Suppressive effects of the flavonoids quercetin and luteolin on the accumulation of lipid rafts after signal transduction via receptors

The Potential Use of Vitamin D3 and Phytochemicals for Their Anti-Ageing Effects

Unlike other vitamins, vitamin D3 is synthesised in skin cells in the body. Vitamin D3 has been known as a bone-related hormone. Recently, however, it has been considered as an immune vitamin. Vitamin D3 deficiency influences the onset of a variety of diseases. Vitamin D3 regulates the production of proinflammatory cytokines such as tumour necrosis factor-α (TNF-α) through binding to vitamin D receptors (VDRs) in immune cells. Since blood levels of vitamin D3 (25-OH-D3) were low in coronavirus disease 2019 (COVID-19) patients, there has been growing interest in the importance of vitamin D3 to maintaining a healthy condition. On the other hand, phytochemicals are compounds derived from plants with over 7000 varieties and have various biological activities. They mainly have health-promoting effects and are classified as terpenoids, carotenoids, flavonoids, etc. Flavonoids are known as the anti-inflammatory compounds that control TNF-α production. Chronic inflammation is induced by the continuous production of TNF-α and is the fundamental cause of diseases like obesity, dyslipidaemia, diabetes, heart and brain diseases, autoimmune diseases, Alzheimer's disease, and cancer. In addition, the ageing process is induced by chronic inflammation. This review explains the cooperative effects of vitamin D3 and phytochemicals in the suppression of inflammatory responses, how it balances the natural immune response, and its link to anti-ageing effects. In addition, vitamin D3 and phytochemicals synergistically contribute to anti-ageing by working with ageing-related genes. Furthermore, prevention of ageing processes induced by the chronic inflammation requires the maintenance of healthy gut microbiota, which is related to daily dietary habits. In this regard, supplementation of vitamin D3 and phytochemicals plays an important role. Recently, the association of the prevention of the non-disease condition called "ME-BYO" with the maintenance of a healthy condition has been an attractive regimen, and the anti-ageing effect discussed here is important for a healthy and long life.

Molecular docking as a tool for the discovery of novel insight about the role of acid sphingomyelinase inhibitors in SARS- CoV-2 infectivity

Recently, COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants, caused > 6 million deaths. Symptoms included respiratory strain and complications, leading to severe pneumonia. SARS-CoV-2 attaches to the ACE-2 receptor of the host cell membrane to enter. Targeting the SARS-CoV-2 entry may effectively inhibit infection. Acid sphingomyelinase (ASMase) is a lysosomal protein that catalyzes the conversion of sphingolipid (sphingomyelin) to ceramide. Ceramide molecules aggregate/assemble on the plasma membrane to form "platforms" that facilitate the viral intake into the cell. Impairing the ASMase activity will eventually disrupt viral entry into the cell. In this review, we identified the metabolism of sphingolipids, sphingolipids' role in cell signal transduction cascades, and viral infection mechanisms. Also, we outlined ASMase structure and underlying mechanisms inhibiting viral entry 40 with the aid of inhibitors of acid sphingomyelinase (FIASMAs). In silico molecular docking analyses of FIASMAs with inhibitors revealed that dilazep (S = - 12.58 kcal/mol), emetine (S = - 11.65 kcal/mol), pimozide (S = - 11.29 kcal/mol), carvedilol (S = - 11.28 kcal/mol), mebeverine (S = - 11.14 kcal/mol), cepharanthine (S = - 11.06 kcal/mol), hydroxyzin (S = - 10.96 kcal/mol), astemizole (S = - 10.81 kcal/mol), sertindole (S = - 10.55 kcal/mol), and bepridil (S = - 10.47 kcal/mol) have higher inhibition activity than the candidate drug amiodarone (S = - 10.43 kcal/mol), making them better options for inhibition.

Decrease in cholesterol in the cell membrane is essential for Nrf2 activation by quercetin

Quercetin is a flavonoid with various cytoprotective effects. We previously reported that quercetin exerts anti-allergic, anti-oxidative, and anti-fibrotic activities via the induction of heme oxygenase (HO)-1. However, the mechanisms by which quercetin induces HO-1 to exhibit cytoprotective effects are poorly understood. We focused on its action on the cell membrane, which is the first part of the cell to interact with the extracellular environment. The cell membrane contains lipid rafts and caveolae, which play important roles in cellular signaling. A recent study showed that nuclear factor E2-related factor 2 (Nrf2), a transcription factor regulating anti-oxidative enzymes including HO-1, interacts with caveolin-1 (Cav-1), a component of caveolae, to regulate cellular anti-oxidative capacity. In this study, we investigated the changes in the cell membrane that leads to the induction of HO-1 by quercetin. Quercetin decreased the amount of cholesterol in the raft fractions, which in turn promoted the induction of HO-1. It also changed the composition of the lipid rafts and decreased and increased the expression of Cav-1 in the raft and non-raft fractions, respectively. Nrf2, which was localized in the cell membrane under resting conditions, was translocated along with Cav-1 to the nucleus after exposure to quercetin. These findings indicate for the first time that the HO-1-dependent cytoprotective effects of quercetin are mediated by the structural changes in lipid rafts brought about by decreasing the amount of cholesterol in the cell membrane, which thereby results in the translocation of the Cav-1-Nrf2 complex to the nucleus and induces the expression of HO-1.

Prevention of Metabolic Syndrome by Phytochemicals and Vitamin D

In recent years, attention has focused on the roles of phytochemicals in fruits and vegetables in maintaining and improving the intestinal environment and preventing metabolic syndrome. A high-fat and high-sugar diet, lack of exercise, and excess energy accumulation in the body can cause metabolic syndrome and induce obesity, diabetes, and disorders of the circulatory system and liver. Therefore, the prevention of metabolic syndrome is important. The current review shows that the simultaneous intake of phytochemicals contained in citruses and grapes together with vitamin D improves the state of gut microbiota and immunity, preventing metabolic syndrome and related diseases. Phytochemicals contained in citruses include polyphenols such as hesperidin, rutin, and naringin; those in grapes include quercetin, procyanidin, and oleanolic acid. The intake of these phytochemicals and vitamin D, along with prebiotics and probiotics, nurture good gut microbiota. In general, Firmicutes are obese-prone gut microbiota and Bacteroidetes are lean-prone gut microbiota; good gut microbiota nurture regulatory T cells, which suppress inflammatory responses and upregulate immunity. Maintaining good gut microbiota suppresses TNF-α, an inflammatory cytokine that is also considered to be a pathogenic contributor adipokine, and prevents chronic inflammation, thereby helping to prevent metabolic syndrome. Maintaining good gut microbiota also enhances adiponectin, a protector adipokine that prevents metabolic syndrome. For the prevention of metabolic syndrome and the reduction of various disease risks, the intake of phytochemicals and vitamin D will be important for human health in the future.

Potential of Compounds Originating from the Nature to Act in Hepatocellular Carcinoma Therapy by Targeting the Tumor Immunosuppressive Microenvironment: A Review

Hepatocellular carcinoma (HCC), the most prevalent subtype of liver cancer, is the second main reason for cancer-related deaths worldwide. In recent decades, sufficient evidence supported that immunotherapy was a safe and effective treatment option for HCC. However, tolerance and frequent recurrence and metastasis occurred in patients after immunotherapy due to the complicated crosstalk in the tumor immunosuppressive microenvironment (TIME) in HCC. Therefore, elucidating the TIME in HCC and finding novel modulators to target TIME for attenuating immune suppression is critical to optimize immunotherapy. Recently, studies have shown the potentially immunoregulatory activities of natural compounds, characterized by multiple targets and pathways and low toxicity. In this review, we concluded the unique role of TIME in HCC. Moreover, we summarized evidence that supports the hypothesis of natural compounds to target TIME to improve immunotherapy. Furthermore, we discussed the comprehensive mechanisms of these natural compounds in the immunotherapy of HCC. Accordingly, we present a well-grounded review of the naturally occurring compounds in cancer immunotherapy, expecting to shed new light on discovering novel anti-HCC immunomodulatory drugs from natural sources.

Systematic Understanding of the Mechanisms of Flos Chrysanthemi Indici-mediated Effects on Hypertension via Computational Target Fishing

AIMS AND OBJECTIVE

Hypertension-induced stroke and coronary artery disease are significant causes of global morbidity and mortality. Metabolic hypertension has recently become the leading cause of hypertension. Flos Chrysanthemi Indici (CIF) has a long history as a treatment of hypertension as part of traditional Chinese medicine. However, its mechanisms of activity remain largely unknown. This study was aimed to uncover the potential anti-hypertensive mechanisms of CIF based on network pharmacology.

MATERIALS AND METHODS

In this research, a systems pharmacology approach integrating the measurement of active compounds, target fishing, gene screening, Gene Ontology (GO) pathway analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) Orthology Based Annotation System (KOBAS) database analysis, and compound-target network construction were performed to explore the anti-hypertensive mechanisms of CIF.

RESULTS

These studies revealed that 12 bioactive compounds in CIF had good druggability, 5 of which were flavonoids. After screening, 8 of those 12 bioactive compounds interacted with 118 hypertensionrelated target genes, which were mapped to 218 signal pathways. Network analysis showed that these targets were associated with improving insulin resistance, improving vascular function, inhibiting renninangiotensin- aldosterone system (RAAS), inhibiting the sympathetic nervous system (SNS) and regulating other physiological processes.

CONCLUSION

In summary, CIF is predicted to target multiple proteins and pathways to form a network that exerts systematic pharmacological effects in order to regulate blood pressure and metabolic disorder.

Interaction of drugs with lipid raft membrane domains as a possible target

Introduction

Plasma membranes are not the homogeneous bilayers of uniformly distributed lipids but the lipid complex with laterally separated lipid raft membrane domains, which provide receptor, ion channel and enzyme proteins with a platform. The aim of this article is to review the mechanistic interaction of drugs with membrane lipid rafts and address the question whether drugs induce physicochemical changes in raft-constituting and raft-surrounding membranes.

Methods

Literature searches of PubMed/MEDLINE and Google Scholar databases from 2000 to 2020 were conducted to include articles published in English in internationally recognized journals. Collected articles were independently reviewed by title, abstract and text for relevance.

Results

The literature search indicated that pharmacologically diverse drugs interact with raft model membranes and cellular membrane lipid rafts. They could physicochemically modify functional protein-localizing membrane lipid rafts and the membranes surrounding such domains, affecting the raft organizational integrity with the resultant exhibition of pharmacological activity. Raft-acting drugs were characterized as ones to decrease membrane fluidity, induce liquid-ordered phase or order plasma membranes, leading to lipid raft formation; and ones to increase membrane fluidity, induce liquid-disordered phase or reduce phase transition temperature, leading to lipid raft disruption.

Conclusion

Targeting lipid raft membrane domains would open a new way for drug design and development. Since angiotensin-converting enzyme 2 receptors which are a cell-specific target of and responsible for the cellular entry of novel coronavirus are localized in lipid rafts, agents that specifically disrupt the relevant rafts may be a drug against coronavirus disease 2019.

Allergy Modulation by N-3 Long Chain Polyunsaturated Fatty Acids and Fat Soluble Nutrients of the Mediterranean Diet

The Mediterranean diet, containing valuable nutrients such as n-3 long chain poly-unsaturated fatty acids (LCPUFAs) and other fat-soluble micronutrients, is known for its health promoting and anti-inflammatory effects. Its valuable elements might help in the battle against the rising prevalence of non-communicable diseases (NCD), including the development of allergic diseases and other (chronic) inflammatory diseases. The fat fraction of the Mediterranean diet contains bioactive fatty acids but can also serve as a matrix to dissolve and increase the uptake of fat-soluble vitamins and phytochemicals, such as luteolin, quercetin, resveratrol and lycopene with known immunomodulatory and anti-inflammatory capacities. Especially n-3 LCPUFAs such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) derived from marine oils can target specific receptors or signaling cascades, act as eicosanoid precursors and/or alter membrane fluidity and lipid raft formation, hereby exhibiting anti-inflammatory properties. Beyond n-3 LCPUFAs, fat-soluble vitamins A, D, E, and K1/2 have the potential to affect pro-inflammatory signaling cascades by interacting with receptors or activating/inhibiting signaling proteins or phosphorylation in immune cells (DCs, T-cells, mast cells) involved in allergic sensitization or the elicitation/effector phase of allergic reactions. Moreover, fat-soluble plant-derived phytochemicals can manipulate signaling cascades, mostly by interacting with other receptors or signaling proteins compared to those modified by fat-soluble vitamins, suggesting potential additive or synergistic actions by applying a combination of these nutrients which are all part of the regular Mediterranean diet. Research concerning the effects of phytochemicals such as polyphenols has been hampered due to their poor bio-availability. However, their solubility and uptake are improved by applying them within the dietary fat matrix. Alternatively, they can be prepared for targeted delivery by means of pharmaceutical approaches such as encapsulation within liposomes or even unique nanoparticles. This review illuminates the molecular mechanisms of action and possible immunomodulatory effects of n-3 LCPUFAs and fat-soluble micronutrients from the Mediterranean diet in allergic disease development and allergic inflammation. This will enable us to further appreciate how to make use of the beneficial effects of n-3 LCPUFAs, fat-soluble vitamins and a selection of phytochemicals as active biological components in allergy prevention and/or symptom reduction.

Potential Therapeutic Targets of Quercetin and Its Derivatives: Its Role in the Therapy of Cognitive Impairment

Quercetin (QC) is a flavonoid and crucial bioactive compound found in a variety of vegetables and fruits. In preclinical studies, QC has demonstrated broad activity against several diseases and disorders. According to recent investigations, QC is a potential therapeutic candidate for the treatment of nervous system illnesses because of its protective role against oxidative damage and neuroinflammation. QC acts on several molecular signals, including ion channels, neuroreceptors, and inflammatory receptor signaling, and it also regulates neurotrophic and anti-oxidative signaling molecules. While the study of QC in neurological disorders has focused on numerous target molecules, the role of QC on certain molecular targets such as G-protein coupled and nuclear receptors remains to be investigated. Our analysis presents several molecular targets of QC and its derivatives that demonstrate the pharmacological potential against cognitive impairment. Consequently, this article may guide future studies using QC and its analogs on specific signaling molecules. Finding new molecular targets of QC and its analogs may ultimately assist in the treatment of cognitive impairment.

The Potential Use of Grape Phytochemicals for Preventing the Development of Intestine-Related and Subsequent Inflammatory Diseases

BACKGROUND

Grape phytochemicals prevent intestine-related and subsequent other inflammatory diseases. Phytochemicals and vitamin D are useful for the regulation of inflammatory responses. Phytochemicals is the generic name for terpenoids, carotenoids, and flavonoids that consist of a variety of chemicals contained in vegetables and fruits. There are a variety of grape cultivars that contain many kinds of phytochemicals in their skin and seeds. Grape phytochemicals including Grape Seed Extracts (GSE) have already been used to maintain healthy condition through manipulating inflammatory responses by decreasing the expression of inflammation-related factors.

DISCUSSION

Grape phytochemicals mainly consist of a variety of chemicals that include terpenoid (oleanolic acid), carotenoids (β-carotene, lutein), and flavonoids: flavon-3-ols (quercetin), flavan-3-ols (catechins), anthocyanins, oligomers and polymers (tannins and proanthocyanidins), and resveratrol. Phytochemicals improve the dysbiosis (gut microbiota complication) induced by metabolic syndrome and regulate inflammatory diseases induced by TNF-α production. Once absorbed, flavonoids change into glucuronide-form, move into the bloodstream and reach the inflammatory sites including liver, lung, and sites of arteriosclerosis, where they become active. Furthermore, oleanolic acid acts on TGR5 - the cholic acid receptor, as an agonist of cholic acid. These anti-inflammatory effects of phytochemicals have been proven by the experimental animal studies and the clinical trials.

CONCLUSION

It is expected the new health food products will be created from grape skins and seeds since grape phytochemicals participate in the prevention of inflammatory diseases like intestine-related inflammatory diseases.

Pretreatment with quercetin prevents changes in lymphocytes E-NTPDase/E-ADA activities and cytokines secretion in hyperlipidemic rats

Hyperlipidemia (HL) is a condition associated with endothelial dysfunction and inflammatory disorders. Purinergic system ectoenzymes play an important role in modulating the inflammatory and immune response. This study investigated whether the preventive treatment with quercetin is able to prevent changes caused by hyperlipidemia in the purinergic system, through the activities of E-NTPDase and E-ADA in lymphocytes, and quantify the nucleotides and nucleoside, and the secretion of anti- and proinflammatory cytokines. Animals were divided into saline/control, saline/quercetin 5 mg/kg, saline/quercetin 25 mg/kg, saline/quercetin 50 mg/kg, saline/simvastatin (0.04 mg/kg), hyperlipidemia, hyperlipidemia/quercetin 5 mg/kg, hyperlipidemia/quercetin 25 mg/kg, hyperlipidemia/quercetin 50 mg/kg, and hyperlipidemia/simvastatin. Animals were pretreated with quercetin for 30 days and hyperlipidemia was subsequently induced by intraperitoneal administration of 500 mg/kg of poloxamer-407. Simvastatin was administered after the induction of hyperlipidemia. Lymphocytes were isolated and E-NTPDase and E-ADA activities were determined. Serum was separated for the cytokines and nucleotide/nucleoside quantification. E-NTPDase and E-ADA activities were increased in lymphocytes from hyperlipidemic rats and pretreatment with quercetin was able to prevent the increase in the activities of these enzymes caused by hyperlipidemia. Hyperlipidemic rats when receiving pretreatment with quercetin and treatment with simvastatin showed decreased levels of ATP and ADP when compared to the untreated hyperlipidemic group. The IFN-γ and IL-4 cytokines were increased in the hyperlipidemic group when compared with control group, and decreased when hyperlipidemic rats received the pretreatment with quercetin. However, pretreatment with quercetin was able to prevent the alterations caused by hyperlipidemia probably by regulating the inflammatory process. We can suggest that the quercetin is a promising compound to be used as an adjuvant in the treatment of hyperlipidemia.

LPS-induced renal inflammation is prevented by (-)-epicatechin in rats

This work investigated the capacity of (−)-epicatechin to prevent the renal damage induced by LPS administration in rats. Male Sprague Dawley rats were fed for 4 days a diet without or with supplementation with (−)-epicatechin (80 mg/kg BW/d), and subsequently i.p. injected with lipopolysaccharide (LPS). Six hours after injection, LPS-treated rats exhibited increased plasma creatinine and urea levels as indicators of impaired renal function. The renal cortex of the LPS-treated rats showed: i) increased expression of inflammatory molecules (TNF-α, iNOS and IL-6); ii) activation of several steps of NF-κB pathway; iii) overexpression of TLR4, and iv) higher superoxide anion production and lipid peroxidation index in association with increased levels of gp91^phox and p47^phox (NOX2) and NOX4. Pretreatment with dietary (−)-epicatechin prevented the adverse effects of LPS challenge essentially by inhibiting TLR4 upregulation and NOX activation and the consequent downstream events, e.g. NF-kB activation.

Quercetin Suppresses the Migration and Invasion in Human Colon Cancer Caco-2 Cells Through Regulating Toll-like Receptor 4/Nuclear Factor-kappa B Pathway

Objective:

The migration and invasion features, which were associated with inflammatory response, acted as vital roles in the development of colon cancer. Quercetin, a bioflavonoid compound, was widely spread in vegetables and fruits. Although quercetin exerts antioxidant and anticancer activities, the molecular signaling pathways in human colon cancer cells remain unclear. Hence, the present study was conducted to investigate the suppression of quercetin on migratory and invasive activity of colon cancer and the underlying mechanism.

Materials and Methods:

The effect of quercetin on cell viability, migration, and invasion of Caco-2 cells was analyzed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, wound-healing assay, and transwell chambers assay, respectively. The protein expressions of toll-like receptor 4 (TLR4), nuclear factor-kappa B (NF-κB) p65, mitochondrial membrane potential-2 (MMP-2), and MMP-9 were detected by Western blot assay. The inflammatory factors, such as tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (Cox-2), and interleukin-6 (IL-6), in cell supernatant were detected by enzyme-linked immunosorbent assay.

Results:

The concentration of quercetin <20 μM was chosen for further experiments. Quercetin (5 μM) could remarkably suppress the migratory and invasive capacity of Caco-2 cells. The expressions of metastasis-related proteins of MMP-2, MMP-9 were decreased, whereas the expression of E-cadherin protein was increased by quercetin in a dose-dependent manner. Interestingly, the anti-TLR4 (2 μg) antibody or pyrrolidine dithiocarbamate (PDTC; 1 μM) could affect the inhibition of quercetin on cell migration and invasion, as well as the protein expressions of MMP-2, MMP-9, E-cadherin, TLR4, and NF-κB p65. In addition, quercetin could reduce the inflammation factors production of TNF-α, Cox-2, and IL-6.

Conclusion:

The findings suggested for the 1^st time that quercetin might exert its anticolon cancer activity via the TLR4- and/or NF-κB-mediated signaling pathway.

SUMMARY

Quercetin could remarkably suppress the migratory and invasive capacity of Caco-2 cells

The expressions of metastasis-related proteins of mitochondrial membrane potential-2 (MMP-2), MMP-9 were decreased, whereas the expression of E-cadherin protein was increased by quercetin in a dose-dependent manner

The anti-toll-like receptor 4 (TLR4) antibody or pyrrolidine dithiocarbamate affected the inhibition of quercetin on cell migration and invasion, as well as the protein expressions of MMP-2, MMP-9, E-cadherin, TLR4, and nuclear factor-kappa B p65

Quercetin could reduce the inflammation factors production of tumor necrosis factors-α, cyclooxygenase-2, and interleukin-6.

Abbreviations used: MTT: 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphen yltetrazolium bromide, TLR4: Toll-like receptor 4, NF-κB: Nuclear factor-kappa B, MMP-2: Mitochondrial membrane potential-2, MMP-9: Mitochondrial membrane potential-9, TNF-α: Tumor necrosis factor-α, Cox-2: Cyclooxygenase-2, IL-6: Interleukin-6, ELISA: Enzyme-linked immunosorbent assay, PDTC: Pyrrolidine dithiocarbamate, ROS: Reactive oxygen species, DMSO: Dimethyl sulfoxide, FBS: Fetal bovine serum, DMEM: Dulbecco modified Eagle medium, OD: Optical density, IPP: Image Pro-plus, PBS: Phosphate buffered saline, SD: Standard deviation, ANOVA: One-way analysis of variance, SPSS: Statistical Package for the Social Sciences, ECM: Extracellular matrix, TLRs: Toll-like receptors, LPS: Lipopolysaccharide.

Flavonoids Affect Host-Microbiota Crosstalk through TLR Modulation

Interaction between host cells and microbes is known as crosstalk. Among other mechanisms, this takes place when certain molecules of the micro-organisms are recognized by the toll-like receptors (TLRs) in the body cells, mainly in the intestinal epithelial cells and in the immune cells. TLRs belong to the pattern-recognition receptors and represent the first line of defense against pathogens, playing a pivotal role in both innate and adaptive immunity. Dysregulation in the activity of such receptors can lead to the development of chronic and severe inflammation as well as immunological disorders. Among components present in the diet, flavonoids have been suggested as antioxidant dietary factors able to modulate TLR-mediated signaling pathways. This review focuses on the molecular targets involved in the modulatory action of flavonoids on TLR-mediated signaling pathways, providing an overview of the mechanisms involved in such action. Particular flavonoids have been able to modify the composition of the microbiota, to modulate TLR gene and protein expression, and to regulate the downstream signaling molecules involved in the TLR pathway. These synergistic mechanisms suggest the role of some flavonoids in the preventive effect on certain chronic diseases.

Polyphenols and the modulation of gene expression pathways: can we eat our way out of the danger of chronic disease?

Plant-derived dietary polyphenols may improve some disease states and promote health. Experimental evidence suggests that this is partially attributable to changes in gene expression. The rational use of bioactive food components may therefore present an opportunity to activate or repress selected gene expression pathways and, consequently, to manage or prevent disease. It remains to be determined whether this use of bioactive food components can be done safely. This article reviews the associated controversies and limitations of polyphenol therapy. There is a paucity of clinical data on the rational use of polyphenols, including a lack of knowledge on effective dosage, actual chemical formulations, bioavailability, distribution in tissues, the effect of genetic variations, differences in gut microflora, the synergistic (or antagonistic) effects observed in extracts, and the possible interaction between polyphenols and lipid domains of cell membranes that may alter the function of relevant receptors. The seminal question of why plants make substances that benefit humans remains unanswered, and there is still much to learn in terms of correlative versus causal effects of human exposure to various nutrients. The available data strongly suggest significant effects at the molecular level that represent interactions with the epigenome. The advent of relatively simple technologies is helping the field of epigenetics progress and facilitating the acquisition of multiple types of data that were previously difficult to obtain. In this review, we summarize the molecular basis of the epigenetic regulation of gene expression and the epigenetic changes associated with the consumption of polyphenols that illustrate how modifications in human nutrition may become relevant to health and disease.

Molecular promiscuity of plant polyphenols in the management of age-related diseases: far beyond their antioxidant properties

The use of plant-derived polyphenols for the management of diseases has been under debate in the last decades. Most studies have focused on the specific effects of polyphenols on particular targets, while ignoring their pleiotropic character. The multitargeted character of polyphenols, a plausible consequence of their molecular promiscuity, may suppose an opportunity to fight multifactorial diseases. Therefore, a wider perspective is urgently needed to elucidate whether their rational use as bioactive food components may be valid for the management of diseases. In this chapter, we discuss the most likely targets of polyphenols that may account for their salutary effects from a global perspective. Among these targets, the modulation of signalling and energy-sensitive pathways, oxidative stress and inflammation-related processes, mitochondrial functionality, epigenetic machinery, histone acetylation and membrane-dependent processes play central roles in polyphenols' mechanisms of action.Sufficient evidence on polyphenols has accumulated for them to be considered a serious option for the management of non-communicable diseases, such as cancer and obesity, as well as infectious diseases. The remaining unresolved issues that must be seriously addressed are their bioavailability, metabolite detection, specific molecular targets, interactions and toxicity. The Xenohormesis hypothesis, which postulates that polyphenols are the product of plant evolutive adaptation to stress and conferee their resistance to mammals, offers a reasonable explanation to justify the beneficial and non-toxic effects of plant mixtures, but do not fully meet expectations. Hence, future research must be supported by the use of complex polypharmacology approaches and synergic studies focused on the understanding of the pleiotropic effects of polyphenols. Revisiting polyphenol mechanisms of action with the help of these techniques may allow for the improvement of human health and wellness by using intelligent nutritional intervention.

Achyrocline satureioides (Lam.) D.C. Hydroalcoholic Extract Inhibits Neutrophil Functions Related to Innate Host Defense

Achyrocline satureioides (Lam.) D.C. is a herb native to South America, and its inflorescences are popularly employed to treat inflammatory diseases. Here, the effects of the in vivo actions of the hydroalcoholic extract obtained from inflorescences of A. satureioides on neutrophil trafficking into inflamed tissue were investigated. Male Wistar rats were orally treated with A. satureioides extract, and inflammation was induced one hour later by lipopolysaccharide injection into the subcutaneous tissue. The number of leukocytes and the amount of chemotactic mediators were quantified in the inflammatory exudate, and adhesion molecule and toll-like receptor 4 (TLR-4) expressions and phorbol-myristate-acetate- (PMA-) stimulated oxidative burst were quantified in circulating neutrophils. Leukocyte-endothelial interactions were quantified in the mesentery tissue. Enzymes and tissue morphology of the liver and kidney were evaluated. Treatment with A. satureioides extract reduced neutrophil influx and secretion of leukotriene B4 and CINC-1 in the exudates, the number of rolling and adhered leukocytes in the mesentery postcapillary venules, neutrophil L-selectin, β 2-integrin and TLR-4 expression, and oxidative burst, but did not cause an alteration in the morphology and activities of liver and kidney. Together, the data show that A. satureioides extract inhibits neutrophil functions related to the innate response and does not cause systemic toxicity.

Quercetin modulates activities of Taiwan cobra phospholipase A2 via its effects on membrane structure and membrane-bound mode of phospholipase A2

The goal of the present study is to elucidate the mechanism of quercetin on modulating Naja naja atra phospholipase A2 (PLA2) activities. Sphingomyelin inhibited PLA2 enzymatic activity and membrane-damaging activity against egg yolk phosphatidylcholine (EYPC), while cholesterol and quercetin abrogated the sphingomeyelin inhibitory effect. Quercetin incorporation led to a reduction in PLA2 enzymatic activity and membrane-damaging activity toward EYPC/sphingomyelin/cholesterol vesicles. Both cholesterol and quercetin increased detergent resistance and reduced membrane fluidity of EYPC/sphingomyelin vesicles. Quercetin reduced detergent insolubility but increased ordered lipid packing of EYPC/sphingomyelin/cholesterol vesicles. Acrylamide quenching studies and trinitrophenylation of Lys residues revealed that quercetin altered the membrane-bound mode of PLA2 differently upon absorption onto the membrane bilayers of different lipid compositions. However, 8-anilinonaphthalene sulphonate-binding assay revealed that quercetin marginally affected the interaction between active site of PLA2 with phospholipid vesicles. Collectively, our data indicate that membrane-inserted quercetin modulates PLA2 interfacial activity and membrane-damaging activity via its effects on membrane structure and membrane-bound mode of PLA2.

Effects of quercetin on exercise potential and exercise-induced cytokines in the horse

The goal of this experiment was to test the hypothesis that quercetin would alter markers of athletic performance as well as markers of exercise-induced inflammation. Six healthy, unfit Standardbred mares (∼500 kg, age 4-5 years) were assigned to one of two treatments (quercetin or water) in an experiment conducted in a crossover fashion. The horses were dosed via a nasogastric tube twice a day (08:00 and 20:00) with either 6 g of quercetin in 2 l tap water or 2 l water for 3.5 d. Two hours after the seventh and final dose, a graded exercise test (GXT) was run. During the test the treadmill remained at a fixed 6% grade. At t=0 the treadmill was started at a speed of 4 m/s. Each following minute the treadmill speed was increased by 1 m/s, up to a maximum speed of 11 m/s. Blood and muscle samples were collected before the initial dosing, before exercise and after the GXT to measure markers of inflammation. There was a significant (P<0.10) increase in run time to fatigue when the horses were dosed with quercetin. The VO2recovery time was shortened significantly when compared to water-treated trials. There were exercise-induced increases (P<0.10) in haematocrit and the plasma concentrations of total protein, glucose, and lactate as well as expression of mRNA for TNF-α, IL-1, interferon-γ, granzyme-B (GrB) in blood. However, quercetin only affected (P<0.10) the expression of mRNA for GrB. Intramuscular levels of IL-1 and GrB also increased significantly with exercise, but there was no effect (P≯0.10) from quercetin treatment. This study provides evidence that quercetin could be useful in enhancing exercise performance, although the mechanism for this enhancement is unclear.

Effects of flavonoids and other polyphenols on inflammation

Flavonoids are a family of polyphenolic compounds which are widespread in nature (vegetables) and are consumed as part of the human diet in significant amounts. There are other types of polyphenols, including, for example, tannins and resveratrol. Flavonoids and related polyphenolic compounds have significant antiinflammatory activity, among others. This short review summarizes the current knowledge on the effects of flavonoids and related polyphenolic compounds on inflammation, with a focus on structural requirements, the mechanisms involved, and pharmacokinetic considerations. Different molecular (cyclooxygenase, lipoxygenase) and cellular targets (macrophages, lymphocytes, epithelial cells, endothelium) have been identified. In addition, many flavonoids display significant antioxidant/radical scavenging properties. There is substantial structural variation in these compounds, which is bound to have an impact on their biological profile, and specifically on their effects on inflammatory conditions. However, in general terms there is substantial consistency in the effects of these compounds despite considerable structural variations. The mechanisms have been studied mainly in myeloid cells, where the predominant effect is an inhibition of NF-κB signaling and the downregulation of the expression of proinflammatory markers. At present there is a gap in knowledge of in vitro and in vivo effects, although the pharmacokinetics of flavonoids has advanced considerably in the last decade. Many flavonoids have been studied for their intestinal antiinflammatory activity which is only logical, since the gastrointestinal tract is naturally exposed to them. However, their potential therapeutic application in inflammation is not restricted to this organ and extends to other sites and conditions, including arthritis, asthma, encephalomyelitis, and atherosclerosis, among others.

Immunomodulatory, beta-cell, and neuroprotective actions of fenugreek oil from alloxan-induced diabetes

Immunological disorders and nephropathy are among the most frequent and serious complications of diabetes mellitus. This shows that fewer infiltrated inflammatory cells evidenced by reverted back to near the normal value of white blood cell, mean corpuscular volume, and lymphocytes counts as interleukin-6 in pancreas. Also, fenugreek oil significantly improved blood glucose levels, glucose intolerance, and insulin sensitivity compared to the diabetic group. The pancreatic islet and less beta-cells damage were observed after the administration of fenugreek oil to diabetic rats. Moreover, diabetic rats showed low activities of superoxide dismutase, catalase, glutathione peroxidase, and reduced glutathione content in kidney, which were restored to near normal levels by treatment with fenugreek oil. The increased levels of lipid peroxidation, creatinine, albumin, and urea in diabetic rats decreased significantly in diabetic rats treated with fenugreek oil. Diabetic rats treated with fenugreek oil restored almost a normal architecture of pancreas and kidney. In conclusion, this study reveals the efficacy of fenugreek oil in the amelioration of diabetes, hematological status, and renal toxicity which may be attributed to its immunomodulatory activity and insulin stimulation action along with its antioxidant potential.

Flavonoids exert distinct modulatory actions on cyclooxygenase 2 and NF-kappaB in an intestinal epithelial cell line (IEC18)

BACKGROUND AND PURPOSE

Cyclooxygenase 2 (COX-2) is involved in inflammatory bowel disease, but the effect of flavonoids at the intestinal epithelial level is unknown. We aimed to characterize the effect and structure-activity relationship of nine selected flavonoids on COX-2 expression in intestinal epithelial cell (IEC)18 cells. We also investigated the signal transduction pathway(s) responsible for the effects observed.

EXPERIMENTAL APPROACH

Intestinal epithelial cell 18, a non-tumour cell line with intestinal epithelial phenotype, was used. COX-2 was measured by Western blot and the involvement of the NF-kappaB pathway assessed by Western blot, pharmacological inhibition, luciferase reporter assays and nuclear translocation experiments.

KEY RESULTS

The effect of flavonoids on COX-2 expression depended on the experimental conditions tested [non-stimulated and lipopolysaccharide (LPS)-stimulated]. Flavonoids caused an increase in COX-2 expression and NF-kappaB-dependent gene transcription under basal conditions. Conversely, under LPS stimulation flavonoids increased, decreased or did not affect COX-2 levels depending on the specific type. Variable effects were observed on extracellular signal regulated kinase/p38/c-Jun N-terminal kinase phosphorylation and p50/65 nuclear translocation.

CONCLUSION AND IMPLICATIONS

The effect of flavonoids on COX-2 expression depended on the balance of the interference with IkappaB-alpha phosphorylation and other signalling targets, and therefore depends on the experimental conditions and on the type of flavonoids. This is expected to result in different effects in inflammatory conditions. In general, flavonoids may limit epithelial COX-2 expression in inflammatory conditions while favouring it when inflammation is not present.

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.