The dietary flavonol quercetin ameliorates angiotensin II-induced redox signaling imbalance in a human umbilical vein endothelial cell model of endothelial dysfunction via ablation of p47phox expression

Flavonoids and their role in oxidative stress, inflammation, and human diseases

Oxidative stress and chronic inflammation are important drivers in the pathogenesis and progression of many chronic diseases, such as cancers of the breast, kidney, lung, and others, autoimmune diseases (rheumatoid arthritis), cardiovascular diseases (hypertension, atherosclerosis, arrhythmia), neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, Huntington's disease), mental disorders (depression, schizophrenia, bipolar disorder), gastrointestinal disorders (inflammatory bowel disease, colorectal cancer), and other disorders. With the increasing demand for less toxic and more tolerable therapies, flavonoids have the potential to effectively modulate the responsiveness to conventional therapy and radiotherapy. Flavonoids are polyphenolic compounds found in fruits, vegetables, grains, and plant-derived beverages. Six of the twelve structurally different flavonoid subgroups are of dietary significance and include anthocyanidins (e.g. pelargonidin, cyanidin), flavan-3-ols (e.g. epicatechin, epigallocatechin), flavonols (e.g. quercetin, kaempferol), flavones (e.g. luteolin, baicalein), flavanones (e.g. hesperetin, naringenin), and isoflavones (daidzein, genistein). The health benefits of flavonoids are related to their structural characteristics, such as the number and position of hydroxyl groups and the presence of C2C3 double bonds, which predetermine their ability to chelate metal ions, terminate ROS (e.g. hydroxyl radicals formed by the Fenton reaction), and interact with biological targets to trigger a biological response. Based on these structural characteristics, flavonoids can exert both antioxidant or prooxidant properties, modulate the activity of ROS-scavenging enzymes and the expression and activation of proinflammatory cytokines (e.g., interleukin-1beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α)), induce apoptosis and autophagy, and target key signaling pathways, such as the nuclear factor erythroid 2-related factor 2 (Nrf2) and Bcl-2 family of proteins. This review aims to briefly discuss the mutually interconnected aspects of oxidative and inflammatory mechanisms, such as lipid peroxidation, protein oxidation, DNA damage, and the mechanism and resolution of inflammation. The major part of this article discusses the role of flavonoids in alleviating oxidative stress and inflammation, two common components of many human diseases. The results of epidemiological studies on flavonoids are also presented.

3'-Sialyllactose protects against LPS-induced endothelial dysfunction by inhibiting superoxide-mediated ERK1/2/STAT1 activation and HMGB1/RAGE axis

AIM

Endothelial hyperpermeability is an early stage of endothelial dysfunction associated with the progression and development of atherosclerosis. 3'-Sialyllactose (3'-SL) is the most abundant compound in human milk oligosaccharides, and it has the potential to regulate endothelial dysfunction. This study investigated the beneficial effects of 3'-SL on lipopolysaccharide (LPS)-induced endothelial dysfunction in vitro and in vivo.

MAIN METHODS

We established LPS-induced endothelial dysfunction models in both cultured bovine aortic endothelial cells (BAECs) and mouse models to determine the effects of 3'-SL. Western blotting, qRT-PCR analysis, immunofluorescence staining, and en face staining were employed to clarify underlying mechanisms. Superoxide production was measured by 2',7'-dichlorofluorescin diacetate, and dihydroethidium staining.

KEY FINDINGS

LPS significantly decreased cell viability, whereas 3'-SL treatment mitigated these effects via inhibiting ERK1/2 activation. Mechanistically, 3'-SL ameliorated LPS-induced ROS accumulation leading to ERK1/2 activation-mediated STAT1 phosphorylation and subsequent inhibition of downstream transcriptional target genes, including VCAM-1, TNF-α, IL-1β, and MCP-1. Interestingly, LPS-induced ERK1/2/STAT1 activation leads to the HMGB1 release from the nucleus into the extracellular space, where it binds to RAGE, while 3'-SL suppressed EC hyperpermeability by suppressing the HMGB1/RAGE axis. This interaction also led to VE-cadherin endothelial junction disassembly and endothelial cell monolayer disruption through ERK1/2/STAT1 modulation. In mouse endothelium, en face staining revealed that 3'-SL abolished LPS-stimulated ROS production and VCAM-1 overexpression.

SIGNIFICANCE

Our findings suggest that 3'-SL inhibits LPS-induced endothelial hyperpermeability by suppressing superoxide-mediated ERK1/2/STAT1 activation and HMGB1/RAGE axis. Therefore, 3'-SL may be a potential therapeutic agent for preventing the progression of atherosclerosis.

To Explore the Putative Molecular Targets of Diabetic Nephropathy and their Inhibition Utilizing Potential Phytocompounds

BACKGROUND

This review critically addresses the putative molecular targets of Diabetic Nephropathy (DN) and screens effective phytocompounds that can be therapeutically beneficial, and highlights their mechanistic modalities of action.

INTRODUCTION

DN has become one of the most prevalent complications of clinical hyperglycemia, with individual-specific variations in the disease spectrum that leads to fatal consequences. Diverse etiologies involving oxidative and nitrosative stress, activation of polyol pathway, inflammasome formation, Extracellular Matrix (ECM) modifications, fibrosis, and change in dynamics of podocyte functional and mesangial cell proliferation adds up to the clinical complexity of DN. Current synthetic therapeutics lacks target-specific approach, and is associated with the development of inevitable residual toxicity and drug resistance. Phytocompounds provides a vast diversity of novel compounds that can become an alternative therapeutic approach to combat the DN.

METHODS

Relevant publications were searched and screened from research databases like GOOGLE SCHOLAR, PUBMED and SCISEARCH. Out of 4895 publications, the most relevant publications were selected and included in this article.

RESULT

This study critically reviews over 60 most promising phytochemical and provides with their molecular targets, that can be of pharmacological significance in context to current treatment and concomitant research in DN.

CONCLUSION

This review highlights those most promising phytocompounds that have the potential of becoming new safer naturally-sourced therapeutic candidates and demands further attention at clinical level.

Quercetin Relieves the Excised Great Saphenous Vein Oxidative Damage and Inflammatory Reaction

Objective

The patency and quality of transplanted great saphenous vein (GSV) can seriously influence the physical state and life quality of patients who accepted the coronary artery bypass grafting (CABG). Quercetin is known for antioxidant, antithrombotic, anti-inflammatory, and antitumor properties. In this study, we examined the protection of quercetin to the great saphenous vein from oxidative and inflammatory damage.

Methods

The GSVs were collected from 15 patients undergoing CABG and cultured. Treated the veins by H₂O₂ and detected the NO, SOD, and MDA content by the relevant kits to explore the quercetin protection against oxidative damage. Then, for another group of GSVs, sheared them and detected the inflammatory cytokines, such as IL-6, TNFα, CCL20, PCNA, and VEGF. Collect the veins for H&E staining and PCNA and VEGF immunofluorescent staining.

Results

Pretreatment by quercetin reduced the production of NO and MDA induced by H₂O₂, and increased SOD activity. Quercetin also supressed the mRNA expressions of IL-6, TNFα after mechanical damage and had no influence on CCL20 and VEGF. Consistent with the lower expression of PCNA treated by quercetin, the vein intima was thinner.

Conclusion

These results demonstrated that quercetin protects GSVs by reducing the oxidative damage and inflammatory response and also suppresses the abnormal thickening of venous endothelium by inhibiting cell proliferation. It reminded that, to some extent, quercetin has the potential to release the great saphenous vein graft damage.

Quercetin and resveratrol ameliorate nickel-mediated hypercontraction in isolated Wistar rat aorta

PURPOSE

The ameliorative potential of quercetin and resveratrol on isolated endothelium-intact aortic rings incubated with nickel was examined.

METHOD

The effect of varying concentrations of quercetin and resveratrol was investigated on isolated Wistar rat aortic rings using an organ bath system over vasoconstrictor phenylephrine (PE) at 1 µM. To delineate the mechanism of action, isolated aortic rings were pre-incubated with pharmacological modulators, such as verapamil 1 µM, apocynin 100 µM, indomethacin 100 µM or N-G-nitro-L-arginine methyl ester (L-NAME) 100 µM, separately, before incubation with 100 µM quercetin and 30 µM resveratrol. To assess the ameliorative and prophylactic potentials of quercetin and resveratrol, aortic rings were also incubated with quercetin or resveratrol for 40 min, followed by incubation with nickel for 40 min.

RESULTS

At 100 µM, quercetin caused 29% inhibition of contraction, while resveratrol at 30 µM caused 55% inhibition of contraction in aortic rings compared with control. Aortic rings incubated with contractile modulators, such as verapamil, apocynin, indomethacin or N-G-nitro-L-arginine methyl ester (L-NAME), along with quercetin or resveratrol at their concentrations producing maximum relaxant effect, showed that both of these natural compounds exert their relaxant effect by inhibiting the generation of reactive oxygen species (ROS) from endothelial and smooth muscle cells, blocking voltage-gated calcium channels, and increasing the release of nitric oxide (NO). The mediation of hypercontraction by nickel is due to the increased ROS and the influx of calcium through voltage-dependent calcium channels. These natural compounds are shown to counter the nickel-induced effects, appearing as effective ameliorators.

CONCLUSION

In this study, we found that quercetin and resveratrol act as ameliorators of nickel-mediated hypercontraction by decreasing ROS and enhancing NO release from endothelial cells.

Nanoencapsulation of Polyphenols as Drugs and Supplements for Enhancing Therapeutic Profile - A Review

Polyphenolic phytoconstituents have been widely in use worldwide since ages and are categorised as secondary metabolites of plants. The application of polyphenols such as quercetin, resveratrol. curcumin as nutritional supplement has been researched widely. The use of polyphenols, and specifically quercetin for improving the memory and mental endurance have shown significant effects among rats. Even though similar results has not been resonated among human but encouraging preclinical results have encouraged researchers to explore other polyphenols to study the effects as supplements among athletes. The phytopharmacological research has elucidated the use of natural polyphenols to prevent and treat various physiological and metabolic disorders owing to its free radical scavenging properties, anti-inflammatory, anti-cancer and immunomodulatory effects. In spite of the tremendous pharmacological profile, one of the most dominant problem regarding the use of polyphenolic compounds is their low bioavailability. Nanonization is considered as one of the most prominent approaches among many. This article aims to review and discuss the molecular mechanisms of recently developed nanocarrier-based drug delivery systems for polyphenols and its application as drugs and supplements. Nanoformulations of natural polyphenols are bioactive agents, such as quercetin, kaempferol, fisetin, rutin, hesperetin, and naringenin epigalloccatechin-3-gallate, genistein, ellagic acid, gallic acid, chlorogenic acid, ferulic acid, curcuminoids and stilbenes is expected to have better efficacy. These delivery systems are expected to provide higher penetrability of polyphenols at cellular levels and exhibit a controlled release of the drugs. It is widely accepted that natural polyphenols do demonstrate significant therapeutic effect. However, the hindrances in their absorption, specificity and bioavailability can be overcome using nanotechnology.

Ethyl Acetate Fraction and Isolated Phenolics Derivatives from Mandevilla moricandiana Identified by UHPLC-DAD-ESI-MSn with Pharmacological Potential for the Improvement of Obesity-Induced Endothelial Dysfunction

Endothelial dysfunction in obesity plays a key role in the development of cardiovascular diseases, and it is characterized by increased vascular tonus and oxidative stress. Thus, this study aimed to investigate the vasodilatory and antioxidant activities of Mandevilla moricandiana ethyl acetate fraction and subfractions. Vascular effects were investigated on aorta isolated from control and monosodium glutamate (MSG) induced-obese Wistar rats, and antioxidant activity was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC) methods. The ethyl acetate fraction (MMEAF) induced a concentration-dependent vasodilation on aortic rings through the NO pathway, with the involvement of histamine H1 and estrogen ERα receptors and showed potent antioxidant activity. In aorta of MSG obese rats, maximal relaxation to acetylcholine was increased in the presence of MMEAF (3 µg/mL), indicating that MMEAF ameliorated obesity-induced endothelial dysfunction. Quercetin and kaempferol aglycones and their correspondent glycosides, as well as caffeoylquinic acid derivatives, A-type procyanidin trimer, ursolic and oleanolic triterpenoid acids were identified in subfractions from MMEAF and seem to be the metabolites responsible for the vascular and antioxidant activities of this fraction.

Rutin Modulates MAPK Pathway Differently from Quercetin in Angiotensin II-Induced H9c2 Cardiomyocyte Hypertrophy

Rutin is a flavonoid with antioxidant property. It has been shown to exert cardioprotection against cardiomyocyte hypertrophy. However, studies regarding its antihypertrophic property are still lacking, whether it demonstrates similar antihypertrophic effect to its metabolite, quercetin. Hence, this study aimed to investigate the effects of both flavonoids on oxidative stress and mitogen-activated protein kinase (MAPK) pathway in H9c2 cardiomyocytes that were exposed to angiotensin II (Ang II) to induce hypertrophy. Cardiomyocytes were exposed to Ang II (600 nM) with or without quercetin (331 μM) or rutin (50 μM) for 24 h. A group given vehicle served as the control. The concentration of the flavonoids was chosen based on the reported effective concentration to reduce cell hypertrophy or cardiac injury in H9c2 cells. Exposure to Ang II increased cell surface area, intracellular superoxide anion level, NADPH oxidase and inducible nitric oxide synthase activities, and reduced cellular superoxide dismutase activity and nitrite level, which were similarly reversed by both rutin and quercetin. Rutin had no significant effects on phosphorylated proteins of extracellular signal-related kinases (ERK1/2) and p38 but downregulated phosphorylated c-Jun N-terminal kinases (JNK1/2), which were induced by Ang II. Quercetin, on the other hand, had significantly downregulated the phosphorylated proteins of ERK1/2, p38, and JNK1/2. The quercetin inhibitory effect on JNK1/2 was stronger than the rutin. In conclusion, both flavonoids afford similar protective effects against Ang II-induced cardiomyocyte hypertrophy, but they differently modulate MAPK pathway.

Insights to potential antihypertensive activity of berry fruits

Hypertension is one of the main risk factors for cardiovascular disease and causes widespread morbidity and mortality worldwide. Although several antihypertensive drugs have been proposed for management of high blood pressure, changing lifestyle, including diet, has attracted interest recently. In this sense, consumption of fruits and vegetables, which are rich in vitamins, minerals, and phytochemicals, has been assigned as an efficient therapeutics. Berry fruits contain various bioactive compounds with potential health implications such as antioxidant, antimicrobial, anticancer, and anti-inflammatory properties. The main mechanisms responsible for antihypertensive activity mainly arise from the activity of flavonoids, minerals, and vitamins, as well as fibers. The objective of this review is to provide a summary of studies regarding the effect of berry fruits on the hypertensive animals and humans. The mechanisms involved in reducing blood pressure by each group of compounds have been highlighted. It can be concluded that berries' bioactive compounds are efficient in mitigation of hypertension through improvement of vascular function, angiotensin-converting enzyme's (ACE) inhibitory activity, increasing endothelial nitric oxide synthase (eNOS) activity, and nitric oxide (NO) production, besides anti-oxidative and anti-inflammatory activities. These fruits can be considered as potential sources of invaluable compounds for development of antihypertensive foods and pharmaceuticals.

The effect of quercetin on endothelial cells is modified by heterocellular interactions

Single cell-type models are useful for determining mechanisms, but in vivo, cell-cell interactions are important, and neighbouring cells can impact endothelial cell function. Quercetin can attenuate endothelial dysfunction by modulating vascular tone and reducing inflammation. We determined the effect of quercetin on a co-culture between Human Umbilical Vein Endothelial Cells (HUVEC) and human HepG2 hepatic cells or human LHCN-M2 muscle cells. Heme oxygenase-1 (HO-1) mRNA and protein were decreased, pyruvate dehydrogenase kinase (PDK) 4 and glucose transporter (GLUT) 3 mRNA increased, and GLUT1 protein decreased in HUVEC when cultured with HepG2. GLUT transporters, but not the other targets, were similarly regulated in co-culture with muscle cells. Some but not all of the effects were mediated by lactate and transforming growth factor β1. Quercetin added apically to the endothelial cells upregulated HO-1 and downregulated PDK4 both in monoculture and in co-culture, but the total PDK4 levels were higher in the presence of HepG2 cells. In the absence of general permeability changes, glucose transport across the endothelial monolayer was elevated in the presence of HepG2 cells, however this effect was moderated by quercetin applied on the apical side of the endothelial cells. At lower glucose concentration, apical quercetin also promoted glucose uptake in HepG2 cells. Co-culturing HUVEC with the HepG2 cells showed capacity to modulate quercetin-elicited changes in endothelial gene transcription and glucose transport.

Recent Advances in the Knowledge of Naturally-derived Bioactive Compounds as Modulating Agents of the Renin-angiotensin-aldosterone System: Therapeutic Benefits in Cardiovascular Diseases

BACKGROUND

One of the biggest challenges to public health worldwide is to reduce the number of events and deaths related to the cardiovascular diseases. Numerous approaches have been applied to reach this goal, and drug treatment intervention has been indispensable along with an effective strategy for reducing both cardiovascular morbidity and mortality. Renin-angiotensin-aldosterone system (RAAS) blockade is currently one of the most important targets of cardiovascular drug therapy. Many studies have proven the valuable properties of naturally-derived bioactive compounds to treat cardiovascular diseases.

METHODS

The goal of this review, therefore, is to discuss the recent developments related to medicinal properties about natural compounds as modulating agents of the RAAS, which have made them an attractive alternative to be available to supplement the current therapy options.

RESULTS

Data has shown that bioactive compounds isolated from several natural products act either by inhibiting the angiotensin-converting enzyme or directly by modulating the AT1 receptors of angiotensin II, which consequently changes the entire classical axis of this system.

CONCLUSION

While there are a few evidence about the positive actions of different classes of secondary metabolites for the treatment of cardiovascular and renal diseases, data is scarce about the clinical assays established to demonstrate their value in humans.

Spironolactone in Combination with α-glycosyl Isoquercitrin Prevents Steatosis-related Early Hepatocarcinogenesis in Rats through the Observed NADPH Oxidase Modulation

Administration of the diuretic, spironolactone (SR), can inhibit chronic liver diseases. We determined the effects of SR alone or in combination with the antioxidant α-glycosyl isoquercitrin (AGIQ) on hyperlipidemia- and steatosis-related precancerous lesions in high-fat diet (HFD)-fed rats subjected to a two-stage hepatocarcinogenesis model. Rats were fed with control basal diet or HFD, which was administered with SR alone or in combination with an antioxidant AGIQ in drinking water. An HFD increased body weight, intra-abdominal fat (adipose) tissue weight, and plasma lipids, which were reduced by coadministration of SR and AGIQ. SR and AGIQ coadministration also reduced hepatic steatosis and preneoplastic glutathione S-transferase placental form-positive foci, in association with decrease in NADPH oxidase (NOX) subunit p22phox-positive cells and an increase in active-caspase-3-positive cells in the foci. Hepatic gene expression analysis revealed that the coadministration of SR and AGIQ altered mRNA levels of lipogenic enzymes ( Scd1 and Fasn), antioxidant-related enzymes ( Catalase), NOX component ( P67phox), and anti-inflammatory transcriptional factor ( Pparg). Our results indicated that SR in combination with AGIQ had the potential of suppressing hyperlipidemia- and steatosis-related early hepatocarcinogenesis through the reduced expression of NOX subunits.