Mitochondrial Oxidative Phosphorylation Regulates the Fate Decision between Pathogenic Th17 and Regulatory T Cells

Metabolic and ionic control of T cells in asthma endotypes

CD4+ T cells play a central role in orchestrating the immune response in asthma, with dysregulated ion channel profiles and altered metabolic signatures contributing to disease progression and severity. An important classification of asthma is based on the presence of T-helper cell type 2 (Th2) inflammation, dividing patients into Th2-high and Th2-low endotypes. These distinct endotypes have implications for disease severity, treatment response, and prognosis. By elucidating how ion channels and energy metabolism control Th cells in asthma, this review contributes to the pathophysiological understanding and the prospective development of personalized therapeutic treatment strategies for patients suffering from distinct asthma endotypes.

Balancing immune activation with Itk

Development of protective immune responses relies on a balance between proinflammatory CD4 T helper (Th) cell populations such as Th17 cells and regulatory CD4 T cells (Tregs) that keep immune activation in check. Evidence that interleukin-2-inducible T cell kinase (Itk) regulates this balance supports therapeutic applications for Itk inhibition.

Tumor microenvironment induced switch to mitochondrial metabolism promotes suppressive functions in immune cells

Understanding the intricacies of the metabolic phenotype in immune cells and its plasticity within the tumor microenvironment is pivotal in understanding the pathology and prognosis of cancer. Unfavorable conditions and cellular stress in the tumor microenvironment (TME) exert a profound impact on cellular functions in immune cells, thereby influencing both tumor progression and immune responses. Elevated AMP:ATP ratio, a consequence of limited glucose levels, activate AMP-activated protein kinase (AMPK) while concurrently repressing the activity of mechanistic target of rapamycin (mTOR) and hypoxia-inducible factor 1-alpha (HIF-1α). The intricate balance between AMPK, mTOR, and HIF-1α activities defines the metabolic phenotype of immune cells in the TME. These Changes in metabolic phenotype are strongly associated with immune cell functions and play a crucial role in creating a milieu conducive to tumor progression. Insufficiency of nutrient and oxygen supply leads to a metabolic shift in immune cells characterized by a decrease in glycolysis and an increase in oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO) rates. In most cases, this shift in metabolism is accompanied by a compromise in the effector functions of these immune cells. This metabolic adaptation prompts immune cells to turn down their effector functions, entering a quiescent or immunosuppressive state that may support tumor growth. This article discusses how tumor microenvironment alters the metabolism in immune cells leading to their tolerance and tumor progression, with emphasis on mitochondrial metabolism (OXPHOS and FAO).

The kinase ITK controls a Ca2+-mediated switch that balances TH17 and Treg cell differentiation

The balance of proinflammatory T helper type 17 (TH17) and anti-inflammatory T regulatory (Treg) cells is crucial for immune homeostasis in health and disease. The differentiation of naïve CD4+ T cells into TH17 and Treg cells depends on T cell receptor (TCR) signaling mediated, in part, by interleukin-2-inducible T cell kinase (ITK), which stimulates mitogen-activated protein kinases (MAPKs) and Ca2+ signaling. Here, we report that, in the absence of ITK activity, naïve murine CD4+ T cells cultured under TH17-inducing conditions expressed the Treg transcription factor Foxp3 and did not develop into TH17 cells. Furthermore, ITK inhibition in vivo during allergic inflammation increased the Treg:TH17 ratio in the lung. These switched Foxp3+ Treg-like cells had suppressive function, and their transcriptomic profile resembled that of differentiated, induced Treg (iTreg) cells, but their chromatin accessibility profiles were intermediate between TH17 and iTreg cells. Like iTreg cells, switched Foxp3+ Treg-like cells had reductions in the expression of genes involved in mitochondrial oxidative phosphorylation and glycolysis, in the activation of the mechanistic target of rapamycin (mTOR) signaling pathway, and in the abundance of the TH17 pioneer transcription factor BATF. This ITK-dependent switch between TH17 and Treg cells depended on Ca2+ signaling but not on MAPKs. These findings suggest potential strategies for fine-tuning TCR signal strength through ITK to control the balance of TH17 and Treg cells.

Metabolic reprogramming and dysregulated IL-17 production impairs CD4 T cell function post sepsis

Sepsis survivors are at high risk for infection-related rehospitalization and mortality for years following the resolution of the acute septic event. These infection-causing microorganisms generally do not cause disease in immunocompetent hosts, suggesting that the post-septic immune response is compromised. Given the importance of CD4 T cells in the development of long-lasting protective immunity, we analyzed their post-septic function. Here we showed that sepsis induced chronic increased and non-specific production of IL-17 by CD4 T cells, resulting in the inability to mount an effective immune response to a secondary pneumonia challenge. Altered cell function was associated with metabolic reprogramming, characterized by mitochondrial dysfunction and increased glycolysis. This metabolic reprogramming began during the acute septic event and persisted long after sepsis had resolved. Our findings reveal cell metabolism as a potential therapeutic target. Given the critical role of cell metabolism in the physiological and pathophysiological processes of immune cells, these findings reveal a potential new therapeutic target to help mitigate sepsis survivors' susceptibility to secondary infections.

Niclosamide Enema for Active Distal Ulcerative Colitis: A Phase 1, Open-Label Study

BACKGROUND

Oral and rectal formulations of 5-aminosalicylic acid are the first-line therapy for mild-to-moderate, distal ulcerative colitis (UC), but such a treatment is not effective in one-third of patients. Niclosamide is a small molecule, developed and approved as an orally administered drug to treat helminthic infections, with an excellent safety profile. Preclinical work showed that niclosamide is an anti-inflammatory agent, thereby providing the rationale to explore its safety and efficacy in patients with UC. This phase 1, open-label trial was aimed at assessing the safety of niclosamide formulated as an enema in patients with mild-to-moderate, distal UC, who relapsed on maintenance therapy with oral and/or rectal 5-aminosalicylic acid.

METHODS

Seventeen patients with active UC received niclosamide enema (150 mg/60 mL) twice a day for 6 weeks. The primary endpoint was the safety of niclosamide treatment. Secondary endpoints included clinical remission and improvements in endoscopic Mayo/histologic scores. Endoscopic remission percentages exclude participants meeting criteria at baseline for endoscopic remission.

RESULTS

Niclosamide was well tolerated by all 17 patients that were enrolled and treated. No serious adverse event was registered. Fifteen mild adverse events were registered in 6 patients and considered to be unrelated to the treatment. Clinical remission was achieved in 10 (59%) of 17 patients. Improvements of endoscopic Mayo score and histologic Geboes score were seen in 7 (58%) of 12 and 7 (41.2%) of 17 patients, respectively.

CONCLUSIONS

Niclosamide enema treatment is safe and well tolerated. Niclosamide improves clinical symptoms and endoscopic/histologic signs of UC; however, appropriately designed placebo-controlled clinical trials are required to confirm efficacy.

Remodeling of T-cell mitochondrial metabolism to treat autoimmune diseases

T cells are key drivers of the pathogenesis of autoimmune diseases by producing cytokines, stimulating the generation of autoantibodies, and mediating tissue and cell damage. Distinct mitochondrial metabolic pathways govern the direction of T-cell differentiation and function and rely on specific nutrients and metabolic enzymes. Metabolic substrate uptake and mitochondrial metabolism form the foundational elements for T-cell activation, proliferation, differentiation, and effector function, contributing to the dynamic interplay between immunological signals and mitochondrial metabolism in coordinating adaptive immunity. Perturbations in substrate availability and enzyme activity may impair T-cell immunosuppressive function, fostering autoreactive responses and disrupting immune homeostasis, ultimately contributing to autoimmune disease pathogenesis. A growing body of studies has explored how metabolic processes regulate the function of diverse T-cell subsets in autoimmune diseases such as systemic lupus erythematosus (SLE), multiple sclerosis (MS), autoimmune hepatitis (AIH), inflammatory bowel disease (IBD), and psoriasis. This review describes the coordination of T-cell biology by mitochondrial metabolism, including the electron transport chain (ETC), oxidative phosphorylation, amino acid metabolism, fatty acid metabolism, and one‑carbon metabolism. This study elucidated the intricate crosstalk between mitochondrial metabolic programs, signal transduction pathways, and transcription factors. This review summarizes potential therapeutic targets for T-cell mitochondrial metabolism and signaling in autoimmune diseases, providing insights for future studies.

The immune cell transcriptome is modulated by vitamin D3 supplementation in people with a first demyelinating event participating in a randomized placebo-controlled trial

Vitamin D deficiency is a risk factor for developing multiple sclerosis. The PrevANZ trial was conducted to determine if vitamin D3 supplementation can prevent recurrent disease activity in people with a first demyelinating event. As a sub-study of this trial, we investigated the effect of supplementation on peripheral immune cell gene expression. Participants were randomized to 1000, 5000 or 10,000 international units daily of vitamin D3 or placebo. Peripheral blood was collected at baseline and 12 weeks and sent for ribonucleic acid sequencing. Datasets from 55 participants were included. Gene expression was modulated by high dose supplementation. Antigen presentation and viral response pathways were upregulated. Oxidative phosphorylation and immune signaling pathways, including tumor necrosis factor-alpha and interleukin-17 signaling, were downregulated. Overall, vitamin D3 supplementation for 12 weeks modulated the peripheral immune cell transcriptome with induction of anti-inflammatory gene expression profiles. Our results support a dose-dependent effect of vitamin D3 supplementation on immune gene expression.

Group 3 innate lymphoid cells: A trained Gutkeeper

Group 3 innate lymphoid cells (ILC3s) are tissue-resident immune lymphocytes that critically regulate intestinal homeostasis, organogenesis, and immunity. ILC3s possess the capacity to "sense" the inflammatory environment within tissues, especially in the context of pathogen challenges that imprints durable non-antigen-specific changes in ILC3 function. As such, ILC3s become a new actor in the emerging field of trained innate immunity. Here, we summarize recent discoveries regarding ILC3 responses to bacterial challenges and the role these encounters play in triggering trained innate immunity. We further discuss how signaling events throughout ILC3 ontogeny potentially control the development and function of trained ILC3s. Finally, we highlight the open questions surrounding ILC3 "training" the answers to which may reveal new insights into innate immunity. Understanding the fundamental concepts behind trained innate immunity could potentially lead to the development of new strategies for improving immunity-based modulation therapies for inflammation, infectious diseases, and cancer.

Interleukin 21 Drives a Hypermetabolic State and CD4+ T-Cell-Associated Pathogenicity in Chronic Intestinal Inflammation

BACKGROUND & AIMS

Incapacitated regulatory T cells (Tregs) contribute to immune-mediated diseases. Inflammatory Tregs are evident during human inflammatory bowel disease; however, mechanisms driving the development of these cells and their function are not well understood. Therefore, we investigated the role of cellular metabolism in Tregs relevant to gut homeostasis.

METHODS

Using human Tregs, we performed mitochondrial ultrastructural studies via electron microscopy and confocal imaging, biochemical and protein analyses using proximity ligation assay, immunoblotting, mass cytometry and fluorescence-activated cell sorting, metabolomics, gene expression analysis, and real-time metabolic profiling utilizing the Seahorse XF analyzer. We used a Crohn's disease single-cell RNA sequencing dataset to infer the therapeutic relevance of targeting metabolic pathways in inflammatory Tregs. We examined the superior functionality of genetically modified Tregs in CD4+ T-cell-induced murine colitis models.

RESULTS

Mitochondria-endoplasmic reticulum appositions, known to mediate pyruvate entry into mitochondria via voltage-dependent anion channel 1 (VDAC1), are abundant in Tregs. VDAC1 inhibition perturbed pyruvate metabolism, eliciting sensitization to other inflammatory signals reversible by membrane-permeable methyl pyruvate supplementation. Notably, interleukin (IL) 21 diminished mitochondria-endoplasmic reticulum appositions, resulting in enhanced enzymatic function of glycogen synthase kinase 3 β, a putative negative regulator of VDAC1, and a hypermetabolic state that amplified Treg inflammatory response. Methyl pyruvate and glycogen synthase kinase 3 β pharmacologic inhibitor (LY2090314) reversed IL21-induced metabolic rewiring and inflammatory state. Moreover, IL21-induced metabolic genes in Tregs in vitro were enriched in human Crohn's disease intestinal Tregs. Adoptively transferred Il21r-/- Tregs efficiently rescued murine colitis in contrast to wild-type Tregs.

CONCLUSIONS

IL21 triggers metabolic dysfunction associated with Treg inflammatory response. Inhibiting IL21-induced metabolism in Tregs may mitigate CD4+ T-cell-driven chronic intestinal inflammation.

Metabolic regulation of the Th17/Treg balance in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a long-lasting and inflammatory autoimmune condition affecting the gastrointestinal tract, impacting millions of individuals globally. The balance between T helper 17 (Th17) cells and regulatory T cells (Tregs) is pivotal in the pathogenesis and progression of IBD. This review summarizes the pivotal role of Th17/Treg balance in maintaining intestinal homeostasis, elucidating how its dysregulation contributes to the development and exacerbation of IBD. It comprehensively synthesizes the current understanding of how dietary factors regulate the metabolic pathways influencing Th17 and Treg cell differentiation and function. Additionally, this review presents evidence from the literature on the potential of dietary regimens to regulate the Th17/Treg balance as a strategy for the management of IBD. By exploring the intersection between diet, metabolic regulation, and Th17/Treg balance, the review reveals innovative therapeutic approaches for IBD treatment, offering a promising perspective for future research and clinical practice.

Dexamethasone protects against asthma via regulating Hif-1α-glycolysis-lactate axis and protein lactylation

PURPOSE

Asthma can not be eradicated till now and its control primarily relies on the application of corticosteroids. Recently, glycolytic reprogramming has been reportedly contributed to asthma, this study aimed to reveal whether the effect of corticosteroids on asthma control is related to their regulation of glycolysis and glycolysis-dependent protein lactylation.

METHODS

Ovalbumin (OVA) aeroallergen was used to challenge mice and stimulate human macrophage cell line THP-1 following dexamethasone (DEX) treatment. Airway hyperresponsiveness, airway inflammation, the expressions of key glycolytic enzymes and pyroptosis markers, the level of lactic acid, real-time glycolysis and oxidative phosphorylation (OXPHOS), and protein lactylation were analyzed.

RESULTS

DEX significantly attenuated OVA-induced eosinophilic airway inflammation, including airway hyperresponsiveness, leukocyte infiltration, goblet cell hyperplasia, Th2 cytokines production and pyroptosis markers expression. Meanwhile, OVA-induced Hif-1α-glycolysis axis was substantially downregulated by DEX, which resulted in low level of lactic acid. Besides, key glycolytic enzymes in the lungs of asthmatic mice were notably co-localized with F4/80-positive macrophages, indicating metabolic shift to glycolysis in lung macrophages during asthma. This was confirmed in OVA-stimulated THP-1 cells that DEX treatment resulted in reductions in pyroptosis, glycolysis and lactic acid level. Finally, protein lactylation was found significantly increased in the lungs of asthmatic mice and OVA-stimulated THP-1 cells, which were both inhibited by DEX.

CONCLUSION

Our present study revealed that the effect of DEX on asthma control was associated with its suppressing of Hif-1α-glycolysis-lactateaxis and subsequent protein lactylation, which may open new avenues for the therapy of eosinophilic asthma.

Inhibition of Mitochondrial Translation Ameliorates Imiquimod-Induced Psoriasis-Like Skin Inflammation by Targeting Vγ4+ γδ T Cells

Psoriasis is an inflammatory skin disorder that is characterized by keratinocyte hyperproliferation in response to immune cell infiltration and cytokine secretion in the dermis. γδ T cells expressing the Vγ4 TCR chain are among the highest contributors of IL-17A, which is a major cytokine that drives a psoriasis flare, making Vγ4+ γδ T cells a suitable target to restrict psoriasis progression. In this study, we demonstrate that mitochondrial translation inhibition within Vγ4+ γδ T cells effectively reduced erythema, scaling, and skin thickening in a murine model of psoriatic disease. The antibiotic linezolid, which blocks mitochondrial translation, inhibited the production of mitochondrial-encoded protein cytochrome c oxidase in Vγ4+ γδ T cells and systemically reduced the frequencies of IL-17A+ Vγ4+ γδ T cells, effectively resolving IL-17A-dependent inflammation. Inhibiting mitochondrial translation could be a novel metabolic approach to interrupt IL-17A signaling in Vγ4+ T cells and reduce psoriasis-like skin pathophysiology.

Coccidiosis and necrotic enteritis model may have a greater impact than dietary anti-interleukin-10 on broiler chicken systemic immunometabolic responses

Dietary egg yolk-derived anti-interleukin (IL)-10 may preserve broiler chicken performance during coccidiosis due to Eimeria spp. infection while effects on secondary Clostridium perfringens (necrotic enteritis) are unknown. Some necrotic enteritis models implement Salmonella Typhimurium to improve repeatability; however, Salmonella upregulation of IL-10 may be a confounder when evaluating anti-IL-10. The study objective was to investigate anti-IL-10 effects on systemic cytokine concentrations and immunometabolism during E. maxima ± C. perfringens challenge in models ± S. Typhimurium. Three 25 d replicate studies using Ross 308 chicks were conducted in wire-floor cages (32 cages/ replicate) with chicks assigned to diets ± 0.03% anti-IL-10. 640 chicks (20/ cage; replicates 1 and 2) were inoculated with sterile saline ± 1×108 colony forming units (CFU) S. Typhimurium while 480 chicks (15/ cage) were placed in replicate 3. In all replicates, blood samples were collected on d 14 (6 chicks/treatment) before administering 15,000 sporulated E. maxima M6 oocysts to S. Typhimurium-inoculated (replicates 1 and 2) or challenge-designated chicks (replicate 3). Half the E. maxima-challenged chicks received 1×108 CFU C. perfringens on d 18 and 19. Blood samples were collected at 1, 3, 7, and 11 d post-inoculation (dpi) with E. maxima and 1, 3, and 7 dpi with secondary C. perfringens. Plasma cytokines were determined by ELISA while immunometabolic assays evaluated peripheral blood mononuclear cell ATP production and glycolytic rate responses. Data were analyzed with diet and challenge fixed effects plus associated interactions (SAS 9.4; P ≤ 0.05). Replicates 1 and 2 showed few immunometabolic responses within 3 dpi with E. maxima, but 25 to 31% increased ATP production and 32% increased compensatory glycolysis at 1 dpi with C. perfringens in challenged vs. unchallenged chicks (P ≤ 0.04). In replicate 3, total ATP production and compensatory glycolysis were increased 25 and 40%, respectively, by the E. maxima main effect at 1dpi (P ≤ 0.05) with unobserved responsiveness to C. perfringens. These outcomes indicate that model type had greater impacts on systemic immunity than anti-IL-10.

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.

Unlocking potential: the role of the electron transport chain in immunometabolism

The electron transport chain (ETC) couples electron transfer with proton pumping to generate ATP and it also regulates particular innate and adaptive immune cell function. While NLRP3 inflammasome activation was initially linked to reactive oxygen species (ROS) produced from Complexes I and III, recent research suggests that an intact ETC fueling ATP is needed. Complex II may be responsible for Th1 cell proliferation and in some cases, effector cytokine production. Complex III is required for regulatory T (Treg) cell function, while oxidative phosphorylation (OXPHOS) and Complexes I, IV, and V sustain proliferation and antibody production in B lymphocytes, with OXPHOS also being required for B regulatory (Breg) cell function. Despite challenges, the ETC shows therapeutic targeting potential for immune-related diseases and in immuno-oncology.

Deficiency of thioredoxin-interacting protein results in age-related thrombocytopenia due to megakaryocyte oxidative stress

BACKGROUND

Platelets are generated from megakaryocytes (MKs), mainly located in the bone marrow (BM). Megakaryopoiesis can be affected by genetic disorders, metabolic diseases, and aging. The molecular mechanisms underlying platelet count regulation have not been fully elucidated.

OBJECTIVES

In the present study, we investigated the role of thioredoxin-interacting protein (TXNIP), a protein that regulates cellular metabolism in megakaryopoiesis, using a Txnip-/- mouse model.

METHODS

Wild-type (WT) and Txnip-/- mice (2-27-month-old) were studied. BM-derived MKs were analyzed to investigate the role of TXNIP in megakaryopoiesis with age. The global transcriptome of BM-derived CD41+ megakaryocyte precursors (MkPs) of WT and Txnip-/- mice were compared. The CD34+ hematopoietic stem cells isolated from human cord blood were differentiated into MKs.

RESULTS

Txnip-/- mice developed thrombocytopenia at 4 to 5 months that worsened with age. During ex vivo megakaryopoiesis, Txnip-/- MkPs remained small, with decreased levels of MK-specific markers. Critically, Txnip-/- MkPs exhibited reduced mitochondrial reactive oxygen species, which was related to AKT activity. Txnip-/- MkPs also showed elevated glycolysis alongside increased glucose uptake for ATP production. Total RNA sequencing revealed enrichment for oxidative stress- and apoptosis-related genes in differentially expressed genes between Txnip-/- and WT MkPs. The effects of TXNIP on MKs were recapitulated during the differentiation of human cord blood-derived CD34+ hematopoietic stem cells.

CONCLUSION

We provide evidence that the megakaryopoiesis pathway becomes exhausted with age in Txnip-/- mice with a decrease in terminal, mature MKs that response to thrombocytopenic challenge. Overall, this study demonstrates the role of TXNIP in megakaryopoiesis, regulating mitochondrial metabolism.

Somatostatin-SSTR3-GSK3 modulates human T-cell responses by inhibiting OXPHOS

Introduction

Somatostatin (SST) is a peptide hormone primarily synthesized in the digestive and nervous systems. While its impact on the endocrine system is well-established, accumulating evidence suggests a crucial role for SST and its analogues in modulating immune responses. Despite this, the precise mechanism through which SST regulates T cells has remained largely unknown.

Methods

To elucidate the impact of SST on human T cells, we conducted a series of experiments involving cell culture assays, molecular analyses, and metabolic profiling. Human T cells were treated with SST, and various parameters including proliferation, cytokine production, and metabolic activities were assessed. Additionally, we employed pharmacological inhibitors and genetic manipulations to dissect the signaling pathways mediating SST's effects on T cells.

Results

We showed that SST diminishes T-cell proliferation by influencing IL-2 production and T-cell mitochondrial respiration, while having no discernible impact on TCR-induced glycolysis. Our findings also identified that the regulatory influence of SST on T-cell responses and metabolism is contingent on its receptor, SSTR3. Moreover, we demonstrated that SST governs T-cell responses and metabolism by acting through the T-cell metabolic checkpoint GSK3.

Discussion

Our study provides novel insights into the immunoregulatory function of SST in human T cells, highlighting the complex interplay between hormonal signaling and immune regulation. Understanding the molecular mechanisms underlying SST's effects on T cells may offer therapeutic opportunities for manipulating immune responses in various pathological conditions.

Mitochondrial and metabolic dysfunction of peripheral immune cells in multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disorder characterized by the infiltration of inflammatory cells and demyelination of nerves. Mitochondrial dysfunction has been implicated in the pathogenesis of MS, as studies have shown abnormalities in mitochondrial activities, metabolism, mitochondrial DNA (mtDNA) levels, and mitochondrial morphology in immune cells of individuals with MS. The presence of mitochondrial dysfunctions in immune cells contributes to immunological dysregulation and neurodegeneration in MS. This review provided a comprehensive overview of mitochondrial dysfunction in immune cells associated with MS, focusing on the potential consequences of mitochondrial metabolic reprogramming on immune function. Current challenges and future directions in the field of immune-metabolic MS and its potential as a therapeutic target were also discussed.

Unraveling the complexity of STAT3 in cancer: molecular understanding and drug discovery

Signal transducer and activator of transcription 3 (STAT3) is a transcriptional factor involved in almost all cancer hallmark features including tumor proliferation, metastasis, angiogenesis, immunosuppression, tumor inflammation, metabolism reprogramming, drug resistance, cancer stemness. Therefore, STAT3 has become a promising therapeutic target in a wide range of cancers. This review focuses on the up-to-date knowledge of STAT3 signaling in cancer. We summarize both the positive and negative modulators of STAT3 together with the cancer hallmarks involving activities regulated by STAT3 and highlight its extremely sophisticated regulation on immunosuppression in tumor microenvironment and metabolic reprogramming. Direct and indirect inhibitors of STAT3 in preclinical and clinical studies also have been summarized and discussed. Additionally, we highlight and propose new strategies of targeting STAT3 and STAT3-based combinations with established chemotherapy, targeted therapy, immunotherapy and combination therapy. These efforts may provide new perspectives for STAT3-based target therapy in cancer.

GLUT-1/PKM2 loop dysregulation in patients with non-ST-segment elevation myocardial infarction promotes metainflammation

AIMS

The functional capacity of the immune cells is strongly dependent on their metabolic state and inflammatory responses are characterized by a greater use of glucose in immune cells. This study is aimed to establish the role of glucose metabolism and its players [glucose transporter 1 (GLUT-1) and pyruvate kinase isozyme M2 (PKM2)] in the dysregulation of adaptive immunity and inflammation observed in patients with non-ST-segment elevation myocardial infarction (NSTEMI).

METHODS AND RESULTS

We enrolled 248 patients allocated to three groups: NSTEMI patients, chronic coronary syndromes (CCS) patients, healthy subjects (HSs). NSTEMI patients showed higher expression of GLUT-1 and an enhanced glucose uptake in T cells when compared with CCS patients (P < 0.0001; P = 0.0101, respectively) and HSs (P = 0.0071; P = 0.0122, respectively). PKM2 had a prevalent nuclear localization in T lymphocytes in NSTEMI (P = 0.0005 for nuclear vs. cytoplasm localization), while in CCS and HS, it was equally distributed in both compartments. In addition, the nuclear fraction of PKM2 was significantly higher in NSTEMI compared with HS (P = 0.0023). In NSTEMI patients, treatment with Shikonin and Fasentin, which inhibits PKM2 enzyme activity and GLUT-1-mediated glucose internalization, respectively, led to a significant reduction in GLUT-1 expression along with the down-regulation of pro-inflammatory cytokine expression.

CONCLUSION

NSTEMI patients exhibit dysregulation of the GLUT-1/PKM2 metabolic loop characterized by nuclear translocation of PKM2, where it acts as a transcription regulator of pro-inflammatory genes. This detrimental loop might represent a new therapeutic target for personalized medicine.

Control of CD4+ T cells to restrain inflammatory diseases via eukaryotic elongation factor 2 kinase

CD4+ T cells, particularly IL-17-secreting helper CD4+ T cells, play a central role in the inflammatory processes underlying autoimmune disorders. Eukaryotic Elongation Factor 2 Kinase (eEF2K) is pivotal in CD8+ T cells and has important implications in vascular dysfunction and inflammation-related diseases such as hypertension. However, its specific immunological role in CD4+ T cell activities and related inflammatory diseases remains elusive. Our investigation has uncovered that the deficiency of eEF2K disrupts the survival and proliferation of CD4+ T cells, impairs their ability to secrete cytokines. Notably, this dysregulation leads to heightened production of pro-inflammatory cytokine IL-17, fosters a pro-inflammatory microenvironment in the absence of eEF2K in CD4+ T cells. Furthermore, the absence of eEF2K in CD4+ T cells is linked to increased metabolic activity and mitochondrial bioenergetics. We have shown that eEF2K regulates mitochondrial function and CD4+ T cell activity through the upregulation of the transcription factor, signal transducer and activator of transcription 3 (STAT3). Crucially, the deficiency of eEF2K exacerbates the severity of inflammation-related diseases, including rheumatoid arthritis, multiple sclerosis, and ulcerative colitis. Strikingly, the use of C188-9, a small molecule targeting STAT3, mitigates colitis in a murine immunodeficiency model receiving eEF2K knockout (KO) CD4+ T cells. These findings emphasize the pivotal role of eEF2K in controlling the function and metabolism of CD4+ T cells and its indispensable involvement in inflammation-related diseases. Manipulating eEF2K represents a promising avenue for novel therapeutic approaches in the treatment of inflammation-related disorders.

Calculation of ATP production rates using the Seahorse XF Analyzer

Oxidative phosphorylation and glycolysis are the dominant ATP-generating pathways in mammalian metabolism. The balance between these two pathways is often shifted to execute cell-specific functions in response to stimuli that promote activation, proliferation, or differentiation. However, measurement of these metabolic switches has remained mostly qualitative, making it difficult to discriminate between healthy, physiological changes in energy transduction or compensatory responses due to metabolic dysfunction. We therefore present a broadly applicable method to calculate ATP production rates from oxidative phosphorylation and glycolysis using Seahorse XF Analyzer data and empirical conversion factors. We quantify the bioenergetic changes observed during macrophage polarization as well as cancer cell adaptation to in vitro culture conditions. Additionally, we detect substantive changes in ATP utilization upon neuronal depolarization and T cell receptor activation that are not evident from steady-state ATP measurements. This method generates a single readout that allows the direct comparison of ATP produced from oxidative phosphorylation and glycolysis in live cells. Additionally, the manuscript provides a framework for tailoring the calculations to specific cell systems or experimental conditions.

Dexamethasone protects against Aspergillus fumigatus-induced severe asthma via modulating pulmonary immunometabolism

Severe asthma is a difficult-to-treat chronic airway inflammatory disease requiring systemic corticosteroids to achieve asthma control. It has recently been shown that drugs targeting immunometabolism have elicited anti-inflammatory effects. The purpose of this study was to investigate potential immunometabolic modulatory actions of systemic dexamethasone (Dex) in an Aspergillus fumigatus (Af)-induced severe asthma model. Mice were repeatedly exposed to the Af aeroallergen before systemic treatment with Dex. Simultaneous measurements of airway inflammation, real-time glycolytic and oxidative phosphorylation (OXPHOS) activities, expression levels of key metabolic enzymes, and amounts of metabolites were studied in lung tissues, and in primary alveolar macrophages (AMs) and eosinophils. Dex markedly reduced Af-induced eosinophilic airway inflammation, which was coupled with an overall reduction in lung glycolysis, glutaminolysis, and fatty acid synthesis. The anti-inflammatory effects of Dex may stem from its immunometabolic actions by downregulating key metabolic enzymes including pyruvate dehydrogenase kinase, glutaminase, and fatty acid synthase. Substantial suppression of eosinophilic airway inflammation by Dex coincided with a specific escalation of mitochondrial proton leak in primary lung eosinophils. Besides, while our findings confirmed that inflammation corresponds with an upregulation of glycolysis, it was accompanied with an unexpectedly stable or elevated OXPHOS in the lungs and activated immune cells, respectively. Our findings reveal that the anti-inflammatory effects of Dex in severe asthma are associated with downregulation of pyruvate dehydrogenase kinase, glutaminase, and fatty acid synthase, and the augmentation of mitochondrial proton leak in lung eosinophils. These enzymes and biological processes may be valuable targets for therapeutic interventions against severe asthma.

Supplementation with EPA and DHA omega-3 fatty acids improves peripheral immune cell mitochondrial dysfunction and inflammation in subjects with obesity

Omega-3 fatty acids (w-3 FA) have anti-inflammatory effects and improve mitochondrial function. Nonetheless, little is known about their effect on mitochondrial bioenergetics of peripheral blood mononuclear cells (PBMCs) in individuals with obesity. Thus, this study aimed to determine the mitochondrial bioenergetics status and cell subset composition of PBMCs during obesity, before and after 1 month supplementation with w-3 FA. We performed a case-control study with twelve women with normal BMI (lean group) and 19 with grade 2 obesity (obese group), followed by a before-after prospective study where twelve subjects with obesity received a 1 month intervention with 5.25 g of w-3 FA (3.5 g eicosapentaenoic (EPA) and 1.75 g docosahexaenoic (DHA) acids), and obtained PBMCs from all participants. Mitochondrial bioenergetic markers, including basal and ATP-production associated respiration, proton leak, and nonmitochondrial respiration, were higher in PBMCs from the obese group vs. the lean group. The bioenergetic health index (BHI), a marker of mitochondrial function, was lower in the obese vs. the lean group. In addition, Th1, Th2, Th17, CD4+ Tregs, CD8+ Tregs, and Bregs, M1 monocytes and pDCreg cells were higher in PBMCs from the obese group vs. the lean group. The w-3 FA intervention improved mitochondrial function, mainly by decreasing nonmitochondrial respiration and increasing the reserve respiratory capacity and BHI. The intervention also reduced circulating pro-inflammatory and anti-inflammatory lymphocyte and monocytes subsets in individuals with obesity. The mitochondrial dysfunction of PBMCs and the higher proportion of peripheral pro-inflammatory and anti-inflammatory immune cells in subjects with obesity, improved with 1 month supplementation with EPA and DHA.

Boosting NAD preferentially blunts Th17 inflammation via arginine biosynthesis and redox control in healthy and psoriasis subjects

To evaluate whether nicotinamide adenine dinucleotide-positive (NAD+) boosting modulates adaptive immunity, primary CD4+ T cells from healthy control and psoriasis subjects were exposed to vehicle or nicotinamide riboside (NR) supplementation. NR blunts interferon γ (IFNγ) and interleukin (IL)-17 secretion with greater effects on T helper (Th) 17 polarization. RNA sequencing (RNA-seq) analysis implicates NR blunting of sequestosome 1 (sqstm1/p62)-coupled oxidative stress. NR administration increases sqstm1 and reduces reactive oxygen species (ROS) levels. Furthermore, NR activates nuclear factor erythroid 2-related factor 2 (Nrf2), and genetic knockdown of nrf2 and the Nrf2-dependent gene, sqstm1, diminishes NR amelioratory effects. Metabolomics analysis identifies that NAD+ boosting increases arginine and fumarate biosynthesis, and genetic knockdown of argininosuccinate lyase ameliorates NR effects on IL-17 production. Hence NR via amino acid metabolites orchestrates Nrf2 activation, augments CD4+ T cell antioxidant defenses, and attenuates Th17 responsiveness. Oral NR supplementation in healthy volunteers similarly increases serum arginine, sqstm1, and antioxidant enzyme gene expression and blunts Th17 immune responsiveness, supporting evaluation of NAD+ boosting in CD4+ T cell-linked inflammation.

DOT1L regulates lung developmental epithelial cell fate and adult alveolar stem cell differentiation after acute injury

AT2 cells harbor alveolar stem cell activity in the lung and can self-renew and differentiate into AT1 cells during homeostasis and after injury. To identify epigenetic pathways that control the AT2-AT1 regenerative response in the lung, we performed an organoid screen using a library of pharmacological epigenetic inhibitors. This screen identified DOT1L as a regulator of AT2 cell growth and differentiation. In vivo inactivation of Dot1l leads to precocious activation of both AT1 and AT2 gene expression during lung development and accelerated AT1 cell differentiation after acute lung injury. Single-cell transcriptome analysis reveals the presence of a new AT2 cell state upon loss of Dot1l, characterized by increased expression of oxidative phosphorylation genes and changes in expression of critical transcription and epigenetic factors. Taken together, these data demonstrate that Dot1l controls the rate of alveolar epithelial cell fate acquisition during development and regeneration after acute injury.

Mitochondria during T cell aging

Mitochondrial dysfunction is a hallmark of aging that contributes to inflammaging. It is characterized by alterations of the mitochondrial DNA, reduced respiratory capacity, decreased mitochondrial membrane potential and increased reactive oxygen species production. These primary alterations disrupt other interconnected and important mitochondrial-related processes such as metabolism, mitochondrial dynamics and biogenesis, mitophagy, calcium homeostasis or apoptosis. In this review, we gather the current knowledge about the different mitochondrial processes which are altered during aging, with special focus on their contribution to age-associated T cell dysfunction and inflammaging.

Canagliflozin impairs T cell effector function via metabolic suppression in autoimmunity

Augmented T cell function leading to host damage in autoimmunity is supported by metabolic dysregulation, making targeting immunometabolism an attractive therapeutic avenue. Canagliflozin, a type 2 diabetes drug, is a sodium glucose co-transporter 2 (SGLT2) inhibitor with known off-target effects on glutamate dehydrogenase and complex I. However, the effects of SGLT2 inhibitors on human T cell function have not been extensively explored. Here, we show that canagliflozin-treated T cells are compromised in their ability to activate, proliferate, and initiate effector functions. Canagliflozin inhibits T cell receptor signaling, impacting on ERK and mTORC1 activity, concomitantly associated with reduced c-Myc. Compromised c-Myc levels were encapsulated by a failure to engage translational machinery resulting in impaired metabolic protein and solute carrier production among others. Importantly, canagliflozin-treated T cells derived from patients with autoimmune disorders impaired their effector function. Taken together, our work highlights a potential therapeutic avenue for repurposing canagliflozin as an intervention for T cell-mediated autoimmunity.

Augmenting TCR signal strength and ICOS costimulation results in metabolically fit and therapeutically potent human CAR Th17 cells

IL-17-producing antigen-specific human T cells elicit potent antitumor activity in mice. Yet, refinement of this approach is needed to position it for clinical use. While activation signal strength regulates IL-17 production by CD4+ T cells, the degree to which T cell antigen receptor (TCR) and costimulation signal strength influences Th17 immunity remains unknown. We discovered that decreasing TCR/costimulation signal strength by incremental reduction of αCD3/costimulation beads progressively altered Th17 phenotype. Moreover, Th17 cells stimulated with αCD3/inducible costimulator (ICOS) beads produced more IL-17A, IFNγ, IL-2, and IL-22 than those stimulated with αCD3/CD28 beads. Compared with Th17 cells stimulated with the standard, strong signal strength (three beads per T cell), Th17 cells propagated with 30-fold fewer αCD3/ICOS beads were less reliant on glucose and favored the central carbon pathway for bioenergetics, marked by abundant intracellular phosphoenolpyruvate (PEP). Importantly, Th17 cells stimulated with weak αCD3/ICOS beads and redirected with a chimeric antigen receptor that recognizes mesothelin were more effective at clearing human mesothelioma. Less effective CAR Th17 cells generated with high αCD3/ICOS beads were rescued by overexpressing phosphoenolpyruvate carboxykinase 1 (PCK1), a PEP regulator. Thus, Th17 therapy can be improved by using fewer activation beads during manufacturing, a finding that is cost effective and directly translatable to patients.

Immunometabolism at the Heart of Cardiovascular Disease

Immune cell function among the myocardium, now more than ever, is appreciated to regulate cardiac function and pathophysiology. This is the case for both innate immunity, which includes neutrophils, monocytes, dendritic cells, and macrophages, as well as adaptive immunity, which includes T cells and B cells. This function is fueled by cell-intrinsic shifts in metabolism, such as glycolysis and oxidative phosphorylation, as well as metabolite availability, which originates from the surrounding extracellular milieu and varies during ischemia and metabolic syndrome. Immune cell crosstalk with cardiac parenchymal cells, such as cardiomyocytes and fibroblasts, is also regulated by complex cellular metabolic circuits. Although our understanding of immunometabolism has advanced rapidly over the past decade, in part through valuable insights made in cultured cells, there remains much to learn about contributions of in vivo immunometabolism and directly within the myocardium. Insight into such fundamental cell and molecular mechanisms holds potential to inform interventions that shift the balance of immunometabolism from maladaptive to cardioprotective and potentially even regenerative. Herein, we review our current working understanding of immunometabolism, specifically in the settings of sterile ischemic cardiac injury or cardiometabolic disease, both of which contribute to the onset of heart failure. We also discuss current gaps in knowledge in this context and therapeutic implications.

Aurora kinase A/AURKA functionally interacts with the mitochondrial ATP synthase to regulate energy metabolism and cell death

Cancer cells often hijack metabolic pathways to obtain the energy required to sustain their proliferation. Understanding the molecular mechanisms underlying cancer cell metabolism is key to fine-tune the metabolic preference of specific tumors, and potentially offer new therapeutic strategies. Here, we show that the pharmacological inhibition of mitochondrial Complex V delays the cell cycle by arresting breast cancer cell models in the G0/G1 phase. Under these conditions, the abundance of the multifunctional protein Aurora kinase A/AURKA is specifically lowered. We then demonstrate that AURKA functionally interacts with the mitochondrial Complex V core subunits ATP5F1A and ATP5F1B. Altering the AURKA/ATP5F1A/ATP5F1B nexus is sufficient to trigger G0/G1 arrest, and this is accompanied by decreased glycolysis and mitochondrial respiration rates. Last, we discover that the roles of the AURKA/ATP5F1A/ATP5F1B nexus depend on the specific metabolic propensity of triple-negative breast cancer cell lines, where they correlate with cell fate. On one hand, the nexus induces G0/G1 arrest in cells relying on oxidative phosphorylation as the main source of energy. On the other hand, it allows to bypass cell cycle arrest and it triggers cell death in cells with a glycolytic metabolism. Altogether, we provide evidence that AURKA and mitochondrial Complex V subunits cooperate to maintain cell metabolism in breast cancer cells. Our work paves the way to novel anti-cancer therapies targeting the AURKA/ATP5F1A/ATP5F1B nexus to lower cancer cell metabolism and proliferation.

Interleukin-21 Drives a Hypermetabolic State and CD4+ T Cell-associated Pathogenicity in Chronic Intestinal Inflammation

BACKGROUND & AIMS

Incapacitated regulatory T cells (Tregs) contribute to immune-mediated diseases. Inflammatory Tregs are evident during human inflammatory bowel disease (IBD); however, mechanisms driving the development of these cells and their function are not well understood. Therefore, we investigated the role of cellular metabolism in Tregs relevant to gut homeostasis.

METHODS

Using human Tregs, we performed mitochondrial ultrastructural studies via electron microscopy and confocal imaging, biochemical and protein analyses using proximity ligation assay, immunoblotting, mass cytometry and fluorescence-activated cell sorting, metabolomics, gene expression analysis, and real-time metabolic profiling utilizing Seahorse XF analyzer. We utilized Crohn's disease single-cell RNA sequencing dataset to infer therapeutic relevance of targeting metabolic pathways in inflammatory Tregs. We examined the superior functionality of genetically-modified Tregs in CD4+ T cell-induced murine colitis models.

RESULTS

Mitochondria-endoplasmic reticulum (ER) appositions, known to mediate pyruvate entry into mitochondria via VDAC1, are abundant in Tregs. VDAC1 inhibition perturbed pyruvate metabolism, eliciting sensitization to other inflammatory signals reversible by membrane-permeable methyl pyruvate (MePyr) supplementation. Notably, IL-21 diminished mitochondria-ER appositions, resulting in enhanced enzymatic function of glycogen synthase kinase 3 β (GSK3β), a putative negative regulator of VDAC1, and a hypermetabolic state that amplified Treg inflammatory response. MePyr and GSK3β pharmacologic inhibitor (LY2090314) reversed IL-21-induced metabolic rewiring and inflammatory state. Moreover, IL-21-induced metabolic genes in Tregs in vitro were enriched in human Crohn's disease intestinal Tregs. Adoptively transferred Il21r-/- Tregs efficiently rescued murine colitis in contrast to wild-type Tregs.

CONCLUSIONS

IL-21 triggers metabolic dysfunction associated with Treg inflammatory response. Inhibiting IL-21-induced metabolism in Tregs may mitigate CD4+ T cell-driven chronic intestinal inflammation.

Intrinsic STAT4 Expression Controls Effector CD4 T Cell Migration and Th17 Pathogenicity

Effector CD4 T cells are central to the development of autoimmune chronic inflammatory diseases, yet factors that mediate pathogenicity remain ill-defined. Single-nucleotide polymorphisms in the human STAT4 locus are associated with susceptibility to multiple autoimmune disorders, and Stat4 is linked to the pathogenic Th17 gene signature; however, Th17 cells differentiate independently of STAT4. Hence the interplay between STAT4 and CD4 T cell function, especially Th17 cells, during autoimmune disease is unclear. In this article, we demonstrate that CD4 T cell-intrinsic STAT4 expression is essential for the induction of autoimmune CNS inflammation in mice, in part by regulating the migration of CD4 T cells to the inflamed CNS. Moreover, unbiased transcriptional profiling revealed that STAT4 controls the expression of >200 genes in Th17 cells and is important for the upregulation of genes associated with IL-23-stimulated, pathogenic Th17 cells. Importantly, we show that Th17 cells specifically require STAT4 to evoke autoimmune inflammation, highlighting, to our knowledge, a novel function for STAT4 in Th17 pathogenicity.

Lysosomal acid lipase regulates bioenergetic process during the cytodifferentiation of human periodontal ligament cells

Lipid metabolism is one of energy metabolic pathways that produce adenosine triphosphate (ATP). In this pathway, lysosomal acid lipase (LAL) encoded by Lipase A (LIPA), plays an important role in catalyzing lipids to fatty acids (FAs), which drive oxidative phosphorylation (OXPHOS) and generate ATP. Previously, we found that a LIPA single nucleotide polymorphism rs143793106, which decreases the LAL activity, suppressed the cytodifferentiation of human periodontal ligament (HPDL) cells. However, the mechanisms underlying that suppression are still not fully clarified. Thus, we aimed to investigate the mechanisms regulating the cytodifferentiation of HPDL cells by LAL in terms of energy metabolism. We performed the osteogenic induction of HPDL cells with or without Lalistat-2, a LAL inhibitor. To visualize lipid droplet (LD) utilization, we performed confocal microscopy on HPDL cells. We also performed real-time PCR to analyze the gene expression of calcification-related and metabolism-related genes. Furthermore, we measured the ATP production rate from two major energy production pathways, OXPHOS and glycolysis, and OXPHOS-related parameters of HPDL cells during their cytodifferentiation. We found that LDs were utilized during the cytodifferentiation of HPDL cells. Alkaline phosphatase (ALPL), collagen type 1 alpha 1 chain (COL1A1), ATP synthase F1 subunit alpha (ATP5F1A), and carnitine palmitoyltransferase 1A (CPT1A) mRNA expressions were upregulated, whereas lactate dehydrogenase A (LDHA) mRNA expression was downregulated. Additionally, total ATP production rate was significantly increased. In contrast, in the presence of Lalistat-2, LD utilization was inhibited and ALPL, COL1A1, and ATP5F1A mRNA expression was downregulated. Additionally, ATP production rate and spare respiratory capacity of the OXPHOS pathway were decreased in HPDL cells during their cytodifferentiation. Collectively, the defect of LAL in HPDL cells decreased LD utilization and OXPHOS capacity, resulting in reduced energy to sustain the adequate ATP production required for the cytodifferentiation of HPDL cells. Thus, LAL is important for periodontal tissue homeostasis as a regulator of bioenergetic process of HPDL cells.

ITK signaling regulates a switch between T helper 17 and T regulatory cell lineages via a calcium-mediated pathway

The balance of pro-inflammatory T helper type 17 (Th17) and anti-inflammatory T regulatory (Treg) cells is crucial in maintaining immune homeostasis in health and disease conditions. Differentiation of naïve CD4+ T cells into Th17/Treg cells is dependent upon T cell receptor (TCR) activation and cytokine signaling, which includes the kinase ITK. Signals from ITK can regulate the differentiation of Th17 and Treg cell fate choice, however, the mechanism remains to be fully understood. We report here that in the absence of ITK activity, instead of developing into Th17 cells under Th17 conditions, naïve CD4+ T cells switch to cells expressing the Treg marker Foxp3 (Forkhead box P3). These switched Foxp3+ Treg like cells retain suppressive function and resemble differentiated induced Tregs in their transcriptomic profile, although their chromatin accessibility profiles are intermediate between Th17 and induced Tregs cells. Generation of the switched Foxp3+ Treg like cells was associated with reduced expression of molecules involved in mitochondrial oxidative phosphorylation and glycolysis, with reduced activation of the mTOR signaling pathway, and reduced expression of BATF. This ITK dependent switch between Th17 and Treg cells was reversed by increasing intracellular calcium. These findings suggest potential strategies for fine tune the TCR signal strength via ITK to regulate the balance of Th17/Treg cells.

Treatment with Exogenously Added Catalase Alters CD8 T Cell Memory Differentiation and Function

Cell-based immunotherapy is a promising approach to cancer treatment. However, the metabolically hostile tumor microenvironment (TME) poses a major barrier to this therapeutic approach. Metabolic reprogramming may enhance T cell effector function and support longevity and persistence within the TME. Metabolic processes lead reactive oxygen species (ROS) production, which are mandatory mediators of signaling and immune cell functions, but detrimental when present in excess. Catalase (CAT) is an intracellular antioxidant enzyme that scavenges hydrogen peroxide (H2 O2 ), a central ROS member with a plethora of biological effects. H2 O2 is produced intracellularly and extracellularly, diffusing freely between the two compartments. In this study, it is found that scavenging extracellular H2 O2 by CAT supplementation has a major impact on the cell redox state, decreased intracellular ROS, but enhanced activation and altered memory differentiation. Under in vitro chronic activation conditions, CAT treatment favors CD8 T cells with less exhausted phenotype, increased activation and memory markers, and high bioenergetic capacity. Under in vitro acute activation conditions, CAT treatment selectively prevents differentiation transition from the stem cell memory/naive (TSCM /TN )- to the central memory (TCM )-like phenotype, while enhancing activation and polyfunctionality. The study highlights the critical role of H2 O2 as a "hidden player" in T cell fitness and memory differentiation.

A chemokine network of T cell exhaustion and metabolic reprogramming in renal cell carcinoma

Renal cell carcinoma (RCC) is frequently infiltrated by immune cells, a process which is governed by chemokines. CD8+ T cells in the RCC tumor microenvironment (TME) may be exhausted which most likely influence therapy response and survival. The aim of this study was to evaluate chemokine-driven T cell recruitment, T cell exhaustion in the RCC TME, as well as metabolic processes leading to their functional anergy in RCC. Eight publicly available bulk RCC transcriptome collectives (n=1819) and a single cell RNAseq dataset (n=12) were analyzed. Immunodeconvolution, semi-supervised clustering, gene set variation analysis and Monte Carlo-based modeling of metabolic reaction activity were employed. Among 28 chemokine genes available, CXCL9/10/11/CXCR3, CXCL13/CXCR5 and XCL1/XCR1 mRNA expression were significantly increased in RCC compared to normal kidney tissue and also strongly associated with tumor-infiltrating effector memory and central memory CD8+ T cells in all investigated collectives. M1 TAMs, T cells, NK cells as well as tumor cells were identified as the major sources of these chemokines, whereas T cells, B cells and dendritic cells were found to predominantly express the cognate receptors. The cluster of RCCs characterized by high chemokine expression and high CD8+ T cell infiltration displayed a strong activation of IFN/JAK/STAT signaling with elevated expression of multiple T cell exhaustion-associated transcripts. Chemokinehigh RCCs were characterized by metabolic reprogramming, in particular by downregulated OXPHOS and increased IDO1-mediated tryptophan degradation. None of the investigated chemokine genes was significantly associated with survival or response to immunotherapy. We propose a chemokine network that mediates CD8+ T cell recruitment and identify T cell exhaustion, altered energy metabolism and high IDO1 activity as key mechanisms of their suppression. Concomitant targeting of exhaustion pathways and metabolism may pose an effective approach to RCC therapy.

Aryl hydrocarbon receptor activity downstream of IL-10 signaling is required to promote regulatory functions in human dendritic cells

Interleukin (IL)-10 is a main player in peripheral immune tolerance, the physiological mechanism preventing immune reactions to self/harmless antigens. Here, we investigate IL-10-induced molecular mechanisms generating tolerogenic dendritic cells (tolDC) from monocytes. Using genomic studies, we show that IL-10 induces a pattern of accessible enhancers exploited by aryl hydrocarbon receptor (AHR) to promote expression of a set of core genes. We demonstrate that AHR activity occurs downstream of IL-10 signaling in myeloid cells and is required for the induction of tolerogenic activities in DC. Analyses of circulating DCs show that IL-10/AHR genomic signature is active in vivo in health. In multiple sclerosis patients, we instead observe significantly altered signature correlating with functional defects and reduced frequencies of IL-10-induced-tolDC in vitro and in vivo. Our studies identify molecular mechanisms controlling tolerogenic activities in human myeloid cells and may help in designing therapies to re-establish immune tolerance.

Allogeneic cord blood regulatory T cells can resolve lung inflammation

BACKGROUND AIMS

CD4⁺CD25⁺CD127^lo regulatory T cells (Tregs) are responsible for maintaining immune homeostasis. Tregs can be rendered defective and deficient as a result of the immune imbalance seen in lung injury, and such dysfunction can play a major role in continued tissue inflammation. The authors hypothesized that adoptive therapy with healthy allogeneic umbilical cord blood (UCB)-derived Tregs may be able to resolve inflammation.

RESULTS

Ex vivo-expanded UCB Tregs exhibited a unique phenotype with co-expression of CD45RA⁺CD45RO⁺ >80% and lung homing markers, including CD49d. UCB Tregs did not turn pathogenic when exposed to IL-6. Co-culture with increasing doses of dexamethasone led to a synergistic increase in UCB Treg-induced apoptosis of conventional T cells (Tcons), which translated into significantly higher suppression of proliferating Tcons, especially at a lower Treg:Tcon ratio. Multiple injections of UCB Tregs led to their preferential accumulation in lung tissue in an immune injury xenogenic model. A significant decrease in lung resident cytotoxic CD8⁺ T cells (P = 0.0218) correlated with a sustained decrease in their systemic distribution compared with controls (P < 0.0001) (n = 7 per arm) as well as a decrease in circulating human soluble CD40 ligand level (P = 0.031). Tissue architecture was preserved in the treatment arm, and a significant decrease in CD3⁺ and CD8⁺ burden was evident in immunohistochemistry analysis.

CONCLUSIONS

UCB Treg adoptive therapy is a promising therapeutic strategy for treatment of lung injury.

Regulation of T Cell Activation and Metabolism by Transforming Growth Factor-Beta

Transforming growth factor beta (TGFβ) receptor signalling regulates T cell development, differentiation and effector function. Expression of the immune-associated isoform of this cytokine, TGFβ1, is absolutely required for the maintenance of immunological tolerance in both mice and humans, whilst context-dependent TGFβ1 signalling regulates the differentiation of both anti- and pro-inflammatory T cell effector populations. Thus, distinct TGFβ-dependent T cell responses are implicated in the suppression or initiation of inflammatory and autoimmune diseases. In cancer settings, TGFβ signals contribute to the blockade of anti-tumour immune responses and disease progression. Given the key functions of TGFβ in the regulation of immune responses and the potential for therapeutic targeting of TGFβ-dependent pathways, the mechanisms underpinning these pleiotropic effects have been the subject of much investigation. This review focuses on accumulating evidence suggesting that modulation of T cell metabolism represents a major mechanism by which TGFβ influences T cell immunity.

Th17 Cells: Orchestrators of Mucosal Inflammation and Potential Therapeutic Targets

T helper 17 (Th17) cells represent a specialized subgroup of effector CD4+ T cells known for their role in provoking neutrophil-driven tissue inflammation, particularly within mucosal tissues. Although they are pivotal for defending the host against extracellular bacteria and fungi, they have also been associated with development of various T cell-mediated inflammatory conditions, autoimmune diseases, and even cancer. Notably, Th17 cells exhibit a dual nature, with different Th17 cell subtypes showcasing distinct effector functions and varying capacities to incite autoimmune tissue inflammation. Furthermore, Th17 cells exhibit significant plasticity, which carries important functional implications, both in terms of their expression of cytokines typically associated with other effector T cell subsets and in their interactions with regulatory CD4+ T cells. The intricate balance of Th17 cytokines can also be a double-edged sword in inflammation, autoimmunity, and cancer. Within this article, we delve into the mechanisms that govern the differentiation, function, and adaptability of Th17 cells. We culminate with an exploration of therapeutic potentials in harnessing the power of Th17 cells and their cytokines. Targeted interventions to modulate Th17 responses are emerging as promising strategies for autoimmunity, inflammation, and cancer treatment. By precisely fine-tuning Th17-related pathways, we may unlock new avenues for personalized therapeutic approaches, aiming to restore immune balance, alleviate the challenges of these disorders, and ultimately enhance the quality of life for individuals affected by them.

Regulatory T Cells: Liquid and Living Precision Medicine for the Future of VCA

Transplant rejection remains a challenge especially in the field of vascularized composite allotransplantation (VCA). To blunt the alloreactive immune response' stable levels of maintenance immunosupression are required. However' the need for lifelong immunosuppression poses the risk of severe side effects, such as increased risk of infection, metabolic complications, and malignancies. To balance therapeutic efficacy and medication side effects, immunotolerance promoting immune cells (especially regulatory T cells [Treg]) have become of great scientific interest. This approach leverages immune system mechanisms that usually ensure immunotolerance toward self-antigens and prevent autoimmunopathies. Treg can be bioengineered to express a chimeric antigen receptor or a T-cell receptor. Such bioengineered Treg can target specific antigens and thereby reduce unwanted off-target effects. Treg have demonstrated beneficial clinical effects in solid organ transplantation and promising in vivo data in VCAs. In this review, we summarize the functional, phenotypic, and immunometabolic characteristics of Treg and outline recent advancements and current developments regarding Treg in the field of VCA and solid organ transplantation.

Selenoprotein I deficiency in T cells promotes differentiation into tolerant phenotypes while decreasing Th17 pathology

Selenoprotein I (SELENOI) is an ethanolamine phospholipid transferase contributing to cellular metabolism and the synthesis of glycosylphosphatidylinositol (GPI) anchors. SELENOI knockout (KO) in T cells has been shown to impair metabolic reprogramming during T cell activation and reduce GPI-anchored Thy-1 levels, which are both crucial for Th17 differentiation. This suggests SELENOI may be important for Th17 differentiation, and we found that SELENOI was indeed up-regulated early during the activation of naïve CD4+ T cells in Th17 conditions. SELENOI KO reduced RORγt mRNA levels by decreasing SOX5 and STAT3 binding to promoter and enhancer regions in the RORC gene encoding this master regulator of Th17 cell differentiation. Differentiation of naïve CD4+ T cells into inflammatory versus tolerogenic Th cell subsets was analyzed and results showed that SELENOI deficiency skewed differentiation away from pathogenic Th17 cells (RORγt+ and IL-17A+ ) while promoting tolerogenic phenotypes (Foxp3+ and IL-10+ ). Wild-type and T cell-specific SELENOI KO mice were subjected to experimental autoimmune encephalitis (EAE), with KO mice exhibiting diminished clinical symptoms, reduced CNS pathology and decreased T cell infiltration. Flow cytometry showed that SELENOI T cell KO mice exhibited lower CD4+ RORγt+ and CD4+ IL-17A+ T cells and higher CD4+ CD25+ FoxP3+ T cells in CNS tissues of mice subjected to EAE. Thus, the metabolic enzyme SELENOI is up-regulated to promote RORγt transcription that drives Th17 differentiation, and SELENOI deficiency shifts differentiation toward tolerogenic phenotypes while protecting against pathogenic Th17 responses.

Transcriptional Behavior of Regulatory T Cells Predicts IBD Patient Responses to Vedolizumab Therapy

BACKGROUND

Inflammatory bowel disease (IBD) involves chronic T cell-mediated inflammatory responses. Vedolizumab (VDZ), a monoclonal antibody against α4β7 integrin, inhibits lymphocyte extravasation into intestinal mucosae and is effective in ulcerative colitis (UC) and Crohn's disease (CD).

AIM

We sought to identify immune cell phenotypic and gene expression signatures that related to response to VDZ.

METHODS

Peripheral blood (PBMC) and lamina propria mononuclear cells (LPMCs) were analyzed by flow cytometry and Cytofkit. Sorted CD4 + memory (Tmem) or regulatory T (Treg) cells from PBMC and LPMC were analyzed by RNA sequencing (RNA-seq). Clinical response (≥2-point drop in partial Mayo scores [UC] or Harvey-Bradshaw index [CD]) was assessed 14 to 22 weeks after VDZ initiation. Machine-learning models were used to infer combinatorial traits that predicted response to VDZ.

RESULTS

Seventy-one patients were enrolled: 37 received VDZ and 21 patients remained on VDZ >2 years. Fourteen of 37 patients (38%; 8 UC, 6 CD) responded to VDZ. Immune cell phenotypes and CD4 + Tmem and Treg transcriptional behaviors were most divergent between the ileum and colon, irrespective of IBD subtype or inflammation status. Vedolizumab treatment had the greatest impact on Treg metabolic pathways, and response was associated with increased expression of genes involved in oxidative phosphorylation. The strongest clinical predictor of VDZ efficacy was concurrent use of thiopurines. Mucosal tissues offered the greatest number of response-predictive biomarkers, whereas PBMC Treg-expressed genes were the best predictors in combinatorial models of response.

CONCLUSIONS

Mucosal and peripheral blood immune cell phenotypes and transcriptional profiles can inform VDZ efficacy and inform new opportunities for combination therapies.

Vitamin B5 rewires Th17 cell metabolism via impeding PKM2 nuclear translocation

Metabolic rewiring is essential for Th17 cells' functional identity to sense and interpret environmental cues. However, the environmental metabolic checkpoints with specific regulation of Th17 cells, manifesting potential therapeutic opportunities to autoimmune diseases, remain largely unknown. Here, by screening more than one hundred compounds derived from intestinal microbes or diet, we found that vitamin B5 (VB5) restrains Th17 cell differentiation as well as related autoimmune diseases such as experimental autoimmune encephalomyelitis and colitis. Mechanistically, VB5 is catabolized into coenzyme A (CoA) in a pantothenate kinase (PANK)-dependent manner, and in turn, CoA binds to pyruvate kinase isoform 2 (PKM2) to impede its phosphorylation and nuclear translocation, thus inhibiting glycolysis and STAT3 phosphorylation. In humans, reduced serum VB5 levels are found in both IBD and MS patients. Collectively, our study demonstrates a role of VB5 in Th17 cell metabolic reprograming, thus providing a potential therapeutic intervention for Th17 cell-associated autoimmune diseases.

OXPHOS promotes apoptotic resistance and cellular persistence in TH17 cells in the periphery and tumor microenvironment

T cell proliferation and cytokine production are bioenergetically and biosynthetically costly. The inability to meet these metabolic demands results in altered differentiation, accompanied by impaired effector function, and attrition of the immune response. Interleukin-17-producing CD4 T cells (TH17s) are mediators of host defense, autoimmunity, and antitumor immunity in the setting of adoptive T cell therapy. TH17s are long-lived cells that require mitochondrial oxidative phosphorylation (OXPHOS) for effector function in vivo. Considering that TH17s polarized under standardized culture conditions are predominately glycolytic, little is known about how OXPHOS regulates TH17 processes, such as their ability to persist and thus contribute to protracted immune responses. Here, we modified standardized culture medium and identified a culture system that reliably induces OXPHOS dependence in TH17s. We found that TH17s cultured under OXPHOS conditions metabolically resembled their in vivo counterparts, whereas glycolytic cultures were dissimilar. OXPHOS TH17s exhibited increased mitochondrial fitness, glutamine anaplerosis, and an antiapoptotic phenotype marked by high BCL-XL and low BIM. Limited mitophagy, mediated by mitochondrial fusion regulator OPA-1, was critical to apoptotic resistance in OXPHOS TH17s. By contrast, glycolytic TH17s exhibited more mitophagy and an imbalance in BCL-XL to BIM, thereby priming them for apoptosis. In addition, through adoptive transfer experiments, we demonstrated that OXPHOS protected TH17s from apoptosis while enhancing their persistence in the periphery and tumor microenvironment in a murine model of melanoma. Together, our work demonstrates how metabolism regulates TH17 cell fate and highlights the potential for therapies that target OXPHOS in TH17-driven diseases.

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.