Glucose uptake is limiting in T cell activation and requires CD28-mediated Akt-dependent and independent pathways

T cell aging and exhaustion: Mechanisms and clinical implications

T cell senescence and exhaustion represent critical aspects of adaptive immune system dysfunction, with profound implications for health and the development of disease prevention and therapeutic strategies. These processes, though distinct, are interconnected at the molecular level, leading to impaired effector functions and reduced proliferative capacity of T cells. Such impairments increase susceptibility to diseases and diminish the efficacy of vaccines and treatments. Importantly, T cell senescence and exhaustion can dynamically influence each other, particularly in the context of chronic diseases. A deeper understanding of the molecular mechanisms underlying T cell senescence and exhaustion, as well as their interplay, is essential for elucidating the pathogenesis of related diseases and restoring dysfunctional immune responses. This knowledge will pave the way for the development of targeted therapeutic interventions and strategies to enhance immune competence. This review aims to summarize the characteristics, mechanisms, and disease associations of T cell senescence and exhaustion, while also delineating the distinctions and intersections between these two states to enhance our comprehension.

Estrogen-Driven Maintenance of GLUT1/GLUT4/SGLT1 under glucose starvation drives energy homeostasis in bovine PMNs

The negative energy balance (NEB) and fluctuations in estrogen (17β-estradiol, E2) during the perinatal period alter glucose metabolism in bovine polymorphonuclear neutrophils (PMN) by affecting the activity of glucose transporters. In the peripheral blood, glucose uptake by PMNs is primarily dependent on the Glucose transporter type1 (GLUT1), Glucose transporter type4 (GLUT4), and Sodium-glucose cotransporter1 (SGLT1). However, the mechanisms through which E2 regulates energy metabolism in these cells, particularly through the modulation of glucose transporter activity, are currently unclear. This study aimed to explore the regulatory mechanisms underlying the effect of E2 on the homeostasis of glucose metabolism in PMNs. The results revealed that E2 enhances the expression of GLUT1, GLUT4, and SGLT1 (P < 0.05) and increases hexokinase (HK) activity (P < 0.05) in PMNs. Additionally, E2 was found to inhibit Glycogen synthase kinase-3β (GSK-3β) activity (P < 0.05), increase glycogen and ATP levels (P < 0.05), and reduce apoptosis in PMNs. When PMNs were treated with 5 μM STF-31 (GLUT1 inhibitor) or 50 μM Phlorizin (SGLT2 inhibitor), their GSK-3β activity was significantly increased (P < 0.05). Further analysis indicated that E2 helps maintain cellular glycogen and ATP homeostasis in PMNs by regulating the competitive interactions among GLUT1, GLUT4, and SGLT1. Additionally, when cells were treated with 100 μM AF-1890 (HK inhibitor), the expression of GLUT1, GLUT4, and SGLT1 was significantly reduced (P < 0.05). However, E2 mitigated the inhibitory effect of AF-1890 on HK activity and reduced its influence on intracellular energy levels by promoting the expression of GLUT1, GLUT4, and SGLT1. This study demonstrates that E2 positively regulates the expression of GLUT1, GLUT4 and SGLT1 in PMNs, facilitating glucose uptake under low-glucose conditions. E2 also negatively regulates GSK-3β activity increasing cellular glycogen and ATP levels and thus maintaining energy homeostasis in these cells.

Mitigating T-cell mitochondrial dysfunction in CLL to augment CAR T-cell therapy: evaluation in an immunocompetent model

ABSTRACT

An unmet clinical need in chronic lymphocytic leukemia (CLL) is emerging due to the rapidly expanding group of patients with double refractory (Bruton's tyrosine kinase- and B-cell lymphoma 2-inhibitor) disease. So far, autologous T-cell-based therapies, including chimeric antigen receptor (CAR) T cells, have limited success in CLL, which has been attributed to an acquired CLL-mediated T-cell dysfunction and subset skewing toward effector cells at the expense of memory formation. T-cell responses rely on dynamic metabolic processes, particularly mitochondrial fitness. Although mitochondrial disruptions have been observed in solid tumor-infiltrating lymphocytes, their impact on T-cell immunity in lymphoproliferative disorders is unknown. Recent findings indicate that mitochondrial mass in CAR T cells correlates with CLL clinical outcomes. This prompted our investigation into the mitochondrial fitness in CLL T cells. Integrated metabolic and functional analyses revealed impaired, depolarized mitochondria across all T-cell subsets in untreated patients with CLL, leading to further ex vivo and in vivo mouse studies on the underlying signaling alterations. Multiomics profiling of transcriptome and epigenome revealed significant alterations in mitochondrial signaling, diminished adenosine monophosphate-activated protein kinase and autophagy activity, and upregulated glycolysis coupled with hyperactivation of Akt. Inhibition of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway during CLL T-cell culture induced metabolic reprogramming, enhancing mitochondrial activity, expression of peroxisome proliferator-activated receptor-gamma coactivator 1-alpha, and memory differentiation. Underscoring clinical relevance, supplementation with the PI3Kδ inhibitor idelalisib during CAR T-cell manufacturing improved persistence and long-term leukemia-free remissions in an immunocompetent murine model. Our study suggests that modulating the abnormal CLL T-cell metabolism can enhance the efficacy of autologous T-cell therapies.

Nck1 Regulates Glucose Metabolism in Primary Human T Cells

Non-catalytic region of tyrosine kinase 1 (Nck1) is an adaptor protein found in many cell types and plays several functions. In T cells, Nck1 is functionally associated with a T cell receptor (TCR)-mediated actin rearrangement, insulin signalling, PI3K/Akt/mTOR pathway, and lipid production. However, the role of Nck1 in regulating glucose metabolism in T cells is still largely unknown. In the present study, the role of Nck1 in glucose metabolism in primary human T cells was investigated. Plasmid encoding Nck1-specific short hairpin RNA (shRNA) was delivered to primary T cells to mediate Nck1 silencing. Plasmids encoding Nck1-specific short hairpin RNA (shRNA) were delivered to primary human T cells to mediate Nck1 silencing. Nck1-knockdown (N1KD) cells were analysed for processes related to glucose metabolism and function. Despite an increased expression of glucose transporter 1 (GLUT1) in N1KD cells, these cells exhibited impaired glucose uptake and ATP production, indicating dysfunction of GLUT1 or altered intracellular glucose metabolism. Nck1 depletion disrupted metabolic signalling characterised by reduced TXNIP and phosphoribosomal protein S6 (pS6) levels, along with an increased phosphorylation of Akt and AMPK. The reduced extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) found in N1KD cells indicated impaired glycolysis and oxidative phosphorylation. Functionally, these metabolic alterations were associated with impaired T cell activation, reduced proliferation, and increased apoptosis. Collectively, Nck1 critically regulated glucose metabolism in T cells, linking metabolic reprogramming to immune function and cell survival.

Lymphocyte subsets and the increased risk for opportunistic infections in severe restrictive anorexia nervosa

Restrictive anorexia nervosa (AN-R) is characterized not only by psychiatric manifestations but also by significant medical complications. Patients commonly exhibit immune alterations, potentially increasing their susceptibility to infections. While direct evidence linking AN-R to heightened rates of opportunistic infections remains inconclusive, clinical observations suggest a higher incidence of complications and delayed febrile response in patients with infections. Concurrently, malnutrition, a frequent cause of secondary immunodeficiencies, exacerbates this susceptibility by compromising immune function. This paper investigates the immunological profiles of two patients with long-term AN-R who developed severe infections: one with disseminated Mycobacterium kansasii and the other with a co-infection of pulmonary Aspergillus fumigatus and Mycobacterium celatum. These cases, alongside data collected from previously published case reports summarized in this study, highlight the impact of altered immune function associated with mentioned population. The paper aims to explain the underlying mechanisms of immune dysfunction. Proactive monitoring of immune status and incorporating such assays into clinical practice may benefit early detection, effective management, and ultimately, improved outcomes.

Cholesterol homeostasis and lipid raft dynamics at the basis of tumor-induced immune dysfunction in chronic lymphocytic leukemia

Autologous T-cell therapies show limited efficacy in chronic lymphocytic leukemia (CLL), where acquired immune dysfunction prevails. In CLL, disturbed mitochondrial metabolism has been linked to defective T-cell activation and proliferation. Recent research suggests that lipid metabolism regulates mitochondrial function and differentiation in T cells, yet its role in CLL remains unexplored. This comprehensive study compares T-cell lipid metabolism in CLL patients and healthy donors, revealing critical dependence on exogenous cholesterol for human T-cell expansion following TCR-mediated activation. Using multi-omics and functional assays, we found that T cells present in viably frozen samples of patients with CLL (CLL T cells) showed impaired adaptation to cholesterol deprivation and inadequate upregulation of key lipid metabolism transcription factors. CLL T cells exhibited altered lipid storage, with increased triacylglycerols and decreased cholesterol, and inefficient fatty acid oxidation (FAO). Functional consequences of reduced FAO in T cells were studied using samples from patients with inherent FAO disorders. Reduced FAO was associated with lower T-cell activation but did not affect proliferation. This implicates low cholesterol levels as a primary factor limiting T-cell proliferation in CLL. CLL T cells displayed fewer and less clustered lipid rafts, potentially explaining the impaired immune synapse formation observed in these patients. Our findings highlight significant disruptions in lipid metabolism as drivers of functional deficiencies in CLL T cells, underscoring the pivotal role of cholesterol in T-cell proliferation. This study suggests that modulating cholesterol metabolism could enhance T-cell function in CLL, presenting novel immunotherapeutic approaches to improve outcome in this challenging disease.

ICI-induced cardiovascular toxicity: mechanisms and immune reprogramming therapeutic strategies

The advent of immune checkpoint inhibitors (ICIs) has revolutionized cancer treatment, offering life-saving benefits to tumor patients. However, the utilize of ICI agents is often accompanied by immune-related adverse events (irAEs), among which cardiovascular toxicities have attracted more and more attention. ICI induced cardiovascular toxicities predominantly present as acute myocarditis and chronic atherosclerosis, both of which are driven by excessive immune activation. Reprogramming of T cells and macrophages has been demonstrated as a pivotal factor in the pathogenesis of these complications. Therapeutic strategies targeting glycolysis, fatty acid oxidation, reactive oxygen species (ROS) production and some other key signaling have shown promise in mitigating immune hyperactivation and inflammation. In this review, we explored the intricate mechanisms underlying ICI-induced cardiovascular toxicities and highlighted the protective potential of immune reprogramming. We emphasize the roles of T cell and macrophage reprogramming in the heart and vasculature, showcasing their contributions to both short-term and long-term regulation of cardiovascular health. Ultimately, a deeper understanding of these processes will not only enhance the safety of ICIs but also pave the way for innovative strategies to manage immune-related toxicities in cancers therapy.

Novel insights and an updated review of metabolic syndrome in immune-mediated organ transplant rejection

Metabolic syndrome (MetS) is a group of symptoms that are characterized by abnormal changes in metabolic substances such as glucose, lipids, proteins, and bile acids. MetS is a common complication after organ transplantation and can further affect the survival and physiological function of the graft by reprograming the patient's immune environment. Additionally, MetS can influence the occurrence of post-transplant complications, such as infections. In recent years, research into the epidemiology and mechanisms of MetS has grown significantly. In this review, we summarize the mechanisms of MetS after transplantation and the mechanisms of hyperglycemia, insulin resistance, hyperlipidemia, abnormal bile acids, and abnormal amino acids on the body's immune cells as related to the effect of metabolic disorders on immune rejection after liver, kidney, heart, skin and other organ transplantation. Finally, we provide an overview of current treatment strategies and offer insights into potential future therapies for managing MetS in transplant recipients.

Inhibition of energy metabolism in macrophages to block MPS for enhancing the chemotherapy efficacy

Various biological barriers hinder the effective use of administered nanoparticles, with the mononuclear phagocyte system (MPS) being a major obstacle to their in vivo efficacy. Glucose metabolism is an important factor for macrophages to perform MPS clearance in vivo. In this study, energy metabolism-blocking nanoparticles PEG-S-S-PLA@RGD @Dox@BAY876 (RPDB NPs) were developed to change drug distribution in the body, improving the efficacy of chemotherapy. First, BAY876 showed an excellent inhibition effects on macrophage energy metabolism in vitro. This inhibitory behavior of energy metabolism reduced the aggregation of nanoparticles in macrophages. Similarly, the migration capacity of macrophages was also limited by reduced energy metabolism. Second, the fluorescence distribution in the mice also showed that the fluorescence intensity of RPDB NPs in the liver was about 40% of that of RPD NPs, suggesting that reducing energy metabolism helps to downregulate the uptake of mononuclear phagocytic cell (MPS), and change the distribution of the drug in vivo. Furthermore, anti-tumor effects of RPDB NPs were evaluated both in vivo and in vitro. In vivo, RPDB nanomicelles inhibited breast cancer by up to 68.3%, higher than other administration groups. Moreover, the pathological section of tumor exhibited a significantly greater increase in cell apoptosis in RPDB NPs group. Hence, inhibition of macrophage energy metabolism is a promising approach to eliminate MPS effects, while also opening up a new window for the effective inhibition of tumors development and metastasis.

Impacts of transient exposure of human T cells to low oxygen, temperature, pH and nutrient levels relevant to bioprocessing for cell therapy applications

BACKGROUND

T-cell therapy advances have stimulated the development of bioprocesses to address the specialized needs of cell therapy manufacturing. During concentrated cell washing, the cells are frequently exposed to transiently reduced oxygen, temperature, pH, and nutrient levels. Longer durations of these conditions can be caused by process deviations or, if they are not harmful, be used to ease the scheduling of process stages during experiments as well as manufacturing.

METHODS

To avoid unpredictable impacts on T-cell quality during bioprocessing, we measured the influences of such environmental exposures generated by settling 250 million activated human T cells per mL, for up to 6 h at temperatures from 4 to 37°C.

RESULTS

The measured glucose concentration decreased to as low as 0.5 mM and the pH to 6, while lactate increased up to 55 mM. The concentrated cell conditions at 37°C resulted in by far the greatest losses in viable cell numbers with, on average, only 58% and 41% of the cells recovered after 3 and 6 h, respectively. Likewise, their subsequent cell expansion cultures were substantially reduced even after only 3 h of exposure, and with decreased percentages of central memory T cells and increased percentages of effector memory and effector T cells. Although under similar environmental conditions at room temperatures, the negative impacts of high cell concentrations were greatly diminished for up to 3 h. At 4°C the transient conditions were less extreme, and the cells well maintained for 6 h.

CONCLUSIONS

Overall, when developing processes and devices for T-cell therapy manufacturing that involve concentrated cells, the results of this study indicate that more practically feasible room temperatures can be used for up to 3 h to obtain high viable cell recoveries whereas lower temperatures such as 4°C should be used if there is a need for more prolonged concentrated T-cell conditions.

Redirecting glucose flux during in vitro expansion generates epigenetically and metabolically superior T cells for cancer immunotherapy

Cellular therapies are living drugs whose efficacy depends on persistence and survival. Expansion of therapeutic T cells employs hypermetabolic culture conditions to promote T cell expansion. We show that typical in vitro expansion conditions generate metabolically and functionally impaired T cells more reliant on aerobic glycolysis than those expanding in vivo. We used dichloroacetate (DCA) to modulate glycolytic metabolism during expansion, resulting in elevated mitochondrial capacity, stemness, and improved antitumor efficacy in murine T cell receptor (TCR)-Tg and human CAR-T cells. DCA-conditioned T cells surprisingly show no elevated intratumoral effector function but rather have improved engraftment. DCA conditioning decreases reliance on glucose, promoting usage of serum-prevalent physiologic carbon sources. Further, DCA conditioning promotes metabolic flux from mitochondria to chromatin, resulting in increased histone acetylation at key longevity genes. Thus, hyperglycemic culture conditions promote expansion at the expense of metabolic flexibility and suggest pharmacologic metabolic rewiring as a beneficial strategy for improvement of cellular immunotherapies.

Deciphering T-cell exhaustion in the tumor microenvironment: paving the way for innovative solid tumor therapies

In solid tumors, the tumor microenvironment (TME) is a complex mix of tumor, immune, stromal cells, fibroblasts, and the extracellular matrix. Cytotoxic T lymphocytes (CTLs) constitute a fraction of immune cells that may infiltrate into the TME. The primary function of these T-cells is to detect and eliminate tumor cells. However, due to the immunosuppressive factors present in the TME primarily mediated by Myeloid-Derived Suppressor Cells (MDSCs), Tumor associated macrophages (TAMs), Cancer Associated Fibroblasts (CAFs) as well as the tumor cells themselves, T-cells fail to differentiate into effector cells or become dysfunctional and are unable to eliminate the tumor. In addition, chronic antigen stimulation within the TME also leads to a phenomenon, first identified in chronic lymphocytic choriomeningitis virus (LCMV) infection in mice, where the T-cells become exhausted and lose their effector functions. Exhausted T-cells (Tex) are characterized by the presence of remarkably conserved inhibitory receptors, transcription and signaling factors and the downregulation of key effector molecules. Tex cells have been identified in various malignancies, including melanoma, colorectal and hepatocellular cancers. Recent studies have indicated novel strategies to reverse T-cell exhaustion. These include checkpoint inhibitor blockade targeting programmed cell death protein 1 (PD-1), T-cell immunoglobulin and mucin-domain containing-3 (Tim-3), cytotoxic T-lymphocyte associated protein 4 (CTLA-4), or combinations of different immune checkpoint therapies (ICTs) or combination of ICTs with cytokine co-stimulation. In this review, we discuss aspects of T-cell dysfunction within the TME with a focus on T-cell exhaustion. We believe that gaining insight into the mechanisms of T-cell exhaustion within the TME of human solid tumors will pave the way for developing therapeutic strategies to target and potentially re-invigorate exhausted T-cells in cancer.

Lipid Metabolism and Immune Function: Chemical Tools for Insights into T-Cell Biology

Lipids are essential biomolecules playing critical roles in cellular processes, including energy storage, membrane structure, and signaling. This review highlights the chemical tools that have been developed to study the role of lipid metabolism in immune function, focusing on T-cell biology. Fatty acids (FAs), as core lipid components, influence immune responses through structural, signaling, and metabolic roles. Recent studies reveal how specific FAs modulate T-cell activation, proliferation, and function, with implications for regulatory and effector subsets. Emerging tools, such as fluorescence-based lipids and click chemistry, enable precise tracking of lipid uptake and metabolism at the single-cell level, addressing limitations of traditional bulk methods. Advances in metabolomics and proteomics offer further insights into lipid-mediated immune regulation. Understanding these mechanisms provides opportunities to target lipid metabolism in therapeutic strategies for cancer and other immune-related diseases. The integration of lipidomic technologies into immunology uncovers novel perspectives on how lipids shape immune responses at cellular and molecular scales.

[Immune Checkpoints Mediate Tumor Immune Regulation through Metabolic Pathways]

Immune checkpoints include a series of receptor-ligand pairs that play a key role in the proliferation, activation, and immune regulatory responses of immune cells. Although immune checkpoint inhibitors (ICIs), such as programmed death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) have achieved good therapeutic effects in clinical practice, some patients still experience ineffective treatment and immune resistance. A large amount of evidence has shown that immune checkpoint proteins are related to cell metabolism during immune regulation. On the one hand, immune checkpoints connect to alter the metabolic reprogramming of tumor cells to compete for nutrients required by immune cells. On the other hand, immune checkpoints regulate the metabolic pathways of immune cells, such as phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) to affect the activation of immune cells. Based on a review of the literature, this article reviews the mechanisms by which PD-1, CTLA-4, T cell immunoreceptor with Ig and ITIM domains (TIGIT), T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), cluster of differentiation 47 (CD47), and indoleamine 2,3-dioxygenase 1 (IDO1) regulate cell metabolic reprogramming, and looks forward to whether targeting the ligand-receptor pairs of immune checkpoints in a "dual regulation" manner and inhibiting metabolic pathways can effectively solve the problem of tumor immune resistance.
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Intrinsic STING of CD8 + T cells regulates self-metabolic reprogramming and memory to exert anti-tumor effects

BACKGROUND

Our team has previously found that the stimulator of interferon genes (STING) plays a more significant anti-tumor role in host immune cells than in tumor cells. Although STING is necessary for CD8 + T cells to exert immunological activity, its effect on CD8 + T cells remains debatable. In this study, we used both in vitro and in vivo models to explore the metabolic effects of STING on CD8 + T cells.

METHODS

Peripheral blood lymphocytes were procured from non-small cell lung cancer (NSCLC) patients receiving anti-PD-1 therapy to investigate the correlation between STING expression levels, CD8 + T-cell subsets, and immunotherapy efficacy. STING knockout (STING-KO) mice were used for in vivo studies. RNA-seq, seahorse, flow cytometry, electron microscopy, qPCR, immunofluorescence, western blotting, and immunoprecipitation were performed to explore the underlying mechanisms of STING in regulating CD8 + T cell function.

RESULTS

We discovered that the expression level of STING in immune cells exhibited a significant correlation with immunotherapy efficacy, as well as with the proportion of central memory CD8 + T cells. Moreover, we found that the loss of the STING gene results in a reduction in the number of mitochondria and a change in the metabolic pathway selection, thereby inducing excessive glycolysis in CD8 + T cells. This excessive glycolysis generates high levels of lactate, which further inhibits IFN-γ secretion and impacts memory T cell differentiation. Correcting the glycolysis disorder partially restored function and IFN-γ secretion, rescued the central memory CD8 + T subset, and improved immunotherapy in STING-KO mice. This provides a new treatment strategy for patients with low STING expression and a poor response to immunotherapy.

CONCLUSION

Intrinsic STING of CD8 + T cells affects their function through the HK2/Lactate/IFN-γ axis and affects memory differentiation by regulating glycolysis.

Role of T cell metabolism in brain tumor development: a genetic and metabolic approach

BACKGROUND

Malignant brain tumors are among the most lethal cancers. Recent studies emphasized the crucial involvement of the immune system, especially T cells, in driving tumor progression and influencing patient outcomes. The emerging field of immunometabolism has shown that metabolic pathways play a pivotal role in regulating immune responses within the tumor microenvironment. This study aims to clarify the relationships between specific T cell phenotypes, circulating metabolites, and malignant brain tumors.

METHODS

We utilized a multiple mendelian randomization approach to investigate the associations between T cell phenotypes and malignant brain tumors, as well as the role of plasma metabolites in mediating these interactions. Instrumental variables were selected based on stringent criteria, and multiple mendelian randomization methods were utilized to identify causal pathways and metabolites potentially mediating these effects.

RESULTS

Our analysis identified significant associations between seven distinct T cell phenotypes, including various CD8 + and regulatory T cell subsets, and the presence of malignant brain tumors. We also identified 87 plasma metabolites correlated with these tumors. Notably, metabolites such as octadecanedioylcarnitine (C18-DC) and eicosanedioate (C20-DC) were implicated in modulating the risk of developing malignant brain tumors. Furthermore, metabolites such as 5-dodecenoate (12:1n7) and arachidonate (20:4n6) were found to influence tumor risk, particularly in relation to CD28 - CD8 + T cells.

CONCLUSION

The study identifies key T cell phenotypes and plasma metabolites involved in the pathogenesis of malignant brain tumors, offering potential biomarkers and therapeutic targets for future interventions.

Why and how citrate may sensitize malignant tumors to immunotherapy

Immunotherapy, either alone or in combination with chemotherapy, has demonstrated limited efficacy in a variety of solid cancers. Several factors contribute to explaining primary or secondary resistance. Among them, cancer cells, whose metabolism frequently relies on aerobic glycolysis, promote exhaustion of cytotoxic immune cells by diverting the glucose in the tumor microenvironment (TME) to their own profit, while secreting lactic acid that sustains the oxidative metabolism of immunosuppressive cells. Here, we propose to combine current treatment based on the use of immune checkpoint inhibitors (ICIs) with high doses of sodium citrate (SCT) because citrate inhibits cancer cell metabolism (by targeting both glycolysis and oxidative metabolism) and may active anti-tumor immune response. Indeed, as showed in preclinical studies, SCT reduces cancer cell growth, promoting cell death and chemotherapy effectiveness. Furthermore, since the plasma membrane citrate carrier pmCIC is mainly expressed in cancer cells and low or not expressed in immune and non-transformed cells, we argue that the inhibition of cancer cell metabolism by SCT may increase glucose availability in the TME, thus promoting functionality of anti-tumor immune cells. Concomitantly, the decrease in the amount of lactic acid in the TME may reduce the functionality of immunosuppressive cells. Preclinical studies have shown that SCT can enhance the anti-tumor immune response through an enhancement of T cell infiltration and activation, and a repolarization of macrophages towards a TAM1-like phenotype. Therefore, this simple and cheap strategy may have a major impact to increase the efficacy of current immunotherapies in human solid tumors and we encourage testing it in clinical trials.

Immunometabolism In Brain Aging and Neurodegeneration: Bridging Metabolic Pathways and Immune Responses

The complex set of interactions between the immune system and metabolism, known as immunometabolism, has emerged as a critical regulator of disease outcomes in the central nervous system. Numerous studies have linked metabolic disturbances to impaired immune responses in brain aging, neurodegenerative disorders, and brain injury. In this review, we will discuss how disruptions in brain immunometabolism balance contribute to the pathophysiology of brain dysfunction. The first part of the review summarizes the contributions of critical immune cell populations such as microglia, astrocytes, and infiltrating immune cells in mediating inflammation and metabolism in CNS disorders. The remainder of the review addresses the impact of metabolic changes on immune cell activation and disease progression in brain aging, Alzheimer's disease, Parkinson's disease, multiple sclerosis, stroke, spinal cord injury, and traumatic brain injury. Furthermore, we also address the therapeutic potential of targeting immunometabolic pathways to reduce neuroinflammation and slow disease progression. By focusing on the interactions among brain immune cells and the metabolic mechanisms they recruit in disease, we present a comprehensive overview of brain immunometabolism in human health and disease.

Metabolic immunoengineering approaches to enhance CD8+ T cell-based cancer immunotherapy

Many cancer immunotherapies rely on robust CD8+ T cells capable of eliminating cancer cells and establishing long-term tumor control. Recent insights into immunometabolism highlight the importance of nutrients and metabolites in T cell activation and differentiation. Within the tumor microenvironment (TME), CD8+ tumor-infiltrating lymphocytes (TILs) undergo metabolic adaptations to survive but compromise their effector function and differentiation. Targeting metabolism holds promise for enhancing CD8+ T cell-mediated antitumor immunity. Here, we overview the metabolic features of CD8+ TILs and their impact on T cell effector function and differentiation. We also highlight immunoengineering strategies by leveraging the Yin-Yang of metabolic modulation for improving cancer immunotherapy.

GM-CSF engages multiple signaling pathways to enhance pro-inflammatory cytokine responses in human monocytes during Legionella infection

The proinflammatory cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) is required for host defense against a wide range of pathogens. We previously found that GM-CSF enhances inflammatory cytokine production in murine monocytes and is required for in vivo control of the intracellular bacterial pathogen Legionella pneumophila . It is unclear whether GM-CSF similarly augments cytokine production in human monocytes during bacterial infection. Here, we find that GM-CSF enhances inflammatory cytokine expression in Legionella- infected human monocytes by engaging multiple signaling pathways. Legionella - and TLR-dependent NF-𝜅B signaling is a prerequisite signal for GM-CSF to promote cytokine expression. Then, GM-CSF-driven JAK2/STAT5 signaling is required to augment cytokine expression in Legionella -infected human monocytes. We also found a role for PI-3K/Akt/mTORC1 signaling in GM-CSF-dependent upregulation of cytokine expression. Finally, glycolysis and amino acid metabolism are also critical for GM-CSF to boost cytokine gene expression in human monocytes during infection. Our findings show that GM-CSF-mediated enhancement of cytokine expression in infected human monocytes is regulated by multiple signaling pathways, thereby allowing the host to fine tune antibacterial immunity.

Metabolic drives affecting Th17/Treg gene expression changes and differentiation: impact on immune-microenvironment regulation

The CD4+ T-cell population plays a vital role in the adaptive immune system by coordinating the immune response against different pathogens. A significant transformation occurs in CD4+ cells during an immune response, as they shift from a dormant state to an active state. This transformation leads to extensive proliferation, differentiation, and cytokine production, which contribute to regulating and coordinating the immune response. Th17 and Treg cells are among the most intriguing CD4+ T-cell subpopulations in terms of genetics and metabolism. Gene expression modulation processes rely on and are linked to metabolic changes in cells. Lactylation is a new model that combines metabolism and gene modulation to drive Th17/Treg differentiation and functional processes. The focus of this review is on the metabolic pathways that impact lymphocyte gene modulation in a functionally relevant manner.

Starvation and infection: The role of sickness-associated anorexia in metabolic adaptation during acute infection

Sickness-associated anorexia, the reduction in appetite seen during infection, is a widely conserved and well-recognized symptom of acute infection, yet there is very little understanding of its functional role in recovery. Anorexic sickness behaviours can be understood as an evolutionary strategy to increase tolerance to pathogen-mediated illness. In this review we explore the evidence for mechanisms and potential metabolic benefits of sickness-associated anorexia. Energy intake can impact on the immune response, control of inflammation and tissue stress, and on pathogen fitness. Fasting mediators including hormone-sensitive lipase, peroxisome proliferator-activated receptor-alpha (PPAR-α) and ketone bodies are potential facilitators of infection recovery through multiple pathways including suppression of inflammation, adaptation to lipid utilising pathways, and resistance to pathogen-induced cellular stress. However, the effect and benefit of calorie restriction is highly heterogeneous depending on both the infection and the metabolic status of the host, which has implications regarding clinical recommendations for feeding during different infections.

The Warburg Effect: Is it Always an Enemy?

The Warburg effect, also known as 'aerobic' glycolysis, describes the preference of cancer cells to favor glycolysis over oxidative phosphorylation for energy (adenosine triphosphate-ATP) production, despite having high amounts of oxygen and fully active mitochondria, a phenomenon first identified by Otto Warburg. This metabolic pathway is traditionally viewed as a hallmark of cancer, supporting rapid growth and proliferation by supplying energy and biosynthetic precursors. However, emerging research indicates that the Warburg effect is not just a strategy for cancer cells to proliferate at higher rates compared to normal cells; thus, it should not be considered an 'enemy' since it also plays complex roles in normal cellular functions and/or under stress conditions, prompting a reconsideration of its purely detrimental characterization. Moreover, this review highlights that distinguishing glycolysis as 'aerobic' and 'anaerobic' should not exist, as lactate is likely the final product of glycolysis, regardless of the presence of oxygen. Finally, this review explores the nuanced contributions of the Warburg effect beyond oncology, including its regulatory roles in various cellular environments and the potential effects on systemic physiological processes. By expanding our understanding of these mechanisms, we can uncover novel therapeutic strategies that target metabolic reprogramming, offering new avenues for treating cancer and other diseases characterized by metabolic dysregulation. This comprehensive reevaluation not only challenges traditional views but also enhances our understanding of cellular metabolism's adaptability and its implications in health and disease.

Metabolic Reprogramming of Immune Cells in the Tumor Microenvironment

Metabolic reprogramming of immune cells within the tumor microenvironment (TME) plays a pivotal role in shaping tumor progression and responses to therapy. The intricate interplay between tumor cells and immune cells within this ecosystem influences their metabolic landscapes, thereby modulating the immune evasion tactics employed by tumors and the efficacy of immunotherapeutic interventions. This review delves into the metabolic reprogramming that occurs in tumor cells and a spectrum of immune cells, including T cells, macrophages, dendritic cells, and myeloid-derived suppressor cells (MDSCs), within the TME. The metabolic shifts in these cell types span alterations in glucose, lipid, and amino acid metabolism. Such metabolic reconfigurations can profoundly influence immune cell function and the mechanisms by which tumors evade immune surveillance. Gaining a comprehensive understanding of the metabolic reprogramming of immune cells in the TME is essential for devising novel cancer therapeutic strategies. By targeting the metabolic states of immune cells, it is possible to augment their anti-tumor activities, presenting new opportunities for immunotherapeutic approaches. These strategies hold promise for enhancing treatment outcomes and circumventing the emergence of drug resistance.

Glucose-albumin ratio (GAR) as a novel biomarker for predicting postoperative pneumonia (POP) in older adults with hip fractures

Postoperative pneumonia (POP) is a common complication after hip fracture surgery and is associated with increased mortality and other complications in elderly patients. This study aims to evaluate biomarkers, especially the glucose-albumin ratio (GAR), for predicting POP in elderly hip fracture patients. A total of 1279 elderly patients admitted to our hospital with hip fractures were included. We assessed 29 biomarkers and focused on GAR to determine its prognostic and predictive value for POP. Multivariable logistic regression and propensity score-matched analyses were conducted to calculate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for POP, adjusting for potential confounders. Receiver operating characteristic (ROC) curves were utilized to determine the optimal cut-off of GAR for predicting POP. Among the biomarkers and combinations assessed, GAR demonstrated superior predictive capability for POP in elderly hip fracture patients. ROC analyses showed moderate predictive accuracy of GAR for POP, with an area under the curve of 0.750. Using the optimal cut-off of 0.175, the high GAR group was significantly associated with increased odds of POP (adjusted OR 2.14, 95%, CI 1.50-3.05). These associations remained significant after propensity score matching and subgroup analyses. Dose-response relationships between GAR and POP were observed. In conclusion, GAR may be a promising biomarker to predict POP risk in elderly hip fracture patients. Further studies are warranted to validate its clinical utility. However, this study has certain limitations, including its retrospective design, potential for selection bias due to the exclusion criteria, and the single-center nature of the study, which should be addressed in future prospective, multicenter studies.

Metabolic adaptations in prostate cancer

Prostate cancer is one of the most commonly diagnosed cancers in men and is a major cause of cancer-related deaths worldwide. Among the molecular processes that contribute to this disease, the weight of metabolism has been placed under the limelight in recent years. Tumours exhibit metabolic adaptations to comply with their biosynthetic needs. However, metabolites also play an important role in supporting cell survival in challenging environments or remodelling the tumour microenvironment, thus being recognized as a hallmark in cancer. Prostate cancer is uniquely driven by androgen receptor signalling, and this knowledge has also influenced the paths of cancer metabolism research. This review provides a comprehensive perspective on the metabolic adaptations that support prostate cancer progression beyond androgen signalling, with a particular focus on tumour cell intrinsic and extrinsic pathways.

Immunometabolism: signaling pathways, homeostasis, and therapeutic targets

Immunometabolism plays a central role in sustaining immune system functionality and preserving physiological homeostasis within the organism. During the differentiation and activation, immune cells undergo metabolic reprogramming mediated by complex signaling pathways. Immune cells maintain homeostasis and are influenced by metabolic microenvironmental cues. A series of immunometabolic enzymes modulate immune cell function by metabolizing nutrients and accumulating metabolic products. These enzymes reverse immune cells' differentiation, disrupt intracellular signaling pathways, and regulate immune responses, thereby influencing disease progression. The huge population of immune metabolic enzymes, the ubiquity, and the complexity of metabolic regulation have kept the immune metabolic mechanisms related to many diseases from being discovered, and what has been revealed so far is only the tip of the iceberg. This review comprehensively summarized the immune metabolic enzymes' role in multiple immune cells such as T cells, macrophages, natural killer cells, and dendritic cells. By classifying and dissecting the immunometabolism mechanisms and the implications in diseases, summarizing and analyzing advancements in research and clinical applications of the inhibitors targeting these enzymes, this review is intended to provide a new perspective concerning immune metabolic enzymes for understanding the immune system, and offer novel insight into future therapeutic interventions.

Expression of the large amino acid transporter SLC7A5/LAT1 on immune cells is enhanced in primary sclerosing cholangitis-associated cholangiocarcinoma and correlates with poor prognosis in cholangiocarcinoma

Biliary tract cancers (BTC) are rare lethal malignancies arising along the biliary tree. Unfortunately, effective therapeutics are lacking and the prognosis remains dismal even for patients eligible for surgical resection. Therefore, novel therapeutic approaches along with early detection strategies and prognostic markers are urgently needed. Primary sclerosing cholangitis (PSC) is a chronic disease of the bile ducts leading to fibrosis and ultimately cirrhosis. Patients with PSC have a 5-20% lifetime risk of developing BTC; yet the molecular mechanisms that underpin the development of PSC- associated biliary tract cancer (PSC-BTC) have not been fully elucidated. SLC7A5/LAT1, a large amino acid transporter, has been shown to modulate cell growth and proliferation as well as other intracellular processes in solid tumors. In this study, we evaluated SLC7A5 expression in PSC-BTC and in sporadic BTC (sBTC) and its role as a prognostic factor. Analysis of the TGCA cohort showed a significantly higher expression of SLC7A5 in tumor tissue compared with adjacent normal tissue (p = 0.0002) in BTC. In our cohort (comprised of 69 BTC patients including 16 PSC-BTC), SLC7A5/LAT1 expression was observed in both tumor and intratumoral immune cells. A significantly higher percentage of SLC7A5/LAT1 positive intratumoral immune cells was observed in PSC-BTC compared with sBTC (p = 0.004). Multiplex immunofluorescence co-detection by indexing (CODEX) analysis identified CD4+ regulatory T lymphocytes and CD68+ macrophages as the largest immune cell populations expressing LAT1. SLC7A5/LAT1 expression as well as a higher intratumoral infiltration of SLC7A5/LAT1-positive immune cells (≥2%) were associated with a shorter overall survival in our cohort (LogRank test, p = 0.04 and p = 0.008; respectively). SLC7A5/LAT1 expressing tumors are higher staged tumors (pT3/4 versus pT1/2, p = 0.048). These results underline the potential use of SLC7A5/LAT1 as a prognostic marker in BTC. Furthermore, the higher frequency of SLC7A5/LAT1 positive immune cells in PSC-BTC compared to sBTC may hint at the potential role of SLC7A5/LAT1 in inflammation-driven carcinogenesis.

PI3K-dependent reprogramming of hexokinase isoforms controls glucose metabolism and functional responses of B lymphocytes

B lymphocyte activation triggers metabolic reprogramming essential for B cell differentiation and mounting a healthy immune response. Here, we investigate the regulation and function of glucose-phosphorylating enzyme hexokinase 2 (HK2) in B cells. We report that both activation-dependent expression and mitochondrial localization of HK2 are regulated by the phosphatidylinositol 3-kinase (PI3K) signaling pathway. B cell-specific deletion of HK2 in mice caused mild perturbations in B cell development. HK2-deficient B cells show impaired functional responses in vitro and adapt to become less dependent on glucose and more dependent on glutamine. HK2 deficiency impairs glycolysis, alters metabolite profiles, and alters flux of labeled glucose carbons into downstream pathways. Upon immunization, HK2-deficient mice exhibit impaired germinal center, plasmablast, and antibody responses. HK2 expression in primary human chronic lymphocytic leukemia (CLL) cells was associated with recent proliferation and could be reduced by PI3K inhibition. Our study implicates PI3K-dependent modulation of HK2 in B cell metabolic reprogramming.

Glucose-dependent glycosphingolipid biosynthesis fuels CD8+ T cell function and tumor control

Glucose is essential for T cell proliferation and function, yet its specific metabolic roles in vivo remain poorly defined. Here, we identify glycosphingolipid (GSL) biosynthesis as a key pathway fueled by glucose that enables CD8+ T cell expansion and cytotoxic function in vivo. Using 13C-based stable isotope tracing, we demonstrate that CD8+ effector T cells use glucose to synthesize uridine diphosphate-glucose (UDP-Glc), a precursor for glycogen, glycan, and GSL biosynthesis. Inhibiting GSL production by targeting the enzymes UGP2 or UGCG impairs CD8+ T cell expansion and cytolytic activity without affecting glucose-dependent energy production. Mechanistically, we show that glucose-dependent GSL biosynthesis is required for plasma membrane lipid raft integrity and aggregation following TCR stimulation. Moreover, UGCG-deficient CD8+ T cells display reduced granzyme expression and tumor control in vivo. Together, our data establish GSL biosynthesis as a critical metabolic fate of glucose-independent of energy production-required for CD8+ T cell responses in vivo.

Identifying metabolic limitations in the tumor microenvironment

Solid tumors are characterized by dysfunctional vasculature that limits perfusion and delivery of nutrients to the tumor microenvironment. Limited perfusion coupled with the high metabolic demand of growing tumors has led to the hypothesis that many tumors experience metabolic stress driven by limited availability of nutrients such as glucose, oxygen, and amino acids in the tumor. Such metabolic stress has important implications for the biology of cells in the microenvironment, affecting both disease progression and response to therapies. Recently, techniques have been developed to identify limiting nutrients and resulting metabolic stresses in solid tumors. These techniques have greatly expanded our understanding of the metabolic limitations in tumors. This review will discuss these experimental tools and the emerging picture of metabolic limitations in tumors arising from recent studies using these approaches.

Acidity induces durable enhancement of Treg cell suppressive functions for tumor immune evasion

The microenvironment within solid tumors often becomes acidic due to various factors associated with abnormal metabolism and cellular activities, including increased lactate production as a result of dysregulated tumor glycolysis. Recently, we have identified multiple tumor microenvironment (TME) factors that potentiate regulatory T (Treg) cell function in evading anti-tumor immunosurveillance. Despite the strong correlation between lactate and acidity, the potential roles of acidity in intratumoral Treg cell adaptation and underlying molecular mechanisms have gone largely unstudied. In this study, we demonstrate that acidity significantly enhances immunosuppressive functions of nTreg cells, but not iTreg cells, without altering the expression of either FoxP3 or the cell surface receptors CD25, CTLA4, or GITR in these cells. Surprisingly, the addition of lactate, often considered a major contributor to increased acidity of the TME, completely abolished the acidity-induced enhancement of nTreg suppressive functions. Consistently, metabolic flux analyses showed elevated basal mitochondrial respiratory capacity and ATP-coupled respiration in acidity-treated nTreg cells without altering glycolytic capacity. Genome-wide transcriptome and metabolomics analyses revealed alterations in multiple metabolic pathways, particularly the one-carbon folate metabolism pathway, with reduced SAM, folate, and glutathione, in nTreg cells exposed to low pH conditions. Addition of a one-carbon metabolic contributor, formate, diminished the acidity-induced enhancement in nTreg cell suppressive functions, but neither SAM nor glutathione could reverse the phenotype. Remarkably, in vitro transient treatment of nTreg cells resulted in sustained enhancement of their functions, as evidenced by more vigorous tumor growth observed in mice adoptively receiving acidity-treated nTreg cells. Further analysis of intratumoral infiltrated T cells confirmed a significant reduction in CD8+ T cell frequency and their granzyme B production. In summary, our study elucidates how acidity-mediated metabolic reprogramming leads to sustained Treg-mediated tumor immune evasion.

Focusing on CD8+ T-cell phenotypes: improving solid tumor therapy

Vigorous CD8+ T cells play a crucial role in recognizing tumor cells and combating solid tumors. How T cells efficiently recognize and target tumor antigens, and how they maintain the activity in the "rejection" of solid tumor microenvironment, are major concerns. Recent advances in understanding of the immunological trajectory and lifespan of CD8+ T cells have provided guidance for the design of more optimal anti-tumor immunotherapy regimens. Here, we review the newly discovered methods to enhance the function of CD8+ T cells against solid tumors, focusing on optimizing T cell receptor (TCR) expression, improving antigen recognition by engineered T cells, enhancing signal transduction of the TCR-CD3 complex, inducing the homing of polyclonal functional T cells to tumors, reversing T cell exhaustion under chronic antigen stimulation, and reprogramming the energy and metabolic pathways of T cells. We also discuss how to participate in the epigenetic changes of CD8+ T cells to regulate two key indicators of anti-tumor responses, namely effectiveness and persistence.

Physiologically Achievable Concentration of 2-Deoxy-D-Glucose Stimulates IFN-γ Secretion in Activated T Cells In Vitro

2-deoxy-D-glucose (2DG) is a glycolysis and protein N-glycosylation inhibitor with promising anti-tumor and immunomodulatory effects. However, 2DG can also suppress T cell function, including IFN-γ secretion. Few human T cell studies have studied low-dose 2DG, which can increase IFN-γ in a Jurkat clone. We therefore investigated 2DG's effect on IFN-γ in activated human T cells from PBMCs, with 2DG treatment commenced either concurrently with activation or 48 h after activation. Concurrent 2DG treatment decreased IFN-γ secretion in a dose-dependent manner. However, 2DG treatment of pre-activated T cells had a hormetic effect on IFN-γ, with 0.15-0.6 mM 2DG (achievable in vivo) increasing and >2.4 mM 2DG reducing its secretion. In contrast, IL-2 levels declined monotonously with increasing 2DG concentration. Lower 2DG concentrations reduced PD-1 and increased CD69 expression regardless of treatment timing. The absence of increased T-bet or Eomes expression or IFNG transcription suggests another downstream mechanism. 2DG dose-dependently induced the unfolded protein response, suggesting a possible role in increased IFN-γ secretion, possibly by increasing the ER folding capacity for IFN-γ via increased chaperone expression. Overall, low-dose, short-term 2DG exposure could potentially improve the T cell anti-tumor response.

Lipid metabolism: a central modulator of RORγt-mediated Th17 cell differentiation

Among the T helper cell subsets, Th17 cells contribute to the development of various inflammatory and autoimmune diseases, including psoriasis, rheumatoid arthritis, inflammatory bowel disease, steroid-resistant asthma, and multiple sclerosis. Retinoid-related orphan receptor gamma t (RORγt), a nuclear hormone receptor, serves as a master transcription factor for Th17 cell differentiation. Recent findings have shown that modulating the metabolic pathway is critical for Th17 cell differentiation, particularly through the engagement of de novo lipid biosynthesis. Suppression of lipid biosynthesis, either through the pharmacological inhibition or gene deletion of related enzymes in CD4+ T cells, results in significant impairment of Th17 cell differentiation. Mechanistic studies indicate that metabolic fluxes through both the fatty acid and cholesterol biosynthetic pathways have a pivotal role in the regulation of RORγt activity through the generation of endogenous RORγt lipid ligands. This review discusses recent discoveries highlighting the importance of lipid metabolism in Th17 cell differentiation and function, as well as exploring specific molecular pathways involved in RORγt activation through cellular lipid metabolism. We further elaborate on a pioneering therapeutic approach to improve inflammatory and autoimmune disorders via the inhibition of RORγt.

Enhanced tumor response to adoptive T cell therapy with PHD2/3-deficient CD8 T cells

While adoptive cell therapy has shown success in hematological malignancies, its potential against solid tumors is hindered by an immunosuppressive tumor microenvironment (TME). In recent years, members of the hypoxia-inducible factor (HIF) family have gained recognition as important regulators of T-cell metabolism and function. The role of HIF signalling in activated CD8 T cell function in the context of adoptive cell transfer, however, has not been explored in full depth. Here we utilize CRISPR-Cas9 technology to delete prolyl hydroxylase domain-containing enzymes (PHD) 2 and 3, thereby stabilizing HIF-1 signalling, in CD8 T cells that have already undergone differentiation and activation, modelling the T cell phenotype utilized in clinical settings. We observe a significant boost in T-cell activation and effector functions following PHD2/3 deletion, which is dependent on HIF-1α, and is accompanied by an increased glycolytic flux. This improvement in CD8 T cell performance translates into an enhancement in tumor response to adoptive T cell therapy in mice, across various tumor models, even including those reported to be extremely resistant to immunotherapeutic interventions. These findings hold promise for advancing CD8 T-cell based therapies and overcoming the immune suppression barriers within challenging tumor microenvironments.

Pharmacologic LDH inhibition redirects intratumoral glucose uptake and improves antitumor immunity in solid tumor models

Tumor reliance on glycolysis is a hallmark of cancer. Immunotherapy is more effective in controlling glycolysis-low tumors lacking lactate dehydrogenase (LDH) due to reduced tumor lactate efflux and enhanced glucose availability within the tumor microenvironment (TME). LDH inhibitors (LDHi) reduce glucose uptake and tumor growth in preclinical models, but their impact on tumor-infiltrating T cells is not fully elucidated. Tumor cells have higher basal LDH expression and glycolysis levels compared with infiltrating T cells, creating a therapeutic opportunity for tumor-specific targeting of glycolysis. We demonstrate that LDHi treatment (a) decreases tumor cell glucose uptake, expression of the glucose transporter GLUT1, and tumor cell proliferation while (b) increasing glucose uptake, GLUT1 expression, and proliferation of tumor-infiltrating T cells. Accordingly, increasing glucose availability in the microenvironment via LDH inhibition leads to improved tumor-killing T cell function and impaired Treg immunosuppressive activity in vitro. Moreover, combining LDH inhibition with immune checkpoint blockade therapy effectively controls murine melanoma and colon cancer progression by promoting effector T cell infiltration and activation while destabilizing Tregs. Our results establish LDH inhibition as an effective strategy for rebalancing glucose availability for T cells within the TME, which can enhance T cell function and antitumor immunity.

Mitochondrial ATP generation is more proteome efficient than glycolysis

Metabolic efficiency profoundly influences organismal fitness. Nonphotosynthetic organisms, from yeast to mammals, derive usable energy primarily through glycolysis and respiration. Although respiration is more energy efficient, some cells favor glycolysis even when oxygen is available (aerobic glycolysis, Warburg effect). A leading explanation is that glycolysis is more efficient in terms of ATP production per unit mass of protein (that is, faster). Through quantitative flux analysis and proteomics, we find, however, that mitochondrial respiration is actually more proteome efficient than aerobic glycolysis. This is shown across yeast strains, T cells, cancer cells, and tissues and tumors in vivo. Instead of aerobic glycolysis being valuable for fast ATP production, it correlates with high glycolytic protein expression, which promotes hypoxic growth. Aerobic glycolytic yeasts do not excel at aerobic growth but outgrow respiratory cells during oxygen limitation. We accordingly propose that aerobic glycolysis emerges from cells maintaining a proteome conducive to both aerobic and hypoxic growth.

Immunometabolic alteration of CD4+ T cells in the pathogenesis of primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a prevalent autoimmune disorder wherein CD4+ T cells play a pivotal role in its pathogenesis. However, the underlying mechanisms driving the hyperactivity of CD4+ T cells in pSS remain poorly understood. This study aimed to investigate the potential role of immunometabolic alterations in driving the hyperactivity of CD4+ T cells in pSS. We employed Seahorse XF assay to evaluate the metabolic phenotype of CD4+ T cells, conducted flow cytometry to assess the effector function and differentiation of CD4+ T cells and measured the level of intracellular reactive oxygen species (ROS). Additionally, transcriptome sequencing, PCR, and Western blotting were utilized to examine the expression of glycolytic genes. Our investigation revealed that activated CD4+ T cells from pSS patients exhibited elevated aerobic glycolysis, rather than oxidative phosphorylation, resulting in excessive production of IFN-γ and IL-17A. Inhibition of glycolysis by 2-Deoxy-D-glucose reduced the expression of IFN-γ and IL-17A in activated CD4+ T cells and mitigated the differentiation of Th1 and Th17 cells. Furthermore, the expression of glycolytic genes, including CD3E, CD28, PIK3CA, AKT1, mTOR, MYC, LDHA, PFKL, PFKFB3, and PFKFB4, was upregulated in activated CD4+ T cells from pSS patients. Specifically, the expression and activity of LDHA were enhanced, contributing to an increased level of intracellular ROS. Targeting LDHA with FX-11 or inhibiting ROS with N-acetyl-cysteine had a similar effect on reversing the dysfunction of activated CD4+ T cells from pSS patients. Our study unveils heightened aerobic glycolysis in activated CD4+ T cells from pSS patients, and inhibition of glycolysis or its metabolite normalizes the dysfunction of activated CD4+ T cells. These findings suggest that aerobic glycolysis may be a promising therapeutic target for the treatment of pSS.

Immune cells phenotype and bioenergetic measures in CD4+ T cells differ between high and low feed efficient dairy cows

Identifying sources of variance that contribute to residual feed intake (RFI) can aid in improving feed efficiency. The objectives of this study were to investigate immune cells phenotype and bioenergetic measures in CD4+ T cells in low feed efficient (LE) and high feed efficient (HE) dairy cows. Sixty-four Holstein cows were enrolled at 93 ± 22 days in milk (DIM) and monitored for 7 weeks to measure RFI. Cows with the highest RFI (LE; n = 14) or lowest RFI (HE; n = 14) were selected to determine immune cells phenotype using flow cytometry. Blood was sampled in the same LE and HE cows at 234 ± 22 DIM to isolate peripheral blood mononuclear cells, followed by magnetic separation of CD4+ T lymphocytes using bovine specific monoclonal antibodies. The metabolic function of isolated CD4+ T lymphocytes was evaluated under resting and activated states. An increased expression of CD62L+ cells within CD8+ T lymphocytes and CD21+ B lymphocytes was observed in HE cows compared to LE cows. CD4+ T lymphocytes of HE cows exhibited an increased mitochondrial and glycolytic activity in resting and activated states compared to LE cows. These data suggest that immune cells in HE cows exhibit an increased metabolic function, which might influence nutrient partitioning and utilization and serve as a source of variation in feed efficiency that warrants future investigation.

GLUT1 overexpression enhances CAR T cell metabolic fitness and anti-tumor efficacy

The tumor microenvironment presents many obstacles to effective chimeric antigen receptor (CAR) T cell therapy, including glucose competition from tumor and myeloid cells. Using mouse models of acute lymphoblastic leukemia (ALL), renal cell carcinoma (RCC), and glioblastoma (GBM), we show that enforced expression of the glucose transporter GLUT1 enhances anti-tumor efficacy and promotes favorable CAR-T cell phenotypes for two clinically relevant CAR designs, 19-28z and IL13Rα2-BBz. In the NALM6 ALL model, 19-28z-GLUT1 promotes T stem cell-like memory formation and prolongs survival. RNA sequencing of these CAR-T cells reveals that the overexpression of GLUT1, but not GLUT3, enriches for genes involved in glycolysis, mitochondrial respiration, and memory precursor phenotypes. Extending these data, 19-28z-GLUT1 CAR-T cells improve tumor control and response to rechallenge in an RCC patient-derived xenograft model. Furthermore, IL13Rα2-BBz CAR-T cells overexpressing GLUT1 prolong the survival of mice bearing orthotopic GBMs and exhibit decreased exhaustion markers. This novel engineering approach can offer a competitive advantage to CAR-T cells in harsh tumor environments where glucose is limiting.

Unraveling the Role of Reactive Oxygen Species in T Lymphocyte Signaling

Reactive oxygen species (ROS) are central to inter- and intracellular signaling. Their localized and transient effects are due to their short half-life, especially when generated in controlled amounts. Upon T cell receptor (TCR) activation, regulated ROS signaling is primarily initiated by complexes I and III of the electron transport chain (ETC). Subsequent ROS production triggers the activation of nicotinamide adenine dinucleotide phosphate oxidase 2 (NADPH oxidase 2), prolonging the oxidative signal. This signal then engages kinase signaling cascades such as the mitogen-activated protein kinase (MAPK) pathway and increases the activity of REDOX-sensitive transcription factors such as nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1). To limit ROS overproduction and prevent oxidative stress, nuclear factor erythroid 2-related factor 2 (Nrf2) and antioxidant proteins such as superoxide dismutases (SODs) finely regulate signal intensity and are capable of terminating the oxidative signal when needed. Thus, oxidative signals, such as T cell activation, are well-controlled and critical for cellular communication.

Fasting and Glucose Metabolism Differentially Impact Peripheral Inflammation in Human Type 2 Diabetes

Cytokines produced by peripheral T-helper 1/17 cells disproportionately contribute to the inflammation (i.e., metaflammation) that fuels type 2 diabetes (T2D) pathogenesis. Shifts in the nutrient milieu could influence inflammation through changes in T-cell metabolism. We aimed to determine whether changes in glucose utilization alter cytokine profiles in T2D. Peripheral blood mononuclear cells (PBMCs), CD4+ T-cells, and CD4+CD25- T-effector (Teff) cells were isolated from age-matched humans classified by glycemic control and BMI. Cytokines secreted by CD3/CD28-stimulated PBMCs and Teff were measured in supernatants with multiplex cytokine assays and a FLEXMAP-3D. Metabolic activity of stimulated CD4+ T-cells was measured by a Seahorse XFe96 analyzer. In this study, we demonstrated that T-cell stimulated PBMCs from non-fasted people with T2D produced higher amounts of cytokines compared to fasting. Although dysglycemia characterizes T2D, cytokine production by PBMCs or CD4+ T-cells in T2D was unaltered by hyperglycemic media. Moreover, pharmacological suppression of mitochondrial glucose oxidation did not change T-cell metabolism in T2D, yet enhanced cytokine competency. In conclusion, fasting and glucose metabolism differentially impact peripheral inflammation in human T2D, suggesting that glucose, along with fatty acid metabolites per our previous work, partner to regulate metaflammation. These data expose a major disconnect in the use of glycemic control drugs to target T2D-associated metaflammation.

TNF-α signals through ITK-Akt-mTOR to drive CD4+ T cell metabolic reprogramming, which is dysregulated in rheumatoid arthritis

Upon activation, T cells undergo metabolic reprogramming to meet the bioenergetic demands of clonal expansion and effector function. Because dysregulated T cell cytokine production and metabolic phenotypes coexist in chronic inflammatory disease, including rheumatoid arthritis (RA), we investigated whether inflammatory cytokines released by differentiating T cells amplified their metabolic changes. We found that tumor necrosis factor-α (TNF-α) released by human naïve CD4+ T cells upon activation stimulated the expression of a metabolic transcriptome and increased glycolysis, amino acid uptake, mitochondrial oxidation of glutamine, and mitochondrial biogenesis. The effects of TNF-α were mediated by activation of Akt-mTOR signaling by the kinase ITK and did not require the NF-κB pathway. TNF-α stimulated the differentiation of naïve cells into proinflammatory T helper 1 (TH1) and TH17 cells, but not that of regulatory T cells. CD4+ T cells from patients with RA showed increased TNF-α production and consequent Akt phosphorylation upon activation. These cells also exhibited increased mitochondrial mass, particularly within proinflammatory T cell subsets implicated in disease. Together, these findings suggest that T cell-derived TNF-α drives their metabolic reprogramming by promoting signaling through ITK, Akt, and mTOR, which is dysregulated in autoinflammatory disease.

Slc43a2+ T cell metastasis from spleen to brain in RGNNV infected teleost

The origin of T cells in the teleost's brain is unclear. While viewing the central nervous system (CNS) as immune privileged has been widely accepted, previous studies suggest that T cells residing in the thymus but not in the spleen of the teleost play an essential role in communicating with the peripheral organs. Here, we identified nine T cell subpopulations in the thymus and spleen of orange-spotted grouper (Epinephelus coioices) through single-cell RNA-sequencing analysis. After viral CNS infection with red-spotted grouper nervous necrosis virus (RGNNV), the number of slc43a2+ T cells synchronously increased in the spleen and brain. During the infection tests in asplenic zebrafish (tlx1▲ zebrafish model), no increase in the number of slc43a2+ T cells was observed in the brain. Single-cell transcriptomic analysis indicated that slc43a2+ T cells mature and functionally differentiate within the spleen and then migrate into the brain to trigger an immune response. This study suggests a novel route for T cell migration from the spleen to the brain during viral infection in fish.

Harnessing Immune Cell Metabolism to Modulate Alloresponse in Transplantation

Immune cell metabolism plays a pivotal role in shaping and modulating immune responses. The metabolic state of immune cells influences their development, activation, differentiation, and overall function, impacting both innate and adaptive immunity. While glycolysis is crucial for activation and effector function of CD8 T cells, regulatory T cells mainly use oxidative phosphorylation and fatty acid oxidation, highlighting how different metabolic programs shape immune cells. Modification of cell metabolism may provide new therapeutic approaches to prevent rejection and avoid immunosuppressive toxicities. In particular, the distinct metabolic patterns of effector and suppressive cell subsets offer promising opportunities to target metabolic pathways that influence immune responses and graft outcomes. Herein, we review the main metabolic pathways used by immune cells, the techniques available to assay immune metabolism, and evidence supporting the possibility of shifting the immune response towards a tolerogenic profile by modifying energetic metabolism.

Nutrients: Signal 4 in T cell immunity

T cells are integral in mediating adaptive immunity to infection, autoimmunity, and cancer. Upon immune challenge, T cells exit from a quiescent state, followed by clonal expansion and effector differentiation. These processes are shaped by three established immune signals, namely antigen stimulation (Signal 1), costimulation (Signal 2), and cytokines (Signal 3). Emerging findings reveal that nutrients, including glucose, amino acids, and lipids, are crucial regulators of T cell responses and interplay with Signals 1-3, highlighting nutrients as Signal 4 to license T cell immunity. Here, we first summarize the functional importance of Signal 4 and the underlying mechanisms of nutrient transport, sensing, and signaling in orchestrating T cell activation and quiescence exit. We also discuss the roles of nutrients in programming T cell differentiation and functional fitness and how nutrients can be targeted to improve disease therapy. Understanding how T cells respond to Signal 4 nutrients in microenvironments will provide insights into context-dependent functions of adaptive immunity and therapeutic interventions.

CD8+ T cell metabolic flexibility elicited by CD28-ARS2 axis-driven alternative splicing of PKM supports antitumor immunity

Metabolic flexibility has emerged as a critical determinant of CD8+ T-cell antitumor activity, yet the mechanisms driving the metabolic flexibility of T cells have not been determined. In this study, we investigated the influence of the nuclear cap-binding complex (CBC) adaptor protein ARS2 on mature T cells. In doing so, we discovered a novel signaling axis that endows activated CD8+ T cells with flexibility of glucose catabolism. ARS2 upregulation driven by CD28 signaling reinforced splicing factor recruitment to pre-mRNAs and affected approximately one-third of T-cell activation-induced alternative splicing events. Among these effects, the CD28-ARS2 axis suppressed the expression of the M1 isoform of pyruvate kinase in favor of PKM2, a key determinant of CD8+ T-cell glucose utilization, interferon gamma production, and antitumor effector function. Importantly, PKM alternative splicing occurred independently of CD28-driven PI3K pathway activation, revealing a novel means by which costimulation reprograms glucose metabolism in CD8+ T cells.

Integrative temporal multi-omics reveals uncoupling of transcriptome and proteome during human T cell activation

Engagement of the T cell receptor (TCR) triggers molecular reprogramming leading to the acquisition of specialized effector functions by CD4 helper and CD8 cytotoxic T cells. While transcription factors, chemokines, and cytokines are known drivers in this process, the temporal proteomic and transcriptomic changes that regulate different stages of human primary T cell activation remain to be elucidated. Here, we report an integrative temporal proteomic and transcriptomic analysis of primary human CD4 and CD8 T cells following ex vivo stimulation with anti-CD3/CD28 beads, which revealed major transcriptome-proteome uncoupling. The early activation phase in both CD4 and CD8 T cells was associated with transient downregulation of the mRNA transcripts and protein of the central glucose transport GLUT1. In the proliferation phase, CD4 and CD8 T cells became transcriptionally more divergent while their proteome became more similar. In addition to the kinetics of proteome-transcriptome correlation, this study unveils selective transcriptional and translational metabolic reprogramming governing CD4 and CD8 T cell responses to TCR stimulation. This temporal transcriptome/proteome map of human T cell activation provides a reference map exploitable for future discovery of biomarkers and candidates targeting T cell responses.

EP300 restores the glycolytic activity and anti-tumor function of CD8+ cytotoxic T cells in nasopharyngeal carcinoma

Competition for glucose may metabolically limit T cells during cancer progression. This study shows that culturing in the condition medium (CM) of NPC c6661 cells restricted glycolytic and immune activities of CD8+ T cells. These cells also exhibited limited tumor-eliminating effects in mouse xenograft tumor models. Glucose supplementation restored glycolysis and immune activity of CD8+ T cells in vitro and in vivo by rescuing the expression of E1A binding protein p300 (EP300). EP300 upregulated bromodomain PHD finger transcription factor (BPTF) expression by catalyzing H3K27ac modification, and BPTF further activated AT-rich interaction domain 1A (ARID1A) transcription. Either BPTF or ARID1A knockdown in CD8+ T cells reduced their glycolytic activity, decreased the secretion of cytotoxic molecules, and blocked the tumor-killing function in mice. Overall, this study demonstrates that EP300 restores the glycolytic and anti-tumor activities of CD8+ T cells in the glucose restriction condition in NPC through the BPTF/ARID1A axis.