The AMP analog AICAR modulates the Treg/Th17 axis through enhancement of fatty acid oxidation

Lipid metabolism in tumor-infiltrating regulatory T cells: perspective to precision immunotherapy

Regulatory T cells (Tregs) are essential to the negative regulation of the immune system, as they avoid excessive inflammation and mediate tumor development. The abundance of Tregs in tumor tissues suggests that Tregs may be eliminated or functionally inhibited to stimulate antitumor immunity. However, immunotherapy targeting Tregs has been severely hampered by autoimmune diseases due to the systemic elimination of Tregs. Recently, emerging studies have shown that metabolic regulation can specifically target tumor-infiltrating immune cells, and lipid accumulation in TME is associated with immunosuppression. Nevertheless, how Tregs actively regulate metabolic reprogramming to outcompete effector T cells (Teffs), and how lipid metabolic reprogramming contributes to the immunomodulatory capacity of Tregs have not been fully discussed. This review will discuss the physiological processes by which lipid accumulation confers a metabolic advantage to tumor-infiltrating Tregs (TI-Tregs) and amplifies their immunosuppressive functions. Furthermore, we will provide a summary of the driving effects of various metabolic regulators on the metabolic reprogramming of Tregs. Finally, we propose that targeting the lipid metabolism of TI-Tregs could be efficacious either alone or in conjunction with immune checkpoint therapy.

Immmunometabolism of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a potentially fatal chronic autoimmune disease which is underlain by complex dysfunction of the innate and adaptive immune systems. Although a series of well-defined genetic and environmental factors have been implicated in disease etiology, neither the development nor the persistence of SLE is well understood. Given that several disease susceptibility genes and environmental factors interact and influence inflammatory lineage specification through metabolism, the field of immunometabolism has become a forefront of cutting edge research. Along these lines, metabolic checkpoints of pathogenesis have been identified as targets of effective therapeutic interventions in mouse models and validated in clinical trials. Ongoing studies focus on mitochondrial oxidative stress, activation of the mechanistic target of rapamycin, calcium signaling, glucose utilization, tryptophan degradation, and metabolic cross-talk between gut microbiota and the host immune system.

Mitochondrial-regulated Tregs: potential therapeutic targets for autoimmune diseases of the central nervous system

Regulatory T cells (Tregs) can eliminate autoreactive lymphocytes, induce self-tolerance, and suppress the inflammatory response. Mitochondria, as the energy factories of cells, are essential for regulating the survival, differentiation, and function of Tregs. Studies have shown that patients with autoimmune diseases of the central nervous system, such as multiple sclerosis, neuromyelitis optica spectrum disorder, and autoimmune encephalitis, have aberrant Tregs and mitochondrial damage. However, the role of mitochondrial-regulated Tregs in autoimmune diseases of the central nervous system remains inconclusive. Therefore, this study reviews the mitochondrial regulation of Tregs in autoimmune diseases of the central nervous system and investigates the possible mitochondrial therapeutic targets.

T Lymphocyte Metabolic Features and Techniques to Modulate Them

T cells demonstrate high degree of complexity and broad range of functions, which distinguish them from other immune cells. Throughout their lifetime, T lymphocytes experience several functional states: quiescence, activation, proliferation, differentiation, performance of effector and regulatory functions, memory formation, and apoptosis. Metabolism supports all functions of T cells, providing lymphocytes with energy, biosynthetic substrates, and signaling molecules. Therefore, T cells usually restructure their metabolism as they transition from one functional state to another. Strong association between the metabolism and T cell functions implies that the immune response can be controlled by manipulating metabolic processes within T lymphocytes. This review aims to highlight the main metabolic adaptations necessary for the T cell function, as well as the recent progress in techniques to modulate metabolic features of lymphocytes.

Identification and validation of a fatty acid metabolism gene signature for the promotion of metastasis in liver cancer

Metastasis is a fatal status for liver cancer, and the identification of an effective prediction model and promising therapeutic target is essential. Given the known relationship between fatty acid (FA) metabolism and the liver, the present study aimed to investigate dysregulation of genes associated with FA metabolism in liver cancer. Bioinformatics analyses were performed on data from patients with hepatocellular carcinoma (HCC) obtained from The Cancer Genome Atlas database using R software packages. Online public tools such as the Human Protein Atlas, Tumor Immune Single-Cell Hub and the University of Alabama at Birmingham Cancer Data Analysis portal were also utilized. Some essential results were further verified using in vitro experiments using HepG2 liver cancer cells. A signature consisting of three genes associated with the progression and prognosis of HCC and FA metabolism was identified. When samples were scored based on the expression of these genes and divided according to the median value, the higher score group showed a worse outcome and repressive immune microenvironment than the lower score group. Downstream pathways such as hypoxia, IL6/JAK/STAT3 and epithelial-mesenchymal transition were found to be significantly activated in the higher score group. As the core factor in the signature, mitochondrial ribosomal protein L35 (MRPL35) was found to be upregulated in HCC and to have certain impacts on the dysregulation of effective immunity. Further investigations and in vitro experiments indicated that MRPL35 facilitates the migration and invasion abilities of liver cancer, and the resistance of HCC to treatment. These findings have important implications regarding the characteristics and mechanisms of metastasis in liver cancer, and provide a promising signature based on FA metabolism-related genes that may be used to predict outcomes and explored as a novel therapeutic target in liver cancer.

Targeting regulatory T cell metabolism in disease: Novel therapeutic opportunities

Regulatory T cells (Tregs) are essential for immune homeostasis and suppression of pathological autoimmunity but can also play a detrimental role in cancer progression via inhibition of anti-tumor immunity. Thus, there is broad applicability for therapeutic Treg targeting, either to enhance function, for example, through adoptive cell therapy (ACT), or to inhibit function with small molecules or antibody-mediated blockade. For both of these strategies, the metabolic state of Tregs is an important consideration since cellular metabolism is intricately linked to function. Mounting evidence has shown that targeting metabolic pathways can selectively promote or inhibit Treg function. This review aims to synthesize the current understanding of Treg metabolism and discuss emerging metabolic targeting strategies in the contexts of transplantation, autoimmunity, and cancer. We discuss approaches to gene editing and cell culture to manipulate Treg metabolism during ex vivo expansion for ACT, as well as in vivo nutritional and pharmacological interventions to modulate Treg metabolism in disease states. Overall, the intricate connection between metabolism and phenotype presents a powerful opportunity to therapeutically tune Treg function.

PROTECTIVE EFFECTS OF HUMANIN-G IN HEMORRHAGIC SHOCK IN FEMALE MICE VIA AMPKα1-INDEPENDENT MECHANISMS

ABSTRACT

Introduction: Despite therapeutic advances in hemorrhagic shock, mortality from multiple organ failure remains high. We previously showed that the α1 subunit of AMP-activated protein kinase (AMPK), a crucial regulator of mitochondrial function, exerts a protective role in hemorrhagic shock. Humanin is a mitochondrial peptide with cytoprotective properties against cellular stress. Here, we investigated whether AMPKα1 influences systemic levels of endogenous humanin in hemorrhagic shock and whether treatment with the synthetic analog humanin-G affords beneficial effects. Methods: AMPKα1 wild-type (WT) and knockout (KO) female mice were subjected to hemorrhagic shock followed by resuscitation with blood and lactated Ringer's solution. In short-term studies, mice were treated with humanin-G or vehicle and sacrificed at 3 h after resuscitation; in survival studies, mice were treated with PEGylated humanin-G and monitored for 7 days. Results: Compared with the vehicle WT group, KO mice exhibited severe hypotension, cardiac mitochondrial damage, and higher plasma levels of Th17 cytokines but had similar lung injury and similar plasma elevation of endogenous humanin. Treatment with humanin-G improved lung injury, mean arterial blood pressure, and survival in both WT and KO mice, without affecting systemic cytokine or humanin levels. Humanin-G also ameliorated cardiac mitochondrial damage and increased adenosine triphosphate levels in KO mice. Beneficial effects of humanin-G were associated with lung cytoplasmic and nuclear activation of the signal transducer and activator of transcription-3 (STAT3) in AMPKα1-independent manner with marginal or no effects on mitochondrial STAT3 and complex I subunit GRIM-19. Conclusions: Our data indicate that circulating levels of humanin increase during hemorrhagic shock in AMPKα1-independent fashion as a defense mechanism to counteract metabolic derangement and that administration of humanin-G affords beneficial effects through STAT3 activation even in the absence of a functional AMPKα1.

LKB1 isoform expression modulates T cell plasticity downstream of PKCθ and IL-6

Following activation, CD4 T cells undergo metabolic and transcriptional changes as they respond to external cues and differentiate into T helper (Th) cells. T cells exhibit plasticity between Th phenotypes in highly inflammatory environments, such as colitis, in which high levels of IL-6 promote plasticity between regulatory T (Treg) cells and Th17 cells. Protein Kinase C theta (PKCθ) is a T cell-specific serine/threonine kinase that promotes Th17 differentiation while negatively regulating Treg differentiation. Liver kinase B1 (LKB1), also a serine/threonine kinase and encoded by Stk11, is necessary for Treg survival and function. Stk11 can be alternatively spliced to produce a short variant (Stk11_S) by transcribing a cryptic exon. However, the contribution of Stk11 splice variants to Th cell differentiation has not been previously explored. Here we show that in Th17 cells, the heterogeneous ribonucleoprotein, hnRNPLL, mediates Stk11 splicing into its short splice variant, and that Stk11_S expression is diminished when Hnrnpll is depleted using siRNA knock-down approaches. We further show that PKCθ regulates hnRNPLL and, thus, Stk11_S expression in Th17 cells. We provide additional evidence that exposing induced (i)Tregs to IL-6 culminates in Stk11 splicing downstream of PKCθAltogether our data reveal a yet undescribed outside-in signaling pathway initiated by IL-6, that acts through PKCθ and hnRNPLL to regulate Stk11 splice variants and facilitate Th17 cell differentiation. Furthermore, we show for the first time, that this pathway can also be initiated in developing iTregs exposed to IL-6, providing mechanistic insight into iTreg phenotypic stability and iTreg to Th17 cell plasticity.

Lipid metabolism of hepatocellular carcinoma impacts targeted therapy and immunotherapy

Hepatocellular carcinoma (HCC) is a common malignant tumor that affecting many people's lives globally. The common risk factors for HCC include being overweight and obese. The liver is the center of lipid metabolism, synthesizing most cholesterol and fatty acids. Abnormal lipid metabolism is a significant feature of metabolic reprogramming in HCC and affects the prognosis of HCC patients by regulating inflammatory responses and changing the immune microenvironment. Targeted therapy and immunotherapy are being explored as the primary treatment strategies for HCC patients with unresectable tumors. Here, we detail the specific changes of lipid metabolism in HCC and its impact on both these therapies for HCC. HCC treatment strategies aimed at targeting lipid metabolism and how to integrate them with targeted therapy or immunotherapy rationally are also presented.

Artesunate targets cellular metabolism to regulate the Th17/Treg cell balance

INTRODUCTION

Metabolic reprogramming is one of the important mechanisms of cell differentiation, and different cells have different preferences for energy sources. During the differentiation of naive CD4 + T cells into Th17 and Treg cells, these cells show specific energy metabolism characteristics. Th17 cells depend on enhanced glycolysis, fatty acid synthesis, and glutaminolysis. In contrast, Treg cells are dependent on oxidative phosphorylation, fatty acid oxidation, and amino acid depletion. As a potent antimalarial drug, artesunate has been shown to modulate the Th17/Treg imbalance and regulate cell metabolism.

METHODOLOGY

Relevant literatures on ART, cellular metabolism, glycolysis, lipid metabolism, amino acid metabolism, CD4 + T cells, Th17 cells, and Treg cells published from January 1, 2010 to now were searched in PubMed database.

CONCLUSION

In this review, we will highlight recent advances in which artesunate can restore the Th17/Treg imbalance in disease states by altering T-cell metabolism to influence differentiation and lineage selection. Data from the current study show that few studies have focused on the effect of ART on cellular metabolism. ART can affect the metabolic characteristics of T cells (glycolysis, lipid metabolism, and amino acid metabolism) and interfere with their differentiation lineage, thereby regulating the balance of Th17/Treg and alleviating the symptoms of the disease.

Immuno-metabolic control of the balance between Th17-polarized and regulatory T-cells during HIV infection

Th17-polarized CD4⁺ effector T-cells together with their immunosuppressive regulatory T-cell (Treg) counterparts, with transcriptional profiles governed by the lineage transcription factors RORγt/RORC2 and FOXP3, respectively, are important gatekeepers at mucosal interfaces. Alterations in the Th17/Treg ratios, due to the rapid depletion of Th17 cells and increased Treg frequencies, are a hallmark of both HIV and SIV infections and a marker of disease progression. The shift in Th17/Treg balance, in favor of increased Treg frequencies, contributes to gut mucosal permeability, immune dysfunction, and microbial translocation, subsequently leading to chronic immune activation/inflammation and disease progression. Of particular interest, Th17 cells and Tregs share developmental routes, with changes in the Th17 versus Treg fate decision influencing the pro-inflammatory versus anti-inflammatory responses. The differentiation and function of Th17 cells and Tregs rely on independent yet complementary metabolic pathways. Several pathways have been described in the literature to be involved in Th17 versus Treg polarization, including 1) the activity of ectonucleotidases CD39/CD73; 2) the increase in TGF-β1 production; 3) a hypoxic environment, and subsequent upregulation in hypoxia-inducible factor-1α (HIF-1α); 4) the increased mTOR activity and glycolysis induction; 5) the lipid metabolism, including fatty acid synthesis, fatty acids oxidation, cholesterol synthesis, and lipid storage, which are regulated by the AMPK, mevalonate and PPARγ pathways; and 6) the tryptophan catabolism. These metabolic pathways are understudied in the context of HIV-1 infection. The purpose of this review is to summarize the current knowledge on metabolic pathways that are dysregulated during HIV-1 infection and their impact on Th17/Treg balance.

Role of FABP5 in T Cell Lipid Metabolism and Function in the Tumor Microenvironment

To evade immune surveillance, tumors develop a hostile microenvironment that inhibits anti-tumor immunity. Recent immunotherapy breakthroughs that target the reinvigoration of tumor-infiltrating T lymphocytes (TIL) have led to unprecedented success in treating some cancers that are resistant to conventional therapy, suggesting that T cells play a pivotal role in anti-tumor immunity. In the hostile tumor microenvironment (TME), activated T cells are known to mainly rely on aerobic glycolysis to facilitate their proliferation and anti-tumor function. However, TILs usually exhibit an exhausted phenotype and impaired anti-tumor activity due to the limited availability of key nutrients (e.g., glucose) in the TME. Given that different T cell subsets have unique metabolic pathways which determine their effector function, this review introduces our current understanding of T cell development, activation signals and metabolic pathways. Moreover, emerging evidence suggests that fatty acid binding protein 5 (FABP5) expression in T cells regulates T cell lipid metabolism and function. We highlight how FABP5 regulates fatty acid uptake and oxidation, thus shaping the survival and function of different T cell subsets in the TME.

Substrate stiffness enhances human regulatory T cell induction and metabolism

Regulatory T cells (Tregs) provide an essential tolerance mechanism to suppress the immune response. Induced Tregs hold the potential to treat autoimmune diseases in adoptive therapy and can be produced with stimulating signals to CD3 and CD28 in presence of the cytokine TGF-β and IL-2. This report examines the modulation of human Treg induction by leveraging the ability of T cells to sense the mechanical stiffness of an activating substrate. Treg induction on polyacrylamide gels (PA-gels) was sensitive to the substrate's elastic modulus, increasing with greater material stiffness. Single-cell RNA-Seq analysis revealed that Treg induction on stiffer substrates involved greater use of oxidative phosphorylation (OXPHOS). Inhibition of ATP synthase significantly reduced the rate of Treg induction and abrogated the difference among gels while activation of AMPK (AMP-activated protein kinase) increased Treg induction on the softer sample but not on the harder sample. Treg induction is thus mechanosensitive and OXPHOS-dependent, providing new strategies for improving the production of these cells for cellular immunotherapy.

AMPK activator AICAR in combination with anti-mouse IL10 mAb restores the functionality of intra-tumoral Tfh cells in the 4T1 mouse model

4T1 cell-mediated TNBC breast cell carcinoma is a highly malignant mice tumor model which resembles an advanced stage of breast cancer in humans. Tumor progression occurs depending on the intra-tumoral balance of pro- and anti- tumorigenic immune cells. Enhancement of T-cell-mediated anti-tumor immunity will be advantageous for inhibiting tumor progression and improving the efficacy of cancer therapy. This study is focused on alleviating suppressed anti-tumor immune response by improving CD4⁺ T follicular helper cell (Tfh) response in 4T1 mice. We employed anti-IL10 mAb along with metabolic drugs 2-deoxy-D-glucose (2DG) which inhibits the glycolytic pathway and Cpt1a inhibitor Etomoxir which inhibits FAO. AMPK activator AICAR with or without anti-IL10 mAb was also used to ameliorate metabolic stress and exhaustion faced by immune cells. Our results demonstrate that synergistic treatment with 2DG/Etomoxir + anti-IL10 mAb induced Tfh cell, memory B, and GC B cell response more potently compared to treatment with 2DG or Etomoxir treatment alone as observed in several LNs and tumor tissue of 4T1 mouse. However, AICAR + anti-IL10 mAb increased the frequency of intratumoral Tfh cells, simultaneously downregulated Tfr cells; and improved humoral response by stimulating upregulation of memory B, GC B, and plasmablasts in tumor-draining, axillary, and mesenteric LNs of 4T1 mouse.

A deubiquitination module essential for Treg fitness in the tumor microenvironment

The tumor microenvironment (TME) enhances regulatory T (T_reg) cell stability and immunosuppressive functions through up-regulation of lineage transcription factor Foxp3, a phenomenon known as T_reg fitness or adaptation. Here, we characterize previously unknown TME-specific cellular and molecular mechanisms underlying T_reg fitness. We demonstrate that TME-specific stressors including transforming growth factor-β (TGF-β), hypoxia, and nutrient deprivation selectively induce two Foxp3-specific deubiquitinases, ubiquitin-specific peptidase 22 (Usp22) and Usp21, by regulating TGF-β, HIF, and mTOR signaling, respectively, to maintain T_reg fitness. Simultaneous deletion of both USPs in T_reg cells largely diminishes TME-induced Foxp3 up-regulation, alters T_reg metabolic signatures, impairs T_reg-suppressive function, and alleviates T_reg suppression on cytotoxic CD8⁺ T cells. Furthermore, we developed the first Usp22-specific small-molecule inhibitor, which dramatically reduced intratumoral T_reg Foxp3 expression and consequently enhanced antitumor immunity. Our findings unveil previously unappreciated mechanisms underlying T_reg fitness and identify Usp22 as an antitumor therapeutic target that inhibits T_reg adaptability in the TME.

Regulatory T cells as metabolic sensors

Compelling experimental evidence links immunity and metabolism. In this perspective, we propose forkhead-box-P3 (FoxP3)⁺CD4⁺CD25⁺ regulatory T (Treg) cells as key metabolic sensors controlling the immunological state in response to their intrinsic capacity to perceive nutritional changes. Treg cell high anabolic state in vivo, residency in metabolically crucial districts, and recirculation between lymphoid and non-lymphoid sites enable them to recognize the metabolic cues and adapt their intracellular metabolism and anti-inflammatory function at the paracrine and systemic levels. As privileged regulators at the interface between neuroendocrine and immune systems, the role of Treg cells in maintaining metabolic homeostasis makes these cells promising targets of therapeutic strategies aimed at restoring organismal homeostasis not only in autoimmune but also metabolic disorders.

Metabolic requirements of Th17 cells and of B cells: Regulation and defects in health and in inflammatory diseases

The immune system protects from infections and cancer through complex cellular networks. For this purpose, immune cells require well-developed mechanisms of energy generation. However, the immune system itself can also cause diseases when defective regulation results in the emergence of autoreactive lymphocytes. Recent studies provide insights into how differential patterns of immune cell responses are associated with selective metabolic pathways. This review will examine the changing metabolic requirements of Th17 cells and of B cells at different stages of their development and activation. Both cells provide protection but can also mediate diseases through the production of autoantibodies and the production of proinflammatory mediators. In health, B cells produce antibodies and cytokines and present antigens to T cells to mount specific immunity. Th17 cells, on the other hand, provide protection against extra cellular pathogens at mucosal surfaces but can also drive chronic inflammation. The latter cells can also promote the differentiation of B cells to plasma cells to produce more autoantibodies. Metabolism-regulated checkpoints at different stages of their development ensure the that self-reactive B cells clones and needless production of interleukin (IL-)17 are limited. The metabolic regulation of the two cell types has some similarities, e.g. the utility of hypoxia induced factor (HIF)1α during low oxygen tension, to prevent autoimmunity and regulate inflammation. There are also clear differences, as Th17 cells only are vulnerable to the lack of certain amino acids. B cells, unlike Th17 cells, are also dependent of mechanistic target of rapamycin 2 (mTORC2) to function. Significant knowledge has recently been gained, particularly on Th17 cells, on how metabolism regulates these cells through influencing their epigenome. Metabolic dysregulation of Th17 cells and B cells can lead to chronic inflammation. Disease associated alterations in the genome can, in addition, cause dysregulation to metabolism and, thereby, result in epigenetic alterations in these cells. Recent studies highlight how pathology can result from the cooperation between the two cell types but only few have so far addressed the key metabolic alterations in such settings. Knowledge of the impact of metabolic dysfunction on chronic inflammation and pathology can reveal novel therapeutic targets to treat such diseases.

Therapeutic efficacy of FASN inhibition in preclinical models of HCC

BACKGROUND AND AIMS

Aberrant activation of fatty acid synthase (FASN) is a major metabolic event during the development of HCC. We evaluated the therapeutic efficacy of TVB3664, a FASN inhibitor, either alone or in combination, for HCC treatment.

APPROACH AND RESULTS

The therapeutic efficacy and the molecular pathways targeted by TVB3664, either alone or with tyrosine kinase inhibitors or the checkpoint inhibitor anti-programmed death ligand 1 antibody, were assessed in human HCC cell lines and multiple oncogene-driven HCC mouse models. RNA sequencing was performed to elucidate the effects of TVB3664 on global gene expression and tumor metabolism. TVB3664 significantly ameliorated the fatty liver phenotype in the aged mice and AKT-induced hepatic steatosis. TVB3664 monotherapy showed moderate efficacy in NASH-related murine HCCs, induced by loss of phosphatase and tensin homolog and MET proto-oncogene, receptor tyrosine kinase (c-MET) overexpression. TVB3664, in combination with cabozantinib, triggered tumor regression in this murine model but did not improve the responsiveness to immunotherapy. Global gene expression revealed that TVB3664 predominantly modulated metabolic processes, whereas TVB3664 synergized with cabozantinib to down-regulate multiple cancer-related pathways, especially the AKT/mammalian target of rapamycin pathway and cell proliferation genes. TVB3664 also improved the therapeutic efficacy of sorafenib and cabozantinib in the FASN-dependent c-MYC-driven HCC model. However, TVB3664 had no efficacy nor synergistic effects in FASN-independent murine HCC models.

CONCLUSIONS

This preclinical study suggests the limited efficacy of targeting FASN as monotherapy for HCC treatment. However, FASN inhibitors could be combined with other drugs for improved effectiveness. These combination therapies could be developed based on the driver oncogenes, supporting precision medicine approaches for HCC treatment.

Targeting lipid metabolism reprogramming of immunocytes in response to the tumor microenvironment stressor: A potential approach for tumor therapy

The tumor microenvironment (TME) has become a major research focus in recent years. The TME differs from the normal extracellular environment in parameters such as nutrient supply, pH value, oxygen content, and metabolite abundance. Such changes may promote the initiation, growth, invasion, and metastasis of tumor cells, in addition to causing the malfunction of tumor-infiltrating immunocytes. As the neoplasm develops and nutrients become scarce, tumor cells transform their metabolic patterns by reprogramming glucose, lipid, and amino acid metabolism in response to various environmental stressors. Research on carcinoma metabolism reprogramming suggests that like tumor cells, immunocytes also switch their metabolic pathways, named “immunometabolism”, a phenomenon that has drawn increasing attention in the academic community. In this review, we focus on the recent progress in the study of lipid metabolism reprogramming in immunocytes within the TME and highlight the potential target molecules, pathways, and genes implicated. In addition, we discuss hypoxia, one of the vital altered components of the TME that partially contribute to the initiation of abnormal lipid metabolism in immune cells. Finally, we present the current immunotherapies that orchestrate a potent antitumor immune response by mediating the lipid metabolism of immunocytes, highlight the lipid metabolism reprogramming capacity of various immunocytes in the TME, and propose promising new strategies for use in cancer therapy.

The emerging role of microbiota-derived short-chain fatty acids in immunometabolism

The accumulating evidence revealed that microbiota plays a significant function in training, function, and the induction of host immunity. Once this interaction (immune system-microbiota) works correctly, it enables the production of protective responses against pathogens and keeps the regulatory pathways essential for maintaining tolerance to innocent antigens. This concept of immunity and metabolic activity redefines the realm of immunometabolism, paving the way for innovative therapeutic interventions to modulate immune cells through immune metabolic alterations. A body of evidence suggests that microbiota-derived metabolites, including short-chain fatty acids (SCFAs) such as butyrate, acetate, and propionate, play a key role in immune balance. SCFAs act on many cell types to regulate various vital biological processes, including host metabolism, intestinal function, and the immune system. Such SCFAs generated by gut bacteria also impact immunity, cellular function, and immune cell fate. This is a new concept of immune metabolism, and better knowledge about how lifestyle affects intestinal immunometabolism is crucial for preventing and treating disease. In this review article, we explicitly focus on the function of SCFAs in the metabolism of immune cells, especially macrophages, neutrophils, dendritic cells (DCs), B cells, T (Th) helper cells, and cytotoxic T cells (CTLs).

P2 Receptors: Novel Disease Markers and Metabolic Checkpoints in Immune Cells

Extracellular ATP (eATP) and P2 receptors are novel emerging regulators of T-lymphocyte responses. Cellular ATP is released via multiple pathways and accumulates at sites of tissue damage and inflammation. P2 receptor expression and function are affected by numerous single nucleotide polymorphisms (SNPs) associated with diverse disease conditions. Stimulation by released nucleotides (purinergic signalling) modulates several T-lymphocyte functions, among which energy metabolism. Energy metabolism, whether oxidative or glycolytic, in turn deeply affects T-cell activation, differentiation and effector responses. Specific P2R subtypes, among which the P2X7 receptor (P2X7R), are either up- or down-regulated during T-cell activation and differentiation; thus, they can be considered indexes of activation/quiescence, reporters of T-cell metabolic status and, in principle, markers of immune-mediated disease conditions.

Gene model-related m6A expression levels predict the risk of preeclampsia

Background

This is the first study to explore the potential functions and expression patterns of RNA N6-methyladenosine (m6A) and potential related genes in preeclampsia.

Methods

We identified two m6A modification patterns through unsupervised cluster analysis and validated them by principal component analysis. We quantified the relative abundance of specific infiltrating immunocytes using single-sample gene set enrichment analysis (ssGSEA) and the Wilcoxon test. To screen hub genes related to m6A regulators, we performed weighted gene coexpression network analysis. Functional enrichment analysis was conducted for differential signalling pathways and cellular processes. Preeclampsia patients were grouped by consensus clustering based on differentially expressed hub genes and the relationship between different gene-mediated classifications and clinical features.

Results

Two m6A clusters in preeclampsia, cluster A and cluster B, were determined based on the expression of 17 m6A modification regulators; ssGSEA revealed seven significantly different immune cell subtypes between the two clusters. A total of 1393 DEGs and nine potential m6A-modified hub genes were screened. We divided the patients into two groups based on the expression of these nine genes. We found that almost all the patients in m6A cluster A were classified into hub gene cluster 1 and that a lower gestational age may be associated with more m6A-associated events.

Conclusions

This study revealed that hub gene-mediated classification is consistent with m6A modification clusters for predicting the clinical characteristics of patients with preeclampsia. Our results provide new insights into the molecular mechanisms of preeclampsia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01254-4.

Fatty Acid Metabolism and T Cells in Multiple Sclerosis

Cellular metabolic remodeling is intrinsically linked to the development, activation, differentiation, function, and survival of T cells. T cells transition from a catabolic, naïve state to an anabolic effector state upon T cell activation. Subsequently, specialization of T cells into T helper (Th) subsets, including regulatory T cells (Treg), requires fine-tuning of metabolic programs that better support and optimize T cell functions for that particular environment. Increasingly, studies have shown that changes in nutrient availability at both the cellular and organismal level during disease states can alter T cell function, highlighting the importance of better characterizing metabolic-immune axes in both physiological and disease settings. In support of these data, a growing body of evidence is emerging that shows specific lipid species are capable of altering the inflammatory functional phenotypes of T cells. In this review we summarize the metabolic programs shown to support naïve and effector T cells, and those driving Th subsets. We then discuss changes to lipid profiles in patients with multiple sclerosis, and focus on how the presence of specific lipid species can alter cellular metabolism and function of T cells.

P2Y1R Ligation Suppresses Th17 Cell Differentiation and Alleviates Colonic Inflammation in an AMPK-Dependent Manner

P2Y1 receptor is a G-protein-coupled receptor that plays a critical role in the immune response of inflammatory bowel diseases. However, its regulatory effects on CD4⁺ T cell response have not been fully elucidated. The study aimed to characterize the role of P2Y1R in Th17 cell differentiation and colonic inflammation. Our results demonstrated that P2Y1R was significantly increased in the splenocytes of colitic mice, which was positively associated with the expression of RORγt and IL-17A. P2Y1R deficiency significantly ameliorated DSS-induced colitis and its Th17 responses. In parallel, P2Y1R deficiency greatly impaired the differentiation of Th17 cell, down-regulated the mRNA expression of IL-17A and RORγt, and protein expression of RORγt in vitro. More importantly, it was found that P2Y1R deficiency markedly increased AMPK phosphorylation of Th17 polarized CD4⁺ T cells, and antagonist of AMPK significantly reversed the inhibitory effect of P2Y1R deficiency on Th17 cell generation in vivo and in vitro. Overall, these findings demonstrated that P2Y1R deficiency could suppress Th17 cell differentiation in an AMPK-dependent manner to ameliorate colitis, and P2Y1R can act as an important regulator of Th17 cell differentiation to control colonic inflammation.

The activation of PPARγ enhances Treg responses through up-regulating CD36/CPT1-mediated fatty acid oxidation and subsequent N-glycan branching of TβRII/IL-2Rα

BACKGROUND

Peroxisome proliferator-activated receptor gamma (PPARγ) is an enhancer of Treg responses, but the mechanisms remain elusive. This study aimed to solve this problem in view of cellular metabolism.

METHODS

Three recognized PPARγ agonists (synthetic agonist: rosiglitazone; endogenous ligand: 15d-PGJ2; natural product: morin) were used as the tools to activate PPARγ. The fatty acid oxidation (FAO) was evaluated through the detection of fatty acid uptake, oxygen consumption rate, mitochondrial mass, mitochondrial membrane potential and acetyl-CoA level. The involvement of UDP-GlcNAc/N-linked glycosylation axis and the exact role of PPARγ in the action of PPARγ agonists were determined by flow cytometry, Q-PCR, western blotting, a commercial kit for enzyme activity and CRISPR/Cas9-mediated knockout.

RESULTS

Rosiglitazone, 15d-PGJ2 and morin all increased the frequency of CD4⁺Foxp3⁺ Treg cells generated from naïve CD4⁺ T cells, boosted the transcription of Foxp3, IL-10, CTLA4 and TIGIT, and facilitated the function of Treg cells. They significantly promoted FAO in differentiating Treg cells by up-regulating the levels of CD36 and CPT1 but not other enzymes involved in FAO such as ACADL, ACADM, HADHA or HADHB, and siCD36 or siCPT1 dampened PPARγ agonists-promoted Treg responses. Moreover, PPARγ agonists enhanced UDP-GlcNAc biosynthesis and subsequent N-linked glycosylation, but did not affect the expressions of N-glycan branching enzymes Mgat1, 2, 4 and 5. Notably, the enzyme activity of phosphofructokinase (PFK) was inhibited by PPARγ agonists and the effect was limited by siCD36 or siCPT1, implying PFK to be a link between PPARγ agonists-promoted FAO and UDP-GlcNAc biosynthesis aside from acetyl-CoA. Furthermore, PPARγ agonists facilitated the cell surface abundance of TβRII and IL-2Rα via N-linked glycosylation, thereby activating TGF-β/Smads and IL-2/STAT5 signaling, and the connection between N-linked glycosylation and Treg responses was revealed by tunicamycin. However, the increased surface abundance of CD36 was demonstrated to be mainly owing to PPARγ agonists-up-regulated overall expression. Finally, PPARγ antagonist GW9662 or CRISPR/Cas9-mediated knockout of PPARγ constrained the effects of rosiglitazone, 15d-PGJ2 and morin, confirming the exact role of PPARγ.

CONCLUSIONS

The activation of PPARγ enhances Treg responses through up-regulating CD36/CPT1-mediated fatty acid oxidation and subsequent N-glycan branching of TβRII/IL-2Rα, which is beneficial for inflammatory and autoimmune diseases. Video Abstract.

Impact of Lipid Metabolism on Antitumor Immune Response

Simple Summary

One of the causes of failure of anticancer therapies is the reprogramming of lipid metabolism. Cells of innate and adaptive immunity present in the tumor microenvironment can be affected by this metabolic switch and thus present changes in their anti- or protumor phenotype. In this review, modifications induced by lipid metabolism will be described for innate immune cells, such as macrophages, dendritic cells and MDSCs, and also for adaptive immune cells, such as CD4+ and CD8+ T cells and B cells. Finally, antitumor therapeutic strategies targeting lipid metabolism will be presented.

Abstract

Over the past decade, metabolic reprogramming has been defined as a hallmark of cancer. More recently, a large number of studies have demonstrated that metabolic reprogramming can modulate the differentiation and functions of immune cells, and thus modify the antitumor response. Increasing evidence suggests that modified energy metabolism could be responsible for the failure of antitumor immunity. Indeed, tumor-infiltrating immune cells play a key role in cancer, and metabolic switching in these cells has been shown to help determine their phenotype: tumor suppressive or immune suppressive. Recent studies in the field of immunometabolism focus on metabolic reprogramming in the tumor microenvironment (TME) by targeting innate and adaptive immune cells and their associated anti- or protumor phenotypes. In this review, we discuss the lipid metabolism of immune cells in the TME as well as the effects of lipids; finally, we expose the link between therapies and lipid metabolism.

Metabolism Characteristics of Th17 and Regulatory T Cells in Autoimmune Diseases

The abnormal number and functional deficiency of immune cells are the pathological basis of various diseases. Recent years, the imbalance of Th17/regulatory T (Treg) cell underlies the occurrence and development of inflammation in autoimmune diseases (AID). Currently, studies have shown that material and energy metabolism is essential for maintaining cell survival and normal functions and the altered metabolic state of immune cells exists in a variety of AID. This review summarizes the biology and functions of Th17 and Treg cells in AID, with emphasis on the advances of the roles and regulatory mechanisms of energy metabolism in activation, differentiation and physiological function of Th17 and Treg cells, which will facilitate to provide targets for the treatment of immune-mediated diseases.

The Interplay of Hypoxia Signaling on Mitochondrial Dysfunction and Inflammation in Cardiovascular Diseases and Cancer: From Molecular Mechanisms to Therapeutic Approaches

Simple Summary

The regulation of hypoxia has recently emerged as having a central impact in mitochondrial function and dysfunction in various diseases, including the major disorders threatening worldwide: cardiovascular diseases and cancer. Despite the studies in this matter, its effective role in protection and disease progression even though its direct molecular mechanism in both disorders is still to be elucidated. This review aims to cover the current knowledge about the effect of hypoxia on mitochondrial function and dysfunction, and inflammation, in cardiovascular diseases and cancer, and reports further therapeutic strategies based on the modulation of hypoxic pathways.

Abstract

Cardiovascular diseases (CVDs) and cancer continue to be the primary cause of mortality worldwide and their pathomechanisms are a complex and multifactorial process. Insufficient oxygen availability (hypoxia) plays critical roles in the pathogenesis of both CVDs and cancer diseases, and hypoxia-inducible factor 1 (HIF-1), the main sensor of hypoxia, acts as a central regulator of multiple target genes in the human body. Accumulating evidence demonstrates that mitochondria are the major target of hypoxic injury, the most common source of reactive oxygen species during hypoxia and key elements for inflammation regulation during the development of both CVDs and cancer. Taken together, observations propose that hypoxia, mitochondrial abnormality, oxidative stress, inflammation in CVDs, and cancer are closely linked. Based upon these facts, this review aims to deeply discuss these intimate relationships and to summarize current significant findings corroborating the molecular mechanisms and potential therapies involved in hypoxia and mitochondrial dysfunction in CVDs and cancer.

Pathophysiological Integration of Metabolic Reprogramming in Breast Cancer

Simple Summary

Tumors exhibit metabolic changes that differentiate them from the normal tissues from which they derive. These metabolic changes favor tumor growth, are primarily induced by cancer cells, and produce metabolic and functional changes in the surrounding stromal cells. There is a close functional connection between the metabolic changes in tumor cells and those that appear in the surrounding stroma. A better understanding of intratumoral metabolic interactions may help identify new vulnerabilities that will facilitate new, more individualized treatment strategies against cancer. We review the metabolic changes described in tumor and stromal cells and their functional changes and then consider, in depth, the metabolic interactions between the cells of the two compartments. Although these changes are generic, we illustrate them mainly with reference to examples in breast cancer.

Abstract

Metabolic changes that facilitate tumor growth are one of the hallmarks of cancer. The triggers of these metabolic changes are located in the tumor parenchymal cells, where oncogenic mutations induce an imperative need to proliferate and cause tumor initiation and progression. Cancer cells undergo significant metabolic reorganization during disease progression that is tailored to their energy demands and fluctuating environmental conditions. Oxidative stress plays an essential role as a trigger under such conditions. These metabolic changes are the consequence of the interaction between tumor cells and stromal myofibroblasts. The metabolic changes in tumor cells include protein anabolism and the synthesis of cell membranes and nucleic acids, which all facilitate cell proliferation. They are linked to catabolism and autophagy in stromal myofibroblasts, causing the release of nutrients for the cells of the tumor parenchyma. Metabolic changes lead to an interstitium deficient in nutrients, such as glucose and amino acids, and acidification by lactic acid. Together with hypoxia, they produce functional changes in other cells of the tumor stroma, such as many immune subpopulations and endothelial cells, which lead to tumor growth. Thus, immune cells favor tissue growth through changes in immunosuppression. This review considers some of the metabolic changes described in breast cancer.

HuR-Targeted Inhibition Impairs Th2 Proinflammatory Responses in Asthmatic CD4+ T Cells

RNA-binding protein HuR (ELAVL1) is a master regulator of gene expression in human pathophysiology. Its dysregulation plays an important role in many diseases. We hypothesized that HuR plays an important role in Th2 inflammation in asthma in both mouse and human. To address this, we used a model of airway inflammation in a T cell-specific knockout mouse model, distal lck-Cre HuR^fl/fl, as well as small molecule inhibitors in human peripheral blood-derived CD4⁺ T cells. Peripheral CD4⁺ T cells were isolated from 26 healthy control subjects and 45 asthmatics (36 type 2 high and 9 non-type 2 high, determined by blood eosinophil levels and fraction of exhaled NO). Our mouse data showed conditional ablation of HuR in T cell-abrogated Th2 differentiation, cytokine production, and lung inflammation. Studies using human T cells showed that HuR protein levels in CD4⁺ T cells were significantly higher in asthmatics compared with healthy control subjects. The expression and secretion of Th2 cytokines were significantly higher in asthmatics compared with control subjects. AMP-activated protein kinase activator treatment reduced the expression of several cytokines in both type 2 high and non-type 2 high asthma groups. However, the effects of CMLD-2 (a HuR-specific inhibitor) were more specific to endotype-defining cytokines in type 2 high asthmatics. Taken together, these data suggest that HuR plays a permissive role in both allergen and non-allergen-driven airway inflammation by regulating key genes, and that interfering with its function may be a novel method of asthma treatment.

The role of metabolism in Th17 cell differentiation and autoimmune diseases

T helper 17 cells (Th17) have been associated with the pathogenesis of autoimmune and inflammatory diseases, which makes them become a sharp focus when the researchers are seeking therapeutic target for these diseases. A growing body of evidence has suggested that cellular metabolism dictates Th17 cell differentiation and effector function. Moreover, various studies have disclosed that metabolism is linked to the occurrence of autoimmune diseases. In this article, we reviewed the most recent findings regarding the importance of metabolism in Th17 cell differentiation and autoimmune diseases and also discussed the modulation mechanisms of glycolysis, fatty acid and cholesterol synthesis, and amino acids metabolism for Th17 cell differentiation. This review summarized the potential therapeutic or preventing strategies for Th17 cell-mediated autoimmune diseases.

Immunometabolism modulation, a new trick of edible and medicinal plants in cancer treatment

The edible and medicinal plants (EMPs) are becoming an abundant source for cancer prevention and treatment since the natural and healthy trend for modern human beings. Currently, there are more than one hundred species of EMPs widely used and listed by the national health commission of China, and most of them indicate immune or metabolic regulation potential in cancer treatment with numerous studies over the past two decades. In the present review, we focused on the metabolic influence in immunocytes and tumor microenvironment, including immune response, immunosuppressive factors and cancer cells, discussing the immunometabolic potential of EMPs in cancer treatment. There are more than five hundred references collected and analyzed through retrieving pharmacological studies deposited in PubMed by medical subject headings and the corresponding names derived from pharmacopoeia of China as a sole criterion. Finally, the immunometabolism modulation of EMPs was sketch out implying an immunometabolic control in cancer treatment.

Immunometabolic Therapeutic Targets of Graft-versus-Host Disease (GvHD)

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative option in the treatment of aggressive malignant and non-malignant blood disorders. However, the benefits of allo-HSCT can be compromised by graft-versus-host disease (GvHD), a prevalent and morbid complication of allo-HSCT. GvHD occurs when donor immune cells mount an alloreactive response against host antigens due to histocompatibility differences between the donor and host, which may result in extensive tissue injury. The reprogramming of cellular metabolism is a feature of GvHD that is associated with the differentiation of donor CD4+ cells into the pathogenic Th1 and Th17 subsets along with the dysfunction of the immune-suppressive protective T regulatory cells (Tregs). The activation of glycolysis and glutaminolysis with concomitant changes in fatty acid oxidation metabolism fuel the anabolic activities of the proliferative alloreactive microenvironment characteristic of GvHD. Thus, metabolic therapies such as glycolytic enzyme inhibitors and fatty acid metabolism modulators are a promising therapeutic strategy for GvHD. We comprehensively review the role of cellular metabolism in GvHD pathogenesis, identify candidate therapeutic targets, and describe potential strategies for augmenting immunometabolism to ameliorate GvHD.

Crosstalk of Microorganisms and Immune Responses in Autoimmune Neuroinflammation: A Focus on Regulatory T Cells

Regulatory T cells (Tregs) are the major determinant of peripheral immune tolerance. Many Treg subsets have been described, however thymus-derived and peripherally induced Tregs remain the most important subpopulations. In multiple sclerosis, a prototypical autoimmune disorder of the central nervous system, Treg dysfunction is a pathogenic hallmark. In contrast, induction of Treg proliferation and enhancement of their function are central immune evasion mechanisms of infectious pathogens. In accordance, Treg expansion is compartmentalized to tissues with high viral replication and prolonged in chronic infections. In friend retrovirus infection, Treg expansion is mainly based on excessive interleukin-2 production by infected effector T cells. Moreover, pathogens seem also to enhance Treg functions as shown in human immunodeficiency virus infection, where Tregs express higher levels of effector molecules such as cytotoxic T-lymphocyte-associated protein 4, CD39 and cAMP and show increased suppressive capacity. Thus, insights into the molecular mechanisms by which intracellular pathogens alter Treg functions might aid to find new therapeutic approaches to target central nervous system autoimmunity. In this review, we summarize the current knowledge of the role of pathogens for Treg function in the context of autoimmune neuroinflammation. We discuss the mechanistic implications for future therapies and provide an outlook for new research directions.

Does Altered Cellular Metabolism Underpin the Normal Changes to the Maternal Immune System during Pregnancy?

Pregnancy is characterised by metabolic changes that occur to support the growth and development of the fetus over the course of gestation. These metabolic changes can be classified into two distinct phases: an initial anabolic phase to prepare an adequate store of substrates and energy which are then broken down and used during a catabolic phase to meet the energetic demands of the mother, placenta and fetus. Dynamic readjustment of immune homeostasis is also a feature of pregnancy and is likely linked to the changes in energy substrate utilisation at this time. As cellular metabolism is increasingly recognised as a key determinant of immune cell phenotype and function, we consider how changes in maternal metabolism might contribute to T cell plasticity during pregnancy.

Oleic acid restores suppressive defects in tissue-resident FOXP3 Tregs from patients with multiple sclerosis

FOXP3+ Tregs rely on fatty acid β-oxidation-driven (FAO-driven) oxidative phosphorylation (OXPHOS) for differentiation and function. Recent data demonstrate a role for Tregs in the maintenance of tissue homeostasis, with tissue-resident Tregs possessing tissue-specific transcriptomes. However, specific signals that establish tissue-resident Treg programs remain largely unknown. Tregs metabolically rely on FAO, and considering the lipid-rich environments of tissues, we hypothesized that environmental lipids drive Treg homeostasis. First, using human adipose tissue to model tissue residency, we identified oleic acid as the most prevalent free fatty acid. Mechanistically, oleic acid amplified Treg FAO-driven OXPHOS metabolism, creating a positive feedback mechanism that increased the expression of FOXP3 and phosphorylation of STAT5, which enhanced Treg-suppressive function. Comparing the transcriptomic program induced by oleic acid with proinflammatory arachidonic acid, we found that Tregs sorted from peripheral blood and adipose tissue of healthy donors transcriptomically resembled the Tregs treated in vitro with oleic acid, whereas Tregs from patients with multiple sclerosis (MS) more closely resembled an arachidonic acid transcriptomic profile. Finally, we found that oleic acid concentrations were reduced in patients with MS and that exposure of MS Tregs to oleic acid restored defects in their suppressive function. These data demonstrate the importance of fatty acids in regulating tissue inflammatory signals.

ACLY ubiquitination by CUL3-KLHL25 induces the reprogramming of fatty acid metabolism to facilitate iTreg differentiation

Inducible regulatory T (iTreg) cells play a central role in immune suppression. As iTreg cells are differentiated from activated T (Th0) cells, cell metabolism undergoes dramatic changes, including a shift from fatty acid synthesis (FAS) to fatty acid oxidation (FAO). Although the reprogramming in fatty acid metabolism is critical, the mechanism regulating this process during iTreg differentiation is still unclear. Here we have revealed that the enzymatic activity of ATP-citrate lyase (ACLY) declined significantly during iTreg differentiation upon transforming growth factor β1 (TGFβ1) stimulation. This reduction was due to CUL3-KLHL25-mediated ACLY ubiquitination and degradation. As a consequence, malonyl-CoA, a metabolic intermediate in FAS that is capable of inhibiting the rate-limiting enzyme in FAO, carnitine palmitoyltransferase 1 (CPT1), was decreased. Therefore, ACLY ubiquitination and degradation facilitate FAO and thereby iTreg differentiation. Together, we suggest TGFβ1-CUL3-KLHL25-ACLY axis as an important means regulating iTreg differentiation and bring insights into the maintenance of immune homeostasis for the prevention of immune diseases.

Lupus susceptibility gene Esrrg modulates regulatory T cells through mitochondrial metabolism

Estrogen-related receptor γ (Esrrg) is a murine lupus susceptibility gene associated with T cell activation. Here, we report that Esrrg controls Tregs through mitochondria homeostasis. Esrrg deficiency impaired the maintenance and function of Tregs, leading to global T cell activation and autoimmunity in aged mice. Further, Esrrg-deficient Tregs presented an impaired differentiation into follicular Tregs that enhanced follicular helper T cells' responses. Mechanistically, Esrrg-deficient Tregs presented with dysregulated mitochondria with decreased oxygen consumption as well as ATP and NAD+ production. In addition, Esrrg-deficient Tregs exhibited decreased phosphatidylinositol and TGF-β signaling pathways and increased mTOR complex 1 activation. We found that the expression of human ESRRG, which is high in Tregs, was lower in CD4+ T cells from patients with lupus than in healthy controls. Finally, knocking down ESRRG in Jurkat T cells decreased their metabolism. Together, our results reveal a critical role of Esrrg in the maintenance and metabolism of Tregs, which may provide a genetic link between lupus pathogenesis and mitochondrial dysfunction in T cells.

The energy sensor AMPK orchestrates metabolic and translational adaptation in expanding T helper cells

The importance of cellular metabolic adaptation in inducing robust T cell responses is well established. However, the mechanism by which T cells link information regarding nutrient supply to clonal expansion and effector function is still enigmatic. Herein, we report that the metabolic sensor adenosine monophosphate-activated protein kinase (AMPK) is a critical link between cellular energy demand and translational activity and, thus, orchestrates optimal expansion of T cells in vivo. AMPK deficiency did not affect T cell fate decision, activation, or T effector cell generation; however, the magnitude of T cell responses in murine in vivo models of T cell activation was markedly reduced. This impairment was global, as all T helper cell subsets were similarly sensitive to loss of AMPK which resulted in reduced T cell accumulation in peripheral organs and reduced disease severity in pathophysiologically as diverse models as T cell transfer colitis and allergic airway inflammation. T cell receptor repertoire analysis confirmed similar clonotype frequencies in different lymphoid organs, thereby supporting the concept of a quantitative impairment in clonal expansion rather than a skewed qualitative immune response. In line with these findings, in-depth metabolic analysis revealed a decrease in T cell oxidative metabolism, and gene set enrichment analysis indicated a major reduction in ribosomal biogenesis and mRNA translation in AMPK-deficient T cells. We, thus, provide evidence that through its interference with these delicate processes, AMPK orchestrates the quantitative, but not the qualitative, manifestation of primary T cell responses in vivo.

The Alterations in and the Role of the Th17/Treg Balance in Metabolic Diseases

Chronic inflammation plays an important role in the development of metabolic diseases. These include obesity, type 2 diabetes mellitus, and metabolic dysfunction-associated fatty liver disease. The proinflammatory environment maintained by the innate immunity, including macrophages and related cytokines, can be influenced by adaptive immunity. The function of T helper 17 (Th17) and regulatory T (Treg) cells in this process has attracted attention. The Th17/Treg balance is regulated by inflammatory cytokines and various metabolic factors, including those associated with cellular energy metabolism. The possible underlying mechanisms include metabolism-related signaling pathways and epigenetic regulation. Several studies conducted on human and animal models have shown marked differences in and the important roles of Th17/Treg in chronic inflammation associated with obesity and metabolic diseases. Moreover, Th17/Treg seems to be a bridge linking the gut microbiota to host metabolic disorders. In this review, we have provided an overview of the alterations in and the functions of the Th17/Treg balance in metabolic diseases and its role in regulating immune response-related glucose and lipid metabolism.

The Natural History of T Cell Metabolism

The cells of the immune system, particularly the T lymphocytes, have two main features that distinguish them from the cells of other tissues. They proliferate after activation and have the ability to move in tissues and organs. These characteristics compel them to develop metabolic plasticity in order to fulfil their immune function. This review focuses on the different known mechanisms that allow T cells to adapt their metabolism to the real-life circumstances they operate in, whether it is to exit quiescence, to differentiate into effector cells, or to participate in immune memory formation. Some of the metabolic adaptations to environmental variations that T cells are likely to undergo in their immune monitoring function are also discussed.

Metabolic regulation in the immune response to cancer

Metabolic reprogramming in tumor‐immune interactions is emerging as a key factor affecting pro‐inflammatory carcinogenic effects and anticancer immune responses. Therefore, dysregulated metabolites and their regulators affect both cancer progression and therapeutic response. Here, we describe the molecular mechanisms through which microenvironmental, systemic, and microbial metabolites potentially influence the host immune response to mediate malignant progression and therapeutic intervention. We summarized the primary interplaying factors that constitute metabolism, immunological reactions, and cancer with a focus on mechanistic aspects. Finally, we discussed the possibility of metabolic interventions at multiple levels to enhance the efficacy of immunotherapeutic and conventional approaches for future anticancer treatments.

Preclinical Development of FA5, a Novel AMP-Activated Protein Kinase (AMPK) Activator as an Innovative Drug for the Management of Bowel Inflammation

Acadesine (ACA), a pharmacological activator of AMP-activated protein kinase (AMPK), showed a promising beneficial effect in a mouse model of colitis, indicating this drug as an alternative tool to manage IBDs. However, ACA displays some pharmacodynamic limitations precluding its therapeutical applications. Our study was aimed at evaluating the in vitro and in vivo effects of FA-5 (a novel direct AMPK activator synthesized in our laboratories) in an experimental model of colitis in rats. A set of experiments evaluated the ability of FA5 to activate AMPK and to compare the efficacy of FA5 with ACA in an experimental model of colitis. The effects of FA-5, ACA, or dexamethasone were tested in rats with 2,4-dinitrobenzenesulfonic acid (DNBS)-induced colitis to assess systemic and tissue inflammatory parameters. In in vitro experiments, FA5 induced phosphorylation, and thus the activation, of AMPK, contextually to the activation of SIRT-1. In vivo, FA5 counteracted the increase in spleen weight, improved the colon length, ameliorated macroscopic damage score, and reduced TNF and MDA tissue levels in DNBS-treated rats. Of note, FA-5 displayed an increased anti-inflammatory efficacy as compared with ACA. The novel AMPK activator FA-5 displays an improved anti-inflammatory efficacy representing a promising pharmacological tool against bowel inflammation.

Butyrate enhances CPT1A activity to promote fatty acid oxidation and iTreg differentiation

Inducible regulatory T (iTreg) cells play a crucial role in immune suppression and are important for the maintenance of immune homeostasis. Mounting evidence has demonstrated connections between iTreg differentiation and metabolic reprogramming, especially rewiring in fatty acid oxidation (FAO). Previous work showed that butyrate, a specific type of short-chain fatty acid (SCFA) readily produced from fiber-rich diets through microbial fermentation, was critical for the maintenance of intestinal homeostasis and capable of promoting iTreg generation by up-regulating histone acetylation for gene expression as an HDAC inhibitor. Here, we revealed that butyrate could also accelerate FAO to facilitate iTreg differentiation. Moreover, butyrate was converted, by acyl-CoA synthetase short-chain family member 2 (ACSS2), into butyryl-CoA (BCoA), which up-regulated CPT1A activity through antagonizing the association of malonyl-CoA (MCoA), the best known metabolic intermediate inhibiting CPT1A, to promote FAO and thereby iTreg differentiation. Mutation of CPT1A at Arg243, a reported amino acid required for MCoA association, impaired both MCoA and BCoA binding, indicating that Arg243 is probably the responsible site for MCoA and BCoA association. Furthermore, blocking BCoA formation by ACSS2 inhibitor compromised butyrate-mediated iTreg generation and mitigation of mouse colitis. Together, we unveil a previously unappreciated role for butyrate in iTreg differentiation and illustrate butyrate-BCoA-CPT1A axis for the regulation of immune homeostasis.

Single Cell RNA-Seq Analysis Identifies Differentially Expressed Genes of Treg Cell in Early Treatment-Naive Rheumatoid Arthritis By Arsenic Trioxide

Objective: Early treatment-naïve rheumatoid arthritis (RA) has defective regulatory T (Treg) cells and increased inflammation response. In this study, we aim to illustrate the regulation of Treg cells in pathogenesis of early rheumatoid arthritis by arsenic trioxide (As₂O₃).

Methods: We studied the effects of As₂O₃ on gene expression in early treatment-naïve RA Treg cells with single cell RNA-seq (scRNA-seq). Treg cells were sorted from peripheral blood mononuclear cells (PBMCs) and purified by fluorescence-activated cell sorting (FACS) and cultured with or without As₂O₃ (at 0.1 µM) for 24 h. Total RNA was isolated and sequenced, and functional analysis was performed against the Gene Ontology (GO) database. Results for selected genes were confirmed with RT-qPCR.

Results: As₂O₃ exerts no significant effect on CD4⁺ T-cell apoptosis under physical condition, and selectively modulate ^CD4+ T cells toward Treg cells not Th17 cells under special polarizing stimulators. As₂O₃ increased the expression of 200 and reduced that of 272 genes with fold change (FC) 2.0 or greater. Several genes associated with inflammation, Treg-cell activation and differentiation as well as glucose and amino acids metabolism were among the most strongly affected genes. GO function analysis identified top ten ranked significant biological process (BPs), molecular functions (MFs), and cell components (CCs) in treatment and nontreatment Treg cells. In GO analysis, genes involved in the immunoregulation, cell apoptosis and cycle, inflammation, and cellular metabolism were enriched among the significantly affected genes. The KEGG pathway enrichment analysis identified the forkhead box O (FoxO) signal pathway, apoptosis, cytokine–cytokine receptor interaction, cell cycle, nuclear factor-kappa B (NF-κB) signaling pathway, tumor necrosis factor α (TNF-α), p53 signaling pathway, and phosphatidylinositol 3′-kinase (PI3K)-Akt signaling pathway were involved in the pathogenesis of early treatment-naïve RA.

Conclusion: This is the first study investigating the genome-wide effects of As₂O₃ on the gene expression of treatment-naïve Treg cells. In addition to clear anti-inflammatory and immunoregulation effects, As₂O₃ affect amino acids and glucose metabolism in Treg cells, an observation that might be particularly important in the metabolic phenotype of treatment-naïve RA.

CD4+ T-cell differentiation and function: Unifying glycolysis, fatty acid oxidation, polyamines NAD mitochondria

The progression through different steps of T-cell development, activation, and effector function is tightly bound to specific cellular metabolic processes. Previous studies established that T-effector cells have a metabolic bias toward aerobic glycolysis, whereas naive and regulatory T cells mainly rely on oxidative phosphorylation. More recently, the field of immunometabolism has drifted away from the notion that mitochondrial metabolism holds little importance in T-cell activation and function. Of note, T cells possess metabolic promiscuity, which allows them to adapt their nutritional requirements according to the tissue environment. Altogether, the integration of these metabolic pathways culminates in the generation of not only energy but also intermediates, which can regulate epigenetic programs, leading to changes in T-cell fate. In this review, we discuss the recent literature on how glycolysis, amino acid catabolism, and fatty acid oxidation work together with the tricarboxylic acid cycle in the mitochondrion. We also emphasize the importance of the electron transport chain for T-cell immunity. We also discuss novel findings highlighting the role of key enzymes, accessory pathways, and posttranslational protein modifications that distinctively regulate T-cell function and might represent prominent candidates for therapeutic purposes.

SZB120 Exhibits Immunomodulatory Effects by Targeting eIF2α to Suppress Th17 Cell Differentiation

IL-17-secreting Th17 cells play an important role in the pathogenesis of various inflammatory and autoimmune diseases. IL-17-targeted biologics and small molecules are becoming promising treatments for these diseases. In this study, we report that SZB120, a derivative of the natural compound 3-acetyl-β-boswellic acid, inhibits murine Th17 cell differentiation by interacting with the α-subunit of eukaryotic initiation factor 2 (eIF2α). We showed that SZB120 directly interacts with eIF2α and contributes to serine 51 phosphorylation of eIF2α. The suppressive effect of SZB120 on Th17 cell differentiation was reversed by GSK2606414, an inhibitor of eIF2α phosphokinase. Phosphorylation of eIF2α induced by SZB120 decreased the protein expression of IκBζ, which is important for Th17 cell differentiation. Notably, interaction with eIF2α by SZB120 also impaired glucose uptake and glycolysis in T cells. In vivo, SZB120 treatment of C57BL/6 mice significantly attenuated IL-17/Th17-mediated autoimmune disease. Our study indicates that SZB120 is a promising drug candidate for IL-17/Th17-mediated inflammatory diseases.

Revisiting preeclampsia: a metabolic disorder of the placenta

Preeclampsia (PE) is a leading cause of maternal and neonatal mortality and morbidity worldwide, impacting the long-term health of both mother and offspring. PE has long been characterized by deficient trophoblast invasion into the uterus and consequent placental hypoperfusion, yet the upstream causative factors and effective interventional targets for PE remain unknown. Alterations in the metabolism of preeclamptic placentas are thought to result from placental ischemia, while disturbances of the metabolism and of metabolites in PE pathogenesis are largely ignored. In fact, as one of the largest fetal organs at birth, the placenta consumes a considerable amount of glucose and fatty acid. Increasing evidence suggests glucose and fatty acid exist as energy substrates and regulate placental development through bioactive derivates. Moreover, recent findings have revealed that the placental metabolism adapts readily to environmental changes, altering its response to nutrients and endocrine signals; this adaptability optimizes pregnancy outcomes by diversifying available carbon sources for energy production, hormone synthesis, angiogenesis, immune activation, and tolerance, and fetoplacental growth. These observations raise the possibility that carbohydrate and lipid metabolism abnormalities play a role in both the etiology and clinical progression of PE, sparking a renewed interest in the interrelationship between PE and metabolic dysregulation. This review will focus on key metabolic substrates and regulatory molecules in the placenta and aim to provide novel insights with respect to the metabolism's role in modulating placental development and functions. Further investigations from this perspective are poised to decipher the etiology of PE and suggest potential therapies.