TY - JOUR
T1 - Mechanisms of Chronic Fialuridine Hepatotoxicity as Revealed in Primary Human Hepatocyte Spheroids
AU - Hendriks, Delilah F.G.
AU - Hurrell, Tracey
AU - Riede, Julia
AU - Van Der Horst, Muriëlle
AU - Tuovinen, Sarianna
AU - Ingelman-Sundberg, Magnus
N1 - Publisher Copyright:
© 2019 The Author(s) 2019. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For permissions, please e-mail: [email protected].
PY - 2019/10/1
Y1 - 2019/10/1
N2 - Drug hepatotoxicity is often delayed in onset. An exemplar case is the chronic nature of fialuridine hepatotoxicity, which resulted in the deaths of several patients in clinical trials as preclinical studies failed to identify this human-specific hepatotoxicity. Conventional preclinical in vitro models are mainly designed to evaluate the risk of acute drug toxicity. Here, we evaluated the utility of 3D spheroid cultures of primary human hepatocytes (PHHs) to assess chronic drug hepatotoxicity events using fialuridine as an example. Fialuridine toxicity was only detectable after 7 days of repeated exposure. Clinical manifestations, including reactive oxygen species formation, lipid accumulation, and induction of apoptosis, were readily identified. Silencing the expression or activity of the human equilibrative nucleoside transporter 1 (ENT1), implicated in the mitochondrial transport of fialuridine, modestly protected PHH spheroids from fialuridine toxicity. Interference with the phosphorylation of fialuridine into the active triphosphate metabolites by silencing of thymidine kinase 2 (TK2) provided substantial protection, whereas simultaneous silencing of ENT1 and TK2 provided near-complete protection. Fialuridine-induced mitochondrial dysfunction was suggested by a decrease in the expression of mtDNA-encoded genes, which correlated with the onset of toxicity and was prevented under the simultaneous silencing of ENT1 and TK2. Furthermore, interference with the expression or activity of ribonucleotide reductase (RNR), which is critical to deoxyribonucleoside triphosphate (dNTP) pool homeostasis, resulted in selective potentiation of fialuridine toxicity. Our findings demonstrate the translational applicability of the PHH 3D spheroid model for assessing drug hepatotoxicity events which manifest only under chronic exposure conditions.
AB - Drug hepatotoxicity is often delayed in onset. An exemplar case is the chronic nature of fialuridine hepatotoxicity, which resulted in the deaths of several patients in clinical trials as preclinical studies failed to identify this human-specific hepatotoxicity. Conventional preclinical in vitro models are mainly designed to evaluate the risk of acute drug toxicity. Here, we evaluated the utility of 3D spheroid cultures of primary human hepatocytes (PHHs) to assess chronic drug hepatotoxicity events using fialuridine as an example. Fialuridine toxicity was only detectable after 7 days of repeated exposure. Clinical manifestations, including reactive oxygen species formation, lipid accumulation, and induction of apoptosis, were readily identified. Silencing the expression or activity of the human equilibrative nucleoside transporter 1 (ENT1), implicated in the mitochondrial transport of fialuridine, modestly protected PHH spheroids from fialuridine toxicity. Interference with the phosphorylation of fialuridine into the active triphosphate metabolites by silencing of thymidine kinase 2 (TK2) provided substantial protection, whereas simultaneous silencing of ENT1 and TK2 provided near-complete protection. Fialuridine-induced mitochondrial dysfunction was suggested by a decrease in the expression of mtDNA-encoded genes, which correlated with the onset of toxicity and was prevented under the simultaneous silencing of ENT1 and TK2. Furthermore, interference with the expression or activity of ribonucleotide reductase (RNR), which is critical to deoxyribonucleoside triphosphate (dNTP) pool homeostasis, resulted in selective potentiation of fialuridine toxicity. Our findings demonstrate the translational applicability of the PHH 3D spheroid model for assessing drug hepatotoxicity events which manifest only under chronic exposure conditions.
KW - 3D spheroid culture
KW - chronic drug hepatotoxicity
KW - fialuridine
KW - primary human hepatocytes
UR - http://www.scopus.com/inward/record.url?scp=85077103447&partnerID=8YFLogxK
U2 - 10.1093/toxsci/kfz195
DO - 10.1093/toxsci/kfz195
M3 - Article
C2 - 31505000
AN - SCOPUS:85077103447
SN - 1096-6080
VL - 171
SP - 385
EP - 395
JO - Toxicological Sciences
JF - Toxicological Sciences
IS - 2
ER -