Kathrin Klein

University of Tübingen

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Ulrich M. Zanger

Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology

Matthias Schwab

University of Tübingen

Michel Eichelbaum

Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology

Elke Schaeffeler

University of Tübingen

Stefan Winter

University of Tübingen

Andreas K. Nüssler

University of Tübingen

Roman Tremmel

Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology

Ute Hofmann

Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology

Oliver Burk

Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology

P. Neuhaus

Charité - Universitätsmedizin Berlin

Cooperative Institutions

University of Tübingen

119

Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology

104

Heidelberg University

Robert Bosch (Germany)

Karolinska Institutet

Chinese Academy of Sciences

Ruhr University Bochum

German Cancer Research Center

Charité - Universitätsmedizin Berlin

University Hospital Heidelberg

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Influence of Omeprazole on Multidrug Resistance Protein 3 Expression in Human Liver

Journal of Pharmacology and Experimental Therapeutics (2003)

Monika Hitzl Kathrin Klein Ulrich M. Zanger Péter Fritz Andreas K. Nüssler

Multidrug resistance protein (MRP) 3 transports bile salts and conjugated xenobiotics from cells (hepatocytes and enterocytes) into the blood. Hepatic MRP3 expression is low under normal conditions but is markedly up-regulated during cholestasis. Since little is known about additional factors increasing human hepatic MRP3 expression, we investigated the variability of MRP3 expression in a large collection of human livers and factors contributing to variable MRP3 expression in liver and HepG2 cells. MRP3 was measured in 62 human livers from patients with and without omeprazole treatment and in HepG2 cells with and without omeprazole or β-naphthoflavone treatment. Livers of patients treated with omeprazole showed 4.8-fold (P< 0.0001) higher MRP3 protein expression compared with the remainder of the population. Accordingly, MRP3 mRNA and protein were induced 2.4- and 1.8-fold, respectively (P < 0.01 andP < 0.05), in HepG2 cells treated with omeprazole. Finally, MRP3 was induced in HepG2 cells by β-naphthoflavone. In summary, treatment with omeprazole and β-naphthoflavone is a determinant of variable human hepatic MRP3 expression.

Efflux

10.1124/jpet.102.043547

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Citations (47)

A Predominate Role of CYP1A2 for the Metabolism of Nabumetone to the Active Metabolite, 6-Methoxy-2-naphthylacetic Acid, in Human Liver Microsomes

Drug Metabolism and Disposition (2009)

Miia Turpeinen Ute Hofmann Kathrin Klein Thomas E. Mürdter Matthias Schwab

Nabumetone, a widely used nonsteroidal anti-inflammatory drug, requires biotransformation into 6-methoxy-2-naphthylacetic acid (6-MNA), a close structural analog to naproxen, to achieve its analgesic and anti-inflammatory effects. Despite its wide use, the enzymes involved in metabolism have not been identified. In the present study, several in vitro approaches were used to identify the cytochrome P450 (P450) enzyme(s) responsible for 6-MNA formation. In human liver microsomes (HLMs) 6-MNA formation displayed monophasic Michaelis-Menten kinetics with apparent K_m and V_max values (mean ± S.D.) of 75.1 ± 15.3 μM and 1304 ± 226 pmol/min/mg protein, respectively, and formation rate of 6-MNA varied approximately 5.5-fold (179–983 pmol/min/mg protein). 6-MNA activity correlated strongly with both CYP1A2-mediated phenacetin O-deethylation activity and CYP1A2 protein content (r = 0.85 and 0.74, respectively; p < 0.0001 for both). Additional correlations were found with model activities of CYP2C19 and CYP3A4. Of 11 cDNA-expressed recombinant P450s used, recombinant CYP1A2 was the major form catalyzing the 6-MNA formation with an apparent K_m of 45 μM and V_max of 8.7 pmol/min/pmol P450. Minor fractions were catalyzed by recombinant P450s CYP1A1, CYP2B6, CYP2C19, CYP2D6, and CYP2E1. Experiments with P450-selective chemical inhibitors and monoclonal anti-P450 antibodies showed that furafylline, a mechanism-based inhibitor CYP1A2, and anti-CYP1A2 antibody markedly inhibited 6-MNA formation, whereas inhibitors for other P450s did not show significant inhibitory effects. Taken together, these studies indicate that the formation of the active metabolite of nabumetone, 6-MNA, is predominantly catalyzed by CYP1A2 in HLMs with only minor contribution of other P450s.

Phenacetin

Nabumetone

Biotransformation

10.1124/dmd.108.025700

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Citations (48)

The truncated splice variant of peroxisome proliferator-activated receptor alpha, PPARα-tr, autonomously regulates proliferative and pro-inflammatory genes

BMC Cancer (2015)

Maria Thomas Christine Bayha Kathrin Klein Simon Müller Thomas S. Weiß

The peroxisome proliferator-activated receptor alpha (PPARα) controls lipid/energy homeostasis and inflammatory responses. The truncated splice variant PPARα-tr was suggested to exert a dominant negative function despite being unable to bind consensus PPARα DNA response elements.The distribution and variability factor of each PPARα variant were assessed in the well-characterized cohort of human liver samples (N = 150) on the mRNA and protein levels. Specific siRNA-mediated downregulation of each transcript as well as specific overexpression with subsequent qRT-PCR analysis of downstream genes was used for investigation of specific functional roles of PPARα-wt and PPARα-tr forms in primary human hepatocytes.Bioinformatic analyses of genome-wide liver expression profiling data suggested a possible role of PPARα-tr in downregulating proliferative and pro-inflammatory genes. Specific gene silencing of both forms in primary human hepatocytes showed that induction of metabolic PPARα-target genes by agonist WY14,643 was prevented by PPARα-wt knock-down but neither prevented nor augmented by PPARα-tr knock-down. WY14,643 treatment did not induce proliferative genes including MYC, CDK1, and PCNA, and knock-down of PPARα-wt had no effect, while PPARα-tr knock-down caused up to 3-fold induction of these genes. Similarly, induction of pro-inflammatory genes IL1B, PTGS2, and CCL2 by IL-6 was augmented by knock-down of PPARα-tr but not of PPARα-wt. In contrast to human proliferative genes, orthologous mouse genes were readily inducible by WY14,643 in PPARα-tr non-expressing AML12 mouse hepatocytes. Induction was augmented by overexpression of PPARα-wt and attenuated by overexpression of PPARα-tr. Pro-inflammatory genes including IL-1β, CCL2 and TNFα were induced by WY14,643 in mouse and human cells and both PPARα forms attenuated induction. As potential mechanism of PPARα-tr inhibitory action we suggest crosstalk with WNT/β-catenin pathway. Finally, treatment with WY14,643 in the presence of PPARα-tr resulted in the significant reduction of cell viability of AML12 and human ovarian cancer cell line, SKOV3.Our data suggest that the truncated PPARα splice variant functions as an endogenous inhibitor of proliferative and pro-inflammatory genes in human cells and that its absence in mouse may explain species-specific differences in fibrate-induced hepatocarcinogenesis.

10.1186/s12885-015-1500-x

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Citations (31)

Three haplotypes associated with CYP2A6 phenotypes in Caucasians

Pharmacogenetics and Genomics (2005)

Michael Haberl Birgit Anwald Kathrin Klein Regina Weil Christine Fu

The human cytochrome P450 2A6 (CYP2A6) enzyme metabolizes several xenobiotic compounds of clinical or toxicological importance. We aimed to identify genetic variants and major CYP2A6 haplotypes associated with CYP2A6 phenotypic variation. CYP2A6 mRNA level, protein level, activity and haplotypes were determined in Caucasian liver samples via real-time polymerase chain reaction, Western blot, coumarin 7-hydroxylation, DNA sequencing and genotyping, respectively. Phenotypes were then analyzed for associations with haplotypes. CYP2A6 transcript, protein and activity levels were correlated among each other. In 45 African-American, 156 Caucasian, 47 Chinese, 50 Japanese and 47 Korean DNA samples, we detected 95 different polymorphisms in the CYP2A6 gene, 49 of which had not been described previously. Caucasian variants formed 33 haplotypes which built four clades. Allele *9B and the CYP2A7/2A6 partial deletion allele CYP2A6*12B were both associated with decreased expression. The latter haplotype extends at least over 147 kb up into the CYP2B6 gene. A haplotype almost identical to allele *1A was associated with decreased expression and activity of CYP2A6 compared to all other haplotypes. In summary A CYP2A6*1A-like allele, *9B and *12B are major genetic determinants of CYP2A6 phenotype variation in Caucasians.

CYP2A6

10.1097/01.fpc.0000171517.22258.f1

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Citations (99)

Impact of Genetic Polymorphism in Relation to Other Factors on Expression and Function of Human Drug-Metabolizing P450s

Toxicology Mechanisms and Methods (2005)

Ulrich M. Zanger Kathrin Klein Tanja Richter Claudia Toscano Jörg Zukunft

A major cause for unpredictable drug response is the enormous variability of drug-metabolizing cytochrome P450s (CYPs) in human liver in which genetic polymorphisms, regulation of gene expression, and physiological factors, including sex, may play a role. To dissect these different factors, we established a large human liver bank with extensive clinical documentation. Recent work concentrated on CYPs 2D6, 2B6, and the 3A family. CYP2D6 expression is highly polymorphic with over 70 alleles. Using liver samples and DNA from phenotyped patients, we further elucidated the genetic basis of phenotypic differences and demonstrated a novel role of alternative splicing, leading to decreased enzyme activity. These studies further emphasize the intricacy of genetic regulation at the CYP2D6 locus. In contrast, CYP2B6, the human orthologue of the rodent phenobarbital-inducible P450 2B, is known to be inducible by a range of substances, but our recent studies also show a high degree of genetic polymorphism. However, the role of polymorphism in determining CYP2B6 expression and function is less decisive as compared with CYP2D6. Thus, with respect to the balance between genetic and nongenetic factors controlling expression, CYP2B6 appears to take an intermediate position. CYP3A4 is the major P450 of human liver and contributes critically to the metabolism of at least half of all drugs. CYP3A4 expression variability is not influenced much by genetic polymorphism. Studies in our liver bank confirm that both induction and down-regulation occur as a consequence of drug treatment. As a further major determinant of hepatic CYP3A4 expression, we found sexual dimorphism, with women expressing at least twice the amount of CYP3A4 protein than men. This surprising result explains the many pharmacokinetic findings of faster metabolism of CYP3A4 drug substrates in women. In conclusion, these data illustrate how various factors contribute to the individual CYP profile in human liver.

CYP2B6

Genetic Variability

10.1080/15376520590918847

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Citations (20)

Polymorphic Variation in TPMT Is the Principal Determinant of TPMT Phenotype: A Meta‐Analysis of Three Genome‐Wide Association Studies

Clinical Pharmacology & Therapeutics (2016)

R Tamm Reedik Mägi Roman Tremmel Stefan Winter Evelin Mihailov

Thiopurine‐related hematotoxicity in pediatric acute lymphoblastic leukemia (ALL) and inflammatory bowel diseases has been linked to genetically defined variability in thiopurine S‐methyltransferase (TPMT) activity. While gene testing of TPMT is being clinically implemented, it is unclear if additional genetic variation influences TPMT activity with consequences for thiopurine‐related toxicity. To examine this possibility, we performed a genome‐wide association study (GWAS) of red blood cell TPMT activity in 844 Estonian individuals and 245 pediatric ALL cases. Additionally, we correlated genome‐wide genotypes to human hepatic TPMT activity in 123 samples. Only genetic variants mapping to chromosome 6, including the TPMT gene region, were significantly associated with TPMT activity ( P < 5.0 × 10 ‐8 ) in each of the three GWAS and a joint meta‐analysis of 1,212 cases (top hit P = 1.2 × 10 ‐72 ). This finding is consistent with TPMT genotype being the primary determinant of TPMT activity, reinforcing the rationale for genetic testing of TPMT alleles in routine clinical practice to individualize mercaptopurine dosage.

Thiopurine methyltransferase

Genome-wide Association Study

Mercaptopurine

Genotype-phenotype distinction

Genetic Association

10.1002/cpt.540

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Citations (40)

Variability in human hepatic MRP4 expression: influence of cholestasis and genotype

The Pharmacogenomics Journal (2007)

Ulrike Gradhand Thomas Lang Elke Schaeffeler Hartmut Glaeser Heike Tegude

Expression (computer science)

10.1038/sj.tpj.6500451

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Citations (90)

Polymorphic CYP2B6 : Molecular Mechanisms and Emerging Clinical Significance

Pharmacogenomics (2007)

Ulrich M. Zanger Kathrin Klein Tanja Saußele Julia Blievernicht Marco H. Hofmann

Polymorphisms in drug-metabolizing enzymes and drug transporters contribute to wide and inheritable variability in drug pharmacokinetics, response and toxicity. One of the less well-studied human cytochrome P450s is (CYP)2B6, a homologue of the rodent phenobarbital-inducible CYP2B enzymes. Clinically used drug substrates include cytostatics (cyclophosphamide), HIV drugs (efavirenz and nevirapine), antidepressants (bupropion), antimalarials (artemisinin), anesthetics (propofol) and synthetic opioids (methadone). Contrary to the model polymorphisms of CYP2D6 and CYP2C19, which were discovered by adverse drug reactions, pharmacogenetic study of CYP2B6 was initiated by reverse genetics approaches and subsequent functional and clinical studies. With over 100 described SNPs, numerous complex haplotypes and distinct ethnic frequencies, CYP2B6 is one of the most polymorphic CYP genes in humans. In this review, we summarize general biomolecular and pharmacological features and present a detailed up-to-date description of genetic polymorphisms, including a discussion of recent clinical applications of CYP2B6 pharmacogenetics.

CYP2B6

Efavirenz

Nevirapine

Pharmacogenomics

10.2217/14622416.8.7.743

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Citations (256)

Membrane Associated Progesterone Receptors: Promiscuous Proteins with Pleiotropic Functions – Focus on Interactions with Cytochromes P450

Frontiers in Pharmacology (2017)

Chang Seon Ryu Kathrin Klein Ulrich M. Zanger

Membrane-associated progesterone receptors (MAPR) are a group of four rather small, partially homologous proteins, which share a similar non-covalent heme-binding domain that is related to cytochrome b5, a well-known functional interaction partner of microsomal cytochrome P450 (CYP) monooxygenase systems. Apart from their structural similarities the four proteins progesterone membrane component 1 (PGRMC1, also referred to as IZA, sigma-2 receptor, Dap1), PGRMC2, neudesin (NENF) and neuferricin (CYB5D2) display surprisingly divergent and multifunctional physiological properties related to cholesterol/steroid biosynthesis, drug metabolism and response, iron homeostasis, heme trafficking, energy metabolism, autophagy, apoptosis, cell cycle regulation, cell migration, neural functions, and tumorigenesis and cancer progression. The purpose of this mini-review is to briefly summarize the structural and functional properties of MAPRs with particular focus on their interactions with the CYP system. For PGRMC1, originally identified as a non-canonical progesterone-binding protein that mediates some immediate non-genomic actions of progesterone, available evidence indicates mainly activating interactions with steroidogenic CYPs including CYP11A1, CYP21A2, CYP17, CYP19, CYP51A1, and CYP61A1, while interactions with drug metabolizing CYPs including CYP2C2, CYP2C8, CYP2C9, CYP2E1, and CYP3A4 were either ineffective or slightly inhibitory. For the other MAPRs the evidence is so far less conclusive. We also point out that experimental limitations question some of the previous conclusions. Use of appropriate model systems should help to further clarify the true impact of these proteins on CYP-mediated metabolic pathways.

Cytochrome b5

10.3389/fphar.2017.00159

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Citations (100)

Genomics of ADME gene expression: mapping expression quantitative trait loci relevant for absorption, distribution, metabolism and excretion of drugs in human liver

The Pharmacogenomics Journal (2011)

Adrian Schröder Kathrin Klein Stefan Winter Matthias Schwab Marina de Nadai Bonin Gomes

Expression quantitative trait loci (eQTL) analysis is a powerful approach toward identifying genetic loci associated with quantitative changes in gene expression. We applied genome-wide association analysis to a data set of >300 000 single-nucleotide polymorphisms and >48 000 mRNA expression phenotypes obtained by Illumina microarray profiling of 149 human surgical liver samples obtained from Caucasian donors with detailed medical documentation. Of 1226 significant associations, only 200 were validated when comparing with a previously published similar study. Potential explanations for low replication rate include differences in microarray platforms, statistical modeling, covariates considered and origin and collection procedures of tissues. Focused analysis revealed a subset of 95 associations related to absorption, distribution, metabolism and excretion of drugs. Of these, 21 were true replications and 74 were newly discovered associations in enzymes, transporters, transcriptional regulators and other genes. This study extends our knowledge about the genetics of inter-individual variability of gene expression with particular emphasis on pharmacogenomics.

ADME

Pharmacogenomics

Genome-wide Association Study

Genetic Association

10.1038/tpj.2011.44

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Citations (102)