bims-imicid Biomed News
on Immunometabolism of infection, cancer and immune-mediated disease
Issue of 2022‒12‒25
thirty papers selected by
Dylan Ryan
University of Cambridge

  1. Biochem J. 2022 Dec 22. 479(24): 2499-2510
      Immune cells are metabolically plastic and respond to inflammatory stimuli with large shifts in metabolism. Itaconate is one of the most up-regulated metabolites in macrophages in response to the gram negative bacterial product LPS. As such, itaconate has recently been the subject of intense research interest. The artificial derivatives, including 4-Octyl Itaconate (4-OI) and Dimethyl Itaconate (DI) and naturally produced isomers, mesaconate and citraconate, have been tested in relation to itaconate biology with similarities and differences in the biochemistry and immunomodulatory properties of this family of compounds emerging. Both itaconate and 4-OI have been shown to modify cysteines on a range of target proteins, with the modification being linked to a functional change. Targets include KEAP1 (the NRF2 inhibitor), GAPDH, NLRP3, JAK1, and the lysosomal regulator, TFEB. 4-OI and DI are more electrophilic, and are therefore stronger NRF2 activators, and inhibit the production of Type I IFNs, while itaconate inhibits SDH and the dioxygenase, TET2. Additionally, both itaconate and derivates have been shown to be protective across a wide range of mouse models of inflammatory and infectious diseases, through both distinct and overlapping mechanisms. As such, continued research involving the comparison of itaconate and related molecules holds exciting prospects for the study of cysteine modification and pathways for immunomodulation and the potential for new anti-inflammatory therapeutics.
    Keywords:  immunometabolism; infection; inflammation; itaconate; post-translational modification
  2. Cells. 2022 Dec 15. pii: 4072. [Epub ahead of print]11(24):
      Atherosclerosis is a complex metabolic disease characterized by the dysfunction of lipid metabolism and chronic inflammation in the intimal space of the vessel. As the most abundant innate immune cells, monocyte-derived macrophages play a pivotal role in the inflammatory response, cholesterol metabolism, and foam cell formation. In recent decades, it has been demonstrated that monocytes and macrophages can establish innate immune memory (also termed trained immunity) via endogenous and exogenous atherogenic stimuli and exhibit a long-lasting proinflammatory phenotype. The important cellular metabolism processes, including glycolysis, oxidative phosphorylation (OXPHOS), the tricarboxylic acid (TCA) cycle, fatty acid synthesis, and cholesterol synthesis, are reprogrammed. Trained monocytes/macrophages with innate immune memory can be persistently hyperactivated and can undergo extensive epigenetic rewiring, which contributes to the pathophysiological development of atherosclerosis via increased proinflammatory cytokine production and lipid accumulation. Here, we provide an overview of the regulation of cellular metabolic processes and epigenetic modifications of innate immune memory in monocytes/macrophages as well as the potential endogenous and exogenous stimulations involved in the progression of atherosclerosis that have been reported recently. These elucidations might be beneficial for further understanding innate immune memory and the development of therapeutic strategies for inflammatory diseases and atherosclerosis.
    Keywords:  atherosclerosis; epigenetic rewiring; innate immune memory; macrophage; metabolic reprogramming
  3. Cells. 2022 Dec 18. pii: 4113. [Epub ahead of print]11(24):
      Mitochondria engage in multiple cellular and extracellular signaling pathways ranging from metabolic control, antiviral and antibacterial host defense to the modulation of inflammatory responses following cellular damage and stress. The remarkable contributions of these organelles to innate and adaptive immunity, shape cell phenotype and modulate their functions during infection, after trauma and in the setting of inflammatory disease. We review the latest knowledge of mitochondrial biology and then discuss how these organelles may impact immune cells to drive aberrant immune responses in critical disease.
    Keywords:  adaptive immunity; critical illness; immunometabolism; immunosuppression; inflammation; innate immunity; mitochondria; mitochondrial danger-associated-molecular-pattern; trauma
  4. Molecules. 2022 Dec 12. pii: 8801. [Epub ahead of print]27(24):
      Short-chain fatty acids (SCFAs) are important anti-inflammatory metabolites of intestinal flora. Oxidized low-density lipoprotein (ox-LDL)-induced macrophage activation is critical for the formation of atherosclerosis plaque. However, the association between SCFAs and ox-LDL-induced macrophage activation with respect to the formation of atherosclerosis plaque has not yet been elucidated. The present study investigated whether SCFAs (sodium acetate, sodium propionate, and sodium butyrate) can affect ox-LDL-induced macrophage activation and potential signaling pathways via regulation of the expression of the NLRP3/Caspase-1 pathway. Using human monocyte-macrophage (THP-1) cells as a model system, it was observed that ox-LDL not only induced cell inflammatory injury but also activated the NLRP3/Caspase-1 pathway. The exogenous supplementation of three SCFAs could significantly inhibit cell inflammatory injury induced by ox-LDL. Moreover, three SCFAs decreased the expression of IL-1β and TNF-α via the inactivation of the NLRP3/Caspase-1 pathway induced by ox-LDL. Furthermore, three SCFAs affected cellular metabolism in ox-LDL-induced macrophages, as detected by untargeted metabolomics analysis. The results of the present study indicated that three SCFAs inhibited ox-LDL-induced cell inflammatory injury by blocking the NLRP3/Caspase-1 pathway, thereby improving cellular metabolism. These findings may provide novel insights into the role of SCFA intervention in the progression of atherosclerotic plaque formation.
    Keywords:  anti-inflammation; cellular metabolism; metabolomics; oxidized low-density lipoprotein; short chain fatty acids
  5. Antioxidants (Basel). 2022 Dec 08. pii: 2426. [Epub ahead of print]11(12):
      BACKGROUND: CD4+ T cells critically contribute to the initiation and perturbation of inflammation. When CD4+ T cells enter inflamed tissues, they adapt to hypoxia and oxidative stress conditions, and to a reduction in nutrients. We aimed to investigate how this distinct environment regulates T cell responses within the inflamed joints of patients with childhood rheumatism (JIA) by analyzing the behavior of NRF2-the key regulator of the anti-oxidative stress response-and its signaling pathways.METHODS: Flow cytometry and quantitative RT-PCR were used to perform metabolic profiling of T cells and to measure the production of inflammatory cytokines. Loss of function analyses were carried out by means of siRNA transfection experiments. NRF2 activation was induced by treatment with 4-octyl-Itaconate (4-OI).
    RESULTS: Flow cytometry analyses revealed a high metabolic status in CD4+ T cells taken from synovial fluid (SF) with greater mitochondrial mass, and increased glucose and fatty acid uptake. This resulted in a heightened oxidative status of SF CD4+ T cells. Despite raised ROS levels, expression of NRF2 and its target gene NQO1 were lower in CD4+ T cells from SF than in those from blood. Indeed, NRF2 activation of CD4+ T cells downregulated oxidative stress markers, altered the metabolic phenotype and reduced secretion of IFN-γ.
    CONCLUSION: NRF2 could be a potential regulator in CD4+ T cells during chronic inflammation and could instigate a drift toward disease progression or regression, depending on the inflammatory environment.
    Keywords:  JIA; NRF2; ROS; immunometabolism; redox metabolism
  6. J Immunother Cancer. 2022 Dec;pii: e005644. [Epub ahead of print]10(12):
      BACKGROUND: B cells play a pivotal role in regulating the immune response. The induction of B cell-mediated immunosuppressive function requires B cell activating signals. However, the mechanisms by which activated B cells mediate T-cell suppression are not fully understood.METHODS: We investigated the potential contribution of metabolic activity of activated B cells to T-cell suppression by performing in vitro experiments and by analyzing clinical samples using mass cytometry and single-cell RNA sequencing.
    RESULTS: Here we show that following activation, B cells acquire an immunoregulatory phenotype and promote T-cell suppression by metabolic competition. Activated B cells induced hypoxia in T cells in a cell-cell contact dependent manner by consuming more oxygen via an increase in their oxidative phosphorylation (OXPHOS). Moreover, activated B cells deprived T cells of glucose and produced lactic acid through their high glycolytic activity. Activated B cells thus inhibited the mammalian target of rapamycin pathway in T cells, resulting in suppression of T-cell cytokine production and proliferation. Finally, we confirmed the presence of tumor-associated B cells with high glycolytic and OXPHOS activities in patients with melanoma, associated with poor response to immune checkpoint blockade therapy.
    CONCLUSIONS: We have revealed for the first time the immunomodulatory effects of the metabolic activity of activated B cells and their possible role in suppressing antitumor T-cell responses. These findings add novel insights into immunometabolism and have important implications for cancer immunotherapy.
    Keywords:  B-lymphocytes; T-lymphocytes; immunomodulation; immunotherapy; melanoma
  7. Environ Sci Technol. 2022 Dec 22.
      To gather enough energy to respond to harmful stimuli, most immune cells quickly shift their metabolic profile. This process of immunometabolism plays a critical role in the regulation of immune cell function. Triclosan, a synthetic antibacterial component present in a wide range of consumer items, has been shown to cause immunotoxicity in a number of organisms. However, it is unclear whether and how triclosan impacts immunometabolism. Here, human macrophages were used as model cells to explore the modulatory effect of triclosan on immunometabolism. Untargeted metabolomics using integrated liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) revealed that triclosan changed the global metabolic profile of macrophages. Furthermore, Seahorse energy analysis and 13C isotope-based metabolic flux analysis revealed that triclosan decreased mitochondrial respiratory activity and promoted a metabolic transition from oxidative phosphorylation to glycolysis. Triclosan also polarizes macrophages to the proinflammatory M1 phenotype and activates the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing receptor 3 (NLRP3) inflammasome, which is consistent with triclosan-induced metabolic phenotypic modifications. Collectively, these findings showed that triclosan exposure at micromolar concentrations caused metabolic reprogramming in macrophages, which triggered an inflammatory response. These findings are important for understanding the immunotoxicity caused by triclosan, which is necessary for determining the risk posed by triclosan in the environment.
    Keywords:  bioenergetics; ecotoxicology; endocrine disrupting chemicals; energy metabolism; mitochondria
  8. Biomaterials. 2022 Dec 17. pii: S0142-9612(22)00613-5. [Epub ahead of print]293 121973
      Although different metabolic pathways have been associated with distinct macrophage phenotypes, the field of utilizing metabolites to modulate macrophage phenotype is in a nascent stage. In this report, we developed microparticles based on polymerization of alpha-ketoglutarate (a Krebs cycle metabolite), with or without encapsulation of spermine (a polyamine metabolite), to modulate cell phenotype that are critical for resolution of inflammation. Poly (alpha-ketoglutarate) microparticles encapsulated and released spermine (spermine (encap)paKG MPs) in vitro, which was accelerated in an acidic environment. When delivered to bone marrow-derived-macrophages, spermine (encap)paKG MPs induced a complex phenotypic profile outside of the typical M1/M2 paradigm, with distinct effects in the presence or absence of the pro-inflammatory stimulus lipopolysaccharide. Of particular interest was the increase in expression of CD163, which has been linked to anti-inflammatory responses in sepsis. Therefore, we systemically administered spermine (encap)paKG MPs to two different murine models of sepsis using acute or chronic injection of LPS. Macrophages and neutrophils in the liver and spleen of animals treated with spermine (encap)paKG MPs increased expression of CD163, concomitant with normalizing of glycolysis and oxidative phosphorylation, in both models. Overall, these results show that spermine (encap)paKG MPs modulate macrophage phenotype in vitro and in vivo, with potential applications in inflammation-associated diseases.
    Keywords:  Biomaterials; Immunoengineering; Immunometabolism; Macrophages; Sepsis
  9. Pathog Dis. 2022 Dec 19. pii: ftac047. [Epub ahead of print]
      Hypoxia-inducible factor (HIF)1α is a transcription factor involved in cellular metabolism and regulation of immune cell effector functions. Here, we studied the role of HIF1α in myeloid cells during pneumonia caused by the major causative pathogen, Streptococcus pneumoniae (Spneu). Mice deficient for HIF1α in myeloid cells (LysMcreHif1αfl/fl) were generated to study the in vitro responsiveness of bone marrow-derived macrophages (BMDMs) and alveolar macrophages (AMs) to the Gram-positive bacterial wall component lipoteichoic acid (LTA) and heat-killed Spneu, and the in vivo host response after infection with Spneu via the airways. Both BMDMs and AMs released more lactate upon stimulation with LTA or Spneu, indicative of enhanced glycolysis; HIF1α-deficiency in these cells was associated with diminished lactate release. In BMDMs, HIF1α-deficiency resulted in reduced secretion of tumor necrosis factor (TNF)α and interleukin (IL)-6 upon activation with Spneu but not LTA, while HIF1α-deficient AMs secreted less TNFα and IL-6 in response to LTA, and TNFα after Spneu stimulation. However, no difference was found in the host response of LysMcreHif1αfl/fl mice after Spneu infection as compared to controls. Similar in vivo findings were obtained in neutrophil (Mrp8creHif1αfl/fl) HIF1α-deficient mice. These data suggest that myeloid HIF1α is dispensable for the host defense during pneumococcal pneumonia.
    Keywords:   Streptococcus pneumoniae ; Hypoxia-inducible factor 1α; macrophages; neutrophils; pneumonia
  10. Vaccines (Basel). 2022 Dec 12. pii: 2127. [Epub ahead of print]10(12):
      Metabolomics is emerging as a promising tool to understand the effect of immunometabolism for the development of novel host-directed alternative therapies. Immunometabolism can modulate both innate and adaptive immunity in response to pathogens and vaccinations. For instance, infections can affect lipid and amino acid metabolism while vaccines can trigger bile acid and carbohydrate pathways. Metabolomics as a vaccinomics tool, can provide a broader picture of vaccine-induced biochemical changes and pave a path to potentiate the vaccine efficacy. Its integration with other systems biology tools or treatment modes can enhance the cure, response rate, and control over the emergence of drug-resistant strains. Mycobacterium tuberculosis (Mtb) infection can remodel the host metabolism for its survival, while there are many biochemical pathways that the host adjusts to combat the infection. Similarly, the anti-TB vaccine, Bacillus Calmette-Guerin (BCG), was also found to affect the host metabolic pathways thus modulating immune responses. In this review, we highlight the metabolomic schema of the anti-TB vaccine and its therapeutic applications. Rewiring of immune metabolism upon BCG vaccination induces different signaling pathways which lead to epigenetic modifications underlying trained immunity. Metabolic pathways such as glycolysis, central carbon metabolism, and cholesterol synthesis play an important role in these aspects of immunity. Trained immunity and its applications are increasing day by day and it can be used to develop the next generation of vaccines to treat various other infections and orphan diseases. Our goal is to provide fresh insight into this direction and connect various dots to develop a conceptual framework.
    Keywords:  Bacillus Calmette-Guerin; Mycobacterium tuberculosis; epigenetics and immunity; immunometabolism; metabolomics; trained immunity; tuberculosis; vaccine metabolism; vaccinomics
  11. Immunohorizons. 2022 Dec 01. 6(12): 837-850
      Hematopoiesis integrates cytokine signaling, metabolism, and epigenetic modifications to regulate blood cell generation. These processes are linked, as metabolites provide essential substrates for epigenetic marks. In this study, we demonstrate that ATP citrate lyase (Acly), which metabolizes citrate to generate cytosolic acetyl-CoA and is of clinical interest, can regulate chromatin accessibility to limit myeloid differentiation. Acly was tested for a role in murine hematopoiesis by small-molecule inhibition or genetic deletion in lineage-depleted, c-Kit-enriched hematopoietic stem and progenitor cells from Mus musculus. Treatments increased the abundance of cell populations that expressed the myeloid integrin CD11b and other markers of myeloid differentiation. When single-cell RNA sequencing was performed, we found that Acly inhibitor-treated hematopoietic stem and progenitor cells exhibited greater gene expression signatures for macrophages and enrichment of these populations. Similarly, the single-cell assay for transposase-accessible chromatin sequencing showed increased chromatin accessibility at genes associated with myeloid differentiation, including CD11b, CD11c, and IRF8. Mechanistically, Acly deficiency altered chromatin accessibility and expression of multiple C/EBP family transcription factors known to regulate myeloid differentiation and cell metabolism, with increased Cebpe and decreased Cebpa and Cebpb. This effect of Acly deficiency was accompanied by altered mitochondrial metabolism with decreased mitochondrial polarization but increased mitochondrial content and production of reactive oxygen species. The bias to myeloid differentiation appeared due to insufficient generation of acetyl-CoA, as exogenous acetate to support alternate compensatory pathways to produce acetyl-CoA reversed this phenotype. Acly inhibition thus can promote myelopoiesis through deprivation of acetyl-CoA and altered histone acetylome to regulate C/EBP transcription factor family activity for myeloid differentiation.
  12. Life (Basel). 2022 Dec 06. pii: 2034. [Epub ahead of print]12(12):
      Mitochondrial dysfunction and immune cell dysfunction are commonplace in sepsis and are associated with increased mortality risk. The short chain fatty acid, butyrate, is known to have anti-inflammatory effects and promote mitochondrial biogenesis. We therefore explored the immunometabolic effects of butyrate in an animal model of sepsis. Isolated healthy human volunteer peripheral mononuclear cells were stimulated with LPS in the presence of absence of butyrate, and released cytokines measured. Male Wistar rats housed in metabolic cages received either intravenous butyrate infusion or placebo commencing 6 h following faecal peritonitis induction. At 24 h, splenocytes were isolated for high-resolution respirometry, and measurement of mitochondrial membrane potential (MMP), reactive oxygen species (mtROS), and intracellular cytokines (TNF alpha, IL-10) using flow cytometry. Isolated splenocytes from septic and septic butyrate treated rats were stimulated with LPS for 18 h and the effects of butyrate on cytokine release assessed. Ex vivo, butyrate (1.8 mM) reduced LPS-induced TNF alpha (p = 0.019) and IL-10 (p = 0.001) release by human PBMCs. In septic animals butyrate infusion reduced the respiratory exchange ratio (p < 0.001), consistent with increased fat metabolism. This was associated with a reduction in cardiac output (p = 0.001), and increased lactate (p = 0.031) compared to placebo-treated septic animals (p < 0.05). Butyrate treatment was associated with a reduction in splenocyte basal respiration (p = 0.077), proton leak (p = 0.022), and non-mitochondrial respiration (p = 0.055), and an increase in MMP (p = 0.007) and mtROS (p = 0.027) compared to untreated septic animals. Splenocyte intracellular cytokines were unaffected by butyrate, although LPS-induced IL-10 release was impaired (p = 0.039). In summary, butyrate supplementation exacerbates myocardial and immune cell mitochondrial dysfunction in a rat model of faecal peritonitis.
    Keywords:  butyrate; fatty acids; immunity; mitochondria; nutrition; sepsis
  13. J Neuroinflammation. 2022 Dec 17. 19(1): 305
      Saturated very long-chain fatty acids (VLCFA, ≥ C22), enriched in brain myelin and innate immune cells, accumulate in X-linked adrenoleukodystrophy (X-ALD) due to inherited dysfunction of the peroxisomal VLCFA transporter ABCD1. In its severest form, X-ALD causes cerebral myelin destruction with infiltration of pro-inflammatory skewed monocytes/macrophages. How VLCFA levels relate to macrophage activation is unclear. Here, whole transcriptome sequencing of X-ALD macrophages indicated that VLCFAs prime human macrophage membranes for inflammation and increased expression of factors involved in chemotaxis and invasion. When added externally to mimic lipid release in demyelinating X-ALD lesions, VLCFAs did not activate toll-like receptors in primary macrophages. In contrast, VLCFAs provoked pro-inflammatory responses through scavenger receptor CD36-mediated uptake, cumulating in JNK signalling and expression of matrix-degrading enzymes and chemokine release. Following pro-inflammatory LPS activation, VLCFA levels increased also in healthy macrophages. With the onset of the resolution, VLCFAs were rapidly cleared in control macrophages by increased peroxisomal VLCFA degradation through liver-X-receptor mediated upregulation of ABCD1. ABCD1 deficiency impaired VLCFA homeostasis and prolonged pro-inflammatory gene expression upon LPS treatment. Our study uncovers a pivotal role for ABCD1, a protein linked to neuroinflammation, and associated peroxisomal VLCFA degradation in regulating macrophage plasticity.
    Keywords:  Extracellular matrix degradation; Immune response; Lipid metabolism; Neuroinflammation; X-linked adrenoleukodystrophy
  14. Molecules. 2022 Dec 09. pii: 8715. [Epub ahead of print]27(24):
      In recent years, sodium butyrate has gained increased attention for its numerous beneficial properties. However, whether sodium butyrate could alleviate inflammatory damage by macrophage activation and its underlying mechanism remains unclear. The present study used an advanced glycosylation products- (AGEs-) induced inflammatory damage model to study whether sodium butyrate could alleviate oxidative stress, inflammation, and metabolic dysfunction of human monocyte-macrophage originated THP-1 cells in a PI3K-dependent autophagy pathway. The results indicated that sodium butyrate alleviated the AGEs-induced oxidative stress, decreased the level of reactive oxygen species (ROS), increased malondialdehyde (MDA) and mRNA expression of pro-inflammatory cytokines of interleukin (IL)-1β and tumor necrosis factor (TNF)-α, and increased the content of superoxide dismutase (SOD). Sodium butyrate reduced the protein expression of the NLR family, pyrin domain-containing protein 3 (NLRP3) and Caspase-1, and decreased the nucleus expression of nuclear factor-kappaB (NF-κB). Sodium butyrate decreased the expression of light-chain-associated protein B (LC3B) and Beclin-1, and inhibited autophagy. Moreover, sodium butyrate inhibited the activation of the PI3K/Akt pathway in AGEs-induced THP-1 cells. In addition, the metabolomics analysis showed that sodium butyrate could affect the production of phosphatidylcholine, L-glutamic acid, UDP-N-acetylmuraminate, biotinyl-5'-AMP, and other metabolites. In summary, these results revealed that sodium butyrate inhibited autophagy and NLRP3 inflammasome activation by blocking the PI3K/Akt/NF-κB pathway, thereby alleviating oxidative stress, inflammation, and metabolic disorder induced by AGEs.
    Keywords:  advanced glycation end products; cellular metabolism; diabetic nephropathy; inflammatory damage; sodium butyrate
  15. Trends Microbiol. 2022 Dec 17. pii: S0966-842X(22)00322-5. [Epub ahead of print]
      Plant metabolites are critical components of immune signaling pathways; however, how these small molecules contribute to plant immunity remains largely elusive. Emerging evidence demonstrates that the rice nucleotide-binding leucine-rich repeat receptor (NLR)-interacting proteins regulate the biosynthesis of ethylene, hydroxycinnamoylputrescines and diterpenoid phytoalexins to modulate plant immunity.
    Keywords:  Magnaporthe oryzae; immune signaling; metabolism; rice
  16. Biomedicines. 2022 Dec 02. pii: 3113. [Epub ahead of print]10(12):
      Many people infected with the SARS-CoV-2 suffer long-term symptoms, such as "brain fog", fatigue and clotting problems. Explanations for "long COVID" include immune imbalance, incomplete viral clearance and potentially, mitochondrial dysfunction. As conditions with sub-optimal mitochondrial function are associated with initial severity of the disease, their prior health could be key in resistance to long COVID and recovery. The SARs virus redirects host metabolism towards replication; in response, the host can metabolically react to control the virus. Resolution is normally achieved after viral clearance as the initial stress activates a hormetic negative feedback mechanism. It is therefore possible that, in some individuals with prior sub-optimal mitochondrial function, the virus can "tip" the host into a chronic inflammatory cycle. This might explain the main symptoms, including platelet dysfunction. Long COVID could thus be described as a virally induced chronic and self-perpetuating metabolically imbalanced non-resolving state characterised by mitochondrial dysfunction, where reactive oxygen species continually drive inflammation and a shift towards glycolysis. This would suggest that a sufferer's metabolism needs to be "tipped" back using a stimulus, such as physical activity, calorie restriction, or chemical compounds that mimic these by enhancing mitochondrial function, perhaps in combination with inhibitors that quell the inflammatory response.
    Keywords:  Kreb’s cycle; SARS-CoV-2; hormesis; inflammation; lifestyle; long COVID; metabolic flexibility; mitochondria; platelets
  17. Cardiovasc Res. 2022 Dec 20. pii: cvac189. [Epub ahead of print]
      OBJECTIVE: Neutrophil extracellular trap formation (NETosis) increases atherosclerotic plaque vulnerability and athero-thrombosis. However, mechanisms promoting NETosis during atherogenesis are poorly understood. We have shown that cholesterol accumulation due to myeloid cell deficiency of the cholesterol transporters ATP Binding Cassette A1 and G1 (ABCA1/G1) promotes NLRP3 inflammasome activation in macrophages and neutrophils and induces prominent NETosis in atherosclerotic plaques. We investigated whether NETosis is a cell intrinsic effect in neutrophils or is mediated indirectly by cellular crosstalk from macrophages to neutrophils involving IL-1β.METHODS AND RESULTS: We generated mice with neutrophil or macrophage-specific Abca1/g1 deficiency (S100A8CreAbca1fl/flAbcg1fl/fl or CX3CR1CreAbca1fl/flAbcg1fl/fl mice, respectively), and transplanted their bone marrow into low-density lipoprotein receptor knockout mice. We then fed the mice a cholesterol-rich diet. Macrophage, but not neutrophil Abca1/g1 deficiency activated inflammasomes in macrophages and neutrophils, reflected by caspase-1 cleavage, and induced NETosis in plaques. NETosis was suppressed by administering an interleukin (IL)-1β neutralizing antibody. The extent of NETosis in plaques correlated strongly with the degree of neutrophil accumulation, irrespective of blood neutrophil counts, and neutrophil accumulation was decreased by IL-1β antagonism. In vitro, IL-1β or media transferred from Abca1/g1 deficient macrophages increased NETosis in both control and Abca1/Abcg1 deficient neutrophils. This cell-extrinsic effect of IL-1β on NETosis was blocked by an NLRP3 inhibitor.
    CONCLUSIONS: These studies establish a new link between inflammasome mediated IL-1β production in macrophages and NETosis in atherosclerotic plaques. Macrophage-derived IL-1β appears to increase NETosis both by increasing neutrophil recruitment to plaques and by promoting neutrophil NLRP3 inflammasome activation.
  18. Biomolecules. 2022 Dec 11. pii: 1851. [Epub ahead of print]12(12):
      Innate immune cells such as monocytes and macrophages contain high levels of arachidonic acid (AA), part of which can be mobilized during cellular activation for the formation of a vast array of bioactive oxygenated metabolites. Monocytes and macrophages present in inflammatory foci typically incorporate large amounts of AA, not only in membrane phospholipids, but also in neutral lipids such as triacylglycerol. Thus, it was of interest to investigate the metabolic fate of these two AA pools in macrophages. Utilizing a variety of radiolabeling techniques to distinguish the phospholipid and triacylglycerol pools, we show in this paper that during an acute stimulation of the macrophages with yeast-derived zymosan, the membrane phospholipid AA pool acts as the major, if not the only, source of releasable AA. On the contrary, the AA pool in triacylglycerol appears to be used at a later stage, when the zymosan-stimulated response has declined, as a source to replenish the phospholipid pools that were consumed during the activation process. Thus, phospholipids and triacylglycerol play different in roles AA metabolism and dynamics during macrophage activation.
    Keywords:  arachidonic acid; inflammation; membrane phospholipid; monocytes/macrophages; phospholipase A2; triacylglycerol
  19. Cell Metab. 2022 Dec 12. pii: S1550-4131(22)00504-6. [Epub ahead of print]
      Effective therapies are lacking for patients with advanced colorectal cancer (CRC). The CRC tumor microenvironment has elevated metabolic waste products due to altered metabolism and proximity to the microbiota. The role of metabolite waste in tumor development, progression, and treatment resistance is unclear. We generated an autochthonous metastatic mouse model of CRC and used unbiased multi-omic analyses to reveal a robust accumulation of tumoral ammonia. The high ammonia levels induce T cell metabolic reprogramming, increase exhaustion, and decrease proliferation. CRC patients have increased serum ammonia, and the ammonia-related gene signature correlates with altered T cell response, adverse patient outcomes, and lack of response to immune checkpoint blockade. We demonstrate that enhancing ammonia clearance reactivates T cells, decreases tumor growth, and extends survival. Moreover, decreasing tumor-associated ammonia enhances anti-PD-L1 efficacy. These findings indicate that enhancing ammonia detoxification can reactivate T cells, highlighting a new approach to enhance the efficacy of immunotherapies.
    Keywords:  ammonia; cancer metabolism; immunotherapy; tumor microenvironment
  20. Metabolites. 2022 Dec 01. pii: 1205. [Epub ahead of print]12(12):
      The mannose receptor C-type 1 (Mrc1) is a C-type lectin receptor expressed on the immune cells and sinusoidal endothelial cells (ECs) of several tissues, including the bone marrow (BM). Parallel to systemic metabolic alterations and hematopoietic cell proliferation, high-fat diet (HFD) feeding increases the expression of Mrc1 in sinusoidal ECs, thus calling for the investigation of its role in bone marrow cell reprogramming and the metabolic profile during obesity. Mrc1-/- mice and wild-type (WT) littermates were fed an HFD (45% Kcal/diet) for 20 weeks. Weight gain was monitored during the diet regimen and glucose and insulin tolerance were assessed. Extensive flow cytometry profiling, histological, and proteomic analyses were performed. After HFD feeding, Mrc1-/- mice presented impaired medullary hematopoiesis with reduced myeloid progenitors and mature cells in parallel with an increase in BM adipocytes compared to controls. Accordingly, circulating levels of neutrophils and pro-inflammatory monocytes decreased in Mrc1-/- mice together with reduced infiltration of macrophages in the visceral adipose tissue and the liver compared to controls. Liver histological profiling coupled with untargeted proteomic analysis revealed that Mrc1-/- mice presented decreased liver steatosis and the downregulation of proteins belonging to pathways involved in liver dysfunction. This profile was reflected by improved glucose and insulin response and reduced weight gain during HFD feeding in Mrc1-/- mice compared to controls. Our data show that during HFD feeding, mannose receptor deficiency impacts BM and circulating immune cell subsets, which is associated with reduced systemic inflammation and resistance to obesity development.
    Keywords:  Mrc1; bone marrow; inflammation; obesity
  21. iScience. 2022 Dec 22. 25(12): 105683
      Obesity and diabetes are associated with inflammation and altered plasma levels of several metabolites, which may be involved in disease progression. Some metabolites can activate G protein-coupled receptors (GPCRs) expressed on immune cells where they can modulate metabolic inflammation. Here, we find that 3-hydroxydecanoate is enriched in the circulation of obese individuals with type 2 diabetes (T2D) compared with nondiabetic controls. Administration of 3-hydroxydecanoate to mice promotes immune cell recruitment to adipose tissue, which was associated with adipose inflammation and increased fasting insulin levels. Furthermore, we demonstrate that 3-hydroxydecanoate stimulates migration of primary human and mouse neutrophils, but not monocytes, through GPR84 and Gαi signaling in vitro. Our findings indicate that 3-hydroxydecanoate is a T2D-associated metabolite that increases inflammatory responses and may contribute to the chronic inflammation observed in diabetes.
    Keywords:  Cell biology; Immunology; Pathophysiology
  22. Nat Immunol. 2022 Dec 21.
      CD8+ T cells are critical for elimination of cancer cells. Factors within the tumor microenvironment (TME) can drive these cells to a hypofunctional state known as exhaustion. The most terminally exhausted T (tTex) cells are resistant to checkpoint blockade immunotherapy and might instead limit immunotherapeutic efficacy. Here we show that intratumoral CD8+ tTex cells possess transcriptional features of CD4+Foxp3+ regulatory T cells and are similarly capable of directly suppressing T cell proliferation ex vivo. tTex cell suppression requires CD39, which generates immunosuppressive adenosine. Restricted deletion of CD39 in endogenous CD8+ T cells resulted in slowed tumor progression, improved immunotherapy responsiveness and enhanced infiltration of transferred tumor-specific T cells. CD39 is induced on tTex cells by tumor hypoxia, thus mitigation of hypoxia limits tTex suppression. Together, these data suggest tTex cells are an important regulatory population in cancer and strategies to limit their generation, reprogram their immunosuppressive state or remove them from the TME might potentiate immunotherapy.
  23. Nat Metab. 2022 Dec;4(12): 1756-1774
      Microglia continuously survey the brain parenchyma and actively shift status following stimulation. These processes demand a unique bioenergetic programme; however, little is known about the metabolic determinants in microglia. By mining large datasets and generating transgenic tools, here we show that hexokinase 2 (HK2), the most active isozyme associated with mitochondrial membrane, is selectively expressed in microglia in the brain. Genetic ablation of HK2 reduced microglial glycolytic flux and energy production, suppressed microglial repopulation, and attenuated microglial surveillance and damage-triggered migration in male mice. HK2 elevation is prominent in immune-challenged or disease-associated microglia. In ischaemic stroke models, however, HK2 deletion promoted neuroinflammation and potentiated cerebral damages. The enhanced inflammatory responses after HK2 ablation in microglia are associated with aberrant mitochondrial function and reactive oxygen species accumulation. Our study demonstrates that HK2 gates both glycolytic flux and mitochondrial activity to shape microglial functions, changes of which contribute to metabolic abnormalities and maladaptive inflammation in brain diseases.
  24. iScience. 2022 Dec 22. 25(12): 105682
      Chronic inflammation of the immune privileged cornea originating from viral or nonviral conditions results in significant vision loss. Topical corticosteroids are the common treatments for corneal inflammation, but the drugs cause serious and potentially blinding side effects in the long term. Therefore, new standalone and/or synergistic anti-inflammatory therapies with lower side effects are desperately needed. Here, we show that the aromatic fatty acid phenylbutyrate (PBA) acts as a potent inhibitor of inflammation in preclinical ocular-inflammation models. PBA prevents the transcription as well as translation of pro-inflammatory cytokines by LPS and poly(I:C) via persistent inhibition of NF-κB signaling. PBA quickens the resolution of ocular inflammation in mice by decreasing corneal thickness and immune cell infiltration. More importantly, PBA can synergize with the dexamethasone to antagonize NF-κB signaling at lower drug concentrations. Our results demonstrate that PBA therapy exerts previously unreported anti-inflammatory effects in the eye and facilitates corneal healing during persistent inflammation.
    Keywords:  Immune response; Molecular medicine; Ophthalmology
  25. Curr Neuropharmacol. 2022 Dec 16.
      Sepsis-associated encephalopathy (SAE) is a diffuse brain dysfunction caused by sepsis that manifests as a range of brain dysfunctions from delirium to coma. It is a relatively common complication of sepsis associated with poor patient prognosis and mortality. The pathogenesis of SAE involves neuroinflammatory responses, neurotransmitter dysfunction, blood-brain barrier (BBB) disruption, abnormal blood flow regulation, etc. Neuroinflammation caused by hyperactivation of microglia is considered to be a key factor in disease development, which can cause a series of chain reactions, including BBB disruption and oxidative stress. Metabolic reprogramming has been found to play a central role in microglial activation and executive functions. In this review, we describe the pivotal role of energy metabolism in microglial activation and functional execution and demonstrate that the regulation of microglial metabolic reprogramming might be crucial in the development of clinical therapeutics for neuroinflammatory diseases like SAE.
    Keywords:  Metabolic; Microglia; Neuroinflammation; Sepsis-associated encephalopathy
  26. Metabolites. 2022 Dec 14. pii: 1263. [Epub ahead of print]12(12):
      In this study, we demonstrated that chitosan-applied zebrafish (Danio rerio) tissue metabolite alteration, metabolic discrimination, and metabolic phenotypic expression occurred. The spectroscopy of solid-state 1H nuclear magnetic resonance (ss 1H-NMR) has been used. Chitosan has no, or low, toxicity and is a biocompatible biomaterial; however, the metabolite mechanisms underlying the biological effect of chitosan are poorly understood. The zebrafish is now one of the most popular ecotoxicology models. Zebrafish were exposed to chitosan concentrations of 0, 50, 100, 200, and 500 mg/L, and the body tissue was subjected to metabolites-targeted profiling. The zebrafish samples were measured via solvent-suppressed and T2-filtered methods with in vivo zebrafish metabolites. The metabolism of glutamate, glutamine, glutathione (GSH), taurine, trimethylamine (TMA), and its N-oxide (TMAO) is also significantly altered. Here, we report the quantification of metabolites and the biological application of chitosan. The metabolomics profile of chitosan in zebrafish has been detected, and the results indicated disturbed amino acid metabolism, the TCA cycle, and glycolysis. Our results demonstrate the potential of comparative metabolite profiling for discovering bioactive metabolites and they highlight the power of chitosan-applied chemical metabolomics to uncover new biological insights.
    Keywords:  NMR spectroscopy; chitosan; metabolic phenotyping; metabolic profiling; metabolites; metabolomics; zebrafish (Danio rerio)
  27. Metabolites. 2022 Dec 16. pii: 1277. [Epub ahead of print]12(12):
      The complex manifestations of COVID-19 are still not fully decoded on the molecular level. We combined quantitative the nuclear magnetic resonance (NMR) spectroscopy serum analysis of metabolites, lipoproteins and inflammation markers with clinical parameters and a targeted cytokine panel to characterize COVID-19 in a large (534 patient samples, 305 controls) outpatient cohort of recently tested PCR-positive patients. The COVID-19 cohort consisted of patients who were predominantly in the initial phase of the disease and mostly exhibited a milder disease course. Concerning the metabolic profiles of SARS-CoV-2-infected patients, we identified markers of oxidative stress and a severe dysregulation of energy metabolism. NMR markers, such as phenylalanine, inflammatory glycoproteins (Glyc) and their ratio with the previously reported supramolecular phospholipid composite (Glyc/SPC), showed a predictive power comparable to laboratory parameters such as C-reactive protein (CRP) or ferritin. We demonstrated interfaces between the metabolism and the immune system, e.g., we could trace an interleukin (IL-6)-induced transformation of a high-density lipoprotein (HDL) to a pro-inflammatory actor. Finally, we showed that metadata such as age, sex and constitution (e.g., body mass index, BMI) need to be considered when exploring new biomarkers and that adding NMR parameters to existing diagnoses expands the diagnostic toolbox for patient stratification and personalized medicine.
    Keywords:  SARS-CoV-2; biomarker; glycoprotein; inflammation; lipoproteins; metabolomics
  28. Methods Mol Biol. 2023 ;2610 1-16
      Sphingolipids are a critical family of membrane lipids with diverse functions in eukaryotic cells, and a growing body of literature supports that these lipids play essential roles during the lifecycles of viruses. While small molecule inhibitors of sphingolipid synthesis and metabolism are widely used, the advent of CRISPR-based genomic editing techniques allows for nuanced exploration into the manners in which sphingolipids influence various stages of viral infections. Here we describe some of these critical considerations needed in designing studies utilizing genomic editing techniques for manipulating the sphingolipid metabolic pathway, as well as the current body of literature regarding how viruses depend on the products of this pathway. Here, we highlight the ways in which sphingolipids affect viruses as these pathogens interact with and influence their host cell and describe some of the many open questions remaining in the field.
    Keywords:  Ceramide; Genetic editing; Host–pathogen interactions; Lipid metabolism; Sphingolipids; Sphingomyelin; Sphingosine; Sphingosine-1-phosphate; Viral infection; Virus
  29. Eur J Pharmacol. 2022 Dec 16. pii: S0014-2999(22)00584-2. [Epub ahead of print] 175323
      Glutamine, as the most abundant amino acid in the body, participates in the biological synthesis of nucleotides and other non-essential amino acids in the process of cell metabolism. Recent studies showed that glutamine metabolic reprogramming is an important signal during cancer development and progression. This metabolic signature in cancer cells can promote the development of cancer by activating multiple signaling pathways and oncogenes. It can also be involved in tumor immune regulation and promote the development of drug resistance to tumors. In this review, we mainly summarize the role of glutamine metabolic reprogramming in tumors, including the regulation of multiple signaling pathways. We further discussed the promising tumor treatment strategy by targeting glutamine metabolism alone or in combination with chemotherapeutics.
    Keywords:  Glutamine; Multidrug resistance; Tumor immunotherapy; Tumor metabolism
  30. J Immunol. 2022 Dec 21. pii: ji2200592. [Epub ahead of print]
      Cryptococcal meningoencephalitis caused by Cryptococcus neoformans infection is the most common cause of death in HIV/AIDS patients. Macrophages are pivotal for the regulation of immune responses to cryptococcal infection by either playing protective function or facilitating fungal dissemination. However, the mechanisms underlying macrophage responses to C. neoformans remain unclear. To analyze the transcriptomic changes and identify the pathogenic factors of macrophages, we performed a comparative transcriptomic analysis of alveolar macrophage responses during C. neoformans infection. Alveolar macrophages isolated from C. neoformans-infected mice showed dynamic gene expression patterns, with expression change from a protective M1 (classically activated)-like to a pathogenic M2 (alternatively activated)-like phenotype. Arg1, the gene encoding the enzyme arginase 1, was found as the most upregulated gene in alveolar macrophages during the chronic infection phase. The in vitro inhibition of arginase activity resulted in a reduction of cryptococcal phagocytosis, intracellular growth, and proliferation, coupled with an altered macrophage response from pathogenic M2 to a protective M1 phenotype. In an in vitro model of the blood-brain barrier, macrophage-derived arginase was found to be required for C. neoformans invasion of brain microvascular endothelium. Further analysis of the degree of virulence indicated a positive correlation between arginase 1 expression in macrophages and cryptococcal brain dissemination in vivo. Thus, our data suggest that a dynamic macrophage activation that involves arginase expression may contribute to the cryptococcal disease by promoting cryptococcal growth, proliferation, and the invasion to the brain endothelium.