Mitogenic activity of (-)epigallocatechin gallate on B-cells and investigation of its structure-function relationship

Research progress of epigallocatechin-3-gallate (EGCG) on anti-pathogenic microbes and immune regulation activities

At the end of 2019, the COVID-19 virus spread worldwide, infecting millions of people. Infectious diseases induced by pathogenic microorganisms such as the influenza virus, hepatitis virus, and Mycobacterium tuberculosis are also a major threat to public health. The high mortality caused by infectious pathogenic microorganisms is due to their strong virulence, which leads to the excessive counterattack by the host immune system and severe inflammatory damage of the immune system. This paper reviews the efficacy, mechanism and related immune regulation of epigallocatechin-3-gallate (EGCG) as an anti-pathogenic microorganism drug. EGCG mainly shows both direct and indirect anti-infection effects. EGCG directly inhibits early infection by interfering with the adsorption on host cells, inhibiting virus replication and reducing bacterial biofilm formation and toxin release; EGCG indirectly inhibits infection by regulating immune inflammation and antioxidation. At the same time, we reviewed the bioavailability and safety of EGCG in vivo. At present, the bioavailability of EGCG can be improved to some extent using nanostructured drug delivery systems and molecular modification technology in combination with other drugs. This study provides a theoretical basis for the development of EGCG as an adjuvant drug for anti-pathogenic microorganisms.

Immunomodulatory Effects of Green Tea Polyphenols

Green tea and its bioactive components, especially polyphenols, possess many health-promoting and disease-preventing benefits, especially anti-inflammatory, antioxidant, anticancer, and metabolic modulation effects with multi-target modes of action. However, the effect of tea polyphenols on immune function has not been well studied. Moreover, the underlying cellular and molecular mechanisms mediating immunoregulation are not well understood. This review summarizes the recent studies on the immune-potentiating effects and corresponding mechanisms of tea polyphenols, especially the main components of (-)-epigallocatechin-3-gallate (EGCG) and (-)-epicatechin-3-gallate (ECG). In addition, the benefits towards immune-related diseases, such as autoimmune diseases, cutaneous-related immune diseases, and obesity-related immune diseases, have been discussed.

Nutritional Modulation of Immune Function: Analysis of Evidence, Mechanisms, and Clinical Relevance

It is well-established that the nutritional deficiency or inadequacy can impair immune functions. Growing evidence suggests that for certain nutrients increased intake above currently recommended levels may help optimize immune functions including improving defense function and thus resistance to infection, while maintaining tolerance. This review will examine the data representing the research on prominent intervention agents n-3 polyunsaturated fatty acids (PUFA), micronutrients (zinc, vitamins D and E), and functional foods including probiotics and tea components for their immunological effects, working mechanisms, and clinical relevance. Many of these nutritive and non-nutritive food components are related in their functions to maintain or improve immune function including inhibition of pro-inflammatory mediators, promotion of anti-inflammatory functions, modulation of cell-mediated immunity, alteration of antigen-presenting cell functions, and communication between the innate and adaptive immune systems. Both animal and human studies present promising findings suggesting a clinical benefit of vitamin D, n-3 PUFA, and green tea catechin EGCG in autoimmune and inflammatory disorders, and vitamin D, vitamin E, zinc, and probiotics in reduction of infection. However, many studies report divergent and discrepant results/conclusions due to various factors. Chief among them, and thus call for attention, includes more standardized trial designs, better characterized populations, greater consideration for the intervention doses used, and more meaningful outcome measurements chosen.

Green tea EGCG, T-cell function, and T-cell-mediated autoimmune encephalomyelitis

Autoimmune diseases are common, disabling immune disorders affecting millions of people. Recent studies indicate that dysregulated balance of different CD4⁺ T-cell subpopulations plays a key role in immune pathogenesis of several major autoimmune diseases. Green tea and its active ingredient, epigallocatechin-3-gallate (EGCG), have been shown to modulate immune cell functions and improve some autoimmune diseases in animal models. In a series of studies we determined EGCG's effect on T-cell functions and its application in autoimmune diseases. We first observed that EGCG inhibited CD4⁺ T-cell expansion induced by polyclonal (mitogens or anti-CD3/CD28) or antigen-specific stimulation. We then showed that EGCG suppressed expansion and cell cycle progression of naïve CD4⁺ T by modulating cell cycle-related proteins. EGCG also inhibited naive CD4⁺ T-cell differentiation into Th1 and Th17 effector subsets by impacting their respective signaling transducers and transcription factors. These results suggest that EGCG may improve T-cell-mediated autoimmune diseases. Using the experimental autoimmune encephalomyelitis (EAE) mice, an animal model for human multiple sclerosis, we found that dietary supplementation with EGCG attenuated the disease's symptoms and pathology. These EGCG-induced changes are associated with findings in the immune and inflammation profiles in lymphoid tissues and the central nervous system: a reduction in proliferation of autoreactive T cells, production of proinflammatory cytokines, and Th1 and Th17 subpopulations, and an increase in regulatory T-cell populations. These results suggest that green tea or its active components may have a preventive and therapeutic potential in dealing with T-cell-mediated autoimmune diseases. However, the translational value of these findings needs to be validated in future human studies.

Green Tea Epigallocatechin-3-Gallate Suppresses Autoimmune Arthritis Through Indoleamine-2,3-Dioxygenase Expressing Dendritic Cells and the Nuclear Factor, Erythroid 2-Like 2 Antioxidant Pathway

Background

The activity of one of the major catechins in Green Tea, the polyphenol (−)-epigallocatechin-3-gallate (EGCG), has been shown to have a variety of health benefits. Recent studies suggest that EGCG can modulate both the innate and adaptive arms of the immune system. The goal of the current studies was to examine the immunomodulatory effects and mechanisms of action of EGCG on experimental arthritis in mice.

Methods

EGCG (10 mg/kg) was administered by oral gavage after CIA induction, while control mice were administered phosphate buffered saline (PBS). Disease mechanisms were studied in both groups of mice. Phenotypes were examined using repeated measure analysis of variance (ANOVA) and data from in vitro and ex vivo experiments were analyzed for significance using the Mann-Whitney U test.

Results

EGCG treatment ameliorated clinical symptoms and reduced histological scores in arthritic mice. Serum type-II collagen-specific immunoglobulin (Ig) IgG2a antibodies were significantly lower in EGCG-fed mice compared to PBS-treated mice. EGCG significantly suppressed T cell proliferation and relative frequencies of CD4 T cells, CD8 T cells and B cell subsets including marginal zone B cells, T1 and T2 transitional B cells, while increasing the frequency of CD4⁺ Foxp3⁺ regulatory T cells (Tregs) and indoleamine‐2,3‐dioxygenase (IDO) expression by CD11b⁺ dendritic cells (DC). Splenic CD11b⁺ DC from EGCG fed mice induced an increased frequency of Tregs via an IDO-dependent mechanism in in vitro cultures. Importantly, joint homogenates from EGCG-fed mice exhibited significantly increased levels of Nuclear Factor, Erythroid 2-Like 2 (Nrf-2) and Heme oxygenase-1 (HO-1) compared with PBS-fed mice.

Conclusions

This is the first report of upregulation of the Nrf-2 antioxidant pathway in EGCG-mediated immunoregulation. EGCG ameliorated experimental arthritis in mice by eliciting IDO-producing DCs, increasing frequencies of T regs and inducing the activation of the Nrf-2 antioxidant pathway. It remains to be established whether EGCG is useful for the prevention and treatment of rheumatoid arthritis and other inflammatory disorders.

Analysis of the effect of the active compound of green tea (EGCG) on the proliferation of peripheral blood mononuclear cells

Background

Cancer immunotherapy requires proper manipulation of the immune system, lymphocytes in particular, in order to identify and destroy the cancer cells as non-self. In this study we investigated the effect of the flavonoid present in green tea, namely epigallocatechin-3-gallate (EGCG), on the proliferation of, and IFN-γ production by, peripheral blood mononuclear cells (PBMC) from breast cancer patients stimulated with a mitogen, anti-CD3 and the common breast cancer peptides Her-2/neu, and p53.

Methods

Blood samples were collected from 25 patients with breast cancer at the Kuwait Cancer Control Centre (KCCC). The patients were newly diagnosed, and had not undergone any treatment or surgery at the time of sample collection. The control group consisted of 25 healthy women age-matched (±5 years) to the patients. PBMC were isolated from the patients and controls, and were cultured separately with the mitogen PHA, anti-CD3 antibodies, and Her-2/neu and p53 in the presence or absence of standardized doses of EGCG. The degree of proliferation and interferon-γ [IFN-γ) release were then analyzed.

Results

EGCG significantly suppressed the proliferation of PBMC in response to stimulation separately with (i) the mitogen, (ii) anti-CD3, and (iii) the cancer antigen peptides. IFN-γ production was also significantly suppressed by EGCG in vitro.

Conclusions

EGCG appears to have an immunosuppressive effect on the proliferation of PBMC, indicating that EGCG is worth exploring for immunomodulatory effects in autoimmune diseases and tissue transplantation.

Immunomodulating effects of epigallocatechin-3-gallate from green tea: mechanisms and applications

Consuming green tea or its active ingredient, epigallocatechin-3-gallate (EGCG), has been shown consistently to benefit the healthy functioning of several body systems. In the immune system specifically, accumulating evidence has revealed an immunomodulating effect of green tea/EGCG. Several types of immune cells in both the innate and adaptive immune systems are known to be affected in varying degrees by green tea/EGCG. Among them, the dramatic effect on T cell functions has been repeatedly demonstrated, including T cell activation, proliferation, differentiation, and production of cytokines. In particular, dysregulated T cell function with respect to different subsets of CD4(+) T cells is a critical pathogenic factor in the development of autoimmune inflammatory diseases. Recent studies have shown that EGCG affects the differentiation of naïve CD4(+) T cells into different effector subsets in a way that would be expected to favorably impact autoimmunity. Consistent with these findings, studies using animal models of autoimmune diseases have reported disease improvement in animals treated with green tea/EGCG. Altogether, these studies identify and support the use of EGCG as a potential therapeutic agent in preventing and ameliorating T cell-mediated autoimmune diseases. Given the paucity of information in human studies, the translational value of these findings needs to be verified in future research.

Evaluation of green tea by-product and green tea plus probiotics on the growth performance, meat quality and immunity of growing–finishing pigs

The present study was conducted to evaluate the effects of green tea by-product (GTB) and green tea plus probiotics (GT+P) on the growth performance, carcass characteristics, meat quality, blood parameters and immunity of growing–finishing pigs. In total, 80 crossbreed growing pigs were assigned to receive four dietary treatments for a period of 8 weeks. The dietary treatments were a basal diet (control), basal diet supplemented with 0.003% chlortetracycline (antibiotic), basal diet with 0.5% GTB (GTB) and basal diet containing 0.5% GT+P (GT+P). The results of our study indicated that bodyweight gain increased (P < 0.05) in response to the addition of GT+P to the basal diet. Crude protein and crude ash content, and shear values of loin meat were significantly (P < 0.05) increased in the GT+P group, although moisture and juiciness were decreased (P < 0.05). The GTB group had higher (P < 0.05) serum glucose concentrations, whereas the GT+P exhibited lower (P < 0.05) insulin concentrations. The values of thiobarbituric acid-reactive substances of fresh loin meat and meat that had been preserved for 1 week were lower (P < 0.05) in the GT+P group than those of the control and GTB groups. The growth of spleen cells incubated in concanavalin A (Con A) and lipopolysaccharide (LPS) medium was statistically higher (P < 0.05) for the GT+P group than for the GTB or antibiotic group. IL-6 and TNF-α production by spleen cells induced by Con A and LPS was increased in the GTB and GT+P group (P < 0.05) compared with the antibiotic group. Taken together, the results of the present study indicated that GT+P exerts positive effects on weight gain, meat composition, blood parameters and immunity in pigs, and could be used as an alternative to antibiotics for growing–finishing pig feeds.

Tea polyphenols inhibit rat osteoclast formation and differentiation

Matrix metalloproteinases (MMPs) play an important role in degeneration of the matrix associated with bone and cartilage. Regulation of osteoclast activity is essential in the treatment of bone disease, including osteoporosis and rheumatoid arthritis. Polyphenols in green tea, particularly epigallocatechin-3-gallate (EGCG), inhibit MMPs expression and activity. However, the effects of the black tea polyphenol, theaflavin-3,3'-digallate (TFDG), on osteoclast and MMP activity are unknown. Therefore, we examined whether TFDG and EGCG affect MMP activity and osteoclast formation and differentiation in vitro. TFDG or EGCG (10 and 100 µM) was added to cultures of rat osteoclast precursors cells and mature osteoclasts. Numbers of multinucleated osteoclasts and actin rings decreased in polyphenol-treated cultures relative to control cultures. MMP-2 and MMP-9 activities were lower in TFDG- and EGCG-treated rat osteoclast precursor cells than in control cultures. MMP-9 mRNA levels declined significantly in TFDG-treated osteoclasts in comparison to control osteoclasts. TFDG and EGCG inhibited the formation and differentiation of osteoclasts via inhibition of MMPs. TFDG may suppress actin ring formation more effectively than EGCG. Thus, TFDG and EGCG may be suitable agents or lead compounds for the treatment of bone resorption diseases.

Epigallocatechin-3-gallate directly suppresses T cell proliferation through impaired IL-2 utilization and cell cycle progression

Previously, we demonstrated that in vitro epigallocatechin-3-gallate (EGCG) supplementation inhibited T cell response in mouse spleen cells. In this study, we confirmed this effect of EGCG in mice fed 0.3% EGCG for 6 wk. A coculture with all the combinations of preincubating antigen-presenting cells and T cells with or without EGCG showed that EGCG suppressed antigen-induced T cell proliferation, mainly through a direct effect on T cells. To determine the mechanisms for this effect of EGCG, we stimulated purified mouse T cells with anti-CD3/CD28 in the presence of EGCG (2.5-15 micromol/L) and found that EGCG dose-dependently inhibited cell division and cell cycle progression and this effect of EGCG was more pronounced in CD4(+) than in CD8(+) T cells. Interleukin (IL)-2 concentrations in EGCG-treated cell cultures showed no difference up to 24 h but were higher in the cultures at 48 h compared with the untreated control cells. However, intracellular staining showed no difference between EGCG-treated and untreated control cells in IL-2 synthesis, but EGCG-treated cells expressed less IL-2 receptor (IL-2R) compared with untreated control cells. EGCG did not affect mRNA expression of IL-2 and IL-2R. These results indicate that EGCG-induced IL-2 accumulation in 48 h cultures is due to its reduced utilization. In summary, EGCG directly inhibits T cell proliferative response to both polyclonal and antigen-specific stimulation. CD4(+) cells are more responsive to EGCG than CD8(+) cells. Future studies should determine the effect of EGCG on CD4(+) cell subsets to assess its application in T cell-mediated autoimmune diseases.

Immune-modulating efficacy of a polyphenol-rich beverage on symptoms associated with the common cold: a double-blind, randomised, placebo-controlled, multi-centric clinical study

In the present study, the immune-modulating efficacy of a polyphenol-rich beverage on symptoms associated with the common cold was evaluated. For this purpose, ninety-eight patients reporting common cold symptoms that began no longer than 24 h before the study intervention were randomly assigned to consume either the test beverage or placebo twice per d for 10 d. The severity of the disease was expressed as the total score of the five cold symptoms 'general feeling of sickness', 'headache and/or joint aches', 'sore throat and/or difficulty swallowing', 'hoarseness and/or cough' and 'stuffy nose/sniffle'. Consequently, the decrease from 10.2 (sd 3.1) points at the beginning to 2.1 (sd 2.7) points by the end of the study in the verum group demonstrated a clear improvement, whereas in the placebo group only a reduction from 10.5 (sd 3.0) to 6.3 (sd 3.8) points could be observed. The mean difference between the groups (primary efficacy criterion) of 3.9 points was highly significant (P < 0.01). At the end of the study there were highly significantly (P < 0.01) more patients in the verum group complaint free than in the placebo group (secondary efficacy criterion). In addition to these self-reported values, several local findings of the physical examination were also significantly improved in the verum group.

Preclinical development of the green tea catechin, epigallocatechin gallate, as an HIV-1 therapy

BACKGROUND

Previously, we presented evidence that at physiologic concentrations the green tea catechin, epigallocatechin gallate (EGCG), inhibited attachment of HIV-1 glycoprotein 120 to the CD4 molecule on T cells, but the downstream effects of EGCG on HIV-1 infectivity were not determined.

OBJECTIVE

To evaluate the inhibition of HIV-1 infectivity by EGCG and begin preclinical development of EGCG as a possible therapy.

METHODS

PBMCs, CD4(+) T cells, and macrophages were isolated from blood of HIV-1-uninfected donors. HIV-1 infectivity was assessed by an HIV-1 p24 ELISA. Cell survival was assessed by cell viability by Trypan blue exclusion assay, cell growth by thymidine incorporation, and apoptosis by flow-cytometric analysis of annexin-V binding.

RESULTS

Epigallocatechin gallate inhibited HIV-1 infectivity on human CD4(+) T cells and macrophages in a dose-dependent manner. At a physiologic concentration of 6 mumol/L, EGCG significantly inhibited HIV-1 p24 antigen production across a broad spectrum of both HIV-1 clinical isolates and laboratory-adapted subtypes (B [P < .001], C, D, and G [P < .01]). The specificity of the EGCG-induced inhibition was substantiated by the failure of EGCG derivatives lacking galloyl and/or pyrogallol side groups to alter HIV-1 p24 levels. EGCG-induced inhibition of HV-1 infectivity was not a result of cytotoxicity, cell growth inhibition, or apoptosis.

CONCLUSION

We conclude that by preventing the attachment of HIV-1-glycoprotein 120 to the CD4 molecule, EGCG inhibits HIV-1 infectivity. Because this inhibition can be achieved at physiologic concentrations, the natural anti-HIV agent EGCG is a candidate as an alternative therapy in HIV-1 therapy.

Cytotoxic effects of digalloyl dimer procyanidins in human cancer cell lines

Flavanols, a class of polyphenols present in certain plant-based foods, have received increasing attention for their putative anticancer activity. In vitro and in vivo studies, which have compared the effectiveness of various monomer flavanols, indicate that the presence of a galloyl residue on the 3 position on the C-ring enhances the cytotoxicity of these compounds. Procyanidins, oligomerized flavanols, have been reported to be more cytotoxic than monomer flavanols in a variety of human cancer cell lines. Given the above, we evaluated the potential anticancer properties of dimer procyanidins that contain galloyl groups. Specifically, the cytotoxicity of synthetic digalloyl dimer B1 and B2 esters {[3-O-galloyl]-(-)-epicatechin-(4beta,8)-(+)-catechin-3-O-gallate (DGB1) and [3-O-galloyl]-(-)-epicatechin-(4beta,8)-(+)-epicatechin-3-O-gallate (DGB2), respectively} were tested in a number of in vitro models. DGB1 produced significant cytotoxicity in a number of human cancer cell lines evaluated by three independent methods: ATP content, MTT and MTS assays. For the three most sensitive cell lines, exposure to DGB1 and DGB2 for 24, 48 or 72 h was associated with a reduction in cell number and an inhibition of cell proliferation. Digalloyl dimers exerted significantly higher cytotoxic effects than the structurally related flavanols, (-)-epicatechin, (+)-catechin, (-)-epicatechin gallate, (-)-epigallocatechin gallate, (-)-catechin gallate and dimer B1 and B2. These results support the concept that the incorporation of galloyl groups and the oligomerization of flavanols enhances the cytotoxic effects of typical monomer flavanols. The therapeutic value of these compounds and their derivative forms as anticancer agents merits further investigation in whole animal models.

Tumor-induced thymic involution via inhibition of IL-7Rα and its JAK-STAT signaling pathway: Protection by black tea

Down-regulation of cell-mediated immune functions occurring at late stages of cancer may be related to the thymic involution since thymus is the major site of T cell maturation, proliferation, and differentiation. We found that in Ehrlich's ascites carcinoma (EAC)-bearing mice there was profound depletion of CD4+ and CD8+ cells in peripheral blood with severely damaged thymus on 21st day of tumor inoculation. However, treatment with black tea at an antitumor dose of 2.5% significantly reduced such depletion and protected the thymus considerably from tumor onslaught. A search for the underlying mechanism revealed EAC-induced IL-7Ralpha down-regulation, inhibition of JAK3 and STAT5 phosphorylation, and decrease in Bcl-2/Bax ratio in thymocytes that finally led to thymocyte apoptosis in one hand and T cell maturation block on the other. Interestingly, black tea treatment prevented IL-7Ralpha down-regulation and protected the signaling cascade through JAK-STAT thereby inhibiting tumor-induced thymic apoptosis and ensuring proper functioning of this organ in tumor-bearing host.

Nutraceutical Therapies for Degenerative Joint Diseases: A Critical Review

There is growing recognition of the importance of nutritional factors in the maintenance of bone and joint health, and that nutritional imbalance combined with endocrine abnormalities may be involved in the pathogenesis of osteoarthritis (OA) and osteochondritis dissecans (OCD). Despite this, dietary programs have played a secondary role in the management of these connective tissue disorders. Articular cartilage is critically dependent upon the regular provision of nutrients (glucose and amino acids), vitamins (particularly vitamin C), and essential trace elements (zinc, magnesium, and copper). Therefore, dietary supplementation programs and nutraceuticals used in conjunction with non-steroidal, anti-inflammatory drugs (NSAIDs) may offer significant benefits to patients with joint disorders, such as OA and OCD. This article examines the available clinical evidence for the efficacy of nutraceuticals, antioxidant vitamin C, polyphenols, essential fatty acids, and mineral cofactors in the treatment of OA and related joint disorders in humans and veterinary species. This article also attempts to clarify the current state of knowledge. It also highlights the need for additional targeted research to elucidate the changes in nutritional status and potential alterations to the expression of plasma membrane transport systems in synovial structures in pathophysiological states, so that current therapy and future treatments may be better focused.

The effect of a catechin-rich extract ofCocos nucifera on lymphocytes proliferation

Catechins are polyphenols with antioxidant activity. The fruit Cocos nucifera (Palmae) has a fi ber husk rich in catechins and the local population of northeast Brazil uses it as a medicine against various diseases. An anti-bacterial and anti-viral activity has been already observed using this substance. Plant extracts, from other sources, rich in catechins are inhibitory to tumour cells, suppressing their proliferation. The aim of the present work was to verify if catechins isolated from Cocos nucifera were capable of inhibiting cell proliferation. An extract obtained from Cocos nucifera was purified through adsorption chromatography using the resin XAD-2. The purified material was used in cultures of an erythroleukaemia cell line (K562) and on normal human peripheral blood lymphocytes. Cell viability was assessed using MTT. Cellular proliferation was measured by [(3)H]-thymidine incorporation and cell cycle analysis in a fl ow cytometer. A dose-dependent inhibitory effect was observed on tumour cells and on lymphocytes activated by phytohemaglutinin (PHA) or phorbol ester. For PHA this effect was irreversible being already established on the fi rst four hours of culture.

Tea and health

Tea is a pleasant, popular, socially accepted, economical, and safe drink that is enjoyed every day by hundreds of millions of people across all continents. Tea also provides a dietary source of biologically active compounds that help prevent a wide variety of diseases. It is the richest source of a class of antioxidants called flavonoids and contains many other beneficial compounds such as vitamins and fluoride. A growing body of evidence suggests that moderate consumption of tea may protect against several forms of cancer, cardiovascular diseases, the formation of kidney stones, bacterial infections, and dental cavities. Future research needs to define the actual magnitude of health benefits, establish the safe range of tea consumption associated with these benefits, and elucidate potential mechanisms of action.

Recent topics in anti-oxidative factors

Lipids and anti-oxidative factors regulate immune functions such as immunoglobulin production and chemical mediator release. For example, polyunsaturated fatty acids (PUFA) enhance IgE production of isolated rat lymphocytes, but not in the presence of alpha-tocopherol. In addition, anti-oxidative factors such as tea polyphenols and flavonoids exert inhibitory effect on chemical mediator release from rat peritoneal exudate cells (PEC). Some of these immunoregulatory activities of food components could be expressed in vivo. Oral administrations of perilla and fish oils or tea polyphenols led to a significant decrease of LTB4 releasing activity of rat PEC, but IgE production enhancing activity of PUFA was not expressed in vivo. On the other hand, alpha-tocopherol feeding enhanced serum IgA level as well as IgA productivity of mesenteric lymph node lymphocytes. These results suggest that dietary fats and antioxidants are effective for the alleviation of allergic symptom and activation of immune functions.

Protective effect of Japanese green tea extract on gnotobiotic mice infected with an Escherichia coli O157:H7 strain

We examined the effect of Japanese green tea extract (JGTE) on enterohemorrhagic Escherichia coli (EHEC) O157:H7 infection in a gnotobiotic mouse model. Gnotobiotic mice inoculated with an EHEC strain developed neurologic and systemic symptoms, usually culminating in death. In contrast, none of mice receiving dietary JGTE showed clinical signs or death. This report describes the effect of JGTE, which includes the inhibition of bacterial growth in vivo. The Shiga-like toxin (SLT) level in the feces of the JGTE diet group was significantly lower than that of the control group.

Erythrocyte-dependent mitogenic activity of epigallocatechin gallate on mouse splenic B cells

We previously reported that epigallocatechin gallate (EGCg), the main constituent of tea catechins, displays mitogenic effect on mouse splenic B cells. During research into the mechanism(s), it was found that the mitogenic activity of EGCg was dependent on the presence of red blood cells (RBC). When RBC in T cell-depleted spleen cells were removed, EGCg did not enhance the proliferation of B cells and even showed toxic effect at 25-50 micrograms/ml. When mouse, rabbit or sheep RBC as well as RBC-ghosts were added into the cultures, EGCg showed the mitogenic activity at a range of 1-50 micrograms/ml. Thereafter, we preincubated RBC with EGCg at 4 degrees C for various times and then washed the RBC to remove free EGCg in the suspensions. The EGCg-preincubated RBC also enhanced B cell proliferation. As short as ten minutes was sufficient for EGCg to bind to RBC membrane. These results indicate that EGCg first attached to the membrane of RBC and then stimulated B cell proliferation. The above results suggest an important immunoregulatory function of RBC.

Bactericidal catechins damage the lipid bilayer

The mode of antibacterial action of, the green tea (Camellia sinensis) extracts, (-)-epigallocatechin gallate (EGCg) and (-)-epicatechin (EC) was investigated. Strong bactericidal EGCg caused leakage of 5,6-carboxyfluorescein from phosphatidylcholine liposomes (PC), but EC with very weak bactericidal activity caused little damage to the membrane. Phosphatidylserine and dicetyl phosphate partially protected the membrane from EGCg-mediated damage when reconstituted into the liposome membrane with PC. EGCg, but not EC, caused strong aggregation and NPN-fluorescence quenching of PC-liposomes and these actions were markedly lowered in the presence of negatively charged lipids. These results show that bactericidal catechins primarily act on and damage bacterial membranes. The observation that Gram-negative bacteria are more resistant to bactericidal catechins than Gram-positive bacteria can be explained to some extent by the presence of negatively charged lipopolysaccharide.