丙烯酰胺及其代谢物环氧丙酰胺的神经毒性研究

通过丙烯酰胺(AA)及其代谢物环氧丙酰胺(GA)的比较神经毒性研究,探讨了体内代谢过程对AA毒性的影响。5组大鼠分别用AA25mg/kg和50mg/kg;GA50mg/kg和100mg/kg及生理     

关注某些医用产品中丙烯酰胺的潜在风险

根据世界卫生组织发布的有关文件。简要概述了丙烯酰胺以及代谢产物在动物方面的研究和有限的人体研究情况．主要涉及神经毒性、生育毒性、致癌性和遗传毒性及其可能发生的机制等。结果表明：丙烯酰胺引起的神经毒性可能与丙烯酰胺有关；导致动物多器官肿瘤的发生与丙烯酰胺的代谢产物环氧丙酰胺有关。     

丙烯酰胺及其代谢产物的大鼠组织分布研究

丙烯酰胺(acrylamide,AA)是一种高水溶性的小分子有机物,可经皮迅速吸收。其聚合物聚丙烯酰胺广泛用于饮水净化、污水处理、食品加工、造纸和采矿业,AA单体用于粘合剂和纺织品制造等工业以及在建筑行业生产水泥和土壤的稳定剂。目前,在工业加工中暴露于AA的工人数以万计,分子生物学实验室的科研人员也有潜在接触。最近又在多种食品中发现AA的存在[1]。研究表明AA在大鼠、小鼠体内通过细胞色素P4502El(CYP2E1)代谢为环氧丙酰胺(glycidamide,GA),通过这种高活性的环氧化物而产生基因毒性[2-3]。通过高效液相色谱检测AA及其代谢产物GA…     

抗肿瘤药的神经毒性

恶性肿瘤病人在化疗期间或化疗后，常可出现神经系统症状。特别是接受长期化疗者更易发生。由于这些症状较复杂，造成诊断困难。此外，诸如肿瘤脑内转移、脑膜瘤、原发肿瘤的瘤外效应、代谢或电解质紊乱、感染、精神症状和放疗与其他药物的毒性效应均使诊断更为复杂。许多细胞毒药物可引起中枢或外周神经毒性，且一般不引起神经毒性的药物经动脉内、鞘内或高剂量给药也可能引起神经毒性。现将可弓I起神经毒性的抗肿瘤药物分述如下。1抗代谢药1．五甲氨噪吟MTX神经毒性包括可逆的急性、亚急性和较重而不可逆的迟发性反应。MTX在常用剂量时…     

拟胆碱药和抗胆碱药用以研究情感障碍和应激的乙酰胆碱假说

机体的应激反应包括胃肠道、心血管、行为、镇痛、免疫、内分泌、精神行为和精神病理等多种变化。动物实验表明,应激时的各种表现可能通过中枢神经递质包括去甲肾上腺素(NA)、多巴胺、5-羟色胺(5-HT)和γ-氨基丁酸、GABA)等的复杂变化。乙酰胆碱(ACh)是一种中枢和外周植物神经系统的重要递质,也可能参予应激反应。本文概述应用拟胆碱药和抗胆碱药作为工具,研究ACh 在应激时行为、神经内分泌和心血管反应的作用。应激引起的ACh 活性变化     

甲基汞对大鼠的行为致畸效应研究

目的探讨妊娠期甲基汞暴露对Wistar大鼠的母体毒性及仔代的行为致畸效应.方法 Wistar孕鼠80只于妊娠第6～9天采用甲基汞0.00、0.01、0.05和2.00mg·kg-1@d-1连续灌胃染毒.分别进行母体毒性、胚胎毒性、仔鼠早期生理发育和神经行为发育指标、仔鼠迷宫和程序控制行为测试、亲仔两代大鼠脑组织形态学观察和单胺类神经递质(去甲肾上腺素、多巴胺、5-羟色胺)的测定.整个实验采用双盲法.结果未观察到明显的母体毒性;3个剂量组胎仔的体重、尾长均低于对照组(P＜0.01);各剂量组仔鼠的体重增长、早期生理及神经行为发育滞后于对照组(P＜0.05);各剂量组仔鼠迷宫错误次数均比对照组多(P＜0.05),具有剂量-效应关系(rs=0.257,P＜0.05);程序控制行为学习成绩比对照组降低(P＜0.05),有剂量-效应关系(rs=-0.727 3,P＜0.01);各剂量组母鼠和仔鼠脑组织均未见形态学改变,但脑组织单胺类神经递质含量均比对照组明显增高(P＜0.05),有剂量-效应关系(s=0.712 4～0.925 7,P＜0.01).结论甲基汞在不引起可观察到母体毒性剂量下,就可产生胚胎毒性,影响仔鼠神经系统的发育,导致神经行为功能的改变.     

mPEG-PLGA-mPEG系列纳米粒的毒性与其结构的关系

目的 研究丙交酯/乙交酯/聚乙二醇(LA/GA/PEG)共聚物(mPEG-PLGA-mPEG)系列材料所制备的空白纳米粒的细胞毒性,并考察毒性与材料结构的关系.方法 采用MTT法测定与空白纳米粒培养48 h后的正常人肝细胞Chang的细胞存活率,采用Origin软件分析mPEG-PLGA-mPEG材料中的PEG分子量,并考察PEG的含量和LA/GA比例对毒性的交互作用.结果 PEG的分子量和含量对纳米粒的毒性影响较明显,LA/GA比例对其影响较小.结论 控制合成mPEG-PLGA-mPEG的材料中所使用PEG的分子量和含量,可降低mPEG-PLGA-mPEG所制备纳米粒的毒性.     

3种乌头类中药在大鼠体内外的神经毒性

目的 考察几种常见乌头类中药的神经毒性.方法 采用体内、外给药的方法,大鼠连续90 d经口给予生川乌和生草乌,检测其对大鼠神经行为、血液、血液生化及脑组织的影响;采用大鼠胚胎海马神经元体外培养的方法,研究生川乌、生草乌和生附子对神经细胞的体外毒性.结果 经口给予生川乌和生草乌后,大鼠的神经行为、血液与血液生化指标无变化,脑组织检查未见异常;体外试验结果表明,生川乌、生草乌及生附子对大鼠海马神经元具有一定毒性,呈剂量效应关系,毒性强度为生草乌＞生川乌＞生附子.结论 乌头类中药在大鼠整体动物试验中未见神经毒性作用,但在海马神经元体外培养模型中,表现出神经毒性,这可能与血脑屏障及体内代谢有关.     

丙戊酸钠抗抑郁作用涉及改善氧化应激平衡和提升脑源性神经营养因子表达

目的:探讨丙戊酸钠减轻慢性不可预见刺激(CUS)致大鼠抑郁行为是否与改善机体氧化应激功能及脑源性神经营养因子(BDNF)表达有关.方法:雄性SD大鼠60只,随机分为对照组(CG),模型组(MG),丙戊酸钠灌胃正常组(VAPC)和丙戊酸钠灌胃模型组(VAPM).以开场试验和强迫游泳试验评价大鼠焦虑抑郁行为;采用常规生物化学方法测定大脑皮质丙二醛(MDA)含量及超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活力;荧光定量PCR和Western blot检测海马脑源性神经营养因子(BDNF) mRNA和蛋白表达.结果:与CG组相比,MG组大鼠开场试验水平得分和垂直得分明显降低,强迫游泳试验不动时间显著延长,MDA含量升高,SOD及CAT活力明显下降,海马BDNF mRNA和蛋白表达均明显降低.给予丙戊酸钠可明显阻遏上述变化,但对正常大鼠无明显影响.结论:CUS致大鼠焦虑抑郁行为与体内氧化及抗氧化失衡,海马BDNF表达减少有关;丙戊酸钠能阻遏这种变化,从而显示减轻CUS所致大鼠焦虑抑郁行为作用.     

药物代谢酶遗传多态性对药物神经毒性的影响

神经毒性是药物常见的毒性反应之一。神经系统对药物引起的损害尤其敏感,药物引起神经系统结构和功能的微小改变即可表现出严重的精神或行为异常,因此药物引起的神经毒性越来越得到人们的关注。药物引起的神经毒性存在个体差异,其中遗传因素对这种差异的产生发挥重要作用。药物代谢酶影响药物体内的生物转化过程,因此代谢酶的遗传多态性在一定程度上决定了不同个体对药物神经毒性的易感性。本篇综述将着重探讨药物代谢酶中的细胞色素P450酶、谷胱甘肽转移酶和N-乙酰转移酶遗传多态性对药物神经毒性易感性的影响。     

Estimation of safe dietary intake levels of acrylamide for humans

Acrylamide (AA), a human neurotoxicant and rat tumorigen, is produced in starchy foods when cooked. AA is also an industrial chemical used in polyacrylamide production. A safety evaluation of ingested AA by humans was conducted using a newly developed, state-of-the-art physiologically-based toxicokinetic (PBPK or PBTK) model to compare internal doses of AA and its metabolite glycidamide (GA) in humans and rats. Based on modes of action (MoA), a nonlinear dose–response approach was applied for neurotoxicity (non-genotoxicity) and carcinogenicity (mixed: genotoxicity and epigenetic MoA). Tolerable daily intake (TDI) for neurotoxicity from AA was estimated to be 40 μg/kg-day; TDIs for cancer were estimated to be 2.6 and 16 μg/kg-day based on AA or GA, respectively. Margins of exposure (MoE) were calculated for average AA consumers to be 300 and 500 based on AA and GA, respectively; for cancer, the MoE for average AA consumers was estimated to be 200 and 1200 based on AA and GA, respectively. For high consumers of AA, MoEs were somewhat less.     

Toxicokinetics of acrylamide and glycidamide in Fischer 344 rats

Acrylamide (AA) is a widely studied industrial chemical that is neurotoxic, mutagenic to somatic and germ cells, and carcinogenic in rodents. The recent discovery of AA at ppm levels in a wide variety of commonly consumed foods has energized research efforts worldwide to define toxic mechanisms, particularly toxicokinetics and bioavailability. This study compares the toxicokinetics of AA and its epoxide metabolite, glycidamide (GA), in serum and tissues of male and female F344 rats following acute exposure by intravenous, gavage, and dietary routes at 0.1 mg/kg AA or intravenous and gavage routes with an equimolar amount of GA. AA was rapidly absorbed after oral dosing, was widely distributed to tissues, was efficiently converted to GA, and produced increased levels of GA-DNA adducts in liver. GA was also rapidly absorbed, widely distributed to tissues, and produced increased liver DNA adduct levels. AA bioavailability after aqueous gavage was 60--98% and from the diet was 32--44%; however, first-pass metabolism or other kinetic change resulted in much higher internal exposures to GA (2- to 7-fold) when compared to the intravenous route. A similar effect on metabolism to GA following oral administration was previously observed under an identical exposure paradigm in mice. Furthermore, DNA adduct formation in rat liver showed the same proportionality with the respective GA AUC value as did mice in the previous study. These findings suggest that as the AA content in food is reduced, species-differences in GA formation and subsequent DNA adduct formation may be minimized. These findings provide additional information needed to assess genotoxic risks from the low levels of AA that are pervasive in the food supply.     

DNA adduct formation from acrylamide via conversion to glycidamide in adult and neonatal mice

Acrylamide (AA) is a high production volume chemical with many industrial uses; however, recent findings of ppm levels in starchy foods cooked at high temperature have refocused worldwide attention on the neurotoxicity, germ cell mutagenicity, and carcinogenicity of AA. Oxidative metabolism of AA to its epoxide metabolite, glycidamide (GA), has been observed in experimental animals and humans and may be associated with many of the toxic effects of AA exposure, including formation of N7-(2-carbamoyl-2-hydroxyethyl)guanine (N7-GA-Gua) in vivo. This paper describes the characterization of two new GA-derived DNA adducts formed in vitro, N3-(2-carbamoyl-2-hydroxyethyl)adenine (N3-GA-Ade) and N1-(2-carboxy-2-hydroxyethyl)-2'-deoxyadenosine. A sensitive method for quantification of N7-GA-Gua and N3-GA-Ade, based on LC with tandem mass spectrometry and isotope dilution, was developed and validated for use in measuring DNA adduct formation in selected tissues of adult and whole body DNA of 3 day old neonatal mice treated with AA and GA. In adult mice, DNA adduct formation was observed in liver, lung, and kidney with levels of N7-GA-Gua around 2000 adducts/10(8) nucleotides and N3-GA-Ade around 20 adducts/10(8) nucleotides. Adduct levels were modestly higher in adult mice dosed with GA as opposed to AA; however, treatment of neonatal mice with GA produced 5-7-fold higher whole body DNA adduct levels than with AA, presumably reflective of lower oxidative enzyme activity in newborn mice. DNA adduct formation from AA treatment in adult mice showed a supralinear dose-response relationship, consistent with saturation of oxidative metabolism at higher doses. These results increase our understanding of the mutagenic potential of GA and provide further evidence for a genotoxic mechanism in AA carcinogenesis.     

Relationships between biomarkers of exposure and toxicokinetics in Fischer 344 rats and B6C3F1 mice administered single doses of acrylamide and glycidamide and multiple doses of acrylamide

Acrylamide (AA) is a widely studied industrial chemical that is neurotoxic, mutagenic to somatic and germ cells and carcinogenic in rodents. AA is also formed in many commonly consumed starchy foods during cooking. Our previous toxicokinetic investigations of AA and its important genotoxic metabolite, glycidamide (GA), in rodents showed that AA is highly bioavailable from oral routes of administration, is widely distributed to tissues and that the dietary route, in particular, favors metabolism to GA. Measurements of DNA adducts in many tissues supported the hypothesis that AA is carcinogenic in rodent bioassays through metabolism to GA. The current investigation describes the development and validation of methodology for measuring hemoglobin (Hb) adducts with AA and GA in the same rodents previously used for toxicokinetic and DNA adduct measurements. The goal was to investigate possible relationships between these circulating biomarkers of exposure and serum toxicokinetic parameters for AA and GA and tissue GA-DNA adducts in rodents from both single and repeated dosing with AA. Significant correlations were observed between GA-Hb and liver GA-DNA adducts for either single or multiple dosing regimens with AA. Using available GA-Hb adduct data, empirical and allometric relationships permitted estimation of liver DNA adducts in humans in the range of 0.06-0.3 adducts/10(8) nucleotides. This approach may prove useful in extrapolating human cancer risks from findings in rodent bioassays.     

Metabolism and metabolic inhibition of gambogic acid in rat liver microsomes

AIM: To study the metabolism of gambogic acid (GA) and the effects of selective cytochrome P-450 (CYP450) inhibitors on the metabolism of GA in rat liver microsomes in vitro. METHODS: Rat liver microsomes were used to perform metabolism studies. Various selective CYP450 inhibitors were used to investigate their effects on the metabolism of GA and the principal CYP450 isoform involved in the formation of major metabolite M(1) in rat liver microsomes. Types of inhibition in an enzyme kinetics model were used to model the interaction. RESULTS: GA was rapidly metabolized to two phase I metabolites, M(1) and M(2), in rat liver microsomes. M(1) and M(2) were tentatively presumed to be the hydration metabolite and epoxide metabolite of GA, respectively. alpha-Naphthoflavone uncompetitively inhibited the formation of M(1) while ketoconazole, sulfaphenazole, diethyl dithiocarbamate and quinidine had little or no inhibitory effects on the formation of M(1). CONCLUSION: GA is rapidly metabolized in rat liver microsomes and M(1) is crucial for the elimination of GA. Cytochrome P-450 1A2 is the major rat CYP involved in the metabolism of GA.     

Urinary excretion of acrylamide and metabolites in Fischer 344 rats and B6C3F(1) mice administered a single dose of acrylamide

Acrylamide (AA) is a widely studied industrial chemical that is neurotoxic, mutagenic to somatic and germ cells, and carcinogenic in mice and rats. AA is also formed during cooking in many commonly consumed starchy foods. Our previous toxicokinetic investigations of AA and its genotoxic metabolite, glycidamide (GA), in rodents showed that AA is highly bioavailable from oral routes of administration, is widely distributed to tissues, and that the dietary route, in particular, favors metabolism to GA. Formation and accumulation of mutagenic GA-DNA adducts in many tissues support the hypothesis that AA is carcinogenic in rodent bioassays through metabolism to GA. The current investigation describes the quantification of 24 h urinary metabolites, including free AA and GA and their mercapturic acid conjugates (AAMA and GAMA, respectively), using LC/MS/MS in F344 rats and B6C3F(1) mice following a dose of 0.1 mg/kg bw given by intravenous, gavage, and dietary routes of administration. Similar groups of rodents were used previously for serum/tissue toxicokinetic and adduct determinations (DNA and hemoglobin). The goal was to investigate relationships between urinary and circulating biomarkers of exposure, toxicokinetic parameters for AA and GA, and tissue GA-DNA adducts in rodents from single doses of AA. Significant linear correlations were observed between urinary levels of AA with AAMA and GA with GAMA in the current data sets for rats and mice. Concentrations of AA and AAMA correlated significantly with average AUC values determined previously for AA in groups of rats and mice similarly dosed with AA. Urinary GA and GAMA concentrations showed significant correlations with average AUC values for GA and liver GA-DNA adducts determined previously in rats and mice similarly dosed with AA. Despite statistical significance, considerable inter-animal variability was observed in all urinary measurements, which limited the degree of correlation with either average toxicokinetic or biomarker data collected from different groups of animals. These results suggest that urinary measurements of AA and its metabolites may be useful for prediction of internal exposures to AA and GA.     

Cytogenetic damage induced by acrylamide and glycidamide in mammalian cells: correlation with specific glycidamide-DNA adducts.

Acrylamide (AA) is a suspected human carcinogen generated in carbohydrate-rich foodstuffs upon heating. Glycidamide (GA), formed via epoxidation, presumably mediated by cytochrome P450 2E1, is thought to be the active metabolite playing a central role in AA genotoxicity. In this work we investigated DNA damage induced by AA and GA in mammalian cells, using V79 Chinese hamster cells. For this purpose, we evaluated two cytogenetic end points, chromosomal aberrations (CAs) and sister chromatid exchanges (SCEs), as well as the levels of specific GA-DNA adducts, namely, N7-(2-carbamoyl-2-hydroxyethyl)guanine (N7-GA-Gua) and N3-(2-carbamoyl-2-hydroxyethyl)adenine (N3-GA-Ade) using high-performance liquid chromatography coupled with tandem mass spectrometry. GA was more cytotoxic and clastogenic than AA. Both AA and GA induced CAs (breaks and gaps) and decreased the mitotic index. GA induced SCEs in a dose-responsive manner; with AA, SCEs were increased at only the highest dose tested (2mM). A linear dose-response relationship was observed between the GA concentration and the levels of N7-GA-Gua. This adduct was detected for concentrations as low as 1 microM GA. N3-GA-Ade was also detected, but only at very high GA concentrations (>or= 250 microM). There was a very strong correlation between the levels of N7-GA-Gua in the GA- and AA-treated cells and the extent of SCE induction. Such correlation was not apparent for CAs. These data suggest that the induction of SCEs by AA is associated with the metabolism of AA to GA and subsequent formation of depurinating DNA adducts; however, other mechanisms must be involved in the induction of CAs.     

纳米材料的神经毒性作用机制及评价方法

近年来,纳米材料在多种生物医学领域被广泛应用,其生物安全性也受到越来越多的关注。多种纳米材料可穿透血脑屏障进入中枢神经系统,产生神经毒性。本文讨论了纳米材料进入中枢神经系统的方式及因素;纳米材料的特异性以及非特异性的中枢神经毒性效应、外周神经毒性及其作用机制;并论述了国内外用于体内神经毒性、体外神经细胞培养模型的神经毒性以及替代的评价方法,为纳米材料的安全性评价及神经毒性探究提供参考。     

The metabolism of 5-(4-acetamidophenyl)pyrazin-2(1H)-one in rat, dog and cynomolgus monkey

1. The metabolism and disposition of 14C-acetamidophenyl pyrazinone has been studied in rat, dog and cynomolgus monkey. The compound was well absorbed and rapidly excreted in urine and faeces by all three species. 2. Distribution of 14C-pyrazinone was rapid and extensive with the exception of the central nervous system where concentrations were at, or below, the limit of detection. 3. Whereas, in in vitro studies, metabolites (but not the parent compound) weakly inhibited some activities of the cytochrome P-450 system, there was evidence from in vivo studies in the rat that the compound and/or its metabolite(s) are weak selective inducers of cytochrome P-450. 4. Metabolite patterns were similar in all three species. The major route of metabolism was glucuronidation at the oxygen of the pyrazinone ring. Other metabolites originated from metabolism by gut microflora with subsequent hepatic metabolism.