A novel approach of proteomics and transcriptomics to study the mechanism of action of the antioxidant-iron chelator green tea polyphenol (-)-epigallocatechin-3-gallate

Low-dose bisphenols exposure sex-specifically induces neurodevelopmental toxicity in juvenile rats and the antagonism of EGCG

Bisphenols (BPs) can negatively affect neurobehaviors in rats, whereas the mechanism remains unclear. Here, the mechanism of BPs-induced neurodevelopmental toxicity and its effective detoxification measures were investigated in vitro and in vivo. In in vitro experiments, primary hippocampal neurons from neonatal rats of different genders were treated with bisphenol A (BPA), bisphenol S (BPS) and bisphenol B (BPB) at 1 nM-100 μM, epigallocatechin gallate (EGCG) and G15, an antagonist of G protein-coupled estrogen receptor (GPER) for 7 d. Results indicated that BPs affected neuronal morphogenesis, impaired GABA synthesis and Glu/GABA homeostasis. Neuronal morphogenetic damage induced by low-doses BPA may be mediated by GPER. Neurotoxicity of BPS is weaker than BPA and BPB. In in vivo studies, exposure to BPA (0.5 μg/kg·bw/day) on PND 10-40 caused oxidative stress and inflammation in rat hippocampus, disrupted neuronal morphogenesis and neurotransmitter homeostasis, ultimately impaired spatial memory of rats. Males are more sensitive to BPA exposure than females. Both in vivo and in vitro studies indicated that EGCG, a phytoestrogen, can alleviate BPA-induced neurotoxicity. Taken together, low-doses BPA exposure sex-specifically disrupted neurodevelopment and further impaired learning and memory ability in rats, which may be mediated by GPER. Promisingly, EGCG effectively mitigated the BPA-induced neurodevelopmental toxicity.

Epigallocatechin Gallate (EGCG) for Parkinson's Disease

In the last couple of decades, we have experienced increased use of nutraceuticals worldwide with a demand for organic foods, which has been elevated to an extent probably unmatched with other periods of our civilization. One of the nutraceuticals that gained attention is epigallocatechin gallate (EGCG), a polyphenol in green tea. It has been suggested that diseases of the central nervous system (CNS) can benefit from consuming some antioxidants, despite current results showing little evidence for their use in preventing and treating these diseases. ECGC may be beneficial in delaying the neurodegeneration of the substantia nigra (SN) regardless of the origin of Parkinson's disease (PD). This review covers the effect of EGCG on vitro and animal models of PD, the potential mechanisms of neuroprotection involved and summaries recent clinical trials in human PD. This review also aims to provide an investigative analysis of the current knowledge in this field and identify putative crucial issues. Environmental factors such as dietary habits, drug use, and social interaction are all factors that influence the evolution of neurodegenerative diseases. Therefore, the use of nutraceuticals requires further investigation. This article is protected by copyright. All rights reserved.

Tea (Camellia sinensis): A Review of Nutritional Composition, Potential Applications, and Omics Research

Tea (Camelliasinensis) is the world’s most widely consumed non-alcoholic beverage with essential economic and health benefits since it is an excellent source of polyphenols, catechins, amino acids, flavonoids, carotenoids, vitamins, and polysaccharides. The aim of this review is to summarize the main secondary metabolites in tea plants, and the content and distribution of these compounds in six different types of tea and different organs of tea plant were further investigated. The application of these secondary metabolites on food processing, cosmetics industry, and pharmaceutical industry was reviewed in this study. With the rapid advancements in biotechnology and sequencing technology, omics analyses, including genome, transcriptome, and metabolome, were widely used to detect the main secondary metabolites and their molecular regulatory mechanisms in tea plants. Numerous functional genes and regulatory factors have been discovered, studied, and applied to improve tea plants. Research advances, including secondary metabolites, applications, omics research, and functional gene mining, are comprehensively reviewed here. Further exploration and application trends are briefly described. This review provides a reference for basic and applied research on tea plants.

Computational analyses of mechanism of action (MoA): data, methods and integration

The elucidation of a compound's Mechanism of Action (MoA) is a challenging task in the drug discovery process, but it is important in order to rationalise phenotypic findings and to anticipate potential side-effects. Bioinformatic approaches, advances in machine learning techniques and the increasing deposition of high-throughput data in public databases have significantly contributed to recent advances in the field, but it is not straightforward to decide which data and methods are most suitable to use in a given case. In this review, we focus on these methods and data and their applications in generating MoA hypotheses for subsequent experimental validation. We discuss compound-specific data such as -omics, cell morphology and bioactivity data, as well as commonly used supplementary prior knowledge such as network and pathway data, and provide information on databases where this data can be accessed. In terms of methodologies, we discuss both well-established methods (connectivity mapping, pathway enrichment) as well as more developing methods (neural networks and multi-omics integration). Finally, we review case studies where the MoA of a compound was successfully suggested from computational analysis by incorporating multiple data modalities and/or methodologies. Our aim for this review is to provide researchers with insights into the benefits and drawbacks of both the data and methods in terms of level of understanding, biases and interpretation - and to highlight future avenues of investigation which we foresee will improve the field of MoA elucidation, including greater public access to -omics data and methodologies which are capable of data integration.

Neurodegenerative Diseases and Flavonoids: Special Reference to Kaempferol

Neurodegenerative diseases like Alzheimer's disease, Parkinson's disease, Huntington's disease, Multiple Sclerosis and Ischemic stroke have become a major health problem worldwide. Pre-clinical studies have demonstrated the beneficial effects of flavonoids on neurodegenerative diseases and suggest them to be used as therapeutic agents. Kaempferol is found in many plants such as tea, beans, broccoli, strawberries, and neuroprotective effects against the development of many neurodegenerative diseases such as Parkinson, Alzheimer's disease and Huntington's disease. The present study summarizes the neuroprotective effects of kaempferol in various models of neurodegenerative diseases. Kaempferol delays the initiation as well as the progression of neurodegenerative disorders by acting as a scavenger of free radicals and preserving the activity of various antioxidant enzymes. Kaempferol can cross the Blood-Brain Barrier (BBB), and therefore results in an enhanced protective effect. The multi-target property of kaempferol makes it a potential dietary supplement in preventing and treating neurodegenerative diseases.

Polyphenols as Potential Metal Chelation Compounds Against Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease affecting more than 50 million people worldwide. The pathology of this multifactorial disease is primarily characterized by the formation of amyloid-β (Aβ) aggregates; however, other etiological factors including metal dyshomeostasis, specifically copper (Cu), zinc (Zn), and iron (Fe), play critical role in disease progression. Because these transition metal ions are important for cellular function, their imbalance can cause oxidative stress that leads to cellular death and eventual cognitive decay. Importantly, these transition metal ions can interact with the amyloid-β protein precursor (AβPP) and Aβ42 peptide, affecting Aβ aggregation and increasing its neurotoxicity. Considering how metal dyshomeostasis may substantially contribute to AD, this review discusses polyphenols and the underlying chemical principles that may enable them to act as natural chelators. Furthermore, polyphenols have various therapeutic effects, including antioxidant activity, metal chelation, mitochondrial function, and anti-amyloidogenic activity. These combined therapeutic effects of polyphenols make them strong candidates for a moderate chelation-based therapy for AD.

Aryl Hydrocarbon Receptor Role in Co-Ordinating SARS-CoV-2 Entry and Symptomatology: Linking Cytotoxicity Changes in COVID-19 and Cancers; Modulation by Racial Discrimination Stress

There is an under-recognized role of the aryl hydrocarbon receptor (AhR) in co-ordinating the entry and pathophysiology of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) that underpins the COVID-19 pandemic. The rise in pro-inflammatory cytokines during the 'cytokine storm' induce indoleamine 2,3-dioxygenase (IDO), leading to an increase in kynurenine that activates the AhR, thereby heightening the initial pro-inflammatory cytokine phase and suppressing the endogenous anti-viral response. Such AhR-driven changes underpin the heightened severity and fatality associated with pre-existent high-risk medical conditions, such as type II diabetes, as well as to how racial discrimination stress contributes to the raised severity/fatality in people from the Black Asian and Minority Ethnic (BAME) communities. The AhR is pivotal in modulating mitochondrial metabolism and co-ordinating specialized, pro-resolving mediators (SPMs), the melatonergic pathways, acetyl-coenzyme A, and the cyclooxygenase (COX) 2-prostaglandin (PG) E2 pathway that underpin 'exhaustion' in the endogenous anti-viral cells, paralleling similar metabolic suppression in cytolytic immune cells that is evident across all cancers. The pro-inflammatory cytokine induced gut permeability/dysbiosis and suppression of pineal melatonin are aspects of the wider pathophysiological underpinnings regulated by the AhR. This has a number of prophylactic and treatment implications for SARS-CoV-2 infection and cancers and future research directions that better investigate the biological underpinnings of social processes and how these may drive health disparities.

A Brief Review on the Neuroprotective Mechanisms of Vitexin

The neural dysfunction is triggered by cellular and molecular events that provoke neurotoxicity and neural death. Currently, neurodegenerative diseases are increasingly common, and available treatments are focused on relieving symptoms. Based on the above, in this review we describe the participation of vitexin in the main events involved in the neurotoxicity and cell death process, as well as the use of vitexin as a therapeutic approach to suppress or attenuate neurodegenerative progress. Vitexin contributes to increasing neuroprotective factors and pathways and counteract the targets that induce neurodegeneration, such as redox imbalance, neuroinflammation, abnormal protein aggregation, and reduction of cognitive and/or motor impairment. The results obtained provide substantial evidence to support the scientific exploration of vitexin in these pathologies, since their effects are still little explored for this direction.

Ferrosenescence: The iron age of neurodegeneration?

Aging has been associated with iron retention in many cell types, including the neurons, promoting neurodegeneration by ferroptosis. Excess intracellular iron accelerates aging by damaging the DNA and blocking genomic repair systems, a process we define as ferrosenescence. Novel neuroimaging and proteomic techniques have pinpointed indicators of both iron retention and ferrosenescence, allowing for their early correction, potentially bringing prevention of neurodegenerative disorders within reach. In this review, we take a closer look at the early markers of iron dyshomeostasis in neurodegenerative disorders, focusing on preventive strategies based on nutritional and microbiome manipulations.

Potential neuroprotective properties of epigallocatechin-3-gallate (EGCG)

Neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) enforce an overwhelming social and economic burden on society. They are primarily characterized through the accumulation of modified proteins, which further trigger biological responses such as inflammation, oxidative stress, excitotoxicity and modulation of signalling pathways. In a hope for cure, these diseases have been studied extensively over the last decade to successfully develop symptom-oriented therapies. However, so far no definite cure has been found. Therefore, there is a need to identify a class of drug capable of reversing neural damage and preventing further neural death. This review therefore assesses the reliability of the neuroprotective benefits of epigallocatechin-gallate (EGCG) by shedding light on their biological, pharmacological, antioxidant and metal chelation properties, with emphasis on their ability to invoke a range of cellular mechanisms in the brain. It also discusses the possible use of nanotechnology to enhance the neuroprotective benefits of EGCG.

Epigallocatechin-3-gallate rescues LPS-impaired adult hippocampal neurogenesis through suppressing the TLR4-NF-κB signaling pathway in mice

Adult hippocampal dentate granule neurons are generated from neural stem cells (NSCs) in the mammalian brain, and the fate specification of adult NSCs is precisely controlled by the local niches and environment, such as the subventricular zone (SVZ), dentate gyrus (DG), and Toll-like receptors (TLRs). Epigallocatechin-3-gallate (EGCG) is the main polyphenolic flavonoid in green tea that has neuroprotective activities, but there is no clear understanding of the role of EGCG in adult neurogenesis in the DG after neuroinflammation. Here, we investigate the effect and the mechanism of EGCG on adult neurogenesis impaired by lipopolysaccharides (LPS). LPS-induced neuroinflammation inhibited adult neurogenesis by suppressing the proliferation and differentiation of neural stem cells in the DG, which was indicated by the decreased number of Bromodeoxyuridine (BrdU)-, Doublecortin (DCX)- and Neuronal Nuclei (NeuN)-positive cells. In addition, microglia were recruited with activatingTLR4-NF-κB signaling in the adult hippocampus by LPS injection. Treating LPS-injured mice with EGCG restored the proliferation and differentiation of NSCs in the DG, which were decreased by LPS, and EGCG treatment also ameliorated the apoptosis of NSCs. Moreover, pro-inflammatory cytokine production induced by LPS was attenuated by EGCG treatment through modulating the TLR4-NF-κB pathway. These results illustrate that EGCG has a beneficial effect on impaired adult neurogenesis caused by LPSinduced neuroinflammation, and it may be applicable as a therapeutic agent against neurodegenerative disorders caused by inflammation.

Modulation of neurotrophic signaling pathways by polyphenols

Polyphenols are an important class of phytochemicals, and several lines of evidence have demonstrated their beneficial effects in the context of a number of pathologies including neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease. In this report, we review the studies on the effects of polyphenols on neuronal survival, growth, proliferation and differentiation, and the signaling pathways involved in these neurotrophic actions. Several polyphenols including flavonoids such as baicalein, daidzein, luteolin, and nobiletin as well as nonflavonoid polyphenols such as auraptene, carnosic acid, curcuminoids, and hydroxycinnamic acid derivatives including caffeic acid phentyl ester enhance neuronal survival and promote neurite outgrowth in vitro, a hallmark of neuronal differentiation. Assessment of underlying mechanisms, especially in PC12 neuronal-like cells, reveals that direct agonistic effect on tropomyosin receptor kinase (Trk) receptors, the main receptors of neurotrophic factors including nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) explains the action of few polyphenols such as 7,8-dihydroxyflavone. However, several other polyphenolic compounds activate extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/Akt pathways. Increased expression of neurotrophic factors in vitro and in vivo is the mechanism of neurotrophic action of flavonoids such as scutellarin, daidzein, genistein, and fisetin, while compounds like apigenin and ferulic acid increase cyclic adenosine monophosphate response element-binding protein (CREB) phosphorylation. Finally, the antioxidant activity of polyphenols reflected in the activation of Nrf2 pathway and the consequent upregulation of detoxification enzymes such as heme oxygenase-1 as well as the contribution of these effects to the neurotrophic activity have also been discussed. In conclusion, a better understanding of the neurotrophic effects of polyphenols and the concomitant modulations of signaling pathways is useful for designing more effective agents for management of neurodegenerative diseases.

Protective Mechanisms of Flavonoids in Parkinson's Disease

Parkinson's disease is a chronic, debilitating neurodegenerative movement disorder characterized by progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta region in human midbrain. To date, oxidative stress is the well accepted concept in the etiology and progression of Parkinson's disease. Hence, the therapeutic agent is targeted against suppressing and alleviating the oxidative stress-induced cellular damage. Within the past decades, an explosion of research discoveries has reported on the protective mechanisms of flavonoids, which are plant-based polyphenols, in the treatment of neurodegenerative disease using both in vitro and in vivo models. In this paper, we have reviewed the literature on the neuroprotective mechanisms of flavonoids in protecting the dopaminergic neurons hence reducing the symptoms of this movement disorder. The mechanism reviewed includes effect of flavonoids in activation of endogenous antioxidant enzymes, suppressing the lipid peroxidation, inhibition of inflammatory mediators, flavonoids as a mitochondrial target therapy, and modulation of gene expression in neuronal cells.

Epicatechin Reduces Striatal MPP⁺-Induced Damage in Rats through Slight Increases in SOD-Cu,Zn Activity

Parkinson's disease is a neurodegenerative disorder characterized by movement alterations caused by reduced dopaminergic neurotransmission in the nigrostriatal pathway, presumably by oxidative stress (OS). MPP⁺ intrastriatal injection leads to the overproduction of free radicals (FR). The increasing formation of FR produces OS, a decline in dopamine (DA) content, and behavioral disorders. Epicatechin (EC) has shown the ability to be FR scavenger, an antioxidant enzyme inductor, a redox state modulator, and transition metal chelator. Acute administration of 100 mg/kg of EC significantly prevented (P < 0.05) the circling MPP⁺-induced behavior (10 μg/8 μL). Likewise, EC significantly (P < 0.05) reduced the formation of fluorescent lipid products caused by MPP⁺. MPP⁺ injection produced (P < 0.05) increased enzymatic activity of the constitutive nitric oxide synthase (cNOS). This effect was blocked with acute EC pretreatment. Cu/Zn-dependent superoxide dismutase (Cu/Zn-SOD) activity was significantly (P < 0.05) reduced as a consequence of MPP⁺ damage. EC produced a slight increase (≈20%) in Cu/Zn-SOD activity in the control group. Such effects persisted in animals injured with MPP⁺. The results show that EC is effective against MPP⁺-induced biochemical and behavioral damage, which is possible by an increase in Cu/Zn-SOD activity.

Epigallocatechin-3-gallate enhances clearance of phosphorylated tau in primary neurons

OBJECTIVES

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by intracellular accumulations of phosphorylated forms of the microtubule binding protein tau. This study aimed to explore a novel mechanism for enhancing the clearance of these pathological tau species using the green tea flavonoid epigallocatechin-3-gallate (EGCG). EGCG is a potent antioxidant and an activator of the Nrf2 transcriptional pathway. Nrf2 activators including EGCG have shown promise in mitigating amyloid pathology in vitro and in vivo. This study assessed whether EGCG could also alter tau clearance.

METHODS

Rat primary cortical neuron cultures were treated on day in vitro 8 with EGCG and analyzed for changes in gene and protein expression using luciferase assay, q-PCR, and western blotting.

RESULTS

EGCG treatment led to a significant decrease in the protein levels of three AD-relevant phospho-tau epitopes. Unexpectedly, EGCG does not appear to be facilitating this effect through the Nrf2 pathway or by increasing autophagy in general. However, EGCG did significantly increase mRNA expression of the key autophagy adaptor proteins NDP52 and p62.

DISCUSSION

In this study, we show that EGCG enhances the clearance of AD-relevant phosphorylated tau species in primary neurons. Interestingly, this result appears to be independent of both Nrf2 activation and enhanced autophagy - two previously reported mechanisms of phytochemical-induced tau clearance. EGCG did significantly increase expression of two autophagy adaptor proteins. Taken together, these results demonstrate that EGCG has the ability to increase the clearance of phosphorylated tau species in a highly specific manner, likely through increasing adaptor protein expression.

Quercetin and related polyphenols: new insights and implications for their bioactivity and bioavailability

The physiological functions and mechanisms of action of quercetin and its related polyphenols are highlighted, including their effects on brain, blood vessels, muscle, and intestinal microflora.

Effect of antioxidants supplementation on aging and longevity

If aging is due to or contributed by free radical reactions, as postulated by the free radical theory of aging, lifespan of organisms should be extended by administration of exogenous antioxidants. This paper reviews data on model organisms concerning the effects of exogenous antioxidants (antioxidant vitamins, lipoic acid, coenzyme Q, melatonin, resveratrol, curcumin, other polyphenols, and synthetic antioxidants including antioxidant nanoparticles) on the lifespan of model organisms. Mechanisms of effects of antioxidants, often due to indirect antioxidant action or to action not related to the antioxidant properties of the compounds administered, are discussed. The legitimacy of antioxidant supplementation in human is considered.

Nucleoside 5'-phosphorothioate derivatives as oxidative stress protectants in PC12 cells

Iron-induced oxidative damage of mitochondria contributes to cellular death seen in neurodegenerative diseases, therefore, there is a demand for nontoxic, biocompatible, and effective Fe-ion chelators. We evaluated the chelation of Fe(II) by phosphate derivatives using ferrozine as an indicator. We studied the effect of phosphate derivatives on inhibiting Fe(II)-induced oxidative stress in PC12 cells, and metabolic stability in PC12 cells was evaluated. Nucleotides containing phosphorothioate moieties inhibited ROS formation better than natural nucleotides and were more metabolically stable in PC12 cells. Finally, we elucidated that these nucleotides activate the MAP-kinase pathway that contributes to protection of PC12 cells under oxidative stress.

Caffeoylquinic acid-rich purple sweet potato extract, with or without anthocyanin, imparts neuroprotection and contributes to the improvement of spatial learning and memory of SAMP8 mouse

The effects of caffeoylquinic acid (CQA)-rich purple sweet potato (PSP) extract, with (PSPEa) or without (PSPEb) anthocyanin, on the improvement of spatial learning and memory of senescence-accelerated prone mouse strain (SAMP) 8 was determined. SAMP8 was treated with 20 mg/kg/day of PSPEa or PSPEb for 30 days. The effect on spatial learning and memory and the molecular mechanism of this effect were determined in vivo (SAMP8) and in vitro (SH-SY5Y cells). PSPEa or PSPEb reduced the escape latency time of SAMP8 by 17.0 ± 8.0 and 14.2 ± 5.8 s (P < 0.01), respectively. PSPEa administration induced an overexpression of antioxidant-, energy metabolism-, and neuronal plasticity-related proteins in the brain of SAMP8. Additionally, PSPEa and PSPEb increased the cell viability by 141.6 and 133% as compared to Aβ1-42-treated cells. These findings suggest that PSP rich in CQA derivatives with or without anthocyanidine had a neuroprotective effect on mouse brain and can improve the spatial learning and memory of SAMP8.

A natural antioxidant pine bark extract, Oligopin®, regulates the stress chaperone HSPB1 in human skeletal muscle cells: a proteomics approach

The gradual loss of muscle mass affecting all the elderly (sarcopenia) is most likely due to a decreased number and/or function of satellite cells. Accumulation of reactive oxygen species (ROS) has been clearly correlated to sarcopenia and could contribute to the impairment of satellite cell function. In this study, we analyzed the protective mechanism of action of a natural pine bark extract (Oligopin®) in human muscle satellite cells exposed to oxidative stress (H2O2). This polyphenol belongs to the flavonoid family and was able to abolish the H2 O2-induced apoptotic cell death. A large-scale proteomic strategy allowed us to identify several proteins that may function as early regulators of ROS-mediated events in muscle cells. Interestingly, we identified the stress chaperone heat shock protein beta-1, a main protector of muscle necrosis, as a target of Oligopin® and showed that this polyphenol was able to modulate its stress induced phosphorylation.

Potential role of green tea catechins in various disease therapies: progress and promise

Green tea (from the plant Camellia sinensis), a beverage whose consumption started 5000 years ago in China, has important biological and pharmacological properties. The beneficial effects of green tea have been attributed to the presence of phenolic compounds that are powerful anti-oxidants and free iron scavengers. Of all the catechins found in green tea, namely (-)-epicatechin-3-gallate, (-)-epigallocatechin, (-)-epicatechin and (-)-epigallocatechin-3-gallate (EGCG), EGCG is the most abundant and powerful. It is widely believed that green tea may protect against death from all causes, especially cardiovascular diseases (coronary heart disease and stroke) owing to the presence of catechins associated with green tea consumption. Other health benefits include various types of cancer chemoprevention, weight loss and protective effects against neurodegenerative diseases (Alzheimer's disease and Parkinson's disease). Thus far, numerous pharmacological activities regulating disease-specific molecular targets have been reported in vitro for EGCG concentrations in the micromolar range, which are physiologically irrelevant. Although most of the studies have shown benefits with two to three cups of green tea per day, the optimal dose has not yet been established to enable any solid conclusions to be drawn regarding the various health benefits of green tea or its constituents in humans. With Phase I trials providing information on the safety profile and pharmacokinetics of EGCG, the window of opportunity is wider to undertake well-controlled long-term human studies to enable a full understanding of the protective effects of green tea catechins on various parameters in different settings.

Opportunities and challenges for nutritional proteomics in cancer prevention

Knowledge gaps persist about the efficacy of cancer prevention strategies based on dietary food components. Adaptations to nutrient supply are executed through tuning of multiple protein networks that include transcription factors, histones, modifying enzymes, translation factors, membrane and nuclear receptors, and secreted proteins. However, the simultaneous quantitative and qualitative measurement of all proteins that regulate cancer processes is not practical using traditional protein methodologies. Proteomics offers an attractive opportunity to fill this knowledge gap and unravel the effects of dietary components on protein networks that impinge on cancer. The articles presented in this supplement are from talks proffered in the "Nutrition Proteomics and Cancer Prevention" session at the American Institute for Cancer Research Annual Research Conference on Food, Nutrition, Physical Activity and Cancer held in Washington, DC on October 21 and 22, 2010. Recent advances in MS technologies suggest that studies in nutrition and cancer prevention may benefit from the adoption of proteomic tools to elucidate the impact on biological processes that govern the transition from normal to malignant phenotype; to identify protein changes that determine both positive and negative responses to food components; to assess how protein networks mediate dose-, time-, and tissue-dependent responses to food components; and, finally, for predicting responders and nonresponders. However, both the limited accessibility to proteomic technologies and research funding appear to be hampering the routine adoption of proteomic tools in nutrition and cancer prevention research.

Natural polyphenols against neurodegenerative disorders: potentials and pitfalls

Within the last years, a rapidly growing number of polyphenolic compounds with neuroprotective effects have been described. Many efforts have been made to explore the mechanisms behind the neuroprotective action of polyphenols. However, many pathways and mechanisms considered for mediating these effects are rather general than specific. Moreover, despite the beneficial effects of polyphenols in experimental treatment of neurodegeneration, little has been achieved in bringing them into routine clinical applications. In this review, we have summarized the protective effects of polyphenols against neurodegeneration, and we have also discussed some of the barricades in translating these biochemical compounds, into relevant therapeutics for neurodegenerative diseases.

Flavonoids as modulators of memory and learning: molecular interactions resulting in behavioural effects

There is considerable interest in the potential of a group of dietary-derived phytochemicals known as flavonoids in modulating neuronal function and thereby influencing memory, learning and cognitive function. The present review begins by detailing the molecular events that underlie the acquisition and consolidation of new memories in the brain in order to provide a critical background to understanding the impact of flavonoid-rich diets or pure flavonoids on memory. Data suggests that despite limited brain bioavailability, dietary supplementation with flavonoid-rich foods, such as blueberry, green tea and Ginkgo biloba lead to significant reversals of age-related deficits on spatial memory and learning. Furthermore, animal and cellular studies suggest that the mechanisms underpinning their ability to induce improvements in memory are linked to the potential of absorbed flavonoids and their metabolites to interact with and modulate critical signalling pathways, transcription factors and gene and/or protein expression which control memory and learning processes in the hippocampus; the brain structure where spatial learning occurs. Overall, current evidence suggests that human translation of these animal investigations are warranted, as are further studies, to better understand the precise cause-and-effect relationship between flavonoid intake and cognitive outputs.

Determining the effects of antioxidants on oxidative stress induced carbonylation of proteins

There is potential that the pathological effects of oxidative stress (OS) associated diseases such as diabetes could be ameliorated with antioxidants, but this will require a clearer understanding of the pathway(s) by which proteins are damaged by OS. This study reports the development and use of methods that assess the efficacy of dietary antioxidant supplementation at a mechanistic level. Data reported here evaluate the impact of green tea supplementation on oxidative stress induced post-translational modifications (OSi-PTMs) in plasma proteins of Zucker diabetic fatty (ZDF) rats. The mechanism of antioxidant protection was examined through both the type and amount of OSi-PTMs using mass spectrometry based identification and quantification. Carbonylated proteins in freshly drawn blood samples were derivatized with biotin hydrazide. Proteins thus biotinylated were selected from plasma samples of green tea fed diabetic rats and control animals by avidin affinity chromatography, further fractionated by reversed phase chromatography (RPC); fractions from the RPC column were tryptic digested, and the tryptic digest was fractionated by RPC before being identified by tandem mass spectrometry (MS/MS). Relative quantification of peptides bearing carbonylation sites was achieved for the first time by RPC-MS/MS using selective reaction monitoring (SRM). Seventeen carbonylated peptides were detected and quantified in both control and treated plasma. The relative concentration of eight was dramatically different between control and green tea treated animals. Seven of the OSi-PTM bearing peptides had dropped dramatically in concentration with treatment while one increased, indicating differential regulation of carbonylation by antioxidants. Green tea antioxidants were found to reduce carbonylation of proteins by lipid peroxidation end products most, followed by advanced glycation end products to a slightly lower extent. Direct oxidation of proteins by reactive oxygen species (ROS) was protected the least by green tea.

Green tea polyphenol EGCG suppresses lung cancer cell growth through upregulating miR-210 expression caused by stabilizing HIF-1α

(-)-Epigallocatechin-3-gallate (EGCG) has been reported to affect many cellular regulatory pathways. This study aims to determine whether EGCG could target microRNA (miRNA), one of the mechanisms for cells to achieve subtle change in multiple targets. We found that, in both human and mouse lung cancer cells in culture, EGCG specifically upregulated the expression of miR-210, a major miRNA regulated by HIF-1α. Furthermore, we found that overexpression of miR-210 led to reduced cell proliferation rate and anchorage-independent growth as well as reduced sensitivity to EGCG. On the mechanisms of miR-210 regulation by EGCG, we demonstrated that the regulation was mediated through the hypoxia-response element in miR-210 promoter. Consistently, the upregulation of miR-210 was found to be correlated with the stabilized HIF-1α in lung cancer cell lines after EGCG treatment. This EGCG-induced stabilization of HIF-1α was further shown by the stabilization of HA-tagged HIF-1α but not the P402A/P564A-mutated HIF-1α by EGCG, suggesting that EGCG targets the oxygen-dependent degradation (ODD) domain. Direct evidence was obtained by affinity binding assay showing that EGCG specifically binds HIF-1α with a K(d) = 3.47 μM. This result suggests that EGCG binding interferes with the hydroxylation of key Pro residues in the ODD domain, preventing HIF-1α from the Pro hydroxylation-dependent ubiquitination and subsequent proteosome-mediated degradation. In summary, our results demonstrated, for the first time, the elevation of miR-210 by EGCG in lung cancer cell lines and this is mediated by the stabilization of HIF-1α. This event contributes to the anticancer activity of EGCG.

Synthetic and natural iron chelators: therapeutic potential and clinical use

Iron-chelation therapy has its origins in the treatment of iron-overload syndromes. For many years, the standard for this purpose has been deferoxamine. Recently, considerable progress has been made in identifying synthetic chelators with improved pharmacologic properties relative to deferoxamine. Most notable are deferasirox (Exjade(®)) and deferiprone (Ferriprox(®)), which are now available clinically. In addition to treatment of iron overload, there is an emerging role for iron chelators in the treatment of diseases characterized by oxidative stress, including cardiovascular disease, atherosclerosis, neurodegenerative diseases and cancer. While iron is not regarded as the underlying cause of these diseases, it does play an important role in disease progression, either through promotion of cellular growth and proliferation or through participation in redox reactions that catalyze the formation of reactive oxygen species and increase oxidative stress. Thus, iron chelators may be of therapeutic benefit in many of these conditions. Phytochemicals, many of which bind iron, may also owe some of their beneficial properties to iron chelation. This review will focus on the advances in iron-chelation therapy for the treatment of iron-overload disease and cancer, as well as neurodegenerative and chronic inflammatory diseases. Established and novel iron chelators will be discussed, as well as the emerging role of dietary plant polyphenols that effectively modulate iron biochemistry.

Towards a unifying, systems biology understanding of large-scale cellular death and destruction caused by poorly liganded iron: Parkinson's, Huntington's, Alzheimer's, prions, bactericides, chemical toxicology and others as examples

Exposure to a variety of toxins and/or infectious agents leads to disease, degeneration and death, often characterised by circumstances in which cells or tissues do not merely die and cease to function but may be more or less entirely obliterated. It is then legitimate to ask the question as to whether, despite the many kinds of agent involved, there may be at least some unifying mechanisms of such cell death and destruction. I summarise the evidence that in a great many cases, one underlying mechanism, providing major stresses of this type, entails continuing and autocatalytic production (based on positive feedback mechanisms) of hydroxyl radicals via Fenton chemistry involving poorly liganded iron, leading to cell death via apoptosis (probably including via pathways induced by changes in the NF-κB system). While every pathway is in some sense connected to every other one, I highlight the literature evidence suggesting that the degenerative effects of many diseases and toxicological insults converge on iron dysregulation. This highlights specifically the role of iron metabolism, and the detailed speciation of iron, in chemical and other toxicology, and has significant implications for the use of iron chelating substances (probably in partnership with appropriate anti-oxidants) as nutritional or therapeutic agents in inhibiting both the progression of these mainly degenerative diseases and the sequelae of both chronic and acute toxin exposure. The complexity of biochemical networks, especially those involving autocatalytic behaviour and positive feedbacks, means that multiple interventions (e.g. of iron chelators plus antioxidants) are likely to prove most effective. A variety of systems biology approaches, that I summarise, can predict both the mechanisms involved in these cell death pathways and the optimal sites of action for nutritional or pharmacological interventions.

Neuroprotective multifunctional iron chelators: from redox-sensitive process to novel therapeutic opportunities

Accumulating evidence suggests that many cytotoxic signals occurring in the neurodegenerative brain can initiate neuronal death processes, including oxidative stress, inflammation, and accumulation of iron at the sites of the neuronal deterioration. Neuroprotection by iron chelators has been widely recognized with respect to their ability to prevent hydroxyl radical formation in the Fenton reaction by sequestering redox-active iron. An additional neuroprotective mechanism of iron chelators is associated with their ability to upregulate or stabilize the transcriptional activator, hypoxia-inducible factor-1alpha (HIF-1alpha). HIF-1alpha stability within the cells is under the control of a class of iron-dependent and oxygen-sensor enzymes, HIF prolyl-4-hydroxylases (PHDs) that target HIF-1alpha for degradation. Thus, an emerging novel target for neuroprotection is associated with the HIF system to promote stabilization of HIF-1alpha and increase transcription of HIF-1-related survival genes, which have been reported to be regulated in patient's brains afflicted with diverse neurodegenerative diseases. In accordance, a new potential therapeutic strategy for neurodegenerative diseases is explored, by which iron chelators would inhibit PHDs, target the HIF-1-signaling pathway and ultimately activate HIF-1-dependent neuroprotective genes. This review discusses two interrelated approaches concerning therapy targets in neurodegeneration, sharing in common the implementation of iron chelation activity: antioxidation and HIF-1-pathway activation.

Green tea polyphenol epigallocatechin-3-gallate: inflammation and arthritis. [corrected]

A number of factors including inflammation and oxidative stress are believed to play a role in the development of chronic joint diseases. Green tea has become a popular drink and is consumed throughout the world. Extracts of green tea and polyphenols present therein have been shown to inhibit the inflammatory responses in vitro in different cell types and the development of arthritis in animal model studies. There is considerable evidence that (-)-epigallocatechin-3-gallate (EGCG), the predominant green tea polyphenol which mimic its effects, inhibits enzyme activities and signal transduction pathways that play important roles in inflammation and joint destruction in arthritis. After oral consumption EGCG become bioavailable and proteomic studies suggest that EGCG may directly interact with a large set of protein targets and alter the physiological response of the cells. Taken together these and other studies identify and support the use of EGCG as a possible chemopreventive agent with a potential to inhibit the development of arthritis. Here we review the biological effects of EGCG in an attempt to understand its pivotal molecular targets that directly affect the inflammation and joint destruction process for prevention and/or for the development of new therapeutics for arthritis in humans.

Pyrithione-zinc Prevents UVB-induced Epidermal Hyperplasia by Inducing HIF-1alpha

Epidermal keratinocytes overgrow in response to ultraviolet-B (UVB), which may be associated with skin photoaging and cancer development. Recently, we found that HIF-1alpha controls the keratinocyte cell cycle and thereby contributes to epidermal homeostasis. A further study demonstrated that HIF-1alpha is down-regulated by UVB and that this process is involved in UVB-induced skin hyperplasia. Therefore, we hypothesized that the forced expression of HIF-1alpha in keratinocytes would prevent UVB-induced keratinocyte overgrowth. Among several agents known to induce HIF-1alpha, pyrithione-zinc (Py-Zn) overcame the UVB suppression of HIF-1alpha in cultured keratinocytes. Mechanistically, Py-Zn blocked the degradation of HIF-1alpha protein in keratinocytes, while it did not affect the synthesis of HIF-1alpha. Moreover, the p21 cell cycle inhibitor was down-regulated after UVB exposure, but was robustly induced by Py-Zn. In mice repeatedly irradiated with UVB, the epidermis became hyperplastic and HIF-1alpha disappeared from nuclei of epidermal keratinocytes. However, a cream containing Py-Zn effectively prevented the skin thickening and up-regulated HIF-1alpha to the normal level. These results suggest that Py-Zn is a potential agent to prevent UVB-induced photoaging and skin cancer development. This work also provides insight into a molecular target for treatment of UVB-induced skin diseases.

Dietary regulation of P-gp function and expression

Food-drug interactions have been associated with clinically important pharmacokinetic and pharmacodynamic changes of a drug. The aim of this paper is to review the regulation of P-glycoprotein (P-gp) by dietary components and to correlate the changes in cellular P-gp function and expression with drug bioavailability. In summary, the published literature has provided extensive data supporting the modulation of drug bioavailability through P-gp regulation by components in food groups such as fruit juices, spices, herbs, cruciferous vegetables and green tea. Most of these data were, however, derived from in vitro cell models and, except for the St John's wort, the clinical significance of most reported interactions remains to be clarified. Studies on piperine and capsaicin have underscored an often poor correlation between in vivo and in vitro data, whereas experiments involving curcumin highlighted differences between acute and chronic consumption of a dietary component on P-gp function and expression in vivo. A better understanding of the pharmacokinetic and pharmacodynamic profiles of the dietary components will aid in addressing these knowledge gaps.

Challenges associated with metal chelation therapy in Alzheimer's disease

A close association between brain metal dishomeostasis and the onset and/or progression of Alzheimer's disease (AD) has been clearly established in a number of studies, although the underlying biochemical mechanisms remain obscure. This observation renders chelation therapy an attractive pharmacological option for the treatment of this disease. However, a number of requirements must be fulfilled in order to adapt chelation therapy to AD so that the term "metal targeted strategies" seems now more appropriate. Indeed, brain metal redistribution rather than brain metal scavenging and removal is the major goal of this type of intervention. The most recent developments in metal targeted strategies for AD will be discussed using, as useful examples, clioquinol, curcumin, and epigallocatechin, and the future perspectives will also be outlined.

Neuroprotective molecular mechanisms of (-)-epigallocatechin-3-gallate: a reflective outcome of its antioxidant, iron chelating and neuritogenic properties

Tea, the major source of dietary flavonoids, particularly the epicatechins, signifies the second most frequently consumed beverage worldwide, which varies its status from a simple ancient cultural drink to a nutrient component, endowed possible beneficial neuro-pharmacological actions. Accumulating evidence suggests that oxidative stress, resulting in reactive oxygen species generation, plays a pivotal role in neurodegenerative diseases, supporting the implementation of radical scavengers and metal chelating agents, such as natural tea polyphenols, for therapy. Vast epidemiology data indicate a correlation between occurrence of neurodegenerative disorders, such as Parkinson's and Alzheimer's diseases, and green tea consumption. In particular, recent literature strengthens the perception that diverse molecular signaling pathways, participating in the neuroprotective activity of the major green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG), renders this natural compound as potential agent to reduce the risk of various neurodegenerative diseases. In the current review, we discuss the studies concerning the mechanisms of action implicated in EGCG-induced neuroprotection and discuss the vision to translate these findings into a lifestyle arena.

Select phytochemicals suppress human T-lymphocytes and mouse splenocytes suggesting their use in autoimmunity and transplantation

We have considered a novel "rational" gene targeting approach for treating pathologies whose genetic bases are defined using select phytochemicals. We reason that one such potential application of this approach would be conditions requiring immunosuppression such as autoimmune disease and transplantation, where the genetic target is clearly defined; i.e., interleukin-2 and associated T-cell activation. Therefore, we hypothesized that select phytochemicals can suppress T-lymphocyte proliferation both in vitro and in vivo. The immunosuppressive effects of berry extract, curcumin, quercetin, sulforaphane, epigallocatechin gallate (EGCG), resveratrol, alpha-tocopherol, vitamin C and sucrose were tested on anti-CD3 plus anti-CD28-activated primary human T-lymphocytes in culture. Curcumin, sulforaphane, quercetin, berry extract and EGCG all significantly inhibited T-cell proliferation, and this effect was not due to toxicity. IL-2 production was also reduced by these agents, implicating this important T-cell cytokine in proliferation suppression. Except for berry extract, these same agents also inhibited mouse splenic T-cell proliferation and IL-2 production. Subsequent in vivo studies revealed that quercetin (but not sulforaphane) modestly suppressed mouse splenocyte proliferation following supplementation of BALB/c mice diets. This effect was especially prominent if corrected for the loss of supplement "recall" as observed in cultured T-cells. These results suggest the potential use of these select phytochemicals for treating autoimmune and transplant patients, and support our strategy of using select phytochemicals to treat genetically-defined pathologies, an approach that we believe is simple, healthy, and cost-effective.

Simultaneous manipulation of multiple brain targets by green tea catechins: a potential neuroprotective strategy for Alzheimer and Parkinson diseases

Current therapeutic approaches for Alzheimer and Parkinson disease (AD and PD, respectively) are merely symptomatic, intended for the treatment of symptoms, but offer only partial benefit, without any disease-modifying activity. Novel promising strategies suggest the use of antiinflammatory drugs, antioxidants, iron-complexing molecules, neurotrophic factor delivery, inhibitors of the amyloid precursor protein (APP)-processing secretases, gamma and beta (that generate the amyloid-beta peptides, Abeta), anti-Abeta aggregation molecules, the interference with lipid cholesterol metabolism and naturally occurring plant flavonoids to potentially reverse the course of the diseases. Human epidemiological and new animal data suggest that tea drinking may decrease the incidence of dementia, AD, and PD. In particular, its main catechin polyphenol constituent (-)-epigallocatechin-3-gallate (EGCG) has been shown to exert neuroprotective/neurorescue activities in a wide array of cellular and animal models of neurological disorders. In the current article, we review the literature on the impact of the multimodal activities of green tea polyphenols and their neuroprotective effect on AD and PD.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Nutrigenomics and antioxidants

Since the complete sequencing of the human genome, the era of the ‘omics’ has appeared. Among them, a new discipline called ‘nutrigenomics’ emerged from the interface of nutrition research and genetics. Its aim is to understand how nutrients modulate gene expression. This powerful tool allows determinination of new biomarkers and the molecular pathways by which our diet may have a potential protective effect against degenerative diseases such as cancer. On one hand, cellular metabolism produces continuous oxidative stress and reactive oxygen species with mutagenic and oncogenic effects. On the other hand, diet provides natural antioxidants present in various fruits and vegetables that may prevent diseases. This review first reports the main antioxidants provided by diet and the main results from epidemiological studies of their role in health. Second, we describe how nutrigenomics could provide new insights into nutrition research and innovative developments through neutraceutical products and a personalized medicine.