Publications by authors named "Deborah Rudin"

10 Publications

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α-PPP and its derivatives are selective partial releasers at the human norepinephrine transporter: A pharmacological characterization of interactions between pyrrolidinopropiophenones and uptake1 and uptake2 monoamine transporters.

Neuropharmacology 2021 Apr 20;190:108570. Epub 2021 Apr 20.

Medical University of Vienna, Center for Physiology and Pharmacology, Institute of Pharmacology, Währingerstraße 13A, 1090, Vienna, Austria; AddRess Centre for Addiction Research and Science, Medical University of Vienna, Währingerstraße 13A, 1090, Vienna, Austria. Electronic address:

While classical cathinones, such as methcathinone, have been shown to be monoamine releasing agents at human monoamine transporters, the subgroup of α-pyrrolidinophenones has thus far solely been characterized as monoamine transporter reuptake inhibitors. Herein, we report data from previously undescribed α-pyrrolidinopropiophenone (α-PPP) derivatives and compare them with the pharmacologically well-researched α-PVP (α-pyrrolidinovalerophenone). Radiotracer-based in vitro uptake inhibition assays in HEK293 cells show that the investigated α-PPP derivatives inhibit the human high-affinity transporters of dopamine (hDAT) and norepinephrine (hNET) in the low micromolar range, with α-PVP being ten times more potent. Similar to α-PVP, no relevant pharmacological activity was found at the human serotonin transporter (hSERT). Unexpectedly, radiotracer-based in vitro release assays reveal α-PPP, MDPPP and 3Br-PPP, but not α-PVP, to be partial releasing agents at hNET (EC values in the low micromolar range). Furthermore, uptake inhibition assays at low-affinity monoamine transporters, i.e., the human organic cation transporters (hOCT) 1-3 and human plasma membrane monoamine transporter (hPMAT), bring to light that all compounds inhibit hOCT1 and 2 (IC values in the low micromolar range) while less potently interacting with hPMAT and hOCT3. In conclusion, this study describes (i) three new hybrid compounds that efficaciously block hDAT while being partial releasers at hNET, and (ii) highlights the interactions of α-PPP-derivatives with low-affinity monoamine transporters, giving impetus to further studies investigating the interaction of drugs of abuse with OCT1-3 and PMAT.
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http://dx.doi.org/10.1016/j.neuropharm.2021.108570DOI Listing
April 2021

Genome-Wide Association Study of Metamizole-Induced Agranulocytosis in European Populations.

Genes (Basel) 2020 Oct 29;11(11). Epub 2020 Oct 29.

Department of Clinical Chemistry, Inselspital Bern University Hospital, University of Bern, 3010 Bern, Switzerland.

Agranulocytosis is a rare yet severe idiosyncratic adverse drug reaction to metamizole, an analgesic widely used in countries such as Switzerland and Germany. Notably, an underlying mechanism has not yet been fully elucidated and no predictive factors are known to identify at-risk patients. With the aim to identify genetic susceptibility variants to metamizole-induced agranulocytosis (MIA) and neutropenia (MIN), we conducted a retrospective multi-center collaboration including cases and controls from three European populations. Association analyses were performed using genome-wide genotyping data from a Swiss cohort (45 cases, 191 controls) followed by replication in two independent European cohorts (41 cases, 273 controls) and a joint discovery meta-analysis. No genome-wide significant associations ( < 1 × 10) were observed in the Swiss cohort or in the joint meta-analysis, and no candidate genes suggesting an immune-mediated mechanism were identified. In the joint meta-analysis of MIA cases across all cohorts, two candidate loci on chromosome 9 were identified, rs55898176 (OR = 4.01, 95%CI: 2.41-6.68, = 1.01 × 10) and rs4427239 (OR = 5.47, 95%CI: 2.81-10.65, = 5.75 × 10), of which the latter is located in the gene previously implicated in hematopoiesis. This first genome-wide association study for MIA identified suggestive associations with biological plausibility that may be used as a stepping-stone for post-GWAS analyses to gain further insight into the mechanism underlying MIA.
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http://dx.doi.org/10.3390/genes11111275DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7716224PMC
October 2020

High-Throughput Sequencing to Investigate Associations Between HLA Genes and Metamizole-Induced Agranulocytosis.

Front Genet 2020 21;11:951. Epub 2020 Aug 21.

Department of Clinical Chemistry, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.

Agranulocytosis is a rare and potentially life-threatening complication of metamizole (dipyrone) intake that is characterized by a loss of circulating neutrophil granulocytes. While the mechanism underlying this adverse drug reaction is not well understood, involvement of the immune system has been suggested. In addition, associations between genetic variants in the Human Leukocyte Antigen (HLA) region and agranulocytosis induced by other drugs have been reported. The aim of the present study was to assess whether genetic variants in classical HLA genes are associated with the susceptibility to metamizole-induced agranulocytosis (MIA) in a European population by targeted resequencing of eight HLA genes. A case-control cohort of Swiss patients with a history of neutropenia or agranulocytosis associated with metamizole exposure ( = 53), metamizole-tolerant ( = 39) and unexposed controls ( = 161) was recruited for this study. A high-throughput resequencing (HTS) and high-resolution typing method was used to sequence and analyze eight HLA loci in a discovery subset of this cohort ( = 31 cases, = 38 controls). Identified candidate alleles were investigated in the full Swiss cohort as well as in two independent cohorts from Germany and Spain using HLA imputation from genome-wide SNP array data. In addition, variant calling based on HTS data was performed in the discovery subset for the class I genes , -, and - using the HLA-specific mapper . Eight candidate alleles ( < 0.05) were identified in the discovery subset, of which - was associated with MIA in the full Swiss cohort ( < 0.01) restricted to agranulocytosis (ANC < 0.5 × 10/L) cases. However, no candidate allele showed a consistent association in the Swiss, German and Spanish cohorts. Analysis of individual sequence variants in class I genes produced consistent results with HLA typing but did not reveal additional small nucleotide variants associated with MIA. Our results do not support an HLA-restricted T cell-mediated immune mechanism for MIA. However, we established an efficient high-resolution (three-field) eight-locus HTS HLA resequencing method to interrogate the HLA region and demonstrated the feasibility of its application to pharmacogenetic studies.
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http://dx.doi.org/10.3389/fgene.2020.00951DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7473498PMC
August 2020

Reactive Metamizole Metabolites Enhance the Toxicity of Hemin on the ATP Pool in HL60 Cells by Inhibition of Glycolysis.

Biomedicines 2020 Jul 14;8(7). Epub 2020 Jul 14.

Division of Clinical Pharmacology & Toxicology, University Hospital Basel, Spitalstrasse 21, 4031 Basel, Switzerland.

Metamizole is an analgesic, whose pharmacological and toxicological properties are attributed to N-methyl-aminoantipyrine (MAA), its major metabolite. In the presence of heme iron, MAA forms reactive metabolites, which are toxic for granulocyte precursors. Since decreased cellular ATP is characteristic for MAA-associated toxicity, we studied the effect of MAA with and without hemin on energy metabolism of HL60 cells, a granulocyte precursor cell line. The combination MAA/hemin depleted the cellular ATP stronger than hemin alone, whereas MAA alone was not toxic. This decrease in cellular ATP was observed before plasma membrane integrity impairment. MAA/hemin and hemin did not affect the proton leak but increased the maximal oxygen consumption by HL60 cells. This effect was reversed by addition of the radical scavenger -acetylcysteine. The mitochondrial copy number was not affected by MAA/hemin or hemin. Hemin increased mitochondrial superoxide generation, which was not accentuated by MAA. MAA decreased cellular ROS accumulation in the presence of hemin. In cells cultured in galactose (favoring mitochondrial ATP generation), MAA/hemin had less effect on the cellular ATP and plasma membrane integrity than in glucose. MAA/hemin impaired glycolysis more than hemin or MAA alone, and -acetylcysteine blunted this effect of MAA/hemin. MAA/hemin decreased protein expression of pyruvate kinase more than hemin or MAA alone. In conclusion, cellular ATP depletion appears to be an important mechanism of MAA/hemin toxicity on HL60 cells. MAA itself is not toxic on HL60 cells up to 100 µM but boosts the inhibitory effect of hemin on glycolysis through the formation of reactive metabolites.
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http://dx.doi.org/10.3390/biomedicines8070212DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7400389PMC
July 2020

Acute Liver Failure in a Patient Treated With Metamizole.

Front Pharmacol 2019 11;10:996. Epub 2019 Sep 11.

Division of Clinical Pharmacology & Toxicology, University Hospital Basel, Basel, Switzerland.

We report on a patient who developed acute liver failure while being treated with metamizole. After liver transplantation, the patient recovered rapidly. Liver biopsy showed massive necrosis and lobular infiltration of lymphocytes. A lymphocyte transformation test performed 20 months after transplantation was positive for metamizole. investigations with -methyl-4-aminoantipyrine (MAA) and 4-aminoantipyrine (AA), the two active metabolites of metamizole, did not reveal relevant toxicity in HepG2 and HepaRG cells. The demonstration of activated lymphocytes by the lymphocyte transformation test and the absence of relevant cytotoxicity by MAA and AA in hepatocyte cell lines suggest an immunological mechanism of metamizole-associated hepatotoxicity.
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http://dx.doi.org/10.3389/fphar.2019.00996DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6749849PMC
September 2019

Metamizole-associated neutropenia: Comparison of patients with neutropenia and metamizole-tolerant patients.

Eur J Intern Med 2019 Oct 3;68:36-43. Epub 2019 Aug 3.

Clinical Pharmacology and Toxicology, Department of General Internal Medicine, Inselspital Bern University Hospital, University of Bern, Freiburgstrasse 18, 3010 Bern, Switzerland; Institute of Pharmacology, University of Bern, Freiburgstrasse 18, 3010 Bern, Switzerland. Electronic address:

Reports of metamizole-induced neutropenia have increased in Switzerland and Germany over the last decades, most likely reflecting increased use of metamizole. To date, there are no effective strategies to identify patients at increased risk of metamizole-induced neutropenia. In this observational, multi-center comparative study, characteristics of patients with metamizole-associated neutropenia were compared with patients treated with metamizole without developing adverse hematological reactions. Patients with metamizole-induced neutropenia treated at the University Hospitals Basel and Bern between 2005 and 2017 were included. Tolerant comparison patients with continuous metamizole treatment (≥500 mg/day for at least 28 days) were recruited from GP offices and community pharmacies. Forty-eight patients with metamizole-induced neutropenia, consisting of 23 and 25 cases with inpatient-acquired and outpatient-acquired neutropenia, respectively, were compared to 39 metamizole tolerant comparison patients. Median latency until first diagnosis of neutropenia was 6 days (1-61 days) in inpatient cases and 19 days (2-204 days) in outpatient cases. There was no association between non-myelotoxic and non-immunosuppressive co-medication (p = .6627), history of drug allergy (p = .1304), and preexisting auto-immune diseases (p = .2313) and the development of metamizole-induced neutropenia. Our results suggest that autoimmune diseases, history of drug allergy, and concomitant treatment with non-myelotoxic and non-immunosuppressive drugs are likely not individual risk factors for metamizole-associated neutropenia.
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http://dx.doi.org/10.1016/j.ejim.2019.07.029DOI Listing
October 2019

Toxicity of metamizole on differentiating HL60 cells and human neutrophil granulocytes.

Toxicology 2019 10 26;426:152254. Epub 2019 Jul 26.

Division of Clinical Pharmacology & Toxicology, University Hospital Basel, Schanzenstrasse 55, 4031, Basel, Switzerland; Department of Biomedicine, University of Basel, Hebelstrasse 20, 4031, Basel, Switzerland; Swiss Centre for Applied Human Toxicology (SCAHT), Missionsstrasse 64, 4055, Basel, Switzerland. Electronic address:

Metamizole is an analgesic and antipyretic with a superior analgesic efficacy than paracetamol. Since metamizole can cause neutropenia and agranulocytosis, it is currently used in only few countries. In a previous study, we have shown that N-methyl-4-aminoantipyrine (MAA), the active metamizole metabolite, reacts with hemin and forms an electrophilic metabolite that is toxic for HL60 cells, but not for mature neutrophil granulocytes. In the current study, we investigated the toxicity of hemin (12.5 μM) and MAA (100 μM) on differentiating HL60 cells. In undifferentiated HL60 cells, hemin decreased the viability and this effect was significantly increased by MAA. Similarly, hemin/MAA was more toxic than hemin alone on human cord blood cells. At 3 days (metamyelocyte stage) and 5 days of differentiation (mature neutrophils), hemin/MAA was not toxic on HL60 cells, whereas hemin alone was still toxic. No toxicity was observed on freshly isolated human neutrophils. The protein expression of enzymes responsible for hemin metabolism increased with HL60 cell differentiation. Inhibition of heme oxygenase-1 or cytochrome P450 reductase increased the toxicity of hemin and hemin/MAA in undifferentiated, but only for hemin in differentiated HL60 cells. Similar to the enzymes involved in hemin metabolism, the protein expression of enzymes involved in antioxidative defense and the cellular glutathione pool increased with HL60 cell differentiation. In conclusion, HL60 cells become resistant to the toxicity of hemin/MAA and partly also of hemin during their differentiation. This resistance is associated with the development of heme metabolism and of the antioxidative defense system including the cellular glutathione pool.
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http://dx.doi.org/10.1016/j.tox.2019.152254DOI Listing
October 2019

-Halogenation Affects Monoamine Transporter Inhibition Properties and Hepatocellular Toxicity of Amphetamines and Methcathinones.

Front Pharmacol 2019 24;10:438. Epub 2019 Apr 24.

Division of Clinical Pharmacology and Toxicology, Department of Biomedicine, University Hospital Basel, University of Basel, Basel, Switzerland.

Halogenated derivatives of amphetamine-type stimulants are appearing on the drug market, often with altered pharmacological profile and sometimes different legal status compared to the non-halogenated substances. The aim of the present study was to investigate the pharmacological profile and hepatocellular toxicity of -halogenated amphetamines and cathinones. The potential of amphetamine, 4-fluoroamphetamine, 4-chloroamphetamine, methcathinone, 4-fluoromethcathinone, and 4-chloromethcathinone to inhibit the monoamine transporters for norepinephrine, dopamine, and serotonin was determined in transporter-transfected human embryonic kidney 293 cells. Cell membrane integrity, ATP content, oxygen consumption rate, and superoxide levels were measured in human hepatoma HepG2 cells after exposure to the substances for 24 h. All compounds inhibited the norepinephrine transporter at submicromolar concentrations and the dopamine transporter at low micromolar concentrations. The selectivity of the compounds to inhibit the dopamine serotonin transporter decreased with increasing size of the -substituent, resulting in potent serotonin uptake inhibition for the halogenated derivatives. All substances depleted the cellular ATP content at lower concentrations (0.25-2 mM) than cell membrane integrity loss occurred (≥0.5 mM), suggesting mitochondrial toxicity. The amphetamines and 4-chloromethcathinone additionally impaired the mitochondrial respiratory chain, confirming mitochondrial toxicity. The following toxicity rank order for the -substituents was observed: chloride > fluoride > hydrogen. In conclusion, -halogenation of stimulants increases the risk for serotonergic neurotoxicity. Furthermore, -halogenation may increase hepatic toxicity mediated by mitochondrial impairment in susceptible users.
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http://dx.doi.org/10.3389/fphar.2019.00438DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6491784PMC
April 2019

Non-immunological toxicological mechanisms of metamizole-associated neutropenia in HL60 cells.

Biochem Pharmacol 2019 05 14;163:345-356. Epub 2019 Jan 14.

Division of Clinical Pharmacology & Toxicology, University Hospital, Basel, Switzerland; Department of Biomedicine, University of Basel, Switzerland; Swiss Centre of Applied Human Toxicology (SCAHT), Basel, Switzerland. Electronic address:

Metamizole is an analgesic and antipyretic, but can cause neutropenia and agranulocytosis. We investigated the toxicity of the metabolites N-methyl-4-aminoantipyrine (MAA), 4-aminoantipyrine (AA), N-formyl-4-aminoantipyrine (FAA) and N-acetyl-4-aminoantipyrine (AAA) on neutrophil granulocytes and on HL60 cells (granulocyte precursor cell line). MAA, FAA, AA, and AAA (up to 100 µM) alone were not toxic for HL60 cells or granulocytes. In the presence of the myeloperoxidase substrate HO, MAA reduced cytotoxicity for HL60 cells at low concentrations (<50 µM), but increased cytotoxicity at 100 µM HO. Neutrophil granulocytes were resistant to HO and MAA. Fe and Fe were not toxic to HL60 cells, irrespective of the presence of HO and MAA. Similarly, MAA did not increase the toxicity of lactoferrin, hemoglobin or methemoglobin for HL60 cells. Hemin (hemoglobin degradation product containing a porphyrin ring and Fe) was toxic on HL60 cells and cytotoxicity was increased by MAA. EDTA, N-acetylcystein and glutathione prevented the toxicity of hemin and hemin/MAA. The absorption spectrum of hemin changed concentration-dependently after addition of MAA, suggesting an interaction between Fe and MAA. NMR revealed the formation of a stable MAA reaction product with a reaction pathway involving the formation of an electrophilic intermediate. In conclusion, MAA, the principle metabolite of metamizole, increased cytotoxicity of hemin by a reaction involving the formation of an electrophilic metabolite. Accordingly, cytotoxicity of MAA/hemin could be prevented by the iron chelator EDTA and by the electron donors NAC and glutathione. Situations with increased production of hemin may represent a risk factor for metamizole-associated granulocytopenia.
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http://dx.doi.org/10.1016/j.bcp.2019.01.011DOI Listing
May 2019

N-demethylation of N-methyl-4-aminoantipyrine, the main metabolite of metamizole.

Eur J Pharm Sci 2018 Jul 8;120:172-180. Epub 2018 May 8.

Clinical Pharmacology and Toxicology, Department of General Internal Medicine, Inselspital, Bern University Hospital, University of Bern and Institute of Pharmacology, University of Bern, Switzerland.

Metamizole is an old analgesic used frequently in some countries. Active metabolites of metamizole are the non-enzymatically generated N-methyl-4-aminoantipyrine (4-MAA) and its demethylation product 4-aminoantipyrine (4-AA). Previous studies suggested that 4-MAA demethylation can be performed by hepatic cytochrome P450 (CYP) 3A4, but the possible contribution of other CYPs remains unclear. Using human liver microsomes (HLM), liver homogenate and HepaRG cells, we could confirm 4-MAA demethylation by CYPs. Based on CYP induction (HepaRG cells) and CYP inhibition (HLM) we could identify CYP2B6, 2C8, 2C9 and 3A4 as major contributors to 4-MAA demethylation. The 4-MAA demethylation rate by HLM was 280 pmol/mg protein/h, too low to account for in vivo 4-MAA demethylation in humans. Since peroxidases can perform N-demethylation, we investigated horseradish peroxidase and human myeloperoxidase (MPO). Horse radish peroxidase efficiently demethylated 4-MAA, depending on the hydrogen peroxide concentration. This was also true for MPO; this reaction was saturable with a K of 22.5 μM and a maximal velocity of 14 nmol/min/mg protein. Calculation of the entire body MPO capacity revealed that the demethylation capacity by granulocyte/granulocyte precursors was approximately 600 times higher than the liver capacity and could account for 4-MAA demethylation in humans. 4-MAA demethylation could also be demonstrated in MPO-expressing granulocyte precursor cells (HL-60). In conclusion, 4-MAA can be demethylated in the liver by several CYPs, but hepatic metabolism cannot fully explain 4-MAA demethylation in humans. The current study suggests that the major part of 4-MAA is demethylated by circulating granulocytes and granulocyte precursors in bone marrow.
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http://dx.doi.org/10.1016/j.ejps.2018.05.003DOI Listing
July 2018