Metabolism of aflatoxin B1 in turkey liver microsomes: the relative roles of cytochromes P450 1A5 and 3A37

The extreme sensitivity of turkeys to aflatoxin B₁ (AFB₁) is associated with efficient epoxidation by hepatic cytochromes P450 (P450) 1A5 and 3A37 to exo-aflatoxin B₁-8,9-epoxide (exo-AFBO). The combined presence of 1A5 and 3A37, which obey different kinetic models, both of which metabolize AFB₁ to the exo-AFBO and to detoxification products aflatoxin M₁ (AFM₁) and aflatoxin Q₁ (AFQ₁), respectively, complicates the kinetic analysis of AFB₁ in turkey liver microsomes (TLMs). Antisera directed against 1A5 and 3A37, thereby individually removing the catalytic contribution of these enzymes, were used to identify the P450 responsible for epoxidating AFB₁ in TLMs. In control TLMs, AFB₁ was converted to exo-AFBO in addition to AFM₁ and AFQ₁ confirming the presence of functional 1A5 and 3A37. Pretreatment with anti-1A5 inhibited exo-AFBO formation, especially at low, submicromolar (~ 0.1 μM), while anti-3A37, resulted in inhibition of exo-AFBO formation, but at higher (> 50 μM) AFB₁ concentrations. Metabolism in immunoinhibited TLMs resembled that of individual enzymes: 1A5 produced exo-AFBO and AFM₁, conforming to Michaelis-Menten, while 3A37 produced exo-AFBO and AFQ₁ following the kinetic Hill equation. At 0.1 μM AFB₁, close to concentrations in livers of exposed animals, 1A5 contributed to 98% of the total exo-AFBO formation. At this concentration, 1A5 accounted for a higher activation:detoxification (50:1, exo-AFBO: AFM₁) compared to 3A37 (0.15: 1, exo-AFBO: AFQ₁), suggesting that 1A5 is high, while 3A4 is the low affinity enzyme in turkey liver. The data support the conclusion that P450 1A5 is the dominant enzyme responsible for AFB₁ bioactivation and metabolism at environmentally-relevant AFB₁ concentrations in turkey liver.     

酸枣仁中黄曲霉毒素B1残留测定的不确定度评定

 目的 对高效液相色谱法测定酸枣仁中黄曲霉毒素B1残留量的不确定度进行评定。方法 对HPLC测定酸枣仁中黄曲霉毒素B1残留量的全过程进行分析,同时结合酸枣仁中黄曲霉毒素B1的HPLC方法验证数据,对分析过程中称量、供试品溶液及对照品溶液制备等影响因素引起的不确定度进行评价,最后根据各分量计算出合成不确定度并进行了扩展。结果 酸枣仁中黄曲霉毒素残留量B1为6.218 μg·kg^-1,置信概率（P）为95%时,其扩展不确定度为0.496 μg·kg^-1。 结论 该方法适用于HPLC测定酸枣仁中黄曲霉毒素B1残留量的不确定度评定,为黄曲霉毒素分析过程的不确定度评定提供了重要参考。     

植物乳杆菌F22对肝脏和肠道微生物菌群的影响研究

目的研究植物乳杆菌F22(Lactobacillus.plantarum F22)对肝脏和肠道微生物菌群的影响。方法 5 w龄雄性昆明小鼠60只,随机分为:低剂量植物乳杆菌F22[1×109 CFU/0.5ml磷酸缓冲液(PBS)]+黄曲霉毒素B1(AFB1)(250μg/kg bw)、高剂量植物乳杆菌F22(1×1010 CFU/0.5 ml PBS)+AFB1(250μg/kg bw)、AFB1(250μg/kg bw)、和无菌PBS液4组,Ⅰ、Ⅱ、Ⅲ、Ⅳ分别灌胃对应试物共10 d,之后,测定血清指标、肝组织结构及肠道菌群数量。结果 AFB1攻毒使小鼠血清白蛋白(ALB)、球蛋白(GLOB)和总蛋白(TP)含量均降低(P0.05);谷草转氨酶(GOT)、谷丙转氨酶(GPT)和碱性磷酸酶(AKP)活性极显著升高(P0.01);肝脏组织切片可见肝细胞广泛性变性和坏死,肠道菌群失调,乳酸菌、双歧杆菌和总厌氧菌数量下降,肠杆菌、肠球菌和总需氧菌数量升高。在灌胃植物乳杆菌F22后,以上现象均得到改善,并随剂量增加恢复效果更好。结论植物乳杆菌F22作为肠道益生菌对AFB1中毒小鼠肝脏和肠道微生态失调具有缓解作用。     

Aflatoxin levels in common foods of South Western Uganda: a risk factor to hepatocellular carcinoma

KITYA D., BBOSA G.S. & MULOGO E. (2010) European Journal of Cancer Care
Aflatoxin levels in common foods of South Western Uganda: a risk factor to hepatocellular carcinoma Prolonged exposure to aflatoxins by humans and animals leads to adverse effects to the various body systems of affected individuals including death. Studies have linked aflatoxins to hepatocellular carcinoma (HCC). In Uganda, HCC is observed to be on increase in communities of South‐Western Uganda. A cross‐sectional study was therefore conducted in five districts of the region and 90 various food samples were collected for total aflatoxin determination. They included ground nuts, cassava, millet, sorghum flour and eshabwe sauce. The aflatoxin levels were determined using Vicam aflatest method. The results were compared with acceptable European Union aflatoxin levels. Aflatoxin levels in the food samples ranged from 0 to 55 ppb with a mean total aflatoxin level of 15.7 ± 4.9 ppb. Eshabwe sauce had the highest mean total aflatoxin levels (18.6 ± 2.4 ppb). Traditional methods of food processing in this study were found to be contributing risk factor of food contamination and hence the observed increased HCC cases and mortalities in the region.     

Mutagenicity and Mutagens of the Red Chili Pepper as Gallbladder Cancer Risk Factor in Chilean Women

High consumption of red chili pepper has been shown to be a risk factor for gallbladder cancer (GBC) inChilean women with gallstones, and included mutagens may be important in this context. We aimed to investigatethe mutagenicity and mutagens in Chilean red chili pepper in the Ames test using Salmonella typhimurium strainsTA98, TA1537, TA100, and TA1535 with and without metabolic activation (S9 mix). Pure capsaicin was testedfor mutagenicity using strain TA98. The presence of aflatoxins was evaluated by two-dimensional thin layerchromatography, and then the concentrations of aflatoxins B1, B2, G1, and G2 were measured by an HPLCsystem. In strain TA98, the mean numbers of revertant colonies with and without the S9 mix were 2.5- and 2.2-fold higher than those of each negative control, respectively. However, pure capsaicin did not show mutagenicactivity in strain TA98. Aflatoxin contamination of red chili pepper was confirmed, and the concentrations ofaflatoxins B1 and G1 were 4.4 ng/g and 0.5 ng/g, respectively. Our findings suggest that low-level but protractedexposure to aflatoxins may be associated with the development of GBC in Chilean women who carry gallstones.     

人体血清中黄曲霉毒素-白蛋白加合物的测定及应用

黄曲霉毒素B1 (AFB1 )是人类原发性肝癌 (HCC)的主要病因之一 ,发展和应用AFB1 及其体内分子生物标记物敏感、特异的检测方法对肝癌高危人群的筛检具有重要意义。人体血清中黄曲霉毒素 白蛋白加合物 (AFB ALB)的测定已应用于人体黄曲霉毒素暴露水平与肝癌的研究 ,本研究旨在建立敏感特异的AFB ALB的测定方法。该方法选择使用Microcon 5 0微型浓缩器使白蛋白快速分离 ,改变了用沉淀和其他分离白蛋白的方法 ,同时由于在同一装置内加入蛋白分解酶消化 ,从而减少了转移操作步骤 ,增加了白蛋白的回收率 ,对消化样品采用竞争性放射免疫测定 (RIA)法进行AFB ALB的测定 ,提高了测定的敏感性及特异性。应用改进的方法对我国江苏启东和广西扶绥两肝癌高发区居民的血样进行了测定 ,表明该地区人群黄曲霉毒素暴露较普遍 ,血清AFB ALB阳性率高。