Antihypertensive effects of the flavonoid quercetin

Quercetin ameliorates cardiovascular, hepatic, and metabolic changes in diet-induced metabolic syndrome in rats

Metabolic syndrome is a risk factor for cardiovascular disease and nonalcoholic fatty liver disease (NAFLD). We investigated the responses to the flavonol, quercetin, in male Wistar rats (8-9 wk old) divided into 4 groups. Two groups were given either a corn starch-rich (C) or high-carbohydrate, high-fat (H) diet for 16 wk; the remaining 2 groups were given either a C or H diet for 8 wk followed by supplementation with 0.8 g/kg quercetin in the food for the following 8 wk (CQ and HQ, respectively). The H diet contained ~68% carbohydrates, mainly as fructose and sucrose, and ~24% fat from beef tallow; the C diet contained ~68% carbohydrates as polysaccharides and ~0.7% fat. Compared with the C rats, the H rats had greater body weight and abdominal obesity, dyslipidemia, higher systolic blood pressure, impaired glucose tolerance, cardiovascular remodeling, and NAFLD. The H rats had lower protein expressions of nuclear factor (erythroid-derived 2)-related factor-2 (Nrf2), heme oxygenase-1 (HO-1), and carnitine palmitoyltransferase 1 (CPT1) with greater expression of NF-κB in both the heart and the liver and less expression of caspase-3 in the liver than in C rats. HQ rats had higher expression of Nrf2, HO-1, and CPT1 and lower expression of NF-κB than H rats in both the heart and the liver. HQ rats had less abdominal fat and lower systolic blood pressure along with attenuation of changes in structure and function of the heart and the liver compared with H rats, although body weight and dyslipidemia did not differ between the H and HQ rats. Thus, quercetin treatment attenuated most of the symptoms of metabolic syndrome, including abdominal obesity, cardiovascular remodeling, and NAFLD, with the most likely mechanisms being decreases in oxidative stress and inflammation.

Quercetin Protects against Cadmium-Induced Renal Uric Acid Transport System Alteration and Lipid Metabolism Disorder in Rats

Hyperuricemia and dyslipidemia are involved in Cd nephrotoxicity. The aim of this study was to determine the effect of quercetin, a dietary flavonoid with anti-hyperuricemic and anti-dyslipidemic properties, on the alteration of renal UA transport system and disorder of renal lipid accumulation in 3 and 6 mg/kg Cd-exposed rats for 4 weeks. Cd exposure induced hyperuricemia with renal XOR hyperactivity and UA excretion dysfunction in rats. Simultaneously, abnormal expression levels of renal UA transport-related proteins including RST, OAT1, MRP4 and ABCG2 were observed in Cd-exposed rats with inhibitory activity of renal Na⁺-K⁺-ATPase. Furthermore, Cd exposure disturbed lipid metabolism with down-regulation of AMPK and its downstream targets PPARα, OCTN2 and CPT1 expressions, and up-regulation of PGC-1β and SREBP-1 expressions in renal cortex of rats. We had proved that Cd-induced disorder of renal UA transport and production system might have cross-talking with renal AMPK-PPARα/PGC-1β signal pathway impairment, contributing to Cd nephrotoxicity of rats. Quercetin was found to be effective against Cd-induced dysexpression of RST and OAT1 with XOR hyperactivity and impairment of AMPK-PPARα/PGC-1β signal pathway, resulting in renal lipid accumulation reduction of rats.

ApoE genotype: from geographic distribution to function and responsiveness to dietary factors

ApoE is a key protein in lipid metabolism with three major isoforms.ApoEallele frequencies show non-random global distribution especially in Europe with highapoEε3frequency in the Mediterranean area, whereas theapoEε4genotype is enriched in Northern Europe. TheapoEε4genotype is one of the most important genetic risk factors for age-dependent chronic diseases, including CVD and Alzheimer's disease (AD). The apoE polymorphism has been shown to impact on blood lipids, biomarkers of oxidative stress and chronic inflammation, which all may contribute to the isoform-dependent disease risk. Studies in mice and human subjects indicate that theapoEε3but not theapoEε4genotype may significantly benefit from dietary flavonoids (e.g. quercetin) andn-3 fatty acids. Metabolism of lipid soluble vitamins E and D is likewise differentially affected by theapoEgenotype. Epidemiological and experimental evidence suggest a better vitamin D status inapoEε4than ε3subjects indicating a certain advantage of ε4over ε3. The present review aims at evaluation of current data available on interactions between apoE polymorphism and dietary responsiveness to flavonoids, fat soluble vitamins andn-3 fatty acids. Likewise, distinct geographic distribution and chronic disease risk of the different apoE isoforms are addressed.

Mechanisms underlying the diuretic effects of Tropaeolum majus L. extracts and its main component isoquercitrin

ETHNOPHARMACOLOGICAL RELEVANCE

Previous studies have shown that the extracts obtained from Tropaeolum majus L., and its main compound isoquercitrin (ISQ), exhibit pronounced diuretic effects, supporting the ethnopharmacological use of this plant. The aim of this study was to evaluate the efficacy and mechanisms underlying the diuretic action of an ethanolic extract of Tropaeolum majus (HETM), its purified fraction (TMLR), and its main compound ISQ, in spontaneously hypertensive rats (SHR).

MATERIALS AND METHODS

The diuretic effects of HETM (300mg/kg; p.o.), TMLR (100mg/kg; p.o.), and ISQ (10mg/kg; p.o.), were compared with classical diuretics in 7days repeated-dose treatment. The urinary volume, sodium, potassium, chloride, bicarbonate, conductivity, pH and density were estimated in the sample collected for 15h. The plasmatic concentration of sodium, potassium, urea, creatinine, aldosterone, vasopressin, nitrite and angiotensin converting enzyme (ACE) activity were measured in samples collected at the end of the experiment (seventh day). Using pharmacological antagonists or inhibitors, we determine the involvement of bradykinin, prostaglandin and nitric oxide (NO) in ISQ-induced diuresis. In addition, reactive oxygen species (ROS) and the activity of erythrocytary carbonic anhydrase and renal Na(+)/K(+)/ATPase were evaluated in vitro.

RESULTS

HETM, TMLR and ISQ increased diuresis similarly to spironolactone and also presented K(+)-sparing effects. All groups presented both plasmatic aldosterone levels and ACE activity reduced. Previous treatment with HOE-140 (a B2-bradykinin receptor antagonist), or indomethacin (a cyclooxygenase inhibitor), or L-NAME (a NO synthase inhibitor), fully avoided the diuretic effect of ISQ. In addition, the 7days treatment with ISQ resulted in increased plasmatic levels of nitrite and reducing ROS production. Moreover, the renal Na(+)/K(+)/ATPase activity was significantly decreased by ISQ.

CONCLUSION

Our results suggest that the mechanisms through ISQ and extracts of Tropaeolum majus increase diuresis in SHR rats are mainly related to ACE inhibition, increased bioavailability of bradykinin, PGI2, and nitric oxide, besides an inhibitory effect on Na(+)/K(+)-ATPase.

Purification of berry flavonol glycosides by long-bed gel permeation chromatography

While Sephadex LH-20 gel is frequently employed as a stationary phase during pre-separations and in open column chromatography systems, its separation power in long-bed gel permeation chromatography (GPC) applications is much less prevalent. Aimed at the characterization of bioactive constituents, a long-bed GPC protocol was established for lingonberry juice concentrate. The method included pre-fractionation over HP-20 resin to eliminate sugars and organic acids as well as a major part of other predominant berry flavonoids (anthocyanins, flavan-3-ols and proanthocyanidins), prior to the elution of the fraction containing 10% (w/w) of quercetin glycosides (QGs). Subsequently, seven major QGs were purified using a 10-m Sephadex LH-20 system and isocratic elution with methanol. The total mass recovery was 99.3±1.4%, after eluting the highly-retained compounds from the employed pre-column with 70% acetone. Injecting 1070 mg per run, the yield of purified QGs ranged from 2 to 6 mg per collected single fraction. The LC-UV/PDA purities of isolated Q-3-O-α-rhamnoside and Q-3-O-β-galactoside were 82 and 94 area% at 250 nm, while the three Q-pentosides showed purities of 59, 30, and 57 area%. By comparison, purity assessment of these isolates by quantitative ¹H NMR (total integral and modified 100% method) led to significantly lower purities of 70 and 52% for Q-rha and Q-gal and 38, 25 and 46% for Q-pentosides, respectively. This can be explained by the presence of hidden residual complexity (RC), which is revealed by the quantitative NMR method. This finding has potentially broader implication as it reveals an unexpected degree of RC in GPC fractions. Despite remarkable separation power for congeneric flavonoids, long-bed GPC on Sephadex LH-20 produces materials, which require careful analysis of purity before interpreting bioassay results.

Transport and bioactivity of cyanidin 3-glucoside into the vascular endothelium

Flavonoids are dietary components involved in decreasing oxidative stress in the vascular endothelium and thus the risk of endothelial dysfunction. However, their very low concentrations in plasma place this role in doubt. Thus, a relationship between the effective intracellular concentration of flavonoids and their bioactivity needs to be assessed. This study examined the uptake of physiological concentrations of cyanidin 3-glucoside, a widespread dietary flavonoid, into human vascular endothelial cells. Furthermore, the involvement of the membrane transporter bilitranslocase (TC No. 2.A.65.1.1) as the key underlying molecular mechanism for membrane transport was investigated by using purified anti-sequence antibodies binding at the extracellular domain of the protein. The experimental observations were carried out in isolated plasma membrane vesicles and intact endothelial cells from human endothelial cells (EA.hy926) and on an ischemia-reperfusion model in isolated rat hearts. Cyanidin 3-glucoside was transported via bilitranslocase into endothelial cells, where it acted as a powerful intracellular antioxidant and a cardioprotective agent in the reperfusion phase after ischemia. These findings suggest that dietary flavonoids, despite their limited oral bioavailability and very low postabsorption plasma concentrations, may provide protection against oxidative stress-based cardiovascular diseases. Bilitranslocase, by mediating the cellular uptake of some flavonoids, is thus a key factor in their protective activity on endothelial function.

Quercetin reduces high-fat diet-induced fat accumulation in the liver by regulating lipid metabolism genes

To understand the molecular mechanisms underlying the influence of quercetin on the physiological effects of hyperlipidemia, we investigated its role in the prevention of high-fat diet (HFD)-induced obesity and found that it regulated hepatic gene expression related to lipid metabolism. Quercetin supplementation in mice significantly reduced the HFD-induced gains in body weight, liver weight, and white adipose tissue weight compared with the mice fed only with HFD. It also significantly reduced HFD-induced increases in serum lipids, including cholesterol, triglyceride, and thiobarbituric acid-reactive substance (TBARS). Consistent with the reduced liver weight and white adipose tissue weight, hepatic lipid accumulation and the size of lipid droplets in the epididymal fat pads were also reduced by quercetin supplementation. To further investigate how quercetin may reduce obesity, we analyzed lipid metabolism-related genes in the liver. Quercetin supplementation altered expression profiles of several lipid metabolism-related genes, including Fnta, Pon1, Pparg, Aldh1b1, Apoa4, Abcg5, Gpam, Acaca, Cd36, Fdft1, and Fasn, relative to those in HFD control mice. The expression patterns of these genes observed by quantitative reverse transcriptase-polymerase chain reaction were confirmed by immunoblot assays. Collectively, our results indicate that quercetin prevents HFD-induced obesity in C57B1/6 mice, and its anti-obesity effects may be related to the regulation of lipogenesis at the level of transcription.

Regulation of inflammatory cytokines in lipopolysaccharide-stimulated RAW 264.7 murine macrophage by 7-O-methyl-naringenin

7-O-Methylnaringenin, extracted from Rhododendron speciferum, belongs to the flavanone class of polyphenols. In the present study, we investigated the anti-inflammatory effects of 7-O-methylnaringenin on cytokine production by lipopoly-saccharide (LPS)-stimulated RAW 264.7 macrophages in vitro. The results showed that pretreatment with 10, 20 or 40 μg/mL of 7-O-methylnaringenin could downregulate tumour necrosis factor (TNF-α), interleukin (IL-6) and interleukin (IL-1β) in a dose-dependent manner. Furthermore, we investigated the signal transduction mechanisms to determine how 7-O-methylnaringenin affects RAW 264.7 macrophages. The activation of mitogen-activated protein kinases (MAPK) and IκBα were measured by Western blotting. The data showed that 7-O-methylnaringenin could downregulate LPS-induced levels of phosphorylation of ERK1/2, JNK and IκBα. These observations indicated that 7-O-methylnaringenin modulated inflammatory cytokine responses by blocking NF-қB, ERK1/2 and JNK/MAPKs activation.

Ameliorative Potential of Quercetin Against Paracetamol-induced Oxidative Stress in Mice Blood

The aim of the present study was to evaluate the ameliorative potential of quercetin (QC) against paracetamol (PCM)-induced oxidative stress and biochemical alterations in mice blood. A total of 36 mice were randomly allocated into six groups, six mice in each. Group I served as healthy controls, while groups II and III were administered with N-acetylcysteine (NAC) and QC alone respectively. Group IV was administered with PCM alone. Groups V and VI were administered with PCM on day 0 followed by NAC and QC, respectively, for 6 consecutive days. On day 7^th blood samples were obtained and subjected for the assays of oxidative stress and serum biochemical panels. Erythrocytic lipid peroxides contents of alone PCM-intoxicated mice were significantly higher, while reduced glutathione contents were found to be significantly lower in comparison with the healthy controls. The activities of antioxidant enzymes were also found to be singnificantly lower in these mice. Additionally, significantly increased activities of serum aspartate transaminase, alanine transaminase and alkaline phosphatase, as well as levels of bilirubin, urea and creatinine were revealed by these mice. Postadministration with QC remarkably alleviated the over production of MDA and improved GSH levels in PCM-intoxicated mice blood. In addition, antioxidant enzymes; glutathione peroxidase, glutathione-S-transferase, superoxide dismutase and catalase activities were also improved significantly in these mice. QC had also considerably ameliorated the altered biochemical parameters toward normalcy. Thus, it can be concluded that QC may constitute a remedy against PCM-induced oxidative stress and reno-hepatic injuries.

Quercetin production from rutin by a thermostable β-rutinosidase from Pyrococcus furiosus

Pyrococcus furiosus β-glucosidase converted rutin to quercetin and rutinose disaccharide with a ratio of 1:1, with no glucose, L-rhamnose, and isoquercitrin, indicating that the enzyme is a β-rutinosidase. The specific activity for flavonoid glycosides followed the order of isoquercitrin > quercitrin > rutin. The conversion of rutin to quercetin was optimal at pH 5.0 and 95°C in the presence of 0.5% dimethyl sulfoxide with a half-life of 101 h, a k(cat) of 1.6 min(-1), and a K(m) of 0.3 mM. Under the improved conditions, the enzyme produced 6.5 mM quercetin from 10 mM rutin after 150 min, with a molar yield of 65% and a productivity of 2.6 mM/h. This productivity is the highest reported thus far among enzymatic transformations.

Protective effects of quercetin against hydrogen peroxide-induced apoptosis in human neuronal SH-SY5Y cells

Hydrogen peroxide (H(2)O(2)) is a major reactive oxygen species that has been implicated in various neurodegenerative diseases. Quercetin, one of the plant flavonoids, has been reported to harbor various physiological properties including antioxidant activity. In this study, we investigated the neuroprotective effects of quercetin against H(2)O(2)-induced apoptosis in human neuronal SH-SY5Y cells. H(2)O(2)-mediated cytotoxicity and lactate dehydrogenase release were suppressed in a quercetin concentration-dependent manner. In addition, quercetin repressed the expression of the pro-apoptotic Bax gene and enhanced that of the anti-apoptotic Bcl-2 gene in SH-SY5Y cells. Moreover, quercetin effectively inhibited the activation of the caspase cascade that leads to DNA fragmentation, a key feature of apoptosis, and subsequent cell death. These results indicate the importance of quercetin in protecting against H(2)O(2)-mediated neuronal cell death. Thus, quercetin might potentially serve as an agent for prevention of neurodegenerative diseases caused by oxidative stress and apoptosis.

Kinetic studies of the effects of Temodal and quercetin on astrocytoma cells

The aim of the present study was to investigate the kinetics of the effects exerted by Temodal and quercetin on the survival of the human astrocytoma MOGGCCM cell line. Our results indicate that quercetin was toxic and induced necrosis, whereas Temodal induced autophagy-mediated cell death most effectively. The amount of cell death directly correlated with drug concentration and length of exposure. During combined administration of both drugs, Temodal attenuated the cytotoxic effects of quercetin. Combinations of both drugs were effective in inducing programmed cell death, but the type of cell death was concentration-dependent. Co-administration of Temodal (100 μM) with a low quercetin concentration (5 μM) resulted in a very significant induction of autophagy; however, after treatment with quercetin at a higher concentration (30 μM), apoptosis became the primary mechanism of cell death. The sequence of drug administration was also important. The highest number of dead cells was observed after simultaneous administration of both drugs or after pre-incubation with Temodal followed by treatment with quercetin. Apoptosis was identified through activation of the mitochondrial pathway including cleavage of caspase-3 and release of cytochrome c. Autophagy was identified through increased levels of LC3II. Our results indicate that Temodal and quercetin are synergistic inducers of programmed cell death, better together than applied separately. This drug combination appears to be a potent and promising therapeutic relevant to the treatment of gliomas.

Quercetin regulates organic ion transporter and uromodulin expression and improves renal function in hyperuricemic mice

BACKGROUND

Renal organic ion transporters and uromodulin (UMOD) play the important roles in renal urate excretion and function. Hyperuricemia is considered as a risk factor for the development of renal dysfunction. The flavonoid quercetin in diets exerts the hypouricemic and nephroprotective effects.

PURPOSES

To evaluate the effects of quercetin on renal organic ion transporters and UMOD in hyperuricemic mice.

METHODS

Kun-Ming mice were divided into normal and hyperuricemic groups receiving water, 25, 50 and 100 mg/kg quercetin, 5 mg/kg allopurinol, respectively. Hyperuricemic mice were orally gavaged with 250 mg/kg oxonate daily for 1 week. Quercetin and allopurinol were orally gavaged on the day when oxonate or water was given 1 h later. After 1 week, serum uric acid, creatinine and blood urea nitrogen concentrations, excretion of urate and creatinine, and fractional excretion of uric acid were measured. The mRNA and protein levels of renal urate transporter 1 (mURAT1), glucose transporter 9 (mGLUT9), organic anion transporter 1 (mOAT1) and organic cation/carnitine transporters (mOCT1, mOCT2, mOCTN1 and mOCTN2) in mice were analyzed. Simultaneously, UMOD levels in serum, urine and kidney, as well as renal UMOD mRNA expression were detected.

RESULTS

Quercetin significantly restored oxonate-induced abnormalities of these biochemical indexes compared with normal vehicle group. Furthermore, it remarkably prevented expression changes of renal organic ion transporters and UMOD, and UMOD level alteration in hyperuricemic mice.

CONCLUSIONS

These results suggest that quercetin has the uricosuric and nephroprotective actions mediated by regulating the expression levels of renal organic ion transporters and UMOD.

Vasorelaxant and hypotensive effects of the extract and the isolated flavonoid rutin obtained from Polygala paniculata L

Objectives

This study aimed to investigate the in-vitro and in-vivo cardiovascular effects of the crude hydroalcoholic extract from Polygala paniculata (HEPP) in rats.

Methods

The procedures were performed on aortic rings and on normotensive anaesthetized rats.

Key findings

When tested in endothelium-intact aorta rings, HEPP (30–1000 µg/ml) produced a significant non-concentration-dependent relaxing effect (∼40%), which was completely prevented by incubation with L-NAME (nitric oxide synthase inhibitor), ODQ (soluble guanylate cyclase inhibitor) and partially inhibited by tetraethylammonium (TEA; a non-selective potassium channel blocker) and charybdotoxin (a large- and intermediate-conductance calcium-activated potassium channel blocker). In contrast, atropine (a muscarinic receptor antagonist) or pyrilamine(a histamine H1 receptor antagonist) had no effect. Furthermore, oral administration of HEPP (30–300 mg/kg) in anaesthetized rats caused a dose-dependent and sustained hypotensive action. This effect was unchanged by atropine or TEA, but was strongly reduced in rats continuously infused with L-NAME or methylene blue. Moreover, rutin (1–3 mg/kg) administered by an intravenous route also caused a dose-dependent hypotensive effect in rats.

Conclusions

Our results demonstrated that the extract obtained from P. paniculata induces potent hypotensive and vasorelaxant effects that are dependent on the nitric oxide/guanylate cyclase pathway. These effects could be related, at least in part, to the rutin contents in this extract.

Quercetin and cancer chemoprevention

Several molecules present in the diet, including flavonoids, can inhibit the growth of cancer cells with an ability to act as "chemopreventers". Their cancer-preventive effects have been attributed to various mechanisms, including the induction of cell-cycle arrest and/or apoptosis as well as the antioxidant functions. The antioxidant activity of chemopreventers has recently received a great interest, essentially because oxidative stress participates in the initiation and progression of different pathological conditions, including cancer. Since antioxidants are capable of preventing oxidative damage, the wide use of natural food-derived antioxidants is receiving greater attention as potential anti-carcinogens. Among flavonoids, quercetin (Qu) is considered an excellent free-radical scavenging antioxidant, even if such an activity strongly depends on the intracellular availability of reduced glutathione. Apart from antioxidant activity, Qu also exerts a direct, pro-apoptotic effect in tumor cells, and can indeed block the growth of several human cancer cell lines at different phases of the cell cycle. Both these effects have been documented in a wide variety of cellular models as well as in animal models. The high toxicity exerted by Qu on cancer cells perfectly matches with the almost total absence of any damages for normal, non-transformed cells. In this review we discuss the molecular mechanisms that are based on the biological effects of Qu, and their relevance for human health.

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.

Vasorelaxant and antihypertensive effect of Cocos nucifera Linn. endocarp on isolated rat thoracic aorta and DOCA salt-induced hypertensive rats

ETHNOPHARMACOLOGICAL RELEVANCE

The fruits of Cocos nucifera Linn. (Arecaceae) have long been used in traditional medicine for the treatment of cardio-metabolic disorders.

AIM OF THE STUDY

To evaluate the ethanolic extract of Cocos nucifera Linn. endocarp (CNE) for its vasorelaxant activity on isolated rat aortic rings and antihypertensive effects in deoxycorticosterone acetate (DOCA) salt-induced hypertensive rats.

MATERIALS AND METHODS

Cocos nucifera Linn. endocarp was extracted with ethanol and characterized by HPLC. CNE was examined for its in vitro vascular relaxant effects in isolated norepinephrine, phenylephrine or potassium chloride pre-contracted aortic rings (both intact endothelium and denuded). In vivo anti-hypertensive studies were conducted in DOCA salt-induced uninephrectomized male Wistar rats.

RESULTS

Removal of endothelium or pretreatment of aortic rings (intact endothelium) with l-NNA (10μM) or ODQ (10 μM) followed by addition of contractile agonists prior to CNE significantly blocked the CNE-induced relaxation. Indomethacin (10μM) and atropine (1 μM) partially blocked the relaxation, whereas glibenclamide (10 μM) did not alter it. CNE significantly reduced the mean systolic blood pressure in DOCA salt-induced hypertensive rats (from 185.3 ± 4.7 mmHg to 145.6±6.1 mmHg). The activities observed were supported by the polyphenols, viz. chlorogenic acid, vanillic acid and ferulic acid identified in the extract.

CONCLUSIONS

These findings reveal that the vasorelaxant and antihypertensive effects of CNE, through nitric oxide production in a concentration and endothelium-dependent manner, is due to direct activation of nitric oxide/guanylate cyclase pathway, stimulation of muscarinic receptors and/or via cyclooxygenase pathway.

Habitual intake of flavonoid subclasses and incident hypertension in adults

BACKGROUND

Dietary flavonoids have beneficial effects on blood pressure in intervention settings, but there is limited information on habitual intake and risk of hypertension in population-based studies.

OBJECTIVE

We examined the association between habitual flavonoid intake and incident hypertension in a prospective study in men and women.

DESIGN

A total of 87,242 women from the Nurses' Health Study (NHS) II, 46,672 women from the NHS I, and 23,043 men from the Health Professionals Follow-Up Study (HPFS) participated in the study. Total flavonoid and subclass intakes were calculated from semiquantitative food-frequency questionnaires collected every 4 y by using an updated and extended US Department of Agriculture database.

RESULTS

During 14 y of follow-up, 29,018 cases of hypertension in women and 5629 cases of hypertension in men were reported. In pooled multivariate-adjusted analyses, participants in the highest quintile of anthocyanin intake (predominantly from blueberries and strawberries) had an 8% reduction in risk of hypertension [relative risk (RR): 0.92; 95% CI: 0.86, 0.98; P < 0.03] compared with that for participants in the lowest quintile of anthocyanin intake; the risk reduction was 12% (RR: 0.88; 95% CI: 0.84, 0.93; P < 0.001) in participants ≤60 y of age and 0.96 (0.91, 1.02) in participants >60 y of age (P for age interaction = 0.02). Although intakes of other subclasses were not associated with hypertension, pooled analyses for individual compounds suggested a 5% (95% CI: 0.91, 0.99; P = 0.005) reduction in risk for the highest compared with the lowest quintiles of intake of the flavone apigenin. In participants ≤60 y of age, a 6% (95% CI: 0.88, 0.97; P = 0.002) reduction in risk was observed for the flavan-3-ol catechin when the highest and the lowest quintiles were compared.

CONCLUSIONS

Anthocyanins and some flavone and flavan-3-ol compounds may contribute to the prevention of hypertension. These vasodilatory properties may result from specific structural similarities (including the B-ring hydroxylation and methyoxylation pattern).

Activation of the erythrocyte plasma membrane redox system by resveratrol: a possible mechanism for antioxidant properties

Resveratrol is one of the most widely studied of all the plant-produced polyphenols and has diverse, beneficial health effects including anti-cancer and cardio-protective effects. Many of the biological actions of this polyphenol have been attributed to its antioxidant properties. Erythrocytes contain a plasma membrane redox system (PMRS), which transfers electrons from intracellular donors (NADH and/or ascorbate (ASC)) to extracellular acceptors. There is evidence that the intracellular ASC donates electrons to extracellular ascorbate free radicals (AFRs) via the PMRS, which encompasses an AFR reductase; such a redox system enables the cells to effectively counteract oxidative processes.We present evidence to show that human erythrocytes take up resveratrol, and once inside the cell, resveratrol can donate electrons to extracellular electron acceptors through the erythrocyte PMRS and AFR reductase. Incubating human erythrocytes with resveratrol (10 μM) caused a significant activation of the PMRS (41%) and AFR reductase (30%) over (basal level) the control; the effect of resveratrol was concentration-dependent. The electron donating ability of resveratrol is slightly less than that observed with quercetin. The role of resveratrol in activating the erythrocyte PMRS and AFR reductase may assume significance in all disease conditions in which there is a decrease in plasma antioxidant potential.

Cocoa flavanols: effects on vascular nitric oxide and blood pressure

Diets rich in fruits and vegetables have been associated with benefits for human health. Those effects have been partially ascribed to their content in flavonoids, compounds that are present in many edible plants and its derived foods. In humans, a significant number of studies has been developed analyzing the effect of foods and beverages rich in flavonoids on the presence and progression of risk factors associated to cardiovascular diseases, including hypertension. Cocoa derived products, rich in flavanols, have been thoroughly studied and demonstrated to be efficient improving endothelial function and decreasing blood pressure in humans and animals. However, the final chemical species and the mechanism/s responsible for these effects have not been completely defined. In this paper we present data supporting the hypothesis that flavanols could define superoxide anion production and then, establish optimal nitric oxide levels and blood pressure.

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.

Bimodal action of the flavonoid quercetin on basophil function: an investigation of the putative biochemical targets

Background

Flavonoids, a large group of polyphenolic metabolites derived from plants have received a great deal of attention over the last several decades for their properties in inflammation and allergy. Quercetin, the most abundant of plant flavonoids, exerts a modulatory action at nanomolar concentrations on human basophils. As this mechanism needs to be elucidated, in this study we focused the possible signal transduction pathways which may be affected by this compound. Methods: K2-EDTA derived leukocyte buffy coats enriched in basophil granulocytes were treated with different concentrations of quercetin and triggered with anti-IgE, fMLP, the calcium ionophore A23187 and the phorbol ester PMA in different experimental conditions. Basophils were captured in a flow cytometry analysis as CD123bright/HLADRnon expressing cells and fluorescence values of the activation markers CD63-FITC or CD203c-PE were used to produce dose response curves. The same population was assayed for histamine release.

Results

Quercetin inhibited the expression of CD63 and CD203c and the histamine release in basophils activated with anti-IgE or with the ionophore: the IC50 in the anti-IgE model was higher than in the ionophore model and the effects were more pronounced for CD63 than for CD203c. Nanomolar concentrations of quercetin were able to prime both markers expression and histamine release in the fMLP activation model while no effect of quercetin was observed when basophils were activated with PMA. The specific phosphoinositide-3 kinase (PI3K) inhibitor wortmannin exhibited the same behavior of quercetin in anti-IgE and fMLP activation, thus suggesting a role for PI3K involvement in the priming mechanism.

Conclusions

These results rule out a possible role of protein kinase C in the complex response of basophil to quercetin, while indirectly suggest PI3K as the major intracellular target of this compound also in human basophils.

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.

Anti-ageing and rejuvenating effects of quercetin

Homeostasis is a key feature of the cellular lifespan. Its maintenance influences the rate of ageing and it is determined by several factors, including efficient proteolysis. The proteasome is the major cellular proteolytic machinery responsible for the degradation of both normal and damaged proteins. Alterations of proteasome function have been recorded in various biological phenomena including ageing and replicative senescence. Proteasome activities and function are decreased upon replicative senescence, whereas proteasome activation confers enhanced survival against oxidative stress, lifespan extension and maintenance of the young morphology longer in human primary fibroblasts. Several natural compounds possess anti-ageing/anti-oxidant properties. In this study, we have identified quercetin (QUER) and its derivative, namely quercetin caprylate (QU-CAP) as a proteasome activator with anti-oxidant properties that consequently influence cellular lifespan, survival and viability of HFL-1 primary human fibroblasts. Moreover, when these compounds are supplemented to already senescent fibroblasts, a rejuvenating effect is observed. Finally, we show that these compounds promote physiological alterations when applied to cells (i.e. whitening effect). In summary, these data demonstrate the existence of naturally occurring anti-ageing products that can be effectively used through topical application.

Polyphenols from red wine are potent modulators of innate and adaptive immune responsiveness

It is well known that the consumption of dietary polyphenols leads to beneficial effects for human health as in the case of prevention and/or attenuation of cardiovascular, inflammatory, neurodegenerative and neoplastic diseases. This review summarizes the role of polyphenols from red wine in the immune function. In particular, using healthy human peripheral blood mononuclear cells, we have demonstrated the in vitro ability of Negroamaro, an Italian red wine, to induce the release of nitric oxide and both pro-inflammatory and anti-inflammatory cytokines, thus leading to the maintenance of the immmune homeostasis in the host. All these effects were abrogated by deprivation of polyphenols from red wine samples. We have also provided evidence that Negromaro polyphenols are able to activate extracellular regulated kinase and p38 kinase and switch off the NF-kappaB pathway via an increased expression with time of the IkappaBalpha phosphorylated form. These mechanisms may represent key molecular events leading to inhibition of the pro-inflammatory cascade and atherogenesis. In conclusion, according to the current literature and our own data, moderate consumption of red wine seems to be protective for the host in the prevention of several diseases, even including aged-related diseases by virtue of its immunomodulating properties.

Regulation of inflammatory mediators in lipopolysaccharide-stimulated RAW 264.7 cells by 2''-hydroxy-3''-en-anhydroicaritin involves down-regulation of NF-kappaB and MAPK expression

2''-hydroxy-3''-en-anhydroicaritin, a flavone, was isolated from the Chinese medicinal herb Epimedium brevicornum for the first time. In our previous study, we have carried out a screening program to identify the anti-inflammatory potentials of 2''-hydroxy-3''-en-anhydroicaritin. In the present study, we further found that this compound regulated lipopolysaccharide (LPS)-induced levels of nitric oxide (NO), and prostaglandin E(2) (PGE(2)) (**p<0.01 or *p<0.05), and reduced levels of iNOS and COX-2 in RAW 264.7 macrophages in a concentration-dependent manner. We further investigated signal transduction mechanisms to determine how 2''-hydroxy-3''-en-anhydroicaritin affects RAW264.7 macrophages pretreated with 0.5, 2.5, or 12.5mg/L of 2''-hydroxy-3''-en-anhydroicaritin 1h prior to treatment with 1mg/L of LPS. Thirty minutes later, cells were harvested and mitogen-activated protein kinases (MAPK) activation and I kappaB alpha were measured by western blotting. Alternatively, the macrophages were fixed and nuclear factor-kappaB (NF-kappaB) activation was measured by immunocytochemical analysis. Signal transduction studies showed that the flavone significantly inhibited extracellular signal-regulated kinase (ERK), p38, and c-jun NH2-terminal kinase (JNK) phosphorylation protein expression. The flavone also inhibited p65-NF-kappaB translocation into the nucleus by I kappaB alpha degradation. Therefore, 2''-hydroxy-3''-en-anhydroicaritin may inhibit LPS-induced production of inflammatory cytokines by blocking NF-kappaB and MAPK signaling in RAW264.7 cells.

The activity of medicinal plants and secondary metabolites on eosinophilic inflammation

Eosinophils are leukocytes that are present in several body compartments and in the blood at relatively low numbers under normal conditions. However, an increase in the number of eosinophils, in the blood or in the tissues, is observed in allergic or parasitic disorders. Although some progress has been made in understanding the development of eosinophil-mediated inflammation in allergic and parasitic diseases, the discovery of new compounds to control eosinophilia has lagged behind other advances. Plant-derived secondary metabolites are the basis for many drugs currently used to treat pathologic conditions, including eosinophilic diseases. Several studies, including our own, have demonstrated that plant extracts and secondary metabolites can reduce eosinophilia and eosinophil recruitment in different experimental animal models. In this review, we summarize these studies and describe the anti-eosinophilic activity of various plant extracts, such as Ginkgo biloba, Allium cepa, and Lafoensia pacari, as well as those of secondary metabolites (compounds isolated from plant extracts), such as quercetin and ellagic acid. In addition, we highlight the medical potential of these plant-derived compounds for treating eosinophil-mediated inflammation, such as asthma and allergy.

Combating Combination of Hypertension and Diabetes in Different Rat Models

Rat experimental models are used extensively for studying physiological mechanisms and treatments of hypertension and diabetes co-existence. Each one of these conditions is a major risk factor for cardiovascular disease (CVD), and the combination of the two conditions is a potent enhancer of CVD. Five major animal models that advanced our understanding of the mechanisms and therapeutic approaches in humans are discussed in this review: Zucker, Goto-Kakizaki, SHROB, SHR/NDmcr-cp and Cohen Rosenthal diabetic hypertensive (CRDH) rats. The use of various drugs, such as angiotensin-converting enzyme (ACE) inhibitors (ACEIs), various angiotensin receptor blockers (ARBs), and calcium channel blockers (CCBs), to combat the effects of concomitant pathologies on the combination of diabetes and hypertension, as well as the non-pharmacological approach are reviewed in detail for each rat model. Results from experiments on these models indicate that classical factors contributing to the pathology of hypertension and diabetes combination—Including hypertension, hyperglycemia, hyperinsulinemia and hyperlipidemia—can now be treated, although these treatments do not completely prevent renal complications. Animal studies have focused on several mechanisms involved in hypertension/diabetes that remain to be translated into clinical medicine, including hypoxia, oxidative stress, and advanced glycation. Several target molecules have been identified that need to be incorporated into a treatment modality. The challenge continues to be the identification and interpretation of the clinical evidence from the animal models and their application to human treatment.

Nutritional improvement of the endothelial control of vascular tone by polyphenols: role of NO and EDHF

Numerous studies indicate that regular intake of polyphenol-rich beverages (red wine and tea) and foods (chocolate, fruit, and vegetables) is associated with a protective effect on the cardiovascular system in humans and animals. Beyond the well-known antioxidant properties of polyphenols, several other mechanisms have been shown to contribute to their beneficial cardiovascular effects. Indeed, both experimental and clinical studies indicate that polyphenols improve the ability of endothelial cells to control vascular tone. Experiments with isolated arteries have shown that polyphenols cause nitric oxide (NO)-mediated endothelium-dependent relaxations and increase the endothelial formation of NO. The polyphenol-induced NO formation is due to the redox-sensitive activation of the phosphatidylinositol3-kinase/Akt pathway leading to endothelial NO synthase (eNOS) activation subsequent to its phosphorylation on Ser 1177. Besides the phosphatidylinositol3-kinase/Akt pathway, polyphenols have also been shown to activate eNOS by increasing the intracellular free calcium concentration and by activating estrogen receptors in endothelial cells. In addition to causing a rapid and sustained activation of eNOS by phosphorylation, polyphenols can increase the expression level of eNOS in endothelial cells leading to an increased formation of NO. Moreover, the polyphenol-induced endothelium-dependent relaxation also involves endothelium-derived hyperpolarizing factor, besides NO, in several types of arteries. Altogether, polyphenols have the capacity to improve the endothelial control of vascular tone not only in several experimental models of cardiovascular diseases such as hypertension but also in healthy and diseased humans. Thus, these experimental and clinical studies highlight the potential of polyphenol-rich sources to provide vascular protection in health and disease.

Serum lipid and blood pressure responses to quercetin vary in overweight patients by apolipoprotein E genotype

Our objective was to examine the effect of a quercetin supplementation on blood pressure, lipid metabolism, markers of oxidative stress, inflammation, and body composition in an at-risk population of 93 overweight-obese volunteers aged 25-65 y with metabolic syndrome traits in relation to apolipoprotein (apo) E genotype. Participants were randomized to receive 150 mg/d quercetin in a double-blinded, placebo-controlled, crossover trial with 6-wk treatment periods separated by a 5-wk washout period. Retrospectively, 5 apoE genotype variants were found (epsilon2/epsilon3, n = 3; epsilon3/epsilon3, n = 60; epsilon3/epsilon4, n = 23; epsilon2/epsilon4, n = 4; and epsilon4/epsilon4, n = 3). Participants were classified into the following 3 apoE phenotypes: apoE2 (n = 3), apoE3 (n = 60), and apoE4 (n = 26). Data were analyzed for apoE3 and apoE4 subgroups. Quercetin decreased systolic blood pressure by 3.4 mm Hg (P < 0.01) in the apoE3 group, whereas no significant effect was observed in the apoE4 group. Quercetin decreased serum HDL cholesterol (P < 0.01) and apoA1 (P < 0.01) and increased the LDL:HDL cholesterol ratio (P < 0.05) in the apoE4 subgroup, whereas the apoE3 subgroup had no significant changes in these variables. Quercetin significantly decreased plasma oxidized LDL and tumor necrosis factor-alpha in the apoE3 and apoE4 groups, whereas no significant inter-group differences were found. Serum C-reactive protein and nutritional status (body weight, waist circumference, fat mass, fat-free mass) were unaffected compared with placebo. In conclusion, quercetin exhibited blood pressure-lowering effects in overweight-obese carriers of the apo epsilon3/epsilon3 genotype but not in carriers of the epsilon4 allele. Furthermore, quercetin supplementation resulted in a reduction in HDL cholesterol and apoA1 in apo epsilon4 carriers.

ATZ (3-amino-1,2,4-triazole) injected into the fourth cerebral ventricle influences the Bezold-Jarisch reflex in conscious rats

OBJECTIVES

Many studies have investigated the importance of oxidative stress on the cardiovascular system. In this study we evaluated the effects of central catalase inhibition on cardiopulmonary reflex in conscious Wistar rats.

METHODS

Male Wistar rats were implanted with a stainless steel guide cannula in the fourth cerebral ventricle. The femoral artery and vein were cannulated for mean arterial pressure and heart rate measurement and for drug infusion, respectively. After basal mean arterial pressure and heart rate recordings, the cardiopulmonary reflex was tested with a dose of phenylbiguanide (PBG, 8 μg/kg, bolus). Cardiopulmonary reflex was evaluated before and μ l15 minutes after 1.0 μl 3-amino-1,2,4-triazole (ATZ, 0.01 g/100 μl)0.01 g/100 μl) injection into the fourth cerebral ventricle. Vehicle treatment did not change cardiopulmonary reflex responses.

RESULTS

Central ATZ significantly increased hypotensive responses without influencing the bradycardic reflex.

CONCLUSION

ATZ injected into the fourth cerebral ventricle increases sympathetic inhibition but does not change the parasympathetic component of the cardiopulmonary reflex in conscious Wistar rats.

Stimulus-specific regulation of CD63 and CD203c membrane expression in human basophils by the flavonoid quercetin

BACKGROUND

Flavonoids, such as quercetin, were reported to inhibit histamine release and cytokine production by basophils, but there is no evidence describing their action on membrane markers and intracellular biochemical pathways.

OBJECTIVE

The aim of the study was to examine the effect of several quercetin doses on an in vitro human basophil activation system that evaluates up-regulation of membrane markers in response to agonists.

METHODS

Leukocyte buffy coats from K(2)-EDTA anti-coagulated blood were treated with different concentrations of quercetin and triggered with anti-IgE ("allergy model") and with N-formyl-Met-Leu-Phe (fMLP) ("inflammation model"). Basophils were captured as CD123(bright)/HLA-DR(non-expressing) cells in a flow cytometry analysis and fluorescence values of CD63-FITC, CD203c-PE and CD123-PECy5 were used to produce dose response curves.

RESULTS

Quercetin at a dose of 10 microg/ml strongly inhibited CD63 and CD203c membrane up-regulation triggered by both agonists, but it neither affected cell viability nor changed the expression of the phenotypic marker CD123. The anti-IgE model appeared highly sensitive to the effect of quercetin: a dose as low as 0.01 microg/ml was able to significantly decrease CD63 and CD203c membrane expression. In the fMLP model the dose response was different: quercetin doses from 0.01 to 0.1 microg/ml significantly increased up-regulation of membrane markers, achieving the highest effect with CD63.

CONCLUSION

Very low doses of quercetin, within the pharmacological range, inhibit IgE-mediated membrane marker's up-regulation but prime the response to the chemotactic peptide fMLP; this stimulus specificity may have implications on the possible therapeutic action of the flavonoid in different pathologies.

Antihypertensive and endothelium-dependent vasodilator effects of aqueous extract of Cistus ladaniferus

Cistus ladaniferus L. (Cistaceae) is a medicinal plant originated from the Mediterranean region which exerts different pharmacological effects. In the present study, our goal was to examine whether the plant possessed antihypertensive properties. Aqueous extract of Cistus leaves (AEC, 500mg/kg/day) reduced systemic blood pressure (SBP) in two animal models of hypertension, the l-NAME and renovascular two kidney-one clip (2K-1C) hypertensive rats. In the former, AEC prevented the increase in SBP when co-administered with l-NAME during four weeks (164+/-3mm Hg in l-NAME vs. 146+/-1mm Hg in l-NAME+AEC, p<0.001). In the latter, AEC reversed the increase in SBP when administered during four weeks after installation of the hypertension (146+/-5mm Hg with AEC vs. 179+/-6mm Hg without, p<0.05). AEC treatment also reversed the endothelial dysfunction observed in both animal models of hypertension. A direct effect on cardiac and vascular tissue was also tested by examining the contractile effects of AEC in rat isolated aortic rings and Langendorff perfused hearts. AEC (10mg/L) had no effect on left ventricular developed pressure and heart rate in isolated perfused heart. However, AEC produced a strong relaxation of pre-contracted rat aortic rings (80+/-2% relaxation, n=25). When the rings were denuded from endothelium or were incubated with 1mM Nomega-nitro-l-arginine (l-NNA), the relaxant effect of AEC was lost. We conclude that C. ladaniferus possesses antihypertensive properties which are mainly due to an endothelium-dependent vasodilatory action.