NADPH-细胞色素P-450还原酶的制备及在外来化合物代谢中的作用

ＮＡＤＰＨ－细胞色素Ｐ－４５０还原酶是肝微粒体酶系的主要组成成分。本文报道了一种简单经济制备还原酶的方法，并通过ＮＡＤＰＨ的氧化证明还原酶及细胞色素Ｐ－４５０２Ｂ１重组酶系能代谢苯、二氯乙烯和石棉。但代谢过程中的中间产物未能引起质粒ＤＮＡ电泳图谱的变化。     

CYP2E1基因多态性与肿瘤易感性研究进展

90％以上的肿瘤是由各种环境因素与职业因素引起，而大部分的外源性致癌物需经过Ⅰ相和Ⅱ相代谢酶的代谢活化才与体内生物大分子作用启动致癌过程。细胞色素P450 2E1(cytochrome P450s 2E1，CYP2E1)是人体内重要的Ⅰ相代谢酶类，参与N-亚硝胺类化合物等多种前致癌物的代谢活化过程，在体内各组织器官中有不同的表达。CYP2E1活性的表达受多种因素影响，存在多种限制性片段长度多态性，与人类肿瘤易感性间存在密切关系。     

CYP450酶基因多态性对芬太尼个体化用药的影响

细胞色素P450酶与90％临床药物代谢相关,已发现家族中CYP2D6、CYP3A4和CYP3A5参与芬太尼等镇痛药物的Ⅰ相代谢反应.基因多态性可影响细胞色素P450酶的活性和功能,产生明显的芬太尼药代动力学个体间差异,导致不同基因型的携带者表现出镇痛效果、安全剂量范围及毒副作用发生率的差异.芬太尼是常用的阿片类镇痛药,...     

细胞色素P450 2E1基因多态性与胃癌易患性

目的研究与前致癌物亚硝胺类代谢活化有关的细胞色素P450 2E1(cytochromeP450 2E1,CYP2E1)基因多态性与胃癌易患性的关系,探讨环境因素与遗传因素在胃癌发病中的作用.方法采用病例-对照分子流行病学方法,调查原发性胃癌患者和对照各48例,以聚合酶链反应-限制性片段长度多态(PCR-RFLP)检测被调查者的CYP2E1基因RsaⅠ位点的多态性,条件Logistic回归模型进行资料分析.结果 CYP2E1 A、B和C 3种基因型在病例组中的构成比分别为68.8%,29.2%和2.1%,对照组分别为45.83%,47.92%和6.25%,2组差异无统计学意义(x2=5.389,P=0.068).而病例和对照组CYP2E1基因Rsa Ⅰ位点等位基因c1和c2频率分别为83.3%,16.7%和69.8%,30.2%,差异有统计学意义(x2=5.241,P＜0.05).环境因素中食盐、香肠和熟食的过多摄入以及肿瘤家庭史和c1等位基因作为胃癌的危险因素进入回归模型,而经常喝茶作为保护性因子可能降低胃癌的发生危险.结论 CYP2E1基因Rsa Ⅰ位点等位基因c1与胃癌易感性相关联;某些饮食因素与胃癌的发生有关.     

Styrene trimer may increase thyroid hormone levels via down-regulation of the aryl hydrocarbon receptor (AhR) target gene UDP-glucuronosyltransferase

BACKGROUND: Styrene trimers (STs) are polystyrene-container-eluted materials that are sometimes detected in packaged foods. Although the possible endocrine-disrupting effects of STs, such as estrogenic activities, have been reported, their potential thyroid toxicity, such as that caused by the related endocrine disruptor 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), has not been studied in detail. OBJECTIVE: Using wild-type and aryl hydrocarbon receptor (Ahr)-null mice, we investigated whether 2,4,6-triphenyl-1-hexene (ST-1), an isomer of STs, influences thyroxin (T(4)) levels in the same manner as TCDD, which induces UDP-glucuronosyltransferase (UGT) via the AhR, resulting in a decrease in T(4) levels in the plasma of mice. METHODS: Both wild-type and Ahr-null mice (five mice per group) were treated for 4 days by gavage with ST-1 (0, 32, or 64 micromol/kg). RESULTS: High-dose (64 micromol/kg) ST-1 decreased the expression of AhR, cytochrome P450 (CYP) 1A1/2, UGT1A1/A6, and CYP2B10 mRNAs and the enzyme activity for CYP1A and UGT1A only in the wild-type mice. This dose decreased AhR DNA binding, but paradoxically increased AhR translocation to the nucleus. In contrast, a high dose of ST-1 increased T(4) levels in the plasma in wild-type mice but did not influence T(4) levels in AhR-null mice. CONCLUSIONS: Although ST-1 treatment might cause an increase in AhR levels in the nucleus by inhibiting AhR export, this chemical down-regulated AhR mRNA, thus leading to down-regulation of AhR target genes and an increase in plasma T(4) levels.     

CRABPs Alter all-trans-Retinoic Acid Metabolism by CYP26A1 via Protein-Protein Interactions

Cellular retinoic acid binding proteins (CRABP1 and CRABP2) bind all-trans-retinoic acid (atRA), the active metabolite of vitamin A, with high affinity. CRABP1 and CRABP2 have been shown to interact with the atRA-clearing cytochrome P450 enzymes CYP26B1 and CYP26C1 and with nuclear retinoic acid receptors (RARs). We hypothesized that CRABP1 and CRABP2 also alter atRA metabolism and clearance by CYP26A1, the third key atRA-metabolizing enzyme in the CYP26 family. Based on stopped-flow experiments, atRA bound CRABP1 and CRABP2 with K_d values of 4.7 nM and 7.6 nM, respectively. The unbound atRA K_m values for 4-OH-atRA formation by CYP26A1 were 4.7 ± 0.8 nM with atRA, 6.8 ± 1.7 nM with holo-CRABP1 and 6.1 ± 2.7 nM with holo-CRABP2 as a substrate. In comparison, the apparent k_cat value was about 30% lower (0.71 ± 0.07 min⁻¹ for holo-CRABP1 and 0.75 ± 0.09 min⁻¹ for holo-CRABP2) in the presence of CRABPs than with free atRA (1.07 ± 0.08 min⁻¹). In addition, increasing concentrations in apo-CRABPs decreased the 4-OH-atRA formation rates by CYP26A1. Kinetic analyses suggest that apo-CRABP1 and apo-CRABP2 inhibit CYP26A1 (K_i = 0.39 nM and 0.53 nM, respectively) and holo-CRABPs channel atRA for metabolism by CYP26A1. These data suggest that CRABPs play a critical role in modulating atRA metabolism and cellular atRA concentrations.     

Evidence-based prevention (EBP): A review of cytochrome P450 expression in the bronchial epithelium and new approach to lung cancer prevention

The number of fatalities in Japan attributable to lung cancer exceeded 50000 in 2001. It is socially desirable that various markers, which can be utilized for the prevention of lung cancer, be established. We believe that smoking or exposure to carcinogens in air induces mutations in bronchial and alveolar epithelia, leading to the development of lung cancer. It would be useful to have markers of individual differences in susceptibility to chemical carcinogen-induced lung cancer 1) to identify genetic polymorphisms of enzymes metabolizing chemical carcinogens and 2) to investigate the expression of enzymes metabolizing chemical carcinogens. In this paper, we review CYP expression in the bronchial epithelium. CYP1, CYP2 and CYP3 are expressed in the bronchial epithelium. We also show the relationship between the genetic polymorphisms of cytochrome P450 (CYP) and a person’s susceptibility to chemical carcinogen-induced lung cancer. We demonstrate the relationship between cigarette consumption and the CYP expression profile in the bronchial epithelium. To maintain and promote public health, we must apply evidence, such as CYP polymorphisms and CYP profiles to disease prevention and also to aggressively advance evidence-based prevention (EBP) of lung cancer. This article is based upon the research that was given Encouragement Award at the 75th Annual Meeting of the Japanese Society for Hygiene held in Niigata, Japan on March 27–30, 2005.     

EC-SOD和CYP 1A1-MspⅠ基因多态性与口腔癌的相关性研究

目的 探讨吸烟和细胞外超氧化物歧化酶(extracellular superoxide dismutase,EC-SOD )、细胞色素P450（cytochrom P450,CYP）1A1-MspⅠ基因多态性与口腔癌发病之间的关系。方法 采用病例-对照研究的方法 ,以670例口腔癌患者（病例组）及670例非癌对照者（对照组）的外周血白细胞为样本,利用聚合酶链反应（polymerase chain reaction,PCR）技术检测EC-SOD和CYP1A1-MspⅠ基因多态性,并分析吸烟和2种代谢酶基因多态性与口腔癌的相关性。结果 病例组EC-SOD（C/G）和 CYP1A1-MspⅠ突变纯合型（m2/m2）基因频率分布分别为39.40%、68.81%,而对照组的频率分布分别为21.34%、43.88%,二者差异有均统计学意义（均P<0.05）;EC-SOD（C/G）者患口腔癌的风险显著增加（OR=2.40,95%CI=1.73~4.32）,CYP1A1-MspⅠ（m2/m2）者患口腔癌的风险也显著增加（OR=2.82,95%CI=1.84~4.41）;基因突变的协同分析发现EC-SOD(C/G)/CYP1A1-MspⅠ(m2/m2)在病例组和对照组中的分布频率分别为30.60%和7.16%,差异有统计学意义（P<0.05）;EC-SOD(C /G)/CYP1A1-MspⅠ(m2/m2)者患口腔癌的风险显著增加（OR=6.87,95%CI=2.18~9.45）;病例组的吸烟率明显高于对照组（P<0.05）,EC-SOD(C/G)/CYP1A1-MspⅠ(m2/m2)与吸烟有协同作用（OR=44.48,95%CI=17.63~62.07）,EC-SOD(C/G)/CYP1A1-MspⅠ(m2/m2)与吸烟指数（SI>400）有协同作用（OR=248.81,95%CI=175.46~384.37）。结论 EC-SOD(C/G)和CYP1A1-MspⅠ(m2/m2)是口腔癌的易感因素,吸烟与口腔癌的易感性也有关,EC-SOD(C/G)/CYP1A1-MspⅠ(m2/m2)与吸烟在口腔癌的发生上有协同作用。     

肺癌易感性标记物与肺癌关系的病例对照研究

目的探讨谷胱甘肽转移酶(GST)和细胞色素CYP1A1、CYP2E1多态性与肺癌易感性的关系。方法用病例对照研究方法，收集广东籍新发原发性肺癌病人91例及同期非肺部疾患住院病人91例作对照。采用聚合酶链式反应(PCR)和限制性片段长度多态性(RFLP)技术检测病例和对照的CYP1A1、CYP2E1和GSTM1基因多态性。结果CYP1A1突变型(m2m2)与野生型(m1m1)比较，OR值1．51；CYP2E1C1C1型与C1C2型比较，OR值1．80；C2C2型与C1C2型比较，OR值5．48；GSTM1基因缺失型与正常型比较；OR值1．26。两种基因联合分析结果表明：GSTM，基因缺失并携带CYP1A1m2m2与GSTM1基因正常并携带CYP1A1m1m1者比较，OR值2．29，GSTM1基因缺失并携带CYP2E1C1C1型者与GSTM1基因正常并携带CYP2E1C1C2型者比较，OR值2．13，携带CYP1A1m2m2型以及CYP2E1C1C1型者与携带CYP1A1m1m1型和CYPE1C1C2型者比较，OR值3．00。3种基因联合作用分析结果表明：携带CYP1A1m2m2型以及CYP2E1C1C1型并且GSTM1基因缺失者比携带CYP1A1m1m1型和CYP2E1ClC2型且GSTM1基因正常者提高了患肺癌的危险性，OR值3．97。结论CYP1A1、CYP2E1和GSTM1在单因素分析中末显示出与肺癌风险的联系，2个基因和3种基因的联合作用似乎可以提高患肺癌的危险性，但无统计学意义。提示这3种基因均不是肺癌个体易感性的主效基因，可能是次效基因。     

Nutrient supplement use by healthy elderly.

As part of a nutritional status survey of 691 non-institutionalized men and women aged 60 years and older, supplement use was reported by 45% of the males and 55% of the females. Supplement use was more prevalent in females than males at each age decade. Vitamins C and E were the most commonly used supplements. Mean dietary nutrient intakes were calculated from a 3-day food diary. The percentage of dietary intakes falling below 2/3 1980 Recommended Dietary Allowance (RDA) was comparable for users and non-users of supplements. Use of supplements markedly decreased the proportion of subjects with inadequate nutrient intake (using a 2/3 RDA criterion), particularly for vitamins B6, B12, and D, folic acid, and calcium. However, for both males and females, potentially excessive intake levels (10 times the RDA) of thiamin, vitamin A, and vitamin E supplementation were observed.     

Bidirectional Influences of Cranberry on the Pharmacokinetics and Pharmacodynamics of Warfarin with Mechanism Elucidation

Cranberry is a dietary supplement popularly used for the prophylaxis of urinary tract infection. Interestingly, cranberry–warfarin interactions in clinical reports have shown bidirectional outcomes. (±) Warfarin, a widely prescribed anticoagulant, but with a narrow therapeutic index, contains equal amounts of S- and R-warfarin, of which S-warfarin is more active. The aim of this study was to investigate the effects of different ingestion times of cranberry on the pharmacokinetics and pharmacodynamics of warfarin. Rats were orally administered (±) warfarin (0.2 mg/kg) with and without cranberry (5.0 g/kg) at 0.5 h prior to the warfarin, and at 10 h after the warfarin. The plasma concentrations of S- and R-warfarin were determined by LC/MS. The results indicate that cranberry ingested at 0.5 h before (±) warfarin significantly decreased the systemic exposures of S-warfarin and R-warfarin. Conversely, when cranberry was ingested at 10 h after (±) warfarin, the elimination of S-warfarin was significantly inhibited, and the anticoagulation effect of (±) warfarin was significantly enhanced. The results of the mechanism studies indicate that cranberry activated the breast cancer resistance protein (BCRP), which mediated the efflux transports of S-warfarin and R-warfarin. Moreover, the metabolites of cranberry inhibited cytochrome P450 (CYP) 2C9, the main metabolizing enzyme for S-warfarin. In conclusion, cranberry affected the pharmacokinetics of (±) warfarin in a bidirectional manner by activating the BCRP by CJ during absorption and inhibiting the BCRP and CYP2C9 by CMs during elimination, depending on the ingestion time of CJ. The combined use of cranberry with warfarin should be avoided.     

Phytoestrogens and breast cancer prevention: possible mechanisms of action

OBJECTIVE: Phytoestrogens display an array of pharmacologic properties, and in recent years investigation of their potential as anticancer agents has increased dramatically. In this article we review the published literature related to phytoestrogens and breast cancer as well as suggest the possible mechanisms that may underlie the relationship between phytoestrogens and breast cancer. DATA SOURCES: Electronic searches on phytoestrogens and breast cancer were performed on MEDLINE and EMBASE in June 2007. No date restriction was placed on the electronic search. DATA EXTRACTION: We focused on experimental data from published studies that examined the characteristics of phytoestrogens using in vivo or in vitro models. We also include human intervention studies in this review. DATA SYNTHESIS: We evaluated evidence regarding the possible mechanisms of phytoestrogen action. Discussions of these mechanisms were organized into those activities related to the estrogen receptor, cell growth and proliferation, tumor development, signaling pathways, and estrogen-metabolizing enzymes. CONCLUSIONS: We suggest that despite numerous investigations, the mechanisms of phytoestrogen action in breast cancer have yet to be elucidated. It remains uncertain whether these plant compounds are chemoprotective or whether they may produce adverse outcomes related to breast carcinogenesis.     

Chemopreventive effect of dietary polyphenols in colorectal cancer cell lines

Colorectal cancer (CRC) is the second most fatal and the third most diagnosed type of cancer worldwide. Despite having multifactorial causes, most CRC cases are mainly determined by dietary factors. In recent years, a large number of studies have attributed a protective effect to polyphenols and foods containing these compounds (fruits and vegetables) against CRC. Indeed, polyphenols have been reported to interfere with cancer initiation, promotion, and progression, acting as chemopreventive agents. The aim of this review is to summarize the main chemopreventive properties of some polyphenols (quercetin, rutin, myricetin, chrysin, epigallocatechin-3-gallate, epicatechin, catechin, resveratrol, and xanthohumol) against CRC, observed in cell culture models. From the data reviewed in this article, it can be concluded that these compounds inhibit cell growth, by inducing cell cycle arrest and/or apoptosis; inhibit proliferation, angiogenesis, and/or metastasis; and exhibit anti-inflammatory and/or antioxidant effects. In turn, these effects involve multiple molecular and biochemical mechanisms of action, which are still not completely characterized. Thus, caution is mandatory when attempting to extrapolate the observations obtained in CRC cell line studies to humans.