甲基莲心碱在大鼠肝微粒体CYP450系统中的代谢特征

目的研究甲基莲心碱(Nef)在大鼠肝微粒体系的代谢特性,探明参与Nef代谢的CYP450亚酶种类及其在Nef代谢中的作用。方法应用CYP3A特异性诱导剂地塞米松(DEX)、CYP2B诱导剂苯巴比妥(PB)、CYP1A诱导剂β-萘黄酮(β-NF)分别对W istar大鼠进行在体诱导,建立肝微粒体温孵及NADPH再生体系,HPLC紫外检测法测定Nef及其代谢产物。观察Nef代谢消失率与代谢特征,研究上述各诱导剂和CYP3A特异性抑制剂三乙酰竹桃霉素(TAO)对Nef体外代谢的影响。结果Nef在大鼠微粒体系代谢呈饱和现象;温孵液中代谢产物生成的量与底物Nef的浓度具有良好的相关性(r=0.993);Nef在DEX、PB诱导组大鼠肝微粒体温孵液中的生物转化较对照组明显加快(P<0.01),DEX组又较PB组的Nef药物代谢率差异有显著性(P<0.01),而β-NF组未显现诱导作用,其药物代谢率分别为:DEX组80.6%±9.5%;PB组61.5%±6.7%;β-NF组20.7%±1.5%;对照组19.9%±1.6%;TAO呈量效依赖性抑制Nef在肝微粒体温孵液中的代谢。结论研究结果提示Nef具有酶促动力学代谢特性;CYP3A及CYP2B是介导Nef在大鼠体内生物转化的CYP450亚酶,其中主要参与Nef代谢的为CYP3A。     

基于细胞色素氧化酶CYP2D6的何首乌肝细胞毒性及相关成分研究

目的探究何首乌及其主要成分对人肝细胞L02中细胞色素氧化酶CYP2D6 mRNA表达的影响以及抑制CYP2D6活性或表达对何首乌肝细胞毒性的影响及相关成分辨识。方法利用实时荧光定量PCR(RT-qPCR)确定何首乌水提物(Polygoni Multiflori Radix,PMR)及其主要成分对L02细胞CYP2D6 mRNA表达的影响;使用CYP2D6抑制剂奎尼丁初步探究PMR对CYP2D6低活性L02细胞系的细胞毒作用;构建CYP2D6沉默的L02细胞系L02-shCYP2D6,进一步研究L02细胞中CYP2D6表达降低对PMR及其主要成分肝细胞毒性的影响;可能的肝细胞毒性成分与人肝微粒体进行体外孵育,通过考察加入不同CYP450酶特异性抑制剂对其代谢消除率的影响,探究影响其代谢的主要CYP450酶。结果在实验浓度下,PMR和芦荟大黄素(AE)对CYP2D6 mRNA表达有显著抑制作用(P<0.01),大黄素(EM)无明显影响,2,3,5,4’-四羟基二苯乙烯-2-O-β-D-葡萄糖苷(TSG)仅在高浓度有一定激活作用,其余浓度无影响;PMR联合奎尼丁作用于L02细胞,发现PMR在高浓度下对L02细胞有一定毒性(P<0.01),各浓度抑制剂与之联用后均明显加重了其肝细胞毒性(P<0.01);PMR及其主要成分作用于CYP2D6敲低的L02细胞系,除TSG在高浓度下提升了肝细胞毒性外(P<0.01),PMR、EM、AE在实验浓度范围内肝细胞毒性均显著增加(P<0.01);人肝微粒体体外孵育实验显示,CYP2D6为EM、AE重要的代谢酶。结论PMR能够抑制肝细胞中CYP2D6的表达,而CYP2D6的低活性或低表达能够加重PMR肝细胞毒性,其中主要的毒性成分为EM和AE。     

海藻-昆布药对对大鼠肝微粒体代谢酶的影响及肝毒性研究

目的 发现不同剂量海藻-昆布药对提取物对大鼠肝微粒体代谢酶的诱导或抑制作用, 预测服用海藻-昆布药对时可能出现的药物-药物相互作用及肝脏毒性。方法 雌雄各半SD大鼠18只, 被随机分为海藻-昆布药对低、高剂量组和对照组, 低、高剂量组大鼠分别ig给予海藻-昆布药对提取物10.8、86.4 g/(kg·d), 连续经口给药15 d后麻醉处死, 取肝组织制备肝微粒体及HE染色石蜡切片。通过肝微粒体体外孵育方法测定3种肝脏CYP450同工酶特异性底物非那西丁(CYP1A2)、氯唑沙宗(CYP2E1)及咪达唑仑(CYP3A4)的降解和代谢产物生成量来评价肝药酶的诱导或抑制作用, 并以光镜下的组织病理切片检查来考察其肝毒性。结果 低剂量组大鼠无显著诱导或抑制3种CYP450代谢酶亚型1A2、2E1和3A4现象, 肝组织出现了肝窦扩张、轻度水肿等适应性改变, 高剂量组能显著诱导CYP3A4亚型, 但也不能显著的诱导或抑制肝微粒体代谢酶CYP1A2、CYP2E1亚型, 肝组织出现了脂肪变、点状坏死等可逆性损伤。结论 海藻-昆布药对具有诱导肝微粒体代谢酶CYP3A4的作用和轻微的肝细胞毒性, 高剂量经口给药能引起有临床意义的CYP450酶的诱导现象和肝脏损伤并可能导致不期望的药物-药物相互作用。     

细胞色素P450酶系对喹乙醇诱导的肾细胞凋亡的影响

目的采用体外细胞培养系统,研究肝脏微粒体细胞色素P450同工酶对喹乙醇(OLA)毒性的影响,筛选和确定影响喹乙醇毒性的主要细胞色素P450同工酶,探索CYP450酶系选择性介导OLA-ROS-细胞凋亡途径。方法(1)以体外培养的人类肾小管上皮细胞(HK-2)作为检测OLA致肾小管毒性的细胞模型,以脏微粒体混合酶系(S9)加入到HK-2细胞培养中模拟体内代谢环境,将CYP450同工酶(CYP2D6、NADPH:P450还原酶、CYP2A、CYP3A、CYP2C、CYP2E1和CYP1A1/CYP1A2)的化学抑制剂分别加入培养体系中,造成不同P450同工酶活性抑制状况,通过细胞增殖抑制率(MTT)试验来检测OLA单独染毒或OLA与抑制剂联合染毒情况下的细胞毒性。(2)通过流式细胞仪DCF法检测各CYP450同工酶抑制剂对OLA所致HK-2细胞ROS产生情况的影响,筛选HK-2细胞内影响OLA作用的主要CYP450同工酶,推测其代谢路径。结果 (1)MTT检测发现,OLA+S9+α-萘黄酮组与OLA+S9组之间以及OLA+4-甲基吡唑+S9组与OLA+S9组之间细胞活性差异有统计学意义(P0.05),表明通过抑制CYP4501A酶以及CPY2E1活性可以使OLA的细胞毒性减轻。(2)OLA能够呈剂量依赖性的诱发细胞内ROS含量升高,且加入CYP1A抑制剂以及CPY2E1抑制剂后,可显著减少HK-2细胞ROS的产生量。结论 OLA通过CYP1A和CYP2E1的代谢诱导HK-2细胞生成ROS,进而可能诱发HK-2细胞的凋亡产生细胞毒性和肾毒性。     

海藻–昆布药对对大鼠肝微粒体代谢酶的影响及肝毒性研究

目的发现不同剂量海藻–昆布药对提取物对大鼠肝微粒体代谢酶的诱导或抑制作用,预测服用海藻–昆布药对时可能出现的药物–药物相互作用及肝脏毒性。方法雌雄各半SD大鼠18只,被随机分为海藻–昆布药对低、高剂量组和对照组,低、高剂量组大鼠分别ig给予海藻–昆布药对提取物10.8、86.4 g/(kg·d),连续经口给药15 d后麻醉处死,取肝组织制备肝微粒体及HE染色石蜡切片。通过肝微粒体体外孵育方法测定3种肝脏CYP450同工酶特异性底物非那西丁(CYP1A2)、氯唑沙宗(CYP2E1)及咪达唑仑(CYP3A4)的降解和代谢产物生成量来评价肝药酶的诱导或抑制作用,并以光镜下的组织病理切片检查来考察其肝毒性。结果低剂量组大鼠无显著诱导或抑制3种CYP450代谢酶亚型1A2、2E1和3A4现象,肝组织出现了肝窦扩张、轻度水肿等适应性改变,高剂量组能显著诱导CYP3A4亚型,但也不能显著的诱导或抑制肝微粒体代谢酶CYP1A2、CYP2E1亚型,肝组织出现了脂肪变、点状坏死等可逆性损伤。结论海藻–昆布药对具有诱导肝微粒体代谢酶CYP3A4的作用和轻微的肝细胞毒性,高剂量经口给药能引起有临床意义的CYP450酶的诱导现象和肝脏损伤并可能导致不期望的药物–药物相互作用。     

丙戊酸药物肝毒性的研究进展

药物肝毒性是临床医师和患者十分关注的问题。英国药物安全委员会对1964～2000年间英国儿童致死性药物副作用统计发现,最常见的死因为肝功衰竭,占15．11％(50／331)。引起肝功衰竭的主要药物是丙戊酸盐类药物(Valproic acid,VPA),占9．37％(31／331)。VPA引起的致死性肝坏死更容易发生在婴儿。因此,深入研究VPA肝毒性的发生机理和防治措施,对防治该药毒副作用,促进该药在临床的安全应用,均有重要意义。     

银杏叶醇提取物对异烟肼和利福平肝毒性保护作用的实验研究

目的:观察银杏叶醇提取物对异烟肼和利福平肝毒性的保护作用及其机制探讨。方法:分别测定肝损害组和银杏叶醇提取物大、小剂量组小鼠的血清谷丙转胺酶(SGPT)、肝指数、肝匀浆丙二醛(MDA)含量、肝微粒体P₄₅₀和线粒体Ca²⁺ ATP酶活性,以及肝病理检查,并与对照组比较。结果:银杏叶醇提取物大、小剂量均可对抗异烟肼和利福平引起的MDA、SGPT、肝微粒体P₄₅₀ 的增高(P<0.05) ,以及对抗其引起的形态学改变;银杏叶醇提取物大剂量对抗其线粒体Ca²⁺ ATP酶活性的降低。结论:银杏叶醇提取物可对抗异烟肼和利福平所致肝毒性。     

单壁碳纳米管对人肝细胞HepG2的毒性和肝代谢酶影响的研究CSCD

目的探究单壁碳纳米管(single-walled carbon nanotube,SWCNT)对人肝癌细胞Hep G2的毒性及对肝代谢酶的影响。方法0.25、0.5和1 mg/ml SWCNT处理Hep G2细胞24、48和72 h,采用噻唑蓝比色法[3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide,MTT]测定SWCNT对肝癌细胞Hep G2增殖的抑制作用。蛋白印迹法(Western blot)检测肝代谢酶儿茶酚-O-甲基转移酶(Catechol-O-methyltransferase,COMT)、谷胱甘肽S转移酶P1(Glutathione S-transferase pi gene,GSTP1)和细胞色素P450亚酶(Cytochrome P450,family 1,subfamily A,CYP1A1)蛋白表达量的变化。酶联免疫吸附(enzyme-linked immuno sorbent assay,ELISA)法检测细胞上清中相关代谢酶的浓度。结果与对照组相比,0.25、0.5和1 mg/ml的SWCNT对Hep G2细胞的增殖具有明显抑制作用,差异均具有统计学意义(P<0.05,P<0.01)。Western blot结果显示,随着药物浓度的增加,COMT、GSTP1和CYP1A1的蛋白水平均明显降低,差异具有统计学意义(P<0.05,P<0.01)。ELISA实验结果显示,0.5和1 mg/ml的SWCNT处理细胞后,GSTP1和CYP1A1的浓度明显降低,且差异有统计学意义(P<0.05),而COMT浓度降低,但差异并无统计学意义(P>0.05)。结论与对照组相比,0.25~1 mg/ml的SWCNT可以抑制Hep G2细胞的增殖,且呈一定的剂量和时间依赖性。SWCNT可以一定程度地抑制肝代谢酶COMT、GSTP1和CYP1A1的表达,可能与其导致细胞毒性相关。     

抑制CYP2E1增强何首乌水提物肝毒性作用及其毒性成分筛选研究

目的研究肝细胞色素氧化酶P450(CYP450)亚型CYP2E1与何首乌肝毒性的关系并筛选有关毒性成分。方法MTT法检测CYP2E1特异性抑制剂二乙基二硫代氨基甲酸钠(DDTC)作用后何首乌水提物(PMR)对人肝细胞L02的毒性作用,及PMR和6种成分2,3,5,4'-四羟基二苯乙烯-2-O-β-D-葡萄糖苷(2,3,5,4-tetrahydroxy stilbene glycoside,TSG)、大黄素-8-O-β-D-葡萄糖苷(emodin-8-O-β-D-glucoside,EG)、大黄素(emodin,EM)、没食子酸(gallic acid,GA)、大黄素甲醚(physcione,PH)和大黄酸(rhein,RH)对稳定转染shCYP2E1的HepaRG细胞的毒性作用;利用CYP2E1特异性抑制剂4-甲基吡唑(4-methylpyrazole,4-MP)作用大鼠,进一步验证何首乌对大鼠的肝毒性作用与CYP2E1抑制的关系。结果DDTC处理L02细胞24 h后,CYP2E1活性显著下降(P<0.05),PMR联用DDTC后细胞活力明显下降(与PMR、DDTC组相比,P<0.01);成功构建了HepaRG-shCYP2E1细胞系,与空质粒对照组相比,其CYP2E1 mRNA表达下降70%以上;与对照组相比,何首乌提取物PMR、EM、PH及RH对HepaRG-shCYP2E1的细胞毒作用显著增加(P<0.01),而TSG和EG在一定浓度下细胞毒作用降低(P<0.01);大鼠实验表明,何首乌与CYP2E1抑制剂联合作用于大鼠后,与空白组、抑制剂组相比,ALT及AST的水平均明显升高,与何首乌组相比,AST水平显著升高,说明大鼠体内CYP2E1被抑制后,何首乌的肝毒性作用增强。结论CYP2E1活性或表达下降可导致何首乌水提物肝细胞毒性及大鼠肝毒性增加,其毒性成分可能为游离蒽醌类成分EM,PH及RH。     

银杏叶提取物和丹参酮对细胞色素P-450和谷胱甘肽转移酶的影响

目的:观察银杏叶提取物(GbE)和丹参酮(Tan)对大鼠细胞色素P450 (CYP)亚型和谷胱甘肽转移酶(GT) 的影响。方法:SD大鼠一日一次灌胃给药10日后,选用CYP1A1,1A2,2B1,2E1及3A特异性代谢底物,检测它们在肝和肾微粒体中的活性,还同时对肺、肝和肾组织中的GT和丙二醛(MDA)及肝组织的一氧化氮(NO)进行了观察。结果:GbE和Tan均可升高(2-9.5倍)肝中CYP1A1,1A2,和2B1的活性(P<0.01);GbE可诱导(1.6倍)CYP3A(P<0.01),高剂量时对CYP2E1也有诱导作用,但Tan对CYP3A没有作用,对CYP2E1有显著的抑制(1.9倍,P<0.01)作用;GbE还可升高(5.6-8.9倍) 肾CYP1A1和1A2(2.6倍)的活性(P<0.01),但Tan无此作用,Tan可诱导肝GT的活性(P<0.05),GbE可抑制肾GT(P<0.01),Tan对肺和肾、GbE对肝和肺中的GT无影响,此外,GbE还可显著降低肺、肾和肝组织中的MDA(P<0.01)和肝中的NO(P<0.01)。结论:GbE和Tan对CYP的调节作用将会影响与其合用药物在体内的代谢消除,进一步证明了GbE为一有效的抗氧化剂和NO抑制剂。     

Valproic acid I: time course of lipid peroxidation biomarkers, liver toxicity, and valproic acid metabolite levels in rats.

A single dose of valproic acid (VPA), which is a widely used antiepileptic drug, is associated with oxidative stress in rats, as recently demonstrated by elevated levels of 15-F(2t)-isoprostane (15-F(2t)-IsoP). To determine whether there was a temporal relationship between VPA-associated oxidative stress and hepatotoxicity, adult male Sprague-Dawley rats were treated ip with VPA (500 mg/kg) or 0.9% saline (vehicle) once daily for 2, 4, 7, 10, or 14 days. Oxidative stress was assessed by determining plasma and liver levels of 15-F(2t)-IsoP, lipid hydroperoxides (LPO), and thiobarbituric acid reactive substances (TBARs). Plasma and liver 15-F(2t)-IsoP were elevated and reached a plateau after day 2 of VPA treatment compared to control. Liver LPO levels were not elevated until day 7 of treatment (1.8-fold versus control, p < 0.05). Liver and plasma TBARs were not increased until 14 days (2-fold vs. control, p < 0.05). Liver toxicity was evaluated based on serum levels of alpha-glutathione S-transferase (alpha-GST) and by histology. Serum alpha-GST levels were significantly elevated by day 4, which corresponded to hepatotoxicity as shown by the increasing incidence of inflammation of the liver capsule, necrosis, and steatosis throughout the study. The liver levels of beta-oxidation metabolites of VPA were decreased by day 14, while the levels of 4-ene-VPA and (E)-2,4-diene-VPA were not elevated throughout the study. Overall, these findings indicate that VPA treatment results in oxidative stress, as measured by levels of 15-F(2t)-IsoP, which precedes the onset of necrosis, steatosis, and elevated levels of serum alpha-GST.     

Valproyl-dephosphoCoA: a novel metabolite of valproate formed in vitro in rat liver mitochondria.

The mitochondrial metabolism of valproic acid (VPA) was investigated in vitro to elucidate its beta-oxidation pathway since the characterization of VPA intermediates in the acyl-CoA thioester form, and not just in their free acid form, has not been fully achieved. Intact rat liver mitochondria were incubated with [4,5-3H2]VPA and [2-3H]VPA. The respective intermediates, valproyl-CoA, Delta2(E)-valproyl-CoA, 3-hydroxyvalproyl-CoA, and 3-oxovalproyl-CoA were analyzed by reverse phase high performance liquid chromatography (HPLC) with radioisotope and UV detection. An unknown metabolite, originating from both labeled substrates, was detected. It was identified as valproyl-dephosphoCoA (valproyl-dephCoA) by fast atom bombardment mass spectrometry (FAB-MS) analysis of the corresponding HPLC peak fraction. The FAB-MS spectrum of the authentic chemically synthesized valproyl-dephCoA proved to be consistent with that of the unknown compound. Valproyl-dephCoA is produced from valproyl-CoA in mitochondria, probably via a phosphatase-catalyzed reaction. This conversion was shown to be more dependent on the energy state involving [AXP] ([AXP] = [ATP] + [ADP] + [AMP]) and [phosphate] concentrations rather than the strict mitochondrial [ATP]/[ADP] ratio. The results indicate that higher concentrations of AXP and phosphate inhibit the dephosphorylation of valproyl-CoA. A complete understanding of the toxic significance of valproyl-dephCoA formation in vivo as a potential inhibitor of fatty acid beta-oxidation is important to clarify the pathogenesis of VPA-associated hepatotoxicity.     

Oxidative stress as a mechanism of valproic acid-associated hepatotoxicity

Valproic acid (2-n-propylpentanoic acid; VPA) has several therapeutic indications, but it is used primarily as an anticonvulsant. VPA is a relatively safe drug, but its use is associated with idiosyncratic hepatotoxicity, which in some cases may lead to fatality. The underlying mechanism responsible for the hepatotoxicity is still not well understood, but various hypotheses have been proposed, including oxidative stress. This article discusses the experimental evidence on the effect of VPA on the various indices of oxidative stress and on the potential role of oxidative stress in VPA-associated hepatotoxicity.     

Potential relationships between transaminase abnormality and valproic acid clearance or serum carnitine concentrations in Japanese epileptic patients

This study tested the hypothesis that the determinants of mild liver injury are prerequisites for more severe idiosyncratic hepatotoxicity. This study verified whether the possible risk factors for rare idiosyncratic valproic acid (VPA)-induced hepatotoxicity, VPA clearance and/or serum carnitine concentrations are common to those for a mild elevation in transaminases in VPA-treated patients. VPA clearance was calculated in 172 Japanese patients with epilepsy, using a non-linear mixed-effects regression program. Carnitine concentrations were determined in a subset of 60 patients. The relationships between VPA clearance, carnitine concentration and levels of transaminases and ammonia were evaluated by Pearson's correlation coefficients. The final model of VPA apparent clearance (CL/F) was as follows: CL/F (L h(-1) = 0.012 x (BW/40)(0.34) x dose(0.55) x 0.90(gender) x 1.32(PHT) x 1.11(CBZ) x 1.12(PB), where BW = total body weight (kg); gender = 1 if female, 0 if male; PHT/CBZ/PB = 1 if phenytoin, carbamazepine, or phenobarbital, respectively, is coadministrated, otherwise 0. Either a higher VPA clearance or acyl/free carnitine ratio and a lower total and/or free carnitine concentration, but not VPA concentration, were associated with the mild elevation in transaminases or ammonia. These results support the initial hypothesis, while also helping to clarify the mechanism of severe idiosyncratic hepatotoxicity with VPA.     

The relationship between glucuronide conjugate levels and hepatotoxicity after oral administration of valproic acid

The aim of this study was to investigate the relationship between hepatotoxicity, levels of glucuronide conjugates of valproic acid (VPA), and the toxic metabolites of VPA (4-ene VPA and 2,4-diene VPA). We also examined whether hepatotoxicity could be predicted by the urinary excretion levels of VPA and its toxic metabolites. VPA was administrated orally in rats in amounts ranging from 20 mg/kg to 500 mg/kg. Free and total (free plus glucuronide conjugated) VPA, 4-ene VPA, and 2,4-diene VPA were quantified in urine and liver using gas chromatography-mass spectrometry. Serum levels of aspartate aminotransferase, alanine aminotransferase, and α-glutathione S-transferase (α-GST) were also determined to measure the level of hepatotoxicity. The serum α-GST level increased slightly at the 20 mg/kg dose, and substantially increased at the 100 and 500 mg/kg dose; aspartate aminotransferase and alanine aminotransferase levels did not change with the administration of increasing doses of VPA. The liver concentration of free 4-ene VPA and the urinary excretion of total 4-ene VPA were the only measures that correlated with the increase in the serum α-GST level (p < 0.094 and p < 0.023 respectively). From these results, we conclude that hepatotoxicity of VPA correlates with liver concentration of 4-ene VPA and can be predicted by the urinary excretion of total 4-ene VPA.     

Oxidative Stress as a Mechanism of Valproic Acid-Associated Hepatotoxicity

Valproic acid (2-n-propylpentanoic acid; VPA) has several therapeutic indications, but it is used primarily as an anticonvulsant. VPA is a relatively safe drug, but its use is associated with idiosyncratic hepatotoxicity, which in some cases may lead to fatality. The underlying mechanism responsible for the hepatotoxicity is still not well understood, but various hypotheses have been proposed, including oxidative stress. This article discusses the experimental evidence on the effect of VPA on the various indices of oxidative stress and on the potential role of oxidative stress in VPA-associated hepatotoxicity.     

Influence of concomitant antiepileptic drugs on plasma lamotrigine concentration in adult Japanese epilepsy patients

Lamotrigine (LTG) is an antiepileptic drug (AED) that was approved in Japan in 2008. We evaluated the influence of AEDs that induce hepatic enzymes (including phenytoin (PHT), phenobarbital (PB), carbamazepine (CBZ)), valproic acid (VPA), and various combinations of these drugs, on plasma LTG concentration in adult Japanese epilepsy patients. A total of 621 patients (mean age 34.4±11.8 years) were evaluated retrospectively. We calculated the concentration to dose ratio (CD ratio) for LTG with different AED regimens, and employed multiple regression analysis to determine factors influencing the LTG concentration. There was a linear correlation between the dose and concentration of LTG in patients treated with LTG (group I), LTG+VPA (group II), LTG+inducers (group III), or LTG+VPA+inducers (group IV). The mean CD ratio of patients on LTG monotherapy was 1.43±0.4 (μg/mL)/(mg/kg). When LTG was combined with VPA, the CD ratio increased about 2.2-fold, but there was no significant correlation between the CD ratio and VPA concentration. The mean CD ratios calculated in patients receiving LTG+PHT, LTG+PB, and LTG+CBZ were 0.56, 0.84, and 0.91, respectively. Addition of PHT significantly reduced the CD ratio in a concentration-dependent manner, in comparison with PB and CBZ (p<0.005 and p<0.001, respectively). Stepwise multiple regression analysis showed that the coefficient of determination of groups I, II, III, and IV were 0.94, 0.94, 0.90, and 0.91, respectively. In the clinical setting, these findings can help to estimate LTG concentrations and predict the inducing or inhibiting effects of concomitant AEDs.     

Subchronic effects of valproic acid on gene expression profiles for lipid metabolism in mouse liver

Valproic acid (VPA) is used clinically to treat epilepsy, however it induces hepatotoxicity such as microvesicular steatosis. Acute hepatotoxicity of VPA has been well documented by biochemical studies and microarray analysis, but little is known about the chronic effects of VPA in the liver. In the present investigation, we profiled gene expression patterns in the mouse liver after subchronic treatment with VPA. VPA was administered orally at a dose of 100 mg/kg/day or 500 mg/kg/day to ICR mice, and the livers were obtained after 1, 2, or 4 weeks. The activities of serum liver enzymes did not change, whereas triglyceride concentration increased significantly. Microarray analysis revealed that 1325 genes of a set of 32,996 individual genes were VPA responsive when examined by two-way ANOVA (P<0.05) and fold change (>1.5). Consistent with our previous results obtained using an acute VPA exposure model (Lee et al., Toxicol Appl Pharmacol. 220:45-59, 2007), the most significantly over-represented biological terms for these genes included lipid, fatty acid, and steroid metabolism. Biological pathway analysis suggests that the genes responsible for increased biosynthesis of cholesterol and triglyceride, and for decreased fatty acid beta-oxidation contribute to the abnormalities in lipid metabolism induced by subchronic VPA treatment. A comparison of the VPA-responsive genes in the acute and subchronic models extracted 15 commonly altered genes, such as Cyp4a14 and Adpn, which may have predictive power to distinguish the mode of action of hepatotoxicants. Our data provide a better understanding of the molecular mechanisms of VPA-induced hepatotoxicity and useful information to predict steatogenic hepatotoxicity.     

Gene expression profiles of murine fatty liver induced by the administration of valproic acid

Valproic acid (VPA) has been used as anticonvulsants, however, it induces hepatotoxicity such as microvesicular steatosis and necrosis in the liver. To explore the mechanisms of VPA-induced steatosis, we profiled the gene expression patterns of the mouse liver that were altered by treatment with VPA using microarray analysis. VPA was orally administered as a single dose of 100 mg/kg (low-dose) or 1000 mg/kg (high-dose) to ICR mice and the animals were killed at 6, 24, or 72 h after treatment. Serum alanine aminotransferase and aspartate aminotransferase levels were not significantly altered in the experimental animals. However, symptoms of steatosis were observed at 72 h with low-dose and at 24 h and 72 h with high-dose. After microarray data analysis, 1910 genes were selected by two-way ANOVA (P<0.05) as VPA-responsive genes. Hierarchical clustering revealed that gene expression changes depended on the time rather than the dose of VPA treatment. Gene profiling data showed striking changes in the expression of genes associated with lipid, fatty acid, and steroid metabolism, oncogenesis, signal transduction, and development. Functional categorization of 1156 characteristically up- and down-regulated genes (cutoff >1.5-fold) revealed that 60 genes were involved in lipid metabolism that was interconnected with biological pathways for biosynthesis of triglyceride and cholesterol, catabolism of fatty acid, and lipid transport. This gene expression profile may be associated with the known steatogenic hepatotoxicity of VPA and it may provide useful information for prediction of hepatotoxicity of unknown chemicals or new drug candidates through pattern recognition.     

Effect of pretreatment with some mixed-function oxidase enzyme inducers on the acute hepatotoxicity of coumarin in the rat

Male Sprague-Dawley rats were pretreated with saline, corn oil, sodium phenobarbitone (PB) (100 mg/kg body weight/day), 20-methylcholanthrene (20 MC) (20 mg/kg body weight/day) or Aroclor 1254 (ARO) (100 mg/kg body weight/day) by daily ip injections for 5 days. Animals were then given single oral doses of either 250 or 500 mg coumarin/kg body weight and hepatotoxicity was assessed after 24 hr. Coumarin produced hepatotoxicity, which comprised hepatocyte necrosis and elevation of plasma alanine aminotransferase and aspartate aminotransferase activities, in all pretreated groups. Hepatic microsomal cytochrome P-450 levels were reduced after coumarin administration. In rats pretreated with saline, corn oil or PB, coumarin produced centrilobular hepatic necrosis, whereas in rats pretreated with 20 MC or ARO, coumarin produced periportal hepatic necrosis. These results demonstrate that mixed-function oxidase enzyme inducers can modulate acute coumarin-induced hepatotoxicity in the rat. As coumarin is known to be bioactivated by cytochrome P-450-dependent enzymes, the change in the lobular distribution of toxicity after pretreatment with 20 MC or ARO is presumably due to the induction of particular cytochrome P-450 isoenzymes in periportal hepatocytes.