加替沙星和环丙沙星对大鼠肝微粒体酶系的影响

目的研究加替沙星和环丙沙星对大鼠肝微粒体细胞色素P450酶系的影响.方法Wistar大鼠经加替沙星和环丙沙星400mg/kg灌胃给药,qd×7d后,应用差速离心法制备大鼠肝微粒体,采用Lowry法测定蛋白浓度,应用分光光度计法检测6种肝微粒体细胞色素P450酶含量及活性,并用单因素方差分析进行统计.结果加替沙星组中6种细胞色素P450酶测定结果与空白对照组相比差异无统计学意义,而环丙沙星能抑制6种细胞色素P450酶中的b5、NADPH-CytC还原酶、氨基比林N-脱甲基酶、红霉素N-脱甲基酶和7-乙氧基香豆素脱烃酶的活性,对CYP450酶系有选择性抑制作用.结论加替沙星对大鼠肝微粒体CYP450酶系无显著影响,而环丙沙星对CYP450酶系有选择性抑制作用.     

加替沙星和环丙沙星对大鼠肝微粒体酶系的影响

目的:研究加替沙星和环丙沙星对大鼠肝微粒体细胞色素P450酶系的影响.方法:Wistar大鼠经加替沙星和环丙沙星400mg/kg灌胃给药,qd×7d后,应用差速离心法制备大鼠肝微粒体,采用Lowry法测定蛋白浓度,应用分光光度计法检测6种肝微粒体细胞色素P450酶含量及活性,并用单因素方差分析进行统计.结果:加替沙星组中6种细胞色素P450酶测定结果与空白对照组相比差异无统计学意义,而环丙沙星能抑制6种细胞色素P450酶中的b5、NADPH-CytC还原酶、氨基比林N-脱甲基酶、红霉素N-脱甲基酶和7-乙氧基香豆素脱烃酶的活性,对CYP450酶系有选择性抑制作用.结论:加替沙星对大鼠肝微粒体CYP450酶系无显著影响,而环丙沙星对CYP450酶系有选择性抑制作用.     

心肌缺血再灌注损伤对大鼠肝细胞色素P450酶代谢的影响

目的探讨心肌缺血再灌注状态下,大鼠肝代谢功能和相关的氧化/抗氧化能力变化。方法雄性SD大鼠随机分为5组,除假手术组外,制备在体心肌缺血再灌注模型,并于缺血40min、再灌注15,60和180min分别处死大鼠,检测血浆丙氨酸转氨酶(ALT)和天冬氨酸转氨酶(AST)活性,肝匀浆丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性;以红霉素N-脱甲基酶、五氧基异噁唑O-脱乙基酶和苯胺羟化酶法为探针测定肝细胞色素P450(CYP)3A,CYP2B1和CYP2E1催化功能;RT-PCR法检测肝Ⅰ相药物代谢酶CYP3A1,CYP2B1/2,CYP2E1,以及Ⅱ相解毒酶NAD(P)H醌氧化还原酶(NQO1)及其上游因子NF-E2相关因子(Nrf2)mRNA水平。结果再灌注60 min,肝匀浆MDA含量升高(P<0.05),SOD活力下降(P<0.01);再灌注180 min时,血浆ALT和AST活性升高(P<0.05)。Nrf2基因于再灌注60 min时显著激活(P<0.05),下游因子NQO1 mRNA于再灌注180 min时明显上调(P<0.05)。CYP3A催化功能和mRNA水平分别于再灌注60和180 min开始明显降低(P<0.05);CYP2B1/2 mRNA和催化功能水平分别于再灌注15和180 min开始明显降低(P<0.05);CYP2E1催化功能无明显改变。结论大鼠心肌缺血再灌注可引起肝组织氧化应激及并导致功能损伤。在再灌注早期,具有抗氧化功能的NQO1在转录水平显著上调,其机制可能与上游因子Nrf2被激活相关;CYP3A和CYP2B催化功能在转录和(或)转录后水平明显下调。     

复方丹参滴丸对大鼠肝细胞色素P450酶的影响

目的观察复方丹参滴丸及其单味药对大鼠肝细胞色素P450酶(CYP)主要亚型的影响。方法 SD大鼠分别ig给予复方丹参滴丸0.3258 g.kg-1,丹参0.27 g.kg-1,三七0.0528 g.kg-1和冰片0.003 g.kg-1,每天1次,连续28 d,取大鼠肝微粒体,与CYP1A2,CYP2B6,CYP2C12,CYP2C13,CYP2D2和CYP3A1特异性底物探针共孵育,用高效液相色谱-质谱联用仪(HPLC-MS/MS)测定底物的代谢产物,分析CYP1A2,CYP2B6,CYP2C12,CYP2C13,CYP2D2和CYP3A1酶活性,同时用PCR方法检测cyp1a2,cyp2b1/2,cyp2c11,cyp2e1和cyp3a1 mRNA表达的变化。结果与正常对照组相比,苯巴比妥(阳性对照)对CYP2D2和CYP3A1活性有明显抑制作用,对CYP1A2,CYP2B6,CYP2C12和CYP2C13有明显诱导作用(P<0.05,P<0.01);复方丹参滴丸对CYP1A2和CYP2B6活性有明显抑制作用,对CYP2D2有诱导作用(P<0.05);丹参对CYP1A2和CYP2B6活性有明显抑制作用(P<0.05);三七对CYP1A2,CYP2B6,CYP2C13和CYP2D2活性有明显抑制作用(P<0.05);冰片明显抑制CYP1A2,CYP2B6,CYP2C12,CYP2C13和CYP2D2活性(P<0.01),且抑制强度高于复方丹参滴丸。与正常对照组相比,苯巴比妥对cyp1a2和cyp2b1/2 mRNA水平有明显诱导作用(P<0.05);复方丹参滴丸、丹参和三七对cyp1a2,cyp2b1/2,cyp2c11,cyp2e1和cyp3a1 mRNA水平无明显影响;冰片对cyp1a2,cyp2b1/2和cyp2c11 mRNA水平有明显抑制作用(P<0.05,P<0.01)。结论复方丹参滴丸中各单味药对CYP酶的影响强于全方对CYP酶的影响,其中以冰片对药物代谢酶的影响最为显著。     

细胞色素P450酶系在药物代谢中的作用

该文从细胞色素P450概述、参与药物代谢的人类细胞色素P450亚型、细胞色素P450与药物的相互作用、细胞色素P450多态性在药物不良反应中的作用及细胞色素P450酶系产生药物不良反应的机制等方面综述细胞色素P450酶系对药物代谢的影响，为指导临床合理用药，避免药物不良反应及个体化用药提供参考。     

四氯化碳抑制大鼠肝细胞色素P450同工酶的研究

细胞色素Ｐ45 0 (ＣｙｔｃｈｒｏｍｅＰ45 0 ,ＣＹＰ) ,是四氯化碳(ＣＣｌ4 )在体内进行代谢活化的主要酶类。研究表明 ,ＣＣｌ4 的活化产物 ,如·ＣＣｌ3 等对ＣＹＰ酶类本身也产生破坏作用 ,而不同亚型ＣＹＰ对于ＣＣｌ4 的破坏作用表现不同的敏感性 ,并且可能受到不同剂量不同接触时间等因素影响[1～ 3] 。弄清这些问题 ,对揭示ＣＣｌ4 对机体的损伤机制 ,及对有效地进行ＣＣｌ4 的防护都有一定的意义。鉴于此 ,本实验主要对ＣＣｌ4对苯巴比妥钠 (ＰＢ)诱导型ＣＹＰ2Ｂ1和 3 甲基胆蒽 (3 ＭＣ)诱导型ＣＹＰ1Ａ1和 1Ａ2抑制作用的剂量效应…     

探讨细胞色素P450酶系和药物的代谢情况

在药物代谢过程中细胞色素P450酶系具有十分重要的作用。此类酶主要存在于肝微粒当中,在生物转化过程承担了十分重要的功能。其活性与药物代谢速率具有密切的关联性,甚至可对药物清除产生直接作用。基于上述特点学术界将其作药物代谢过程中的第一相酶。本文对细胞色素P450酶系和药物的代谢进行了分析并对细胞色素P450酶系的作用进行了综合性阐述,提出了相应的观点,供以参考。     

细胞色素P450酶系和药物不良反应

细胞色素P450酶系在药物代谢中扮演了重要角色。本描述了许多环境和基因的因素,这些因素调整人体酶和它们的药物底物的活性。在一些情况下,细胞色素P450酶具有基因的多态性,导致对某些药物在表型上明显慢和明显快的代谢。慢代谢（PMs）易发生与浓度相关的药物不良反应,而快代谢（EMs）则对药物相互作用易感;其中抑制的相互作用可能会由于血浆浓度的增中而导致毒性。药物代谢被改变是药物不良反应的重要原因。     

中成药对细胞色素P450酶的影响

通过参阅大量近年来国内外有关中成药对药物代谢酶细胞色素P450酶影响的文献,对中成药对细胞色素P450酶的研究的文献进行整理和分析.发现一些中成药对细胞色素P450酶确实存在不同程度的抑制或诱导作用.因此深入研究中成药对细胞色素P450酶活性的影响,既有助于指导中成药在临床上的合理使用以避免因药物相互作用导致的不良反应...     

大鼠肝微粒体细胞色素P450酶系检测方法学研究

目的 :建立大鼠肝微粒体蛋白含量以及肝微粒体细胞色素P4 5 0酶系含量与活性测定的紫外和荧光分光光度方法。方法 :应用差速离心法提取大鼠肝微粒体 ,Lowery法测定肝微粒体蛋白浓度 ,应用紫外和荧光分光光度法测定肝微粒体细胞色素P4 5 0酶系含量及活性。结果 :牛血清白蛋白标准曲线的线性范围为 2 5～ 2 5 0mg·L-1,最低检测限为2 5mg·L-1,相关系数r为 0 .9975 ;紫外分光光度法测定细胞色素P4 5 0和细胞色素b5含量及NADPH CytC还原酶活性的结果显示方法灵敏 ;测定氨基比林N 脱甲基酶、红霉素N 脱甲基酶活性的甲醛标准曲线 ,线性范围为 0 .0 5～ 0 .5mmol·L-1,最低检测限为 0 .0 5mmol·L-1,相关系数r为 0 .9988;测定 7 乙氧基香豆素脱烃酶活性的resorufin标准曲线线性范围为 1～ 8μmol·L-1,最低检测限为 1μmol·L-1,相关系数r为 0 .9998。结论 :紫外和荧光分光光度方法测定大鼠肝微粒体细胞色素P4 5 0酶系中 6种酶的含量及活性的灵敏可靠 ,重复性较好。     

糖肝康对糖尿病慢性肝损伤模型大鼠肝脏结构和细胞色素P450的影响

目的：观察糖肝康对糖尿病慢性肝损伤大鼠肝脏组织光镜病理结构、电镜超微结构和肝功能、细胞色素P450（ CYP450）的影响。方法将50只大鼠分为正常组、模型组、糖肝康小剂量组、糖肝康大剂量组、降糖甲组5组,每组10只。用链脲佐菌素和四氯化碳腹腔注射建立糖尿病慢性肝损伤大鼠模型。干预12周后,应用光镜和电镜观察各组大鼠肝脏病理结构和超微结构改变,比较各组大鼠肝功能,比较各组大鼠CYP4501A1,CYP4502E1,CYP4503A1指标。结果光镜下,模型组大鼠肝细胞大量脂肪变性、增生有异型性,可见核分裂象,肝小叶间有少量纤维组织增生;糖肝康大剂量组肝脏结构基本正常。电镜下,模型组大鼠肝细胞体积小,核变形、皱缩,有切迹,核仁明显,常染色质团块状,异染色质边聚,线粒体肿胀,亦可见线粒体空泡化,线粒体嵴模糊;内质网肿胀;可见大量脂滴。糖肝康大剂量组肝细胞结构基本正常。糖肝康小剂量组与模型组相比,ALT明显降低（P＜0．05）;糖肝康大剂量组与模型组相比,ALT明显降低（P＜0．01）;降糖甲组与模型组相比,ALT明显降低（P＜0．01）;糖肝康大剂量组与降糖甲组相比,ALT明显降低（P＜0．05）。糖肝康小剂量组与模型组相比,AST明显降低（ P＜0．01）;糖肝康大剂量组与模型组相比,AST明显降低（P＜0．01）;降糖甲组与模型组相比,AST明显降低（P＜0．05）;糖肝康大剂量组与降糖甲组相比,AST明显降低（P＜0．01）。糖肝康小剂量组、糖肝康大剂量组分别与模型组相比,CYP4501A1,CYP4502E1,CYP4503A1的表达均降低（P＜0．05）;降糖甲组与模型组相比,CYP4501A1, CYP4502E1,CYP4503A1的表达均降低（P＜0．05）;糖肝康大剂量组与降糖甲组相比,CYP4501A1,CYP4502E1,CYP4503A1的表达均明显降低（ P＜0．05）。结论糖肝康对肝脏的病理改变起到一定改善作用,还可以通过调节肝功能,CYP4501A1,CYP4502E1,CYP4503A1的表达,起到对肝脏的保护作用。     

肠道细胞色素P450代谢酶研究进展

细胞色素P450(CYP450s)为肠道主要I相代谢酶,目前发现有CYP1A1、CYP2C9、CYP2C19、CYP2J2、CYP2D6、CYP3A4、CYP3A5 7种同工酶。肠道CYP在药物代谢及药物相互作用中发挥重要作用,与药物疗效及不良反应密切相关。基因多态性及个体差异均影响药物代谢,导致临床疗效差别。该文就肠道CYP各亚型相关研究进展做一综述。     

Time-dependent inhibition of human drug metabolizing cytochromes P450 by tricyclic antidepressants

AIMS

To investigate time-dependent inhibition (TDI) of human drug metabolizing CYP enzymes by tricyclic antidepressants (TCAs).

METHODS

CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A/CYP3A4 activities were investigated following co- and preincubation with TCAs using human liver microsomes (HLM) and human recombinant CYP proteins (expressed in Escherichia coli) as the enzyme sources. A two-step incubation method was employed to examine the in vitro mechanism-based inactivation (MBI) criteria. Potential metabolite–intermediate complex (MIC) formation was studied by spectral analysis.

RESULTS

TCAs generally exhibited significant TDI of recombinant CYP1A2, CYP2C19 and CYP2D6 (>10% positive inhibition differences between co- and preincubation conditions). TDI of recombinant CYP2C9 was minor (<10%), and was minor or absent in experiments utilizing recombinant CYP3A4 or HLM as the enzyme sources. Where observed, TDI of recombinant CYP occurred via alkylamine MIC formation, but evidence to support similar behaviour in HLM was limited. Indeed, only secondary amine TCAs reduced the apparent P450 content of HLM (3–6%) consistent with complexation. As a representative TCA, nortriptyline fulfilled the in vitro MBI criteria using recombinant CYP2C19 and CYP3A4 (K_I and k_inact values of 4 µm and 0.19 min⁻¹, and 70 µm and 0.06 min⁻¹), but not with the human liver microsomal enzymes.

CONCLUSIONS

TCAs appear to have minimal potential for MBI of human liver microsomal CYP enzymes involved in drug metabolism. HLM and recombinant CYP (expressed in E. coli) are not equivalent enzyme sources for evaluating the TDI associated with some drugs.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Much of the literature evidence for mechanism-based inactivation (MBI) of CYP by tricyclic antidepressants is limited to studies in rat liver microsomes.
• One report from this laboratory characterized MBI of human recombinant CYP2C8 by nortriptyline.

WHAT THIS STUDY ADDS

• Tricyclic antidepressants form alkylamine metabolite-intermediate complexes with human recombinant CYP enzymes (expressed in Escherichia coli) relatively easily, resulting in time-dependent inhibition.
• Evidence to support similar irreversible inhibition using human liver microsomal (HLM) fractions is limited.
• HLM and recombinant CYP (expressed in E. coli) are not equivalent enzyme sources for evaluating the time-dependent inhibition of human drug metabolizing CYP that is associated with some drugs.

     

Effects of Phyllanthus amarus on the pharmacokinetics of midazolam and cytochrome P450 activities in rats

1. Phyllanthus amarus, a commonly used medicinal herb, was investigated for possible herb–drug interactions. The effect on CYP3A-mediated drug metabolism in rats after single dose administration of P. amarus extract was investigated using midazolam (MDZ) as a probe substrate. The effect of multiple dose administration of P. amarus extract on activity and expression of various CYP isoforms were studied.

2. Oral administration of P. amarus extract (800?mg/kg) 1?h before oral MDZ increased the C_max and AUC_0–-∞ of MDZ by 3.9- and 9.6-fold and decreased the clearance by 12%, but did not alter the pharmacokinetics of intravenous MDZ.

3. Daily administration of P. amarus extract (200 or 800?mg/kg/day) for 15 days in rats increased the activity and expression of CYP3A and CYP2B1/2. In contrast, the activities and expressions of CYP1A, CYP2C and CYP2E1 were not significantly changed.

4. The dual effects of P. amarus extract on CYP enzymes were demonstrated. Single dose administration of the extract increased oral bioavailability of MDZ through inhibition of intestinal CYP3A whereas repeated administration of the extract slightly induced hepatic CYP3A and CYP2B1/2 in rats, which suggested that herb–drug interactions by P. amarus may potentially occur via CYP3A and 2B.

     

Interaction of dexloxiglumide, a cholecystokinin type-1 receptor antagonist, with human cytochromes P450

Dexloxiglumide (DEX) is a cholecystokinin type-1 receptor antagonist under development for the treatment of constipation-predominant irritable bowel syndrome. Studies of the potential interaction of DEX with human cytochromes P450 (CYPs) were conducted in vitro. DEX (300 micro M), both with and without a 15-min pre-incubation, was incubated with pooled human liver microsomes and substrates selective for each of eight CYPs. This resulted in >30% inhibition of tolbutamide 4-methyl-hydroxylase (CYP2C9/10) and lauric acid 11-hydroxylase (CYP2E1) activities. Mean K(i) (SD) for CYP2C9/10 and CYP2E1 were 69.0 (24.3) and 426 (60) microM, respectively. Incubations of [(14)C]DEX with pooled human liver microsomes produced one major phase I metabolic fraction, with V(max)=131 pmol/min/mg protein and K(m)=23.7 microM. Further incubations with (i) liver microsomes from 16 individual donors (correlation analysis), (ii) Supersomes trade mark and (iii) selective chemical inhibitors, implicated CYP3A4/5, CYP2B6 and CYP2C9 in the formation of this component. Thus, DEX interacts with CYP2C9 both as inhibitor (K(i)=69.0 microM) and as substrate in vitro. However, based on the maximum concentration (27 microM) after repeated oral doses of 200 mg t.i.d. and the unbound fraction (0.03) of DEX in human plasma, no clinically relevant metabolic interactions with other CYP substrates are predicted.     

Synthesis,biological evaluation and docking studies of trans‐stilbene methylthio derivatives as cytochromes P450 family 1 inhibitors

Cytochromes P450 family 1 (CYP1) are responsible for the metabolism of procarcinogens, for example polycyclic aromatic hydrocarbons and aromatic and heterocyclic amines. The inhibition of CYP1 activity is examined in terms of chemoprevention and cancer chemotherapy. We designed and synthesized a series of trans‐stilbene derivatives possessing a combination of methoxy and methylthio functional groups attached in different positions to the trans‐stilbene skeleton. We determined the effects of synthesized compounds on the activities of human recombinant CYP1A1, CYP1A2 and CYP1B1 and, to explain the variation of inhibitory potency of methoxystilbene derivatives and their methylthio analogues, we employed computational analysis. The compounds were docked to CYP1A1, CYP1A2 and CYP1B1 binding sites with the use of Accelrys Discovery Studio 4.0 by the CDOCKER procedure. For CYP1A2 and CYP1B1, values of scoring functions correlated well with inhibitory potency of stilbene derivatives. All compounds were relatively poor inhibitors of CYP1A2 that possess the most narrow and flat enzyme cavity among CYP1s. For the most active CYP1A1 inhibitor, 2‐methoxy‐4′‐methylthio‐trans‐stilbene, a high number of molecular interactions was observed, although the interaction energies were not distinctive.