Endothelial dysfunction coincides with an enhanced nitric oxide synthase expression and superoxide anion production

Asymptomatic hyperuricemia: to treat or not a threat? A clinical and evidence-based approach to the management of hyperuricemia in the context of cardiovascular diseases

Asymptomatic hyperuricemia is defined by serum uric acid levels above 6.2 mg/dl in women and 7 mg/dl in men. In the presence of monosodium urate crystal formation and articular inflammation, hyperuricemia may become symptomatic (namely nephrolithiasis and gout). Uric acid results from purine catabolism and is at the centre of a complex metabolic interplay that involves oxidative stress, inflammation, renin-angiotensin-aldosterone system (RAAS) activation and insulin resistance. Uric acid levels present a continuous relation with conditions like hypertension and chronic kidney disease (CKD) and are reported to have an impact on risk of cardiovascular events. However, whether elevated uric acid is a causal agent and thus a possible therapeutic target is still uncertain and matter of further investigation. Treating symptomatic hyperuricemia involves lowering uric acid drugs and controlling inflammation. Urate-lowering agents are well tolerated but show minimal impact on cardiovascular events in patients with gout. Use of direct-acting urate-lowering agents in asymptomatic hyperuricemia associated with cardiovascular diseases does not warrant a clear benefit, whereas addressing cardiovascular issues with guideline-recommended therapies lowers uric acid and reduces the occurrence of cardiovascular events. Regular assessment of uric acid and clinical symptoms is advised before starting and renewing a urate-lowering treatment.

Exploring the therapeutic potential of tetrahydrobiopterin for heart failure with preserved ejection fraction: A path forward

A large number of patients are affected by classical heart failure (HF) symptomatology with preserved ejection fraction (HFpEF) and multiorgan syndrome. Due to high morbidity and mortality rate, hospitalization and mortality remain serious socioeconomic problems, while the lack of effective pharmacological or device treatment means that HFpEF presents a major unmet medical need. Evidence from clinical and basic studies demonstrates that systemic inflammation, increased oxidative stress, and impaired mitochondrial function are the common pathological mechanisms in HFpEF. Tetrahydrobiopterin (BH4), beyond being an endogenous co-factor for catalyzing the conversion of some essential biomolecules, has the capacity to prevent systemic inflammation, enhance antioxidant resistance, and modulate mitochondrial energy production. Therefore, BH4 has emerged in the last decade as a promising agent to prevent or reverse the progression of disorders such as cardiovascular disease. In this review, we cover the clinical progress and limitations of using downstream targets of nitric oxide (NO) through NO donors, soluble guanylate cyclase activators, phosphodiesterase inhibitors, and sodium-glucose co-transporter 2 inhibitors in treating cardiovascular diseases, including HFpEF. We discuss the use of BH4 in association with HFpEF, providing new evidence for its potential use as a pharmacological option for treating HFpEF.

Arginase-1 Deletion in Erythrocytes Promotes Vascular Calcification via Enhanced GSNOR (S-Nitrosoglutathione Reductase) Expression and NO Signaling in Smooth Muscle Cells

BACKGROUND

Erythrocytes (red blood cells) participate in the control of vascular NO bioavailability. The purpose of this study was to determine whether and how genetic deletion of ARG1 (arginase-1) affects vascular smooth muscle cell NO signaling, osteoblastic differentiation, and atherosclerotic lesion calcification.

METHODS

Atherosclerosis-prone mice with conditional, erythrocyte-restricted deletion of ARG1 (apoE^-/- red blood cell.ARG1 knockout) were generated and vascular calcification studied using molecular imaging of the osteogenic activity agent OsteoSense, Alizarin staining or immunohistochemistry, qPCR of osteogenic markers and ex vivo assays.

RESULTS

Atherosclerotic lesion size at the aortic root did not differ, but calcification was significantly more pronounced in apoE^-/- mice lacking erythrocyte ARG1. Incubation of murine and human VSMCs with lysed erythrocyte membranes from apoE^-/- red blood cell. ARG1-knockout mice accelerated their osteogenic differentiation, and mRNA transcripts of osteogenic markers decreased following NO scavenging. In addition to NO signaling via sGC (soluble guanylyl cyclase), overexpression of GSNOR (S-nitrosoglutathione reductase) enhanced degradation of S-nitrosoglutathione to glutathione and reduced protein S-nitrosation of HSP (heat shock protein)-70 were identified as potential mechanisms of vascular smooth muscle cell calcification in mice lacking ARG1 in erythrocytes, and calcium phosphate deposition was enhanced by heat shock and prevented by GSNOR inhibition. Messenger RNA levels of enzymes metabolizing the arginase products L-ornithine and L-proline also were elevated in VSMCs, paralleled by increased proliferation, myofibroblast marker and collagen type 1 expression.

CONCLUSIONS

Our findings support an important role of erythrocyte ARG1 for NO bioavailability and L-arginine metabolism in VSMCs, which controls atherosclerotic lesion composition and calcification.

Involvement of shedding induced by ADAM17 on the nitric oxide pathway in hypertension

A Disintegrin and Metalloprotease 17 (ADAM17), also called tumor necrosis factor-ɑ (TNF-ɑ) convertase (TACE), is a well-known protease involved in the sheddase of growth factors, chemokines and cytokines. ADAM17 is also enrolled in hypertension, especially by shedding of angiotensin converting enzyme type 2 (ACE2) leading to impairment of angiotensin 1–7 [Ang-(1–7)] production and injury in vasodilation, induction of renal damage and cardiac hypertrophy. Activation of Mas receptor (MasR) by binding of Ang-(1–7) induces an increase in the nitric oxide (NO) gaseous molecule, which is an essential factor of vascular homeostasis and blood pressure control. On the other hand, TNF-ɑ has demonstrated to stimulate a decrease in nitric oxide bioavailability, triggering a disrupt in endothelium-dependent vasorelaxation. In spite of the previous studies, little knowledge is available about the involvement of the metalloprotease 17 and the NO pathways. Here we will provide an overview of the role of ADAM17 and Its mechanisms implicated with the NO formation.

The Ultrastructure of Skeletal Muscle Capillaries of Streptozotocin Diabetic Rats and the Therapeutic Effect of Benfluorex

Diabetes mellitus is a serious disease worldwide and causes other associated diseases. In this study, we observed the effect of streptozotocin (STZ)-induced diabetes and benfluorex treatment on muscular capillary ultrastructure. Adult male rats were used as the test subjects and each individual was intraperitoneally injected with one dose of STZ (45 mg/kg) to induce diabetes. Doses (50 mg/kg) of benfluorex were given to the subjects with tap water by intragastric gavage application once daily for 21 days. At the end of day 21, muscle tissues were obtained from animals and examined under transmission electron microscopy. From the data obtained with the electron microscope, it was observed that the control group had typical continuous capillary vascular structures in their muscles, while STZ caused disruptive disorder of the muscle cells in the capillary wall of the STZ-diabetic group. Additionally, the thickening of the basement membrane around endothelial cells, loss of mitochondrial crista in the muscle cells, enlarged endothelial cells, and narrowed vessel lumen were observed in the muscle tissue. The findings of our study revealed that STZ-induced diabetes disrupted the vascular structure, while benfluorex partially improved it.

Renin-angiotensin system overactivation in perivascular adipose tissue contributes to vascular dysfunction in heart failure

Perivascular adipose tissue (PVAT) dysfunction is associated with vascular damage in cardiometabolic diseases. Although heart failure (HF)-induced endothelial dysfunction is associated with renin-angiotensin system (RAS) activation, no data have correlated this syndrome with PVAT dysfunction. Thus, the aim of the present study was to investigate whether the hyperactivation of the RAS in PVAT participates in the vascular dysfunction observed in rats with HF after myocardial infarction surgery. Wire myograph studies were carried out in thoracic aorta rings in the presence and absence of PVAT. An anticontractile effect of PVAT was observed in the rings of the control rats in the presence (33%) or absence (11%) of endothelium. Moreover, this response was substantially reduced in animals with HF (5%), and acute type 1 angiotensin II receptor (AT1R) and type 2 angiotensin II receptor (AT2R) blockade restored the anticontractile effect of PVAT. In addition, the angiotensin-converting enzyme 1 (ACE1) activity (26%) and angiotensin II levels (51%), as well as the AT1R and AT2R gene expression, were enhanced in the PVAT of rats with HF. Associated with these alterations, HF-induced lower nitric oxide bioavailability, oxidative stress and whitening of the PVAT, which suggests changes in the secretory function of this tissue. The ACE1/angiotensin II/AT1R and AT2R axes are involved in thoracic aorta PVAT dysfunction in rats with HF. These results suggest PVAT as a target in the pathophysiology of vascular dysfunction in HF and provide new perspectives for the treatment of this syndrome.

Lysed Erythrocyte Membranes Promote Vascular Calcification

BACKGROUND

Intraplaque hemorrhage promotes atherosclerosis progression, and erythrocytes may contribute to this process. In this study we examined the effects of red blood cells on smooth muscle cell mineralization and vascular calcification and the possible mechanisms involved.

METHODS

Erythrocytes were isolated from human and murine whole blood. Intact and lysed erythrocytes and their membrane fraction or specific erythrocyte components were examined in vitro using diverse calcification assays, ex vivo by using the murine aortic ring calcification model, and in vivo after murine erythrocyte membrane injection into neointimal lesions of hypercholesterolemic apolipoprotein E-deficient mice. Vascular tissues (aortic valves, atherosclerotic carotid artery specimens, abdominal aortic aneurysms) were obtained from patients undergoing surgery.

RESULTS

The membrane fraction of lysed, but not intact human erythrocytes promoted mineralization of human arterial smooth muscle cells in culture, as shown by Alizarin red and van Kossa stain and increased alkaline phosphatase activity, and by increased expression of osteoblast-specific transcription factors (eg, runt-related transcription factor 2, osterix) and differentiation markers (eg, osteopontin, osteocalcin, and osterix). Erythrocyte membranes dose-dependently enhanced calcification in murine aortic rings, and extravasated CD235a-positive erythrocytes or Perl iron-positive signals colocalized with calcified areas or osteoblast-like cells in human vascular lesions. Mechanistically, the osteoinductive activity of lysed erythrocytes was localized to their membrane fraction, did not involve membrane lipids, heme, or iron, and was enhanced after removal of the nitric oxide (NO) scavenger hemoglobin. Lysed erythrocyte membranes enhanced calcification to a similar extent as the NO donor diethylenetriamine-NO, and their osteoinductive effects could be further augmented by arginase-1 inhibition (indirectly increasing NO bioavailability). However, the osteoinductive effects of erythrocyte membranes were reduced in human arterial smooth muscle cells treated with the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide or following inhibition of NO synthase or the NO receptor soluble guanylate cyclase. Erythrocytes isolated from endothelial NO synthase-deficient mice exhibited a reduced potency to promote calcification in the aortic ring assay and after injection into murine vascular lesions.

CONCLUSIONS

Our findings in cells, genetically modified mice, and human vascular specimens suggest that intraplaque hemorrhage with erythrocyte extravasation and lysis promotes osteoblastic differentiation of smooth muscle cells and vascular lesion calcification, and also support a role for erythrocyte-derived NO.

Dissection of heterocellular cross-talk in vascularized cardiac tissue mimetics

Cellular specialization and interaction with other cell types in cardiac tissue is essential for the coordinated function of cell populations in the heart. The complex interplay between cardiomyocytes, endothelial cells and fibroblasts is necessary for adaptation but can also lead to pathophysiological remodeling. To understand this complex interplay, we developed 3D vascularized cardiac tissue mimetics (CTM) to study heterocellular cross-talk in hypertrophic, hypoxic and fibrogenic environments. This 3D platform responds to physiologic and pathologic stressors and mimics the microenvironment of diseased tissue. In combination with endothelial cell fluorescence reporters, these cardiac tissue mimetics can be used to precisely visualize and quantify cellular and functional responses upon stress stimulation. Utilizing this platform, we demonstrate that stimulation of α/β-adrenergic receptors with phenylephrine (PE) promotes cardiomyocyte hypertrophy, metabolic maturation and vascularization of CTMs. Increased vascularization was promoted by conditioned medium of PE-stimulated cardiomyocytes and blocked by inhibiting VEGF or upon β-adrenergic receptor antagonist treatment, demonstrating cardiomyocyte-endothelial cross-talk. Pathophysiological stressors such as severe hypoxia reduced angiogenic sprouting and increased cell death, while TGF β2 stimulation increased collagen deposition concomitant to endothelial-to-mesenchymal transition. In sum, we have developed a cardiac 3D culture system that reflects native cardiac tissue function, metabolism and morphology - and for the first time enables the tracking and analysis of cardiac vascularization dynamics in physiology and pathology.

Platelet Oxidative Stress and its Relationship with Cardiovascular Diseases in Type 2 Diabetes Mellitus Patients

Enhanced platelet activation and thrombosis are linked to various cardiovascular diseases (CVD). Among other mechanisms, oxidative stress seems to play a pivotal role in platelet hyperactivity. Indeed, upon stimulation by physiological agonists, human platelets generate and release several types of reactive oxygen species (ROS) such as O2 -, H2O2 or OH-, further amplifying the platelet activation response via various signalling pathways, including, formation of isoprostanes, Ca2+ mobilization and NO inactivation. Furthermore, excessive platelet ROS generation, incorporation of free radicals from environment and/or depletion of antioxidants induce pro-oxidant, pro-inflammatory and platelet hyperaggregability effects, leading to the incidence of cardiovascular events. Here, we review the current knowledge regarding the effect of oxidative stress on platelet signaling pathways and its implication in CVD such as type 2 diabetes mellitus. We also summarize the role of natural antioxidants included in vegetables, fruits and medicinal herbs in reducing platelet function via an oxidative stress-mediated mechanism.

Mechanical pressure unloading therapy reverses thoracic aortic structural and functional changes in a hypertensive rat model

OBJECTIVES

Hypertension can impair structure and function of blood vessels. Experimental data describing the reverse remodeling process after a mechanical pressure unloading therapy in the vasculature is limited. We studied the influence of pressure unloading on both the structural and functional alterations of the aorta in a hypertensive rat model.

METHODS

Using isolated thoracic aortic rings in an in-vitro organ bath system, endothelium-dependent and endothelium-independent vasorelaxation were studied 6-weeks or 12-weeks after abdominal aortic banding (aortic banding-6-week or aortic banding-12-week), and 6-weeks after an aortic debanding procedure performed after the sixth experimental week of aortic banding (aortic banding + debanding-12-week). Age-matched rats were sham-operated (sham-6-week or sham-12-week). The aortic morphometry and histological fibrosis were studied, and the mRNA-expression of metalloproteinase (MMP)-2, tissue inhibitor of metalloproteinase (TIMP)-2, and soluble guanylate cyclase subunits GUCY1a3 and GUCY1b3 were determined.

RESULTS

Aortic banding significantly increased systolic, diastolic, and pulse pressures. Structural changes (increased intima-media thickness and area normalized to body weight, aortic collagen content, higher MMP-2 and TIMP-2, and lower GUCY1a3 and GUCY1b3 mRNA-levels) and functional alterations (impaired endothelium-dependent and endothelium-independent vasorelaxation) have already taken place after 6 weeks of aortic banding. Pressure unloading, after established vascular changes, improved vascular function, resulted in reduced collagen content, and decreased both MMP-2 and TIMP-2 mRNA-expression.

CONCLUSION

Pressure-overload-induced vascular changes regressed due to mechanical unloading. Furthermore, debanding leads to a reductive tendency in fibrosis-associated gene expression and collagen accumulation. Collectively, the addition of drugs that target fibrosis to existing hypertensive treatment may present an attractive therapy against vascular remodeling.

The Plasma Membrane: A Platform for Intra- and Intercellular Redox Signaling

Membranes are of outmost importance to allow for specific signal transduction due to their ability to localize, amplify, and direct signals. However, due to the double-edged nature of reactive oxygen species (ROS)—toxic at high concentrations but essential signal molecules—subcellular localization of ROS-producing systems to the plasma membrane has been traditionally regarded as a protective strategy to defend cells from unwanted side-effects. Nevertheless, specialized regions, such as lipid rafts and caveolae, house and regulate the activated/inhibited states of important ROS-producing systems and concentrate redox targets, demonstrating that plasma membrane functions may go beyond acting as a securing lipid barrier. This is nicely evinced by nicotinamide adenine dinucleotide phosphate (NADPH)-oxidases (NOX), enzymes whose primary function is to generate ROS and which have been shown to reside in specific lipid compartments. In addition, membrane-inserted bidirectional H₂O₂-transporters modulate their conductance precisely during the passage of the molecules through the lipid bilayer, ensuring time-scaled delivery of the signal. This review aims to summarize current evidence supporting the role of the plasma membrane as an organizing center that serves as a platform for redox signal transmission, particularly NOX-driven, providing specificity at the same time that limits undesirable oxidative damage in case of malfunction. As an example of malfunction, we explore several pathological situations in which an inflammatory component is present, such as inflammatory bowel disease and neurodegenerative disorders, to illustrate how dysregulation of plasma-membrane-localized redox signaling impacts normal cell physiology.

The effects of ketamine and thiopental used alone or in combination on the brain, heart, and bronchial tissues of rats

INTRODUCTION

We compared the side effects of ketamine and thiopental used alone and of a ketamine/thiopental combination dose on the brain,heart, and bronchial tissues of rats.

MATERIAL AND METHODS

Three groups received intraperitoneal injections of 30 mg/kg ketamine (K-30); 15 mg/kg thiopental (T-15); or of both in combination (KTSA). These doses were doubled in another set of study groups (K-60, T-30, and KTA groups, respectively). Optimal anesthesia duration was examined in all groups.

RESULTS

Anesthesia did not occur with 30 mg/kg ketamine or 15 mg/kg thiopental. However, when used alone ketamine and thiopental led to oxidative stress in the striatum, heart, and bronchial tissues. Conversely, combined administration of anesthetics and subanesthetic doses were found not to create oxidative stress in any of these areas. The highest level of adrenaline in blood samples collected from the tail veins was measured in the KTA-60, and the lowest amount in the T-30. Creatine kinase activity was highest in the KTA-60 group (p < 0.001). When we compared for all 5 groups to untreated control group; the creatine kinase-MB activities were significiantly different in K-30, T-15 and T-30 (p < 0.001).

CONCLUSIONS

The studied doses of ketamine led to oxidative stress by increasing the amount of adrenaline. Thiopental increased oxidative stress with decreases in adrenaline. A longer anesthetic effect with minimal adverse events may be achieved by ketamine and thiopental in combination.

Angiotensin Receptor Expression and Vascular Endothelial Dysfunction in Obstructive Sleep Apnea

BACKGROUND

Obstructive sleep apnea (OSA) is associated with vascular endothelial dysfunction (VED) in otherwise healthy patients. The role of renin-angiotensin system (RAS) in the OSA induced VED is not well understood.

METHODS

Recently diagnosed OSA patients with very low cardiovascular disease (CVD) risk (Framingham score <5%) were studied at diagnosis and after 12 weeks of verified continuous positive airway pressure (CPAP) therapy. Participants underwent biopsy of gluteal subcutaneous tissue at baseline and after CPAP. Microcirculatory endothelial expression of angiotensin receptors type-1 (AT-1) and type-2 (AT-2) was measured in the subcutaneous tissue using quantitative confocal microscopy techniques. The ex-vivo effect of AT-1 receptor blockade (ARB) on endothelial superoxide production was also measured before and after CPAP treatment.

RESULTS

In OSA patients (n = 11), microcirculatory endothelial AT1 expression decreased from 873 (200) (fluorescence units) at baseline to 393 (59) units after 12 weeks of CPAP (P = 0.02). AT2 expression did not decrease significantly in these patients (479 (75) to 329 (58) post CPAP (P = 0.08)). The ex-vivo addition of the losartan to the microcirculatory endothelium resulted in decreased superoxide expression in the vascular walls from 14.2 (2.2) units to 4.2 (0.8) P < 0.001; while it had no effect on post-CPAP patient tissue (P = 0.64).

CONCLUSIONS

In OSA patients with no to minimal CVD risk, VED is associated with upregulation of AT-1 expression that is reversible with CPAP. Endothelial oxidative stress was reversible with ARB. RAS activation may play an important role in the development of early CVD risk in OSA patients.

Age-, Gender-, and in Vivo Different Doses of Isoproterenol Modify in Vitro Aortic Vasoreactivity and Circulating VCAM-1

Different human-like cardiomyopathies associated to β-adrenergic stimulation are experimentally modeled in animals through variations in dose, route, and duration of administration of different cardiotoxic drugs. However, associated changes in the vasculature and their relation to systemic inflammation, and the influence of cardiovascular diseases risk factors (gender and age) upon them are seldom analyzed. Here we studied the effect of age and gender on the vasoreactivity of aortas from mice subjected to in vivo repeated β-adrenergic stimulation with different doses of isoproterenol (ISO) in association with circulating inflammatory cytokines. Young (2 months) and old (18 months) male and female mice received 0 (control), 5, 40, 80 or 160 μg/g/d of ISO (7 days, s.c.). IL-1α, IL-4 and vascular cell adhesion molecule-1 (VCAM-1) were quantified in plasma. In vitro, norepinephrine-induced vasoconstriction and acetylcholine-induced relaxation were measured in aortas. No differences in contraction, relaxation, IL-1α, and IL-4 were found between control young males and females. Age decreased contraction in males and relaxation was lower in females and abolished in males. VCAM-1 was higher in young males than in females and increased in old mice. Vasoconstriction in ISO-treated mice results as a bell-shaped curve on contraction in young and old males, with lower values in the latter. In females, ISO-160 increased contraction in young females but decreased it in old females. Vasorelaxation was reduced in ISO-treated young males and females. ISO-80 and 160 reduced vasorelaxation in old females, and intermediate doses relaxed aortas from old males. VCAM-1 was higher in young and old males with ISO-80 and 160; while VCAM-1 was higher only with ISO-160 in old females. Our results demonstrate that repeated β-adrenergic stimulation modifies vascular reactivity depending on gender, age, and dose. Females were less sensitive to alterations in vasoreactivity, and young females required a higher amount of the adrenergic stimuli than old females to show vascular alterations. Changes were independent of IL-1α and IL-4. VCAM-1 only changed in old females stimulated with ISO 160. Our results highlight the relevance of considering and comparing in the same study females and aged organisms to improve the accuracy of applications to clinical studies.

Circulating Total Bilirubin and Future Risk of Hypertension in the General Population: The Prevention of Renal and Vascular End-Stage Disease (PREVEND) Prospective Study and a Mendelian Randomization Approach

BACKGROUND

Circulating total bilirubin is known to be inversely and independently associated with future risk of cardiovascular disease. However, the relationship of circulating total bilirubin with incident hypertension is uncertain. We aimed to assess the association of total bilirubin with future hypertension risk and supplemented this with a Mendelian randomization approach to investigate any causal relevance to the association.

METHODS AND RESULTS

Plasma total bilirubin levels were measured at baseline in the PREVEND (Prevention of Renal and Vascular End-Stage Disease) prospective study of 3989 men and women without hypertension. Hazard ratios (95% confidence intervals) of total bilirubin with incident hypertension were assessed. New-onset hypertension was recorded in 1206 participants during a median follow-up of 10.7 years. Baseline total bilirubin was approximately log-linearly associated with hypertension risk. Age- and sex-adjusted hazard ratio for hypertension per 1-SD increase in loge total bilirubin was 0.86 (0.81-0.92; P<0.001), which was attenuated to 0.94 (0.88-0.99; P=0.040) after further adjustment for established risk factors and other potential confounders. The association was marginally significant on further adjustment for high-sensitivity C-reactive protein (0.94; 0.88-1.00; P=0.067). A genetic variant at the UGT1A1*28 locus consistently shown to be strongly associated with circulating bilirubin levels-rs6742078-was not significantly associated with blood pressure or hypertension (P>0.05 for all), arguing against a strong causal association of circulating bilirubin with blood pressure.

CONCLUSIONS

The weak and inverse association of circulating total bilirubin with future hypertension risk may be driven by biases such as unmeasured confounding and/or reverse causation. Further evaluation is warranted.

Lecithin derived from ω-3 PUFA fortified eggs decreases blood pressure in spontaneously hypertensive rats

Hypertension is the most common risk factor for stroke, coronary heart disease and heart failure, which are the leading causes of death worldwide. Dietary patterns and supplements intakes are becoming important factors in the hypertension. The aim of this study was to estimate the effects of new generation egg yolk phospholipids rich in lecithin (SL) esterified with omega-3 and omega-6 fatty acids on blood pressure in hypertensive rats (SHR). Here we have reported that lecithin (SL) derived from egg yolk lowers blood pressure in pathology of hypertension. The SHR rats treated with SL had significantly lower blood pressure than control group (157/104 vs. 178/121 mmHg; P < 0.05) and down-regulated mesenteric artery over-response to norepinephrine and potassium chloride, giving similar arterial response as for normotensive Wistar Kyoto rats (WKY). Hypertensive rats treated by SL demonstrated significantly lower serum level of inflammatory factors. This work also indicates that SL treatment lowers heart rate and reduces the serum level of oxidative stress marker - nitrotyrosine - by 30–34% in both hypertensive and normotensive animals. Phospholipids with lecithin derived from PUFA fortified eggs may be a valuable dietary supplement in prophylaxis of hypertension and in patients with hypertension, however, this requires further studies on humans.

Protective Effect of Edaravone Against Cyclosporine-Induced Chronic Nephropathy Through Antioxidant and Nitric Oxide Modulating Pathways in Rats

BACKGROUND

Cyclosporine A (CsA) is an immunosuppressant with therapeutic indications in various immunological diseases; however, its use is associated with chronic nephropathy. Oxidative stress has a crucial role in CsA-induced nephrotoxicity. The present study evaluates the protective effect of edaravone on CsA-induced chronic nephropathy and investigates its antioxidant and nitric oxide modulating property.

METHODS

Male Sprague-Dawley rats (n=66) were distributed into nine groups, including a control (group 1) (n=7). Eight groups received CsA (15 mg/kg) for 28 days while being treated. The groups were categorized as: Group 2: Vehicle (n=10)Groups 3, 4, and 5: Edaravone (1, 5, and 10 mg/kg) (n=7 each)Group 6: Diphenyliodonium chloride, a specific endothelial nitric oxide synthase (eNOS) inhibitor (n=7)Group 7: Aminoguanidine, a specific inducible nitric oxide synthase (iNOS) inhibitor (n=7)Group 8: Edaravone (10 mg/kg) plus diphenyliodonium chloride (n=7)Group 9: Edaravone (10 mg/kg) plus aminoguanidine (n=7) Blood urea nitrogen and serum creatinine levels, malondialdehyde, superoxide dismutase, and glutathione reductase enzyme activities were measured using standard kits. Renal histopathological evaluations and measurements of eNOS and iNOS gene expressions by RT-PCR were also performed. Data were analyzed using one-way analysis of variance (ANOVA) followed by Tukey's test (SPSS software version 18.0).

RESULTS

Edaravone (10 mg/kg) significantly attenuated CsA-induced oxidative stress, renal dysfunction, and kidney tissue injury. Aminoguanidine improved the renoprotective effect of edaravone. Edaravone reduced the elevated mRNA level of iNOS, but could not alter the level of eNOS mRNA significantly.

CONCLUSION

Edaravone protects against CsA-induced chronic nephropathy using antioxidant property and probably through inhibiting iNOS gene expression.

Novel putative pharmacological therapies to protect the right ventricle in pulmonary hypertension: a review of current literature

Pulmonary hypertension (PH) is defined by elevated mean pulmonary artery pressure following the pathological remodelling of small pulmonary arteries. An increase in right ventricular (RV) afterload results in RV hypertrophy and RV failure. The pathophysiology of PH, and RV remodelling in particular, is not well understood, thus explaining, at least in part, why current PH therapies have a limited effect. Existing therapies mostly target the pulmonary circulation. Because the remodelled RV fails to support normal cardiac function, patients eventually succumb from RV failure. Developing novel therapies that directly target the function of the RV may therefore benefit patients with PH. In the past decade, several promising studies have investigated novel cardioprotective strategies in experimental models of PH. This review aims to comprehensively discuss and highlight these novel experimental approaches to confer, in the long-term, greater health benefit in patients with PH.

Effect of tempol and tempol plus catalase on intra-renal haemodynamics in spontaneously hypertensive stroke-prone (SHSP) and Wistar rats

Vasoconstriction within the renal medulla contributes to the development of hypertension. This study investigated the role of reactive oxygen species (ROS) in regulating renal medullary and cortical blood perfusion (MBP and CBP respectively) in both stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar rats. CBP and MBP were measured using a laser-Doppler flow meter before and after intra-renal infusion of tempol, the superoxide dismutase (SOD) mimetic or tempol plus catalase, the hydrogen peroxide-degrading enzyme. Tempol infusion significantly elevated blood perfusion within the renal medulla (MBP) in both SHRSP (by 43 ± 7%, P < 0.001) and Wistar rats (by 17 ± 2%, P < 0.05) but the magnitude of the increase was significantly greater in the SHRSP (P < 0.01). When the enzyme catalase and tempol were co-infused, MBP was again significantly increased in SHRSP (by 57 ± 6%, P < 0.001) and Wistar rats (by 33 ± 6%, P < 0.001), with a significantly greater increase in perfusion being induced in the SHRSP relative to the Wistar rats (P < 0.01). Notably, this increase was significantly greater than in those animals infused with tempol alone (P < 0.01). These results suggest that ROS plays a proportionally greater role in reducing renal vascular compliance, particularly within the renal medulla, in normotensive and hypertensive animals, with effects being greater in the hypertensive animals. This supports the hypothesis that SHRSP renal vasculature might be subjected to elevated level of oxidative stress relative to normotensive animals.

Hydrogen Peroxide as a Paracrine Vascular Mediator: Regulation and Signaling Leading to Dysfunction

Numerous studies have demonstrated the ability of a variety of vascular cells, including endothelial cells, smooth muscle cells, and fibroblasts, to produce reactive oxygen species (ROS). Until recently, major emphasis was placed on the production of superoxide anion (O2–) in the vasculature as a result of its ability to directly attenuate the biological activity of endothelium-derived nitric oxide (NO). The short half-life and radius of diffusion of O2– drastically limit the role of this ROS as an important paracrine hormone in vascular biology. On the contrary, in recent years, the O2– metabolite hydrogen peroxide (H2O2) has increasingly been viewed as an important cellular signaling agent in its own right, capable of modulating both contractile and growth-promoting pathways with more far-reaching effects. In this review, we will assess the vascular production of H2O2, its regulation by endogenous scavenger systems, and its ability to activate a variety of vascular signaling pathways, thereby leading to vascular contraction and growth. This discussion will include the ability of H2O2 to (i) Initiate calcium flux as well as (ii) stimulate pathways leading to sensitization of contractile elements to calcium. The latter involves a variety of protein kinases that have also been strongly implicated in vascular hypertrophy. Previous Intensive study has emphasized the ability of NADPH oxidase-derived O2– and H2O2 to activate these pathways in cultured smooth muscle cells. However, growing evidence indicates a considerably more complex array of unique oxidase systems in the endothelium, media, and adventitia that appear to participate in these deleterious effects in a sequential and temporal manner. Taken together, these findings seem consistent with a paracrine effect of H2O2 across the vascular wall.

Oxidative Stress and Salvia miltiorrhiza in Aging-Associated Cardiovascular Diseases

Aging-associated cardiovascular diseases (CVDs) have some risk factors that are closely related to oxidative stress. Salvia miltiorrhiza (SM) has been used commonly to treat CVDs for hundreds of years in the Chinese community. We aimed to explore the effects of SM on oxidative stress in aging-associated CVDs. Through literature searches using Medicine, PubMed, EMBASE, Cochrane library, CINAHL, and Scopus databases, we found that SM not only possesses antioxidant, antiapoptotic, and anti-inflammatory effects but also exerts angiogenic and cardioprotective activities. SM may reduce the production of reactive oxygen species by inhibiting oxidases, reducing the production of superoxide, inhibiting the oxidative modification of low-density lipoproteins, and ameliorating mitochondrial oxidative stress. SM also increases the activities of catalase, manganese superoxide dismutase, glutathione peroxidase, and coupled endothelial nitric oxide synthase. In addition, SM reduces the impact of ischemia/reperfusion injury, prevents cardiac fibrosis after myocardial infarction, preserves cardiac function in coronary disease, maintains the integrity of the blood-brain barrier, and promotes self-renewal and proliferation of neural stem/progenitor cells in stroke. However, future clinical well-designed and randomized control trials will be necessary to confirm the efficacy of SM in aging-associated CVDs.

HyPer Family Probes: State of the Art

SIGNIFICANCE

Hydrogen peroxide (H2O2) is not only a key mediator of oxidative stress but also one of the most important cellular second messengers. This small short-lived molecule is involved in the regulation of a wide range of different biological processes, including regulation of cellular signaling pathways. Studying the role of H2O2 in living systems would be challenging without modern approaches. A genetically encoded fluorescent biosensor, HyPer, is one of the most effective tools for this purpose.

RECENT ADVANCES

HyPer has been used by many investigators of redox signaling in various models of different scales: from cytoplasmic subcompartments and single cells to tissues of whole organisms. In many studies, the results obtained using HyPer have enabled a better understanding of the roles of H2O2 in these biological processes. However, much remains to be learned.

CRITICAL ISSUES

In this review, we focus on the uses of HyPer. We provide a general description of HyPer and its improved versions. Separate chapters are devoted to the results obtained by various groups who have used this biosensor for their experiments in living cells and organisms.

FUTURE DIRECTIONS

HyPer is an effective tool for H2O2 imaging in living systems as indicated by the increasing numbers of publications each year since its development. However, this biosensor requires further improvements. In particular, much brighter and more pH-stable versions of HyPer are necessary for imaging in mammalian tissues. Antioxid. Redox Signal. 24, 731-751.

Scavenging of nitric oxide by hemoglobin in the tunica media of porcine coronary arteries

Scavenging of nitric oxide (NO) often interferes with studies on NO signaling in cell-free preparations. We observed that formation of cGMP by NO-stimulated purified soluble guanylate cyclase (sGC) was virtually abolished in the presence of cytosolic preparations of porcine coronary arteries, with the scavenging activity localized in the tunica media (smooth muscle layer). Electrochemical measurement of NO release from a donor compound and light absorbance spectroscopy showed that cytosolic preparations contained a reduced heme protein that scavenged NO. This protein, which reacted with anti-human hemoglobin antibodies, was efficiently removed from the preparations by haptoglobin affinity chromatography. The cleared cytosols showed only minor scavenging of NO according to electrochemical measurements and did not decrease cGMP formation by NO-stimulated sGC. In contrast, the column flow-through caused a nearly 2-fold increase of maximal sGC activity (from 33.1 ± 1.6 to 54.9 ± 2.2 μmol × min(-1) × mg(-1)). The proteins retained on the affinity column were identified as hemoglobin α and β subunits. The results indicate that hemoglobin, presumably derived from vasa vasorum erythrocytes, is present and scavenges NO in preparations of porcine coronary artery smooth muscle. Selective removal of hemoglobin-mediated scavenging unmasked stimulation of maximal NO-stimulated sGC activity by a soluble factor expressed in vascular tissue.

Endothelial dysfunction in DOCA-salt-hypertensive mice: role of neuronal nitric oxide synthase-derived hydrogen peroxide

Endothelial dysfunction is a common problem associated with hypertension and is considered a precursor to the development of micro- and macro-vascular complications. The present study investigated the involvement of nNOS (neuronal nitric oxide synthase) and H2O2 (hydrogen peroxide) in the impaired endothelium-dependent vasodilation of the mesenteric arteries of DOCA (deoxycorticosterone acetate)-salt-hypertensive mice. Myograph studies were used to investigate the endothelium-dependent vasodilator effect of ACh (acetylcholine). The expression and phosphorylation of nNOS and eNOS (endothelial nitric oxide synthase) were studied by Western blot analysis. Immunofluorescence was used to examine the localization of nNOS and eNOS in the endothelial layer of the mesenteric artery. The vasodilator effect of ACh is strongly impaired in mesenteric arteries of DOCA-salt-hypertensive mice. Non-selective inhibition of NOS sharply reduced the effect of ACh in both DOCA-salt-hypertensive and sham mice. Selective inhibition of nNOS and catalase led to a higher reduction in the effect of ACh in sham than in DOCA-salt-hypertensive mice. Production of H2O2 induced by ACh was significantly reduced in vessels from DOCA-salt-hypertensive mice, and it was blunted after nNOS inhibition. The expression of both eNOS and nNOS was considerably lower in DOCA-salt-hypertensive mice, whereas phosphorylation of their inhibitory sites was increased. The presence of nNOS was confirmed in the endothelial layer of mesenteric arteries from both sham and DOCA-salt-hypertensive mice. These results demonstrate that endothelial dysfunction in the mesenteric arteries of DOCA-salt-hypertensive mice is associated with reduced expression and functioning of nNOS and impaired production of nNOS-derived H2O2 Such findings offer a new perspective for the understanding of endothelial dysfunction in hypertension.

Oxidised palm oil and sucrose induced hyperglycemia in normal rats: effects of Sclerocarya birrea stem barks aqueous extract

Background

Consumption of foods rich in carbohydrates and fats, result in an increase in obesity and consequently type 2 diabetes. The present study was carried out to evaluate the effects of oxidised palm oil and sucrose (SOPO +S) on some metabolic parameters and to investigate the effects of aqueous extract from barks of Sclerocarrya birrea on SOPO + S induced damages.

Methods

During 16 weeks, animals received every day a supplement of oxidised palm oil (10 %) and 10 % sucrose as drinking water). Control rat received standard diet and drinking water without sucrose. At the end of this period, animal presenting intolerance in glucose test and insensitivity to insulin were continuously feed with hypercaloric diet along with the administration of the plant extract (150 or 300 mg/kg) or glibenclamide (10 mg/kg) during three weeks. OGTT was performed; insulin sensitivity was assessed by performing insulin tolerance test and determining insulin sensitivity index (Kitt). Several parameters were evaluated including body weight, abdominal fat mass, blood glucose levels, blood pressure, serum lipid profile, and serum transaminases (ALT and AST). Oxidative parameters were measured by MDA levels, nitrites levels, SOD levels, reduced glutathione content and by enzyme activities of SOD and catalase.

Results

Animal receiving a supplement of oxidised palm oil and sucrose showed hyperglycaemia, glucose intolerance, insulin resistance and a significant increase in body weight and abdominal fat mass compared to normal rats. In addition, there was a significant increase of SOD in aorta and heart, nitrites in liver and kidney, malondialdehyde (MDA) in heart, liver and kidney. It was also observed a significant reduction in the activities of the SOD and catalase in liver, kidney and reduced glutathione levels in heart. Concomitant treatment of plant extract with SOPO + S brought glycaemia and blood pressure towards normal value, restored glucose tolerance and insulin sensitivity. The plant extract prevent the increase or decrease in the activity of the enzyme depending to the organ, reduced MDA and nitrites levels.

Conclusion

These results highlighted the hyperglycaemic and oxidant character of SOPO + S diet and confirm the hypoglycaemic, and antioxidant action of sclerocarya birrea aqueous extract in diabetes.

The role of endothelial mechanosensitive genes in atherosclerosis and omics approaches

Atherosclerosis is the leading cause of morbidity and mortality in the U.S., and is a multifactorial disease that preferentially occurs in regions of the arterial tree exposed to disturbed blood flow. The detailed mechanisms by which d-flow induces atherosclerosis involve changes in the expression of genes, epigenetic patterns, and metabolites of multiple vascular cells, especially endothelial cells. This review presents an overview of endothelial mechanobiology and its relation to the pathogenesis of atherosclerosis with special reference to the anatomy of the artery and the underlying fluid mechanics, followed by a discussion of a variety of experimental models to study the role of fluid mechanics and atherosclerosis. Various in vitro and in vivo models to study the role of flow in endothelial biology and pathobiology are discussed in this review. Furthermore, strategies used for the global profiling of the genome, transcriptome, miR-nome, DNA methylome, and metabolome, as they are important to define the biological and pathophysiological mechanisms of atherosclerosis. These "omics" approaches, especially those which derive data based on a single animal model, provide unprecedented opportunities to not only better understand the pathophysiology of atherosclerosis development in a holistic and integrative manner, but also to identify novel molecular and diagnostic targets.

Angiotensin-(1-7) administration benefits cardiac, renal and progenitor cell function in db/db mice

BACKGROUND AND PURPOSE

Diabetic patients are at an increased risk of cardiovascular disease, in part due to inflammation and oxidative stress. These two pathological mechanisms also affect other organs and cells including the kidneys and progenitor cells. Angiotensin-(1-7) [Ang-(1-7)] has previously been shown to counterbalance pathological effects of angiotensin II, including inflammation and oxidative stress. The aim of this study was to investigate the effects of short-term (2 weeks) Ang-(1-7) treatment on cardiovascular and renal function in a mouse model of type 2 diabetes (db/db).

EXPERIMENTAL APPROACH

Eight- to nine-week-old db/db mice were administered either vehicle, Ang-(1-7) alone, or Ang-(1-7) combined with an inhibitor (losartan, PD123319, A-779, L-NAME or icatibant) daily for 14 days.

KEY RESULTS

An improvement in physiological heart function was observed in Ang-(1-7)-treated mice. Ang-(1-7) also reduced cardiomyocyte hypertrophy, fibrosis and inflammatory cell infiltration of the heart tissue and increased blood vessel number. These changes were blocked by antagonists of the MAS1, AT2 and bradykinin receptors and inhibition of NO formation. Treatment with Ang-(1-7) reduced glomerular damage and oxidative stress in kidney tissue. Bone marrow and circulating endothelial progenitors, as well as bone marrow mesenchymal stem cells, were increased in mice treated with Ang-(1-7).

CONCLUSIONS AND IMPLICATIONS

Short-term Ang-(1-7) treatment of young db/db mice improved heart function and reduced kidney damage. Treatment also improved bone marrow and circulating levels of endothelial and mesenchymal stem cells. All of this may contribute to improved cardiovascular and renal function.

Metal rich particulate matter impairs acetylcholine-mediated vasorelaxation of microvessels in mice

Background

Exposure to PM_2.5 (particulate matter <2.5 μm) has been associated with changes in endothelial function. PM_2.5 was collected from two Chinese cities, Jinchang (JC) and Zhangye (ZH), both with similar PM_2.5 concentrations. However, JC had levels of nickel (Ni), selenium (Se), copper (Cu), and arsenic (As) that were 76, 25, 17, and 7 fold higher than that measured in ZH, respectively. We used this unique PM sample to delineate the chemical components that drive pulmonary and systemic effects and explore the mechanism(s) by which vascular dysfunction is caused.

Methods

Male FVB/N mice received oropharyngeal aspiration of water or PM_2.5 from JC, ZH or ZH spiked with one of the following elements at the same concentrations found in the JC PM (Ni = 4.76; As = 2.36; Se = 0.24; Cu = 2.43 μg/mg) followed by evaluation of markers of pulmonary and systemic inflammation. Mesenteric arteries were isolated for gene expression or functional response to various agonists (Phenylephrine, Acetylcholine, and Sodium Nitroprusside) and inhibitors (L-NAME, Apocynin, and VAS2870) ex vivo.

Results

Protein and total cell counts from lung lavage revealed significant pulmonary inflammation from ZH (p < 0.01) and JC and ZH + NiSO₄ (p < 0.001) as compared to control and a significant decrease in mesenteric artery relaxation (p < 0.001) and this decrease is blunted in the presence of NADPH oxidase inhibitors. Significant increases in gene expression (TNF-α, IL-6, Nos3; p < 0.01; NOX4; p < 0.05) were observed in JC and ZH + NiSO₄, as well as significantly higher concentrations of VEGF and IL-10 (p < 0.01, p < 0.001; respectively).

Conclusions

Our results indicate that the specific toxicity observed in PM from JC is likely due to the nickel component in the PM. Further, since VAS2870 was the most successful inhibitor to return vessels to baseline relaxation values, NADPH Oxidase is implicated as the primary source of PM-induced O₂^•-.

Serum bilirubin and the risk of hypertension

BACKGROUND

Experimental studies suggest oxidative stress could lead to the development of hypertension. Serum bilirubin is a major contributor to the antioxidant capacity in blood plasma and has been identified as an independent cardiovascular risk factor in cohort studies. However, data on the relationship between bilirubin and blood pressure are scarce and inconclusive.

METHODS

We analysed data from the National Health and Nutrition Examination Surveys (NHANES) 1999-2012 (N=31069). Fifty multiple imputed data sets were generated and analysed to avoid selection/confounding bias due to excluding individuals/variables with missing values. A minimal sufficient adjustment set of variables (MSAS) needed to estimate the unconfounded effect of bilirubin on blood pressure and hypertension (systolic/diastolic blood pressure ≥ 140/90 mmHg or using antihypertensive medication) was identified using the back-door criterion and included in all regression models.

RESULTS

After adjustment for the MSAS variables, systolic blood pressure decreased progressively up to -2.5 mmHg (p<0.001) and the prevalence of hypertension was up to 25% lower (P<0.001) in those with bilirubin ≥ 1.0 mg/dl-the highest two deciles-compared with those with 0.1-0.4 mg/dl-the lowest decile. Sensitivity analyses showed these results were unlikely to be explained by residual confounding or selection bias.

CONCLUSIONS

High serum bilirubin may decrease the risk of hypertension by inactivating and inhibiting the synthesis of reactive oxygen species in vascular cells. Strategies to boost the bioavailability of circulating and tissue bilirubin or to mimic bilirubin's antioxidant properties could have a significant impact on prevention and control of hypertension as well as coronary heart disease.

L-Leucine and NO-mediated cardiovascular function

Reduced availability of nitric oxide (NO) in the vasculature is a major factor contributing to the impaired action of insulin on blood flow and, therefore, insulin resistance in obese and diabetic subjects. Available evidence shows that vascular insulin resistance plays an important role in the pathogenesis of cardiovascular disease, the leading cause of death in developed nations. Interestingly, increased concentrations of L-leucine in the plasma occur in obese humans and other animals with vascular dysfunction. Among branched-chain amino acids, L-leucine is unique in inhibiting NO synthesis from L-arginine in endothelial cells and may modulate cardiovascular homeostasis in insulin resistance. Results of recent studies indicate that L-leucine is an activator of glutamine:fructose-6-phosphate aminotransferase (GFAT), which is the first and a rate-controlling enzyme in the synthesis of glucosamine (an inhibitor of endothelial NO synthesis). Through stimulating the mammalian target of rapamycin signaling pathway and thus protein synthesis, L-leucine may enhance GFAT protein expression, thereby inhibiting NO synthesis in endothelial cells. We propose that reducing circulating levels of L-leucine or endothelial GFAT activity may provide a potentially novel strategy for preventing and/or treating cardiovascular disease in obese and diabetic subjects. Such means may include dietary supplementation with either α-ketoglutarate to enhance the catabolism of L-leucine in the small intestine and other tissues or with N-ethyl-L-glutamine to inhibit GFAT activity in endothelial cells. Preventing leucine-induced activation of GFAT by nutritional supplements or pharmaceutical drugs may contribute to improved cardiovascular function by enhancing vascular NO synthesis.

Differential effects of leptin and adiponectin in endothelial angiogenesis

Obesity is a major health burden with an increased risk of cardiovascular morbidity and mortality. Endothelial dysfunction is pivotal to the development of cardiovascular disease (CVD). In relation to this, adipose tissue secreted factors termed "adipokines" have been reported to modulate endothelial dysfunction. In this review, we focus on two of the most abundant circulating adipokines, that is, leptin and adiponectin, in the development of endothelial dysfunction. Leptin has been documented to influence a multitude of organ systems, that is, central nervous system (appetite regulation, satiety factor) and cardiovascular system (endothelial dysfunction leading to atherosclerosis). Adiponectin, circulating at a much higher concentration, exists in different molecular weight forms, essentially made up of the collagenous fraction and a globular domain, the latter being investigated minimally for its involvement in proinflammatory processes including activation of NF-κβ and endothelial adhesion molecules. The opposing actions of the two forms of adiponectin in endothelial cells have been recently demonstrated. Additionally, a local and systemic change to multimeric forms of adiponectin has gained importance. Thus detailed investigations on the potential interplay between these adipokines would likely result in better understanding of the missing links connecting CVD, adipokines, and obesity.

Hypoxia and reoxygenation induce endothelial nitric oxide synthase uncoupling in endothelial cells through tetrahydrobiopterin depletion and S-glutathionylation

Ischemia-reperfusion injury is accompanied by endothelial hypoxia and reoxygenation that trigger oxidative stress with enhanced superoxide generation and diminished nitric oxide (NO) production leading to endothelial dysfunction. Oxidative depletion of the endothelial NO synthase (eNOS) cofactor tetrahydrobiopterin can trigger eNOS uncoupling, in which the enzyme generates superoxide rather than NO. Recently, it has also been shown that oxidative stress can induce eNOS S-glutathionylation at critical cysteine residues of the reductase site that serves as a redox switch to control eNOS coupling. While superoxide can deplete tetrahydrobiopterin and induce eNOS S-glutathionylation, the extent of and interaction between these processes in the pathogenesis of eNOS dysfunction in endothelial cells following hypoxia and reoxygenation remain unknown. Therefore, studies were performed on endothelial cells subjected to hypoxia and reoxygenation to determine the severity of eNOS uncoupling and the role of cofactor depletion and S-glutathionylation in this process. Hypoxia and reoxygenation of aortic endothelial cells triggered xanthine oxidase-mediated superoxide generation, causing both tetrahydrobiopterin depletion and S-glutathionylation with resultant eNOS uncoupling. Replenishing cells with tetrahydrobiopterin along with increasing intracellular levels of glutathione greatly preserved eNOS activity after hypoxia and reoxygenation, while targeting either mechanism alone only partially ameliorated the decrease in NO. Endothelial oxidative stress, secondary to hypoxia and reoxygenation, uncoupled eNOS with an altered ratio of oxidized to reduced glutathione inducing eNOS S-glutathionylation. These mechanisms triggered by oxidative stress combine to cause eNOS dysfunction with shift of the enzyme from NO to superoxide production. Thus, in endothelial reoxygenation injury, normalization of both tetrahydrobiopterin levels and the glutathione pool are needed for maximal restoration of eNOS function and NO generation.

Zinc-Excess Intake Causes the Deterioration of Renal Function Accompanied by an Elevation in Systemic Blood Pressure Primarily Through Superoxide Radical-Induced Oxidative Stress

Using rats fed 22 g/d of a control diet containing 0.005% zinc (Zn) or 2 Zn-excess diets containing 0.05% or 0.2% Zn for 4 weeks, we examined the mechanisms involved in the deterioration of renal function induced by Zn-excess intake. An increase in Zn intake elevated mean blood pressure (BP) and reduced renal blood flow (RBF) and inulin clearance in a dose-dependent manner. This decline in inulin clearance may be derived from a fall in RBF. Administration of the nitric oxide (NO) synthase inhibitor, Nω-nitro-l-arginine methyl ester, markedly increased mean BP and significantly decreased RBF in the 3 groups of rats. Administration of the exogenous superoxide radical (OO−) scavenger, tempol, significantly decreased mean BP and substantially increased RBF in all groups of rats. These observations suggest that both an elevation in systemic BP and a reduction in RBF seen in the 2 Zn-excess diet groups result from a decrease in the action of the vasodilator, NO, through the formation of peroxynitrite based on the nonenzymatic reaction of NO and increased OO−. Indeed, the activity of the endogenous OO− scavenger, copper/Zn-superoxide dismutase, was significantly reduced in the vessel wall of rats fed 2 Zn-excess diets versus a control diet. 8-Hydroxy-2′-deoxyguanosine formation caused by OO− generation was notably elevated in the kidneys of rats fed 2 Zn-excess diets relatively to rats fed a control diet. Thus, Zn-excess intake leads to the aggravation of renal function concomitantly with an increase in systemic BP predominantly through the oxidative stress caused by OO−.

Phosphate binding reduces aortic angiotensin-converting enzyme and enhances nitric oxide bioactivity in experimental renal insufficiency

BACKGROUND

Disturbed calcium-phosphorus metabolism is associated with increased kidney angiotensin-converting enzyme (ACE) in experimental chronic renal insufficiency (CRI). However, information about the effects of phosphate binding and loading on vascular ACE is lacking.

METHODS

Fifteen weeks after 5/6 nephrectomy (NX), rats were placed on a phosphate-binding (NX+Ca, 3.0% Ca), phosphate-loading (NX+Pi, 1.5% Pi), or control diet for 12 weeks (NX and sham).

RESULTS

Aortic ACE, blood pressure, plasma phosphate, and parathyroid hormone were increased in the NX and NX+Pi groups, but were reduced with phosphate binding. Endothelium-mediated relaxations of isolated mesenteric conduit artery rings to acetylcholine were impaired in the NX and NX+Pi groups, but did not differ from sham in NX+Ca rats. Experiments with nitric oxide (NO) synthase inhibition in vitro suggested that the NO-mediated component of acetylcholine response was lower in the NX and NX+Pi groups, but did not differ from sham in NX+Ca rats. In all NX groups, aortic endothelial NO synthase (eNOS) was reduced, while plasma and urine concentrations of NO metabolites were increased. Aortic nitrated proteins and calcification were increased in the NX and NX+Pi groups when compared with the NX+Ca and sham groups.

CONCLUSION

Hypertension in the NX model of CRI was associated with reduced vasorelaxation, decreased eNOS, and increased ACE and nitrated proteins in the aorta. Phosphate binding with calcium carbonate enhanced vasorelaxation via endogenous NO and suppressed elevation of ACE and nitrated proteins, suggesting reduced vascular oxidative stress. Our findings support the view that correction of the calcium-phosphorus balance prevents CRI-induced vascular pathophysiology.

Low-molecular-weight fucoidan protects endothelial function and ameliorates basal hypertension in diabetic Goto-Kakizaki rats

Endothelial dysfunction, characterized by impairment of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) bioavailability, has been implicated in diabetic cardiovascular pathogenesis. In this study, low-molecular-weight fucoidan (LMWF), which has multiple biological activities including anti-inflammatory and anti-oxidative properties, was investigated for its protective effect against endothelial dysfunction in Goto-Kakizaki type 2 diabetic rats. LMWF (50, 100, or 200 mg/kg/day) or probucol (100 mg/kg/day) were given to diabetic rats for 12 weeks. Basal blood pressure, acetylcholine- or flow-mediated relaxation of mesenteric and paw arteries, endothelium-dependent dilation of aorta, eNOS phosphorylation, and NO production were measured using laser Doppler flowmetry, force myograph, hematoxylin and eosin staining, western blot analysis, and an NO assay. We found that LMWF robustly ameliorated the basal hypertension and impairment of endothelium-dependent relaxation in the aorta, as well as mesenteric and paw arteries in diabetic rats. In addition, the reduction in eNOS phosphorylation at Ser1177, eNOS expression, and NO production because of diabetes were partially reversed by LMWF treatment. However, probucol, a lipid-modifying drug with antioxidant properties, displayed only mild effects. Moreover, LMWF induced, in a dose-dependent manner, endothelium-dependent vasodilation and eNOS phosphorylation at Ser1177 in normal aorta, and also promoted Ser1177 phosphorylation and NO synthesis in primary cultured vasoendothelial cells. Thus, these data demonstrate for the first time that fucoidan protects vasoendothelial function and reduces basal blood pressure in type 2 diabetes rats via, at least in part, preservation of eNOS function. Fucoidan is therefore a potential candidate drug for protection of endothelium in diabetic cardiovascular complications.

Amlodipine increased endothelial nitric oxide and decreased nitroxidative stress disproportionately to blood pressure changes

BACKGROUND

Clinical trials have shown that amlodipine reduces cardiovascular events at a rate that is not predicted by changes in brachial arterial pressure alone. These findings may be explained, in part, by the pleiotropic effects of amlodipine on endothelial cell (EC) function. In this study, we elucidated the effect of amlodipine on nitric oxide (NO) bioavailability and cytotoxic peroxynitrite (ONOO(-)) and blood pressure (BP).

METHODS

Spontaneously hypertensive rats (SHRs) were treated with vehicle or amlodipine (5 mg/kg/day) for 8 weeks and compared with untreated, baseline rats. NO and ONOO(-) release from aortic and glomerular ECs were measured ex vivo using amperometric nanosensors following maximal stimulation with calcium ionophore. BP was measured using the tail-cuff method.

RESULTS

As compared with baseline, vehicle treatment had reduced aortic endothelial NO release from 157 ± 11 nM to 55 ± 6 nM and increased ONOO(-) from 69 ± 7 nM to 156 ± 19 nM. The NO/ONOO(-) ratio, a comprehensive measurement of eNOS function, decreased from 2.3 ± 0.3 to 0.3 ± 0.1. Compared with vehicle, amlodipine treatment restored NO to 101 ± 3 nM, decreased ONOO(-) to 50 ± 4 nM, and increased the NO/ONOO(-) ratio to 2.0 ± 0.2, a level similar to baseline. Similar changes were observed for glomerular ECs. Mean arterial blood pressure increased from 149 ± 3 mm Hg (baseline) to 174 ± 1 mm Hg (vehicle). Amlodipine slightly, but significantly, decreased mean arterial blood pressure to 167 ± 3 mm Hg vs. vehicle treatment.

CONCLUSIONS

Amlodipine increased NO bioavailability and decreased nitroxidative stress in SHRs with EC dysfunction disproportionately to BP changes. These direct, vascular effects of amlodipine on EC function may contribute to reduced risk for atherothrombotic events as observed in clinical trials.

Depressor action and vasorelaxation of methylene chloride fraction extracted from Rubus coreanum

Introduction

The present study was designed to examine whether methylene chloride (CH₂Cl₂) fraction extracted from Rubus coreanum affects the contractility of the isolated thoracic aortic strips and blood pressure of normotensive rats.

Methods

One of the common carotid arteries or of the femoral arteries was catheterized with a polyethylene tubing. The tubing was connected to a pressure transducer, and pulse of the mean arterial blood pressure was recorded on a biological polygraph continuously.

Results

The CH₂Cl₂ fraction (range, 200 to 800 μg/mL) significantly depressed both phenylephrine (PE, 10 μM)- and high K⁺ (56 mM)-induced contractile responses of the isolated thoracic aortic strips in a concentration-dependent fashion. In the simultaneous presence of N^ω-nitro-L-arginine methyl ester hydrochloride (L-NAME) (an inhibitor of nitric oxide [NO] synthase, 300 μM) and the CH₂Cl₂ fraction (400 μg/mL), both PE- and high K⁺-induced contractile responses were recovered to the significant level of the corresponding control response in comparison with inhibition of CH₂Cl₂ fraction treatment alone. Moreover, in the simultaneous presence of the CH₂Cl₂ fraction after pretreatment with 0.4% CHAPS (3-[(3-cholamidopropyl) dimethylammonio]-1-propane sulfonate), both PE- and high K⁺-induced contractile responses were recovered to the significant level of the corresponding control response compared to the inhibitory response of CH₂Cl₂ fraction treatment alone. Also, in anesthetized rats, the CH₂Cl₂ fraction (range, 0.3 to 3.0 mg/kg) injected into a femoral vein dose-dependently produced depressor responses. This hypotensive action of the CH₂Cl₂ fraction was greatly inhibited after treatment with phentolamine (1 mg/kg), chlorisondamine (1 mg/kg), L-NAME (3 mg/kg/30 min), or sodium nitroprusside (30 μg/kg/30 min). Intravenous infusion of the CH₂Cl₂ fraction (range, 1.0 to 10.0 mg/kg/30 min) markedly inhibited norepinephrine-induced pressor responses.

Discussion

Taken together, these results demonstrate that the CH₂Cl₂ fraction causes vascular relaxation in the isolated rat thoracic aortic strips as well as hypotensive action in anesthetized rats. These vasorelaxation and hypotension of the CH₂Cl₂ fraction seem to be mediated at least by the increased NO production through the activation of NO synthase of the vascular endothelium and the inhibitory adrenergic modulation.

Electronic supplementary material

The online version of this article (doi:10.1186/s40885-014-0006-1) contains supplementary material, which is available to authorized users.

Effects of octreotide on nitric oxide synthase expression in the small intestine of high fat diet-induced obese rats

SUMMARY

OBJECTIVE

To investigate whether obesity induced by high fat diet is associated with expression of neuronal, endothelial, and inducible nitric oxide synthase (nNOS, eNOS, and iNOS) in the intestine, and to test the effects of the somatostatin analog octreotide on this expression.

METHODS

The study included high fat diet-induced obese and normal control rats. The obese rats were further separated into an obese control group and an octreotide intervention group. Rats in the intervention group were injected with 40 μg/kg octreotide every 12 h for 8 days. Expressions of nNOS, eNOS, and iNOS in the small intestine were analyzed by RT-PCR and immunohistochemistry. The NO level of small intestinal homogenate was measured with an ELISA kit.

RESULTS

The body weight; Lee's index; small intestinal eNOS and iNOS mRNA and protein expression levels; nNOS protein expression levels; and small intestinal homogenate NO levels were all significantly higher in the obese control group than in the normal controls (p < 0.01); nNOS mRNA expression was also higher in the obese control group, but not significantly so. Octreotide intervention significantly reduced the body weight and small intestinal homogenate NO level of the obese rats relative to the obese control group (p < 0.05). The mRNA and protein expression levels of eNOS and iNOS; the protein expression level of nNOS in the small intestine were also significantly lower in the octreotide intervention group than in the obese control group (p < 0.01), while nNOS mRNA expression was lower but not significantly so.

CONCLUSION

High fat diet-induced obesity is associated with elevated small intestinal nNOS, eNOS, and iNOS expression levels. Octreotide treatment can inhibit nNOS, eNOS, and iNOS expression and lead to weight loss.

Contribution of oxidative stress to endothelial dysfunction in hypertension

Endothelial dysfunction is the hallmark of hypertension, which is a multifactorial disorder. In the cardiovascular system reactive oxygen species play a pivotal role in controlling the endothelial function and vascular tone. Physiologically, the endothelium-derived relaxing factors (EDRFs) and endothelium-derived contractile factors (EDCFs) that have functions on the vascular smooth muscle cells. The relaxation induced by the EDRFs nitric oxide (NO), prostacyclin, and the endothelium-derived hyperpolarization factor (EDHF) could be impaired in hypertension. The impaired ability of endothelial cells to release NO along with enhanced EDCFs production has been described to contribute to the endothelium dysfunction, which appears to lead to several cardiovascular diseases. The present review discusses the role of oxidative stress, vascular endothelium, and vascular tone control by EDRFs, mainly NO, and EDCFs in different models of experimental hypertension.

Impact of SOD in eNOS uncoupling: a two-edged sword between hydrogen peroxide and peroxynitrite

In endothelial cell dysfunction, the uncoupling of eNOS results in higher superoxide (O(2)(•-)) and lower NO production and a reduction in NO availability. Superoxide reacts with NO to form a potent oxidizing agent peroxynitrite (ONOO(-)) resulting in nitrosative and nitroxidative stresses and dismutates to form hydrogen peroxide. Studies have shown superoxide dismutase (SOD) plays an important role in reduction of O(2)(•-) and ONOO(-) during eNOS uncoupling. However, the administration or over-expression of SOD was ineffective or displayed deleterious effects in some cases. An understanding of interactions of the two enzyme systems eNOS and SOD is important in determining endothelial cell function. We analyzed complex biochemical interactions involving eNOS and SOD in eNOS uncoupling. A computational model of biochemical pathway of the eNOS-related NO and O(2)(•-) production and downstream reactions involving NO, O(2)(•-), ONOO(-), H(2)O(2) and SOD was developed. The effects of SOD concentration on the concentration profiles of NO, O(2)(•-), ONOO(-) and H(2)O(2) in eNOS coupling/uncoupling were investigated. The results include (i) SOD moderately improves NO production and concentration during eNOS uncoupling, (ii) O(2)(•-) production rate is independent of SOD concentration, (iii) Increase in SOD concentration from 0.1 to 100 μM reduces O(2)(•-) concentration by 90% at all [BH(4)]/[TBP] ratios, (iv) SOD reduces ONOO(-) concentration and increases H(2)O(2) concentration during eNOS uncoupling, (v) Catalase can reduce H(2)O(2) concentration and (vi) Dismutation rate by SOD is the most sensitive parameter during eNOS uncoupling. Thus, SOD plays a dual role in eNOS uncoupling as an attenuator of nitrosative/nitroxidative stress and an augmenter of oxidative stress.

Pleiotropic effects of calcium channel blockers

Clinical trials have reported reduced cardiovascular events with certain antihypertensive agents at a rate that could not be predicted by changes in brachial arterial pressure alone. These findings may be explained, in part, by pleiotropic effects of these agents and modulation of central blood pressures. This review focuses on the mechanisms by which calcium channel blockers exert pleiotropic effects, both alone and in combination with statins and inhibitors of the renin-angiotensin system. The essential role of nitric oxide (NO) in maintaining endothelial function and the relationship between NO and reactive oxygen species are discussed in the context of the etiology of hypertension. The importance of managing global cardiovascular risk is emphasized, as hypertension commonly clusters with dyslipidemia and loss of glucose control. From a mechanistic viewpoint, these risk factors contribute to endothelial dysfunction, oxidative stress, and inflammation in a synergistic fashion. A greater understanding of the mechanisms of actions of these cardiovascular agents may lead to more effective drug combinations, to the benefit of individual patients. Furthermore, by elucidating the biological mechanisms by which cardiovascular risk factors lead to vascular injury, we may highlight common pathways and identify novel therapeutic targets.

Polymer nanoreactors with dual functionality: simultaneous detoxification of peroxynitrite and oxygen transport

The design of multifunctional systems is in focus today as a key strategy for coping with complex challenges in various domains that include chemistry, medicine, environmental sciences, and technology. Herein, we introduce protein-containing polymer nanoreactors with dual functionality: peroxynitrite degradation and oxygen transport. Vesicles made of poly-(2-methyloxazoline)-poly(dimethylsiloxane)-poly(2-methyloxazoline) successfully encapsulated hemoglobin (Hb), which serves as a model protein because of its dual function in oxygen transport and peroxynitrite degradation. By inserting channel proteins, the polymer membranes of vesicles permitted passage of various compounds that served for the assessment of in situ Hb activity. The requisite conformational changes in the protein structure and the change in oxidation states that took place within the confined space of the vesicle cavity demonstrated that Hb preserved its dual functionality: peroxynitrite degradation and oxygen transport. The functionality of our nanoreactor, combined with its simple procedure of production and extensive stability over several months, supports it as a promising system for further medical applications.

The role of tetrahydrobiopterin in inflammation and cardiovascular disease

The cofactor tetrahydrobiopterin (BH4) is required for nitric oxide (NO) production by all nitric oxide synthase (NOS) enzymes and is a key regulator of cellular redox signalling. When BH4 levels become limiting NOS enzymes become 'uncoupled' and produce superoxide rather than NO. Endothelial cell BH4 is required for the maintenance of vascular function through NO production, and reduced BH4 levels are associated with vascular dysfunction. Evidence increasingly points to important roles for BH4 and NOS enzymes in other vascular cell types. Leukocytes have a fundamental role in atherosclerosis, and new evidence points to a role in the control of hypertension. Leukocytes are a major site of iNOS expression, and the regulation of this isoform is another mechanism by which BH4 availability may modulate disease. This review provides an overview of BH4 control of NOS function in both endothelial cells and leukocytes in the context of vascular disease and current therapeutic evaluations.

In utero exposure to benzo(a)pyrene predisposes offspring to cardiovascular dysfunction in later-life

In utero exposure of the fetus to benzo(a)pyrene [B(a)P], a polycyclic aromatic hydrocarbon, is thought to dysregulate cardiovascular development. To investigate the effects of in utero B(a)P exposure on cardiovascular development, timed-pregnant Long Evans Hooded (LEH) rats were exposed to diluent or B(a)P (150, 300, 600 and 1200 μg/kg/BW) by oral gavage on embryonic (E) days E14 (the metamorphosing embryo stage) through E17 (the 1st fetal stage). There were no significant effects of in utero exposure to B(a)P on the number of pups born per litter or in pre-weaning growth curves. Pre-weaning profiles for B(a)P metabolite generation from cardiovascular tissue were shown to be dose-dependent and elimination of these metabolites was shown to be time-dependent in exposed offspring. Systolic blood pressure on postnatal day P53 in the middle and high exposure groups of offspring were significantly elevated as compared to controls. Microarray and quantitative real-time PCR results were directly relevant to a biological process pathway in animal models for "regulation of blood pressure". Microarray and quantitative real-time PCR analysis revealed upregulation of mRNA expression for angiotensin (AngII), angiotensinogen (AGT) and endothelial nitric oxide synthase (eNOS) in exposed offspring. Biological network analysis and gene set enrichment analysis subsequently identified potential signaling mechanisms and molecular pathways that might explain the elevated systolic blood pressures observed in B(a)P-exposed offspring. Our findings suggest that in utero exposure to B(a)P predispose offspring to functional deficits in cardiovascular development that may contribute to cardiovascular dysfunction in later life.

Decreased production of neuronal NOS-derived hydrogen peroxide contributes to endothelial dysfunction in atherosclerosis

BACKGROUND AND PURPOSE

Reduced NO availability has been described as a key mechanism responsible for endothelial dysfunction in atherosclerosis. We previously reported that neuronal NOS (nNOS)-derived H(2)O(2) is an important endothelium-derived relaxant factor in the mouse aorta. The role of H(2)O(2) and nNOS in endothelial dysfunction in atherosclerosis remains undetermined. We hypothesized that a decrease in nNOS-derived H(2)O(2) contributes to the impaired vasodilatation in apolipoprotein E-deficient mice (ApoE(-/-)).

EXPERIMENTAL APPROACH

Changes in isometric tension were recorded on a myograph; simultaneously, NO and H(2)O(2) were measured using carbon microsensors. Antisense oligodeoxynucleotides were used to knockdown eNOS and nNOS in vivo. Western blot and confocal microscopy were used to analyse the expression and localization of NOS isoforms.

KEY RESULTS

Aortas from ApoE(-/-) mice showed impaired vasodilatation paralleled by decreased NO and H(2)O(2) production. Inhibition of nNOS with L-Arg(NO2) -L-Dbu, knockdown of nNOS and catalase, which decomposes H(2)O(2) into oxygen and water, decreased ACh-induced relaxation by half, produced a small diminution of NO production and abolished H(2)O(2) in wild-type animals, but had no effect in ApoE(-/-) mice. Confocal microscopy showed increased nNOS immunostaining in endothelial cells of ApoE(-/-) mice. However, ACh stimulation of vessels resulted in less phosphorylation on Ser852 in ApoE(-/-) mice.

CONCLUSIONS AND IMPLICATIONS

Our data show that endothelial nNOS-derived H(2)O(2) production is impaired and contributes to endothelial dysfunction in ApoE(-/-) aorta. The present study provides a new mechanism for endothelial dysfunction in atherosclerosis and may represent a novel target to elaborate the therapeutic strategy for vascular atherosclerosis.