TU Darmstadt / ULB / TUbiblio

Gene expression profiling in primary rat hepatocytes for the prediction of hepatotoxicity

Lauer, Birthe (2012)
Gene expression profiling in primary rat hepatocytes for the prediction of hepatotoxicity.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

New human pharmaceuticals are required by law to be tested in pre-clinical studies in order to predict any potential drug side effects. However, during the last decade the number of new drug approvals has markedly decreased while the cost of drug development has increased. The reasons for this are twofold: firstly, due to adverse effects in humans which are not predicted by animal studies, leading to the compound’s failure in late phases of the development process, and secondly because some drug candidates never reach clinical trials due to intolerable toxic effects in animals. Thus, a need exists for new in vitro assays to be developed which enable the detection of a compound’s toxicity prior to animal studies. A better pre-selection of drug candidates could increase the success rate during preclinical trials since very toxic compounds could be excluded from animal tests. Furthermore in vitro tests also provide mechanistic information which supports the interpretation of in vivo observations, as well as play a role in human safety assessment, since these tests could be performed in both animal and human cells. The present study describes one part of the research activities associated with the project Predict-IV financed by the European Commission. Predict-IV’s aim is the development of a non-animal based prediction system for the toxicity of new drugs related to the organs kidney and liver as well as the central nervous system. In the liver work package primary human and rat hepatocytes as well as the human hepatoma cell line HepaRG were treated for 14 days with toxic and non-toxic doses of eleven pharmaceutical reference substances of known in vivo toxicity. After one, three and 14 days, respectively, samples for proteomic, metabolomic, genomic and kinetic analyses were collected. The genomic endpoint was investigated by performing a whole-genome gene expression analysis with Illumina BeadChips. In the present study the global gene expression profiles of primary rat hepatocytes were interpreted biologically after treatment with seven of the eleven reference compounds to investigate the potential of drug-treated rat primary hepatocytes to reflect the in vivo effects noted in the literature. In this study the pharmaceutical mode of action was distinguished from off-target mechanisms which were discussed in relation to hepatotoxic effects in vivo. In accordance with its pharmaceutical mode of action, the PPARα-agonist Fenofibrate increased the expression of genes involved in lipid metabolism. In addition, genes were also induced which indicated the formation of oxidative stress and the depletion of glutathione which was considered to be a basic mechanism of Fenofibrate’s hepatotoxicity. Similar results were found for EMD335823, supporting the assumption that this withdrawn drug candidate is also a PPARα-agonist. However, the small number of genes deregulated by Valproic acid and Acetaminophen was insufficient to reflect any in vivo effects probably related to cellular treatment with too small doses. The PPARγ-agonists Troglitazone and Rosiglitazone induced genes which coded for drug-metabolizing enzymes known to oxidize these substances, especially Troglitazone, into reactive potentially cytotoxic metabolites. Additional genes involved in the metabolism of glutathione and the response to oxidative stress, a major toxic mechanism of Troglitazone and Rosiglitazone, were upregulated. Since both compounds pharmacologically act on muscle cells their mode of action could not be reconstructed. Metformin which acts on the liver without causing severe adverse effects was used as negative control. It deregulated a large number of genes but its gene expression profile clearly differed from that of the hepatotoxic compounds. In the last chapter of this study the genes commonly deregulated by Fenofibrate, EMD335823, Troglitazone, Rosiglitazone and Metformin were discussed. The major part of these genes was involved in lipid metabolism which seemed to be related to the mode of action of the tested compounds since PPARα- and PPARγ-agonists regulate lipid and glucose homeostasis. In conclusion the whole-genome gene expression profile of drug treated primary rat hepatocytes reflected cellular mechanisms which could explain hepatotoxic effects in vivo. During the next phases of Predict-IV the gene expression profiles of rat and human primary hepatocytes and HepaRG cells treated with all of the eleven reference compounds will be compared. The gene expression profiles of the four reference compounds not discussed in this study will be compared with their protein expression profiles. Additionally, the real cellular concentration of the test compounds and the kinetic of their metabolism will be calculated. Furthermore, species-specific effects as well as the responsiveness of the cell line compared to primary cells will be investigated in order to define the cell system best suited for an early predictive screening system. Finally, genomic and proteomic markers should be defined and validated which could enable the early prediction of new drugs’ hepatotoxic potential in future.

Typ des Eintrags: Dissertation
Erschienen: 2012
Autor(en): Lauer, Birthe
Art des Eintrags: Erstveröffentlichung
Titel: Gene expression profiling in primary rat hepatocytes for the prediction of hepatotoxicity
Sprache: Englisch
Referenten: Layer, Prof. Dr. Paul ; Laube, Prof. Dr. Bodo
Publikationsjahr: 29 Juli 2012
Datum der mündlichen Prüfung: 10 Februar 2011
URL / URN: urn:nbn:de:tuda-tuprints-30649
Kurzbeschreibung (Abstract):

New human pharmaceuticals are required by law to be tested in pre-clinical studies in order to predict any potential drug side effects. However, during the last decade the number of new drug approvals has markedly decreased while the cost of drug development has increased. The reasons for this are twofold: firstly, due to adverse effects in humans which are not predicted by animal studies, leading to the compound’s failure in late phases of the development process, and secondly because some drug candidates never reach clinical trials due to intolerable toxic effects in animals. Thus, a need exists for new in vitro assays to be developed which enable the detection of a compound’s toxicity prior to animal studies. A better pre-selection of drug candidates could increase the success rate during preclinical trials since very toxic compounds could be excluded from animal tests. Furthermore in vitro tests also provide mechanistic information which supports the interpretation of in vivo observations, as well as play a role in human safety assessment, since these tests could be performed in both animal and human cells. The present study describes one part of the research activities associated with the project Predict-IV financed by the European Commission. Predict-IV’s aim is the development of a non-animal based prediction system for the toxicity of new drugs related to the organs kidney and liver as well as the central nervous system. In the liver work package primary human and rat hepatocytes as well as the human hepatoma cell line HepaRG were treated for 14 days with toxic and non-toxic doses of eleven pharmaceutical reference substances of known in vivo toxicity. After one, three and 14 days, respectively, samples for proteomic, metabolomic, genomic and kinetic analyses were collected. The genomic endpoint was investigated by performing a whole-genome gene expression analysis with Illumina BeadChips. In the present study the global gene expression profiles of primary rat hepatocytes were interpreted biologically after treatment with seven of the eleven reference compounds to investigate the potential of drug-treated rat primary hepatocytes to reflect the in vivo effects noted in the literature. In this study the pharmaceutical mode of action was distinguished from off-target mechanisms which were discussed in relation to hepatotoxic effects in vivo. In accordance with its pharmaceutical mode of action, the PPARα-agonist Fenofibrate increased the expression of genes involved in lipid metabolism. In addition, genes were also induced which indicated the formation of oxidative stress and the depletion of glutathione which was considered to be a basic mechanism of Fenofibrate’s hepatotoxicity. Similar results were found for EMD335823, supporting the assumption that this withdrawn drug candidate is also a PPARα-agonist. However, the small number of genes deregulated by Valproic acid and Acetaminophen was insufficient to reflect any in vivo effects probably related to cellular treatment with too small doses. The PPARγ-agonists Troglitazone and Rosiglitazone induced genes which coded for drug-metabolizing enzymes known to oxidize these substances, especially Troglitazone, into reactive potentially cytotoxic metabolites. Additional genes involved in the metabolism of glutathione and the response to oxidative stress, a major toxic mechanism of Troglitazone and Rosiglitazone, were upregulated. Since both compounds pharmacologically act on muscle cells their mode of action could not be reconstructed. Metformin which acts on the liver without causing severe adverse effects was used as negative control. It deregulated a large number of genes but its gene expression profile clearly differed from that of the hepatotoxic compounds. In the last chapter of this study the genes commonly deregulated by Fenofibrate, EMD335823, Troglitazone, Rosiglitazone and Metformin were discussed. The major part of these genes was involved in lipid metabolism which seemed to be related to the mode of action of the tested compounds since PPARα- and PPARγ-agonists regulate lipid and glucose homeostasis. In conclusion the whole-genome gene expression profile of drug treated primary rat hepatocytes reflected cellular mechanisms which could explain hepatotoxic effects in vivo. During the next phases of Predict-IV the gene expression profiles of rat and human primary hepatocytes and HepaRG cells treated with all of the eleven reference compounds will be compared. The gene expression profiles of the four reference compounds not discussed in this study will be compared with their protein expression profiles. Additionally, the real cellular concentration of the test compounds and the kinetic of their metabolism will be calculated. Furthermore, species-specific effects as well as the responsiveness of the cell line compared to primary cells will be investigated in order to define the cell system best suited for an early predictive screening system. Finally, genomic and proteomic markers should be defined and validated which could enable the early prediction of new drugs’ hepatotoxic potential in future.

Alternatives oder übersetztes Abstract:
Alternatives AbstractSprache

Die Prüfung neuer Arzneimittel in präklinischen Studien zur Voraussage potentieller Nebenwirkungen ist gesetzlich vorgeschrieben. In den letzten zehn Jahren sank die Anzahl an neu zugelassenen Wirkstoffen jedoch merklich, während die Kosten für deren Entwicklung anstiegen. Die Gründe hierfür sind zum einen Nebenwirkungen am Menschen, die durch Tierstudien nicht vorhergesagt werden konnten und zum Scheitern der Substanz in späten Entwicklungsphasen führten. Zum anderen gelangten einige Wirkstoffkandidaten aufgrund nicht tolerierbarer toxischer Effekte im Tier erst gar nicht in die klinischen Studien. Daher ist es notwending, in vitro-Tests zu entwickeln, die es ermöglichen, die Toxizität neuer Wirkstoffe vor dem Beginn der Tierstudien zu erkennen. Denn eine bessere Vorauswahl von Wirkstoffkandidaten für die präklinischen Studien könnte deren Erfolgsquote erhöhen, da sehr toxische Stoffe erst gar nicht am Tier getestet würden. Zudem liefern in vitro-Tests mechanistische Informationen, die die Interpretation von Beobachtungen in präklinischen und klinischen Studien unterstützen, da diese Tests mit tierischen und humanen Zellen durchgeführt werden können. Die vorliegende Dissertation beschreibt einen Teil der Forschungsarbeiten, die im Rahmen des von der Europäischen Union geförderten Projektes Predict-IV durchgeführt wurden. Das Ziel von Predict-IV ist die Entwicklung eines tierversuchs-freien Prädiktionsmodells für die Toxizität neuer pharmazeutischer Wirkstoffe für die Organe Niere und Leber sowie das Zentrale Nervensystem. Im Bereich der Leber wurden primäre Human- und Rattenhepatozyten sowie die humane Hepatomazelllinie HepaRG über 14 Tage mit einer toxischen und einer nicht-toxischen Dosis von elf pharamazeutischen Referenzsubstanzen mit bekannter in vivo Toxizität behandelt. Nach einem, drei bzw. 14 Tagen erfolgte die Probennahme für Proteom- und Metabolomanalysen bzw. genetische und kinetische Untersuchungen. Die genetischen Analysen wurden mit Hilfe einer globalen Genexpressionsanalyse mit Illumina BeadChips durchgeführt. In der vorliegenden Arbeit wurden die globalen Genexpressionsprofile von primären Rattenhepatozyten biologisch interpretiert, die mit sieben der elf Referenzsubstanzen behandelt worden waren. Das Ziel der Arbeit war, zu untersuchen, inwieweit wirkstoffbehandelte Rattenhepatozyten in der Literatur beschriebene in vivo-Effekte widerspiegeln. Dabei wurde der pharmakologische Wirkprozess von solchen Effekten abgegrenzt, die im Bezug zu in vivo-Toxizitäten diskutiert wurden. Der PPARα-Agonist Fenofibrat erhöhte in Korrelation zu dessen pharmakologischen Wirkmechanismus die Expression von Genen, die für Enzyme des Lipidmetabolismus codieren. Zudem wurden Gene induziert, die im Zusammenhang mit oxidativem Stress und Glutathiondepletion stehen, den grundlegenden Mechanismen der Hepatotoxizität von Fenofibrat. Ähnliche Ergebnisse wurden für EMD335823 erzielt, was die Annahme stützt, dass auch dieser gestoppte Wirkstoffkandidat ein PPARα-Agonist ist. Valproinsäure und Acetaminophen deregulierten eine sehr geringe Anzahl von Genen, wodurch eine Rekonstruktion der in vivo-Effekte nicht möglich war. Dies schien in der Behandlung der Zellen mit einer zu geringen Dosis begründet gewesen zu sein. Die PPARγ-Agonisten Troglitazon und Rosiglitazon induzierten Gene, die für arzneimittel-metabolisierende Enzyme codieren, die speziell Troglitazon zu einem potentiell zytotoxischen Metaboliten oxidieren. Zusätzlich wurde die Expression von Genen erhöht, die in den Glutathionmetabolismus und die Antwort auf oxidativen Stress als Hauptmechanismus der Toxizität von Troglitazon und Rosiglitazon involviert sind. Da beide Substanzen pharmakologisch hauptsächlich in Muskelzellen agieren, konnte ihr Wirkmechanismus nicht rekonstruiert werden. Metformin, das pharmakologisch in der Leber wirkt ohne schwere Nebenwirkungen zu verursachen, wurde als Negativkontrolle benutzt. Es deregulierte eine große Anzahl von Genen. Das Genexpressionsprofil unterschied sich jedoch deutlich von dem der hepatotoxischen Substanzen. Im letzten Kapitel der vorliegenden Arbeit wurden die durch Fenofibrat, EMD335823, Troglitazon, Rosiglitazon und Metformin gemeinsam deregulierten Gene diskutiert. Der größte Teil dieser Gene war in den Lipidmetabolismus involviert, was mit dem Wirkmechanismus der untersuchten Substanzen zusammenzuhängen schien, da PPARα- und PPARγ-Agonisten den Lipid- und Glucosehaushalt regulieren. Abschließend kann gesagt werden, dass die globalen Genexpressionsprofile der wirkstoffbehandelten primären Rattenhepatozyten zelluläre Mechanismen widerspiegelten, mit Hilfe derer hepatotoxische in vivo-Effekte erklärt werden können. Innerhalb der nächsten Schritte von Predict-IV werden die Genexpressionsprofile von primären Ratten- und Humanhepatozyten sowie HepaRG-Zellen verglichen, die mit allen elf Referenzsubstanzen behandelt wurden. Des Weiteren werden die Genexpressionsprofile der vier Substanzen, die in der vorliegenden Arbeit nicht diskutiert wurden, mit den Proteinexpressionsprofilen der behandelten Zellen verglichen werden. Zusätzlich werden die wahren Substanzkonzentrationen in der Zelle sowie die Kinetik des Substanzabbaus gemessen werden. Abschließend werden Speziesunterschiede sowie die Responsivität der HepaRG-Zellen im Vergleich zu den Primärzellen untersucht werden, um herauszufinden, welches Zellkultursystem am besten für den Aufbau eines frühen Screening-Tests geeignet ist. Zudem sollen Marker auf Gen- und Proteinebene gefunden und validiert werden, die in Zukunft die frühe Vorhersage der Hepatotoxizität neuer Wirkstoffkandidaten ermöglichen könnten.

Deutsch
Sachgruppe der Dewey Dezimalklassifikatin (DDC): 500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie
Fachbereich(e)/-gebiet(e): 10 Fachbereich Biologie
Hinterlegungsdatum: 08 Aug 2012 10:04
Letzte Änderung: 05 Mär 2013 10:02
PPN:
Referenten: Layer, Prof. Dr. Paul ; Laube, Prof. Dr. Bodo
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: 10 Februar 2011
Export:
Suche nach Titel in: TUfind oder in Google
Frage zum Eintrag Frage zum Eintrag

Optionen (nur für Redakteure)
Redaktionelle Details anzeigen Redaktionelle Details anzeigen