Effect of quercetin on paraoxonase 2 levels in RAW264.7 macrophages and in human monocytes--role of quercetin metabolism

Quercetin promotes the proportion and maturation of NK cells by binding to MYH9 and improves cognitive functions in aged mice

BACKGROUND

Quercetin is a flavonol compound widely distributed in plants that possesses diverse biological properties, including antioxidative, anti-inflammatory, anticancer, neuroprotective and senescent cell-clearing activities. It has been shown to effectively alleviate neurodegenerative diseases and enhance cognitive functions in various models. The immune system has been implicated in the regulation of brain function and cognitive abilities. However, it remains unclear whether quercetin enhances cognitive functions by interacting with the immune system.

RESULTS

In this study, middle-aged female mice were administered quercetin via tail vein injection. Quercetin increased the proportion of NK cells, without affecting T or B cells, and improved cognitive performance. Depletion of NK cells significantly reduces cognitive ability in mice. RNA-seq analysis revealed that quercetin modulated the RNA profile of hippocampal tissues in aging animals towards a more youthful state. In vitro, quercetin significantly inhibited the differentiation of Lin-CD117+ hematopoietic stem cells into NK cells. Furthermore, quercetin promoted the proportion and maturation of NK cells by binding to the MYH9 protein.

CONCLUSIONS

In summary, our findings suggest that quercetin promotes the proportion and maturation of NK cells by binding to the MYH9 protein, thereby improving cognitive performance in middle-aged mice.

A critical examination of human data for the biological activity of quercetin and its phase-2 conjugates

This critical review examines evidence for beneficial effects of quercetin phase-2 conjugates from clinical intervention studies, volunteer feeding trials, and in vitro work. Plasma concentrations of quercetin-3-O-glucuronide (Q3G) and 3'-methylquercetin-3-O-glucuronide (3'MQ3G) after supplementation may produce beneficial effects in macrophages and endothelial cells, respectively, especially if endogenous deglucuronidation occurs, and lower blood uric acid concentration via quercetin-3'-O-sulfate (Q3'S). Unsupplemented diets produce much lower concentrations (<50 nmol/l) rarely investigated in vitro. At 10 nmol/l, Q3'S and Q3G stimulate or suppress, respectively, angiogenesis in endothelial cells. Statistically significant effects have been reported at 100 nmol/l in breast cancer cells (Q3G), primary neuron cultures (Q3G), lymphocytes (Q3G and3'MQ3G) and HUVECs (QG/QS mixture), but it is unclear whether these translate to a health benefit in vivo. More sensitive and more precise methods to measure clinically significant endpoints are required before a conclusion can be drawn regarding effects at normal dietary concentrations. Future requirements include better understanding of inter-individual and temporal variation in plasma quercetin phase-2 conjugates, their mechanisms of action including deglucuronidation and desulfation both in vitro and in vivo, tissue accumulation and washout, as well as potential for synergy or antagonism with other quercetin metabolites and metabolites of other dietary phytochemicals.

Insights on Quercetin Therapeutic Potential for Neurodegenerative Diseases and its Nano-technological Perspectives

The neurodegeneration process begins in conjunction with the aging of the neurons. It manifests in different parts of the brain as Aβ plaques, neurofibrillary tangles, Lewy bodies, Pick bodies, and other structures, which leads to progressive loss or death of neurons. Quercetin (QC) is a flavonoid compound found in fruits, tea, and other edible plants have antioxidant effects that have been studied from subcellular compartments to tissue levels in the brain. Also, quercetin has been reported to possess a neuroprotective role by decreasing oxidative stress-induced neuronal cell damage. The use of QC for neurodegenerative therapy, the existence of the blood-brain barrier (BBB) remains a significant barrier to improving the clinical effectiveness of the drug, so finding an innovative solution to develop simultaneous BBB-crossing ability of drugs for treating neurodegenerative disorders and improving neurological outcomes is crucial. The nanoparticle formulation of QC is considered beneficial and useful for its delivery through this route for the treatment of neurodegenerative diseases seems necessary. Increased QC accumulation in the brain tissue and more significant improvements in tissue and cellular levels are among the benefits of QC-involved nanostructures.

Quercetin as a possible complementary therapy in multiple sclerosis: Anti-oxidative, anti-inflammatory and remyelination potential properties

Multiple sclerosis (MS) is a complex autoimmune disorder of the central nervous system (CNS) which causes various symptoms such as fatigue, dyscoordination weakness and visual weakness. The intricacy of the immune system and obscure etiology are the main reasons for the lack of a definite treatment for MS. Oxidative stress is one of the most important key factors in MS pathogenesis. It can enhance inflammation, neurodegeneration and autoimmune-mediated processes, which can lead to excessive demyelination and axonal disruption. Recently, promising effects of Quercetin as a non-pharmacological anti-oxidant therapy have been reported in preclinical studies of MS disease. In this review, we provide a compendium of preclinical and clinical studies that have investigated the effects of Quercetin on MS disease to evaluate its potential utility as a complementary therapy in MS. Quercetin treatment in MS disease not only protects the CNS against oxidative stress and neuroinflammation, but it also declines the demyelination process and promotes remyelination potential. The present study clarifies the reported knowledge on the beneficial effects of Quercetin against MS, with future implication as a neuroprotective complementary therapy.

Behavioral and biochemical investigations to explore the efficacy of quercetin and folacin in experimental diabetes induced vascular endothelium dysfunction and associated dementia in rats

OBJECTIVES

Vascular dementia (VaD), being strongly associated with metabolic conditions is a major health concern around the world. Diabetes is a major risk factor for the development of VaD. This study investigates the efficacy of quercetin and folacin in diabetes induced vascular endothelium dysfunction and related dementia.

METHODS

Single dose streptozotocin (STZ) (50 mg/kg i.p) was administered to albino Wistar rats (male, 200-250 g) by dissolving in citrate buffer. Morris water maze (MWM) and attentional set shifting tests were used to assess the spatial learning, memory, reversal learning, and executive functioning in animals. Body weight, serum glucose, serum nitrite/nitrate, vascular endothelial function, aortic superoxide anion, brains' oxidative markers (thiobarbituric acid reactive species-TBARS, reduced glutathione-GSH, superoxide dismutase-SOD, and catalase-CAT), mitochondrial enzyme complex (I, II, and IV), inflammatory markers (interleukin-IL-6, IL-10, tumor necrosis factor-TNF-α, and myeloperoxidase-MPO), and acetylcholinesterase activity-AChE were also assessed. Quercetin (30 mg kg-1/60 mg kg-1) and folacin (30 mg kg-1/60 mg kg-1) were used as the treatment drugs. Donepezil (0.5 mg kg-1) was used as a positive control.

RESULTS

STZ administered rats showed reduction in learning, memory, reversal learning, executive functioning, impairment in endothelial function, increase in brains' oxidative stress; inflammation; AChE activity, and decrease in mitochondrial complex (I, II, and IV) activity. Administration of quercetin and folacin in two different doses, significantly attenuated the STZ induced diabetes induced impairments in the behavioral, endothelial, and biochemical parameters.

CONCLUSIONS

STZ administration caused diabetes and VaD which was attenuated by the administration of quercetin and folacin. Therefore, these agents may be studied further for the assessment of their full potential in diabetes induced VaD conditions.

Neuropharmacological interventions of quercetin and its derivatives in neurological and psychological disorders

Quercetin is a naturally occurring bioactive flavonoid abundant in many plants and fruits. Quercetin and its derivatives have shown an array of pharmacological activities in preclinical tests against various illnesses and ailments. Owing to its protective role against oxidative stress and neuroinflammation, quercetin is a possible therapeutic choice for the treatment of neurological disorders. Quercetin and its derivatives can modulate a variety of signal transductions, including neuroreceptor, neuroinflammatory receptor, and redox signaling events. The research on quercetin and its derivatives in neurology-related illnesses mainly focused on the targets, such as redox stress, neuroinflammation, and signaling pathways; however, the function of quercetin and its derivatives on specific molecular targets, such as nuclear receptors and proinflammatory mediators are yet to be explored. Findings showed that various molecular targets of quercetin and its derivatives have therapeutic potential against psychological and neurodegenerative disorders.

Quercetin's Effects on Glutamate Cytotoxicity

The potentially therapeutic effects of the naturally abundant plant flavonoid quercetin have been extensively studied. An extensive body of literature suggests that quercetin's powerful antioxidant effects may relate to its ability to treat disease. Glutamate excitotoxicity occurs when a neuron is overstimulated by the neurotransmitter glutamate and causes dysregulation of intracellular calcium concentrations. Quercetin has been shown to be preventative against many forms of neuronal cell death resulting from glutamate excitotoxicity, such as oncosis, intrinsic apoptosis, mitochondrial permeability transition, ferroptosis, phagoptosis, lysosomal cell death, parthanatos, and death by reactive oxygen species (ROS)/reactive nitrogen species (RNS) generation. The clinical importance for the attenuation of glutamate excitotoxicity arises from the need to deter the continuous formation of tissue infarction caused by various neurological diseases, such as ischemic stroke, seizures, neurodegenerative diseases, and trauma. This review aims to summarize what is known concerning glutamate physiology and glutamate excitotoxic pathophysiology and provide further insight into quercetin's potential to hinder neuronal death caused by cell death pathways activated by glutamate excitotoxicity. Quercetin's bioavailability may limit its use clinically, however. Thus, future research into ways to increase its bioavailability are warranted.

Suitability of Banana and Plantain Fruits in Modulating Neurodegenerative Diseases: Implicating the In Vitro and In Vivo Evidence from Neuroactive Narratives of Constituent Biomolecules

Active principles in plant-based foods, especially staple fruits, such as bananas and plantains, possess inter-related anti-inflammatory, anti-apoptotic, antioxidative, and neuromodulatory activities. Neurodegenerative diseases affect the functionality of the central and peripheral nervous system, with attendant cognitive deficits being hallmarks of these conditions. The dietary constitution of a wide range of bioactive compounds identified in this review further iterates the significance of the banana and plantain in compromising, halting, or preventing the pathological mechanisms of neurological disorders. The neuroprotective mechanisms of these biomolecules have been identified by using protein expression regulation and specific gene/pathway targeting, such as the nuclear and tumor necrosis factors, extracellular signal-regulated and mitogen-activated protein kinases, activator protein-1, and the glial fibrillary acidic protein. This review establishes the potential double-edged neuro-pharmacological fingerprints of banana and plantain fruits in their traditionally consumed pulp and less utilized peel component for human nutrition.

Astragalus mongholicus Bunge (Fabaceae): Bioactive Compounds and Potential Therapeutic Mechanisms Against Alzheimer’s Disease

Astragalus mongholicus Bunge (Fabaceae) (also known as Astragali radix-AR), a widely used herb by Traditional Chinese Medicine practitioners, possesses a wide range of pharmacological effects, and has been used to treat Alzheimer’s disease (AD) historically. Its bioactive compounds are categorized into four families: saponins, flavonoids, polysaccharides, and others. AR’s bioactive compounds are effective in managing AD through a variety of mechanisms, including inhibiting Aβ production, aggregation and tau hyperphosphorylation, protecting neurons against oxidative stress, neuroinflammation and apoptosis, promoting neural stem cell proliferation and differentiation and ameliorating mitochondrial dysfunction. This review aims to shed light upon the chemical constituents of AR and the mechanisms underlying the therapeutic effect of each compound in manging AD. Also presented are clinical studies which reported successful management of AD with AR and other herbs. These will be helpful for drug development and clinical application of AR to treat AD.

Airway epithelial Paraoxonase-2 in obese asthma

Background

Obesity in asthmatics has been associated with higher airway oxidative stress in which dysfunctional mitochondria are a potential contributing source of excess free radicals. Paraoxonase 2 (PON2) plays an important role in reducing mitochondrial-derived oxidative stress and could, therefore, have therapeutic potential in these patients.

Objectives

We used primary human bronchial epithelial cells (HBECs) from asthmatics and healthy controls to evaluate: a) protein levels of Paraoxonase 2 and b) to test the potential protective effect of quercetin supplementation in cells under oxidative stress conditions.

Results

Compared to lean controls, obese asthmatics had significantly lower PON2 airway epithelial levels (respectively, 1.08 vs. 0.47 relative units normalized by GAPDH) (p-value < 0.006). Treating HBECs in vitro for 24 hrs. with 25μM quercetin significantly increased PON2 protein levels: 15.5 treated cells vs. 9.8 untreated cells (relative units normalized by GAPDH) (p value = 0.004). Notably, compared to untreated cells, quercetin supplementation reduces mitochondrial superoxide and hydrogen peroxide production on HBECs cells exposed to different oxidative stress triggers such as 1–2 Naphthoquinone (1–2 NQ) and hydrogen peroxide, suggesting that PON2 might play a protective role ameliorating oxidative injury on human airway epithelium.

Conclusion

Compared to lean controls, obese asthmatics have significantly reduced PON2 levels in airway epithelial cells. Treatment with quercetin in vitro increased PON2 protein levels and prevented oxidative stress from different types of stimuli. Hence, quercetin supplementation may be a potential therapeutic strategy to prevent obesity-mediated airway oxidative stress in obese asthmatics.

Insights into the role of paraoxonase 2 in human pathophysiology

Paraoxonase 2 (PON2) is a ubiquitously expressed intracellular enzyme that is known to have a protective role from oxidative stress. Clinical studies have also demonstrated the significance of PON2 in the manifestation of cardiovascular and several other diseases, and hence, it is considered an important biomarker. Recent findings of its expression in brain tissue suggest its potential protective effect on oxidative stress and neuroinflammation. Polymorphisms of PON2 in humans are a risk factor in many pathological conditions, suggesting a possible mechanism of its anti-oxidative property probably through lactonase activity. However, exogenous factors may also modulate the expression and activity of PON2. Hence, this review aims to report the mechanism by which PON2 expression is regulated and its role in oxidative stress disorders such as neurodegeneration and tumor formation. The role of PON2 owing to its lactonase activity in bacterial infectious diseases and association of PON2 polymorphism with pathological conditions are also highlighted.

Insights into the role of paraoxonase 2 in human pathophysiology

Paraoxonase 2 (PON2) is a ubiquitously expressed intracellular enzyme that is known to have a protective role from oxidative stress. Clinical studies have also demonstrated the significance of PON2 in the manifestation of cardiovascular and several other diseases, and hence, it is considered an important biomarker. Recent findings of its expression in brain tissue suggest its potential protective effect on oxidative stress and neuroinflammation. Polymorphisms of PON2 in humans are a risk factor in many pathological conditions, suggesting a possible mechanism of its anti-oxidative property probably through lactonase activity. However, exogenous factors may also modulate the expression and activity of PON2. Hence, this review aims to report the mechanism by which PON2 expression is regulated and its role in oxidative stress disorders such as neurodegeneration and tumor formation. The role of PON2 owing to its lactonase activity in bacterial infectious diseases and association of PON2 polymorphism with pathological conditions are also highlighted.

Neuropharmacological Effects of Quercetin: A Literature-Based Review

Quercetin (QUR) is a natural bioactive flavonoid that has been lately very studied for its beneficial properties in many pathologies. Its neuroprotective effects have been demonstrated in many in vitro studies, as well as in vivo animal experiments and human trials. QUR protects the organism against neurotoxic chemicals and also can prevent the evolution and development of neuronal injury and neurodegeneration. The present work aimed to summarize the literature about the neuroprotective effect of QUR using known database sources. Besides, this review focuses on the assessment of the potential utilization of QUR as a complementary or alternative medicine for preventing and treating neurodegenerative diseases. An up-to-date search was conducted in PubMed, Science Direct and Google Scholar for published work dealing with the neuroprotective effects of QUR against neurotoxic chemicals or in neuronal injury, and in the treatment of neurodegenerative diseases. Findings suggest that QUR possess neuropharmacological protective effects in neurodegenerative brain disorders such as Alzheimer’s disease, Amyloid β peptide, Parkinson’s disease, Huntington's disease, multiple sclerosis, and amyotrophic lateral sclerosis. In summary, this review emphasizes the neuroprotective effects of QUR and its advantages in being used in complementary medicine for the prevention and treatment o of different neurodegenerative diseases.

Human Paraoxonase-2 (PON2): Protein Functions and Modulation

PON1, PON2, and PON3 belong to a family of lactone hydrolyzing enzymes endowed with various substrate specificities. Among PONs, PON2 shows the highest hydrolytic activity toward many acyl-homoserine lactones (acyl-HL) involved in bacterial quorum-sensing signaling. Accordingly, defense against pathogens, such as Brevundimonas aeruginosa (B. aeruginosa), was postulated to be the principal function of PON2. However, recent findings have highlighted the importance of PON2 in oxidative stress control, inhibition of apoptosis, and the progression of various types of malignancies. This review focuses on all of these aspects of PON2.

Dietary Polyphenols and Mitochondrial Function: Role in Health and Disease

Mitochondria are cytoplasmic double-membraned organelles that are involved in a myriad of key cellular regulatory processes. The loss of mitochondrial function is related to the pathogenesis of several human diseases. Over the last decades, an increasing number of studies have shown that dietary polyphenols can regulate mitochondrial redox status, and in some cases, prevent or delay disease progression. This paper aims to review the role of four dietary polyphenols - resveratrol, curcumin, epigallocatechin-3-gallate nd quercetin - in molecular pathways regulated by mitochondria and their potential impact on human health. Cumulative evidence showed that the aforementioned polyphenols improve mitochondrial functions in different in vitro and in vivo experiments. The mechanisms underlying the polyphenols' beneficial effects include, among others, the attenuation of oxidative stress, the regulation of mitochondrial metabolism and biogenesis and the modulation of cell-death signaling cascades, among other mitochondrial-independent effects. The understanding of the chemicalbiological interactions of dietary polyphenols, namely with mitochondria, may have a huge impact on the treatment of mitochondrial dysfunction-related disorders.

MicroRNA profiling in kidney in pigs fed ochratoxin A contaminated diet

OTA is a toxic metabolite produced by fungus belonging to Aspergillus and Penicillium genera. Kidney is the main target of this toxin; OTA is considered as one of the etiological factors at the origin of the human Balkan endemic nephropathy. microRNA are short non-coding transcrips (18-22 nucleotides in length) regulating key cellular processes. Various miRNAs have been established to play important roles in development of renal carcinoma and urothelial cancer. The objective of this study is to analyse the miRNA profiling in the kidney of piglets experimentally intoxicated with feed contaminated with OTA. Fifteen piglets (five pigs/group) were randomly distributed into 3 groups, fed normal diet (Group 1: control), or diets contaminated with OTA in two concentrations: 50 μg OTA/kg feed (Group 2: 50 μg OTA/kg feed) or 200 μg OTA/kg feed (Group 3: 200 μg OTA/kg feed) for 28 days. At the end of the experiment blood samples were taken for serological analyses. Animals from control group and 200 μg OTA/kg feed were sacrificed and kidney samples were taken for histological and molecular analyses. As resulted from molecular profiling study there are 8 miRNA differentially expressed in OTA kidney vs control kidney, in which five miRNA were overexpressed in the kidney of OTA intoxicated animals: miR-497 (FC = 6.34), miR-133a-3p (FC = 5.75), miR-423-3p (FC = 5.48), miR-34a (FC = 1.68), miR-542-3p (1.65) while three miRNA were downregulated: miR-421-3p (FC = -3.96); miR-490 (FC = -3.87); miR-9840-3p (FC = -2.13). The altered miRNAs as effect of OTA are strongly connected to the engine of cancer, disturbing nodal points in different pathways, as TP53 signalling. This proof-of-concept study proves the actual utility of miRNAs as biomarkers of mycotoxin exposure, including OTA.

The role of traditional Chinese medicine in the treatment of atherosclerosis through the regulation of macrophage activity

Atherosclerosis (AS) is the main cause of ischemic cardiovascular, cerebrovascular and peripheral vascular diseases. Macrophage activity has been proven to play a critical role during the AS pathological process, which involves the adhesion, aggregation of mononuclear-macrophages, cell differentiation of M1/M2 macrophages as part of complex mechanisms occurring during lipid metabolism, apoptosis, autophagy, inflammation and immune reaction. Therefore, the development of effective AS treatments is likely to target macrophage activity. Certain herbal extracts (such as Salvia miltiorrhiza) have exhibited enormous potential for AS treatment in the past. Here, we aim to provide a summary on the current understanding of the type of action and the underlying target/pathway in macrophage regulation of certain herbal extracts used in Traditional Chinese Medicine for treatment of AS.

Cardiovascular Effects of Flavonoids

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Cardiovascular Disease (CVD) is the major cause of death worldwide, especially in Western society. Flavonoids are a large group of polyphenolic compounds widely distributed in plants, present in a considerable amount in fruit and vegetable. Several epidemiological studies found an inverse association between flavonoids intake and mortality by CVD. The antioxidant effect of flavonoids was considered the main mechanism of action of flavonoids and other polyphenols. In recent years, the role of modulation of signaling pathways by direct interaction of flavonoids with multiple protein targets, namely kinases, has been increasingly recognized and involved in their cardiovascular protective effect. There are strong evidence, in in vitro and animal experimental models, that some flavonoids induce vasodilator effects, improve endothelial dysfunction and insulin resistance, exert platelet antiaggregant and atheroprotective effects, and reduce blood pressure. Despite interacting with multiple targets, flavonoids are surprisingly safe. This article reviews the recent evidence about cardiovascular effects that support a beneficial role of flavonoids on CVD and the potential molecular targets involved.

Critical Evaluation of Gene Expression Changes in Human Tissues in Response to Supplementation with Dietary Bioactive Compounds: Moving Towards Better-Quality Studies

Pre-clinical cell and animal nutrigenomic studies have long suggested the modulation of the transcription of multiple gene targets in cells and tissues as a potential molecular mechanism of action underlying the beneficial effects attributed to plant-derived bioactive compounds. To try to demonstrate these molecular effects in humans, a considerable number of clinical trials have now explored the changes in the expression levels of selected genes in various human cell and tissue samples following intervention with different dietary sources of bioactive compounds. In this review, we have compiled a total of 75 human studies exploring gene expression changes using quantitative reverse transcription PCR (RT-qPCR). We have critically appraised the study design and methodology used as well as the gene expression results reported. We herein pinpoint some of the main drawbacks and gaps in the experimental strategies applied, as well as the high interindividual variability of the results and the limited evidence supporting some of the investigated genes as potential responsive targets. We reinforce the need to apply normalized procedures and follow well-established methodological guidelines in future studies in order to achieve improved and reliable results that would allow for more relevant and biologically meaningful results.

Metabolism of Phenolic Compounds in LPS-stimulated Raw264.7 Cells Can Impact Their Anti-inflammatory efficacy: Indication of Hesperetin

Raw264.7 is a murine macrophage-like cell line commonly used to study the anti-inflammatory efficacy of natural compounds. However, the impacts of long-time incubation on the tested compounds are often inappropriately ignored. Among 77 natural phenolic compounds (mainly flavonoids), only 36 remain more than 70% after a 15-h incubation in cell culture medium at 37 °C. Interestingly, for those compounds with a relatively good chemical stability, the presence of Raw264.7 cells could accelerate their disappearance in the medium, indicating that cellular metabolism occurred. As a representative phenolic, hesperetin was found to be efficiently metabolized by Raw264.7 cells and the metabolite was identified as a glucuronide in the further investigation. The glucuronidation activity is constitutive in this cell line. At certain concentration levels of hesperetin, the ability of hesperetin to inhibit PGD₂ production in LPS-induced Raw264.7 cells was significantly enhanced by introducing β-glucuronidase, which can hydrolyze hesperetin glucuronide, into the incubation medium. The results indicate that glucuronidation and excretion of hesperetin can significantly impact its bioactivity in Raw264.7 cells.

The role of paraoxonase in cancer

The paraoxonase (PON) gene family includes three proteins, PON1, PON2 and PON3. PON1 and PON3 are both associated with high-density lipoprotein (HDL) particles and exert anti-oxidant and anti-inflammatory properties. PON2 and PON3 are intracellular enzymes which modulate mitochondrial superoxide anion production and endoplasmic reticulum (ER) stress-induced apoptosis. The pleiotropic roles exerted by PONs have been mainly investigated in cardiovascular and neurodegenerative diseases. In recent years, overexpression of PON2 and PON3 has been observed in cancer cells and it has been proposed that both enzymes could be involved in tumor survival and stress resistance. Moreover, a lower activity of serum PON1 has been reported in cancer patients. This review summarizes literature data on the role of PONs in human cancers and their potential role as a target for antitumor drugs.

The Paraoxonase Gene Cluster Protects Against Abdominal Aortic Aneurysm Formation

Objective—

Abdominal aortic aneurysm (AAA) is a life-threatening vascular pathology, the pathogenesis of which is closely related to oxidative stress. However, an effective pharmaceutical treatment is lacking because the exact cause of AAA remains unknown. Here, we aimed at delineating the role of the paraoxonases (PONs) gene cluster (PC), which prevents atherosclerosis through the detoxification of oxidized substrates, in AAA formation.

Approach and Results—

PC transgenic (Tg) mice were crossed to an Apoe −/− background, and an angiotensin II–induced AAA mouse model was used to analyze the effect of the PC on AAA formation. Four weeks after angiotensin II infusion, PC-Tg Apoe −/− mice had a lower AAA incidence, smaller maximal abdominal aortic external diameter, and less medial elastin degradation than Apoe −/− mice. Importantly, PC-Tg Apoe −/− mice exhibited lower aortic reactive oxidative species production and oxidative stress than did the Apoe −/− control mice. As a consequence, the PC transgene alleviated angiotensin II–induced arterial inflammation and suppressed arterial extracellular matrix degradation. Specifically, on angiotensin II stimulation, PC-Tg vascular smooth muscle cells exhibited lower levels of reactive oxidative species production and a decrease in the activities and expression levels of matrix metalloproteinase-2 and matrix metalloproteinase-9. Moreover, PC-Tg serum also enhanced vascular smooth muscle cell oxidative stress resistance and further decreased the expression levels of matrix metalloproteinase-2 and matrix metalloproteinase-9, indicating that circulatory and vascular smooth muscle cell PC members suppress oxidative stress in a synergistic manner.

Conclusions—

Our findings reveal, for the first time, a protective role of the PC in AAA formation and suggest PONs as promising targets for AAA prevention.

Synthesis and cardiovascular protective effects of quercetin 7-O-sialic acid

Oxidative stress and inflammation play important roles in the pathogenesis of cardiovascular disease (CVD). Oxidative stress-induced desialylation is considered to be a primary step in atherogenic modification, and therefore, the attenuation of oxidative stress and/or inflammatory reactions may ameliorate CVD. In this study, quercetin 7-O-sialic acid (QA) was synthesized aiming to put together the cardiovascular protective effect of quercetin and the recently reported anti-oxidant and anti-atherosclerosis functions of N-acetylneuraminic acid. The biological efficacy of QA was evaluated in vitro in various cellular models. The results demonstrated that 50 μM QA could effectively protect human umbilical vein endothelial cells (HUVEC, EA.hy926) against hydrogen peroxide- or oxidized low-density lipoprotein-induced oxidative damage by reducing the production of reactive oxygen species. QA attenuated hydrogen peroxide-induced desialylation of HUVEC and lipoproteins. QA decreased lipopolysaccharide-induced secretion of tumour necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1), and it significantly reduced the expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, TNF-α and MCP-1. Furthermore, QA effectively promoted cholesterol efflux from Raw 264.7 macrophages to apolipoprotein A-1 and high-density lipoprotein by up-regulating ATP-binding cassette transporter A1 and G1, respectively. Results indicated that the novel compound QA exhibited a better capacity than quercetin for anti-oxidation, anti-inflammation, cholesterol efflux promotion and biomolecule protection against desialylation and therefore could be a candidate compound for the prevention or treatment of CVD.

Bioactive effects of quercetin in the central nervous system: Focusing on the mechanisms of actions

Quercetin, a ubiquitous flavonoid that is widely distributed in plants is classified as a cognitive enhancer in traditional and oriental medicine. The protective effects of quercetin for the treatment of neurodegenerative disorders and cerebrovascular diseases have been demonstrated in both in vitro and in vivo studies. The free radical scavenging activity of quercetin has been well-documented, wherein quercetin has been observed to exhibit protective effects against oxidative stress mediated neuronal damage by modulating the expression of NRF-2 dependent antioxidant responsive elements, and attenuation of neuroinflammation by suppressing NF-κB signal transducer and activator of transcription-1 (STAT-1). Several in vitro and in vivo studies have also shown that quercetin destabilizes and enhances the clearance of abnormal protein such as beta- amyloid peptide and hyperphosphorlyated tau, the key pathological hallmarks of Alzheimer's disease. Quercetin enhances neurogenesis and neuronal longevity by modulating a broad number of kinase signaling cascades such as phophoinositide 3- kinase (P13-kinase), AKT/PKB tyrosine kinase and Protein kinase C (PKC). Quercetin has also been well reported for its ability to reverse cognitive impairment and memory enhancement during aging. The current review focuses on summarizing the recent findings on the neuroprotective effect of quercetin, its mechanism of action and its possible roles in the prevention of neurological disorders.

Paraoxonases-1, -2 and -3: What are their functions?

Paraoxonase-1 (PON1), an esterase/lactonase primarily associated with plasma high-density lipoprotein (HDL), was the first member of this family of enzymes to be characterized. Its name was derived from its ability to hydrolyze paraoxon, the toxic metabolite of the insecticide parathion. Related enzymes PON2 and PON3 were named from their evolutionary relationship with PON1. Mice with each PON gene knocked out were generated at UCLA and have been key for elucidating their roles in organophosphorus (OP) metabolism, cardiovascular disease, innate immunity, obesity, and cancer. PON1 status, determined with two-substrate analyses, reveals an individual's functional Q192R genotype and activity levels. The three-dimensional structure for a chimeric PON1 has been useful for understanding the structural properties of PON1 and for engineering PON1 as a catalytic scavenger of OP compounds. All three PONs hydrolyze microbial N-acyl homoserine lactone quorum sensing factors, quenching Pseudomonas aeruginosa's pathogenesis. All three PONs modulate oxidative stress and inflammation. PON2 is localized in the mitochondria and endoplasmic reticulum. PON2 has potent antioxidant properties and is found at 3- to 4-fold higher levels in females than males, providing increased protection against oxidative stress, as observed in primary cultures of neurons and astrocytes from female mice compared with male mice. The higher levels of PON2 in females may explain the lower frequency of neurological and cardiovascular diseases in females and the ability to identify males but not females with Parkinson's disease using a special PON1 status assay. Less is known about PON3; however, recent experiments with PON3 knockout mice show them to be susceptible to obesity, gallstone formation and atherosclerosis. Like PONs 1 and 2, PON3 also appears to modulate oxidative stress. It is localized in the endoplasmic reticulum, mitochondria and on HDL. Both PON2 and PON3 are upregulated in cancer, favoring tumor progression through mitochondrial protection against oxidative stress and apoptosis.

Regulatory effects of dioxin-like and non-dioxin-like PCBs and other AhR ligands on the antioxidant enzymes paraoxonase 1/2/3

Paraoxonase 1 (PON1), an antioxidant enzyme, is believed to play a critical role in many diseases, including cancer. PCBs are widespread environmental contaminants known to induce oxidative stress and cancer and to produce changes in gene expression of various pro-oxidant and antioxidant enzymes. Thus, it appeared of interest to explore whether PCBs may modulate the activity and/or gene expression of PON1 as well. In this study, we compared the effects of dioxin-like and non-dioxin-like PCBs and of various aryl hydrocarbon receptor (AhR) ligands on PON1 regulation and activity in male and female Sprague-Dawley rats. Our results demonstrate that (i) the non-dioxin-like PCB154, PCB155, and PCB184 significantly reduced liver and serum PON1 activities, but only in male rats; (ii) the non-dioxin-like PCB153, the most abundant PCB in many matrices, did not affect PON1 messenger RNA (mRNA) level in the liver but significantly decreased serum PON1 activity in male rats; (iii) PCB126, an AhR ligand and dioxin-like PCB, increased both PON1 activities and gene expression; and (iv) even though three tested AhR ligands induced CYP1A in several tissues to a similar extent, they displayed differential effects on the three PONs and AhR, i.e., PCB126 was an efficacious inducer of PON1, PON2, PON3, and AhR in the liver, while 3-methylcholantrene induced liver AhR and lung PON3, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent AhR agonist, increased only PON3 in the lung, at the doses and exposure times used in these studies. These results show that PCBs may have an effect on the antioxidant protection by paraoxonases in exposed populations and that regulation of gene expression through AhR is highly diverse.

Mechanisms of Neuroprotection by Quercetin: Counteracting Oxidative Stress and More

Increasing interest has recently focused on determining whether several natural compounds, collectively referred to as nutraceuticals, may exert neuroprotective actions in the developing, adult, and aging nervous system. Quercetin, a polyphenol widely present in nature, has received the most attention in this regard. Several studies in vitro, in experimental animals and in humans, have provided supportive evidence for neuroprotective effects of quercetin, either against neurotoxic chemicals or in various models of neuronal injury and neurodegenerative diseases. The exact mechanisms of such protective effects remain elusive, though many hypotheses have been formulated. In addition to a possible direct antioxidant effect, quercetin may also act by stimulating cellular defenses against oxidative stress. Two such pathways include the induction of Nrf2-ARE and induction of the antioxidant/anti-inflammatory enzyme paraoxonase 2 (PON2). In addition, quercetin has been shown to activate sirtuins (SIRT1), to induce autophagy, and to act as a phytoestrogen, all mechanisms by which quercetin may provide its neuroprotection.

Selective oxidative stress and cholesterol metabolism in lipid-metabolizing cell classes: Distinct regulatory roles for pro-oxidants and antioxidants

Atherogenesis is associated with macrophage cholesterol and oxidized lipids accumulation and foam cell formation. However, two other major lipid-metabolizing cell classes, namely intestinal and liver cells, are also associated with atherogenesis. This study demonstrates that manipulations of cellular oxidative stress (by fatty acids, glucose, low-density lipoprotein, angiotensin II, polyphenolic antioxidants, or the glutathione/paraoxonase 1 systems) have some similar, but also some different effects on cholesterol metabolism in macrophages (J774A.1) versus intestinal cells (HT-29) versus liver cells (HuH7). Cellular oxidative stress was ≈3.5-folds higher in both intestinal and liver cells versus macrophages. In intestinal cells or liver cells versus macrophages, the cholesterol biosynthesis rate was increased by 9- or 15-fold, respectively. In both macrophages and intestinal cells C-18:1 and C-18:2 but not C-18:0, fatty acids significantly increased oxidative stress, whereas in liver cells oxidative stress was significantly decreased by all three fatty acids. In liver cells, trans C-18:1 versus cis C-18:1, unlike intestinal cells or macrophages, significantly increased cellular oxidative stress and cellular cholesterol biosynthesis rate. Pomegranate juice (PJ), red wine, or their phenolics gallic acids or quercetin significantly reduced cellular oxidation mostly in macrophages. Recombinant PON1 significantly decreased macrophage (but not the other cells) oxidative stress by ≈30%. We conclude that cellular atherogenesis research should look at atherogenicity, not only in macrophages but also in intestinal and liver cells, to advance our understanding of the complicated mechanisms behind atherogenesis. © 2015 BioFactors, 41(4):273-288, 2015.

Paraoxonase-2 (PON2) in brain and its potential role in neuroprotection

Paraoxonase 2 (PON2) is a member of a gene family which also includes the more studied PON1, as well as PON3. PON2 is unique among the three PONs, as it is expressed in brain tissue. PON2 is a lactonase and displays anti-oxidant and anti-inflammatory properties. PON2 levels are highest in dopaminergic regions (e.g. striatum), are higher in astrocytes than in neurons, and are higher in brain and peripheral tissues of female mice than male mice. At the sub-cellular level, PON2 localizes primarily in mitochondria, where it scavenges superoxides. Lack of PON2 (as in PON2(-/-) mice), or lower levels of PON2 (as in male mice compared to females) increases susceptibility to oxidative stress-induced toxicity. Estradiol increases PON2 expression in vitro and in vivo, and provides neuroprotection against oxidative stress. Such neuroprotection is not present in CNS cells from PON2(-/-) mice. Similar results are also found with the polyphenol quercetin. PON2, given its cellular localization and antioxidant and anti-inflammatory actions, may represent a relevant enzyme involved in neuroprotection, and may represent a novel target for neuroprotective strategies. Its differential expression in males and females may explain gender differences in the incidence of various diseases, including neurodevelopmental, neurological, and neurodegenerative diseases.

Paraoxonases and chemokine (C-C motif) ligand-2 in noncommunicable diseases

Oxidative stress and inflammation underpin most diseases; their mechanisms are inextricably linked. Chronic inflammation is associated with oxidation, anti-inflammatory cascades are linked to decreased oxidation, increased oxidative stress triggers inflammation, and redox balance inhibits the inflammatory cellular response. Whether or not oxidative stress and inflammation represent the cause or consequence of cellular pathology, they contribute significantly to the pathogenesis of noncommunicable diseases (NCD). The incidence of obesity and other related metabolic disturbances are increasing, as are age-related diseases due to a progressively aging population. Relationships between oxidative stress, inflammatory signaling, and metabolism are, in the broad sense of energy transformation, being increasingly recognized as part of the problem in NCD. In this chapter, we summarize the pathologic consequences of an imbalance between circulating and cellular paraoxonases, the system for scavenging excessive reactive oxygen species and circulating chemokines. They act as inducers of migration and infiltration of immune cells in target tissues as well as in the pathogenesis of disease that perturbs normal metabolic function. This disruption involves pathways controlling lipid and glucose homeostasis as well as metabolically driven chronic inflammatory states that encompass several response pathways. Dysfunction in the endoplasmic reticulum and/or mitochondria represents an important feature of chronic disease linked to oxidation and inflammation seen as self-reinforcing in NCD. Therefore, correct management requires a thorough understanding of these relationships and precise interpretation of laboratory test results.

Dietary antioxidants (selenium and N-acetylcysteine) modulate paraoxonase 1 (PON1) in PCB 126-exposed rats

Environmental pollutants polychlorinated biphenyls (PCBs), especially dioxin-like PCBs, cause oxidative stress and associated toxic effects, including cancer and possibly atherosclerosis. We previously reported that PCB 126, the most potent dioxin-like PCB congener, not only decreases antioxidants such as hepatic selenium (Se), Se-dependent glutathione peroxidase, and glutathione (GSH) but also increases levels of the antiatherosclerosis enzyme paraoxonase 1 (PON1) in liver and serum. To probe the interconnection of these three antioxidant systems, Se, GSH, and PON1, we examined the influence of varying levels of dietary Se and N-acetylcysteine (NAC), a scavenger of reactive oxygen species (ROS) and precursor for GSH synthesis, on PON1 in the absence and presence of PCB 126 exposure. Male Sprague-Dawley rats, fed diets with differing Se levels (0.02, 0.2, or 2 ppm) or NAC (1%), were treated with a single intraperitoneal injection of corn oil or various doses of PCB 126 and euthanized 2 weeks later. PCB 126 significantly increased liver PON1 mRNA, protein level and activity, and serum PON1 activity in all dietary groups but did not consistently increase thiobarbituric acid levels (thiobarbituric acid reactive substances, TBARS), an indicator of lipid oxidation and oxidative stress, in liver or serum. Inadequate (high or low) dietary Se decreased baseline and PCB 126-induced aryl hydrocarbon receptor (AhR) expression but further increased PCB 126-induced cytochrome P450 1A1 (CYP1A1) expression, the enzyme believed to be the cause for PCB 126-induced oxidative stress. In addition, a significant inverse relationship was observed not only between dietary Se levels and PON1 mRNA and PON1 activity but also with TBARS levels in the liver, suggesting significant antioxidant protection from dietary Se. NAC lowered serum baseline TBARS levels in controls and increased serum PON1 activity but lowered liver PON1 activities in animals treated with 1 μmol/kg PCB 126, suggesting antioxidant activity by NAC primarily in serum. These results also show an unexpected predominantly inverse relationship between Se or NAC and PON1 during control and PCB 126 exposure conditions. These interactions should be further explored in the development of dietary protection regimens.

Modulation of paraoxonase 2 (PON2) in mouse brain by the polyphenol quercetin: a mechanism of neuroprotection?

Quercetin is a common flavonoid polyphenol which has been shown to exert neuroprotective actions in vitro and in vivo. Though quercetin has antioxidant properties, it has been suggested that neuroprotection may be ascribed to its ability of inducing the cell's own defense mechanisms. The present study investigated whether quercetin could increase the levels of paraoxonase 2 (PON2), a mitochondrial enzyme expressed in brain cells, which has been shown to have potent antioxidant properties. PON2 protein, mRNA, and lactonase activity were highest in mouse striatal astrocytes. Quercetin increased PON2 levels, possibly by activating the JNK/AP-1 pathway. The increased PON2 levels induced by quercetin resulted in decreased oxidative stress and ensuing toxicity induced by two oxidants. The neuroprotective effect of quercetin was significantly diminished in cells from PON2 knockout mice. These findings suggest that induction of PON2 by quercetin represents an important mechanism by which this polyphenol may exert its neuroprotective action.

Genistein as a potential inducer of the anti-atherogenic enzyme paraoxonase-1: studies in cultured hepatocytes in vitro and in rat liver in vivo

A number of cardioprotective effects, including the reduced oxidation of the low-density lipoprotein (LDL) particles, have been attributed to dietary soy isoflavones. Paraoxonase 1 (PON1), an enzyme mainly synthesized in the liver, may exhibit anti-atherogenic activity by protecting LDL from oxidation. Thus, dietary and pharmacological inducers of PON1 may decrease cardiovascular disease risk. Using a luciferase reporter gene assay we screened different flavonoids for their ability to induce PON1 in Huh7 hepatocytes in culture. Genistein was the most potent flavonoid with regard to its PON1-inducing activity, followed by daidzein, luteolin, isorhamnetin and quercetin. Other flavonoids such as naringenin, cyanidin, malvidin and catechin showed only little or no PON1-inducing activity. Genistein-mediated PON1 transactivation was partly inhibited by the oestrogen-receptor antagonist fulvestrant as well as by the aryl hydrocarbon receptor antagonist 7-ketocholesterol. In contrast to genistein, the conjugated genistein metabolites genistein-7-glucuronide, genistein-7-sulfate and genistein-7,4'-disulfate were only weak inducers of PON1 transactivation. Accordingly, dietary genistein supplementation (2 g/kg diet over three weeks) in growing rats did not increase hepatic PON1 mRNA and protein levels as well as plasma PON1 activity. Thus, genistein may be a PON1 inducer in cultured hepatocytes in vitro, but not in rats in vivo.

Yerba mate (Ilex paraguariensis) enhances the gene modulation and activity of paraoxonase-2: in vitro and in vivo studies

OBJECTIVE

Paraoxonase-2 (PON-2) is an intracellular antioxidant enzyme that can be modulated by polyphenols. The aim of this study was to verify whether yerba mate (Ilex paraguariensis), a plant species rich in phenolic compounds, modulates gene expression and the activity of PON-2 in macrophages in vitro and in monocytes from peripheral blood and monocyte-derived macrophages obtained after the ingestion of green or roasted yerba mate infusions by healthy subjects.

METHODS

THP-1 macrophages were incubated with increasing amounts of yerba mate extracts or chlorogenic and caffeic acids (1-10 μmol/L). The in vivo effects of yerba mate or water (control) intakes were evaluated acutely (2 h after ingestion) and in the short term (after daily ingestion for 7 d) in 20 healthy women.

RESULTS

In general, there was no difference between the two kinds of yerba mate studied. Yerba mate extracts or chlorogenic acid at 1 and 3 μmol/L increased PON-2 relative gene expression in THP-1 macrophages (P < 0.05), whereas higher concentrations (5 and 10 μmol/L) increased the activity only. Caffeic acid induced PON-2 activity only. The acute ingestion of yerba mate infusions increased relative gene expression and PON-2 activity in monocytes (P < 0.05), whereas the consumption of yerba mate for 7 d increased PON-2 relative gene expression (P < 0.05) and had a tendency to increase PON-2 activity in monocytes and monocyte-derived macrophages.

CONCLUSION

It is suggested that green or roasted yerba mate modulates positively the mRNA relative expression and activity of the PON-2 enzyme in monocytes and macrophages, which may prevent cellular oxidative stress.

Effect of the intake of resveratrol, resveratrol phosphate, and catechin-rich grape seed extract on markers of oxidative stress and gene expression in adult obese subjects

BACKGROUND

The preventive effect of resveratrol (RES) on the development of human diseases has been verified by numerous epidemiological studies. Resveratrol triphosphate (RTP) is a stable derivative of RES in which phosphate groups protect the phenolic groups.

AIMS

This study compared the effect of RTP on biochemical and molecular markers of oxidative stress to equimolar doses (0.66 mmol) of RES and catechin-rich grape seed extract (CGSE) in a model of oxidative and metabolic stress associated with obesity in humans.

METHODS

Thirty-two obese subjects (BMI between 30 and 40) were enrolled. They all received 1 capsule of placebo/day for 28 days before being randomly devised into three arms receiving 1 capsule/day of RES, CGSE, or RTP during the following consecutive 28 days. Blood samples were collected at baseline, after the end of placebo intake, and after the end of the investigational product intake. Biochemical parameters of oxidative stress and blood expression of 200 redox-related genes were determined at each time point.

RESULTS

RTP and CGSE showed better antioxidant activities compared to RES and induced important modulations of gene expression.

CONCLUSION

The results suggest that RTP and CGSE could contribute to a significant reduction of oxidative stress in obese subjects.

Eucommiae Cortex Inhibits TNF-α and IL-6 Through the Suppression of Caspase-1 in Lipopolysaccharide-Stimulated Mouse Peritoneal Macrophages

Eucommiae cortex (EC) is used in various traditional Korean medicines in the form of tonics, analgesics, and sedatives. However, the underlying mechanism of its anti-inflammatory effect remains unclear. This study attempts to determine the effects of EC on lipopolysaccharide (LPS)-induced inflammatory responses in mouse peritoneal macrophages. The findings of the study show that EC inhibits the LPS-induced production of tumor necrosis factor-alpha and interleukin-6. Exposure to EC also reduces an inflammation-induced increase in the levels of cyclooxigenase-2 and the production of prostaglandin E 2 and nitric oxide in mouse peritoneal macrophages. Furthermore, EC suppresses the activation of nuclear factor-kappa B and caspase-1. These results provide novel insights into the pharmacological action of EC and indicate that EC has a potential in the treatment of inflammatory diseases.

The human paraoxonase gene cluster as a target in the treatment of atherosclerosis

The paraoxonase (PON) gene cluster contains three adjacent gene members, PON1, PON2, and PON3. Originating from the same fungus lactonase precursor, all of the three PON genes share high sequence identity and a similar β propeller protein structure. PON1 and PON3 are primarily expressed in the liver and secreted into the serum upon expression, whereas PON2 is ubiquitously expressed and remains inside the cell. Each PON member has high catalytic activity toward corresponding artificial organophosphate, and all exhibit activities to lactones. Therefore, all three members of the family are regarded as lactonases. Under physiological conditions, they act to degrade metabolites of polyunsaturated fatty acids and homocysteine (Hcy) thiolactone, among other compounds. By detoxifying both oxidized low-density lipoprotein and Hcy thiolactone, PONs protect against atherosclerosis and coronary artery diseases, as has been illustrated by many types of in vitro and in vivo experimental evidence. Clinical observations focusing on gene polymorphisms also indicate that PON1, PON2, and PON3 are protective against coronary artery disease. Many other conditions, such as diabetes, metabolic syndrome, and aging, have been shown to relate to PONs. The abundance and/or activity of PONs can be regulated by lipoproteins and their metabolites, biological macromolecules, pharmacological treatments, dietary factors, and lifestyle. In conclusion, both previous results and ongoing studies provide evidence, making the PON cluster a prospective target for the treatment of atherosclerosis.

Modulation of miRNA expression by dietary polyphenols in apoE deficient mice: a new mechanism of the action of polyphenols

BACKGROUND

Polyphenols are the most abundant antioxidants in the human diet and are widespread constituents of fruits and beverages, such as tea, coffee or wine. Epidemiological, clinical and animal studies support a role of polyphenols in the prevention of various diseases, such as cardiovascular diseases, cancers or neurodegenerative diseases. Recent findings suggest that polyphenols could interact with cellular signaling cascades regulating the activity of transcription factors and consequently affecting the expression of genes. However, the impact of polyphenol on the expression of microRNA, small non-coding RNAs, has not yet been studied. The aim of this study was to investigate the impact of dietary supplementation with polyphenols at nutritional doses on miRNA expression in the livers of apolipoprotein E-deficient mice (apoE⁻/⁻) jointly with mRNA expression profiling.

METHODOLOGY/PRINCIPAL FINDINGS

Using microarrays, we measured the global miRNA expression in the livers of wild-type (C57B6/J) mice or apoE⁻/⁻ mice fed diets supplemented with one of nine different polyphenols or a control diet. This analysis revealed that knock-out of the apoE gene induced significant modulation in the expression of miRNA. Moreover, changes in miRNA expression were observed after polyphenol supplementation, and five miRNAs (mmu-miR-291b-5p, mmu-miR-296-5p, mmu-miR-30c-1*, mmu-miR-467b* and mmu-miR-374*) were identified as being commonly modulated by these polyphenols. We also observed that these polyphenols counteracted the modulation of miRNA expression induced by apoE mutation. Pathway analyses on these five miRNA-target genes revealed common pathways, some of which were also identified from a pathway analysis on mRNA profiles.

CONCLUSION

This in vivo study demonstrated for the first time that polyphenols at nutritional doses modulate the expression of miRNA in the liver. Even if structurally different, all polyphenols induced a similar miRNA expression profile. Common pathways were identified from both miRNA-target and mRNA analysis, revealing cellular functions that could be regulated by polyphenols at both the miRNA and mRNA level.

Human paraoxonase 2

Human paraoxonase 2 (PON2), which is a member of the paraoxonase family, possesses unique properties that distinguish it from PON1 and PON3. PON2 is ubiquitously expressed in many different tissue types and is highly expressed in the vital organs, such as the heart and lungs. Early research revealed that PON2 is exclusively intracellularly found, wherein it functions as an anti-oxidative protein by reducing intracellular and local oxidative stress. Studies in the last five years have demonstrated that PON2 protects against atherosclerosis by preventing low-density lipoprotein (LDL) oxidation, reversing the oxidation of mildly oxidised LDL, inhibiting monocyte chemotaxis, and increasing cholesterol efflux. Recently, emerging evidence has proposed that PON2 is an anti-atherosclerotic and may be associated with cardiovascular disease (CVD). The number of investigations concerning the relationship between two common PON2 polymorphisms and CVD among different ethnic groups and regions is rapidly growing. Here, we briefly review the developments in PON2 research by focusing on past and recent findings.

Curcumin induces paraoxonase 1 in cultured hepatocytes in vitro but not in mouse liver in vivo

Paraoxonase 1 (PON1) is an enzyme that is mainly synthesised in the liver and protects LDL from oxidation, thereby exhibiting antiatherogenic properties. Using a luciferase reporter gene assay, we tested curcumin for its ability to induce PON1 in Huh7 hepatocytes in culture. Curcumin ( ≥ 10 μmol/l) dose-dependently induced PON1 transactivation in Huh7 cells. However, dietary supplementation of female B6C3F1 mice with curcumin (500 mg/kg diet) for 2 weeks did not increase the hepatic PON1 mRNA and protein levels. No curcumin was detectable in the plasma of the 12 h fasted mice. In conclusion, curcumin may be a potent PON1 inducer in cultured cells in vitro, but not in the liver of curcumin-fed mice because of its low concentrations in vivo.

The three-gene paraoxonase family: physiologic roles, actions and regulation

The paraoxonase (PON) gene family is composed of three members (PON1, PON2, PON3) that share considerable structural homology and are located adjacently on chromosome 7 in humans. By far the most-studied member is PON1, a high-density lipoprotein-associated esterase/lactonase, also endowed with the capacity to hydrolyze organophosphates, but all the three proteins prevent oxidative stress and fight inflammation. They therefore seem central to a wide variety of human illnesses, including atherosclerosis, diabetes mellitus, mental disorders and inflammatory bowel disease. The major goal of this review is to highlight the regulation of each of the paraoxonase components by diverse nutritional molecules and pharmacological agents as well as a number of pathophysiological events, such as oxidative stress and inflammation. Considerable and detailed cell-based studies and animal model experiments have been provided to allow a thorough scrutiny of PON modulation, which will increase our understanding and ability to target these genes in order to efficiently increase their transcriptional activity and decrease the risks of developing different disorders.

Effect of quercetin and its metabolites isorhamnetin and quercetin-3-glucuronide on inflammatory gene expression: role of miR-155

In the present study the effect of quercetin and its major metabolites quercetin-3-glucuronide (Q3G) and isorhamnetin on inflammatory gene expression was determined in murine RAW264.7 macrophages stimulated with lipopolysaccharide. Quercetin and isorhamnetin but not Q3G significantly decreased mRNA and protein levels of tumor necrosis factor alpha. Furthermore a significant decrease in mRNA levels of interleukin 1β, interleukin 6, macrophage inflammatory protein 1α and inducible nitric oxide synthase was evident in response to the quercetin treatment. However Q3G did not affect inflammatory gene expression. Anti-inflammatory properties of quercetin and isorhamnetin were accompanied by an increase in heme oxygenase 1 protein levels, a downstream target of the transcription factor Nrf2, known to antagonize chronic inflammation. Furthermore, proinflammatory microRNA-155 was down-regulated by quercetin and isorhamnetin but not by Q3G. Finally, anti-inflammatory properties of quercetin were confirmed in vivo in mice fed quercetin-enriched diets (0.1 mg quercetin/g diet) over 6 weeks.

Quercetin supplementation and its effect on human monocyte gene expression profiles in vivo

Quercetin has been described as having a wide range of beneficial effects in humans, ranging from anti-carcinogenic properties to reducing the risk of CVD. Nevertheless, underlying molecular mechanisms have been mostly investigated in vitro. Here, we tested whether a daily supplementation of quercetin leads to reproducible changes in human monocyte gene expression profiles. In study I, quercetin in varying dosages was given to healthy subjects for 2 weeks. RNA from monocytes isolated at the beginning and end of the study from subjects receiving 150 mg quercetin per d was subjected to transcriptome-wide microarray analysis. In study II, a double-blind cross-over study, twenty subjects exhibiting a ‘cardiovascular risk phenotype’ received 150 mg quercetin or placebo daily for 6 weeks each and served as the verification group. Microarray analysis revealed a number of differentially expressed genes. The most significantly represented functional groups were those of the immune system, nucleic acid metabolism, apoptosis and O-glycan biosynthesis. Twenty-four genes were chosen for technical replication and independent verification by quantitative real-time PCR. When comparing placebo and quercetin treatment, four genes showed significantly different expression changes (C1GALT1, O-glycan biosynthesis; GM2A, glycolipid catabolism; HDGF, cell proliferation; SERPINB9, apoptosis). However, these were minimal in respect to magnitude of fold change. In conclusion, although microarray analysis revealed extensive effects of quercetin on gene expression, the employment of a placebo-controlled study design showed no comparable results for twenty-four verification targets. This emphasises the need for stringent designs in nutritional intervention studies with the aim to identify relevant changes in gene expression.