The Antihypertensive Effect of Quercetin in Young Spontaneously Hypertensive Rats; Role of Arachidonic Acid Metabolism

Untargeted metabolomics revealed that quercetin improves rat renal metabolic disorders induced by chronic unpredictable mild stress

Depression is a serious mental disease, and its accompanying abnormal changes in peripheral organs, including the kidney, are easy to be ignored. The metabolic abnormalities of the kidney and other organs will inevitably affect the progress of depression through the circulatory system. Quercetin has attracted much attention as a flavonoid with anti-inflammatory, antioxidant, neuroprotective, and antidepressant potential. Chronic unpredictable mild stress (CUMS) model is a reliable and effective animal model of depression. We hypothesize that quercetin has the potential to alleviate the abnormalities in renal metabolic profile induced by CUMS. An ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) platform was used to analyze renal metabolites, and the obtained data were analyzed using the Progenesis QI software for peak alignment, peak picking, and data normalization. Based on the data processing method with fold change > 2 or < 0.5, the false discovery rate corrected was p < 0.05, and a variable importance in projection score was > 1; a total of 16 differential metabolites were identified, including L-histidine, D-glucose 1-phosphate, cytidine, D-Ribulose 5-phosphate, D-xylulose 5-phosphate, uridine monophosphate (UMP), uracil, glucuronide, prostaglandin-F2α (PGF2ɑ), arachidonic acid, 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), 14,15-epoxyeicosatrienoic acid (14,15-EET), deoxycytidine, anserine, carnosine, and PC (14:0). Among them, the intensities of anserine, carnosine, L-histidine, and 14,15-EET were significantly reduced (p < 0.01), while the intensities of other metabolites were significantly increased in the CUMS group compared with the control group (p < 0.01). When CUMS model rats received high-dose quercetin treatment, the intensities of above differential metabolites were significantly restored (p < 0.05 or p < 0.01). Further, pathway enrichment analysis revealed abnormalities in arachidonic acid (AA) metabolism, pyrimidine metabolism, amino acid metabolism, and pentose and glucuronide acid interconversion in the kidney. The renal histopathological examination revealed CUMS induced renal tubular epithelial cell shedding and glomerular atrophy. High-dose quercetin can improve renal metabolic disorders and renal pathological changes caused by CUMS. Mechanistically, quercetin improves renal metabolic disorders by enhancing the antioxidant capacity and inhibiting the secretion of inflammatory factors. Moreover, quercetin can regulate renal AA metabolism disorder by inhibiting soluble epoxide hydrolase activity. High-dose quercetin (50 mg/kg bw) has a certain protective effect on kidney damage induced by CUMS, providing new strategies for quercetin to prevent depression.

A Narrative Review of Protective Effects of Natural Compounds Against Lipopolysaccharide-Induced Injuries

Lipopolysaccharide (LPS) is a large amphipathic glycoconjugate molecule in the cell wall of Gram-negative bacteria. This bacterial endotoxin binds to toll-like receptor 4 (TLR4) and stimulates the inflammatory reactions and oxidative stress. The current paper presents the protective effects of natural compounds against LPS-induced injuries. The relevant findings were extracted from PubMed, Web of Science, Scopus, and Google Scholar databases from the beginning of 2005 until the end of September 2023 were employed. The results of in vitro and in vivo studies indicated that thymoquinone, crocin, carvacrol, and quercetin effectively attenuated LPS-induced damages via lowering the level of inflammatory cytokines and free radicals. These natural compounds could also amplify the antioxidant defense against LPS by increasing the activity of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT). In addition, a part of the protective effects of these phytochemicals against detrimental impacts of LPS is attributed to their ability to downregulate the TLR4 expression and to inhibit the NF-κB signaling pathway. Briefly, the protective effects of natural compounds mentioned in current review against LPS-caused damages mainly are mediated by their anti-inflammatory and antioxidant activities.

The Role of Quercetin, a Flavonoid in the Management of Pathogenesis Through Regulation of Oxidative Stress, Inflammation, and Biological Activities

Quercetin, a flavonoid found in vegetables and fruits, has been extensively studied for its health benefits and disease management. Its role in the prevention of various pathogenesis has been well-documented, primarily through its ability to inhibit oxidative stress, inflammation, and enhance the endogenous antioxidant defense mechanisms. Electronic databases such as Google Scholar, Scopus, PubMed, Medline, and Web of Science were searched for information regarding quercetin and its role in various pathogeneses. The included literature comprised experimental studies, randomized controlled trials, and epidemiological studies related to quercetin, while editorials, case analyses, theses, and letters were excluded. It has been reported to have a wide range of health benefits including hepatoprotective, antidiabetic, anti-obesity, neuroprotective, cardioprotective, wound healing, antimicrobial, and immunomodulatory effects, achieved through the modulation of various biological activities. Additionally, numerous in vitro and in vivo studies have shown that quercetin's efficacies in cancer management involve inhibiting cell signaling pathways, such as inflammation, cell cycle, and angiogenesis, activating cell signaling pathways including tumor suppressor genes, and inducing apoptosis. This review aims to provide a comprehensive understanding of the health benefits of quercetin in various pathogeneses. Additionally, this review outlines the sources of quercetin, nanoformulations, and its applications in health management, along with key findings from important clinical trial studies. Limited clinical data regarding quercetin's safety and mechanism of action are available. It is important to conduct more clinical trials to gain a deeper understanding of the disease-preventive potential, mechanisms of action, safety, and optimal therapeutic dosages. Furthermore, more research based on nanoformulations should be performed to minimize/overcome the hindrance associated with bioavailability, rapid degradation, and toxicity.

Decreased blood pressure with acute administration of quercetin in L-NAME-induced hypertensive rats

Quercetin is known to reduce blood pressure (BP); however, its acute effects are unclear. We investigated the acute effects of quercetin on BP, aortic mechanical properties and vascular reactivity in female Sprague-Dawley (SD) rats. Hypertension was induced using L-NAME (40 mg/kg/day). Quercetin (4.5 mg/kg) was administered intravenously. Mechanical properties of the aortae were measured by echo-tracking in normotensive and hypertensive rats. L-NAME and quercetin quantities in the aorta were determined using AP-MALDI-MSI. Vascular reactivity was performed in mesenteric and renal arteries. L-NAME increased BP and PWVβ while decreasing strain. Quercetin decreased BP and ameliorated PWVβ in L-NAME-induced hypertensive rats. Ex vivo, the acetylcholine (ACh)-induced increase in tension at 100 μM was reduced in renal arteries when exposed to quercetin while phenylephrine (Phe)-induced contractile response was augmented. In quiescent rings of renal arteries incubated with L-NAME (10 μM) and TRAM-34 (1 μM), the ACh-induced vasoconstrictions were inhibited by quercetin. Quercetin resulted in concentration-dependent vasodilation in mesenteric arteries and increased its sensitivity to ACh-induced relaxations. Quercetin lowered BP in L-NAME-induced hypertensive rats, likely due to changes in aortic mechanical properties and relaxation of resistance arteries. Further research is warranted to clarify the acute effects of quercetin on renal arteries in this hypertensive model.

Unrevealing the mechanisms behind the cardioprotective effect of wheat polyphenolics

Cardiovascular diseases pose a major threat to both life expectancy and quality of life worldwide, and a concerning level of disease burden has been attained, particularly in middle- and low-income nations. Several drugs presently in use lead to multiple adverse events. Thus, it is urgently needed to develop safe, affordable, and effective management of cardiovascular diseases. Emerging evidence reveals a positive association between polyphenol consumption and cardioprotection. Whole wheat grain and allied products are good sources of polyphenolic compounds bearing enormous cardioprotective potential. Polyphenolic extract of the entire wheat grain contains different phenolic compounds viz. ferulic acid, caffeic acid, chlorogenic acid, p-coumaric acid, sinapic acid, syringic acid, vanillic acid, apigenin, quercetin, luteolin, etc. which exert cardioprotection by reducing oxidative stress and interfering with different toxicological processes. The antioxidant capacity has been thought to exert the cardioprotective mechanism of wheat grain polyphenolics, which predominantly suppresses oxidative stress, inflammation and fibrosis by downregulating several pathogenic signaling events. However, the combined effect of polyphenolics appears to be more prominent than that of a single molecule, which might be attained due to the synergy resulting in multimodal cardioprotective benefits from multiple phenolics. The current article covers the bioaccessibility and possible effects of wheat-derived polyphenolics in protecting against several cardiovascular disorders. This review discusses the mechanistic pharmacology of individual wheat polyphenols on the cardiovascular system. It also highlights the comparative superiority of polyphenolic extracts over a single phenolic.

Polysaccharide Based Self-Driven Tubular Micro/Nanomotors as a Comprehensive Platform for Quercetin Loading and Anti-inflammatory Function

Quercetin (QR) is a natural flavonoid with strong anti-inflammatory properties, but it suffers from poor water solubility and bioavailability. Micro/nanomotors (NMs) are tiny devices that convert external energy or chemical fuels into an autonomous motion. They are characterized by their small size, rapid movement, and self-assembly capabilities, which can enhance the delivery of bioactive ingredients. The study synthesized natural polysaccharide-based nanotubes (NTs) using a layer-by-layer self-assembly method and combined with urease (Ure), glucose oxidase (GOx), and Fe3O4 to create three types of NMs. These NMs were well-dispersed and biocompatible. In vitro experiments showed that NMs-Fe3O4 has excellent photothermal conversion properties and potential for use in photothermal therapy. Cellular inflammation model results demonstrated that QR-loaded NMs were not only structurally stable but also improved bioavailability and effectively inhibited the release of inflammatory mediators such as IL-1β and IL-6, providing a safe and advanced carrier system for the effective use of bioactive components in food.

Inhibition of soluble epoxide hydrolase by natural isothiocyanates

GOAL

The long-term goal of our research is to develop safe and effective soluble epoxide hydrolase (sEH) inhibitors. The objective of this study is to evaluate the potency and selectivity of six natural isothiocyanates (ITCs) as sEH inhibitors.

METHODS

Molecular docking was used to model likely interactions between the ligands and receptors. The sEH inhibitory activity was tested using a validated fluorescence-based assay and PHOME as a substrate. To evaluate their selectivity as sEH inhibitors, the inhibitory potential of the ITCs was determined on microsomal epoxide hydrolase (mEH) and cytochrome P450 (CYP) enzymes in human liver microsomes. Probe substrates such as styrene oxide (mEH substrate) and established substrates for CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 were used in this study. The metabolites of these substrates were analyzed using validated LC-MS/MS and HPLC-UV assays.

RESULTS

Molecular Docking revealed significant differences in binding site preference among the ITCs in silico and pointed to important interactions between the ligands and the catalytic residues of the sEH enzyme. In vitro, the ITCs showed varying degrees of sEH inhibition, but sulforaphane (SFN) and phenyl isothiocyanate (PITC) were the most potent inhibitors with IC50 values of 3.65 and 7.5 μM, respectively. mEH was not significantly inhibited by any of the ITCs. Erucin and iberin were the only ITCs that did not inhibit the activity of any of the tested CYP enzymes.

CONCLUSION

Our results demonstrate that natural ITCs have the potential to offer safe, selective, and potent sEH inhibition.

Quercetin Protects Against Hypertensive Renal Injury by Attenuating Apoptosis: An Integrated Approach Using Network Pharmacology and RNA Sequencing

ABSTRACT

Quercetin is known for its antihypertensive effects. However, its role on hypertensive renal injury has not been fully elucidated. In this study, hematoxylin and eosin staining, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining, and Annexin V staining were used to assess the pathological changes and cell apoptosis in the renal tissues of angiotensin II (Ang II)-infused mice and Ang II-stimulated renal tubular epithelial cell line (NRK-52E). A variety of technologies, including network pharmacology, RNA-sequencing, immunohistochemistry, and Western blotting, were performed to investigate its underlying mechanisms. Network pharmacology analysis identified multiple potential candidate targets (including TP53, Bcl-2, and Bax) and enriched signaling pathways (including apoptosis and p53 signaling pathway). Quercetin treatment significantly alleviated the pathological changes in renal tissues of Ang II-infused mice and reversed 464 differentially expressed transcripts, as well as enriched several signaling pathways, including those related apoptosis and p53 pathway. Furthermore, quercetin treatment significantly inhibited the cell apoptosis in renal tissues of Ang II-infused mice and Ang II-stimulated NRK-52E cells. In addition, quercetin treatment inhibited the upregulation of p53, Bax, cleaved-caspase-9, and cleaved-caspase-3 protein expression and the downregulation of Bcl-2 protein expression in both renal tissue of Ang II-infused mice and Ang II-stimulated NRK-52E cells. Moreover, the molecular docking results indicated a potential binding interaction between quercetin and TP53. Quercetin treatment significantly attenuated hypertensive renal injury and cell apoptosis in renal tissues of Ang II-infused mice and Ang II-stimulated NRK-52E cells and by targeting p53 may be one of the potential underlying mechanisms.

Dietary Polyphenols against Oxidative Stress in Head and Neck Cancer: What's New, What's Next

Head and neck cancers (HNC) are a worldwide health problem, accounting for over 5% of all types of cancers. Their varied nature makes it sometimes difficult to find clear explanations for the molecular mechanisms that underline their onset and development. While chemio- and radiotherapy are clearly not to be dismissed, we cannot undervalue the effect that polyphenols - especially dietary polyphenols - can have in helping us to cope with this medical emergency. By influencing several different proteins involved in numerous different metabolic pathways, polyphenols can have a broad spectrum of biological action and can hopefully act synergistically to tackle down head and neck cancer. Moreover, being natural molecules, polyphenols does not present any side effects and can even enhance drugs efficacy, making our clinical therapy against head and neck cancer more and more effective. Certainly, oxidative stress plays an important role, altering several molecular pathways, lowering the body's defenses, and ultimately helping to create a microenvironment conducive to the appearance and development of the tumor. In this regard, the regular and constant intake of foods rich in polyphenols can help counteract the onset of oxidative stress, improving the health of the general population. In this review, we highlight the role of polyphenols in managing oxidative stress, with such positive effects that they can be considered new tools to use in our anti-head and neck cancer strategy.

Thymus atlanticus: A Source of Nutrients with Numerous Health Benefits and Important Therapeutic Potential for Age-Related Diseases

Thymus atlanticus (Lamiaceae) is a plant endemic to the Mediterranean basin that is found in significant quantities in the arid regions of Morocco. Thymus atlanticus is used in traditional medicine to treat infectious and non-infectious diseases. It is also used for the isolation of essential oils and for the seasoning of many dishes in the Mediterranean diet. The major constituents of Thymus atlanticus are saponins, flavonoids, tannins, alkaloids, various simple and hydroxycinnamic phenolic compounds, and terpene compounds. Several of these compounds act on signaling pathways of oxidative stress, inflammation, and blood sugar, which are parameters often dysregulated during aging. Due to its physiochemical characteristics and biological activities, Thymus atlanticus could be used for the prevention and/or treatment of age-related diseases. These different aspects are treated in the present review, and we focused on phytochemistry and major age-related diseases: dyslipidemia, cardiovascular diseases, and type 2 diabetes.

Quercetin attenuates angiotensin II-induced proliferation of vascular smooth muscle cells and p53 pathway activation in vitro and in vivo

Quercetin is an essential flavonoid mostly found in herbal plants, fruits, and vegetables, which exhibits anti-hypertension properties. However, its pharmacological impact on angiotensin II (Ang II) induced the increase of blood pressure along with in-depth mechanism needs further exploration. The present study pointed out the anti-hypertensive role of quercetin and its comprehensive fundamental mechanisms. Our data showed that quercetin treatment substantially reduced the increase in blood pressure, pulse wave velocity, and aortic thickness of abdominal aorta in Ang II-infused C57BL/6 mice. RNA sequencing revealed that quercetin treatment reversed 464 differentially expressed transcripts in the abdominal aorta of Ang II-infused mice. Moreover, overlapping KEGG-enriched signaling pathways identified multiple common pathways between the comparison of Ang II versus control and Ang II + quercetin versus Ang II. Likewise, these pathways included cell cycle as well as p53 pathways. Transcriptome was further validated by immunohistochemistry, indicating that quercetin treatment significantly decreased the Ang II-induced expression of proliferating cell nuclear antigen (PCNA), cyclin-dependent kinase-4 (CDK4), and cyclin D1, while increased protein expression of p53, and p21 in abdominal aortic tissues of mice. In vitro, quercetin treatment meaningfully decreased the cell viability, arrested cell cycle at G0/G1 phase, and up-regulated the p53 and p21 proteins expression, as well as down-regulated the protein expression of cell cycle-related markers, for example, CDK4, cyclin D1 in Ang II stimulated vascular smooth muscle cells (VSMCs). This study addresses pharmacologic and mechanistic perspectives of quercetin against Ang-II-induced vascular injury and the increase of blood pressure.

Bio-Actives from Natural Products with Potential Cardioprotective Properties: Isolation, Identification, and Pharmacological Actions of Apigenin, Quercetin, and Silibinin

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide. As a result, pharmaceutical and non-pharmaceutical interventions modifying risk factors for CVDs are a top priority of scientific research. Non-pharmaceutical therapeutical approaches, including herbal supplements, have gained growing interest from researchers as part of the therapeutic strategies for primary or secondary prevention of CVDs. Several experimental studies have supported the potential effects of apigenin, quercetin, and silibinin as beneficial supplements in cohorts at risk of CVDs. Accordingly, this comprehensive review focused critically on the cardioprotective effects/mechanisms of the abovementioned three bio-active compounds from natural products. For this purpose, we have included in vitro, preclinical, and clinical studies associated with atherosclerosis and a wide variety of cardiovascular risk factors (hypertension, diabetes, dyslipidemia, obesity, cardiac injury, and metabolic syndrome). In addition, we attempted to summarize and categorize the laboratory methods for their isolation and identification from plant extracts. This review unveiled many uncertainties which are still unexplored, such as the extrapolation of experimental results to clinical practice, mainly due to the small clinical studies, heterogeneous doses, divergent constituents, and the absence of pharmacodynamic/pharmacokinetic analyses.

Therapeutic effect of oral quercetin in hamsters infected with Leishmania Viannia braziliensis

Leishmaniasis is a parasitic disease caused by several species of intracellular protozoa of the genus Leishmania that present manifestations ranging from cutaneous ulcers to the fatal visceral form. Leishmania Viannia braziliensis is an important species associated with American tegumentary leishmaniasis and the main agent in Brazil, with variable sensitivity to available drugs. The search for new therapeutic alternatives to treat leishmaniasis is an urgent need, especially for endemic countries. Not only is quercetin well known for its antioxidant activity in radical scavenging but also several other biological effects are described, including anti-inflammatory, antimicrobial, and pro-oxidant activities. This study aimed to investigate the flavonoid quercetin's therapeutic potential in L. (V.) braziliensis infection. Quercetin showed antiamastigote (IC50 of 21 ± 2.5 µM) and antipromastigote (25 ± 0.7 µM) activities and a selectivity index of 22. The treatment of uninfected or L. (V.) braziliensis-infected macrophages with quercetin increased reactive oxygen species (ROS)/H202 generation without altering Nitric Oxide (NO) production. Oral treatment with quercetin of infected hamsters, starting at 1 week of infection for 8 weeks, reduced the lesion thickness (p > 0.01) and parasite load (p > 0.001). The results of this study suggest that the antiamastigote activity of the flavonoid quercetin in vitro is associated, at least in part, with the modulation of ROS production by macrophages. The efficacy of oral quercetin treatment in hamsters infected with L. (V.) braziliensis was presented for the first time and shows its promising therapeutic potential.

Integrating serum pharmacochemistry and network pharmacology to identify chemical markers for quality control of Apocyni Veneti Folium

INTRODUCTION

Apocyni Veneti Folium (AVF) is a commonly used traditional Chinese medicinal herb for the treatment of hypertension. Chemical markers are crucial for the quality control of herbal medicines; however, the therapeutic components of AVF remain to be well elucidated.

OBJECTIVES

This study was intended to integrate serum pharmacochemistry and network pharmacology to identify chemical markers of AVF and establish an efficacy-related quality control method of AVF.

MATERIAL AND METHODS

Ultra-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UPLC-QTOF-MS/MS) was applied to identify the absorbed AVF constituents in rat serum. Network pharmacology was further used to identify anti-hypertension-related chemical markers. Subsequently, a quantitative method was established using UPLC with diode array detection (DAD) and applied for quality evaluation of commercial AVF samples.

RESULTS

Thirteen prototype constituents were unequivocally or tentatively characterized in serum samples, among which quercetin, kaempferol, hyperoside, isoquercitrin, chlorogenic acid, cryptochlorogenic acid, and neochlorogenic acid were identified as dominant chemicals related to anti-hypertensive efficacy. The quantitative data showed that the total contents of seven marker components even showed 2-fold variation among 14 batches of commercial AVF samples with RSD values ranging from 12.15% to 75.61%. Hierarchical cluster analysis and heatmap analysis showed that 14 batches of commercial AVF samples could be divided into three main groups.

CONCLUSION

The chemical markers obtained from this study could be applicable for efficacy-related quality control of AVF.

Taxillus chinensis (DC.) Danser: a comprehensive review on botany, traditional uses, phytochemistry, pharmacology, and toxicology

BACKGROUND

Taxillus chinensis (DC.) Danser (T. chinensis), known as "Sangjisheng" in Chinese, is a member of the family Loranthaceae, with the traditional functions of "dispelling wind dampness, strengthening bones and muscles, and preventing miscarriage". Since Eastern Han dynasty, it has been used for the treatment of rheumatoid arthritis, arthralgia, threatened abortion, and hypertension. Nowadays, T. chinensis is included in the 2020 Edition of the Chinese Pharmacopoeia as Taxilli Herba. The purpose of this review is to summarize the latest research on T. chinensis in recent years, and make critical comments, so as to provide reference for the clinical application and modern research of T. chinensis.

MAIN BODY

In this review, we summarize the botany, traditional uses, and research advances in the phytochemistry and pharmacological effects of T. chinensis. Its toxicity has also been discussed. The published literature on current pharmacological and toxicological data has also been assessed. To date, approximately 110 compounds, including flavonoids, phenolic acids, phenylpropanoids, tannins, glycosides, amino acids, and nucleosides, have been identified in T. chinensis. Flavonoids are considered the most vital bioactive ingredients in T. chinensis. Pharmacological studies have demonstrated that T. chinensis possesses anti-inflammatory, antioxidant, anticancer, antimicrobial, antiviral, diuretic, antihypertensive, antihyperglycemic, and other properties.

CONCLUSION

Currently, research on T. chinensis is in the preliminary stages, and further research is required to understand the active compounds present and mechanisms of action. We hope that this comprehensive review of T. chinensis will serve as a background for further research.

Catechin Reduces Blood Pressure in Spontaneously Hypertensive Rats through Modulation of Arachidonic Acid Metabolism

(1) Background: hypertension affects approximately half of the adults in the United States (roughly 116 million). The cytochrome P450 (CYP)-mediated metabolism of arachidonic acid (AA) in the kidney has been found to play a major role in the pathogenesis of hypertension. This study examines the anti-hypertensive effect of the natural polyphenolic compound catechin (CAT) and investigates if it impacts the metabolism of AA in the kidney in comparison to captopril (CAP): a commonly used antihypertensive drug. (2) Methods: spontaneously hypertensive rats (SHR) were randomly divided into five groups. The treatment groups were administered CAT in drinking water at doses of 10 and 50 mg/kg. A positive control group received CAP at a dose of 10 mg/kg in the drinking water, and one group received both CAP and CAT at doses of 10 mg/kg and 50 mg/kg, respectively. Blood pressure was monitored weekly for five weeks. The activity of the two major enzymes involved in AA metabolism in the kidney, namely CYP4A and soluble epoxide hydrolase (sEH), were analyzed. (3) Results: CAP monotherapy was found to reduce blood pressure compared to the control untreated rats but did not demonstrate any effect on AA metabolism. Low- and high-dose CAT resisted the rise in blood pressure observed in the untreated SHR and significantly lowered blood pressure compared to the control group, respectively. Only rats treated with high CAT doses demonstrated significant inhibition of CYP4A and sEH enzyme activities. The coadministration of CAP and a high dose of CAT resulted in more pronounced blood pressure-lowering effects, but no more significant effects on AA metabolism were found compared to a high dose of CAT alone. (4) Conclusion: the modulation of AA metabolism in the kidney contributes, at least partially, to the blood pressure-lowering effect of CAT in SHR rats.

Quercetin inhibits angiotensin II-induced vascular smooth muscle cell proliferation and activation of JAK2/STAT3 pathway: A target based networking pharmacology approach

The rapid growth of vascular smooth muscle cells (VSMCs) represents crucial pathological changes during the development of hypertensive vascular remodeling. Although quercetin exhibits significantly therapeutic effects on antihypertension, the systematic role of quercetin and its exact mode of action in relation to the VSMCs growth and its hypertension-related networking pharmacology is not well-documented. Therefore, the effect of quercetin was investigated using networking pharmacology followed by in vitro strategies to explore its efficacy against angiotensin II (Ang II)-induced cell proliferation. Putative genes of hypertension and quercetin were collected using database mining, and their correlation was investigated. Subsequently, a network of protein-protein interactions was constructed and gene ontology (GO) analysis was performed to identify the role of important genes (including CCND1) and key signaling pathways [including cell proliferation and Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway]. We therefore further investigated the effects of quercetin in Ang II-stimulated VSMCs. This current research revealed that quercetin significantly reduced the cell confluency, cell number, and cell viability, as well as expression of proliferating cell nuclear antigen (PCNA) in Ang II-stimulated VSMCs. Mechanistic study by western blotting confirmed that quercetin treatment attenuated the activation of JAK2 and STAT3 by reducing its phosphorylation in Ang II stimulated VSMCs. Collectively, the current study revealed the inhibitory effects of quercetin on proliferation of Ang II stimulated VSMCs, by inhibiting the activation of JAK2/STAT3 signaling might be one of underlying mechanisms.

Protective effect of quercetin on kidney diseases: From chemistry to herbal medicines

Kidney injuries may trigger renal fibrosis and lead to chronic kidney disease (CKD), but effective therapeutic strategies are still limited. Quercetin is a natural flavonoid widely distributed in herbal medicines. A large number of studies have demonstrated that quercetin may protect kidneys by alleviating renal toxicity, apoptosis, fibrosis and inflammation in a variety of kidney diseases. Therefore, quercetin could be one of the promising drugs in the treatment of renal disorders. In the present study, we review the latest progress and highlight the beneficial role of quercetin in kidney diseases and its underlying mechanisms. The pharmacokinetics and bioavailability of quercetin and its proportion in herbal medicine will also be discussed.

Potential Pharmaceutical Applications of Quercetin in Cardiovascular Diseases

Quercetin, as a member of flavonoids, has emerged as a potential therapeutic agent in cardiovascular diseases (CVDs) in recent decades. In this comprehensive literature review, our goal was a critical appraisal of the pathophysiological mechanisms of quercetin in relation to the classical cardiovascular risk factors (e.g., hyperlipidemia), atherosclerosis, etc. We also assessed experimental and clinical data about its potential application in CVDs. Experimental studies including both in vitro methods and in vivo animal models mainly outline the following effects of quercetin: (1) antihypertensive, (2) hypolipidemic, (3) hypoglycemic, (4) anti-atherosclerotic, and (5) cardioprotective (suppressed cardiotoxicity). From the clinical point of view, there are human studies and meta-analyses implicating its beneficial effects on glycemic and lipid parameters. In contrast, other human studies failed to demonstrate consistent favorable effects of quercetin on other cardiometabolic risk factors such as MS, obesity, and hypertension, underlying the need for further investigation. Analyzing the reason of this inconsistency, we identified significant drawbacks in the clinical trials’ design, while the absence of pharmacokinetic/pharmacodynamic tests prior to the studies attenuated the power of clinical results. Therefore, additional well-designed preclinical and clinical studies are required to examine the therapeutic mechanisms and clinical efficacy of quercetin in CVDs.

Combined use of systemic quercetin, glutamine and alpha-tocopherol attenuates myocardial fibrosis in diabetic rats

This study aimed to analyze the effects of the quercetin (100 mg/kg), 1% glutamine and 1% α-tocopherol antioxidants in the myocardium of rats with streptozotocin-induced diabetes mellitus. Twenty male rats were subdivided into four groups (n = 5): N (normoglycemic); D (diabetic); NT (normoglycemic treated with antioxidants); and DT (diabetic treated with antioxidants) treated for 60 days. Clinical parameters, oxidative stress markers, inflammatory cytokines, myocardial collagen fibers and immunoexpression of superoxide dismutase 1 (SOD-1), glutathione peroxidase-1 (GPx-1), interleukin-1β (IL-1-β), transforming growth factor-beta (TGF-β), and fibroblast growth factor-2 (FGF-2) were evaluated. Results showed reduced body weight, hyperphagia, polydipsia and hyperglycemic state in groups D and DT. The levels of glutathione (GSH) were higher in NT and DT compared to N (p < 0.01) and D (p < 0.001) groups, respectively. Greater GSH levels were found in DT when compared to N animals (p < 0.001). In DT, there was an increase in IL-10 in relation to N, D and NT (p < 0.05), while GPx-1 expression was similar to N and lower compared to D (p < 0.001). TGF-β expression in DT was greater than N (p < 0.001) group, whereas FGF-2 in DT was higher than in the other groups (p < 0.001). A significant reduction in collagen fibers (type I) was found in DT compared to D (p < 0.05). The associated administration of quercetin, glutamine and α-tocopherol increased the levels of circulating interleukin-10 (IL-10) and GSH, and reduced the number of type I collagen fibers. Combined use of systemic quercetin, glutamine and alpha-tocopherol attenuates myocardial fibrosis in diabetic rats.

The Modulation of Arachidonic Acid Metabolism and Blood Pressure-Lowering Effect of Honokiol in Spontaneously Hypertensive Rats

Background: Cardiovascular diseases have consistently been the leading cause of death in the United States over the last two decades, with 30% of the adult American population having hypertension. The metabolites of arachidonic acid (AA) in the kidney play an important role in blood pressure regulation. The present study investigates the antihypertensive effect of honokiol (HON), a naturally occurring polyphenol, and examines its correlation to the modulation of AA metabolism. Methods: Spontaneously hypertensive rats (SHR) were randomly divided into four groups. Treatment groups were administered HON intraperitoneally at concentrations of 5, 20, and 50 mg/kg. Blood pressure was monitored at seven-day intervals. After a total of 3 weeks of treatment, the rats were euthanized and the kidney tissues were collected to examine the activity of the two major enzymes involved in AA metabolism in the kidney, namely cytochrome P450 (CYP)4A and soluble epoxide hydrolase (sEH). Results: Rats treated with HON did not experience the rise in blood pressure observed in the untreated SHR. High-dose HON significantly reduced blood pressure and inhibited the activity and protein expression of the CYP4A enzyme in the rat kidney. The activity of the sEH enzyme in renal cytosol was significantly inhibited by medium and high doses of HON. Conclusion: Our data demonstrate the antihypertensive effect of HON and provide a novel mechanism for its underlying cardioprotective properties.

Targeting Cardiovascular Diseases by Flavonols: An Update

Flavonols are one of the most plentiful flavonoid subclasses found in natural products and are extensively used as dietary supplements. Numerous in vitro and in vivo studies have shown the cardioprotective properties of flavonols, especially quercetin. This group of substances exerts positive impacts primarily due to their antiatherogenic, antithrombotic, and antioxidant activities. The potential of flavonols to promote vasodilation and regulation of apoptotic processes in the endothelium are other beneficial effects on the cardiovascular system. Despite promising experimental findings, randomized controlled trials and meta-analyses have yielded inconsistent results on the influence of these substances on human cardiovascular parameters. Thus, this review aims to summarize the most recent clinical data on the intake of these substances and their effects on the cardiovascular system. The present study will help clinicians and other healthcare workers understand the value of flavonol supplementation in both subjects at risk for cardiovascular disease and patients with cardiovascular diseases.

O-Glycoside quercetin derivatives: Biological activities, mechanisms of action, and structure-activity relationship for drug design, a review

Quercetin as a valuable natural flavonoid has shown extensive biological activities, including anticancer, antioxidant, antibacterial, antiinflammatory, anti-Alzheimer, antifungal, antiviral, antithalassemia, iron chelation, antiobesity, antidiabetic, antihypertension, and antiphospholipase A2 (PLA2) activities, by the modulation of various targets and signaling pathways that have attracted much attention. However, the low solubility and poor bioavailability of quercetin have limited its applications; therefore, the researchers have tried to design and synthesize many new derivatives of quercetin through different strategies to modify quercetin restrictions and improve its biological activities. This review categorized the O-glycoside derivatives of Quercetin into two main classes, 3-O-glycoside and other O-glycoside derivatives. Also, it studied biological activities, structure-activity relationship (SAR), and the action mechanism of O-glycoside quercetin derivatives. Overall, we summarized past and present research for discovering new potent lead compounds.

Quercetin derivatives: Drug design, development, and biological activities, a review

More studies are needed to develop new drugs for problems associated with drug resistance and unfavorable side effects. The natural flavonoid of quercetin revealed a wide range of biological activities by the modulation of various targets and signaling pathways. However, quercetin's low solubility and poor bioavailability have restricted its applicability; as a result, researchers have attempted to design and synthesize numerous novel quercetin derivatives using various methodologies in order to modify quercetin's constraints; the physico-chemical properties of quercetin's molecular scaffold make it appealing for drug development; low molecular mass and chemical groups are two of these characteristics. Therefore, the biological activities of quercetin derivatives, as well as the relationship between activity and chemical structure and their mechanism of action, were investigated. These quercetin-based molecules could be valuable in the creation and discovery of medications for a number of diseases.

Quercetin Attenuates Cardiac Hypertrophy by Inhibiting Mitochondrial Dysfunction Through SIRT3/PARP-1 Pathway

Cardiac hypertrophy is an important characteristic in the development of hypertensive heart disease. Mitochondrial dysfunction plays an important role in the pathology of cardiac hypertrophy. Recent studies have shown that sirtuin 3 (SIRT3)/poly (ADP-ribose) polymerase-1 (PARP-1) pathway modulation inhibits cardiac hypertrophy. Quercetin, a natural flavonol agent, has been reported to attenuate cardiac hypertrophy. However, the molecular mechanism is not completely elucidated. In this study, we aimed to explore the mechanism underlying the protective effect of quercetin on cardiac hypertrophy. Spontaneously hypertensive rats (SHRs) were treated with quercetin (20 mg/kg/d) for 8 weeks to evaluate the effects of quercetin on blood pressure and cardiac hypertrophy. Additionally, the mitochondrial protective effect of quercetin was assessed in H9c2 cells treated with Ang II. SHRs displayed aggravated cardiac hypertrophy and fibrosis, which were attenuated by quercetin treatment. Quercetin also improved cardiac function, reduced mitochondrial superoxide and protected mitochondrial structure in vivo. In vitro, Ang II increased the mRNA level of hypertrophic markers including atrial natriuretic factor (ANF) and β-myosin heavy chain (β-MHC), whereas quercetin ameliorated this hypertrophic response. Moreover, quercetin prevented mitochondrial function against Ang II induction. Importantly, mitochondrial protection and PARP-1 inhibition by quercetin were partly abolished after SIRT3 knockdown. Our results suggested that quercetin protected mitochondrial function by modulating SIRT3/PARP-1 pathway, contributing to the inhibition of cardiac hypertrophy.

Quercetin: A Bioactive Compound Imparting Cardiovascular and Neuroprotective Benefits: Scope for Exploring Fresh Produce, Their Wastes, and By-Products

Quercetin, a bioactive secondary metabolite, holds incredible importance in terms of bioactivities, which has been proved by in vivo and in vitro studies. The treatment of cardiovascular and neurological diseases by quercetin has been extensively investigated over the past decade. Quercetin is present naturally in appreciable amounts in fresh produce (fruits and vegetables). However, today, corresponding to the growing population and global demand for fresh fruits and vegetables, a paradigm shift and focus is laid towards exploring industrial food wastes and/or byproducts as a new resource to obtain bioactive compounds such as quercetin. Based on the available research reports over the last decade, quercetin has been suggested as a reliable therapeutic candidate for either treating or alleviating health issues, mainly those of cardiovascular and neurological diseases. In the present review, we have summarized some of the critical findings and hypotheses of quercetin from the available databases foreseeing its future use as a potential therapeutic agent to treat cardiovascular and neurological diseases. It is anticipated that this review will be a potential reference material for future research activities to be undertaken on quercetin obtained from fresh produce as well as their respective processing wastes/byproducts that rely on the circular concept.

Matrix Metalloproteinases and Their Role in Mechanisms Underlying Effects of Quercetin on Heart Function in Aged Zucker Diabetic Fatty Rats

Several mechanisms may contribute to cardiovascular pathology associated with diabetes, including dysregulation of matrix metalloproteinases (MMPs). Quercetin (QCT) is a substance with preventive effects in treatment of cardiovascular diseases and diabetes. The aim of the present study was to explore effects of chronic QCT administration on changes in heart function in aged lean and obese Zucker Diabetic Fatty (ZDF) rats and that in association with MMPs. Signaling underlying effects of diabetes and QCT were also investigated. In the study, we used one-year-old lean and obese ZDF rats treated for 6 weeks with QCT. Results showed that obesity worsened heart function and this was associated with MMP-2 upregulation, MMP-28 downregulation, and inhibition of superoxide dismutases (SODs). Treatment with QCT did not modulate diabetes-induced changes in heart function and MMPs. However, QCT activated Akt kinase and reversed effects of diabetes on SODs inhibition. In conclusion, worsened heart function due to obesity involved changes in MMP-2 and MMP-28 and attenuation of antioxidant defense by SOD. QCT did not have positive effects on improvement of heart function or modulation of MMPs. Nevertheless, its application mediated activation of adaptive responses against oxidative stress through Akt kinase and prevention of diabetes-induced negative effects on antioxidant defense by SODs.