没食子酸丙酯对脑缺血大鼠神经元SAPK/JNK及p38MAPK激活的抑制作用

目的探讨没食子酸丙酯对大鼠脑缺血再灌注模型缺血区周边组织神经元损伤的保护作用及其可能机制。方法通过Nissl和TUNEL染色法检测阳性神经元数量，蛋白免疫印迹、免疫组化法观察活化型Caspase-3，SAPK/JNK，p38MAPK及其磷酸化组分的表达。结果没食子酸丙酯干预后，SAPK/JNK，p-SAPK/JNK(1 h)，p38MAPK，p-p38MAPK(6 h)及活化型Caspase-3(12 h)表达均减弱，TUNEL阳性神经元减少(24 h)，Nissl阳性神经元增多(24 h)，神经元凋亡率明显降低。结论没食子酸丙酯保护缺血再灌注后神经元损伤的机制可能与抑制SAPK/JNK及p38MAPK的激活有关。     

L-(-)-表没食子儿茶素没食子酸酯对二甲基胂酸促小鼠肺肿瘤发生的抑制与其抑制氧化应激

目的探讨抗氧化茶多酚L-(-)-表没食子儿茶素没食子酸酯[(-)epigallocatechin gallate,EGCG]对二甲基胂酸(dimethylarsinic acid,DMA(V))促小鼠肺肿瘤发生的抑制作用与氧化应激关系。方法利用4-硝基喹啉-1-氧化物(4-nitroquinoline 1-oxide,4NQO)作为始动剂,DMA(V)作为促进剂的致小鼠肺肿瘤两阶段动物模型。观察绿茶提取物中最有效的EGCG对DMA(V)致肿瘤发生的作用,同时通过高效液相色谱法(HPLC)测量小鼠肺中DNA氧化损伤的生物标志物8-氧-2’-脱氧鸟嘌呤核苷(8-oxo-2’-deoxyguanosine,8-oxodG)的变化。结果EGCG明显抑制4NQO与DMA(V)诱发小鼠肺肿瘤数(P<0.05)和肺组织中8-oxodG的生成(P<0.05)。结论EGCG对DMA(V)促肺肿瘤的抑制作用可能与其抑制氧化应激有关。     

Anticarcinogenic Activity of Green Tea Polyphenols

The main physiologically active polyphenol in green tea extractis (–)-epigallocatechin gallate (EGCG). Green tea extracthas an advantage over EGCG as a cancer chemopreventive agentfor humans, as is apparent from the Japanese custom of injestinggreen tea on a daily basis. Green tea extract similarly inhibitedprotein kinase C activation by teleocidin, a tumor promoter,as did EGCG. In addition, EGCG and green tea extract showedinhibitory effects on the growth of lung and mammary cancercell lines with similar potencies. An experiment using the estrogen-dependentMCF-7 cell line showed the mechanisms of action of these compoundsto be inhibiting the interaction of estrogen with its receptors.Considering our previous results of a single application ofEGCG to mouse skin inhibiting the specific binding of ³H-12-0-tetradecanoylphorbol-13-acetate(³H-TPA) and ³H-okadaic acid, we postulated that EGCG and compoundsin green tea extracts would block the interaction of tumor promoters,hormones and growth factors with their receptors: a kind ofsealing effect. The sealing effect would account for reversiblegrowth arrest, and may be induced by various kinds of compond.     

蛇葡萄根化学成分的研究

从蛇葡萄根中分离出8种单体化合物,鉴定为β-香树脂醇、白桦脂醇、香草酸、没食子酸乙酯、山奈酚、3,5-二甲氧基-4-羟基苯甲酸、香橙素和藜芦醇,均为首次从该植物中分离得到。     

The effect of epigallocatechin gallate on intestinal motility in mice

Objectives The epigallocatechin-3-gallate (EGCg) that is present in human diet originates mainly from tea leaves. Catechins have a number of possible application as medicines, however, there is no consistent evidence showing their influence on the gastrointestinal tract. Thus, the aim of the present study was to investigate the effect of EGCg on the motility of the murine isolated intestine. Methods Segments of jejunum submerged in Krebs buffer were exposed to EGCg and the response was recorded under isometric conditions. Results EGCg induced a dose-dependent inhibition of spontaneous activity in the jejunum. EGCg induced a decrease in the amplitude and frequency of jejunal contractions. moreover, the rythmicity of spontaneous, activity was altered in the presence of EGCg. A significant effect of EGCg was observed in the presence of 10⁻⁴ M. The effect of EGCg was in part inhibited by pretreatment with methylene blue (guanylate cyclase inhibitor), while tetrodotoxin, (sodium channel blocker), L-nitro arginine methyl ester (nitric oxide synthase inhibitor), and N-ethylmaleimide (adenylate cyclase inhibitor) showed no effect. Conclusions The results of the present study suggest that EGCg inhibits the motility of the jejunum by direct action on smooth muscle cells where a guanylate cyclase-dependent mechanism may be partly involved.     

Effects of (−)-epigallocatechin gallate (EGCG) on DNA strand breaks as evaluated by single-cell gel electrophoresis (SCG) in human lymphocytes

(−)-Epigallocatechin gallate (EGCG), a catechin polyphenol component, is the main ingredient of green tea extract. Although the anti-carcinogenic and cancer inhibitory effects of EGCG have been widely reported, its genotoxicity is not clear and seldom reported. In this study, we examined the effects of EGCG on DNA strand breaks in the isolated lymphocytes and whole blood lymphocytes obtained from two smoking subjects and a nonsmoking healthy subject using a single cell gel electrophoresis (SCG) assay. The results showed that after 2 hrs of treating the isolated lymphocytes from the smokers, EGCG induced a significant, increase in DNA strand breaks at concentrations from 2.5×10⁻⁵ M to 2.0×10⁻⁴ M, while after 2 hrs of treating the whole blood obtained from the same smokers, EGCG suppressed the DNA strand breaks in the lymphocytes at concentrations of 1.0×10⁻⁴ M and 2.0×10⁻⁴ M. A similar suppressive result was also shown in the whole blood lymphocytes from the nonsmoker at nearly the same concentrations, while at concentrations of 1.0×10⁻³ M or 2.0×10⁻³ M, EGCG induced a significant increase in DNA strand breaks in the whole blood lymphocytes from the nonsmoker. This result suggests that EGCG is not only inhibitory against DNA strand breaks in whole blood, but also genotoxic to the isolated or whole blood lymphocytes at high concentrations. Thus, more research is needed to comprehensively assess the effects of EGCG on genetic materials.     

(-)-Epigallocatechin Gallate Inhibits the Pacemaker Activity of Interstitial Cells of Cajal of Mouse Small Intestine

The effects of (-)-epigallocatechin gallate (EGCG) on pacemaker activities of cultured interstitial cells of Cajal (ICC) from murine small intestine were investigated using whole-cell patch-clamp technique at 30℃ and Ca²⁺ image analysis. ICC generated spontaneous pacemaker currents at a holding potential of -70 mV. The treatment of ICC with EGCG resulted in a dose-dependent decrease in the frequency and amplitude of pacemaker currents. SQ-22536, an adenylate cyclase inhibitor, and ODQ, a guanylate cyclase inhibitor, did not inhibit the effects of EGCG. EGCG-induced effects on pacemaker currents were not inhibited by glibenclamide, an ATP-sensitive K⁺ channel blocker and TEA, a Ca²⁺-activated K⁺ channel blocker. Also, we found that EGCG inhibited the spontaneous [Ca²⁺]_i oscillations in cultured ICC. In conclusion, EGCG inhibited the pacemaker activity of ICC and reduced [Ca²⁺]_i oscillations by cAMP-, cGMP-, ATP-sensitive K+ channel-independent manner.     

Tea catechin auto-oxidation dimers are accumulated and retained by Caco-2 human intestinal cells

Despite the presence of bioactive catechin B-ring auto-oxidation dimers in tea, little is known regarding their absorption in humans. Our hypothesis for this research is that catechin auto-oxidation dimers are present in teas and are absorbable by human intestinal epithelial cells. Dimers (theasinensins [THSNs] and P-2 analogs) were quantified in commercial teas by high-performance liquid chromatography-mass spectrometry. (−)-Epigallocatechin (EGC) and (−)-epigallocatechin gallate (EGCG) homodimers were present at 10 to 43 and 0 to 62 μmol/g leaf, respectively. The EGC-EGCG heterodimers were present at 0 to 79 μmol/g. The potential intestinal absorption of these dimers was assessed using Caco-2 intestinal cells. Catechin monomers and dimers were detected in cells exposed to media containing monomers and preformed dimers. Accumulation of dimers was significantly greater than monomers from test media. Three-hour accumulation of EGC and EGCG was 0.19% to 0.55% and 1.24% to 1.35%, respectively. Comparatively, 3-hour accumulation of the EGC P-2 analog and THSNs C/E was 0.89% ± 0.28% and 1.53% ± 0.36%, respectively. Accumulation of P-2 and THSNs A/D was 6.93% ± 2.1% and 10.1% ± 3.6%, respectively. The EGCG-EGC heterodimer P-2 analog and THSN B 3-hour accumulation was 4.87% ± 2.2% and 4.65% ± 2.8%, respectively. One-hour retention of P-2 and THSNs A/D was 171% ± 22% and 29.6% ± 9.3% of accumulated amount, respectively, suggesting intracellular oxidative conversion of THSNs to P-2. These data suggest that catechin dimers present in the gut lumen may be readily absorbed by intestinal epithelium.     

Exposure and toxicity of green tea polyphenols in fasted and non-fasted dogs

Standardized green tea extract was evaluated for exposure and toxicity in Beagle dogs following oral dosing by capsules. The main component (−)-epigallocatechin gallate (EGCG) accounted for 56–72% of the material. A 9-month chronic study (0, 200, 500, and 1000 mg/kg/day) was done in fasted dogs to take advantage of the reported improved catechin bioavailability with fasting. Extensive morbidity, mortality, and pathology of many major organs led to its early termination at 6.5 months and prevented identification of the toxicity mechanisms. A follow-up 13-week study examined the exposure to and toxicity of the extract. In general, toxicities were less severe than in the chronic study during the same interval. Dosing in a fed state resulted in considerably lower and less variable exposure than found under fasted conditions. Toxicity was less frequent and of lesser severity with lower exposure but limited sample size and large variability prevented reaching that definitive conclusion. Differences in mortality and morbidity between the preliminary terminated chronic and follow-up subchronic studies with the same dose of the same drug lot and similar exposure were not fully resolved as there may be other as yet unclear confounding factors.     

C-PG血小板聚集试验在单采血小板捐献者筛查中的应用

本研究探讨以阳离子没食子酸丙酯（C-PG）为激活剂的血小板聚集试验用于单采血小板捐献者筛查的可行性,并调查血小板献血者血小板功能缺陷的发生率.测定不同浓度C-PG诱导的健康献血者的血小板聚集率,以确定C-PG的最适应用浓度;检测30名志愿者服用阿司匹林前和服药24小时后的血小板聚集率,以确定血小板功能不良的筛查界点值;检测483例血小板捐献者的C-PG诱导的血小板聚集率,并对聚集功能不良者进行活化血浆凝固时间（APCT）测定.结果表明：血小板聚集率随C-PG浓度的增加而升高,当C-PG浓度达200μmol/L时,血小板聚集率达最高;服用阿司匹林24小时后的血小板聚集率与服药前相比,均表现明显减低（P＜0.001）,但以C-PG诱导180秒时的血小板聚集率减低最显著.血小板功能不良的筛查界点值确定为C-PG诱导180秒时的血小板聚集率小于20%;在483例血小板捐献者中,检出25例有血小板聚集功能不良,其中有11例表现为血小板促凝血活性减低.结论：C-PG诱导的血小板聚集试验能有效的检出血小板功能不良者,适用于血小板捐献者血小板功能的筛选;在血小板献血者中,血小板功能缺陷者的检出率大约为5%.