The effects of Chinese tea on the occurrence of esophageal tumors induced by N-nitrosomethylbenzylamine in rats.

BACKGROUND. Based on previous studies on the blocking effect of Chinese tea in the formation of N-nitroso compounds in rats and humans, experiments were carried out to study the effects of Chinese tea on the occurrence of esophageal tumors induced by N-nitrosomethylbenzylamine (NMBzA) in rats. METHODS. In the first experiment, rats were given two precursors of NMBzA, i.e., sodium nitrite and methyl benzylamine, p.o. After 12 weeks, the incidence of esophageal tumors was 95%. However, in the five groups of tea (green tea, jasmine tea, black tea, and oolong tea)-treated rats, the incidences were only 5-19%. In the second experiment, preformed NMBzA was administered to rats. RESULTS. The incidences of esophageal tumors in the five tea-treated groups were 42-67%, while in the positive control group, without tea, the incidence was 90%. Histopathological examination showed the same protective effects of tea treatment. In a separate study, a significant reduction of O6-methylguanine (MeG) and the ratio of O6-MeG to N7-MeG was observed in rats treated with oolong tea and jasmine tea.     

不同膳食硒水平对甲基苄基亚硝胺(NMBzA)诱发大鼠食道肿瘤及小鼠前胃肿瘤的影响

本实验对膳食中不同硒含量与NMBzA诱发大鼠食道肿瘤及小鼠前胃肿瘤的关系进行了研究。分别将断乳Wistar大鼠和断乳昆明种小鼠随机分成缺硒(硒含量<0.02ppm)组;正常硒(0.2ppm)组;补硒(2.0ppm)组;和对照组(0.2ppm)。除对照组外,各组动物灌胃给予NMBzA。其中大鼠自第5周至第18周实验结束,每周一次给药3mg/kg体重,小鼠第2～7周,每周一次给药1mg/kg体重,第8～12周,每周二次,每次0.7mg/kg体重。实验结束时分别进行病理学检查。结果大鼠食道肿瘤及小鼠前胃肿瘤发生率在各实验组间无显著性差异。     

Green tea, phytic acid, and inositol in combination reduced the incidence of azoxymethane-induced colon tumors in Fisher 344 male rats

Experimental as well as epidemiologic studies in human populations provide evidence that consumption of phytochemicals reduces the incidence of degenerative diseases. Green tea (GT) catechins are known for their antioxidative potential. Phytic acid (PA) also acts as a natural antioxidant and may have numerous health benefits. This experiment was designed to investigate the inhibitory effects of combinations of 1% and 2% GT, PA, and inositol (I) in reducing the incidence of azoxymethane-induced colon tumors in Fisher 344 male rats. After an acclimatization period of 1 week, nine groups of rats (15 rats per group) were initially assigned to consume AIN 93 G diet and later AIN 93 M diet after 20 weeks of age. Treatments were given in drinking water. All rats received azoxymethane injections (16 mg/kg of body weight) subcutaneously at 7 and 8 weeks of age. Rats were killed at 45 weeks of age by CO(2) euthanasia. Tumor incidence (93.76%) and the number of tumors per tumor-bearing rat ratio (2.25) were significantly (P<.05) higher in the control group compared with treatment groups. Glutathione S-transferase activity was significantly (P<.05) higher in rats fed combinations of 2% GT+PA+I and GT+PA (33.25 ± 1.23 and 29.83 ± 1.10 μmol/mL, respectively) compared with other groups. These findings suggest that the synergistic effect of the 2% level of GT, PA, and I may reduce the incidence of colon tumors and therefore have potential as a chemopreventive agent.     

茶对二甲基苯并蒽诱发金黄色地鼠口腔癌预防作用的研究

选用二甲基苯并蒽（ Ｄ Ｍ Ｂ Ａ）诱发的金黄色地鼠口腔癌模型,研究绿茶、茶色素和混合茶对口腔癌的预防作用,并探讨其防癌机制。试验设阳性对照组（局部涂０５％ Ｄ Ｍ Ｂ Ａ,每周３次,共１５周）、３个饮茶试验组（在涂 Ｄ Ｍ Ｂ Ａ２周前开始分别饮１５％ 绿茶、０１％ 茶色素和０５％ 混合茶至１５周实验结束）和阴性对照组（仅涂丙酮）。结果表明,与阳性对照组相比,绿茶、茶色素和混合茶组对平均瘤数目的抑制率分别为４２６％ 、５０８％ 和６７２％ ,平均瘤负荷抑制率分别为７９４％ 、８８５％ 和９５５％ ;在３组中以混合茶对口腔癌的抑制效果最强。在涂 Ｄ Ｍ Ｂ Ａ 后的第６、１０和１５周,３个茶试验组中均见到口腔上皮细胞微核形成,每核银染核仁组织区（ Ａｇ Ｎ Ｏ Ｒ）颗粒数目和表皮生长因子受体（ Ｅ Ｇ Ｆ Ｒ）的表达低于阳性对照组。表明饮茶对 Ｄ Ｍ Ｂ Ａ 诱发的动物口腔癌有明显的预防作用,而茶预防 Ｄ Ｍ Ｂ Ａ 引起的粘膜细胞 Ｄ Ｎ Ａ 损伤和抑制粘膜细胞增殖可能是其预防口腔癌的重要作用机制。     

Inhibition of lung carcinogenesis and effects on angiogenesis and apoptosis in A/J mice by oral administration of green tea

Oral administration of tea (Camellia sinensis) has been shown to inhibit the formation and growth of several tumor types in animal models. The present study investigated the effects of treatment with different concentrations of green tea on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in female A/J mice. Two days after a single dose of NNK (100 mg/kg body weight, i.p.), the mice were given 0.1, 0.2, 0.4, and 0.6% green tea solution (1, 2, 4, and 6 g of tea solids, respectively, dissolved in 1 l of water), 0.02% caffeine, or water as the sole source of drinking fluid until the termination of the experiment. Only the treatment with 0.6% tea preparation significantly reduced lung tumor multiplicity (mean +/- SE, 6.07 +/- 0.77 vs. 8.60 +/- 0.50 tumors per mouse, P = 0.018). Treatment with 0.6% tea also inhibited angiogenesis, as indicated by the lower microvessel density (number of blood vessels/mm2) based on immunostaining for the von Willebrand factor antigen (81.9 +/- 9.5 vs. 129.4 +/- 8.2, P = 0.0018) and anti-CD31 antibody staining (465.3 +/- 61.4 vs. 657.1 +/- 43.6, P = 0.0012). Significantly lower vascular endothelial growth factor immunostaining scores were also observed in the 0.6% tea-treated group (0.98 +/- 0.17 vs. 1.43 +/- 0.07, P = 0.006). The apoptosis index was significantly higher in lung adenomas from 0.6% tea-treated mice based on morphological analysis of cell apoptosis (2.51 +/- 0.18% vs. 1.57 +/- 0.11%, P = 0.00005), and the result was further confirmed using the TUNEL method. Inhibition of angiogenesis and the induction of apoptosis by green tea may be closely related to the inhibition of pulmonary carcinogenesis.     

维生素E和硒缺乏促进大鼠食管肿瘤发生及氧化应激机制的研究

目的探讨维生素E(VE)和硒(Se)营养缺乏对食管肿瘤发生的影响及其氧化应激机制。方法 110只雄性F344大鼠随机分为3组:VE/Se缺乏组,VE/Se正常组和溶剂对照组。VE/Se缺乏组和VE/Se正常组动物皮下注射N-甲基苄基亚硝胺(NMBzA)染毒,染毒剂量为0.35 mg/kg BW,每周3次,连续5周。溶剂对照组动物皮下注射等体积的20%二甲基亚砜(DMSO)。VE/Se缺乏组给予低VE/Se饲料(VE 46U/kg,Se 0.05mg/kg),VE/Se正常组、溶剂对照组给予正常饲料(VE 80U/kg,Se 0.15mg/kg)。在实验第25周解剖动物,进行食管肿瘤肉眼观察及病理检查。动物血浆VE水平采用高效液相色谱法检测,Se水平采用荧光法检测。食管组织中细胞增殖和DNA氧化损伤分别采用5-溴脱氧尿嘧啶(BrdU)和8羟基脱氧鸟苷(8-OH-dG)免疫组织化学法检测。动物血浆、食管及肝脏谷胱甘肽过氧化物酶(GPX)、谷胱甘肽转移酶(GST)活性采用试剂盒法检测。结果动物血浆VE和Se水平VE/Se缺乏组显著低于VE/Se正常组,VE/Se正常组略低于溶剂对照组。VE/Se缺乏组动物食管肉眼可见肿瘤发生率、平均肿瘤数量及病理损伤数量均显著高于VE/Se正常组(P<0.05);与VE/Se正常组相比,VE/Se缺乏组动物食管组织细胞增殖水平、8-OH-dG水平显著升高(P<0.05);动物血浆、食管及肝脏GPX和GST活性显著降低(P<0.05)。结论维生素E和硒缺乏能够加快细胞增殖,显著促进NMBzA诱发的大鼠食管肿瘤的发生,机体氧化应激、DNA氧化损伤在食管癌变过程中具有重要作用。     

Suppression of azoxymethane-induced preneoplastic lesions and inhibition of cyclooxygenase-2 activity in the colonic mucosa of rats drinking a crude green tea extract

We determined the effects of a crude green tea extract given as drinking fluid on the promotion/progression phase of colon carcinogenesis in rats after induction of the neoplastic process by azoxymethane. Adult Wistar rats were given azoxymethane (15 mg/kg i.p.) once a week for two weeks. One week after the second injection, the rats were randomly divided into two groups. One group (n = 8) received daily prepared aqueous solutions of green tea extracts (GTE; 0.02%, wt/vol); the control group (n = 8) received tap water. After six weeks, rats receiving GTE showed a 60% reduction in the number of colonic preneoplastic lesions (aberrant crypts). The number of individual crypts per aberrant crypt focus (crypt multiplicity) was significantly reduced in the GTE group; the majority (80%) of the remaining aberrant foci contained only one or two preneoplastic crypts. A significant and selective decrease of cyclooxygenase (COX)-2 activity was observed in the colon of rats receiving GTE (23 +/- 3 vs. 117 +/- 30 mU/mg protein in controls), whereas COX-1 showed no alterations. Our data demonstrate that GTE reduces COX-2 and suppresses the formation of colonic preneoplastic lesions. They provide new insights into the mechanism of chemopreventive and anti-inflammatory properties of green tea.     

ETHANOL-MEDIATED PROMOTION OF OESOPHAGEAL CARCINOGENESIS: ASSOCIATION WITH LIPID PEROXIDATION AND CHANGES IN PHOSPHOLIPID FATTY ACID PROFILE OF THE TARGET TISSUE

Ethanol consumption is a high risk factor for oesophageal carcinomaand studies indicate that it acts as a promoter of N-nitrosomethylbenzylamine(NMBzA)-induced oesophageal carcinogenesis. The studies describedhere indicate that ethanol-induced promotion was related withan increase in indices of lipid peroxidation in the target oesophagealtissue and that such an increase was associated with significantchanges in the fatty acid profile of phospholipids. Young Sprague-Dawleyrats were treated with NMBzA, 2.5 mg/kg body weight, three timesa week for 3 weeks, and a week afterwards fed a 7% ethanolicdiet that was continued until their death at 10 months. Cumulativeethane exhaled by rats was measured a week before their deathand was found to increase significantly with NMBzA treatmentbut more so when followed by ethanol consumption. Cholesterol,phospholipids, and some indices of lipid peroxidation were measuredin the oesophagus and liver. Whereas the levels of cholesteroland phospholipids were not affected in control-fed rats withor without the NMBzA treatment, ethanol consumption by eitherthe untreated or NMBzA-treated rats caused a significant increasein the targeted oesophagus as well as the liver, the major siteof ethanol and carcinogen metabolism. Ethanol consumption alsoincreased all the indices of lipid peroxidation, i.e. malondialdehyde,lipid fluorescence, diene- and triene-conjugates; the largestincreases were observed in rats that received both NMBzA andethanol. A comparison of the fatty acid profile of phospholipidsfrom the oesophagus and liver indicated significant alterationsboth with the NMBzA treatment and ethanol consumption. However,the fatty acid profile with regard to its peroxidability wassignificantly modified only with ethanol consumption and onlyin the oesophagus of the NMBzA-treated or untreated rats. Also,hepatic phospholipids showed a substantial increase in linolenateand no change in arachidonate, but the oesophageal phospholipidsexhibited a pronounced increase in the levels of C18:3, C20:2,C20:3, C20:3' and C22:6 with a significant increase in arachidonatewhen use of ethanol followed the NMBzA treatment, suggestinga disorder in lipid and eicosanoid metabolism. We propose thatethanol may promote carcinogenesis through excessive cell proliferationinduced by disordered lipid and eicosanoid metabolism that maycause a selective outgrowth of the initiated cells.     

Consumption of green tea alters glial fibriliary acidic protein immunoreactivity in the spinal cord astrocytes of STZ-diabetic rats

We examined the effect of green tea consumption on glial fibriliary acidic protein (GFAP) expression in spinal cord of streptozotocin (STZ) treated rats. Three groups (n = 10) were used in this study: (i) controls; (ii) STZ-induced diabetic rats given tap water; and (iii) an STZ-induced diabetic group given green tea. Immunohistochemistry showed a significant (P < 0.001) decrease in the number of GFAP immunoreactive astrocytes in spinal cord sections of diabetic rats compared to non-diabetic controls. Diabetic rats treated with green tea showed a significant (P < 0.01) increase in the number GFAP-immunoreactive astrocytes in all the spinal cord gray areas as compared to water-drinking diabetic rats. Immunoblotting confirmed that the diabetic spinal cord tissue expressed 71.0 +/- 7.0% less GFAP compared to non-diabetic controls and that the GFAP content in diabetic rats increased up to 86.34 +/- 18.74% compared to non-diabetic controls after 12 weeks of green tea consumption. In conclusion, consumption of green tea may represent an achievable adjunct therapy for improving changes seen in diabetic spinal cord.