Presence Of Epigallocatechin-3-gallate Research Articles

Identification and comparison of protein composition of biofilms in response to EGCG from Enterococcus faecalis and Staphylococcus lugdunensis, which showed opposite patterns in biofilm-forming abilities

Bacterial biofilm is resistant to conventional antibiotic treatments, leading to complications associated with many infection-related human diseases. Epigallocatechin Gallate (EGCG), a phenolic catechin enriched in green tea, is recognized for its anti-bacterial and anti-biofilm activities. In this study, we examined the protein components of the biofilms formed in the absence or presence of EGCG using Enterococcus faecalis and Staphylococcus lugdunensis, which had shown opposing patterns in biofilm formation. A clustering heatmap revealed that the two microorganisms expressed the different protein sets in response to EGCG. Proteins that were noticeably upregulated included those associated with stress responsiveness and gluconeogenesis in E. faecalis, and gene modification in S. lugdunensis. Conversely, downregulated proteins were related to tRNA-modifying enzyme activity in E. faecalis, and anabolic metabolism in S. lugdunensis. Among the proteins identified only in EGCG-responsive biofilms, enzymes involved in de novo purine biosynthesis were enriched in E. faecalis, while proteins likely to cause DNA instability and pathogenicity changes were abundantly present in S. lugdunensis. The classification based on gene ontology (GO) terms by microorganism exhibited that metabolic process or catabolic activity was at the top rank in E. faecalis with more than 33 proteins, and in S. lugdunensis, localization or transport was highly ranked with 4 proteins. These results support the hypothesis that EGCG might cause different cellular programs in each microorganism. Finally, comparison of the proteomes between two groups that form biofilms to similar extents discovered that 2 proteins were commonly found in the weak biofilm-forming groups (E. faecalis and EGCG-responding S. lugudunensis), whereas 9 proteins were common among the strong biofilm-forming groups (S. lugdunensis and EGCG-responding E. faecalis). It was suggested that these proteins could serve as potential indicators to detect the presence and predict the extent of biofilm formation by multiple microorganisms. Taken all together, proteomics data and analyses performed in this study provided useful and new information on the proteins embedded in the biofilms formed at the specific conditions, which can aid in diagnosis and the development of tailored treatment strategies.

Epigallocatechin gallate modification of physicochemical, structural and functional properties of egg yolk granules

The aim of this study was to prepare protein-polyphenol covalent complexes by treating egg yolk granules (EYG) with alkali in the presence of epigallocatechin gallate (EGCG) and characterize the physicochemical, structural, and functional properties of these covalent complexes. Results revealed that the optimal covalent binding occurred when the concentration of EGCG reached 0.15% (w/w), resulting in a grafting rate of 1.51 ± 0.03%. As the amount of EGCG increased, corresponding increases were observed in the particle size and ζ-potential of the complexes, thereby enhancing their stability. Furthermore, our analysis using fluorescence spectroscopy, FTIR, SEM, and SDS-PAGE collectively demonstrated the formation of a covalent complex between EYG and EGCG. Notably, the covalent complexes exhibited improved antioxidant activity and emulsifying properties. Overall, this study establishes a theoretical framework for the future practical application of EYG, emphasizing the potential of EGCG to modify its structural and functional characteristics.

Nanocomplex of (−)-epigallocatechin-3-gallate and glycated ovalbumin based on natural deep eutectic solvents: Binding analysis and functional improvement

Natural deep eutectic solvents (NADES) are considered an efficient reaction medium for the production of glycated proteins. By optimizing the Maillard reaction conditions through response surface analysis, a glycation product (GOVA) of ovalbumin (OVA) with high grafting degree (92.2%) was prepared in choline chloride/glucose NADES. The binding information of (−)-epigallocatechin-3-gallate (EGCG) to OVA/GOVA was acquired by fluorescence spectroscopy and molecular docking. The interaction strength of GOVA + EGCG was higher than that of OVA + EGCG. Hydrogen bonding and van der Waals forces were the major driving forces in the binding process. Glycation and EGCG binding reduced the surface hydrophobicity, α-helix content and digestibility of OVA. Compared with OVA, the particle sizes of GOVA and GOVA + EGCG were increased by 54.8% and 87.7%, respectively. In addition, glycation increased the emulsifying activity index and foaming capacity of OVA by 32.6% and 20.0%, respectively, which was further increased in the presence of EGCG. The encapsulation of OVA, especially GOVA, improved the antioxidant activity, stability and bioaccessibility of EGCG. The results suggest that the glycated proteins based on NADES may provide an effective alternative for the protection and transport of bioactive ingredients in the food industries.

A combination of green tea polysaccharide conjugate and bovine serum albumin and its emulsion-stabilizing characteristics

Tea polysaccharide conjugates (TPC) and bovine serum albumin (BSA) have emulsifying properties, but they have certain shortcomings when used alone as emulsifiers. This study aimed to combine TPC and BSA to form a complex for applications to achieve the complementary advantages between them. The TPC/BSA complex was physicochemically characterized, and the results showed an improvement in its surface hydrophobicity. TPC/BSA emulsions with different concentrations (0.20–1.00 wt%) were prepared using TPC/BSA complex as the emulsifier. The effects of heat treatment, pH, and metal ions on the stability of TPC/BSA and BSA emulsions were investigated, and TPC/BSA emulsion systems loaded with epigallocatechin gallate (EGCG) and epigallocatechin (EGC) were constructed. TPC/BSA emulsion droplets were smaller than 1.00 wt% TPC emulsion droplets, and the particle size of 0.20 wt% TPC/BSA emulsion increased slightly during storage at 25 °C. Further, 0.20 wt% TPC/BSA emulsions became less stable after heat treatment, whereas the particle size of other concentrations did not change significantly after treatment at 70 ℃–90 °C. TPC/BSA emulsions were more stable at pH 6.0–9.0. Both were less affected by Na+, weakly affected by Ca2+ than BSA emulsion, and significantly affected by Al3+. TPC/BSA emulsion had a good protection effect on EGCG and EGC. The presence of EGCG and EGC improved the stability of the emulsion system, which remained stable for 90 days.

The effect of cations and epigallocatechin gallate on in vitro salivary lubrication

Ionic valency influences oral processing by changing salivary behavior and merits more attention since little is known. In this study, the influence of three ionic valences (monovalent, divalent and trivalent), ionic strength and epigallocatechin gallate (EGCG) on lubricating properties of saliva were investigated. Tribological measurements were used to characterize the lubrication response of KCl, MgCl2, FeCl3, and AlCl3 in combination with EGCG to the ex vivo salivary pellicle. KCl at 150 mM ionic strength provided extra lubrication via hydration lubrication. Contrarily, trivalent salts aggregated together with the salivary mucins via ionic cross-link interactions, which led to a decrease in salivary lubrication. FeCl3 and AlCl3 affected the salivary lubrication differently, which was attributed to changes in the pH. Finally, in presence of EGCG, FeCl3 interacted with EGCG via chelating interactions, preventing salivary protein aggregation. This resulted in less desorption of the salivary film, retaining the lubrication ability of salivary proteins.

Influence of Epigallocatechin Gallate on Quality of Cooked Harpiosquillid Mantis Shrimp (Harpiosquilla raphidea) Subjected to Multiple Freeze-Thaw Cycles

Effects of epigallocatechin gallate (EGCG) at 200 or 400 ppm on quality changes of cooked Harpiosquillid mantis shrimp (Harpiosquilla raphidea) (CHMS) meat subjected to varying freeze-thaw cycles (F-T-C; 0, 1, 3, and 5) were studied. With augmenting F-T-C, the CHMS meat underwent deterioration to higher extent as indicated by upsurges in exudate loss, tougher texture along with increased microbial counts. The addition of EGCG could retard those changes in a dose-dependent manner. Furthermore, EGCG prevented microbial growth as ascertained by lower counts and total volatile basic nitrogen (TVB) content. Lipid oxidation was also impeded in the presence of EGCG, especially at a high concentration as evidenced by lowered malondialdehyde (MDA), while maintaining polyunsaturated fatty acids, particularly EPA and DHA when F-T-C raised. Total disulfide bond content and surface hydrophobicity of CHMS added with EGCG were lower than those of the control. Those alterations were more retarded as EGCG concentration increased. Therefore EGCG at 400 ppm effectively prevented quality loss of CHMS meat during repeated F-T process.

Sustained antioxidant properties of epigallocatechin gallate loaded halloysite for PLA as potentially durable materials

AbstractHalloysite nanotube (HNT) was etched by hydrochloric acid, and epigallocatechin gallate (EGCG) was loaded into the etched HNT (HH) to prepare loaded antioxidant (HH‐E) for polylactic acid (PLA) with improved thermal‐oxidative stability. The loading process was confirmed by TGA and FT‐IR, and the loading capacity was 16.15%. The presence of EGCG on the surface of etched HNT was further confirmed by nitrogen adsorption and TEM. The effect of loaded EGCG on thermal‐oxidative stability of PLA was characterized by the change in OOT values of PLA after the aging process under 140°C. The results showed that HH‐E increased OOT values of PLA from 231.2°C to 293.6°C at first, indicating that HH‐E provided PLA with excellent thermal‐oxidative stability. Furthermore, as can be seen from the trend of OOT changing over aging time, during the 14 days aging process, OOT values of PLA composites with HH‐E decreased more slowly than that of PLA composites with EGCG alone, endowing PLA with sustainable thermal‐oxidative stability. Further kinetic analysis showed that the apparent activation energy of the degradation process (Ea) of PLA composites with HH‐E changed less than that of PLA composites with EGCG alone, which showed that the loading system provided PLA better sustainable stability. Moreover, the isothermal crystallization process of modified PLA was characterized by DSC and POM. The results showed that HH‐E provided heterogeneous crystal nucleus for PLA, reducing the half crystallization time (t0.5) and improvement of crystallization rate for PLA. These results prove that HH‐E exhibited excellent performance in improving the thermal stability and crystallization property of PLA, showing multifunctional characterization.

Study of polysaccharide gels at Prof. Nishinari's laboratory

Studies performed at Prof. Katsuyoshi Nishinari's laboratory are overviewed. The gelation and gel properties of gellan gum were investigated by rheological and thermal analyses. The change in the elastic modulus of gellan gum gels due to the temperature or immersion in salt solutions was interpreted from the model that Prof. Nishinari proposed. The fracture behavior of the large deformation of gellan gum gels was also explained by this model. The gel of xyloglucan from tamarind seed, in particular, a thermoreversible cold-setting gel that formed in the presence of epigallocatechin gallate or Na-type gellan, was studied. As examples of recent collaborative works with Prof. Nishinari, the gelation of β-glucan extracted from Sparassis crispa, an edible mushroom, and the application of sodium alginate and low methoxy pectin to rice noodles are also described.

Action mechanisms of two key xanthine oxidase inhibitors in tea polyphenols and their combined effect with allopurinol.

Tea polyphenols have been reported to have the effect of lowering uric acid. However, there are few studies on the inhibitory effects and molecular mechanisms of specific catechins on the urate-metabolizing enzyme xanthine oxidase (XO). In this research, multiple spectroscopic methods and computer simulations were used to determine the inhibitory ability and mechanisms of epigallocatechin gallate (EGCG) and gallocatechin gallate (GCG) on XO. Herein, EGCG and GCG reversibly inhibited XO activity in a mixed manner, with IC50 values of 40.50 ± 0.32 and 33.60 ± 0.53 μmol L-1 , and also decreased the superoxide anion radical (O2 - ) of the catalytic system by reducing the XO molecule and inhibiting the formation of uric acid. The combination of EGCG or GCG with allopurinol showed synergistic inhibition on XO. The binding of EGCG or GCG to XO with moderate affinity formed a stable complex by hydrogen bonds and van der Waals forces. The presence of EGCG and GCG made the structure of XO more stable and compact. The two inhibitors bound to the vicinity of flavin adenine dinucleotide (FAD) in XO, hindering the entry of substrate; thus the activity of XO was suppressed. Both EGCG and GCG are excellent natural XO inhibitors, and inhibited the activity of XO by occupying the channel of the substrate to enter the active center and interfering with the dual substrate reaction catalyzed by XO. These findings provide a scientific basis for the application of catechins in dietary supplements and medicines with lowering uric acid effects. © 2022 Society of Chemical Industry.

The Importance of Val386 in Transmembrane Domain 8 for the Activation of OATP1B3 by Epigallocatechin Gallate.

Estrone-3-sulfate (E3S) uptake mediated by organic anion transporting polypeptide 1B3 (OATP1B3) can be activated by epigallocatechin gallate (EGCG). In this study, by using chimeric transporters and site-directed mutagenesis, we found that Val386 in transmembrane domain 8 (TM8) is essential for OATP1B3's activation by EGCG. Kinetic studies showed that the loss of activation of 1B3-TM8 and 1B3-V386F in the presence of EGCG is due to their decreased substrate binding affinity and reduced maximal transport rate. The overall transport efficiencies of OATP1B3, 1B3-TM8, and 1B3-V386F in the absence and presence of EGCG are 8.6 ± 0.7 vs 15.9 ± 1.4 (p < 0.05), 11.2 ± 2.1 vs 2.7 ± 0.3 (p < 0.05), and 10.2 ± 1.0 vs 2.5 ± 0.3 (p < 0.05), respectively. While 1B3-V386F cannot be activated by EGCG, its transport activity for EGCG is also diminished. OATP1B3's activation by EGCG is substrate-dependent as EGCG inhibits OATP1B3-mediated pravastatin uptake. Furthermore, the activation of OATP1B3-mediated E3S uptake by quercetin 3-O-α-l-arabinopyranosyl(1 → 2)-α-l-rhamnopyranoside is not affected by TM8 and V386F. Taken together, the activation of OATP1B3 by small molecules is substrate- and modulator-dependent, and V386 in TM8 plays a critical role in the activation of OATP1B3-mediated E3S uptake by EGCG.

Impact of non-covalent bound polyphenols on conformational, functional properties and in vitro digestibility of pea protein

This study investigated the effects of the non-covalent interaction of pea protein isolate (PPI) with epigallocatechin-3-gallate (EGCG), chlorogenic acid (CA) and resveratrol (RES) on the structural and functional properties of proteins. The conformational changes of the protein structure with EGCG, CA and RES were analyzed using fourier transform infrared spectroscopy. Polyphenols strongly quenched the intrinsic fluorescence of PPI mainly through static quenching. The main interaction force was hydrogen bonding and van der Waals forces for PPI-EGCG, the main interaction force of PPI-CA complex was electrostatic interaction, while RES and PPI were bound by hydrophobic interaction. Free sulfhydryl groups and surface hydrophobicity significantly decreased in PPI after binding with phenolic compounds. The presence of EGCG, CA and RES enhanced the emulsification, foaming and in vitro digestibility of PPI. These results illustrate the potential applications of PPI-polyphenol complexes in food formulations.

Epigallocatechin gallate (EGCG) restores 25-hydroxy vitamin D levels in rheumatoid arthritis patients by attenuating ROS-mediated activation of NF-κB

Purpose: To investigate the mechanism by which epigallocatechin gallate (EGCG) attenuates ROS-induced pathogenesis in a rheumatoid arthritis (RA) patients.&#x0D; Methods: Fifty patients (33 male and 17 female) aged between 25 and 60 years who satisfied ACR 1987 criteria for active RA, and thirty healthy individuals were recruited. Total peripheral blood mononuclear cells (PBMCs), neutrophils and monocytes were isolated from the blood samples of RA patients and healthy donors using commercial extraction kits. Levels of reactive oxygen species (ROS) and superoxide radical (O2-) in isolated cells were measured using fluorescence spectroscopy while the levels of the associated inflammatory cytokines (TNF-α and IL-6) were determined in PBMCs isolated from RA patients using enzyme linked immunosorbent assay (ELISA). These parameters were monitored in EGCG-treated and untreated cells. Moreover, the status of 25(OH) vitamin D and NK-κB were investigated in lipopolysaccharide (LPS)-challenged PBMCs in the presence and absence of EGCG.&#x0D; Results: Elevated levels of superoxide radical and ROS were observed in neutrophils from RA patients in the absence of ECGC, but in the presence of EGCG, the levels of the two parameters were significantly reduced (p &lt; 0.05). Similarly, EGCG treatment downregulated the ROS-mediated increases in TNF-α and IL-6 in the PBMCs from RA patients (p &lt; 0.05). Treatment of PBMCs with the ROS-inducing agent, LPS, resulted in the activation of NK-κB via phosphorylation, and also depletion of 25(OH) vitamin D levels (p &lt; 0.05). However, pre-treatment of the LPS-challenged cells with EGCG inhibited NK-κB activation and 25(OH)-vitamin D depletion (p &lt; 0.05). Moreover, 25(OH)vitamin D levels were restored in the presence of NK-κB inhibitor, flavopiridol, thereby confirming the direct regulatory role of NK-κB in 25(OH) vitamin D levels.&#x0D; Conclusion: EGCG restores 25(OH) vitamin D levels by attenuating ROS-mediated NK-κB activation. Thus, EGCG may be a promising drug candidate for RA.

Effect of a Tea Polyphenol on Different Levels of Exposure of Nicotine and Tobacco Extract on Streptococcus mutans Biofilm Formation.

Objective: The purpose of this study was to compare the effects of different levels of nicotine and tobacco extract exposure on Streptococcus mutans biofilm formation and the inhibitory effect of the polyphenol epigallocatechin-3 gallate (EGCG) found in green tea. This study addressed the results of biofilm assays with EGCG and varying relative concentrations of nicotine and tobacco extract consistent with primary, secondary and tertiary levels of smoking exposure. Primary smoking exposure to nicotine has been demonstrated to significantly increase biofilm formation, while EGCG has been demonstrated to reduce S. mutans biofilm formation.Methods: S. mutans was treated with varying levels of nicotine or cigarette smoke condensate (CSC) concentrations (0–32 mg/ml and 0–2 mg/ml, respectively) in Tryptic Soy broth supplemented with 1% sucrose for different lengths of time simulating primary, secondary and tertiary smoking exposure with and without 0.25 mg/ml EGCG. The amount of total growth and biofilm formed was determined using a spectrophotometric crystal violet dye staining assay.Results: For both nicotine and CSC, primary exposure displayed overall significantly less growth compared to secondary exposure. For nicotine, secondary exposure demonstrated significantly greater growth than tertiary exposure levels. Overall, significantly greater total bacterial growth and biofilm formation in the presence of nicotine and CSC was observed in the absence of EGCG than in the presence of EGCG. However, biofilm growth was not significantly different among different concentrations of CSC.Conclusion: The results of this study help illustrate that nicotine-induced S. mutans biofilm formation is reduced by the presence of EGCG. This provides further evidence of the potential beneficial properties of polyphenols.

Mitochondria-Mediated Moderation of Apoptosis by EGCG in Cytotoxic Neuronal Cells Induced by Lead (Pb) and Amyloid Peptides.

The developmental, epigenetic, and epidemiological studies on lead (Pb) toxicity have reported a strong connection between lead exposure and the progression of Alzheimer's disease (AD). The amyloid peptides were the main triggering elements, in the generation of extracellular plaques through which multiple cellular signaling events such as apoptosis and primarily oxidant-antioxidant balancing system will be affected, which leads to neuronal cell death. Our previous studies indicated that epigallocatechin gallate (EGCG), abundantly present in green tea, was found to be effective in alleviating the metal-induced neurotoxicity at the cellular level in terms of cell viability and apoptosis The aim of this study was to explore the protective mechanism of EGCG on the markers of oxidant-antioxidant system and mitochondria, which are involved in metal-induced neuronal cell death. Initially, the IC50 values for lead(Pb-5µM), amyloid peptides (AP(1-40)-60µM; AP(1-40)-8µM), and EC50 value for EGCG(50µM) were determined by both time- (12h, 24h, 48h) and concentration-dependent manner and analyzed by MTT assay. The experimental groups were designed initially by treating with Pb and APs individually and in different combinations along with the presence of EGCG and are compared to the Pb and AP treated group without EGCG exposure. The cell lysates were used for analyzing oxidative stress markers by standardized laboratory protocol and the expression of mitochondrial markers such as VDAC and cytochrome C which were analyzed by both western blot and real-time PCR. Our results indicate that the EGCG-treated group has shown a significant increase in antioxidant marker expression levels (GSH, SOD, catalase, vitamin C) and a decrease in oxidative stress marker (NOS, MDA) levels when compared to the group without EGCG treatment (p < 0.05). Similarly, a significant decrease in expression levels of VDAC and cytochrome c were observed in the EGCG-treated group when compared to the group without EGCG treatment (p < 0.05). Our approach revealed that EGCG protects SH-SY5Y cells from Pb- and AP-induced cytotoxicity by regulating voltage-dependent anion channel (VDAC) expression and oxidant-antioxidant system and inhibits neuronal cell death.

Detection of Amyloid-β Fibrils Using Track-Etched Nanopores: Effect of Geometry and Crowding.

Several neurodegenerative diseases have been linked to proteins or peptides that are prone to aggregate in different brain regions. Aggregation of amyloid-β (Aβ) peptides is recognized as the main cause of Alzheimer's disease (AD) progression, leading to the formation of toxic Aβ oligomers and amyloid fibrils. The molecular mechanism of Aβ aggregation is complex and still not fully understood. Nanopore technology provides a new way to obtain kinetic and morphological aspects of Aβ aggregation at a single-molecule scale without labeling by detecting the electrochemical signal of the peptides when they pass through the hole. Here, we investigate the influence of nanoscale geometry (conical and bullet-like shape) of a track-etched nanopore pore and the effect of molecular crowding (polyethylene glycol-functionalized pores) on Aβ fibril sensing and analysis. Various Aβ fibril samples that differed by their length were produced by sonication of fibrils obtained in the presence of epigallocatechin gallate. The conical nanopore functionalized with polyethylene glycol (PEG) 5 kDa is suitable for discrimination of the fibril size from relative current blockade. The bullet-like-shaped nanopore enhances the amplitude of the current and increases the dwell time, allowing us to well discern the fibrils. Finally, the nanopore crowded with PEG 20 kDa enhances the relative current blockade and increases the dwell time; however, the discrimination is not improved compared to the "bullet-shaped" nanopore.

Competitive binding of synergistic antioxidant chlorogenic acid and (−)-epigallocatechin gallate with lysozyme: Insights from multispectroscopic characterization, molecular docking and activity evaluation

The individual and combined binding of two active polyphenols, (−)-epigallocatechin gallate (EGCG) and chlorogenic acid (CGA), to lysozyme was studied at the molecular level by multispectroscopic techniques and molecular docking. The thermodynamic parameters obtained from fluorescence data indicated that the main driving force for the binding of CGA to lysozyme was electrostatic interaction while the binding of EGCG was mainly driven by hydrogen bonding and van der Waals’ forces. The results of circular dichroism spectroscopy and dynamic light scattering showed that the α-helical content and particle size of lysozyme decreased and increased, respectively, in the presence of EGCG and/or CGA. The competitive binding of EGCG and CGA to lysozyme was confirmed by molecular docking. The binding of EGCG and/or CGA inhibited the activity of lysozyme. The combination of EGCG and CGA had synergistic antioxidant activity and cytotoxicity to HeLa cells. Response surface methodology was used to analyze the maximum synergistic antioxidant activity between EGCG and CGA. The lysozyme + EGCG/CGA interaction weakened and enhanced the antioxidant activity and cytotoxicity of EGCG/CGA, respectively. These results would provide ideas for the combined application of EGCG and CGA in the fields of functional foods and pharmaceuticals.

Role of epigallocatechin gallate in collagen hydrogels modification based on physicochemical characterization and molecular docking

Collagen Type I derived from fish is mainly limited by its poor physicochemical properties for further applications. In this study, we developed epigallocatechin gallate (EGCG) cross-linked collagen hydrogels (EC hydrogels) to realize physicochemical improvements, basing on the interaction mechanism between collagen and EGCG. The integrity of collagen framework with slight secondary structure change in the presence of EGCG was confirmed. The stronger stability of collagen fibrils was proved by slower swelling ratio, declined enzymatic degradation, improved thermal analysis and mechanical test due to EGCG modification. To illustrate the potential mechanism between collagen and EGCG, molecular docking was used to identify both covalent (CN bond, between lysine of collagen and C2-ring B of EGCG) and non-covalent bonds (hydrogen bond and hydrophobic interaction) within in EC hydrogel. Taken together, this work would offer some insights into the further study about the interaction between EGCG and collagen.

Epigallocatechin Gallate for Management of Heavy Metal-Induced Oxidative Stress: Mechanisms of Action, Efficacy, and Concerns.

In this review, we highlight the effects of epigallocatechin gallate (EGCG) against toxicities induced by heavy metals (HMs). This most active green tea polyphenol was demonstrated to reduce HM toxicity in such cells and tissues as testis, liver, kidney, and neural cells. Several protective mechanisms that seem to play a pivotal role in EGCG-induced effects, including reactive oxygen species scavenging, HM chelation, activation of nuclear factor erythroid 2-related factor 2 (Nrf2), anti-inflammatory effects, and protection of mitochondria, are described. However, some studies, especially in vitro experiments, reported potentiation of harmful HM actions in the presence of EGCG. The adverse impact of EGCG on HM toxicity may be explained by such events as autooxidation of EGCG, EGCG-mediated iron (Fe3+) reduction, depletion of intracellular glutathione (GSH) levels, and disruption of mitochondrial functions. Furthermore, challenges hampering the potential EGCG application related to its low bioavailability and proper dosing are also discussed. Overall, in this review, we point out insights into mechanisms that might account for both the beneficial and adverse effects of EGCG in HM poisoning, which may have a bearing on the design of new therapeutics for HM intoxication therapy.

The Major Constituent of Green Tea, Epigallocatechin-3-Gallate (EGCG), Inhibits the Growth of HPV18-Infected Keratinocytes by Stimulating Proteasomal Turnover of the E6 and E7 Oncoproteins.

Epigallocatechin-3-gallate (EGCG), the primary bioactive polyphenol in green tea, has been shown to inhibit the growth of human papilloma virus (HPV)-transformed keratinocytes. Here, we set out to examine the consequences of EGCG treatment on the growth of HPV18-immortalised foreskin keratinocytes (HFK-HPV18) and an authentic HPV18-positive vulvar intraepithelial neoplasia (VIN) clone, focusing on its ability to influence cell proliferation and differentiation and to impact on viral oncogene expression and virus replication. EGCG treatment was associated with degradation of the E6 and E7 oncoproteins and an upregulation of their associated tumour suppressor genes; consequently, keratinocyte proliferation was inhibited in both monolayer and organotypic raft culture. While EGCG exerted a profound effect on cell proliferation, it had little impact on keratinocyte differentiation. Expression of the late viral protein E4 was suppressed in the presence of EGCG, suggesting that EGCG was able to block productive viral replication in differentiating keratinocytes. Although EGCG did not alter the levels of E6 and E7 mRNA, it enhanced the turnover of the E6 and E7 proteins. The addition of MG132, a proteasome inhibitor, to EGCG-treated keratinocytes led to the accumulation of the E6/E7 proteins, showing that EGCG acts as an anti-viral, targeting the E6 and E7 proteins for proteasome-mediated degradation.

Effects of epigallocatechin-3-gallate and acyclovir on herpes simplex virus type 1 infection in oral epithelial cells

Herpes simplex virus type 1 (HSV-1) is the pathogenic agent of human diseases, including gingivostomatitis and herpes labialis. The anti-viral activities of the tea polyphenol, epigallocatechin-3-gallate (EGCG), have been demonstrated. This study examined the combined effects of EGCG and the antiviral drug, acyclovir (ACV), on infection of HSV-1 in oral epithelial cells. Cell viability was examined using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide. Viral yields were determined using the plaque assay. Viral proteins were detected using Western blotting analysis or confocal laser scanning microscopy. Viral DNA was detected using the real-time polymerase chain reaction. Cytotoxic effects of HSV-1 on the viability of oral epithelial cells were evidently reduced in the presence of EGCG (25μg/ml) or/and ACV (50μg/ml). Viral yields were also significantly reduced by treatment of cells with EGCG or/and ACV. Expression of viral immediate early protein, infected cell protein 0 (ICP0), was greatly inhibited when cells were treated with EGCG. Combined effects of EGCG and ACV were more evident for the expression of viral thymidine kinase, ICP5 and glycoprotein D. EGCG, but not ACV, significantly reduced the levels of viral particles and viral DNA during viral entry phase. However, at 20h post infection, the intracellular viral DNA was evidently reduced in HSV-1 infected cells treated with EGCG and ACV. Moreover, the stimulatory effects of HSV-1 on phosphorylation of c-Jun N-terminal kinase could be reduced by ACV. The results demonstrated the additive effects of EGCG and ACV on HSV-1 infection in oral epithelial cells.