Inhibition of Azoxymethane-induced Colon Carcinogenesis in Rat by Green Tea Polyphenol Fraction

The effect of green tea polyphenol fraction (GTP) on azoxymethane(AOM)-induced colon carcino-genesis was investigated in male Fischer rate. The rats were given AOM (7.4 mg/kg body weight) s.c. once a week for 10 weeks. A week after the treatment, they were divided into three groups: AOM-control (26 rats), AOM-GTP1 (26 rats) and AOM-GTP2 (25 rats). AOM-GTPl and AOM-GTP2 groups respectively received 0.01 and 0.1% GTP in drinking water from week 11 to 26. AOM-control group received tap water throughout this experiment. Autopsy on week 26 showed that tumor incidence and average numbers of tumors per rat in the AOM-GTPl and AOM-GTP2 groups were significantly lower than those of the AOM-control group: 38.1% and 47.6% versus 77.3%; 0.6 and 0.7 versus 1.5. Thus, it was concluded that GTP inhibited the development of AOM-indnced colon carcinogenesis. The inhibition by GTP did not show significant dose dependence.     

Effects Of Dietary Fat, Butylated Hydroxytoluene And Propyl Gallate On Microsomal Drug Metabolism In Rats

Dietary butylated hydroxytoluene, but not propyl gallate, increased liver size, microsomal cytochrome P₄₅₀ concentration and related drug metabolism. The kind and amount of dietary fat did not alter the effects of either antioxidant.     

Mutachromosomal effects of tert-butylhydroquinone in bone-marrow cells of mice

When given to mice either in a single ip injection of 200 mg/kg body weight or in 30 daily oral doses of 2 mg/kg, tert-butylhydroquinone had severe clastogenic effects on the bone-marrow cells. However mitostatic activity was observed only with the acute treatment.     

EGCG改善高浓度TNF-α对人皮肤创伤愈合中成纤维细胞的抑制作用

目的: 探讨高浓度肿瘤坏死因子α(TNF-α)对人皮肤创伤愈合中成纤维细胞的抑制作用以及表没食子儿茶素没食子酸酯(EGCG)的干预效应。方法: 体外培养原代人皮肤成纤维细胞,以10 μg/L TNF-α作用24 h或联合EGCG预处理干预,用细胞计数试剂盒观察细胞增殖,细胞划痕愈合实验观察成纤维细胞的迁移,Western blotting法研究I型胶原蛋白的表达。结果: TNF-α显著抑制皮肤成纤维细胞的增殖和迁移,EGCG呈浓度依赖性地改善TNF-α的增殖抑制作用,以EGCG(40 μmol/L)预处理后,TNF-α对细胞迁移的抑制作用也得到恢复。Western blotting发现TNF-α还能抑制I型胶原蛋白的表达,而加入EGCG(40 μmol/L)后其表达有显著恢复。结论: EGCG能显著改善高浓度TNF-α对人皮肤成纤维细胞增殖和迁移的抑制作用,并恢复I型胶原的表达,从而促进皮肤创口的愈合。     

EGCG与肿瘤细胞Wnt信号转导通路的研究进展

<正>表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)是茶叶中一种重要的多酚类物质,约占儿茶素总量的80%,具有抗癌、抗心血管疾病、抗自由基损害、降低低密度胆固醇等作用。     

Epigallocatechin gallate inhibits angiotensin II-induced endothelial barrier dysfunction via inhibition of the p38 MAPK/HSP27 pathway

Aim:

To investigate the effect of epigallocatechin gallate (EGCG) on angiotensin II (Ang II)-induced stress fiber formation and hyperpermeability in endothelial cells.

Methods:

Human umbilical vein endothelial cells (HUVECs) were treated with Ang II in the absence or presence of EGCG or mitogen-activated protein kinases (MAPKs) inhibitors. The resulting stress fibers were stained with rhodamine-phalloidin and examined using confocal microscopy. The permeability of the endothelium was tested with fluorescein-isothiocyanate labeled bovine serum albumin (FITC-BSA), and the phosphorylation levels of several proteins were determined using Western blot analysis.

Results:

Ang II (1-100 nmol/L) treatment markedly provoked stress fiber formation and hyperpermeability in HUVECs in a time- and dose-dependent manner. These effects were abolished by pretreatment with the p38 MAPK inhibitor SB203580 10 μmol/L, indicating that the Ang II-induced endothelial barrier dysfunction was via activation of the p38 MAPK/HSP27 pathway. Furthermore, treatment with EGCG (5-25) μmol/L inhibited Ang II-induced activation of the p38 MAPK/HSP27 pathway, thereby reducing endothelial stress fiber formation and hyperpermeability.

Conclusion:

Our data demonstrate that EGCG inhibits Ang II-induced endothelial stress fiber formation and hyperpermeability via inactivation of p38 MAPK/HSP27 pathway, and suggest that EGCG may protect against endothelial barrier dysfunction and injury.     

Effect of butylated hydroxytoluene,curcumin, propyl gallate and thiabendazole on cytochrome P450 forms in cultured human hepatocytes

1.?The objective of this study was to investigate the effects of four food chemicals, namely butylated hydroxytoluene (BHT), curcumin (CC), propyl gallate (PG) and thiabendazole (TB), on cytochrome P450 (CYP) forms in cultured human hepatocytes.

2.?Treatment of human hepatocytes for 72 h with 2–200 µM TB produced concentration-dependent increases in CYP1A2, CYP2B6 and CYP3A4 mRNA levels, whereas treatment with BHT increased CYP2B6 and CYP3A4 mRNA levels. CYP1A2, CYP2B6 and CYP3A4 mRNA levels were induced around 48-, 21- and 9-fold, respectively, by 200 µM TB, with CYP2B6 and CYP 3A4 mRNA levels being induced around 12- and 7-fold, respectively, by 200 µM BHT.

3.?In contrast, the treatment of human hepatocytes for 72 h with PG and CC had little or no effect on CYP mRNA levels.

4.?The treatment of human hepatocytes with TB also induced CYP1A-dependent 7-ethoxyresorufin O-deethylase activity, whereas BHT induced CYP3A-dependent testosterone 6β-hydroxylase activity.

5.?In summary, the results demonstrate that TB is a mixed inducer of CYP forms in human hepatocytes inducing CYP1A, CYP2B and CYP3A forms, whereas BHT is an inducer of CYP2B and CYP3A forms.     

Naturally occurring flavonoids as inhibitors of purified cytosolic glutathione S-transferase

1. Flavonoids are known to modulate catalytic activity and expression of various enzymes. Glutathione S-transferases (GSTs) are the important biotransformation enzymes defending cells against potentially toxic xenobiotics. Therefore, the modulation of GST activity may influence detoxification of xenobiotics. The aim of this study was to evaluate the in vitro inhibitory activity of several dietary flavonoids towards purified equine liver cytosolic GST.

2. Pure GST was incubated in the presence or absence of flavonoids (10 nM–100 µM), its activity was assayed using 1-chloro-2,4-dinitrobenzene (CDNB) as a substrate, and half maximal inhibitory concentrations (IC₅₀) were determined. The obtained results were confirmed by GST activity staining of native polyacrylamide gel electrophoresis (PAGE) gels. For the most potent inhibitor, the inhibition kinetics study was performed.

3. From 24 flavonoids tested, the most potent GST inhibitor was gallocatechin gallate (IC₅₀ = 1.26 µM). The inhibition kinetics of this compound followed noncompetitive mechanism versus both glutathione (K_i = 35.9 µM) and CDNB (K_i = 34.1 µM).

4. The inhibitory potency of different flavonoids for GST activity depended mainly on the pattern of hydroxylation and number of hydroxyl groups in the ring B. Especially, pyrogallol-type catechins with 3-OH group esterified with gallic acid showed strong potential to inhibit GST in vitro.

     

粉背南蛇藤醋酸乙酯部位中黄酮类成分的研究

目的 研究粉背南蛇藤醋酸乙酯部位的黄酮类化合物。方法 利用正相、反相硅胶和凝胶色谱柱分离技术分离制备,通过理化性质和核磁共振、质谱等波谱数据鉴定化合物的结构。结果 分离鉴定了4个化合物,分别为大豆素（1）、表没食子儿茶素（2）、没食子儿茶素（3）、大豆素-7-O-β-D-吡喃葡萄糖苷（4）。结论 所有化合物均为首次从该植物中分离得到。