bims-imicid Biomed News
on Immunometabolism of infection, cancer and immune-mediated disease
Issue of 2024‒01‒07
23 papers selected by
Dylan Ryan, University of Cambridge

  1. Cell Metab. 2024 Jan 02. pii: S1550-4131(23)00456-4. [Epub ahead of print]36(1): 209-221.e6
      Metabolic status is crucial for stem cell functions; however, the metabolic heterogeneity of endogenous stem cells has never been directly assessed. Here, we develop a platform for high-throughput single-cell metabolomics (hi-scMet) of hematopoietic stem cells (HSCs). By combining flow cytometric isolation and nanoparticle-enhanced laser desorption/ionization mass spectrometry, we routinely detected >100 features from single cells. We mapped the single-cell metabolomes of all hematopoietic cell populations and HSC subpopulations with different division times, detecting 33 features whose levels exhibited trending changes during HSC proliferation. We found progressive activation of the oxidative pentose phosphate pathway (OxiPPP) from dormant to active HSCs. Genetic or pharmacological interference with OxiPPP increased reactive oxygen species level in HSCs, reducing HSC self-renewal upon oxidative stress. Together, our work uncovers the metabolic dynamics during HSC proliferation, reveals a role of OxiPPP for HSC activation, and illustrates the utility of hi-scMet in dissecting metabolic heterogeneity of immunophenotypically defined cell populations.
    Keywords:  6-phosphogluconic acid; HSC; MALDI-MS; hematopoietic stem cell; hi-scMet; metabolism; metabolomic heterogeneity; nanoparticle; pentose phosphate pathway; single-cell metabolomics
  2. J Biol Chem. 2024 Jan 02. pii: S0021-9258(23)02649-2. [Epub ahead of print] 105620
      Sterile alpha and HEAT/Armadillo motif-containing protein (SARM1) was recently described as a NAD+-consuming enzyme, and has previously been shown to regulate immune responses in macrophages. Neuronal SARM1 is known to contribute to axon degeneration due to its NADase activity. However, how SARM1 affects macrophage metabolism has not been explored. Here, we show that macrophages from Sarm1-/- mice display elevated NAD+ concentrations and lower cyclic ADPR, a known product of SARM1-dependent NAD+ catabolism. Further, SARM1-deficient macrophages showed an increase in the reserve capacity of oxidative phosphorylation and glycolysis compared to wild-type cells. Stimulation of macrophages to a pro-inflammatory state by lipopolysaccharide (LPS), revealed that SARM1 restricts the ability of macrophages to upregulate glycolysis and limits the expression of the pro-inflammatory gene Il1b, but boosts expression of anti-inflammatory Il10. In contrast, we show macrophages lacking SARM1 induced to an anti-inflammatory state by IL-4 stimulation display increased oxidative phosphorylation and glycolysis, and reduced expression of the anti-inflammatory gene, Fizz1. Overall, these data show that SARM1 fine-tunes immune gene transcription in macrophages via consumption of NAD+ and altered macrophage metabolism.
    Keywords:  NAD(+); NADase; SARM1; cADPR; cytokine induction; macrophages; metabolism
  3. Gut. 2024 Jan 04. pii: gutjnl-2023-330543. [Epub ahead of print]
    TRR241 IBDome Consortium
      OBJECTIVE: Mucosal T cells play a major role in inflammatory bowel disease (IBD). However, their immunometabolism during intestinal inflammation is poorly understood. Due to its impact on cellular metabolism and proinflammatory immune cell function, we here focus on the enzyme ATP citrate lyase (ACLY) in mucosal T cell immunometabolism and its relevance for IBD.DESIGN: ACLY expression and its immunometabolic impact on colitogenic T cell function were analysed in mucosal T cells from patients with IBD and in two experimental colitis models.
    RESULTS: ACLY was markedly expressed in colon tissue under steady-state conditions but was significantly downregulated in lamina propria mononuclear cells in experimental dextran sodium sulfate-induced colitis and in CD4+ and to a lesser extent in CD8+ T cells infiltrating the inflamed gut in patients with IBD. ACLY-deficient CD4+ T cells showed an impaired capacity to induce intestinal inflammation in a transfer colitis model as compared with wild-type T cells. Assessment of T cell immunometabolism revealed that ACLY deficiency dampened the production of IBD-relevant cytokines and impaired glycolytic ATP production but enriched metabolites involved in the biosynthesis of phospholipids and phosphatidylcholine. Interestingly, the short-chain fatty acid butyrate was identified as a potent suppressor of ACLY expression in T cells, while IL-36α and resolvin E1 induced ACLY levels. In a translational approach, in vivo administration of the butyrate prodrug tributyrin downregulated mucosal infiltration of ACLYhigh CD4+ T cells and ameliorated chronic colitis.
    CONCLUSION: ACLY controls mucosal T cell immunometabolism and experimental colitis. Therapeutic modulation of ACLY expression in T cells emerges as a novel strategy to promote the resolution of intestinal inflammation.
  4. Discov Immunol. 2023 ;pii: kyad011. [Epub ahead of print]2(1):
      Elucidating the relationship between cellular metabolism and T cell function has substantially advanced our understanding of how T cells are regulated in response to activation. The metabolic profiles of circulating or peripheral T cells have been well-described, yet less is known regarding how complex local microenvironments shape or modulate the bioenergetic profile of tissue-resident T lymphocytes. Intraepithelial lymphocytes expressing the γδ T cell receptor (γδ IEL) provide immunosurveillance of the intestinal epithelium to limit tissue injury and microbial invasion; however, their activation and effector responses occur independently of antigen recognition. In this review, we will summarize the current knowledge regarding γδ T cell and IEL metabolic profiles and how this informs our understanding of γδ IEL metabolism. We will also discuss the role of the gut microbiota in shaping the metabolic profile of these sentinel lymphocytes, and in turn, how these bioenergetics contribute to regulation of γδ IEL surveillance behavior and effector function. Improved understanding of the metabolic processes involved in γδ IEL homeostasis and function may yield novel strategies to amplify the protective functions of these cells in the context of intestinal health and disease.
    Keywords:  immunometabolism; intestine; intraepithelial lymphocytes; γδ T cells
  5. Res Sq. 2023 Dec 14. pii: [Epub ahead of print]
      Mounting effective immunity against pathogens and tumors relies on the successful metabolic programming of T cells by extracellular fatty acids 1-3 . During this process, fatty-acid-binding protein 5 (FABP5) imports lipids that fuel mitochondrial respiration and sustain the bioenergetic requirements of protective CD8 + T cells 4,5 . Importantly, however, the mechanisms governing this crucial immunometabolic axis remain unexplored. Here we report that the cytoskeletal organizer Transgelin 2 (TAGLN2) is necessary for optimal CD8 + T cell fatty acid uptake, mitochondrial respiration, and anti-cancer function. We found that TAGLN2 interacts with FABP5, enabling the surface localization of this lipid importer on activated CD8 + T cells. Analysis of ovarian cancer specimens revealed that endoplasmic reticulum (ER) stress responses elicited by the tumor microenvironment repress TAGLN2 in infiltrating CD8 + T cells, enforcing their dysfunctional state. Restoring TAGLN2 expression in ER-stressed CD8 + T cells bolstered their lipid uptake, mitochondrial respiration, and cytotoxic capacity. Accordingly, chimeric antigen receptor T cells overexpressing TAGLN2 bypassed the detrimental effects of tumor-induced ER stress and demonstrated superior therapeutic efficacy in mice with metastatic ovarian cancer. Our study unveils the role of cytoskeletal TAGLN2 in T cell lipid metabolism and highlights the potential to enhance cellular immunotherapy in solid malignancies by preserving the TAGLN2-FABP5 axis.
  6. Cell Metab. 2024 Jan 02. pii: S1550-4131(23)00465-5. [Epub ahead of print]
      Itaconate is a metabolite that synthesized from cis-aconitate in mitochondria and transported into the cytosol to exert multiple regulatory effects in macrophages. However, the mechanism by which itaconate exits from macrophages remains unknown. Using a genetic screen, we reveal that itaconate is exported from cytosol to extracellular space by ATP-binding cassette transporter G2 (ABCG2) in an ATPase-dependent manner in human and mouse macrophages. Elevation of transcription factor TFEB-dependent lysosomal biogenesis and antibacterial innate immunity are observed in inflammatory macrophages with deficiency of ABCG2-mediated itaconate export. Furthermore, deficiency of ABCG2-mediated itaconate export in macrophages promotes antibacterial innate immune defense in a mouse model of S. typhimurium infection. Thus, our findings identify ABCG2-mediated itaconate export as a key regulatory mechanism that limits TFEB-dependent lysosomal biogenesis and antibacterial innate immunity in inflammatory macrophages, implying the potential therapeutic utility of blocking itaconate export in treating human bacterial infections.
    Keywords:  ABCG2; TFEB; exporter; innate immunity; itaconate; lysosomal biogenesis; macrophages
  7. Cell Metab. 2024 Jan 02. pii: S1550-4131(23)00461-8. [Epub ahead of print]36(1): 176-192.e10
      The efficacy of chimeric antigen receptor (CAR) T cell therapy is hampered by relapse in hematologic malignancies and by hyporesponsiveness in solid tumors. Long-lived memory CAR T cells are critical for improving tumor clearance and long-term protection. However, during rapid ex vivo expansion or in vivo tumor eradication, metabolic shifts and inhibitory signals lead to terminal differentiation and exhaustion of CAR T cells. Through a mitochondria-related compound screening, we find that the FDA-approved isocitrate dehydrogenase 2 (IDH2) inhibitor enasidenib enhances memory CAR T cell formation and sustains anti-leukemic cytotoxicity in vivo. Mechanistically, IDH2 impedes metabolic fitness of CAR T cells by restraining glucose utilization via the pentose phosphate pathway, which alleviates oxidative stress, particularly in nutrient-restricted conditions. In addition, IDH2 limits cytosolic acetyl-CoA levels to prevent histone acetylation that promotes memory cell formation. In combination with pharmacological IDH2 inhibition, CAR T cell therapy is demonstrated to have superior efficacy in a pre-clinical model.
    Keywords:  chimeric antigen receptor T cell; enasidenib; exhaustion; histone acetylation; isocitrate dehydrogenase 2; memory T cell formation; nutrient-restricted conditions; pentose phosphate pathway
  8. Cell Death Differ. 2024 Jan 05.
      Efferocytosis and metabolic reprogramming of macrophages play crucial roles in myocardial infarction (MI) repair. TREM2 has been proven to participate in phagocytosis and metabolism, but how it modulates myocardial infarction remains unclear. In this study, we showed that macrophage-specific TREM2 deficiency worsened cardiac function and impaired post-MI repair. Using RNA-seq, protein and molecular docking, and Targeted Metabolomics (LC-MS), our data demonstrated that macrophages expressing TREM2 exhibited decreased SLC25A53 transcription through the SYK-SMAD4 signaling pathway after efferocytosis, which impaired NAD+ transport into mitochondria, downregulated SLC25A53 thereby causing the breakpoint in the TCA cycle and subsequently increased itaconate production. In vitro experiments confirmed that itaconate secreted by TREM2+ macrophages inhibited cardiomyocyte apoptosis and promoted fibroblast proliferation. Conversely, overexpression of TREM2 in macrophages could improve cardiac function. In summary, our study reveals a novel role for macrophage-specific TREM2 in MI, connecting efferocytosis to immune metabolism during cardiac repair.
  9. Nat Commun. 2024 Jan 02. 15(1): 97
      The crosstalk between the bone and adipose tissue is known to orchestrate metabolic homeostasis, but the underlying mechanisms are largely unknown. Herein, we find that GCA + (grancalcin) immune cells accumulate in the bone marrow and release a considerable amount of GCA into circulation during obesity. Genetic deletion of Gca in myeloid cells attenuates metabolic dysfunction in obese male mice, whereas injection of recombinant GCA into male mice causes adipose tissue inflammation and insulin resistance. Mechanistically, we found that GCA binds to the Prohibitin-2 (PHB2) receptor on adipocytes and activates the innate and adaptive immune response of adipocytes via the PAK1-NF-κB signaling pathway, thus provoking the infiltration of inflammatory immune cells. Moreover, we show that GCA-neutralizing antibodies improve adipose tissue inflammation and insulin sensitivity in obese male mice. Together, these observations define a mechanism whereby bone marrow factor GCA initiates adipose tissue inflammation and insulin resistance, showing that GCA could be a potential target to treat metainflammation.
  10. Nat Commun. 2024 Jan 02. 15(1): 163
      Monocarboxylate transporter 1 (MCT1) exhibits essential roles in cellular metabolism and energy supply. Although MCT1 is highly expressed in activated B cells, it is not clear how MCT1-governed monocarboxylates transportation is functionally coupled to antibody production during the glucose metabolism. Here, we report that B cell-lineage deficiency of MCT1 significantly influences the class-switch recombination (CSR), rendering impaired IgG antibody responses in Mct1f/fMb1Cre mice after immunization. Metabolic flux reveals that glucose metabolism is significantly reprogrammed from glycolysis to oxidative phosphorylation in Mct1-deficient B cells upon activation. Consistently, activation-induced cytidine deaminase (AID), is severely suppressed in Mct1-deficient B cells due to the decreased level of pyruvate metabolite. Mechanistically, MCT1 is required to maintain the optimal concentration of pyruvate to secure the sufficient acetylation of H3K27 for the elevated transcription of AID in activated B cells. Clinically, we found that MCT1 expression levels are significantly upregulated in systemic lupus erythematosus patients, and Mct1 deficiency can alleviate the symptoms of bm12-induced murine lupus model. Collectively, these results demonstrate that MCT1-mediated pyruvate metabolism is required for IgG antibody CSR through an epigenetic dependent AID transcription, revealing MCT1 as a potential target for vaccine development and SLE disease treatment.
  11. JCI Insight. 2024 Jan 04. pii: e169138. [Epub ahead of print]
      Intrahepatic macrophages in nonalcoholic steatohepatitis (NASH) are heterogenous and include proinflammatory recruited monocyte derived macrophages. The receptor for advanced glycation end products (RAGE) is expressed on macrophages and can be activated by damage associated molecular patterns (DAMPs) upregulated in NASH, yet the role of macrophage-specific RAGE signaling in NASH is unclear. Therefore, we hypothesized that RAGE expressing macrophages are proinflammatory and mediate liver inflammation in NASH. Compared to healthy controls, RAGE expression was increased in liver biopsies from human NASH patients. In a high -fat, -fructose, and -cholesterol (FFC)-induced murine model of NASH, RAGE expression was increased, specifically on recruited macrophages. FFC mice that received a pharmacological inhibitor of RAGE (TTP488), and myeloid-specific RAGE knockout mice (RAGE-MKO) had attenuated liver injury associated with a reduced accumulation of RAGE+ recruited macrophages. Transcriptomic analysis suggested that pathways of macrophage and T-cell activation were upregulated by FFC diet, inhibited by TTP488 treatment, and reduced in RAGE-MKO mice. Correspondingly, the secretome of ligand-stimulated bone marrow derived macrophages from RAGE-MKO mice had an attenuated capacity to activate CD8+ T cells. Our data implicate RAGE as what we propose to be a novel and potentially targetable mediator of the proinflammatory signaling of recruited macrophages in NASH.
    Keywords:  Drug therapy; Hepatitis; Hepatology; Inflammation; Macrophages
  12. Front Med. 2024 Jan 02.
      Macrophages, a heterogeneous population of innate immune cells, exhibit remarkable plasticity and play pivotal roles in coordinating immune responses and maintaining tissue homeostasis within the context of metabolic diseases. The activation of inflammatory macrophages in obese adipose tissue leads to detrimental effects, inducing insulin resistance through increased inflammation, impaired thermogenesis, and adipose tissue fibrosis. Meanwhile, adipose tissue macrophages also play a beneficial role in maintaining adipose tissue homeostasis by regulating angiogenesis, facilitating the clearance of dead adipocytes, and promoting mitochondrial transfer. Exploring the heterogeneity of macrophages in obese adipose tissue is crucial for unraveling the pathogenesis of obesity and holds significant potential for targeted therapeutic interventions. Recently, the dual effects and some potential regulatory mechanisms of macrophages in adipose tissue have been elucidated using single-cell technology. In this review, we present a comprehensive overview of the intricate activation mechanisms and diverse functions of macrophages in adipose tissue during obesity, as well as explore the potential of drug delivery systems targeting macrophages, aiming to enhance the understanding of current regulatory mechanisms that may be potentially targeted for treating obesity or metabolic diseases.
    Keywords:  adipose tissue homeostasis; adipose tissue macrophages; inflammation; obesity
  13. Cell Rep. 2024 Jan 03. pii: S2211-1247(23)01672-8. [Epub ahead of print]43(1): 113661
      Myeloid-derived suppressor cells (MDSCs) impair antitumor immune responses. Identifying regulatory circuits during MDSC development may bring new opportunities for therapeutic interventions. We report that the V-domain suppressor of T cell activation (VISTA) functions as a key enabler of MDSC differentiation. VISTA deficiency reduced STAT3 activation and STAT3-dependent production of polyamines, which causally impaired mitochondrial respiration and MDSC expansion. In both mixed bone marrow (BM) chimera mice and myeloid-specific VISTA conditional knockout mice, VISTA deficiency significantly reduced tumor-associated MDSCs but expanded monocyte-derived dendritic cells (DCs) and enhanced T cell-mediated tumor control. Correlated expression of VISTA and arginase-1 (ARG1), a key enzyme supporting polyamine biosynthesis, was observed in multiple human cancer types. In human endometrial cancer, co-expression of VISTA and ARG1 on tumor-associated myeloid cells is associated with poor survival. Taken together, these findings unveil the VISTA/polyamine axis as a central regulator of MDSC differentiation and warrant therapeutically targeting this axis for cancer immunotherapy.
    Keywords:  CP: Cancer; CP: Immunology; GM-CSF; IL-6; MDSC differentiation; STAT3; VISTA; mitochondrial function; myeloid-derived suppressor cells; polyamine; tumor-associated myeloid cells
  14. Clin Exp Allergy. 2024 Jan 04.
      BACKGROUND: Vancomycin, a glycopeptide antibiotic used for Gram-positive bacterial infections, has been linked with drug reaction with eosinophilia and systemic symptoms (DRESS) in HLA-A*32:01-expressing individuals. This is associated with activation of T lymphocytes, for which glycolysis has been isolated as a fuel pathway following antigenic stimulation. However, the metabolic processes that underpin drug-reactive T-cell activation are currently undefined and may shed light on the energetic conditions needed for the elicitation of drug hypersensitivity or tolerogenic pathways. Here, we sought to characterise the immunological and metabolic pathways involved in drug-specific T-cell activation within the context of DRESS pathogenesis using vancomycin as model compound and drug-reactive T-cell clones (TCCs) generated from healthy donors and vancomycin-hypersensitive patients.METHODS: CD4+ and CD8+ vancomycin-responsive TCCs were generated by serial dilution. The Seahorse XFe96 Analyzer was used to measure the extracellular acidification rate (ECAR) as an indicator of glycolytic function. Additionally, T-cell proliferation and cytokine release (IFN-γ) assay were utilised to correlate the bioenergetic characteristics of T-cell activation with in vitro assays.
    RESULTS: Model T-cell stimulants induced non-specific T-cell activation, characterised by immediate augmentation of ECAR and rate of ATP production (JATPglyc). There was a dose-dependent and drug-specific glycolytic shift when vancomycin-reactive TCCs were exposed to the drug. Vancomycin-reactive TCCs did not exhibit T-cell cross-reactivity with structurally similar compounds within proliferative and cytokine readouts. However, cross-reactivity was observed when analysing energetic responses; TCCs with prior specificity for vancomycin were also found to exhibit glycolytic switching after exposure to teicoplanin. Glycolytic activation of TCC was HLA restricted, as exposure to HLA blockade attenuated the glycolytic induction.
    CONCLUSION: These studies describe the glycolytic shift of CD4+ and CD8+ T cells following vancomycin exposure. Since similar glycolytic switching is observed with teicoplanin, which did not activate T cells, it is possible the master switch for T-cell activation is located upstream of metabolic signalling.
    Keywords:  DRESS; T lymphocytes; drug hypersensitivity; glycolysis; vancomycin
  15. Nat Immunol. 2024 Jan 04.
      Tumor cells and surrounding immune cells undergo metabolic reprogramming, leading to an acidic tumor microenvironment. However, it is unclear how tumor cells adapt to this acidic stress during tumor progression. Here we show that carnosine, a mobile buffering metabolite that accumulates under hypoxia in tumor cells, regulates intracellular pH homeostasis and drives lysosome-dependent tumor immune evasion. A previously unrecognized isoform of carnosine synthase, CARNS2, promotes carnosine synthesis under hypoxia. Carnosine maintains intracellular pH (pHi) homeostasis by functioning as a mobile proton carrier to accelerate cytosolic H+ mobility and release, which in turn controls lysosomal subcellular distribution, acidification and activity. Furthermore, by maintaining lysosomal activity, carnosine facilitates nuclear transcription factor X-box binding 1 (NFX1) degradation, triggering galectin-9 and T-cell-mediated immune escape and tumorigenesis. These findings indicate an unconventional mechanism for pHi regulation in cancer cells and demonstrate how lysosome contributes to immune evasion, thus providing a basis for development of combined therapeutic strategies against hepatocellular carcinoma that exploit disrupted pHi homeostasis with immune checkpoint blockade.
  16. PLoS Pathog. 2023 Dec;19(12): e1011892
      Staphylococcus aureus is a dangerous pathogen that evolved refined immuno-evasive strategies to antagonize host immune responses. This involves the biogenesis of death-effector deoxyribonucleosides, which kill infectious foci-penetrating macrophages. However, the exact mechanisms whereby staphylococcal death-effector deoxyribonucleosides and coupled imbalances of intracellular deoxyribonucleotide species provoke immune cell death remain elusive. Here, we report that S. aureus systematically promotes an overload of deoxyribonucleotides to trigger mitochondrial rupture in macrophages, a fatal event that induces assembly of the caspase-9-processing apoptosome and subsequent activation of the intrinsic pathway of apoptosis. Remarkably, genetic disruption of this cascade not only helps macrophages coping with death-effector deoxyribonucleoside-mediated cytotoxicity but also enhances their infiltration into abscesses thereby ameliorating pathogen control and infectious disease outcomes in laboratory animals. Combined with the discovery of protective alleles in human CASP9, these data highlight the role of mitochondria-centered apoptosis during S. aureus infection and suggest that gene polymorphisms may shape human susceptibility toward a predominant pathogen.
  17. Gut Microbes. 2024 Jan-Dec;16(1):16(1): 2297872
      Hyperbaric oxygen (HBO) therapy is a well-established method for improving tissue oxygenation and is typically used for the treatment of various inflammatory conditions, including infectious diseases. However, its effect on the intestinal mucosa, a microenvironment known to be physiologically hypoxic, remains unclear. Here, we demonstrated that daily treatment with hyperbaric oxygen affects gut microbiome composition, worsening antibiotic-induced dysbiosis. Accordingly, HBO-treated mice were more susceptible to Clostridioides difficile infection (CDI), an enteric pathogen highly associated with antibiotic-induced colitis. These observations were closely linked with a decline in the level of microbiota-derived short-chain fatty acids (SCFAs). Butyrate, a SCFA produced primarily by anaerobic microbial species, mitigated HBO-induced susceptibility to CDI and increased epithelial barrier integrity by improving group 3 innate lymphoid cell (ILC3) responses. Mice displaying tissue-specific deletion of HIF-1 in RORγt-positive cells exhibited no protective effect of butyrate during CDI. In contrast, the reinforcement of HIF-1 signaling in RORγt-positive cells through the conditional deletion of VHL mitigated disease outcome, even after HBO therapy. Taken together, we conclude that HBO induces intestinal dysbiosis and impairs the production of SCFAs affecting the HIF-1α-IL-22 axis in ILC3 and worsening the response of mice to subsequent C. difficile infection.
    Keywords:  HIF-1; Hyperbaric oxygen; ILC3; butyrate; clostridioides difficile; innate lymphoid cells; microbiota
  18. Biomed Pharmacother. 2023 Dec 28. pii: S0753-3322(23)01890-5. [Epub ahead of print]170 116092
      Atherosclerosis significantly contributes to the development of cardiovascular diseases (CVD) and is characterized by lipid retention and inflammation within the artery wall. Multiple immune cell types are implicated in the pathogenesis of atherosclerosis, macrophages play a central role as the primary source of inflammatory effectors in this pathogenic process. The metabolic influences of lipids on macrophage function and fatty acid β-oxidation (FAO) have similarly drawn attention due to its relevance as an immunometabolic hub. This review discusses recent findings regarding the impact of mitochondrial-dependent FAO in the phenotype and function of macrophages, as well as transcriptional regulation of FAO within macrophages. Finally, the therapeutic strategy of macrophage FAO in atherosclerosis is highlighted.
    Keywords:  Atherosclerosis; Fatty acid oxidation; Macrophage; NLRP3 inflammasome; Peroxisome proliferator-activated receptors
  19. J Crohns Colitis. 2024 Jan 02. pii: jjad217. [Epub ahead of print]
      BACKGROUND AND AIMS: Free D-amino acids, which have different functions from L-amino acids, have recently been discovered in various tissues. However, studies on the potential interactions between intestinal inflammation and D-amino acids are limited. We examined the inhibitory effects of D-alanine on the pathogenesis of intestinal inflammation.METHODS: We investigated serum D-amino acid levels in 40 patients with ulcerative colitis and 34 healthy volunteers. For 7 d, acute colitis was induced using dextran sulfate sodium in C57BL/6J mice. Plasma D-amino acid levels were quantified in mice with dextran sulfate sodium-induced colitis, and these animals were administered D-alanine via intraperitoneal injection. IFN-γ, IL-12p35, IL-17A, and IL-23p19 mRNA expression in the colonic mucosa was measured using real-time PCR. In vitro proliferation assays were performed to assess naïve CD4+ T cell activation under Th-skewing conditions. Bone marrow cells were stimulated with mouse macrophage-colony stimulating factor to generate mouse bone marrow-derived macrophages.
    RESULTS: Serum D-alanine levels were significantly lower in patients with ulcerative colitis than in healthy volunteers. Dextran sulfate sodium-treated mice had significantly lower plasma D-alanine levels than control mice. D-alanine-treated mice had significantly lower disease activity index than control mice. IFN-γ, IL-12p35, IL-17A, and IL-23p19 mRNA expression levels were significantly lower in D-alanine-administered mice than in control mice. D-alanine suppressed naïve T cell differentiation into Th1 cells in vitro and inhibited the production of IL-12p35 and IL-23p19 in bone marrow-derived macrophages.
    CONCLUSIONS: Our results suggest that D-alanine prevents dextran sulfate sodium-induced colitis in mice and suppresses IL-12p35 and IL-23p19 production in macrophages.
    Keywords:  D-alanine; D-amino acid; ulcerative colitis
  20. Front Biosci (Landmark Ed). 2023 Dec 01. 28(12): 328
      BACKGROUND: Metabolic reprogramming provides a new perspective for understanding cancer. The targeting of dysregulated metabolic pathways may help to reprogram the immune status of the tumor microenvironment (TME), thereby increasing the effectiveness of immune checkpoint therapy. Colorectal cancer (CRC), especially colon adenocarcinoma (COAD), is associated with poor patient survival. The aim of the present study was to identify novel pathways involved in the development and prognosis of COAD, and to explore whether these pathways could be used as targets to improve the efficacy of immunotherapy.METHODS: Metabolism-related differentially expressed genes (MRDEGs) between tumor and normal tissues were identified using The Cancer Genome Atlas (TCGA) dataset, together with metabolism-related prognostic genes (MRPGs). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was performed separately for the MRDEGs and MRPGs. Gene Set Variation Analysis (GSVA) was also performed to explore the role of purine metabolism in COAD tumorigenesis. Consensus clustering of purine metabolism genes with the overall survival (OS) of patients and with anti-tumor immunity was also performed. Pearson correlation analysis was used to identify potential targets that correlated strongly with the expression of immune checkpoints.
    RESULTS: A 6-gene signature that had independent prognostic significance for COAD was identified, together with a predictive model for risk stratification and prognosis. The most significantly enriched pathway amongst MRDEGs and MRPGs was purine metabolism. Differentially expressed purine metabolism genes could divide patients into two clusters with distinct prognosis and anti-tumor immunity. Further analysis suggested that purine metabolism was involved in anti-tumor immunity.
    CONCLUSIONS: This study confirmed the importance of metabolism-related pathways and in particular purine metabolism in the tumorigenesis, prognosis and anti-tumor immunity of COAD. We identified a 6-gene prognostic signature comprised of EPHX2, GPX3, PTGDS, NAT2, ACOX1 and CPT2. In addition, four potential immune-metabolic checkpoints (GUCY1A1, GUCY1B1, PDE1A and PDE5A) were identified, which could be used to improve the efficacy of immunotherapy in COAD.
    Keywords:  colon adenocarcinoma; immune-metabolic checkpoints; metabolic reprogramming; purine metabolism
  21. Nat Biotechnol. 2024 Jan 02.
      The success of chimeric antigen receptor (CAR) T cell therapy in treating several hematopoietic malignancies has been difficult to replicate in solid tumors, in part because of T cell exhaustion and eventually dysfunction. To counter T cell dysfunction in the tumor microenvironment, we metabolically armored CAR T cells by engineering them to secrete interleukin-10 (IL-10). We show that IL-10 CAR T cells preserve intact mitochondrial structure and function in the tumor microenvironment and increase oxidative phosphorylation in a mitochondrial pyruvate carrier-dependent manner. IL-10 secretion promoted proliferation and effector function of CAR T cells, leading to complete regression of established solid tumors and metastatic cancers across several cancer types in syngeneic and xenograft mouse models, including colon cancer, breast cancer, melanoma and pancreatic cancer. IL-10 CAR T cells also induced stem cell-like memory responses in lymphoid organs that imparted durable protection against tumor rechallenge. Our results establish a generalizable approach to counter CAR T cell dysfunction through metabolic armoring, leading to solid tumor eradication and long-lasting immune protection.
  22. J Nutr Biochem. 2024 Jan 02. pii: S0955-2863(23)00295-4. [Epub ahead of print] 109562
      BACKGROUND AND AIMS: Ketogenic diets (KD) are very high-fat low-carbohydrate diets that promote nutritional ketosis and are widely used for weight loss, although concerns about potential adverse cardiovascular effects remain. We investigated a very high-fat KD's vascular impact and plasma metabolic signature compared to a non-ketogenic high-fat diet (HFD).MATERIAL AND METHODS: Apolipoprotein E deficient (ApoE -/-) mice were fed a KD (%kcal: 81:1:18, fat/carbohydrates/protein) or a non-ketogenic high-fat diet with half of the fat content (HFD) (%kcal: 40:42:18, fat/carbohydrates/protein) for 12 weeks. Plasma samples were used to quantify the major ketone body beta-hydroxybutyrate (BHB) and several pro-inflammatory cytokines (IL-6, MCP-1, MIP-1alpha, and TNF alpha), and to targeted metabolomic profiling by mass spectrometry. In addition, aortic atherosclerotic lesions were quantified ex-vivo by magnetic resonance imaging (MRI) on a 14-tesla system.
    RESULTS: KD was atherogenic when compared to the control diet, but KD mice when compared to the HFD group (1) had markedly higher levels of BHB and lower levels of cytokines than HFD mice, confirming the presence of ketosis that alleviated the well-established fat-induced systemic inflammation; (2) displayed significant changes in the plasma metabolome that included a decrease in lipophilic and increase in hydrophilic metabolites; (3) had significantly lower levels of several atherogenic lipid metabolites, including phosphatidylcholines, cholesterol esters, sphingomyelins, and ceramides; (4) presented significantly lower aortic plaque burden.
    CONCLUSION: KD was atherogenic and was associated with specific metabolic changes but alleviated the fat-induced inflammation and lessened the progression of atherosclerosis when compared to the HFD.
    Keywords:  aortic atheroma; apolipoprotein E deficient mice; diets and vascular disease; ketogenic diets; nutritional ketosis
  23. Front Mol Neurosci. 2023 ;16 1299314
      Microglia are crucial for brain homeostasis, and dysfunction of these cells is a key driver in most neurodegenerative diseases, including peroxisomal leukodystrophies. In X-linked adrenoleukodystrophy (X-ALD), a neuroinflammatory disorder, very long-chain fatty acid (VLCFA) accumulation due to impaired degradation within peroxisomes results in microglial defects, but the underlying mechanisms remain unclear. Using CRISPR/Cas9 gene editing of key genes in peroxisomal VLCFA breakdown (Abcd1, Abcd2, and Acox1), we recently established easily accessible microglial BV-2 cell models to study the impact of dysfunctional peroxisomal β-oxidation and revealed a disease-associated microglial-like signature in these cell lines. Transcriptomic analysis suggested consequences on the immune response. To clarify how impaired lipid degradation impacts the immune function of microglia, we here used RNA-sequencing and functional assays related to the immune response to compare wild-type and mutant BV-2 cell lines under basal conditions and upon pro-inflammatory lipopolysaccharide (LPS) activation. A majority of genes encoding proinflammatory cytokines, as well as genes involved in phagocytosis, antigen presentation, and co-stimulation of T lymphocytes, were found differentially overexpressed. The transcriptomic alterations were reflected by altered phagocytic capacity, inflammasome activation, increased release of inflammatory cytokines, including TNF, and upregulated response of T lymphocytes primed by mutant BV-2 cells presenting peptides. Together, the present study shows that peroxisomal β-oxidation defects resulting in lipid alterations, including VLCFA accumulation, directly reprogram the main cellular functions of microglia. The elucidation of this link between lipid metabolism and the immune response of microglia will help to better understand the pathogenesis of peroxisomal leukodystrophies.
    Keywords:  adrenoleukodystrophy; antigen presentation; immune response; inflammation; microglia; peroxisome; phagocytosis