Nrf2-mediated metabolic reprogramming of tolerogenic dendritic cells is protective against aplastic anemia

NRF2 Plays a Crucial Role in the Tolerogenic Effect of Ethyl Pyruvate on Dendritic Cells

Ethyl pyruvate (EP) is a redox-active compound that has been previously shown to be effective in restraining immune hyperactivity in animal models of various autoimmune and chronic inflammatory diseases. Importantly, EP has also been proven to have a potent tolerogenic effect on dendritic cells (DCs). Here, the influence of EP on the signaling pathways in DCs relevant for their tolerogenicity, including anti-inflammatory NRF2 and pro-inflammatory NF-κB, was explored. Specifically, the effects of EP on DCs obtained by GM-CSF-directed differentiation of murine bone marrow precursor cells and matured under the influence of lipopolysaccharide (LPS) were examined via immunocytochemistry and RT-PCR. EP counteracted LPS-imposed morphological changes and down-regulated the LPS-induced expression of pro-inflammatory mediators in DCs. While it reduced the activation of NF-κB, EP potentiated NRF2 and downstream antioxidative molecules, thus implying the regulation of NRF2 signaling pathways as the major reason for the tolerizing effects of EP on DCs.

The crucial role of NRF2 in erythropoiesis and anemia: Mechanisms and therapeutic opportunities

The nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor crucial in cellular defense against oxidative and electrophilic stresses. Recent research has highlighted the significance of NRF2 in normal erythropoiesis and anemia. NRF2 regulates genes involved in vital aspects of erythroid development, including hemoglobin catabolism, inflammation, and iron homeostasis in erythrocytes. Disrupted NRF2 activity has been implicated in various pathologies involving abnormal erythropoiesis. In this review, we summarize the progress made in understanding the mechanisms of NRF2 activation in erythropoiesis and explore the roles of NRF2 in various types of anemia. This review also discusses the potential of targeting NRF2 as a new therapeutic approach to treat anemia.

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.

Advances in understanding of dendritic cell in the pathogenesis of acute kidney injury

Acute kidney injury (AKI) is characterized by a rapid decline in renal function and is associated with a high morbidity and mortality rate. At present, the underlying mechanisms of AKI remain incompletely understood. Immune disorder is a prominent feature of AKI, and dendritic cells (DCs) play a pivotal role in orchestrating both innate and adaptive immune responses, including the induction of protective proinflammatory and tolerogenic immune reactions. Emerging evidence suggests that DCs play a critical role in the initiation and development of AKI. This paper aimed to conduct a comprehensive review and analysis of the role of DCs in the progression of AKI and elucidate the underlying molecular mechanism. The ultimate objective was to offer valuable insights and guidance for the treatment of AKI.

Chemotherapy-induced microbiota exacerbates the toxicity of chemotherapy through the suppression of interleukin-10 from macrophages

The gut microbiota has been shown to influence the efficacy and toxicity of chemotherapy, thereby affecting treatment outcomes. Understanding the mechanism by which microbiota affects chemotherapeutic toxicity would have a profound impact on cancer management. In this study, we report that fecal microbiota transplantation from oxaliplatin-exposed mice promotes toxicity in recipient mice. Splenic RNA sequencing and macrophage depletion experiment showed that the microbiota-induced toxicity of oxaliplatin in mice was dependent on macrophages. Furthermore, oxaliplatin-mediated toxicity was exacerbated in Il10-/- mice, but not attenuated in Rag1-/- mice. Adoptive transfer of macrophage into Il10-/- mice confirmed the role of macrophage-derived IL-10 in the improvement of oxaliplatin-induced toxicity. Depletion of fecal Lactobacillus and Bifidobacterium was associated with the exacerbation of oxaliplatin-mediated toxicity, whereas supplementation with these probiotics alleviated chemotherapy-induced toxicity. Importantly, IL-10 administration and probiotics supplementation did not attenuate the antitumor efficacy of chemotherapy. Clinically, patients with colorectal cancer exposed to oxaliplatin exhibited downregulation of peripheral CD45+IL-10+ cells. Collectively, our findings indicate that microbiota-mediated IL-10 production influences tolerance to chemotherapy, and thus represents a potential clinical target.

Impact of resveratrol and zinc on biomarkers of oxidative stress induced by Trichinella spiralis infection

Trichinellosis is a re-emerging worldwide foodborne zoonosis. Oxidative stress is one of the most common detrimental effects caused by trichinellosis. In addition, Trichinella infection poses an infinite and major challenge to the host's immune system. Resistance and side effects limit the efficiency of the existing anti-trichinella medication. Given that concern, this work aimed to investigate the anti-helminthic, antioxidant, anti-inflammatory and immunomodulatory effects of resveratrol and zinc during both phases of Trichinella spiralis infection. Sixty-four Swiss albino mice were divided into four equal groups: non-infected control, infected control, infected and treated with resveratrol, and infected and treated with zinc. Animals were sacrificed on the 7th and 35th days post-infection for intestinal and muscular phase assessments. Drug efficacy was assessed by biochemical, parasitological, histopathological, immunological, and immunohistochemical assays. Resveratrol and zinc can be promising antiparasitic, antioxidant, anti-inflammatory, and immunomodulatory agents, as evidenced by the significant decrease in parasite burden, the significant improvement of liver and kidney function parameters, the increase in total antioxidant capacity (TAC), the reduction of malondialdehyde (MDA) level, the increase in nuclear factor (erythroid-derived 2)-like-2 factor expression, and the improvement in histopathological findings. Moreover, both drugs enhanced the immune system and restored the disturbed immune balance by increasing the interleukin 12 (IL-12) level. In conclusion, resveratrol and zinc provide protection for the host against oxidative harm and the detrimental effects produced by the host's defense response during Trichinella spiralis infection, making them promising natural alternatives for the treatment of trichinellosis.

Monomethyl fumarate prevents alloimmune rejection in mouse heart transplantation by inducing tolerogenic dendritic cells

Dendritic cells (DCs) are important targets for eliciting allograft rejection after transplantation. Previous studies have demonstrated that metabolic reprogramming of DCs can transform their immune functions and induce their differentiation into tolerogenic DCs. In this study, we aim to investigate the protective effects and mechanisms of monomethyl fumarate (MMF), a bioactive metabolite of fumaric acid esters, in a mouse model of allogeneic heart transplantation. Bone marrow-derived DCs are harvested and treated with MMF to determine the impact of MMF on the phenotype and immunosuppressive function of DCs by flow cytometry and T-cell proliferation assays. RNA sequencing and Seahorse analyses are performed for mature DCs and MMF-treated DCs (MMF-DCs) to investigate the underlying mechanism. Our results show that MMF prolongs the survival time of heart grafts and inhibits the activation of DCs in vivo. MMF-DCs exhibit a tolerogenic phenotype and function in vitro. RNA sequencing and Seahorse analyses reveal that MMF activates the Nrf2 pathway and mediates metabolic reprogramming. Additionally, MMF-DC infusion prolongs cardiac allograft survival, induces regulatory T cells, and inhibits T-cell activation. MMF prevents allograft rejection in mouse heart transplantation by inducing tolerogenic DCs.

Immunomodulatory effects of icariin in a myocardial infarction mouse model

Myocardial infarction (MI) is a prevalent cardiovascular disease defined by myocardial ischemia and hypoxic damage caused by plaque rupture, thrombosis, lumen stenosis, or blockage in the coronary artery. However, the development of emergency percutaneous coronary interventional therapy has enabled the rapid restoration of blood perfusion to ischemic myocardium and the rescue of dying myocardium cells. Some dying myocardium cells have caused irreversible damage and impaired cardiac function recovery in recent years. Icariin has been utilized to treat various ailments as a natural chemical extract. In this study, we employed a variety of approaches to observe MI, including western blotting, quantitative RT–PCR, immunohistochemistry, and flow cytometric analysis using icariin. As demonstrated by the research findings, icariin may prevent MI-induced cell apoptosis. This is accomplished by inhibiting proinflammatory factors via the Nrf2/HO-1 signaling pathways. These data imply that icariin may be an effective treatment for MI.

Naringenin Regulates FKBP4/NR3C1/NRF2 Axis in Autophagy and Proliferation of Breast Cancer and Differentiation and Maturation of Dendritic Cell

NRF2 is an important regulatory transcription factor involved in tumor immunity and tumorigenesis. In this study, we firstly identified that FKBP4/NR3C1 axis was a novel negative regulator of NRF2 in human breast cancer (BC) cells. The effect of FKBP4 appeared to be at protein level of NRF2 since it could not suppress the expression of NRF2 at mRNA level. Bioinformatics analysis and in vitro experiments further demonstrated that FKBP4 regulated NRF2 via regulating nuclear translocation of NR3C1. We then reported that naringenin, a flavonoid, widely distributed in citrus and tomato, could suppress autophagy and proliferation of BC cells through FKBP4/NR3C1/NRF2 signaling pathway in vitro and in vivo. Naringenin was also found to promote dendritic cell (DC) differentiation and maturation through FKBP4/NR3C1/NRF2 axis. Therefore, our study found that naringenin could induce inhibition of autophagy and cell proliferation in BC cells and enhance DC differentiation and maturation, at least in part, though regulation of FKBP4/NR3C1/NRF2 signaling pathway. Identification of FKBP4/NR3C1/NRF2 axis would provide insights for novel anti-tumor strategy against BC among tumor microenvironment.

Protective effects of Nrf2 against sepsis-induced hepatic injury

AIM

This study was designed to investigate the changes of liver injury and Nrf2 signaling pathway in the process of sepsis. We also aimed to examine the role of Nrf2 in resisting oxidative stress and relieving inflammation in sepsis-induced hepatic injury.

MAIN METHODS

By operating cecal ligation and puncture (CLP) on Nrf2^-/- mice and wild type mice, a sepsis-induced hepatic injury model was established. We compared and contrasted the wild type mice with the Nrf2^-/- mice during sepsis-induced hepatic injury, and evaluated the liver damage by biochemical analyses and staining hematoxylin-eosin (HE). Western blot or real-time PCR was performed to detect Nrf2 and its regulated genes NQO-1, GCLM and HO-1. Additionally, we detected the expressions and secretion of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), Interleukin-6 (IL-6), IL-1β and anti-inflammatory cytokines IL-10. We assessed the oxidative stress through the levels of MDA and NO.

KEY FINDINGS

The results showed that Nrf2 expressions at mRNA and protein levels were increased 1 day after CLP, namely the early stage of sepsis. Compared with wild type mice after CLP, Nrf2^-/- mice showed more severe liver injury, accompanied by higher expression of inflammatory cytokines and oxidative stress. Notably, Nrf2-regulated genes GCLM and NQO-1, were strongly downregulated in Nrf2^-/- mice.

SIGNIFICANCE

Nrf2 was probably implicated in decreasing inflammatory cytokine levels and counteracting oxidative stress to alleviate sepsis-induced hepatic injury, mainly through regulating GCLM and NQO-1 in the early stage after CLP.

Nrf2 Participates in M2 Polarization by Trichinella spiralis to Alleviate TNBS-Induced Colitis in Mice

Trichinella spiralis induced alternative activated macrophages (M2), leading to protect against Crohn's disease, known as Th1 -related inflammation, which enhances oxidative stress in the host. However, the relationship of oxidative stress and T. spiralis -mediated immune response is still unknown. In our study, we showed that nuclear factor erythroid 2-related factor-2 (Nrf2), a key transcription factor in antioxidant, participated in M2 polarization induced by T. spiralis muscle larval excretory/secretory (ES) products in vitro. ES -treated M2 were injected intravenously after TNBS challenge and we demonstrated that ES-M could alleviate the severity of the colitis in mice. Adoptive transfer of ES -treated M2 decreased the level of IFN-γ and increased the levels of IL-4 and IL-10 in vivo. However, the capacity of ES -treated Nrf2 KO macrophages to treat colitis was dramatically impaired. ES -treated Nrf2 KO macrophages was insufficient to result in the elevated levels of IL-4 and IL-10. These findings indicate that Nrf2 was required for M2 polarization induced by T. spiralis ES to alleviate colitis in mice.

Dendritic Cells: Versatile Players in Renal Transplantation

Dendritic cells (DCs) induce and regulate adaptive immunity through migrating and maturing in the kidney. In this procedure, they can adopt different phenotypes—rejection-associated DCs promote acute or chronic injury renal grafts while tolerogenic DCs suppress the overwhelmed inflammation preventing damage to renal functionality. All the subsets interact with effector T cells and regulatory T cells (Tregs) stimulated by the ischemia–reperfusion procedure, although the classification corresponding to different effects remains controversial. Thus, in this review, we discuss the origin, maturation, and pathological effects of DCs in the kidney. Then we summarize the roles of divergent DCs in renal transplantation: taking both positive and negative stages in ischemia–reperfusion injury (IRI), switching phenotypes to induce acute or chronic rejection, and orchestrating surface markers for allograft tolerance via alterations in metabolism. In conclusion, we prospect that multidimensional transcriptomic analysis will revolute researches on renal transplantation by addressing the elusive mononuclear phagocyte classification and providing a holistic view of DC ontogeny and subpopulations.

Identification of a subset of immunosuppressive P2RX1-negative neutrophils in pancreatic cancer liver metastasis

The immunosuppressive microenvironment that is shaped by hepatic metastatic pancreatic ductal adenocarcinoma (PDAC) is essential for tumor cell evasion of immune destruction. Neutrophils are important components of the metastatic tumor microenvironment and exhibit heterogeneity. However, the specific phenotypes, functions and regulatory mechanisms of neutrophils in PDAC liver metastases remain unknown. Here, we show that a subset of P2RX1-negative neutrophils accumulate in clinical and murine PDAC liver metastases. RNA sequencing of murine PDAC liver metastasis-infiltrated neutrophils show that P2RX1-deficient neutrophils express increased levels of immunosuppressive molecules, including PD-L1, and have enhanced mitochondrial metabolism. Mechanistically, the transcription factor Nrf2 is upregulated in P2RX1-deficient neutrophils and associated with PD-L1 expression and metabolic reprogramming. An anti-PD-1 neutralizing antibody is sufficient to compromise the immunosuppressive effects of P2RX1-deficient neutrophils on OVA-activated OT1 CD8+ T cells. Therefore, our study uncovers a mechanism by which metastatic PDAC tumors evade antitumor immunity by accumulating a subset of immunosuppressive P2RX1-negative neutrophils.

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive metastatic disease characterized by an immunosuppressive microenvironment. Here the authors show that a subset of P2RX1-negative neutrophils with immunosuppressive properties accumulate in PDAC metastatic liver tissues and promote tumor growth.

Tolerogenic Dendritic Cells: The Pearl of Immunotherapy in Organ Transplantation

Over a half century, organ transplantation has become an effective method for the treatment of end-stage visceral diseases. Although the application of immunosuppressants (IS) minimizes the rate of allograft rejection, the common use of IS bring many adverse effects to transplant patients. Moreover, true transplant tolerance is very rare in clinical practice. Dendritic cells (DCs) are thought to be the most potent antigen-presenting cells, which makes a bridge between innate and adaptive immunity. Among their subsets, a small portion of DCs with immunoregulatory function was known as tolerogenic DC (Tol-DC). Previous reports demonstrated the ability of adoptively transferred Tol-DC to approach transplant tolerance in animal models. In this study, we summarized the properties, ex vivo generation, metabolism, and clinical attempts of Tol-DC. Tol-DC is expected to become a substitute for IS to enable patients to achieve immune tolerance in the future.

Metabolic Reprogramming is a Hallmark of Metabolism Itself

The reprogramming of metabolism has been identified as one of the hallmarks of cancer. It is becoming more and more frequent to connect other diseases with metabolic reprogramming. This article aims to argue that metabolic reprogramming is not driven by disease but instead is the main hallmark of metabolism, based on its dynamic behavior that allows it to continuously adapt to changes in the internal and external conditions.

Circular RNA circSnx5 Controls Immunogenicity of Dendritic Cells through the miR-544/SOCS1 Axis and PU.1 Activity Regulation

Dendritic cells (DCs) can orchestrate either immunogenic or tolerogenic responses to relay information on the functional state. Emerging studies indicate that circular RNAs (circRNAs) are involved in immunity; however, it remains unclear whether they govern DC development and function at the transcriptional level. In this study, we identified a central role for a novel circRNA, circSnx5, in modulating DC-driven immunity and tolerance. Ectopic circSnx5 suppresses DC activation and promotes the development of tolerogenic functions of DCs, while circSnx5 knockdown promotes their activation and inflammatory phenotype. Mechanistically, circSnx5 can act as a miR-544 sponge to attenuate miRNA-mediated target depression on suppressor of cytokine signaling 1 (SOCS1) and inhibit nuclear translocation of PU.1, regulating DC activation and function. Furthermore, the main splicing factors (SFs) were identified in DCs, of which heterogeneous nuclear ribonucleoprotein (hnRNP) C was essential for circSnx5 generation. Moreover, our data demonstrated that vaccination with circSnx5-conditioned DCs prolonged cardiac allograft survival in mice and alleviated experimental autoimmune myocarditis. Taken together, our results revealed circSnx5 as a key modulator to fine-tune DC function, suggesting that circSnx5 may serve as a potential therapeutic avenue for immune-related diseases.

Current Concepts of the Pathogenesis of Aplastic Anemia

Abnormal activation of the immune system plays an important role in the pathogenesis of aplastic anemia (AA). Various immune cells and cytokines constitute a complex immune network, leading to bone marrow failure. The known pathogenesis is an increase of the myeloid dendritic cell (mDC)/ plasmacytoid dendritic cell (pDC) ratio, which causes the ratio of T helper (Th)1/Th2 to be skewed in favor of Th1 and eventually leads to an abnormal activation of cytotoxic T lymphocyte (CTL). The antigens that stimulate T cells in the context of AA remain unknown. In this process, regulatory T (Treg), Th17, natural killer (NK) cell, memory T cell and negative hematopoietic regulatory factors are also involved. In addition, genetic background (e.g., chromosomal abnormalities, telomere attrition, somatic cell mutations), abnormal bone marrow hematopoietic microenvironment and viral infection may also contribute to the pathogenesis of AA. This review summarizes the recent studies of the pathogenesis of AA and the current status of AA research.

Analyzing the Metabolic Phenotype of Bone Marrow-Derived Dendritic Cells by Assessing Their Oxygen Consumption and Extracellular Acidification

Dendritic cells (DCs) are the bridge between innate and T cell-dependent adaptive immunity, and are promising therapeutic targets for cancer and immune-mediated disorders. In the recent past, DCs have gained significant interest to manipulate them for the treatment of cancer and immune-mediated disorders. This can be achieved by differentiating them into either immunogenic or tolerogenic DCs (TolDCs), by modulating their metabolic pathways, including glycolysis, oxidative phosphorylation, and fatty acid metabolism, to orchestrate their desired function. For immunogenic DCs, this maturation shifts the metabolic profile to a glycolytic metabolic state and leads to the use of glucose as a carbon source, whereas TolDCs prefer oxidative phosphorylation (OXPHOS) and fatty acid oxidation for their energy resource.Understanding the metabolic regulation of DC subsets and functions at large not only will improve our understanding of DC biology and immune regulation, but can also open up opportunities for treating immune-mediated ailments and cancers by tweaking endogenous T-cell responses through DC-based immunotherapies. Here we describe a method to analyze this dichotomous metabolic reprogramming of the DCs for generating reliable and effective DC cell therapy products. We, hereby, report how to measure the OXPHOS and glycolysis level of DCs. We focus on the metabolic reprogramming of TolDCs using a pharmacological nuclear factor (erythroid-derived 2)-like-2 factor (Nrf2) activator as an example to illustrate the metabolic profile of TolDCs.

Loss of exosomal MALAT1 from ox-LDL-treated vascular endothelial cells induces maturation of dendritic cells in atherosclerosis development

Objectives: Maturation of dendritic cells (DCs) contributes to atherosclerosis (AS) development. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is a long non-coding RNA (lncRNA) that is involved in tumorigenesis. This study was designed to explore the role of exosomes from oxidized low-density lipoprotein (oxLDL)-treated vascular endothelial cells (VECs) in regulating DCs maturation in AS, and to elucidate whether MALAT1 was involved in this process.

Methods: Human umbilical VECs (HUVECs) were treated with or without ox-LDL, after which exosomes were isolated and then co-cultured with immature DCs (iDCs). The phenotypic profile and cell endocytosis in DCs were examined to assess the degree of maturation of DCs. The interaction between MALAT1 and NRF2 protein in DCs was evaluated using RNA pull-down assay and RNA immunoprecipitation. A mouse model of AS was eatablished by feeding ApoE knockout (ApoE^−/-) mice with a high-fat diet for 12 weeks.

Results: The ox-LDL-HUVECs-Exos exhibited lower MALAT1 expression when compared with HUVECs-Exos. Furthermore, exosomes from ox-LDL-treated MALAT1-overexpressing-HUVECs (ox-LDL-HUVECs-Exos^Lv-MALAT1) released elevated expression of MALAT1 to iDCs, which interacted with NRF2 and activated NRF2 signaling, and thereby inhibited ROS accumulation and DCs maturation. Further in vivo experiments showed that a decrease in MALAT1 content in mouse VECs-Exos might be associated with mouse AS progression.

Conclusion: Loss of exosomal MALAT1 from ox-LDL-treated VECs induces DCs maturation in atherosclerosis development.