The FA pathway counteracts oxidative stress through selective protection of antioxidant defense gene promoters
ABSTRACT Oxidative stress has been implicated in the pathogenesis of many human diseases including Fanconi anemia (FA), a genetic disorder associated with BM failure and cancer. Here we show that major antioxidant defense genes are down-regulated in FA patients, and that gene down-regulation is selectively associated with increased oxidative DNA damage in the promoters of the antioxidant defense genes. Assessment of promoter activity and DNA damage repair kinetics shows that increased initial damage, rather than a reduced repair rate, contributes to the augmented oxidative DNA damage. Mechanistically, FA proteins act in concert with the chromatin-remodeling factor BRG1 to protect the promoters of antioxidant defense genes from oxidative damage. Specifically, BRG1 binds to the promoters of the antioxidant defense genes at steady state. On challenge with oxidative stress, FA proteins are recruited to promoter DNA, which correlates with significant increase in the binding of BRG1 within promoter regions. In addition, oxidative stress-induced FANCD2 ubiquitination is required for the formation of a FA-BRG1-promoter complex. Taken together, these data identify a role for the FA pathway in cellular antioxidant defense.
- SourceAvailable from: Zhengyuan Xia[Show abstract] [Hide abstract]
ABSTRACT: Brahma-related gene 1 (Brg1) is a key gene in inducing the expression of important endogenous antioxidant enzymes, including heme oxygenase-1 (HO-1) which is central to cardioprotection, while cardiac HO-1 expression is reduced in diabetes. It is unknown whether or not cardiac Brg1 expression is reduced in diabetes. We hypothesize that cardiac Brg1 expression is reduced in diabetes which can be restored by antioxidant treatment with N-acetylcysteine (NAC). Control (C) and streptozotocin-induced diabetic (D) rats were treated with NAC in drinking water or placebo for 4 weeks. Plasma and cardiac free15-F2t-isoprostane in diabetic rats were increased, accompanied with increased plasma levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin 6 (IL-6), while cardiac Brg1, p-STAT3 and HO-1 protein expression levels were significantly decreased. Left ventricle weight/body weight ratio was higher, while the peak velocities of early (E) and late (A) flow ratio was lower in diabetic than in C rats. NAC normalized tissue and plasma levels of 15-F2t-isoprostane, significantly increased cardiac Brg1, HO-1 and p-STAT3 protein expression levels and reduced TNF-alpha and IL-6, resulting in improved cardiac function. In conclusion, myocardial Brg1 is reduced in diabetes and enhancement of cardiac Brg1 expression may represent a novel mechanism whereby NAC confers cardioprotection.Journal of Diabetes Research 06/2013; 2013:716219. DOI:10.1155/2013/716219 · 3.54 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Oxidative stress plays a key role in carcinogenesis. Oxidative damage to cell components can lead to the initiation, promotion and progression of cancer. Oxidative stress is also a distinctive sign in several genetic disorders characterized by a cancer predisposition such as ataxia-telangiectasia, Fanconi anemia, Down syndrome, Beckwith-Wiedemann syndrome and Costello syndrome. Taking into account the link between oxidative stress and cancer, the capacity of antioxidant agents to prevent or delay neoplastic development has been tested in various studies, both in vitro and in vivo, with interesting and promising results. In recent years, research has been conducted into the molecular mechanisms linking oxidative stress to the pathogenesis of the genetic syndromes we consider in this review, with the resulting identification of possible new therapeutic targets. The aim of this review is to focus on the oxidative mechanisms intervening in carcinogenesis in cancer-prone genetic disorders and to analyze the current status and future prospects of antioxidants.
- [Show abstract] [Hide abstract]
ABSTRACT: The commonly accepted definition of Fanconi anemia (FA) relying on DNA repair deficiency is submitted to a critical review starting from the early reports pointing to mitomycin C bioactivation and to the toxicity mechanisms of diepoxybutane and a group of nitrogen mustards causing DNA crosslinks in FA cells. A critical analysis of the literature prompts revisiting the FA phenotype and crosslinker sensitivity in terms of an oxidative stress (OS) background, redox-related anomalies of FA (FANC) proteins, and mitochondrial dysfunction. This re-appraisal of FA basic defect might lead to innovative approaches both in elucidating FA phenotypes and in clinical management. Pediatr Blood Cancer © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.Pediatric Blood & Cancer 03/2015; 62(7). DOI:10.1002/pbc.25452 · 2.56 Impact Factor