Quercetin downregulates NADPH oxidase, increases eNOS activity and prevents endothelial dysfunction in spontaneously hypertensive rats

Novel nanocomposite stent coating releasing resveratrol and quercetin reduces neointimal hyperplasia and promotes re-endothelialization

Late-term thrombosis associated with drug-eluting stents may be due to the non-selective actions of antimitogenic drugs on endothelial cells, leading to delayed vascular healing after stenting angioplasty. Currently, there is a need for stent-based therapies that can both attenuate neointimal hyperplasia and promote re-endothelialization. The aim of this study was to compare the effects of a resveratrol (R)- and quercetin (Q)-eluting stent with that of a bare metal stent (BMS) on neointimal hyperplasia and re-endothelialization in a rat model of arterial angioplasty and stenting. Miniature stents (2.5×1.25mm) were sprayed with nanocomposite coatings containing two concentrations of R:Q (50:25μg/cm(2) (RQ1) or 150:75μg/cm(2) (RQ2)). The stents were deployed into the common carotid artery of rats and their impact on vascular remodeling was compared to that of BMS. Luminal stenosis in arteries stented with RQ2-eluting stents was reduced by 64.6% (p<0.05) compared to arteries stented with BMS. Accompanying this effect was a 59.8% reduction in macrophage infiltration (p<0.05). There were no differences found between RQ1 and BMS. Finally, the RQ2-coated stent accelerated re-endothelialization by 50% compared with BMS (p<0.05). Thus, compared with BMS, local delivery of R and Q from a stent platform significantly reduced in-stent stenosis, while promoting re-endothelialization. These data suggest that R and Q may be favorable candidates for novel stent coatings, potentially reducing the risk of late thrombosis associated with drug-eluting stents.

Flavonoid-rich apples and nitrate-rich spinach augment nitric oxide status and improve endothelial function in healthy men and women: a randomized controlled trial

Flavonoids and nitrates in fruits and vegetables may protect against cardiovascular disease. Dietary flavonoids and nitrates can augment nitric oxide status via distinct pathways, which may improve endothelial function and lower blood pressure. Recent studies suggest that the combination of flavonoids and nitrates can enhance nitric oxide production in the stomach. Their combined effect in the circulation is unclear. Here, our objective was to investigate the independent and additive effects of flavonoid-rich apples and nitrate-rich spinach on nitric oxide status, endothelial function, and blood pressure. A randomized, controlled, crossover trial with healthy men and women (n=30) was conducted. The acute effects of four energy-matched treatments (control, apple, spinach, and apple+spinach), administered in random order, were compared. Measurements included plasma nitric oxide status, assessed by measuring S-nitrosothiols+other nitrosylated species (RXNO) and nitrite, blood pressure, and endothelial function, measured as flow-mediated dilatation of the brachial artery. Results are means and 95% CI. Relative to control, all treatments resulted in higher RXNO (control, 33 nmol/L, 26, 42; apple, 51 nmol/L, 40, 65; spinach, 86 nmol/L, 68, 110; apple+spinach, 69 nmol/L, 54, 88; P<0.01) and higher nitrite (control, 35 nmol/L, 27, 46; apple, 69 nmol/L, 53, 90; spinach, 99 nmol/L, 76, 129; apple+spinach, 80 nmol/L, 61, 104; P<0.01). Compared to control, all treatments resulted in higher flow-mediated dilatation (P<0.05) and lower pulse pressure (P<0.05), and apple and spinach resulted in lower systolic blood pressure (P<0.05). No significant effect was observed on diastolic blood pressure. The combination of apple and spinach did not result in additive effects on nitric oxide status, endothelial function, or blood pressure. In conclusion, flavonoid-rich apples and nitrate-rich spinach can independently augment nitric oxide status, enhance endothelial function, and lower blood pressure acutely, outcomes that may benefit cardiovascular health.

Extract of Scutellaria baicalensis Georgi root exerts protection against myocardial ischemia-reperfusion injury in rats

Ischemic heart disease is a major cause of death in the world. Common therapies, such as primary coronary angioplasty and thrombolysis, are applied to restore blood supply to the heart, limit infarct size and reduce mortality. However, the restoration of blood supply would generate reactive oxygen species in damaged sites of the myocardium, intensifying the damage to the cardiac tissues. Radix Scutellariae baicalensis (Huangqin) is a well-known herb in traditional Chinese medicine with high antioxidant power. In this study, extract of the dry root of Scutellaria baicalensis Georgi (Sb) was confirmed to have a high content of flavonoids and phenolic compounds. The cardioprotective effects of the Sb extracts (3, 30 and 300 mg/kg) were evaluated in myocardial ischemia-reperfusion injuried rats. The results showed that animals that had received five-day pretreatment of the Sb extract (30 mg/kg) had a significant reduction in myocardial infarct size and a marked increase in the activity of catalase in the liver. The Sb extract could additionally enhance acetylcholine-induced vasorelaxation. It was proposed that the Sb extract exerted its cardioprotection by stimulating the catalase activity and improving vascular elasticity.

Cytochrome P450 1B1 contributes to renal dysfunction and damage caused by angiotensin II in mice

Cytochrome P450 1B1 contributes to the development of angiotensin II-induced hypertension and associated cardiovascular pathophysiology. In view of the critical role of angiotensin II in the kidney, as well as in salt and water homeostasis, and blood pressure regulation, we determined the contribution of cytochrome P450 1B1 to renal dysfunction and injury associated with angiotensin II-induced hypertension in male Cyp1b1(+/+) and Cyp1b1(-/-) mice. Angiotensin II infusion (700 ng/kg per minute) given by miniosmotic pumps for 13 and 28 days increased systolic blood pressure in Cyp1b1(+/+) mice; this increase was significantly reduced in Cyp1b1(-/-) mice. Angiotensin II increased renal Cyp1b1 activity, vascular resistance, and reactivity to vasoconstrictor agents and caused endothelial dysfunction in Cyp1b1(+/+) but not Cyp1b1(-/-) mice. Angiotensin II increased water consumption and urine output, decreased urine osmolality, increased urinary Na(+) and K(+) excretion, and caused proteinuria and albuminuria in Cyp1b1(+/+) mice that was diminished in Cyp1b1(-/-) mice. Infusion of angiotensin II for 28 but not 13 days caused renal fibrosis, tubular damage, and inflammation in Cyp1b1(+/+) mice, which was minimized in Cyp1b1(-/-) mice. Angiotensin II increased levels of 12- and 20-hydroxyeicosatetraenoic acids; reactive oxygen species; and activity of NADPH oxidase, extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, and c-Src in the kidneys of Cyp1b1(+/+) but not Cyp1b1(-/-) mice. These data suggest that increased thirst, renal dysfunction, and injury and inflammation associated with angiotensin II-induced hypertension in mice depend on cytochrome P450 1B1 activity, thus indicating that cytochrome P450 1B1 could serve as a novel target for treating renal disease and hypertension.

Involvement of cytochrome P-450 1B1 in renal dysfunction, injury, and inflammation associated with angiotensin II-induced hypertension in rats

We investigated the contribution of cytochrome P-450 1B1 (CYP1B1) to renal dysfunction and organ damage associated with ANG II-induced hypertension in rats. ANG II (300 ng·kg(-1)·min(-1)) or vehicle were infused for 2 wk, with daily injections of a selective CYP1B1 inhibitor, 2,4,3',5'-tetramethoxystilbene (TMS; 300 μg/kg ip), or its vehicle. ANG II increased blood pressure and renal CYP1B1 activity that were prevented by TMS. ANG II also increased water intake and urine output, decreased glomerular filtration rate, increased urinary Na(+) and K(+) excretion, and caused proteinuria, all of which were prevented by TMS. ANG II infusion caused hypertrophy, endothelial dysfunction, and increased reactivity of renal and interlobar arteries to vasoconstrictor agents and renal vascular resistance and interstitial fibrosis as indicated by accumulation of α-smooth muscle actin, fibronectin, and collagen, and inflammation as indicated by increased infiltration of CD-3(+) cells; these effects were inhibited by TMS. ANG II infusion also increased production of reactive oxygen species (ROS) and activities of NADPH oxidase, ERK1/2, p38 MAPK, and c-Src that were prevented by TMS. TMS alone had no effect on any of the above parameters. These data suggest that CYP1B1 contributes to the renal pathophysiological changes associated with ANG II-induced hypertension, most likely via increased ROS production and activation of ERK1/2, p38 MAPK, and c-Src and that CYP1B1 could serve as a novel target for treating renal disease associated with hypertension.

Rooibos (Aspalathus linearis) offers cardiac protection against ischaemia/reperfusion in the isolated perfused rat heart

Rooibos, a unique South African herbal tea, is known to be an important source of unique polyphenolic compounds. In the present study we have quantified the main polyphenolic compounds in both fermented/traditional and unfermented/"green" rooibos (Aspalathus linearis) and evaluated its cardioprotective effects against ischaemia/reperfusion injury. Male Wistar rats consumed aqueous rooibos and green tea (Camellia sinensis) extracts (2%, w/v) for 7 weeks before their hearts were rapidly excised and perfused in a working heart perfusion apparatus. The results showed that the rooibos supplemented hearts significantly improved aortic output recovery after reperfusion when compared to the green tea supplemented hearts. Additionally, we showed that the rooibos extracts, containing the highest amount of flavonols, significantly decreased the level of cleaved caspase-3 and PARP, both pro-apoptotic proteins, during reperfusion when compared to green tea. Green tea supplementation increased phosphorylation of total PKB/Akt, Akt (threonine 308) and Akt (serine 473). The rooibos extracts did not cause significant change in the levels of the pro-survival PKB/Akt (threonine 308 and serinet 473). The GSH/GSSG ratio in the hearts of the green tea supplemented group was significantly (p<0.05) lower when compared to RF (37.78±28.63), RU (33.20±4.13) and C (45.50±14.96). The results clearly demonstrate the cardio-protective properties of aqueous rooibos extracts via the inhibition of apoptosis which can possibly be related to the flavonol content of this unique South African herbal tea.

Chronic ( − )-epicatechin improves vascular oxidative and inflammatory status but not hypertension in chronic nitric oxide-deficient rats

The present study analysed the effects of the flavanol ( − )-epicatechin in rats after chronic inhibition of NO synthesis with NG-nitro-l-arginine methyl ester (l-NAME), at doses equivalent to those achieved in the studies involving human subjects. Wistar rats were randomly divided into four groups: (1) control-vehicle, (2) l-NAME, (3) l-NAME-epicatechin 2 (l-NAME-Epi 2) and (4) l-NAME-epicatechin 10 (l-NAME-Epi 10). Rats were daily given by oral administration for 4 weeks: vehicle, ( − )-epicatechin 2 or 10 mg/kg. Animals in the l-NAME groups daily received l-NAME 75 mg/100 ml in drinking-water. The evolution in systolic blood pressure and heart rate, and morphological and plasma variables, proteinuria, vascular superoxide, reactivity and protein expression at the end of the experiment were analysed. Chronic ( − )-epicatechin treatment did not modify the development of hypertension and only weakly affected the endothelial dysfunction induced by l-NAME but prevented the cardiac hypertrophy, the renal parenchyma and vascular lesions and proteinuria, and blunted the prostanoid-mediated enhanced endothelium-dependent vasoconstrictor responses and the cyclo-oxygenase-2 and endothelial NO synthase (eNOS) up-regulation. Furthermore, ( − )-epicatechin also increased Akt and eNOS phosphorylation and prevented the l-NAME-induced increase in systemic (plasma malonyldialdehyde and urinary 8-iso-PGF2α) and vascular (dihydroethidium staining, NADPH oxidase activity and p22phox up-regulation) oxidative stress, proinflammatory status (intercellular adhesion molecule-1, IL-1β and TNFα up-regulation) and extracellular-signal-regulated kinase 1/2 phosphorylation. The present study shows for the first time that chronic oral administration of ( − )-epicatechin does not improve hypertension but reduced pro-atherogenic pathways such as oxidative stress and proinflammatory status of the vascular wall induced by blockade of NO production.

Flavonoids from Inula britannica reduces oxidative stress through inhibiting expression and phosphorylation of p47(phox) in VSMCs

CONTEXT

Inula britanica Linn. (Compositae) is a traditional Chinese medicinal herb that has been used to treat bronchitis and inflammation. The total flavonoid extracts (TFEs) isolated from its flowers can inhibit neointimal formation induced by balloon injury in vivo.

OBJECTIVE

To investigate the mechanism by which TFE suppresses oxidative stress generation and the subsequent inflammation response in vitro.

MATERIALS AND METHODS

The cultured vascular smooth muscle cells (VSMCs) form rats were exposed to oxidative stress following pretreatment with or without TFE at different concentration. Then, fluorescence staining was used to detect superoxide anion (O₂(˙-)) production, and the lever of maleic dialdehyde (MDA) and superoxide dismutase (SOD) was measured at the same time. Furthermore, tumor necrosis factor-α (TNF-α) was measured by enzyme linked immunosorbent assay (ELISA), reverse transcription-PCR and western blot were performed to detect the expression activity of p47(phox) gene, and immunoprecipitation was used to test the level of p47(phox) phosphorylation.

RESULTS

TFE inhibited the production of O₂(˙-) induced by H₂O₂ in VSMCs, with decrease in secretion of TNF-α; elevated the activity of SOD in the medium, similar to the effect of quercetin; reduced the level of MDA in culture medium of VSMCs. The pretreatment with TFE resulted in decrease the level of p47(phox) mRNA and protein, and even p47(phox) phosphorylation in VSMCs, compared with H₂O₂ control.

DISCUSSION AND CONCLUSION

These findings demonstrate that TFE is capable of attenuating the oxidative stress generation and the subsequent inflammation response via preventing the overexpression and activation of p47(phox) and the increased TNF-α secretion in VSMCs in vitro.

Quercetin has a protective role on histopathological findings on testicular ischaemia-reperfusion injury in rats

We investigated the effects of quercetin on pathological findings on testicular ischaemia-reperfusion (I/R) injury in rats. Twenty-four male Wistar albino rats were randomly assigned into four groups: Group 1, control (n = 5); Group 2, sham (n = 4); Group 3, I/R (n = 8); and Group 4, I/R + quercetin (n = 7). Bilateral testicular artery and vein were occluded for 1 h, followed by reperfusion in I/R and I/R + quercetin animals. Quercetin (20 mg kg(-1) per day) was administrated once daily by gavage to Group 1 and Group 4, respectively, after reperfusion. At the end of the study, bilateral orchiectomies were performed for histopathologic examination. The tissue damage was evaluated with light microscopy. Normal inter-stitium and seminiferous tubules were observed in control group. In the sham group, rats were seen minimal oedema around the seminiferous tubules and congested vascular structures. In Group 3, oedema, vascular congestion and haemorrhage between seminiferous tubules were observed. In Group 4, histopathologic features were markedly less than Group 3 (P = 0.03). Our study demonstrated that quercetin seems to have a protective effect on testis histopathology in rats with testicular I/R.

Chronic treatment with quercetin does not inhibit angiotensin-converting enzyme in vivo or in vitro

The precise mechanisms explaining the anti-hypertensive effects produced by quercetin are not fully known. Here, we tested the hypothesis that chronic quercetin treatment inhibits the angiotensin-converting enzyme (ACE). We examined whether quercetin treatment for 14 days reduces in vivo responses to angiotensin I or enhances the responses to bradykinin in anaesthetised rats. We measured the changes in systemic arterial pressure induced by angiotensin I in doses of 0.03-10 μg/kg, by angiotensin II in doses of 0.01-3 μg/kg, and to bradykinin in doses of 0.03-10 μg/kg in anaesthetised rats pre-treated with vehicle (controls), or daily quercetin 10 mg/kg intraperitoneally for 14 days, or a single i.v. dose of captopril 2 mg/kg. Plasma ACE activity was determined by a fluorometric method. Plasma quercetin concentrations were assessed by high performance liquid chromatography. Quercetin treatment induced no significant changes in the hypertensive responses to angiotensin I and angiotensin II, as well in the hypotensive responses to bradykinin (all p>0.05). Conversely, as expected, a single dose of captopril inhibited the hypertensive responses to angiotensin I and potentiated the bradykinin responses (all p<0.01), while no change was found in the vascular responses to angiotensin II (all p>0.05). In addition, although we found significant amounts of quercetin in plasma samples (mean=206 ng/mL), no significant differences were found in plasma ACE activity in rats treated with quercetin compared with those found in the control group (50±6 his-leu nmol/min/mL and 40±7 his-leu nmol/min/mL, respectively; p>0.05). These findings provide strong evidence indicating that quercetin does not inhibit ACE in vivo or in vitro and indicate that other mechanisms are probably involved in the antihypertensive and protective cardiovascular effects associated with quercetin.

The role of caveolae in endothelial cell dysfunction with a focus on nutrition and environmental toxicants

Complications of vascular diseases, including atherosclerosis, are the number one cause of death in Western societies. Dysfunction of endothelial cells is a critical underlying cause of the pathology of atherosclerosis. Lipid rafts, and especially caveolae, are enriched in endothelial cells, and down-regulation of the caveolin-1 gene may provide protection against the development of atherosclerosis. There is substantial evidence that exposure to environmental pollution is linked to cardiovascular mortality, and that persistent organic pollutants can markedly contribute to endothelial cell dysfunction and an increase in vascular inflammation. Nutrition can modulate the toxicity of environmental pollutants, and evidence suggests that these affect health and disease outcome associated with chemical insults. Because caveolae can provide a regulatory platform for pro-inflammatory signalling associated with vascular diseases such as atherosclerosis, we suggest a link between atherogenic risk and functional changes of caveolae by environmental factors such as dietary lipids and organic pollutants. For example, we have evidence that endothelial caveolae play a role in uptake of persistent organic pollutants, an event associated with subsequent production of inflammatory mediators. Functional properties of caveolae can be modulated by nutrition, such as dietary lipids (e.g. fatty acids) and plant-derived polyphenols (e.g. flavonoids), which change activation of caveolae-associated signalling proteins. The following review will focus on caveolae providing a platform for pro-inflammatory signalling, and the role of caveolae in endothelial cell functional changes associated with environmental mediators such as nutrients and toxicants, which are known to modulate the pathology of vascular diseases.

Caveolae: a regulatory platform for nutritional modulation of inflammatory diseases

Dietary intervention strategies have proven to be an effective means of decreasing several risk factors associated with the development of atherosclerosis. Endothelial cell dysfunction influences vascular inflammation and is involved in promoting the earliest stages of lesion formation. Caveolae are lipid raft microdomains abundant within the plasma membrane of endothelial cells and are responsible for modulating receptor-mediated signal transduction, thus influencing endothelial activation. Caveolae have been implicated in the regulation of enzymes associated with several key signaling pathways capable of determining intracellular redox status. Diet and plasma-derived nutrients may modulate an inflammatory outcome by interacting with and altering caveolae-associated cellular signaling. For example, omega-3 fatty acids and several polyphenolics have been shown to improve endothelial cell function by decreasing the formation of ROS and increasing NO bioavailability, events associated with altered caveolae composition. Thus, nutritional modulation of caveolae-mediated signaling events may provide an opportunity to ameliorate inflammatory signaling pathways capable of promoting the formation of vascular diseases, including atherosclerosis.

Lack of synergistic interaction between quercetin and catechin in systemic and pulmonary vascular smooth muscle

Due to their ubiquitous distribution, flavonoids from different classes are commonly present together in foods. However, little is known about the interactions between them. The flavonol quercetin and the flavan-3-ol (+)-catechin are among the most abundant flavonoids in the diet. In the present study, we have analysed the interactions between these two flavonoids on vascular function using two pure compounds and mixtures of these flavonoids in 1:0·1, 1:1 or 1:10 proportions. Quercetin induced a more potent concentration-dependent relaxant effect than catechin in the isolated rat aorta, and the isobolographic analysis of the mixtures showed no synergistic or antagonistic effects between them, i.e. their effects were additive. Quercetin was more potent in mesenteric than in pulmonary arteries. Catechin had weak effects in these vessels and did not modify the effects of quercetin. Endothelial dysfunction induced by increased oxidative stress by the superoxide dismutase inhibitor diethyldithiocarbamate was prevented by quercetin, whereas catechin showed a weak effect and the 1:1 mixture an intermediate effect compared with the pure compounds. Quercetin but not catechin showed a pro-oxidant and NO-scavenging effect, which was not prevented by catechin. In conclusion, catechin was less potent than quercetin as a vasodilator, pro-oxidant or to prevent endothelial dysfunction, and there were no synergistic interactions between quercetin and catechin.

A wild blueberry-enriched diet (Vaccinium angustifolium) improves vascular tone in the adult spontaneously hypertensive rat

The effect of a wild blueberry-enriched diet on vasoconstriction and vasorelaxation was examined in the adult, 20-week-old spontaneously hypertensive rat (SHR) after 8 weeks of a control (C) or an 8% wild blueberry (WB) diet. Nitric oxide (NO)- and cyclooxygenase (COX)-mediated aortic responses were examined ex vivo with the agonists L-phenylephrine (Phe) and acetylcholine (Ach), in the absence or presence of the NO synthase (NOS) inhibitor L-NG-monomethyl arginine (L-NMMA) or the COX inhibitor mefenamic acid (MFA). The vasoconstriction elicited by Phe was reduced in the WB group, attributed to the NO pathway, favoring a lower vascular tone under basal conditions. Acetylcholine-induced vasorelaxation in the WB group was possibly mediated through the COX, but not the NO pathway. These findings document the potential of wild blueberries to modify major pathways of vasomotor control and improve the vascular tone in the adult SHR with endothelial dysfunction.

Modulation of Gi Proteins in Hypertension: Role of Angiotensin II and Oxidative Stress

Guanine nucleotide regulatory proteins (G-proteins) play a key role in the regulation of various signal transduction systems including adenylyl cyclase/cAMP and phospholipase C (PLC)/phosphatidyl inositol turnover (PI). These are implicated in the modulation of a variety of physiological functions such as platelet functions, cardiovascular functions, including arterial tone and reactivity. Several abnormalities in adenylyl cyclase activity, cAMP levels and G proteins have shown to be responsible for the altered cardiac performance and vascular functions observed in cardiovascular disease states. The enhanced or unaltered levels of inhibitory G-proteins (Giα-2 and Giα-3) and mRNA have been reported in different models of hypertension, whereas Gsα levels were shown to be unaltered. These changes in G-protein expression were associated with Gi functions. The enhanced levels of Giα proteins precede the development of blood pressure and suggest that overexpression of Gi proteins may be one of the contributing factors for the pathogenesis of hypertension. The augmented levels of vasoactive peptides, including angiotensin II (AngII), were shown to contribute to enhanced expression of Giα proteins and associated adenylyl cyclase signaling and thereby increased blood pressure. In addition, enhanced oxidative stress in hypertension due to Ang II may also be responsible for the enhanced expression of Giα proteins observed in hypertension. The mechanism by which oxidative stress enhances the expression of Gi proteins appears to be through the activation of mitogen activated protein (MAP) kinase activity.

Dealcoholized red wine reverse vascular remodeling in an experimental model of metabolic syndrome: role of NAD(P)H oxidase and eNOS activity

The present study examines the effect of chronic administration of dealcoholized red wine Malbec (DRW) on vascular remodeling and NAD(P)H oxidase and endothelial nitric oxide synthase activity (eNOS) in an experimental model of metabolic syndrome induced by fructose administration. Thirty-day old male Wistar rats were fed a normal rat diet (control) or the same diet plus 10% fructose in drinking water (FFR). During the last 4 weeks of a 10-week period of the corresponding diet, a subgroup of control and FFR (n=8 each) received DRW in their drinking water. Systolic blood pressure (SBP), a homeostasis model assessment of insulin resistance (HOMA-IR), aortic NAD(P)H oxidase and eNOS activity in the heart and vascular tissue were evaluated. Vascular remodeling was evaluated in the left carotid artery (CA) and interlobar, arcuate and interlobular renal arteries (RA) through lumen to media (L/M) ratio determination. At the end of the study FFR increased the SBP (p < 0.001), HOMA-IR (p < 0.001), and aortic NAD(P)H oxidase activity (p < 0,05) but reduced cardiac and vascular eNOS activity (p < 0.01), L/M ratio in CA (p < 0.001) and RA (p < 0.01) compared with the C group. DRW reduced SBP (p < 0.05), aortic NAD(P)H oxidase (p < 0.05), and recovered eNOS activity (p < 0.001) and L/M in CA (p < 0.001) and RA (p < 0.001) compared with FFR. This study provides new data about the beneficial effect of DRW on oxidative stress and vascular remodeling in the experimental model of metabolic syndrome. Data suggest the participation of mechanisms involving oxidative stress in FFR alterations and the usefulness of natural antioxidant substances present in red wine in the reversion of these changes.

2,3',4,5'-Tetramethoxystilbene prevents deoxycorticosterone-salt-induced hypertension: contribution of cytochrome P-450 1B1

Reactive oxygen species (ROS) contribute to various models of hypertension, including deoxycorticosterone acetate (DOCA)-salt-induced hypertension. Recently, we have shown that ROS, generated by cytochrome P-450 1B1 (CYP1B1) from arachidonic acid, mediate vascular smooth muscle cell growth caused by angiotensin II. This study was conducted to determine the contribution of CYP1B1 to hypertension and associated pathophysiological changes produced by DOCA (30 mg/kg) given subcutaneously per week with 1% NaCl + 0.1% KCl in drinking water to uninephrectomized rats for 6 wk. DOCA-salt treatment increased systolic blood pressure (SBP). Injections of the selective inhibitor of CYP1B1, 2,3',4,5'-tetramethoxystilbene (TMS; 300 μg/kg ip every 3rd day) initiated at the 4th week of DOCA-salt treatment normalized SBP and decreased CYP1B1 activity but not its expression in the aorta, heart, and kidney. TMS also inhibited cardiovascular and kidney hypertrophy, prevented the increase in vascular reactivity and endothelial dysfunction, and minimized the increase in urinary protein and K(+) output and the decrease in urine osmolality, Na(+) output, and creatinine clearance associated with DOCA-salt treatment. These pathophysiological changes caused by DOCA-salt treatment and associated increase in vascular superoxide production, NADPH oxidase activity, and expression of NOX-1, and ERK1/2 and p38 MAPK activities in the aorta, heart, and kidney were inhibited by TMS. These data suggest that CYP1B1 contributes to DOCA-salt-induced hypertension and associated pathophysiological changes, most likely as a result of increased ROS production and ERK1/2 and p38 MAPK activity, and could serve as a novel target for the development of agents like TMS to treat hypertension.

Flavonols and cardiovascular disease

Flavonols, and specially quercetin, are widely distributed in plants and are present in considerable amounts in fruits and vegetables. In addition to their anti-oxidant effect, flavonols interfere with a large number of biochemical signaling pathways and, therefore, physiological and pathological processes. There is solid evidence that, in vitro, quercetin and related flavonols exert endothelium-independent vasodilator effects, protective effect on nitric oxide and endothelial function under conditions of oxidative stress, platelet antiaggregant effects, inhibition of LDL oxidation, reduction of adhesion molecules and other inflammatory markers and prevention of neuronal oxidative and inflammatory damage. The metabolites of quercetin show partial protective effects on endothelial function and LDL oxidation. Quercetin produces undisputed antihypertensive and antiatherogenic effects, prevents endothelial dysfunction and protects the myocardium from ischemic damage. It has no clear effects on serum lipid profile and on insulin resistance. Human intervention trials with isolated flavonols demonstrate an antihypertensive effect. The meta-analysis of epidemiological studies show an inverse association between flavonol (together with flavone) intake and coronary heart disease and stroke. Therefore, although there is no solid proof yet, a substantial body of evidence suggests that quercetin may prevent the most common forms of cardiovascular disease contributing to the protective effects afforded by fruits and vegetables.

Regulation of SIRT1 in cellular functions: role of polyphenols

Sirtuin 1 (SIRT1) is known to deacetylate histones and non-histone proteins including transcription factors thereby regulating metabolism, stress resistance, cellular survival, cellular senescence/aging, inflammation-immune function, endothelial functions, and circadian rhythms. Naturally occurring dietary polyphenols, such as resveratrol, curcumin, quercetin, and catechins, have antioxidant and anti-inflammatory properties via modulating different pathways, such as NF-kappaB- and mitogen activated protein kinase-dependent signaling pathways. In addition, these polyphenols have also been shown to activate SIRT1 directly or indirectly in a variety of models. Therefore, activation of SIRT1 by polyphenols is beneficial for regulation of calorie restriction, oxidative stress, inflammation, cellular senescence, autophagy/apoptosis, autoimmunity, metabolism, adipogenesis, circadian rhythm, skeletal muscle function, mitochondria biogenesis and endothelial dysfunction. In this review, we describe the regulation of SIRT1 by dietary polyphenols in various cellular functions in response to environmental and pro-inflammatory stimuli.

The potential role of honey and its polyphenols in preventing heart diseases: a review

Honey is rich in phenolic compounds, which act as natural antioxidants and are becoming increasingly popular because of their potential role in contributing to human health. A wide range of phenolic constituents is present in honey like quercetin, caffeic acid phenethyl ester (CAPE), acacetin, kaempferol, galangin which have promising effect in the treatment of cardiovascular diseases. Many epidemiological studies have shown that regular intake of phenolic compounds is associated with reduced risk of heart diseases. In coronary heart disease, the protective effects of phenolic compounds include mainly antithrombotic, anti-ischemic, anti-oxidant, and vasorelaxant. It is suggested that flavonoids decrease the risk of coronary heart disease by three major actions: improving coronary vasodilatation, decreasing the ability of platelets in the blood to clot, and preventing low-density lipoproteins (LDLs) from oxidizing. In this review paper, we discussed the preventive role of polyphenols of honey against cardiovascular diseases.

Vascular superoxide production by endothelin-1 requires Src non-receptor protein tyrosine kinase and MAPK activation

ET-1 induces vascular O(2)(*-) production via activation of NADPH oxidase. We have investigated whether c-Src and MAPKs activation are involved in ET-1-induced vascular oxidative response. At 2 h, ET-1 induced an increase in NADPH oxidase-driven O(2)(*-) production in rat isolated aortic rings, which was completely suppressed in PP2 (c-Src inhibitor)-pretreated rings, whereas PP3 (inactive analogue of PP2) was without effect. ET-1 increased the levels of phospho-c-Src, the active form of c-Src, and the phosphorylation of cortactin, a Src-specific substrate. Both c-Src and cortactin phosphorylation induced by ET-1 were prevented by PP2. The increased expression of p47(phox), the main cytosolic subunit of NADPH oxidase, induced by ET-1 was also prevented by PP2. The increased vascular O(2)(*-) production and p47(phox) up-regulation induced by ET-1 was only inhibited in aortic rings coincubated with the ERK1/2 inhibitor, PD98059; being without effects both the p38 MAPK inhibitor, SB203580, and JNK inhibitor, SP600125. Aortic rings incubation with ET-1 increased the phosphorylation of ERK1/2. This effect was suppressed by coincubation with PP2 showing that this event is down-stream of c-Src activation. In conclusion, ET-1 induces NADPH oxidase-driven O(2)(*-) generation through increase of p47(phox) protein expression. The signalling pathway for this effect involves c-Src activation and ERK1/2 phosphorylation.

Specific Dietary Polyphenols Attenuate Atherosclerosis in Apolipoprotein E–Knockout Mice by Alleviating Inflammation and Endothelial Dysfunction

Objective— Animal and clinical studies have suggested that polyphenols in fruits, red wine, and tea may delay the development of atherosclerosis through their antioxidant and anti-inflammatory properties. We investigated whether individual dietary polyphenols representing different polyphenolic classes, namely quercetin (flavonol), (−)-epicatechin (flavan-3-ol), theaflavin (dimeric catechin), sesamin (lignan), or chlorogenic acid (phenolic acid), reduce atherosclerotic lesion formation in the apolipoprotein E (ApoE) −/− gene–knockout mouse.

Methods and Results— Quercetin and theaflavin (64-mg/kg body mass daily) significantly attenuated atherosclerotic lesion size in the aortic sinus and thoracic aorta ( P <0.05 versus ApoE −/− control mice). Quercetin significantly reduced aortic F 2 -isoprostane, vascular superoxide, vascular leukotriene B 4 , and plasma-sP-selectin concentrations; and augmented vascular endothelial NO synthase activity, heme oxygenase-1 protein, and urinary nitrate excretion ( P <0.05 versus control ApoE −/− mice). Theaflavin showed similar, although less extensive, significant effects. Although (−)-epicatechin significantly reduced F 2 -isoprostane, superoxide, and endothelin-1 production ( P <0.05 versus control ApoE −/− mice), it had no significant effect on lesion size. Sesamin and chlorogenic acid treatments exerted no significant effects. Quercetin, but not (−)-epicatechin, significantly increased the expression of heme oxygenase-1 protein in lesions versus ApoE −/− controls.

Conclusion— Specific dietary polyphenols, in particular quercetin and theaflavin, may attenuate atherosclerosis in ApoE −/− gene–knockout mice by alleviating inflammation, improving NO bioavailability, and inducing heme oxygenase-1. These data suggest that the cardiovascular protection associated with diets rich in fruits, vegetables, and some beverages may in part be the result of flavonoids, such as quercetin.

3,3',4',5,7-Pentamethylquercetin reduces angiotensin II-induced cardiac hypertrophy and apoptosis in rats

Quercetin has been shown to possess beneficial pharmacological properties in treatment of heart disease, but lack of stability and bioavailability limits its clinical use. In this study, we investigated for the first time the effect of a methylated form of quercetin, 3,3',4',5,7-pentamethylquercetin (PMQ), on myocardial protection in rats. Angiotensin II was delivered to Sprague-Dawley rats subcutaneously, while PMQ (5 mg/kg) was administered by oral gavage; blood pressure was monitored daily. The production of NADPH oxidase was measured, and cardiac hypertrophy and apoptosis were detected. The results revealed that PMQ could downregulate the expression of the NADPH oxidase gene and reduce angiotensin II- induced cardiac hypertrophy and apoptosis in rats. Therefore, we believe that PMQ showed beneficial effects on myocardium in angiotensin II-administered rats, and its potential to be used for treatment of cardiovascular disease deserves further attention.

Polyphenol-containing azuki bean (Vigna angularis) seed coats attenuate vascular oxidative stress and inflammation in spontaneously hypertensive rats

We investigated the effects of azuki bean (Vigna angularis) seed coats (ABSC), which contain polyphenols, on the vascular oxidative stress and inflammation associated with hypertension. Spontaneously hypertensive rats (SHR) and control normotensive Wistar-Kyoto (WKY) rats were divided into 2 groups each. One group was fed 0% ABSC; the other, a 1.0% ABSC-containing diet. Tail systolic blood pressure (SBP) was examined throughout ABSC treatment. At 8 weeks, vascular superoxide (O(2)(-)) production was measured by lucigenin-enhanced chemiluminescence. mRNA expressions of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits, macrophage chemoattractant protein-1 (MCP-1) and its receptor C-C chemokine receptor 2 (CCR2) in the aorta were analyzed by reverse transcriptase-polymerase chain reaction. Protein expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were determined by western blotting. Polyphenol-containing ABSC suppressed the elevation of SBP throughout the treatment period. The NADPH-stimulated O(2)(-) level decreased significantly in the aorta of ABSC-treated SHR compared with the level of untreated SHR. The p47phox and Nox4 mRNA expression increased significantly in untreated SHR compared with that in WKY rats. Conversely, the level of p47phox mRNA was significantly lower in ABSC-treated SHR than in untreated SHR. The protein abundance of both iNOS and COX-2 was significantly decreased in the aorta of the ABSC-treated SHR compared with this abundance in untreated SHR. The MCP-1 and CCR2 mRNA expressions increased in untreated SHR, and these levels were significantly lower in ABSC-treated SHR. In conclusion, our results suggested that polyphenol-containing ABSC could attenuate vascular oxidative stress and inflammation during the progression of hypertension, and this may lead to an improvement in hypertension.

Quercetin: A Treatment for Hypertension?-A Review of Efficacy and Mechanisms

Quercetin is a polyphenolic flavonoid. Common sources in the diet are apples, onions, berries, and red wine. Epidemiological studies have found an inverse relationship between dietary quercetin intake and cardiovascular disease. This has led to in vitro, in vivo, and clinical research to determine the mechanism by which quercetin exerts cardio-protective effects. Recent studies have found a reduction in blood pressure when hypertensive (>140 mm Hg systolic and >90 mm Hg diastolic) animals and humans are supplemented with quercetin. Proposed mechanisms for the antihypertensive effect of quercetin include decreased oxidative stress, inhibition of angiotensin converting enzyme activity, improved endothelial function, direct action on the vascular smooth muscle, and/or modulation in cell signaling and gene expression. Although in vitro and in vivo evidence exists to support and refute each possibility, it is likely that quercetin influences multiple targets via a combination of known and as yet undiscovered mechanisms. The purpose of this review is to examine the mechanisms whereby quercetin might reduce blood pressure in hypertensive individuals.

Polyphenol-induced endothelium-dependent relaxations role of NO and EDHF

The Mediterranean diet has been associated with greater longevity and quality of life in epidemiological studies. Indeed, because of the abundance of fruits and vegetables and a moderate consumption of wine, the Mediterranean diet provides high amounts of polyphenols thought to be essential bioactive compounds that might provide health benefits in terms of cardiovascular diseases and mortality. Several polyphenol-rich sources, such as grape-derived products, cocoa, and tea, have been shown to decrease mean blood pressure in patients with hypertension. The improvement of the endothelial function is likely to be one of the mechanisms by which polyphenols may confer cardiovascular protection. Indeed, polyphenols are able to induce nitric oxide (NO)-mediated endothelium-dependent relaxations in a large number of arteries including the coronary artery; they can also induce endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxations in some of these arteries. Altogether, these mechanisms might contribute to explain the antihypertensive and cardio-protective effects of polyphenols in vivo. The aim of this review was to provide a nonexhaustive analysis of the effect of several polyphenol-rich sources and isolated compounds on the endothelium in in vitro, ex vivo, and in vivo models as well as in humans.

Expression of bilitranslocase in the vascular endothelium and its function as a flavonoid transporter

AIMS

Ingestion of flavonoid-rich beverages acutely affects endothelial function, causing vasodilation. This effect might be dependent on flavonoid transport into the endothelium. We investigated flavonoid uptake into vascular endothelial cells and whether this was mediated by bilitranslocase (TC 2.A.65.1.1), a bilirubin-specific membrane carrier that also transports various dietary flavonoids.

METHODS AND RESULTS

Human and rat aortic primary endothelial cells as well as Ea.hy 926 cells were found to express bilitranslocase, as assessed by immunocytochemistry and immunoblotting analysis using anti-sequence bilitranslocase antibodies targeting two distinct extracellular epitopes of the carrier. Bilitranslocase function was tested by measuring the rate of bromosulfophthalein (a standard bilitranslocase transport substrate) uptake into endothelial cells and was inhibited not only by bilitranslocase antibodies but also by quercetin (a flavonol). Similarly, uptake of both quercetin and malvidin 3-glucoside (an anthocyanin) were also found to be antibody-inhibited. Quercetin uptake into cells was inhibited by bilirubin, suggesting flavonoid uptake via a membrane pathway shared with bilirubin.

CONCLUSION

The uptake of some flavonoids into the vascular endothelium occurs via the bilirubin-specific membrane transporter bilitranslocase. This offers new insights into the vascular effects of both flavonoids and bilirubin.

Akt downregulation by flavin oxidase-induced ROS generation mediates dose-dependent endothelial cell damage elicited by natural antioxidants

High intake of natural antioxidants (NA) from plant-derived foods and beverages is thought to provide cardiovascular benefits. The endothelium plays a pivotal role in cardiovascular homeostasis, and for this reason, the molecular events resulting from NA actions on endothelial cells (ECs) are actively investigated. Here, we show the direct impact of two NA, coumaric acid and resveratrol, on intracellular reactive oxygen species levels, protein carbonylation, and cell physiology in human ECs. While at lower doses, both NA promoted antioxidant effects, at moderately high doses, NA elicited a dose-dependent pro-oxidant effect, which was followed by apoptosis, cell damage, and phospho-Akt downregulation. NA-induced pro-oxidant effects were counteracted by N-acetyl cysteine and diphenyleneiodonium (DPI), suggesting a role for flavin oxidases in NA-induced toxicity. DPI also prevented NA-induced phospho-Akt downregulation indicating that Akt can work downstream of flavin oxidases in mediating cellular responses to NA. Stimulation of phospho-Akt by insulin dramatically counteracted NA-induced cell death, an effect abolished by Akt inhibition further suggesting that mechanistically Akt regulates cell survival in response to NA-induced stress. Although further studies are required to better characterize the molecular mechanism of NA-induced cell toxicity, our study is the first to show in a human vascular model that moderately high doses of NA can induce cell damage mediated by flavoproteins and the Akt pathway.

Lack of beneficial metabolic effects of quercetin in adult spontaneously hypertensive rats

Insulin sensitivity is partly dependent on insulin-mediated nitric oxide (NO) release and antioxidants may decrease insulin resistance by amelioring NO bioavailability. The effects of chronic therapy with the antioxidant quercetin on blood pressure, vascular function and glucose tolerance in male spontaneously hypertensive rats (SHR), a model of genetically hypertension and insulin resistance, were analyzed. Rats were divided into four groups, WKY vehicle, WKY quercetin, SHR vehicle and SHR quercetin. Animals were daily administered by gavage for four weeks: vehicle, quercetin in vehicle (10mg/kg body weight). Blood pressure was followed by tail-cuff plethysmography. Chronic quercetin treatment reduced systolic blood pressure, and significantly reduced left ventricular (-10%) and renal (-6%) hypertrophy. However, oral glucose tolerance test, homeostatic model assessment of insulin resistance, total cholesterol and triglycerides were unaffected by quercetin in both strains of rats. It also improved the blunted aortic endothelium-dependent relaxation to acetylcholine, without affecting both endothelium-dependent relaxation to insulin and endothelium-independent relaxation to sodium nitroprusside in SHR. In WKY rats, quercetin in vitro and in vivo, impaired the relaxation to insulin. Quercetin reduced both plasma malondialdehyde levels and aortic superoxide production in SHR. Furthermore, quercetin inhibited insulin-stimulated protein kinase B (Akt)- and endothelial NO synthase (eNOS) phosphorylation. In conclusion, quercetin reduced blood pressure, left ventricular and renal hypertrophy and improved NO-dependent acetylcholine relaxation. However, and despite its antioxidant effects, quercetin was unable to improve insulin sensitivity possibly through its specific interference with the insulin signalling pathway.

Research into Specific Modulators of Vascular Sex Hormone Receptors in the Management of Postmenopausal Cardiovascular Disease

Cardiovascular disease (CVD) is more common in men and postmenopausal women than premenopausal women, suggesting vascular benefits of female sex hormones. Studies on the vasculature have identified estrogen receptors ERα, ERβ and a novel estrogen binding membrane protein GPR30, that mediate genomic and/or non-genomic effects. Estrogen promotes endothelium-dependent relaxation by inducing the production/activity of nitric oxide, prostacyclin, and hyperpolarizing factor, and inhibits the mechanisms of vascular smooth muscle contraction including [Ca(2+)](i), protein kinase C, Rho kinase and mitogen-activated protein kinase. Additional effects of estrogen on the cytoskeleton, matrix metalloproteinases and inflammatory factors contribute to vascular remodeling. However, the experimental evidence did not translate into vascular benefits of menopausal hormone therapy (MHT), and the HERS, HERS-II and WHI clinical trials demonstrated adverse cardiovascular events. The discrepancy has been partly related to delayed MHT and potential changes in the vascular ER amount, integrity, affinity, and downstream signaling pathways due to the subjects' age and preexisting CVD. The adverse vascular effects of MHT also highlighted the need of specific modulators of vascular sex hormone receptors. The effectiveness of MHT can be improved by delineating the differences in phramcokinetics and pharmacodynamics of natural, synthetic, and conjugated equine estrogens. Estriol, "hormone bioidenticals" and phytoestrogens are potential estradiol substitutes. The benefits of low dose MHT, and transdermal or vaginal estrogens over oral preparations are being evaluated. Specific ER modulators (SERMs) and ER agonists are being developed to maximize the effects on vascular ERs. Also, the effects of estrogen are being examined in the context of the whole body hormonal environment and the levels of progesterone and androgens. Thus, the experimental vascular benefits of estrogen can be translated to the outcome of MHT in postmenopausal CVD, as more specific modulators of sex hormone receptors become available and are used at the right dose, route of administration and timing, depending on the subject's age and preexisting cardiovascular condition.

Flavonoids from Inula britannica L. inhibit injury-induced neointimal formation by suppressing oxidative-stress generation

AIM OF THE STUDY

We aimed to investigate whether and how the total flavonoid extracts (TFE) from Inula britannica L. block neointimal hyperplasia induced by balloon injury in rats.

MATERIALS AND METHODS

Rats were administered orally TFE doses of 12.5, 25 and 50 mg/kg/d by gastric gavage from 3 days before balloon injury to 14 days after the injury. The ratio of intima (I) to media (M) thickness (I/M) in carotid arteries was examined by morphological analyses. The MDA content and SOD activity in plasma were measured. The O(2)(-) production in vascular tissues was detected in situ. The expression of p47(phox) in carotid arteries was analyzed by Western blot analysis and immunohistochemistry.

RESULTS

The rats treated with TFE 50 mg/kg/d showed a reduction in neointimal hyperplasia, and the ratio of I/M of balloon injured-carotid arteries was significantly reduced by over 70% after TFE treatment, compared with the injured group. The inhibitory effect of TFE on neointimal hyperplasia was almost consistent with that of atorvastatin, a positive control. The plasma SOD activity was obviously increased by TFE treatment (P<0.01), while plasma MDA production was markedly decreased by TFE treatment (P<0.05). On day 14 after balloon injury, the carotid arteries showed an increase in O(2)(-) production that was most evident in the neointimal and medial layer of the vessel. Thus, TFE significantly inhibited injury-induced O(2)(-) production and p47(phox) expression in carotid arteries.

CONCLUSION

Our results suggest that TFE inhibit the neointimal hyperplasia after balloon injury, at least partly, by suppressing oxidative-stress generation.

Polyphenol-containing azuki bean (Vigna angularis) extract attenuates blood pressure elevation and modulates nitric oxide synthase and caveolin-1 expressions in rats with hypertension

BACKGROUND AND AIMS

Azuki beans (Vigna angularis) contain polyphenols such as proanthocyanidins that exhibit potential radical scavenging activities. We herein investigated the effects of polyphenol-containing azuki bean extract (ABE) on elevated blood pressure, nitric oxide (NO) production, and expressions of endothelial NO synthase (eNOS), inducible NOS (iNOS), and caveolin-1 proteins in the aorta and kidney of chronically hypertensive rats.

METHODS AND RESULTS

Spontaneously hypertensive rats (SHRs/Izm) with approximately 200 mm Hg systolic blood pressure (SBP) were randomly divided into 2 groups fed either 0% or 0.9% ABE-containing diet. Age-matched normotensive Wistar-Kyoto rats were used as the control. The content of 24-h urinary nitrate/nitrite (NOx) excretion was measured to evaluate NO production. After 8 weeks of treatment, the eNOS, iNOS, and caveolin-1 protein expressions in the aorta and kidney were analyzed by western blotting. The SBP of the ABE-treated SHR was significantly lower than that of the untreated SHR. The level of 24-h urinary NOx excretion was significantly higher in the ABE-treated SHR than in the untreated SHR. The eNOS and iNOS expressions in the aorta and kidney were remarkably upregulated in the untreated SHR but suppressed in the ABE-treated SHR. The vascular and renal caveolin-1 expressions were upregulated in the ABE-treated SHR.

CONCLUSIONS

ABE reduced the elevated blood pressure and increased NO production in long-term treatment. It may be associated with the modulation of eNOS and iNOS protein expressions in the aorta and kidney during the development of hypertension.

Protective effect of quercetin, a polyphenolic compound, on mouse corpus cavernosum

Flavonoids are plant-based phenolic compounds, and quercetin is the most abundant dietary member of this family. One of the most important characteristics of quercetin is its antioxidant property. The aim of this study was to investigate antioxidant effects of quercetin on corpora cavernosa of mice. Corpora cavernosa were isolated in organ baths, precontracted with phenylephrine (0.5 microm) and relaxant responses were mediated by acetylcholine (0.1-1 microm), electrical field stimulation (EFS, 1-16 Hz, 0.5 ms, 30 V) or acidified sodium nitrite (a NaNO(2), 0.5 mm). Superoxide anion generators; pyrogallol (50 microm), hydroquinone (100 microm), LY 83583 (6-Anilinoquinolin-5,8-quinone, 10 microm) and superoxide dismutase (SOD) inhibitor; diethyldithiocarbamic acid (DETCA, 8 mm) were used in order to expose corpus cavernosa to oxidant stress. Acetylcholine (0.1-1 microm) induced relaxant responses were significantly inhibited in LY 83583 (10 microm) and DETCA + LY 83583 applicated trials. EFS-induced relaxant responses were significantly inhibited in DETCA (8 mm) and DETCA + LY 83583 administrated trials. On the other hand, acidified sodium nitrite-induced responses were inhibited by all of the superoxide anion generators tested. Quercetin (10 microm) failed to improve the inhibitions on endothelium and electrically stimulated responses. Acidified sodium nitrite (0.5 mm) mediated relaxant responses were significantly restored by quercetin except the groups in which LY 83583 were used. The data suggest that quercetin acts as a protective agent in mouse corpus cavernosum, increasing the bioavailability of exogenous nitric oxide by protecting it from superoxide anion (O(2)(-)).

Sesamin improves endothelial dysfunction in renovascular hypertensive rats fed with a high-fat, high-sucrose diet

The present study was designed to evaluate the possible in vivo protective effects of sesamin on hypertension and endothelial function in two-kidney, one-clip renovascular hypertensive rats fed with a high-fat, high-sucrose diet (2K1C rats on HFS diet). Sesamin was orally administered for 8 weeks in 2K1C rats on HFS diet. Then, the serum malondialdehyde level was determined. The protein expression of endothelial nitric oxide synthase (eNOS), nitrotyrosine and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47(phox) in aortas was detected by Western blotting. Vasorelaxation response to acetylcholine and nitroprusside, and functional assessment of nitric oxide (NO) bioactivity were also determined in aortic rings. Sesamin treatment reduced systolic blood pressure, improved vasodilatation induced by acetylcholine and enhanced NO bioactivity in the thoracic aortas. These changes were associated with increased eNOS, decreased malondialdehyde content, and reduced nitrotyrosine and p47(phox) protein expression. All these results suggest that chronic treatment with sesamin reduces hypertension and improves endothelial dysfunction through upregulation of eNOS expression and reduction of NO oxidative inactivation in 2K1C rats on HFS diet.

Chronic treatment with pravastatin prevents early cardiovascular changes in spontaneously hypertensive rats

BACKGROUND AND PURPOSE

This study investigates the effect of pravastatin on blood pressure, cardiovascular remodelling and impaired endothelial function induced as early signs of cardiovascular disease in young spontaneously hypertensive rats (SHR).

EXPERIMENTAL APPROACH

Eight-week-old SHR were treated for 4 weeks with pravastatin (20 mg kg(-1) day(-1)). Systolic blood pressure was measured periodically during the study using the tail-cuff method. At the end of the study, the left ventricular weight /body weight ratio was used as an index of left ventricular hypertrophy (LVH). Vascular function, superoxide (O(2)(-*)) production and structure were studied in aortic rings. Lipid peroxidation was measured in plasma (thiobarbituric acid reactive substances assay).

KEY RESULTS

Systolic blood pressure was lower in treated SHR than in control SHR, at the end of the study (171 +/- 1 vs. 159 +/- 2 mmHg, P < 0.05), and LVH was significantly reduced by pravastatin (2.7 +/- 0.02 vs. 2.5 +/- 0.01 mg g(-1), P < 0.05). Vascular responses to sodium nitroprusside and phenylephrine were similar in both groups; nevertheless, the relaxation response to acetylcholine was higher in the treated rats (45.6 +/- 2.6 vs. 58.1 +/- 3.2 %, P < 0.05). Vascular O(2)(-*) and plasma thiobarbituric acid reactive substances were reduced by pravastatin treatment, and urinary nitrites was elevated. Finally aortic wall became thinner after pravastatin treatment.

CONCLUSIONS AND IMPLICATIONS

Chronic treatment with pravastatin attenuated the increase of systolic blood pressure in SHR, prevented early LVH and improved vascular structure and function. These effects were accompanied by decreased measures of oxidative stress and improvements in NO production.

Endothelial function and cardiovascular disease: Effects of quercetin and wine polyphenols

Endothelial dysfunction is an early pathophysiological feature and independent predictor of poor prognosis in most forms of cardiovascular diseases. Epidemiological studies report an inverse association between dietary flavonoid consumption and mortality from cardiovascular diseases. In the present paper, we review the effects of flavonoids, especially quercetin and wine polyphenols, on endothelial function and dysfunction and its potential protective role in hypertension, ischemic heart disease and stroke. In vitro studies show that flavonoids may exert multiple actions on the NO-guanylyl cyclase pathway, endothelium-derived hyperpolarizing factor(s) and endothelin-1 and protect endothelial cells against apoptosis. In vivo, flavonoids prevent endothelial dysfunction and reduce blood pressure, oxidative stress and end-organ damage in hypertensive animals. Moreover, some clinical studies have shown that flavonoid-rich foods can improve endothelial function in patients with hypertension and ischemic heart disease. Altogether, the available evidence indicates that quercetin and wine polyphenols might be of therapeutic benefit in cardiovascular diseases even though prospective controlled clinical studies are still lacking.

Lipid rafts and caveolae and their role in compartmentation of redox signaling

Membrane (lipid) rafts and caveolae, a subset of rafts, are cellular domains that concentrate plasma membrane proteins and lipids involved in the regulation of cell function. In addition to providing signaling platforms for G-protein-coupled receptors and certain tyrosine kinase receptors, rafts/caveolae can influence redox signaling. This review discusses molecular characteristics of and methods to study rafts/caveolae, determinants that contribute to the localization of molecules in these entities, an overview of signaling molecules that show such localization, and the contribution of rafts/caveolae to redox signaling. Of particular note is the evidence that endothelial nitric oxide synthase (eNOS), NADPH oxygenase, and heme oxygenase, along with other less well-studied redox systems, localize in rafts and caveolae. The precise basis for this localization and the contribution of raft/caveolae-localized redox components to physiology and disease are important issues for future studies.

Attenuation of lipopolysaccharide-mediated left ventricular dysfunction by glutamine preconditioning

OBJECTIVE

Myocardial dysfunction is often seen during the inflammatory response to major surgery at 4 to 6h postoperatively. The aim of this study was to investigate the effect of glutamine pretreatment, as a means of preconditioning, on lipopolysaccharide-induced myocardial dysfunction.

METHODS

C57BL/6 mice were randomized into four groups: Control; lipopolysaccharide; glutamine plus lipopolysaccharide; and Quercetin, an inhibitor of heat shock protein synthesis plus glutamine and lipopolysaccharide. Left ventricular function was assessed at 6h following lipopolysaccharide (LPS) insult by invasive hemodynamics. Heat shock protein (HSP)72 in heart tissue was determined by Western immunoblot at 12h after glutamine administration.

RESULTS

Administration of lipopolysaccharide resulted in significant decrease in left ventricular end systolic pressure (LVESP) (69.1 +/- 2.52 mm Hg versus 106.3 +/- 3.36 mm Hg in controls), reduced dP/dtmax (4704.1 +/- 425.31 mm Hg/s versus 9389.8 +/- 999.4 mm Hg/s in controls), and the increase in left ventricular end diastolic pressure (LVEDP) (5.10 +/- 0.28 mm Hg versus 2.16 +/- 0.27 mm Hg in controls) (P < 0.05). Peritoneal injection of 25 g/kg of glutamine 12 h prior to lipopolysaccharide exposure induced HSP72 expression in heart tissues and attenuated lipopolysaccharide-induced left ventricular dysfunction: LVESP 85.94 +/- 3.8 mm Hg (P < 0.05), dP/dtmax 8331 +/- 425 mm Hg (P < 0.05), LVEDP 2.32 +/- 0.23 mm Hg (P < 0.01). Quercetin partially attenuated glutamine induced HSP72 expression and blocked the protective response of glutamine.

CONCLUSION

These data demonstrate that cardioprotection with glutamine is associated with induction of HSP72 and may be an approach to activating the preconditioning response in the heart in clinical practise.

3',4'-Dihydroxyflavonol prevents diabetes-induced endothelial dysfunction in rat aorta

AIMS

Diabetes increases oxidant stress and impairs endothelium-dependent relaxation. We investigated whether the antioxidant 3',4'-dihydroxyflavonol (DiOHF) reduces the release of superoxide (O(2)(-)) and preserves endothelial function in aortae from diabetic rats.

MAIN METHODS

Type-1 diabetes was induced in Sprague-Dawley rats by streptozotocin (STZ) treatment (55 mg/kg i.v.) and vascular reactivity and superoxide generation were assessed in aortic rings using standard organ bath techniques and lucigenin-enhanced chemiluminescence respectively.

KEY FINDINGS

Eight weeks after STZ treatment blood glucose was elevated (39.4+/-0.4 mM) compared to citrate treated control rats (5.5+/-0.1 mM, P<0.05) and there was an increased aortic generation of O(2)(-) (control 670+/-101, diabetic 1535+/-249 units/mg dry weight, P<0.05). In aortic rings acetylcholine (ACh)-induced relaxation was impaired (R(max) control 78+/-2, diabetic 66+/-3%, P<0.01) whereas endothelium-independent relaxation to sodium nitroprusside (SNP) was unaffected (R(max) control 100+/-1, diabetic 101+/-2%). When aortic rings were acutely exposed to DiOHF (10(-5) M) there was a significant reduction in the detection of O(2)(-) (control 124+/-15, diabetic 165+/-21 units/mg, P<0.01) and enhanced relaxation to ACh (R(max) control 84+/-3, diabetic 87+/-3%). Two separate groups of rats (control and diabetic) were treated daily with DiOHF (5 mg/kg i.p.) for 7 days. DiOHF treatment reduced superoxide generation in diabetic aortae (untreated diabetic 1471+/-358, DiOHF-treated diabetic 580+/-115 units/mg, P<0.05) and enhanced acetylcholine-induced relaxation (R(max) untreated diabetic 58+/-5, DiOHF-treated diabetic 71+/-4%, P<0.05).

SIGNIFICANCE

DiOHF, acutely in vitro or after 1 week treatment in vivo, reduces oxidant stress and preserves endothelium-dependent relaxation in aortae from diabetic rats.

Bioactivity of Grape Chemicals for Human Health

Grapevine ( Vitis vinifera) products, grape and grape juice, represent a valuable source of bioactive phytochemicals, synthesized by three secondary metabolic pathways (phenylpropanoid, isoprenoid and alkaloid biosynthetic routes) and stored in different plant tissues. In the last decades, compelling evidence suggested that regular consumption of these products may contribute to reducing the incidence of chronic illnesses, such as cancer, cardiovascular diseases, ischemic stroke, neurodegenerative disorders and aging, in a context of the Mediterranean dietary tradition. The health benefits arising from grape product intake can be ascribed to the potpourri of biologically active chemicals occurring in grapes. Among them, the recently discovered presence of melatonin adds a new element to the already complex grape chemistry. Melatonin, and its possible synergistic action with the great variety of polyphenols, contributes to further explaining the observed health benefits associated with regular grape product consumption.