Attenuation of senescence-induced oxidative exacerbations in aged rat brain by (-)-epigallocatechin-3-gallate

Cellular Red-Ox system in health and disease: The latest update

Cells are continually exposed to reactive oxygen species (ROS) generated during cellular metabolism. Apoptosis, necrosis, and autophagy are biological processes involving a feedback cycle that causes ROS molecules to induce oxidative stress. To adapt to ROS exposure, living cells develop various defense mechanisms to neutralize and use ROS as a signaling molecule. The cellular redox networks combine signaling pathways that regulate cell metabolism, energy, cell survival, and cell death. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) are essential antioxidant enzymes that are required for scavenging ROS in various cell compartments and response to stressful situations. Among the non-enzymatic defenses, vitamin C, glutathione (GSH), polyphenols, carotenoids, vitamin E, etc., are also essential. This review article describes how ROS are produced as byproducts of oxidation/reduction (redox) processes and how the antioxidants defense system is directly or indirectly engaged in scavenging ROS. In addition, we used computational methods to determine the comparative profile of binding energies of several antioxidants with antioxidant enzymes. The computational analysis demonstrates that antioxidants with a high affinity for antioxidant enzymes regulate their structures.

The Role and Mechanisms of Action of Catechins in Neurodegenerative Diseases

The prevalence, incidence and mortality rates of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease are gradually increasing. New approaches are being developed to manage the progression and treatment of neurodegenerative diseases. Catechins, polyphenolic compounds, are key compounds that demonstrate therapeutic effects with their properties such as antioxidant, anti-inflammatory, anti-apoptotic properties in the prevention and treatment of neurodegenerative diseases. The therapeutic effects of catechins have been exhaustively studied in human and animal models. Catechins can have anti-inflammatory effects by suppressing inflammatory pathways and cytokines, as well as antioxidant effects such as chelating metal ions and scavenging radicals. They might reduce phosphorylation of tau proteins, aggregation of amyloid-beta and apoptotic proteins release. They can also decrease alpha-synuclein accumulation and increase dopamine levels. With all these effects, they can have an effect on neurodegenerative diseases. This review points to the potential mechanisms of catechins in neurodegenerative diseases, based on their findings in the literature review.Key teaching pointsCatechins can reduce amyloid-β plaque aggregation and tau phosphorylation.Catechins can decrease alfa-synuclein levels.Catechins can protect neuronal cells with their anti-apoptotic effect.More comprehensive studies are needed to clarify this issue.

Redox and Other Biological Activities of Tea Catechins That May Affect Health: Mechanisms and Unresolved Issues

The beneficial health effects of green tea have been attributed to tea catechins. However, the molecular mechanisms of action, especially those in vivo, remain unclear. This article reviews the redox and other activities of tea catechins, using (-)-epigallocatechin-3-gallate (EGCG), as an example. EGCG is a well-known antioxidant. However, EGCG can be oxidized to generate reactive oxygen species and EGCG quinone. We propose that EGCG quinone can react with Keap-1 to activate Nrf2-regulated cytoprotective enzymes. Tissue levels of catechins are important for their biological activities; a section is devoted to reviewing the biological fates of tea catechins after ingestion. Possible EGCG oxidation in vivo and whether the oligomeric forms are biologically active in animals are discussed. We also review the effects of EGCG on the activities of enzymes, receptors, and other signaling molecules through binding and raise a question about whether the autoxidation of EGCG in vitro may lead to artifacts or misinterpretation in some studies. Finally, we discuss the challenges in the extrapolation of in vitro results to situations in vivo and the translation of laboratory studies to humans.

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.

The Role of Antioxidants in the Interplay between Oxidative Stress and Senescence

Cellular senescence is an irreversible state of cell cycle arrest occurring in response to stressful stimuli, such as telomere attrition, DNA damage, reactive oxygen species, and oncogenic proteins. Although beneficial and protective in several physiological processes, an excessive senescent cell burden has been involved in various pathological conditions including aging, tissue dysfunction and chronic diseases. Oxidative stress (OS) can drive senescence due to a loss of balance between pro-oxidant stimuli and antioxidant defences. Therefore, the identification and characterization of antioxidant compounds capable of preventing or counteracting the senescent phenotype is of major interest. However, despite the considerable number of studies, a comprehensive overview of the main antioxidant molecules capable of counteracting OS-induced senescence is still lacking. Here, besides a brief description of the molecular mechanisms implicated in OS-mediated aging, we review and discuss the role of enzymes, mitochondria-targeting compounds, vitamins, carotenoids, organosulfur compounds, nitrogen non-protein molecules, minerals, flavonoids, and non-flavonoids as antioxidant compounds with an anti-aging potential, therefore offering insights into innovative lifespan-extending approaches.

Antioxidant Phytochemicals for the Prevention of Fluoride-Induced Oxidative Stress and Apoptosis: a Review

Fluorosis is a major public health problem globally. The non-availability of specific treatment and the irreversible nature of dental and skeletal lesions poses a challenge in the management of fluorosis. Oxidative stress is known to be one of the most important mechanisms of fluoride toxicity. Fluoride promotes the accumulation of reactive oxygen species by inhibiting the activity of antioxidant enzymes, resulting in the excessive production of reactive oxygen species at the cellular level which further leads to activation of cell death processes such as apoptosis. Phytochemicals that act as antioxidants have the potential to protect cells from oxidative stress. Evidence confirms that clinical symptoms of fluorosis can be mitigated to some extent or prevented by long-term intake of antioxidants and plant products. The primary purpose of this review is to examine recent findings that focus on the amelioration of fluoride-induced oxidative stress and apoptosis by natural and synthetic phytochemicals and their molecular mechanisms of action.

Assessment of Antioxidant, Immunomodulatory Activity of Oxidised Epigallocatechin-3-Gallate (Green Tea Polyphenol) and Its Action on the Main Protease of SARS-CoV-2—An In Vitro and In Silico Approach

Owing to the instability of Epigallocatechin Gallate (EGCG), it may undergo auto-oxidation and form oxidised products or dimers. In the present study, we aimed to evaluate the therapeutic effects, including antioxidation and immunomodulatory action, of the Oxidised Epigallocatechin Gallate (O-EGCG) as compared to native EGCG and the action of these compounds on main protease (Mpro) docking against SARS-CoV-2. HCT-116 (Human Colon Cancer) cell lines were used to estimate the total antioxidant capacity and lipid peroxidation levels and pro-inflammatory markers (human IL-6, IL-1β, TNF-α). Further, molecular docking analysis was performed by AutoDock and visualised in Discovery studio. Improved antioxidant capacity of O-EGCG was observed, and there was a significant decrease in the inflammatory markers (IL-1β, IL-6, and TNF-α) when O-EGCG was applied as compared to EGCG. The O-EGCG was shown to be strongly associated with the highest docking score and active site residues of IL-1, IL-6, and TNF- α, as well as the Mpro of SARS-CoV-2, according to in silico approach. The in vitro and in silico analyses indicate an improved therapeutic action of the oxidised form of EGCG. The effective inhibitory action of O-EGCG against SARS-CoV-2 suggests further exploration of the compound against COVID-19 and its efficacy. However, in vivo studies and understanding of the mechanism of action of O-EGCG may yield a better opinion on the use of O-EGCG and future human clinical trials.

Epigallocatechin Gallate Alleviates Down-Regulation of Thioredoxin in Ischemic Brain Damage and Glutamate-Exposed Neuron

Epigallocatechin gallate (EGCG) is one of polyphenol that is abundant in green tea. It has anti-oxidative activity and exerts neuroprotective effects in ischemic brain damage. Ischemic conditions induce oxidative stress and result in cell death. Thioredoxin is a small redox protein that plays an important role in the regulation of oxidation and reduction. This study was designed to investigate the regulation of thioredoxin by EGCG in ischemic brain damage. Middle cerebral artery occlusion (MCAO) was performed to induce focal cerebral ischemia in male Sprague-Dawley rats. The EGCG (50 mg/kg) or was administered before MCAO surgical operation. Neurological behavior test, reactive oxygen species (ROS), and lipid peroxidation (LPO) measurement were performed 24 h after MCAO. The cerebral cortex was isolated for further experiments. EGCG alleviated MCAO-induced neurological deficits and increases in ROS and LPO levels. EGCG also ameliorated the decrease in thioredoxin expression by MCAO. This finding was confirmed using various techniques such as Western blot analysis, reverse transcription PCR, and immunofluorescence staining. Results of immunoprecipitation showed that MCAO decreases the interaction between apoptosis signal-regulating kinase 1 (ASK1) and thioredoxin, while EGCG treatment attenuates this decrease. EGCG also attenuated decrease of cell viability and thioredoxin expression in glutamate-exposed neuron in a dose-dependent manner. It alleviated the increase of caspase-3 by glutamate exposure. However, this effect of EGCG on caspase-3 change was weakened in thioredoxin siRNA-transfected neurons. These findings suggest that EGCG exerts a neuroprotective effect by regulating thioredoxin expression and modulating ASK1 and thioredoxin binding in ischemic brain damage.

Flavonoids as natural phenolic compounds and their role in therapeutics: an overview

BACKGROUND

Natural plants and plant-derived formulations have been used by mankind from the ancient period of time. For the past few years, many investigations elaborated the therapeutic potential of various secondary chemicals present in the plants. Literature revealed that the various secondary metabolites, viz. phenolics and flavonoids, are responsible for a variety of therapeutic action in humans.

MAIN BODY

In the present review, an attempt has been made to compile the exploration of natural phenolic compounds with major emphasis on flavonoids and their therapeutic potential too. Interestingly, long-term intake of many dietary foods (rich in phenolics) proved to be protective against the development and management of diabetes, cancer, osteoporosis, cardiovascular diseases and neurodegenerative diseases, etc.

CONCLUSION

This review presents an overview of flavonoid compounds to use them as a potential therapeutic alternative in various diseases and disorders. In addition, the present understanding of phenolics and flavonoids will serve as the basis for the next scientific studies.

Nutraceutical Approaches of Autophagy and Neuroinflammation in Alzheimer's Disease: A Systematic Review

Aging and the emergence of age-associated illnesses are one of the major challenges of our present society. Alzheimer’s disease (AD) is closely associated with aging and is defined by increasing memory loss and severe dementia. Currently, there are no therapy options available that halt AD progression. This work investigates three hallmarks of the disease (autophagy, neuroinflammation, and senescence) and systematically analyzes if there is a beneficial effect from three substances derived from food sources, the so called “nutraceuticals” epigallocatechin gallate, fisetin, and spermidine, on these hallmarks. The results imply a positive outlook for the reviewed substances to qualify as a novel treatment option for AD. A combination of nutraceutical substances and other preventive measures could have significant clinical impact in a multi-layered therapy approach to counter AD.

Effects of (-)-epicatechin on neuroinflammation and hyperphosphorylation of tau in the hippocampus of aged mice

Evidence has implicated oxidative stress (OS) and inflammation as drivers of neurodegenerative pathologies. We previously reported on the beneficial effects of (-)-epicatechin (Epi) treatment on aging-induced OS and its capacity to restore modulators of mitochondrial biogenesis in the prefrontal cortex of 26-month-old male mice. In the present study using the same mouse model of aging, we examined the capacity of Epi to mitigate hippocampus OS, inflammation, hyperphosphorylation of tau protein, soluble β-amyloid protein levels, cell survival, memory, anxiety-like behavior levels and systemic inflammation. Mice were subjected to 4 weeks of Epi treatment (1 mg kg^-1 day^-1) and samples of the hippocampus were obtained. Assessments of the OS markers, protein carbonyls, and malondialdehyde levels demonstrated their significant increase (∼3 fold) with aging that were partially suppressed by Epi. The protein levels of the glial fibrillary acidic protein, inflammatory factor 1 (Iba1), pro-inflammatory cytokines, interleukins (IL-1β, IL-3, 5, 6 and 15), cyclooxygenase 2, tumor necrosis factor α, nuclear factor-activated B cells and interferon γ increase with aging and were also significantly decreased with Epi treatment. However, anti-inflammatory cytokines, IL-1ra, IL-10 and 11 decrease with aging and were restored with Epi. Epi also reversed the aging effects on the hyperphosphorylation of tau, increased soluble β-amyloid levels (∼2 fold), cellular death (as per caspase 3 and 9 activity), and reduced nerve growth factor and triggering receptor expressed on myeloid cells 2 levels. Measures of anxiety like-behavior and memory demonstrated improvements with Epi treatment. Indicators of systemic inflammation increase with aging and Epi was capable of decreasing blood inflammatory markers. Altogether, the results show a significant capacity of Epi to mitigate hippocampus OS and inflammation leading to improved brain function.

Micronutrients: Essential Treatment for Inflammatory Arthritis?

PURPOSE OF REVIEW

Synovial inflammation is characteristic of inflammatory chronic arthropathies and can cause progressive articular damage, chronic pain, and functional loss. Scientific research has increasingly focused on investigating anti-inflammatory micronutrients present in fruits, vegetables, spices, seeds, tea, and wine. This review aims to examine the anti-inflammatory effect of polyphenols (phytonutrients present in plants) and other micronutrients described in randomized clinical trials conducted in patients with chronic inflammatory arthropathies.

RECENT FINDINGS

There is an increasing evidence that differences in micronutrient intake might play an essential role in pathogenesis, therapeutic response, and remission of synovitis. Randomized clinical trials with specific micronutrient- or nutrient-enriched food intake show improvement of symptoms and modulation of both pro- and anti-inflammatory mediators. We found convincing evidence of the anti-inflammatory effect of several micronutrients in arthritis symptoms and inflammation. Although in clinical practice nutritional recommendations to patients with chronic joint inflammation are not consistently prescribed, the addition of these nutrients to day-to-day eating habits could potentially change the natural history of inflammatory arthritis. Future research is needed for a consensus on the specific nutritional recommendations for patients with chronic synovial inflammation.

Mitochondria-targeted hydrogen sulfide attenuates endothelial senescence by selective induction of splicing factors HNRNPD and SRSF2

Cellular senescence is a key driver of ageing, influenced by age-related changes to the regulation of alternative splicing. Hydrogen sulfide (H₂S) has similarly been described to influence senescence, but the pathways by which it accomplishes this are unclear.We assessed the effects of the slow release H₂S donor Na-GYY4137 (100 µg/ml), and three novel mitochondria-targeted H₂S donors AP39, AP123 and RT01 (10 ng/ml) on splicing factor expression, cell proliferation, apoptosis, DNA replication, DNA damage, telomere length and senescence-related secretory complex (SASP) expression in senescent primary human endothelial cells.All H₂S donors produced up to a 50% drop in senescent cell load assessed at the biochemical and molecular level. Some changes were noted in the composition of senescence-related secretory complex (SASP); IL8 levels increased by 24% but proliferation was not re-established in the culture as a whole. Telomere length, apoptotic index and the extent of DNA damage were unaffected. Differential effects on splicing factor expression were observed depending on the intracellular targeting of the H₂S donors. Na-GYY4137 produced a general 1.9 - 3.2-fold upregulation of splicing factor expression, whereas the mitochondria-targeted donors produced a specific 2.5 and 3.1-fold upregulation of SRSF2 and HNRNPD splicing factors only. Knockdown of SRSF2 or HNRNPD genes in treated cells rendered the cells non-responsive to H₂S, and increased levels of senescence by up to 25% in untreated cells.Our data suggest that SRSF2 and HNRNPD may be implicated in endothelial cell senescence, and can be targeted by exogenous H₂S. These molecules may have potential as moderators of splicing factor expression and senescence phenotypes.

Epigallocatechin-3-Gallate Attenuates Microglial Inflammation and Neurotoxicity by Suppressing the Activation of Canonical and Noncanonical Inflammasome via TLR4/NF-κB Pathway

SCOPE

In this study, it has been investigated whether the neuroprotective efficacy of epigallocatechin-3-gallate (EGCG) is mediated by inhibition of canonical and noncanonical inflammasome activation via toll-like receptor 4 (TLR4)/NF-κB pathway both in LPS+Aβ-induced microglia in vitro and in APP/PS1 mice in vivo.

METHODS AND RESULTS

In BV2 cells, EGCG inhibits the expressions of Iba-1, cleaved IL-1β, and cleaved IL-18 induced by LPS+Aβ. Then, the supernatants are used to treat SH-SY5Y cells, and EGCG treatment significantly recovers the neurotoxicity from LPS+Aβ-induced microglial conditioned media. Subsequently, it has been found that EGCG reduces the microglial expressions of caspase-1 p20, NLRP3, and caspase-11 p26. Furthermore, the expression levels of Toll-like receptor 4 (TLR4), p-IKK/IKK, and p-NF-κB/NF-κB were decreased after EGCG treatment. As expected, when a caspase-1 specific inhibitor Z-YVAD-FMK, and an IKK and caspase-11 inhibitor wedelolactone are used for blocking, Z-YVAD-FMK and wedelolactone exacerbate the inhibitory efficacy than using EGCG alone. Finally, consistent with the results obtained in BV2 cells, EGCG treatment reduces microglial inflammation and neurotoxicity by suppressing the activation of canonical NLRP3 and noncanonical caspase-11-dependent inflammasome via TLR4/NF-κB pathway in LPS+Aβ-induced rat primary microglia and hippocampus of APP/PS1 mice.

CONCLUSION

EGCG attenuates microglial inflammation and neurotoxicity by inhibition of canonical NLRP3 and noncanonical caspase-11-dependent inflammasome activation via TLR4/NF-κB pathway.

Triptriolide antagonizes triptolide-induced nephrocyte apoptosis via inhibiting oxidative stress in vitro and in vivo

Triptolide(T9) is a predominant bioactive component extracted from Chinese herb Tripterygium wilfordii Hook F. (TwHF), and has multiple pharmacological activities, such as immunosuppressive and anti-inflammatory activities, et al. However, severe adverse effects and toxicity, particularly nephrotoxicity, limit its clinical application. It has been demonstrated that the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway could alleviate T9-induced nephrocyte damage. The aim of this study was to investigate the potential protective role of triptriolide (T11) against T9-induced nephrocyte apoptosis in vitro and in vivo. Renal injury models were established in human kidney 2 (HK2) cells and BALB/c mice using T9, and the protective effects of T11 were probed in vitro and in vivo, respectively. T9 induced nephrocyte damage in HK2 cells and BALB/c mice by induction of reactive oxygen species (ROS), lactate dehydrogenase (LDH), malondialdehyde (MDA) and glutathione (GSH) and reduction of superoxide dismutase (SOD), which resulted in the apoptosis of nephrocyte and injury of renal function. While, pretreatment of T11 effectively reversed these changes, resulting in the obvious decrease of oxidative stress and renal function parameters, ameliorated nephrocyte apoptosis, improved cell morphology, and higher increase of Nrf2, NAD(P)H: quinine oxidoreductase 1 (NQO1) and heme oxygenase 1 (HO-1) protein levels in vitro and in vivo. Altogether, T11 protected against T9-induced nephrocyte apoptosis possibly via suppressing oxidative stress.

Neuroprotective Role of Phytochemicals

Neurodegenerative diseases are normally distinguished as disorders with loss of neurons. Various compounds are being tested to treat neurodegenerative diseases (NDs) but they possess solitary symptomatic advantages with numerous side effects. Accumulative studies have been conducted to validate the benefit of phytochemicals to treat neurodegenerative diseases including Alzheimer's disease (AD) and Parkinson's disease (PD). In this present review we explored the potential efficacy of phytochemicals such as epigallocatechin-3-galate, berberin, curcumin, resveratrol, quercetin and limonoids against the most common NDs, including Alzheimer's disease (AD) and Parkinson's disease (PD). The beneficial potentials of these phytochemicals have been demonstrated by evidence-based but more extensive investigation needs to be conducted for reducing the progression of AD and PD.

Possible Mechanisms of Green Tea and Its Constituents against Cancer

A number of epidemiological, clinical, and experimental researches have indicated that administration of green tea appears to have anti-cancer activity. According to findings of laboratory cell culture studies, a diverse mechanism has been observed underlying the effects of green tea catechins against cancer. These mechanisms include anti-oxidant activity, cell cycle regulation, receptor tyrosine kinase pathway inhibition, immune system modulation, and epigenetic modification control. This review discusses the results of these studies to provide more insight into the effects of green tea administration on cancers observed to date in this research field.

Effects of the Green Tea Polyphenol Epigallocatechin-3-Gallate on Glioma: A Critical Evaluation of the Literature

The review discusses the effects of Epigallocatechin-3-gallate Gallate (EGCG) on glioma as a basis for future research on clinical application of EGCG. Epidemiological studies on the effects of green tea or EGCG on the risk of glioma is inconclusive due to the limited number of studies, the inclusion of all tea types in these studies, and the focus on caffeine rather than EGCG. In vivo experiments using EGCG monotherapy are inconclusive. Nevertheless, EGCG induces cell death, prevents cellular proliferation, and limits invasion in multiple glioma cell lines. Furthermore, EGCG enhances the efficacy of anti-glioma therapies, including irradiation, temozolomide, carmustine, cisplatin, tamoxifen, and TNF-related apoptosis-inducing ligand, but reduces the effect of bortezomib. Pro-drugs, co-treatment, and encapsulation are being investigated to enhance clinical applicability of EGCG. Mechanisms of actions of EGCG have been partly elucidated. EGCG has both anti-oxidant and oxidant properties. EGCG inhibits pro-survival proteins, such as telomerase, survivin, GRP78, PEA15, and P-gp. EGCG inhibits signaling of PDGFR, IGF-1R, and 67LR. EGCG reduces invasiveness of cancer cells by inhibiting the activities of various metalloproteinases, cytokines, and chemokines. Last, EGCG inhibits some NADPH-producing enzymes, thus disturbing redox status and metabolism of glioma cells. In conclusion, EGCG may be a suitable adjuvant to potentiate anti-glioma therapies.

Epigallocatechin-3-gallate ameliorates erectile function in aged rats via regulation of PRMT1/DDAH/ADMA/NOS metabolism pathway

Aging-related ED is predominantly attributed to neurovascular dysfunction mediated by NO suppression and increased oxidative stress in penis. The alterations of protein arginine methyltransferases 1 (PRMT1)/dimethylarginine dimethylaminohydrolase (DDAH)/asymmetrical dimethylarginine (ADMA)/NO synthase (NOS) pathway regulate NO production in the vascular endothelium. Epigallocatechin-3-gallate (EGCG) is one of the most abundant and antioxidative ingredients isolated from green tea. In the present study, 40 Sprague-Dawley rats were randomly distributed into four groups: one young rat group and three aged rat groups treated with daily gavage feedings of EGCG at doses of 0, 10 mg kg⁻¹, and 100 mg kg⁻¹ for 12 weeks, respectively. Erectile function was assessed by electrical stimulation of the cavernous nerves with intracavernous pressure (ICP) measurement. After euthanasia, penile tissue was investigated using Western blot and ELISA to assess the PRMT1/DDAH/ADMA/NOS metabolism pathway. Superoxide dismutase (SOD) and malondialdehyde (MDA) levels were detected by colorimetry. We also evaluated smooth muscle contents. The ratio of maximal ICP and mean systemic arterial pressure (MAP) was markedly higher in EGCG-treated aged rats than in untreated aged rats. We found that DDAH1 and DDAH2 were expressed in cavernosal tissue, and they were downregulated in corpora of aged rats. The administration of EGCG upregulated the expression and activity of DDAH. In contrast, EGCG treatment downregulated the expression of PRMT1 and ADMA content. Moreover, EGCG-treated rats showed an improvement in smooth muscle expression, the ratio of smooth muscle cell/collagen fibril, SOD activity, and MDA levels when compared with untreated aged rats.

Possible role of antioxidative capacity of (-)-epigallocatechin-3-gallate treatment in morphological and neurobehavioral recovery after sciatic nerve crush injury

OBJECTIVE This study examined the capacity of the major polyphenolic green tea extract (-)-epigallocatechin-3-gallate (EGCG) to suppress oxidative stress and stimulate the recovery and prompt the regeneration of sciatic nerve after crush injury. METHODS Adult male Wistar rats were randomly assigned to one of 4 groups: 1) Naïve, 2) Sham (sham injury, surgical control group), 3) Crush (sciatic nerve crush injury treated with saline), and 4) Crush+EGCG (sciatic nerve crush injury treated with intraperitoneally administered EGCG, 50 mg/kg). All animals were tested for motor and sensory neurobehavioral parameters throughout the study. Sciatic nerve and spinal cord tissues were harvested and processed for morphometric and stereological analysis. For the biochemical assays, the time points were Day 1, Day 7, Day 14, and Day 28 after nerve injury. RESULTS After sciatic nerve crush injury, the EGCG-treated animals (Crush+EGCG group) showed significantly better recovery of foot position and toe spread and 50% greater improvement in motor recovery than the saline-treated animals (Crush group). The Crush+EGCG group displayed an early hopping response at the beginning of the 3rd week postinjury. Animals in the Crush+EGCG group also showed a significant reduction in mechanical allodynia and hyperalgesia latencies and significant improvement in recovery from nociception deficits in both heat withdrawal and tail flick withdrawal latencies compared with the Crush group. In both the Crush+EGCG and Crush groups, quantitative evaluation revealed significant morphological evidence of neuroregeneration according to the following parameters: mean cross-sectional area of axons, myelin thickness in the sciatic nerve (from Week 4 to Week 8), increase of myelin basic protein concentration and gene expression in both the injured sciatic nerve and spinal cord, and fiber diameter to axon diameter ratio and myelin thickness to axon diameter ratio at Week 2 after sciatic nerve injury. However, the axon area remained much smaller in both the Crush+EGCG and Crush groups compared with the Sham and Naïve groups. The number of axons per unit area was significantly decreased in the Crush+EGCG and Crush groups compared with controls. Sciatic nerve injury produced generalized oxidative stress manifested as a significant increase of isoprostanes in the urine and decrease of the total antioxidant capacity (TAC) of the blood from Day 7 until Day 14. EGCG-treated rats showed significantly less increase of isoprostanes than saline-treated animals and also showed full recovery of TAC levels by Day 14 after nerve injury. In spinal cord tissue analysis, EGCG-treated animals showed induced glutathione reductase and suppressed induction of heme oxygenase 1 gene expression compared with nontreated animals. CONCLUSIONS EGCG treatment suppressed the crush-induced production of isoprostanes and stimulated the recovery of the TAC and was associated with remarkable alleviation of motor and sensory impairment and significant histomorphological evidence of neuronal regeneration following sciatic nerve crush injury in rats. The findings of this study suggest that EGCG can be used as an adjunctive therapeutic remedy for nerve injury. However, further investigations are needed to establish the antioxidative mechanism involved in the regenerative process after nerve injury. Only upregulation of glutathione reductase supports the idea that EGCG is acting indirectly via induction of enzymes or transcription factors.

The protective role of plant biophenols in mechanisms of Alzheimer's disease

Self-assembly of amyloid beta peptide (Aβ) into the neurotoxic oligomers followed by fibrillar aggregates is a defining characteristic of Alzheimer's disease (AD). Several lines of proposed hypotheses have suggested the mechanism of AD pathology, though the exact pathophysiological mechanism is not yet elucidated. The poor understanding of AD and multitude of adverse responses reported from the current synthetic drugs are the leading cause of failure in the drug development to treat or halt the progression of AD and mandate the search for safer and more efficient alternatives. A number of natural compounds have shown the ability to prevent the formation of the toxic oligomers and disrupt the aggregates, thus attracted much attention. Referable to the abundancy and multitude of pharmacological activities of the plant active constituents, biophenols that distinguish them from the other phytochemicals as a natural weapon against the neurodegenerative disorders. This review provides a critical assessment of the current literature on in vitro and in vivo mechanistic activities of biophenols associated with the prevention and treatment of AD. We have contended the need for more comprehensive approaches to evaluate the anti-AD activity of biophenols at various pathologic levels and to assess the current evidences. Consequently, we highlighted the various problems and challenges confronting the AD research, and offer recommendations for future research.

Polyphenols in Health and Disease

Deadly diseases, such as cardiovascular diseases and cancer, remain the major health problems worldwide. Research in cardiovascular diseases and genome-wide association studies were successful in indentifying the gene loci associated with these threatening diseases. Yet, a substantial number of casual factors remain unexplained. Over the last decade, a better understanding of molecular and biochemical mechanisms of cardiac diseases led to developing a rationale for combining various protective agents, such as polyphenols, to target multiple signaling pathways. The present review article summarizes recent advances of the use of polyphenols against diseases, such as cardiac diseases.

Cancer Preventive Activities of Tea Catechins

Catechins are widely occurring in our diet and beverages. The cancer-preventive activities of catechins have been extensively studied. Of these, (-)-epigallocatechin-3-gallate (EGCG), the principal catechin in green tea, has received the most attention. The inhibitory activities of tea catechins against carcinogenesis and cancer cell growth have been demonstrated in a large number of laboratory studies. Many mechanisms for modulating cancer signaling and metabolic pathways have been proposed based on numerous studies in cell lines with EGCG, the most active tea catechin. Nevertheless, it is not known whether many of these mechanisms indeed contribute to the anti-cancer activities in animals and in humans. Human studies have provided some results for the cancer preventive activities of tea catechins; however, the activities are not strong. This article reviews the cancer preventive activities and mechanisms of action of tea catechins involving their redox activities, biochemical properties and binding to key enzymes or signal transduction proteins. These mechanisms lead to suppression of cell proliferation, increased apoptosis and inhibition of angiogenesis. The relevance of the proposed mechanisms for cancer prevention are assessed in the light of the situation in vivo. The potential and possible problems in the application of tea and tea-derived products for cancer prevention are discussed.

Polyphenols in dementia: From molecular basis to clinical trials

Dementia is common in the elderly, but there are currently no effective therapies available to prevent or treat this syndrome. In the last decade, polyphenols (particularly curcumin, resveratrol and tea catechins) have been under very close scrutiny as potential therapeutic agents for neurodegenerative diseases, diabetes, inflammatory diseases and aging. Data were collected from Web of Science (ISI Web of Knowledge), Pubmed and Medline (from 2000 to 2015), by searching for the keywords "dementia" AND "curcumin", "resveratrol", "EGCG", "tea catechins". The same keywords were used to investigate the current state of clinical trials recorded in the NIH clinicaltrials.gov registry. Starting from the intrinsic properties of the compounds, we explain their specific action in patients with AD and the most common types of dementia. The pharmacological actions of curcumin, resveratrol and tea catechins have mainly been attributed to their antioxidant activity, interaction with cell signaling pathways, anti-inflammatory effect, chelation of metal ions, and neuroprotection. Evidence from in vitro and in vivo studies on polyphenols have demonstrated that they may play an integral role in preventing and treating diseases associated with neurodegeneration. Furthermore, we critically analyze the clinical trials that we found, which investigate the real pharmacological actions and the possible side effects of these compounds. This review highlights the potential role of polyphenols in the prevention/treatment of dementia and describes the current limitations of research in this field.

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.

Ocoxin® oral solution slows down tumor growth in an experimental model of colorectal cancer metastasis to the liver in Balb/c mice

Liver metastatic disease is the main cause of death in colorectal cancer (CRC) patients. During metastatic spread of the disease an imbalance in the oxidative stress and inflammation plays a crucial role in tumor progression. In order to improve the efficacy of current therapies, new complementary therapeutic approaches are being analyzed including biologically active compounds with low side effects. The anti-inflammatory and anti-oxidant properties of Ocoxin^® oral solution (OOS) prompt us to analyze its effect on the metastatic development of CRC to the liver. First, in vitro effect of OOS in tumor cell viability and migration was analyzed. Second, in vivo effect of different dosage patterns and concentrations in the development of hepatic metastasis was analyzed by intrasplenic inoculation of C26 colon carcinoma cells in Balb/c mice. Third, the expression of alpha smooth muscle actin, caspase-3 and Ki-67 expression was quantified by immunohistochemistry, then gene expression levels of inflammatory factors were measured by quantitative RT-PCR. According to our results, OOS reduced tumor cell viability and migration in vitro. Moreover, in vivo daily administration of OOS from the 7th day after tumor cell inoculation decreased the total area and size of metastatic foci in the liver. Furthermore, cell proliferation and fibroblast recruitment was decreased in tumor foci while a higher number of apoptotic cells were observed. Finally, RNA levels for the inflammatory mediators COX-2, IFNγ, IL1β, IL6 and TNFα were reduced in total liver. In conclusion, OOS reduced the metastatic development of colorectal cancer to the liver by increasing apoptosis, and decreasing tumor cell proliferation and fibroblast recruitment in the tumor foci, as well as the expression of inflammatory mediators in total liver. These results point out OOS as a potential supplement to be applied as complementary therapy for the treatment of liver metastasis from colorectal cancer.

Effects of an antioxidant beverage on biomarkers of oxidative stress in Alzheimer's patients

PURPOSE

The purpose of the study was to test whether daily consumption of a beverage with high antioxidant power, combining extracts of green tea and apple over a period of 8 months, would affect blood and urinary concentrations of biomarkers of oxidative stress in Alzheimer's patients.

METHODS

The study included 100 subjects, 48 of them were Alzheimer's patients, aged 76.5 ± 3.5 years, and 52 were control subjects, aged 79 ± 4 years, without dementia. Three blood and urine samples were taken from each participant, the first (T i) before starting the antioxidant or placebo beverage intake, the second (T m) 4 months after the antioxidant or placebo beverage intake and the third (T f) 8 months after the antioxidant or placebo beverage intake, and concentrations of biomarkers of oxidative stress were measured on serum, lysed erythrocytes or urine by UV-Vis spectrophotometry or by competitive in vitro enzyme-linked immunosorbent assay, according to the parameter analyzed.

RESULTS

The administration of the antioxidant beverage to the Alzheimer's patients prevented the decrease in total antioxidant status in the moderate phase of the disease (T i = 1.40 ± 0.10 mmol/L vs T f = 1.20 ± 0.08 mmol/L), increased values of glutathione peroxidase and superoxide dismutase in initial (165 and 24 % respectively) and moderate phase (75 and 85 % respectively), and prevented the increase in protein carbonyls in moderate phase (T i = 0.17 ± 0.07 nmol/mg protein vs T f = 0.21 ± 0.06 nmol/mg protein), with a significant decrease in protein carbonyls since the fourth month of the intake in initial phase (T m = 0.21 ± 0.06 nmol/mg protein vs T f = 0.11 ± 0.05 nmol/mg protein).

CONCLUSION

Our results suggest that antioxidant beverage could be used as a natural complementary therapy for alleviate or decrease the oxidative stress effects in the stages of Alzheimer's disease.

Epigallocatechin-3-Gallate, a Promising Molecule for Parkinson's Disease?

Parkinson's disease (PD) is the second most common neurodegenerative disease, and it is characterized by the loss of the neurotransmitter dopamine and neuronal degeneration in the substantia nigra pars compacta. Thus far, current therapeutic strategies have failed to address neuronal degeneration. It has been reported that overproduction of reactive oxygen species, resulting in oxidative stress, and neuroinflammation play an important role in neurodegenerative diseases through the induction of macromolecular oxidative damage and modulation of intracellular signaling pathways concurring to neuronal cell death. Indeed, anti-oxidant and anti-inflammatory drugs have been the subject of recommendation as a complementary therapy alongside an effective symptomatic treatment to hamper the progression of PD. Today, much attention is paid to polyphenols in light of their potent capacity to reduce oxidative stress and inflammation, while having much fewer side effects than most other drugs. Camellia sinensis L. is the most common ancient herbal tea prepared as a beverage worldwide and it possesses numerous beneficial effects on human health. Epigallocatechin-3-gallate is the best-known bioactive component of C. sinensis and is recognized to exert potent neuroprotective effects against oxidative stress, neuroinflammation, protein aggregation, autophagy, and neuronal cell death in vitro as well as in vivo. The present review appraises the available literature on the beneficial role of epigallocatechin-3-gallate pertaining to dopaminergic degeneration characteristic of PD with particular emphasis on its possible mechanisms of action.

Attenuation of progressive hearing loss in DBA/2J mice by reagents that affect epigenetic modifications is associated with up-regulation of the zinc importer Zip4

Various factors that are important for proper hearing have been identified, including serum levels of zinc. Here we investigated whether epigenetic regulatory pathways, which can be modified by environmental factors, could modulate hearing. RT-PCR detected expression of genes encoding DNA methyltransferase and histone deacetylase (Hdac) in the postnatal as well as adult mouse auditory epithelium. DBA/2J mice, which are a model for progressive hearing loss, were injected subcutaneously with one or a combination of the following reagents: <smallcaps>L</smallcaps>-methionine as a methyl donor, valproic acid as a pan-Hdac inhibitor, and folic acid and vitamin B12 as putative factors involved in age-related hearing loss. The mice were treated from ages 4 to 12 weeks (N ≥ 5), and auditory brainstem response (ABR) thresholds were measured at 8, 16, and 32 kHz. Treatment of the mice with a combination of <smallcaps>L</smallcaps>-methionine and valproic acid (M+V) significantly reduced the increase in the ABR threshold at 32 kHz. Treatment with any of these reagents individually produced no such effect. Microarray analyses detected 299 gene probes that were significantly up- or down-regulated in the cochleae of mice treated with M+V compared with the control vehicle-treated mice. Quantitative RT-PCR confirmed significant up-regulation of a zinc importer gene, Zip4, in the cochleae of mice treated with M+V. Immunohistochemistry demonstrated an intense Zip4 signal in cochlear tissues such as the lateral wall, organ of Corti, and spiral ganglion. Finally, mice treated with the Zip4 inducer (–)-epigallocatechin-3-O-gallate showed a significant reduction in the increase of the ABR threshold at 32 kHz and up-regulation of Zip4 expression in the cochlea. This study suggests that epigenetic regulatory pathways can modify auditory function and that zinc intake in the cochlea via Zip4 mediates maintenance of mammalian hearing.

Daily consumption of white tea (Camellia sinensis (L.)) improves the cerebral cortex metabolic and oxidative profile in prediabetic Wistar rats

Diabetes mellitus (DM) is a major public health problem and its incidence is rising dramatically. The brain, particularly the cerebral cortex, is very susceptible to glucose fluctuations and hyperglycaemia-induced oxidative stress. Tea (Camellia sinensis (L.)) is widely consumed; however, the antidiabetic properties of white tea remain largely unexplored. In the present study, we investigated the effects of daily consumption of white tea on the cerebral cortex of prediabetic rats. The cerebral cortex metabolic profile was evaluated, and the expression levels of GLUT, phosphofructokinase-1, lactate dehydrogenase (LDH) and monocarboxylate transporter 4 were assessed. LDH activity was also determined. The cerebral cortex oxidative profile was determined by evaluating its antioxidant power, lipid peroxidation and protein oxidation levels. Catalase, glutathione, glutamate, N-acetylaspartate, aspartate, choline, γ-aminobutyric acid, taurine and valine contents were determined. Daily consumption of white tea ameliorated glucose tolerance and insulin sensitivity. Moreover, white tea altered the cortex glycolytic profile, modulating GLUT expression and lactate and alanine contents. Finally, white tea consumption restored protein oxidation and lipid peroxidation levels and catalase expression, and improved antioxidant capacity. In conclusion, daily consumption of white tea improved the cerebral cortex metabolic and oxidative profile in prediabetic rats, suggesting it as a good, safe and inexpensive strategy to prevent DM-related effects in the cerebral cortex.

Activation of Nrf2 protects against triptolide-induced hepatotoxicity

Triptolide, the major active component of Tripterygium wilfordii Hook f. (TWHF), has a wide range of pharmacological activities. However, the toxicities of triptolide, particularly the hepatotoxicity, limit its clinical application. The hepatotoxicity of triptolide has not been well characterized yet. The aim of this study was to investigate the role of NF-E2-related factor 2 (Nrf2) in triptolide-induced toxicity and whether activation of Nrf2 could protect against triptolide-induced hepatotoxicity. The results showed that triptolide caused oxidative stress and cell damage in HepG2 cells, and these toxic effects could be aggravated by Nrf2 knockdown or be counteracted by overexpression of Nrf2. Treatment with a typical Nrf2 agonist, sulforaphane (SFN), attenuated triptolide-induced liver dysfunction, structural damage, glutathione depletion and decrease in antioxidant enzymes in BALB/C mice. Moreover, the hepatoprotective effect of SFN on triptolide-induced liver injury was associated with the activation of Nrf2 and its downstream targets. Collectively, these results indicate that Nrf2 activation protects against triptolide-induced hepatotoxicity.

Effects of Tea Catechins on Cancer Signaling Pathways

The inhibitory activities of tea catechins against carcinogenesis and cancer cell growth have been demonstrated in a large number of laboratory studies. Many mechanisms for modulating cancer signaling and metabolic pathways have been proposed based on numerous studies in cell lines with (-)-epigallocatechin-3-gallate, the most abundant and active tea catechin. Nevertheless, the molecular basis for the proposed mechanisms and whether these mechanisms indeed contribute to the anticancer activities in vivo are not clearly known. This chapter reviews the basic redox properties of tea catechins, their binding to key enzymes and signal transduction proteins, and other mechanisms that lead to suppression of cell proliferation, increased apoptosis, and inhibition of angiogenesis. More weight is put on studies in vivo over experiments in vitro. It also discusses key issues involved in extrapolating results from cell line studies to mechanistic insights in vivo.

Antioxidant effect of garlic (Allium sativum) and black seeds (Nigella sativa) in healthy postmenopausal women

Objectives:

The objective of this study is to investigate the antioxidant effects of garlic extract and crude black seeds’ consumption on blood oxidant/antioxidant levels in healthy postmenopausal women.

Methods:

In total, 30 healthy postmenopausal women (mean age = 50.31 ± 4.23 years) participated. They ingested two garlic soft gels per day (each is equivalent to 1000 mg of fresh garlic bulb) and crude black seed grounded to powder in a dose of 3 g/day for 8 weeks. Oxidant (malondialdehyde) activity in plasma and antioxidants superoxide dismutase and glutathione peroxidase activities in erythrocytes were studied.

Results:

Significant low levels of plasma malondialdehyde with increased erythrocyte glutathione peroxidase and superoxide dismutase activities.

Discussion:

Menopause is associated with an increase in oxidative stress and a decrease in some antioxidant parameters. Consumption of garlic extracts and crude black seeds may have a beneficial effect on improved balance between blood oxidants and antioxidants in healthy postmenopausal women.

The role of iron-induced fibrin in the pathogenesis of Alzheimer's disease and the protective role of magnesium

Amyloid hypothesis of Alzheimer's disease (AD) has recently been challenged by the increasing evidence for the role of vascular and hemostatic components that impair oxygen delivery to the brain. One such component is fibrin clots, which, when they become resistant to thrombolysis, can cause chronic inflammation. It is not known, however, why some cerebral thrombi are resistant to the fibrinolytic degradation, whereas fibrin clots formed at the site of vessel wall injuries are completely, although gradually, removed to ensure proper wound healing. This phenomenon can now be explained in terms of the iron-induced free radicals that generate fibrin-like polymers remarkably resistant to the proteolytic degradation. It should be noted that similar insoluble deposits are present in AD brains in the form of aggregates with Abeta peptides that are resistant to fibrinolytic degradation. In addition, iron-induced fibrin fibers can irreversibly trap red blood cells (RBCs) and in this way obstruct oxygen delivery to the brain and induce chronic hypoxia that may contribute to AD. The RBC-fibrin aggregates can be disaggregated by magnesium ions and can also be prevented by certain polyphenols that are known to have beneficial effects in AD. In conclusion, we argue that AD can be prevented by: (1) limiting the dietary supply of trivalent iron contained in red and processed meat; (2) increasing the intake of chlorophyll-derived magnesium; and (3) consumption of foods rich in polyphenolic substances and certain aliphatic and aromatic unsaturated compounds. These dietary components are present in the Mediterranean diet known to be associated with the lower incidence of AD and other degenerative diseases.

Epigallocatechin-3-gallate: a useful, effective and safe clinical approach for targeted prevention and individualised treatment of neurological diseases?

Neurodegenerative disorders show an increasing prevalence in a number of highly developed countries. Often, these diseases require life-long treatment mostly with drugs which are costly and mostly accompanied by more or less serious side-effects. Their heterogeneous manifestation, severity and outcome pose the need for individualised treatment options. There is an intensive search for new strategies not only for treating but also for preventing these diseases. Green tea and green tea extracts seem to be such a promising and safe alternative. However, data regarding the beneficial effects and possible underlying mechanism, specifically in clinical trials, are rare and rather controversial or non-conclusive. This review outlines the existing evidence from preclinical studies (cell and tissue cultures and animal models) and clinical trials regarding preventive and therapeutic effects of epigallcatechin-3-gallate in neurodegenerative diseases and considers antioxidative vs. pro-oxidative properties of the tea catechin important for dosage recommendations.

Antioxidant therapy: still in search of the 'magic bullet'

The therapeutic potential of natural phenolic antioxidants in human diseases associated with oxidative damage has received great attention to date. Appraisal of literature evidences that, in general, antioxidant therapy has enjoyed relative successes in preclinical studies but little benefits in human intervention studies or clinical trials. In fact, despite the huge, largely untapped potential therapeutic benefit of natural phenolic antioxidants, such as vitamins, non-flavonoid and flavonoid compounds, they appear not to be suitable drug candidates. The problem may be related, among others, to their non-drug-likeness properties. Though controversial the results obtained so far confirm the importance of exploring phenolic natural systems as safe templates for the design of new antioxidants. To support the assumption an outlook of the lead structural optimization process to improve ADME properties was given by means of natural hydroxycinnamic acids as a case study. The optimization of drug physicochemical properties and the development of appropriate delivery antioxidant systems can provide in the next future a way out to attain effective therapeutic antioxidant agents.