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Nuclear factor erythroid-derived factor 2-related factor 2 regulates transcription of CCAAT/enhancer-binding protein ? during adipogenesis.

ABSTRACT: Nuclear factor erythroid-derived factor 2-related factor 2 (Nrf2) is a cap-n-collar basic leucine zipper transcription factor that is involved in the cellular adaptive response to oxidative stress. Our previous study reported that targeted disruption of the Nrf2 gene in mice decreases adipose tissue mass and protects against obesity induced by a high-fat diet. Deficiency of Nrf2 in preadipocytes and mouse embryonic fibroblasts led to impaired adipogenesis. Consistent with these findings, the current study found that lack of Nrf2 in primary cultured mouse preadipocytes and 3T3-L1 cells hampered adipogenic differentiation induced by hormonal cocktails. Stable knockdown of Nrf2 in 3T3-L1 cells blocked the enhanced adipogenesis caused by deficiency of kelch-like ECH-associated protein 1 (Keap1), a Cul3-adapter protein that allows for Nrf2 to be ubiquinated and degraded by the 26S protesome complex. In addition, increased production of reactive oxygen species (ROS) and activation of Nrf2 occurred at the very early stage upon adipogenic hormonal challenge in 3T3-L1 cells, followed by an immediate induction of CCAAT/enhancer-binding protein ? (C/EBP?). Knockdown of Nrf2 led to reduced expression of C/EBP? induced by adipogenic hormonal cocktails, chemical Nrf2 activators or Keap1 silencing. Cebp? promoter-driven reporter assays and chromatin immunoprecipitation suggested that Nrf2 associates with a consensus antioxidant response element (ARE) binding site in the promoter of the Cebp? gene during adipogenesis and upregulates its expression. These findings demonstrate a novel role of Nrf2 beyond xenobiotic detoxification and antioxidant response, and suggest that Nrf2 is one of the transcription factors that control the early events of adipogenesis by regulating expression of Cebp?.

SUBMITTER: Hou Y

PROVIDER: S-EPMC3307524 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Nuclear factor erythroid-derived factor 2-related factor 2 regulates transcription of CCAAT/enhancer-binding protein β during adipogenesis.

Hou Yongyong Y Xue Peng P Bai Yushi Y Liu Dianxin D Woods Courtney G CG Yarborough Kathy K Fu Jingqi J Zhang Qiang Q Sun Guifan G Collins Sheila S Chan Jefferson Y JY Yamamoto Masayuki M Andersen Melvin E ME Pi Jingbo J

Free radical biology & medicine 20111028 2

Nuclear factor erythroid-derived factor 2-related factor 2 (Nrf2) is a cap-n-collar basic leucine zipper transcription factor that is involved in the cellular adaptive response to oxidative stress. Our previous study reported that targeted disruption of the Nrf2 gene in mice decreases adipose tissue mass and protects against obesity induced by a high-fat diet. Deficiency of Nrf2 in preadipocytes and mouse embryonic fibroblasts led to impaired adipogenesis. Consistent with these findings, the cur ...[more]

PMID: 22138520

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Project description:The sensitization of hepatocytes to cell death from tumor necrosis factor ? (TNF?) underlies many forms of hepatic injury, including that from toxins. Critical for hepatocyte resistance to TNF? toxicity is activation of nuclear factor ?B (NF-?B) signaling, which prevents TNF?-induced death by the up-regulation of protective proteins. To further define the mechanisms of hepatocyte sensitization to TNF? killing, immunoblot analysis comparing livers from mice treated with lipopolysaccharide (LPS) alone or LPS together with the hepatotoxin galactosamine (GalN) was performed to identify TNF?-induced protective proteins blocked by GalN. Levels of CCAAT/enhancer-binding protein ? (C/EBP?) were increased after LPS treatment but not GalN/LPS treatment. In a nontransformed rat hepatocyte cell line, TNF?-induced increases in C/EBP? protein levels were dependent on NF-?B-mediated inhibition of proteasomal degradation. Pharmacological inhibition of c-Jun N-terminal kinase (JNK) did not affect C/EBP? degradation, indicating that the process was JNK-independent. C/EBP? functioned to prevent cell death as adenoviral C/EBP? overexpression blocked TNF?-induced apoptosis in cells sensitized to TNF? toxicity by NF-?B inhibition. C/EBP? inhibited TNF?-induced caspase 8 activation and downstream mitochondrial cytochrome c release and caspase 3 and caspase 7 activation. Studies in primary hepatocytes from c/ebp?(-/-) mice confirmed that loss of C/EBP? increased death from TNF?. c/ebp?(-/-) mice were also sensitized to liver injury from a nontoxic dose of LPS or TNF?. The absence of jnk2 failed to reverse the GalN-induced block in C/EBP? induction by LPS, again demonstrating that C/EBP? degradation was JNK-independent.C/EBP? is up-regulated by TNF? and mediates hepatocyte resistance to TNF? toxicity by inhibiting caspase-dependent apoptosis. In the absence of NF-?B signaling, proteasomal degradation of C/EBP? is increased by a JNK-independent mechanism and promotes death from TNF?.

Project description:Dysregulation of the ubiquitin-proteasome system has been implicated in the pathogenesis of several metabolic disorders, including obesity, diabetes, and non-alcoholic fatty liver disease; however, the mechanisms controlling pathogenic metabolic disorders remain unclear. Transcription factor CCAAT/enhancer binding protein beta (C/EBPβ) regulates adipogenic genes. The study showed that the expression level of C/EBPβ is post-translationally regulated by the deubiquitinase ubiquitin-specific protease 1 (USP1) and that USP1 expression is remarkably upregulated during adipocyte differentiation and in the adipose tissue of mice fed a high-fat diet (HFD). We found that USP1 directly interacts with C/EBPβ. Knock-down of USP1 decreased C/EBPβ protein stability and increased its ubiquitination. Overexpression of USP1 regulates its protein stability and ubiquitination, whereas catalytic mutant of USP1 had no effect on them. It suggests that USP1 directly deubiquitinases C/EBPβ and increases the protein expression, leading to adipogenesis and lipid accumulation. Notably, the USP1-specific inhibitor ML323-originally developed to sensitize cancer cells to DNA-damaging agents-decreased adipocyte differentiation and lipid accumulation in 3T3-L1 cells without cytotoxicity. Oral gavage of ML323 was administered to HFD-fed mice, which showed weight loss and improvement in insulin and glucose sensitivity. Both fat mass and adipocyte size in white adipose tissues were significantly reduced by ML323 treatment, which also reduced the expression of genes involved in adipogenesis and inflammatory responses. ML323 also reduced lipid accumulation, hepatic triglycerides, free fatty acids, and macrophage infiltration in the livers of HFD-fed mice. Taken together, we suggest that USP1 plays an important role in adipogenesis by regulating C/EBPβ ubiquitination, and USP1-specific inhibitor ML323 is a potential treatment option and further study by ML323 is needed for clinical application for metabolic disorders.

Dataset Information

Nuclear factor erythroid-derived factor 2-related factor 2 regulates transcription of CCAAT/enhancer-binding protein ? during adipogenesis.

Publications

Nuclear factor erythroid-derived factor 2-related factor 2 regulates transcription of CCAAT/enhancer-binding protein β during adipogenesis.

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