犬尿氨酸代谢通路在抑郁症中的研究进展

犬尿氨酸代谢通路(KP)是色氨酸代谢的主要途径.越来越多的研究表明,色氨酸经KP代谢产生的一系列活性物质与抑郁症的发生、发展密切相关.有研究表示,抑郁症患者炎症因子水平的升高与KP代谢密切相关,如导致神经毒性产物QUIN增高、保护产物KYNA降低.文章主要对KP、代谢产物及其参与抑郁症的发病与治疗等相关问题进行综述.     

β-肾上腺素受体拮抗剂的多形性氧化物及其临床药动学

许多药物的药理作用以及毒性反应均与其在体内的氧化代谢产物有关。作者通过大量文献资料,对β-肾上腺素受体拮抗药物的氧化代谢产物及其对药效的影响进行了探讨。有些异喹胍类药物的反应有较广泛的易变性,可能就是由于其氧化代谢产物的多形性,而多数β-阻断剂能广泛地发生氧化,如     

氟喹诺酮类药物的神经毒性及其防治进展

［摘要］氟喹诺酮类药物不良反应中有关神经毒性反应的报道日渐增多,同类中不同品种产生神经毒性具有明显的差异。氟喹诺酮类神经毒性症状在药物毒性反应中可表现出其自身独有的特点,产生神经毒性与多种风险因素有关,使用前应充分了解其可能发生的各种反应的防治原则与方法,争取最佳疗效,预防和减少神经毒性不良反应的发生。     

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.     

利福平致肝脏毒性的代谢组学特征研究*

目的:研究大鼠灌胃抗结核病药物利福平后其尿液的代谢表型改变及其与组织病理学和血浆生化指标的相关性,寻找可能的毒性标志物,探讨代谢组学在药物毒理学研究中的应用。方法:Wistar大鼠灌胃给予利福平0,25,50和100mg·kg-1,qd,连续14d。收集最后一次给药后的24h尿样,测定1H-NMR谱,并进行血浆生化指标测定和肝脏组织病理学检查。结果:常规毒性评价方法发现大鼠在高剂量表现出轻度肝毒性;给药组尿样1H-NMR谱中葡萄糖和牛磺酸明显增加,2-酮戊二酸和枸橼酸明显降低。各组动物在不同剂量下的代谢谱变化与肝脏病理和血浆生化改变相一致,并且其敏感性优于常规毒理学检测指标。结论:大鼠尿液1H-NMR代谢产物谱与利福平毒性作用强度密切相关,利福平引起的肝毒性与三羧酸循环能量代谢和糖代谢有关。代谢组学分析在毒理学研究中有着广泛的应用前景。     

局麻药脊髓神经毒性的研究进展及预防

随着人们对局麻药毒副作用的逐渐认识,局麻药的神经毒性也越来越受到重视.但局麻药的脊髓神经毒性机理仍有待于阐明,可能与局麻药自身毒性有关,也可能与之诱导的神经细胞凋亡有关.局麻药神经毒性在很大程度上与其浓度、剂量及与神经细胞接触时间相关.本文就局麻药脊髓神经毒性发生机制及预防的研究进展做一综述.     

药物代谢产物安全性评价策略

药物代谢产物存在质和／或量的种属差异，现综述药物代谢产物安全性评价的重要性及评价策略和评价项目。当发现代谢产物是人特有或人体主要代谢产物高于给药剂量或全身暴露量（二者中的较低者）的10％，特别是这些物质比毒性试验动物体内水平高时更应关注其安全性，必须及早确证这些代谢产物，并进行一般毒性试验、遗传毒性试验、胚胎一胎仔发育试验和致癌试验等。     

丙烯酰胺及其代谢产物神经毒理的研究

本文利用神经行为、生理、病理、生化和代谢方法,研究了丙烯酰胺(AA)及其代谢物环氧丙酰胺(GA)对中枢及外周神经系统的损害在中毒不同阶段中的变化规律及剂量-反应关系,并试图阐明其可能的分子机理。AA和GA染毒可引起大鼠行为功能受损。AA是蓄积性神经毒,可引起中枢和周围神经系统的远端轴突病。GA的神经毒性略低于AA。AA所影响神经系统的糖代谢,其神经毒性可归因于影响能量代谢和细胞内Ca~(2+)稳态。乙酰半胱氨酸-S-丙酰胺(CSP)是大鼠尿中AA的主要代谢物,并可能作为AA接触工人的生物监测指标。     

化合物结构与代谢激活的毒性分析

药物开发的不同阶段，人们通过系列的体外试验研究、动物实验以及随后人体应用的结果试图揭示药物的毒副作用，目的是为确保人体用药的安全性。其中代谢转化诱导的毒性占据药物毒性的很大一方面，尤其反应性代谢产物引发的毒性近几年越来越引起重视。本文综述了几类代表性化合物结构产生反应性代谢产物的情况，包括苯醌亚胺、噻吩环、氮翁离子、环氧化物、硫脲等，试图从代谢角度揭示药物分子结构与药物毒性之间的关系，为药物的设计与开发提供参考。     

小分子药物开发中的药物代谢及代谢产物安全性评价

药物代谢是小分子药物开发过程中的一项重要研究内容,在药物开发的不同阶段,需开展一系列体外和体内试验阐明其在人体和动物中的代谢特征。种属间的代谢差异,可能导致人体和动物中的代谢产物存在明显不同,某些代谢产物可能仅在人体中出现,或者在人体中的暴露量远高于标准毒理学试验中所用动物种属的暴露水平,标准毒理学试验可能无法充分识别这些临床相关代谢产物的安全性风险。因此,在非临床试验中可能需要对可能导致安全性担忧的代谢产物进行安全性评估。结合工作实践和国内外相关技术指南,本文初步探讨了小分子药物开发过程中代谢产物的研究策略,界定了何种代谢产物可能会导致安全性担忧,何时以及如何鉴定这些可能引起安全性担忧的代谢产物,并就如何进行代谢产物非临床安全性评价提供了建议,以期为研究者和监管机构提供参考。     

Effects of acrylamide on rodent reproductive performance

Acrylamide monomer causes peripheral neurotoxicity, mutagenicity, clastogenicity, male reproductive toxicity, prenatal lethality, and endocrine-related tumors in rodents. Acrylamide (and/or its metabolite glycidamide) binds to dopamine receptors and spermatid protamines and inhibits activity of kinesin and dyneine, resulting in interference with neuronal intracellular transport and sperm motility. Glycidamide binds to various proteins and DNA. Acrylamide at low doses decreases litter size, with rats more sensitive than mice. At higher doses, sperm morphology and motility and neurotoxicity are affected, which decreases mating frequency. Acrylamide does not affect female reproduction (females exhibit neurotoxicity). Dominant lethal mutations cause decreased newborn litter size. The mechanisms of action appear to be: (1) acrylamide/glycidamide binding to spermatid protamines, causing dominant lethality and effects on sperm morphology; and (2) acrylamide binding to motor proteins, causing distal axonopathy, including hindlimb weakness/paresis, and effects on mounting, sperm motility, and intromission. Glycidamide-induced mutations appear to play no role in reproductive or neurologic toxicity.     

Formation of hemoglobin adducts of acrylamide and its epoxide metabolite glycidamide in the rat

A method was developed for the determination of hemoglobin (Hb) adducts formed by the neurotoxic agent acrylamide and its mutagenic epoxide metabolite glycidamide. The method was based on simultaneous measurements of the cysteine adducts formed by these two agents by means of gas chromatography/mass spectrometry in hydrolyzed hemoglobin samples. Rats were injected ip with acrylamide or glycidamide in doses ranging from 0 to 100 mg/kg body wt, and the hemoglobin adduct levels were determined. The hemoglobin binding index of acrylamide to cysteine was found to be 6400 pmol (g Hb)-1/mumol (kg body wt)-1, higher than for any other substance studied so far in the rat, and 1820 pmol (g Hb)-1/mumol (kg body wt)-1 for glycidamide. In rats injected with acrylamide, formation of adducts of the parent compound was approximately linear with dose (0-100 mg/kg), whereas adducts of the epoxide metabolite glycidamide generated a concave curve, presumably reflecting the Michaelis-Menten kinetics of its formation. On the basis of the rate constants for cysteine adduct formation determined in vitro, the first-order rates of elimination of acrylamide and glycidamide from the blood compartment of rats were estimated to be 0.37 and 0.48 hr-1, respectively, using a linear kinetic model. It was further estimated that the percentage of acrylamide converted to glycidamide in the rat decreased from 51% following administration of 5 mg/kg to 13% after a dose of 100 mg/kg. Subchronic treatment of rats with acrylamide (10 mg/kg/day for 10 days or 3.3 mg/kg/day for 30 days) confirmed that the conversion rate of acrylamide to glycidamide, as determined from hemoglobin adduct formation, is higher at low-administered doses. These findings suggest that dose-rate effects may significantly affect risk estimates of this compound and that different low-dose extrapolation procedures should be employed for effects induced by the parent compound acrylamide and those induced by the metabolite glycidamide.     

Acrylamide is metabolized to glycidamide in the rat: evidence from hemoglobin adduct formation

Acrylamide is an important industrial chemical which is neurotoxic to experimental animals as well as humans and recently has been shown to be mutagenic and carcinogenic. Despite much research it is still unclear whether the parent compound or a metabolite is responsible for the observed toxic effects. Contradictory results as to the role of cytochrome P-450 mediated metabolism of acrylamide in the induction of neurotoxic effects prompted us to investigate the possible formation of glycidamide, a reactive epoxide metabolite. The formation of this epoxide was strongly indicated by the identification by means of gas chromatography-mass spectrometry of derivatized S-(2-carboxy-2-hydroxyethyl)cysteine in hydrolyzed hemoglobin samples from rats treated with acrylamide in vivo and in microsomal suspensions of acrylamide with cysteine in vitro. This amino acid was found to be present in uninduced and phenobarbital-induced Sprague-Dawley rats and absent in controls, but occurred in lower amounts than the adduct derived from the parent compound, S-(2-carboxyethyl)cysteine. This finding suggests that the possible role of glycidamide in the neurotoxicity and carcinogenicity of acrylamide should be evaluated further.     

Transplacental transfer of acrylamide and glycidamide are comparable to that of antipyrine in perfused human placenta

Most drugs can penetrate the placenta but there are only a few studies on placental transfer of environmental toxic compounds. In this study, we used dual recirculating human placental perfusion to determine the transfer rate through the placenta of a neurotoxic and carcinogenic compound found in food, acrylamide and its genotoxic metabolite glycidamide. Putative acrylamide metabolism into glycidamide during the 4-h perfusions and acrylamide-derived DNA adducts in placental DNA after perfusions were also analyzed. Placentas were collected immediately after delivery and kept physiologically functional as confirmed by antipyrine kinetics, glucose consumption and leak from fetal to maternal circulation. Acrylamide (5 or 10 microg/ml) or glycidamide (5 microg/ml), both with antipyrine (100 microg/ml), was added to maternal circulation. Acrylamide and glycidamide were analyzed in the perfusion medium by liquid chromatography/mass spectrometry. Acrylamide and glycidamide crossed the placenta from maternal to fetal circulation with similar kinetics to antipyrine, suggesting fetal exposure if the mother is exposed. The concentrations in maternal and fetal circulations equilibrated within 2h for both studied compounds and with both concentrations. Acrylamide metabolism into glycidamide was not detected during the 4-h perfusions. Moreover, DNA adducts were undetectable in the placentas after perfusions. However, fetuses may be exposed to glycidamide after maternal metabolism. Although not found in placental tissue after 4h of perfusion, it is possible that glycidamide adducts are formed in fetal DNA.     

Approaches to acrylamide physiologically based toxicokinetic modeling for exploring child-adult dosimetry differences

Dietary exposure to acrylamide is common as a result of its formation during the cooking of carbohydrate foods. This leads to widespread human exposure in adults and children alike. Acrylamide is neurotoxic and is metabolized by cytochrome P-450 (CYP) 2E1 to a mutagenic epoxide, glycidamide. This article describes a modeling framework for assessing acrylamide and glycidamide dosimetry in rats and human adults and children. The challenges in building a physiologically based toxicokinetic (PBTK) model that is compatible with existing rat and human data are described, with an emphasis on calibration against the hemoglobin adduct database. This exploratory PBTK model was adapted to children by incorporating life-stage-specific parameters consistent with children's changing physiology and metabolic capacity for processes involved in acrylamide disposition in terms of CYP2E1, glutathione conjugation, and epoxide hydrolase. Monte Carlo analysis was used to simulate the distribution of internal doses to gain an initial understanding of the range of child/adult differences possible. This analysis suggests modest dosimetry differences between children and adults, with area-under-the-curve (AUC) doses for the 99th percentile child up to fivefold greater than the median adult for both acrylamide and glycidamide. Early life immaturities tended to exert a greater effect on acrylamide than glycidamide dosimetry because immaturities in CYP2E1 and glutathione counteract one another for glycidamide AUC, but both lead to greater acrylamide dose. The analysis points toward glutathione conjugation parameters as being particularly influential and uncertain in early life, making this a key area for future research.     

An absorption study of dietary administered acrylamide in swine.

Acrylamide is a food toxicant suspected to be carcinogenic to humans. It is formed in the heat processing of carbohydrate-rich food. A current issue in food safety is whether acrylamide actually represents a risk for human health. At present, available information is insufficient to reach any conclusions. Inter alias, a still unclear matter is the fraction of acrylamide ingested by food that is absorbed and metabolized. This study compared the in vivo relative absorption of acrylamide formed in cooked food with that of the pure compound dissolved in drinking water using the pig (25 Italian Large White females) as the animal model. Acrylamide intakes of about 0.8 and 8 microg kg(-1) pig body wt day(-1) equal to one and ten times, respectively, the maximum average acrylamide daily intake for humans from the diet (expressed on a body wt basis) in industrialized countries, were chosen for the study. Adducts with the N-terminal valine of haemoglobin formed by acrylamide and its epoxide metabolite glycidamide, were used as exposure markers. Analyses were carried out by gas chromatography/mass spectrometry following in-house method validation. Both for the low and the high dose regimen, the glycidamide adduct levels in swine globins were lower of the limit of quantification of the method. As concerns acrylamide adducts, it was found that the relative absorption of acrylamide from feed and water was the same and that there is a direct proportionality between the adduct concentration and acrylamide intake.     

Carcinogenicity of glycidamide in B6C3F1 mice and F344/N rats from a two-year drinking water exposure

Acrylamide is a contaminant in baked and fried starchy foods, roasted coffee, and cigarette smoke. Previously we reported that acrylamide is a multi-organ carcinogen in B6C3F₁ mice and F344/N rats, and hypothesized that acrylamide is activated to an ultimate carcinogen through metabolism to the epoxide glycidamide. We have now examined the carcinogenic effects of glycidamide administered at 0, 0.0875, 0.175, 0.35 and 0.70 mM in drinking water to the same strains of rodents for two years. In male and female mice, there were significant increases in tumors of the Harderian gland, lung, forestomach, and skin. Female mice also had an increased incidence of tumors of the mammary gland and ovary. In male and female rats, there were significant increases in thyroid gland and oral cavity neoplasms and mononuclear cell leukemia. Male rats also had increases in tumors of the epididymis/testes and heart, while female rats demonstrated increases in tumors of the mammary gland, clitoral gland, and forestomach. A similar spectrum of tumors was obtained in mice and rats administered acrylamide. These data indicate that, under the conditions of these bioassays, acrylamide is efficiently metabolized to glycidamide and that the carcinogenic activity of acrylamide is due to its conversion into glycidamide.     

Analysis of hemoglobin adducts from acrylamide, glycidamide, and ethylene oxide in paired mother/cord blood samples from Denmark

The knowledge about fetal exposure to acrylamide/glycidamide from the maternal exposure through food is limited. Acrylamide, glycidamide, and ethylene oxide are electrophiles and form adducts with hemoglobin (Hb), which could be used for in vivo dose measurement. In this study, a method for analysis of Hb adducts by liquid chromatography-mass spectrometry, the adduct FIRE procedure, was applied to measurements of adducts from these compounds in maternal blood samples (n = 87) and umbilical cord blood samples (n = 219). The adduct levels from the three compounds, acrylamide, glycidamide, and ethylene oxide, were increased in tobacco smokers. Highly significant correlations were found between cord and maternal blood with regard to measured adduct levels of the three compounds. The mean cord/maternal hemoglobin adduct level ratios were 0.48 (range 0.27-0.86) for acrylamide, 0.38 (range 0.20-0.73) for glycidamide, and 0.43 (range 0.17-1.34) for ethylene oxide. In vitro studies with acrylamide and glycidamide showed a lower (0.38-0.48) rate of adduct formation with Hb in cord blood than with Hb in maternal blood, which is compatible with the structural differences in fetal and adult Hb. Together, these results indicate a similar life span of fetal and maternal erythrocytes. The results showed that the in vivo dose in fetal and maternal blood is about the same and that the placenta gives negligible protection of the fetus to exposure from the investigated compounds. A trend of higher levels of the measured adducts in cord blood with gestational age was observed, which may reflect the gestational age-related change of the cord blood Hb composition toward a higher content of adult Hb. The results suggest that the Hb adduct levels measured in cord blood reflect the exposure to the fetus during the third trimester. The evaluation of the new analytical method showed that it is suitable for monitoring of background exposures of the investigated electrophilic compounds in large population studies.     

Alcohol influence on acrylamide to glycidamide metabolism assessed with hemoglobin-adducts and questionnaire data

Our purpose was to investigate whether alcohol (ethanol) consumption could have an influence on the metabolism of acrylamide to glycidamide in humans exposed to acrylamide through food. We studied a subsample from a population-based case–control study of prostate cancer in Sweden (CAPS). Questionnaire data for alcohol intake estimates was compared to the ratio of hemoglobin-adduct levels for acrylamide and glycidamide, used as a measure of individual differences in metabolism. Data from 161 non-smoking men were processed with regard to the influence of alcohol on the metabolism of acrylamide to glycidamide. A negative, linear trend of glycidamide-adduct to acrylamide-adduct-level ratios with increasing alcohol intake was observed and the strongest association (p-value for trend = 0.02) was obtained in the group of men with the lowest adduct levels (?47 pmol/g globin) when alcohol intake was stratified by acrylamide-adduct levels. The observed trend is likely due to a competitive effect between ethanol and acrylamide as both are substrates for cytochrome P450 2E1. Our results, strongly indicating that ethanol influence metabolism of acrylamide to glycidamide, partly explain earlier observations of only low to moderate associations between questionnaire data on dietary acrylamide intake and hemoglobin-adduct levels.     

Acrylamide and its metabolite induce neurotoxicity via modulation of protein kinase C and AMP-activated protein kinase pathways

Acrylamide is known as a neurotoxicant found in commonly consumed food as well as in human body. However, the underlying mechanisms involved in neurotoxicity by acrylamide and its metabolite, glycidamide remain largely unknown. In this study, we have examined the interplay between CYP2E1, AMPK, ERK and PKC in acrylamide-induced neurotoxicity associated with autophagy in PC12 cells. Acrylamide-induced cell death was mediated by CYP2E1 expression and the activation of ERK, PKC-ɑ and PKC-δ, whereas AMPK knockdown exacerbated the acrylamide-induced neurotoxic effects. PKC-ɑ, but not PKC-δ, plays an upstream regulator of ERK and AMPK. Moreover, AMPK activation suppressed ERK, and CYP2E1 and AMPK bilaterally inhibit each other. Furthermore, acrylamide increased autophagy with impaired autophagic flux, evidenced by the increased beclin-1, LC3-II and p62 protein. Acrylamide-induced neuronal death was ameliorated by 3-methyladenine, an autophagy inhibitor, whereas neuronal death was exacerbated by chloroquine, a lysosomal inhibitor. Interestingly, PKC-δ siRNA, but not PKC-ɑ siRNA, dramatically reduced acrylamide-induced beclin-1 and LC3-II levels, whereas AMPK siRNA further increased beclin-1, LC3-II and p62 protein levels. Glycidamide, a major metabolite, mimicked acrylamide only with a higher potency. Taken together, acrylamide- and glycidamide-induced neurotoxicity may involve cytotoxic autophagy, which is mediated by interplay between PKCs and AMPK pathways.