动物体内细胞色素酶P3A4与饲料黄曲霉毒素B1毒性的关系

黄曲霉毒素B1(aflatoxin B1,AFB1)作为黄曲霉主要的代谢产物之一,进入动物体内后主要影响动物的抗氧化系统和免疫系统,是霉菌毒素中主要的致病致癌物质。AFB1代谢主要存在于动物肝脏中,肝微粒体中的细胞色素酶P450(cytochrome P450,CYP450s)是动物体内参与多种药物及毒物代谢的主要酶类。细胞色素酶P3A4(cytochrome P3A4,CYP3A4)是CYP450s的同工酶,主要参与肝脏内AFB1的代谢。进入动物机体内的AFB1经CYP3A4代谢的产物一部分与DNA、RNA结合产生致毒效应;另一部分在谷胱甘肽过氧化物酶(GSH-Px)、谷胱甘肽硫转移酶(GST)等作用下进入血液和尿液,发生解毒效应。在饲料中添加抗氧化剂对于缓解AFB1的毒性有良好效果。饲料中添加一些天然物质或化学成分可以适当抑制肝脏内CYP3A4的活性,对于研究AFB1对机体的损伤具有重要意义,还可为开发新的饲料添加剂提供新思路。     

绿原酸对原代大鼠肝细胞CYP3A1的影响

绿原酸是杜仲、金银花等传统中药的清热解毒、抗菌消炎的主要药效成分.药理学研究证明,绿原酸具有抗菌、抗病毒、抗氧化、清除自由基、止血、降血压、降血脂及保肝利胆等作用[1-3].细胞色素P450酶(CYP450)主要存在于肝脏中.参与一系列药物的代谢,对维持机体内环境稳定有重要作用,是药理学、毒理学研究的热点.CYP3A约占CYP450总量的25%~28%,约有60%的药物经肝脏CYP3A代谢[4].在药物代谢中起着重要作用.CYP3A1是大鼠CYP3A家族最主要的亚型,它的活性高低直接影响许多药物的治疗效果和毒性反应.因此,研究药物对肝细胞CYP3A1的诱导作用对临床安全用药有重要意义.     

连翘苷对原代大鼠肝细胞CYP3A1的影响

连翘是常用中药,具有清热解毒、消肿散结之功效,主治温热、丹毒、斑疹、疮疡肿毒、瘰疬等病症,其有效成分连翘苷具有较强的抑菌、抗病毒能力.细胞色素:P450酶(CYP450)主要存在于肝脏中,参与一系列的药物代谢,对维持机体内环境稳定有重要作用,是药理学、毒理学研究的热点.细胞色素P4503A酶(CYP3A)占CYP450总量的25%～28%.约有60%的药物经肝脏CYP3A代谢,在药物代谢中起着重要作用.     

双峰驼肝脏CYP3A亚酶活性的初步研究

CYP3A亚酶参与45%~60%常用药物的生物转化,在机体处置外源性物质的过程中发挥着重要作用。为了探讨双峰驼肝脏CYP3A亚酶活性,采用改进的钙离子沉淀法制备肝微粒悬液,并借助生物化学方法对双峰驼CYP3A亚酶活性进行了初步研究。结果表明,钙离子沉淀法制备的双峰驼肝微粒体蛋白含量为(1.541±0.264)mg/mL,CYP总酶含量为(0.412±0.063)nmol/mg,红霉素-N-脱甲基酶的活性为(1.159±0.001)nmol/(mg·min)。以上研究结果为今后借助探针药物检测双峰驼CYP3A亚酶的体外代谢活性的深入研究奠定了基础。     

黄芩苷对原代大鼠肝细胞CYP3A1的影响

胶原酶二步灌流法获取原代大鼠肝细胞,用不同浓度的黄芩苷处理1~3 d,Western Blot法检测细胞色素P4503A1(CYP3A1)的表达。结果表明,通过胶原酶灌流法,每只大鼠可获得2-4×108个肝细胞,存活率约为95%。低浓度(<10μmol/L)的黄芩苷处理后,肝细胞CYP3A1的表达随黄芩苷浓度的增加和处理时间的延长而呈升高的趋势。高浓度(>10μmol/L)黄芩苷对细胞产生毒性,原代大鼠肝细胞可用于黄芩苷药物代谢的研究,为探讨其他药物的代谢打下了基础。     

细胞色素P4502A5研究概述

在细胞色素P450（cytochrome P450,CYP）超家族中,小鼠肝脏的细胞色素P4502A5（cytochrome P4502A5,CYP2A5）可被结构不相关的肝毒性化合物诱导,在肝炎和肝毒性过程中发挥独特的增量调节作用。研究CYP2A5的基因表达调控、催化、诱导或抑制机制及其在化学异物代谢中的作用对于指导人类临床合理用药、预防癌症发生、提高药物疗效和降低药物的毒副作用具有重要意义。作者对CYP2A5的特性、影响因素及其与疾病的关系进行了综述。     

CYP2A5表达机制的研究进展

细胞色素P450(Cytochrome P450,CYP450)属于亚铁血红素单加氧酶超家族,参与生理过程中重要化合物的生物合成,包括类固醇、脂肪酸、类花生酸类物质、脂溶性维生素、胆汁酸等.同时CYP450也是最主要的代谢外源化合物的酶,例如,药物、环境毒物.其介导的外源化合物的代谢是肝脏解毒系统中重要的一部分.细胞色素P4502A5(cytochrome P4502A5,CYP2A5)是鼠类CYP450酶系中的重要成员,与人类CYP2a6同源,在蛋白质序列和底物特异性上,与CYP2a6、CYP2a13高度相似,并且有相同的代谢底物,包括香豆素、尼古丁、可替宁、睾丸素、烟草类致癌物及亚硝胺类等[1].     

猪肝微粒体中细胞色素P450 CYP2A19和CYP1A的分离

细胞色素P450为一类蛋白质超家族,在许多化学物质的生物转化中起重要作用,如纯化的CYPs可用于结构的研究或测定药物的代谢途径。本研究中,猪肝微粒体细胞色素P450（CYP）经octylamino琼脂糖和羟基磷灰石柱层析,纯化出CYP1A和CYP2A19两种CYPs。经Western blotting鉴定,抗大鼠和人的CYP1A2抗体能识别猪cYP1A;抗人的CYP2A6抗体能识别CYP2A19。     

香猪CYP3A29基因3′-UTR结构变异及其与肌肉雄激素水平的关联分析

【目的】探究猪特有的细胞色素P450超家族3A亚族成员29(cytochrome P450 3A 29,CYP3A29)基因3′-UTR区核苷酸结构变异(structural variation, SV)对该基因表达的影响,解析该结构变异与香猪肉质性状形成的关系。【方法】以香猪、大白猪为研究对象,应用UCSC、miRBase、PITA、RBPsuite等软件预测CYP3A29基因3′-UTR区结构变异区间所包含的重复元件、miRNA和RBP结合位点;采用PCR方法对结构变异位点进行基因分型;计算群体基因型频率、基因频率及Hardy-Weinberg平衡状态;采用实时荧光定量PCR检测该变异对CYP3A29基因表达的影响;利用ELISA法检测香猪肌肉组织中CYP3A29蛋白含量和雄激素(T、DHT)水平,并使用SPSS 17.0软件对T、DHT含量与不同基因型进行Pearson相关性分析。【结果】生物信息学分析显示,CYP3A29基因3′-UTR的结构变异区全长303 bp,该变异区存在1个长为241 bp的短散在元件(short interspersed element, SINE),...     

高脂诱导非酒精性脂肪肝对CYP2A5表达的影响

为了研究高脂诱导脂肪肝对CYP2A5表达的影响,选取雄性C57BL/6J小鼠18只,随机分成对照组(control)、高脂组(NAFLD)和阳性对照组(PYR),每组6只,分别饲喂基础饲料和高脂饲料,阳性对照组饲喂基础饲料在处死前一天给予吡唑诱导,连续8周后小鼠断颈处死,取肝脏测定mRNA,CYP2A5的蛋白表达和酶活性。其结果阳性对照组CYP2A5的mRNA、蛋白表达和酶活性与对照组相比分别增加229%、80%、151%差异极显著(P0.01)。高脂诱导组与对照组相比CYP2A5的mRNA、蛋白表达和酶活性分别增加69%、34%、43%(P0.01)。表明高脂诱导非酒精性脂肪肝可增加CYP2A5的mRNA、蛋白表达水平和酶活力。     

Reaction phenotyping of vinblastine metabolism in dogs

Vinblastine is a vinca alkaloid used either as a single agent or in combination therapy for the treatment of canine mast cell tumours and lymphomas. The objective of this study was to determine which isoform of cytochrome P450 enzyme is responsible for the majority of vinblastine metabolism in dogs. A panel of eight recombinant canine cytochrome P450 enzymes (CYP1A1, CYP1A2, CYP3A12, CYP3A26, CYP2B11, CYP2C41, CYP2C21 and CYP2D15) were incubated in vitro with vinblastine. Findings were confirmed by the use of canine polyclonal antibodies of cytochrome P450 enzymes (CYP1A1, CYP3A12, CYP2B11 and CYP2C21) that were pre‐incubated with individual and pooled hepatic microsomes that were purified from canine liver. Substrate depletion was observed in the presence of recombinant CYP3A12, whereas depletion did not substantially occur when microsomes were pre‐incubated with polyclonal antibodies against CYP3A12. These findings confirmed that CYP3A12 is the major cytochrome P450 isoform responsible for the metabolism of vinblastine in dogs.     

Effects of fluoroquinolones on CYP4501A and 3A in male broilers

The inhibitory effects of fluoroquinolones on the enzyme activity, protein levels and mRNA expression of liver cytochrome P450 (CYP) 1A and 3A were investigated in male broiler chicks. Enrofloxacin (20 mg/kg), sarafloxacin (8 mg/kg) and marbofloxacin (5.5 mg/kg) were administrated in drinking water for 7 consecutive days. A cocktail of the probe drugs caffeine and dapsone was used to determine CYP1A and 3A activity. Western blot analysis and real-time PCR were used to determine the effects on protein levels of CYP1A and 3A, and on CYP1A4, 1A5, 3A37 mRNA levels. Enrofloxacin increased the half-life of elimination for both caffeine and dapsone, and decreased expression of CYP1A and 3A protein. Marbofloxacin decreased the metabolism of caffeine and expression of CYP1A protein. However, no change in mRNA expression was observed for any treatment group. This suggested that high doses of enrofloxacin and marbofloxacin, but not sarafloxacin, inhibit CYP in chick liver raising the possibility of drug-drug interaction when using these compounds.     

小型猪肝脏细胞色素P450基因CYP3A29克隆与序列分析

设计引物通过RT-PCR扩增巴马香猪和贵州小型猪香猪药物代谢关键P450基因CYP3A29基因的全长编码区,纯化并克隆入pMD 18-T载体,通过序列测定和比对分析其序列变异情况。17头小型猪共发现CYP3A29基因的5个单核苷酸变异位点,均表现为同义替换,对编码的氨基酸序列无影响;猪CYP3A29的单核苷酸变异和品系相关,在不同品系中可表现出品系特有的单核苷酸变异;贵州小型香猪G3 a2902发现1个可变剪接,缺失89 bp并产生移码,改变编码蛋白。本研究克隆的巴马香猪和贵州小型香猪CYP3A29基因及其序列变异情况,可为其作为药物代谢模型的应用提供技术资料。     

Midazolam oxidation in cattle liver microsomes: The role of cytochrome P450 3A

In humans, the cytochrome P450 3A (CYP3A) subfamily is involved in midazolam (MDZ) biotransformation into 1′- and 4-hydroxy metabolites, and the former serves as a probe for CYP3A catalytic activity. In veterinary species is still crucial to identify enzyme- and species-specific CYP substrates; thus, the aim of this study was to characterize MDZ oxidation in cattle liver. A HPLC-UV method was used to measure 1′- and 4-hydroxy MDZ (1′- and 4-OHMDZ, respectively) formation in cattle liver microsomes and assess the role of CYP3A by an immunoinhibition study. Moreover, MDZ hydroxylation was evaluated in 300 cattle liver samples and results were correlated with testosterone hydroxylation. Formation of both metabolites conformed to a single-enzyme Michaelis–Menten kinetics. Values of V_max and K_m were 0.67 nmol/min/mg protein and 6.16 μM for 4-OHMDZ, and 0.06 nmol/min/mg protein and 10.08 μM for 1′-OHMDZ. An anti-rat CYP3A1 polyclonal antibody inhibited up to 50% and 94% 1′- and 4-OHMDZ formation, respectively. MDZ oxidation in liver microsomes was poorly correlated with testosterone hydroxylation. In conclusion, cattle metabolized MDZ to 1′-OHMDZ and 4-OHMDZ. The immunoinhibition results indicated a major contribution of CYP3As to 4-OHMDZ formation and the involvement of other CYPs in 1′-OHMDZ production, paving the way for further investigations.     

Effect of breed and gender on bovine liver cytochrome P450 3A (CYP3A) expression and inter-species comparison with other domestic ruminants

The cytochrome P450 (P450) superfamily represents a group of relevant enzymes in the field of drug metabolism and several exogenous or constitutional factors contribute to regulate its expression. Cattle represent an important source of animal-derived food-products and studies concerning the P450 expression are needed for the extrapolation of pharmacotoxicological data from one species to another and for the evaluation of the consumer's risk associated with the consumption of harmful residues found in foodstuffs. In the present study, possible breed-, gender- and species-differences in P4503A (the P450 subfamily more expressed in the human liver) expression were studied in vitro in Piedmontese (PDM) and Limousin (LIM) meat cattle breeds of both sexes and in domestic Ruminants (cattle, sheep and goats). Cytochrome P450 and P4503A contents as well as CYP3A-dependent drug metabolising enzymes (DME) were measured in liver microsomes. Significant lower levels of P450 (P < 0.001) and P4503A (P < 0.05) contents were observed in PDM vs. LIM of both sexes; the P4503A-dependent DME activities were significantly (P values ranging from 0.05 up to 0.001) higher in PDM cattle, particularly in males. A gender-effect in DME activities was noticed (P < 0.05) only in PDM male cattle. With regards to the species, the expression of both P4503A apoprotein and some of the related DME activities were more pronounced in sheep (P < 0.01 vs. cattle) and in goats (P < 0.05 vs. sheep; P < 0.01 vs. cattle) than in cattle. The significant differences in P4503A expression observed in LIM and PDM cattle are consistent with previously published data on strain- and breed-differences pointed out in rats and men. As far as a possible sex-effect is concerned, no clear-cut evidence is likely to be drawn. Finally, P4503A expression was more relevant in small ruminants.     

Altered vitamin D metabolic system in follicular cysts of sows

This study aimed to examine 25OHD₃ concentration in the fluid of follicular and follicular lutein cysts of sows in comparison with preovulatory follicles as well as immunolocalize vitamin D metabolic enzymes (CYP27B1 and CYP24A1) and determine their protein abundances in the cyst wall. We have shown for the first time that 25OHD₃ level in the fluid of both cyst types was significantly lower than in preovulatory follicles. Furthermore, we have demonstrated CYP27B1 and CYP24A1 protein immunolocalization and abundance in follicular and follicular lutein cysts. The abundance of protein for both metabolic enzymes was decreased in ovarian cysts when compared to preovulatory follicles. We propose that altered VD metabolism in ovarian cyst might associate with their formation in sows.     

Skatole metabolism in the intact pre-pubescent male pig: The relationship between hepatic enzyme activity and skatole concentrations in plasma and fat

The objective of this study was to evaluate, in the pre-pubescent intact male pig, the relationship between skatole levels and the activity of hepatic cytochrome P4502E1 (CYP2E1), cytochrome P4502A (CYP2A), aldehyde oxidase (AO), and phenol sulfotransferase 1A1 (SULT1A1). The activity of these enzymes has been positively associated with skatole clearance in mature boars. Twenty-four intact male pigs were weaned at 28 days of age and slaughtered 2 weeks postweaning, at which time caecal contents, blood, fat, and liver samples were collected. Caecal contents and fat were analyzed for skatole concentrations, and plasma was analyzed for skatole and steroid hormone (testosterone (T), dehydroepiandrosterone (DHEAS), estrone sulphate (E₁S)) concentrations. CYP2A, CYP2E1, and AO, as well as SULT1A1 activities were evaluated in liver samples. Stepwise regression was utilized considering plasma or fat skatole concentration as the dependent variables and hormone concentrations and enzyme activities as independent variables. The activities of the enzymes CYP2A, CYP2E1, and AO and concentrations of the hormones T, DHEAS, or E₁S were not correlated with concentrations of skatole in plasma or fat. However, SULT1A1 activity was negatively correlated with plasma (r = − 0.70, P < 0.05) and backfat (r = − 0.41, P < 0.05) skatole concentrations. Furthermore, this correlation was improved in plasma (r = − 0.88, P < 0.05) and fat (r = − 0.63, P < 0.05) when the concentrations of skatole in caecal contents was included as an independent variable in the multiple regression analysis, demonstrating the importance of measuring skatole production in these studies. T, DHEAS, and E₁S concentrations in plasma were not correlated with the activity of any of the enzymes evaluated. This study suggests that SULT1A1 is important in the metabolism of skatole in pre-pubescent pigs and the overall metabolism of skatole in the pre-pubescent pig differs from that in the mature boar.     

In vitro complex formation and inhibition of hepatic cytochrome P450 activity by different macrolides and tiamulin in goats and cattle

In humans, clinically relevant drug-drug interactions occur with some macrolide antibiotics via the formation of stable metabolic intermediate (MI) complexes with enzymes of the cytochrome P4503A (CYP3A) subfamily. The formation of such complexes can result in a decreased biotransformation rate of simultaneously administered drugs. In previous studies it was shown that the veterinary antibiotic tiamulin was also able to form a stable MI complex in pigs and rats. In the present study the relative CYP3A inhibiting potency and MI complex formation of a series of macrolide antibiotics and tiamulin were studied in microsomal fractions of goat and cattle and in a cell-line expressing bovine CYP3A. Tiamulin and triacetyloleandomycin (TAO) were found to be effective inhibitors of CYP450 activity in all systems tested. Erythromycin and tilmicosin were found to be relatively less effective inhibitors of CYP450 activity in microsomes, and their activity in the bovine CYP3A4 expressing cell line was relatively weak. Tylosin was shown to be a weak inhibitor in microsomes and not in the cell line, whereas spiramycin had no effect at all. MI-complex formation measured by spectral analysis was seen with TAO, tiamulin, erythromycin and tylosin, but not with tilmicosin and spiramycin. Although additional factors play a role in vivo, these results may explain potential drug-drug interactions and differences between related compounds in this respect.     

矢车菊素上调CYP7A1表达促进脂肪变性L02细胞内胆固醇降解

为了研究矢车菊素对肝细胞胆固醇代谢的影响,以人肝细胞系L02为研究对象,采用软脂酸建立肝细胞脂肪变性模型并通过不同浓度矢车菊素处理,采用ELISA检测细胞内胆固醇及胆汁酸浓度,RT—PCR和Westernblot检测胆固醇降解限速酶CYP7A11i3．RNA及蛋白表达水平。结果显示：与空白组相比,10g／L和30g／L软脂酸组L02细胞内胆固醇水平随软脂酸浓度增加而升高（P〈0．05）,而胆汁酸水平没有明显变化,此过程伴随cYP7A1蛋白表达上调（P〈0．05）。舍有30g／L软脂酸的模型细胞组内添加5mg／L以上矢车菊素可显著降低细胞内胆固醇水平并同时增加胆汁酸浓度（P〈0．05）,此过程伴随CYP7A1mRNA及蛋白的显著上调（P〈0．05）;当矢车菊素添加剂量为20mg／L时,与模型组相比CYP7A1蛋白极显著上调（P〈0．01）。结果提示,矢车菊素能够通过促进L02细胞CYP7A1蛋白表达,实现促进脂肪变性肝细胞胆固醇代谢的调节作用。