基因多态性对钙离子通道阴滞剂类抗高血压药物药动学及疗效的影响

钙离子通道阻滞剂是常用的一种高血压治疗药物,其中又以二氢吡啶类钙离子通道阻滞剂为主要代表,常见的有硝苯地平、氨氯地平、非洛地平等。然而,不同的患者个体对此类抗高血压药物可产生不同的降压效果,这种差异是环境和遗传共同作用的结果。基因多态性决定了药物代谢酶、转运体以及作用受体的差异,是导致药物疗效差异的重要原因之一。综述药物代谢酶、转运体和作用受体的基因多态性对钙离子通道阻滞剂类抗高血压药物的药动学和疗效的影响。     

氨氯地平药物基因组学研究进展

氨氯地平为第3代二氢吡啶类钙拮抗剂,是临床上常用的治疗高血压和心绞痛的药物之一,其降压效果存在个体差异.这种差异是多种遗传因素和环境因素交互作用的结果.基因的多态性是造成药物疗效差异的主要因素之一.本文阐述其基因多态性对氨氯地平的药代动力学特征和降压疗效的影响.     

细胞色素P450(CYP)3A5与CYP2C19基因多态性对伏立康唑在健康人体的药代动力学特征的影响

目的研究中国健康人体内细胞色素P450(CYP)3A5、CYP2C19基因多态性对伏立康唑药代动力学的影响。方法用RFLP-PCR法对受试者进行全血CYP3A5、CYP2C19基因分型;建立人血浆中伏立康唑的LC-MS测定方法,检测血药浓度;并对受试者单次口服伏立康唑200 mg后的系列血药浓度进行测定。结果伏立康唑200 mg,CYP2C19突变纯合子的AUC0-36、AUC0-∞值均显著高于野生组;也显著高于突变杂合组;而CL/F值则明显低于野生组。T1/2﹑Cmax等在各组间无统计学差异;伏立康唑各药代动力学参数在CYP3A5各组间均无统计学差异。结论中国人体内CYP2C19基因多态性对伏立康唑的药代动力学过程有显著影响;而CYP3A5基因多态性对伏立康唑的药代动力学过程无明显影响。     

非洛地平

<正> 非洛地平是一类钙拮抗剂(钙离子通道阻滞剂),是二氢吡啶衍生物,分子式为C_(18)H_(19)C_(12)NO_4。目前临床上大多采用其缓释片,可持续释放非洛地平。有2.5mg、5mg、10mg 3种不同剂量规格供口服给药。1 临床药理1.1 作用机理非洛地平是二氢吡啶衍生物家族中一类钙离子通道拮抗剂(钙离子通道阻滞剂)。它可逆性的与     

细胞色素P450 3A5和多药耐药基因遗传变异的联合效应对克拉霉素药代动力学的影响

目的 观察CYP3A5*3和MDR1 C3435T遗传变异的联合效应对中国健康受试者克拉霉素(大环内酯类抗生素)药代动力学的影响.方法 45名受试者服用单剂量克拉霉素胶囊250 mg,HPLC-MS法测定血药浓度.PCR-ASA法和PCR-RFLP法分别测定受试者CYP3A53和MDR1 C3435T的基因型,按基因型分组,比较基因多态性对克拉霉素药代动力学的影响.结果 在45名受试者中,CYP3A5*3各基因型分布,不受MDR1 C3435T基因型的影响;而2者的基因突变均不同程度地协同影响克拉霉素药代动力学参数Cmax、AUC0-24和tmax.结论 CYP3A5*3和MDR1 C3435T遗传变异及协同作用是影响克拉霉素药代动力学特性的重要因素.     

异基因造血干细胞移植受者CYP3A4及CYP3A5基因多态性对他克莫司血药浓度及疗效的影响

目的 研究P4503A4*18B(CYP3A4*18B)及3A5*3(CYP3A5*3)突变频率,探讨基因多态性与异基因造血干细胞移植受者他克莫司(Tac)血药浓度的关系.方法 采用原位杂交荧光染色脱氧核糖核酸测序技术检测CYP3A4、CYP3A5基因型,酶联免疫吸附技术测定受者Tac浓度.比较术后7、15、30 d不同基因型受者间Tac浓度/剂量(C0/D)的差异.结果 16例中,CYP3A4*18B、CYP3A5*3突变等位基因发生的频率分别是25％和75％.CYP3A5纯合突变型受者中,CYP3A4野生纯合型者的浓度剂量比高于CYP3A4突变型.结论 异基因造血干细胞移植受者CYP3A4*18B和CYP3A5*3基因多态性对TAC药代动力学的影响显著,可以考虑应用临床.     

新型钙拮抗剂-氨氯地平

钙拮抗剂通过抑制钙离子的内流,而有益于治疗缺血性心脏病、心律失常和高血压。近年来,对钙拮抗剂的研究增多,本文就药代动力学、抗高血压、抗心绞痛、抗心衰及副作用等方面,对新一代钙拮抗剂———氨氯地平进行讨论。1　药效及药代动力学氨氯地平为二氢吡啶类衍生物,通过抑制外周血管和冠状动脉平滑肌细胞慢通道的钙离子内流,而明显地舒张外周冠状血管床。Ｍｕｒｄｏｃｈ等[1]在实验中证明:氨氯地平主要作用于外周血管,亦扩张冠状动脉,对窦房结或房室结无明显影响,亦无明显负性肌力作用;增加肾血流量,血药浓度达峰时间为6～12ｈ,生物利用度…     

CYP3A5~*3和CYP3A4~*18B基因多态性对肾移植患者环孢素药代动力学的影响

目的回顾性研究肾脏移植后1mon,CYP3A5*3和CYP3A4*18B基因多态性对CsA药代动力学参数的影响。方法采用PCR-RFLP方法分析了63名肾脏移植患者CYP3A5*3和CYP3A4*18B基因型;荧光偏正免疫法用于检测肾移植患者静脉全血中的CsA浓度。结果在63名肾移植患者中,CYP3A5*3和CYP3A4*18B突变等位基因发生频率分别为0.770(95CI:0.767～0.773),0.235(95CI:0.235～0.241),而且这些等位基因表现出完全连锁不平衡。在移植术后1mon内,携带CYP3A4*1/*1野生型纯合子患者的C0以及剂量校正谷血浓度(C0/D)均明显高于携带CYP3A4*1/*18B杂合子或CYP3A4*18B/*18B突变型纯合子患者(P<0.05,Mann-WhitneyUtest);CYP3A5*1/*1基因型组的给药剂量明显高于CYP3A5*1/*3或CYP3A5*3/*3基因型组(P=0.004<0.01,Kruakal-Wallistest);CYP34*18B和CYP3A5*3联合考虑,对于CYP3A5表达组,同样发现C0、C0/D在CYP3A4*1/*1组C0以及C0/D均明显高于CYP3A4*1/*18B或CYP3A4*18B/*18B组(P<0.05,Mann-WhitneyUtest);而其他药动学参数在CYP3A5*3及CYP3A4*18B各组间相比差异则没有统计学意义。结论CYP3A5*3和(或)CYP3A4*18B基因多态性对肾移植后1monCsA药代动力学有一定影响,移植前CYP3A5*3基因型的分析仍需进一步研究。     

细胞色素 P4503 A4与 P4503 A5及多药耐药基因多态性对氨氯地平降压疗效影响研究

目的：探讨细胞色素 P450（ CYP）3A4倡1G、CYP3A5倡3及多药耐药（MDR1） C1236T、MDR1 G2677T／A和MDR1 C3435T基因多态性对氨氯地平降压疗效的影响。方法纳入159名原发性高血压患者,予氨氯地平5 mg· d－1干预4周,检测相关基因型,分析不同个体CYP3A4、3A5及MDR1相关基因型分布特征,考察不同单核苷酸多态性（ SNP）及MDR1单倍体对氨氯地平降压疗效的影响。结果 CYP3A4倡1G倡1G 基因型舒张压（ DBP）下降幅度显著低于CYP3A4倡1G倡1和CYP3A4倡1倡1（P＜0.05）;CYP3A5倡3倡3基因型DBP下降幅度显著高于CYP3A5倡1倡3和CYP3A5倡1倡1（P＜0.05）;MDR1 C1236T CC、MDR1 G2677T／A AA基因型收缩压（SBP）下降幅度显著高于其他基因型（P＜0.05）;MDR1 C3435T各基因型治疗前后SBP、DBP下降幅度差异均无统计学意义（P＞0.05）。携带MDR1 C3435T CC、MDR1 C3435T CT基因型的患者的DBP下降幅度,女性显著高于男性（ P＜0.05）。对MDR1单倍体分析,各组单倍体治疗前后 SBP、DBP 下降幅度差异均无统计学意义（ P ＞0.05）。结论CYP3A5倡3、CYP3A4倡1G基因多态性可影响氨氯地平降压疗效,MDR1各单倍体未发现与氨氯地平降压疗效相关。     

他克莫司基因组学在肝移植的应用及其研究进展

他克莫司是一种新型强效免疫抑制剂,在临床广泛应用于肝移植等器官移植术后的抗排异治疗。在肝移植人群中,他克莫司的药代动力学及血药浓度存在个体差异,其用药的个体差异与细胞色素P450酶系CYP3A5和P糖蛋白的基因多态性之间存在较密切联系。本文对他克莫司的药效学、药代动力学、血药浓度范围及其药物基因组学的研究进展进行了综述。     

Enzymatic characteristics of CYP3A5 and CYP3A4: a comparison of in vitro kinetic and drug-drug interaction patterns

CYP3A4 and CYP3A5 exhibit significant overlap in substrate specificity, but can differ in catalytic activity and regioselectivity. To investigate their characteristics further, the enzymatic reactions of the two CYP3A enzymes were compared using midazolam, nifedipine, testosterone and terfenadine as substrates. Both CYP3A5 and CYP3A4 showed sigmoid and substrate inhibition patterns for testosterone 6beta-hydroxylation and terfenadine t-butylhydroxylation (TFDOH), respectively. In the other reactions, the kinetic model for CYP3A5 was not similar to that for CYP3A4. An inhibition study demonstrated that the interactions between alpha-naphthoflavone (alphaNF) and CYP3A substrates were different for the two CYP3A enzymes. alphaNF stimulated nifedipine oxidation catalysed by CYP3A5, but did not stimulate that catalysed by CYP3A4. alphaNF at less than 32 microM inhibited TFDOH catalysed by CYP3A5, but did not inhibit that catalysed by CYP3A4. These results indicate that CYP3A5 has different enzymatic characteristics from CYP3A4 in some CYP3A catalysed reactions.     

Enzymatic characteristics of CYP3A5 and CYP3A4: A comparison of in vitro kinetic and drug–drug interaction patterns

CYP3A4 and CYP3A5 exhibit significant overlap in substrate specificity, but can differ in catalytic activity and regioselectivity. To investigate their characteristics further, the enzymatic reactions of the two CYP3A enzymes were compared using midazolam, nifedipine, testosterone and terfenadine as substrates. Both CYP3A5 and CYP3A4 showed sigmoid and substrate inhibition patterns for testosterone 6β-hydroxylation and terfenadine t-butylhydroxylation (TFDOH), respectively. In the other reactions, the kinetic model for CYP3A5 was not similar to that for CYP3A4. An inhibition study demonstrated that the interactions between α-naphthoflavone (αNF) and CYP3A substrates were different for the two CYP3A enzymes. αNF stimulated nifedipine oxidation catalysed by CYP3A5, but did not stimulate that catalysed by CYP3A4. αNF at less than 32?µM inhibited TFDOH catalysed by CYP3A5, but did not inhibit that catalysed by CYP3A4. These results indicate that CYP3A5 has different enzymatic characteristics from CYP3A4 in some CYP3A catalysed reactions.     

Interaction of lapatinib with cytochrome P450 3A5

Lapatinib, an oral tyrosine kinase inhibitor used for breast cancer, has been reported to cause idiosyncratic hepatotoxicity. Recently, it has been found that lapatinib forms a metabolite-inhibitor complex (MIC) with CYP3A4 via the formation of an alkylnitroso intermediate. Because CYP3A5 is highly polymorphic compared with CYP3A4 and also oxidizes lapatinib, we investigated the interactions of lapatinib with CYP3A5. Lapatinib inactivated CYP3A5 in a time-, concentration-, and NADPH-dependent manner using testosterone as a probe substrate with K(I) and k(inact) values of 0.0376 mM and 0.0226 min(-1), respectively. However, similar results were not obtained when midazolam was used as the probe substrate, suggesting that inactivation of CYP3A5 by lapatinib is site-specific. Poor recovery of CYP3A5 activity postdialysis and the lack of a Soret peak confirmed that lapatinib does not form a MIC with CYP3A5. The reduced CO difference spectrum further suggested that a large fraction of the reactive metabolite of lapatinib is covalently adducted to the apoprotein of CYP3A5. GSH trapping of a reactive metabolite of lapatinib formed by CYP3A5 confirmed the formation of a quinoneimine-GSH adduct derived from the O-dealkylated metabolite of lapatinib. In silico docking studies supported the preferential formation of an O-dealkylated metabolite of lapatinib by CYP3A5 compared with an N-hydroxylation reaction that is predominantly catalyzed by CYP3A4. In conclusion, lapatinib appears to be a mechanism-based inactivator of CYP3A5 via adduction of a quinoneimine metabolite.     

Effect of intestinal CYP3A5 on postoperative tacrolimus trough levels in living-donor liver transplant recipients

It has been reported that hepatic and intestinal cytochrome P450 (CYP) 3A4, CYP3A5 and P-glycoprotein affect the pharmacokinetics of tacrolimus, and that these proteins are associated with the large inter-individual variation in the pharmacokinetics of this drug. We previously showed that the concentration/dose ratio of tacrolimus tended to be lower in recipients of living-donor liver transplantation (LDLT) with a CYP3A5*1/*1-carrying graft. However, the effect of intestinal CYP3A5 remains to be elucidated. In the present study, we examined the CYP3A5 genotype in both recipients and donors, and the effect of the recipients' polymorphism on the concentration/dose ratio of tacrolimus in patients after LDLT. The CYP3A5*3 allele frequency was 80% in recipients and 77% in donors. The intestinal CYP3A5 mRNA expression level was significantly associated with genotype. The tacrolimus concentration/dose ratio was lower in recipients with the CYP3A5*1/*1 and *1/*3 genotype (CYP3A5 expressors) compared to the CYP3A5*3/*3 genotype (non-expressors). Amongst the combination of CYP3A5 genotypes between the graft liver and the native intestine, CYP3A5 expressors in both the graft liver and the native intestine had the lowest concentration/dose ratio of tacrolimus during 35 days after LDLT. Patients with the intestinal CYP3A5*1 genotype tended to require a higher dose of tacrolimus compared to the other group with the same hepatic CYP3A5 genotype. These results indicate that intestinal CYP3A5, as well as hepatic CYP3A5, plays an important role in the first-pass effect of orally administered tacrolimus.     

Differential mechanism-based inhibition of CYP3A4 and CYP3A5 by verapamil.

The genetic basis for polymorphic expression of CYP3A5 has been recently identified, but the significance of CYP3A5 expression is unclear. The purpose of this study is to quantify the capability of verapamil, a mechanism-based inhibitor of CYP3A, and its metabolites to inhibit the activities of CYP3A4 and CYP3A5, and to determine whether CYP3A5 expression in human liver microsomes alters the inhibitory potency of verapamil. Testosterone 6beta-hydroxylation or midazolam 1'-hydroxylation was used to quantify CYP3A activity. The possibility that verapamil and its metabolites form metabolic-intermediate complex (MIC) with CYP3A was assessed using dual beam spectrophotometry. Verapamil and N-desalkylverapamil (D617) were found to have little inhibitory effect on cDNA-expressed CYP3A5 activity and did not form a MIC with cDNA-expressed CYP3A5 as indicated by the appearance of the characteristic peak at 455 nm. At 50 microM, norverapamil showed time-dependent inhibition of CYP3A5 (30%), but to a much lesser extent compared with that of CYP3A4 (80%). The estimated values of the inactivation parameters k(inact) and K(I) of norverapamil were 4.53 microM and 0.07 min(-1) for cDNA-expressed CYP3A5, and 10.3 microM and 0.30 min(-1) for cDNA-expressed CYP3A4. Human liver microsomes that expressed CYP3A5 were less inhibited by both verapamil and norverapamil. The inactivation efficiency of verapamil and norverapamil was 30 times and 45 times lower, respectively, for CYP3A5-expressing microsomes compared with CYP3A5-non-expressing microsomes. These findings indicate that the presence of variable CYP3A5/CYP3A4 expression in the liver may contribute to the interindividual variability associated with verapamil-mediated drug interactions.     

CYP3A5 genotype-phenotype analysis in the human kidney reveals a strong site-specific expression of CYP3A5 in the proximal tubule in carriers of the CYP3A5*1 allele

Interindividual variability in the drug-metabolizing activity of the CYP3A5 enzyme is mainly due to a single nucleotide polymorphism in CYP3A5, leading to low expression in homozygous CYP3A5*3/*3 individuals compared with CYP3A5*1 allele carriers. In the human kidney, expression of CYP3A5 has been implicated in blood pressure regulation and calcineurin inhibitor-associated nephrotoxicity. The effect of the CYP3A5*1/*3 polymorphism on the expression level and protein distribution within the human kidney is not well characterized. Therefore, we performed a genotype-phenotype analysis of CYP3A5 mRNA and protein expression in the human kidney. To this end, we analyzed sections of normal kidney tissue obtained from 93 white individuals undergoing nephrectomy by quantitative mRNA expression analysis. Qualitative protein expression analysis of CYP3A5 was performed by immunohistochemistry. Mean renal mRNA expression of carriers of the CYP3A5*1 (n = 12) allele was more than 18-fold higher than that of CYP3A5*3/*3 carriers (n = 81, p < 0.001). Immunohistochemical analysis demonstrated CYP3A5 protein in all epithelia of the nephron in kidney sections with the CYP3A5*3/*3 genotype. In carriers of the CYP3A5*1 allele, a strong increase in protein expression of CYP3A5 was detected, and this was confined to the proximal tubule. This study confirms a significant effect of the CYP3A5*1/*3 polymorphism on CYP3A5 expression in the normal human kidney and reveals a strong nephron segment-specific difference in the CYP3A5 protein expression limited to the proximal tubule.     

A significant drug-metabolizing role for CYP3A5?

Recent research on CYP3A5 in vitro and in humans has provided discordant information on whether CYP3A5 plays a significant role in the metabolism of CYP3A substrates in vivo. For example, six separate studies have reported CYP3A5 to contribute between 2 and 60% of the total hepatic CYP3A. Suggested explanations for the reported differences in hepatic CYP3A5 levels are evaluated in this article. Furthermore, a sensitivity analysis of the contribution of CYP3A5 (in addition to CYP3A4) to the metabolism of a "midazolam"-type substrate based on recently published in vitro and clinical data is compared with the results of two in vivo studies that investigated the influence of CYP3A5 genotype on midazolam pharmacokinetics. The sensitivity analysis predicts an approximately 3-fold lower AUCoral for midazolam for those expressing the highest hepatic and intestinal levels of CYP3A5 (e.g., possessing CYP3A5*1 alleles) compared with those individuals who express insignificant amounts of CYP3A5, assuming CYP3A4 levels are the same in both groups and that CYP3A5 levels do not exceed those of CYP3A4 in CYP3A5*1 homozygotes. In contrast, the two in vivo studies show no statistically significant influence of CYP3A5 genotype on midazolam pharmacokinetics. The discordance between the prediction and the results from the two in vivo studies is discussed.     

Significance of the minor cytochrome P450 3A isoforms

Cytochrome P450 (CYP) 3A4 is responsible for most CYP3A-mediated drug metabolism but the minor isoforms CYP3A5, CYP3A7 and CYP3A43 also contribute. CYP3A5 is the best studied of the minor CYP3A isoforms. It is well established that only approximately 20% of livers express CYP3A5. The most common reason for the absence of expression is a splice site mutation. The frequency of variant alleles shows interethnic differences, with the wild-type CYP3A5*1 allele more common in Africans than Caucasians and Asians. In individuals who express CYP3A5, the percentage contributed to total hepatic CYP3A by this isoform is still unclear, with estimates ranging from 17% to 50%. CYP3A5 is also expressed in a range of extrahepatic tissues. Only limited information is available on the regulation of CYP3A5 expression but it appears to be inducible via the glucocorticoid receptor, pregnane X receptor and constitutive androstane receptor-beta, as for CYP3A4. Although information on the substrate specificity of CYP3A5 is limited compared with CYP3A4, there have been a number of recent pharmacokinetic studies on a small range of substrates in individuals of known genotype to investigate the contribution of CYP3A5. In the case of midazolam, ciclosporin, nifedipine and docetaxel, clearance by individuals with a CYP3A5-expressing genotype did not differ from that for nonexpressors, but in the case of tacrolimus, eight independent studies have demonstrated faster clearance by those carrying one or two CYP3A5*1 alleles. This may reflect faster turnover of tacrolimus by CYP3A5 than the other substrates. CYP3A5 genotype may affect cancer susceptibility. Certain combined CYP3A4/CYP3A5 haplotypes show differential susceptibility to prostate cancer and there is a nonsignificant increase in the risk of small-cell lung cancer for a CYP3A5*1/*1 genotype. Females positive for CYP3A5*1 appear to reach puberty earlier, which may affect breast cancer risk. CYP3A5*1 homozygotes may have higher systolic blood pressure.CYP3A7 is predominantly expressed in fetal liver but is also found in some adult livers and extrahepatically. The molecular basis for expression in adult liver relates to upstream polymorphisms, which appear to increase homology to CYP3A4 and make regulation of expression more similar. CYP3A7 has a specific role in hydroxylation of retinoic acid and 16alpha-hydroxylation of steroids, and is therefore of relevance both to normal development and carcinogenesis.CYP3A43 is the most recently discovered CYP3A isoform. In addition to a low level of expression in liver, it is expressed in prostate and testis. Its substrate specificity is currently unclear. Polymorphisms predicting absence of active enzyme have been identified.