Transgenic Expression of PRSS1R122H Sensitizes Mice to Pancreatitis
Mutations in the trypsinogen gene (PRSS1) cause human hereditary pancreatitis. However, it is not clear how mutant forms of PRSS1 contribute to disease development. We studied the effects of expressing mutant forms of human PRSS1 in mice.
The nuclear hypoxia-regulated NLUCAT1 long non-coding RNA contributes to an aggressive phenotype in lung adenocarcinoma through regulation of oxidative stress
Lung cancer is the leading cause of cancer death worldwide, with poor prognosis and a high rate of recurrence despite early surgical removal. Hypoxic regions within tumors represent sources of aggressiveness and resistance to therapy. Although long non-coding RNAs (lncRNAs) are increasingly recognized as major gene expression regulators, their regulation and function following hypoxic stress are still largely unexplored. Combining profiling studies on early-stage lung adenocarcinoma (LUAD) biopsies and on A549 LUAD cell lines cultured in normoxic or hypoxic conditions, we identified a subset of lncRNAs that are both correlated with the hypoxic status of tumors and regulated by hypoxia in vitro. We focused on a new transcript, NLUCAT1, which is strongly upregulated by hypoxia in vitro and correlated with hypoxic markers and poor prognosis in LUADs. Full molecular characterization showed that NLUCAT1 is a large nuclear transcript composed of six exons and mainly regulated by NF-κB and NRF2 transcription factors. CRISPR-Cas9-mediated invalidation of NLUCAT1 revealed a decrease in proliferative and invasive properties, an increase in oxidative stress and a higher sensitivity to cisplatin-induced apoptosis. Transcriptome analysis of NLUCAT1-deficient cells showed repressed genes within the antioxidant and/or cisplatin-response networks. We demonstrated that the concomitant knockdown of four of these genes products, GPX2, GLRX, ALDH3A1, and PDK4, significantly increased ROS-dependent caspase activation, thus partially mimicking the consequences of NLUCAT1 inactivation in LUAD cells. Overall, we demonstrate that NLUCAT1 contributes to an aggressive phenotype in early-stage hypoxic tumors, suggesting it may represent a new potential therapeutic target in LUADs.
Synergy between arsenic trioxide and JQ1 on autophagy in pancreatic cancer
Pancreatic cancer is a deadliest type of malignancy and lacks effective intervention. We here report a potential strategy for treatment of this malignancy by the combination of arsenic trioxide (ATO) and BET bromodomain inhibitor JQ1. These two agents synergistically modulate multistages of autophagy and thus induce apoptosis effectively in pancreatic cancer cells. Our genomic and biochemical data have demonstrated that crosstalks between ER stress and autophagy play crucial roles during ATO-induced apoptosis, in which NRF2 may stand at the crossroad between cell death and survival. This has been further strengthened by our finding that NRF2 depletion renders insensitive cells into sensitive ones in regard to ATO treatment-caused cell death. The knockdown of NRF2 and the addition of JQ1 result in similar molecular/cellular effects in promoting effective ATO-induced apoptosis in cells that are insensitive to ATO treatment alone. Thus, the combination of ATO and JQ1 may represent a new treatment strategy for pancreatic cancer.
Deglycation of NRF2 by FN3K Promotes Oncogenesis and Drug Resistance
Fructosamine-3-kinase (FN3K) activity promotes oncogenesis in models of liver and lung cancer.
Rare and common genetic variations in the Keap1/Nrf2 antioxidant response pathway impact thyroglobulin gene expression and circulating levels, respectively
Nuclear factor, erythroid 2-like 2 (Nrf2) is a transcription factor that has been gaining attention in the field of pharmacology and especially in the chemoprevention of diseases such as cancer, metabolic and neurodegenerative diseases, etc. This is because natural compounds such as sulforaphane, which is found in broccoli sprout extracts, can activate Nrf2. The repertoire of the roles of Nrf2 is ever increasing; besides its traditional antioxidant and cytoprotective effects, Nrf2 can have other functions as a transcription factor. We have recently shown that Nrf2 directly regulates the expression of thyroglobulin (Tg), which is the most abundant thyroidal protein and the precursor of thyroid hormones. Two functional binding sites for Nrf2 (antioxidant response elements, AREs) were identified in the regulatory region of the TG gene. Interestingly, we then observed that one of these AREs harbors a rare single-nucleotide polymorphism (SNP). Also recently, we performed the first genome-wide association study (GWAS) for common SNPs that impact the circulating levels of Tg. Based on these investigations, we were triggered (i) to investigate whether common SNPs in the Nrf2 pathway correlate with circulating Tg levels; and (ii) to examine whether the rare SNP in one of the TG regulatory AREs may affect gene expression. To address the first question, we analyzed GWAS data from a general population and its two subpopulations, one with thyroid disease and/or abnormal thyroid function tests and the other without, in which circulating Tg levels had been measured. Statistically significant associations with Tg levels were observed in the genes encoding Nrf2 and Keap1, including, notably, a known functional SNP in the promoter of the gene encoding Nrf2. Regarding the rare SNP (rs778940395) in the proximal ARE of the TG enhancer, luciferase reporter gene expression studies in PCCL3 rat thyroid follicular cells showed that this SNP abrogated the basal and sulforaphane- or TSH-induced luciferase activity, behaving as a complete loss-of-function mutation. Thus, both rare and common genetic variation in the Keap1/Nrf2 pathway can impact TG expression and Tg circulating levels, respectively.
NRF2/ABCB1-mediated efflux and PARP1-mediated dampening of DNA damage contribute to doxorubicin resistance in chronic hypoxic HepG2 cells
Transarterial chemoembolization (TACE)-induced hypoxia can trigger residual liver cancer cells to present a more aggressive phenotype associated with chemoresistance, but the underlying mechanisms are still unknown. In this study, the human liver cancer cell line HepG2 was pre-cultured in different oxygen environments to examine the possible mechanisms of hypoxia-induced doxorubicin resistance. Our study showed that HepG2 cells pre-cultured in a chronic intermittent hypoxic environment exhibited significant resistance to doxorubicin, evidenced by increased intracellular doxorubicin efflux, relatively higher cell proliferation, lower apoptosis and decreased DNA damage. These changes were accompanied by high levels of NRF2 and ABCB1 under conditions of both chronic and acute hypoxia; and PARP1 gene expression only under conditions of chronic hypoxia. SiRNA-mediated silencing of NRF2 gene expression down-regulated the expression of ABCB1 and increased the intracellular doxorubicin accumulation and cell apoptosis both in acute and chronic hypoxic HepG2 cells. Moreover, silencing of PARP1 gene expression increased the doxorubicin-induced DNA damage and cell apoptosis in chronic hypoxic cells. On the basis of these findings, we concluded that NRF2/ABCB1-mediated efflux and PARP1-mediated DNA repair contribute to doxorubicin resistance in chronic hypoxic HepG2 cells. This article is protected by copyright. All rights reserved.
The Role of Nrf2 in the Antioxidant Cellular Response to Medical Ozone Exposure
Ozone (O) is a natural, highly unstable atmospheric gas that rapidly decomposes to oxygen. Although not being a radical molecule, O is a very strong oxidant and therefore it is potentially toxic for living organisms. However, scientific evidence proved that the effects of O exposure are dose-dependent: high dosages stimulate severe oxidative stress resulting in inflammatory response and tissue injury, whereas low O concentrations induce a moderate oxidative eustress activating antioxidant pathways. These properties make O a powerful medical tool, which can be used as either a disinfectant or an adjuvant agent in the therapy of numerous diseases. In this paper, the cellular mechanisms involved in the antioxidant response to O exposure will be reviewed with special reference to the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) and its role in the efficacy of ozone therapy.
Ferroportin downregulation promotes cell proliferation by modulating the Nrf2-miR-17-5p axis in multiple myeloma
Recent findings demonstrate that aberrant downregulation of the iron-exporter protein, ferroportin (FPN1), is associated with poor prognosis and osteoclast differentiation in multiple myeloma (MM). Here, we show that FPN1 was downregulated in MM and that clustered regularly interspaced short palindromic repeat (CRISPR)-mediated FPN1 knockout promoted MM cell growth and survival. Using a microRNA target-scan algorithm, we identified miR-17-5p as an FPN1 regulator that promoted cell proliferation and cell cycle progression, and inhibited apoptosis-both in vitro and in vivo. miR-17-5p inhibited retarded tumor growth in a MM xenograft model. Moreover, restoring FPN1 expression at least partially abrogated the biological effects of miR-17-5p in MM cells. The cellular iron concentration regulated the expression of the iron-regulatory protein (IRP) via the 5'-untranslated region of IRP messenger RNA and modulated the post-transcriptional stability of FPN1. Bioinformatics analysis with subsequent chromatin immunoprecipitation-polymerase chain reaction and luciferase activity experiments revealed that the transcription factor Nrf2 drove FPN1 transcription through promoter binding and suppressed miR-17-5p (which also increased FPN1 expression). Nrf2-mediated FPN1 downregulation promoted intracellular iron accumulation and reactive oxygen species. Our study links FPN1 transcriptional and post-transcriptional regulation with MM cell growth and survival, and validates the prognostic value of FPN1 and its utility as a novel therapeutic target in MM.
Dietary melatonin attenuates chromium-induced lung injury via activating the Sirt1/Pgc-1α/Nrf2 pathway
Exposure to chromium (Cr) causes a number of respiratory diseases, including lung cancer and pulmonary fibrosis. However, there is currently no safe treatment for Cr-induced lung damage. Here, we used in vivo and in vitro approaches to examine the protective effects of melatonin (MEL) on Cr-induced lung injury and to identify the underlying molecular mechanisms. We found that treatment of rats or a mouse lung epithelial cell MLE-12 with MEL attenuated K2Cr2O7-induced lung injury by reducing the production of oxidative stress and inflammatory mediators and inhibiting cell apoptosis. MEL treatment upregulated the expression of silent information regulator 1 (Sirt1), which deacetylated the transcriptional coactivator peroxisome proliferator-activated receptor-γ coactivator-1α (Pgc-1α). In turn, this increased the expression of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and key anti-oxidant target genes. These results suggest that melatonin attenuates chromium-induced lung injury via activating the Sirt1/Pgc-1α/Nrf2 pathway. Dietary MEL supplement may be a potential new strategy for the treatment of Cr poisoning.
Bardoxolone methyl analog attenuates proteinuria-induced tubular damage by modulating mitochondrial function
Multiple clinical studies have shown that bardoxolone methyl, a potent activator of nuclear factor erythroid 2-related factor 2 (Nrf2), is effective in increasing glomerular filtration rate in patients with chronic kidney disease. However, whether an Nrf2 activator can protect tubules from proteinuria-induced tubular damage anti-inflammatory and antioxidative stress mechanisms is unknown. Using an Institute of Cancer Research-derived glomerulonephritis (ICGN) mouse model of nephrosis, we examined the effects of dihydro-CDDO-trifluoroethyl amide (dh404), a rodent-tolerable bardoxolone methyl analog, in protecting the tubulointerstitium; dh404 markedly suppressed tubular epithelial cell damage in the renal interstitium of ICGN mice. The tubular epithelial cells of ICGN mice showed a decrease in the size and number of mitochondria, as well as the breakdown of the crista structure, whereas the number and ultrastructure of mitochondria were maintained by the dh404 treatment. To further determine the effect of dh404 on mitochondrial function, we used human proximal tubular cells . Stimulation with albumin and free fatty acid increased mitochondrial reactive oxygen species (ROS). However, dh404 administration diminished mitochondrial ROS. Our data show that dh404 significantly reduced proteinuria-induced tubular cell mitochondrial damage, suggesting that improved redox balance and mitochondrial function and suppression of inflammation underlie the cytoprotective mechanism of Nrf2 activators, including bardoxolone methyl, in diabetic kidney disease.-Nagasu, H., Sogawa, Y., Kidokoro, K., Itano, S., Yamamoto, T., Satoh, M., Sasaki, T., Suzuki, T., Yamamoto, M., Wigley, W. C., Proksch, J. W., Meyer, C. J., Kashihara, N. Bardoxolone methyl analog attenuates proteinuria-induced tubular damage by modulating mitochondrial function.
Antioxidant Defenses: A Context-Specific Vulnerability of Cancer Cells
Reactive oxygen species (ROS) are well known for their capacity to cause DNA damage, augment mutagenesis, and thereby promote oncogenic transformation. Similarly, agents that reduce ROS levels (antioxidants) are frequently thought to have anti-cancer properties given their propensity to minimize DNA damage and mutagenesis. However, numerous clinical studies focused on antioxidants suggest that this is a facile premise and that antioxidant capacity can be important for cancer cells in a similar fashion to normal cells. As a consequence of this realization, numerous laboratories have been motivated to investigate the biological underpinnings explaining how and when antioxidant activity can potentially be beneficial to cancer cells. Relatedly, it has become clear that the reliance of cancer cells on antioxidant activity in certain contexts represents a potential vulnerability that could be exploited for therapeutic gain. Here, we review some of the recent, exciting findings documenting how cancer cells utilized antioxidant activity and under what circumstances this activity could represent an opportunity for selective elimination of cancer cells.
Can Nrf2 Modulate the Development of Intestinal Fibrosis and Cancer in Inflammatory Bowel Disease?
One of the main mechanisms carried out by the cells to counteract several forms of stress is the activation of the nuclear factor erythroid 2-related factor (Nrf2) signaling. Nrf2 signaling controls the expression of many genes through the binding of a specific -acting element known as the antioxidant response element (ARE). Activation of Nrf2/ARE signaling can mitigate several pathologic mechanisms associated with an autoimmune response, digestive and metabolic disorders, as well as respiratory, cardiovascular, and neurodegenerative diseases. Indeed, several studies have demonstrated that Nrf2 pathway plays a key role in inflammation and in cancer development in many organs, including the intestine. Nrf2 appears to be involved in inflammatory bowel disease (IBD), an immune-mediated chronic and disabling disease, with a high risk of developing intestinal fibrotic strictures and cancer. Currently, drugs able to increase cytoprotective Nrf2 function are in clinical trials or already being used in clinical practice to reduce the progression of some degenerative conditions. The role of Nrf2 in cancer development and progression is controversial, and drugs able to inhibit abnormal levels of Nrf2 are also under investigation. The goal of this review is to analyze and discuss Nrf2-dependent signals in the initiation and progression of intestinal fibrosis and cancers occurring in IBD.
Histone chaperone FACT complex mediates oxidative stress response to promote liver cancer progression
Facilitates Chromatin Transcription (FACT) complex is a histone chaperone participating in DNA repair-related and transcription-related chromatin dynamics. In this study, we investigated its oncogenic functions, underlying mechanisms and therapeutic implications in human hepatocellular carcinoma (HCC).
Keap1/Nrf2 Signaling: A New Player in Thyroid Pathophysiology and Thyroid Cancer
The Keap1/Nrf2 pathway is a key mediator of general redox and tissue-specific homeostasis. It also exerts a dual role in cancer, by preventing cell transformation of normal cells but promoting aggressiveness, and drug resistance of malignant ones. Although Nrf2 is well-studied in other tissues, its roles in the thyroid gland are only recently emerging. This review focuses on the involvement of Keap1/Nrf2 signaling in thyroid physiology, and pathophysiology in general, and particularly in thyroid cancer. Studies in mice and cultured follicular cells have shown that, under physiological conditions, Nrf2 coordinates antioxidant defenses, directly increases thyroglobulin production and inhibits its iodination. Increased Nrf2 pathway activation has been reported in two independent families with multinodular goiters due to germline loss-of-function mutations in . Nrf2 pathway activation has also been documented in papillary thyroid carcinoma (PTC), due to somatic mutations, or epigenetic modifications in , or other pathway components. In PTC, such Nrf2-activating mutations have been associated with tumor aggressiveness. Furthermore, polymorphisms in the prototypical Nrf2 target genes and have been associated with extra-thyroidal extension and metastasis. More recently, mutations in the Nrf2 pathway have also been found in Hürthle-cell (oncocytic) thyroid carcinoma. Finally, in , and models of poorly-differentiated, and undifferentiated (anaplastic) thyroid carcinoma, Nrf2 activation has been associated with resistance to experimental molecularly-targeted therapy. Thus, Keap1/Nrf2 signaling is involved in both benign and malignant thyroid conditions, where it might serve as a prognostic marker or therapeutic target.
17-β estradiol exerts anti-inflammatory effects through activation of Nrf2 in mouse embryonic fibroblasts
Several reports indicate crosstalk between the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and estrogen, which has a protective effect in colorectal cancer (CRC). The aim of this study was to investigate the role of Nrf2 signaling in the anti-inflammatory effect of estrogen using Nrf2 knockout (Nrf2 KO) mouse embryonic fibroblasts (MEFs), a powerful system to test the function of target genes due to their easy accessibility, and rapid growth rates. After inducing inflammation by tumor necrosis factor alpha (TNF-α), the effects of 17β-estradiol (E2) on the expression of proinflammatory mediators [i.e., NF-κB and inducible nitric oxide synthase (iNOS)] and estrogen receptors were evaluated by Western blot. In wild type (WT) MEFs, E2 treatment ameliorated TNF-α-induced nuclear translocation of NF-κB and expression of its target protein iNOS. Estrogen receptor beta (ERβ) expression was decreased by TNF-α-induced inflammation and restored by E2 treatment. When treated to WT MEFs, E2 induced nuclear translocation of Nrf2. The inhibitory effect of E2 on TNF-α-induced enhancement of iNOS was markedly dampened in Nrf2 KO MEFs. Notably, ERβ expression was significantly diminished in Nrf2 KO MEFs compared to that in WT cells. Promoter Database (EPD) revealed two putative anti-oxidant response elements (AREs) within the mouse ERβ promoter. Furthermore, in WT MEFs, E2 treatment repressed TNF-α-induced expression of iNOS protein and recovered by 4-(2-phenyl-5,7-bis(trifluoromethyl)pyrazolo(1,5-a)pyrimidin-3-yl)phenol (PHTPP), a selective ERβ antagonist, treatment, but not in Nrf2 KO MEFs. In conclusion, Nrf2 plays a pivotal role in the anti-inflammatory of estrogen by direct regulating the expression of ERβ.