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

Isolation of eugenyl β-primeveroside from Camellia sasanqua and its anticancer activity in PC3 prostate cancer cells

Most studies of tea trees have focused on their ornamental properties, there are fewer published studies on their medical values. The purpose of this study was to compare the chemical constituents and the biological potential of the water extract of leaves in eight species of Camellia including Camellia sinensis. Among eight Camellia species, Camellia sasanqua showed potent anticancer activities in prostate cancer PC3 cells. In addition to catechins, the major component, eugenyl β-primeveroside was detected in C. sasanqua. Eugenyl β-primeveroside blocked the progression of cell cycle at G1 phase by inducing p53 expression and further upregulating p21 expression. Moreover, eugenyl β-primeveroside induced apoptosis in PC3 prostate cancer cells. Our results suggest that C. sasanqua may have anticancer potential.

Epigallocatechin gallate attenuates cardiopulmonary bypass-associated lung injury

BACKGROUND

Lung dysfunction constitutes a severe complication after major cardiac surgery with cardiopulmonary bypass (CPB), substantially contributing to postoperative morbidity and mortality. The current possibilities of preventive and therapeutic interventions, however, remain insufficient. We, therefore, investigated the effects of intraoperative application of the antioxidant and anti-inflammatory green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) on CPB-associated lung injury.

MATERIALS AND METHODS

Thirty piglets (8-15 kg) were divided into four groups: sham-operated and saline-treated control group (n = 7); sham-operated and EGCG-treated control group (EGCG-control group; n = 7); CPB group (n = 10); and CPB + EGCG group (n = 6). The CPB groups underwent 120 min of CPB followed by 90 min of recovery time. In the CPB + EGCG group, EGCG (10 mg/kg body weight) was administered intravenously before and after CPB. Hemodynamic monitoring, blood gas analysis, hematoxylin-eosin staining, and immunohistochemistry of lung tissue were performed.

RESULTS

Histologic examination revealed thickening of the alveolar wall and enhanced alveolar neutrophil infiltration in the CPB group (P < 0.05) compared with those in the control group, which was prevented by EGCG (P < 0.05). In the CPB group, higher formation of poly(ADP-ribose) and nuclear translocation of apoptosis-inducing factor was detected in comparison with those in the control group (P < 0.001), which were both reduced in the CPB + EGCG group (P < 0.001). Compared with the control group, the EGCG-control group showed thickening of the alveolar wall and increased neutrophil infiltration (P < 0.05).

CONCLUSIONS

CPB leads to lung edema, pulmonary neutrophil infiltration, and presumably initiation of poly(ADP-ribose) polymerase-dependent cell death signaling in the lung. EGCG appears to attenuate CPB-associated lung injury, suggesting that this may provide a novel pharmacologic approach.

A randomized controlled trial of green tea catechins in protection against ultraviolet radiation-induced cutaneous inflammation

BACKGROUND

Safe systemic protection from the health hazards of ultraviolet radiation (UVR) in sunlight is desirable. Green tea is consumed globally and is reported to have anti-inflammatory properties, which may be mediated through the impact on cyclooxygenase and lipoxygenase pathways. Recent data suggest that green tea catechins (GTCs) reduce acute UVR effects, but human trials examining their photoprotective potential are scarce.

OBJECTIVE

We performed a double-blind, randomized, placebo-controlled trial to examine whether GTCs protect against clinical, histologic, and biochemical indicators of UVR-induced inflammation.

DESIGN

Healthy adults (aged 18-65 y, phototypes I-II) were randomly allocated to 1350 mg encapsulated green tea extract (540 mg GTC) with 50 mg vitamin C or placebo twice daily for 3 mo. Impact on skin erythema, dermal leukocytic infiltration, and concentrations of proinflammatory eicosanoids was assessed after solar-simulated UVR challenge, and subject compliance was determined through assay of urinary GTC metabolite epigallocatechin glucuronide.

RESULTS

Volunteers were assigned to the active (n = 25) or the placebo (n = 25) group. After supplementation, median (IQR) sunburn threshold (minimal erythema dose) was 28 (20-28) and 20 (20-28) mJ/cm(2) in the active and placebo groups, respectively (nonsignificant), with no difference in AUC analysis for measured erythema index after a geometric series of 10 UVR doses. Skin immunohistochemistry showed increased neutrophil and CD3(+) T-lymphocyte numbers post-UVR in both groups (P < 0.01) with no statistically significant differences between groups after supplementation. Cyclooxygenase and lipoxygenase metabolites prostaglandin E2 (vasodilator) and 12-hydroxyeicosatetraenoicacid (chemoattractant), respectively, increased after UVR (P < 0.05), with no differences between supplementation groups.

CONCLUSION

Oral GTC (1080 mg/d) with vitamin C over 3 mo did not significantly reduce skin erythema, leukocyte infiltration, or eicosanoid response to UVR inflammatory challenge. This trial was registered at clinicaltrials.gov as NCT01032031.

Protective effect of epigallocatechin gallate, a major constituent of green tea, against renal ischemia-reperfusion injury in rats

BACKGROUND

Renal ischemia-reperfusion (I/R) injury plays an important role in the acute kidney injury. The pathogenetic mechanisms potential I/R injury is involved in apoptosis and inflammation. Epigallocatechin gallate (EGCG), a major constituent of green tea, has been shown to have anti-inflammatory and anti-apoptotic activities. This study aimed to explore the underlying effects and mechanisms of EGCG on renal I/R injury in a rat model.

MATERIALS AND METHODS

We induced renal I/R injury in SD rats by clamping the left renal artery for 45 min followed by 24-h reperfusion, along with a contralateral nephrectomy. We randomly allocated 30 rats to three groups (n = 10): sham group, IRI group, and EGCG group. We preconditioned rats intraperitoneally with EGCG (50 mg/kg) or vehicle (50 mg/kg) 45 min before inducing renal ischemia. We collected serum and kidneys at 24 h after reperfusion. Renal function and histologic damage were assessed. We also determined markers of inflammation and apoptosis in kidneys or serum.

RESULTS

EGCG pretreatment can significantly reduce renal dysfunction, histologic change and the expression of tumor necrosis factor-α, IL-1β, IL-6, Bax and cleavage caspase 3 induced by I/R injury and increase the expression of Bax and caspase 3. Moreover, EGCG pretreatment can further induce the activation of p38 mitogen-activated protein kinase in kidney, with no influence on the expression of p38.

CONCLUSIONS

EGCG treatment can decrease renal ischemia-reperfusion injury by suppressing inflammation and cell apoptosis. Thus, EGCG may represent a potential strategy to reduce renal I/R injury.

Impact of tea drinking upon tuberculosis: a neglected issue

BACKGROUND

Tuberculosis (TB) is a global public health issue posing serious harm to the human health. Many studies have suggested that smoking and excessive alcohol consumption are risk factors for TB. Laboratory evidence suggests that EGCG in tea leaves can arrest the growth of tubercle bacillus. Can drinking tea lead to decreased susceptibility of TB in humans?

METHODS

A total of 574 TB patients and 582 healthy controls were recruited to participate in this case-control study. Self-designed questionnaire was used to collect data. Unconditioned logistic regression analysis was conducted to identify the associations between tea drinking and TB.

RESULTS

Tea drinking has a negative association with TB, with OR = 0.583(0.423, 0.804) and P < 0.05. Drinking black tea, oolong and green tea are all negative association with TB, with OR being 0.683(0.517, 0.902), 0.674(0.508, 0.894) and 0.534(0.349, 0.817) respectively and P < 0.05. Trend χ (2) test indicated a decreasing risk for TB with increased tea consumption, with P < 0.05.

CONCLUSION

There is a significance negative association between tea drinking and TB. Promoting the consumption of tea as the daily drink among populations, particularly those with high TB risk, may reduce the incidence of TB in the populations.

Diet and upper gastrointestinal malignancies

Diet is believed to modulate cancer risk and this relationship has been widely studied in the gastrointestinal tract. Observational epidemiologic studies have provided most of the evidence about the effects of diet on cancer risk because clinical trials to determine nutritional exposures are often impossible, impractical, or unaffordable. Although a few foods or nutrients are thought to protect against specific types of cancer, it seems clear that the strength and even direction of dietary associations (increasing or decreasing risk) is organ-site- and even histology-specific, along the gastrointestinal tract. Although some hypotheses are supported by a substantial body of observational data (drinking hot maté [an infusion of the herb Ilex Paraguarensis] contributes to esophageal cancer), there are not much data to support others. We discuss some highly touted hypotheses and draw interim conclusions about what is known and what could be done to improve the level of evidence. The complex nature of diet and its associations can be productively investigated with disease-specific studies. However, public health recommendations for normal-risk individuals regarding diet and gastrointestinal cancer should probably emphasize the importance of eating for overall health rather than eating specific foods to reduce risk for specific cancers.

Overexpression of miR-126 sensitizes osteosarcoma cells to apoptosis induced by epigallocatechin-3-gallate

Background

miR-126 plays an important role in the proliferation, invasion, migration, and chemotherapeutics resistance in cancer. Epigallocatechin-3-gallate (EGCG), as the major polyphenolic constituent present in green tea, is a promising anticancer agent. However, the role of miR-126 in EGCG anticancer remains unclear. Here, we investigated the effects of miR-126 and EGCG on cell viability, apoptosis, cell cycle distribution of osteosarcoma cells and the sensitization of miR-126 on osteosarcoma cells to EGCG.

Methods

The cell viability, apoptosis and cycle distribution were analyzed using MTT assay and flow cytometry.

Results

Our results showed that EGCG (0.025, 0.05, 0.1, 0.2 g/L) suppresses proliferation of osteosarcoma MG63 and U2OS cells in a concentration-dependent and time-dependent manner and the inhibitory effects of 0.05 g/L EGCG on U2OS cells were roughly equivalent to 20 μM cisplatin (DDP); miR-126 could promote apoptosis and inhibit proliferation in U2OS cells but without significant effects on cell cycle G1 phase arrest; EGCG suppressed proliferation of U2OS cells through induction of cell cycle G1 arrest and apoptotic death; overexpression of miR-126 enhanced the inhibitory effects of EGCG on proliferation in U2OS cells via promotion of apoptosis.

Conclusions

Our results demonstrate that enhanced expression of miR-126 increased the sensitivity of osteosarcoma cells to EGCG through induction of apoptosis.

Epigallocatechin-3-gallate sensitizes IFN-γ-stimulated CD4+ T cells to apoptosis via alternative activation of STAT1

Epigallocatechin-3-gallate (EGCG) exerts anti-inflammatory properties on immune cells and binds to CD4 molecules. However, the effects of EGCG on CD4(+) T cells remain largely unknown. Here, we found that EGCG enhanced IFN-γ-induced signal transducer and activator of transcription 1 (STAT1) activation in primary CD4(+) T cells from C57BL/6 mice and in a human leukemic CD4(+) T-cell line of Hut 78 cells, while it inhibited the classical pathway of IFN-γ signaling including activating phosphorylations of Janus kinase (JAK) 1, JAK2 and STAT3, forming interferon-γ activated sequence (GAS)-binding STAT1 homodimers, and producing pro-inflammatory chemokine (C-X-C motif) ligand 9 (CXCL9). CD4 blockade did not suppress the increase in IFN-γ-induced STAT1 activation in CD4(+) T cells by EGCG. Furthermore, activation of Src kinase was also triggered by IFN-γ plus EGCG in both Hut 78 and primary CD4(+) T cells. Interestingly, EGCG promoted apoptosis of CD4(+) T cells treated with IFN-γ. The increases in STAT1 activation and apoptosis induced by EGCG in IFN-γ-activated CD4(+) T cells were almost completely abolished by a selective Src family kinase inhibitor, SU6656. Moreover, EGCG alleviates CD4(+) CD45RB(hi) CD25(-) T cell transfer induced colitis with less accumulation of CD4(+) T cells in the colon. In conclusion, the present study reports an alternative activation of STAT1 via Src by EGCG in IFN-γ-activated CD4(+) T cells, which promotes the apoptosis of IFN-γ-activated CD4(+) T cells and contributes to the improvement of T cell-mediated colitis. Our findings suggest a novel role of EGCG in regulating IFN-γ signaling and controlling inflammation.

Epigallocatechin-3-gallate improves plantaris muscle recovery after disuse in aged rats

Aging exacerbates muscle loss and slows the recovery of muscle mass and function after disuse. In this study we investigated the potential that epigallocatechin-3-gallate (EGCg), an abundant catechin in green tea, would reduce signaling for apoptosis and promote skeletal muscle recovery in the fast plantaris muscle and the slow soleus muscle after hindlimb suspension (HLS) in senescent animals. Fischer 344 × Brown Norway inbred rats (age 34 months) received either EGCg (50 mg/kg body weight), or water daily by gavage. One group of animals received HLS for 14 days and a second group of rats received 14 days of HLS, then the HLS was removed and they recovered from this forced disuse for 2 weeks. Animals that received EGCg over the HLS followed by 14 days of recovery, had a 14% greater plantaris muscle weight (p<0.05) as compared to the animals treated with the vehicle over this same period. Plantaris fiber area was greater after recovery in EGCg (2715.2±113.8 μm(2)) vs. vehicle treated animals (1953.0±41.9 μm(2)). In addition, activation of myogenic progenitor cells was improved with EGCg over vehicle treatment (7.5% vs. 6.2%) in the recovery animals. Compared to vehicle treatment, the apoptotic index was lower (0.24% vs. 0.52%), and the abundance of pro-apoptotic proteins Bax (-22%), and FADD (-77%) was lower in EGCg treated plantaris muscles after recovery. While EGCg did not prevent unloading-induced atrophy, it improved muscle recovery after the atrophic stimulus in fast plantaris muscles. However, this effect was muscle specific because EGCg had no major impact in reversing HLS-induced atrophy in the slow soleus muscle of old rats.