OCT1-mediated cellular drug uptake and interactions between drug transport and drug metabolism

Saadatmand, Ali Reza

dc.contributor.advisor	Brockmöller, Jürgen Prof. Dr.	de
dc.contributor.author	Saadatmand, Ali Reza	de
dc.date.accessioned	2013-01-14T15:06:15Z	de
dc.date.available	2013-01-30T23:50:52Z	de
dc.date.issued	2012-12-07	de
dc.identifier.uri	http://hdl.handle.net/11858/00-1735-0000-000D-EF89-B	de
dc.identifier.uri	http://dx.doi.org/10.53846/goediss-1437
dc.format.mimetype	application/pdf	de
dc.language.iso	eng	de
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/3.0/	de
dc.title	OCT1-mediated cellular drug uptake and interactions between drug transport and drug metabolism	de
dc.type	doctoralThesis	de
dc.title.translated	OCT1-mediated cellular drug uptake and interactions between drug transport and drug metabolism	de
dc.contributor.referee	Brockmöller, Jürgen Prof. Dr.	de
dc.date.examination	2012-10-25	de
dc.subject.dnb	610 Medizin, Gesundheit	de
dc.subject.gok	Medicine	de
dc.description.abstracteng	OCT1 is a polyspecific organic cation transporter belonging to the solute carrier gene family SLC22. Human OCT1 is mainly expressed on the sinusoidal membrane of hepatocytes and thus may play an important role in the hepatocellular uptake and metabolism of cationic drugs. Becide this OCT1 is highly polymorphic with 9% of Caucasians carrying functional amino acid substitutions in both their OCT1 alleles. These amino acid substitutions are known to decrease or abolish OCT1 activity. Therefore these variants may significantly affect pharmacokinetics and consequently efficacy and adverse effects of all those drugs, which are transported at typical therapeutic concentrations by OCT1. On the other hand, drugs when enter into the hepatocytes are metabolized by metabolizing enzymes such as the cytochrome P450 enzyme 2D6 (CYP2D6). CYP2D6 is one of the most important drug metabolizing enzymes in the liver and is also highly polymorphic. Since such intracellular metabolism changes the concentration gradient at the outer cell membrane and at intracellular compartments, a combined analysis of drug membrane transport and intracellular drug metabolism may give insights with general importance. The aims of this study were to investigate whether OCT1 mediates the cellular uptake of clinically relevant drugs, what is the effect of the common genetic polymorphisms in OCT1on the uptake and how the interaction between the OCT1 and CYP2D6 may affect drug transport and metabolism. To do this, stable transfection was used to generate HEK293 cells overexpressing OCT1alone, CYP2D6 with its helper enzyme POR, and a combination of OCT1 with CYP2D6 and POR. In addition to these 3 constracts reflecting transport, metabolism and transport+metabolism, I generated cells overexpressing variant OCT1s carrying the five common amino acid substitution polymorphisms known in Caucasians, Arg61Cys, Gly401Ser, and a single deletion of Met420, or combination of Met420 deletion with Cys88Arg or Gly465Arg. Drug uptake and metabolism was analysed using high pressure liquid chromatography to quantify the intracellular concentration of the parental drugs and their metabolites. Our results demonstrated that OCT1 mediates the cellular uptake of different groups of drugs. The antiemetic tropisetron and O-desmethyltramadol, the active metabolite of the opioid tramadol, were shown to be inhibitors and substrates of OCT1. The uptake of tropisetron and O-desmethyltramadol was abolished if any of the five common polymorphic OCT1 variants was expressed. On the other hand, the antiemetic Abstract viii ondansetron and the opioid tramadol itself were no substrates, but only inhibitors of OCT1. A prototypic substrate of the enzyme CYP2D6 is debrisoquine. It was unknown how debrisoquine enters into cells. I demonstrated that it is an inhibitor and a substrate of OCT1 (IC50 of 6.2 +- 0.8	de
dc.contributor.coReferee	Burckhardt, Gerhard Prof. Dr.	de
dc.contributor.thirdReferee	Ahsen, Nicolas von Prof. Dr.	de
dc.subject.topic	Biology (incl. Psychology)	de
dc.subject.ger	Organic Cation Transporter Isoform 1 (OCT1)	de
dc.subject.ger	Cytochrom P450 metabolisierenden Enzym (CYP2D6)	de
dc.subject.ger	medikament-Aufnahme	de
dc.subject.ger	Metabolisierung	de
dc.subject.eng	Organic Cation Transporter isoform 1 (OCT1)	de
dc.subject.eng	Cytochrom P450 metabolizing enzyme (CYP2D6)	de
dc.subject.eng	drug uptake	de
dc.subject.eng	drug metabolism	de
dc.subject.bk	44.38 Pharmakologie	de
dc.identifier.urn	urn:nbn:de:gbv:7-webdoc-3827-3	de
dc.identifier.purl	webdoc-3827	de
dc.affiliation.institute	Biologische Fakultät	de
dc.identifier.ppn	737897791	de

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Fakultät für Biologie und Psychologie (inkl. GAUSS) [1620]

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