Pharmacodynamic characterization of chemopreventive triterpenoids as exceptionally potent inducers of Nrf2-regulated genes

Transcriptional Dynamics of NRF2 Overexpression and KEAP1-NRF2 Inhibitors in Human Cell Line and Primary Lung Cells

Oxidative stress in the human lung is caused by both internal (e.g., inflammation) and external stressors (smoking, pollution, and infection) to drive pathology in a number of lung diseases. Cellular damage caused by oxidative damage is reversed by several pathways, one of which is the antioxidant response. This response is regulated by the transcriptional factor NRF2, which has the ability to regulate the transcription of more than 250 genes. In disease, this balance is overwhelmed, and the cells are unable to return to homeostasis. Several pharmacological approaches aim to improve the antioxidant capacity by inhibiting the interaction of NRF2 with its key cytosolic inhibitor, KEAP1. Here, we evaluate an alternative approach by overexpressing NRF2 from chemically modified RNAs (cmRNAs). Our results demonstrate successful expression of functional NRF2 protein in human cell lines and primary cells. We establish a kinetic transcriptomic profile to compare antioxidant response gene expression after treatment of primary human bronchial epithelial cells with either KEAP1 inhibitors or cmRNAs. The key gene signature is then applied to primary human lung fibroblasts and alveolar macrophages to uncover transcriptional preferences in each cell system. This study provides a foundation for the understanding of NRF2 dynamics in the human lung and provides initial evidence of alternative ways for pharmacological interference.

Glutathione synthesis in the mouse liver supports lipid abundance through NRF2 repression

Cells rely on antioxidants to survive. The most abundant antioxidant is glutathione (GSH). The synthesis of GSH is non-redundantly controlled by the glutamate-cysteine ligase catalytic subunit (GCLC). GSH imbalance is implicated in many diseases, but the requirement for GSH in adult tissues is unclear. To interrogate this, we have developed a series of in vivo models to induce Gclc deletion in adult animals. We find that GSH is essential to lipid abundance in vivo. GSH levels are highest in liver tissue, which is also a hub for lipid production. While the loss of GSH does not cause liver failure, it decreases lipogenic enzyme expression, circulating triglyceride levels, and fat stores. Mechanistically, we find that GSH promotes lipid abundance by repressing NRF2, a transcription factor induced by oxidative stress. These studies identify GSH as a fulcrum in the liver's balance of redox buffering and triglyceride production.

Development of LC-MS/MS method for cyanoenone triterpenoid determination to support CNS tissue distribution study

Aims: Cyanoenone triterpenoids penetrate the CNS, exhibiting biological activity via the nuclear factor E2-related factor (Nrf2) pathway. This is the first report on methods for the quantification of cyanonenone triterpenoids' distribution in various CNS tissues by LC-MS/MS. Materials & methods: The analyte was extracted from brain tissue homogenate using protein precipitation and supported liquid extraction. Results & conclusion: The assay validated a quantification range of 3.00-3000 ng/g in brain tissue samples as low as 5 mg. All parameters, including interference (≤20% at LLOQ) and accuracy/precision (15%, with 20% at LLOQ), met acceptance criteria. This assay supported a CNS distribution study, analyzing more than 10 mouse brain regions successfully.

Investigational new drugs for the treatment of chronic renal failure: an overview of the literature

INTRODUCTION

Chronic kidney disease (CKD) is widespread throughout the world, with a high social and health impact. It is considered a 'silent killer' for its sudden onset without symptoms in the early stages of the disease. The main goal of nephrologists is to slow the progression of kidney disease and treat the associated symptoms with a range of new medications.

AREAS COVERED

The aim of this systematic review is to analyze the new investigational drugs for the treatment of chronic renal failure. Data were obtained from the available scientific literature and from the ClinicalTrials.gov website.

EXPERT OPINION

Among the drugs currently being researched, SGLT2 inhibitors appear to be the most promising drugs for the treatment of CKD, has they have slower progression of CKD and protection of cardiorenal function. An important role in the future of CKD treatment is played by autologous cell-therapy, which appears to be a new frontier in the treatment of CKD. Other therapeutic strategies are currently being investigated and have been shown to slow the progression of CKD. However, further studies are needed to determine whether these approaches may offer benefits in slowing the progression of CKD in the near future.

Regulation of immunomodulatory networks by Nrf2-activation in immune cells: Redox control and therapeutic potential in inflammatory diseases

Inflammatory diseases present a serious health challenge due to their widespread prevalence and the severe impact on patients' lives. In the quest to alleviate the burden of these diseases, nuclear factor erythroid 2-related factor 2 (Nrf2) has emerged as a pivotal player. As a transcription factor intimately involved in cellular defense against metabolic and oxidative stress, Nrf2's role in modulating the inflammatory responses of immune cells has garnered significant attention. Recent findings suggest that Nrf2's ability to alter the redox status of cells underlies its regulatory effects on immune responses. Our review delves into preclinical and clinical evidence that underscores the complex influence of Nrf2 activators on immune cell phenotypes, particularly in the inflammatory milieu. By offering a detailed analysis of Nrf2's role in different immune cell populations, we cast light on the potential of Nrf2 activators in shaping the immune response towards a more regulated state, mitigating the adverse effects of inflammation through modeling redox status of immune cells. Furthermore, we explore the innovative use of nanoencapsulation techniques that enhance the delivery and efficacy of Nrf2 activators, potentially advancing the treatment strategies for inflammatory ailments. We hope this review will stimulate the development and expansion of Nrf2-targeted treatments that could substantially improve outcomes for patients suffering from a broad range of inflammatory diseases.

Effects of NRF2 polymorphisms on safety and efficacy of bardoxolone methyl: subanalysis of TSUBAKI study

BACKGROUND

In the TSUBAKI study, bardoxolone methyl significantly increased measured and estimated glomerular filtration rates (GFR) in patients with multiple forms of chronic kidney disease (CKD), including Japanese patients with type 2 diabetes and stage 3-4 CKD. Since bardoxolone methyl targets the nuclear factor erythroid 2-related factor 2 pathway, this exploratory analysis of the TSUBAKI study investigated the impact of the regulatory single nucleotide polymorphism, rs6721961, on the effects of bardoxolone methyl.

METHODS

Japanese patients aged 20-79 years with type 2 diabetes and stage 3-4 CKD were randomized to bardoxolone methyl 5-15 mg/day (titrated as tolerated) or placebo for 16 weeks. Genotype frequency, clinical characteristics, renal function, and adverse events were primarily assessed.

RESULTS

Of 104 patients (bardoxolone methyl n = 55, placebo n = 49); 57% were genotype C/C, 32% C/A and 12% A/A. The frequency of the A/A genotype was higher among patients with diabetic kidney disease than in the general Japanese population (~ 5%). Measured and estimated GFRs increased from baseline in all genotypes receiving bardoxolone methyl. There were no significant differences between genotypes for safety parameters, including blood pressure, bodyweight, and levels of B-type natriuretic peptide, or in the type and frequency of adverse events, suggesting that the efficacy and safety of bardoxolone methyl are unaffected by the rs6721961 polymorphism-617 (C→A) genotype.

CONCLUSIONS

Our approach of combining genome analysis with clinical trials for an investigational drug provides important and useful clues for exploring the efficacy and safety of the drug.

TRIAL REGISTRATION

ClinicalTrials.gov; NCT02316821.

Aflatoxin B1 induces infertility, fetal deformities, and potential therapies

Aflatoxin B1 (AFB1) is a subsidiary poisonous metabolite, archetypally spawned by Aspergillus flavus and A. parasiticus, which are often isolated in warm or tropical countries across the world. AFB1 is capable of disrupting the functioning of several reproductive endocrine glands by interrupting the enzymes and their substrates that are liable for the synthesis of various hormones in both males and females. In men, AFB1 is capable of hindering testicular development, testicular degeneration, and reduces reproductive capabilities. In women, a direct antagonistic interaction of AFB1 with steroid hormone receptors influencing gonadal hormone production of estrogen and progesterone was responsible for AFB1-associated infertility. AFB1 is potentially teratogenic and is responsible for the development of malformation in humans and animals. Soft-tissue anomalies such as internal hydrocephalus, microphthalmia, cardiac defects, augmented liver lobes, reproductive changes, immune modifications, behavioral changes and predisposition of animals and humans to neoplasm development are AFB1-associated anomalies. Substances such as esculin, selenium, gynandra extract, vitamins C and E, oltipraz, and CDDO-Im are potential therapies for AFB1. Thus, this review elucidates the pivotal pathogenic roles of AFB1 in infertility, fetal deformities, and potential therapies because AFB1 toxicity is a key problem globally.

Molecular docking, synthesis, characteristics and preliminary cytotoxic study of new coumarin-sulfonamide derivatives as histone deacetylase inhibitors

OBJECTIVE

Aim: To evaluate the cytotoxic activity of newly synthesized a series of novel HDAC inhibitors comprising sulfonamide as zinc binding group and Coumarin as cap groups.

PATIENTS AND METHODS

Materials and Methods: The utilization of sulfonamide as zinc binding group and Coumarin as cap groups known to possess antitumor activity in the designed of new histone deacetylase inhibitors and using the docking and MTT assay to evaluate the compounds.

RESULTS

Results: Four compounds have been synthesized and characterized successfully by ART-FTIR, NMR and ESI-Ms. The synthesized compound assessed for their cytotoxic activity against hepatoblastoma HepG2 (IC50, I=0.094, II=0.040, III=0.032, IV=0.046, SAHA=0.141) and human colon adenocarcinoma MCF-7 (IC50, I=0.135, II=0.050, III= 0.065, IV=0.059, SAHA=0.107). The binding mode to the active site of [HDAC6] were determined by docking study which give results that they might be good inhibitors for [HDAC6].

CONCLUSION

Conclusions: The synthesized compounds (I, II, III and IV) showed a comparable cytotoxic result with FDA approved drug (SAHA) toward HepG2 and MCF-7 cancer cell lines and their docking analysis provided a preliminary indication that they are viable [HDAC6] candidates.

Bardoxolone methyl inhibits the infection of rabies virus via Nrf2 pathway activation in vitro

BACKGROUND

Rabies is a widespread, fatal, infectious disease. Several antivirals against rabies virus (RABV) infection have been reported, but no approved, RABV-specific antiviral drugs that inhibit RABV infection in the clinic after symptom onset are available. Therefore, more effective drugs to reduce rabies fatalities are urgently needed. Bardoxolone methyl (CDDO-Me), an FDA-approved compound that has long been known as an antioxidant inflammatory modulator and one of the most potent nuclear factor erythroid-derived 2-like 2 (Nrf2) activators, protects myelin, axons, and CNS neurons by Nrf2 activation. Therefore, we investigated the potency of its anti-RABV activity in vitro.

METHODS

The mouse neuroblastoma cell line Neuro2a (N2a) and three RABV strains of different virulence were used; the cytotoxicity and anti-RABV activity of CDDO-Me in N2a cells were evaluated by CCK-8 assay and direct fluorescent antibody (DFA) assay. Pathway activation in N2a cells infected with the RABV strains SC16, CVS-11 or CTN upon CDDO-Me treatment was evaluated by western blotting (WB) and DFA assay.

RESULTS

CDDO-Me significantly inhibited infection of the three RABV strains of differing virulence (SC16, CVS-11 and CTN) in N2a cells. We also examined whether CDDO-Me activates the Nrf2-associated pathway upon infection with RABV strains of differing virulence. Nrf2, phosphorylated sequestosome (SQSTM1), SQSTM1, hemoglobin oxygenase (HO-1) and NAD(P)H dehydrogenase quinone 1 (NQO1) expression in N2a cells increased to varying degrees with CDDO-Me treatment, accompanied by Kelch-like ECH-associated protein 1 (Keap1) dissociation, upon infection with SC16, CVS-11 or CTN. The activation of SQSTM1 phosphorylation was significantly associated with the degradation of Keap-1 in CDDO-Me-treated N2a cells upon RABV infection. Furthermore, N2a cells pretreated with the Nrf2-specific inhibitor ATRA showed a significant decrease in HO-1 and NQO1 expression and a decrease in the anti-RABV efficacy of CDDO-Me. These inhibitory effects were observed upon infection with three RABV strains of differing virulence.

CONCLUSION

CDDO-Me inhibited RABV infection via Nrf2 activation, promoting a cytoprotective defense response in N2a cells. Our study provides a therapeutic strategy for RABV inhibition and neuroprotection during viral infection.

Discovery of a novel OGT inhibitor through high-throughput screening based on Homogeneous Time-Resolved Fluorescence (HTRF)

O-GlcNAcylation is a specific type of post-translational glycosylation modification, which is regulated by two enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Aberrant overexpression of OGT is associated with the development of many solid tumors. In this study, we have developed and optimized a sensitive Homogeneous Time-Resolved Fluorescence (HTRF) assay then identified a novel OGT inhibitor CDDO (also called Bardoxolone) through a high-throughput screening (HTS) based on HTRF assay. Further characterization suggested that CDDO is an effective OGT inhibitor with an IC50 value of 6.56 ± 1.69 μM. CPMG-NMR analysis confirmed that CDDO is a direct binder of OGT with a binding affinity (Kd) of approximately 1.7 μM determined by the MST analysis. Moreover, HDX-MS analysis indicated that CDDO binds to the TPR domain and N-Terminal domain of OGT, which was further confirmed by the enzymatic competition experiments as the binding of CDDO to OGT was not affected by the catalytic site binding inhibitor OSMI-4. Our docking modeling analysis further predicted the possible interactions between CDDO and OGT, providing informative molecular basis for further optimization of the inhibitor in the future. Together, our results suggested CDDO is a new inhibitor of OGT with a distinct binding pocket from the reported OGT inhibitors. Our work paved a new direction for developing OGT inhibitors driven by novel mechanisms.

Nrf2 activation improves experimental rheumatoid arthritis

Rheumatoid arthritis is a systemic autoimmune disease with pain and functional disorder of joints. Multiple strategies toward treatment of the rheumatoid arthritis are operating, while there are concerns of serious adverse effects of the therapeutic drugs. Here, we show that activation of Nrf2 (Nuclear factor erythroid 2-related factor 2) efficiently improves arthritis of SKG mice, which develop T cell-mediated autoimmune arthritis by zymosan A injection. We found that genetic Nrf2 activation by knockdown of Keap1 (Kelch-like ECH-associated protein 1), a negative regulator of Nrf2, repressed arthritis by inhibiting the expression of pro-inflammatory cytokines and inducing the expression of antioxidant enzymes in SKG mice. In addition, oral administration of CDDO-Im, a representative chemical inducer of Nrf2, had effects of both prevention and treatment toward arthritis of SKG mice in an Nrf2-dependent manner. We also found that Nrf2 activation through myeloid-cell lineage-specific Keap1 disruption did not achieve significant improvement in the arthritis of SKG mice. In contrast, expressions of pro-inflammatory cytokine genes were decreased, and those of antioxidant enzyme genes were increased in fibroblast-like synoviocytes (FLS) isolated from SKG mouse. Our results thus demonstrate that Nrf2 activation exerts marked anti-arthritis effects in the SKG experimental rheumatoid arthritis model mice, supporting the contention that the Nrf2 activation is a new therapeutic strategy for the rheumatoid arthritis.

CRISPR/Cas9-Based Screening of FDA-Approved Drugs for NRF2 Activation: A Novel Approach to Discover Therapeutics for Non-Alcoholic Fatty Liver Disease

With the rising prevalence of obesity, non-alcoholic fatty liver disease (NAFLD) now affects 20-25% of the global population. NAFLD, a progressive condition associated with oxidative stress, can result in cirrhosis and liver cancer in 10% and 3% of patients suffering NAFLD, respectively. Therapeutic options are currently limited, emphasizing the need for novel treatments. In this study, we examined the potential of activating the transcription factor NRF2, a crucial player in combating oxidative stress, as an innovative approach to treating NAFLD. Utilizing a CRISPR/Cas9-engineered human HEK293T cell line, we were able to monitor the expression of heme oxygenase-1 (HMOX1), an NRF2 target, using a Nanoluc luciferase tag. Our model was validated using a known NRF2 activator, after which we screened 1200 FDA-approved drugs, unearthing six compounds (Disulfiram, Thiostrepton, Auranofin, Thimerosal, Halofantrine, and Vorinostat) that enhanced NRF2 activity and antioxidant response. These compounds demonstrated protective effects against oxidative stress induced by hydrogen peroxide and lipid droplets accumulation in vitro with hepatoma HUH-7 cells. Our study underscores the utility of CRISPR/Cas9 tagging with Nanoluc luciferase in identifying potential NRF2 activators, paving the way for potential NAFLD therapeutics.

Analgesic Effects of Fisetin, Peimine, Astaxanthin, Artemisinin, Bardoxolone Methyl and 740 Y-P and Their Influence on Opioid Analgesia in a Mouse Model of Neuropathic Pain

Treatment of neuropathic pain remains a challenge for modern medicine due to the insufficiently understood molecular mechanisms of its development and maintenance. One of the most important cascades that modulate the nociceptive response is the family of mitogen-activated protein (MAP) kinases and phosphatidylinositol-3-kinase (PI3K), as well as nuclear factor erythroid 2-related factor 2 (Nrf2). The aim of this study was to determine the effect of nonselective modulators of MAP kinases-fisetin (ERK1/2 and NFκB inhibitor, PI3K activator), peimine (MAPK inhibitor), astaxanthin (MAPK inhibitor, Nrf2 activator) and artemisinin (MAPK inhibitor, NFκB activator), as well as bardoxolone methyl (selective activator of Nrf2) and 740 Y-P (selective activator of PI3K)-in mice with peripheral neuropathy and to compare their antinociceptive potency and examine their effect on analgesia induced by opioids. The study was performed using albino Swiss male mice that were exposed to chronic constriction injury of the sciatic nerve (CCI model). Tactile and thermal hypersensitivity was measured using von Frey and cold plate tests, respectively. Single doses of substances were administered intrathecally on day 7 after CCI. Among the tested substances, fisetin, peimine, and astaxanthin effectively diminished tactile and thermal hypersensitivity in mice after CCI, while artemisinin did not exhibit analgesic potency in this model of neuropathic pain. Additionally, both of the activators tested, bardoxolone methyl and 740 Y-P, also showed analgesic effects after intrathecal administration in mice exposed to CCI. In the case of astaxanthin and bardoxolone methyl, an increase in analgesia after combined administration with morphine, buprenorphine, and/or oxycodone was observed. Fisetin and peimine induced a similar effect on tactile hypersensitivity, where analgesia was enhanced after administration of morphine or oxycodone. In the case of 740 Y-P, the effects of combined administration with each opioid were observed only in the case of thermal hypersensitivity. The results of our research clearly indicate that substances that inhibit all three MAPKs provide pain relief and improve opioid effectiveness, especially if they additionally block NF-κB, such as peimine, inhibit NF-κB and activate PI3K, such as fisetin, or activate Nrf2, such as astaxanthin. In light of our research, Nrf2 activation appears to be particularly beneficial. The abovementioned substances bring promising results, and further research on them will broaden our knowledge regarding the mechanisms of neuropathy and perhaps contribute to the development of more effective therapy in the future.

The Triterpenoid Nrf2 Activator, CDDO-Me, Decreases Neutrophil Senescence in a Murine Model of Joint Damage

The synthetic 2-cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me) is a potent activator of the erythroid 2-p45-derived factor 2, Nrf2, a leucine-zipper regulator of the antioxidant response. Herein, we investigated the effect of CDDO-Me on neutrophil function in a murine model of joint damage. Collagenase-induced osteoarthritis (CIOA) was initiated by the intra-articular injection of collagenase in the knee-joint cavity of Balb/c mice. CDDO-Me was administrated intra-articularly twice a week starting at day 7 post-CIOA, and its effect was evaluated at day 14. Neutrophils in blood and bone marrow (BM), cell apoptosis, necrosis, expression of C-X-C chemokine receptor 4 (CXCR4), beta-galactosidase (β-Gal), and Nrf2 levels were measured by flow cytometry. In vitro, CDDO-Me promoted cell survival, reduced cell necrosis, and increased Nrf2 levels by 1.6 times. It decreased surface CXCR4 expression and reduced the frequency of senescent β-Gal+CXCR4+ neutrophils by three times. In vivo, the degree of knee-joint damage in CIOA was correlated with upregulated CXCR4 on CD11b+ neutrophils. CDDO-Me improved the disease histological score, increased the levels of Nrf2, and downregulated surface CXCR4 on mature BM cells. Our data suggest that CDDO-Me may act as a potent regulator of neutrophil senescence during the progression of knee-joint damage.

Development of Moringa oleifera as functional food targeting NRF2 signaling: antioxidant and anti-inflammatory activity in experimental model systems

Pharmacological activation of nuclear factor erythroid 2 related factor 2 (NRF2) provides protection against several environmental diseases by inhibiting oxidative and inflammatory injury. Besides high in protein and minerals, Moringa oleifera leaves contain several bioactive compounds, predominantly isothiocyanate moringin and polyphenols, which are potent inducers of NRF2. Hence, M. oleifera leaves represent a valuable food source that could be developed as a functional food for targeting NRF2 signaling. In the current study, we have developed a palatable M. oleifera leaf preparation (henceforth referred as ME-D) that showed reproducibly a high potential to activate NRF2. Treatment of BEAS-2B cells with ME-D significantly increased NRF2-regulated antioxidant genes (NQO1, HMOX1) and total GSH levels. In the presence of brusatol (a NRF2 inhibitor), ME-D-induced increase in NQO1 expression was significantly diminished. Pre-treatment of cells with ME-D mitigated reactive oxygen species, lipid peroxidation and cytotoxicity induced by pro-oxidants. Furthermore, ME-D pre-treatment markedly inhibited nitric oxide production, secretory IL-6 and TNF-α levels, and transcriptional expression of Nos2, Il-6, and Tnf-α in macrophages exposed to lipopolysaccharide. Biochemical profiling by LC-HRMS revealed glucomoringin, moringin, and several polyphenols in ME-D. Oral administration of ME-D significantly increased NRF2-regulated antioxidant genes in the small intestine, liver, and lungs. Lastly, prophylactic administration of ME-D significantly mitigated lung inflammation in mice exposed to particulate matter for 3-days or 3-months. In conclusion, we have developed a pharmacologically active standardized palatable preparation of M. oleifera leaves as a functional food to activate NRF2 signaling, which can be consumed as a beverage (hot soup) or freeze-dried powder for reducing the risk from environmental respiratory disease.

Cell Rearrangement and Oxidant/Antioxidant Imbalance in Huntington's Disease

Huntington's Disease (HD) is a hereditary neurodegenerative disorder caused by the expansion of a CAG triplet repeat in the HTT gene, resulting in the production of an aberrant huntingtin (Htt) protein. The mutant protein accumulation is responsible for neuronal dysfunction and cell death. This is due to the involvement of oxidative damage, excitotoxicity, inflammation, and mitochondrial impairment. Neurons naturally adapt to bioenergetic alteration and oxidative stress in physiological conditions. However, this dynamic system is compromised when a neurodegenerative disorder occurs, resulting in changes in metabolism, alteration in calcium signaling, and impaired substrates transport. Thus, the aim of this review is to provide an overview of the cell's answer to the stress induced by HD, focusing on the role of oxidative stress and its balance with the antioxidant system.

The Complex Genetic and Epigenetic Regulation of the Nrf2 Pathways: A Review

Nrf2 is a major transcription factor that significantly regulates-directly or indirectly-more than 2000 genes. While many of these genes are involved in maintaining redox balance, others are involved in maintaining balance among metabolic pathways that are seemingly unrelated to oxidative stress. In the past 25 years, the number of factors involved in the activation, nuclear translocation, and deactivation of Nrf2 has continued to expand. The purpose of this review is to provide an overview of the remarkable complexity of the tortuous sequence of stop-and-go signals that not only regulate expression or repression, but may also modify transcriptional intensity as well as the specificity of promoter recognition, allowing fluidity of its gene expression profile depending on the various structural modifications the transcription factor encounters on its journey to the DNA. At present, more than 45 control points have been identified, many of which represent sites of action of the so-called Nrf2 activators. The complexity of the pathway and the synergistic interplay among combinations of control points help to explain the potential advantages seen with phytochemical compositions that simultaneously target multiple control points, compared to the traditional pharmaceutical paradigm of "one-drug, one-target".

Antioxidant Phytochemicals as Potential Therapy for Diabetic Complications

The global prevalence of diabetes continues to increase partly due to rapid urbanization and an increase in the aging population. Consequently, this is associated with a parallel increase in the prevalence of diabetic vascular complications which significantly worsen the burden of diabetes. For these diabetic vascular complications, there is still an unmet need for safe and effective alternative/adjuvant therapeutic interventions. There is also an increasing urge for therapeutic options to come from natural products such as plants. Hyperglycemia-induced oxidative stress is central to the development of diabetes and diabetic complications. Furthermore, oxidative stress-induced inflammation and insulin resistance are central to endothelial damage and the progression of diabetic complications. Human and animal studies have shown that polyphenols could reduce oxidative stress, hyperglycemia, and prevent diabetic complications including diabetic retinopathy, diabetic nephropathy, and diabetic peripheral neuropathy. Part of the therapeutic effects of polyphenols is attributed to their modulatory effect on endogenous antioxidant systems. This review attempts to summarize the established effects of polyphenols on endogenous antioxidant systems from the literature. Moreover, potential therapeutic strategies for harnessing the potential benefits of polyphenols for diabetic vascular complications are also discussed.

Nrf2 Pathway in Huntington's Disease (HD): What Is Its Role?

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease that occurs worldwide. Despite some progress in understanding the onset of HD, drugs that block or delay symptoms are still not available. In recent years, many treatments have been proposed; among them, nuclear transcriptional factor-2 (Nrf2) enhancer compounds have been proposed as potential therapeutic agents to treat HD. Nrf2 triggers an endogenous antioxidant pathway activated in different neurodegenerative disorders. Probably, the stimulation of Nrf2 during either the early phase or before HD symptoms' onset, could slow or prevent striatum degeneration. In this review, we present the scientific literature supporting the role of Nrf2 in HD and the potential prophylactic and therapeutic role of this compound.

Applications of covalent chemistry in targeted protein degradation

Proteolysis-targeting chimeras (PROTACs) and targeted covalent inhibitors (TCIs) are currently two exciting strategies in the fields of chemical biology and drug discovery. Extensive research in these two fields has been conducted, and significant progress in these fields has resulted in many clinical candidates, some of which have been approved by FDA. Recently, a novel concept termed covalent PROTACs that combine these two strategies has emerged and gained an increasing interest in the past several years. Herein, we briefly review and highlight the mechanism and advantages of TCIs and PROTACs, respectively, and the recent development of covalent PROTACs using irreversible and reversible covalent chemistry.

Sex differences in resilience to ferroptosis underlie sexual dimorphism in kidney injury and repair

In both humans and mice, repair of acute kidney injury is worse in males than in females. Here, we provide evidence that this sexual dimorphism results from sex differences in ferroptosis, an iron-dependent, lipid-peroxidation-driven regulated cell death. Using genetic and single-cell transcriptomic approaches in mice, we report that female sex confers striking protection against ferroptosis, which was experimentally induced in proximal tubular (PT) cells by deleting glutathione peroxidase 4 (Gpx4). Single-cell transcriptomic analyses further identify the NFE2-related factor 2 (NRF2) antioxidant protective pathway as a female resilience mechanism against ferroptosis. Genetic inhibition and pharmacological activation studies show that NRF2 controls PT cell fate and plasticity by regulating ferroptosis. Importantly, pharmacological NRF2 activation protects male PT cells from ferroptosis and improves cellular plasticity as in females. Our data highlight NRF2 as a potential therapeutic target to prevent failed renal repair after acute kidney injury in both sexes by modulating cellular plasticity.

DNA Methylome and Transcriptome Study of Triterpenoid CDDO in TPA-Mediated Skin Carcinogenesis Model

Overexposure to ultraviolet radiation and environmental carcinogens drive skin cancer development through redox imbalance and gene mutation. Antioxidants such as triterpenoids have exhibited anti-oxidative and anti-inflammatory potentials to alleviate skin carcinogenesis. This study investigated the methylome and transcriptome altered by tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) or TPA with 2-cyano 2,3-dioxoolean-1,9-dien-28-oic acid (CDDO). The results show that CDDO blocks TPA-induced transformation dose dependently. Several differential expressed genes (DEGs) involved in skin cell transformation, while counteracted by CDDO, were revealed by differential expression analysis including Lyl1, Lad1, and Dennd2d. In CpG methylomic profiles, the differentially methylated regions (DMRs) in the promoter region altered by TPA while showing the opposite methylation status in the CDDO treatment group were identified. The correlation between DNA methylation and RNA expression has been established and DMRs showing inverse correlation were further studied as potential therapeutic targets. From the CpG methylome and transcriptome results, CDDO significantly restored gene expression of NAD(P)H:quinone oxidoreductase 1 (Nqo1) inhibited by TPA by decreasing their promoter CpG methylation. Ingenuity Pathways Analysis (IPA) shows that CDDO neutralized the effect of TPA through modulating cell cycles, cell migration, and inflammatory and immune response regulatory pathways. Notably, Tumor Necrosis Factor Receptor 2 (TNFR2) signaling was significantly downregulated by CDDO potentially contributing to prevention of TPA-induced cell transformation. Overall, incorporating the transcriptome, CpG methylome, and signaling pathway network, we reveal potential therapeutic targets and pathways by which CDDO could reverse TPA-induced carcinogenesis. The results could be useful for future human study and targets development for skin cancer.

Activation of Nrf2 to Optimise Immune Responses to Intracerebral Haemorrhage

Haemorrhage into the brain parenchyma can be devastating. This manifests as spontaneous intracerebral haemorrhage (ICH) after head trauma, and in the context of vascular dementia. Randomised controlled trials have not reliably shown that haemostatic treatments aimed at limiting ICH haematoma expansion and surgical approaches to reducing haematoma volume are effective. Consequently, treatments to modulate the pathophysiological responses to ICH, which may cause secondary brain injury, are appealing. Following ICH, microglia and monocyte derived cells are recruited to the peri-haematomal environment where they phagocytose haematoma breakdown products and secrete inflammatory cytokines, which may trigger both protective and harmful responses. The transcription factor Nrf2, is activated by oxidative stress, is highly expressed by central nervous system microglia and macroglia. When active, Nrf2 induces a transcriptional programme characterised by increased expression of antioxidant, haem and heavy metal detoxification and proteostasis genes, as well as suppression of proinflammatory factors. Therefore, Nrf2 activation may facilitate adaptive-protective immune cell responses to ICH by boosting resistance to oxidative stress and heavy metal toxicity, whilst limiting harmful inflammatory signalling, which can contribute to further blood brain barrier dysfunction and cerebral oedema. In this review, we consider the responses of immune cells to ICH and how these might be modulated by Nrf2 activation. Finally, we propose potential therapeutic strategies to harness Nrf2 to improve the outcomes of patients with ICH.

Randomized, double-blind, placebo-controlled phase 3 study of bardoxolone methyl in patients with diabetic kidney disease: Design and baseline characteristics of AYAME study

BACKGROUND

Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease (ESKD), but currently available treatments do not improve kidney function or prevent the initiation of dialysis/kidney replacement therapy. A previous study demonstrated that bardoxolone methyl improves the estimated glomerular filtration rate (eGFR), but the study was prematurely terminated because of an imbalance in heart failure between treatment groups. The subsequent phase 2 TSUBAKI study demonstrated no incidence of heart failure and an improved eGFR and GFR as determined by inulin clearance in DKD patients.

METHODS

This randomized, double-blind, placebo-controlled multicenter phase 3 study was designed to assess the efficacy and safety of bardoxolone methyl in DKD patients with an eGFR of ≥ 15.0 to < 60.0 mL/min/1.73 m2 and urinary albumin/creatinine ratio of ≤3500 mg/g but without risk factors for heart failure. The primary endpoint is the time to onset of a ≥ 30% decrease in the eGFR or ESKD. Randomized patients (1:1) have been under treatment with once-daily oral bardoxolone methyl (5, 10, or 15 mg by intra-patient dose adjustment) or placebo for at least 3 years. Results The 1013 patients' mean age is 65.9 years, 21.5% are female, the mean eGFR is 37.84 mL/min/1.73 m2, and the median urinary albumin/creatinine ratio is 351.80 mg/g.

CONCLUSIONS

Appropriate patients are enrolled in this study. This study will investigate the long-term efficacy and safety of bardoxolone methyl in DKD patients covering a wider range of the eGFR (≥15.0 to < 60.0 mL/min/1.73 m2) and albuminuria (≤3500 mg/g) compared with previous studies.

Pharmacological characterization of a novel peptide inhibitor of the Keap1-Nrf2 protein-protein interaction

LAS200813 is a novel bicyclic lipopeptide that activates Nrf2 by binding to Keap1, thereby antagonising the Keap1-Nrf2 protein-protein interaction. In this work we report the pharmacological characterization of LAS200813 in Nrf2-dependent translational preclinical models. LAS200813 binds to Keap1 with high affinity (IC₅₀: 0.73 nM) and is able to induce the translocation of Nrf2 to the nucleus. Furthermore, LAS200813 increases the expression of Nrf2 target genes in human bronchial epithelial cells (EC₅₀ of 96 and 70 nM for srxn1 and nqo1, respectively). Similarly, the intratracheal administration of LAS200813 to rats increases the expression of Nrf2-dependent genes in lung tissue, an effect that lasts for a few hours. Moreover, in cells exposed to cigarette smoke, LAS200813 shows an antioxidant effect by increasing the production of glutathione and prevents cellular apoptosis. In conclusion, the results described herein demonstrate that LAS200813 is a potent non-electrophilic Nrf2-activating peptide designed to be administered by inhaled route which may be a potential therapeutic strategy for respiratory diseases driven by oxidative stress.

NRF2 is a critical regulator and therapeutic target of metal implant particle-incurred bone damage

Aseptic metal implant loosening due to wear particle-induced bone damage is a major complication of total joint arthroplasty often leading to revision surgery, of which the key regulators mediating the processes are not clearly defined. Here we reported that in a mouse model of calvarial osteolysis, titanium particles (TiPs) and cobalt-chromium-molybdenum particles induced severe osteolysis accompanied by marked suppression of a master redox transcriptional factor NRF2 (Nuclear factor erythroid derived 2-related factor 2). Nfe2l2 knockout mice treated with TiPs developed worse osteolytic alterations compared with wild-type mice. On the contrary, NRF2 restoration by an NRF2 agonist TBHQ (tert-butylhydroquinone) effectively alleviated the osteolysis and the abnormal expression of NRF2 downstream antioxidant enzymes, inflammatory cytokines and osteogenic factors. Further, TiPs induced adverse osteoblastogenesis and osteoclastogenesis in cultured bone cells, which were substantially blocked by TBHQ in an NRF2 inhibition-sensitive manner. Consistently, the osteoprotective effects of TBHQ observed in wild-type mice were largely limited in Nfe2l2 knockout mice. Collectively, our data suggest that NRF2 suppression is a critical causal event of metal wear particle-incurred osteolysis, and the strategies reinstating NRF2 are effective to lessen the bone damage and potentially reduce the incidence of metal implant loosening.

Conjugates of Lupane Triterpenoids with Arylpyrimidines: Synthesis and Anti-inflammatory Activity

Semisynthetic triterpenoid betulonic acid is of significant interest due to its biological activity and synthetic application. In this study, we report the synthesis of hybrid compounds, containing betulonic acid carboxamide and arylpyrimidine fragments. A total of 15 conjugates were prepared using the cyclocondensation reaction of new terpenoid alkynyl ketones with amidinium salts. The main synthetic approach to betulonic acid amide-derived alkynylketones was based on the cross-coupling reaction of N-(4-ethynylphenyl)- or N-(2-(4-ethynylphenyl)-1-(methoxycarbonyl)ethyl)- substituted betulonic acid carboxamide with aroylchlorides. Cyclocondensation of alkynones with amidine or guanidine hydrochlorides by reflux in MeCN in the presence of K₂CO₃ led to the formation of terpenoid pyrimidine hybrids in 52-89% isolated yield. Anti-inflammatory properties of new type of triterpenoid-pyrimidine conjugates were studied using the histamine- and concanavalin A- induced mouse paw edema models. In a model of acute inflammation betulonic acid amide-arylpyrimidines containing a 4-fluorophenyl substituent at the C-6 position of pyrimidine ring exhibited significant and selective anti-inflammatory activity. Compounds containing the 4-bromophenyl- substituent in the pyrimidine ring revealed selective anti-inflammatory activity in the model of immunogenic inflammation (concanavalin-A model). It should be noted that the methoxycarbonyl substituted ethane link between pharmacophore ligands (betulonic acid carboxamide and arylpyrimidine) has a significant effect on anti-inflammatory activity in both in vivo models of inflammation. It was shown by molecular docking that the new derivatives are incorporated into the binding site of the protein Keap1 Kelch-domain by their pyrimidine substituent with the formation of more non-covalent bonds.

Drugs in Clinical Development to Treat Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst formation that ultimately leads to kidney failure in most patients. Approximately 10% of patients who receive kidney replacement therapy suffer from ADPKD. To date, a vasopressin V2 receptor antagonist (V2RA) is the only drug that has been proven to attenuate disease progression. However, aquaresis-related adverse events limit its widespread use. Data on the renoprotective effects of somatostatin analogues differ largely between studies and medications. This review discusses new drugs that are investigated in clinical trials to treat ADPKD, such as cystic fibrosis transmembrane conductance regulator (CFTR) modulators and micro RNA inhibitors, and drugs already marketed for other indications that are being investigated for off-label use in ADPKD, such as metformin. In addition, potential methods to improve the tolerability of V2RAs are discussed, as well as methods to select patients with (likely) rapid disease progression and issues regarding the translation of preclinical data into clinical practice. Since ADPKD is a complex disease with a high degree of interindividual heterogeneity, and the mechanisms involved in cyst growth also have important functions in various physiological processes, it may prove difficult to develop drugs that target cyst growth without causing major adverse events. This is especially important since long-standing treatment is necessary in this chronic disease. This review therefore also discusses approaches to targeted therapy to minimize systemic side effects. Hopefully, these developments will advance the treatment of ADPKD.

A Pivotal Role of Nrf2 in Neurodegenerative Disorders: A New Way for Therapeutic Strategies

Clinical and preclinical research indicates that neurodegenerative diseases are characterized by excess levels of oxidative stress (OS) biomarkers and by lower levels of antioxidant protection in the brain and peripheral tissues. Dysregulations in the oxidant/antioxidant balance are known to be a major factor in the pathogenesis of neurodegenerative diseases and involve mitochondrial dysfunction, protein misfolding, and neuroinflammation, all events that lead to the proteostatic collapse of neuronal cells and their loss. Nuclear factor-E2-related factor 2 (Nrf2) is a short-lived protein that works as a transcription factor and is related to the expression of many cytoprotective genes involved in xenobiotic metabolism and antioxidant responses. A major emerging function of Nrf2 from studies over the past decade is its role in resistance to OS. Nrf2 is a key regulator of OS defense and research supports a protective and defending role of Nrf2 against neurodegenerative conditions. This review describes the influence of Nrf2 on OS and in what way Nrf2 regulates antioxidant defense for neurodegenerative conditions. Furthermore, we evaluate recent research and evidence for a beneficial and potential role of specific Nrf2 activator compounds as therapeutic agents.

The Intestinal Redox System and Its Significance in Chemotherapy-Induced Intestinal Mucositis

Chemotherapy-induced intestinal mucositis (CIM) is a significant dose-limiting adverse reaction brought on by the cancer treatment. Multiple studies reported that reactive oxygen species (ROS) is rapidly produced during the initial stages of chemotherapy, when the drugs elicit direct damage to intestinal mucosal cells, which, in turn, results in necrosis, mitochondrial dysfunction, and ROS production. However, the mechanism behind the intestinal redox system-based induction of intestinal mucosal injury and necrosis of CIM is still undetermined. In this article, we summarized relevant information regarding the intestinal redox system, including the composition and regulation of redox enzymes, ROS generation, and its regulation in the intestine. We innovatively proposed the intestinal redox “Tai Chi” theory and revealed its significance in the pathogenesis of CIM. We also conducted an extensive review of the English language-based literatures involving oxidative stress (OS) and its involvement in the pathological mechanisms of CIM. From the date of inception till July 31, 2021, 51 related articles were selected. Based on our analysis of these articles, only five chemotherapeutic drugs, namely, MTX, 5-FU, cisplatin, CPT-11, and oxaliplatin were shown to trigger the ROS-based pathological mechanisms of CIM. We also discussed the redox system-mediated modulation of CIM pathogenesis via elaboration of the relationship between chemotherapeutic drugs and the redox system. It is our belief that this overview of the intestinal redox system and its role in CIM pathogenesis will greatly enhance research direction and improve CIM management in the future.

In vitro study on effect of bardoxolone methyl on cisplatin-induced cellular senescence in human proximal tubular cells

Bardoxolone methyl [methyl-2-cyano-3, 12-dioxooleana-1, 9(11)dien-28-oate (CDDO-Me)], an activator of the nuclear factor erythroid-derived 2-related factor2 pathway, is a potential therapeutic candidate for the treatment of kidney diseases. However, its effect against cellular senescence remains unclear. This study aimed to investigate whether CDDO-Me protects cells against cisplatin-induced cellular senescence using an in vitro model. The human renal proximal tubular epithelial cell line HK-2 was treated with cisplatin for 6 h, followed by treatment with or without CDDO-Me (0.1 or 0.2 μmol/L). Senescence markers were analyzed using western blotting and real-time PCR. Apoptosis was evaluated through TUNEL staining. Cisplatin induced changes in the levels of markers specific for proliferation, cell cycle, and senescence in a time- and dose-dependent manner. Furthermore, IL-6 and IL-8 levels in the culture medium increased markedly. These data suggested that cellular senescence-like alterations occurred in HK-2 cells exposed to cisplatin. CDDO-Me treatment reversed the cisplatin-mediated alterations in the levels of cellular senescence markers. The antioxidant enzymes, HO1, NQO1, GPX1, and CAT were upregulated by CDDO-Me treatment. Furthermore, CDDO-Me treatment induced apoptosis in cisplatin-exposed HK-2 cells. Pretreatment with Ac-DEVD-CHO, the caspase inhibitor, suppressed the reversal effect of CDDO-Me against cisplatin-induced cellular senescence-like alterations. This study showed that CDDO-Me attenuated cisplatin-induced premature senescence of HK-2 cells. This beneficial effect may be related to Nrf2 activation. Our findings also showed that CDDO-Me induced apoptosis in cisplatin-treated HK-2 cells, potentially protecting the kidneys from cellular senescence. CDDO-Me appears to be a candidate treatment for acute kidney injury.

NRF2 and Hypoxia-Inducible Factors: Key Players in the Redox Control of Systemic Iron Homeostasis

Significance: Oxygen metabolism and iron homeostasis are closely linked. Iron facilitates the oxygen-carrying capacity of blood, and its deficiency causes anemia. Conversely, excess free iron is detrimental for stimulating the formation of reactive oxygen species, causing tissue damage. The amount and distribution of iron thus need to be tightly regulated by the liver-expressed hormone hepcidin. This review analyzes the roles of key oxygen-sensing pathways in cellular and systemic regulation of iron homeostasis; specifically, the prolyl hydroxylase domain (PHD)/hypoxia-inducible factor (HIF) and the Kelch-like ECH-associated protein 1/NF-E2 p45-related factor 2 (KEAP1/NRF2) pathways, which mediate tissue adaptation to low and high oxygen, respectively. Recent Advances: In macrophages, NRF2 regulates genes involved in hemoglobin catabolism, iron storage, and iron export. NRF2 was recently identified as the molecular sensor of iron-induced oxidative stress and is responsible for BMP6 expression by liver sinusoidal endothelial cells, which in turn activates hepcidin synthesis by hepatocytes to restore systemic iron levels. Moreover, NRF2 orchestrates the activation of antioxidant defenses that are crucial to protect against iron toxicity. On the contrary, low iron/hypoxia stabilizes renal HIF2a via inactivation of iron-dependent PHD dioxygenases, causing an erythropoietic stimulus that represses hepcidin via an inhibitory effect of erythroferrone on bone morphogenetic proteins. Intestinal HIF2a is also stabilized, increasing the expression of genes involved in dietary iron absorption. Critical Issues: An intimate crosstalk between oxygen-sensing pathways and iron regulatory mechanisms ensures that fluctuations in systemic iron levels are promptly detected and restored. Future Directions: The realization that redox-sensitive transcription factors regulate systemic iron levels suggests novel therapeutic approaches. Antioxid. Redox Signal. 35, 433-452.

Distinct Regulations of HO-1 Gene Expression for Stress Response and Substrate Induction

Heme oxygenase-1 (HO-1) is the key enzyme for heme catabolism and cytoprotection. Whereas HO-1 gene expression in response to various stresses has been investigated extensively, the precise mechanisms by which HO-1 gene expression is regulated by the HO-1 substrate heme remain elusive. To systematically examine whether stress-mediated induction and substrate-mediated induction of HO-1 utilize similar or distinct regulatory pathways, we developed an HO-1-DsRed-knock-in reporter mouse in which the HO-1 gene is floxed by loxP sites and the DsRed gene has been inserted. Myeloid lineage-specific recombination of the floxed locus led to fluorescence derived from expression of the HO-1-DsRed fusion protein in peritoneal macrophages. We also challenged general recombination of the locus and generated mice harboring heterozygous recombinant alleles, which enabled us to monitor HO-1-DsRed expression in the whole body in vivo and ex vivo. HO-1 inducers upregulated HO-1-DsRed expression in myeloid lineage cells isolated from the mice. Notably, analyses of peritoneal macrophages from HO-1-DsRed mice lacking NRF2, a major regulator of the oxidative/electrophilic stress response, led us to identify NRF2-dependent stress response-mediated HO-1 induction and NRF2-independent substrate-mediated HO-1 induction. Thus, the HO-1 gene is subjected to at least two distinct levels of regulation, and the available lines of evidence suggest that substrate induction in peritoneal macrophages is independent of CNC family-based regulation.

Inhibition of the NRF2/KEAP1 Axis: A Promising Therapeutic Strategy to Alter Redox Balance of Cancer Cells

Significance: The nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (NRF2/KEAP1) pathway is a crucial and highly conserved defensive system that is required to maintain or restore the intracellular homeostasis in response to oxidative, electrophilic, and other types of stress conditions. The tight control of NRF2 function is maintained by a complex network of biological interactions between positive and negative regulators that ultimately ensure context-specific activation, culminating in the NRF2-driven transcription of cytoprotective genes. Recent Advances: Recent studies indicate that deregulated NRF2 activation is a frequent event in malignant tumors, wherein it is associated with metabolic reprogramming, increased antioxidant capacity, chemoresistance, and poor clinical outcome. On the other hand, the growing interest in the modulation of the cancer cells' redox balance identified NRF2 as an ideal therapeutic target. Critical Issues: For this reason, many efforts have been made to identify potent and selective NRF2 inhibitors that might be used as single agents or adjuvants of anticancer drugs with redox disrupting properties. Despite the lack of specific NRF2 inhibitors still represents a major clinical hurdle, the researchers have exploited alternative strategies to disrupt NRF2 signaling at different levels of its biological activation. Future Directions: Given its dualistic role in tumor initiation and progression, the identification of the appropriate biological context of NRF2 activation and the specific clinicopathological features of patients cohorts wherein its inactivation is expected to have clinical benefits, will represent a major goal in the field of cancer research. In this review, we will briefly describe the structure and function of the NRF2/ KEAP1 system and some of the most promising NRF2 inhibitors, with a particular emphasis on natural compounds and drug repurposing. Antioxid. Redox Signal. 34, 1428-1483.

Targeted de-repression of neuronal Nrf2 inhibits α-synuclein accumulation

Many neurodegenerative diseases are associated with neuronal misfolded protein accumulation, indicating a need for proteostasis-promoting strategies. Here we show that de-repressing the transcription factor Nrf2, epigenetically shut-off in early neuronal development, can prevent protein aggregate accumulation. Using a paradigm of α-synuclein accumulation and clearance, we find that the classical electrophilic Nrf2 activator tBHQ promotes endogenous Nrf2-dependent α-synuclein clearance in astrocytes, but not cortical neurons, which mount no Nrf2-dependent transcriptional response. Moreover, due to neuronal Nrf2 shut-off and consequent weak antioxidant defences, electrophilic tBHQ actually induces oxidative neurotoxicity, via Nrf2-independent Jun induction. However, we find that epigenetic de-repression of neuronal Nrf2 enables them to respond to Nrf2 activators to drive α-synuclein clearance. Moreover, activation of neuronal Nrf2 expression using gRNA-targeted dCas9-based transcriptional activation complexes is sufficient to trigger Nrf2-dependent α-synuclein clearance. Thus, targeting reversal of the developmental shut-off of Nrf2 in forebrain neurons may alter neurodegenerative disease trajectory by boosting proteostasis.

Activation of Nrf2 decreases bile acid concentrations in livers of female mice

1. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of oxidative/electrophilic stress. Studies suggest a role of Nrf2 in regulating bile acid (BA) metabolism in male mice. However, whether Nrf2 is important for BA homeostasis in female mice remains undefined. In this study, we systematically investigated the effect of Nrf2 activation, either through CDDO-imidazolide (CDDO-Im) treatment or genetic modulation of Kelch-like ECH associating protein 1 (Keap1), on BA homeostasis in female mice.2. Both pharmacological and genetic Nrf2 activation increased mRNA levels of multidrug resistance-associated protein 2 and 3 (Mrp2 and Mrp3), two Nrf2 target genes, in livers and ilea of female mice. Both pharmacological and genetic activation of Nrf2 decreased BA concentrations in the liver, which did not appear to be due to increased biliary BA excretion or decreased ileal BA absorption. Importantly, both pharmacological and genetic activation of Nrf2 downregulated hepatic Cyp7a1 mRNA, which might be attributable to the upregulation of the Fxr-Fgf15 signalling in the ileum.3. To conclude, Nrf2 activation lowers BA concentrations in livers of female mice, which appears to be attributable to the decreased hepatic BA synthesis.

Discovery and SAR studies of 3-amino-4-(phenylsulfonyl)tetrahydrothiophene 1,1-dioxides as non-electrophilic antioxidant response element (ARE) activators

The transcription factor NRF2 controls resistance to oxidative insult and is thus a key therapeutic target for treating a number of disease states associated with oxidative stress and aging. We previously reported CBR-470-1, a bis-sulfone which activates NRF2 by increasing the levels of methylglyoxal, a metabolite that covalently modifies NRF2 repressor KEAP1. Here, we report the design, synthesis, and structure activity relationship of a series of bis-sulfones derived from this unexplored chemical template. We identify analogs with sub-micromolar potencies, 7f and 7g, as well as establish that efficacious NRF2 activation can be achieved by non-toxic analogs 7c, 7e, and 9, a key limitation with CBR-470-1. Further efforts to identify non-covalent NRF2 activators of this kind will likely provide new insight into revealing the role of central metabolism in cellular signaling.

Protective Role of Nrf2 in Renal Disease

Chronic kidney disease (CKD) is one of the fastest-growing causes of death and is predicted to become by 2040 the fifth global cause of death. CKD is characterized by increased oxidative stress and chronic inflammation. However, therapies to slow or prevent CKD progression remain an unmet need. Nrf2 (nuclear factor erythroid 2-related factor 2) is a transcription factor that plays a key role in protection against oxidative stress and regulation of the inflammatory response. Consequently, the use of compounds targeting Nrf2 has generated growing interest for nephrologists. Pre-clinical and clinical studies have demonstrated that Nrf2-inducing strategies prevent CKD progression and protect from acute kidney injury (AKI). In this article, we review current knowledge on the protective mechanisms mediated by Nrf2 against kidney injury, novel therapeutic strategies to induce Nrf2 activation, and the status of ongoing clinical trials targeting Nrf2 in renal diseases.

Molecular Mechanisms That Link Oxidative Stress, Inflammation, and Fibrosis in the Liver

Activated hepatic stellate cells (HSCs) and myofibroblasts are the main producers of extracellular matrix (ECM) proteins that form the fibrotic tissue that leads to hepatic fibrosis. Reactive oxygen species (ROS) can directly activate HSCs or induce inflammation or programmed cell death, especially pyroptosis, in hepatocytes, which in turn activates HSCs and fibroblasts to produce ECM proteins. Therefore, antioxidants and the nuclear factor E2-related factor-2 signaling pathway play critical roles in modulating the profibrogenic response. The master proinflammatory factors nuclear factor-κB (NF-κB) and the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome may coordinate to produce and activate profibrogenic molecules such as interleukins 1β and 18, which effectively activate HSCs, to produce large amounts of fibrotic proteins. Furthermore, the NLRP3 inflammasome activates pro-caspase 1, which is upregulated by NF-κB, to produce caspase 1, which induces pyroptosis via gasdermin and the activation of HSCs. ROS play central roles in the activation of the NF-κB and NLRP3 signaling pathways via IκB (an inhibitor of NF-κB) and thioredoxin-interacting protein, respectively, thereby linking the molecular mechanisms of oxidative stress, inflammation and fibrosis. Elucidating these molecular pathways may pave the way for the development of therapeutic tools to interfere with specific targets.

NRF2 and the Ambiguous Consequences of Its Activation during Initiation and the Subsequent Stages of Tumourigenesis

NF-E2 p45-related factor 2 (NRF2, encoded in the human by NFE2L2) mediates short-term adaptation to thiol-reactive stressors. In normal cells, activation of NRF2 by a thiol-reactive stressor helps prevent, for a limited period of time, the initiation of cancer by chemical carcinogens through induction of genes encoding drug-metabolising enzymes. However, in many tumour types, NRF2 is permanently upregulated. In such cases, its overexpressed target genes support the promotion and progression of cancer by suppressing oxidative stress, because they constitutively increase the capacity to scavenge reactive oxygen species (ROS), and they support cell proliferation by increasing ribonucleotide synthesis, serine biosynthesis and autophagy. Herein, we describe cancer chemoprevention and the discovery of the essential role played by NRF2 in orchestrating protection against chemical carcinogenesis. We similarly describe the discoveries of somatic mutations in NFE2L2 and the gene encoding the principal NRF2 repressor, Kelch-like ECH-associated protein 1 (KEAP1) along with that encoding a component of the E3 ubiquitin-ligase complex Cullin 3 (CUL3), which result in permanent activation of NRF2, and the recognition that such mutations occur frequently in many types of cancer. Notably, mutations in NFE2L2, KEAP1 and CUL3 that cause persistent upregulation of NRF2 often co-exist with mutations that activate KRAS and the PI3K-PKB/Akt pathway, suggesting NRF2 supports growth of tumours in which KRAS or PKB/Akt are hyperactive. Besides somatic mutations, NRF2 activation in human tumours can occur by other means, such as alternative splicing that results in a NRF2 protein which lacks the KEAP1-binding domain or overexpression of other KEAP1-binding partners that compete with NRF2. Lastly, as NRF2 upregulation is associated with resistance to cancer chemotherapy and radiotherapy, we describe strategies that might be employed to suppress growth and overcome drug resistance in tumours with overactive NRF2.

Evaluation of Cytotoxicity and α-Glucosidase Inhibitory Activity of Amide and Polyamino-Derivatives of Lupane Triterpenoids

A series of two new and twenty earlier synthesized branched extra-amino-triterpenoids obtained by the direct coupling of betulinic/betulonic acids with polymethylenpolyamines, or by the cyanoethylation of lupane type alcohols, oximes, amines, and amides with the following reduction were evaluated for cytotoxicity toward the NCI-60 cancer cell line panel, α-glucosidase inhibitory, and antimicrobial activities. Lupane carboxamides, conjugates with diaminopropane, triethylenetetramine, and branched C3-cyanoethylated polyamine methyl betulonate showed high cytotoxic activity against most of the tested cancer cell lines with GI50 that ranged from 1.09 to 54.40 µM. Betulonic acid C28-conjugate with triethylenetetramine and C3,C28-bis-aminopropoxy-betulin were found to be potent micromolar inhibitors of yeast α-glucosidase and to simultaneously inhibit the endosomal reticulum α-glucosidase, rendering them as potentially capable to suppress tumor invasiveness and neovascularization, in addition to the direct cytotoxicity. Plausible mechanisms of cytotoxic action and underlying disrupted molecular pathways were elucidated with CellMinner pattern analysis and Gene Ontology enrichment analysis, according to which the lead compounds exert multi-target antiproliferative activity associated with oxidative stress induction and chromatin structure alteration. The betulonic acid diethylentriamine conjugate showed partial activity against methicillin-resistant S. aureus and the fungi C. neoformans. These results show that triterpenic polyamines, being analogs of steroidal squalamine and trodusquemine, are important substances for the search of new drugs with anticancer, antidiabetic, and antimicrobial activities.

Bardoxolone conjugation enables targeted protein degradation of BRD4

Targeted protein degradation (TPD) has emerged as a powerful tool in drug discovery for the perturbation of protein levels using heterobifunctional small molecules. E3 ligase recruiters remain central to this process yet relatively few have been identified relative to the ~ 600 predicted human E3 ligases. While, initial recruiters have utilized non-covalent chemistry for protein binding, very recently covalent engagement to novel E3's has proven fruitful in TPD application. Herein we demonstrate efficient proteasome-mediated degradation of BRD4 by a bifunctional small molecule linking the KEAP1-Nrf2 activator bardoxolone to a BRD4 inhibitor JQ1.

Anti-Inflammatory Activity of Kurarinone Involves Induction of HO-1 via the KEAP1/Nrf2 Pathway

Kurarinone, a flavonoid isolated from the roots of Sophora flavescens, was suggested to exert potent antioxidant and immunosuppressive effects. However, the underlying mechanisms remain unclear. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcription factor that regulates the antioxidant defense system with anti-inflammatory activity. In the present study, we demonstrated that kurarinone activated Nrf2 and increased the expression of antioxidant enzymes, including heme oxygenase-1 (HO-1). Mechanistically, kurarinone downregulated the expression of kelch-like ECH-associated protein 1 (KEAP1), subsequently leading to the activation of Nrf2. Kurarinone also inhibited the expression of the inflammatory cytokine, interleukin (IL)-1β, and inducible nitric oxide synthase (iNos) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. The overexpression of HO-1 suppressed the LPS-induced production of inflammatory mediators in RAW264.7 cells, and the immunosuppressive effects of kurarinone were partially inhibited by a treatment with Tin Protomorphyrin IX (TinPPIX), an inhibitor of HO-1. These results indicate that kurarinone activates the KEAP1/Nrf2 pathway to induce HO-1 expression, thereby exerting immunosuppressive effects.

Constitutive Activation of Nrf2 in Mice Expands Enterogenesis in Small Intestine Through Negative Regulation of Math1

BACKGROUND & AIMS

Notch signaling coordinates cell differentiation processes in the intestinal epithelium. The transcription factor Nrf2 orchestrates defense mechanisms by regulating cellular redox homeostasis, which, as shown previously in murine liver, can be amplified through signaling crosstalk with the Notch pathway. However, interplay between these 2 signaling pathways in the gut is unknown.

METHODS

Mice modified genetically to amplify Nrf2 in the intestinal epithelium (Keap1^f/f::VilCre) were generated as well as pharmacological activation of Nrf2 and subjected to phenotypic and cell lineage analyses. Cell lines were used for reporter gene assays together with Nrf2 overexpression to study transcriptional regulation of the Notch downstream effector.

RESULTS

Constitutive activation of Nrf2 signaling caused increased intestinal length along with expanded cell number and thickness of enterocytes without any alterations of secretory lineage, outcomes abrogated by concomitant disruption of Nrf2. The Nrf2 and Notch pathways in epithelium showed inverse spatial profiles, where Nrf2 activity in crypts was lower than villi. In progenitor cells of Keap1^f/f::VilCre mice, Notch downstream effector Math1, which regulates a differentiation balance of cell lineage through lateral inhibition, showed suppressed expression. In vitro results demonstrated Nrf2 negatively regulated Math1, where 6 antioxidant response elements located in the regulatory regions contributed to this repression.

CONCLUSIONS

Activation of Nrf2 perturbed the dialog of the Notch cascade though negative regulation of Math1 in progenitor cells, leading to enhanced enterogenesis. The crosstalk between the Nrf2 and Notch pathways could be critical for fine-tuning intestinal homeostasis and point to new approaches for the pharmacological management of absorptive deficiencies.

Effects of Bardoxolone Methyl on Hepatic Enzymes in Patients with Type 2 Diabetes Mellitus and Stage 4 CKD

In a multinational placebo‐controlled phase III clinical trial in 2,185 patients with type 2 diabetes mellitus and stage 4 chronic kidney disease, treatment with the Nrf2 activator bardoxolone methyl increased estimated glomerular filtration rate, a measure of kidney function, but also resulted in increases in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma glutamyl transferase. These increases in liver enzyme level(s) were maximal after 4 weeks of treatment and reversible, trending back toward baseline through week 48. Total bilirubin concentrations did not increase, and no cases met Hy’s Law criteria, although two subjects had ALT concentrations that exceeded 10 × the upper limit of the population reference range leading to discontinuation of treatment. Animal and cell culture experiments suggested that the increases in ALT and AST induced by bardoxolone methyl may be related to its pharmacological activity. Bardoxolone methyl significantly induced the mRNA expression of ALT and AST isoforms in cultured cells. Expression of ALT and AST isoforms in liver and kidney also positively correlated with Nrf2 status in mice. Overall, these data suggest that the increases in ALT and AST observed clinically were, at least in part, related to the pharmacological induction of aminotransferases via Nrf2 activation, rather than to any intrinsic form of hepatotoxicity.

CDDO-imidazolide Targets Multiple Amino Acid Residues on the Nrf2 Adaptor, Keap1

Synthetic triterpenoids including CDDO, its methyl ester (CDDO-Me, bardoxolone methyl), and its imidazolide (CDDO-Im) enhance Nrf2-mediated antioxidant and anti-inflammatory activity in many diseases by reacting with thiols on the adaptor protein, Keap1. Unlike monofunctional CDDO-Me, the bifunctional analog, CDDO-Im, has a second reactive site (imidazolide) and can covalently bind to amino acids other than cysteine on target proteins such as glutathione S-transferase pi (GSTP), serum albumin, or Keap1. Here we show for the first time that bifunctional CDDO-Im (in contrast to CDDO-Me), as low as 50 nM, can covalently transacylate arginine and serine residues in GSTP and cross-link them to adjacent cysteine residues. Moreover, we show that CDDO-Im binds covalently to Keap1 by forming permanent Michael adducts with eight different cysteines, and acyl adducts with lysine and several tyrosine residues. Modeling studies suggest that the Tyr 85 adduct stabilizes the Keap1-Cul3 complex, thereby enhancing the potency of CDDO-Im.

Effects of ablation and activation of Nrf2 on bile acid homeostasis in male mice

The role of nuclear factor erythroid 2-related factor 2 (Nrf2) in bile acid (BA) homeostasis remains controversial. In this study, activation of Nrf2 was achieved either pharmacologically by CDDO-imidazolide (CDDO-Im) or genetically through a "gene dose-response" model consisting of Nrf2-null, wild-type (WT), Keap1-knockdown (Keap1-KD), and Keap1-hepatocyte knockout (Keap1-HKO) mice. In WT mice, CDDO-Im increased bile flow and decreased hepatic BAs, which was associated with a down-regulation of the canalicular BA efflux transporter Bsep and an increase in biliary BA excretion. In contrast, hepatic Bsep and biliary BA excretion were not altered in Keap1-KD or Keap1-HKO mice, suggesting that Nrf2 is not important for regulating Bsep or BA-dependent bile flow. In contrast, hepatic Mrp2 and Mrp3 were up-regulated by both pharmacological and genetic activations of Nrf2. Furthermore, ileal BA transporters (Asbt and Ostβ) and cholesterol transporters (Abcg5 and Abcg8) were down-regulated by both pharmacological and genetic activations of Nrf2, suggesting a role of Nrf2 in intestinal absorption of BAs and cholesterol. In Nrf2-null mice, CDDO-Im down-regulated hepatic BA uptake transporters (Ntcp, Oatp1a1, and Oatp1b2), leading to a 39-fold increase of serum BAs. To conclude, the present study demonstrates that activation of Nrf2 in mice up-regulates Mrp2 and Mrp3 in the liver and down-regulates BA and cholesterol transporters in the intestine.

Common Drug Pipelines for the Treatment of Diabetic Nephropathy and Hepatopathy: Can We Kill Two Birds with One Stone?

Type 2 diabetes (T2D) is associated with diabetic nephropathy as well as nonalcoholic steatohepatitis (NASH), which can be called "diabetic hepatopathy or diabetic liver disease". NASH, a severe form of nonalcoholic fatty disease (NAFLD), can sometimes progress to cirrhosis, hepatocellular carcinoma and hepatic failure. T2D patients are at higher risk for liver-related mortality compared with the nondiabetic population. NAFLD is closely associated with chronic kidney disease (CKD) or diabetic nephropathy according to cross-sectional and longitudinal studies. Simultaneous kidney liver transplantation (SKLT) is dramatically increasing in the United States, because NASH-related cirrhosis often complicates end-stage renal disease. Growing evidence suggests that NAFLD and CKD share common pathogenetic mechanisms and potential therapeutic targets. Glucagon-like peptide 1 (GLP-1) receptor agonists and sodium-glucose cotransporter 2 (SGLT2) inhibitors are expected to ameliorate NASH and diabetic nephropathy/CKD. There are no approved therapies for NASH, but a variety of drug pipelines are now under development. Several agents of them can also ameliorate diabetic nephropathy/CKD, including peroxisome proliferator-activated receptors agonists, apoptosis signaling kinase 1 inhibitor, nuclear factor-erythroid-2-related factor 2 activator, C-C chemokine receptor types 2/5 antagonist and nonsteroidal mineral corticoid receptor antagonist. This review focuses on common drug pipelines in the treatment of diabetic nephropathy and hepatopathy.