Epigallocatechin-3-gallate enhances key enzymatic activities of hepatic thioredoxin and glutathione systems in selenium-optimal mice but activates hepatic Nrf2 responses in selenium-deficient mice

Disulfidptosis, A Novel Cell Death Pathway: Molecular Landscape and Therapeutic Implications

Programmed cell death is pivotal for several physiological processes, including immune defense. Further, it has been implicated in the pathogenesis of developmental disorders and the onset of numerous diseases. Multiple modes of programmed cell death, including apoptosis, pyroptosis, necroptosis, and ferroptosis, have been identified, each with their own unique characteristics and biological implications. In February 2023, Liu Xiaoguang and his team discovered "disulfidptosis," a novel pathway of programmed cell death. Their findings demonstrated that disulfidptosis is triggered in glucose-starved cells exhibiting high expression of a protein called SLC7A11. Furthermore, disulfidptosis is marked by a drastic imbalance in the NADPH/NADP+ ratio and the abnormal accumulation of disulfides like cystine. These changes ultimately lead to the destabilization of the F-actin network, causing cell death. Given that high SLC7A11 expression is a key feature of certain cancers, these findings indicate that disulfidptosis could serve as the basis of innovative anti-cancer therapies. Hence, this review delves into the discovery of disulfidptosis, its underlying molecular mechanisms and metabolic regulation, and its prospective applications in disease treatment.

PSMD12 promotes non-small cell lung cancer progression through activating the Nrf2/TrxR1 pathway

BACKGROUND

Non-small cell lung cancer (NSCLC) contributes to the vast majority of cancer-related deaths. Proteasome 26S subunit, non-ATPase 12 (PSMD12), a subunit of 26S proteasome complex, is known to play the tumor-promoting role in several types of cancer but its function in NSCLC remains elusive.

OBJECTIVE

To explore the role and underlying mechanisms of PSMD12 in NSCLC.

METHODS

The PSMD12 expression in human normal lung epithelial cell line (BEAS-2B) and four NSCLC cell lines (A549, NCI-H1299, NCI-H1975, Calu-1) were determined by qRT-PCR and western blot. Malignant phenotypes of NSCLC cells were detected by CCK-8, EdU staining, immunofluorescence staining for E-cadherin, flow cytometry, and Transwell assays to assess cell viability, proliferation, epithelial-mesenchymal transition (EMT), apoptosis, migration and invasion. Dual luciferase assay was used to verify the regulatory role of transcription factor on the promoter.

RESULTS

We identified the upregulation of PSMD12 in NSCLC tissues based on the GEO datasets, which further verified in NSCLC and BEAS-2B cell lines. PSMD12 knockdown significantly suppressed malignant behaviors of NSCLC cells, including cell growth, invasion, and migration, while PSMD12 overexpression presented the opposite effects. Interestingly, we found that PSMD12 upregulated the tumor-promoting factor TrxR1 mRNA expression. For its potential mechanisms, we demonstrated that PSMD12 elevated transcription factor Nrf2 protein level and promoted Nrf2 nuclear translocation. And Nrf2 further increased TrxR1 promoter activity and enhanced TrxR1 transcription. Meanwhile, we proved that TrxR1 overexpression erased the inhibitory effect of PSMD12 knockdown.

CONCLUSION

PSMD12 promotes NSCLC progression by activating the Nrf2/TrxR1 pathway, providing a novel prognostic and therapeutic target for NSCLC treatment.

The effect of theabrownins on the amino acid composition and antioxidant properties of hen eggs

Pu-erh tea theabrownins (TBs) exert beneficial effect on egg quality and antioxidant properties of eggs, but the underlying mechanisms behind this response are unclear. In this study, we investigate the effect of TBs on egg antioxidative activity, amino acid and fatty acid profiles, and the underlying relationship between the TBs and oxidant-sensitive Nrf2 signaling pathway in laying hens. Eighty layers were fed a basal diet (control) and 400 mg/kg of TBs supplemented diet for 12 wk. TBs led to an increase in albumen height and Haugh unit (P < 0.05). The albumen lysine, valine, and tryptophan were higher in layers fed TBs, whereas yolk tryptophan, methionine, vitamin A, and α-tocopherol content were enhanced by TBs (P < 0.05). Eggs albumen and yolk showed higher total antioxidant capacity (T-AOC), reducing power (RP), and the scavenging rate of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH), and lower MDA content than those of eggs from the control group (P < 0.05). Also, magnum Nrf2, hemeoxygenase 1 (HO-1), NAD(P)H quinone dehydrogenase 1 (NQO1), and Bcl2 expression were up-regulated by TBs, whereas magnum proapoptotic gene (Bax, caspase 3, Cyt C) were down-regulated by TBs (P < 0.05). Our findings suggest that TBs improved egg albumen quality and antioxidant activity, and the Nrf2-ARE pathway were found to be involved in this process.

Mechanisms Underlying the Effects of the Green Tea Polyphenol EGCG in Sarcopenia Prevention and Management

Sarcopenia is prevalent among the older population and severely affects human health. Tea catechins may benefit for skeletal muscle performance and protect against secondary sarcopenia. However, the mechanisms underlying their antisarcopenic effect are still not fully understood. Despite initial successes in animal and early clinical trials regarding the safety and efficacy of (-)-epigallocatechin-3-gallate (EGCG), a major catechin of green tea, many challenges, problems, and unanswered questions remain. In this comprehensive review, we discuss the potential role and underlying mechanisms of EGCG in sarcopenia prevention and management. We thoroughly review the general biological activities and general effects of EGCG on skeletal muscle performance, EGCG's antisarcopenic mechanisms, and recent clinical evidence of the aforesaid effects and mechanisms. We also address safety issues and provide directions for future studies. The possible concerted actions of EGCG indicate the need for further studies on sarcopenia prevention and management in humans.

Oxidative Stress, Reductive Stress and Antioxidants in Vascular Pathogenesis and Aging

This review is focused on the mechanisms that regulate health, disease and aging redox status, the signal pathways that counteract oxidative and reductive stress, the role of food components and additives with antioxidant properties (curcumin, polyphenols, vitamins, carotenoids, flavonoids, etc.), and the role of the hormones irisin and melatonin in the redox homeostasis of animal and human cells. The correlations between the deviation from optimal redox conditions and inflammation, allergic, aging and autoimmune responses are discussed. Special attention is given to the vascular system, kidney, liver and brain oxidative stress processes. The role of hydrogen peroxide as an intracellular and paracrine signal molecule is also reviewed. The cyanotoxins β-N-methylamino-l-alanine (BMAA), cylindrospermopsin, microcystins and nodularins are introduced as potentially dangerous food and environment pro-oxidants.

(-)-Epigallocatechin-3-Gallate Attenuates the Adverse Reactions Triggered by Selenium Nanoparticles without Compromising Their Suppressing Effect on Peritoneal Carcinomatosis in Mice Bearing Hepatocarcinoma 22 Cells

Increasing evidence shows that selenium and polyphenols are two types of the most reported compounds in tumor chemoprevention due to their remarkable antitumor activity and high safety profile. The cross-talk between polyphenols and selenium is a hot research topic, and the combination of polyphenols and selenium is a valuable strategy for fighting cancer. The current work investigated the combination anti-peritoneal carcinomatosis (PC) effect of selenium nanoparticles (SeNPs) and green tea (Camellia sinensis) polyphenol (-)-epigallocatechin-3-gallate (EGCG) in mice bearing murine hepatocarcinoma 22 (H22) cells. Results showed that SeNPs alone significantly inhibited cancer cell proliferation and extended the survival time of mice bearing H22 cells. Still, the potential therapeutic efficacy is accompanied by an approximately eighty percent diarrhea rate. When EGCG was combined with SeNPs, EGCG did not affect the tumor proliferation inhibition effect but eliminated diarrhea triggered by SeNPs. In addition, both the intracellular selectively accumulated EGCG without killing effect on cancer cells and the enhanced antioxidant enzyme levels in ascites after EGCG was delivered alone by intraperitoneal injection indicated that H22 cells were insensitive to EGCG. Moreover, EGCG could prevent SeNP-caused systemic oxidative damage by enhancing serum superoxide dismutase, glutathione, and glutathione peroxidase levels in healthy mice. Overall, we found that H22 cells are insensitive to EGCG, but combining EGCG with SeNPs could protect against SeNP-triggered diarrhea without compromising the suppressing efficacy of SeNPs on PC in mice bearing H22 cells and attenuate SeNP-caused systemic toxicity in healthy mice. These results suggest that EGCG could be employed as a promising candidate for preventing the adverse reactions of chemotherapy including chemotherapy-induced diarrhea and systemic toxicity in cancer individuals.

Therapeutic potential of green tea catechin, (-)-epigallocatechin-3-O-gallate (EGCG) in SARS-CoV-2 infection: Major interactions with host/virus proteases

BACKGROUND

The current COVID-19 pandemic from the human pathogenic virus SARS-CoV-2 has resulted in a major health hazard globally. The morbidity and transmission modality of this disease are severe and uncontrollable. As no effective clinical drugs are available for treatment of COVID-19 infection till to date and only vaccination is used as prophylaxis and its efficacy is restricted due to emergent of new variants of SARS-CoV-2, there is an urgent need for effective drugs for its treatment.

PURPOSE

The aim of this review was to provide a detailed analysis of anti-SARS-CoV-2 efficacy of (-)-epigallocatechin-3-O-gallate (EGCG), a major catechin constituent of green tea (Camellia sinensis (L.) Kuntze) beverage to highlight the scope of EGCG in clinical medicine as both prophylaxis and treatment of present COVID-19 infection. In addition, the factors related to poor oral bioavailabilty of EGCG was also analysed for a suggestion for future research in this direction.

STUDY DESIGN

We collected the published articles related to anti-SARS-CoV-2 activity of EGCG against the original strain (Wuhan type) and its newly emerged variants of SARS-CoV-2 virus.

METHODS

A systematic search on the published literature was conducted in various databases including Google Scholar, PubMed, Science Direct and Scopus to collect the relevant literature.

RESULTS

The findings of this search demonstrate that EGCG shows potent antiviral activity against SARS-CoV-2 virus by preventing viral entry and replication in host cells in vitro models. The studies on the molecular mechanisms of EGCG in inhibition of SARS-CoV-2 infection in host cells reveal that EGCG blocks the entry of the virus particles by interaction with the receptor binding domain (RBD) of viral spike (S) protein to host cell surface receptor protease angiotensin-converting enzyme 2 (ACE2) as well as suppression of the expressions of host proteases, ACE2, TMPRSS2 and GRP78, required for viral entry, by Nrf2 activation in host cells. Moreover, EGCG inhibits the activities of SARS-CoV-2 main protease (Mpro), papain-like protease (PLpro), endoribonuclease Nsp15 in vitro models and of RNA-dependent RNA polymerase (RdRp) in molecular docking model for suppression of viral replication. In addition, EGCG significantly inhibits viral inflammatory cytokine production by stimulating Nrf2- dependent host immune response in virus-infected cells. EGCG significantly reduces the elevated levels of HMGB1, a biomarker of sepsis, lung fibrosis and thrombotic complications in viral infections. EGCG potentially inhibits the infection of original (Wuhan type) strain of SARS-CoV-2 and other newly emerged variants as well as the infections of SARS-CoV-2 virus spike-protein of WT and its mutants-mediated pseudotyped viruses . EGCG shows maximum inhibitory effect against SARS-CoV-2 infection when the host cells are pre-incubated with the drug prior to viral infection. A sorbitol/lecithin-based throat spray containing concentrated green tea extract rich in EGCG content significantly reduces SARS-CoV-2 infectivity in oral mucosa. Several factors including degradation in gastrointestinal environment, low absorption in small intestine and extensive metabolism of EGCG are responsible for its poor bioavailability in humans. Pharmacokinetic and metabolism studies of EGCG in humans reveal poor bioavailability of EGCG in human plasma and EGCG-4"-sulfate is its major metabolite. The concentration of EGCG-4"-sulfate in human plasma is almost equivalent to that of free EGCG (Cmax 177.9 vs 233.5 nmol/L). These findings suggest that inhibition of sulfation of EGCG is a crucial factor for improvement of its bioavailability. In vitro study on the mechanism of EGCG sulfonation indicates that sulfotransferases, SULT1A1 and SULT1A3 are responsible for sulfonation in human liver and small intestine, respectively. Some attempts including structural modifications, and nanoformulations of EGCG and addition of nutrients with EGCG have been made to improve the bioavailability of EGCG.

CONCLUSIONS

The findings of this study suggest that EGCG has strong antiviral activity against SARS-CoV-2 infection independent of viral strains (Wuhan type (WT), other variants) by inhibition of viral entry and replication in host cells in vitro models. EGCG may be useful in reduction of this viral load in salivary glands of COVID-19 patients, if it is applied in mouth and throat wash formulations in optimal concentrations. EGCG could be a promising candidate in the development of effective vaccine for prevention of the infections of newly emergent strains of SARS-CoV-2 virus. EGCG might be useful also as a clinical medicine for treatment of COVID-19 patients if its bioavailability in human plasma is enhanced.

Potential of green tea EGCG in neutralizing SARS-CoV-2 Omicron variant with greater tropism toward the upper respiratory tract

Background

COVID-19 due to SARS-CoV-2 infection has had an enormous adverse impact on global public health. As the COVID-19 pandemic evolves, the WHO declared several variants of concern (VOCs), including Alpha, Beta, Gamma, Delta, and Omicron. Compared with earlier variants, Omicron, now a dominant lineage, exhibits characteristics of enhanced transmissibility, tropism shift toward the upper respiratory tract, and attenuated disease severity. The robust transmission of Omicron despite attenuated disease severity still poses a great challenge for pandemic control. Under this circumstance, its tropism shift may be utilized for discovering effective preventive approaches.

Scope and approach

This review aims to estimate the potential of green tea epigallocatechin gallate (EGCG), the most potent antiviral catechin, in neutralizing SARS-CoV-2 Omicron variant, based on current knowledge concerning EGCG distribution in tissues and Omicron tropism.

Key findings and conclusions

EGCG has a low bioavailability. Plasma EGCG levels are in the range of submicromolar concentrations following green tea drinking, or reach at most low μM concentrations after pharmacological intervention. Nonetheless, its levels in the upper respiratory tract could reach concentrations as high as tens or even hundreds of μM following green tea consumption or pharmacological intervention. An approach for delivering sufficiently high concentrations of EGCG in the pharynx has been developed. Convincing data have demonstrated that EGCG at tens to hundreds of μM can dramatically neutralize SARS-CoV-2 and effectively eliminate SARS-CoV-2-induced cytopathic effects and plaque formation. Thus, EGCG, which exhibits hyperaccumulation in the upper respiratory tract, deserves closer investigation as an antiviral in the current global battle against COVID-19, given Omicron's greater tropism toward the upper respiratory tract.

Antioxidant, antihyperglycemic, and antihyperlipidemic properties of Chimonanthus salicifolius S. Y. Hu leaves in experimental animals: modulation of thioredoxin and glutathione systems, renal water reabsorption, and gut microbiota

Introduction

Excessive calorie intake and physical inactivity have dramatically increased nutrient overload-associated disease, becoming a global public health issue. Chimonanthus salicifolius S. Y. Hu (CHI) is a homology plant of food and medicine in China and shows several health benefits.

Methods

This work investigated the antioxidant activity, the alleviating effects, and the mechanism of action on diabetes and hyperlipidemia of CHI leaves.

Results and discussion

Results showed that CHI leaves infusion displayed in vitro antioxidant activity measured by ABTS and ferric reducing antioxidant power methods. In wild-type Kunming mice, CHI leaves infusion consumption activated the hepatic antioxidant enzymes, including glutathione reductase, glutathione S-transferase, glutathione peroxidase and thioredoxin reductase as well as thioredoxin reductase 1. In alloxan-induced type 1 diabetic mice, CHI leaves infusion ameliorated diabetic symptoms, including polyuria, polydipsia, polyphagia and hyperglycemia, in a dose-dependent and time-course manners. The mechanism involved CHI leaves up-regulating renal water reabsorption associated protein - urine transporter A1-and promoting the trafficking of urine transporter A1 and aquaporin 2 to the apical plasma membrane. Despite this, in high-fat diet-induced hyperlipidemic golden hamsters, CHI leaves powder did not significantly effect on hyperlipidemia and body weight gain. This might be attributed to CHI leaves powder increasing the calorie intake. Interestingly, we found that CHI leaves extract containing a lower dose of total flavonoid than CHI leaves powder pronouncedly reduced the levels of total cholesterol, triglyceride, and low-density lipoprotein cholesterol in serum in golden hamsters fed a high-fat diet. Furthermore, CHI leaves extract elevated the diversity of gut microbiota and the abundance of Bifidobacterium and Ruminococcaceae_UCG-014. It also decreased the abundance of Lactobacillus at the genus level in golden hamsters fed a high-fat diet. Overall, CHI leaves benefit oxidative stress prevention and metabolic syndrome amelioration in vivo.

A comprehensive review on modulation of SIRT1 signaling pathways in the immune system of COVID-19 patients by phytotherapeutic melatonin and epigallocatechin-3-gallate

SARS-CoV-2 infection has now become the world's most significant health hazard, with the World Health Organization declaring a pandemic on March 11, 2020. COVID-19 enters the lungs through angiotensin-converting enzyme 2 (ACE2) receptors, alters various signaling pathways, and causes immune cells to overproduce cytokines, resulting in mucosal inflammation, lung damage, and multiple organ failure in COVID-19 patients. Although several antiviral medications have been effective in managing the virus, they have not been effective in lowering the inflammation and symptoms of the illness. Several studies have found that epigallocatechin-3-gallate and melatonin upregulate sirtuins proteins, which leads to downregulation of pro-inflammatory gene transcription and NF-κB, protecting organisms from oxidative stress in autoimmune, respiratory, and cardiovascular illnesses. As a result, the purpose of this research is to understand more about the molecular pathways through which these phytochemicals affect COVID-19 patients' impaired immune systems, perhaps reducing hyperinflammation and symptom severity. PRACTICAL APPLICATIONS: Polyphenols are natural secondary metabolites that are found to be present in plants. EGCG a polyphenol belonging to the flavonoid family in tea has potent anti-inflammatory and antioxidative properties that helps to counter the inflammation and oxidative stress associated with many neurodegenerative diseases. Melatonin, another strong antioxidant in plants, has been shown to possess antiviral function and alleviate oxidative stress in many inflammatory diseases. In this review, we propose an alternative therapy for COVID-19 patients by supplementing their diet with these nutraceuticals that perhaps by modulating sirtuin signaling pathways counteract cytokine storm and oxidative stress, the root causes of severe inflammation and symptoms in these patients.

NRF2 Genetic Polymorphism Modifies the Association of Plasma Selenium Levels With Incident Coronary Heart Disease Among Individuals With Type 2 Diabetes

Plasma selenium and NRF2 promoter variants (e.g., rs6721961) are associated with cardiovascular disease risk in the general population. However, epidemiological evidence on the interaction between plasma selenium and NRF2 genetic susceptibility in relation to incident coronary heart disease (CHD) risk remains scarce, especially among individuals with type 2 diabetes (T2D). Thus, we examined whether rs6721961 in the NRF2 gene might modify the association between plasma selenium levels and incident CHD risk among people with T2D. During a mean (SD) follow-up period of 6.90 (2.96) years, 798 incident CHD cases were identified among 2,251 T2D cases. Risk-allele carriers of rs6721961 had a higher risk of incident CHD among people with T2D (adjusted hazard ratio [HR] 1.17; 95% CI 1.02-1.35) versus nonrisk-allele carriers. Each 22.8-μg/L increase in plasma selenium levels was associated with a reduced risk of incident CHD among risk-allele carriers with T2D (HR 0.80; 95% CI 0.71-0.89), whereas no association was found in those without risk alleles (P for interaction = 0.004), indicating that the NRF2 promoter polymorphism might modify the association between plasma selenium levels and incident CHD risk among people with T2D. Our study findings suggest redox-related genetic variants should be considered to identify populations that might benefit most from selenium supplementation. More mechanistic studies are warranted.

Epigallocatechin-3-O-gallate ameliorates oxidative stress-induced chondrocyte dysfunction and exerts chondroprotective effects via the Keap1/Nrf2/ARE signaling pathway

Oxidative stress-induced degeneration and dysfunction of chondrocytes play a key role in the pathological progression of osteoarthritis (OA), a common degenerative joint disease in the elderly. Epigallocatechin-3-O-gallate (EGCG) increases Nrf2-mediated antioxidase expression levels. We aimed to determine the effects of EGCG on C28/I2 human chondrocytes subjected to interleukin-1β (IL-1β)-induced oxidative stress. EGCG suppressed IL-1β-induced oxidative stress, as indicated by decreased malondialdehyde (MDA) and reactive oxygen species (ROS) generation. Additionally, EGCG attenuated the IL-1β-induced reduction in cartilage matrix generated by chondrocytes by upregulating collagen II, aggrecan, sulfated proteoglycans, and SRY-box transcription factor 9 (SOX9). EGCG reversed the IL-1β-induced increased cyclooxygenase 2 (COX2), inducible nitric oxide synthase (iNOS), collagen X, and matrix metalloproteinases (MMPs). Furthermore, EGCG inhibited apoptosis and senescence of IL-1β-treated chondrocytes, as indicated by the decrease in mitochondrial membrane potential and senescence-associated β-galactosidase-positive cells, respectively. Mechanically, EGCG upregulated nuclear factor erythroid 2-related factor 2 (Nrf2), oxygenase-1 (HO-1), and NADPH quinone oxidoreductase1 (NQO1). The antioxidant and chondroprotective effects of EGCG were blocked by ML385, a Keap1/Nrf2/ARE signaling pathway inhibitor. Thus, EGCG ameliorated oxidative stress-induced chondrocyte dysfunction and exerted chondroprotective effects via Keap1/Nrf2/ARE signaling. This provides a novel perspective on the molecular mechanisms underlying the therapeutic effects of EGCG on OA.

l-Theanine Inhibits (-)-Epigallocatechin-3-gallate Oxidation via Chelating Copper

Our recent study showed that glutamate can inhibit dopamine oxidation via chelating copper. l-Theanine is an amino acid analogue of glutamate, whereas tea (-)-epigallocatechin-3-gallate (EGCG) is similar to dopamine in avidly undergoing oxidation. We thus hypothesized that l-theanine could also restrain EGCG oxidation via chelating copper. The current study scrutinized influences of l-theanine on EGCG oxidation in vitro and in vivo. The in vitro results showed that l-theanine and copper formed an l-theanine-copper complex with impaired redox activity of copper. Accordingly, l-theanine effectively suppressed copper-facilitated EGCG oxidation, hydroxyl radical production, and DNA damage; inhibited EGCG autoxidation which in essence involves catalysis of transition metals such as copper; and reduced EGCG oxidation-associated formation of a quinone adduct with proteins known as quinoproteins. Consistently, l-theanine significantly increased hepatic EGCG levels and reduced hepatic quinoprotein levels and liver injury in mice treated with EGCG. These lines of evidence together suggest that tea l-theanine can protect against tea catechin oxidation.

Dietary supplementation with biogenic selenium nanoparticles alleviate oxidative stress-induced intestinal barrier dysfunction

Selenium (Se) is an essential micronutrient that promotes body health. Endemic Se deficiency is a major nutritional challenge worldwide. The low toxicity, high bioavailability, and unique properties of biogenic Se nanoparticles (SeNPs) allow them to be used as a therapeutic drug and Se nutritional supplement. This study was conducted to investigate the regulatory effects of dietary SeNPs supplementation on the oxidative stress-induced intestinal barrier dysfunction and its association with mitochondrial function and gut microbiota in mice. The effects of dietary SeNPs on intestinal barrier function and antioxidant capacity and its correlation with gut microbiota were further evaluated by a fecal microbiota transplantation experiment. The results showed that Se deficiency caused a redox imbalance, increased the levels of pro-inflammatory cytokines, altered the composition of the gut microbiota, and impaired mitochondrial structure and function, and intestinal barrier injury. Exogenous supplementation with biogenic SeNPs effectively alleviated diquat-induced intestinal barrier dysfunction by enhancing the antioxidant capacity, inhibiting the overproduction of reactive oxygen species (ROS), preventing the impairment of mitochondrial structure and function, regulating the immune response, maintaining intestinal microbiota homeostasis by regulating nuclear factor (erythroid-derived-2)-like 2 (Nrf2)-mediated NLR family pyrin domain containing 3 (NLRP3) signaling pathway. In addition, Se deficiency resulted in a gut microbiota phenotype that is more susceptible to diquat-induced intestinal barrier dysfunction. Supranutritional SeNPs intake can optimize the gut microbiota to protect against intestinal dysfunctions. This study demonstrates that dietary supplementation of SeNPs can prevent oxidative stress-induced intestinal barrier dysfunction through its regulation of mitochondria and gut microbiota.

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.

Nutraceuticals in the Mediterranean Diet: Potential Avenues for Breast Cancer Treatment

The traditional Mediterranean Diet constitutes a food model that refers to the dietary patterns of the population living in countries bordering the Mediterranean Sea in the early 1960s. A huge volume of literature data suggests that the Mediterranean-style diet provides several dietary compounds that have been reported to exert beneficial biological effects against a wide spectrum of chronic illnesses, such as cardiovascular and neurodegenerative diseases and cancer including breast carcinoma. Among bioactive nutrients identified as protective factors for breast cancer, natural polyphenols, retinoids, and polyunsaturated fatty acids (PUFAs) have been reported to possess antioxidant, anti-inflammatory, immunomodulatory and antitumoral properties. The multiple anticancer mechanisms involved include the modulation of molecular events and signaling pathways associated with cell survival, proliferation, differentiation, migration, angiogenesis, antioxidant enzymes and immune responses. This review summarizes the anticancer action of some polyphenols, like resveratrol and epigallocatechin 3-gallate, retinoids and omega-3 PUFAs by highlighting the important hallmarks of cancer in terms of (i) cell cycle growth arrest, (ii) apoptosis, (iii) inflammation and (iv) angiogenesis. The data collected from in vitro and in vivo studies strongly indicate that these natural compounds could be the prospective candidates for the future anticancer therapeutics in breast cancer disease.

Physiological Dose of EGCG Attenuates the Health Defects of High Dose by Regulating MEMO-1 in Caenorhabditis elegans

EGCG, as a dietary-derived antioxidant, has been extensively studied for its beneficial health effects. Nevertheless, it induces the transient increase in ROS and leads to the hormetic extension of lifespan. How exactly biology-benefiting effects with the minimum severe adverse are realized remains unclear. Here, we showed that physiological dose of EGCG could help moderate remission in health side effects exposed to high doses, including shortened lifespan, reduced body size, decreased pharyngeal pumping rate, and dysfunctional body movement in C. elegans. Furthermore, we found this result was caused by the physiological dose of EGCG to block the continued ROS accumulation and triggered acclimation responses after stressor removal. Also, in this process, we observed that EGCG downregulated the key redox protein MEMO-1 to activate the feedback loop of NADPH oxidase-mediated redox signaling. Our data indicates that the feedback signal induced by NADPH oxidase may contribute to the health-protective mechanism of dietary polyphenols in vivo.

Potential protective mechanisms of green tea polyphenol EGCG against COVID-19

Background

The world is in the midst of the COVID-19 pandemic. In this comprehensive review, we discuss the potential protective effects of (−)-epigallocatechin-3-gallate (EGCG), a major constituent of green tea, against COVID-19.

Scope and approach

Information from literature of clinical symptoms and molecular pathology of COVID-19 as well as relevant publications in which EGCG shows potential protective activities against COVID-19 is integrated and evaluated.

Key findings and conclusions

EGCG, via activating Nrf2, can suppress ACE2 (a cellular receptor for SARS-CoV-2) and TMPRSS2, which mediate cell entry of the virus. Through inhibition of SARS-CoV-2 main protease, EGCG may inhibit viral reproduction. EGCG via its broad antioxidant activity may protect against SARS-CoV-2 evoked mitochondrial ROS (which promote SARS-CoV-2 replication) and against ROS burst inflicted by neutrophil extracellular traps. By suppressing ER-resident GRP78 activity and expression, EGCG can potentially inhibit SARS-CoV-2 life cycle. EGCG also shows protective effects against 1) cytokine storm-associated acute lung injury/acute respiratory distress syndrome, 2) thrombosis via suppressing tissue factors and activating platelets, 3) sepsis by inactivating redox-sensitive HMGB1, and 4) lung fibrosis through augmenting Nrf2 and suppressing NF-κB. These activities remain to be further substantiated in animals and humans. The possible concerted actions of EGCG suggest the importance of further studies on the prevention and treatment of COVID-19 in humans. These results also call for epidemiological studies on potential preventive effects of green tea drinking on COVID-19.

Epigallocathechin-O-3-Gallate Inhibits Trypanothione Reductase of Leishmania infantum, Causing Alterations in Redox Balance and Leading to Parasite Death

Leishmania infantum is a protozoan parasite that causes a vector borne infectious disease in humans known as visceral leishmaniasis (VL). This pathology, also caused by L. donovani, presently impacts the health of 500,000 people worldwide, and is treated with outdated anti-parasitic drugs that suffer from poor treatment regimens, severe side effects, high cost and/or emergence of resistant parasites. In previous works we have disclosed the anti-Leishmania activity of (-)-Epigallocatechin 3-O-gallate (EGCG), a flavonoid compound present in green tea leaves. To date, the mechanism of action of EGCG against Leishmania remains unknown. This work aims to shed new light into the leishmanicidal mode of action of EGCG. Towards this goal, we first confirmed that EGCG inhibits L. infantum promastigote proliferation in a concentration-dependent manner. Second, we established that the leishmanicidal effect of EGCG was associated with i) mitochondria depolarization and ii) decreased concentration of intracellular ATP, and iii) increased concentration of intracellular H₂O₂. Third, we found that the leishmanicidal effect and the elevated H₂O₂ levels induced by of EGCG can be abolished by PEG-catalase, strongly suggesting that this flavonoid kills L. infantum promastigotes by disturbing their intracellular redox balance. Finally, we gathered in silico and in vitro evidence that EGCG binds to trypanothione reductase (TR), a central enzyme of the redox homeostasis of Leishmania, acting as a competitive inhibitor of its trypanothione substrate.

GAS5 knockdown alleviates spinal cord injury by reducing VAV1 expression via RNA binding protein CELF2

Long non-coding RNA growth arrest specific transcript 5 (GAS5) has been found to be implicated in the pathogenesis of central nervous diseases and to be a contributor to hypoxic brain injury. However, the roles and molecular mechanisms of GAS5 in spinal cord injury (SCI) have not thoroughly investigated. Here, we reported that GAS5 knockdown improved rat locomotor function and alleviated pathological damage of spinal cord tissues by reducing oxidative stress, caspase-3 activity and vav guanine nucleotide exchange factor 1 (VAV1) expression in SCI rat models. GAS5 knockdown inhibited the increase of malondialdehyde (MDA) level and cell apoptotic rate induced by oxygen-glucose deprivation (OGD) and weakened the inhibitory effects of OGD on superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities and cell viability in RN-Sc cells, suggesting that GAS5 loss mitigated OGD-triggered oxidative stress and cell injury in RN-Sc cells. Molecular mechanism explorations revealed that GAS5 recruited CUGBP, Elav-like family member 2 (CELF2) to the coding region of VAV1 mRNA, resulting in the increase of VAV1 mRNA stability and expression levels. VAV1 knockdown weakened OGD-induced oxidative stress and cell injury in RN-Sc cells. VAV1 loss alleviated GAS5-induced oxidative stress and cell injury in OGD-treated RN-Sc cells. As a conclusion, our findings suggested that GAS5 aggravated SCI by increasing VAV1 expression via binding with CELF2, deepening our understanding on function and molecular basis of GAS5 in SCI.

New insights into the role of the Nrf2 signaling pathway in green tea catechin applications

Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a transcriptional signaling pathway that plays a crucial role in numerous clinical complications. Pivotal roles of Nrf2 have been proved in cancer, autoimmune diseases, neurodegeneration, cardiovascular diseases, diabetes mellitus, renal injuries, respiratory conditions, gastrointestinal disturbances, and general disorders related to oxidative stress, inflammation, apoptosis, gelatinolysis, autophagy, and fibrogenesis processes. Green tea catechins as a rich source of phenolic compounds can deal with various clinical problems and manifestations. In this review, we attempted to focus on intervention between green tea catechins and Nrf2. Green tea catechins especially epigallocatechin gallate (EGCG) elucidated the protective role of Nrf2 and its downstream molecules in various disorders through Keap-1, HO-1, NQO-1, GPx, GCLc, GCLm, NF-kB cross-link, kinases, and apoptotic proteins. Subsequently, we compiled an updated expansions of the Nrf2 role as a gate to manage and protect different disorders and feasible indications of green tea catechins through this signaling pathway. The present review highlighted recent evidence-based data in silico, in vitro, and in vivo studies on an outline for future clinical trials.

Protective Effect of Epigallocatechin-3-Gallate in Hydrogen Peroxide-Induced Oxidative Damage in Chicken Lymphocytes

Epigallocatechin-3-gallate (EGCG) is one of the fundamental compounds in green tea. The present study was to evaluate the protective effect of EGCG in oxidative damage and apoptosis induced by hydrogen peroxide (H₂O₂) in chicken lymphocytes. Results showed that preincubation of lymphocytes with EGCG significantly decreased H₂O₂-reduced cell viability and apoptotic cells with DNA damage, restored the H₂O₂-dependent reduction in total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-PX), superoxide dismutase (SOD), glutathione (GSH), and glutathione disulfide (GSSG), and suppressed the increase in intracellular reactive oxygen species (ROS), nitric oxide (NO), nitric oxide synthesis (NOS), malondialdehyde (MDA), lipid peroxide (LPO), and protein carbonyl (Carbonyl). In addition, preincubation of the cells with EGCG increased mitochondrial membrane potential (MMP) and reduced calcium ion ([Ca²⁺]i) load. The protective effect of EGCG in oxidative damage in lymphocytes was accompanied by mRNA expression of SOD, Heme oxygenase-1 (HO-1), Catalase (CAT), GSH-PX, nuclear factor erythroid 2-related factor 2 (Nrf2), and thioredoxin-1 (Trx-1). As EGCG had been removed before lymphocytes were challenged with H₂O₂, the activation of genes such as Nrf2 and Trx-1 by preincubation with EGCG could be the main reason for EGCG to protect the cells from oxidative damage by H₂O_2. Since oxidative stress is an important mechanism of biological damage and is regarded as the reasons of several pathologies, the present findings may be helpful for the use of tea products to prevent oxidative stress and maintain healthy in both humans and animals.

Epigallocatechin Gallate Slows Retinal Degeneration, Reduces Oxidative Damage, and Modifies Circadian Rhythms in P23H Rats

Retinitis pigmentosa (RP) includes a group of genetic disorders that involve the loss of visual function due to mutations mainly in photoreceptors but also in other retinal cells. Apoptosis, retinal disorganization, and inflammation are common in the progression of the disease. Epigallocatechin gallate (EGCG) has been proved as beneficial in different eye diseases. Pigmented heterozygous P23H rat was used as an animal model of RP. Visual function was assessed by optomotor and electroretinogram (ERG) and circadian rhythms were evaluated by telemetry. Hepatic oxidative damage and antioxidant defenses were assessed using biochemical tests. The visual function of the EGCG P23H group was preserved, with a deterioration in the activity period and lower values in the interdaily stability parameter. Control rats treated with EGCG were less active than the sham group. EGCG increased antioxidant levels in P23H rats but reduced total hepatic antioxidant capacity by almost 42% in control rats compared to the sham group. We conclude that treatment with EGCG improves visual function and antioxidant status in P23H rats but diminishes antioxidant defenses in wild-type control animals, and slightly worsens activity circadian rhythms. Further studies are necessary to clarify the beneficial effects in disease conditions and in healthy organisms.

Green tea polyphenol epigallocatechin-3-gallate improves the antioxidant capacity of eggs

Dietary supplementation with EGCG led to an increase in egg antioxidant activity and antioxidant chemical substances, tryptophan and carotenoid. This may be associated with its increasing effect on the oxidative stress related regulators expression (P38MAPK, Nrf2 and HO-1).

A mouse model of subacute liver failure with ascites induced by step-wise increased doses of (-)-epigallocatechin-3-gallate

Acute liver failure is divided into hyperacute, acute and subacute liver failure. Ascites is a common complication of subacute liver failure. Although animal models of acute liver failure have been established, the study of the pathogenesis of subacute liver failure with ascites complication is hampered by the lack of experimental animal model. The present study aimed at providing a mouse model of subacute liver failure with ascites complication. Kunming mice were intraperitoneally injected with (-)-epigallocatechin-3-gallate (EGCG), a redox-active polyphenol from green tea, for 32 consecutive days with step-wise increased dosage. The EGCG treatment resulted in liver failure as evidenced by extensive hepatocyte necrosis observed histologically along with significant elevation of serum alanine aminotransferase, aspartate aminotransferase, total bilirubin and direct bilirubin levels as well as significant reduction of serum albumin. Liver fibrosis was not observed by Masson staining and fibrosis-associated proteins were not increased. The mortality was less than 12% and the survival mice developed noticeable ascites. Hepatic thioredoxin and glutathione systems were activated by the EGCG. These adaptive responses might render most mice tolerable to the EGCG treatment. The EGCG treatment significantly up-regulated renal urea transporter A1 and promoted its trafficking to apical membrane. These alterations, known to increase water reabsorption, may be responsible, at least in part, for the formation of the ascites. Overall, the mice treated with gradually elevated doses of EGCG exhibits some of the features observed in patients with subacute liver failure, especially ascites. This mouse model is a useful tool for investigating the pathogenesis of subacute liver failure with ascites complication.

Crosstalk of Nrf2 with the Trace Elements Selenium, Iron, Zinc, and Copper

Trace elements, like Cu, Zn, Fe, or Se, are important for the proper functioning of antioxidant enzymes. However, in excessive amounts, they can also act as pro-oxidants. Accordingly, trace elements influence redox-modulated signaling pathways, such as the Nrf2 pathway. Vice versa, Nrf2 target genes belong to the group of transport and metal binding proteins. In order to investigate whether Nrf2 directly regulates the systemic trace element status, we used mice to study the effect of a constitutive, whole-body Nrf2 knockout on the systemic status of Cu, Zn, Fe, and Se. As the loss of selenoproteins under Se-deprived conditions has been described to further enhance Nrf2 activity, we additionally analyzed the combination of Nrf2 knockout with feeding diets that provide either suboptimal, adequate, or supplemented amounts of Se. Experiments revealed that the Nrf2 knockout partially affected the trace element concentrations of Cu, Zn, Fe, or Se in the intestine, liver, and/or plasma. However, aside from Fe, the other three trace elements were only marginally modulated in an Nrf2-dependent manner. Selenium deficiency mainly resulted in increased plasma Zn levels. One putative mediator could be the metal regulatory transcription factor 1, which was up-regulated with an increasing Se supply and downregulated in Se-supplemented Nrf2 knockout mice.

Melatonin and (-)-Epigallocatechin-3-Gallate: Partners in Fighting Cancer

We have demonstrated previously that melatonin attenuates hepatotoxicity triggered by high doses of (−)-epigallocatechin-3-gallate (EGCG) in mice. The current work investigated the influence of melatonin on the oncostatic activity of EGCG in two cancer cell lines, wherein melatonin induced an opposite response of p21. In human tongue cancer TCA8113 cells, melatonin-induced p21 and EGCG-mediated formation of quinoproteins were positively associated with the oncostatic effects of melatonin and EGCG. Melatonin-stimulated an increase in p21 which was correlated with a pronounced nuclear translocation of thioredoxin 1 and thioredoxin reductase 1, both of which are known to induce p21 via promoting p53 trans-activation. Melatonin did not influence the EGCG-mediated increase of quinoprotein formation nor did EGCG impair melatonin-induced p21 up-regulation. Co-treatment with both agents enhanced the cell-killing effect as well as the inhibitory activities against cell migration and colony formation. It is known that p21 also plays a powerful anti-apoptotic role in some cancer cells and confers these cells with a survival advantage, making it a target for therapeutic suppression. In human hepatocellular carcinoma HepG2 cells, melatonin suppressed p21 along with the induction of pro-survival proteins, PI3K and COX-2. However, EGCG prevented against melatonin-induced PI3K and COX-2, and melatonin probably sensitized HepG2 cells to EGCG cytotoxicity via down-regulating p21, Moreover, COX-2 and HO-1 were significantly reduced only by the co-treatment, and melatonin aided EGCG to achieve an increased inhibition on Bcl2 and NFκB. These events occurring in the co-treatment collectively resulted in an enhanced cytotoxicity. In addition, the co-treatment also enhanced the inhibitory activities against cell migration and colony formation. Overall, the results gathered from these two cancer cell lines with a divergent p21 response to melatonin show that the various oncostatic activities of melatonin and EGCG together are more robust than each agent alone, suggesting that they may be useful partners in fighting cancer.

Morin Protects Human Respiratory Cells from PM2.5 Induced Genotoxicity by Mitigating ROS and Reverting Altered miRNA Expression

Chronic fine particulate matter (PM2.5) exposure causes oxidative stress and leads to many diseases in human like respiratory and cardiovascular disorders, and lung cancer. It is known that toxic responses elicited by PM2.5 particles depend on its physical and chemical characteristics that are greatly influenced by the source. Dietary polyphenolic compounds that possess antioxidant and free radical scavenging properties could be used for therapeutic or preventive approaches against air pollution related health hazards. This study evaluates characteristics and toxicity of PM2.5 collected from rural, urban, industrial, and traffic regions in and around Coimbatore City, Tamilnadu, India. Traffic PM2.5 particles contained higher amounts of metals and polycyclic aromatic hydrocarbons (PAHs). It also possessed higher levels of oxidative potential, induced more intracellular reactive oxygen species (ROS), and caused more levels of cell death and DNA damage in human respiratory cells. Its exposure up regulated DNA damage response related miR222, miR210, miR101, miR34a, and miR93 and MycN and suppressed Rad52. Pre-treatment with morin significantly decreased the PM2.5 induced toxicity and conferred protection against PM2.5 induced altered miRNA expression. Results of this study showed that cytoprotective effect of morin is due to its antioxidative and free radical scavenging activity.

Selenium Deficiency Is Associated with Pro-longevity Mechanisms

Selenium (Se) is an essential trace element because of its presence in selenoproteins in the form of selenocysteine residue. Both Se deficiency, which compromises selenoprotein functions, and excess Se, which is toxic, have been associated with altered redox homeostasis and adverse health conditions. Surprisingly, we found that, although Se deficiency led to a drastic decline in selenoprotein expression, mice subjected to this dietary regimen for their entire life had normal lifespans. To understand the molecular mechanisms involved, we performed systemic analyses at the level of metabolome, transcriptome, and microRNA profiling. These analyses revealed that Se deficiency reduced amino acid levels, elevated mononucleotides, altered metabolism, and activated signaling pathways linked to longevity-related nutrient sensing. The data show that the metabolic control associated with nutrient sensing coordinately responds to suppressed selenoprotein functions, resulting in normal lifespan under Se deficiency.

Protective Effects of Inorganic and Organic Selenium on Heat Stress in Bovine Mammary Epithelial Cells

When dairy cows are exposed to high-temperature environment, their antioxidant capacity and productive performance decrease, leading to economic losses. Emerging evidence has shown that selenium (Se) can effectively alleviate heat stress in dairy cows; however, the cellular mechanism underlying this protection is not clear. The purpose of this study was to investigate and compare the protective effects of inorganic Se (sodium selenite, SS) and organic Se (selenite methionine, SM) in MAC-T (mammary alveolar cells-large T antigen, a bovine mammary epithelial cell (BMEC) line) cells during heat stress. MAC-T cells were treated in 4 ways unless otherwise described: (i) cells in the heat treatment (HT) group were cultured at 42.5°C for 1 h and then recovered in 37°C for another 12 h; (ii) the SM group was pretreated with organic Se for 2 h, cultured at 42.5°C for 1 h, and then recovered in 37°C for 12 h; (iii) the SS group was treated similarly to the SM group except that the cells were pretreated with inorganic Se instead of organic Se; and (iv) the control group was continuously cultured in 37°C and received no Se treatment. The results showed that heat shock at 42.5°C for 1 h triggered heat shock response, sabotaged the redox balance, and reduced cell viability in MAC-T cells; and pretreatment of cells with SM or SS effectively alleviated the negative effects of heat shock on the cells. However, the cells were much more sensitive to SS treatment but more tolerant to SM. In addition, two forms of Se appeared to affect the expression of different genes, including nuclear factor erythroid 2-related factor 2 (Nrf2) and inducible nitric oxide synthase (iNOS) in the SM group and thioredoxin reductase 1 (TXNRD1) in the SS group in Nrf2-ARE (antioxidant response element) antioxidant pathway and inflammation response. In summary, results showed the mechanistic differences in the protective effects of organic and inorganic Se on heat stress in BMECs.

Selenium nanoparticles are more efficient than sodium selenite in producing reactive oxygen species and hyper-accumulation of selenium nanoparticles in cancer cells generates potent therapeutic effects

We have previously demonstrated that selenium nanoparticles (SeNPs) administered via oral route possess similar capacities of increasing selenoenzyme activities as the extensively examined sodium selenite, selenomethionine and methylselenocysteine, and yet display the lowest toxicity among these selenium compounds in mouse models. However, the low toxicity of SeNPs found in mammalian systems would lead to the interpretation that the punctate distribution of elemental selenium found in cultured cancer cells subjected to selenite treatment that triggers marked cytotoxicity represents a detoxifying mechanism. The present study found that SeNPs could be reduced by the thioredoxin- or glutaredoxin-coupled glutathione system to generate ROS. Importantly, ROS production by SeNPs in these systems was more efficient than by selenite, which has been recognized as the most redox-active selenium compound for ROS production. This is because multiple steps of reduction from selenite to selenide anion are required; whereas only a single step reduction from the elemental selenium atom to selenide anion is needed to trigger redox cycling with oxygen to produce ROS. We thus speculated that accumulation of SeNPs in cancer cells would result in a strong therapeutic effect, rather than serves a detoxification function. Indeed, we showed herein that preformed SeNPs generated a potent therapeutic effect in a mouse model due to rapid, massive and selective accumulation of SeNPs in cancer cells. Overall, for the first time, we demonstrate that SeNPs have a stronger pro-oxidant property than selenite and hyper-accumulation of SeNPs in cancer cells can generate potent therapeutic effects.

Epigallocatechin-3-gallate partially restored redox homeostasis in arsenite-stressed keratinocytes

Arsenite (AsIII) is known for inducing severe oxidative stress and skin carcinogenesis. Contrastingly, phytochemical, epigallocatechin-3-gallate (EGCG) combats toxic insults. Our study focused on the effect of EGCG on redox status of AsIII-stressed normal human keratinocytes, HaCaT cells. EGCG (50 μm) increased the cell viability by 29% in AsIII (50 μm) insulted HaCaT cells but exhibited pro-oxidant activity by elevated expression of the oxidative stress markers. EGCG was effective not only in reducing AsIII-induced nuclear expression of Nrf2 and Nrf2Ser40 but also in increasing nuclear expression of Keap1 both at protein and mRNA level. EGCG did not have similar effects on all Nrf2 downstream targets. EGCG elevated expression of HO-1 and γ-GCL,showed no change in MRP1 but decreased superoxide dismutase, NAD(P)H dehydrogenase quinone 1 and glutathione S transferase activity in AsIII-treated HaCaT cells. EGCG along with AsIII caused decreased phosphorylation of Nrf2 at ser40 residue, which might have facilitated Keap1-mediated nuclear export and degradation of Nrf2 and paved the pro-survival signal for AsIII-insulted HaCaT cells. In conclusion, it might be indicated that EGCG in spite of inducing the pro-oxidant effect was effective in increasing the viability of AsIII-treated HaCaT cells by partially restoring the Nrf2/Keap1-mediated signaling axis.

Synergistic toxicity of epigallocatechin-3-gallate and diethyldithiocarbamate, a lethal encounter involving redox-active copper

Dithiocarbamates (DTC) are widely used in agricultural, industrial and therapeutic domains. There are ample opportunities for human exposure to DTC. Green tea extracts, with epigallocatechin-3-gallate (EGCG) being the most abundant constituent, have been used as dietary supplements for body weight reduction. Our hypothesis is that DTC can act as a copper ionophore to increase hepatic levels of redox-active copper which promotes EGCG auto-oxidation to produce oxidative stress and toxicity. The results of the present study in a mouse model is consistent with this hypothesis, showing that co-administration of EGCG and diethyldithiocarbamate - a metabolite of disulfiram (a drug for alcohol aversion therapy), both at tolerable levels, caused lethality. The liver was the major organ site of toxicity. The co-administration drastically increased lipid peroxidation, DNA damage and cell apoptosis as well as caused deleterious transcriptional responses including basal and Nrf2 antioxidant systems in the liver. The results suggest that exposure to DTC reduces toxic threshold of dietary polyphenols from green tea and possibly other plants, and vice versa. This novel hypothesis is important to human health, and the dose-response relationship of this synergistic toxicity needs to be further characterized.