血脑屏障上P-糖蛋白与耐药性癫痫关系的研究进展

耐药性癫痫是治愈癫痫的难点,癫痫是脑部神经元高度同步化异常放电的临床综合表现,长期服药造成耐药性,称之为耐药性癫痫。耐药性癫痫与血脑屏障上P-糖蛋白过度表达存在密切关系。本文首先介绍P-糖蛋白的结构和功能,P-糖蛋白阻止抗癫痫药物进入血脑屏障发挥作用,然后阐述血脑屏障上P-糖蛋白与耐药性癫痫关系,最后介绍治疗耐药性癫痫的进展,通过调节P-糖蛋白功能到适度为耐药性癫痫患者带来了福音。     

黄连治疗癫痫的协同作用及对P-糖蛋白介导的抗癫痫药脑转运的调节作用

目的 考察黄连协同抗癫痫药治疗癫痫的疗效及黄连对P-糖蛋白介导的抗癫痫药透过血脑屏障的影响,评价黄连对癫痫的防治作用。方法 选用P-糖蛋白抑制剂维拉帕米和常用抗癫痫药卡马西平,使用戊四唑和士的宁制备小鼠癫痫模型,观察并对比卡马西平单用与联用低、中、高剂量黄连的小鼠潜伏期、惊厥率和死亡率的差异。小鼠分组并灌胃卡马西平、卡马西平加黄连及卡马西平加维拉帕米后,测定脑组织卡马西平浓度并比较。结果 黄连可显著增强卡马西平对抗戊四唑、士的宁所引起的癫痫作用,延长潜伏期和降低惊厥率(P<0.05),明显提高卡马西平的脑浓度(P<0.05)。结论 黄连对癫痫的治疗有良好的增效作用。     

P-糖蛋白抑制剂的研究进展

介绍P-糖蛋白抑制剂的发展、P-糖蛋白抑制剂的特性及第二代和第三代抑制剂的临床应用现状。多药耐药是肿瘤化疗失败原因之一，其以P-糖蛋白的过度表达为特征，导致化疗药物从癌细胞中的外排增加，使疗效降低。因此有效抑制P-糖蛋白的活性可逆转肿瘤的多药耐药性。     

P-糖蛋白抑制药逆转肿瘤多药耐药的研究进展

P-糖蛋白（permeability glycoprotein，P-gp）过度表达是多药耐药（multidrug resistance，MDR）产生的主要原因，P-糖蛋白抑制药可以抑制P-糖蛋白对肿瘤药物的外排作用，使肿瘤细胞内的药物浓度提高，从而逆转肿瘤MDR，第3代P-糖蛋白抑制药具有高效、低毒、选择性高等特点，中药可以通过多种途径抑制P-糖蛋白的表达和功能，从而逆转MDR。     

P-糖蛋白药物外排作用的研究进展

P-糖蛋白是一个ATP依赖性外排泵,在多药耐药肿瘤细胞和血脑屏障上均有高度表达。P-糖蛋白的药物外排作用参与了肿瘤多药耐药性,降低了药物在脑内的浓度。P-糖蛋白抑制剂则可以抑制P-糖蛋白的药物外排作用,从而逆转肿瘤多药耐药性,增加药物的脑摄取量。     

P-糖蛋白及其逆转肿瘤细胞多药耐药性的研究进展

随着化疗药物的广泛使用,肿瘤多药耐药性是导致化疗失败的主要原因之一。而p-糖蛋白（P-gp）介导的多药耐药性已成为目前的研究热点,本文就P—gp的结构、组织分布、P—gp介导的肿瘤细胞的多药耐药性及其逆转的研究现状作一综述。     

血脑屏障上的P-糖蛋白与精神类药物

P-糖蛋白(P-gp)是ABC超家族的重要成员,而许多精神药物包括抗精神分裂症药物和抗抑郁症药物,都是P-gp的底物。本文对近年来国内外有关P-gp对精神药物限制进入血脑屏障的相关研究,进行了综述。     

慢性肝损伤对大鼠脑内P-GP及MRP2功能和表达的影响

血脑屏障（BBB）通过其特有的紧密连接结构和多种药物外排转运体表达以达到限制外周物质进入脑内,保持脑内环境稳态作用。在BBB上主要介导药物/毒物外排的转运体是ATP结合盒（ABC）转运体,包括P-糖蛋白（P-gp）、乳腺癌耐药蛋白（BCRP）和多药耐药相关蛋白（MRPs）。ABC转运体可促进脑内毒物外排或限制毒物入脑,防止脑内毒物蓄积,但这也是多种中枢疾病治疗药物难以入脑,导致治疗失败的原因之一。近来研究显示一些疾病包括中枢神经疾病、糖尿病和肝损伤均可改变BBB上ABC转运体功能与表达,使药物脑内分布改变,导致药物中枢活性或毒性增加。概述几种神经系统疾病、糖尿病和肝损伤等疾病状态下,BBB上ABC转运体功能与表达改变及其临床意义,以期为各疾病状态下的药物-药物相互作用研究提供参考,并为新治疗策略提供思路。

     

Celecoxib treatment restores pharmacosensitivity in a rat model of pharmacoresistant epilepsy

Background and purpose:

A functional link between seizure-induced P-glycoprotein overexpression at the blood–brain barrier and therapeutic failure has been suggested by several studies using rodent epilepsy models and human epileptic tissue. Recently, we reported that interference with the mechanisms that up-regulate P-glycoprotein in response to seizure activity might provide a novel approach to control its expression in the epileptic brain. Based on these data, we hypothesized that blocking the appropriate signalling cascade by cyclooxygenase-2 inhibition should improve brain penetration of antiepileptic drugs and help to overcome drug resistance.

Experimental approach:

Effects of the selective cyclooxygenase-2 inhibitor celecoxib on the response to the P-glycoprotein substrate, phenobarbital, was evaluated in a chronic model of drug-resistant temporal lobe epilepsy in rats. Drug-resistant rats selected from this model exhibit a marked overexpression of P-glycoprotein in the hippocampus and other limbic brain regions.

Key results:

Responders and non-responders were selected from a group of rats with spontaneous recurrent seizures after prolonged treatment with phenobarbital at maximum tolerated doses. The efficacy of phenobarbital was re-evaluated following a 6 day treatment with celecoxib and the frequency of spontaneous recurrent seizures was significantly reduced in both groups of rats, phenobarbital responders or non-responders selected from the previous drug trial.

Conclusions and implications:

Pretreatment with the cyclooxygenase-2 inhibitor restored the anticonvulsant activity of phenobarbital in rats that failed to exhibit a relevant response before celecoxib treatment. Our data provide further support for a novel therapeutic approach to overcome transporter-mediated drug resistance in epilepsies.     

胰岛素抵抗大鼠血脑屏障上P-糖蛋白表达和转运功能的研究

目的:建立胰岛素抵抗大鼠模型,观察胰岛素抵抗大鼠血脑屏障(BBB)上P-糖蛋白(P-gp)的表达和转运功能.方法:采用高脂饲料喂养制备胰岛素抵抗大鼠模型,用口服葡萄糖耐量、胰岛素耐量和胰岛素敏感性指数评价大鼠胰岛素抵抗.用伊文思蓝检测BBB通透性,用透射电镜观察BBB的完整性,用Westem blot测定BBB上P-gp的蛋白水平,用RT-PCR技术检测BBB上mdrla/mdrlb的mRNA水平,用Rh123累积实验测定BBB上P-gp的转运功能.结果:用高脂饲料喂养大鼠6周后,葡萄糖耐量和胰岛素耐量明显异常,空腹胰岛素含量显著升高,胰岛素敏感性显著下降.胰岛素抵抗大鼠BBB上P-gp表达水平和转运功能显著下降,但BBB通透性和完整性未发生明显改变.结论:胰岛素抵抗下调BBB上P-gp表达和转运功能.     

The multidrug transporter P-glycoprotein in pharmacoresistance to antiepileptic drugs

This review provides an overview of the knowledge on P-glycoprotein (P-gp) and its role as a membrane transporter in drug resistance in epilepsy and drug interactions. Overexpression of P-gp, encoded by the ABCB1 gene, is involved in resistance to antiepileptic drugs (AEDs), limits gastrointestinal absorption and brain access of AEDs. Although several association studies on ABCB1 gene with drug disposition and disease susceptibility are completed to date, the data remain unclear and incongruous. Although the literature describes other multidrug resistance transporters, P-gp is the main extensively studied drug efflux transporter in epilepsy.     

P-糖蛋白限制经血脑屏障的尼莫地平转运(英文)

目的:研究P-糖蛋白(P-gp)是否限制尼莫地平(NMD)从血液循环进入脑内。方法:当原代培养的鼠脑微血管内皮细胞(BCEC)长至互相连接成片时,加入含有NMD 10mg/L的Hanks’液37℃温孵,记录细胞摄取NMD的时间过程,将含有NMD和各种不同受试药物的Hanks’液分别加入到不同培养孔中,检测90min时细胞对NMD的摄取量,在细胞摄取NMD 90min后,分别加入红霉素,克拉霉素和环孢素A以检测P-糖蛋白抑制剂对原代培养的脑微血管内皮细胞外排NMD的影响。结果:细胞对NMD的摄取呈时间依赖性,P-gp抑制剂或代谢抑制剂的加入会增加稳态时NMD在细胞内的浓度,P-gp抑制剂的加入也使NMD的外排受到了抑制。结论:P-gp限制NMD进入脑内,P-gp抑制剂的加入可增加NMD的进入。     

新钙调素抑制剂E6对纯化的原代培养大鼠脑微血管内皮细胞上P-糖蛋白活性的影响

目的：研究新的钙调素抑制剂E6对纯化的原代培养大鼠脑微血管内皮细胞上P-糖蛋白活性的影响．方法：使用流式细胞仪纯化大鼠脑微血管内皮细胞，通过检测P-糖蛋白底物罗丹明123在大鼠脑微血管内皮细胞中的荧光评估E6对P糖蛋白功能的影响．结果：使用流式细胞仪能将大鼠脑微血管内皮细胞从其它杂细胞中分离纯化，3，10μmol／LE6和50umol／L维拉帕米能显著提高大鼠脑微血管内皮细胞内罗丹明123的含量（P〈0.01),10μmol/L E6能使罗丹明123的胞内浓度增加接近三倍,而无P-糖蛋白表达的人脐静脉内皮细胞中的罗丹明123浓度则不受影响.结论:E6能显著抑制大鼠脑微血管内皮细胞上P-糖蛋白活性.     

The Effects of Clioquinol on P-glycoprotein Expression and Biometal Distribution in the Mouse Brain Microvasculature

Previous studies have demonstrated that the ionophore clioquinol (CQ), in conjunction with the biometals copper and zinc, increases the expression of P-glycoprotein (P-gp) in human cerebral microvascular endothelial (hCMEC/D3) cells. As P-gp expression and function at the blood-brain barrier (BBB) is of great interest regarding CNS drug access and endogenous toxin trafficking (e.g., amyloid beta), the present study assessed the in vivo translation of these previous in vitro findings. Swiss outbred mice received an 11-day treatment of CQ (30 mg/kg) by oral gavage, after which brain microvessel-enriched fractions (MEFs) and surrounding interfaces (subcortical brain tissue and plasma) were extracted. P-gp expression was quantified in the MEF, and biometal concentrations in all 3 compartments were assessed via inductively coupled plasma mass spectrometry. CQ treatment did not modify the expression of P-gp, nor copper or zinc concentrations in the brain MEF under this treatment regime. Metallomic analysis revealed, however, that CQ reduced potassium and magnesium levels in the brain MEF and also lowered brain iron levels. This study has shown that under this dosing regimen, CQ does not increase BBB P-gp expression in Swiss outbred mice, but that CQ facilitates redistribution of certain metal ions within the brain MEF, plasma, and brain parenchyma.     

Functional Evidence for P-glycoprotein at the Nose-Brain Barrier

No HeadingPurpose. Experiments were performed to assess the brain distribution of [³H]-verapamil, including the influence of delivery route of inhibitor and substrate (nasal vs. systemic) on brain distribution. The anatomic location of P-glycoprotein (P-gp) at the nose-brain barrier also was investigated.Methods. Separate groups of mice were pretreated with rifampin or vehicle nasally or intravenously. [³H]-verapamil was administered either nasally or via in situ brain perfusion, and dose-response profiles were constructed for P-gp inhibition. Localization of P-gp in freshly obtained brain slices and olfactory tissue was evaluated by confocal microscopy.Results. Rifampin inhibited the P-gp–mediated efflux of [³H]-verapamil, regardless of delivery route (I_max = 62 ± 6%). The ED₅₀ for enhancement of [³H]-verapamil uptake by nasal rifampin was 400-fold lower than for intravenous rifampin (0.16 vs. 65 mg/kg, respectively). Microscopy showed that P-gp was located in endothelial cells that line the olfactory bulb and within the olfactory epithelium.Conclusion. Nasal delivery of rifampin enhanced brain uptake of [³H]-verapamil. The magnitude of transport inhibition was dependent on the dose and route of the inhibitor, the time after administration of the inhibitor, and the specific brain region examined. P-gp is localized to both the olfactory epithelium and the endothelial cells that surround the olfactory bulb.     

Multidrug resistance in epilepsy: a pharmacogenomic update

Multidrug resistance is one of the most serious problems in the treatment of epilepsy and is likely to have a complex genetic and environmental basis. Various experimental data support the hypothesis that overexpression of antiepileptic drug transporters may be important. However, key questions concerning their functionality remain unanswered. The first study reporting a positive association – between genetic variation in a putative antiepileptic drug transporter (P-glycoprotein, encoded by ABCB1) and multidrug resistant epilepsy was published in 2003. Since then, several other association genetics studies have sought to confirm this result, but, taken overall, do not support a major role for this polymorphism. Lessons learnt from the ABCB1 studies can help guide future association genetics studies, both for multidrug resistance in epilepsy, and for other epilepsy phenotypes.