title: Brusatol provokes a rapid and transient inhibition of Nrf2 signaling and sensitizes mammalian cells to chemical toxicity-implications for therapeutic targeting of Nrf2.
abstract: The transcription factor Nrf2 regulates the basal and inducible expression of a battery of cytoprotective genes. Whereas numerous Nrf2-inducing small molecules have been reported, very few chemical inhibitors of Nrf2 have been identified to date. The quassinoid brusatol has recently been shown to inhibit Nrf2 and ameliorate chemoresistance in vitro and in vivo. Here, we show that brusatol provokes a rapid and transient depletion of Nrf2 protein, through a posttranscriptional mechanism, in mouse Hepa-1c1c7 hepatoma cells. Importantly, brusatol also inhibits Nrf2 in freshly isolated primary human hepatocytes. In keeping with its ability to inhibit Nrf2 signaling, brusatol sensitizes Hepa-1c1c7 cells to chemical stress provoked by 2,4-dinitrochlorobenzene, iodoacetamide, and N-acetyl-p-benzoquinone imine, the hepatotoxic metabolite of acetaminophen. The inhibitory effect of brusatol toward Nrf2 is shown to be independent of its repressor Keap1, the proteasomal and autophagic protein degradation systems, and protein kinase signaling pathways that are known to modulate Nrf2 activity, implying the involvement of a novel means of Nrf2 regulation. These findings substantiate brusatol as a useful experimental tool for the inhibition of Nrf2 signaling and highlight the potential for therapeutic inhibition of Nrf2 to alter the risk of adverse events by reducing the capacity of nontarget cells to buffer against chemical and oxidative insults. These data will inform a rational assessment of the risk:benefit ratio of inhibiting Nrf2 in relevant therapeutic contexts, which is essential if compounds such as brusatol are to be developed into efficacious and safe drugs.
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: Adedamola
authors.initials: A
authors.lastname: Olayanju
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Copple
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: Holly K
authors.initials: HK
authors.lastname: Bryan
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: George T
authors.initials: GT
authors.lastname: Edge
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: Rowena L
authors.initials: RL
authors.lastname: Sison
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: Min Wei
authors.initials: MW
authors.lastname: Wong
authors.affiliation: School of Chinese Medicine, Chinese University of Hong Kong, Hong Kong, People׳s Republic of China.
authors.forename: Zheng-Quan
authors.initials: ZQ
authors.lastname: Lai
authors.affiliation: School of Chinese Medicine, Chinese University of Hong Kong, Hong Kong, People׳s Republic of China.
authors.forename: Zhi-Xiu
authors.initials: ZX
authors.lastname: Lin
authors.affiliation: Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: Karen
authors.initials: K
authors.lastname: Dunn
authors.affiliation: Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Sanderson
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: Ahmad F
authors.initials: AF
authors.lastname: Alghanem
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Cross
authors.affiliation: Unit for Transplantation Surgery, Department of Clinical Science, Intervention, and Technology, Karolinska University Hospital Huddinge, Stockholm, Sweden.
authors.forename: Ewa C
authors.initials: EC
authors.lastname: Ellis
authors.affiliation: Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Ingelman-Sundberg
authors.affiliation: Department of Hepatobiliary Surgery, Aintree University Hospital NHS Foundation Trust, Liverpool, UK.
authors.forename: Hassan Z
authors.initials: HZ
authors.lastname: Malik
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: Neil R
authors.initials: NR
authors.lastname: Kitteringham
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK. Electronic address: chrissy@liv.ac.uk.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Goldring
authors.affiliation: MRC Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
authors.forename: B Kevin
authors.initials: BK
authors.lastname: Park
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy; D015153:Blotting, Western; D032269:Brucea / Q000737:chemistry; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects*; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D051267:NF-E2-Related Factor 2 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D036702:Quassins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D051267:NF-E2-Related Factor 2; D036702:Quassins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C020237:brusatol
keywords: Brusatol; Cell defense; Chemical stress; Free radicals; Hepatocyte; Keap1; Nrf2; Toxicity