Caco-2细胞中药物转运蛋白的mRNA表达及活力评价

目的 系统研究Caco-2细胞中各药物转运蛋白的mRNA表达水平及转运活力,对比其与人正常肠道中药物转运蛋白表达的差异。方法 实时荧光定量PCR（qRT-PCR）方法测定Caco-2细胞中人肠道相关转运蛋白MDR1、BCRP、MRP2、OATP1A2、OATP2B1和PEPT1的表达水平;将Caco-2细胞接种于Transwell板内培养21 d并给予不同药物转运蛋白的底物及抑制剂,评价Caco-2细胞中相关转运蛋白的转运活性。结果 qRT-PCR结果表明,药物转运蛋白MDR1、MRP2、BCRP和OATP2B1在Caco-2细胞中均有相对高的表达,表达量的顺序为：MDR1 > MRP2 > OATP2B1 > BCRP,在正常人肠道表达量顺序为BCRP > MDR1 > MRP2 > OATP2B1;转运蛋白活力评价表明,各药物转运蛋白的活力测试结果均为阳性,验证了基因的表达水平结果。结论 Caco-2细胞中表达正常人体肠道表达的部分药物转运蛋白（MDR1、MRP2、BCRP和OATP2B1）,表达水平与正常人体肠道中大致相当,但也存在一定差异。     

ABC跨膜转运蛋白外排抑制剂促进药物肠吸收的研究进展

药物的肠吸收受肠道内的外排转运蛋白影响,其中ABC跨膜转运蛋白为目前已知的主要外排转运蛋白。近年开发的可直接抑制转运蛋白外排作用的外排抑制剂大多属于非离子表面活性剂和植物天然成分。本文综述这两类外排抑制剂的研究进展。     

肠道药物转运体及其研究方法

口服药物在肠道中的吸收是决定药物生物利用度的重要因素。肠道中有许多药物膜转运蛋白介导药物的吸收、分布、排泄及药物相互作用等。明确其转运机制有利于提高药物的安全性和有效性,从而指导临床合理用药。通过体内外方法预测药物经转运体在肠道中的转运情况。本文介绍了肠道内转运药物的主要膜转运蛋白,阐述了口服药物经肠道转运机制,概括了研究肠道药物转运体的主要研究方法,并对多种体内外转运体研究方法的优缺点进行了比较。     

MRP1/MRP2与重金属转运的研究进展

多药耐药相关蛋白(multidrug resistance-associatedprotein,MRPs)是ATP结合盒式转运蛋白(ATP-binding cassette,ABC)家族中的一个亚群,1992年由Cole等[1]最初在耐阿霉素小细胞肺癌细胞株H69/AR的研究中发现,该耐药细胞株表达了一种不同于P糖蛋白(P-gp)的蛋白,此后命名为多药耐药相关蛋白1(multidrug resistance-associated protein 1,MRP1/ABCC1)。随后人们又陆续发现多药耐药相关蛋白2(multidrugresistance-associated protein 2,MRP2/ABCC2)及MRPs的其他成员。MRP1和MRP2是细胞代谢产物、药物、     

基于原位单向肠灌流模型研究没食子酸的肠吸收特性

目的考察没食子酸的肠道吸收特性,为提高鞣质类成分生物利用度提供理论依据。方法采用大鼠在体肠单向灌流模型、建立HPLC测定没食子酸的方法,并计算没食子酸在各肠段的吸收速率常数(Ka)及有效表观渗透率系数(Peff);分别研究吸收部位、药物浓度、时间、pH值、P-糖蛋白(P-gp)和多药耐药相关蛋白-2(MRP2)抑制剂对没食子酸吸收的影响。结果没食子酸在不同肠段的Ka顺序为空肠>十二指肠>回肠≈结肠;随着药物浓度的升高,没食子酸的吸收差异无显著性;酸性环境(pH 5.5)有利于没食子酸的吸收;加入P-gp和MRP2抑制剂后,没食子酸的吸收与不加P-gp和MRP2抑制剂比较差异有显著性(P<0.05)。结论没食子酸在大鼠肠道内有较好的吸收,在空肠中吸收最好。初步判断其吸收机制为被动扩散。没食子酸的吸收受P-gp和MRP2的外排影响,可能为P-gp和MRP2底物。     

药物外排泵和转运蛋白对口服药物吸收影响的研究进展

人体肠道的药物外排泵和转运蛋白对口服药物的吸收有较大影响,常见的药物外排泵有P-糖蛋白和多药耐药相关蛋白,会降低相关底物吸收;其它的一些转运蛋白如有机离子转运蛋白家族、H+/单羧酸共转运蛋白和肽转运蛋白可促进相关底物的吸收.作者对药物外排泵和转运蛋白近年来的相关研究进行了综述,并指出了药物外排泵和转运蛋白今后可能的研究方向.     

Caco-2细胞系及其在药物吸收、代谢中的应用

由于小肠的生理结构适用于药物吸收 ,所以口服给药是最广泛、最方便的给药途径之一 ,因此研究药物在肠道的吸收与代谢就显得十分必要。目前用于药物吸收的实验方法主要有 :在体肠回流法 ,肠襻法 ,分离肠粘膜法、外翻囊法等 [1 ]。由于这些方法存在采用动脉组织及其它一些局限性 ,近年来人们尝试使用人肠细胞培养系统来研究药物在肠道的吸收和代谢 ,以快速筛选口服药物。Caco-2细胞模型被认为是目前最好的体外吸收模型 ,可用于快速评估新药的细胞渗透性、阐明药物转运的途径、评价提高膜通透性的方法、确定被动扩散的药物最合适的理化性质和…     

有机阴离子转运肽在药物转运中的作用

溶质运载蛋白家族(solute carrier family,SLC)和ATP结合盒转运蛋白家族(ATP binding cas-sette family,ABC)在药物吸收、消除和组织分布中起重要作用。本综述将对有机阴离子转运肽(or-ganic anion transporting polypeptide,OATP)的最新命名、分类、组织分布、功能及在药物转运中的作用加以介绍。     

植物药对MDR1基因的调控及对P-gp功能的影响

P糖蛋白（P-gp）是由人类MDR1基因编码的磷酸糖蛋白,是三磷酸腺苷（ATP）转运蛋白超家族成员之一,具有ATP依赖性的药物外排泵功能。定向诱变研究显示,P-gp各处都分布着药物结合位点,甚至是ATP结合区域。P—gp在肝、肾、胰腺、小肠、结肠、肾上腺的上皮细胞及血脑屏障表面高度表达,在药物的吸收、分布、排泄过程中发挥着重要作用。     

降血脂药物研究进展

综述了近年来降血脂药物的研究进展,包括他汀类、贝特类、胆固醇吸收抑制刺、胆固醇酯转运蛋白抑制剂、微粒体甘油三酯转运蛋白抑制剂、酰基辅酶A-胆固醇酰基转移酶抑制剂等.     

Multidrug resistance proteins (MRPs) and implication in drug development

The multidrug resistance protein (MRP)‐related ABCC family (MRP1, MRP2, MRP3, MRP4, MRP5, MRP6, MRP7, MRP8, and MRP9) belongs to the ATP‐binding cassette (ABC) superfamily of transport proteins. They are capable of transporting a structurally diverse array of endo‐ and xenobiotics and their metabolites across cell membranes. These transporters play an important role in the absorption, disposition, and elimination of these compounds in the body. In particular, increased expression of these drug transporters in tumor cells is associated with resistance to a number of important chemotherapeutic agents. This review highlights the biochemical and pharmacological properties of MRP1‐9 and their implications in drug development. A detailed study on the biochemical function and regulation of MRPs is important in drug development, as this may help to avoid drug toxicity, drug resistance, and drug‐drug interactions and to optimize cancer chemotherapy. Drug Dev. Res. 64:1–18, 2005. © 2005 Wiley‐Liss, Inc.     

The MRP-related and BCRP/ABCG2 multidrug resistance proteins: biology, substrate specificity and regulation

Several members of different families of the ATP-binding cassette (ABC) superfamily of transport proteins are capable of transporting an extraordinarily structurally diverse array of endo- and xenobiotics and their metabolites across cell membranes. Together, these transporters play an important role in the absorption, disposition and elimination of these chemicals in the body. In tumor cells, increased expression of these drug transporters is associated with resistance to multiple chemotherapeutic agents. In this review, current knowledge of the biochemical, physiological and pharmacological properties of nine members of the multidrug resistance protein (MRP)-related ABCC family (MRP1, MRP2, MRP3, MRP4, MRP5, MRP6, MRP7, ABCC11 and ABCC12) as well as the G family member, ABCG2/BCRP, are summarized. A focus is placed on the structural similarities and differences of these drug transporters as well as the molecular determinants of their substrate specificities and transport activities. Factors that regulate expression of the MRP-related proteins and ABCG2/BCRP are also reviewed.     

Proteomic analysis for the impact of hypercholesterolemia on expressions of hepatic drug transporters and metabolizing enzymes

1. Our objective is to investigate the alterations of hepatic drug transporters and metabolizing enzymes in hypercholesterolemia. Male Sprague–Dawley rats were fed high-cholesterol chows for 8 weeks to induce hypercholesterolemia. Protein levels of hepatic drug transporters and metabolizing enzymes were analyzed by iTRAQ labeling coupled with LC TRIPLE-TOF.

2. Total 239 differentially expressed proteins were identified using proteomic analysis. Among those, protein levels of hepatic drug transporters (MRP2, ABCD3, OAT2, SLC25A12, SCL38A3, SLC2A2 and SLC25A5) and metabolizing enzymes (CYP2B3, CYP2C7, CYP2C11, CYP2C13, CYP4A2 and UGT2B) were markedly reduced, but the levels of CYP2C6 and CYP2E1 were increased in hypercholesterolemia group compared to control. Decreased expressions of drug transporters MRP2 and OAT2 were further confirmed by real time quantitative PCR (RT-qPCR) and western blot.

3. Ingenuity pathway analysis revealed that these differentially expressed proteins were regulated by various signaling pathways including nuclear receptors and inflammatory cytokines. One of the nuclear receptor candidates, liver X receptor alpha (LXRα), was further validated by RT-qPCR and western blot. Additionally, LXRα agonist T0901317 rescued the reduced expressions of MRP2 and OAT2 in HepG2 cells in hypercholesterolemic serum treatment.

4. Our present results indicated that hypercholesterolemia affected the expressions of various drug transporters and metabolizing enzymes in liver via nuclear receptors pathway. Especially, decreased function of LXRα contributes to the reduced expressions of MRP2 and OAT2.     

Why is it Challenging to Predict Intestinal Drug Absorption and Oral Bioavailability in Human Using Rat Model

Purpose To study the correlation of intestinal absorption for drugs with various absorption routes between human and rat, and to explore the underlying molecular mechanisms for the similarity in drug intestinal absorption and the differences in oral bioavailability between human and rat.Materials and Methods The intestinal permeabilities of 14 drugs and three drug-like compounds with different absorption mechanisms in rat and human jejunum were determined by in situ intestinal perfusion. A total of 48 drugs were selected for oral bioavailability comparison. Expression profiles of transporters and metabolizing enzymes in both rat and human intestines (duodenum and colon) were measured using GeneChip analysis.Results No correlation (r ² = 0.29) was found in oral drug bioavailability between rat and human, while a correlation (r ² = 0.8) was observed for drug intestinal permeability with both carrier-mediated absorption and passive diffusion mechanisms between human and rat small intestine. Moderate correlation (with r ² > 0.56) was also found for the expression levels of transporters in the duodenum of human and rat, which provides the molecular mechanisms for the similarity and correlation of drug absorption between two species. In contrast, no correlation was found for the expressions of metabolizing enzymes between rat and human intestine, which indicates the difference in drug metabolism and oral bioavailability in two species. Detailed analysis indicates that many transporters (such as PepT1, SGLT-1, GLUT5, MRP2, NT2, and high affinity glutamate transporter) share similar expression levels in both human and rat with regional dependent expression patterns, which have high expression in the small intestine and low expression in the colon. However, discrepancy was also observed for several other transporters (such as MDR1, MRP3, GLUT1, and GLUT3) in both the duodenum and colon of human and rat. In addition, the expressions of metabolizing enzymes (CYP3A4/CYP3A9 and UDPG) showed 12 to 193-fold difference between human and rat intestine with distinct regional dependent expression patterns.Conclusions The data indicate that rat and human show similar drug intestinal absorption profiles and similar transporter expression patterns in the small intestine, while the two species exhibit distinct expression levels and patterns for metabolizing enzymes in the intestine. Therefore, a rat model can be used to predict oral drug absorption in the small intestine of human, but not to predict drug metabolism or oral bioavailability in human.     

Intestinal efflux transporters and drug absorption

BACKGROUND: The intestinal epithelial membrane expresses ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp), multi-drug resistance-associated proteins (MRPs) and breast cancer resistance protein (BCRP), in addition to various solute carrier (SLC) transporters. These ABC transporters affect the oral bioavailability of their substrate drugs. OBJECTIVE: To review the contribution of ABC efflux transporters such as P-gp, MRP2, MRP3, and BCRP in the intestinal absorption of substrate drugs. METHODS: Discussion was made by focusing on the site-specific expression and function of these ABC transporters, and the solubility and permeability of their substrate compounds. RESULTS/CONCLUSION: The increase in the solubility and permeability of orally administered drugs could be the key to escape barrier function of ABC transporters, especially P-gp.     

Ochratoxin A secretion by ATP-dependent membrane transporters in Caco-2 cells

The ATP-dependent membrane transporters, P-gp, MRP2 and BCRP, localized in the luminal membranes of the intestines, liver and kidney, counteract absorption and increase excretion of xenobiotics and drugs. Previously, it has been suggested that the mycotoxin ochratoxin A (OTA) is a substrate for ATP-dependent transporters, and hence the absorption and secretion of OTA in the Caco-2 cell model was investigated. To this end, Caco-2 cells were cultured as confluent monolayers in bicameral inserts and the transepithelial transport of the mycotoxin was assessed. Caco-2 cells secreted OTA to the luminal side in a concentration-dependent manner. This secretory permeability was higher than the absorptive permeability, while the absorptive permeability remained constant for all OTA concentrations tested. The secretion decreased and absorption increased in the presence of the MRP-inhibitor MK571, the P-gp and BCRP inhibitor GF120918, and the BCRP-inhibitor Ko143, suggesting that the secretion of OTA is mediated by MRP2 and BCRP. Cyclosporine A also decreased the secretory permeability, but did not affect absorptive permeability, while PSC833 did neither change absorption nor secretion of OTA. Hence it can be suggested that OTA is a substrate for MRP2 as well as BCRP. These findings are of interest in evaluating mycotoxin absorption after oral ingestion, tissue distribution and particularly excretion pathways, including renal, biliary and mammary gland excretion.     

New ABC transporters in multi-drug resistance

ATP-binding cassette (ABC) transporters have been the subject of intense scrutiny as potential mediators of clinical drug resistance. Since the identification of MDR1/P-glycoprotein over 15 years ago, it has been recognised that reduced intracellular accumulation of anticancer agents can result in significant degrees of drug resistance. The multi-drug resistance associated protein (MRP1) was the second ABC transporter to be associated with drug resistance, and in the past three years, five additional MRP family members have been recognised. While studies to define the substrate specificity and normal physiology for the new transporters is underway, it appears that the principal function for P-glycoprotein and MRP is protection of the host from xenobiotics. The most recent addition to the list of ABC transporters mediating drug resistance is the half-transporter, MXR/BCRP/ABCP. Overexpression of this transporter is associated with mitoxantrone, anthracycline and camptothecin resistance. The discovery of multiple distinct ABC transporters capable of conferring multi-drug resistance offers the possibility that clinical reversal of drug resistance can be achieved. Studies with P-glycoprotein inhibitors alone have generated mixed results; one potential explanation is that other transporters may be co-expressed. These additional transporters offer new therapeutic targets, as both specific and multi-specific inhibitors should be identified for clinical trials in drug resistance reversal.     

Multidrug resistance-associated proteins and implications in drug development

1.  The multidrug resistance-associated proteins (MRPs) belong to the ATP-binding cassette superfamily (ABCC family) of transporters that are expressed differentially in the liver, kidney, intestine and blood–brain barrier. There are nine human MRPs that transport a structurally diverse array of endo- and xenobiotics as well as their conjugates.
2.  Multidrug resistance-associated protein 1 can be distinguished from MRP2 and MRP3 by its higher affinity for leukotriene C₄. Unlike MRP1, MRP2 functions in the extrusion of endogenous organic anions, such as bilirubin glucuronide and certain anticancer agents. In addition to the transport of glutathione and glucuronate conjugates, MRP3 has the additional capability of mediating the transport of monoanionic bile acids.
3.  Both MRP4 and MRP5 are able to mediate the transport of cyclic nucleotides and confer resistance to certain antiviral and anticancer nucleotide analogues. Hereditary deficiency of MRP6 results in pseudoxanthoma elasticum. In the body, MRP6 is involved in the transport of glutathione conjugates and the cyclic pentapeptide BQ123.
4.  Various MRPs show considerable differences in tissue distribution, substrate specificity and proposed physiological function. These proteins play a role in drug disposition and excretion and thus are implicated in drug toxicity and drug interactions. Increased efflux of natural product anticancer drugs and other anticancer agents mediated by MRPs from cancer cells is associated with tumour resistance.
5.  A better understanding of the function and regulating mechanisms of MRPs could help minimize and avoid drug toxicity and unfavourable drug–drug interactions, as well as help overcome drug resistance.