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Brusatol provokes a rapid and transient inhibition of Nrf2 signaling and sensitizes mammalian cells to chemical toxicity-implications for therapeutic targeting of Nrf2
Brusatol provokes a rapid and transient inhibition of Nrf2 signaling and sensitizes mammalian cells to chemical toxicity-implications for therapeutic targeting of Nrf2
- Source :
- Free Radical Biology & Medicine
- Publication Year :
- 2014
-
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.<br />Highlights • Nrf2 regulates the expression of numerous cytoprotective genes. • We show that the quassinoid brusatol rapidly and transiently inhibits Nrf2 signaling. • Brusatol sensitizes mammalian cells to chemical stress provoked by electrophiles. • Brusatol inhibits Nrf2 independent of its key regulatory mechanisms. • Therapeutic inhibition of Nrf2 could enhance drug-induced adverse effects.
- Subjects :
- Keap1
Carcinoma, Hepatocellular
NF-E2-Related Factor 2
Blotting, Western
Apoptosis
Gclm, glutamate–cysteine ligase regulatory subunit
Brusatol
Free radicals
Cell defense
Real-Time Polymerase Chain Reaction
digestive system
environment and public health
Nrf2, nuclear factor erythroid 2-related factor 2
Nrf2
RT-qPCR, real-time quantitative PCR
Mice
Autophagy
Brucea
Animals
Humans
Hepatocyte
RNA, Messenger
RNA, Small Interfering
AMC, 7-amino-4-methylcoumarin
Cells, Cultured
DNCB, 2,4-dinitrochlorobenzene
Cell Proliferation
Quassins
Toxicity
Reverse Transcriptase Polymerase Chain Reaction
Liver Neoplasms
Original Contribution
respiratory system
Keap1, Kelch-like ECH-associated protein 1
Chemical stress
Oxidative Stress
Gene Expression Regulation
Hepatocytes
HIF-1α, hypoxia-inducible factor 1α
NEM, N-ethylmaleimide
Nqo1, NAD(P)H dehydrogenase quinone 1
IAA, iodoacetamide
NAPQI, N-acetyl-p-benzoquinone imine
Oxidation-Reduction
CDDO-Me, methyl-2-cyano-3,12-dioxooleana-1, 9(11)dien-28-oate
Signal Transduction
Subjects
Details
- ISSN :
- 18734596
- Volume :
- 78
- Database :
- OpenAIRE
- Journal :
- Free radical biologymedicine
- Accession number :
- edsair.pmid..........0120eae82a5a66da0ccda5377b1d32a8