St John's wort modulation and developmental expression of multidrug transporters in the rat

Impact of Curcuma longa extract on the expression level of brain transporters in in vivo model

Introduction: Blood brain barrier and multidrug resistance phenomenon are subjects of many investigations. Mainly, because of their functions in protecting the central nervous system (CNS) by blocking the delivery of toxic substances to the brain. This special function has some disadvantages, like drug delivery to the brain in neurodegenerative diseases

Objective: The aim of this study was to examine how natural and synthetic substances affect the expression levels of genes (Mdr1a, Mdr1b, Mrp1, Mrp2, Oatp1a4, Oatp1a5 and Oatp1c1) that encode transporters in the blood-brain barrier.

Methods: cDNA was synthesized from total RNA isolated from rat hippocampus. The expression level of genes was determined using real-time PCR (RT-PCR) method.

Results: Our findings showed that verapamil, as a synthetic substance, caused the greatest reduction of mRNA level of genes studied. The standardized extract of Curcuma longa reduced the expression level for Mrp1 and Mrp2, whereas the increase of mRNA level was observed for Mdr1b, Oatp1a5 and Oatp1c1.

Conclusions: These results suggests that herbal extracts may play an important role in overcoming the blood brain barrier during pharmacotherapy.

[Psychotropic drugs during pregnancy and lactation: development practice]

INTRODUCTION

Pregnancy and the postpartum periods are particular for the mother's use of drugs. Therapeutic prescription must take into account the potential risk of fetal malformation, newborn's withdrawal syndrome, feeding type and potential risk of untreated maternal mental illness. Recommendations for good practice are constantly remodeling and their conclusions are sometimes contradictory.

METHOD

The aim of this work is to develop an updated review, easy to use for any professional involved in the monitoring or prescription of a psychotropic medication (antidepressants, anxiolytics-hypnotics, neuroleptics, mood stabilizers and substitution treatment of opioid dependance) for pregnant or nursing women.

RESULTS

These updates in tabular form are also based on our clinical experience as a team specializing in perinatal medicine.

Regulation of hepatic ABCC transporters by xenobiotics and in disease states

The subfamily of ABCC transporters consists of 13 members in mammals, including the multidrug resistance-associated proteins (MRPs), sulfonylurea receptors (SURs), and the cystic fibrosis transmembrane conductance regulator (CFTR). These proteins play roles in chemical detoxification, disposition, and normal cell physiology. ABCC transporters are expressed differentially in the liver and are regulated at the transcription and translation level. Their expression and function are also controlled by post-translational modification and membrane-trafficking events. These processes are tightly regulated. Information about alterations in the expression of hepatobiliary ABCC transporters could provide important insights into the pathogenesis of diseases and disposition of xenobiotics. In this review, we describe the regulation of hepatic ABCC transporters in humans and rodents by a variety of xenobiotics, under disease states and in genetically modified animal models deficient in transcription factors, transporters, and cell-signaling molecules.

ABCB1 and ABCG2 expression in the placenta and fetus: an interspecies comparison

IMPORTANCE OF THE FIELD

ABCB1 and ABCG2 are efflux transporters which have a major impact on the pharmacological behavior of numerous drugs. They are expressed, for example, in the intestine, liver, kidney, BBB and placenta. It has become evident that ABCB1 and ABCG2 modify the pharmaco/toxicokinetics in the placenta and fetus and may consequently affect the outcome of pregnancy.

AREAS COVERED IN THIS REVIEW

Comprehensive literature searches were done using PubMed (until June 2010) to identify publications on ABCB1 and ABCG2 expression in placenta and fetal tissues in human, mouse, rat, guinea-pig and rabbit.

WHAT THE READER WILL GAIN

In this review, we aim to provide an overview of the current knowledge on the ABCB1 and ABCG2 transporter expression profiles in the placenta and fetal tissues in humans relative to other species.

TAKE HOME MESSAGE

The available information on ABCB1 and ABCG2 temporal expression profiles in placenta and fetus indicates rather good correlation among human, mouse and rat although some specific differences have been reported. However, at this point no detailed comparisons or comparative functional data are available. Detailed knowledge on the expression patterns and functional activity of ABCB1 and ABCG2 transporters placenta and developing embryo/fetus in different species could possibly help the interspecies extrapolation.

Drug-botanical interactions: a review of the laboratory, animal, and human data for 8 common botanicals

Many Americans use complementary and alternative medicine (CAM) to prevent or alleviate common illnesses, and these medicines are commonly used by individuals with cancer.These medicines or botanicals share the same metabolic and transport proteins, including cytochrome P450 enzymes (CYP), glucuronosyltransferases (UGTs), and P-glycoprotein (Pgp), with over-the-counter and prescription medicines increasing the likelihood of drug-botanical interactions.This review provides a brief description of the different proteins, such as CYPs, UGTs, and Pgp.The potential effects of drug-botanical interactions on the pharmacokinetics and pharmacodynamics of the drug or botanical and a summary of the more common models used to study drug metabolism are described.The remaining portion of this review summarizes the data extracted from several laboratory, animal, and clinical studies that describe the metabolism, transport, and potential interactions of 8 selected botanicals. The 8 botanicals include black cohosh, Echinacea, garlic, Gingko biloba, green tea, kava, milk thistle, and St John's wort; these botanicals are among some of the more common botanicals taken by individuals with cancer.These examples are included to demonstrate how to interpret the different studies and how to use these data to predict the likelihood of a clinically significant drug-botanical interaction.

Xenobiotic, bile acid, and cholesterol transporters: function and regulation

Transporters influence the disposition of chemicals within the body by participating in absorption, distribution, and elimination. Transporters of the solute carrier family (SLC) comprise a variety of proteins, including organic cation transporters (OCT) 1 to 3, organic cation/carnitine transporters (OCTN) 1 to 3, organic anion transporters (OAT) 1 to 7, various organic anion transporting polypeptide isoforms, sodium taurocholate cotransporting polypeptide, apical sodium-dependent bile acid transporter, peptide transporters (PEPT) 1 and 2, concentrative nucleoside transporters (CNT) 1 to 3, equilibrative nucleoside transporter (ENT) 1 to 3, and multidrug and toxin extrusion transporters (MATE) 1 and 2, which mediate the uptake (except MATEs) of organic anions and cations as well as peptides and nucleosides. Efflux transporters of the ATP-binding cassette superfamily, such as ATP-binding cassette transporter A1 (ABCA1), multidrug resistance proteins (MDR) 1 and 2, bile salt export pump, multidrug resistance-associated proteins (MRP) 1 to 9, breast cancer resistance protein, and ATP-binding cassette subfamily G members 5 and 8, are responsible for the unidirectional export of endogenous and exogenous substances. Other efflux transporters [ATPase copper-transporting beta polypeptide (ATP7B) and ATPase class I type 8B member 1 (ATP8B1) as well as organic solute transporters (OST) alpha and beta] also play major roles in the transport of some endogenous chemicals across biological membranes. This review article provides a comprehensive overview of these transporters (both rodent and human) with regard to tissue distribution, subcellular localization, and substrate preferences. Because uptake and efflux transporters are expressed in multiple cell types, the roles of transporters in a variety of tissues, including the liver, kidneys, intestine, brain, heart, placenta, mammary glands, immune cells, and testes are discussed. Attention is also placed upon a variety of regulatory factors that influence transporter expression and function, including transcriptional activation and post-translational modifications as well as subcellular trafficking. Sex differences, ontogeny, and pharmacological and toxicological regulation of transporters are also addressed. Transporters are important transmembrane proteins that mediate the cellular entry and exit of a wide range of substrates throughout the body and thereby play important roles in human physiology, pharmacology, pathology, and toxicology.

Effect of St John's wort on the disposition of fexofenadine in the isolated perfused rat liver

Objectives

This study examined the effects of St John's wort (Hypericum perforatum) on the disposition of fexofenadine, a substrate of P-glycoprotein/organic anion transporting polypeptide, in the isolated perfused rat liver.

Methods

Male Sprague-Dawley rats were given St John's wort, 1000 mg/kg, by intragastric gavage once daily for 14 days. On day 15, livers were isolated surgically and perfused in a recirculating system with fexofenadine (2 μg/ml), either alone or following addition of ciclosporin (0.5 μg/ml) 5 min before the addition of fexofenadine. Perfusate samples and bile were collected for 60 min. Fexofenadine in perfusate, bile and the homogenised livers was measured by HPLC.

Key findings

Administration of St John's wort significantly increased biliary clearance with respect to perfusate and biliary clearance with respect to the concentration in the liver, by 74% and 71%, respectively. This was reversed by ciclosporin.

Conclusions

St John's wort enhanced the elimination of fexofenadine into the bile. This could be because it increases the activity of P-glycoprotein on the canalicular membrane of hepatocytes.