NRF2 Rewires Cellular Metabolism to Support the Antioxidant Response

The transcription factor (nuclear factor-erythroid 2 p45-related factor 2, NRF2) is a master regulator of the cellular response to oxidative insults. While antioxidant response enzymes are well-characterized transcriptional targets of NRF2, it is recently becoming clear that NRF2 also supports cellular detoxification through metabolic rewiring to support the antioxidant systems. In this chapter, we discuss the regulation of NRF2 and how NRF2 activation promotes the antioxidant defense of cells. Furthermore, we discuss how reactive oxygen species influence cellular metabolism and how this affects antioxidant function. We also discuss how NRF2 reprograms cellular metabolism to support the antioxidant response and how this functions to funnel metabolic intermediates into antioxidant pathways. This chapter concludes by exploring how these factors may contribute to both normal physiology and disease

Inhibition of TXNRD or SOD1 overcomes NRF2-mediated resistance to β-lapachone

Alterations in the NRF2/KEAP1 pathway result in the constitutive activation of NRF2, leading to the aberrant induction of antioxidant and detoxification enzymes, including NQO1. The NQO1 bioactivatable agent β-lapachone can target cells with high NQO1 expression but relies in the generation of reactive oxygen species (ROS), which are actively scavenged in cells with NRF2/KEAP1 mutations. However, whether NRF2/KEAP1 mutations influence the response to β-lapachone treatment remains unknown. To address this question, we assessed the cytotoxicity of β-lapachone in a panel of NSCLC cell lines bearing either wild-type or mutant KEAP1. We found that, despite overexpression of NQO1, KEAP1 mutant cells were resistant to β-lapachone due to enhanced detoxification of ROS, which prevented DNA damage and cell death. To evaluate whether specific inhibition of the NRF2-regulated antioxidant enzymes could abrogate resistance to β-lapachone, we systematically inhibited the four major antioxidant cellular systems using genetic and/or pharmacologic approaches. We demonstrated that inhibition of the thioredoxin-dependent system or copper-zinc superoxide dismutase (SOD1) could abrogate NRF2-mediated resistance to β-lapachone, while depletion of catalase or glutathione was ineffective. Interestingly, inhibition of SOD1 selectively sensitized KEAP1 mutant cells to β-lapachone exposure. Our results suggest that NRF2/KEAP1 mutational status might serve as a predictive biomarker for response to NQO1-bioactivatable quinones in patients. Further, our results suggest SOD1 inhibition may have potential utility in combination with other ROS inducers in patients with KEAP1/NRF2 mutations

Ferroptosis in health and disease

Ferroptosis is a pervasive non-apoptotic form of cell death highly relevant in various degenerative diseases and malignancies. The hallmark of ferroptosis is uncontrolled and overwhelming peroxidation of polyunsaturated fatty acids contained in membrane phospholipids, which eventually leads to rupture of the plasma membrane. Ferroptosis is unique in that it is essentially a spontaneous, uncatalyzed chemical process based on perturbed iron and redox homeostasis contributing to the cell death process, but that it is nonetheless modulated by many metabolic nodes that impinge on the cells’ susceptibility to ferroptosis. Among the various nodes affecting ferroptosis sensitivity, several have emerged as promising candidates for pharmacological intervention, rendering ferroptosis-related proteins attractive targets for the treatment of numerous currently incurable diseases. Herein, the current members of a Germany-wide research consortium focusing on ferroptosis research, as well as key external experts in ferroptosis who have made seminal contributions to this rapidly growing and exciting field of research, have gathered to provide a comprehensive, state-of-the-art review on ferroptosis. Specific topics include: basic mechanisms, in vivo relevance, specialized methodologies, chemical and pharmacological tools, and the potential contribution of ferroptosis to disease etiopathology and progression. We hope that this article will not only provide established scientists and newcomers to the field with an overview of the multiple facets of ferroptosis, but also encourage additional efforts to characterize further molecular pathways modulating ferroptosis, with the ultimate goal to develop novel pharmacotherapies to tackle the various diseases associated with – or caused by – ferroptosis.Fil: Berndt, Carsten. Heinrich-Heine University; AlemaniaFil: Alborzinia, Hamed. Heidelberg Institute for Stem Cell Technology and Experimental Medicine; AlemaniaFil: Amen, Vera Skafar. University of Würzburg; AlemaniaFil: Ayton, Scott. University of Melbourne; AustraliaFil: Barayeu, Uladzimir. Heidelberg University; Alemania. German Cancer Research Center; Alemania. Tohoku University Graduate School of Medicine; JapónFil: Bartelt, Alexander. Ludwig Maximilians Universitat; AlemaniaFil: Bayir, Hülya. Columbia University; Estados UnidosFil: Bebber, Christina M.. University of Cologne; AlemaniaFil: Birsoy, Kivanc. The Rockefeller University; Estados UnidosFil: Böttcher, Jan P.. Universitat Technical Zu Munich; AlemaniaFil: Brabletz, Simone. Friedrich-Alexander University of Erlangen-Nürnberg; AlemaniaFil: Brabletz, Thomas. Friedrich-Alexander University of Erlangen-Nürnberg; AlemaniaFil: Brown, Ashley R.. Columbia University; Estados UnidosFil: Brunner Bernhardt, Mauricio Andrés. Goethe Universitat Frankfurt; AlemaniaFil: Bulli, Giorgia. Ludwig Maximilians Universitat; AlemaniaFil: Bruneau, Alix. Goethe Universitat Frankfurt; AlemaniaFil: Chen, Quan. Nankai University; ChinaFil: DeNicola, Gina M.. Moffitt Cancer Center; Estados UnidosFil: Dick, Tobias P.. Ruprecht Karls Universitat Heidelberg; AlemaniaFil: Distefano, Ayelen Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Dixon, Scott J.. University of Stanford; Estados UnidosFil: Engler, Jan B.. University Medical Center Hamburg-Eppendorf; AlemaniaFil: Pagnussat, Gabriela Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Wilhelm, Christoph. Universitat Bonn; AlemaniaFil: Wölk, Michele. University Hospital Carl Gustav Carus; AlemaniaFil: Wu, Katherine. University of New York; Estados UnidosFil: Yang, Xin. Columbia University; Estados UnidosFil: Yu, Fan. Nankai University; ChinaFil: Zou, Yilong. Westlake University; ChinaFil: Conrad, Marcus. Helmholtz Center Munich; Alemani

Ferroptosis in health and disease.

Ferroptosis is a pervasive non-apoptotic form of cell death highly relevant in various degenerative diseases and malignancies. The hallmark of ferroptosis is uncontrolled and overwhelming peroxidation of polyunsaturated fatty acids contained in membrane phospholipids, which eventually leads to rupture of the plasma membrane. Ferroptosis is unique in that it is essentially a spontaneous, uncatalyzed chemical process based on perturbed iron and redox homeostasis contributing to the cell death process, but that it is nonetheless modulated by many metabolic nodes that impinge on the cells susceptibility to ferroptosis. Among the various nodes affecting ferroptosis sensitivity, several have emerged as promising candidates for pharmacological intervention, rendering ferroptosis-related proteins attractive targets for the treatment of numerous currently incurable diseases. Herein, the current members of a Germany-wide research consortium focusing on ferroptosis research, as well as key external experts in ferroptosis who have made seminal contributions to this rapidly growing and exciting field of research, have gathered to provide a comprehensive, state-of-the-art review on ferroptosis. Specific topics include: basic mechanisms, in vivo relevance, specialized methodologies, chemical and pharmacological tools, and the potential contribution of ferroptosis to disease etiopathology and progression. We hope that this article will not only provide established scientists and newcomers to the field with an overview of the multiple facets of ferroptosis, but also encourage additional efforts to characterize further molecular pathways modulating ferroptosis, with the ultimate goal to develop novel pharmacotherapies to tackle the various diseases associated with - or caused by - ferroptosis

K-Ras oncogene-induced ROS detoxification promotes tumorigenesis

The contrasting outcomes of tumor promotion or cellular senescence have both been ascribed to increased levels of reactive oxygen species (ROS). Instead, I demonstrate that endogenous expression of K-RasG12D in primary murine cells and tissues unexpectedly triggers a reduction of ROS due to the activation of an antioxidant program by the Nrf2 transcription factor. Persistent Nrf2 activation maintains the decreased intracellular redox state and promotes hyperproliferation of K-RasG12D expressing cells, and this occurs through engagement of the mitogen activated protein kinase (MAPK) Ras effector pathway. These findings are not shared by cells ectopically overexpressing oncogenic Ras, where transient induction of Nrf2, ROS production and cellular senescence are instead observed. Nrf2 is activated in human and mouse pancreatic cancer, and Nrf2 deficiency or glutathione depletion both impair K-RasG12D – dependent cellular proliferation and carcinogenesis in vivo. Therefore, decreased ROS can promote carcinogenesis, presenting new opportunities to treat and prevent K-Ras mutant cancers

K-Ras oncogene-induced ROS detoxification promotes tumorigenesis

The contrasting outcomes of tumor promotion or cellular senescence have both been ascribed to increased levels of reactive oxygen species (ROS). Instead, I demonstrate that endogenous expression of K-RasG12D in primary murine cells and tissues unexpectedly triggers a reduction of ROS due to the activation of an antioxidant program by the Nrf2 transcription factor. Persistent Nrf2 activation maintains the decreased intracellular redox state and promotes hyperproliferation of K-RasG12D expressing cells, and this occurs through engagement of the mitogen activated protein kinase (MAPK) Ras effector pathway. These findings are not shared by cells ectopically overexpressing oncogenic Ras, where transient induction of Nrf2, ROS production and cellular senescence are instead observed. Nrf2 is activated in human and mouse pancreatic cancer, and Nrf2 deficiency or glutathione depletion both impair K-RasG12D – dependent cellular proliferation and carcinogenesis in vivo. Therefore, decreased ROS can promote carcinogenesis, presenting new opportunities to treat and prevent K-Ras mutant cancers

The Non-Essential Amino Acid Cysteine Becomes Essential for Tumor Proliferation and Survival

The non-essential amino acid cysteine is used within cells for multiple processes that rely on the chemistry of its thiol group. Under physiological conditions, many non-transformed tissues rely on glutathione, circulating cysteine, and the de novo cysteine synthesis (transsulfuration) pathway as sources of intracellular cysteine to support cellular processes. In contrast, many cancers require exogeneous cystine for proliferation and viability. Herein, we review how the cystine transporter, xCT, and exogenous cystine fuel cancer cell proliferation and the mechanisms that regulate xCT expression and activity. Further, we discuss the potential contribution of additional sources of cysteine to the cysteine pool and what is known about the essentiality of these processes in cancer cells. Finally, we discuss whether cyst(e)ine dependency and associated metabolic alterations represent therapeutically targetable metabolic vulnerabilities

mTORC1-Induced HK1-Dependent Glycolysis Regulates NLRP3 Inflammasome Activation

The mammalian target of rapamycin complex 1 (mTORC1) regulates activation of immune cells and cellular energy metabolism. Although glycolysis has been linked to immune functions, the mechanisms by which glycolysis regulates NLRP3 inflammasome activation remain unclear. Here, we demonstrate that mTORC1-induced glycolysis provides an essential mechanism for NLRP3 inflammasome activation. Moreover, we demonstrate that hexokinase 1 (HK1)-dependent glycolysis, under the regulation of mTORC1, represents a critical metabolic pathway for NLRP3 inflammasome activation. Downregulation of glycolysis by inhibition of Raptor/mTORC1 or HK1 suppressed both pro-IL-1β maturation and caspase-1 activation in macrophages in response to LPS and ATP. These results suggest that upregulation of HK1-dependent glycolysis by mTORC1 regulates NLRP3 inflammasome activation