以尿液中6β-羟基氢化可的松/氢化可的松比值评估CYP3A活性及对儿童个体化用药的指导

【作者】 张健；

【导师】 蒋新国；

【作者基本信息】 复旦大学 ， 药剂学， 2008， 硕士

【摘要】 肝脏是药物代谢的主要场所,而肝脏进行生物转化则依赖于微粒体中的多种酶系,其中最重要的是细胞色素P4503A酶(CYP3A)。CYP3A在肝脏的含量极为丰富,是人体肝脏中最主要表达酶,也存在于在人体的其它部位,如肠、胃、食道、外周血液等。目前已经发现临床使用的众多药物都由CYP3A所催化代谢。由于CYP3A酶的影响因素较多,如遗传多态性、激素、年龄、机体状态、营养、疾病、吸烟、饮酒等,其中尤以药物能够显着影响该酶的活性,因此,为使患者获得最佳治疗效果,并避免药物不良反应,真正达到“用药个体化”的目的,需要测定CYP3A酶的活性。目前,CYP3A活性常用的测定方法有红霉素呼吸试验、咪唑安定法等,这些方法均需服用非治疗目的的化学药物。最近,有学者提出测定尿液中游离的氢化可的松(free cortisol,FC)及其代谢产物6β-羟基氢化可的松(6β-hydroxycortisol,6β-OHFC)的方法评价CYP3A酶的活性,因为其利用内源性物质,无需服用任何药物,可能是目前最安全、最简单的CYP3A酶活性测定方法。另一方面,通过尿液中6β-OHFC和FC的比值反映CYP3A酶的活性,还可改善现行根据血药浓度测定对人体造成的损伤性和方法的复杂性,为临床个体化用药提供一个更为简便、可靠的分析手段。本课题拟采用高效液相色谱法(high-performance liquid chromatographic,HPLC)测定尿液中6β-OHFC/FC的方法,首次对中国健康儿童肝药酶CYP3A活性进行大样本的筛查。同时,还对急性淋巴细胞白血病儿童进行探索,希望能为儿童的白血病个体化治疗提供理论基础。本文共分为四部分:第一部分运用HPLC方法测定尿液中6β-OHFC/FC,完成该方法的可行性、准确性评价。第二部分,通过尿液中6β-OHFC/FC的测定,对中国健康儿童肝药酶CYP3A活性进行大样本的筛查,对上海地区儿童的CYP3A活性分布有了较为客观和全面的数据。分析各种因素包括年龄、性别、青春期等对CYP3A活性的影响。第三部分,收集55例白血病患儿,通过对比化疗前后和不同疾病状态下6β-OHFC/FC比值,并且把国际通用作为白血病危险度及预后评估的重要指标微量残留病(Minimal residual disease,MRD)监测与6β-OHFC/FC比值联系起来,结果发现化疗对CYP3A活性有显着影响,并且CYP3A活性与治疗的结果有一定的相关性。提示白血病患儿临床上化疗前后CYP3A酶活性变化与患儿体内某些药物动力学参数有一定的相关性。第四部分,以依托泊苷(Etoposide,VP16)为例,研究不同药酶活性下VP16的血药浓度和半衰期是否存在相关性。结果药酶活性与VP16的血药浓度无相关性,而半衰期跟药酶活性相关,提示药酶活性会影响到VP16的代谢与排泄,关注给药频次的调整将影响到VP16的稳态血药浓度。更多还原

【Abstract】 Liver plays an important role in drug metabolism,and various enzyme systems are responsible for biotransformation in liver.The CYP3A enzymes are the most important and abundantly expressed cytochrome P450 enzymes in liver,and also expressed in intestine, stomach,esophagus and peripheral blood.Furthermore,CYP3A are very important for oxidative biotransformation of endogenous compounds and exogenous chemicals.However, CYP3A enzymes can be influenced by many factors,such as genetic polymorphism, hormone,age,medicine,disease,alcohol and so on.The medicine is the most impotant factor and can conspicuously change the activity of CYP3A enzymes above them.In order to help patients obtaining best therapeutic efficacy,and also refraining from drug adverse reactions, CYP3A enzymatic activity in clinic needs to be measured for the real individual therapy.So far,the common assay methods of CYP3A enzymatic activity include erythromycin breath test,midazolam and so on,but all of them need to take epactal chemicals as probe. Recently,some researchers find that urinary metabolite of endogenous cortisol may estimate CYP3A enzymatic activity.Without probe and non-invasive,urinary metabolite of exogenous cortisol may be the safest and most simple way to estimate CYP3A activity.At the same time, this simple and non-invasive procedure can retrieve medicine concentration measurement insufficient,and also provide a new way for individual therapy.In the study,we plan to screen the CYP3A activity in Chinese healthy children by measuring 6β-hydroxycortisol in urinary excretion through high-performance liquid chromatographic method.Moreover,we will use this new method to study acute lymphoblastic leukemia children,which may help us to gain some new suggestion and theory foundation for individual therapy.There are four parts in the study:The first part:To evaluate the accuratissime and feasibility of stimated cytochrome P450 activity by determining 6β-OHFC/FC in urinary through HPLC method.The second part:By using measure 6β-OHFC/FC in urinary,we study distribute of CYP3A activity in Chinese healthy children,and also analyze all the influnced factors such as age,gender,juvenescent phase and so on.The third part:We enrolled 55 acute leukocythemia children in the study,and then study 6β-OHFC/FC.We contrast the 6β-OHFC/FC proportionalities of AP∶PA chems and different disease to look forward to investigate the possible influencing factors.In the study, we find that chemical will significant chang CYP3A activity.Moreover,there is significant relationship between CYP3A activity and curative effect.This result suggests that maybe it is same relationship beween CYP3A activity and substrate pharmacodynamics.The fourth part:We used VP16 to study the relationship between pharmacokinetics parameter and CYP3A activity.In our study,we found no relationship between VP16 plasma concentration and CYP3A activity,but significant relationship between half life and CYP3A activity is found.This result suggests that CYP3A activity can influence the metabolite and excrete of VP16.So,this phenomenon suggests that the adjustment of administration frequency in clinical can influence the plateau concentration of VP 16.更多还原