Metabolism and related human risk factors for hepatic damage by usnic acid containing nutritional supplements

Usnic acid is a component of nutritional supplements promoted for weight loss that have been associated with liver-related adverse events including mild hepatic toxicity, chemical hepatitis, and liver failure requiring transplant. To determine if metabolism factors might have had a role in defining individual susceptibility to hepatotoxicity, in vitro metabolism studies were undertaken using human plasma, hepatocytes, and liver subcellular fractions. Usnic acid was metabolized to form three monohydroxylated metabolites and two regio-isomeric glucuronide conjugates of the parent drug. Oxidative metabolism was mainly by cytochrome P450 (CYP) 1A2 and glucuronidation was carried out by uridine diphosphate-glucuronosyltransferase (UGT) 1A1 and UGT1A3. In human hepatocytes, usnic acid at 20 µM was not an inducer of CYP1A2, CYP2B6, or CYP3A4 relative to positive controls omeprazole, phenobarbital, and rifampicin, respectively. Usnic acid was a relatively weak inhibitor of CYP2D6 and a potent inhibitor of CYP2C19 (the concentration eliciting 50% inhibition (IC₅₀)?=?9 nM) and CYP2C9 (IC₅₀?=?94 nM), with less potent inhibition of CYP2C8 (IC₅₀?=?1.9 µM) and CYP2C18 (IC₅₀?=?6.3 µM). Pre-incubation of microsomes with usnic acid did not afford any evidence of time-dependent inhibition of CYP2C19, although evidence of slight time-dependent inhibition of CYP2C9 (K_I?=?2.79 µM and K_inact?=?0.022 min^?1) was obtained. In vitro data were used with SimCYP^Rto model potential drug interactions. Based on usnic acid doses in case reports of 450 mg to >1 g day^?1, these in vitro data indicate that usnic acid has significant potential to interact with other medications. Individual characteristics such as CYP1A induction status, co-administration of CYP1A2 inhibitors, UGT1A1 polymorphisms, and related hyperbilirubinaemias, or co-administration of low therapeutic index CYP2C substrates could work alone or in consort with other idiosyncrasy risk factors to increase the risk of adverse events and/or hepatotoxicity. Thus, usnic acid in nutritional supplements might be involved as both victim and/or perpetrator in clinically significant drug–drug interactions.     

肌肉减少症评价肝硬化患者营养状况及其影响因素

目的比较肌肉减少症与传统营养评价方法评估肝硬化患者营养状况,并进一步探讨肝硬化患者影响肌肉减少症发生的因素。方法收集2016年1月至2017年1月我科肝硬化患者资料,比较应用主观全面评价法(SGA)评分、传统营养指标及通过第3腰椎平面CT图像计算第3腰椎骨骼肌质量指数评估肝硬化患者的营养不良发生率。同时将52例肝硬化患者分为肌肉减少症组和非肌肉减少症组,分析2组间各营养指标有无差异,并进一步采用二分类Logistic回归分析法筛选影响肌肉减少症发生的危险因素。结果 52例肝硬化患者肌肉减少症的发生率为64%,2组患者年龄、性别、体质量指数(BMI)、血清白蛋白(ALB)、三头肌皮褶厚度(TSF)、上臂肌围(AMC)差异均有统计学意义(P<0.05)。二分类Logistic回归分析结果示:性别[OR=0.001,95%CI(0.000,0.223),P=0.011]、BMI[OR=0.312,95%CI(0.134,0.722),P=0.007]是肌肉减少症发生的主要危险因素。结论应用肌肉减少症可较客观地评估肝硬化患者的营养状况,且男性肝硬化患者,BMI越低,越容易发生肌肉减少症。     

Interactive toxicity of usnic acid and lipopolysaccharides in human liver HepG2 cells

Usnic acid (UA), a natural botanical product, is a constituent of some dietary supplements used for weight loss. It has been associated with clinical hepatotoxicity leading to liver failure in humans. The present study was undertaken to evaluate the interactive toxicity, if any, of UA with lipopolysaccarides (LPS), a potential contaminant of food, at low non‐toxic concentrations. The human hepatoblastoma HepG2 cells were treated with the vehicle control and test agents, separately and in a binary mixture, for 24 h at 37 ⁰C in 5% CO₂. After the treatment period, the cells were evaluated by the traditional biochemical endpoints of toxicity in combination with the toxicogenomic endpoints that included cytotoxicity, oxidative stress, mitochondrial injury and changes in pathway‐focused gene expression profiles. Compared with the controls, low non‐toxic concentrations of UA and LPS separately showed no effect on the cells as determined by the biochemical endpoints. However, the simultaneous mixed exposure of the cells to their binary mixture resulted in increased cytotoxicity, oxidative stress and mitochondrial injury. The pathway‐focused gene expression analysis resulted in the altered expression of several genes out of 84 genes examined. Most altered gene expressions induced by the binary mixture of UA and LPS were different from those induced by the individual constituents. The genes affected by the mixture were not modulated by either UA or LPS. The results of the present study suggest that the interactions of low nontoxic concentrations of UA and LPS produce toxicity in HepG2 cells. Published 2012. This article is a US Government work and is in the public domain in the USA.     

Metabolism of diazepam and related benzodiazepines by human liver microsomes.

The metabolism of diazepam has been studied in vitro using microsomal preparations from five human livers. An HPLC method was developed for the assay of diazepam, its congeners and its metabolites. Various methods for the incorporation of diazepam into the incubation medium were explored. It was shown that the use of organic solvents or small quantities of hydrochloric acid enhanced the solubility of this substrate. However all of the organic solvents tested were associated with substantial (around 50%) inhibition of metabolism of diazepam by both major pathways (N-demethylation and C3-hydroxylation). The use of hydrochloric acid gave satisfactory solubilization of diazepam, but not of pinazepam, prazepam or halazepam. Detailed metabolic studies were conducted only for diazepam, using neither hydrochloric acid nor organic solvents in the incubation medium. Formation of N-desmethyl-diazepam increased approximately linearly with diazepam concentration to 200 microM, and did not show saturation. Formation of temazepam gave a curved profile over the same range of diazepam concentrations, suggestive of a sigmoidal relationship. Michaelis-Menten parameters could not be determined for either reaction, but intrinsic clearances for N-demethylation varied over a 6-fold range. Diazepam N-demethylation was apparently promoted by the inclusion of temazepam in the incubation medium, while C3-hydroxylation of diazepam was enhanced in the presence of N-desmethyldiazepam. Mephenytoin in the incubation mixture had no effect on diazepam metabolism by either pathway. The present studies have defined some of the methodological problems inherent in in vitro metabolic studies with benzodiazepines, and have shed further light on the metabolism of diazepam in vitro by human liver.     

Metabolism of procainamide to a hydroxylamine by rat and human hepatic microsomes

We have previously demonstrated that procainamide is oxidized to a reactive metabolite. We speculated that this reactive metabolite might be a hydroxylamine and further that it might be responsible for the syndrome of procainamide-induced lupus. We now report that procainamide is metabolized to a hydroxylamine by rat and human hepatic microsomes. The extent of this metabolic oxidation was quantitated by HPLC after conversion of the hydroxylamine to the more stable nitro derivative of procainamide. Formation of the hydroxylamine required NADPH, active microsomes, and oxygen and was inhibited by carbon monoxide, SKF 525-A, and cimetidine. Formation of the hydroxylamine was also studied as a function of time, microsomal protein concentration, and procainamide concentration.     

Metabolism of Zaleplon by human hepatic microsomal cytochrome P450 isoforms

1. The metabolism of Zaleplon (CL-284,846; ZAL) has been studied in human liver microsomal preparations and in cDNA-expressed human cytochrome P450 (CYP) isoforms. 2. Human liver microsomes catalysed the NADPH-dependent N -deethylation of ZAL to DZAL (CL-284,859), but not to two other known in vivo metabolites, namely M1 (CL345,644) and M2 (CL-345,905). Sigmoidal kinetic plots were observed for ZAL deethylation indicating positive cooperativity. 3. The metabolism of ZAL to DZAL was determined in a characterized bank of 24 human liver microsomalpreparations.Good correlations (r² = 0.734-0.937) were observed with caffeine 8-hydroxylase, diazepam 3-hydroxylase, dextromethorphan N-demethylase and testosterone 2β-, 6β- and 15β-hydroxylase activities, which are allcatalysed by CYP3A isoforms. In contrast, poor correlations (r² 0.152-0.428) were observed for enzymatic markers for CYP1A2, CYP2A6, CYP2C9 10, CYP2D6, CYP2E1 and CYP4A9 11. 4. The metabolism of ZAL to DZAL in human liver microsomes was inhibited to 6-15% of control by 5-50 μM of the mechanism-based CYP3A inhibitor troleandomycin. Whereas some inhibition of DZAL formation was observed in the presence of 200 μM diethyldithiocarbamate, 5-50 μM furafylline, 2-20 μM sulphaphenazole, 50-500 μM S-mephenytoin and 1-10 μM quinidine had little effect. 5. Using human B-lymphoblastoid cell microsomes containing cDNA-expressed CYP isoforms, ZAL was metabolized to DZAL by CYP3A4, but not to any great extent by CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP2E1. 6. In contrast with ZAL, the NADPH-dependent N-deethylation of M2 to M1 proceeded at only a very low rate with both human liver microsomes and cDNA-expressed CYP3A4. 7. In summary, by correlation analysis, chemical inhibition studies and the use of cDNA-expressed CYPs, ZAL N -deethylation to DZAL in human liver appears to be catalysed by CYP3A isoforms.     

烧伤科住院患者营养风险筛查

目的 利用营养风险筛查(NRS)方法,评估烧伤科营养支持应用的合理性.调查人选患者营养支持使用情况.方法 应用NRS 2002对烧伤科住院患者进行营养风险评估.统计营养风险率、营养不良发生率、营养支持率、运动能力评分.结果 符合入选标准的住院患者92例,营养风险率58％(53/92)、营养不良率47％ (43/92);营养支持率23％ (21/92);给予营养支持患者平均生活质量评分改善为8.0分,无营养支持患者平均生活质量评分改善为3.8分.结论 利用NRS方法提示烧伤科住院患者的营养风险,给予营养支持的患者生活质量评分有所改善.     

Metabolism of tributyltin and triphenyltin by rat,hamster and human hepatic microsomes

Tributyltin and triphenyltin are metabolized by cytochrome P-450 system enzymes, and their metabolic fate may contribute to the toxicity of the chemicals. In the current study, the in vitro metabolism of tributyltin and triphenyltin by rat, hamster and human hepatic microsomes was investigated to elucidate the metabolic competence for these compounds in humans. The metabolic reaction using microsome-NADPH system that is usually conducted was not applicable to in vitro metabolism of organotins, especially triphenyltin. We therefore examined the effects of dithiothreitol (DTT), one of the antioxidants for sulfhydryl groups, to determine the in vitro metabolism of tributyltin and triphenyltin. As a result, the treatment with 0.1 mM DTT in vitro increased the activity of the microsomal monooxygenase system for metabolism of tributyltin as well as triphenyltin; the total yield of tributyltin and triphenyltin metabolites as tin increased, respectively, by approximately 1.8 and 8.9 times for rat, 2.1 and 1.2 times for hamster, and 1.6 and 1.5 times for human. It is suggested that the organotins directly inactivate cytochrome P-450 because of the interaction with critical sulfhydryl groups of the hemoprotein. We confirmed the utility of this in vitro metabolic system using DTT in the hepatic microsomes of phenobarbital (PB)-pretreated and untreated hamsters. Thus, the in vitro metabolic system described here was applied to a comparative study of the metabolism of organotins in rats, hamsters and humans. Tributyltin was metabolized more readily than triphenyltin in all the species. In humans, the in vitro metabolic pattern resembled that of hamsters, which were susceptible to in vivo triphenyltin toxicity because of incompetent metabolism. It is possible that the hamster is a qualitatively and quantitatively suitable animal model for exploring the influence of tributyltin and triphenyltin in humans.     

心血管疾病相关危险因素分析

目的探讨心血管疾病的相关危险因素。方法比较不同年龄段、不同BMI指数和不同生活习惯的人群中肥胖、高血压、高血糖和血脂异常的发生率。结果不同的年龄、BMI和生活习惯人群中心血管疾病的发生率,差异有统计学意义（P〈0.05）。结论重视健康的生活方式,注重饮食结构的调整,制定合理的运动计划,养成规律的作息习惯,可促进心血管疾病的防治。     

First detection of anatoxin-a in human and animal dietary supplements containing cyanobacteria

Anatoxin-a is a potent neurotoxin produced by several species of cyanobacteria. This alkaloid may cause fatal intoxication to exposed organisms and this has raised concerns over the increasing popularity of food supplements containing cyanobacteria. These are being marketed with alleged health properties for animal and human consumption. These supplements most commonly contain the genera Spirulina (Arthrospira) and Aphanizomenon and their consumption represent a potential route for anatoxin-a exposure in cases where adequate quality control is not undertaken. In this work, several dietary supplements containing cyanobacteria from different commercial suppliers were evaluated for the presence of anatoxin-a by high performance liquid chromatography with fluorescence detection. Additionally, the presence of the previously derivatized anatoxin-a was confirmed by using Gas chromatography–mass spectrometry. A total of 39 samples were analysed in the study. Results showed that three of the samples (7.7%) contained anatoxin-a, at concentrations ranging from 2.50 to 33 μg g⁻¹. Quality control of cyanobacterial food supplements is required to avoid potential health effects in humans and animals.     

Metabolism of 17alpha-hydroxyprogesterone caproate by hepatic and placental microsomes of human and baboons

Recent data from our laboratory revealed the formation of an unknown metabolite of 17 hydroxyprogesterone caproate (17-HPC), used for treatment of preterm deliveries, during its perfusion across the dually perfused human placental lobule. Previously, we demonstrated that the drug is not hydrolyzed, neither in vivo nor in vitro, to progesterone and caproate. Therefore, the hypothesis for this investigation is that 17-HPC is actively metabolized by human and baboon (Papio cynocephalus) hepatic and placental microsomes. Baboon hepatic and placental microsomes were investigated to validate the nonhuman primate as an animal model for drug use during pregnancy. Data presented here indicate that human and baboon hepatic microsomes formed several mono-, di-, and tri-hydroxylated derivatives of 17-HPC. However, microsomes of human and baboon placentas metabolized 17-HPC to its mono-hydroxylated derivatives only in quantities that were a fraction of those formed by their respective livers, except for two metabolites (M16' and M17') that are unique for placenta and contributed to 25% and 75% of the total metabolites formed by human and baboon, respectively. The amounts of metabolites formed, relative to each other, by human and baboon microsomes were different suggesting that the affinity of 17-HPC to CYP enzymes and their activity could be species-dependent.     

Metabolism of 7-benzyloxy-4-trifluoromethylcoumarin by human hepatic cytochrome P450 isoforms

1. The metabolism of 7-benzyloxy-4-trifluoromethylcoumarin (BFC) to 7-hydroxy-4-trifluoromethylcoumarin (HFC) was studied in human liver microsomal preparations and in cDNA-expressed human cytochrome P450 (CYP) isoforms. 2. Kinetic analysis of the NADPH-dependent metabolism of BFC to HFC in four preparations of pooled human liver microsomes revealed mean (±SEM) K_m and V_max of 8.3±1.3 μM and 454±98 pmol/min/mg protein respectively. 3. The metabolism of BFC to HFC was determined in a characterized bank of 24 individual human liver microsomal preparations employing BFC substrate concentrations of 20 and 50 μM (i.e. about two and six times K_m respectively). With 20 μM BFC the highest correlations were observed between BFC metabolism and markers of CYP1A2 (r² = 0.784-0.797) and then with CYP3A (r² = 0.434-0.547) isoforms, whereas with 50 μM BFC the highest correlations were observed between BFC metabolism and markers of CYP3A (r² = 0.679-0.837) and then with CYP1A2 (r² = 0.421-0.427) isoforms. At both BFC substrate concentrations, lower correlations were observed between BFC metabolism and enzymatic markers for CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP4A9/11. 4. Using human β-lymphoblastoid cell microsomes containing cDNA-expressed CYP isoforms, 20 μM BFC was metabolized by CYP1A2 and CYP3A4, with lower rates of metabolism being observed with CYP2C9 and CYP2C19. Kinetic studies with the CYP1A2 and CYP3A4 preparations demonstrated a lower K_m with the CYP1A2 preparation, but a higher V_max with the CYP3A4 preparation. 5. The metabolism of 20 μM BFC in human liver microsomes was inhibited to 37-48% of control by 5-100 μM of the mechanism-based CYP1A2 inhibitor furafylline and to 64-69% of control by 5-100 μM of the mechanism-based CYP3A4 inhibitor roleandomycin. While some inhibition of BFC metabolism was observed in the presence of 100 and 200 μM diethyldithiocarbamate, the addition of 2-50 μM sulphaphenazole, 50-500 μM Smephenytoin and 2-50 μM quinidine had little effect. 6. The metabolism of 20 μM BFC to HFC in human liver microsomes was also inhibited by an antibody to CYP3A4, whereas antibodies to CYP2C8}9 and CYP2D6 had no effect. 7. In summary, by correlation analysis, use of cDNA-expressed CYP isoforms, chemical inhibition and inhibitory antibodies, BFC appears metabolized by a number of CYP isoforms in human liver. BFC metabolism appears to be primarily catalysed by CYP1A2 and CYP3A4, with possibly some contribution by CYP2C9, CYP2C19 and perhaps other CYP isoforms. 8. The results also demonstrate the importance of the selection of an appropriate substrate concentration when conducting reaction phenotyping studies with human hepatic CYP isoforms.     

Metabolism of 7-benzyloxy-4-trifluoromethyl-coumarin by human hepatic cytochrome P450 isoforms

1. The metabolism of 7-benzyloxy-4-trifluoromethylcoumarin (BFC) to 7-hydroxy-4-trifluoromethylcoumarin (HFC) was studied in human liver microsomal preparations and in cDNA-expressed human cytochrome P450 (CYP) isoforms. 2. Kinetic analysis of the NADPH-dependent metabolism of BFC to HFC in four preparations of pooled human liver microsomes revealed mean (+/- SEM) Km and Vmax of 8.3 +/- 1.3 microM and 454 +/- 98 pmol/min/mg protein respectively. 3. The metabolism of BFC to HFC was determined in a characterized bank of 24 individual human liver microsomal preparations employing BFC substrate concentrations of 20 and 50 microM (i.e. about two and six times Km respectively). With 20 microM BFC the highest correlations were observed between BFC metabolism and markers of CYP1A2 (r2 = 0.784-0.797) and then with CYP3A (r2 = 0.434-0.547) isoforms, whereas with 50 microM BFC the highest correlations were observed between BFC metabolism and markers of CYP3A (r2 = 0.679-0.837) and then with CYP1A2 (r2 = 0.421-0.427) isoforms. At both BFC substrate concentrations, lower correlations were observed between BFC metabolism and enzymatic markers for CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP4A9/11. 4. Using human beta-lymphoblastoid cell microsomes containing cDNA-expressed CYP isoforms, 20 microM BFC was metabolized by CYP1A2 and CYP3A4, with lower rates of metabolism being observed with CYP2C9 and CYP2C19. Kinetic studies with the CYP1A2 and CYP3A4 preparations demonstrated a lower Km with the CYP1A2 preparation, but a higher Vmax with the CYP3A4 preparation. 5. The metabolism of 20 microM BFC in human liver microsomes was inhibited to 37-48% of control by 5-100 microM of the mechanism-based CYP1A2 inhibitor furafylline and to 64-69% of control by 5-100 microM of the mechanism-based CYP3A4 inhibitor troleandomycin. While some inhibition of BFC metabolism was observed in the presence of 100 and 200 microM diethyldithiocarbamate, the addition of 2-50 microM sulphaphenazole, 50-500 microm S-mephenytoin and 2-50 microM quinidine had little effect. 6. The metabolism of 20 microM BFC to HFC in human liver microsomes was also inhibited by an antibody to CYP3A4, whereas antibodies to CYP2C8/9 and CYP2D6 had no effect. 7. In summary, by correlation analysis, use of cDNA-expressed CYP isoforms, chemical inhibition and inhibitory antibodies, BFC appears metabolized by a number of CYP isoforms in human liver. BFC metabolism appears to be primarily catalysed by CYP1A2 and CYP3A4, with possibly some contribution by CYP2C9, CYP2C19 and perhaps other CYP isoforms. 8. The results also demonstrate the importance of the selection of an appropriate substrate concentration when conducting reaction phenotyping studies with human hepatic CYP isoforms.     

基因多态性与丙戊酸的药物代谢

丙戊酸(valproate,VPA)是对多种发作类型有效的一线广谱抗癫痫药,同时也用于精神疾病的治疗。但由于其体内药代动力学过程复杂,药物代谢的个体差异大,使得其应用复杂,难以掌握。另外,长期使用VPA对消化系统、肝脏及血液系统均有潜在的毒副作用,甚至发生急性肝坏死,也使其安全性     

Pharmacotherapy and nutritional supplements for seasonal affective disorders: a systematic review

Introduction: A seasonal affective disorder (SAD) is a subtype of unipolar and bipolar major depressive disorders. It is characterized by its annual recurrence of depressive episodes at a particular season, mostly seen in winter and is responsible for 10–20% of the prevalence of major depressive disorders. Some pathophysiological hypotheses, such as the phase delay and the monoamine depletion hypotheses, have been postulated but the exact cause has not been fully unraveled yet. Studies on treatment for SAD in the last decade are lacking. To tackle this chronic disease, attention needs to be drawn to the gaps in this research field.

Areas covered: In this systematic review, the authors give a broad overview of the pharmacological therapy available for SAD. Also, nutritional substances fitting well with the postulated hypotheses are reviewed for the treatment and prevention of SAD. There is a specific focus on the quality of the currently performed studies.

Expert opinion: Light therapy and fluoxetine are the only proven and effective acute treatment options for SAD, while bupropion is the only registered drug for prevention of SAD. This area of research is in dire need of valid large-scale and sufficiently reproducible randomized control trials.     

丙戊酸肝毒性高危因素易感性机制的实验研究

目的探讨丙戊酸(VPA)在不同年龄、以及与酶诱导剂联合用药时肝脏毒副作用差异及其机制。方法婴儿及成年W istar大鼠,以不同剂量VPA及苯巴比妥(PB)灌胃制作动物模型。差速离心法制备肝线粒体。测定血氨、L-肉碱、肝功酶谱、血液凝血因子、VPA与PB血药浓度、肝线粒体呼吸酶系,以及谷胱甘肽(GSH)、丙二醛(MDA)含量等。流式细胞仪、原位杂交法分别检测肝线粒体跨膜电位(MMP)及肝细胞色素P450(CYP450)还原酶mRNA的表达。O il-Red-O染色观察肝细胞脂肪变性。结果①无论婴儿鼠或成年鼠,即使较大剂量VPA/VPA+PB,对肝功酶谱ALT、AST均无明显影响,而凝血因子PT、TT、APTT、Fbg,以及血氨和L-肉碱含量均有明显异常,其中尤以婴儿鼠、以及与酶诱导剂联用时影响更为突出;②较大剂量VPA/VPA+PB使婴儿鼠肝线粒体细胞色素aa3含量分别下降58.80%和61.80%,成年鼠组分别下降37.55%和46.53%。与对照组比较,P均<0.01。检测肝线粒体呼吸链关键酶琥珀酸脱氢酶(SDH)活性表明,仅有较大剂量VPA/VPA+PB婴儿鼠SDH活性与对照组差异有显著性(P<0.01),分别降低44.8%和57.9%。婴儿和成年鼠细胞色素氧化酶(CCO)活性均明显降低(P<0.01),以婴儿鼠降低更明显。无论婴儿鼠或成年鼠组,较大剂量VPA/VPA+PB动物的肝线粒体GSH含量均低于同龄对照组(P<0.01),而线粒体MDA含量均增高(P<0.05),婴儿鼠更严重;③成年各组实验鼠之间肝线粒体MMP差异无显著性,但婴儿鼠中较大剂量VPA+PB组MMP下降21.47%,与对照组差异有显著性(P<0.05);④原位杂交检测显示较大剂量VPA引起婴儿鼠肝内CYP450还原酶mRNA平均光密度值(OD)增加(P<0.05),但对成年鼠无影响。合并使用PB时,则引起各年龄鼠该酶mRNA表达均增强;⑤组织学观察显示,婴儿鼠较大剂量VPA/VPA+PB组均出现门管区为主的肝细胞脂肪变性,脂肪细胞数分别高出成年鼠7.5和12倍,P<0.01。结论VPA对肝脏的毒副作用,主要表现为VPA对肝线粒体功能的影响,且在婴儿鼠年龄以及联合用药等高危因素存在时更为突出。另外,CYP450还原酶表达的明显增强也可能是高危因素时VPA肝毒性明显增强的重要机制之一。在VPA肝毒性高危因素存在时,尤其应警惕其肝毒性,然而,肝功酶谱并不是一种灵敏的用于预测VPA肝严重毒性发生的实验室指标。     

Variable responses of different human cancer cells to the lichen compounds parietin, atranorin, usnic acid and gyrophoric acid

One of the ways for searching for potentially new anti-cancer drugs is the testing of various naturally synthesized compounds. Lichens are a source of unique chemical agents of which some have already been proved to be effective against various cancer in vitro models. Our study reports on the sensitivity of up to nine human cancer cell lines (A2780, HeLa, MCF-7, SK-BR-3, HT-29, HCT-116 p53^+/+, HCT-116 p53^−/−, HL-60 and Jurkat) to the anti-proliferative/cytotoxic effects of four typical secondary metabolites of lichens (parietin, atranorin, usnic acid and gyrophoric acid). Variations in the dynamics of tumour cell line populations were evaluated by the MTT, clonogenic and viability assays, cell proliferation and detachment, cell cycle transition and apoptotic nuclear morphology, thereby confirming their concentration- and time-dependent cytotoxicity. However, in comparison with parietin and gyrophoric acid, the suppression of viability and cell proliferation by usnic acid or atranorin was found to be more efficient at equitoxic doses and correlated more strongly with an increased number of floating cells or a higher apoptotic index. Moreover, the analysis of cell cycle distribution also revealed an accumulation of cells in S-phase. This study has confirmed a differential sensitivity of cancer cell lines to lichen secondary metabolites.     

Metabolism of parabens (4-hydroxybenzoic acid esters) by hepatic esterases and UDP-glucuronosyltransferases in man

Parabens (alkyl esters of 4-hydroxybenzoic acid) are widely used as preservatives in drugs, cosmetic products, and foodstuffs. Safety concerns have recently increased due to the potential health risks associated to exposure to large amounts of these substances. Biotransformation of parabens mainly includes hydrolysis of the ester bond and glucuronidation reactions. The hydrolysis and glucuronidation of a series of six parabens differing by the nature of the alkyl group were investigated in human liver microsomes and plasma, and the major human UDP-glucuronosyltransferase (UGT) isoforms involved in the reaction were identified. Methyl- and ethylparaben were stable in human plasma, with 95% of the initial concentration remaining after 24 h. On the other hand, propyl-, butyl- and benzylparaben concentrations decreased by 50% under similar conditions. In contrast, rapid hydrolysis was measured with human liver microsomes depending on the alkyl chain length, with t(1/2) varying from 22 min for methylparaben to 87 min for butylparaben. All parabens were actively glucuronidated by liver microsomes, in comparison to 4-hydroxybenzoic acid. They were mainly substrates of human recombinant UGT1A1, UGT1A8, UGT1A9, UGT2B7, UGT2B15 and UGT2B17. In conclusion, the parabens were readily metabolized in human liver through esterase hydrolysis and glucuronidation by several UGT isoforms. These results suggest that these parabens do not accumulate in human tissue.