RPA1 binding to NRF2 switches ARE-dependent transcriptional activation to ARE-NRE-dependent repression

PPIA dictates NRF2 stability to promote lung cancer progression

Nuclear factor erythroid 2-related factor 2 (NRF2) hyperactivation has been established as an oncogenic driver in a variety of human cancers, including non-small cell lung cancer (NSCLC). However, despite massive efforts, no specific therapy is currently available to target NRF2 hyperactivation. Here, we identify peptidylprolyl isomerase A (PPIA) is required for NRF2 protein stability. Ablation of PPIA promotes NRF2 protein degradation and blocks NRF2-driven growth in NSCLC cells. Mechanistically, PPIA physically binds to NRF2 and blocks the access of ubiquitin/Kelch Like ECH Associated Protein 1 (KEAP1) to NRF2, thus preventing ubiquitin-mediated degradation. Our X-ray co-crystal structure reveals that PPIA directly interacts with a NRF2 interdomain linker via a trans-proline 174-harboring hydrophobic sequence. We further demonstrate that an FDA-approved drug, cyclosporin A (CsA), impairs the interaction of NRF2 with PPIA, inducing NRF2 ubiquitination and degradation. Interestingly, CsA interrupts glutamine metabolism mediated by the NRF2/KLF5/SLC1A5 pathway, consequently suppressing the growth of NRF2-hyperactivated NSCLC cells. CsA and a glutaminase inhibitor combination therapy significantly retard tumor progression in NSCLC patient-derived xenograft (PDX) models with NRF2 hyperactivation. Our study demonstrates that targeting NRF2 protein stability is an actionable therapeutic approach to treat NRF2-hyperactivated NSCLC.

Human Bocavirus 1 NP1 acts as an ssDNA-binding protein to help AAV2 DNA replication and cooperates with RPA to regulate AAV2 capsid expression

Adeno-associated virus (AAV) requires co-infection with helper virus for efficient replication. We previously reported that Human Bocavirus 1 (HBoV1) genes, including NP1, NS2, and BocaSR, were critical for AAV2 replication. Here, we first demonstrate the essential roles of the NP1 protein in AAV2 DNA replication and protein expression. We show that NP1 binds to single-strand DNA (ssDNA) at least 30 nucleotides (nt) in length in a sequence-independent manner. Furthermore, NP1 colocalized with the BrdU-labeled AAV2 DNA replication center, and the loss of the ssDNA-binding ability of NP1 by site-directed mutation completely abolished AAV2 DNA replication. We used affinity-tagged NP1 protein to identify host cellular proteins associated with NP1 in cells cotransfected with the HBoV1 helper genes and AAV2 duplex genome. Of the identified proteins, we demonstrate that NP1 directly binds to the DBD-F domain of the RPA70 subunit with a high affinity through the residues 101-121. By reconstituting the heterotrimer protein RPA in vitro using gel filtration, we demonstrate that NP1 physically associates with RPA to form a heterologous complex characterized by typical fast-on/fast-off kinetics. Following a dominant-negative strategy, we found that NP1-RPA complex mainly plays a role in expressing AAV2 capsid protein by enhancing the transcriptional activity of the p40 promoter. Our study revealed a novel mechanism by which HBoV1 NP1 protein supports AAV2 DNA replication and capsid protein expression through its ssDNA-binding ability and direct interaction with RPA, respectively.IMPORTANCERecombinant adeno-associated virus (rAAV) vectors have been extensively used in clinical gene therapy strategies. However, a limitation of these gene therapy strategies is the efficient production of the required vectors, as AAV alone is replication-deficient in the host cells. HBoV1 provides the simplest AAV2 helper genes consisting of NP1, NS2, and BocaSR. An important question regarding the helper function of HBoV1 is whether it provides any direct function that supports AAV2 DNA replication and protein expression. Also of interest is how HBoV1 interplays with potential host factors to constitute a permissive environment for AAV2 replication. Our studies revealed that the multifunctional protein NP1 plays important roles in AAV2 DNA replication via its sequence-independent ssDNA-binding ability and in regulating AAV2 capsid protein expression by physically interacting with host protein RPA. Our findings present theoretical guidance for the future application of the HBoV1 helper genes in the rAAV vector production.

A Razor's Edge: Vascular Responses to Acute Inflammatory Lung Injury/Acute Respiratory Distress Syndrome

Historically considered a metabolically inert cellular layer separating the blood from the underlying tissue, the endothelium is now recognized as a highly dynamic, metabolically active tissue that is critical to organ homeostasis. Under homeostatic conditions, lung endothelial cells (ECs) in healthy subjects are quiescent, promoting vasodilation, platelet disaggregation, and anti-inflammatory mechanisms. In contrast, lung ECs are essential contributors to the pathobiology of acute respiratory distress syndrome (ARDS), as the quiescent endothelium is rapidly and radically altered upon exposure to environmental stressors, infectious pathogens, or endogenous danger signals into an effective and formidable regulator of innate and adaptive immunity. These dramatic perturbations, produced in a tsunami of inflammatory cascade activation, result in paracellular gap formation between lung ECs, sustained lung edema, and multi-organ dysfunction that drives ARDS mortality. The astonishing plasticity of the lung endothelium in negotiating this inflammatory environment and efforts to therapeutically target the aberrant ARDS endothelium are examined in further detail in this review.

Fluoride exposure confers NRF2 activation in hepatocyte through both canonical and non-canonical signaling pathways

Due to the high abundance in the Earth's crust and industrial application, fluoride is widely present in our living environment. However, excessive fluoride exposure causes toxicity in different organs. As the most important detoxification and excretion organ, liver is more easily involved in fluoride toxicity than other organs, and oxidative stress is considered as the key mechanism related with fluoride hepatotoxicity. In this study, we mainly investigated the role of nuclear factor erythroid-derived 2-like 2 (NRF2, a core transcription factor in oxidative stress) in fluoride exposure-induced hepatotoxicity as well as the related mechanism. Herein, liver cells (BNL CL.2) were treated with fluoride in different concentrations. The hepatotoxicity and NRF2 signaling pathway were analyzed respectively. Our results indicated that excessive fluoride (over 1 mM) resulted in obvious toxicity in hepatocyte and activated NRF2 and NRF2 target genes. The increased ROS generation after fluoride exposure suppressed KEAP1-induced NRF2 ubiquitylation and degradation. Meanwhile, fluoride exposure also led to blockage of autophagic flux and upregulation of p62, which contributed to activation of NRF2 via competitive binding with KEAP1. Both pharmaceutical activation and genetic activation of NRF2 accelerated fluoride exposure-induced hepatotoxicity. Thus, the upregulation of NRF2 in hepatocyte after fluoride exposure can be regarded as a cellular self-defense, and NRF2-KEAP1 system could be a novel molecular target against fluoride exposure-induced hepatotoxicity.

The novel β-TrCP protein isoform hidden in circular RNA confers trastuzumab resistance in HER2-positive breast cancer

Trastuzumab notably improves the outcome of human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients, however, resistance to trastuzumab remains a major hurdle to clinical treatment. In the present study, we identify a circular RNA intimately linked to trastuzumab resistance. circ-β-TrCP, derived from the back-splicing of β-TrCP exon 7 and 13, confers trastuzumab resistance by regulating NRF2-mediated antioxidant pathway in a KEAP1-independent manner. Concretely, circ-β-TrCP encodes a novel truncated 343-amino acid peptide located in the nucleus, referred as β-TrCP-343aa, which competitively binds to NRF2, blocks SCFβ-TrCP-mediated NRF2 proteasomal degradation, and this protective effect of β-TrCP-343aa on NRF2 protein requires GSK3 activity. Subsequently, the elevated NRF2 transcriptionally upregulates a cohort of antioxidant genes, giving rise to trastuzumab resistance. Moreover, the translation ability of circ-β-TrCP is inhibited by eIF3j under both basal and oxidative stress conditions, and eIF3j is transcriptionally repressed by NRF2, thus forming a positive feedback circuit between β-TrCP-343aa and NRF2, expediting trastuzumab resistance. Collectively, our data demonstrate that circ-β-TrCP-encoded β-TrCP protein isoform drives HER2-targeted therapy resistance in a NRF2-dependent manner, which provides potential therapeutic targets for overcoming trastuzumab resistance.

Liquiritigenin Confers Liver Protection by Enhancing NRF2 Signaling through Both Canonical and Non-canonical Signaling Pathways

Oxidative stress plays a critical role in drug-induced liver injury. In recent years, liquiritigenin (LQ), a natural flavonoid distributed in Glycyrrhizae Radix et Rhizoma (Gan Cao), shows protective effects against oxidative hepatotoxicity. However, the underlying mechanism remains unclear. In this study, we mainly investigated the role of NRF2, a core transcription factor in oxidative stress, in LQ-induced hepatoprotection. Our results indicated that the function of LQ to eliminate reactive oxygen species in liver cells was dependent on NRF2 activation. Both a canonical signaling pathway and a non-canonical signaling pathway are involved in LQ-induced NRF2 activation. LQ induced NRF2 activation in a KEAP1-C151-dependent manner partially. Meanwhile, LQ led to the blockage of autophagic flux and upregulation of p62, which competitively bound with KEAP1 and conferred NRF2 activation in a KEAP1-C151-independent manner. Totally, our study reveals a novel molecular mechanism underlying the hepatoprotection of LQ, providing a new insight into the pathogenesis and therapeutic strategy of oxidative liver injury.

Interplay between Nrf2 and αB-crystallin in the lens and heart of zebrafish under proteostatic stress

A coordinated oxidative stress response, partly triggered by the transcription factor Nrf2, protects cells from the continual production of reactive oxygen species. Left unbuffered, reactive oxygen species can lead to protein aggregation that has been implicated in a spectrum of diseases such as cataract of the ocular lens and myopathy of the heart. While proteostasis is maintained by diverse families of heat shock proteins, the interplay between the oxidative and proteostatic stress responses in the lens and heart has not been investigated. Capitalizing on multiple zebrafish lines that have compromised function of Nrf2 and/or the two zebrafish small heat shock proteins αBa- and αBb-crystallin, we uncovered a transcriptional relationship that leads to a substantial increase in αBb-crystallin transcripts in the heart in response to compromised function of Nrf2. In the lens, the concomitant loss of function of Nrf2 and αBa-crystallin leads to upregulation of the cholesterol biosynthesis pathway, thus mitigating the phenotypic consequences of the αBa-crystallin knockout. By contrast, abrogation of Nrf2 function accentuates the penetrance of a heart edema phenotype characteristic of embryos of αB-crystallin knockout lines. Multiple molecular pathways, such as genes involved in extracellular interactions and implicated in cardiomyopathy, are revealed from transcriptome profiling, thus identifying novel targets for further investigation. Together, our transcriptome/phenotypic analysis establishes an intersection between oxidative stress and chaperone responses in the lens and heart.

Reduced SUMOylation of Nrf2 signaling contributes to its inhibition induced by amyloid-β

Oxidative stress induced by amyloid-β (Aβ) has been considered as one of the important mechanisms in the development of Alzheimer disease (AD). The inhibition of endogenous antioxidant Nrf2 signaling in the brain of AD patients aggravates the oxidative damage, however, the causes of Nrf2 signaling inhibition are unclear. It is reported that smallubiquitin-like modification (SUMOylation) is involved in the process of oxidative injury. To investigate whether and how SUMOylation was involved in the inhibition of Nrf2 signaling pathway induced by Aβ, Aβ intrahippocampal injection rat model and Aβ treated SH-SY5Y cell model were used in the current study. Small interfering RNA and lentivirus transfection were used to intervene SUMOylation, and the level of SUMOylation was assessed by immunoprecipitation. The present in vivo and in vitro studies revealed that SUMOylation levels of Nrf2 and MafF, as well as the overall SUMOylation level were reduced under long-term Aβ insult. Meanwhile, the binding of Nrf2 to MafF was decreased, accompanied by low interaction with antioxidant response element (ARE) area of gene. Down-regulation of SUMO protein exacerbated the Aβ-induced inhibition of Nrf2 signaling pathway, while, enhancement of SUMOylation of Nrf2 and MafF by overexpression of Ubc9 reversed this process. These results imply that reduction in SUMOylation induced by Aβ contributed to the inhibition of Nrf2 signaling, and SUMOylation might be a potential therapeutic target of AD.

Association of NRF2 with HIF-2α-induced cancer stem cell phenotypes in chronic hypoxic condition

The acquisition of the cancer stem cell (CSC) properties is often mediated by the surrounding microenvironment, and tumor hypoxia is considered an important factor for CSC phenotype development. High levels of NRF2 (Nuclear Factor Erythroid 2-Like 2; NFE2L2), a transcription factor that maintains cellular redox balance, have been associated with facilitated tumor growth and therapy resistance. In this study, we investigated the role of NRF2 in hypoxia-induced CSC phenotypes in colorectal cancer cells. Chronic hypoxia for 72 h resulted in CSC phenotypes, including elevation of krupple-like factor 4 (KLF4) and octamer-binding transcription factor 4 (OCT4), and an increase in cancer migration and spheroid growth with concomitant hypoxia-inducible factor 2α (HIF-2α) accumulation. All these chronic hypoxia-induced CSC properties were attenuated following HIF-2α-specific silencing. In this chronic hypoxia model, NRF2 inhibition by shRNA-based silencing or brusatol treatment blocked HIF-2α accumulation, which consequently resulted in decreased CSC marker expression and inhibition of CSC properties such as spheroid growth. In contrast, NRF2 overactivation by genetic or chemical approach enhanced the chronic hypoxia-induced HIF-2α accumulation and cancer migration. As a molecular mechanism of the NRF2-inhibition-mediated HIF-2α dysregulation, we demonstrated that miR-181a-2-3p, whose expression is elevated in NRF2-silenced cells, targeted the HIF-2α 3'UTR and subsequently suppressed the chronic hypoxia-induced HIF-2α and CSC phenotypes. The miR-181a-2-3p inhibitor treatment in NRF2-silenced cells could restore the levels of HIF-2α and CSC markers, and increased cancer migration and sphere formation under chronic hypoxia. In line with this, the miR-181a-2-3p inhibitor transfection could increase tumorigenicity of NRF2-silenced colorectal cancer cells. Collectively, our study suggests the involvement of NRF2/miR181a-2-3p signaling in the development of HIF-2α-mediated CSC phenotypes in sustained hypoxic environments.

NRF2 controls iron homeostasis and ferroptosis through HERC2 and VAMP8

Enhancing the intracellular labile iron pool (LIP) represents a powerful, yet untapped strategy for driving ferroptotic death of cancer cells. Here, we show that NRF2 maintains iron homeostasis by controlling HERC2 (E3 ubiquitin ligase for NCOA4 and FBXL5) and VAMP8 (mediates autophagosome-lysosome fusion). NFE2L2/NRF2 knockout cells have low HERC2 expression, leading to a simultaneous increase in ferritin and NCOA4 and recruitment of apoferritin into the autophagosome. NFE2L2/NRF2 knockout cells also have low VAMP8 expression, which leads to ferritinophagy blockage. Therefore, deletion of NFE2L2/NRF2 results in apoferritin accumulation in the autophagosome, an elevated LIP, and enhanced sensitivity to ferroptosis. Concordantly, NRF2 levels correlate with HERC2 and VAMP8 in human ovarian cancer tissues, as well as ferroptosis resistance in a panel of ovarian cancer cell lines. Last, the feasibility of inhibiting NRF2 to increase the LIP and kill cancer cells via ferroptosis was demonstrated in preclinical models, signifying the impact of NRF2 inhibition in cancer treatment.

Targeting SELPLG/P-selectin glycoprotein ligand 1 in preclinical ARDS: Genetic and epigenetic regulation of the SELPLG promoter

We previously identified a missense single nucleotide polymorphism rs2228315 (G>A, Met62Ile) in the selectin-P-ligand gene (SELPLG), encoding P-selectin glycoprotein ligand 1 (PSGL-1), to be associated with increased susceptibility to acute respiratory distress syndrome (ARDS). These earlier studies demonstrated that SELPLG lung tissue expression was increased in mice exposed to lipopolysaccharide (LPS)- and ventilator-induced lung injury (VILI) suggesting that inflammatory and epigenetic factors regulate SELPLG promoter activity and transcription. In this report, we used a novel recombinant tandem PSGL1 immunoglobulin fusion molecule (TSGL-Ig), a competitive inhibitor of PSGL1/P-selectin interactions, to demonstrate significant TSGL-Ig-mediated decreases in SELPLG lung tissue expression as well as highly significant protection from LPS- and VILI-induced lung injury. In vitro studies examined the effects of key ARDS stimuli (LPS, 18% cyclic stretch to simulate VILI) on SELPLG promoter activity and showed LPS-mediated increases in SELPLG promoter activity and identified putative promoter regions associated with increased SELPLG expression. SELPLG promoter activity was strongly regulated by the key hypoxia-inducible transcription factors, HIF-1α, and HIF-2α as well as NRF2. Finally, the transcriptional regulation of SELPLG promoter by ARDS stimuli and the effect of DNA methylation on SELPLG expression in endothelial cell was confirmed. These findings indicate SELPLG transcriptional regulation by clinically-relevant inflammatory factors with the significant TSGL-Ig-mediated attenuation of LPS and VILI highly consistent with PSGL1/P-selectin as therapeutic targets in ARDS.

Nrf2 Regulates the Expression of CYP2D6 by Inhibiting the Activity of Krüppel-Like Factor 9 (KLF9)

AIMS

The aim of the present study is to gain insight into the biology of Parkinson's disease (PD) and cancer to drive translational advances enabling more effective prevention and/or potential treatments.

BACKGROUND

The expression of Cytochrome P450 2D6 (CYP2D6) is correlated with various diseases such as PD and cancer; therefore, exploring its regulatory mechanism at transcriptional levels is of interest. NF-E2-related factor 2 (Nrf2) has been known to be responsible for regulating phase II and phase III drug-metabolizing genes.

OBJECTIVES

The objectives of this study are to investigate the transcriptional regulation of CYP2D6 by Nrf2 and to analyze its role in PD and cancer.

METHODS

Nrf2 was transiently expressed in human hepatoma Hep3B cells, and the expression of CYP2D6 was examined by RT-qPCR. The promoter activity of CYP2D6 and the DNA binding of Nrf2 were examined by luciferase and ChIP assay, respectively. We then investigated the expression and correlation of Nrf2 and CYP2D6 in the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) datasets.

RESULTS

In the present study, we demonstrated that Nrf2 down-regulated CYP2D6 mRNA expression in hepatoma Hep3B cells. Mechanistically, Nrf2 binds to the antioxidant responsive element (ARE) in the proximity of krüppel- like factor 9 (KLF9)-binding site within the -550/+51 of CYP2D6 promoter. The inhibition and activation of Nrf2 enhanced and suppressed KLF9 effects on CYP2D6 expression, respectively. The expression levels of Nrf2 and CYP2D6 were upregulated and downregulated in the PD patient GEO datasets compared to the healthy control tissues, and Nrf2 was negatively correlated with CYP2D6. In liver cancer patients, decreased CYP2D6 levels were apparent and associated with a lower probability of survival.

CONCLUSION

Our work revealed the inhibitory role of Nrf2 in regulating CYP2D6 expression. Moreover, Nrf2- dependent regulation of CYP2D6 can be used as a prognostic factor and therapeutic strategy in PD and liver cancer.

COX7A1 enhances the sensitivity of human NSCLC cells to cystine deprivation-induced ferroptosis via regulating mitochondrial metabolism

COX7A1, a subunit of cytochrome c oxidase, holds an important position in the super-assembly which integrates into multi-unit heteromeric complexes peripherally in the mitochondrial electron transport chain (ETC). Recently, some studies indicated the significant potential of COX7A1 in cancer metabolism and therapy. However, the underlying metabolic process and therapy mechanism remain unclear. In this study, COX7A1-overexpressed cell line was established via lentivirus transduction. The relationship between COX7A1 and ferroptosis, a novel form of cell death driven by iron-dependent lipid peroxidation, was further analyzed in different human non-small-cell lung carcinoma (NSCLC) cells respectively. Our results showed that COX7A1 increased the sensitivity of NSCLC cells to the ferroptosis induced by cysteine deprivation via enhancing the tricarboxylic acid (TCA) cycle and the activity of complex IV in mitochondrial ETC. Meanwhile, COX7A1 suppressed mitochondrial dynamics as well as mitochondrial biogenesis and mitophagy through blocking autophagic flux. The autophagy activator, rapamycin, relieved the autophagic blockage and further strengthened the sensitivity to cysteine deprivation-induced ferroptosis of NSCLC cells in vitro and in vivo. Taken together, our data indicate the close association of COX7A1 with cysteine deprivation-induced ferroptosis, and provide a novel insight into the therapy mode against human NSCLC.

Urolithin A ameliorates diabetic retinopathy via activation of the Nrf2/HO-1 pathway

Diabetic retinopathy (DR) is a progressive microvascular complication of diabetes mellitus and is characterised by excessive inflammation and oxidative stress. Urolithin A (UA), a major metabolite of ellagic acid, exerts anti-inflammatory and antioxidant functions in various human diseases. This study, for the first time, uncovered the role of UA in DR pathogenesis. Streptozotocin-induced diabetic rats were used to determine the effects of UA on blood glucose levels, retinal structures, inflammation, and oxidative stress. High glucose (HG)-induced human retinal endothelial cells (HRECs) were used to elucidate the anti-inflammatory and antioxidant mechanisms of UA in DR in vitro. The in vivo experiments demonstrated that UA injection reduced blood glucose levels, decreased albumin and vascular endothelial growth factor concentrations, and ameliorated the injured retinal structures caused by DR. UA administration also inhibited inflammation and oxidative damage in the retinal tissues of diabetic rats. Similar anti-inflammatory and antioxidant effects of UA were observed in HRECs induced by HG. Furthermore, we found that UA elevated the levels of nuclear Nrf2 and HO-1 both in vivo and in vitro. Nrf2 silencing reversed the inhibitory effects of UA on inflammation and oxidative stress during DR progression. Together, our findings indicate that UA can ameliorate DR by repressing inflammation and oxidative stress via the Nrf2/HO-1 pathway, which suggests that UA could be an effective drug for clinical DR treatment.

RPA1 controls chromatin architecture and maintains lipid metabolic homeostasis

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease, with a prevalence of 25% worldwide. However, the underlying molecular mechanism involved in the development and progression of the NAFLD spectrum remains unclear. Single-stranded DNA-binding protein replication protein A1 (RPA1) participates in DNA replication, recombination, and damage repair. Here, we show that Rpa1^+/- mice develop fatty liver disease during aging and in response to a high-fat diet. Liver-specific deletion of Rpa1 results in downregulation of genes related to fatty acid oxidation and impaired fatty acid oxidation, which leads to hepatic steatosis and hepatocellular carcinoma. Mechanistically, RPA1 binds gene regulatory regions, chromatin-remodeling factors, and HNF4A and remodels chromatin architecture, through which RPA1 promotes HNF4A transcriptional activity and fatty acid β oxidation. Collectively, our data demonstrate that RPA1 is an important regulator of NAFLD through controlling chromatin accessibility.

Nrf2 Activation Protects Against Organic Dust and Hydrogen Sulfide Exposure Induced Epithelial Barrier Loss and K. pneumoniae Invasion

Agriculture workers report various respiratory symptoms owing to occupational exposure to organic dust (OD) and various gases. Previously, we demonstrated that pre-exposure to hydrogen sulfide (H₂S) alters the host response to OD and induces oxidative stress. Nrf2 is a master-regulator of host antioxidant response and exposures to toxicants is known to reduce Nrf2 activity. The OD exposure-induced lung inflammation is known to increase susceptibility to a secondary microbial infection. We tested the hypothesis that repeated exposure to OD or H₂S leads to loss of Nrf2, loss of epithelial cell integrity and that activation of Nrf2 rescues this epithelial barrier dysfunction. Primary normal human bronchial epithelial (NHBE) cells or mouse precision cut-lung slices (PCLS) were treated with media, swine confinement facility organic dust extract (ODE) or H₂S or ODE+H₂S for one or five days. Cells were also pretreated with vehicle control (DMSO) or RTA-408, a Nrf2 activator. Acute exposure to H₂S and ODE+H₂S altered the cell morphology, decreased the viability as per the MTT assay, and reduced the Nrf2 expression as well as increased the keap1 levels in NHBE cells. Repeated exposure to ODE or H₂S or ODE+H₂S induced oxidative stress and cytokine production, decreased tight junction protein occludin and cytoskeletal protein ezrin expression, disrupted epithelial integrity and resulted in increased Klebsiella pneumoniae invasion. RTA-408 (pharmacological activator of Nrf2) activated Nrf2 by decreasing keap1 levels and reduced ODE+H₂S-induced changes including reversing loss of barrier integrity, inflammatory cytokine production and microbial invasion in PCLS but not in NHBE cell model. We conclude that Nrf2 activation has a partial protective function against ODE and H₂S.

CHML is an NRF2 target gene that regulates mTOR function

The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) is often highly expressed in non-small cell lung cancer (NSCLC). Through its target genes, NRF2 enhances cancer progression and chemo/radioresistance, leading to a poorer prognosis in patients with high NRF2 expression. In this study, we identified CHM-like Rab escort protein (CHML; encoding Rep2) as an NRF2 target gene with an antioxidant response element (ARE) in its promoter region (-1622 to -1612). Analysis of patient data curated by The Cancer Genome Atlas (TCGA) and Oncomine databases revealed that CHML mRNA expression was elevated in lung adenocarcinoma (LUAD) patient tumor tissues and correlated with decreased patient survival. Immunohistochemistry (IHC) analysis of normal versus lung cancer patient tissues revealed that Rep2 protein levels were higher in lung tumors compared with normal tissue, which also correlated with increased levels of NRF2. Importantly, siRNA-mediated knockdown of CHML/Rep2 in A549 NSCLC cells decreased their ability to proliferate. Mechanistically, Rep2 mediates mTOR function, as loss of Rep2 inhibited, whereas overexpression enhanced, mTOR translocation and activation at the lysosome. Our findings identify a novel NRF2-Rep2-dependent regulation of mTOR function.

An Overview of the Nrf2/ARE Pathway and Its Role in Neurodegenerative Diseases

Nrf2 is a basic region leucine-zipper transcription factor that plays a pivotal role in the coordinated gene expression of antioxidant and detoxifying enzymes, promoting cell survival in adverse environmental or defective metabolic conditions. After synthesis, Nrf2 is arrested in the cytoplasm by the Kelch-like ECH-associated protein 1 suppressor (Keap1) leading Nrf2 to ubiquitin-dependent degradation. One Nrf2 activation mechanism relies on disconnection from the Keap1 homodimer through the oxidation of cysteine at specific sites of Keap1. Free Nrf2 enters the nucleus, dimerizes with small musculoaponeurotic fibrosarcoma proteins (sMafs), and binds to the antioxidant response element (ARE) sequence of the target genes. Since oxidative stress, next to neuroinflammation and mitochondrial dysfunction, is one of the hallmarks of neurodegenerative pathologies, a molecular intervention into Nrf2/ARE signaling and the enhancement of the transcriptional activity of particular genes are targets for prevention or delaying the onset of age-related and inherited neurogenerative diseases. In this study, we review evidence for the Nrf2/ARE-driven pathway dysfunctions leading to various neurological pathologies, such as Alzheimer’s, Parkinson’s, and Huntington’s diseases, as well as amyotrophic lateral sclerosis, and the beneficial role of natural and synthetic molecules that are able to interact with Nrf2 to enhance its protective efficacy.

Nrf2 in Cancer, Detoxifying Enzymes and Cell Death Programs

Reactive oxygen species (ROS) play an important role in cell proliferation and differentiation. They are also by-products of aerobic living conditions. Their inherent reactivity poses a threat for all cellular components. Cells have, therefore, evolved complex pathways to sense and maintain the redox balance. Among them, Nrf2 (Nuclear factor erythroid 2-related factor 2) plays a crucial role: it is activated under oxidative conditions and is responsible for the expression of the detoxification machinery and antiapoptotic factors. It is, however, a double edge sword: whilst it prevents tumorigenesis in healthy cells, its constitutive activation in cancer promotes tumour growth and metastasis. In addition, recent data have highlighted the importance of Nrf2 in evading programmed cell death. In this review, we will focus on the activation of the Nrf2 pathway in the cytoplasm, the molecular basis underlying Nrf2 binding to the DNA, and the dysregulation of this pathway in cancer, before discussing how Nrf2 contributes to the prevention of apoptosis and ferroptosis in cancer and how it is likely to be linked to detoxifying enzymes containing selenium.

Genetic and epigenetic regulation of the non-muscle myosin light chain kinase isoform by lung inflammatory factors and mechanical stress

RATIONALE

The myosin light chain kinase gene, MYLK, encodes three proteins via unique promoters, including the non-muscle isoform of myosin light chain kinase (nmMLCK), a cytoskeletal protein centrally involved in regulation of vascular integrity. As MYLK coding SNPs are associated with severe inflammatory disorders (asthma, acute respiratory distress syndrome (ARDS)), we explored clinically relevant inflammatory stimuli and promoter SNPs in nmMLCK promoter regulation.

METHODS

Full-length or serially deleted MYLK luciferase reporter promoter activities were measured in human lung endothelial cells (ECs). SNP-containing non-muscle MYLK (nmMYLK) DNA fragments were generated and nmMYLK promoter binding by transcription factors (TFs) detected by protein-DNA electrophoretic mobility shift assay (EMSA). Promoter demethylation was evaluated by 5-aza-2'-deoxycytidine (5-Aza). A preclinical mouse model of lipopolysaccharide (LPS)-induced acute lung injury (ALI) was utilized for nmMLCK validation.

RESULTS

Lung EC levels of nmMLCK were significantly increased in LPS-challenged mice and LPS, tumor necrosis factor-α (TNF-α), 18% cyclic stretch (CS) and 5-Aza each significantly up-regulated EC nmMYLK promoter activities. EC exposure to FG-4592, a prolyl hydroxylase inhibitor that increases hypoxia-inducible factor (HIF) expression, increased nmMYLK promoter activity, confirmed by HIF1α/HIF2α silencing. nmMYLK promoter deletion studies identified distal inhibitory and proximal enhancing promoter regions as well as mechanical stretch-, LPS- and TNFα-inducible regions. Insertion of ARDS-associated SNPs (rs2700408, rs11714297) significantly increased nmMYLK promoter activity via increased transcription binding (glial cells missing homolog 1 (GCM1) and intestine-specific homeobox (ISX), respectively). Finally, the MYLK rs78755744 SNP (-261G/A), residing within a nmMYLK CpG island, significantly attenuated 5-Aza-induced promoter activity.

CONCLUSION

These findings indicate nmMYLK transcriptional regulation by clinically relevant inflammatory factors and ARDS-associated nmMYLK promoter variants are consistent with nmMLCK as a therapeutic target in severe inflammatory disorders.

Corilagin induces apoptosis and autophagy in NRF2‑addicted U251 glioma cell line

Corilagin, extracted from the Euphorbiaceae and Phyllanthus plants, inhibits the growth of a number of types of tumors. Compared with temozolomide, the traditional chemotherapy drug, corilagin has demonstrated stronger antitumor activity. However, the pharmaceutical mechanism of corilagin in glioma remains unclear. Nuclear factor erythroid 2 like 2 (NFE2L2 or NRF2) is positively associated with several types of tumor including glioma. In the present study, NRF2 expression was higher in glioma tissues compared with non-glioma specimens. Therefore, it was hypothesized that corilagin targets NRF2 regulation of U251 cell apoptosis. The present study used Hoechst 33258 staining to demonstrate that corilagin induced glioma cell apoptosis and observed that the expression of the apoptosis-related gene Bcl-2 was reduced. In addition, corilagin induced autophagy and promoted the conversion of light chain 3 (LC3) protein from LC3I to LC3II. NRF2 expression was downregulated by corilagin stimulation. Furthermore, the gene expression pattern following knockdown of NRF2 in U251 cells using siRNA was consistent with corilagin stimulation. Therefore, it was preliminarily concluded that corilagin induces apoptosis and autophagy by reducing NRF2 expression.

PCB126 Exposure Revealed Alterations in m6A RNA Modifications in Transcripts Associated With AHR Activation

Chemical modifications of proteins, DNA, and RNA moieties play critical roles in regulating gene expression. Emerging evidence suggests the RNA modifications (epitranscriptomics) have substantive roles in basic biological processes. One of the most common modifications in mRNA and noncoding RNAs is N6-methyladenosine (m6A). In a subset of mRNAs, m6A sites are preferentially enriched near stop codons, in 3' UTRs, and within exons, suggesting an important role in the regulation of mRNA processing and function including alternative splicing and gene expression. Very little is known about the effect of environmental chemical exposure on m6A modifications. As many of the commonly occurring environmental contaminants alter gene expression profiles and have detrimental effects on physiological processes, it is important to understand the effects of exposure on this important layer of gene regulation. Hence, the objective of this study was to characterize the acute effects of developmental exposure to PCB126, an environmentally relevant dioxin-like PCB, on m6A methylation patterns. We exposed zebrafish embryos to PCB126 for 6 h starting from 72 h post fertilization and profiled m6A RNA using methylated RNA immunoprecipitation followed by sequencing (MeRIP-seq). Our analysis revealed 117 and 217 m6A peaks in the DMSO and PCB126 samples (false discovery rate 5%), respectively. The majority of the peaks were preferentially located around the 3' UTR and stop codons. Statistical analysis revealed 15 m6A marked transcripts to be differentially methylated by PCB126 exposure. These include transcripts that are known to be activated by AHR agonists (eg, ahrra, tiparp, nfe2l2b) as well as others that are important for normal development (vgf, cebpd, sned1). These results suggest that environmental chemicals such as dioxin-like PCBs could affect developmental gene expression patterns by altering m6A levels. Further studies are necessary to understand the functional consequences of exposure-associated alterations in m6A levels.

Downregulation of miR-17-92 Cluster by PERK Fine-Tunes Unfolded Protein Response Mediated Apoptosis

An important event in the unfolded protein response (UPR) is activation of the endoplasmic reticulum (ER) kinase PERK. The PERK signalling branch initially mediates a prosurvival response, which progresses to a proapoptotic response upon prolonged ER stress. However, the molecular mechanisms of PERK-mediated cell death are not well understood. Here we show that expression of the primary miR-17-92 transcript and mature miRNAs belonging to the miR-17-92 cluster are decreased during UPR. We found that miR-17-92 promoter reporter activity was reduced during UPR in a PERK-dependent manner. Furthermore, we show that activity of the miR-17-92 promoter is repressed by ectopic expression of ATF4 and NRF2. Promoter deletion analysis mapped the region responding to UPR-mediated repression to a site in the proximal region of the miR-17-92 promoter. Hypericin-mediated photo-oxidative ER damage reduced the expression of miRNAs belonging to the miR-17-92 cluster in wild-type but not in PERK-deficient cells. Importantly, ER stress-induced apoptosis was inhibited upon miR-17-92 overexpression in SH-SY5Y and H9c2 cells. Our results reveal a novel function for ATF4 and NRF2, where repression of the miR-17-92 cluster plays an important role in ER stress-mediated apoptosis. Mechanistic details are provided for the potentiation of cell death via sustained PERK signalling mediated repression of the miR-17-92 cluster.

The NRF2-LOC344887 signaling axis suppresses pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and irreversible disease characterized by an increase in differentiation of fibroblasts to myofibroblasts and excessive accumulation of extracellular matrix in lung tissue. Pharmacological activation of NRF2 has proved to be a valuable antifibrotic approach, however the detailed mechanisms of how NRF2 mediates antifibrotic function remain unclear. In this study, we found that the antifibrotic function of sulforaphane (SFN), an NRF2 activator, was largely dependent on LOC344887, a long noncoding RNA. Two functional AREs were identified in both the promoter and intron 1 of LOC344887, which defines LOC344887 as a novel anti-fibrotic NRF2 target gene. RNA-seq analysis revealed that LOC344887 controls genes and signaling pathways associated with fibrogenesis. Deletion or downregulation of LOC344887 enhanced expression of CDH2/N-cadherin, as well as a number of other fibrotic genes and blunted the antifibrotic effects of SFN. Furthermore, LOC344887-mediated downregulation of fibrotic genes may involve the PI3K-AKT signaling pathway, as pharmacologic inhibition of PI3K activity blocked the effects of LOC344887 knockdown. Our findings demonstrate that NRF2-mediated LOC344887 upregulation contributes to the antifibrotic potential of SFN by repressing the expression of CDH2 and other fibrotic genes, providing novel insight into how NRF2 controls the regulatory networks of IPF. This study provides a better understanding of the molecular mechanisms of NRF2 activators against pulmonary fibrosis and presents a novel therapeutic axis for prevention and intervention of fibrosis-related diseases.

NRF2 regulates the sensitivity of human NSCLC cells to cystine deprivation-induced ferroptosis via FOCAD-FAK signaling pathway

Transcription factor nuclear factor-erythroid 2-like 2 (NRF2) mainly regulates cellular antioxidant response, redox homeostasis and metabolic balance. Our previous study illustrated the translational significance of NRF2-mediated transcriptional repression, and the transcription of FOCAD gene might be negatively regulated by NRF2. However, the detailed mechanism and the related significance remain unclear. In this study, we mainly explored the effect of NRF2-FOCAD signaling pathway on ferroptosis regulation in human non-small-cell lung carcinoma (NSCLC) model. Our results confirmed the negative regulation relationship between NRF2 and FOCAD, which was dependent on NRF2-Replication Protein A1 (RPA1)-Antioxidant Response Elements (ARE) complex. In addition, FOCAD promoted the activity of focal adhesion kinase (FAK), which further enhanced the sensitivity of NSCLC cells to cysteine deprivation-induced ferroptosis via promoting the tricarboxylic acid (TCA) cycle and the activity of Complex I in mitochondrial electron transport chain (ETC). However, FOCAD didn't affect GPX4 inhibition-induced ferroptosis. Moreover, the treatment with the combination of NRF2 inhibitor (brusatol) and erastin showed better therapeutic action against NSCLC in vitro and in vivo than single treatment, and the improved therapeutic function partially depended on the activation of FOCAD-FAK signal. Taken together, our study indicates the close association of NRF2-FOCAD-FAK signaling pathway with cysteine deprivation-induced ferroptosis, and elucidates a novel insight into the ferroptosis-based therapeutic approach for the patients with NSCLC.

Replication protein A: a multifunctional protein with roles in DNA replication, repair and beyond

Single-stranded DNA (ssDNA) forms continuously during DNA replication and is an important intermediate during recombination-mediated repair of damaged DNA. Replication protein A (RPA) is the major eukaryotic ssDNA-binding protein. As such, RPA protects the transiently formed ssDNA from nucleolytic degradation and serves as a physical platform for the recruitment of DNA damage response factors. Prominent and well-studied RPA-interacting partners are the tumor suppressor protein p53, the RAD51 recombinase and the ATR-interacting proteins ATRIP and ETAA1. RPA interactions are also documented with the helicases BLM, WRN and SMARCAL1/HARP, as well as the nucleotide excision repair proteins XPA, XPG and XPF–ERCC1. Besides its well-studied roles in DNA replication (restart) and repair, accumulating evidence shows that RPA is engaged in DNA activities in a broader biological context, including nucleosome assembly on nascent chromatin, regulation of gene expression, telomere maintenance and numerous other aspects of nucleic acid metabolism. In addition, novel RPA inhibitors show promising effects in cancer treatment, as single agents or in combination with chemotherapeutics. Since the biochemical properties of RPA and its roles in DNA repair have been extensively reviewed, here we focus on recent discoveries describing several non-canonical functions.

NF-E2-Related Factor 2 Regulates Interferon Receptor Expression and Alters Macrophage Polarization in Lupus

OBJECTIVE

Pristane-induced lupus is associated with nonresolving inflammation and deficiency of proresolving macrophages. Proresolving nonclassic macrophages (NCMs) are less responsive to type I interferon (IFN) than classic macrophages (CMs; which are proinflammatory), reflecting their relative expression levels of the type I IFN receptor (IFNAR). This study was undertaken to investigate the regulation of IFNAR expression in macrophages.

METHODS

We carried out gene expression profiling of purified CMs and NCMs from mice treated with pristane (which develop lupus) or mineral oil (non-lupus controls). Macrophage differentiation and IFNAR expression were examined in mice treated with NF-E2-related factor 2 (Nrf2) activators and inhibitors and in Nrf2-deficient mice. Nrf2 activity was also assessed in blood cells from patients with systemic lupus erythematosus (SLE). Significant differences were determined by Student's t-test.

RESULTS

RNA sequencing revealed increased expression of genes regulated by the transcription factor Nrf2 in NCMs from mineral oil-treated versus pristane-treated mice and in NCMs versus CMs. The Nrf2 activator CDDO-imidazole (CDDO-Im) decreased CMs (P < 0.0001) and promoted the development of proresolving NCMs (P = 0.06), whereas the Nrf2 inhibitor brusatol increased CMs (P < 0.05) and decreased NCMs (P < 0.001). CDDO-Im decreased Ifnar1 (P < 0.001) and IFN-stimulated gene (ISG) expression in macrophages and alleviated oxidative stress (P < 0.05), whereas brusatol had the opposite effect (P < 0.01). Moreover, Ifnar1 and ISG expression levels were higher in Nrf2-knockout mice than controls (P < 0.05). As seen in mice with lupus, SLE patients showed evidence of low Nrf2 activity.

CONCLUSION

Our findings indicate that Nrf2 activation favors the resolution of chronic inflammation in lupus. Since autoantibody production and lupus nephritis depend on IFNAR signaling, the ability of Nrf2 activators to repolarize macrophages and reduce the INF signature suggests that these agents may warrant consideration for treating lupus.

Anticancer properties and mechanism of action of the quassinoid ailanthone

Ailanthone (AIT) is a quassinoid natural product isolated from the worldwide-distributed plant Ailanthus altissima. The drug displays multiple pharmacological properties, in particular significant antitumor effects against a variety of cancer cell lines in vitro. Potent in vivo activities have been evidenced in mice bearing hepatocellular carcinoma, nonsmall cell lung cancer and castration-resistant prostate cancer. This review focusses on the mechanism of action of AIT, notably to highlight the capacity of the drug to activate DNA damage responses, to inhibit the Hsp90 co-chaperone p23 and to modulate the expression of several microRNA. The interconnexion between these effects is discussed. The unique capacity of AIT to downregulate oncogenic miR-21 and to upregulate the tumor suppressor miRNAs miR-126, miR-148a, miR-195, and miR-449a is presented. AIT exploits several microRNAs to exert its anticancer effects in distinct tumor types. AIT is one of the rare antitumor natural products that binds to and strongly inhibits cochaperone p23, opening interesting perspectives to treat cancers. However, the toxicity profile of the molecule may limit its development as an anticancer drug, unless it can be properly formulated to prevent AIT-induced gastro-intestinal damages in particular. The antitumor properties of AIT and analogs are underlined, with the aim to encourage further pharmacological studies with this underexplored natural product and related quassinoids. HIGHLIGHTS: Ailanthone (AIT) is an anticancer quassinoid isolated from Ailanthus altissima It inhibits proliferation and induces cell death of many cancer cell types The drug activates DNA damage response and targets p23 cochaperone Up or downregulation of several microRNA by AIT contributes to the anticancer activity Analogs or specific formulations must be developed to prevent the toxicity of AIT.

Ferrostatin-1 alleviates lipopolysaccharide-induced acute lung injury via inhibiting ferroptosis

Background

Ferroptosis is a newly recognized type of cell death, which is different from traditional necrosis, apoptosis or autophagic cell death. However, the position of ferroptosis in lipopolysaccharide (LPS)-induced acute lung injury (ALI) has not been explored intensively so far. In this study, we mainly analyzed the relationship between ferroptosis and LPS-induced ALI.

Methods

In this study, a human bronchial epithelial cell line, BEAS-2B, was treated with LPS and ferrostatin-1 (Fer-1, ferroptosis inhibitor). The cell viability was measured using CCK-8. Additionally, the levels of malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), and iron, as well as the protein level of SLC7A11 and GPX4, were measured in different groups. To further confirm the in vitro results, an ALI model was induced by LPS in mice, and the therapeutic action of Fer-1 and ferroptosis level in lung tissues were evaluated.

Results

The cell viability of BEAS-2B was down-regulated by LPS treatment, together with the ferroptosis markers SLC7A11 and GPX4, while the levels of MDA, 4-HNE and total iron were increased by LPS treatment in a dose-dependent manner, which could be rescued by Fer-1. The results of the in vivo experiment also indicated that Fer-1 exerted therapeutic action against LPS-induced ALI, and down-regulated the ferroptosis level in lung tissues.

Conclusions

Our study indicated that ferroptosis has an important role in the progression of LPS-induced ALI, and ferroptosis may become a novel target in the treatment of ALI patients.

Genomic and Genetic Approaches to Deciphering Acute Respiratory Distress Syndrome Risk and Mortality

Significance: Acute respiratory distress syndrome (ARDS) is a severe, highly heterogeneous critical illness with staggering mortality that is influenced by environmental factors, such as mechanical ventilation, and genetic factors. Significant unmet needs in ARDS are addressing the paucity of validated predictive biomarkers for ARDS risk and susceptibility that hamper the conduct of successful clinical trials in ARDS and the complete absence of novel disease-modifying therapeutic strategies. Recent Advances: The current ARDS definition relies on clinical characteristics that fail to capture the diversity of disease pathology, severity, and mortality risk. We undertook a comprehensive survey of the available ARDS literature to identify genes and genetic variants (candidate gene and limited genome-wide association study approaches) implicated in susceptibility to developing ARDS in hopes of uncovering novel biomarkers for ARDS risk and mortality and potentially novel therapeutic targets in ARDS. We further attempted to address the well-known health disparities that exist in susceptibility to and mortality from ARDS. Critical Issues: Bioinformatic analyses identified 201 ARDS candidate genes with pathway analysis indicating a strong predominance in key evolutionarily conserved inflammatory pathways, including reactive oxygen species, innate immunity-related inflammation, and endothelial vascular signaling pathways. Future Directions: Future studies employing a system biology approach that combines clinical characteristics, genomics, transcriptomics, and proteomics may allow for a better definition of biologically relevant pathways and genotype-phenotype connections and result in improved strategies for the sub-phenotyping of diverse ARDS patients via molecular signatures. These efforts should facilitate the potential for successful clinical trials in ARDS and yield a better fundamental understanding of ARDS pathobiology.

COX7A1 suppresses the viability of human non-small cell lung cancer cells via regulating autophagy

COX7A1 is a subunit of cytochrome c oxidase, and plays an important role in the super‐assembly that integrates peripherally into multi‐unit heteromeric complexes in the mitochondrial respiratory chain. In recent years, some researchers have identified that COX7A1 is implicated in human cancer cell metabolism and therapy. In this study, we mainly explored the effect of COX7A1 on the cell viability of lung cancer cells. COX7A1 overexpression was induced by vector transfection in NCI‐H838 cells. Cell proliferation, colony formation and cell apoptosis were evaluated in different groups. In addition, autophagy was analyzed by detecting the expression level of p62 and LC3, as well as the tandem mRFP‐GFP‐LC3 reporter assay respectively. Our results indicated that the overexpression of COX7A1 suppressed cell proliferation and colony formation ability, and promoted cell apoptosis in human non‐small cell lung cancer cells. Besides, the overexpression of COX7A1 blocked autophagic flux and resulted in the accumulation of autophagosome via downregulation of PGC‐1α and upregulation of NOX2. Further analysis showed that the effect of COX7A1 overexpression on cell viability was partly dependent of the inhibition of autophagy. Herein, we identified that COX7A1 holds a key position in regulating the development and progression of lung cancer by affecting autophagy. Although the crosstalk among COX7A1, PGC‐1α and NOX2 needs further investigation, our study provides a novel insight into the therapeutic action of COX7A1 against human non‐small cell lung cancer.

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

The nuclear factor (erythroid 2)-like (NRF) transcription factors are a subset of cap'n'collar transcriptional regulators. They consist of three members, NRF1, NRF2, and NRF3, that regulate the expression of genes containing antioxidant-response elements (AREs) in their promoter regions. Although all NRF members regulate ARE-containing genes, each is associated with distinct roles. A comprehensive study of differential and overlapping DNA-binding and transcriptional activities of the NRFs has not yet been conducted. Here, we performed chromatin immunoprecipitation (ChIP)-exo sequencing, an approach that combines ChIP with exonuclease treatment to pinpoint regulatory elements in DNA with high precision, in conjunction with RNA-sequencing to define the transcriptional targets of each NRF member. Our approach, done in three U2OS cell lines, identified 31 genes that were regulated by all three NRF members, 27 that were regulated similarly by all three, and four genes that were differentially regulated by at least one NRF member. We also found genes that were up- or down-regulated by only one NRF member, with 84, 84, and 22 genes that were regulated by NRF1, NRF2, and NRF3, respectively. Analysis of the ARE motifs identified in ChIP peaks revealed that NRF2 prefers binding to AREs flanked by GC-rich regions and that NRF1 prefers AT-rich flanking regions. Thus, sequence preference, likely in combination with upstream signaling events, determines NRF member activation under specific cellular contexts. Our analysis provides a comprehensive description of differential and overlapping gene regulation by the transcriptional regulators NRF1, NRF2, and NRF3.

Phytochemical Combination PB125 Activates the Nrf2 Pathway and Induces Cellular Protection against Oxidative Injury

Bioactive phytochemicals in Rosmarinus officinalis, Withania somnifera, and Sophora japonica have a long history of human use to promote health. In this study we examined the cellular effects of a combination of extracts from these plant sources based on specified levels of their carnosol/carnosic acid, withaferin A, and luteolin levels, respectively. Individually, these bioactive compounds have previously been shown to activate the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor, which binds to the antioxidant response element (ARE) and regulates the expression of a wide variety of cytoprotective genes. We found that combinations of these three plant extracts act synergistically to activate the Nrf2 pathway, and we identified an optimized combination of the three agents which we named PB125 for use as a dietary supplement. Using microarray, quantitative reverse transcription-PCR, and RNA-seq technologies, we examined the gene expression induced by PB125 in HepG2 (hepatocellular carcinoma) cells, including canonical Nrf2-regulated genes, noncanonical Nrf2-regulated genes, and genes which appear to be regulated by non-Nrf2 mechanisms. Ingenuity Pathway Analysis identified Nrf2 as the primary pathway for gene expression changes by PB125. Pretreatment with PB125 protected cultured HepG2 cells against an oxidative stress challenge caused by cumene hydroperoxide exposure, by both cell viability and cell injury measurements. In summary, PB125 is a phytochemical dietary supplement comprised of extracts of three ingredients, Rosmarinus officinalis, Withania somnifera, and Sophora japonica, with specified levels of carnosol/carnosic acid, withaferin A, and luteolin, respectively. Each ingredient contributes to the activation of the Nrf2 pathway in unique ways, which leads to upregulation of cytoprotective genes and protection of cells against oxidative stress and supports the use of PB125 as a dietary supplement to promote healthy aging.