Selective Transport Of Drugs Research Articles

Selection of a suitable animal model to evaluate secretion of drugs in the human milk: a systematic approach

Lack of data on drug secretion in human milk is a concern for safe use of drugs during postpartum. Clinical studies are often difficult to perform; despite substantial improvements in computational methodologies such as physiologically based pharmacokinetic modelling, there is limited clinical data to validate such models for many drugs. Various factors that are likely to impact milk to plasma ratio were identified. A literature search was performed to gather available data on milk composition, total volume of milk produced per day, milk pH, haematocrit, and renal blood flow and glomerular filtration rate in various animal models. BLAST nucleotide and protein tools were used to evaluate the similarities between humans and animals in the expression and predominance of selected drug transporters, metabolic enzymes, and blood proteins. A multistep analysis of all the potential variables affecting drug secretion was considered to identify most appropriate animal model. The practicality of using the animal in a lab setting was also considered. Donkeys and goats were identified as the most suitable animals for studying drug secretion in milk and future studies should be performed in goats and donkeys to validate the preliminary observations.

SURFACE FUNCTIONALIZED EMULSION FOR SELECTIVE DRUGS TRANSPORT

This paper presents the results of functionalization of surfaces of double emulsions drops for selective drug transport and selection of antibodies for targeting brain tumor cells - glioblastoma multiforme (GBM). The functionalization involved physical adsorption of antibodies: anti-CD15 (Hodgkin's disease marker) on oil drops of the emulsion. The interactions between molecules of antibodies and compounds of the oil drops were measured using isothermal titration calorimetry (ITC). Double emulsions were prepared by a one-step method, in a helical flow contactor. The ITC analysis showed that antibodies interacted with emulsion compounds. The change in the heat rates reflecting molecular interactions proved that proteins adhered to oil drops interfaces. Additionally, surface proteins (antibodies) were identified and analyzed for targeting specific GBM cell lines: U87MG, LN229, T98G. The multiple emulsions were created under conditions: the size of the annular gap between the coaxial cylinders was 1.5 mm, the rotational frequency of the inner cylinder was 2162 rpm, the volumetric flow rates of internal water phase to membrane oil phase 1:1 and membrane oil phase to external water phase 1:15. The method of double emulsions preparation has been described more precisely in our previous papers. The sizes of the internal phase drops and the membrane phase drops were determined based on analyzing images captured during microscopic observation of the double emulsion samples.

Regulation of human placental drug transporters in HCV infection and their influence on direct acting antiviral medications

IntroductionThe objectives of this study were to determine how HCV infection affects placental drug transporters, and to determine the role of drug transporters on the cellular accumulation of direct-acting antiviral drugs in human trophoblasts. MethodsEighty-four ABC and SLC transporter genes were first screened in normal and HCV infected pregnant women using PCR profiler array. The changes in expression were confirmed by qPCR and Western blot. The impact of selected drug transporters on the cellular accumulation of radiolabeled antiviral drugs sofosbuvir, entecavir, and tenofovir was measured in primary human trophoblasts (PHT) and BeWo b30 cells in the presence or absence of transporter-specific inhibitors. PHT were then treated with CL097, ssRNA40, and imquimod to determine the impact of Toll-like receptor (TLR) 7/8 activation on drug transporter expression. ResultsThe expression of the ABC efflux transporters ABCB1/P-gp and ABCG2/BCRP was increased in placenta of women with HCV, while the nucleoside transporters SLC29A1/ENT1 and SLC29A2/ENT2 remained unchanged. The accumulation of sofosbuvir and tenofovir was unaffected by inhibition of these transporters in trophoblast cells. Entecavir accumulation was decreased by the inhibition of ENT2. P-gp and BCRP inhibition enhanced entecavir accumulation in BeWo b30, but not PHT. Overall, there was little effect of TLR7/8 activation on these drug transporters, and the accumulation of entecavir in PHT. DiscussionThe data suggest that expression of placental drug transporters and selection of antiviral drug may impact fetal drug exposure in pregnancies complicated by HCV infections.

Polymeric advanced delivery systems for antineoplasic drugs: doxorubicin and 5-fluorouracil

Abstract Conventional pharmaceuticals generally display the inability to transport active ingredients directly to specific regions of the body, amongst some of their main limitations. The distribution of the drugs in the circulatory system may lead to undesired toxicity, and therefore, adverse reactions. To address this situation, a selective transport of drugs is required, that is, releasing drugs specifically to the site of action in appropriate concentrations and in the right time. To achieve this goal, it is necessary to develop delivery systems that respond to several features, such as low toxicity, optimum properties for the transport and release of the drug, as well as a long half-life in the body. This feature paper critically provides an overview of different strategies of controlled drug release for two model antineoplasic drugs, i.e. doxorubicin (DOX) and 5-fluorouracil (5-FU). Any of the presented strategies for drug release possess advantages and disadvantages, and the selection of the strategy used will depend on the targeted tissue and nature of the drug.

Piloting Your Nanovehicle to Overcome Biological Barriers.

Designing an effective nanoparticle for selective drug transport requires careful consideration of the complex biological barriers encountered in transit to the desired target. Here, we review several of these barriers, and provide possible methods for formulating liposomal nanoparticles to overcome them. The methods include the biotinylation of an antibody, and subsequent conjugation to a PEGylated cationic lipid nanoparticle. Additionally, the incorporation of drug, and other relevant characteristics of the nanoparticle are also discussed.

Self-Assembled DNA Nanocentipede as Multivalent Drug Carrier for Targeted Delivery.

An idea drug carrier, with good binding affinity, selectivity, drug payload capacity, and cellular internalized capability, will greatly improve the efficiency of target delivery. Herein a self-assembled and multivalent DNA nanostructure was developed as drug carrier for efficient and targeted delivery. The DNA structure was similar to that of a centipede, composed of trunk and legs: The trunk was a self-assembled DNA scaffold via hybridization chain reaction (HCR) from two biotinylated hairpin monomers created upon initiation by a trigger DNA, and the legs were biotinylated aptamers conjugated to the trunk via streptavidin-biotin affinity interaction. The long trunk of the "DNA nanocentipede" was loaded with doxorubicin (Dox), and the legs were SMMC-7721 cell-binding aptamers (Zy1) which functioned as targeting moieties to firmly and selectively grasp target cells. The results of agarose gel electrophoresis and fluorescence anisotropy confirmed that Zy1-based DNA nanocentipedes (Zy1-Nces) were successfully constructed. Flow cytometric analyses demonstrated that Zy1-Nces were more effective than free Zy1 in binding affinity and selectivity due to a multivalent effect. Confocal microscopy studies demonstrated that the internalization was highly dependent on the higher valences of DNA nanocentipedes without the loss of selectivity. Meanwhile, Zy1-Nces exhibited high drug-loading capacity and selective drug transport. The results of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed enhanced cellular cytotoxicity of the Dox-loaded Zy1-Nces (Zy1-Nces-Dox) to the target SMMC-7721 cells but not negative control L02 cells. This approach is applicable to prepare drug carriers for other targets by construction of the nanocentipedes with relevant nucleic acid fragments.

Trastuzumab - a monoclonal antibody - and dendrimers in a targeted therapy for breast cancer

Breast cancer is the most frequently occurring cancer in women. It has been confirmed that approximately 30% of patients have overexpression of human epidermal growth factor 2 (HER2) on the surface of tumor cells. Trastuzumab - a recombinant, humanized monoclonal antibody - is directed against this receptor. Its use in traditional chemotherapy (with anthracyclines or taxanes) causes an increase of therapy efficiency. However, the systemic toxicity of the anticancer drugs is still a serious problem. Therefore, new solutions are sought, especially in the field of selective drug transport to tumor cells. Dendrimers are composed of a core and branches. They are the bestknown group of nanoparticles. A lot of publications have shown that they can be used as carriers of various types of molecules, including anticancer drugs. The branched structure provides effective protection against premature release of the drug into the circulatory system. It gives a chance to reduce the dose while maintaining a therapeutic effect, and to reduce the toxicity of the drug for normal cells. Furthermore, the surface of dendrimers can be modified by a monoclonal antibody to achieve a targeted therapy. For that reason synthesis of conjugates of trastuzumab, dendrimers, and anticancer drugs is so crucial. This paper presents an overview of publications about the use of trastuzumab in in vitro, in vivo and clinical studies, as well as the latest developments of biology and chemistry, whose goal is to create the perfect, targeted carrier.

The influence of soybean extract on the expression level of selected drug transporters, transcription factors and cytochrome P450 genes encoding phase I drug-metabolizing enzymes.

Soybean phytoestrogens, such as genistein and daidzein, reduce climacteric symptoms and the risk of certain chronic diseases such as cancer and cardiovascular diseases. Despite their widespread use in functional foods and dietary supplements, there is very little data available on their safety and herb-drug interactions, especially with antineoplastic agents. Hence, the aim of our study was to assess the effects of soybean extracts on the expression level of CYP genes and their transcriptional factors. We also investigated the effect of soybean on the mRNA level of transporters, such as P-glycoprotein (MDRI) and multidrug resistance-associated proteins (MRP1, MRP2). Wistar rats were fed a standardized soybean extract (100 mg/kg, p.o.). cDNA was synthesized from total RNA isolated from different tissues (liver and intestinal epithelium) using reverse transcription. Gene expression level was analyzed by RT-PCR method. We demonstrated a significant increase of CYP1A1 mRNA level (by 89%, p = 0.002 and 125%, p = 0.004) as compared with the control group. An increase of AHR and CAR expression after 10 days was also observed (by 60%, p < 0.001 and 52%, p > 0.05, respectively). Additionally an inductive effect for CYP2D1 by 22% (p = 0.008), Mdr1a by 267% (p < 0.0001), Mdr2b by 86% (p < 0.00001), Mrp1 by 9-fold (p < 0.0001), Mrp2 by 83% (p < 0.0001) in the liver and for Mrp2 by 35% (p < 0.001) in the intestinal epithelium, was evaluated. A significant decrease of mRNA level was observed for CYP3A1 (human CYP3A4) in the liver and Mdr1b in the intestinal epithelium. Moreove, we also showed a slight decrease in the amount of mRNA for CAR, PXR and ARNT after 3 days. Our results suggest that Glycine max may change the expression level of CYPs, especially CYP3A4 and CYP1A 7, involved in biotransformation of xenobiotics (drugs, procarcinogens) and may participate in clinically significant interactions with drugs metabolized by these enzymes. Moreover an increase of CYP1A1 (homologue to human CYPIA 1) mRNA level may not only reduce the carcinogenicity of foreign compounds, but may also activate some compounds to their carcinogenicity In case of transporters, it is considered that an increase of their expression in the body may lead to increased fetoprotection. Also, it may reduce both, the exposure of sensitive tissues (e.g. brain, placenta) to xenobiotics and treatment effectiveness of certain diseases. Hence, the search for a safe substance that could effectively modulate transporter activity especially in the treatment of certain hormone -dependent disorders, e.g. osteoporosis and breast cancer occurring mainly in postmenopausal period, continues.

Role of transporters in drug interactions

Over the past few decades, a tremendous amount of work has been done on the molecular characterization of transport proteins in animals and humans, leading to a better understanding of the physiological roles of a number of transport proteins. Furthermore, there is increasing preclinical and clinical evidence to support the importance of transport proteins in the pharmacokinetics and toxicokinetics of a wide variety of structurally diverse drugs. As a consequence, the degree of expression and functionality of transport proteins may directly affect the therapeutic effectiveness, safety and target specificity of drugs. Recently, there has also been increased awareness about potential drug-drug, drug-herb and drug-food interactions involving transporters. Traditionally, a change in metabolic clearance of a drug, particularly via cytochrome P450-mediated metabolism, has been considered the cause of many clinically important drug interactions. However, increasing evidence suggests that some drug interactions result from changes in the activity and/or expression of drug transporters. Accordingly, assessment of the clinical relevance of transporter-mediated drug interactions has become a regulatory issue during the drug approval process and also the evaluation of drug interaction potential has become an integral part of risk assessment during drug development processes. Therefore, this review will highlight the role of some selected drug transporters in drug interactions, as well as their clinical implication.

Reliability and Robustness of Simultaneous Absolute Quantification of Drug Transporters, Cytochrome P450 Enzymes, and Udp-Glucuronosyltransferases in Human Liver Tissue by Multiplexed MRM/Selected Reaction Monitoring Mode Tandem Mass Spectrometry with Nano-Liquid Chromatography

Mass spectrometry (MS)-based multiplexed multiple reaction monitoring quantification of proteins has recently evolved as a versatile tool for accurate, absolute quantification of proteins. The purpose of this study was to examine the validity of the present method with regard to standard bioanalytical criteria for drug transporters, cytochrome P450 (CYP) enzymes and uridine 5′-diphospho-glucuronosyltransferases (UGTs). Membrane preparations from human liver tissue were used for target protein quantification. As a result, the determination coefficients (r2) of all targets were greater than 0.986. In the absence of matrix, inaccuracy values (expressed as % deviation) were −8.1% to 20.3%, whereas imprecision values (expressed as % coefficient of variation) were within 15.9%. In the presence of matrix, which consisted of digested plasma membrane fraction for transporters and digested microsomal membrane fraction for CYP enzymes and UGTs, respectively, the inaccuracy was −15.3%–8.1%, and the imprecision were within 18.9%. Sufficient sample stability of membrane fraction was shown for three freeze–thaw cycles, 32 days at −20°C, and in processed samples for 7 days at 10°C. In conclusion, this study demonstrated, for the first time, that the MS-based assay with nano-liquid chromatography provides adequate reliability and robustness for the quantification of selected drug transporters, P450 enzymes and UGTs. © 2011 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:4037–4043, 2011

A nuclear receptor-mediated xenobiotic response and its implication in drug metabolism and host protection.

Regulation of the Phase I CYP enzymes and Phase II conjugating enzymes is implicated in both drug metabolism and drug-drug interactions. Moreover, the elimination of numerous xenobiotic and endobiotic toxic chemicals also requires a concerted function of Phase I and II enzymes, as well as the membrane spanning drug transporters. The genes that encode these enzymes and transporters are inducible by numerous xenobiotics, yet the inducibility shows clear species specificity. In the last 3-4 years, orphan nuclear receptors (NRs) such as PXR, CAR, and FXR have been established as species-specific xeno-sensors that regulate the expression of Phase I and II enzymes, as well as selected drug transporters. This transcriptional regulation is achieved by binding of these xenobiotic receptors to the NR response elements found within the promoter regions of target genes. The identification of NRs as xenosensors represents a major step forward in understanding the genetic mechanisms controlling the expression of drug metabolizing enzymes. The establishment of NR-mediated and mechanism-guided xenobiotic screening systems by using cultured cells or genetically engineered mouse models has not only advanced our understanding of the molecular complexity of this drug-induced xenobiotic response, but has also provided in vitro and in vivo platforms to facilitate the development of safer drugs.

Selective drug transport and P-glycoprotein activity in an in vitro blood-brain barrier model

To determine whether compounds are able to reach the neural microenvironment, a blood-brain barrier (BBB) co-culture model has been recently developed with bovine brain capillary endothelial cells and newborn rat astrocytes. In this study, the permeability of confluent endothelial cells to various compounds and the functional activity of P-glycoprotein (P-gp), an ATP-dependent pump known to efflux drugs from multidrug-resistant tumoral cells, was assessed. The permeability of the lipophilic compounds imipramine and sulpiride differed in relation to their structure. A good correlation was observed with in vivo brain extraction levels. P-gp activity was estimated by measuring the uptake of [ 3H]vinblastine by the endothelial cells, with or without verapamil, which is known to reverse drug resistance. Intracellular accumulation of the vinca alkaloid was strongly increased after addition of verapamil, suggesting that P-gp is active in these cells. These results provide further support for the use of the co-culture model of bovine brain endothelial cells and rat astrocytes to screen new centrally active drugs.

Cells with Manipulated Functions: New Perspectives for Cell Biology, Medicine, and Technology

AbstractExposure to electrical fields can reversibly increase the electrical conductivity and permeability of a cell membrane, which regulates and directs the exchange of materials and information between the cell and its environment. If cell membranes (or artificial lipid membranes) are exposed to a field pulse of high intensity and short duration (ns to μs), local electrical breakdown occurs in them. This electrical breakdown is associated with a large permeability change in the membrane, which is such that substances or particles (up to the size of genes) which cannot normally permeate through the membrane, are able to traverse the membrane into the cell. The original properties of the membrane are restored within μs to min, depending on the experimental conditions and the membrane properties.Electrical breakdown in the zone of contact between the membranes of cells (or lipid vesicles), which have been made to adhere to each other by the action of weak inhomogeneous alternating electrical fields, leads to fusion of these cells with formation of a single cell having new functional characteristics. The electrical fusion method is very mild, and the yield of fused cells is high.The electrically induced fusion and entrapment of membrane‐impermeable substances and genes in cells provide a new tool for the productions of a wide range of cells with manipulated functions, which could be used (or are being used) for the solution of a number of problems in cell biology, medicine and technology.The application of electrical membrane breakdown to clinical diagnostics, the development of cellular carrier systems for the selective transport of drugs to a site of action within the organism and the potential applications of electrically induced fusion for breeding salt‐tolerant crop plants for converting solar energy into ethanol, for synthesizing natural materials and manipulating genes, are described.