Epigallocatechin gallate suppresses peritoneal fibrosis in mice

Long-term peritoneal dialysis (PD) leads to histological changes in the peritoneal membrane. Angiogenesis and inflammation caused by glucose degradation products (GDPs) play crucial roles in peritoneal fibrosis. One such GDP is methylglyoxal (MGO), which enhances the formation of advanced glycation end products (AGEs). AGEs bind to their receptor (RAGE) and activate nuclear factor-κB (NF-κB), which is a key regulator of angiogenesis and inflammation. Recent studies have indicated that (-)-epigallocatechin gallate (EGCG), a tea polyphenol, inhibits angiogenesis and inflammation. Here, we examined whether EGCG suppresses peritoneal fibrosis in mice. Based on preliminary examination, 2mL of 40mM MGO or PD fluid was injected intraperitoneally and EGCG (50mg/kg) or saline was injected subcutaneously for 3weeks. In comparison to PD fluid+saline-treated mice, the peritoneal tissues of MGO+saline-treated mice showed marked thickening of the submesothelial compact zone. In the submesothelial compact zone of the MGO+saline-treated mice, CD31-positive vessels and vascular endothelial growth factor-positive cells were significantly increased, as were inflammation, F4/80-positive macrophages, and monocyte chemotactic protein-1. Moreover, 8-hydroxydeoxyguanosine, a marker of reactive oxygen species, and NF-κB, determined by Southwestern histochemistry, in the submesothelial compact zone were also increased in MGO+saline-treated mice. These changes were attenuated in MGO+EGCG-treated mice. We demonstrated that EGCG treatment suppresses peritoneal fibrosis via inhibition of NF-κB. Furthermore, EGCG inhibits reactive oxygen species production. The results of this study indicate that EGCG is a potentially novel candidate for the treatment of peritoneal fibrosis.     

Epigallocatechin gallate (EGCG), a major component of green tea, is a dual phosphoinositide-3-kinase/mTOR inhibitor

The PI3K signaling pathway is activated in a broad spectrum of human cancers, either directly by genetic mutation or indirectly via activation of receptor tyrosine kinases or inactivation of the PTEN tumor suppressor. The key nodes of this pathway have emerged as important therapeutic targets for the treatment of cancer. In this study, we show that (−)-epigallocatechin-3-gallate (EGCG), a major component of green tea, is an ATP-competitive inhibitor of both phosphoinositide-3-kinase (PI3K) and mammalian target of rapamycin (mTOR) with K_i values of 380 and 320 nM respectively. The potency of EGCG against PI3K and mTOR is within physiologically relevant concentrations. In addition, EGCG inhibits cell proliferation and AKT phosphorylation at Ser473 in MDA-MB-231 and A549 cells. Molecular docking studies show that EGCG binds well to the PI3K kinase domain active site, agreeing with the finding that EGCG competes for ATP binding. Our results suggest another important molecular mechanism for the anticancer activities of EGCG.     

Structure-activity study of epi-gallocatechin gallate (EGCG) analogs as proteasome inhibitors

The structure-activity relationship of a number of synthetic green tea polyphenol analogs involving modifications of A ring and B ring of epi-gallocatechin gallate (EGCG) as proteasome inhibitors has been examined. It was found that in B ring, a decrease in the number of OH groups led to decreased potency. Introduction of a hydrophobic benzyl group into the 8 position of A ring did not significantly affect the proteasome-inhibitory potency.     

Peroxynitrite does not impair pulmonary and systemic vascular responses.

The effects of peroxynitrite (ONOO-) on vascular responses were investigated in the systemic and hindquarters vascular bed and in the isolated perfused rat lung. Intravenous injections of ONOO- decreased systemic arterial pressure, and injections of ONOO- into the hindquarters decreased perfusion pressure in a dose-related manner. Injections of ONOO- into the lung perfusion circuit increased pulmonary arterial perfusion pressure. Responses to ONOO- were rapid in onset, short in duration, and repeatable without exhibiting tachyphylaxis. Repeated injections of ONOO- did not alter systemic, hindquarters, or pulmonary responses to endothelium-dependent vasodilators or other vasoactive agonists and did not alter the hypoxic pulmonary vasoconstrictor response. Injections of sodium nitrate or nitrite or decomposed ONOO- had little effect on vascular pressures. Pulmonary and hindquarters responses to ONOO- were not altered by a cyclooxygenase inhibitor in a dose that attenuated responses to arachidonic acid. These results demonstrate that ONOO- has significant pulmonary vasoconstrictor, systemic vasodepressor, and vasodilator activity; that short-term repeated exposure does impair vascular responsiveness; and that responses to ONOO- are not dependent on cyclooxygenase product release.     

Epigallocatechin gallate induces telomere fragmentation in HeLa and 293 but not in MRC-5 cells

Telomeres are the tandem repetitive sequence at the end of chromosomes and its integrity is crucial for cell vitality. We studied the effect of (-)-epigallocatechin-3-gallate (EGCG), one of the major tea polyphenols, on telomeres in HeLa, 293 cells and MRC-5 fibroblasts. At concentrations of above 50 microM, EGCG was found to causes telomere fragmentation in HeLa cells as a result of single-strand breaks in a dose-dependent manner. Treatment of EGCG also caused telomere fragmentation in 293 cells but had little or only marginal effect on MRC-5 fibroblasts. The telomere fragments detected by electrophoresis showed a unique size distribution that seems to suggest that the strand breaks were not produced randomly, but with preference at some specific sites. We speculate that the differential effect of EGCG in inducing telomere fragmentation in HeLa and 293 verse MRC-5 cells might be relevant to the apoptosis-inducing effect of EGCG on cancerous cells but not on normal cells.     

CS-US delay does not impair appetitive conditioning in Chasmagnathus

Habituation and appetitive conditioning have been already described in the crab Chasmagnathus. The purpose of this work is to study whether associative learning can be obtained despite a long conditioned stimulus-unconditioned stimulus interval. Results of the first experiment show that the weakening of temporal contiguity does not prevent appetitive conditioning to occur while after a long 4-h delay, conditioning wanes completely. A second experiment was conducted, after one and three days of training respectively, confirming the above results. Though initially neutral the context trace may be still available immediately after training and for the period of two but not after 4:00 h, demonstrating a forward limit for the conditioning window. After 3 days of training, a further decrease in the exploratory activity suggested that a longer training could increase the relative weight of habituation. Conditioning and habituation seem to work as opponent processes in the crab CHASMAGNATHUS GRANULATUS: if habituation training in the box is followed by the administration of reinforcement after a short period of time, appetitive conditioning will take place. However, as this interval is increased, habituation prevails. A persistent effect of the exposure to a given environment that may underlie trace conditioning in this crab is discussed in adaptive terms.     

Epigallocatechin gallate promotes GLUT4 translocation in skeletal muscle

In this study, we investigated whether epigallocatechin gallate (EGCg) affects glucose uptake activity and the translocation of insulin-sensitive glucose transporter (GLUT) 4 in skeletal muscle. A single oral administration of EGCg at 75 mg/kg body weight promoted GLUT4 translocation in skeletal muscle of rats. EGCg significantly increased glucose uptake accompanying GLUT4 translocation in L6 myotubes at 1 nM. The translocation of GLUT4 was also observed both in skeletal muscle of mice and rats ex vivo and in insulin-resistant L6 myotubes. Wortmannin, an inhibitor of phosphatidylinositol 3′-kinase, inhibited both EGCg- and insulin-increased glucose uptakes, while genistein, an inhibitor of tyrosine kinase, failed to inhibit the EGCg-increased uptake. Therefore, EGCg may improve hyperglycemia by promoting GLUT4 translocation in skeletal muscle with partially different mechanism from insulin.     

Epigallocatechin gallate counteracts oxidative stress in docosahexaenoxic acid-treated myocytes

Skeletal muscle is a key organ of mammalian energy metabolism, and its mitochondria are multifunction organelles that are targets of dietary bioactive compounds. The goal of this work was to examine the regulation of mitochondrial dynamics, functionality and cell energy parameters using docosahexaenoic acid (DHA), epigallocatechin gallate (EGCG) and a combination of both in L6 myocytes. Compounds (at 25 μM) were incubated for 4 h. Cells cultured with DHA displayed less oxygen consumption with higher ADP/ATP ratio levels concomitant with downregulation of Cox and Ant1 gene expression. The disruption of energetic homeostasis by DHA, increases intracellular reactive oxygen species (ROS) levels and decreases mitochondrial membrane potential. The defence mechanism to counteract the excess of ROS production was by the upregulation of Ucp2, Ucp3 and MnSod gene expression. Moreover myocytes cultured with DHA had a higher mitochondrial mass with a higher proportion of large and elongated mitochondria, whereas the fission genes Drp1 and Fiss1 and the fusion gene Mfn2 were downregulated. In myocytes co-incubated with DHA and EGCG, ROS levels and the adenosine diphosphate (ADP)/adenosine triphosphate (ATP) ratio were similar to untreated myocytes and the decrease of oxygen consumption, higher mitochondrial mass and the overexpression of Ucp2 and Ucp3 genes were similar to the DHA-treated cells with also a higher amount of mitochondrial deoxyribonucleic acid (DNA), and reduced Drp1 and Fiss1 gene expression levels. In conclusion the addition of EGCG to DHA returned the cells to the control conditions in terms of mitochondrial morphology, energy and redox status, which were unbalanced in the DHA-treated myocytes.     

Epigallocatechin gallate reduces hypoxia-induced apoptosis in human hepatoma cells

Cell detachment from extracellular matrix is closely related to induction of apoptosis. Epigallocatechin gallate (EGCG) has been shown to have antioxidant effect and to protect hypoxia-induced damage. We investigated whether EGCG reduced hypoxia-induced apoptosis and cell detachment in HepG2 cells. EGCG prevented cell death by hypoxia (0.5% O2) in a dose-dependent manner (hypoxic cell viability, 54.67%). RT-PCR and caspase3 activity assay showed that the hypoxia-induced cell death was caused by apoptosis increasing mRNA level of BAX, CASP3, and caspase3 activity. EGCG reduced increase of these mRNA and caspase3 activity. Western blot analysis and immunocytochemistry showed that EGCG increased cell adhesion proteins including E-cadherin (CDH1), tumor-associated calcium signal transducer 1 (TACSTD1), and protein tyrosine kinase 2 (PTK2) decreased by hypoxia. Hypoxia-induced apoptosis in HepG2 cells, and EGCG contributed to the HepG2 cell survival by attenuating the apoptosis.     

Role of epigallocatechin gallate (EGCG) in the treatment of breast and prostate cancer

Green tea and its major constituent epigallocatechin gallate (EGCG) have been extensively studied as a potential treatment for a variety of diseases, including cancer. Epidemiological data have suggested that EGCG may provide protective effects against hormone related cancers, namely breast or prostate cancer. Extensive in vitro investigations using both hormone responsive and non-responsive cell lines have shown that EGCG induces apoptosis and alters the expression of cell cycle regulatory proteins that are critical for cell survival and apoptosis. This review will highlight the important in vitro mechanistic actions elicited by EGCG in various breast and prostate cancer cell lines. Additionally, the actions of green tea/EGCG in in vivo models for these cancers as well as in clinical trials will be discussed.     

Addition of milk does not affect the absorption of flavonols from tea in man

Tea is a major source of flavonols, a subclass of antioxidant flavonoids present in plant foods which potentially are beneficial to human health. Milk added to tea, a frequent habit in the United Kingdom, could inhibit absorption of tea flavonoids, because proteins can bind flavonoids effectively. Eighteen healthy volunteers each consumed two out of four supplements during three days: black tea, black tea with milk, green tea and water. A cup of the supplement was consumed every 2 hours each day for a total of 8 cups a day. The supplements provided about 100 μmol quercetin glycosides and about 60 - 70 μmol kaempferol glycosides. Addition of milk to black tea (15 ml milk to 135 ml tea) did not change the area under the curve of the plasma concentration-time curve of quercetin or kaempferol. Plasma concentrations reached were about 50 nM quercetin and 30 - 45 nM kaempferol. We conclude that flavonols are absorbed from tea and that their bioavailability is not affected by addition of milk.     

Addition of milk does not affect the absorption of flavonols from tea in man

Tea is a major source of flavonols, a subclass of antioxidant flavonoids present in plant foods which potentially are beneficial to human health. Milk added to tea, a frequent habit in the United Kingdom, could inhibit absorption of tea flavonoids, because proteins can bind flavonoids effectively. Eighteen healthy volunteers each consumed two out of four supplements during three days: black tea, black tea with milk, green tea and water. A cup of the supplement was consumed every 2 hours each day for a total of 8 cups a day. The supplements provided about 100 μmol quercetin glycosides and about 60 – 70 μmol kaempferol glycosides. Addition of milk to black tea (15 ml milk to 135 ml tea) did not change the area under the curve of the plasma concentration-time curve of quercetin or kaempferol. Plasma concentrations reached were about 50 nM quercetin and 30 – 45 nM kaempferol. We conclude that flavonols are absorbed from tea and that their bioavailability is not affected by addition of milk.     

Acute caffeine ingestion does not impair glucose tolerance in persons with tetraplegia.

Acute caffeine (Caf) ingestion impairs glucose tolerance in able-bodied humans during an oral glucose tolerance test (OGTT). The mechanism responsible for this effect remains unclear, however, it is suggested to be due to the accompanying increase in epinephrine concentration. We examined whether or not Caf would elicit a glucose intolerance in persons with tetraplegia (TP) who do not exhibit an increased epinephrine response following Caf ingestion. All TP [n = 14; 9 incomplete (Inc) lesion, 5 complete (Com) lesion] completed two OGTT 1 h after consuming either gelatin (Pl) or Caf capsules (dose = 4 mg/kg). Blood samples were collected at baseline (time = 0 min), 1 h after capsule ingestion (time = 60 min), and every 30 min during the OGTT (time = 90-180 min). Glucose, insulin, proinsulin, and C-peptide responses were similar (P > 0.05) between treatments, demonstrating no effect of Caf on glucose tolerance. This lack of a Caf effect may be due to the low epinephrine concentration that remained unchanged (P > 0.05) throughout all experiments. Interestingly, the Com exhibited a 50% higher glucose response (P 0.05) lower insulin response (vs. Inc), suggesting a more pronounced glucose intolerance within this subgroup. Furthermore, nine TP (5 Com, 4 Inc) had glucose levels of >or= 7.8 mM at the end of the OGTT (time = 180 min), classifying them as glucose intolerant. In summary, acute Caf ingestion does not increase epinephrine concentration or impair glucose tolerance in TP.     

Licorice extract does not impair the male reproductive function of rats.

The effect of water extract of licorice (Glycyrrhiza uralensis), one of the most widely used medicinal plants in Oriental nations and in Europe, on male reproductive function was investigated in rats. Licorice extract was prepared as in Oriental clinics and orally administered at doses of 500, 1,000 or 2,000 mg/kg, the upper-limit dose (2,000 mg/kg) recommended in the Toxicity Test guideline of the Korea Food and Drug Administration, to 6-week-old male rats for 9 weeks. Licorice extract neither induced clinical signs, nor affected the daily feed consumption and body weight gain. There were no significant changes in testicular weights, gross and microscopic findings, and daily sperm production between vehicle- and licorice-treated animals, in spite of slight decreases in prostate weight and daily sperm production at the high dose (2,000 mg/kg). In addition, licorice did not affect the motility and morphology of sperm, although the serum testosterone level tended to decrease without significant difference, showing a 28.6% reduction in the high-dose (2,000 mg/kg) group. The results suggest that the no observed adverse-effect level of licorice extract is higher than 2,000 mg/kg, the upper-limit dose, and that long-term exposure to licorice might not cause profound adverse effects.     

Epigallocatechin gallate inhibits intracellular survival of Listeria monocytogenes in macrophages

Epigallocatechin gallate (EGCg), the major tea catechin, is known as a potent anti-microbial and anti-tumor compound. The effects of EGCg on host defense mechanisms against Listeria monocytogenes infection were examined in vitro using mouse peritoneal exudate cells. The study showed that EGCg inhibited the intracellular growth of L. monocytogenes in macrophages. The enhancement of in vitro anti-L. monocytogenes activity by EGCg is not due to the modulation of reactive oxygen intermediates or the production of reactive nitrogen intermediates but due to the inhibition of its escaping from the phagosome into cytosolic space. Anti-L. monocytogenes of EGCg is through the inhibition of hemolytic and cholesterol-binding activity of listeriolysin O, which usually disrupts the phagosomal membrane in the escaping phase of L. monocytogenes.     

Computational and Biochemical Discovery of RSK2 as a Novel Target for Epigallocatechin Gallate (EGCG)

The most active anticancer component in green tea is epigallocatechin-3-gallate (EGCG). Protein interaction with EGCG is a critical step for mediating the effects of EGCG on the regulation of various key molecules involved in signal transduction. By using computational docking screening methods for protein identification, we identified a serine/threonine kinase, 90-kDa ribosomal S6 kinase (RSK2), as a novel molecular target of EGCG. RSK2 includes two kinase catalytic domains in the N-terminal (NTD) and the C-terminal (CTD) and RSK2 full activation requires phosphorylation of both terminals. The computer prediction was confirmed by an in vitro kinase assay in which EGCG inhibited RSK2 activity in a dose-dependent manner. Pull-down assay results showed that EGCG could bind with RSK2 at both kinase catalytic domains in vitro and ex vivo. Furthermore, results of an ATP competition assay and a computer-docking model showed that EGCG binds with RSK2 in an ATP-dependent manner. In RSK2^+/+ and RSK2^-/- murine embryonic fibroblasts, EGCG decreased viability only in the presence of RSK2. EGCG also suppressed epidermal growth factor-induced neoplastic cell transformation by inhibiting phosphorylation of histone H3 at Ser10. Overall, these results indicate that RSK2 is a novel molecular target of EGCG.     

Single millimeter wave treatment does not impair gastrointestinal transit in mice

Millimeter wave treatment (MWT) is based on those biological effects that develop following skin exposure to low power electromagnetic waves. This method of treatment is in wide clinical use in several Eastern European countries for treatment of a variety of conditions, including pain syndromes. However, most treatment modes of MWT were developed empirically, and certain indications and contraindications for the use of MWT remain to be established. In our previous blind experiments we have shown that the hypoalgesic effect of MWT may be quantitatively evaluated, and most probably mediated by the neural system in general, and the system of endogenous opioids in particular. Taking in consideration a well-known ability of opioids to cause gastrointestinal disturbances, which could limit clinical application of MWT, the main aim of the present study was to investigate whether a single MWT, that can produce opioid-related hypoalgesia, may also retard gut transit and colorectal passage in mice. The charcoal meal test was used to quantitatively evaluate upper gastrointestinal transit, and the glass bead test was employed to examine colonic propulsion in mice. MWT was applied to the nose area of mice. The MWT characteristics were: frequency = 61.22 GHz; incident power density = 15 mW/cm(2); and duration = 15 min. The results obtained have shown that MWT does not significantly change small intestinal or colonic transit in mice, and thus suppression of gastrointestinal motility should not be a setback in the clinical use of MWT.     

Low sodium intake does not impair renal compensation of hypoxia-induced respiratory alkalosis.

Acute hypoxia causes hyperventilation and respiratory alkalosis, often combined with increased diuresis and sodium, potassium, and bicarbonate excretion. With a low sodium intake, the excretion of the anion bicarbonate may be limited by the lower excretion rate of the cation sodium through activated sodium-retaining mechanisms. This study investigates whether the short-term renal compensation of hypoxia-induced respiratory alkalosis is impaired by a low sodium intake. Nine conscious, tracheotomized dogs were studied twice either on a low-sodium (LS = 0.5 mmol sodium x kg body wt-1 x day-1) or high-sodium (HS = 7.5 mmol sodium x kg body wt-1 x day-1) diet. The dogs breathed spontaneously via a ventilator circuit during the experiments: first hour, normoxia (inspiratory oxygen fraction = 0.21); second to fourth hour, hypoxia (inspiratory oxygen fraction = 0.1). During hypoxia (arterial PO2 34.4 +/- 2.1 Torr), plasma pH increased from 7.37 +/- 0.01 to 7.48 +/- 0.01 (P < 0.05) because of hyperventilation (arterial PCO2 25.6 +/- 2.4 Torr). Urinary pH and urinary bicarbonate excretion increased irrespective of the sodium intake. Sodium excretion increased more during HS than during LS, whereas the increase in potassium excretion was comparable in both groups. Thus the quick onset of bicarbonate excretion within the first hour of hypoxia-induced respiratory alkalosis was not impaired by a low sodium intake. The increased sodium excretion during hypoxia seems to be combined with a decrease in plasma aldosterone and angiotensin II in LS as well as in HS dogs. Other factors, e.g., increased mean arterial blood pressure, minute ventilation, and renal blood flow, may have contributed.