title: Mechanisms of tolvaptan-induced toxicity in HepG2 cells.
abstract: Tolvaptan, a vasopressin receptor 2 antagonist used to treat hyponatremia, has recently been reported to be associated with an increased risk of liver injury. In this study, we explored the underlying mechanisms of hepatotoxicity of tolvaptan using human HepG2 cells. Tolvaptan inhibited cell growth and caused cell death in a concentration- and time-dependent manner. Tolvaptan treatment led to delayed cell cycle progression, accompanied by decreased levels of several cyclins and cyclin-dependent kinases. Tolvaptan was found to cause DNA damage, as assessed by alkaline comet assays; this was confirmed by increased levels of 8-oxoguanine and phosphorylation of histone H2AX. Exposure of HepG2 cells to tolvaptan enhanced cytochrome C release and triggered apoptosis by modulating Bcl-2 family members. The activation of p38 contributed to tolvaptan-mediated apoptosis via down-regulation of Bcl-2. Proteasome inhibition altered tolvaptan-induced cell cycle deregulation and enhanced tolvaptan-induced apoptosis and cytotoxicity. Moreover, tolvaptan treatment induced autophagy. Inhibition of autophagy by knocking-down an autophagy-related gene increased tolvaptan-induced apoptosis and cytotoxicity. Taken together, our findings suggest that the cytotoxicity of tolvaptan results from delayed cell cycle progression, the induction of DNA damage, and the execution of apoptosis. In addition, a number of signaling pathways were perturbed by tolvaptan and played an important role in its cytotoxicity.
authors: Division of Biochemical Toxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA.
authors: Yuanfeng
authors: Y
authors: Wu
authors: Division of Biochemical Toxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA.
authors: Frederick A
authors: FA
authors: Beland
authors: Division of Biochemical Toxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA.
authors: Si
authors: S
authors: Chen
authors: Division of Neurotoxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA.
authors: Fang
authors: F
authors: Liu
authors: Division of Biochemical Toxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA.
authors: Lei
authors: L
authors: Guo
authors: Division of Biochemical Toxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA. Electronic address: jia-long.fang@fda.hhs.gov.
authors: Jia-Long
authors: JL
authors: Fang
mesh_terms: D065092:Antidiuretic Hormone Receptor Antagonists / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D001552:Benzazepines / Q000633:toxicity*; D002453:Cell Cycle / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation; D056743:Cyclin D3 / Q000378:metabolism; D051358:Cyclin-Dependent Kinase 4 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D004789:Enzyme Activation; D056945:Hep G2 Cells; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism; D061988:Proteasome Inhibitors / Q000494:pharmacology; D000077602:Tolvaptan
chemical_list: D065092:Antidiuretic Hormone Receptor Antagonists; D001552:Benzazepines; D056743:Cyclin D3; D061988:Proteasome Inhibitors; D000077602:Tolvaptan; D051544:Cytochrome P-450 CYP3A; D051358:Cyclin-Dependent Kinase 4; D020928:Mitogen-Activated Protein Kinases; D046988:Proteasome Endopeptidase Complex
keywords: Apoptosis; Autophagy; DNA damage; Liver injury; Proteasome; Tolvaptan