Effects Of Nrf2 Activation Research Articles

Low ozone concentrations do not exert cytoprotective effects on tamoxifen-treated breast cancer cells in vitro.

Medical treatment with low ozone concentrations proved to exert therapeutic effects in various diseases by inducing a cytoprotective antioxidant response through the nuclear factor erythroid derived-like 2 (Nrf2) transcription factor pathway. Low ozone doses are increasingly administered to oncological patients as a complementary treatment to mitigate some adverse side-effects of antitumor treatments. However, a widespread concern exists about the possibility that the cytoprotective effect of Nrf2 activation may confer drug resistance to cancer cells or at least reduce the efficacy of antitumor agents. In this study, the effect of low ozone concentrations on tamoxifen-treated MCF7 human breast cancer cells has been investigated in vitro by histochemical and molecular techniques. Results demonstrated that cell viability, proliferation and migration were generally similar in tamoxifen-treated cells as in cells concomitantly treated with tamoxifen and ozone. Notably, low ozone concentrations were unable to overstimulate the antioxidant response through the Nfr2 pathway, thus excluding a possible ozone-driven cytoprotective effect that would lead to increased tumor cell survival during the antineoplastic treatment. These findings, though obtained in an in vitro model, support the hypothesis that low ozone concentrations do not interfere with the tamoxifen-induced effects on breast cancer cells.

Activation of Nrf2 at Critical Windows of Development Alters Tissue-Specific Protein S-Glutathionylation in the Zebrafish (Danio rerio) Embryo.

Activation of Nrf2-the master regulator of antioxidative response-at different stages of embryonic development has been shown to result in changes in gene expression, but the tissue-specific and downstream effects of Nrf2 activation during development remain unclear. This work seeks to elucidate the tissue-specific Nrf2 cellular localization and the downstream changes in protein S-glutathionylation during critical windows of zebrafish (Danio rerio) development. Wild-type and mutant zebrafish embryos with a loss-of-function mutation in Nrf2a were treated with two canonical activators, sulforaphane (SFN; 40 µM) or tert-butylhydroquinone (tBHQ; 1 µM), for 6 h at either pharyngula, hatching, or the protruding-mouth stage. Nrf2a protein and S-glutathionylation were visualized in situ using immunohistochemistry. At the hatching stage, Nrf2a protein levels were decreased with SFN, but not tBHQ, exposure. Exposure to both activators, however, decreased downstream S-glutathionylation. Stage- and tissue-specific differences in Nrf2a protein and S-glutathionylation were identified in the pancreatic islet and liver. Protein S-glutathionylation in Nrf2a mutant fish was increased in the liver by both activators, but not the islets, indicating a tissue-specific and Nrf2a-dependent dysregulation. This work demonstrates that critical windows of exposure and Nrf2a activity may influence redox homeostasis and highlights the importance of considering tissue-specific outcomes and sensitivity in developmental redox biology.

The Triterpenoid CDDO-Methyl Ester Reduces Tumor Burden, Reprograms the Immune Microenvironment, and Protects from Chemotherapy-Induced Toxicity in a Preclinical Mouse Model of Established Lung Cancer.

NRF2 activation protects epithelial cells from malignancy, but cancer cells can upregulate the pathway to promote survival. NRF2 activators including CDDO-Methyl ester (CDDO-Me) inhibit cancer in preclinical models, suggesting NRF2 activation in other cell types may promote anti-tumor activity. However, the immunomodulatory effects of NRF2 activation remain poorly understood in the context of cancer. To test CDDO-Me in a murine model of established lung cancer, tumor-bearing wildtype (WT) and Nrf2 knockout (KO) mice were treated with 50-100 mg CDDO-Me/kg diet, alone or combined with carboplatin/paclitaxel (C/P) for 8-12 weeks. CDDO-Me decreased tumor burden in an Nrf2-dependent manner. The combination of CDDO-Me plus C/P was significantly (p < 0.05) more effective than either drug alone, reducing tumor burden by 84% in WT mice. CDDO-Me reduced the histopathological grade of WT tumors, with a significantly (p < 0.05) higher proportion of low-grade tumors and a lower proportion of high-grade tumors. These changes were augmented by combination with C/P. CDDO-Me also protected WT mice from C/P-induced toxicity and improved macrophage and T cell phenotypes in WT mice, reducing the expression of CD206 and PD-L1 on macrophages, decreasing immunosuppressive FoxP3+ CD4+ T cells, and increasing activation of CD8+ T cells in a Nrf2-dependent manner.

The Role of NRF2 in Cerebrovascular Protection: Implications for Vascular Cognitive Impairment and Dementia (VCID).

Vascular cognitive impairment and dementia (VCID) represents a broad spectrum of cognitive decline secondary to cerebral vascular aging and injury. It is the second most common type of dementia, and the prevalence continues to increase. Nuclear factor erythroid 2-related factor 2 (NRF2) is enriched in the cerebral vasculature and has diverse roles in metabolic balance, mitochondrial stabilization, redox balance, and anti-inflammation. In this review, we first briefly introduce cerebrovascular aging in VCID and the NRF2 pathway. We then extensively discuss the effects of NRF2 activation in cerebrovascular components such as endothelial cells, vascular smooth muscle cells, pericytes, and perivascular macrophages. Finally, we summarize the clinical potential of NRF2 activators in VCID.

Abstract 3842: Neuroendocrine differentiation and treatment of human SCLC: NRF2 has a role

Abstract SCLC is a lethal form of lung cancer and highly metastatic disease with limited therapeutic options. Four main neuro and non-neuroendocrine SCLC molecular subtypes have been identified which further complicate the efforts of finding targeted therapies. NRF2 is a transcription factor that is known to protect cells from oxidative damage by regulating more than 500 cytoprotective genes. NRF2 is frequently mutated in non-small cell lung cancer (NSCLC), however, whether alterations occur in small cell lung cancer (SCLC) is not clear due to limited sequencing data. Recently, our group has discovered a previously unrecognized role of NRF2 signaling pathway in the development of SCLC using a novel genetically engineered mouse model (GEMM). In this study, we have investigated the role of NRF2 in the progression and regression of human SCLC. Human SCLC cell lines were generated with NRF2E79Q/+ mutation (one of the most common mutations found in human tumors) to allow the constitutive activation of NRF2 in these cells. Results from hSCLC cell lines showed that NRF2 activation in NRF2-negative SCLCs can significantly inhibit their growth. Further, human SCLC gene expression data showed reduced levels of a NRF2 signature as hSCLC neuroendocrine SCLC transforms to non-neuroendocrine subtypes. As an anti-inflammatory pathway, NRF2 is known to inhibit immune cell gene signature. Our in vivo and invitro studies showed that NRF2 inhibits immune cell infiltration in SCLC; and increases PDL1 protein expression. Currently, we are investigating the effect of NRF2 activation in hSCLC growth, neuroendocrine differentiation and immune gene activation in vitro and in vivo. We are also using immune checkpoint inhibitors to determine the best therapeutic options for each SCLC subtype. Citation Format: Samera Hamad, Hansa Joshi, Yahui Li, Helen Toma, Nasrine Bendjilali, Stuart Jefferys, David Corcoran, Weam Elbezanti, Ben Major, Weissman Bernard, Francis Spitz. Neuroendocrine differentiation and treatment of human SCLC: NRF2 has a role [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3842.

A Review of the Potential of Nuclear Factor [Erythroid-Derived 2]-like 2 Activation in Autoimmune Diseases.

An autoimmune disease is the consequence of the immune system attacking healthy cells, tissues, and organs by mistake instead of protecting them. Inflammation and oxidative stress (OS) are well-recognized processes occurring in association with acute or chronic impairment of cell homeostasis. The transcription factor Nrf2 (nuclear factor [erythroid-derived 2]-like 2) is of major importance as the defense instrument against OS and alters anti-inflammatory activities related to different pathological states. Researchers have described Nrf2 as a significant regulator of innate immunity. Growing indications suggest that the Nrf2 signaling pathway is deregulated in numerous diseases, including autoimmune disorders. The advantageous outcome of the pharmacological activation of Nrf2 is an essential part of Nrf2-based chemoprevention and intervention in other chronic illnesses, such as neurodegeneration, cardiovascular disease, autoimmune diseases, and chronic kidney and liver disease. Nevertheless, a growing number of investigations have indicated that Nrf2 is already elevated in specific cancer and disease steps, suggesting that the pharmacological agents developed to mitigate the potentially destructive or transformative results associated with the protracted activation of Nrf2 should also be evaluated. The activators of Nrf2 have revealed an improvement in the progress of OS-associated diseases, resulting in immunoregulatory and anti-inflammatory activities; by contrast, the depletion of Nrf2 worsens disease progression. These data strengthen the growing attention to the biological properties of Nrf2 and its possible healing power on diseases. The evidence supporting a correlation between Nrf2 signaling and the most common autoimmune diseases is reviewed here. We focus on the aspects related to the possible effect of Nrf2 activation in ameliorating pathologic conditions based on the role of this regulator of antioxidant genes in the control of inflammation and OS, which are processes related to the progression of autoimmune diseases. Finally, the possibility of Nrf2 activation as a new drug development strategy to target pathogenesis is proposed.

Nrf2 signaling pathway: current status and potential therapeutic targetable role in human cancers.

Cancer is a borderless global health challenge that continues to threaten human health. Studies have found that oxidative stress (OS) is often associated with the etiology of many diseases, especially the aging process and cancer. Involved in the OS reaction as a key transcription factor, Nrf2 is a pivotal regulator of cellular redox state and detoxification. Nrf2 can prevent oxidative damage by regulating gene expression with antioxidant response elements (ARE) to promote the antioxidant response process. OS is generated with an imbalance in the redox state and promotes the accumulation of mutations and genome instability, thus associated with the establishment and development of different cancers. Nrf2 activation regulates a plethora of processes inducing cellular proliferation, differentiation and death, and is strongly associated with OS-mediated cancer. What's more, Nrf2 activation is also involved in anti-inflammatory effects and metabolic disorders, neurodegenerative diseases, and multidrug resistance. Nrf2 is highly expressed in multiple human body parts of digestive system, respiratory system, reproductive system and nervous system. In oncology research, Nrf2 has emerged as a promising therapeutic target. Therefore, certain natural compounds and drugs can exert anti-cancer effects through the Nrf2 signaling pathway, and blocking the Nrf2 signaling pathway can reduce some types of tumor recurrence rates and increase sensitivity to chemotherapy. However, Nrf2's dual role and controversial impact in cancer are inevitable consideration factors when treating Nrf2 as a therapeutic target. In this review, we summarized the current state of biological characteristics of Nrf2 and its dual role and development mechanism in different tumor cells, discussed Keap1/Nrf2/ARE signaling pathway and its downstream genes, elaborated the expression of related signaling pathways such as AMPK/mTOR and NF-κB. Besides, the main mechanism of Nrf2 as a cancer therapeutic target and the therapeutic strategies using Nrf2 inhibitors or activators, as well as the possible positive and negative effects of Nrf2 activation were also reviewed. It can be concluded that Nrf2 is related to OS and serves as an important factor in cancer formation and development, thus provides a basis for targeted therapy in human cancers.

Activation of Nrf2 signaling pathway by Tectoridin protects against ferroptosis in particulate matter-induced lung injury.

Our previous research showed that ferroptosis plays a crucial role in the pathophysiology of PM2.5-induced lung injury. The present study aimed to investigate the protective role of the Nrf2 signaling pathway and its bioactive molecule tectoridin (Tec) in PM2.5-induced lung injury by regulating ferroptosis. We examined the regulatory effect of Nrf2 on ferroptosis in PM2.5-induced lung injury and Beas-2b cells using Nrf2-knockout (KO) mice and Nrf2 siRNA transfection. Moreover, the effect and underlying mechanism of Tec on PM2.5-induced lung injury were evaluated in vitro and in vivo. As anticipated, Nrf2 deletion increased iron accumulation and ferroptosis-related protein expression in vivo and vitro, further exacerbating lung injury and cell death in response to PM2.5 exposure. Tec significantly activated Nrf2 target genes and ameliorated cell death caused by PM2.5. In addition, Tec prevented lipid peroxidation, iron accumulation, and ferroptosis in vitro, but in siNrf2-treated cells, these effects almost disappeared. In addition, Tec effectively mitigated PM2.5-induced respiratory system damage, as evaluated by HE, PAS, and inflammatory factors. Tec also augmented the antioxidative Nrf2 signaling pathway and prevented changes in ferroptosis-related morphological and biochemical indicators, including MDA levels, GSH depletion and GPX4 and xCT downregulation, in PM2.5-induced lung injury. However, the effects of Tec on ferroptosis and respiratory injury nearly vanished in Nrf2-KO mice. Our data proposed the protective effect of Nrf2 activation on PM2.5-induced lung injury by inhibiting ferroptosis-mediated lipid peroxidation and highlight the potential of Tec as a PM2.5-induced lung injury treatment.

Abstract 5176: CDDO-methyl ester redirects macrophage polarization and reduces lung tumor burden in a Nrf2-dependent manner

Abstract The cytoprotective Nrf2 pathway impacts immune cell function and has been proposed as a target for many inflammation-related diseases, but the effects of Nrf2 activation on immune cells in the cancer context are not well characterized. With Nrf2 activators under development and in clinical trials, it is critical to understand the influence of these drugs on cancer progression. While the anti-inflammatory nature of Nrf2 activation protects healthy cells from malignant transformation, cancer cells can utilize the pathway to promote resistance to anti-cancer drugs and increase tumor cell survival. Up to 30% of human lung adenocarcinomas acquire mutations in the Nrf2 pathway which result in constitutive activation. However, triterpenoids, including CDDO-methyl ester (CDDO-Me, also known as bardoxolone methyl), are potent pharmacological Nrf2 activators with demonstrated anti-cancer activity in preclinical models. Lung cancer is the leading cause of cancer-related mortality worldwide, and macrophages are the most common immune cell type in the lung tumor microenvironment. To investigate Nrf2 activation in macrophages in the context of lung cancer, bone marrow-derived macrophages (BMDMs) were isolated from wild type (WT) and Nrf2 knock out (KO) mice and cultured in conditioned media from lung cancer cells to produce a tumor-educated phenotype. The triterpenoid CDDO-Me had anti-inflammatory effects in BMDMs stimulated with the conventional cytokines IFN-γ and LPS. Conversely, CDDO-Me increased (p &amp;lt; 0.05) the M1 macrophage markers TNFα, IL-6, and MHC-II and decreased the M2 macrophage markers VEGF, CCL2, and CD206 in tumor-educated BMDMs in a Nrf2-dependent manner. The phenotypic changes were observed on transcription, protein, and surface marker levels. This context-dependent reversal of BMDM polarization suggests that Nrf2 activation has different outcomes in different environments. To test CDDO-Me in vivo, lung tumors were initiated with vinyl carbamate in A/J WT and Nrf2 KO mice, and animals were fed either control diet or CDDO-Me (12.5-50 mg/kg of diet) for 16 weeks. CDDO-Me significantly (p &amp;lt; 0.05) decreased tumor number, size, and overall burden and reduced the histopathological severity of tumors in a Nrf2- and dose-dependent manner. Additionally, CDDO-Me increased the infiltration of CD64+ macrophages but decreased CD206+ expression in macrophages in the lungs of WT tumor-bearing mice. Interestingly, CD206 expression was higher on macrophages in the spleen of WT mice treated with CDDO-Me, suggesting a cancer context dependency. Future studies will evaluate the dependency of Nrf2 activation in macrophages for the anti-tumor activity of CDDO-Me. Citation Format: Jess Ann Moerland, Karen T. Liby. CDDO-methyl ester redirects macrophage polarization and reduces lung tumor burden in a Nrf2-dependent manner. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5176.

Nrf2 Activation Does Not Protect from Aldosterone-Induced Kidney Damage in Mice.

Nuclear factor erythroid 2-related factor 2 (Nrf2) is downregulated in chronic kidney disease (CKD). Activation of Nrf2 might be a therapeutic option in CKD. Here we investigate the effect of Nrf2 activation on aldosterone (Aldo)-induced renal injury. Wild-type (WT) mice, transgenic Keap1 hypomorphic (Nrf2ꜛ, genotype results in upregulation of Nrf2 expression) mice and WT mice treated with the Nrf2 activator sulforaphane (Sulf) received Aldo for 4 weeks. In Aldo-treated mice, kidneys were significantly heavier and pathologically altered, reflected by increased urinary albumin levels and tissue damage. In Nrf2ꜛ-Aldo mice the tubule damage marker NGAL was significantly decreased. Increased oxidative damage markers (8-OHdG, 15-isoprostane F2t) were measured in all Aldo-treated groups. Aldo-increased Nrf2 amounts were mainly found in the late tubule system. The amount of phosphorylated and thus putatively active Nrf2 was significantly increased by Aldo only in WT mice. However, expression of Nrf2 target genes NQO1 and HO1 was decreased in all Aldo-infused mice. GSK3β, which promotes Nrf2 degradation, was significantly increased in the kidneys of Aldo-treated WT mice. Neither genetic nor pharmacological Nrf2 activation was able to prevent oxidative injury induced by Aldo, probably due to induction of negative regulators of Nrf2.

The Triterpenoid CDDO-Methyl Ester Redirects Macrophage Polarization and Reduces Lung Tumor Burden in a Nrf2-Dependent Manner.

The NRF2/KEAP1 pathway protects healthy cells from malignant transformation and maintains cellular homeostasis. Up to 30% of human lung tumors gain constitutive NRF2 activity which contributes to cancer cell survival and chemoresistance, but the effects of NRF2 activation in immune cells within the tumor microenvironment are underexplored. Macrophages can promote cancer progression or regression depending on context, and NRF2 activation affects macrophage activity. The NRF2 activator CDDO-Methyl ester (CDDO-Me or bardoxolone methyl) reprogrammed Nrf2 wild-type (WT) tumor-educated bone marrow-derived macrophages (TE-BMDMs) from a tumor-promoting to a tumor-inhibiting phenotype, marked by an increase in M1 markers TNFα, IL-6, and MHC-II and a decrease in the tumor-promoting factors VEGF, CCL2, and CD206. No changes were observed in Nrf2 knockout (KO) TE-BMDMs. CDDO-Me decreased tumor burden (p < 0.001) and improved pathological grade (p < 0.05) in WT but not Nrf2 KO A/J mice. Tumor burden in Nrf2 KO mice was 4.6-fold higher (p < 0.001) than in WT mice, irrespective of treatment. CDDO-Me increased the number of lung-infiltrating macrophages in WT mice but lowered CD206 expression in these cells (p < 0.0001). In summary, Nrf2 KO exacerbates lung tumorigenesis in A/J mice, and CDDO-Me promotes an Nrf2-dependent, anti-cancer macrophage phenotype.

Abstract 3534: The triterpenoid CDDO-Me redirects macrophage polarization and decreases tumor burden in a preclinical model of NSCLC

Abstract The NRF2/KEAP1 pathway regulates cytoprotective mechanisms that protect healthy cells from malignant transformation and maintain cellular homeostasis. Up to 30% of human lung tumors contain a mutation that results in constitutive NRF2 pathway activation, which contributes to cancer cell survival, disease progression, and resistance to chemotherapies. However, the effects of NRF2 activation in immune cells within the tumor microenvironment are underexplored. Macrophages in lung cancers contribute to cancer progression or regression depending on the context, and NRF2 activity affects macrophage activation and trafficking. To evaluate the role of NRF2 activity in macrophages, bone marrow-derived macrophages (BMDMs) from NRF2 wild-type (WT) and knockout (KO) mice were treated to induce anti-tumor (M1), tumor-promoting (M2), and tumor-educated macrophage phenotypes and then treated with the potent NRF2 activator CDDO-Methyl ester (CDDO-Me), also known as bardoxolone methyl. In tumor-educated BMDMs isolated from NRF2 WT mice and cultured in conditioned media from lung cancer cells, CDDO-Me (100 nM) induced a 3-fold increase in mRNA expression of the M1 markers TNF-α and IL-6. The expression of these cytokines was not increased by CDDO-Me in tumor-educated BMDMs isolated from NRF2 KO mice. CDDO-Me also decreased mRNA expression of the angiogenic factor VEGF and the chemokine CCL2 in tumor-educated BMDMs isolated from WT but not NRF2 KO mice. VEGF is expressed by tumor-promoting macrophages and CCL2, a chemotactic factor that recruits M2 macrophages into the lung, is a biomarker of poor prognosis in lung cancer patients. CDDO-Me has potent anti-tumor effects in the A/J mouse model of non-small cell lung cancer (NSCLC), but the mechanism of these effects was unknown. To evaluate, A/J WT and NRF2 KO A/J mice were injected with vinyl carbamate to initiate lung tumors. Two weeks later, mice were fed either a control diet or a diet containing CDDO-Me (50 mg/kg diet: ~12.5 mg/kg body weight) for 16 weeks. Ultrasound confirmed the development of tumors in the lungs of mice throughout the study, and differences in tumor number and lung parenchyma structure were detected at 15 weeks of treatment. CDDO-Me significantly (p&amp;lt;0.05) decreased tumor burden in WT A/J mice. Tumor burden in the NRF2 KO mice was significantly (p&amp;lt;0.05) higher than in WT mice, irrespective of treatment. Tumor count in NRF2 KO A/J mice treated with either vehicle or CDDO-Me was increased 2-fold compared to WT A/J mice on the vehicle control diet. These data show that CDDO-Me promotes an anti-cancer macrophage phenotype in vitro that is dependent on NRF2 activation. Additionally, NRF2 KO increases lung tumor burden in the A/J model of NSCLC and CDDO-Me significantly decreases tumor burden in A/J mice in a NRF2-dependent manner. Future studies will test the effect of CDDO-Me and NRF2 activity on the lung tumor immune microenvironment in vivo. Citation Format: Jess Ann Moerland, Karen T. Liby. The triterpenoid CDDO-Me redirects macrophage polarization and decreases tumor burden in a preclinical model of NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3534.

Leonurine alleviates ferroptosis in cisplatin-induced acute kidney injury by activating the Nrf2 signalling pathway.

Evidence indicates that ferroptosis plays a key role in acute kidney injury induced by cisplatin. The Nrf2/NRF2 pathway regulates oxidative stress, lipid peroxidation and positively regulates cisplatin-induced acute kidney injury, but its effect along with the alkaloid leonurine, found in motherwort, on ferroptosis after such acute kidney injury remains unclear. The anti-ferroptotic effects of Nrf2 and leonurine were assessed in a mouse model of cisplatin-induced acute kidney injury. In vitro, the effects of leonurine on erastin- and RSL3-induced HK-2 human PTEC ferroptosis were examined. Nrf2 deletion induced ferroptosis-related protein expression and iron accumulation in vivo, aggravating cisplatin-induced acute kidney injury. Leonurine activated Nrf2 and prevented iron accumulation, lipid peroxidation and ferroptosis in vitro, being abolished in siNrf2-treated cells. Moreover, leonurine potently inhibited cisplatin-induced renal damage, as assessed by of serum creatinine, blood urea nitrogen, kidney injury molecule-1 and NGAL. Importantly, leonurine activated the Nrf2 antioxidative pathway and preventing changes in ferroptosis-related morphological and biochemical indicators, malondialdehyde level, SOD and GSH depletion, and GPX4 and xCT down-regulation, in cisplatin-induced acute kidney injury. Nrf2 KO mice were more susceptible to ferroptosis after cisplatin-induced acute kidney injury than control mice. The protective effects of leonurine on acute kidney injury and ferroptosis were largely abolished in Nrf2 KO mice. These data suggest that renal protective effects of Nrf2 activation on cisplatin-induced acute kidney injury are achieved, at least partially, by inhibiting lipid peroxide-mediated ferroptosis, highlighting the potential of leonurine in acute kidney injury treatment.

Activation of the Nrf2 Pathway Prevents Mitochondrial Dysfunction Induced by Caspase-3 Cleaved Tau: Implications for Alzheimer's Disease.

Alzheimer’s disease (AD) is characterized by memory and cognitive impairment, accompanied by the accumulation of extracellular deposits of amyloid β-peptide (Aβ) and the presence of neurofibrillary tangles (NFTs) composed of pathological forms of tau protein. Mitochondrial dysfunction and oxidative stress are also critical elements for AD development. We previously showed that the presence of caspase-3 cleaved tau, a relevant pathological form of tau in AD, induced mitochondrial dysfunction and oxidative damage in different neuronal models. Recent studies demonstrated that the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) plays a significant role in the antioxidant response promoting neuroprotection. Here, we studied the effects of Nrf2 activation using sulforaphane (SFN) against mitochondrial injury induced by caspase-3 cleaved tau. We used immortalized cortical neurons to evaluate mitochondrial bioenergetics and ROS levels in control and SFN-treated cells. Expression of caspase-3 cleaved tau induced mitochondrial fragmentation, depolarization, ATP loss, and increased ROS levels. Treatment with SFN for 24 h significantly prevented these mitochondrial abnormalities, and reduced ROS levels. Analysis of Western blots and rt-PCR studies showed that SFN treatment increased the expression of several Nrf2-related antioxidants genes in caspase-3 cleaved tau cells. These results indicate a potential role of the Nrf2 pathway in preventing mitochondrial dysfunction induced by pathological forms of tau in AD.

Cadmium induces the expression of Interleukin-6 through Heme Oxygenase-1 in HK-2 cells and Sprague-Dawley rats

Cadmium is toxic to the kidney through mechanisms involving oxidative stress and inflammation. We studied reciprocal crosstalk among the oxidative stress, inflammation, and the nuclear Nrf2 pathway in cadmium-induced nephrotoxicity on HK-2 human renal proximal tubular epithelial cells. Cadmium chloride (CdCl2) caused cell viability loss, Reactive Oxygen Species (ROS) generation, glutathione reduction, and Interleukin-6 (IL-6) expression, accompanied by Nrf2 activation and Heme Oxygenase-1 (HO-1) expression. Pharmacological treatments demonstrated cytotprotective and anti-inflammatory effects of Nrf2 activation. Intriguingly, inhibition of HO-1 activity mitigated cell viability loss and IL-6 expression in CdCl2-treated cells. Parallel attenuation by HO-1 inhibitor was demonstrated in cadmium-induced ROS generation and glutathione reduction. CdCl2-treated cells also increased levels of ferrous iron, cGMP, Mitogen-Activated Protein Kinases phosphorylation, as well as NF-κB DNA-binding activity. These increments were mitigated by antioxidant N-Acetyl Cysteine, HO-1 inhibitor SnPP, and PKG inhibitor KT5823, and were mimicked by the Carbon Monoxide-releasing compound. In the kidney cortex of CdCl2-exposed Sprague-Dawley rats, we found similar renal injury, histological changes, ROS generation, IL-6 expression, and accompanied pro-oxidant and pro-inflammatory changes. These observations indicated that cadmium-induced nephrotoxicity was associated with oxidative stress and inflammation, and HO-1 likely acts as a linking molecule to induce nephrotoxicity-associated IL-6 expression upon cadmium exposure.

Nrf2 activation mediates the protection of mouse Sertoli Cells damage under acute heat stress conditions

Heat stress is known to negatively impact the reproductive process of livestock, which inevitably leads to a decline in animal fertility. Nuclear factor E2-related factor 2 (Nrf2) is an inducible transcription factor, which is essential for maintaining redox signal transmission against oxidative stress. However, there is no reliable research on the response mechanism of Sertoli Cells (SCs) against heat stress and the activation of Nrf2 when SCs are exposed to heat stress. Here, we used primary mouse SCs and SCs line TM4, along with Nrf2 specific inhibitor to determine the reaction mechanism of SCs to maintain intracellular redox homeostasis and self-survival by activating Nrf2. We found that acute heat stress only affected the vitality of SCs and the expression of functional molecules (tight junction-associated proteins and lactate dehydrogenase A [LDHA]) but did not cause cell apoptosis. When Nrf2 was inhibited, more cell death occurred in TM4 cells post heat stress treatment, along with a greater decrease in cell viability and a significant increase in intracellular ROS levels. Our study clarified for the first time the protective effect of Nrf2 activation on heat stress-induced SCs damage. It explained the possible reasons or mechanisms involved in the survival of SCs, the critical protective cells in the testis, which were not affected by heat stress. This study further improved the response mechanism of SCs in the reproductive injury caused by a high-temperature environment.

Activation of Nrf2 signaling protects hypoxia-induced HTR-8/SVneo cells against ferroptosis.

This article aims to investigate the possible mechanism by which nuclear factor erythroid 2-related factor 2 (Nrf2) signaling exerts protective effects on the progression of preeclampsia (PE). HTR-8/SVneo cells were cultured under hypoxic conditions to establish PE cell model. Cell viability and invasion were respectively examined by CCK-8 assay and transwell assay. The detection of oxidative stress and Fe2+ content was carried out by corresponding commercial kits, and the expression of corresponding proteins and genes was detected by western blot and qPCR. After Nrf2 was overexpressed in HTR-8/SVneo cells, the above assays were conducted to confirm the exact effects of Nrf2 activation on ferroptosis. Hypoxia reduced the invasion of HTR-8/SVneo cells, induced oxidative stress (upregulated levels of glutathione [GSH], malondialdehyde [MDA], and reactive oxygen species [ROS]), and induced ferroptosis which exhibited by upregulated Fe2+ and downregulated expression of solute carrier family 7 member 11/System xCT (SCL7A11), glutathione peroxidase 4 (GPX4), and ferroportin1 (FPN1). Meanwhile, hypoxia promoted the translocation of Nrf2 to the nucleus, leading to Nrf2/HO-1 signaling activation. These changes upon hypoxia induction were strengthened by ferric ammonium citrate (FAC) but were abolished by deferoxamine (DFO). Moreover, Nrf2 overexpression in hypoxia-induced HTR-8/SVneo cells exerted inhibitory effects on levels of GSH, MDA, ROS, and Fe2+ , and promotive effects on Nrf2/HO-1 signaling activation and expression of SCL7A11, GPX4, and FPN1, indicating that Nrf2 overexpression decreased oxidative stress and ferroptosis in hypoxia-induced HTR-8/SVneo cells. Collectively, activation of Nrf2 signaling alleviated hypoxia-induced invasion lacking, oxidative stress, and ferroptosis in hypoxia-induced HTR-8/SVneo cells, suggesting that Nrf2 signaling activation play a protective role in PE, which can provide instructions for the targeted treatment of PE.

NRF2: A potential target for the treatment of diabetic nephropathy

Abstract One of the major complications of diabetes mellitus is diabetic nephropathy (DN), the pathogenesis of which is primarily driven by oxidative stress. As a major regulator of antioxidant responses, the transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) has recently attracted much interest. NRF2 is a primary defense mechanism against the cytotoxic effects of oxidative stress, involving heterogeneous detoxification, the production of antioxidants and anti-inflammatory molecules, DNA repair, nuclear chaperones, and proteasome systems. A myriad of studies in pre-clinical models of DN have consistently demonstrated a beneficial effect of NRF2 activation, suggesting that NRF2 is likely a promising target for treating DN. This has been further supported by findings from clinical trials of bardoxolone methyl, an activator of NRF2, despite the unexpected adverse cardiovascular effects. This review summarizes the support for therapeutic targeting of NRF2 in DN and emphasizes the need for the optimization of NRF2-based treatment with the minimization of potential adverse effects.

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.

Nrf2 activation for kidney disease treatment—a mixed blessing?

Activation of cellular antioxidative signaling is expected to be a silver bullet against kidney diseases, and clinical trials of compounds activating the antioxidant transcription factor Nrf2 have revealed their renoprotective effects. However, cardiac events have been observed in some cases with elevated urinary albumin excretion in these trials. Therefore, elucidating the negative effects of Nrf2 activation is essential. Rush and colleagues demonstrated that Nrf2 activation aggravates podocyte injury, a factor related to proteinuria and cardiac failure.