Differential and overlapping targets of the transcriptional regulators NRF1, NRF2, and NRF3 in human cells

Biomarkers of NRF2 signalling: Current status and future challenges

The cytoprotective transcription factor NRF2 regulates the expression of several hundred genes in mammalian cells and is a promising therapeutic target in a number of diseases associated with oxidative stress and inflammation. Hence, an ability to monitor basal and inducible NRF2 signalling is vital for mechanistic understanding in translational studies. Due to some caveats related to the direct measurement of NRF2 levels, the modulation of NRF2 activity is typically determined by measuring changes in the expression of one or more of its target genes and/or the associated protein products. However, there is a lack of consensus regarding the most relevant set of these genes/proteins that best represents NRF2 activity across cell types and species. We present the findings of a comprehensive literature search that according to stringent criteria identifies GCLC, GCLM, HMOX1, NQO1, SRXN1 and TXNRD1 as a robust panel of markers that are directly regulated by NRF2 in multiple cell and tissue types. We assess the relevance of these markers in clinically accessible biofluids and highlight future challenges in the development and use of NRF2 biomarkers in humans.

Nfe2l3 promotes neuroprotection and long-distance axon regeneration after injury in vivo

Nuclear factor erythroid 2 like (Nfe2l) gene family members 1-3 mediate cellular response to oxidative stress, including in the central nervous system (CNS). However, neuronal functions of Nfe2l3 are unknown. Here, we comparatively evaluated expression of Nfe2l1, Nfe2l2, and Nfe2l3 in singe cell RNA-seq (scRNA-seq)-profiled cortical and retinal ganglion cell (RGC) CNS projection neurons, investigated whether Nfe2l3 regulates neuroprotection and axon regeneration after CNS injury in vivo, and characterized a gene network associated with Nfe2l3 in neurons. We showed that, Nfe2l3 expression transiently peaks in developing immature cortical and RGC projection neurons, but is nearly abolished in adult neurons and is not upregulated after injury. Furthermore, within the retina, Nfe2l3 is enriched in RGCs, primarily neonatally, and not upregulated in injured RGCs, whereas Nfe2l1 and Nfe2l2 are expressed robustly in other retinal cell types as well and are upregulated in injured RGCs. We also found that, expressing Nfe2l3 in injured RGCs through localized intralocular viral vector delivery promotes neuroprotection and long-distance axon regeneration after optic nerve injury in vivo. Moreover, Nfe2l3 provided a similar extent of neuroprotection and axon regeneration as viral vector-targeting of Pten and Klf9, which are prominent regulators of neuroprotection and long-distance axon regeneration. Finally, we bioinformatically characterized a gene network associated with Nfe2l3 in neurons, which predicted the association of Nfe2l3 with established mechanisms of neuroprotection and axon regeneration. Thus, Nfe2l3 is a novel neuroprotection and axon regeneration-promoting factor with a therapeutic potential for treating CNS injury and disease.

Unique and overlapping roles of NRF2 and NRF1 in transcriptional regulation

Transcription is regulated by specific transcription factors that mediate signaling in response to extrinsic and intrinsic stimuli such as nutrients, hormones, and oxidative stresses. Many transcription factors are grouped based on their highly conserved DNA binding domains. Consequently, transcription factors within the same family often exhibit functional redundancy and compensation. NRF2 (NFE2L2) and NRF1 (NFE2L1) belong to the CNC family transcription factors, which are responsible for various stress responses. Although their DNA binding properties are strikingly similar, NRF2 and NRF1 are recognized to play distinct roles in a cell by mediating responses to oxidative stress and proteotoxic stress, respectively. In this review, we here overview the distinct and shared roles of NRF2 and NRF1 in the transcriptional regulation of target genes, with a particular focus on the nuclear protein binding partners associated with each factor.

Natural Allies for Heart Health: Nrf2 Activation and Cardiovascular Disease Management

The term "cardiovascular diseases" (CVD) refers to various ailments that affect the heart and blood vessels, including myocardial ischemia, congenital heart defects, heart failure, rheumatic heart disease, hypertension, peripheral artery disease, atherosclerosis, and cardiomyopathies. Despite significant breakthroughs in preventative measures and treatment choices, CVDs significantly contribute to morbidity and mortality, imposing a considerable financial burden. Oxidative stress (OS) is a fundamental contributor to the development and progression of CVDs, resulting from an inherent disparity in generating reactive oxygen species. The disparity above significantly contributes to the aberrant operation of the cardiovascular system. To tackle this issue, therapeutic intervention primarily emphasizes the nuclear erythroid 2-related factor 2 (Nrf2), a transcription factor crucial in regulating endogenous antioxidant defense systems against OS. The Nrf2 exhibits potential as a promising target for effectively managing CVDs. Significantly, an emerging field of study is around the utilization of natural substances to stimulate the activation of Nrf2, hence facilitating the promotion of cardioprotection. This technique introduces a new pathway for treating CVD. The substances above elicit their advantageous effects by mitigating the impact of OS via initiating Nrf2 signaling. The primary objective of our study is to provide significant insights that can contribute to advancing treatment methods, including natural products. These strategies aim to tackle the obstacles associated with CVDs.

NRF3 suppresses squamous carcinogenesis, involving the unfolded protein response regulator HSPA5

Epithelial skin cancers are extremely common, but the mechanisms underlying their malignant progression are still poorly defined. Here, we identify the NRF3 transcription factor as a tumor suppressor in the skin. NRF3 protein expression is strongly downregulated or even absent in invasively growing cancer cells of patients with basal and squamous cell carcinomas (BCC and SCC). NRF3 deficiency promoted malignant conversion of chemically induced skin tumors in immunocompetent mice, clonogenic growth and migration of human SCC cells, their invasiveness in 3D cultures, and xenograft tumor formation. Mechanistically, the tumor-suppressive effect of NRF3 involves HSPA5, a key regulator of the unfolded protein response, which we identified as a potential NRF3 interactor. HSPA5 levels increased in the absence of NRF3, thereby promoting cancer cell survival and migration. Pharmacological inhibition or knock-down of HSPA5 rescued the malignant features of NRF3-deficient SCC cells in vitro and in preclinical mouse models. Together with the strong expression of HSPA5 in NRF3-deficient cancer cells of SCC patients, these results suggest HSPA5 inhibition as a treatment strategy for these malignancies in stratified cancer patients.

The transcription factor NRF1 (NFE2L1) activates aggrephagy by inducing p62 and GABARAPL1 after proteasome inhibition to maintain proteostasis

The ubiquitin‒proteasome system (UPS) and autophagy are the two primary cellular pathways of misfolded or damaged protein degradation that maintain cellular proteostasis. When the proteasome is dysfunctional, cells compensate for impaired protein clearance by activating aggrephagy, a type of selective autophagy, to eliminate ubiquitinated protein aggregates; however, the molecular mechanisms by which impaired proteasome function activates aggrephagy remain poorly understood. Here, we demonstrate that activation of aggrephagy is transcriptionally induced by the transcription factor NRF1 (NFE2L1) in response to proteasome dysfunction. Although NRF1 has been previously shown to induce the expression of proteasome genes after proteasome inhibition (i.e., the proteasome bounce-back response), our genome-wide transcriptome analyses identified autophagy-related p62/SQSTM1 and GABARAPL1 as genes directly targeted by NRF1. Intriguingly, NRF1 was also found to be indispensable for the formation of p62-positive puncta and their colocalization with ULK1 and TBK1, which play roles in p62 activation via phosphorylation. Consistently, NRF1 knockdown substantially reduced the phosphorylation rate of Ser403 in p62. Finally, NRF1 selectively upregulated the expression of GABARAPL1, an ATG8 family gene, to induce the clearance of ubiquitinated proteins. Our findings highlight the discovery of an activation mechanism underlying NRF1-mediated aggrephagy through gene regulation when proteasome activity is impaired.

The NRF2-p97-NRF2 negative feedback loop

p97 is a ubiquitin-targeted ATP-dependent segregase that regulates proteostasis, in addition to a variety of other cellular functions. Previously, we demonstrated that p97 negatively regulates NRF2 by extracting ubiquitylated NRF2 from the KEAP1-CUL3-RBX1 E3 ubiquitin ligase complex, facilitating proteasomal destruction. In the current study, we identified p97 as an NRF2-target gene that contains a functional ARE, indicating the presence of an NRF2-p97-NRF2 negative feedback loop that maintains redox homeostasis. Using CRISPR/Cas9 genome editing, we generated endogenous p97 ARE-mutated BEAS-2B cell lines. These p97 ARE-mutated cell lines exhibit altered expression of p97 and NRF2, as well as a compromised response to NRF2 inducers. Importantly, we also found a positive correlation between NRF2 activation and p97 expression in human cancer patients. Finally, using chronic arsenic-transformed cell lines, we demonstrated a synergistic effect of NRF2 and p97 inhibition in killing cancer cells with high NRF2 and p97 expression. Our study suggests dual upregulation of NRF2 and p97 occurs in certain types of cancers, suggesting that inhibition of both NRF2 and p97 could be a promising treatment strategy for stratified cancer patients.

Role of NFE2L1 in the Regulation of Proteostasis: Implications for Aging and Neurodegenerative Diseases

A hallmark of aging and neurodegenerative diseases is a disruption of proteome homeostasis ("proteostasis") that is caused to a considerable extent by a decrease in the efficiency of protein degradation systems. The ubiquitin proteasome system (UPS) is the major cellular pathway involved in the clearance of small, short-lived proteins, including amyloidogenic proteins that form aggregates in neurodegenerative diseases. Age-dependent decreases in proteasome subunit expression coupled with the inhibition of proteasome function by aggregated UPS substrates result in a feedforward loop that accelerates disease progression. Nuclear factor erythroid 2- like 1 (NFE2L1) is a transcription factor primarily responsible for the proteasome inhibitor-induced "bounce-back effect" regulating the expression of proteasome subunits. NFE2L1 is localized to the endoplasmic reticulum (ER), where it is rapidly degraded under basal conditions by the ER-associated degradation (ERAD) pathway. Under conditions leading to proteasome impairment, NFE2L1 is cleaved and transported to the nucleus, where it binds to antioxidant response elements (AREs) in the promoter region of proteasome subunit genes, thereby stimulating their transcription. In this review, we summarize the role of UPS impairment in aging and neurodegenerative disease etiology and consider the potential benefit of enhancing NFE2L1 function as a strategy to upregulate proteasome function and alleviate pathology in neurodegenerative diseases.

Mitigation of Cardiovascular Disease and Toxicity through NRF2 Signalling

Cardiovascular toxicity and diseases are phenomena that have a vastly detrimental impact on morbidity and mortality. The pathophysiology driving the development of these conditions is multifactorial but commonly includes the perturbance of reactive oxygen species (ROS) signalling, iron homeostasis and mitochondrial bioenergetics. The transcription factor nuclear factor erythroid 2 (NFE2)-related factor 2 (NRF2), a master regulator of cytoprotective responses, drives the expression of genes that provide resistance to oxidative, electrophilic and xenobiotic stresses. Recent research has suggested that stimulation of the NRF2 signalling pathway can alleviate cardiotoxicity and hallmarks of cardiovascular disease progression. However, dysregulation of NRF2 dynamic responses can be severely impacted by ageing processes and off-target toxicity from clinical medicines including anthracycline chemotherapeutics, rendering cells of the cardiovascular system susceptible to toxicity and subsequent tissue dysfunction. This review addresses the current understanding of NRF2 mechanisms under homeostatic and cardiovascular pathophysiological conditions within the context of wider implications for this diverse transcription factor.

NRF2 and the Moirai: Life and Death Decisions on Cell Fates

Significance: The transcription factor NRF2 (NF-E2-related factor 2) plays an important role as a master regulator of the cellular defense system by activating transcriptional programs of NRF2 target genes encoding multiple enzymes related to cellular redox balance and xenobiotic detoxication. Comprehensive transcriptional analyses continue to reveal an ever-broadening range of NRF2 target genes, demonstrating the sophistication and diversification of NRF2 biological signatures beyond its canonical cytoprotective roles. Recent Advances: Accumulating evidence indicates that NRF2 has a strong association with the regulation of cell fates by influencing key processes of cellular transitions in the three major phases of the life cycle of the cell (i.e., cell birth, cell differentiation, and cell death). The molecular integration of NRF2 signaling into this regulatory program occurs through a wide range of NRF2 target genes encompassing canonical functions and those manipulating cell fate pathways. Critical Issues: A singular focus on NRF2 signaling for dissecting its actions limits in-depth understanding of its intersection with the molecular machinery of cell fate determinations. Compensatory responses of downstream pathways governed by NRF2 executed by a variety of transcription factors and multifactorial signaling crosstalk require further exploration. Future Directions: Further investigations using optimized in vivo models and active engagement of overarching approaches to probe the interplay of widespread pathways are needed to study the properties and capabilities of NRF2 signaling as a part of a large network within the cell fate regulatory domain. Antioxid. Redox Signal. 38, 684-708.

Targeting NRF2 to promote epithelial repair

The transcription factor NRF2 is well known as a master regulator of the cellular stress response. As such, activation of NRF2 has gained widespread attention for its potential to prevent tissue injury, but also as a possible therapeutic approach to promote repair processes. While NRF2 activation affects most or even all cell types, its effect on epithelial cells during repair processes has been particularly well studied. In response to tissue injury, these cells proliferate, migrate and/or spread to effectively repair the damage. In this review, we discuss how NRF2 governs repair of epithelial tissues, and we highlight the increasing number of NRF2 targets with diverse roles in regulating epithelial repair.

Role of Human Aldo-Keto Reductases and Nuclear Factor Erythroid 2-Related Factor 2 in the Metabolic Activation of 1-Nitropyrene via Nitroreduction in Human Lung Cells

1-Nitropyrene (1-NP) is a constituent of diesel exhaust and classified as a group 2A probable human carcinogen. The metabolic activation of 1-NP by nitroreduction generates electrophiles that can covalently bind DNA to form mutations to contribute to cancer causation. NADPH-dependent P450 oxidoreductase (POR), xanthine oxidase (XO), aldehyde oxidase (AOX), and NAD(P)H/quinone oxidoreductase 1 (NQO1) may catalyze 1-NP nitroreduction. We recently found that human recombinant aldo-keto reductases (AKRs) 1C1-1C3 catalyze 1-NP nitroreduction. NQO1 and AKR1C1-1C3 are genes induced by nuclear factor erythroid 2-related factor 2 (NRF2). Despite this knowledge, the relative importance of these enzymes and NRF2 to 1-NP nitroreduction is unknown. We used a combination of pharmacological and genetic approaches to assess the relative importance of these enzymes and NRF2 in the aerobic nitroreduction of 1-NP in human bronchial epithelial cells, A549 and HBEC3-KT. 1-NP nitroreduction was assessed by the measurement of 1-aminopyrene (1-AP), the six-electron reduced metabolite of 1-NP, based on its intrinsic fluorescence properties (λex and λem). We found that co-treatment of 1-NP with salicylic acid, an AKR1C1 inhibitor, or ursodeoxycholate, an AKR1C2 inhibitor, for 48 h decreased 1-AP production relative to 1-NP treatment alone (control) in both cell lines. R-Sulforaphane or 1-(2-cyano-3,12,28-trioxooleana-1,9(11)-dien-28-yl)-1H-imidazole (CDDO-Im), two NRF2 activators, each increased 1-AP production relative to control only in HBEC3-KT cells, which have inducible NRF2. Inhibitors of POR, NQO1, and XO failed to modify 1-AP production relative to control in both cell lines. Importantly, A549 wild-type cells with constitutively active NRF2 produced more 1-AP than A549 cells with heterozygous expression of NFE2L2/NRF2, which were able to produce more 1-AP than A549 cells with homozygous knockout of NFE2L2/NRF2. Together, these data show dependence of 1-NP metabolic activation on AKR1Cs and NRF2 in human lung cells. This is the second example whereby NFE2L2/NRF2 is implicated in the carcinogenicity of diesel exhaust constituents.

NRF3 activates mTORC1 arginine-dependently for cancer cell viability

Cancer cells coordinate the mTORC1 signals and the related metabolic pathways to robustly and rapidly grow in response to nutrient conditions. Although a CNC-family transcription factor NRF3 promotes cancer development, the biological relevance between NRF3 function and mTORC1 signals in cancer cells remains unknown. Hence, we showed that NRF3 contributes to cancer cell viability through mTORC1 activation in response to amino acids, particularly arginine. NRF3 induced SLC38A9 and RagC expression for the arginine-dependent mTORC1 recruitment onto lysosomes, and it also enhanced RAB5-mediated bulk macropinocytosis and SLC7A1-mediated selective transport for arginine loading into lysosomes. Besides, the inhibition of the NRF3-mTORC1 axis impaired mitochondrial function, leading to cancer cell apoptosis. Consistently, the aberrant upregulation of the axis caused tumor growth and poor prognosis. In conclusion, this study sheds light on the unique function of NRF3 in arginine-dependent mTORC1 activation and the pathophysiological aspects of the NRF3-mTORC1 axis in cancer development.

Regulation and Functions of the ER-Associated Nrf1 Transcription Factor

Nrf1 is a member of the nuclear erythroid 2-like family of transcription factors that regulate stress-responsive gene expression in animals. Newly synthesized Nrf1 is targeted to the endoplasmic reticulum (ER) where it is N-glycosylated. N-glycosylated Nrf1 is trafficked to the cytosol by the ER-associated degradation (ERAD) machinery and is subject to rapid proteasomal degradation. When proteasome function is impaired, Nrf1 escapes degradation and undergoes proteolytic cleavage and deglycosylation. Deglycosylation results in deamidation of N-glycosylated asparagine residues to edit the protein sequence encoded by the genome. This truncated and "sequence-edited" form of Nrf1 enters the nucleus where it induces up-regulation of proteasome subunit genes. Thus, Nrf1 drives compensatory proteasome biogenesis in cells exposed to proteasome inhibitor drugs and other proteotoxic insults. In addition to its role in proteasome homeostasis, Nrf1 is implicated in responses to oxidative stress, and maintaining lipid and cholesterol homeostasis. Here, we describe the conserved and complex mechanism by which Nrf1 is regulated and highlight emerging evidence linking this unusual transcription factor to development, aging, and disease.

Redox-metabolic reprogramming of skin in mice lacking functional Nrf2 under basal conditions and cold acclimation

Adaptive responses to environmental and physiological challenges, including exposure to low environmental temperature, require extensive structural, redox, and metabolic reprogramming. Detailed molecular mechanisms of such processes in the skin are lacking, especially the role of nuclear factor erythroid 2-related factor 2 (Nrf2) and other closely related redox-sensitive transcription factors Nrf1, Nrf3, and nuclear respiratory factor (NRF1). To investigate the role of Nrf2, we examined redox and metabolic responses in the skin of wild-type (WT) mice and mice lacking functional Nrf2 (Nrf2 KO) at room (RT, 24 ± 1°C) and cold (4 ± 1°C) temperature. Our results demonstrate distinct expression profiles of major enzymes involved in antioxidant defense and key metabolic and mitochondrial pathways in the skin, depending on the functional Nrf2 and/or cold stimulus. Nrf2 KO mice at RT displayed profound alterations in redox, mitochondrial and metabolic responses, generally akin to cold-induced skin responses in WT mice. Immunohistochemical analyses of skin cell compartments (keratinocytes, fibroblasts, hair follicle, and sebaceous gland) and spatial locations (nucleus and cytoplasm) revealed synergistic interactions between members of the Nrf transcription factor family as part of redox-metabolic reprogramming in WT mice upon cold acclimation. In contrast, Nrf2 KO mice at RT showed loss of NRF1 expression and a compensatory activation of Nrf1/Nrf3, which was abolished upon cold, concomitant with blunted redox-metabolic responses. These data show for the first time a novel role for Nrf2 in skin physiology in response to low environmental temperature, with important implications in human connective tissue diseases with altered thermogenic responses.

Nitroreduction: A Critical Metabolic Pathway for Drugs, Environmental Pollutants, and Explosives

Nitro group containing xenobiotics include drugs, cancer chemotherapeutic agents, carcinogens (e.g., nitroarenes and aristolochic acid) and explosives. The nitro group undergoes a six-electron reduction to form sequentially the nitroso-, N-hydroxylamino- and amino-functional groups. These reactions are catalyzed by nitroreductases which, rather than being enzymes with this sole function, are enzymes hijacked for their propensity to donate electrons to the nitro group either one at a time via a radical mechanism or two at time via the equivalent of a hydride transfer. These enzymes include: NADPH-dependent flavoenzymes (NADPH: P450 oxidoreductase, NAD(P)H-quinone oxidoreductase), P450 enzymes, oxidases (aldehyde oxidase, xanthine oxidase) and aldo-keto reductases. The hydroxylamino group once formed can undergo conjugation reactions with acetate or sulfate catalyzed by N-acetyltransferases or sulfotransferases, respectively, leading to the formation of intermediates containing a good leaving group which in turn can generate a nitrenium or carbenium ion for covalent DNA adduct formation. The intermediates in the reduction sequence are also prone to oxidation and produce reactive oxygen species. As a consequence, many nitro-containing xenobiotics can be genotoxic either by forming stable covalent adducts or by oxidatively damaging DNA. This review will focus on the general chemistry of nitroreduction, the enzymes responsible, the reduction of xenobiotic substrates, the regulation of nitroreductases, the ability of nitrocompounds to form DNA adducts and act as mutagens as well as some future directions.

Signal amplification in the KEAP1-NRF2-ARE antioxidant response pathway

The KEAP1-NRF2-ARE signaling pathway plays a central role in mediating the adaptive cellular stress response to oxidative and electrophilic chemicals. This canonical pathway has been extensively studied and reviewed in the past two decades, but rarely was it looked at from a quantitative signaling perspective. Signal amplification, i.e., ultrasensitivity, is crucially important for robust induction of antioxidant genes to appropriate levels that can adequately counteract the stresses. In this review article, we examined a number of well-known molecular events in the KEAP1-NRF2-ARE pathway from a quantitative perspective with a focus on how signal amplification can be achieved. We illustrated, by using a series of mathematical models, that redox-regulated protein sequestration, stabilization, translation, nuclear trafficking, DNA promoter binding, and transcriptional induction - which are embedded in the molecular network comprising KEAP1, NRF2, sMaf, p62, and BACH1 - may generate highly ultrasensitive NRF2 activation and antioxidant gene induction. The emergence and degree of ultrasensitivity depend on the strengths of protein-protein and protein-DNA interaction and protein abundances. A unique, quantitative understanding of signal amplification in the KEAP1-NRF2-ARE pathway will help to identify sensitive targets for the prevention and therapeutics of oxidative stress-related diseases and develop quantitative adverse outcome pathway models to facilitate the health risk assessment of oxidative chemicals.

Dysfunction of the energy sensor NFE2L1 triggers uncontrollable AMPK signaling and glucose metabolism reprogramming

The antioxidant transcription factor NFE2L1 (also called Nrf1) acts as a core regulator of redox signaling and metabolism homeostasis, and thus, its dysfunction results in multiple systemic metabolic diseases. However, the molecular mechanism(s) by which NFE2L1 regulates glycose and lipid metabolism remains elusive. Here, we found that loss of NFE2L1 in human HepG2 cells led to a lethal phenotype upon glucose deprivation and NFE2L1 deficiency could affect the uptake of glucose. Further experiments revealed that glycosylation of NFE2L1 enabled it to sense the energy state. These results indicated that NFE2L1 can serve as a dual sensor and regulator of glucose homeostasis. The transcriptome, metabolome, and seahorse data further revealed that disruption of NFE2L1 could reprogram glucose metabolism to aggravate the Warburg effect in NFE2L1-silenced hepatoma cells, concomitant with mitochondrial damage. Co-expression and Co-immunoprecipitation experiments demonstrated that NFE2L1 could directly interact and inhibit AMPK. Collectively, NFE2L1 functioned as an energy sensor and negatively regulated AMPK signaling through directly interacting with AMPK. The novel NFE2L1/AMPK signaling pathway delineate the mechanism underlying of NFE2L1-related metabolic diseases and highlight the crosstalk between redox homeostasis and metabolism homeostasis.

DnaJC7 in Amyotrophic Lateral Sclerosis

Protein misfolding is a common basis of many neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). Misfolded proteins, such as TDP-43, FUS, Matrin3, and SOD1, mislocalize and form the hallmark cytoplasmic and nuclear inclusions in neurons of ALS patients. Cellular protein quality control prevents protein misfolding under normal conditions and, particularly, when cells experience protein folding stress due to the fact of increased levels of reactive oxygen species, genetic mutations, or aging. Molecular chaperones can prevent protein misfolding, refold misfolded proteins, or triage misfolded proteins for degradation by the ubiquitin–proteasome system or autophagy. DnaJC7 is an evolutionarily conserved molecular chaperone that contains both a J-domain for the interaction with Hsp70s and tetratricopeptide domains for interaction with Hsp90, thus joining these two major chaperones’ machines. Genetic analyses reveal that pathogenic variants in the gene encoding DnaJC7 cause familial and sporadic ALS. Yet, the underlying ALS-associated molecular pathophysiology and many basic features of DnaJC7 function remain largely unexplored. Here, we review aspects of DnaJC7 expression, interaction, and function to propose a loss-of-function mechanism by which pathogenic variants in DNAJC7 contribute to defects in DnaJC7-mediated chaperoning that might ultimately contribute to neurodegeneration in ALS.

Redox signaling at the crossroads of human health and disease

Redox biology is at the core of life sciences, accompanied by the close correlation of redox processes with biological activities. Redox homeostasis is a prerequisite for human health, in which the physiological levels of nonradical reactive oxygen species (ROS) function as the primary second messengers to modulate physiological redox signaling by orchestrating multiple redox sensors. However, excessive ROS accumulation, termed oxidative stress (OS), leads to biomolecule damage and subsequent occurrence of various diseases such as type 2 diabetes, atherosclerosis, and cancer. Herein, starting with the evolution of redox biology, we reveal the roles of ROS as multifaceted physiological modulators to mediate redox signaling and sustain redox homeostasis. In addition, we also emphasize the detailed OS mechanisms involved in the initiation and development of several important diseases. ROS as a double‐edged sword in disease progression suggest two different therapeutic strategies to treat redox‐relevant diseases, in which targeting ROS sources and redox‐related effectors to manipulate redox homeostasis will largely promote precision medicine. Therefore, a comprehensive understanding of the redox signaling networks under physiological and pathological conditions will facilitate the development of redox medicine and benefit patients with redox‐relevant diseases.

Pseudoautosomal Region 1 Overdosage Affects the Global Transcriptome in iPSCs From Patients With Klinefelter Syndrome and High-Grade X Chromosome Aneuploidies

Klinefelter syndrome (KS) is the most prevalent aneuploidy in males and is characterized by a 47,XXY karyotype. Less frequently, higher grade sex chromosome aneuploidies (HGAs) can also occur. Here, using a paradigmatic cohort of KS and HGA induced pluripotent stem cells (iPSCs) carrying 49,XXXXY, 48,XXXY, and 47,XXY karyotypes, we identified the genes within the pseudoautosomal region 1 (PAR1) as the most susceptible to dosage-dependent transcriptional dysregulation and therefore potentially responsible for the progressively worsening phenotype in higher grade X aneuploidies. By contrast, the biallelically expressed non-PAR escape genes displayed high interclonal and interpatient variability in iPSCs and differentiated derivatives, suggesting that these genes could be associated with variable KS traits. By interrogating KS and HGA iPSCs at the single-cell resolution we showed that PAR1 and non-PAR escape genes are not only resilient to the X-inactive specific transcript (XIST)-mediated inactivation but also that their transcriptional regulation is disjointed from the absolute XIST expression level. Finally, we explored the transcriptional effects of X chromosome overdosage on autosomes and identified the nuclear respiratory factor 1 (NRF1) as a key regulator of the zinc finger protein X-linked (ZFX). Our study provides the first evidence of an X-dosage-sensitive autosomal transcription factor regulating an X-linked gene in low- and high-grade X aneuploidies.

Silencing of Nrf genes in the human placenta as measured by SDS-PAGE and Western Blotting techniques

Nuclear factor erythroid 2-related factor-2 (Nrf2), and the less well characterised proteins Nrf1 and Nrf3, are member of the cap 'n' collar family of transcription factors. Nrf proteins regulate the expression of endogenous antioxidant enzymes and have recently become the targets for various therapeutic treatments. Recently, Nrf proteins have been of particular interest as a target in placental-derived oxidative stress induced pregnancy disorders. Here, we report the presence of Nrf1, Nrf2 and Nrf3 proteins in both human primary trophoblast and human trophoblast choriocarcinoma cell line (BeWo). We also detail the steps taken to successfully silence all Nrf proteins in both human primary trophoblast cells and BeWo via detection of mRNA and protein using quantitative PCR, and SDS-PAGE and Western Blotting respectively.

The NRF2-Dependent Transcriptional Regulation of Antioxidant Defense Pathways: Relevance for Cell Type-Specific Vulnerability to Neurodegeneration and Therapeutic Intervention

Oxidative stress has been implicated in the etiology and pathobiology of various neurodegenerative diseases. At baseline, the cells of the nervous system have the capability to regulate the genes for antioxidant defenses by engaging nuclear factor erythroid 2 (NFE2/NRF)-dependent transcriptional mechanisms, and a number of strategies have been proposed to activate these pathways to promote neuroprotection. Here, we briefly review the biology of the transcription factors of the NFE2/NRF family in the brain and provide evidence for the differential cellular localization of NFE2/NRF family members in the cells of the nervous system. We then discuss these findings in the context of the oxidative stress observed in two neurodegenerative diseases, Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), and present current strategies for activating NFE2/NRF-dependent transcription. Based on the expression of the NFE2/NRF family members in restricted populations of neurons and glia, we propose that, when designing strategies to engage these pathways for neuroprotection, the relative contributions of neuronal and non-neuronal cell types to the overall oxidative state of tissue should be considered, as well as the cell types which have the greatest intrinsic capacity for producing antioxidant enzymes.

Pathophysiological Potentials of NRF3-Regulated Transcriptional Axes in Protein and Lipid Homeostasis

NRF3 (NFE2L3) belongs to the CNC-basic leucine zipper transcription factor family. An NRF3 homolog, NRF1 (NFE2L1), induces the expression of proteasome-related genes in response to proteasome inhibition. Another homolog, NRF2 (NFE2L2), induces the expression of genes related to antioxidant responses and encodes metabolic enzymes in response to oxidative stress. Dysfunction of each homolog causes several diseases, such as neurodegenerative diseases and cancer development. However, NRF3 target genes and their biological roles remain unknown. This review summarizes our recent reports that showed NRF3-regulated transcriptional axes for protein and lipid homeostasis. NRF3 induces the gene expression of POMP for 20S proteasome assembly and CPEB3 for NRF1 translational repression, inhibiting tumor suppression responses, including cell-cycle arrest and apoptosis, with resistance to a proteasome inhibitor anticancer agent bortezomib. NRF3 also promotes mevalonate biosynthesis by inducing SREBP2 and HMGCR gene expression, and reduces the intracellular levels of neural fatty acids by inducing GGPS1 gene expression. In parallel, NRF3 induces macropinocytosis for cholesterol uptake by inducing RAB5 gene expression. Finally, this review mentions not only the pathophysiological aspects of these NRF3-regulated axes for cancer cell growth and anti-obesity potential but also their possible role in obesity-induced cancer development.

Selenomethionine Improves Mitochondrial Function by Upregulating Mitochondrial Selenoprotein in a Model of Alzheimer's Disease

Alzheimer’s disease (AD), the most common neurodegenerative disease in elderly humans, is pathologically characterized by amyloid plaques and neurofibrillary tangles. Mitochondrial dysfunction that occurs in the early stages of AD, which includes dysfunction in mitochondrial generation and energy metabolism, is considered to be closely associated with AD pathology. Selenomethionine (Se-Met) has been reported to improve cognitive impairment and reduce amyloid plaques and neurofibrillary tangles in 3xTg-AD mice. Whether Se-Met can regulate mitochondrial dysfunction in an AD model during this process remains unknown.In this study, the N2a-APP695-Swedish (N2aSW) cell and 8-month-old 3xTg-AD mice were treated with Se-Met in vitro and in vivo. Our study showed that the numbers of mitochondria were increased after treatment with Se-Met. Se-Met treatment also significantly increased the levels of NRF1 and Mfn2, and decreased those of OPA1 and Drp1. In addition, the mitochondrial membrane potential was significantly increased, while the ROS levels and apoptosis rate were significantly decreased, in cells after treatment with Se-Met. The levels of ATP, complex IV, and Cyt c and the activity of complex V were all significantly increased. Furthermore, the expression level of SELENO O was increased after Se-Met treatment. Thus, Se-Met can maintain mitochondrial dynamic balance, promote mitochondrial fusion or division, restore mitochondrial membrane potential, promote mitochondrial energy metabolism, inhibit intracellular ROS generation, and reduce apoptosis. These effects are most likely mediated via upregulation of SELENO O. In summary, Se-Met improves mitochondrial function by upregulating mitochondrial selenoprotein in these AD models.

NGLY1: Insights from C. elegans

Peptide:N-glycanase is an evolutionarily conserved deglycosylating enzyme that catalyzes the removal of N-linked glycans from cytosolic glycoproteins. Recessive mutations that inactivate this enzyme cause NGLY1 deficiency, a multisystemic disorder with symptoms including developmental delay and defects in cognition and motor control. Developing treatments for NGLY1 deficiency will require an understanding of how failure to deglycosylate NGLY1 substrates perturbs cellular and organismal function. In this review, I highlight insights into peptide:N-glycanase biology gained by studies in the highly tractable genetic model animal C. elegans. I focus on the recent discovery of SKN-1A/Nrf1, an N-glycosylated transcription factor, as a peptide:N-glycanase substrate critical for regulation of the proteasome. I describe the elaborate post-translational mechanism that culminates in activation of SKN-1A/Nrf1 via NGLY1-dependent 'sequence editing' and discuss the implications of these findings for our understanding of NGLY1 deficiency.

Differential Yet Integral Contributions of Nrf1 and Nrf2 in the Human HepG2 Cells on Antioxidant Cytoprotective Response against Tert-Butylhydroquinone as a Pro-Oxidative Stressor

In the past 25 years, Nrf2 (nuclear factor erythroid 2-related factor 2, also called NFE2L2) had been preferentially parsed as a master hub of regulating antioxidant, detoxification, and cytoprotective genes; albeit as a matter of fact that Nrf1 (nuclear factor erythroid 2-related factor 1, also called NFE2L1)-rather than Nrf2-is indispensable for cell homeostasis and organ integrity during normal growth and development. Herein, distinct genotypic cell lines (i.e., Nrf1α^-/-, Nrf2^-/-ΔTA, and caNrf2^ΔN) are employed to determine differential yet integral roles of Nrf1 and Nrf2 in mediating antioxidant responsive genes to tert-butylhydroquinone (tBHQ) serving as a pro-oxidative stressor. In Nrf1α^-/- cells, Nrf2 was highly accumulated but also could not fully compensate specific loss of Nrf1α's function in its basal cytoprotective response against endogenous oxidative stress, though it exerted partially inducible antioxidant response, as the hormetic effect of tBHQ, against apoptotic damages. By contrast, Nrf2^-/-ΔTA cells gave rise to a substantial reduction of Nrf1 in both basal and tBHQ-stimulated expression levels and hence resulted in obvious oxidative stress, but it can still be allowed to mediate a potent antioxidant response, as accompanied by a significantly decreased ratio of GSSG (oxidized glutathione) to GSH (reduced glutathione). Conversely, a remarkable increase of Nrf1 expression resulted from the constitutive active caNrf2^ΔN cells, which were not manifested with oxidative stress, whether or not it was intervened with tBHQ. Such inter-regulatory effects of Nrf1 and Nrf2 on the antioxidant and detoxification genes (encoding HO-1, NQO1, GCLC, GCLM, GSR, GPX1, TALDO, MT1E, and MT2), as well on the ROS (reactive oxygen species)-scavenging activities of SOD (superoxide dismutase) and CAT (catalase), were further investigated. The collective results unraveled that Nrf1 and Nrf2 make distinctive yet cooperative contributions to finely tuning basal constitutive and/or tBHQ-inducible expression levels of antioxidant cytoprotective genes in the inter-regulatory networks. Overall, Nrf1 acts as a brake control for Nrf2's functionality to be confined within a certain extent, whilst its transcription is regulated by Nrf2.

Brain-Protective Mechanisms of Transcription Factor NRF2: Toward a Common Strategy for Neurodegenerative Diseases

Neurodegenerative diseases are characterized by the loss of homeostatic functions that control redox and energy metabolism, neuroinflammation, and proteostasis. The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) is a master controller of these functions, and its overall activity is compromised during aging and in these diseases. However, NRF2 can be activated pharmacologically and is now being considered a common therapeutic target. Many gaps still exist in our knowledge of the specific role that NRF2 plays in specialized brain cell functions or how these cells respond to the hallmarks of these diseases. This review discusses the relevance of NRF2 to several hallmark features of neurodegenerative diseases and the current status of pharmacological activators that might pass through the blood-brain barrier and provide a disease-modifying effect. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Pyrroloquinoline-Quinone Is More Than an Antioxidant: A Vitamin-like Accessory Factor Important in Health and Disease Prevention

Pyrroloquinoline quinone (PQQ) is associated with biological processes such as mitochondriogenesis, reproduction, growth, and aging. In addition, PQQ attenuates clinically relevant dysfunctions (e.g., those associated with ischemia, inflammation and lipotoxicity). PQQ is novel among biofactors that are not currently accepted as vitamins or conditional vitamins. For example, the absence of PQQ in diets produces a response like a vitamin-related deficiency with recovery upon PQQ repletion in a dose-dependent manner. Moreover, potential health benefits, such as improved metabolic flexibility and immuno-and neuroprotection, are associated with PQQ supplementation. Here, we address PQQ's role as an enzymatic cofactor or accessory factor and highlight mechanisms underlying PQQ's actions. We review both large scale and targeted datasets demonstrating that a neonatal or perinatal PQQ deficiency reduces mitochondria content and mitochondrial-related gene expression. Data are reviewed that suggest PQQ's modulation of lactate acid and perhaps other dehydrogenases enhance NAD+-dependent sirtuin activity, along with the sirtuin targets, such as PGC-1α, NRF-1, NRF-2 and TFAM; thus, mediating mitochondrial functions. Taken together, current observations suggest vitamin-like PQQ has strong potential as a potent therapeutic nutraceutical.

The Good and Bad of Nrf2: An Update in Cancer and New Perspectives in COVID-19

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a well-known transcription factor best recognised as one of the main regulators of the oxidative stress response. Beyond playing a crucial role in cell defence by transactivating cytoprotective genes encoding antioxidant and detoxifying enzymes, Nrf2 is also implicated in a wide network regulating anti-inflammatory response and metabolic reprogramming. Such a broad spectrum of actions renders the factor a key regulator of cell fate and a strategic player in the control of cell transformation and response to viral infections. The Nrf2 protective roles in normal cells account for its anti-tumour and anti-viral functions. However, Nrf2 overstimulation often occurs in tumour cells and a complex correlation of Nrf2 with cancer initiation and progression has been widely described. Therefore, if on one hand, Nrf2 has a dual role in cancer, on the other hand, the factor seems to display a univocal function in preventing inflammation and cytokine storm that occur under viral infections, specifically in coronavirus disease 19 (COVID-19). In such a variegate context, the present review aims to dissect the roles of Nrf2 in both cancer and COVID-19, two widespread diseases that represent a cause of major concern today. In particular, the review describes the molecular aspects of Nrf2 signalling in both pathological situations and the most recent findings about the advantages of Nrf2 inhibition or activation as possible strategies for cancer and COVID-19 treatment respectively.

The roles of inducible chromatin and transcriptional memory in cellular defense system responses to redox-active pollutants

People are exposed to wide range of redox-active environmental pollutants. Air pollution, heavy metals, pesticides, and endocrine disrupting chemicals can disrupt cellular redox status. Redox-active pollutants in our environment all trigger their own sets of specific cellular responses, but they also activate a common set of general stress responses that buffer the cell against homeostatic insults. These cellular defense system (CDS) pathways include the heat shock response, the oxidative stress response, the hypoxia response, the unfolded protein response, the DNA damage response, and the general stress response mediated by the stress-activated p38 mitogen-activated protein kinase. Over the past two decades, the field of environmental epigenetics has investigated epigenetic responses to environmental pollutants, including redox-active pollutants. Studies of these responses highlight the role of chromatin modifications in controlling the transcriptional response to pollutants and the role of transcriptional memory, often referred to as "epigenetic reprogramming", in predisposing previously exposed individuals to more potent transcriptional responses on secondary challenge. My central thesis in this review is that high dose or chronic exposure to redox-active pollutants leads to transcriptional memories at CDS target genes that influence the cell's ability to mount protective responses. To support this thesis, I will: (1) summarize the known chromatin features required for inducible gene activation; (2) review the known forms of transcriptional memory; (3) discuss the roles of inducible chromatin and transcriptional memory in CDS responses that are activated by redox-active environmental pollutants; and (4) propose a conceptual framework for CDS pathway responsiveness as a readout of total cellular exposure to redox-active pollutants.

TCF11 Has a Potent Tumor-Repressing Effect Than Its Prototypic Nrf1α by Definition of Both Similar Yet Different Regulatory Profiles, With a Striking Disparity From Nrf2

Nrf1 and Nrf2, as two principal CNC-bZIP transcription factors, regulate similar but different targets involved in a variety of biological functions for maintaining cell homeostasis and organ integrity. Of note, the unique topobiological behavior of Nrf1 makes its functions more complicated than Nrf2, because it is allowed for alternatively transcribing and selectively splicing to yield multiple isoforms (e.g., TCF11, Nrf1α). In order to gain a better understanding of their similarities and differences in distinct regulatory profiles, all four distinct cell models for stably expressing TCF11, TCF11^ΔN , Nrf1α or Nrf2 have been herein established by an Flp-In™ T-REx™-293 system and then identified by transcriptomic sequencing. Further analysis revealed that Nrf1α and TCF11 have similar yet different regulatory profiles, although both contribute basically to positive regulation of their co-targets, which are disparate from those regulated by Nrf2. Such disparity in those gene regulations by Nrf1 and Nrf2 was further corroborated by scrutinizing comprehensive functional annotation of their specific and/or common target genes. Conversely, the mutant TCF11^ΔN, resulting from a deletion of the N-terminal amino acids 2-156 from TCF11, resembles Nrf2 with the largely consistent structure and function. Interestingly, our further experimental evidence demonstrates that TCF11 acts as a potent tumor-repressor relative to Nrf1α, albeit both isoforms possess a congruous capability to prevent malignant growth of tumor and upregulate those genes critical for improving the survival of patients with hepatocellular carcinoma.

SIRT1-Related Signaling Pathways and Their Association With Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic and debilitating disease that can exert serious and overwhelming effects on the physical and mental health of premature infants, predominantly due to intractable short- and long-term complications. Oxidative stress is one of the most predominant causes of BPD. Hyperoxia activates a cascade of hazardous events, including mitochondrial dysfunction, uncontrolled inflammation, reduced autophagy, increased apoptosis, and the induction of fibrosis. These events may involve, to varying degrees, alterations in SIRT1 and its associated targets. In the present review, we describe SIRT1-related signaling pathways and their association with BPD. Our intention is to provide new insights into the molecular mechanisms that regulate BPD and identify potential therapeutic targets for this debilitating condition.

The involvement of autophagy in the maintenance of endothelial homeostasis: The role of mitochondria

Endothelial mitochondria play important signaling roles critical for the regulation of various cellular processes, including calcium signaling, ROS generation, NO synthesis or inflammatory response. Mitochondrial stress or disturbances in mitochondrial function may participate in the development and/or progression of endothelial dysfunction and could precede vascular diseases. Vascular functions are also strictly regulated by properly functioning degradation machinery, including autophagy and mitophagy, and tightly coordinated by mitochondrial and endoplasmic reticulum responses to stress. Within this review, current knowledge related to the development of cardiovascular disorders and the importance of mitochondria, endoplasmic reticulum and degradation mechanisms in vascular endothelial functions are summarized.

Defining the Functional Targets of Cap'n'collar Transcription Factors NRF1, NRF2, and NRF3

The NRF transcription factors NRF1, NRF2, and NRF3, are a subset of Cap'n'collar transcriptional regulators which modulate the expression of genes harboring antioxidant-response element (ARE) sequences within their genomic loci. Despite the emerging physiological importance of NRF family members, the repertoire of their genetic targets remains incompletely defined. Here we use RNA-sequencing-based transcriptional profiling and quantitative proteomics to delineate the overlapping and differential genetic programs effected by the three NRF transcription factors. We then create consensus target gene sets regulated by NRF1, NRF2, and NRF3 and define the integrity of these gene sets for probing NRF activity in mammalian cell culture and human tissues. Together, our data provide a quantitative assessment of how NRF family members sculpt proteomes and transcriptomes, providing a framework to understand the critical physiological importance of NRF transcription factors and to establish pharmacologic approaches for therapeutically activating these transcriptional programs in disease.

Changes in the Nrf2/Keap1 Ratio and PON1 Concentration in Plasma of Patients Undergoing the Left Main Coronary Artery Stenting

Nuclear factor erythroid 2-related factor2 (Nrf2), together with its inhibitor Kelch-like ECH-associated protein 1 (Keap1), is a crucial regulator of cellular redox response. Nrf2 binds to the antioxidant response element (ARE) present in the DNA sequence of a broad group of antioxidant compounds, including paraoxonase (PON1), inducing their transcription. This study was to answer the question of the effect of temporary ischemia/oxidative stress resulting from the left main stenting via percutaneous coronary intervention (LMPCI) performed in the patients included in this study on the cellular redox balance, which is guarded by the Nrf2/Keap1 interaction. We expected a reflection of the redox imbalance due to reactive oxygen species (ROS) in the change in PON1 concentration observed in the following stages of the study, as well as in total antioxidant capacity (TAC) levels. Our results showed the mobilization of cellular Nrf2/Keap1 team right after the procedure (pre-LMPCI median: 2.532, range: 0.07-11.88; post-LMPCI median: 3.735, range: 0.1545-16.18; 24 h-LMPCI median: 5.596, range: 0.02-49.18), which suggest being the result of oxidative stress that accompanies percutaneous coronary intervention (PCI). The course of Keap1 and Nrf2 concentrations at all stages of the experiment appeared to show that Keap1 shadowed the Nrf2 to switch off its activity after Nrf2 induced the mobilization of the antioxidant response. We observed an increase in PON1 concentration (pre-LMPCI median: 179.3, range: 49.76-6120; post-LMPCI median: 215.7, range: 3.80-2771) and a decrease in the TAC level immediately after PCI (pre-LMPC: $1.008\pm 0.27\text{I}$ , post-LMPCI: $0.8030\pm 0.27$ ). This study design allowed for the first time to analyze the chronology of mechanisms and the relationship between selected parameters reflecting the redox state in patients’ plasma. We may conclude that ischemia induced by the PCI was the source of imbalance in the Nrf2/Keap1 ratio via oxidative stress, and this leads to an increase in PON1 concentration first and, in the next step, the TAC mobilization.

Roles of NRF3 in the Hallmarks of Cancer: Proteasomal Inactivation of Tumor Suppressors

Simple Summary

This review summarizes recent advances in our understanding of the physiological roles of the NFE2-related factor 2 (NRF2)-related transcription factor NRF3 in cancer. NRF3 confers cells with six so-called “hallmarks of cancer” through upregulating gene expression of specific target genes, leading to tumorigenesis and cancer malignancy. These driver gene-like functions of NRF3 in cancer are distinct from those of NRF2.

Abstract

The physiological roles of the NRF2-related transcription factor NRF3 (NFE2L3) have remained unknown for decades. The remarkable development of human cancer genome databases has led to strong suggestions that NRF3 has functional significance in cancer; specifically, high NRF3 mRNA levels are induced in many cancer types, such as colorectal cancer and pancreatic adenocarcinoma, and are associated with poor prognosis. On the basis of this information, the involvement of NRF3 in tumorigenesis and cancer malignancy has been recently proposed. NRF3 confers cancer cells with selective growth advantages by enhancing 20S proteasome assembly through induction of the chaperone gene proteasome maturation protein (POMP) and consequently promoting degradation of the tumor suppressors p53 and retinoblastoma (Rb) in a ubiquitin-independent manner. This new finding offers insight into the proteasomal but not the genetic inactivation mechanism of tumor suppressors. Moreover, NRF3 promotes cancer malignancy-related processes, including metastasis and angiogenesis. Finally, the molecular mechanisms underlying NRF3 activation have been elucidated, and this knowledge is expected to provide many insights that are useful for the development of anticancer drugs that attenuate NRF3 transcriptional activity. Collectively, the evidence indicates that NRF3 confers cells with six so-called “hallmarks of cancer”, implying that it exhibits cancer driver gene-like function. This review describes recent research advances regarding the newly discovered addiction of cancer cells to NRF3 compared to NRF2.

Natural Nrf2 Modulators for Skin Protection

Since the discovery of antioxidant responsive elements (ARE), which are commonly found in the promoter of the Phase II metabolism/antioxidant enzymes, and nuclear factor erythroid 2-related factor 2 (Nrf2), the transcription factor that binds to ARE, the study conducted in this field has expanded remarkably over the decades, and the Nrf2-mediated pathway is now recognized to occupy a central position in cell defense mechanisms. Induction of the Phase II metabolism/antioxidant enzymes through direct activation of Nrf2 can be a promising strategy for preventing degenerative diseases in general, but a dark side of this strategy should be considered, as Nrf2 activation can enhance the survival of cancer cells. In this review, we discuss the historical discovery of Nrf2 and the regulatory mechanism of the Nrf2-mediated pathway, focusing on the interacting proteins and post-translational modifications. In addition, we discuss the latest studies that examined various natural Nrf2 modulators for the protective roles in the skin, in consideration of their dermatological and cosmetic applications. Studies are reviewed in the order of time of research as much as possible, to help understand how and why such studies were conducted under the circumstances of that time. We hope that this review can serve as a steppingstone in conducting more advanced research by providing a scientific basis for researchers newly entering this field.

Molecular Mechanisms Underlying Hepatocellular Carcinoma Induction by Aberrant NRF2 Activation-Mediated Transcription Networks: Interaction of NRF2-KEAP1 Controls the Fate of Hepatocarcinogenesis

NF-E2-related factor 2 (NRF2) is a basic leucine zipper transcription factor, a master regulator of redox homeostasis regulating a variety of genes for antioxidant and detoxification enzymes. NRF2 was, therefore, initially thought to protect the liver from oxidative stress. Recent studies, however, have revealed that mutations in NRF2 cause aberrant accumulation of NRF2 in the nucleus and exert the upregulation of NRF2 target genes. Moreover, among all molecular changes in hepatocellular carcinoma (HCC), NRF2 activation has been revealed as a more prominent pathway contributing to the progression of precancerous lesions to malignancy. Nevertheless, how its activation leads to poor prognosis in HCC patients remains unclear. In this review, we provide an overview of how aberrant activation of NRF2 triggers HCC development. We also summarize the emerging roles of other NRF family members in liver cancer development.

ER-Resident Transcription Factor Nrf1 Regulates Proteasome Expression and Beyond

Protein folding is a substantively error prone process, especially when it occurs in the endoplasmic reticulum (ER). The highly exquisite machinery in the ER controls secretory protein folding, recognizes aberrant folding states, and retrotranslocates permanently misfolded proteins from the ER back to the cytosol; these misfolded proteins are then degraded by the ubiquitin–proteasome system termed as the ER-associated degradation (ERAD). The 26S proteasome is a multisubunit protease complex that recognizes and degrades ubiquitinated proteins in an ATP-dependent manner. The complex structure of the 26S proteasome requires exquisite regulation at the transcription, translation, and molecular assembly levels. Nuclear factor erythroid-derived 2-related factor 1 (Nrf1; NFE2L1), an ER-resident transcription factor, has recently been shown to be responsible for the coordinated expression of all the proteasome subunit genes upon proteasome impairment in mammalian cells. In this review, we summarize the current knowledge regarding the transcriptional regulation of the proteasome, as well as recent findings concerning the regulation of Nrf1 transcription activity in ER homeostasis and metabolic processes.

NFE2L3 promotes malignant behavior and EMT of human hepatocellular carcinoma (HepG2) cells via Wnt/β‑catenin pathway

Objective: NFE2L3 is a member of the cap 'n' collar basic-region leucine zipper family. NFE2L3 has turned out to be associated with oxidative stress, but the relevance of NFE2L3 in hepatocellular carcinoma (HCC) has remained elusive. This study aimed to investigate the role of NFE2L3 in HCC and explore underlying mechanisms. Methods: Quantitative real-time PCR, western blot and immunohistochemistry were used to detect the mRNA and protein expression of NFE2L3, the expression of epithelial-mesenchymal transition (EMT) markers and Wnt/β-catenin signaling pathway-related proteins. In loss-function experiments, HepG2 cells were transfected with lentiviral vector containing NFE2L3 short hairpin RNA or scramble control. Cell proliferation and migration were measured by Cell Counting Kit-8, Colony formation, EdU incorporation and Transwell assays respectively. Flow cytometry was used to analyze cell cycle and apoptosis. HepG2 cells were subcutaneously injected into nude mice and tumor size was measured once every other day. Results: The results revealed that high expression of NFE2L3 was positively associated with malignant behavior and EMT in HCC. Knockdown of NFE2L3 inhibited cell proliferation and migration, led to cell cycle G0/G1 arrest and induction of cell apoptosis, increased expression of E-cadherin and decreased expression of N‑cadherin, Vimentin, MMP2, CDK2 and PCNA. In addition, tumor growth was inhibited by silencing of NFE2L3 in vivo. Expression of β-catenin and Wnt target genes cyclin D1 and TCF4 was reduced in HepG2-shNFE2L3 cells. Conclusions: NFE2L3 promotes cell proliferation, metastasis, and induces EMT of hepatocellular carcinoma (HepG2) cells via activation of Wnt/β-catenin pathway.