Role of quercetin in vascular physiology

A Comprehensive Review on Potential In Silico Screened Herbal Bioactive Compounds and Host Targets in the Cardiovascular Disease Therapy

Herbal medicines (HMs) have deciphered indispensable therapeutic effects against cardiovascular disease (CVD) (the predominant cause of death worldwide). The conventional CVD therapy approaches have not been efficient and need alternative medicines. The objective of this study was a review of herbal bioactive compound efficacy for CVD therapy based on computational and in silico studies. HM bioactive compounds with potential anti-CVD traits include campesterol, naringenin, quercetin, stigmasterol, tanshinaldehyde, Bryophyllin A, Bryophyllin B, beta-sitosterol, punicalagin, butein, eriodyctiol, butin, luteolin, and kaempferol discovered using computational studies. Some of the bioactive compounds have exhibited therapeutic effects, as followed by in vitro (tanshinaldehyde, punicalagin, butein, eriodyctiol, and butin), in vivo (gallogen, luteolin, chebulic acid, butein, eriodyctiol, and butin), and clinical trials (quercetin, campesterol, and naringenin). The main mechanisms of action of bioactive compounds for CVD healing include cell signaling and inhibition of inflammation and oxidative stress, decrease of lipid accumulation, and regulation of metabolism and immune cells. Further experimental studies are required to verify the anti-CVD effects of herbal bioactive compounds and their pharmacokinetic/pharmacodynamic features.

Quercetin ameliorates acute acrylamide induced spleen injury

Acrylamide is used for industrial and laboratory purposes; it also is produced during cooking of carbohydrate-rich food at high temperature. We investigated the therapeutic potential of quercetin for treatment of acute acrylamide induced injury to the spleen. We used female albino rats treated with acrylamide for 10 days followed by oral administration of quercetin in three doses for 5 days. We observed significantly reduced total body weight, spleen weight, red blood cells, total proteins, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose-6-phophate dehydrogenase, reduced glutathione, concentration of serum IgG and IgM after acrylamide induced toxicity compared to controls. We also found that white blood cells, triglycerides, cholesterol and lipid oxidation were increased significantly after acrylamide induced toxicity in rats compared to controls. Histoarchitecture of spleen was affected adversely by acrylamide toxicity. Administration of quercetin ameliorated adverse effects of acrylamide in a dose-dependent manner. Quercetin appears to ameliorate acrylamide induced injury to the spleen by increasing endogenous antioxidants and improving histoarchitecture and immune function.

Quercetin regulates vascular endothelium function in chronic renal failure via modulation of Eph/Cav-1 signaling

Arteriovenous fistula (AVF) is frequently believed to be the best vascular access for chronic renal failure (CRF) patients. Vascular endothelial cell dysfunction has been implicated in AVF maturation. Quercetin (Quer) is a natural polyphenolic compound widely used in traditional Chinese medicine. We aimed to uncover the impacts of Quer on vascular endothelial cells in a CRF rat model and human umbilical vein endothelial cells (HUVECs) stimulated by lipopolysaccharide (LPS) and serum from rat with CRF. Blood urea nitrogen and serum creatinine levels were tested in CRF rat model after administration of Quer. H&E staining was used to estimate endothelial damage. Nitric oxide (NO), endothelial NO synthase (eNOS), EPH receptor B4 (EphB4), EphrinB2, and p-caveolin-1 (p-Cav-1) levels in the serum were examined by enzyme-linked immunosorbent assay. Western blot was employed to analyze the expressions of eNOS, phosphorylated (p)-eNOS, EphB4, and Cav-1 in arterial tissues and HUVECs. Cell counting kit-8 was applied for assessing cell proliferation. TUNEL (terminal-deoxynucleotidyl transferase-mediated nick end labeling) assay was employed to estimate cell apoptosis. Results showed that Quer ameliorated renal function impairment and endothelial injury in vivo. Meanwhile, Quer boosted the proliferation and suppressed the apoptosis of HUVECs stimulated by LPS and serum from rat with CRF. Additionally, Quer elevated NO and eNOS levels, upregulated p-eNOS expression but downregulated EphB4, EphrinB2, and p-Cav-1 expressions. Moreover, EphB4 inhibitor had the similar effect as Quer treatment in HUVECs stimulated by LPS and serum from rat with CRF. Collectively, Quer might effectively regulate vascular function to prevent AVF failure in CRF via modulation of Eph/Cav-1 signaling.

Quercetin Downregulates Cyclooxygenase-2 Expression and HIF-1α/VEGF Signaling-Related Angiogenesis in a Mouse Model of Abdominal Aortic Aneurysm

Objective

Abdominal aortic aneurysm (AAA) development has been characterized by increased expression of vascular endothelial growth factor (VEGF), which contributes to angiogenesis via cyclooxygenase-2 (COX-2). Quercetin, one of the most common and well-researched flavonoids and abundant in vegetables and fruits, has beneficial effects in inhibiting angiogenesis. This study investigated the antiangiogenic effects of quercetin on experimental aneurysms.

Methods

We utilized the in vivo AAA mouse model induced by the periaortic application of CaCl₂ to examine the effectiveness of quercetin in blocking angiogenesis. Quercetin was administered at 60 mg/kg once daily on the day of the AAA induction and then continued for 6 weeks. Celecoxib, a selective COX-2 inhibitor, was used as the positive control.

Results

Our results demonstrated that quercetin significantly attenuated aneurysm growth in AAA mice and medial neovascularization. Accordingly, quercetin decreased the expression of proangiogenic mediators, including VEGF-A, intercellular adhesion molecule-1, vascular cell adhesion molecule 1, and vascular endothelial cadherin. Quercetin treatment also inhibited the expression of COX-2 and hypoxia-inducible factor 1α (HIF-1α). It was also found that quercetin-3-glucuronide, a major quercetin metabolite, downregulated the expression of COX-2, HIF-1α, VEGF-A, and matrix metalloproteinase activities in aortic vascular smooth muscle cells isolated from AAA mice.

Conclusion

Quercetin attenuates neovascularization during AAA growth, and this effect is mediated via the inhibition of COX-2, which decreases HIF-1α/VEGF signaling-related angiogenesis.

4-Methylcatechol, a Flavonoid Metabolite with Potent Antiplatelet Effects

SCOPE

Intake of flavonoids from the diet can be substantial, and epidemiological studies suggest that these compounds can decrease the incidence of cardiovascular diseases by involvement with increased platelet aggregation. Although parent flavonoids possess antiplatelet effects, the clinical importance is disputable due to their very low bioavailability. Most of them are metabolized by human colon bacteria to smaller phenolic compounds, which reach higher plasma concentrations than the parent flavonoids. In this study, a series of 29 known flavonoid metabolites is tested for antiplatelet potential.

METHODS AND RESULTS

Four compounds appear to have a biologically relevant antiplatelet effect using whole human blood. 4-Methylcatechol (4-MC) is clearly the most efficient being about 10× times more active than clinically used acetylsalicylic acid. This ex vivo effect is also confirmed using a potentially novel in-vivo-like ex ovo hen's egg model of thrombosis, where 4-MC significantly increases the survival of the eggs. The mechanism of action is studied and it seems that it is mainly based on the influence on intracellular calcium signaling.

CONCLUSION

This study shows that some flavonoid metabolites formed by human microflora have a strong antiplatelet effect. This information can help to explain the antiplatelet potential of orally given flavonoids.

Quercetin reduces the transcriptional activity of NF-kB in stable coronary artery disease

OBJECTIVE

The aim of this study was to determine the effect of quercetin on the indicators of chronic systemic inflammation (CSI) in stable coronary artery disease (CAD).

METHODS

This study included 85 patients with CAD, stable angina pectoris, functional class (FC) II, and heart failure (НF) 0-І. Each patient was prescribed beta-blockers, statins, and aspirin. In addition, a total of 30 patients, forming the study group received quercetin at a daily dose of 120mg for two months, while the remaining 55 patients made up the control group. The levels of cytokines, such as tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), and interleukin-10 (IL-10) in serum and the expression of the inhibitor of kappa B α (IkBα) gene in blood mononuclear cells, were determined.

RESULTS

The increased levels of IL-1β and TNF-α, as well as a moderate increase in IL-10 levels, were detected in the serum of patients with CAD. The expression of the IkBα gene (2-δСt) did not differ significantly between the groups. Under the influence of quercetin, levels of IL-1β and TNF-α were reduced and IL-10 levels tended to decrease. In contrast, the serum levels of these cytokines did not change significantly in the control group. The administration of quercetin decreased the expression of the IkBα gene (0.0092±0.0033 against 0.0261±0.0166, р=0.003; 2-δδСt, 2.82±1.39 times) in contrast to the control group.

CONCLUSION

Quercetin showed anti-inflammatory properties in patients with CAD, indicating a decrease in transcriptional activity of the nuclear factor of transcription kappa B (NF-kB).

Two flavonoid metabolites, 3,4-dihydroxyphenylacetic acid and 4-methylcatechol, relax arteries ex vivo and decrease blood pressure in vivo

SCOPE

The flavonoid quercetin reduces arterial blood pressure in animals and humans but the mechanisms remains elusive. The aim of this study was to test the activity of flavonoid microbial metabolites, which can participate on the final vasorelaxant effect.

METHODS AND RESULTS

Both ex vivo (isolated rat thoracic aorta and mesenteric artery) and in vivo (normotensive and spontaneously hypertensive rats) approaches were used in this study. 4-methylcatechol and 3,4-dihydroxyphenylacetic acid (DHPA) had greater vasorelaxant effects on mesenteric artery than 3-(3-hydroxyphenyl)propionic acid, the previously reported metabolite with vasorelaxant effect. In vivo testing confirmed their blood pressure decreasing effect given both as bolus and slow infusion. Their mechanism at molecular level was different.

CONCLUSIONS

This study is the first to show that flavonoid metabolites DHPA and 4-methylcatechol decrease arterial blood pressure and hence a mixture of microbial metabolites formed in the gastrointestinal tract may be responsible for or contribute to the effect of orally ingested quercetin.

The surge of flavonoids as novel, fine regulators of cardiovascular Cav channels

Ion channels underlie a wide variety of physiological processes that involve rapid changes in cell dynamics, such as cardiac and vascular smooth muscle contraction. Overexpression or dysfunction of these membrane proteins are the basis of many cardiovascular diseases that represent the leading cause of morbidity and mortality for human beings. In the last few years, flavonoids, widely distributed in the plant kingdom, have attracted the interest of many laboratories as an emerging class of fine ion, in particular Ca_v, channels modulators. Pieces of in vitro evidence for direct as well as indirect effects exerted by various flavonoids on ion channel currents are now accumulating in the scientific literature. This activity may be responsible, at least in part, for the beneficial and protective effects of dietary flavonoids toward cardiovascular diseases highlighted in several epidemiological studies. Here we examine numerous studies aimed at analysing this feature of flavonoids, focusing on the mechanisms that promote their sometimes controversial activities at cardiovascular Ca_v channels. New methodological approaches, such as molecular modelling and docking to Ca_v1.2 channel α_1c subunit, used to elucidate flavonoids intrinsic mechanism of action, are introduced. Moreover, flavonoid-membrane interaction, bioavailability, and antioxidant activity are taken into account and discussed.

Molecular Properties of Red Wine Compounds and Cardiometabolic Benefits

Wine has been used since the dawn of human civilization. Despite many health benefits, there is still a lot of discussion about the real properties of its components and its actions on cells and molecular interactions. A large part of these issues permeate the fine line between the amount of alcohol that causes problems to organic systems and the amount that could be beneficial for the health. However, even after the process of fermentation, wine conserves different organic compounds from grapes, such as polysaccharides, acids, and phenolic compounds, such as flavonoids and nonflavonoids. These substances have known anti-inflammatory and antioxidant capacities, and are considered as regulatory agents in cardiometabolic process. In this study, the main chemical components present in the wine, its interaction with molecules and biological mechanisms, and their interference with intra- and extracellular signaling are reviewed. Finally, the properties of wine that may benefit cardiovascular system are also revised.

Effect of quercetin and its metabolite on caveolin-1 expression induced by oxidized LDL and lysophosphatidylcholine in endothelial cells

Oxidized low-density lipoprotein contributes to atherosclerotic plaque formation, and quercetin is expected to exert anti-atherosclerotic effects. We previously reported accumulation of conjugated quercetin metabolites in the aorta of rabbits fed high-cholesterol diets with quercetin glucosides, resulting in attenuation of lipid peroxidation and inhibition of lipid accumulation. Caveolin-1, a major structural protein of caveolae in vascular endothelial cells, plays a role in atherosclerosis development. Here we investigated effects of oxidized low-density lipoprotein, quercetin and its metabolite, quercetin 3-O-β-glucuronide, on caveolin-1 expression. Oxidized low-density lipoprotein significantly upregulated caveolin-1 mRNA expression. An oxidized low-density lipoprotein component, lysophosphatidylcholine, also induced expression of both caveolin-1 mRNA and protein. However, lysophosphatidylcholine did not affect the location of caveolin-1 proteins within caveolae structures. Co-treatment with quercetin or quercetin 3-O-β-glucuronide inhibited lysophosphatidylcholine-induced caveolin-1 expression. Quercetin and quercetin 3-O-β-glucuronide also suppressed expression of adhesion molecules induced by oxidized low-density lipoprotein and lysophosphatidylcholine. These results strongly suggest lysophosphatidylcholine derived from oxidized low-density lipoprotein contributes to atherosclerotic events by upregulating caveolin-1 expression, resulting in induction of adhesion molecules. Quercetin metabolites are likely to exert an anti-atherosclerotic effect by attenuating caveolin-1 expression in endothelial cells.

Flavonoid metabolite 3-(3-hydroxyphenyl)propionic acid formed by human microflora decreases arterial blood pressure in rats

There are reports of positive effects of quercetin on cardiovascular pathologies, however, mainly due to its low biovailability, the mechanism remains elusive. Here, we report that one metabolite formed by human microflora (3-(3-hydroxyphenyl)propionic acid)relaxed isolated rat aorta and decreased arterial blood pressure in rats.

Polyphenols: benefits to the cardiovascular system in health and in aging

Numerous studies have demonstrated the importance of naturally occurring dietary polyphenols in promoting cardiovascular health and emphasized the significant role these compounds play in limiting the effects of cellular aging. Polyphenols such as resveratrol, epigallocatechin gallate (EGCG), and curcumin have been acknowledged for having beneficial effects on cardiovascular health, while some have also been shown to be protective in aging. This review highlights the literature surrounding this topic on the prominently studied and documented polyphenols as pertaining to cardiovascular health and aging.