Sildenafil attenuates oxidative stress and endothelial dysfunction in lead-induced hypertension

Lead (Pb) reduces NO bioavailability, impairs the antioxidant system, and increases the generation of reactive oxygen species (ROS). Pb-induced oxidative stress may be responsible for the associated endothelial dysfunction. Sildenafil has shown nitric oxide (NO)-independent action, including antioxidant effects. Therefore, we examined the effects of sildenafil on oxidative stress, reductions of NO and endothelial dysfunction in Pb-induced hypertension. Wistar rats were distributed into three groups: Pb, Pb + sildenafil and Sham. Blood pressure and endothelium-dependent vascular function were recorded. We also examined biochemical determinants of lipid peroxidation and antioxidant function. ROS levels, NO metabolites and NO levels in human umbilical vein endothelial cells (HUVECs) were also evaluated. Sildenafil prevents impairment of endothelium-dependent NO-mediated vasodilation and attenuates Pb-induced hypertension, reduces ROS formation, enhances superoxide dismutase (SOD) activity and antioxidant capacity in plasma and increases NO metabolites in plasma and HUVECs culture supernatants, while no changes were found on measurement of NO released from HUVECs incubated with plasma of the Pb and Pb + sildenafil groups compared with the sham group. In conclusion, sildenafil protects against ROS-mediated inactivation of NO, thus preventing endothelial dysfunction and attenuating Pb-induced hypertension, possibly through antioxidant effects.     

The vascular endothelial growth factor trap aflibercept induces vascular dysfunction and hypertension via attenuation of eNOS/NO signaling in mice

Aflibercept, as a soluble decoy vascular endothelial growth factor receptor, Which has been used as a first-line monotherapy for cancers. Aflibercept often causes cardiovascular toxicities including hypertension, but the mechanisms underlying aflibercept-induced hypertension remain unknown. In this study we investigated the effect of short-term and long-term administration of aflibercept on blood pressure (BP), vascular function, NO bioavailability, oxidative stress and endothelin 1 (ET-1) in mice and cultured endothelial cells. We showed that injection of a single-dose of aflibercept (18.2, 36.4 mg/kg, iv) rapidly and dose-dependently elevated BP in mice. Aflibercept treatment markedly impaired endothelial-dependent relaxation (EDR) and resulted in NADPH oxidases 1 (NOX1)- and NADPH oxidases 4 (NOX4)-mediated generation of ROS, decreased the activation of protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS) concurrently with a reduction in nitric oxide (NO) production and elevation of ET-1 levels in mouse aortas; these effects were greatly attenuated by supplementation of L-arginine (L-arg, 0.5 or 1.0 g/kg, bid, ig) before aflibercept injection. Similar results were observed in L-arg-pretreated cultured endothelial cells, showing markedly decreased ROS accumulation and AKT/eNOS/NO signaling impairment induced by aflibercept. In order to assess the effects of long-term aflibercept on hypertension and to evaluate the beneficial effects of L-arg supplementation, we administered these two drugs to WT mice for up to 14 days (at an interval of two days). Long-term administration of aflibercept resulted in a sustained increase in BP and a severely impaired EDR, which are associated with NOX1/NOX4-mediated production of ROS, increase in ET-1, inhibition of AKT/eNOS/NO signaling and a decreased expression of cationic amino acid transporter (CAT-1). The effects caused by long-term administration were greatly attenuated by L-arg supplementation in a dose-dependent manner. We conclude that aflibercept leads to vascular dysfunction and hypertension by inhibiting CAT-1/AKT/eNOS/NO signaling, increasing ET-1, and activating NOX1/NOX4-mediated oxidative stress, which can be suppressed by supplementation of L-arg. Therefore, L-arg could be a potential therapeutic agent for aflibercept-induced hypertension.     

Puerarin protects pulmonary arteries from hypoxic injury through the BMPRII and PPARγ signaling pathways in endothelial cells

BackgroundRecent evidence indicates that Puerarin has a protective effect on pulmonary arteries. In the present study, we aimed to investigate whether Puerarin could protect pulmonary arterial endothelial cells from hypoxic injury and determine its potential targets.MethodsIn our study, human pulmonary arterial endothelial cells (HPAECs) were injured by hypoxic (1% O₂) incubation. Cell viability was detected by a cell counting kit (CCK8). The production of nitric oxide (NO) was detected by Griess reagent and endothelin-1 (ET-1) was detected by the ELISA method. Oxidative stress was measured by a fluorescence microscope via the fluorescent probe DCFH-DA. Western blotting was employed for studying the mechanism.ResultsThe results show that Puerarin protects HPAECs from hypoxia-induced apoptosis and slightly improves cell viability. Puerarin increases NO and decreases ET-1 to prevent the imbalance between vasoactive substances induced by hypoxia in HPAECs. Puerarin also inhibits the oxidative stress induced by hypoxia. The results from the Western blot show that Puerarin activates the BMPRII/Smad and PPARγ/PI3K/Akt signaling pathways.ConclusionIn conclusion, Puerarin protects HPAECs from hypoxic injury through the inhibition of oxidative stress and the activation of the BMPRII and PPARγ signaling pathways. This work provides insight into the development of Puerarin as a treatment for hypoxic pulmonary hypertension.     

NADPH oxidases regulate endothelial inflammatory injury induced by PM2.5 via AKT/eNOS/NO axis

Fine particulate matter (PM_2.5)-induced detrimental cardiovascular effects have been widely concerned, especially for endothelial cells, which is the first barrier of the cardiovascular system. Among potential mechanisms involved, reactive oxidative species take up a crucial part. However, source of oxidative stress and its relationship with inflammatory response have been rarely studied in PM_2.5-induced endothelial injury. Here, as a key oxidase that catalyzes redox reactions, NADPH oxidase (NOX) was investigated. Human umbilical vein endothelial cells (EA.hy926) were exposed to Standard Reference Material 1648a of urban PM_2.5 for 24 h, which resulted in NOX-sourced oxidative stress, endothelial dysfunction, and inflammation induction. These are manifested by the up-regulation of NOX, increase of superoxide anion and hydrogen peroxide, elevated endothelin-1 (ET-1) and asymmetric dimethylarginine (ADMA) level, reduced nitric oxide (NO) production, and down-regulation of phosphorylation of endothelial NO synthase (eNOS) with increased levels of inducible NO synthase, as well as the imbalance between tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor 1 (PAI-1), and changes in the levels of pro-inflammatory and anti-inflammatory factors. However, administration of NOX1/4 inhibitor GKT137831 alleviated PM_2.5-induced elevated endothelial dysfunction biomarkers (NO, ET-1, ADMA, iNOS, and tPA/PAI-1), inflammatory factors (IL-1β, IL-10, and IL-18), and adhesion molecules (ICAM-1, VCAM-1, and P-selectin) and also passivated NOX-dependent AKT and eNOS phosphorylation that involved in endothelial activation. In summary, PM_2.5-induced NOX up-regulation is the source of ROS in EA.hy926, which activated AKT/eNOS/NO signal response leading to endothelial dysfunction and inflammatory damage in EA.hy926 cells.     

The impact of immunosuppression on endothelial function

Endothelial dysfunction is an early marker for transplant atherosclerosis. Potential mechanisms for allograft endothelial dysfunction include stimulation of alloimmune-dependent pathways, ischemia/reperfusion injury, metabolic alterations, chronic infections, as well as direct endothelial cell activation by immunosuppressive drugs. Thus far, no study has directly compared different immunosuppressive drugs with respect to their potential to modulate endothelial function under normoxic and hypoxic conditions. We examined human microvascular endothelial cells (HMEC-1) in vitro after stimulation with therapeutic concentrations of methylprednisolone (MP), mycophenolic acid (MMF), cyclosporine A (CS), rapamycin (Rapa), and tacrolimus (Tac) to designate the corresponding induction of oxidative stress, apoptosis, metabolic activity, proliferation, endothelin (ET-1) release, and nitric oxide (NO) production. HMEC-1 stimulation with CS, MMF, and Rapa resulted in a stronger induction of oxidative stress compared with MP and Tac. Induction of oxidative stress by immunosuppressives correlated with metabolic activity and apoptosis. Low- and high-dose MMF significantly inhibited cell proliferation under hypoxic conditions, whereas low-dose CS and MP increased endothelial cell proliferation. ET-1 release was significantly elevated by Rapa, Tac, and MP. NO production was significantly enhanced by all immunosuppressive drugs except Tac. Quality and quantity of immunosuppression modify endothelial function and lead to a dose-dependent and oxygenation-state-related endothelial activation. MP and MMF induced minor changes in endothelial function compared with CS, Rapa, and Tac.     

Endothelin-1: the yin and yang on vascular function

Endothelin-1 (ET-1) is a vasoconstrictor secreted by endothelial cells, which acts as the natural counterpart of the vasodilator nitric oxide (NO). ET-1 contributes to vascular tone and regulates cell proliferation through activation of ETA and ETB receptors. Physical factors such as shear stress, or stimuli including thrombin, epinephrine, angiotensin II, growth factors, cytokines and free radicals enhance secretion of ET-1. By contrast, mediators like nitric oxide (NO), cyclic GMP, atrial natriuretic peptide, and prostacyclin reduce the release of endogenous ET-1. Thus, under normal conditions, the effects of the ET-1 are carefully regulated through inhibition or stimulation of ET-1 release from endothelium. Endothelial dysfunction is one of the earliest landmarks of vascular abnormalities. Altered function of endothelium may result from absolute decrease in bioavailability of NO as well as from relative augment in ET-1 synthesis, release or activity. Imbalance in the production of vasodilator and vasoconstrictor agents may contribute to the onset of hemodynamic disorders. Since dysregulation of the endothelin system is important in the pathogenesis of several cardiovascular diseases, the ETA and ETB receptors are attractive therapeutic targets for disorders associated with elevated ET-1 levels. ET receptor antagonists may be regarded as disease-modifying agents thanks to their ability to preserve endothelial integrity when the endothelin system is overactive. This review summarizes the current knowledge on the role of ET-1 in experimental hypertension and describes recent findings on the involvement of MAPK signalling pathways in ET-1 release in hypertension associated with insulin resistance. Moreover, therapeutic applications of ET-1 receptor blockers are also discussed.     

Role of reactive oxygen species and gp91phox in endothelial dysfunction of pulmonary arteries induced by chronic hypoxia

1. This study investigates the role of nitric oxide (NO) and reactive oxygen species (ROS) on endothelial function of pulmonary arteries in a mice model of hypoxia-induced pulmonary hypertension. 2. In pulmonary arteries from control mice, the NO-synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME) potentiated contraction to prostaglandin F2alpha (PGF2alpha) and completely abolished relaxation to acetylcholine. In extrapulmonary but not intrapulmonary arteries, acetylcholine-induced relaxation was slightly inhibited by polyethyleneglycol-superoxide dismutase (PEG-SOD) or catalase. 3. In pulmonary arteries from hypoxic mice, ROS levels (evaluated using dihydroethidium staining) were higher than in controls. In these arteries, relaxation to acetylcholine (but not to sodium nitroprusside) was markedly diminished. L-NAME abolished relaxation to acetylcholine, but failed to potentiate PGF2-induced contraction. PEG-SOD or catalase blunted residual relaxation to acetylcholine in extrapulmonary arteries, but did not modify it in intrapulmonary arteries. Hydrogen peroxide elicited comparable (L-NAME-insensitive) relaxations in extra- and intrapulmonary arteries from hypoxic mice. 4. Exposure of gp91phox(-/-) mice to chronic hypoxia also decreased the relaxant effect of acetylcholine in extrapulmonary arteries. However, in intrapulmonary arteries from hypoxic gp91phox(-/-) mice, the effect of acetylcholine was similar to that obtained in mice not exposed to hypoxia. 5. Chronic hypoxia increases ROS levels and impairs endothelial NO-dependent relaxation in mice pulmonary arteries. Mechanisms underlying hypoxia-induced endothelial dysfunction differ along pulmonary arterial bed. In extrapulmonary arteries from hypoxic mice, endothelium-dependent relaxation appears to be mediated by ROS, in a gp91phox-independent manner. In intrapulmonary arteries, endothelial dysfunction depends on gp91phox, the latter being rather the trigger than the mediator of impaired endothelial NO-dependent relaxation     

Effects of atorvastatin on fine particle-induced inflammatory response, oxidative stress and endothelial function in human umbilical vein endothelial cells

The study is to explore the toxicity of organic extracts and water-soluble fraction of fine particles on human umbilical vein endothelial cells (HUVECs). The exposure doses were 100, 200 and 400 μg/ml, respectively, for two kinds of fractions. Moreover, atorvastatin was used for intervention study. HUVECs were stimulated by 400 μg/ml organic and water soluble extracts, respectively, immediately followed by treatment with atorvastatin in concentrations of 0.1 μmol/L, 1 μmol/L and 10 μmol/L, respectively. Cell viability, malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase (SOD), reactive oxygen species (ROS) and the expression of interleukin-6 beta (IL-6), tumor necrosis factor-α (TNF-α), endothelin-1 and P-selectin were determined in cells. The results showed that MDA and ROS increased in HUVECs after exposed to organic extracts and water-soluble fraction, whereas cell viability, NO and SOD decreased. The mRNA expression of IL-6, TNF-α, endothelin-1 (ET-1) and P-selectin increased after exposed to different fractions. Meanwhile, at the same exposure dose, water-soluble fraction caused more significant increase of MDA, IL-6, TNF-α and P-selectin and decrease of cell viability and NO when compared to organic extracts. Compared to no atorvastatin group, the levels of MDA, ROS and the expression of IL-6, TNF-α, ET-1 and P-selectin decreased in HUVECs in adding atorvastatin group, but cell viability, NO and SOD increased, which indicated that atorvastatin attenuated fine particle-induced inflammatory response, oxidative stress and endothelial damage. The results hinted that the inflammatory response, oxidative stress and endothelial dysfunction might be the mechanisms of cardiovascular injury induced by different fractions of ambient fine particles.     

Alterations in lung arginine metabolism in lambs with pulmonary hypertension associated with increased pulmonary blood flow

Previous studies demonstrate impaired nitric oxide (NO) signaling in children and animal models with congenital heart defects and increased pulmonary blood flow. However, the molecular mechanisms underlying these alterations remain incompletely understood. The purpose of this study was to determine if early changes in arginine metabolic pathways could play a role in the reduced NO signaling demonstrated in our lamb model of congenital heart disease with increased pulmonary blood flow (Shunt lambs). The activities of the arginine recycling enzymes, argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL) were both decreased in lung tissues of Shunt lambs while arginase activity was increased. Associated with these alterations, lung L-arginine levels were decreased. These changes correlated with an increase in NO synthase-derived reactive oxygen species (ROS) generation. This study provides further insights into the molecular mechanisms leading to decreased NO signaling in Shunt lambs and suggests that altered arginine metabolism may play a role in the development of the endothelial dysfunction associated with pulmonary hypertension secondary to increased pulmonary blood flow.     

Mechanisms of hypertension induced by nitric oxide (NO) deficiency: focus on venous function

Loss of endothelial cell-derived nitric oxide (NO) in hypertension is a hallmark of arterial dysfunction. Experimental hypertension created by the removal of NO, however, involves mechanisms in addition to decreased arterial vasodilator activity. These include augmented endothelin-1 (ET-1) release, increased sympathetic nervous system activity, and elevated tissue oxidative stress. We hypothesized that increased venous smooth muscle (venomotor) tone plays a role in Nomega-nitro-L-arginine (LNNA) hypertension through these mechanisms. Rats were treated with the NO synthase inhibitor LNNA (0.5 g/L in drinking water) for 2 weeks. Mean arterial pressure of conscious rats was 119 +/- 2 mm Hg in control and 194 +/- 5 mm Hg in LNNA rats (P<0.05). Carotid arteries and vena cava were removed for measurement of isometric contraction. Maximal contraction to norepinephrine was modestly reduced in arteries from LNNA compared with control rats whereas the maximum contraction to ET-1 was significantly reduced (54% control). Maximum contraction of vena cava to norepinephrine (37% control) also was reduced but no change in response to ET-1 was observed. Mean circulatory filling pressure, an in vivo measure of venomotor tone, was not elevated in LNNA hypertension at 1 or 2 weeks after LNNA. The superoxide scavenger tempol (30, 100, and 300 micromol kg(-1), IV) did not change arterial pressure in control rats but caused a dose-dependent decrease in LNNA rats (-18 +/- 8, -26 +/- 15, and -54 +/- 11 mm Hg). Similarly, ganglionic blockade with hexamethonium caused a significantly greater fall in LNNA hypertensive rats (76 +/- 9 mm Hg) compared with control rats (35 +/- 10 mm Hg). Carotid arteries, vena cava, and sympathetic ganglia from LNNA rats had higher basal levels of superoxide compared with those from control rats. These data suggest that while NO deficiency increases oxidative stress and sympathetic activity in both arterial and venous vessels, the impact on veins does not make a major contribution to this form of hypertension.     

Oxidative stress and endothelial function: therapeutic interventions

Cardiovascular risk factors, such as hypertension, hypercholesterolemia, diabetes mellitus, or chronic smoking, stimulate the production of reactive oxygen species (ROS) in the vascular wall. Oxidative stress and endothelial dysfunction in the coronary and peripheral circulation have important prognostic implications for subsequent cardiovascular events. The pathophysiologic causes of oxidative stress are likely to involve changes in a number of different enzyme systems. Reactive oxygen species (ROS) are produced by various oxidase enzymes, including nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase, xanthine oxidase, uncoupled endothelial NO synthase (eNOS), cyclooxygenase, glucose oxidase, and lipooxygenase, and mitochondrial electron transport. Decreased NO production due to changes in the expression and activity of eNOS and increased degradation of NO, by reaction with superoxide account for the reduction in endothelium-dependent vascular relaxation. Recently, a variety of antioxidants have been extensively studied in clinical trials for the prevention and treatment of atherosclerosis. In small clinical studies both vitamins C and E may improve endothelial function in high-risk patients. However, larger interventional trials have been controversial, suggesting potential harm in certain high-risk populations. Antihypertensive and hypolipidemic medications exhibit well-documented antioxidant effects and improve endothelial function. However, the discussion of recent patents with the novel antioxidant strategies are required to clarify the role of antioxidant intervention in vascular diseases.     

Stress and vascular responses: endothelial dysfunction via lectin-like oxidized low-density lipoprotein receptor-1: close relationships with oxidative stress

Endothelial dysfunction is associated with pathological vascular conditions including atherosclerosis, hypertension, and diabetes. The oxidatively modified form of low-density lipoprotein (LDL) is recognized as a major cause of endothelial dysfunction in atherogenesis. As the receptor for oxidized LDL in endothelial cells, we have identified the lectin-like oxidized LDL receptor-1 (LOX-1). LOX-1 is up-regulated by products of oxidative stresses and the molecules that induce oxidative stresses. Activation of LOX-1 induces the generation of reactive oxygen species and decreases NO released from endothelial cells. LOX-1 activation further induces the expression of endothelin-1, AT(1) receptor, and cell adhesion molecules. Together with these properties, LOX-1 works as an adhesion molecule for activated platelets and neutrophils. Thus, LOX-1, within the close relationships between oxidative stress generation and response, enhances functional changes in endothelial cells that are relevant to the disturbed vascular homeostasis under pathological settings.     

Endothelin-1 enhances oxidative stress, cell proliferation and reduces apoptosis in human umbilical vein endothelial cells: role of ETB receptor, NADPH oxidase and caveolin-1

1 Endothelin-1 (ET-1), an endothelium-derived vasoactive peptide, participates in the regulation of endothelial function through mechanisms that are not fully elucidated. This study examined the impact of ET-1 on oxidative stress, apoptosis and cell proliferation in human umbilical vein endothelial cells (HUVEC). HUVECs were challenged for 24 h with ET-1 (10 pM-10 nM) in the absence or presence of the ET(B) receptor antagonist BQ788 (1 microM) or the NADPH oxidase inhibitor apocynin (1 microM). Reactive oxygen species (ROS) were detected using chloromethyl-2',7'-dichlorodihydrofluorescein diacetate. Apoptosis was evaluated with 4',6'-diamidino-2'-phenylindoladihydrochloride staining and by the caspase-3 assay. Cell proliferation was measured by a colorimetric assay. Expression of NADPH oxidase, Akt, pAkt, Bcl-2, Bax, IkappaB, caveolin-1 and eNOS was evaluated by Western blot analysis. 2 ET-1 significantly enhanced ROS generation and cell proliferation following 24-h incubation, both of which were prevented by BQ788 or apocynin, consistent with the ability of ET-1 to directly upregulate NADPH oxidase. ET-1 itself did not affect apoptosis but attenuated homocysteine-induced apoptosis through an ET(B) receptor-mediated mechanism. Western blot analysis indicated that ET-1 alleviated homocysteine (Hcy)-induced apoptosis, likely acting by antagonizing the Hcy-induced decreases in Akt, pAkt, pAkt-to-Akt, Bcl-2-to-Bax ratios and increases in Bax and caveolin-1 expression. Furthermore, ET-1 downregulated expression of caveolin-1 and eNOS, which was attenuated by BQ788 or apocynin. 3 In summary, our results suggest that ET-1 affects oxidative stress, proliferation and apoptosis possibly through ET(B), NADPH oxidase, Akt, Bax and caveolin-1-mediated mechanisms.     

Placental nitric oxide formation and endothelium‐dependent vasodilation underlie pravastatin effects against angiogenic imbalance,hypertension in pregnancy and intrauterine growth restriction

Pre‐eclampsia and hypertensive disorders of pregnancy are frequently associated with foeto‐placental growth restriction, and that may be triggered by angiogenic imbalance and endothelial dysfunction. Impaired nitric oxide (NO) bioavailability seems to be involved in these pathophysiological changes observed in hypertensive pregnancy. Pravastatin has shown efficacy and to be safe during hypertension in pregnancy. However, NO involvement in pravastatin effects during maternal hypertension and foeto‐placental development is unclear. Therefore, we aimed to examine pravastatin effects on placental NO formation, endothelium‐dependent vasodilation, systolic blood pressure and foeto‐placental development in hypertensive pregnant rats. Biochemical determinants of angiogenesis and oxidative stress were also assessed. Pregnant rats were distributed into four groups: normal pregnancy (Norm‐Preg), pregnancy+pravastatin (Preg‐Prava), hypertensive pregnancy (HTN‐Preg) and hypertensive pregnancy+pravastatin (HTN‐Preg+Prava). Our results showed that pravastatin treatment blunts hypertension and foeto‐placental growth restriction. Also, increases in placental NO levels were found in the HTN‐Preg+Prava group. Pravastatin prevents impaired endothelium‐dependent acetylcholine‐induced vasodilation, exacerbated contractile response to phenylephrine and increases in oxidative stress in the HTN‐Preg+Prava group. Increased soluble fms‐like tyrosine kinase‐1‐to‐placental growth factor (sFlt‐1/PlGF) ratio is reversed by pravastatin treatment in the HTN‐Preg+Prava group. We conclude that NO formation and endothelium‐dependent vasodilation underlie pleiotropic effects associated with pravastatin treatment against hypertension in pregnancy, intrauterine growth restriction, vascular dysfunction and angiogenic imbalance.     

Targeting endothelial senescence by natural products to improve vascular health

It is well established in experimental animals and Humans that endothelial cells, which cover the luminal surface of all blood vessels, have a pivotal role in the control of vascular homeostasis. The protective effect of endothelial cells is mostly due to their ability to respond to circulating hormones, autacoids, blood-and platelet-derived factors, and also to blood flow by inducing potent vasoprotectivemechanismsincluding predominantlythe formation of nitric oxide(NO), and, often also to some extent, endothelium-derived hyperpolarization, and prostacyclin(PGI2). Besides being a potent vasodilator, NO also effectively prevents platelet activation and has anti-thrombotic and anti-atherosclerotic properties.An endothelial dysfunction characterized by a reduced generation of these endothelium-dependent vasodilator mechanisms associated with vascular oxidative stress and the formation of endothelium-derived contracting factors such as contractile prostanoids is often observed in most types of cardiovascular diseases including hypertension, hypercholesterolemia, diabetes, and also during physiological ageing in both experimental animals and Humans.Nutrition-derived polyphenols such as those from grapes, tea, cocoa, and berries have been shown to stimulate the endothelial formation of NO by activating the Src/PI3-kinase/Akt-dependent phosphorylation of endothelial NO synthase(e NOS) and to enhance e NOS expression. As a consequence, the active polyphenols will promote a sustained formation of NO that contributes to protect the vascular system. Polyphenol-rich products have also been shown to improve an established endothelial dysfunction and to delay the onset of the induction of an endothelial dysfunction in several experimental models of cardiovascular diseases including hypertension and in ageing.Moreover, endothelial senescence characterized by cell cycle arrest and the acquisition of a pro-inflammatory and pro-atherothrombotic phenotype has been identified as an early event promotingthe development of endothelial dysfunction. Premature endothelial senescence appears to affect, in particular,arterial sites at risk such as curvatures and bifurcations that are characterized by disturbed flow and low shear stress. The pro-senescent process can be further increased in the presence of a high concentration of glucose, oxidized LDL, and angiotensin Ⅱ. Anthocyanin-rich products have been shown to accumulate preferentially in senescent endothelial cells, to reduce the expression of cell cycle regulators such as p16, p21 and p53, and to improve the endothelial function. The protective effect is mostly due to their ability to reduce vascular oxidative stress by inhibiting the overexpression of NADPH oxidase and the local angiotensin system.Thus, nutrition-derived polyphenols may be an interesting approach to delay the onset of risk factor-and ageing-related endothelial senescence and dysfunction and, hence, to promote vascular health.     

Pharmacological preconditioning with sildenafil: Basic mechanisms and clinical implications

The phosphodiesterase type-5 (PDE5) inhibitor, sildenafil, is the first drug developed for treatment of erectile dysfunction in patients. Experimental data in animals show that sildenafil has a preconditioning-like cardioprotective effect against ischemia/reperfusion injury in the intact heart. Mechanistic studies suggest that sildenafil exerts cardioprotection through NO generated from eNOS/iNOS, activation of protein kinase C/ERK signaling and opening of mitochondrial ATP-sensitive potassium channels. Additional studies show that the drug attenuates cell death resulting from necrosis and apoptosis, and increases the Bcl2/Bax ratio through NO signaling in adult cardiomyocytes. Emerging new data also suggest that sildenafil may be used clinically for treatment of pulmonary arterial hypertension and endothelial dysfunction. Future demonstration of the cardioprotective effect in patients with the relatively safe and effective FDA-approved PDE5 inhibitors such as sildenafil could have an enormous impact on bringing the long-studied phenomenon of ischemic and pharmacologic preconditioning to the clinical forefront.     

Mechanisms of endothelial dysfunction: clinical significance and preventive non-pharmacological therapeutic strategies

Endothelium-derived NO is not only a potent vasodilator but also inhibits platelet aggregation, vascular smooth muscle cell migration and proliferation, monocyte adhesion and adhesion molecule expression, thus protecting the vessel wall against the development of atherosclerosis. Cardiovascular risk factors are associated with an imbalance of the redox equilibrium towards oxidative stress and, therefore, impair the integrity of the endothelium, leading to endothelial activation which involves blunted endothelium-dependent vasodilation (vasodilator dysfunction) as well as inflammatory processes extending to the milieu within the whole vasculature, making plaques prone to rupture. In prospective studies endothelial dysfunction is associated with increased incidence of cardiovascular events. Thus, the prevention of endothelial dysfunction can determine a strong advantage in the clinical outcome of patients with cardiovascular risk factors. Several non-pharmacological interventions can prevent endothelial dysfunction or improve impaired endothelium-dependent vasodilation. Probably the most effective non-pharmacological measure is represented by aerobic physical activity, which can reduce production of oxidative stress associated to increasing age. Moreover, physical activity can improve endothelial dysfunction even in patients with cardiovascular risk factors such as essential hypertension. In addition several other approaches, including vitamin and fish oil supplementation, or tea and red wine consumption, can lead to an improvement of endothelium-dependent vasodilation, possibly by a restoration of NO availability. It is worth noting that most of non-pharmacological measures act by preventing or reducing oxidative stress.