In vitro P-glycoprotein efflux inhibition by atypical antipsychotics is in vivo nicely reflected by pharmacodynamic but less by pharmacokinetic changes
Highlights
► We investigated atypical antipsychotics and their interaction with P-gp at the BBB. ► Inhibitory potency, pharmacokinetics and pharmacodynamics were investigated. ► Amisulpride, N-desmethylclozapine, olanzapine and quetiapine are substrates of P-gp. ► Ranking of drugs for inhibitory potency is reflected in their pharmacodynamics. ► Pharmacodynamic effects were best correlated to brain levels not accessible in humans.
Introduction
Efflux transporters localized at several blood–tissue barriers in the body limit the access of different endogenous and exogenous substances to protected areas of the body and play an important role in disposition of drugs. Especially, the brain is guarded by several transporters localized in the blood–brain barrier. An important protein for the transport of drugs in this barrier is P-glycoprotein (P-gp) (Cordon-Cardo et al., 1989), which is also localized, for example in the hepatocyte canalicular membrane, renal proximal tubules, and the intestinal mucosa (Thiebaut et al., 1987). It is a member of the ATP-binding cassette (ABC) superfamily and is encoded by the multi-drug resistance gene (MDR1, ABCB1). Mice have two genes, mdr1a and mdr1b (Devault and Gros, 1990), which are supposed to have the same function as the sole MDR1 in humans. Single nucleotide polymorphism SNPs have been identified in the MDR1 gene, which lead to a changed P-gp expression and are associated with varying plasma levels of P-gp substrates, for example digoxine (Hoffmeyer et al., 2000). A wide spectrum of drugs, including central nervous system (CNS) acting substances, like antidepressants (amitriptyline, citalopram) (Uhr et al., 2000, Uhr and Grauer, 2003a, Uhr et al., 2003b) and antipsychotics (risperidone) (Doran et al., 2005, Wang et al., 2004a, Wang et al., 2004b) are transported by P-gp. In brains of mdr1a/1b (−/−, −/−) mice concentration differences were observed for several CNS acting P-gp substrates (Doran et al., 2005, Schinkel et al., 1996, Uhr and Grauer, 2003a, Uhr et al., 2003b, Wang et al., 2004a, Wang et al., 2004b). But not only variations in P-gp expression due to gene polymorphisms or deficiency can vary plasma and brain levels of substances, also inhibitors or inducers of P-gp, like verapamil (Nakagami et al., 2005) or St. John's wort (Pfrunder et al., 2003) lead to changes in the pharmacokinetics of concomitantly prescribed drugs.
In this study, affinities of the common atypical antipsychotics amisulpride, clozapine, its active metabolite N-desmethylclozapine, olanzapine, and quetiapine are investigated in terms of substrate and inhibitory properties of P-gp. All substances have antagonistic affinities to the dopamine D2 receptor in combination with properties mainly for the D3 receptor in case of amisulpride and for 5-HT2A, α1, H1, and several other receptors in the case of other antipsychotics. These atypical antipsychotics exhibit, because of their improved receptor profile, less incidence for extrapyramidal side effects compared to the typical antipsychotics, e.g. haloperidol, that are sole dopamine D2 antagonists.
To what extent variations in P-gp expression lead to functional consequences, like behavioral changes, of drugs transported by this protein is investigated in the second part of the study in mdr1a/1b (−/−, −/−) mice compared to wild type (WT) mice by measuring motor impairment typically induced by dopamine D2 receptor antagonism.
Section snippets
Drugs
Amisulpride pure drug substance was kindly supplied by Sanofi-Synthelabo (Berlin, Germany), clozapine was purchased from Sigma-Aldrich Chemie GmbH (Steinheim, Germany), and its metabolite N-desmethylclozapine was kindly donated by Sandoz (Basel, Switzerland). Olanzapine was obtained from Mikromol GmbH (Luckenwalde, Germany) and quetiapine pure drug substance was kindly supplied by Astra Zeneca (London, United Kingdom). These drug substances were dissolved in methanol (HPLC-grade; Merck,
Inhibition of P-gp mediated R123 efflux in P388 cells
Inhibition of P-gp mediated R123 efflux was measured in a microtiter plate based uptake assay using mdr1 over-expressing mouse lymphocytes (P388/mdr1). The corresponding parental cell line P388/par was used to account for effects that are not related to P-gp. The antipsychotic compounds clozapine, N-desmethylclozapine, olanzapine, quetiapine and amisulpride were investigated up to a maximal concentration of 200 μM. In every experiment, 100 μM verapamil (a known P-gp inhibitor) was used as
Discussion
There is increasing evidence from in vitro assays that antipsychotic drugs may modulate P-gp function. However, so far, only little is known about the influence of newer atypical antipsychotic drugs on P-gp, and on its role in the distribution and elimination of antipsychotic compounds (Abou El Ela et al., 2004). Different antipsychotic compounds and a metabolite were investigated for their inhibitory properties in microtiter plate based efflux assays using mdr1 over-expressing P388/mdr1 cells,
Acknowledgments
The work was supported by the Deutsche Forschungsgemeinschaft (DFG Grant, Hi399/6-1).
References (38)
- et al.
In vitro P-glycoprotein affinity for atypical and conventional antipsychotics
Life Sci
(2002) - et al.
Associations between MDR1 gene polymorphisms and schizophrenia and therapeutic response to olanzapine in female schizophrenic patients
J Psychiatr Res
(2008) - et al.
Pharmacodynamic consequences of P-glycoprotein-dependent pharmacokinetics of risperidone and haloperidol in mice
Behav Brain Res
(2008) - et al.
Evaluation of the role of P-glycoprotein in the uptake of paroxetine, clozapine, phenytoin and carbamazapine by bovine retinal endothelial cells
Neuropharmacology
(2005) - et al.
Therapeutic drug monitoring for optimizing amisulpride therapy in patients with schizophrenia
J Psychiatr Res
(2007) - et al.
Amisulpride the ‘atypical’ atypical antipsychotic—comparison to haloperidol, risperidone and clozapine
Schizophr Res
(2008) - et al.
Automated determination of amisulpride by liquid chromatography with column switching and spectrophotometric detection
J Chromatogr B
(2003) - et al.
Automated analysis of quetiapine and other antipsychotic drugs in human blood by high performance-liquid chromatography with column-switching and spectrophotometric detection
J Chromatogr B
(2006) - et al.
abcb1ab P-glycoprotein is involved in the uptake of citalopram and trimipramine into the brain of mice
J Psychiatr Res
(2003) - et al.
Differential enhancement of antidepressant penetration into the brain in mice with abcb1ab (mdr1ab) P-glycoprotein gene disruption
Biol Psychiatry
(2003)
Penetration of amitriptyline, but not of fluoxetine, into brain is enhanced in mice with blood–brain barrier deficiency due to mdr1a P-glycoprotein gene disruption
Neuropsychopharmacology
Identification of P-glycoprotein substrates and inhibitors among psychoactive compounds—implications for pharmacokinetics of selected substrates
J Pharm Pharmacol
Expression, up-regulation, and transport activity of the multidrug-resistance protein Abcg2 at the mouse blood–brain barrier
Cancer Res
Multidrug-resistance gene (P-glycoprotein) is expressed by endothelial cells at blood–brain barrier sites
Proc Natl Acad Sci U S A
Two members of the mouse mdr gene family confer multidrug resistance with overlapping but distinct drug specificities
Mol Cell Biol
The impact of P-glycoprotein on the disposition of drugs targeted for indications of the central nervous system: evaluation using the mdr1a/1b knockout mouse model
Drug Metab Dispos
Effects of cytochrome P450 3A modulators ketoconazole and carbamazepine on quetiapine pharmacokinetics
Br J Clin Pharmacol
How does the benzamide antipsychotic amisulpride get into the brain?—an in vitro approach comparing amisulpride with clozapine
Neuropsychopharmacology
Uptake of clozapine into HL-60 promyelocytic leukaemia cells
Pharmacopsychiatry
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Both authors contributed equally.