Role of Hepatocyte Transporters in Drug-Induced Liver Injury (DILI)-In Vitro Testing.

Bile acids and bile salts (BA/BS) are substrates of both influx and efflux transporters on hepatocytes. Canalicular efflux transporters, such as BSEP and MRP2, are crucial for the removal of BA/BS to the bile. Basolateral influx transporters, such as NTCP, OATP1B1/1B3, and OSTα/β, cooperate with canalicular transporters in the transcellular vectorial flux of BA/BS from the sinusoids to the bile.

Modulation of monepantel secretion into milk by soy isoflavones.

Monepantel (MNP), a novel anthelmintic drug from amino-acetonitrile derivatives, is a substrate for breast cancer resistance protein (BCRP). BCRP-mediated milk secretion of drugs can be altered by isoflavones. In this study, we aimed to show how soy isoflavones and BCRP inhibitors genistein (GEN) and daidzein (DAI) can modulate the secretion of MNP into milk.

Cladribine as a Potential Object of Nucleoside Transporter-Based Drug Interactions.

Cladribine is a nucleoside analog that is phosphorylated in its target cells (B and T-lymphocytes) to its active triphosphate form (2-chlorodeoxyadenosine triphosphate). Cladribine tablets 10 mg (Mavenclad), administered for up to 10 days per year in 2 consecutive years (3.5-mg/kg cumulative dose over 2 years), are used to treat patients with relapsing multiple sclerosis.

Modulation of Urate Transport by Drugs.

Background: Serum urate (SU) levels in primates are extraordinarily high among mammals. Urate is a Janus-faced molecule that acts physiologically as a protective antioxidant but provokes inflammation and gout when it precipitates at high concentrations. Transporters play crucial roles in urate disposition, and drugs that interact with urate transporters either by intention or by accident may modulate SU levels.

Inhibition of ABCG2/BCRP-mediated transport-correlation analysis of various expression systems and probe substrates.

BCRP / ABCG2 is a key determinant of pharmacokinetics of substrate drugs. Several BCRP substrates and inhibitors are of low passive permeability, and the vesicular transport assay works well in this permeability space. Membranes were prepared from BCRP-HEK293, MCF-7/MX, and baculovirus-infected Sf9 cells with (BCRP-Sf9-HAM), and without (BCRP-Sf9) cholesterol loading.

Age-Related Functional and Expressional Changes in Efflux Pathways at the Blood-Brain Barrier.

During the last decade, several articles have reported a relationship between advanced age and changes in the integrity of the blood-brain barrier (BBB). These changes were manifested not only in the morphology and structure of the cerebral microvessels but also in the expression and function of the transporter proteins in the luminal and basolateral surfaces of the capillary endothelial cells. Age-associated downregulation of the efflux pumps ATP-binding cassette transporters (ABC transporters) resulted in increased permeability and greater brain exposure to different xenobiotics and their possible toxicity.

Determination of Reference Values of MDR-ABC Transporter Activities in CD3+ Lymphocytes of Healthy Volunteers Using a Flow Cytometry Based Method.

Background: MDR transporters are important biomarkers of drug resistance in cancer and in autoimmune conditions. We determined the MDR1, MRP1 and BCRP activity in CD3+ lymphocytes using a flow cytometry based method from 120 healthy volunteers in order to describe normal reference values of the activity of these transporters. The effects of gender and age were also determined.

Correlation Analysis of Potential Breast Cancer Resistance Protein Probes in Different Monolayer Systems.

Breast cancer resistance protein (BCRP) is a point of interest in drug-drug interaction safety testing. Therefore, a consensus probe that can be applied as victim in multiple experimental settings is of great benefit. Identification of candidates has been driven by the amount and quality of available clinical data, and as a result, drugs such as sulfasalazine and rosuvastatin have been suggested.

Inhibitor selectivity of CNTs and ENTs.

The concentrative nucleoside transporters (CNT; solute carrier family 28 (SLC28)) and the equilibrative nucleoside transporters (ENT; solute carrier family 29 (SLC29)) are important therapeutic targets but may also mediate toxicity or adverse events. To explore the relative role of the base and the monosaccharide moiety in inhibitor selectivity we selected compounds that either harbor an arabinose moiety or a cytosine moiety, as these groups had several commercially available drug members. The screening data showed that more compounds harboring a cytosine moiety displayed potent interactions with the CNTs than compounds harboring the arabinose moiety.

Baicalin is a substrate of OATP2B1 and OATP1B3.

The use and significance of baicalin, the main bioactive component found in Radix Scutellaria, have been on the rise due to its interesting pharmacological properties. Baicalin, a low passive permeability compound, is directly absorbed from the upper intestine and its hepatic elimination is dominant. However, interaction but no transport studies have implicated organic anion‐transporting polypeptides in its cellular uptake.

Kinetic characterization of bile salt transport by human NTCP (SLC10A1).

The transport of bile acids facilitated by NTCP is an important factor in establishing bile flow. In this study, we examine the kinetics associated with human NTCP-dependent transport of two quantitatively important bile acids comprising the human bile acid pool, chenodeoxycholic acid and glycine-chenodeoxycholate, and secondary bile salt, 3-sulfo-glycolithocholate of potential toxicological significance. The study employed human NTCP overexpressing Chinese Hamster Ovary cells and results compared with taurocholate, a prototypical bile salt commonly used in transporter studies.

Abcb1a (P-glycoprotein) limits brain exposure of the anticancer drug candidate seliciclib in vivo in adult mice.

Seliciclib displayed limited brain exposure in vivo in adult rats with mature blood-brain barrier (BBB). Selicilib was shown to be a specific substrate of human ABCB1 in vitro. To demonstrate that ABCB1/Abcb1 can limit brain exposure in vivo in mice we are showing that seliciclib is a substrate of mouse Abcb1a, the murine ABCB1 ortholog expressed in the BBB as LLC-PK-Abcb1a cells displayed an efflux ratio (ER) of 15.

Species specificity profiling of rat and human organic cation/carnitine transporter Slc22a5/SLC22A5 (Octn2/OCTN2).

The purpose of this study was to characterize the uptake of carnitine, the physiological substrate, and the uptake of 3-(2,2,2-trimethylhydrazinium)propionate, a consensus substrate by rat Octn2 and human OCTN2 transporters as well as to characterize drug-mediated inhibition of l-carnitine uptake by the rat and human orthologs overexpressed in CHO-K1 cells. l-carnitine and 3-(2,2,2-trimethylhydrazinium)propionate were found to be a lower affinity substrate for rat Octn2 (K = 32.66 ± 5.

Membrane Transporters in Physiological Barriers of Pharmacological Importance.

Membrane transporters expressed in barrier forming cell types provide a dual filtration system as unwanted xenobiotics are effluxed by ABC transporters, and compounds essential for the organism, such as nutrients or physiological substrates, are taken up by influx transporters. The majority of efflux transporters apically-localized in barrier forming cell types are ABC transporters that may limit absorption or distribution, and promote excretion. Pharmaceutical scientists are increasingly aware of the limitations these efflux transporters represent.

Investigating ABCB1-Mediated Drug-Drug Interactions: Considerations for In vitro and In vivo Assay Design.

Background: ABCB1 is a key ABC efflux transporter modulating the pharmacokinetics of a large percentage of drugs. ABCB1 is also a site of transporter mediated drug-drug interactions (tDDI). It is the transporter most frequently tested for tDDIs both in vitro and in the clinic.

Multiple ABC Transporters Efflux Baicalin.

Baicalein, the aglycone formed by hydrolysis of baicalin in the intestine, is well absorbed by passive diffusion but subjected to extensive intestinal glucuronidation. Efflux of baicalin, the low passive permeability glucuronide of baicalein from enterocytes, likely depends on a carrier-mediated transport. The present study was designed to explore potential drug-herb interaction by investigating the inhibitory effect of baicalin on the transport of reporter substrates by transporters and to identify the transporters responsible for the efflux of baicalin from enterocytes and hepatocytes.

Pre-Plated Cell Lines for ADMETox Applications in the Pharmaceutical Industry.

Membrane transporters significantly modulate membrane permeability of endobiotics and xenobiotics, such as bile acids and drugs, respectively. Various in vitro methods have been established for both ATP-binding cassette (ABC) transporters to examine cellular efflux and uptake, and for solute carriers (SLC) to examine cellular uptake of substrates. Cell-based systems are the models of choice to test drug-transporter interactions as well as drug-drug interactions for research and regulatory purposes, albeit, for low passive permeability substrates of ABC transporters, vesicular uptake assays are also recommended.

Mechanisms and therapeutic potential of inhibiting drug efflux transporters.

Introduction: The ATP-binding cassette transporters are among the largest transmembrane protein families in humans and are expressed in a wide variety of tissues. By promoting outward transport, they protect cells from the accumulation of undesirable substrates. This protection might lead to suboptimal concentration of chemotherapeutics in the tumor cells, resulting in therapy resistance and poor disease prognosis.

In vitro methods in drug transporter interaction assessment.

Drug transporter proteins recruit to pharmacological barrier tissues and profoundly affect the ADME properties of a large number of drugs. In vitro assays optimized for drug transporters have grown into routine tools in the determination of molecular level interactions as well as prediction of barrier penetration and system level pharmacokinetics. Regulatory position mandates increasing interest in the application of these assays during drug development.

Structure and function of BCRP, a broad specificity transporter of xenobiotics and endobiotics.

The discovery and characterization of breast cancer resistance protein (BCRP) as an efflux transporter conferring multidrug resistance has set off a remarkable trajectory in the understanding of its role in physiology and disease. While the relevance in drug resistance and general pharmacokinetic properties quickly became apparent, the lack of a characteristic phenotype in genetically impaired animals and humans cast doubt on the physiological importance of this ATP-binding cassette family member, similarly to fellow multidrug transporters, despite well-known endogenous substrates. Later, high-performance genetic analyses and fine resolution tissue expression data forayed into unexpected territories concerning BCRP relevance, and ultimately, the rise of quantitative proteomics allows putting observed interactions into absolute frameworks for modeling and insight into interindividual and species differences.