisms that have been demonstrated to be involved in NOX-induced renal injury in diabetes, with particular focus on the role of increased glomerular injury, the development of albuminuria, and tubulointerstitial fibrosis, as well as mitochondrial dysfunction. Furthermore, novel agents targeting NOX isoforms are discussed. Antioxid. Redox Signal. 25, 657-684.

Effects of thyroid hormones on the antioxidative status in the uterus of young adult rats

Thyroid hormones and oxidative stress play significant roles in the normal functioning of the female reproductive system. Nitric oxide (NO), a free radical synthesized by nitric oxide synthases (NOS), participates in the regulation of thyroid function and is also a good biomarker for assessment of the oxidative stress status. Therefore, the purpose of this study was to investigate effects of thyroid hormones on uterine antioxidative status in young adult rats. Thirty immature female Sprague-Dawley rats were randomly divided into three groups: control, hypothyroid (hypo-T) and hyperthyroid (hyper-T). The results showed the body weights decreased significantly in both the hypo-T and hyper-T groups and that uterine weights were decreased significantly in the hypo-T group. The serum concentrations of total triiodothyronine (T3) and thyroxine (T4), as well as estradiol (E2), were significantly decreased in the hypo-T group, but increased in the hyper-T group. The progesterone (P4) concentrations in the hypo- and hyperthyroid rats markedly decreased. Immunohistochemistry results provided evidence that thyroid hormone nuclear receptor α/β (TRα/β) and three NOS isoforms were located in different cell types of rat uteri. The NO content and total NOS and inducible NOS (iNOS) activities were markedly diminished in the hypo-T group but increased in the hyper-T group. Moreover, the activities of both glutathione peroxidase (GSH-Px) and catalase (CAT) exhibited significant decreases and increases in the hypo-T and hyper-T groups, respectively. The malondialdehyde (MDA) contents in both the hypo-T and hyper-T groups showed a significant increase. Total superoxide dismutase (T-SOD) activity in the hypo- and hyper-T rats markedly decreased. In conclusion, these results indicated that thyroid hormones have an important influence on the modulation of uterine antioxidative status.

Mechanisms of cardiac radiation injury and potential preventive approaches

In addition to cytostatic treatment and surgery, the most common cancer treatment is gamma radiation. Despite sophisticated radiological techniques however, in addition to irradiation of the tumor, irradiation of the surrounding healthy tissue also takes place, which results in various side-effects, depending on the absorbed dose of radiation. Radiation either damages the cell DNA directly, or indirectly via the formation of oxygen radicals that in addition to the DNA damage, react with all cell organelles and interfere with their molecular mechanisms. The main features of radiation injury besides DNA damage is inflammation and increased expression of pro-inflammatory genes and cytokines. Endothelial damage and dysfunction of capillaries and small blood vessels plays a particularly important role in radiation injury. This review is focused on summarizing the currently available data concerning the mechanisms of radiation injury, as well as the effectiveness of various antioxidants, anti-inflammatory cytokines, and cytoprotective substances that may be utilized in preventing, mitigating, or treating the toxic effects of ionizing radiation on the heart.

Oral supplementation with a combination of L-citrulline and L-arginine rapidly increases plasma L-arginine concentration and enhances NO bioavailability

BACKGROUND

Chronic supplementation with L-citrulline plus L-arginine has been shown to exhibit anti-atherosclerotic effects. However, the short-term action of this combination on the nitric oxide (NO)-cGMP pathway remains to be elucidated. The objective of the present study was to investigate the acute effects of a combination of oral L-citrulline and L-arginine on plasma L-arginine and NO levels, as well as on blood circulation.

METHODS

Rats or New Zealand white rabbits were treated orally with L-citrulline, or L-arginine, or a combination of each at half dosage. Following supplementation, plasma levels of L-arginine, NOx, cGMP and changes in blood circulation were determined sequentially.

RESULTS

L-Citrulline plus L-arginine supplementation caused a more rapid increase in plasma L-arginine levels and marked enhancement of NO bioavailability, including plasma cGMP concentrations, than with dosage with the single amino acids. Blood flow in the central ear artery in rabbits was also significantly increased by L-citrulline plus L-arginine administration as compared with the control.

CONCLUSION

Our data show for the first time that a combination of oral L-citrulline and L-arginine effectively and rapidly augments NO-dependent responses at the acute stage. This approach may have clinical utility for the regulation of cardiovascular function in humans.

Effects of Oral L-Citrulline Supplementation on Lipoprotein Oxidation and Endothelial Dysfunction in Humans with Vasospastic Angina

BACKGROUND

Decreased nitric oxide (NO) bioavailability and increased lipid oxidation are associated with progressive endothelial dysfunction. L-Citrulline, the effective precursor of L-arginine which is essential as a substrate for endothelial NO synthase (eNOS), is effective in enhancing NO-dependent signaling. However, little is known about the efficacy of L-citrulline supplementation on lipoprotein oxidation and endothelial dysfunction.

METHODS

Twenty-two patients (aged 41 - 64 years old) diagnosed with vasospastic angina with flow-mediated dilation (FMD) of the brachial artery (< 5.5 %) received 800 mg/day of L-citrulline for 8 weeks. FMD (%), blood NOx, asymmetric dimethylarginine (ADMA), small dense LDL, oxidized lipids, amino acids concentrations were measured before and after supplementation.

RESULTS

Compared with baseline values, FMD (%) was significantly improved at 4 and 8 weeks as well as at 4 weeks after the end of intake. L-Citrulline supplementation caused a significant lowering of plasma ADMA levels. Plasma L-arginine/ADMA ratio and NOx levels rose markedly throughout the study period. Moreover, significant reductions of serum oxidized LDL and lectin-like oxidized LDL receptor 1 (LOX-1) ligand containing ApoB (LAB), an indicator of the biological activity of oxidized lipoprotein binding to LOX-1, were observed after L-citrulline intake.

CONCLUSIONS

L-Citrulline supplementation improves endothelial dysfunction, probably due to potentiating NO-dependent reactions and decreasing the state of lipoprotein oxidation in humans.

Assessment of inflammatory and oxidative biomarkers in obesity and their associations with body mass index

The aim of this study was to evaluate the inflammatory and oxidative biomarkers' levels in obese subjects and their associations with body mass index (BMI), in order to investigate the role of these biomarkers in obesity. Fasting glucose, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, apolipoprotein A, apolipoprotein B, albumin, urinary albumin, creatinine, glomerular filtration rate, interleukin-6 (IL-6), nitrate/nitrite (NOx), and ischemia-modified albumin (IMA) were measured in 93 subjects divided according to different BMI. IL-6, urinary albumin, and IMA levels were significantly higher in obese subjects. However, the levels of NOx were significantly lower in this population. Significant correlations between BMI and IL-6 (r = 0.326, P = 0.002), NOx (r = -0.249, P = 0.021), urinary albumin (r = 0.270, P = 0.008), and IMA (r = 0.286, P = 0.005) were reported. We have shown an increase of IL-6, urinary albumin, and IMA combined with lower levels of NOx in obese patients and an association between of these biomarkers with BMI, suggesting a possible interplay of oxidative stress, inflammation, and endothelial dysfunction state in obesity.

Pharmacologic strategies to target oxidative stress in heart failure

Reactive oxygen species (ROS), which are involved in normal physiological functions at low concentrations, can have deleterious effects when produced in excess. Over time, ROS may result in a pathological state of imbalance known as oxidative stress. Oxidative stress has long been implicated in many diseases, and is consistently associated with poor outcomes in heart failure. Most therapies that are currently being used may provide some reduction in oxidative stress, but there is no consensus on the clinical outcomes of various antioxidants. Currently, there are no antioxidant therapies that are being used routinely to specifically target oxidative stress in patients with heart failure. This article reviews the current understanding of ROS generation, and the potential for novel pharmacologic strategies to target oxidative stress in heart failure.

Conflicting effects of nitric oxide and oxidative stress in chronic heart failure: potential therapeutic strategies

Chronic heart failure (CHF) is characterized by decreased nitric oxide (NO) bioavailability. In addition, the beneficial NO turns to be deleterious when it reacts with superoxide anion, leading to peroxynitrite formation. Numerous experimental and clinical studies have reported increased production of reactive oxygen species (superoxide, hydrogen peroxide, hydroxyl radical) both in animals and patients with CHF. Moreover, there are indicative data suggesting mechanisms associated with endothelial dysfunction in states of CHF, mainly attributed to decreased NO bioavailability and enhanced inactivation of the latter. Thus, such molecules appear to be potential targets in patients with CHF. These patients are strong candidates to receive a variety of therapeutic agents, some of which have known antioxidant effects. Classic treatment with statins or angiotensin converting enzyme inhibitors has been found to be beneficial in restoring NO and improving myocardial function and structure. Other agents such as sildenafil and b-blockers along with novel agents such as NO synthase transcription enhancers have been proved to be also beneficial, but their use for such a purpose is still controversial. Approaches using more-effective antioxidants or targeting myocardial oxidant-producing enzymes and oxidative or nitrosative stress might be promising strategies in the future.

Oxidative stress and cardiac hypertrophy: a review

Cardiac hypertrophy (CH) is an adaptive response of the heart to pressure overload. It is a common pathological feature in the natural course of some major cardiovascular diseases, like, hypertension and myocardial infarction. Cardiac hypertrophy is strongly associated with an increased risk of heart failure and sudden cardiac death. The complex and dynamic pathophysiological mechanisms of CH has been the focus of intense scientific investigation, in an effort to design preventive and curative strategies. Oxidative stress has been identified as one of the key contributing factors in the development of cardiac hypertrophy. In this review, evidences supporting the oxidative stress as a cause of cardiac hypertrophy with emphasis on mitochondrial oxidative stress and possible options for pharmacological interventions have been discussed. Reactive oxygen species (ROS) also activate a broad variety of hypertrophy signaling kinases and transcription factors, like, MAP kinase, NF K-B, etc. In addition to profound alteration of cellular function, ROS modulate the extracellular matrix function, evidenced by increased interstitial and perivascular fibrosis. Translocator protein (TSPO) present in the outer mitochondrial membrane is known to be involved in oxidative stress and cardiovascular pathology. Recently, its role in cardiac hypertrophy has been reported by us. All these evidences strongly provide support to beneficial role of drugs which selectively interfere with the generation of free radicals or augment endogenous antioxidants in cardiac hypertrophy.

Oxidative stress as a mediator of cardiovascular disease

During physiological processes molecules undergo chemical changes involving reducing and oxidizing reactions. A molecule with an unpaired electron can combine with a molecule capable of donating an electron. The donation of an electron is termed as oxidation whereas the gaining of an electron is called reduction. Reduction and oxidation can render the reduced molecule unstable and make it free to react with other molecules to cause damage to cellular and sub-cellular components such as membranes, proteins and DNA. In this paper, we have discussed the formation of reactive oxidant species originating from a variety of sources such as nitric oxide (NO) synthase (NOS), xanthine oxidases (XO), the cyclooxygenases, nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase isoforms and metal-catalysed reactions. In addition, we present a treatise on the physiological defences such as specialized enzymes and antioxidants that maintain reduction-oxidation (redox) balance. We have also given an account of how enzymes and antioxidants can be exhausted by the excessive production of reactive oxidant species (ROS) resulting in oxidative stress/nitrosative stress, a process that is an important mediator of cell damage. Important aspects of redox imbalance that triggers the activity of a number of signalling pathways including transcription factors activity, a process that is ubiquitous in cardiovascular disease related to ischemia/reperfusion injury have also been presented.

Patterned electrode-based amperometric gas sensor for direct nitric oxide detection within microfluidic devices

This article describes a thin amperometric nitric oxide (NO) sensor that can be microchannel embedded to enable direct real-time detection of NO produced by cells cultured within the microdevice. A key for achieving the thin ( approximately 1 mm) planar sensor configuration required for sensor-channel integration is the use of gold/indium-tin oxide patterned electrode directly on a porous polymer membrane (pAu/ITO) as the base working electrode. The electrochemically deposited Au-hexacyanoferrate layer on pAu/ITO is used to catalyze NO oxidation to nitrite at lower applied potentials (0.65-0.75 V vs Ag/AgCl) and stabilize current output. Furthermore, use of a gas-permeable membrane to separate internal sensor compartments from the sample phase imparts excellent NO selectivity over common interfering agents (e.g., nitrite, ascorbate, ammonia, etc.) present in culture media and biological fluids. The optimized sensor design reversibly detects NO down to the approximately 1 nM level in stirred buffer and <10 nM in flowing buffer when integrated within a polymeric microfluidic device. We demonstrate utility of the channel-embedded sensor by monitoring NO generation from macrophages cultured within non-gas-permeable microchannels, as they are stimulated with endotoxin.

Hyperinsulinaemia in migraineurs is associated with nitric oxide stress

There is growing evidence that alterations in the insulin and glucose metabolism may be involved in the pathogenesis of migraine. Nitric oxide (NO) stress has been associated with migraine. However, the role of NO on the insulin and glucose metabolism in migraineurs has remained elusive to date. The aim of the present study was to investigate the insulin and glucose metabolism in migraineurs and to determine possible interactions with the NO pathway. One hundred and twenty non-obese probands participated in this study, including 48 migraineurs and 72 healthy volunteers. Various parameters of the NO pathway, glucose metabolism as well as body measurement parameters were determined. We found a highly significantly increased insulin and Homeostasis Model Assessment (HOMA)-index in migraine patients, whereas fasting glucose was decreased. Logistic regression revealed an odds ratio of 5.67 for migraine, when comparing the lowest with the highest quartile of HOMA. Multivariate analysis showed that HOMA, waist-to-length ratio and nitrite as parameters of NO stress were highly significantly correlated. We show here that hyperinsulinaemia is associated with migraine and, furthermore, is correlated with increased NO stress. These findings represent a new pathophysiological mechanism that may be of clinical relevance.

Tracing the origins of postoperative atrial fibrillation: the concept of oxidative stress-mediated myocardial injury phenomenon

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia associated with coronary artery surgery and is an important factor contributing to postoperative morbidity and mortality. Recently, there is growing evidence that dysregulation of the oxidant-antioxidant balance, inflammatory factors and discordant alteration of energy metabolites may play a significant role in its pathogenesis.

DESIGN

We evaluated the link between postoperative atrial fibrillation with inflammatory factors and oxidative stress.

METHODS

We searched all databases in Medline, Pubmed, ISI, the Cochrane database, and Embase. We identified more than 100 trials, multiple metaanalyses, and three sets of practice guidelines for the prevention of PAF in cardiac surgery.

RESULTS

Mechanisms of postoperative AF are likely to be multifactorial and are influenced by preoperative, intraoperative and postoperative factors including a genetic basis. Electrical remodelling is thought to be related to the generation of reactive oxidant species and inflammatory factors during the ischemia-reperfusion phase of cardiac surgery. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase was found to be the primary source of superoxide within the human atrial myocardium (in patients in sinus rhythm and in those with AF) and linked with paroxysmal and chronic AF. Reactive oxidant species cause lipid peroxidation, breakdown of cell membrane, decreased mitochondrial function, calcium overload and apoptosis. This affect was shown to be reversed by exogenous nitric oxide/donors (sodium nitroprusside). Inflammatory factors such as the rise in white blood cell count, C-reactive proteins were implicated in the pathogenesis of AF. In contrast, new evidence identifies statins as having both antioxidant and anti-inflammatory properties and that their use reduces the incidence of postoperative AF (57% in the control vs. 35% in the atorvastatin group). Other antiinflammatory strategies include steroids with one study showing postoperative AF occurred in 21% in the steroid group compared with 51% in the placebo group although their use resulted in an increase in other complications. The mainstay of therapy however, remains to be beta-blockers alone which impart a modest influence on overall rates of AF with a reduction from 33.7 to 16.9% (OR: 0.37, 95% CI: 0.29-0.48). Angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers has been shown in one study to reduce the risk of developing new-onset AF by nearly 50%, although this has not been adequately evaluated in cardiac surgery.

CONCLUSION

Inflammatory factors and oxidative stress play a major role in the pathogenesis of postoperative AF. This review provides an analysis of current evidence in support of efforts directed at antiinflammatory and antioxidant agents as interventions.

Up-regulation of myocardial DNA base excision repair activities in experimental heart failure

Base excision repair (BER) is the major pathway to counteract the genotoxic effect of endogenous DNA damaging agents. The present study investigated the enzymatic activities and gene transcription of DNA glycosylases initiating BER in an experimental heart failure (HF) model. Rats were subjected to myocardial infarction or sham-operated. Twenty-eight days after surgical intervention cell-free protein extracts, total RNA and genomic DNA were isolated to analyze DNA glycosylase and AP-endonuclease activities, transcript levels of DNA glycosylases and accumulation of oxidative DNA damage. The capacity to remove major oxidation products (e.g., formamidopyrimidine and 5-hydroxycytosine) was significantly increased in the border zone of infarcted area, while the capacity to remove the highly mutagenic 8-oxoguanine residue was enhanced both in non-infarcted and infarcted areas of left ventricle (LV). DNA glycosylase activities towards 3-methyladenine and uracil were up-regulated in infarcted and non-infarcted areas of LV, indicating that generation of alkylated and deaminated base lesions on DNA increase during HF. Finally, we found no difference in accumulation of oxidative DNA damage in myocardial tissue between rats with post-myocardial infarction and sham-operated rats. This up-regulation of activities, initiating the BER pathway, could play an important role during HF by counteracting the effect of genotoxic stress, structural damage of tissue and myocardial remodeling.

Vascular endothelium in atherosclerosis

Their strategic location between blood and tissue and their constitutive properties allow endothelial cells (EC) to monitor the transport of plasma molecules, by employing bidirectional receptor-mediated and receptor-independent transcytosis and endocytosis, and to regulate vascular tone, cellular cholesterol and lipid homeostasis. These cells are also involved in signal transduction, immunity, inflammation and haemostasis. Cardiovascular risk factors, such as hyperlipaemia/dyslipidaemia trigger the molecular machinery of EC to respond to insults by modulation of their constitutive functions followed by dysfunction and ultimately by injury and apoptosis. The gradual activation of EC consists initially in the modulation of two constitutive functions: (1) permeability, i.e. increased transcytosis of lipoproteins, and (2) biosynthetic activity, i.e. enhanced synthesis of the basement membrane and extracellular matrix. The increased transcytosis and the reduced efflux of beta-lipoproteins (betaLp) lead to their retention within the endothelial hyperplasic basal lamina as modified lipoproteins (MLp) and to their subsequent alteration (oxidation, glycation, enzymatic modifications). MLp generate chemoattractant and inflammatory molecules, triggering EC dysfunction (appearance of new adhesion molecules, secretion of chemokines, cytokines), characterised by monocyte recruitment, adhesion, diapedesis and residence within the subendothelium. In time, EC in the athero-prone areas alter their net negative surface charge, losing their non-thrombogenic ability, become loaded with lipid droplets and turn into foam cells. Prolonged and/or repeated exposure to cardiovascular risk factors can ultimately exhaust the protective effect of the endogenous anti-inflammatory system within EC. As a consequence, EC may progress to senescence, lose their integrity and detach into the circulation.

High glucose increases RAW 264.7 macrophages activation by lipoteichoic acid from Staphylococcus aureus

BACKGROUND

Type 2 diabetes mellitus is associated with an increased risk of cardiovascular diseases and accelerated atherosclerosis, which has been associated to hyperglycemia and chronic inflammation. Activated macrophages are described to participate in atherosclerosis due to foam cell formation and pro-inflammatory mediators production. Bacterial infections are described to accelerate atherosclerosis, moreover, gram-positive and negative bacterial DNA was described in atherosclerotic plaques.

METHODS

We studied the glucose modulation of RAW 264.7 macrophages activation by the gram-positive bacterial antigen lipoteichoic acid (LTA), evaluating nitrite production, tumor necrosis factor alpha secretion and matrix metalloproteinase 9 activity.

RESULTS

High glucose increased macrophages activation by LTA, evidenced by exacerbated nitric oxide and tumor necrosis factor alpha production, as well matrix metalloproteinase 9 secretion.

CONCLUSIONS

These effects could contribute to atherosclerotic risk parameters, like atherome plaque instability, and participate in chronic inflammation present in type 2 diabetes.

Identification of nitric oxide as an endogenous activator of the AMP-activated protein kinase in vascular endothelial cells

In endothelial cells, the AMP-activated protein kinase (AMPK) is stimulated by sheer stress or growth factors that stimulate release of nitric oxide (NO). We hypothesized that NO might act as an endogenous activator of AMPK in endothelial cells. Exposure of human umbilical vein endothelial cells (HUVECs) to NO donors caused an increase in phosphorylation of both Thr-172 of AMPK and Ser-1177 of endothelial nitric oxide synthase, a downstream enzyme of AMPK. NO-induced activation of AMPK was not affected by inhibition of LKB1, an AMPK kinase. In contrast, inhibition of calcium calmodulin-dependent protein kinase kinase abolished the effect of NO in HUVECs. NO-induced AMPK activation in HeLa S3 cells was abolished by either 1H-(1,2,4)-oxadiazole[4,3-a]quinoxalon-1-one, a potent inhibitor for guanylyl cyclase, or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl ester) (BAPTA-AM), an intracellular Ca(2+) chelator, indicating that NO-induced AMPK activation is guanylyl cyclase-mediated and calcium-dependent. Exposure of HUVECs or isolated mice aortas to either calcium ionophore A23187 or bradykinin significantly increased AMPK Thr-172 phosphorylation, which was abolished by N-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase. Finally, A23187- or bradykinin-enhanced AMPK activation was significantly greater in aortas from wild type mice than those in the aortas of endothelial nitric oxide synthase knock-out mice. Taken together, we conclude that NO might act as an endogenous AMPK activator.

Obesity reduces the bioavailability of nitric oxide in juveniles

OBJECTIVE

There is growing evidence that nitric oxide (NO) is critically involved in obesity and its clinical consequences like cardiovascular disease, hypertension and diabetes. We hypothesize that NO is already involved in the pathophysiology of juvenile obesity. We here determined the role of NO, its metabolites arginine and citrulline in obese and normal weight children.

DESIGN

We investigated 57 obese and 57 normal weight age- and gender-matched juveniles. Various clinical parameters as well as body measurements and intima media thickness were determined.

RESULTS

Obese juveniles revealed highly significant alterations in the NO pathway. NOX and citrulline were decreased in obese compared to normal weight juveniles and negatively correlated with body weight. Arginine was increased in obese juveniles and positively correlated with body weight. We found a significant negative correlation between NOX and oxidized low-density lipoprotein. Analysis of gamma-aminobutyric acid (GABA) revealed correlations with the NO pathway as NOX and citrulline were negatively correlated with GABA and arginine showed a positive correlation.

CONCLUSION

We show here that NO and its metabolites arginine and citrulline are already involved in juvenile obesity that may contribute to atherogenesis via reduced bioavailability of NO. Moreover, we identify GABA as a new parameter in the mechanism of obesity-related NO reduction.

Nitric oxide metabolite levels in preterm labor

AIM

To investigate the role of nitric oxide metabolites as markers of infection in subjects with preterm labor or preterm premature rupture of membranes (PTPROM). PTPROM means that there was spontaneous rupture of fetal membrane before the onset of labor and gestational age was <37 weeks. This occurs because of imbalance between matrix metalloproteinase and tissue inhibitor of matrix metalloproteinase. The cause of this imbalance that leads to degradation of collagen causing PTPROM is infection. The bactericidal, fungicidal, viricidal and tumoricidal activities of macrophages are determined in part by elaboration of nitric oxide, hence nitric oxide levels have been found to be increased in infections.

METHODS

During an 18-month period 50 women with preterm labor or PTPROM and 50 controls were enrolled prospectively. Blood and urine samples were obtained for analysis of nitric oxide metabolites. Patients with known causes of preterm labor were excluded.

RESULT

The nitric oxide metabolites, which included both nitrite levels and citrulline levels were significantly higher both in blood as well as urine in patients with preterm labor and PTPROM compared to controls. Serum nitrite levels in subjects with preterm labor were 376.5 +/- 345 nmol/L while in subjects with PTPROM they were 295.7 +/- 161.1 nmol/L and in controls the levels were 62.7 +/- 33.9 nmol/L. Serum citrulline levels in subjects with preterm labor were 5293.8 +/- 2916.7 nmol/L; in PTPROM they were 6536.6 +/- 609.91 nmol/L and in controls they were 949.8 +/- 67.1 nmol/L. On comparing patients with preterm labor, those in whom preterm labor could not be inhibited had statistically significant higher levels of nitrite in both serum and urine (482.9 +/- 387.7 nmol/L and 754.5 +/- 336.5 nmol/L, respectively) compared to patients in whom labor could be inhibited (172.2 +/- 61.9 nmol/L and 401.8 +/- 236.9 nmol/L, respectively). The citrulline levels were also higher among the group who delivered preterm for both serum and urine (5355.4 +/- 3229.7 nmol/L and 11 482.8 +/- 2541.4 nmol/L, respectively) compared to patients in whom labor could be inhibited (5260.2 +/- 2897.08 nmol/L and 10 651.4 +/- 1502.7 nmol/L, respectively) but this did not reach statistical significance.

CONCLUSION

Higher nitric oxide metabolites in women with preterm labor are marker of subclinical infection.