PDZK1蛋白对药物转运体的调控

PDZK1蛋白通过PDZ结构域与药物转运体结合,显示对药物转运体定位、表达及功能的调控作用。药物转运体介导了众多内源和外源性物质,如营养物质、治疗药物等的跨膜转运,是肿瘤多药耐药及多种疾病发生的关键因素,且在治疗药物的体内处置中具有重要地位。PDZK1蛋白对药物转运体的调控间接影响上述过程。本文就PDZK1对药物转运体的调控作用研究进行综述。     

转运体在药物肾脏排泄中的重要作用

转运体是细胞膜上的功能性蛋白,在肾脏中表达广泛,对许多内源性或外源性物质的肾脏分泌及重吸收起到了至关重要的作用。许多药物（包括有机阴离子药物、有机阳离子药物及肽类药物等）在肾脏排泄的过程中,经主要集中在近端肾小管的转运体主动转运介导。临床合用某些药物时可能在肾脏发生转运体介导的相互作用。从肾脏主要转运体的分布及功能出发,综述其在药物肾脏排泄中的作用。     

有机阴离子转运多肽介导的药物相互作用研究进展

药物转运体介导的药物相互作用正日益受到人们的关注和重视,近年来的研究表明药物转运体对药物的吸收、分布和排出有着重要的作用。有机阴离子转运多肽是一类药物摄取转运体,其表达分布广泛,转运的内源性和外源性的底物众多,一些药物因抑制有机阴离子转运体而导致药物相互作用。本文综述了有机阴离子转运多肽家族不同成员的组织分布、结构特点以及其介导的药物相互作用的最新研究进展。     

转运体介导中药与化学药相互作用研究进展

ATP结合盒转运体家族和溶质转运体家族的转运体参与众多的中药与化学药相互作用过程,因其可介导内外源性药物及其代谢物的跨膜转运。转运体同细胞色素P450酶类似,会对特征底物的血药浓度和组织分布产生一定影响,从而改变药物的药效或者毒副作用。本文综述了具有重要临床意义的P-糖蛋白、乳腺癌耐药蛋白、有机阴离子转运体、有机阳离子转运体和有机阴离子转运多肽等5种转运体所介导的中药与化学药相互作用,以期为临床联合用药提供一定的理论依据。     

肾脏转运体介导抗病毒药物肾排泄的研究进展

目的:了解肾脏转运体介导抗病毒药物肾排泄的研究现状,为临床合理用药提供参考.方法:对近年抗病毒药物与肾脏转运体相关的文献进行综述.结果:有机阴离子转运体(Organic Anion Transporters,OAT1～3)和有机阳离子转运体(Organic Cation Transporters,OCT1～3)介导药物流入细胞内,而ATP结合转运体(ATP Binding Cassette,P-gp,MRP2～5)介导药物从细胞排出.寡肽转运体(Peptide Transporters,PEPT1～2)介导伐昔洛韦双向扩散.结论:通过介导药物的摄取和排出,肾脏转运体在调节体内常用抗病毒药物浓度时发挥重要的作用.     

疾病状态下有机阴离子转运体表达和功能的变化及其机制研究进展

有机阴离子转运体属于溶质转运体22亚家族成员，是一类重要的摄取类转运体，其有多个亚型。有机阴离子转运体在体内介导多种小分子内源性物质的转运，起到维持机体内环境稳态的作用。此外，临床上许多药物也是有机阴离子转运体的底物。研究表明某些疾病可能导致有机阴离子转运体表达和功能的异常改变，进而影响药物的疗效或导致机体内源性物质水平紊乱。对有机阴离子转运体的分布和功能进行简要介绍，并综述了疾病状态下有机阴离子转运体表达和功能变化及其机制的研究进展。     

肝脏转运体和代谢酶在化学性肝损伤中的作用

肝脏是机体重要的代谢和解毒器官。肝细胞膜上存在多种功能性膜蛋白即肝脏药物转运体,它的功能是介导许多内源性及外源性物质如药物摄取进入肝脏,在肝脏内经过一定的代谢转化,最终将其从肝脏排入胆汁。研究发现,转运体和代谢酶在化学性肝损伤的发展过程中发挥重要的作用,其涉及的多种调控机制成为研究热点。就肝脏转运体和代谢酶的分类、转运体和代谢酶在化学性肝损伤中的变化及其调控机制作一综述。     

有机阴离子转运蛋白在外源化学物毒性中的作用

机体接触各种潜在毒性有机阴离子,包括内源性物质如激素、神经递质和细胞代谢产物;外源性化学物质如多种药物、农药和动植物毒素等。快速有效地清除其中的毒性物质是机体最好的防御方式。有机阴离子转运蛋白介导的跨上皮主动转运通常是其中的限速过程。因此,研究有机阴离子转运蛋白的种类、分布及其转运与表达调控机制具有重要的毒理学意义。     

阴离子转运蛋白OAT1和OAT3与药物代谢相互影响的研究进展

阴离子转运蛋白(OAT)OAT1与OAT3同属SLC22A家族,主要在近端肾小管上皮细胞基底侧膜表达,在肝脏、肠和大脑亦有分布.它们介导有机阴离子进入其分布的细胞,进而参与多种药物在肾脏的分泌、重吸收和在体内的分布等.本文从OAT1和OAT3的分子生物学基础、主要功能、介导药物相互作用的机制和毒性的产生,研究其使用的模型、物种间存在的差异以及展望等.     

HMG—CoA还原酶抑制药与转运体OATP1B1

长期以来药物代谢一直被认为是药物分布过程中的主要决定因素。然而，近年来的研究不断证实膜转运体也具有同样重要的作用。事实上，许多外向转运体如MDR1基因编码的P糖蛋白在药物体内分布和药物效应方面的作用已被广泛而深入的加以研究。一些药物在胃肠道、肝和肾脏等许多器官的定向运动中需要内向和外向转运体来协调转运。例如，在外向转运体介导的药物代谢和经胆道排泄之前，分布在肝细胞基底膜上的内向转运体一一有机阴离子转运体超家族（organic anio-transporting polypeptides，OATPs），可促进药物在细胞内集聚。     

Functional characterization of human organic anion transporter 10 (OAT10/SLC22A13) as an orotate transporter

Orotate, a nutritional compound typically utilized as an intermediate in pyrimidine synthesis, has been suggested to undergo renal reabsorption. However, the detailed mechanisms involved in the process remain unclear, with only urate transporter 1 (URAT1/SLC22A12) being indicated as a transporter involved in its tubular uptake. As an attempt to identify transporters involved in that to help clarify the mechanisms, we examined a possibility that organic anion transporter 10 (OAT10/SLC22A13), which is present at the brush border membrane in renal tubular epithelial cells, could transport orotate. The operation of human OAT10 for orotate transport was demonstrated indeed and analyzed in detail in Madin-Darby canine kidney II cells introduced with this transporter by stable transfection. Orotate transport by OAT10 was found to be kinetically saturable with a biphasic characteristic and dependent on Cl⁻. These are unique characteristics previously unknown in its operation for the other substrates. Orotate transport by OAT10 was, on the other hand, inhibited by several anionic compounds known as OAT10 inhibitors. Finally, the rat ortholog of OAT10 was found not to be able to transport orotate, indicating animal species differences in that function. Thus, human OAT10 has been demonstrated to operate for orotate transport with unique characteristics.     

Insulin-like growth factor 1 modulates the phosphorylation,expression, and activity of organic anion transporter 3 through protein kinase A signaling pathway

Organic anion transporter 3 (OAT3) plays a vital role in removing a broad variety of anionic drugs from kidney, thus avoiding their possible toxicity in the body. In the current study, we investigated the role of insulin-like growth factor 1 (IGF-1) in the regulation of OAT3. We showed that IGF-1 induced a dose- and time-dependent increase in OAT3 transport activity, which correlated well with an increase in OAT3 expression. The IGF-1-induced increase in OAT3 expression was blocked by protein kinase A (PKA) inhibitor H89. Moreover, IGF-1 induced an increase in OAT3 phosphorylation, which was also blocked by H89. These data suggest that the IGF-1 modulation of OAT3 occurred through PKA signaling pathway. To further confirm the involvement of PKA, we treated OAT3-expressing cells with PKA activator Bt2-cAMP, followed by examining OAT activity and phosphorylation. We showed that OAT3 activity and phosphorylation were much enhanced in Bt2-cAMP-treated cells as compared to that in control cells. Finally, linsitinib, an anticancer drug that blocks the IGF-1 receptor, abrogated IGF-1-stimulated OAT3 transport activity. In conclusion, our study demonstrated that IGF-1 regulates OAT3 expression and transport activity through PKA signaling pathway, possibly by phosphorylating the transporter.     

Human organic anion transporter 2 is an entecavir,but not tenofovir,transporter

Entecavir (ETV) and tenofovir (TFV) are essential nucleoside analogues in current hepatitis B virus (HBV) treatments. Since these drugs target the HBV polymerase that is localized within human hepatocytes, determining of their cellular uptake process is an important step in fully understanding their pharmacological actions. However, the human hepatic transporters responsible for their uptake have remained unidentified. Therefore, this study aimed at identifying the primary ETV and TFV uptake transporter(s) in human hepatocytes. In transport assays, temperature-sensitive ETV and TFV uptake by human hepatocytes were observed, and their uptake were strongly inhibited by bromosulfophthalein, which is an inhibitor of organic anion transporters/organic anion transporting polypeptides (OATs/OATPs). Given these results, ETV and TFV uptake activities in several human OAT/OATP expression systems were examined. The results showed that, among the transporters tested, only OAT2 possessed ETV transport activity. On the other hand, none of the transporters showed any TFV uptake activity. To summarize, our results identify that human OAT2 is an ETV transporter, thereby suggesting that it plays an important part in the mechanisms underlying ETV antiviral activity. Furthermore, although the hepatic TFV transporters remain unknown, our results have, at least, clarified that these two anti-HBV drugs have different hepatocyte entry routes.     

Probenecid,an organic anion transporter 1 and 3 inhibitor,increases plasma and brain exposure of N-acetylcysteine

1.?N-acetylcysteine (NAC) is being investigated as an antioxidant for several conditions including traumatic brain injury, but the mechanism by which it crosses membrane barriers is unknown. We have attempted to understand how the transporter inhibitor, probenecid, affects NAC pharmacokinetics and to evaluate the interaction of NAC with transporters.

2.?Juvenile Sprague-Dawley rats were administered NAC alone or in combination with probenecid intraperitoneally. Plasma and brain samples were collected serially and NAC concentrations were measured. Transporter studies were conducted with human embryonic kidney-293 cells that overexpress organic anion transporter (OAT)1 or OAT3 and with human multi-drug resistance-associated protein (MRP)1 or MRP4 membrane vesicles.

3.?NAC area under the curve was increased in plasma (1.65-fold) and brain (2.41-fold) by probenecid. The apparent plasma clearance was decreased by 65%. Time- and concentration-dependent NAC uptake that was inhibitable by probenecid was observed with OAT1 and OAT3. No uptake of NAC was observed with MRP1 or MRP4.

4.?Our results indicate for the first time that NAC is substrate for OAT1 and OAT3 and that probenecid increases NAC plasma and brain exposure in vivo. These data provide insight regarding how NAC crosses biological barriers and suggest a promising therapeutic strategy to increase NAC exposure.     

Substrate recognition of renally eliminated angiotensin II receptor blockers by organic anion transporter 4

Organic anion transporter (OAT) 4, which is localized at the apical membrane of human renal proximal tubules, transports olmesartan, an angiotensin II receptor blocker (ARB). Many ARBs, including olmesartan, undergo partial tubular secretion as active forms, and inhibit OAT4-mediated uptake activity. Here, we examined the substrate recognition of various ARBs by OAT4 in order to assess whether OAT4 might be involved in the renal handling of ARBs. Concentration-dependent OAT4-mediated uptake of azilsartan, candesartan, carboxylosartan, losartan, and valsartan was observed with K_m values of 6.6, 31, 7.2, 13, and 1.7 μM, respectively, in the absence of extracellular Cl⁻. In the presence of extracellular Cl⁻, OAT4-mediated uptake of dianionic ARBs (azilsartan, candesartan, carboxylosartan, and valsartan) was lower and reached a steady state faster than in the absence of extracellular Cl⁻. Thus, OAT4 is proposed to use extracellular Cl⁻ as a counterpart for anion efflux. Our results suggest that OAT4 may play a role in the excretion of azilsartan, candesartan, carboxylosartan, and valsartan, as well as olmesartan. In contrast, OAT4-mediated uptake of losartan, a monoanionic ARB, was little affected by extracellular Cl⁻, suggesting that only OAT4-mediated dianion transport is Cl⁻-sensitive.     

In vitro and in vivo evidence of the importance of organic anion transporters (OATs) in drug therapy

Organic anion transporters 1-10 (OAT1-10) and the urate transporter 1 (URAT1) belong to the SLC22A gene family and accept a huge variety of chemically unrelated endogenous and exogenous organic anions including many frequently described drugs. OAT1 and OAT3 are located in the basolateral membrane of renal proximal tubule cells and are responsible for drug uptake from the blood into the cells. OAT4 in the apical membrane of human proximal tubule cells is related to drug exit into the lumen and to uptake of estrone sulfate and urate from the lumen into the cell. URAT1 is the major urate-absorbing transporter in the apical membrane and is a target for uricosuric drugs. OAT10, also located in the luminal membrane, transports nicotinate with high affinity and interacts with drugs. Major extrarenal locations of OATs include the blood-brain barrier for OAT3, the placenta for OAT4, the nasal epithelium for OAT6, and the liver for OAT2 and OAT7. For all transporters we provide information on cloning, tissue distribution, factors influencing OAT abundance, interaction with endogenous compounds and different drug classes, drug/drug interactions and, if known, single nucleotide polymorphisms.     

Expression of organic anion transporter 2 in the human kidney and its potential role in the tubular secretion of guanine-containing antiviral drugs

The organic anion transporters 1 and 3 (OAT1 and OAT3) and organic cation transporter 2 (OCT2) are important for renal tubular drug secretion. In contrast, evidence for OAT2 expression in the human kidney is limited, and its role in renal drug transport is unknown. Both mRNA (real-time polymerase chain reaction) and protein (Western blotting) for OAT2 were detected in renal cortex from eight donors, and interindividual variability in protein levels was 3-fold. OAT2 protein in the renal cortex was localized (by immunohistochemistry) to the basolateral domain of tubules, as were OAT1 and OAT3. The absolute abundance of OAT2 mRNA was similar to that of OAT1 mRNA and 3-fold higher than that of OCT2 mRNA but 10-fold lower than that of OAT3 mRNA. A previous observation that OAT2 transports cGMP led us to examine whether acyclovir, ganciclovir, and penciclovir are OAT2 substrates; they are guanine-containing antivirals that undergo active tubular secretion. Transport of the antivirals into human embryonic kidney cells was stimulated 10- to 20-fold by expression of OAT2, but there was little to no transport of the antivirals by OAT1, OAT3, or OCT2. The K(m) values for acyclovir, ganciclovir, and penciclovir transport were 94, 264, and 277 μM, respectively, and transport efficiencies were relatively high (6-24 μl · min(-1) · mg protein(-1)). This study provides definitive evidence for the expression of OAT2 in the human kidney and is the first to demonstrate that OAT2, compared with OAT1, OAT3, or OCT2, has a preference for antiviral drugs mainly eliminated in the urine via active secretion.     

Interaction of zalcitabine with human organic anion transporter 1

The present study aimed to investigate the interaction of zalcitabine with human organic anion transporter 1 (hOATI) during renal excretion. Contribution of OAT1 to the renal transport of zalcitabine was examined using the transfected cell lines overexpressing the human organic anion transporter1 (CHO/hOAT1 cells). Zalcitabine exhibited the inhibition effect on the cellular uptake of [3H]-PAH in CHO/hOAT1 cells with an IC50 value of 1.23 mM. Furthermore, the cellular uptake of zalcitabine increased threefold with the enhancement of hOATI activity in CHO/hOAT1 cells, while it was significantly reduced in the presence of OAT1 inhibitors such as ketoprofen, naproxen, PAH and 6-carboxyfluorescein. Those results suggest that hOATI contributes at least in part to the cellular uptake of zalcitabine across the basolateral membrane of proximal tubular cells.     

Human organic anion transporter 4 is a renal apical organic anion/dicarboxylate exchanger in the proximal tubules

Human organic anion transporter OAT4 is expressed in the kidney and placenta and mediates high-affinity transport of estrone-3-sulfate (E1S). Because a previous study demonstrated no trans-stimulatory effects by E1S, the mode of organic anion transport via OAT4 remains still unclear. In the present study, we examined the driving force of OAT4 using mouse proximal tubular cells stably expressing OAT4 (S2 OAT4). OAT4-mediated E1S uptake was inhibited by glutarate (GA) (IC50:1.25 mM) and [14C]GA uptake via S2 OAT4 was significantly trans-stimulated by unlabeled GA (5 mM) (P<0.001). [3H]E1S uptake via S2 OAT4 was significantly trans-stimulated by preloaded GA (P<0.001) and its [14C]GA efflux was significantly trans-stimulated by unlabeled E1S in the medium (P<0.05). In addition, both the uptake and efflux of [14C]p-aminohippuric acid (PAH) and [14C]GA via S2 OAT4 were significantly trans-stimulated by unlabeled GA or PAH. The immunoreactivities of OAT4 were observed in the apical membrane of proximal tubules along with those of basolateral organic anion/dicarboxylate exchangers such as hOAT1 and hOAT3 in the same tubular population. These results indicate that OAT4 is an apical organic anion/dicarboxylate exchanger and mainly functions as an apical pathway for the reabsorption of some organic anions in renal proximal tubules driven by an outwardly directed dicarboxylate gradient.