Cross Talk in HEK293 Cells Between Nrf2, HIF, and NF-κB Activities upon Challenges with Redox Therapeutics Characterized with Single-Cell Resolution

TRP14 is the rate-limiting enzyme for intracellular cystine reduction and regulates proteome cysteinylation

It has remained unknown how cells reduce cystine taken up from the extracellular space, which is a required step for further utilization of cysteine in key processes such as protein or glutathione synthesis. Here, we show that the thioredoxin-related protein of 14 kDa (TRP14, encoded by TXNDC17) is the rate-limiting enzyme for intracellular cystine reduction. When TRP14 is genetically knocked out, cysteine synthesis through the transsulfuration pathway becomes the major source of cysteine in human cells, and knockout of both pathways becomes lethal in C. elegans subjected to proteotoxic stress. TRP14 can also reduce cysteinyl moieties on proteins, rescuing their activities as here shown with cysteinylated peroxiredoxin 2. Txndc17 knockout mice were, surprisingly, protected in an acute pancreatitis model, concomitant with activation of Nrf2-driven antioxidant pathways and upregulation of transsulfuration. We conclude that TRP14 is the evolutionarily conserved enzyme principally responsible for intracellular cystine reduction in C. elegans, mice, and humans.

Tweaking the NRF2 signaling cascade in human myelogenous leukemia cells by artificial nano-organelles

NRF2 (nuclear factor erythroid-2-related factor 2) is a key regulator of genes involved in the cell's protective response to oxidative stress. Upon activation by disturbed redox homeostasis, NRF2 promotes the expression of metabolic enzymes to eliminate reactive oxygen species (ROS). Cell internalization of peroxisome-like artificial organelles that harbor redox-regulating enzymes was previously shown to reduce ROS-induced stress and thus cell death. However, if and to which extent ROS degradation by such nanocompartments interferes with redox signaling pathways is largely unknown. Here, we advance the design of H2O2-degrading artificial nano-organelles (AnOs) that exposed surface-attached cell penetrating peptides (CPP) for enhanced uptake and were equipped with a fluorescent moiety for rapid visualization within cells. To investigate how such AnOs integrate in cellular redox signaling, we engineered leukemic K562 cells that report on NRF2 activation by increased mCherry expression. Once internalized, ROS-metabolizing AnOs dampen intracellular NRF2 signaling upon oxidative injury by degrading H2O2. Moreover, intracellular AnOs conferred protection against ROSinduced cell death in conditions when endogenous ROS-protection mechanisms have been compromised by depletion of glutathione or knockdown of NRF2. We demonstrate CPP-facilitated AnO uptake and AnO-mediated protection against ROS insults also in the T lymphocyte population of primary peripheral blood mononuclear cells from healthy donors. Overall, our data suggest that intracellular AnOs alleviated cellular stress by the on-site reduction of ROS.

Fundamentals of redox regulation in biology

Oxidation-reduction (redox) reactions are central to the existence of life. Reactive species of oxygen, nitrogen and sulfur mediate redox control of a wide range of essential cellular processes. Yet, excessive levels of oxidants are associated with ageing and many diseases, including cardiological and neurodegenerative diseases, and cancer. Hence, maintaining the fine-tuned steady-state balance of reactive species production and removal is essential. Here, we discuss new insights into the dynamic maintenance of redox homeostasis (that is, redox homeodynamics) and the principles underlying biological redox organization, termed the 'redox code'. We survey how redox changes result in stress responses by hormesis mechanisms, and how the lifelong cumulative exposure to environmental agents, termed the 'exposome', is communicated to cells through redox signals. Better understanding of the molecular and cellular basis of redox biology will guide novel redox medicine approaches aimed at preventing and treating diseases associated with disturbed redox regulation.

Single-Cell Kinetic Modeling of β-Lapachone Metabolism in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) cells are highly heterogeneous in their metabolism and typically experience elevated reactive oxygen species (ROS) levels such as superoxide and hydrogen peroxide (H2O2) in the tumor microenvironment. Tumor cells survive under these chronic oxidative conditions by upregulating antioxidant systems. To investigate the heterogeneity of cellular responses to chemotherapeutic H2O2 generation in tumor and healthy tissue, we leveraged single-cell RNA-sequencing (scRNA-seq) data to perform redox systems-level simulations of quinone-cycling β-lapachone treatment as a source of NQO1-dependent rapid superoxide and hydrogen peroxide (H2O2) production. Transcriptomic data from 10 HNSCC patient tumors was used to populate over 4000 single-cell antioxidant enzymatic network models of drug metabolism. The simulations reflected significant systems-level differences between the redox states of healthy and cancer cells, demonstrating in some patient samples a targetable cancer cell population or in others statistically indistinguishable effects between non-malignant and malignant cells. Subsequent multivariate analyses between healthy and malignant cellular models pointed to distinct contributors of redox responses between these phenotypes. This model framework provides a mechanistic basis for explaining mixed outcomes of NAD(P)H:quinone oxidoreductase 1 (NQO1)-bioactivatable therapeutics despite the tumor specificity of these drugs as defined by NQO1/catalase expression and highlights the role of alternate antioxidant components in dictating drug-induced oxidative stress.

ROS-activated MAPK/ERK pathway regulates crosstalk between Nrf2 and Hif-1α to promote IL-17D expression protecting the intestinal epithelial barrier under hyperoxia

Reactive oxygen species (ROS) damage to the intestinal barrier is a side effect of prolonged hyperoxia therapy in neonates, which impairs growth and development of the intestine and promotes intestinal diseases. However, the research on clinical prevention and treatment is lacking. Therefore, we investigated the molecular mechanisms of the neonate intestinal response against hyperoxia-derived ROS to find targets for intestinal barrier damage prevention. Human intestinal epithelial cells were incubated under hyperoxia (85% oxygen) to build an in vitro model. ROS and the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway were inhibited to detect the MAPK/ERK pathway, nuclear factor erythroid factor 2-related factor 2 (Nrf2), hypoxia-inducible factor-1α (Hif-1α), and interleukin-17D (IL-17D) expression. Nrf2 was inhibited to detect Hif-1α and IL-17D expression. Hif-1α was inhibited to detect Nrf2, IL-17D, and tight junction proteins expression and apoptosis. Cells were treated with human recombinant IL-17D to detect TNF-α, IL-1β, IL-10, and tight junction proteins expression. ROS, Nrf2, Hif-1α, and IL-17D were upregulated and the MAPK/ERK pathway was activated under hyperoxia. But ROS inhibition downregulated the MAPK/ERK pathway, Nrf2, Hif-1α, and IL-17D. MAPK/ERK pathway inhibition downregulated Nrf2, Hif-1α, and IL-17D. Nrf2 inhibition downregulated Hif-1α and IL-17D. Hif-1α inhibition downregulated Nrf2, IL-17D, tight junction proteins, and exacerbated apoptosis. The recombinant IL-17D downregulated TNF-α, IL-1β, but upregulated IL-10 and tight junction proteins. We concluded that Hyperoxia-generated ROS activated the MAPK/ERK pathway to regulate Nrf2, Hif-1α, and IL-17D expression. Nrf2 and Hif-1α were interdependent and promoted IL-17D. Importantly, Hif-1α and IL-17D expression protected the intestinal epithelial barrier.

Appraisal of the Neuroprotective Effect of Dexmedetomidine: A Meta-Analysis

Dexmedetomidine is an adrenergic receptor agonist that has been regarded as neuroprotective in several studies without an objective measure to it. Thus, the aim of this meta-analysis was to analyze and quantify the current evidence for the neuroprotective effects of dexmedetomidine in animals. The search was performed by querying the National Library of Medicine. Studies were included based on their language, significancy of their results, and complete availability of data on animal characteristics and interventions. Risk of bias was assessed using SYRCLE's risk of bias tool and certainty was assessed using the ARRIVE Guidelines 2.0. Synthesis was performed by calculating pooled standardized mean difference and presented in forest plots and tables. The number of eligible records included per outcome is the following: 22 for IL-1β, 13 for IL-6, 19 for apoptosis, 7 for oxidative stress, 7 for Escape Latency, and 4 for Platform Crossings. At the cellular level, dexmedetomidine was found protective against production of IL-1β (standardized mean difference (SMD) =  - 4.3 [- 4.8; - 3.7]) and IL-6 (SMD =  - 5.6 [- 6.7; - 4.6]), apoptosis (measured through TUNEL, SMD =  - 6.0 [- 6.8; - 4.6]), and oxidative stress (measured as MDA production, SMD =  - 2.0 [- 2.4; - 1.4]) exclusively in the central nervous system. At the organism level, dexmedetomidine improved behavioral outcomes measuring escape latency (SMD = - 2.4 [- 3.3; - 1.6]) and number of platform crossings (SMD = 9.1 [- 6.8; - 11.5]). No eligible study had high risk of bias and certainty was satisfactory for reproducibility in all cases. This meta-analysis highlights the complexity of adrenergic stimulation and sheds light into the mechanisms potentiated by dexmedetomidine, which could be exploited for improving current neuroprotective formulations.

Deregulated transcription factors in cancer cell metabolisms and reprogramming

Metabolic reprogramming is an important cancer hallmark that plays a key role in cancer malignancies and therapy resistance. Cancer cells reprogram the metabolic pathways to generate not only energy and building blocks but also produce numerous key signaling metabolites to impact signaling and epigenetic/transcriptional regulation for cancer cell proliferation and survival. A deeper understanding of the mechanisms by which metabolic reprogramming is regulated in cancer may provide potential new strategies for cancer targeting. Recent studies suggest that deregulated transcription factors have been observed in various human cancers and significantly impact metabolism and signaling in cancer. In this review, we highlight the key transcription factors that are involved in metabolic control, dissect the crosstalk between signaling and transcription factors in metabolic reprogramming, and offer therapeutic strategies targeting deregulated transcription factors for cancer treatment.

Suppression of NRF2 Activity by HIF-1α Promotes Fibrosis after Ischemic Acute Kidney Injury

Acute kidney injury (AKI) is a rapid decline in renal function and can occur after ischemia/reperfusion injury (IRI) to the tubular epithelia. The nuclear factor erythroid-2-related factor 2 (NRF2) pathway protects against AKI and AKI-to-chronic kidney disease (CKD) progression, but we previously demonstrated that severe IRI maladaptively reduced NRF2 activity in mice. To understand the mechanism of this response, we subjected C57BL/6J mice to unilateral kidney IRI with ischemia times that were titrated to induce mild to severe injury. Mild IRI increased NRF2 activity and was associated with renal recovery, whereas severe IRI decreased NRF2 activity and led to progressive CKD. Due to these effects of ischemia, we tested the hypothesis that hypoxia-inducible factor-1α (HIF-1α) mediates NRF2 activity. To mimic mild and severe ischemia, we activated HIF-1α in HK-2 cells in nutrient-replete or nutrient-deficient conditions. HIF-1α activation in nutrient-replete conditions enhanced NRF2 nuclear localization and activity. However, in nutrient-deficient conditions, HIF-1α activation suppressed NRF2 nuclear localization and activity. Nuclear localization was rescued with HIF-1α siRNA knockdown. Our results suggest that severe ischemic AKI leads to HIF-1α-mediated suppression of NRF2, leading to AKI-to-CKD progression.

Assessing Bioavailability and Bioactivity of 4-Hydroxythiazolidine-2-Thiones, Newly Discovered Glucosinolate Degradation Products Formed During Domestic Boiling of Cabbage

Glucosinolates are plant secondary metabolites found in cruciferous vegetables (Brassicaceae) that are valued for their potential health benefits. Frequently consumed representatives of these vegetables, for example, are white or red cabbage, which are typically boiled before consumption. Recently, 3-alk(en)yl-4-hydroxythiazolidine-2-thiones were identified as a class of thermal glucosinolate degradation products that are formed during the boiling of cabbage. Since these newly discovered compounds are frequently consumed, this raises questions about their potential uptake and their possible bioactive functions. Therefore, 3-allyl-4-hydroxythiazolidine-2-thione (allyl HTT) and 4-hydroxy-3-(4-(methylsulfinyl) butyl)thiazolidine-2-thione (4-MSOB HTT) as degradation products of the respective glucosinolates sinigrin and glucoraphanin were investigated. After consumption of boiled red cabbage broth, recoveries of consumed amounts of the degradation products in urine collected for 24 h were 18 ± 5% for allyl HTT and 21 ± 4% for 4-MSOB HTT (mean ± SD, n = 3). To investigate the stability of the degradation products during uptake and to elucidate the uptake mechanism, both an in vitro stomach and an in vitro intestinal model were applied. The results indicate that the uptake of allyl HTT and 4-MSOB HTT occurs by passive diffusion. Both compounds show no acute cell toxicity, no antioxidant potential, and no change in NAD(P)H dehydrogenase quinone 1 (NQO1) activity up to 100 μM. However, inhibition of glycogen synthase kinases-3 (GSK-3) in the range of 20% for allyl HTT for the isoform GSK-3β and 29% for 4-MSOB HTT for the isoform GSK-3α at a concentration of 100 μM was found. Neither health-promoting nor toxic effects of 3-alk(en)yl-4-hydroxythiazolidine-2-thiones were found in the four tested assays carried out in this study, which contrasts with the properties of other glucosinolate degradation products, such as isothiocyanates.

Targeting of Nrf2 improves antitumoral responses by human NK cells, TIL and CAR T cells during oxidative stress

Background

Adoptive cell therapy using cytotoxic lymphocytes is an efficient immunotherapy against solid and hematological cancers. However, elevated levels of reactive oxygen species (ROS) in the hostile tumor microenvironment can impair NK cell and T cell function. Auranofin, a gold (I)-containing phosphine compound, is a strong activator of the transcription factor Nrf2. Nrf2 controls a wide range of downstream targets important for the cells to obtain increased resistance to ROS. In this study, we present a strategy using auranofin to render human cytotoxic lymphocytes resistant toward oxidative stress.

Methods

Melanoma patient-derived tumor infiltrating lymphocytes (TIL) and healthy donor-derived NK cells and CD19-directed CAR T cells were pretreated with a low dose of auranofin. Their resistance toward oxidative stress was assessed by measuring antitumoral responses (killing-assay, degranulation/CD107a, cytokine production) and intracellular ROS levels (flow cytometry) in conditions of oxidative stress. To confirm that the effects were Nrf2 dependent, the transcription level of Nrf2-driven target genes was analyzed by qPCR.

Results

Pretreatment of human TIL and NK cells ex vivo with a low-dose auranofin significantly lowered their accumulation of intracellular ROS and preserved their antitumoral activity despite high H₂O₂ levels or monocyte-derived ROS. Furthermore, auranofin pretreatment of CD19 CAR-T cells or TIL increased their elimination of CD19 +tumor cells or autologous tumor spheroids, respectively, especially during ROS exposure. Analysis of Nrf2-driven target genes revealed that the increased resistance against ROS was Nrf2 dependent.

Conclusion

These novel findings suggest that Nrf2 activation in human cytotoxic lymphocytes could be used to enhance the efficacy of adoptive cell therapy.

Plumbagin reduction by thioredoxin reductase 1 possesses synergy effects with GLUT1 inhibitor on KEAP1-mutant NSCLC cells

Thioredoxin reductase 1 (TrxR1 or TXNRD1) is a major enzyme in cellular redox regulation and is considered as a drug target for cancer therapy. Previous studies have reported that plumbagin caused reactive oxygen species (ROS)-dependent apoptosis via inhibiting TrxR1 activity or being reduced by TrxR1, leading to selectively cancer cell death. However, the mechanism of TrxR1-mediated redox cycling of plumbagin is obscure and the evidence for plumbagin targeting TrxR1 is still lacking. Herein, we demonstrated that TrxR1 catalyzed plumbagin reduction in both selenocysteine (Sec)-dependent and independent manners, and its activity relied on the intact N-terminal motif of TrxR1, but a high-efficiency reduction was supported by the C-terminal thiols. During the redox cycling of plumbagin, excessive ROS production was observed coupled with oxygen. Using LC-MS and TrxR1 mutants, we found that the Sec residue of TrxR1 was modified by plumbagin, which converted the enzyme from antioxidant to pro-oxidant. Furthermore, we evaluated the therapeutic potential of plumbagin in non-small cell lung cancer (NSCLC), and found that Kelch-like ECH-associated protein 1 (KEAP1)-mutant NSCLC cells, which possess constitutive nuclear factor erythroid 2-related factor 2 (NRF2) activity, were insensitive to plumbagin; however, inhibition of glucose transporter 1 (GLUT1) by small-molecule BAY-876 or inhibiting glucose-6-phosphate dehydrogenase (G6PD) by 6-aminonicotinamide (6-AN) overcame the plumbagin-resistance of KEAP1-mutant NSCLC cells. Taken together, this study elucidated the pharmacological mechanism of plumbagin by targeting TrxR1 and revealed the synergy effect of plumbagin and BAY-876, which may be helpful for applying naphthoquinone compounds to chemotherapy, particularly for treating KEAP1-mutant NSCLC cells.

Creation of a synthesis-friendly inflammation-inducible promoter suitable for cell therapy

The development of 'smart' cell-based therapeutics requires cells that first recognize conditions consistent with disease (e.g. inflammation) and then subsequently release therapeutic proteins, thereby reducing potential toxicity from otherwise continuous expression. Promoters containing NF-κB response elements are often used as reporters of inflammation; however, endogenous promoters have crosstalk with other pathways, and current synthetic promoters have many exact sequence repeats of NF-κB response elements which make them both difficult to synthesize and inherently genetically unstable. Herein, a synthesis-friendly inflammation-inducible promoter (named SFNp) was created by the packing of 14 NF-κB response elements, which have no repeats >9 bp, followed by a minimal cytomegalovirus promoter. In stably expressing human embryonic kidney 293 cells, we assessed the ability of SFNp to inducibly transcribe genes for reporting expression, changing cell morphology, and performing cell fusion. These experiments represent simple milestones for potentially using SFNp in the development of cell-based therapeutics. As strongly repeated DNA can compromise the long-term stability of genetic circuits, new designs used in 'smart' cell therapy will become more reliant on synthesis-friendly components like SFNp.

Thiol-disulphide independent in-cell trapping for the identification of peroxiredoxin 2 interactors

Hydrogen peroxide (H2O2) acts as a signalling molecule by oxidising cysteine thiols in proteins. Recent evidence has established a role for cytosolic peroxiredoxins in transmitting H2O2-based oxidation to a multitude of target proteins. Moreover, it is becoming clear that peroxiredoxins fulfil their function in organised microdomains, where not all interactors are covalently bound. However, most studies aimed at identifying peroxiredoxin interactors were based on methods that only detect covalently linked partners. Here, we explore the applicability of two thiol-disulphide independent in-cell trapping methodological approaches in combination with mass spectrometry for the identification of interaction partners of peroxiredoxin 2 (Prdx2). The first is biotin-dependent proximity-labelling (BioID) with a biotin ligase A (BirA*)-fused Prdx2, which has never been applied on redox-active proteins. The second is crosslinker co-immunoprecipitation with an N-terminally His-tagged Prdx2. During the initial characterisation of the tagged Prdx2 constructs, we found that the His-tag, but not BirA*, compromises the peroxidase and signalling activities of Prdx2. Further, the Prdx2 interactors identified with each approach showed little overlap. We therefore concluded that BioID is a more reliable method than crosslinker co-immunoprecipitation. After a stringent mass spec data filtering, BioID identified 13 interactors under elevated H2O2 conditions, including subunit five of the COP9 signalosome complex (CSN5). The Prdx2:CSN5 interaction was further confirmed in a proximity ligation assay. Taken together, our results demonstrate that BioID can be used as a method for the identification of interactors of Prdxs, and that caution should be exercised when interpreting protein-protein interaction results using tagged Prdxs.

Thioredoxin 1 is required for stress granule assembly upon arsenite-induced oxidative stress

Arsenic is a major water pollutant and health hazard, leading to acute intoxication and, upon chronic exposure, several diseases including cancer development. Arsenic exerts its pronounced cellular toxicity through its trivalent oxide arsenite (ASN), which directly inhibits numerous proteins including Thioredoxin 1 (Trx1), and causes severe oxidative stress. Cells respond to arsenic by inhibition of protein synthesis and subsequent assembly of stress granules (SGs), cytoplasmic condensates of stalled mRNAs, translation factors and RNA-binding proteins. The biological role of SGs is diverse and not completely understood; they are important for regulation of cell signaling and survival under stress conditions, and for adapting de novo protein synthesis to the protein folding capacity during the recovery from stress. In this study, we identified Trx1 as a novel component of SGs. Trx1 is required for the assembly of ASN-induced SGs, but not for SGs induced by energy deprivation or heat shock. Importantly, our results show that Trx1 is essential for cell survival upon acute exposure to ASN, through a mechanism that is independent of translation inhibition.

Profiling of Primary and Mature miRNA Expression in Atherosclerosis-Associated Cell Types

[Figure: see text].

Source contributions to multiple toxic potentials of atmospheric organic aerosols

Fine particulate matter (PM_2.5) in the atmosphere is of high priority for air quality management efforts to address adverse health effects in human. We believe that emission control policies, which are traditionally guided by source contributions to PM mass, should also consider source contributions to PM health effects or toxicity. In this study, we estimated source contributions to the toxic potentials of organic aerosols (OA) as measured by a series of chemical and in-vitro biological assays and chemical mass balance model. We selected secondary organic aerosols (SOA), vehicles, biomass open burning, and cooking as possible important OA sources. Fine particulate matter samples from these sources and parallel atmospheric samples from diverse locations and seasons in East Asia were collected for the study. The source and atmospheric samples were analyzed for chemical compositions and toxic potentials, i.e. oxidative potential, inflammatory potential, aryl hydrocarbon receptor (AhR) agonist activity, and DNA-damage, were measured. The toxic potentials per organic carbon (OC) differed greatly among source and ambient particulate samples. The source contributions to oxidative and inflammatory potentials were dominated by naphthalene-derived SOA (NapSOA), followed by open burning and vehicle exhaust. The AhR activity was dominated by open burning, followed by vehicle exhaust and NapSOA. The DNA damage was dominated by vehicle exhaust, followed by open burning. Cooking and biogenic SOA had smaller contributions to all the toxic potentials. Regarding atmospheric OA, urban and roadside samples showed stronger toxic potentials per OC. The toxic potentials of remote samples in summer were consistently very weak, suggesting that atmospheric aging over a long time decreased the toxicity. The toxic potentials of the samples from the forest and the experimentally generated biogenic SOA were low, suggesting that toxicity of biogenic primary and secondary particles is relatively low.

Spleen tyrosine kinase regulates crosstalk of hypoxia-inducible factor-1α and nuclear factor (erythroid-derived2)-like 2 for B cell survival

B cells play a major role in regulating disease incidence through various factors, including spleen tyrosine kinase (Syk), which transmits signals to all hematopoietic lineage cells. Hypoxia-inducible factor (HIF)-1α accumulates under hypoxic conditions, which is also oxidative stress to induce nuclear factor (erythroid-derived 2)-like 2 (Nrf2) responsible for gene expression of antioxidant enzymes. In the present study, we investigated whether B cells are regulated by crosstalk of HIF-1α and Nrf2 via reactive oxygen species (ROS)-mediated Syk activation. When B cells were incubated under hypoxic conditions, Syk phosphorylation, HIF-1α, and Nrf2 levels were increased. Hypoxia-inducible results were consistent with CoCl2 treatment, which mimics hypoxic conditions. Cell viability was reduced by the Syk inhibitor BAY 61-3606. Increased Nrf2 levels due to hypoxia or CoCl2 were inhibited by treatment with a HIF inhibitor. Hypoxia- or CoCl2-induced ROS increased HIF-1α and Nrf2 levels, which were attenuated by treatment with N-acetyl-L-cysteine (NAC), a ROS scavenger. HIF-1α levels were reduced in doxycycline-treated shNrf2 cells. Clobetasol propionate, a Nrf2 inhibitor, also inhibited HIF-1α levels induced by hypoxia or CoCl2. ROS-mediated Syk phosphorylation at tyrosine 525/526 was confirmed by treatment with H2O2, hypoxia, and CoCl2, and attenuated with NAC treatment. Inhibition of Syk phosphorylation by BAY 61-3606 is consistent with a decrease in protein HIF-1α and Nrf2 levels. Taken together, HIF-1α levels might control Nrf2 levels and vice versa, and could be associated with Syk phosphorylation in B cells. The results indicate that B cells could be regulated by crosstalk of HIF-1α and Nrf2 through ROS-mediated Syk activation.

Signals of pseudo-starvation unveil the amino acid transporter SLC7A11 as key determinant in the control of Treg cell proliferative potential

Human CD4⁺CD25^hiFOXP3⁺ regulatory T (Treg) cells are key players in the control of immunological self-tolerance and homeostasis. Here, we report that signals of pseudo-starvation reversed human Treg cell in vitro anergy through an integrated transcriptional response, pertaining to proliferation, metabolism, and transmembrane solute carrier transport. At the molecular level, the Treg cell proliferative response was dependent on the induction of the cystine/glutamate antiporter solute carrier (SLC)7A11, whose expression was controlled by the nuclear factor erythroid 2-related factor 2 (NRF2). SLC7A11 induction in Treg cells was impaired in subjects with relapsing-remitting multiple sclerosis (RRMS), an autoimmune disorder associated with reduced Treg cell proliferative capacity. Treatment of RRMS subjects with dimethyl fumarate (DMF) rescued SLC7A11 induction and fully recovered Treg cell expansion. These results suggest a previously unrecognized mechanism that may account for the progressive loss of Treg cells in autoimmunity and unveil SLC7A11 as major target for the rescue of Treg cell proliferation.

Hydrogen sulfide restores cardioprotective effects of remote ischemic preconditioning in aged rats via HIF-1α/Nrf2 signaling pathway

The present study explored the therapeutic potential of hydrogen sulfide (H₂S) in restoring aging-induced loss of cardioprotective effect of remote ischemic preconditioning (RIPC) along with the involvement of signaling pathways. The left hind limb was subjected to four short cycles of ischemia and reperfusion (IR) in young and aged male rats to induce RIPC. The hearts were subjected to IR injury on the Langendorff apparatus after 24 h of RIPC. The measurement of lactate dehydrogenase, creatine kinase and cardiac troponin served to assess the myocardial injury. The levels of H₂S, cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), nuclear factor erythroid 2-related factor 2 (Nrf2), and hypoxia-inducible factor (HIF-1α) were also measured. There was a decrease in cardioprotection in RIPC-subjected old rats in comparison to young rats along with a reduction in the myocardial levels of H₂S, CBS, CSE, HIF-1α, and nuclear: cytoplasmic Nrf2 ratio. Supplementation with sodium hydrogen sulfide (NaHS, an H₂S donor) and l-cysteine (H₂S precursor) restored the cardioprotective actions of RIPC in old hearts. It increased the levels of H₂S, HIF-1α, and Nrf2 ratio without affecting CBS and CSE. YC-1 (HIF-1α antagonist) abolished the effects of NaHS and l-cysteine in RIPC-subjected old rats by decreasing the Nrf2 ratio and HIF-1α levels, without altering H₂S.The late phase of cardioprotection of RIPC involves an increase in the activity of H₂S biosynthetic enzymes, which increases the levels of H₂S to upregulate HIF-1α and Nrf2. H₂S has the potential to restore aging-induced loss of cardioprotective effects of RIPC by upregulating HIF-1α/Nrf2 signaling.

Tubular Numb promotes renal interstitial fibrosis via modulating HIF-1α protein stability

Tubulointerstitial fibrosis is the ultimate common pathway of all manners of chronic kidney disease. We previously demonstrated that specific deletion of Numb in proximal tubular cells (PTCs) prevented G2/M arrest and attenuated renal fibrosis. However, how Numb modulates cell cycle arrest remains unclear. Here, we showed that Numb overexpression significantly increased the protein level of hypoxia-inducible factor-1α (HIF-1α). Numb overexpression-induced G2/M arrest was blocked by silencing endogenous HIF-1α, subsequently downregulated the expression of cyclin G1 which is an atypical cyclin to promote G2/M arrest of PTCs. Further analysis revealed that Numb-augmented HIF-1α protein was blocked by simultaneously overexpressing MDM2. Moreover, silencing Numb decreased TGF-β1-induceded HIF-1α protein expression. While endogenous MDM2 was knocked down this reduction was reversed, indicating that Numb stabilized HIF-1α protein via interfering MDM2-mediated HIF-1α protein degradation. Interestingly, HIF-1α overexpression significantly upregulated the expression of Numb and silencing endogenous HIF-1α blocked CoCl₂ or TGF-β1-induced Numb expression. Chromatin immunoprecipitation (ChIP) assays demonstrated that HIF-1α binded to the promoter region of Numb. This binding was significantly increased by TGF-β1. Collectively, these data indicate that Numb and HIF-1α cooperates to promote G2/M arrest of PTCs, and thus aggravates tubulointerstitial fibrosis. Numb might be a potential target for the therapy of tubulointerstitial fibrosis.

Characterization of More Selective Central Nervous System Nrf2-Activating Novel Vinyl Sulfoximine Compounds Compared to Dimethyl Fumarate

The Nrf2 transcription factor is a key regulator of redox reactions and considered the main target for the multiple sclerosis (MS) drug dimethyl fumarate (DMF). However, exploration of additional Nrf2-activating compounds is motivated, since DMF displays significant off-target effects and has a relatively poor penetrance to the central nervous system (CNS). We de novo synthesized eight vinyl sulfone and sulfoximine compounds (CH-1-CH-8) and evaluated their capacity to activate the transcription factors Nrf2, NFκB, and HIF1 in comparison with DMF using the pTRAF platform. The novel sulfoximine CH-3 was the most promising candidate and selected for further comparison in vivo and later an experimental model for traumatic brain injury (TBI). CH-3 and DMF displayed comparable capacity to activate Nrf2 and downstream transcripts in vitro, but with less off-target effects on HIF1 from CH-3. This was verified in cultured microglia and oligodendrocytes (OLs) and subsequently in vivo in rats. Following TBI, DMF lowered the number of leukocytes in blood and also decreased axonal degeneration. CH-3 preserved or increased the number of pre-myelinating OL. While both CH-3 and DMF activated Nrf2, CH-3 showed less off-target effects and displayed more selective OL associated effects. Further studies with Nrf2-acting compounds are promising candidates to explore potential myelin protective or regenerative effects in demyelinating disorders.

Comprehensive chemical proteomics for target deconvolution of the redox active drug auranofin

Chemical proteomics encompasses novel drug target deconvolution methods in which compound modification is not required. Herein we use Thermal Proteome Profiling, Functional Identification of Target by Expression Proteomics and multiplexed redox proteomics for deconvolution of auranofin targets to aid elucidation of its mechanisms of action. Auranofin (Ridaura®) was approved for treatment of rheumatoid arthritis in 1985. Because several clinical trials are currently ongoing to repurpose auranofin for cancer therapy, comprehensive characterization of its targets and effects in cancer cells is important. Together, our chemical proteomics tools confirmed thioredoxin reductase 1 (TXNRD1, EC:1.8.1.9) as a main auranofin target, with perturbation of oxidoreductase pathways as the top mechanism of drug action. Additional indirect targets included NFKB2 and CHORDC1. Our comprehensive data can be used as a proteomic signature resource for further analyses of the effects of auranofin. Here we also assessed the orthogonality and complementarity of different chemical proteomics methods that can furnish invaluable mechanistic information and thus the approach can facilitate drug discovery efforts in general.

Effects of Mammalian Thioredoxin Reductase Inhibitors

The mammalian thioredoxin system is driven by NADPH through the activities of isoforms of the selenoprotein thioredoxin reductase (TXNRD, TrxR), which in turn help to keep thioredoxins (TXN, Trx) and further downstream targets reduced. Due to a wide range of functions in antioxidant defense, cell proliferation, and redox signaling, strong cellular aberrations are seen upon the targeting of TrxR enzymes by inhibitors. However, such inhibition can nonetheless have rather unexpected consequences. Accumulating data suggest that inhibition of TrxR in normal cells typically yields a paradoxical effect of increased antioxidant defense, with metabolic pathway reprogramming, increased cellular proliferation, and altered cellular differentiation patterns. Conversely, inhibition of TrxR in cancer cells can yield excessive levels of reactive oxygen species (ROS) resulting in cell death and thus anticancer efficacy. The observed increases in antioxidant capacity upon inhibition of TrxR in normal cells are in part dependent upon activation of the Nrf2 transcription factor, while exaggerated ROS levels in cancer cells can be explained by a non-oncogene addiction of cancer cells to TrxR1 due to their increased endogenous production of ROS. These separate consequences of TrxR inhibition can be utilized therapeutically. Importantly, however, a thorough knowledge of the molecular mechanisms underlying effects triggered by TrxR inhibition is crucial for the understanding of therapy outcomes after use of such inhibitors. The mammalian thioredoxin system is driven by thioredoxin reductases (TXNRD, TrxR), which keeps thioredoxins (TXN, Trx) and further downstream targets reduced. In normal cells, inhibition of TrxR yields a paradoxical effect of increased antioxidant defense upon activation of the Nrf2 transcription factor. In cancer cells, however, inhibition of TrxR yields excessive reactive oxygen species (ROS) levels resulting in cell death and thus anticancer efficacy, which can be explained by a non-oncogene addiction of cancer cells to TrxR1 due to their increased endogenous production of ROS. These separate consequences of TrxR inhibition can be utilized therapeutically.

Therapeutic efficacy of dimethyl fumarate in relapsing-remitting multiple sclerosis associates with ROS pathway in monocytes

Dimethyl fumarate (DMF) is a first-line-treatment for relapsing-remitting multiple sclerosis (RRMS). The redox master regulator Nrf2, essential for redox balance, is a target of DMF, but its precise therapeutic mechanisms of action remain elusive. Here we show impact of DMF on circulating monocytes and T cells in a prospective longitudinal RRMS patient cohort. DMF increases the level of oxidized isoprostanes in peripheral blood. Other observed changes, including methylome and transcriptome profiles, occur in monocytes prior to T cells. Importantly, monocyte counts and monocytic ROS increase following DMF and distinguish patients with beneficial treatment-response from non-responders. A single nucleotide polymorphism in the ROS-generating NOX3 gene is associated with beneficial DMF treatment-response. Our data implicate monocyte-derived oxidative processes in autoimmune diseases and their treatment, and identify NOX3 genetic variant, monocyte counts and redox state as parameters potentially useful to inform clinical decisions on DMF therapy of RRMS.

Selenium Deficiency Is Associated with Pro-longevity Mechanisms

Selenium (Se) is an essential trace element because of its presence in selenoproteins in the form of selenocysteine residue. Both Se deficiency, which compromises selenoprotein functions, and excess Se, which is toxic, have been associated with altered redox homeostasis and adverse health conditions. Surprisingly, we found that, although Se deficiency led to a drastic decline in selenoprotein expression, mice subjected to this dietary regimen for their entire life had normal lifespans. To understand the molecular mechanisms involved, we performed systemic analyses at the level of metabolome, transcriptome, and microRNA profiling. These analyses revealed that Se deficiency reduced amino acid levels, elevated mononucleotides, altered metabolism, and activated signaling pathways linked to longevity-related nutrient sensing. The data show that the metabolic control associated with nutrient sensing coordinately responds to suppressed selenoprotein functions, resulting in normal lifespan under Se deficiency.

Molecular pathways in cancer response to photodynamic therapy

This minireview describes the complexity of the molecular mechanisms involved in the tumor response to photodynamic treatment (PDT). Different aspects of reactive oxygen (ROS) and nitrogen species (RNS) induced by PDT will be examined. In particular, we will discuss the effect of ROS and RNS on cell compartments and the main mechanisms of cell death induced by the treatment. Moreover, we will also examine host defense mechanisms as well as resistance to PDT.

Antiproliferative Effects of the Natural Oxadiazine Nocuolin A Are Associated With Impairment of Mitochondrial Oxidative Phosphorylation

Natural products are interesting sources for drug discovery. The natural product oxadiazine Nocuolin A (NocA) was previously isolated from the cyanobacterial strain Nodularia sp. LEGE 06071 and here we examined its cytotoxic effects against different strains of the colon cancer cell line HCT116 and the immortalized epithelial cell line hTERT RPE-1. NocA was cytotoxic against colon cancer cells and immortalized cells under conditions of exponential growth but was only weakly active against non-proliferating immortalized cells. NocA induced apoptosis by mechanism(s) resistant to overexpression of BCL family members. Interestingly, NocA affected viability and induced apoptosis of HCT116 cells grown as multicellular spheroids. Analysis of transcriptome profiles did not match signatures to any known compounds in CMap but indicated stress responses and induction of cell starvation. Evidence for autophagy was observed, and a decrease in various mitochondrial respiration parameter within 1 h of treatment. These results are consistent with previous findings showing that nutritionally compromised cells in spheroids are sensitive to impairment of mitochondrial energy production due to limited metabolic plasticity. We conclude that the antiproliferative effects of NocA are associated with effects on mitochondrial oxidative phosphorylation.

Concerted redox modulation by sulforaphane alleviates diabetes and cardiometabolic syndrome

Diabetes and cardiometabolic disorders such as hypertension and obesity are major risk factors for the development of cardiovascular disease, with a wealth of evidence suggesting that oxidative stress is linked to the initiation and pathogenesis of these disease processes. With yearly increases in the global incidence of cardiovascular diseases (CVD) and diabetes, numerous studies have focused on characterizing whether upregulating antioxidant defenses through exogenous antioxidants (e.g. vitamin E, vitamin C) or activation of endogenous defenses (e.g. the Nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant defense pathway) may be of benefit. The dietary isothiocyanate sulforaphane (SFN) is currently the subject of several clinical trials for a variety of disease states, including the evaluation of its therapeutic potential to ameliorate diabetic and cardiometabolic complications. SFN is a well characterized and potent Nrf2 inducer, however recent studies suggest its protective actions may be in part mediated by its modulation of various pro-inflammatory (e.g. Nuclear factor-kappa B (NFκB)) and metabolic (e.g. Peroxisome Proliferator-Activator Receptor Gamma (PPARγ)) signaling pathways. The focus of this review is to provide a detailed analysis of the known mechanisms by which SFN modulates Nrf2, NFκB and PPARγ signaling and crosstalk and to provide a critical evaluation of the evidence linking these transcriptional pathways with diabetic and cardiometabolic complications and SFN mediated cytoprotection. To allow comparison between rodent and human studies, we discuss the published bioavailability of SFN metabolites achieved in rodents and man in the context of Nrf2, NFκB and PPARγ signaling. Furthermore, we provide an update on the functional outcomes and implicated signaling pathways reported in recent clinical trials with SFN in Type 2 diabetic patients.

The A to Z of modulated cell patterning by mammalian thioredoxin reductases

Mammalian thioredoxin reductases (TrxRs) are selenocysteine-containing proteins (selenoproteins) that propel a large number of functions through reduction of several substrates including the active site disulfide of thioredoxins (Trxs). Well-known enzymatic systems that in turn are supported by Trxs and TrxRs include deoxyribonucleotide synthesis through ribonucleotide reductase, antioxidant defense through peroxiredoxins and methionine sulfoxide reductases, and redox modulation of a number of transcription factors. Although these functions may be essential for cells due to crucial roles in maintenance of cell viability and proliferation, findings during the last decade reveal that mammals have major redundancy in their cellular reductive systems. The synthesis of glutathione (GSH) and reductive functions of GSH-dependent pathways typically act in parallel with Trx-dependent pathways, with only one of these systems often being sufficient to support viability. Importantly, this does not imply that a modulation of the Trx system will remain without consequences, even when GSH-dependent pathways remain functional. As suggested by several recent findings, the Trx system in general and the TrxRs in particular, function as key regulators of signaling pathways. In this review article we will discuss findings that collectively suggest that modulation in mammalian systems of cytosolic TrxR1 (TXNRD1) or mitochondrial TrxR2 (TXNRD2) influence cell patterning and cellular stress responses. Effects of lower activities include increased adipogenesis, insulin responsiveness, glycogen accumulation, hyperproliferation, and distorted embryonic development, while increased activities correlate with decreased proliferation and extended lifespan, as well as worse cancer prognosis. The molecular mechanisms that underlie these diverse effects, involving regulation of protein phosphorylation cascades and of key transcription factors that guide cellular differentiation pathways, will be discussed. We conclude that the selenium-dependent oxidoreductases TrxR1 and TrxR2 should be considered as key components of signaling pathways that control cell differentiation and cellular stress responses.

Cytotoxicity of portoamides in human cancer cells and analysis of the molecular mechanisms of action

Portoamides are cyclic peptides produced and released by the cyanobacterial strain Phormidium sp. presumably to interfere with other organisms in their ecosystems ("allelopathy"). Portoamides were previously demonstrated to have an antiproliferative effect on human lung carcinoma cells, but the underlying mechanism of this activity has not been described. In the present work, the effects of portoamides on proliferation were examined in eight human cancer cell lines and two non-carcinogenic cell lines, and major differences in sensitivities were observed. To generate hypotheses with regard to molecular mechanisms of action, quantitative proteomics using 2D gel electrophoresis and MALDI-TOF/TOF were performed on the colon carcinoma cell line HT-29. The expression of proteins involved in energy metabolism (mitochondrial respiratory chain and pentose phosphate pathway) was found to be affected. The hypothesis of altered energy metabolism was tested in further experiments. Exposure to portoamides resulted in reduced cellular ATP content, likely due to decreased mitochondrial energy production. Mitochondrial hyperpolarization and reduced mitochondrial reductive capacity was observed in treated cells. Furthermore, alterations in the expression of peroxiredoxins (PRDX4, PRDX6) and components of proteasome subunits (PSB4, PSA6) were observed in portoamide-treated cells, but these alterations were not associated with detectable increases in oxidative stress. We conclude that the cytotoxic activity of portoamides is associated with disturbance of energy metabolism, and alterations in mitochondrial structure and function.

Nrf2-Inducers Counteract Neurodegeneration in Frataxin-Silenced Motor Neurons: Disclosing New Therapeutic Targets for Friedreich's Ataxia

Oxidative stress is actively involved in Friedreich's Ataxia (FA), thus pharmacological targeting of the antioxidant machinery may have therapeutic value. Here, we analyzed the relevance of the antioxidant phase II response mediated by the transcription factor Nrf2 on frataxin-deficient cultured motor neurons and on fibroblasts of patients. The in vitro treatment of the potent Nrf2 activator sulforaphane increased Nrf2 protein levels and led to the upregulation of phase II antioxidant enzymes. The neuroprotective effects were accompanied by an increase in neurites' number and extension. Sulforaphane (SFN) is a natural compound of many diets and is now being used in clinical trials for other pathologies. Our results provide morphological and biochemical evidence to endorse a neuroprotective strategy that may have therapeutic relevance for FA. The findings of this work reinforce the crucial importance of Nrf2 in FA and provide a rationale for using Nrf2-inducers as pharmacological agents.

Time- and cell-resolved dynamics of redox-sensitive Nrf2, HIF and NF-κB activities in 3D spheroids enriched for cancer stem cells

Cancer cells have an altered redox status, with changes in intracellular signaling pathways. The knowledge of how such processes are regulated in 3D spheroids, being well-established tumor models, is limited. To approach this question we stably transfected HCT116 cells with a pTRAF reporter that enabled time- and cell-resolved activity monitoring of three redox-regulated transcription factors Nrf2, HIF and NF-κB in spheroids enriched for cancer stem cells. At the first day of spheroid formation, these transcription factors were activated and thereafter became repressed. After about a week, both HIF and Nrf2 were reactivated within the spheroid cores. Further amplifying HIF activation in spheroids by treatment with DMOG resulted in a dominant quiescent stem-cell-like phenotype, with high resistance to stress-inducing treatments. Auranofin, triggering oxidative stress and Nrf2 activation, had opposite effects with increased differentiation and proliferation. These novel high-resolution insights into spatiotemporal activation patterns demonstrate a striking coordination of redox regulated transcription factors within spheroids not occurring in conventional cell culture models.

Sulforaphane Improves Ischemia-Induced Detrusor Overactivity by Downregulating the Enhancement of Associated Endoplasmic Reticulum Stress, Autophagy, and Apoptosis in Rat Bladder

Atherosclerosis-associated pelvic ischemia has been reported to be a risk factor for bladder dysfunction and subsequent lower urinary tract symptoms (LUTS) in the elderly population. However, the molecular mechanisms of this association remain unclear. We hypothesized that stress-induced cellular responses might play a role in the pathogenesis of ischemia-induced bladder dysfunction. In the present study, the animal model of bladder ischemia was induced by bilateral partial arterial occlusion (BPAO) in rats. We found that BPAO significantly induced the presence of detrusor overactivity (DO) and upregulated the expression of several molecular reactions, including biomarkers in endoplasmic reticulum stress (78 kDa glucose-regulated protein, GRP78 and C/EBP-homologous protein, CHOP), autophagy (Beclin-1, p62 and LC3 II) and apoptosis (caspase 3). BPAO also disturbed the Kelch-like ECH-associated protein 1–nuclear factor erythroid-2-related factor 2 (Keap1–Nrf2) pathways. These responses might collectively alter muscarinic and purinergic signaling and contribute to the presence of DO in the ischemic bladder. Therapeutically, treatment with neither a muscarinic nor purinergic receptor antagonist restored bladder function. Interestingly, sulforaphane effectively attenuated ischemia-enhanced endoplasmic reticulum stress, autophagy and apoptosis in the bladder, subsequently ameliorated ischemia-induced bladder dysfunction and might emerge as a novel strategy to protect the bladder against ischemia-induced oxidative damage.

Time in Redox Adaptation Processes: From Evolution to Hormesis

Life on Earth has to adapt to the ever changing environment. For example, due to introduction of oxygen in the atmosphere, an antioxidant network evolved to cope with the exposure to oxygen. The adaptive mechanisms of the antioxidant network, specifically the glutathione (GSH) system, are reviewed with a special focus on the time. The quickest adaptive response to oxidative stress is direct enzyme modification, increasing the GSH levels or activating the GSH-dependent protective enzymes. After several hours, a hormetic response is seen at the transcriptional level by up-regulating Nrf2-mediated expression of enzymes involved in GSH synthesis. In the long run, adaptations occur at the epigenetic and genomic level; for example, the ability to synthesize GSH by phototrophic bacteria. Apparently, in an adaptive hormetic response not only the dose or the compound, but also time, should be considered. This is essential for targeted interventions aimed to prevent diseases by successfully coping with changes in the environment e.g., oxidative stress.

Entinostat up-regulates the CAMP gene encoding LL-37 via activation of STAT3 and HIF-1α transcription factors

Bacterial resistance against classical antibiotics is a growing problem and the development of new antibiotics is limited. Thus, novel alternatives to antibiotics are warranted. Antimicrobial peptides (AMPs) are effector molecules of innate immunity that can be induced by several compounds, including vitamin D and phenyl-butyrate (PBA). Utilizing a luciferase based assay, we recently discovered that the histone deacetylase inhibitor Entinostat is a potent inducer of the CAMP gene encoding the human cathelicidin LL-37. Here we investigate a mechanism for the induction and also find that Entinostat up-regulates human β-defensin 1. Analysis of the CAMP promoter sequence revealed binding sites for the transcription factors STAT3 and HIF-1α. By using short hairpin RNA and selective inhibitors, we found that both transcription factors are involved in Entinostat-induced expression of LL-37. However, only HIF-1α was found to be recruited to the CAMP promoter, suggesting that Entinostat activates STAT3, which promotes transcription of CAMP by increasing the expression of HIF-1α. Finally, we provide in vivo relevance to our findings by showing that Entinostat-elicited LL-37 expression was impaired in macrophages from a patient with a STAT3-mutation. Combined, our findings support a role for STAT3 and HIF-1α in the regulation of LL-37 expression.