Tea polyphenols and their chemopreventive and therapeutic effects on colorectal cancer

Colorectal cancer(CRC),a multifactorial disease,is usually induced and developed through complex mechanisms,including impact of diet and lifestyle,genomic abnormalities,change of signaling pathways,inflammatory response,oxidation stress,dysbiosis,and so on.As natural polyphenolic phytochemicals that exist primarily in tea,tea polyphenols(TPs)have been shown to have many clinical applications,especially as anticancer agents.Most animal studies and epidemiological studies have demonstrated that TPs can prevent and treat CRC.TPs can inhibit the growth and metastasis of CRC by exerting the antiinflammatory,anti-oxidative or pro-oxidative,and pro-apoptotic effects,which are achieved by modulations at multiple levels.Many experiments have demonstrated that TPs can modulate several signaling pathways in cancer cells,including the mitogen-activated protein kinase pathway,phosphatidylinositol-3 kinase/Akt pathway,Wnt/β-catenin pathway,and 67 kDa laminin receptor pathway,to inhibit proliferation and promote cell apoptosis.In addition,novel studies have also suggested that TPs can prevent the growth and metastasis of CRC by modulating the composition of gut microbiota to improve immune system and decrease inflammatory responses.Molecular pathological epidemiology,a novel multidisciplinary investigation,has made great progress on CRC,and the further molecular pathological epidemiology research should be developed in the field of TPs and CRC.This review summarizes the existing in vitro and in vivo animal and human studies and potential mechanisms to examine the effects of tea polyphenols on CRC.     

An optimal dose of tea polyphenols protects against global cerebral ischemia/reperfusion injury

Previous studies addressing the protection of tea polyphenols against cerebral ischemia/ reperfusion injury often use focal cerebral ischemia models, and the optimal dose is not unified. In this experiment, a cerebral ischemia/reperfusion injury rat model was established using a modified four-vessel occlusion method. Rats were treated with different doses of tea polyphenols (25, 50, 100, 150, 200 mg/kg) via intraperitoneal injection. Results showed that after 2, 6, 12, 24, 48 and 72 hours of reperfusion, peroxide dismutase activity and total antioxidant capacity in brain tissue gradually increased, while malondialdehyde content gradually decreased after tea polyphenol intervention. Tea polyphenols at 200 mg/kg resulted in the most apparent changes. Terminal deoxynucleotidyl transferase-mediated nick end labeling and flow cytometry showed that 200 mg/kg tea polyphenols significantly reduced the number and percentage of apoptotic cells in the hippocampal CA1 region of rats after cerebral ischemia/reperfusion injury. The open field test and elevated plus maze experiments showed that tea polyphenols at 200 mg/kg strengthened exploratory behavior and reduced anxiety of cerebral ischemia/reperfusion injured rats. Experimental findings indicate that tea polyphenols protected rats against cerebral ischemia/ reperfusion injury and 200 mg/kg is regarded as the optimal dose.     

Cavernous antioxidant effect of green tea,epigallocatechin‐3‐gallate with/without sildenafil citrate intake in aged diabetic rats

This study aimed to assess the cavernous antioxidant effect of green tea (GT), epigallocatechin‐3‐gallate (EGCG) with/without sildenafil citrate intake in aged diabetic rats. One hundred and four aged male white albino rat were divided into controls that received ordinary chow, streptozotocin (STZ)‐induced aged diabetic rats, STZ‐induced diabetic rats on infused green tea, induced diabetic rats on epigallocatechin‐3‐gallate and STZ‐induced diabetic rats on sildenafil citrate added to EGCG. After 8 weeks, dissected cavernous tissues were assessed for gene expression of eNOS, cavernous malondialdehyde (MDA), glutathione peroxidase (GPx), cyclic guanosine monophosphate (cGMP), and serum testosterone (T). STZ‐induced diabetic rats on GT demonstrated significant increase in cavernous eNOS, cGMP, GPx and significant decrease in cavernous MDA compared with diabetic rats. Diabetic rats on EGCG demonstrated significant increase in cavernous eNOS, cGMP, GPx and significant decrease in cavernous MDA compared with diabetic rats or diabetic rats on GT. Diabetic rats on EGCG added to sildenafil showed significant increase in cavernous eNOS, cGMP and significant decrease in cavernous MDA compared with other groups. Serum T demonstrated nonsignificant difference between the investigated groups. It is concluded that GT and EGCG have significant cavernous antioxidant effects that are increased if sildenafil is added.     

茶多酚对早期龋进展的影响

目的　探讨茶多酚对牙齿早期龋进展的影响。方法　采用体外脱矿的方法建立牛牙牙釉质和牙本质早期龋模型。将釉质龋及牙本质龋标本随机分为4组（n=6）：空白对照组（DW组）、氟化钠组（NaF组）、茶多酚组（TP组）、茶多酚与氟化钠联合应用组（TP+NaF组）,pH循环实验模拟早期龋的进程。检测pH循环后的脱矿液中钙、磷离子浓度,通过显微硬度计检测牙体硬组织表面显微硬度值,X线能谱分析样本表面钙磷比,并测定再矿化液中羟脯氨酸水平。结果　在牙釉质及牙本质的脱矿液中,TP组钙、磷离子相对释放量与DW组差异无统计学意义,明显高于NaF组和TP+NaF组（P＜0.05）。TP组牙釉质表面显微硬度值与DW组差异无统计学意义,牙本质表面显微硬度值高于DW组;DW组、TP组牙釉质及牙本质表面显微硬度值均低于NaF组和TP+NaF组（P＜0.05）。TP组牙釉质及牙本质表面钙磷比均高于DW组（P＜0.05）,牙釉质表面钙磷比与NaF组和TP+NaF组差异无统计学意义,牙本质表面钙磷比低于NaF组和TP+NaF组（P＜0.05）。NaF组和TP+NaF组牙本质再矿化液中羟脯氨酸水平均低于DW组和TP组（P＜0.05）,TP组与DW组以及TP+NaF组与NaF组间差异均无统计学意义。结论　在早期龋的进展过程中,茶多酚无明显抑制牙釉质及牙本质脱矿的作用,但可通过促进钙磷离子的再沉积促进再矿化的发生。     

安吉白茶茶多酚对D-半乳糖致衰老模型小鼠的抗氧化作用研究

目的:探讨安吉白茶茶多酚对D-半乳糖致衰老模型小鼠的抗氧化作用。方法:72只雄性ICR小鼠随机分为正常组、D-半乳糖模型组、安吉白茶茶多酚低、中、高剂量组,Vc组。除正常组外,余组采用腹腔注射D-半乳糖建立衰老小鼠模型。在造模的同时,给药组分别灌胃相应浓度药物;正常组和模型组每天灌胃等量的生理盐水。连续给药35天后称体重,摘眼球取血,分离血清并测定脏器指数;测定血清和脑组织中超氧化物歧化酶(SOD)活性和丙二醛(MDA)含量。结果:模型组较正常组小鼠体重增量及部分脏器指数显著降低(P0.01),脑组织和血清中MDA含量显著升高,SOD活性显著降低(P0.01);与模型组比较,安吉白茶茶多酚各剂量组小鼠肾脏和脾脏的脏器指数显著性增加(P0.01);各剂量组血清和高剂量组脑组织SOD活性显著增高(P0.01);各剂量组脑组织和中、高剂量组血清中MDA含量显著降低(P0.01),提示安吉白茶茶多酚有良好的抗氧化作用。结论:安吉白茶茶多酚中、高剂量组能够提高D-半乳糖致衰老小鼠抗氧化能力,其机理可能与抑制体内脂质过氧化物的生成,增强抗氧化酶的活性有关。     

The Influence of In Vivo Metabolic Modifications on ADMET Properties of Green Tea Catechins–In Silico Analysis

The health effects of green tea are associated with catechins: (?)-epigallocatechin-3-O-gallate (EGCG), (?)-epigallocatechin, (?)-epicatechin-3-O-gallate, and (?)-epicatechin. An understanding of compound absorption, distribution, metabolism, excretion, and toxicity characteristics is essential for explaining its biological activities. Herein, absorption, distribution, metabolism, excretion, and toxicity properties of in vivo detected metabolites of green tea catechins (GTCs) have been analyzed in silico. The influence of metabolic transformations on absorption, distribution, metabolism, and excretion profiles of GTCs corresponds to the effects of size, charge, and lipophilicity, as already observed for other small molecules. Mutagenic, carcinogenic, or liver toxic effects were predicted only for a few metabolites. Similar to galloylated GTCs EGCG and (--)-epicatechin-3-O-gallate, the sulfo-conjugates were predicted to bind at the warfarin binding site. The low free plasma concentration of these derivatives may be consequential to their serum albumin binding. The activity cliff detected for methylated conjugates of EGCG indicates that GTCs' pro-oxidative activity in bound state comes primarily from free hydroxyl groups of the pyrogallol ring B.     

Oolong tea prevents cardiomyocyte loss against hypoxia by attenuating p‐JNK mediated hypertrophy and enhancing P‐IGF1R,p‐akt,and p‐Badser136 activity and by fortifying NRF2 antioxidation system

Tea, the most widely consumed natural beverage has been associated with reduced mortality risk from cardiovascular disease. Oolong tea is a partially fermented tea containing high levels of catechins, their degree of oxidation varies between 20%‐80% causing differences in their active metabolites. In this study we examined the effect of oolong tea extract (OTE) obtained by oxidation at low‐temperature for short‐time against hypoxic injury and found that oolong tea provides cyto‐protective effects by suppressing the JNK mediated hypertrophic effects and by enhancing the innate antioxidant mechanisms in neonatal cardiomyocytes and in H9c2 cells. OTE effectively attenuates 24 h hypoxia‐triggered cardiomyocyte loss by suppressing caspase‐3‐cleavage and apoptosis in a dose‐dependent manner. OTE also enhances the IGFIR/p‐Akt associated survival‐mechanism involving the elevation of p‐Bad^ser136 in a dose‐dependent manner to aid cellular adaptations against hypoxic challenge. The results show the effects and mechanism of Oolong tea to provide cardio‐protective benefits during hypoxic conditions.