The tea catechin epigallocatechin gallate inhibits NF-κB-mediated transcriptional activation by covalent modification.

Potential health benefits of consuming tea are thought to include anti-inflammatory actions of its constituent flavonoids including catechins, which are well-recognized antioxidants. We analyzed and discovered a novel mechanism by which epigallocatechin gallate (EGCG), the most abundant polyphenol in tea and a putative health-promoting constituent, inhibits activation of the nuclear transcription factor NF-κB, which mediates inflammatory responses to cytokines and other agents. We found that EGCG inhibits NF-κB-p65 transcriptional activity, by preventing NF-κB-p65 binding to κBs in normal human bronchial epithelial cells. We also analyzed the chemical mechanism by which EGCG binds directly to NF-κB-p65, and found that it involves covalent reaction via enones within EGCG ring structures, as the oxidizer diamide, which prevents 1, 4-addition reactions, blocked adduct-forming reaction of biotinylated EGCG with NF-κB-p65. Such blockade was inhibited by competing unlabeled EGCG. Furthermore, such covalent binding reflected irreversible reaction of EGCG with sulfhydryls of NF-κB-p65, as it was inhibited by glutathione but not reversible by it. We identified the reactive sulfhydryl moiety as that of cysteine, as S-carboxymethylation to block cysteine sulfhydryls prevented NF-κB-p65-Cys-alkylation reaction with EGCG. We also tested if EGCG can inhibit NF-κB-p65 binding to DNA within the nucleus, after its phosphorylation and translocation (activation). EGCG did not alter intranuclear phosphorylation levels of NF-κB-p65, but strongly repressed DNA-binding ability of activated NF-κB-p65, indicating that EGCG inhibits NF-κB-p65 DNA binding activity even without altering NF-κB-p65 phosphorylation or expression. These findings thus reveal a novel mechanism by which EGCG inhibits transcriptional activity of NF-κB-p65, that may potentially contribute to anti-inflammatory and health-promoting effects of EGCG and consumption of tea.

Epigallocatechin gallate diminishes cigarette smoke-induced oxidative stress, lipid peroxidation, and inflammation in human bronchial epithelial cells.

Cigarette smoke (CS), the major risk factor of chronic obstructive pulmonary disease (COPD), contains numerous free radicals that can cause oxidative stress and exaggerated inflammatory responses in the respiratory system. Lipid peroxidation which is oxidative degradation of polyunsaturated fatty acids and results in cell damage has also been associated with COPD pathogenesis. Increased levels of lipid peroxidation as well as its end product 4-hydroxynonenal have indeed been detected in COPD patients. Additionally, reactive oxygen species such as those contained in CS can activate nuclear factor-κB signaling pathway, initiating cascades of proinflammatory mediator expression. As emerging evidence attests to the antioxidative and anti-inflammatory properties of tea catechins, we sought to determine whether epigallocatechin gallate, the most abundant tea catechin, can provide protection against oxidative stress, lipid peroxidation, and inflammatory responses caused by CS. We found that EGCG treatment blocked cigarette smoke extract (CSE)-induced oxidative stress as indicated by decreased production and accumulation of reactive oxygen species in airway epithelial cells (AECs). Likewise, lipid peroxidation in CSE-stimulated AECs was suppressed by EGCG. Our findings further suggest that EGCG sequestered 4-hydroxynonenal and interfered with its protein adduct formation. Lastly, we show that EGCG inhibited nuclear factor-κB activation and the downstream expression of proinflammatory mediators. In summary, our study describing the antioxidative and anti-inflammatory effects of EGCG in CSE-exposed AECs provide valuable information about the therapeutic potential of this tea catechin for COPD.

Epigallocatechin gallate suppresses inflammation in human coronary artery endothelial cells by inhibiting NF-κB.

The endothelium is a critical regulator of vascular homeostasis, controlling vascular tone and permeability as well as interactions of leukocytes and platelets with blood vessel walls. Consequently, endothelial dysfunction featuring inflammation and reduced vasodilation are considered central to cardiovascular disease (CVD) pathogenesis and have become a therapeutic area of focus. Type II endothelial cell (EC) activation by stress-related stimuli such as tumor necrosis factor-α (TNF-α) initiates the nuclear factor-κB (NF-κB) signaling pathway, a master regulator of inflammatory responses. Because dysregulated NF-κB signaling has been tightly linked to several CVDs, EC-specific inhibition of NF-κB represents an attractive pharmacological strategy. As accumulating evidence highlights the clinical benefits of tea catechin for multiple diseases including CVDs, we sought to determine whether the tea catechin epigallocatechin gallate (EGCG) that displays antioxidative, anti-inflammatory, hypolipidemic, anti-thrombogenic, and anti-hypertensive properties offers protection against CVDs by suppressing the canonical NF-κB pathway. Our findings indicate that EGCG downregulates multiple components of the TNF-α-induced NF-κB signaling pathway and thereby reduces the consequent increase in inflammatory gene transcription and protein expression. Furthermore, EGCG blocked type II EC activation, evidenced by diminished EC leakage and monocyte adhesion in EGCG-treated cells. In summary, our study advances knowledge of EGCG's anti-inflammatory effects on the NF-κB pathway and hence its benefits on endothelial health, supporting its therapeutic potential for CVDs.

Influence of Altered Hormonal Status on Platelet 5-HT and MAO-B Activity in Cigarette Smokers.

The present study was designed to understand the cigarette smoking-induced alterations in hormones and the resulting changes in platelet serotonin (5-hydroxytryptamine, 5-HT) and monoamine oxidase (MAO-B) activity in chronic smokers. Human male volunteers aged 35 ± 8 years, were divided into two groups, namely controls and smokers (12 ± 2 cigarettes per day for 7-10 years). Results showed that cigarette smoking significantly (p < 0.05) elevated plasma triiodothyronine (T3), cortisol and testosterone levels with significant (p < 0.05) reduction in plasma tryptophan and thyroxin (T4). Moreover, smokers showed reduced platelet 5-HT levels and MAO-B activity. In smokers, plasma cortisol was negatively correlated with tryptophan (r = -0.386), platelet MAO-B (r = -0.264), and 5-HT (r = -0.671), and positively correlated with testosterone (r = 0.428). However, testosterone was negatively correlated with platelet MAO-B (r = -0.315), and 5-HT (r = -.419) in smokers. Further, smokers plasma T3 levels were negatively correlated with platelet MAO-B (r = -0.398), and 5-HT (r = -0.541), whereas T4 levels were positively correlated with platelet MAO-B (r = 0.369), and 5-HT (r = 0.454). In conclusion, our study showed that altered testosterone and cortisol levels may aggravate behavior, mood disturbances and symptoms of depression by decreasing platelet 5-HT and MAO-B activity in smokers.

Alcohol-induced oxidative stress in rat liver microsomes: Protective effect of Emblica officinalis.

The protective effect of Emblica officinalis fruit extract (EFE) against alcohol-induced oxidative damage in liver microsomes was investigated in rats. EFE (250mg/kg b.wt/day) and alcohol (5g/kg b.wt/day, 20%, w/v) were administered orally to animals for 60 days. Alcohol administration significantly increased lipid peroxidation, protein carbonyls with decreased sulfhydryl groups in microsomes, which were significantly restored to normal levels in EFE and alcohol co-administered rats. Alcohol administration also markedly decreased the levels of reduced glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) in the liver microsomes, which were prevented with EFE administration. Further, alcohol administration significantly increased the activities of cytochrome P-450, Na(+)/K(+) and Mg(2+) ATPases and also membrane fluidity. But, administration of EFE along with alcohol restored the all above enzyme activities and membrane fluidity to normal level. Thus, EFE showed protective effects against alcohol-induced oxidative damage by possibly reducing the rate of lipid peroxidation and restoring the various membrane bound and antioxidant enzyme activities to normal levels, and also by protecting the membrane integrity in rat liver microsomes. In conclusion, the polyphenolic compounds including flavonoid and tannoid compounds present in EFE might be playing a major role against alcohol-induced oxidative stress in rats.

Oxidative stress in streptozocin-diabetic rats: Amelioration by mulberry (Morus Indica L.) leaves.

OBJECTIVE: To investigate amelioration of oxidative stress by mulberry (Morus indica L.) leaves in streptozocin (STZ)-diabetic rats, as the leaves of mulberry (Morus indica L.) of Moraceae, are reported to be rich in a number of bioactive principles, i.e. antioxidant vitamins, flavonoids and moracins that can fight against oxidative stress in diabetes. METHOD: Normal wistar albino rats and STZ-diabetic rats were treated with dried mulberry leaf powder at 25% in the diet for a period of 8 weeks. The antioxidant role of mulberry was assessed by determining the effect of the leaves on hepatic lipid peroxidation, a marker of oxidative stress and the activity of hepatic antioxidant enzymes and serum antioxidant vitamins in comparison with untreated normal and diabetic rats. RESULTS: Increased oxidative stress as shown by increased lipid peroxidation and increased activity of catalase (CAT) in hepatic tissue, decreased serum ascorbic acid (vitamin C) and tocopherol (vitamin E) in diabetic rats were countered by mulberry leaves. In addition, decreased activities of hepatic antioxidant enzymes, i.e. glucose-6-phosphate dehydrogenase (G6PDH), glutathione peroxidase (GPx), glutathinone-S-tranferase (GST) and superoxide dismutase (SOD) were significantly increased by 34%, 61%, 19% and 53% respectively in mulberry leaves-treated diabetic rats as compared with diabetic control rats. CONCLUSION: Treatment with mulberry leaves protected STZ-diabetic rats from lipid peroxidation and elevated the activities of defense enzymes. This study reveals ameliorating effect of mulberry leaves on oxidative stress in diabetic rats by the synergistic action of a number of bioactive compounds present in mulberry leaves.

Protective Effect of Emblica officinalis Against Alcohol-Induced Hepatic Injury by Ameliorating Oxidative Stress in Rats.

The effect of Emblica officinalis fruit extract (EFE) against alcohol-induced hepatic damage in rats was investigated in the present study. In vitro studies showed that EFE possesses antioxidant as well nitric oxide (NO) scavenging activity. In vivo administration of alcohol (5 g/kg b.wt/day) for 60 days resulted increased liver lipid peroxidation, protein carbonyls, nitrite plus nitrate levels. Alcohol administration also significantly lowers the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase and reduced glutathione as compared with control rats. Administration of EFE (250 mg/kg body weight) to alcoholic rats significantly brought the plasma enzymes towards near normal level and also significantly reduced the levels of lipid peroxidation, protein carbonyls and restored the enzymic and non-enzymatic antioxidants level. This observation was supplemented by histopathological examination in liver. Our data indicate that the tannoid, flavonoid and NO scavenging compounds present in EFE may offer protection against free radical mediated oxidative stress in rat hepatocytes of animals with alcohol-induced liver injury.

Emblica officinalis protects against alcohol-induced liver mitochondrial dysfunction in rats.

The protective effect of Emblica officinalis, a commonly used botanical in many Ayurvedic preparations, was investigated for its effects on liver mitochondria of ethanol-administered rats. Oxidative stress and reactive oxygen species-mediated toxicity are considered two of the key underlying mechanisms responsible for alcohol-induced liver injury and mitochondrial dysfunction. Alcohol-administered rats showed a significant elevation of plasma transaminases (aspartate and alanine aminotransferases), alkaline phosphatase, and gamma-glutamyl transferase compared to control rats. However, activities of hepatic mitochondrial antioxidant enzymes, viz., superoxide dismutase, glutathione peroxidase, and reduced glutathione, were significantly lower. Chronic alcohol feeding also increased lipid peroxide levels, protein carbonyl content, and overproduction of nitric oxide followed by lowered activities of NADH dehydrogenase, succinate dehydrogenase (SDH), and cytochrome c oxidase and content of cytochromes. Administration of E. officinalis fruit extract (EFE) at a dose of 250 mg/kg of body weight/day to alcoholic rats offers protection by simultaneously lowering the carbonyl content and lipid peroxidation and elevating antioxidant enzyme activities, SDH, NADH dehydrogenase, and cytochrome c oxidase activities, and content of cytochromes in hepatic mitochondria. Our data indicate that EFE administration to chronically alcohol-fed rats offers protection against alcohol-induced alterations. The active tannoid principles and nitric oxide scavenging compounds present in EFE may have contributed to the protection observed.

Lipid abnormalities in streptozotocin-diabetes: Amelioration by Morus indica L. cv Suguna leaves.

AIM: To observe the influence of mulberry (Morus indica L. cv Suguna) leaves on lipid abnormalities in STZ-diabetic rats. MATERIALS AND METHODS: Treatment with dried mulberry leaf powder for a period of 8 weeks in hyperglycemic and hyperlipidemic STZ-diabetic rats. RESULTS: Mulberry leaves regulated fasting blood glucose, ameliorated the abnormalities in lipid profile as indicated by significant (P<0.01) decrease in serum triglycerides, phospholipids, cholesterol and plasma free fatty acids by 50, 6, 31 and 22% respectively in STZ- diabetic rats compared to diabetic control rats which had significantly (P<0.01) raised levels of triglycerides, phospholipids, cholesterol and free fatty acids than the normal control rats. A marked increase in fecal bile acids (154%) was observed in mulberry treated diabetic rats compared to the diabetic control group indicating conversion of cholesterol to bile acids. In addition, mulberry supplementation significantly lowered LDL-C (67%) and VLDL-C (44%) levels and increased HDL-C (53%) and also decreased atherogenic index (58%) significantly when compared to the diabetic control group. CONCLUSION: Besides the diabetic rats, mulberry leaves affected lipid profile in normal rats also indicating hypolipidemic effect as a result of the synergistic action of bioactive compounds.

Antioxidant role of mulberry (Morus indica L. cv. Anantha) leaves in streptozotocin-diabetic rats.

BACKGROUND: The antihyperglycemic and antioxidant role of mulberry (Morus indica L.) leaves were investigated. METHODS: Streptozotocin (STZ)-induced diabetic male Wistar rats were used as experimental models; one group was given 25% dry mulberry leaf powder mixed with the standard diet and another group was given standard diet for a period of 8 weeks. The antihyperglycemic and antioxidant role of mulberry was assessed by determining its effect on blood glucose, lipid peroxidation, reduced glutathione (GSH) concentrations and on the activity of glucose-6-phosphate dehydrogenase (G6PDH) and various antioxidant enzymes in erythrocytes and compared with that of controls. RESULTS: Mulberry-treated diabetic rats showed a significant decrease in fasting blood glucose concentrations indicating a good glycemic control. Increased lipid peroxidation and the activity of catalase (CAT) in erythrocytes observed in diabetic controls were significantly decreased by mulberry leaves (48% and 33%, respectively). Decreased GSH concentrations and the activity of glucose-6-phosphate dehydrogenase and antioxidant enzymes viz., glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST) and superoxide dismutase (SOD) observed in uncontrolled diabetes were improved (52%, 69%, 151%, 95%, 24% and 106%) by mulberry treatment very efficiently. CONCLUSION: Mulberry leaves possess antihyperglycemic and antioxidant properties.

Control of hyperglycemia and retardation of cataract by mulberry (Morus indica L.) leaves in streptozotocin diabetic rats.

Dried leaf powder of mulberry (M. indica L.) when given along with the diet at 25% level to streptozotocin induced diabetic male Wistar albino rats for 8 weeks, controlled hyperglycemia, glycosuria, albuminuria and retarded onset of retinopathy. Untreated diabetic rats showed hyperglycemia, glycosuria, albuminuria and developed lenticular opacity after 8 weeks of experimental period.