bims-imicid 2023-11-19 papers

bims-imicid

Biomed News

on Immunometabolism of infection, cancer and immune-mediated disease

Issue of 2023–11–19
thirty papers selected by
Dylan Ryan, University of Cambridge

Single-cell CRISPR screens in vivo map T cell fate regulomes in cancer.
Fatty acid desaturation and lipoxygenase pathways support trained immunity.
Glutamine metabolism inhibition has dual immunomodulatory and antibacterial activities against Mycobacterium tuberculosis.
Inflammatory macrophages reprogram to immunosuppression by reducing mitochondrial translation.
Salvage therapy expands highly cytotoxic and metabolically fit resilient CD8+ T cells via ME1 up-regulation.
SMPDL3A links cholesterol metabolism to the cGAS-STING pathway.
Trained immunity induced by high-salt diet impedes stroke recovery.
One-carbon unit supplementation fuels tumor-infiltrating T cells and augments checkpoint blockade.
Myeloid Drp1 Deficiency Limits Revascularization in Ischemic Muscles via Inflammatory Macrophage Polarization and Metabolic Reprograming.
Branched-Chain Amino Acid Accumulation Fuels the Senescence-Associated Secretory Phenotype.
Chicoric acid ameliorates sepsis-induced cardiomyopathy via regulating macrophage metabolism reprogramming.
Lipin-1 restrains macrophage lipid synthesis to promote inflammation resolution.
Autofluorescence imaging of endogenous metabolic cofactors in response to cytokine stimulation of classically activated macrophages.
Plasma Cell Differentiation, Antibody Quality, and Initial Germinal Center B Cell Population Depend on Glucose Influx Rate.
1,25-Dihydroxyvitamin D3 Provides Benefits in Vitiligo Based on Modulation of CD8+ T Cell Glycolysis and Function.
Label-free single-cell live imaging reveals fast metabolic switch in T lymphocytes.
Macrophage metabolism, phenotype, function, and therapy in hepatocellular carcinoma (HCC).
IFN-γ lowers tumor growth by increasing glycolysis and lactate production in a nitric oxide-dependent manner: implications for cancer immunotherapy.
Fiber-deficient diet inhibits colitis through the regulation of the niche and metabolism of a gut pathobiont.
Metabolic predictors of response to immune checkpoint blockade therapy.
Butyrate induces STAT3/HIF-1α/IL-22 signaling via GPCR and HDAC3 inhibition to activate autophagy in head kidney macrophages from turbot (Scophthalmus maximus L.).
A critical role for host-derived cystathionine-β-synthase, in Staphylococcus aureus-induced udder infection.
Sex-based differences in natural killer T cell-mediated protection against diet-induced steatohepatitis in Balb/c mice.
Anti-inflammatory reprogramming of microglia cells by metabolic modulators to counteract neurodegeneration; a new role for Ranolazine.
Glucosamine increases macrophage lipid accumulation by regulating the mammalian target of rapamycin signaling pathway.
Adipose tissue macrophage dysfunction is associated with a breach of vascular integrity in NASH.
Glucocorticoids Impair the 7α-Hydroxycholesterol-Enhanced Innate Immune Response.
Caveolin-1 forms a complex with P2X7 receptor and tunes P2X7-mediated ATP signaling in mouse bone marrow-derived macrophages.
Gonadal hormones impart male-biased behavioral vulnerabilities to immune activation via microglial mitochondrial function.
Intermittent Fasting Attenuates Metabolic-Dysfunction-Associated Steatohepatitis by Enhancing the Hepatic Autophagy-Lysosome Pathway.

Nature. 2023 Nov 15.

Single-cell CRISPR screens in vivo map T cell fate regulomes in cancer.

Peipei Zhou, Hao Shi, Hongling Huang, Xiang Sun, Sujing Yuan, Nicole M Chapman, Jon P Connelly, Seon Ah Lim, Jordy Saravia, Anil Kc, Shondra M Pruett-Miller, Hongbo Chi.

CD8+ cytotoxic T cells (CTLs) orchestrate antitumour immunity and exhibit inherent heterogeneity1,2, with precursor exhausted T (Tpex) cells but not terminally exhausted T (Tex) cells capable of responding to existing immunotherapies3-7. The gene regulatory network that underlies CTL differentiation and whether Tex cell responses can be functionally reinvigorated are incompletely understood. Here we systematically mapped causal gene regulatory networks using single-cell CRISPR screens in vivo and discovered checkpoints for CTL differentiation. First, the exit from quiescence of Tpex cells initiated successive differentiation into intermediate Tex cells. This process is differentially regulated by IKAROS and ETS1, the deficiencies of which dampened and increased mTORC1-associated metabolic activities, respectively. IKAROS-deficient cells accumulated as a metabolically quiescent Tpex cell population with limited differentiation potential following immune checkpoint blockade (ICB). Conversely, targeting ETS1 improved antitumour immunity and ICB efficacy by boosting differentiation of Tpex to intermediate Tex cells and metabolic rewiring. Mechanistically, TCF-1 and BATF are the targets for IKAROS and ETS1, respectively. Second, the RBPJ-IRF1 axis promoted differentiation of intermediate Tex to terminal Tex cells. Accordingly, targeting RBPJ enhanced functional and epigenetic reprogramming of Tex cells towards the proliferative state and improved therapeutic effects and ICB efficacy. Collectively, our study reveals that promoting the exit from quiescence of Tpex cells and enriching the proliferative Tex cell state act as key modalities for antitumour effects and provides a systemic framework to integrate cell fate regulomes and reprogrammable functional determinants for cancer immunity.

DOI: https://doi.org/10.1038/s41586-023-06733-x
Nat Commun. 2023 Nov 15. 14(1): 7385

Fatty acid desaturation and lipoxygenase pathways support trained immunity.

Anaísa V Ferreira, Juan Carlos Alarcon-Barrera, Jorge Domínguez-Andrés, Özlem Bulut, Gizem Kilic, Priya A Debisarun, Rutger J Röring, Hatice N Özhan, Eva Terschlüsen, Athanasios Ziogas, Sarantos Kostidis, Yassene Mohammed, Vasiliki Matzaraki, George Renieris, Evangelos J Giamarellos-Bourboulis, Mihai G Netea, Martin Giera.

Infections and vaccines can induce enhanced long-term responses in innate immune cells, establishing an innate immunological memory termed trained immunity. Here, we show that monocytes with a trained immunity phenotype, due to exposure to the Bacillus Calmette-Guérin (BCG) vaccine, are characterized by an increased biosynthesis of different lipid mediators (LM) derived from long-chain polyunsaturated fatty acids (PUFA). Pharmacological and genetic approaches show that long-chain PUFA synthesis and lipoxygenase-derived LM are essential for the BCG-induced trained immunity responses of human monocytes. Furthermore, products of 12-lipoxygenase activity increase in monocytes of healthy individuals after BCG vaccination. Grasping the underscoring lipid metabolic pathways contributes to our understanding of trained immunity and may help to identify therapeutic tools and targets for the modulation of innate immune responses.

DOI: https://doi.org/10.1038/s41467-023-43315-x
Nat Commun. 2023 Nov 16. 14(1): 7427

Glutamine metabolism inhibition has dual immunomodulatory and antibacterial activities against Mycobacterium tuberculosis.

Sadiya Parveen, Jessica Shen, Shichun Lun, Liang Zhao, Jesse Alt, Benjamin Koleske, Robert D Leone, Rana Rais, Jonathan D Powell, John R Murphy, Barbara S Slusher, William R Bishai.

As one of the most successful human pathogens, Mycobacterium tuberculosis (Mtb) has evolved a diverse array of determinants to subvert host immunity and alter host metabolic patterns. However, the mechanisms of pathogen interference with host metabolism remain poorly understood. Here we show that a glutamine metabolism antagonist, JHU083, inhibits Mtb proliferation in vitro and in vivo. JHU083-treated mice exhibit weight gain, improved survival, a 2.5 log lower lung bacillary burden at 35 days post-infection, and reduced lung pathology. JHU083 treatment also initiates earlier T-cell recruitment, increased proinflammatory myeloid cell infiltration, and a reduced frequency of immunosuppressive myeloid cells when compared to uninfected and rifampin-treated controls. Metabolomic analysis of lungs from JHU083-treated Mtb-infected mice reveals citrulline accumulation, suggesting elevated nitric oxide (NO) synthesis, and lowered levels of quinolinic acid which is derived from the immunosuppressive metabolite kynurenine. JHU083-treated macrophages also produce more NO potentiating their antibacterial activity. When tested in an immunocompromised mouse model of Mtb infection, JHU083 loses its therapeutic efficacy suggesting the drug's host-directed effects are likely to be predominant. Collectively, these data reveal that JHU083-mediated glutamine metabolism inhibition results in dual antibacterial and host-directed activity against tuberculosis.

DOI: https://doi.org/10.1038/s41467-023-43304-0
Nat Commun. 2023 Nov 17. 14(1): 7471

Inflammatory macrophages reprogram to immunosuppression by reducing mitochondrial translation.

Marlies Cortés, Agnese Brischetto, M C Martinez-Campanario, Chiara Ninfali, Verónica Domínguez, Sara Fernández, Raquel Celis, Anna Esteve-Codina, Juan J Lozano, Julia Sidorova, Gloria Garrabou, Anna-Maria Siegert, Carlos Enrich, Belén Pintado, Manuel Morales-Ruiz, Pedro Castro, Juan D Cañete, Antonio Postigo.

Acute inflammation can either resolve through immunosuppression or persist, leading to chronic inflammation. These transitions are driven by distinct molecular and metabolic reprogramming of immune cells. The anti-diabetic drug Metformin inhibits acute and chronic inflammation through mechanisms still not fully understood. Here, we report that the anti-inflammatory and reactive-oxygen-species-inhibiting effects of Metformin depend on the expression of the plasticity factor ZEB1 in macrophages. Using mice lacking Zeb1 in their myeloid cells and human patient samples, we show that ZEB1 plays a dual role, being essential in both initiating and resolving inflammation by inducing macrophages to transition into an immunosuppressed state. ZEB1 mediates these diverging effects in inflammation and immunosuppression by modulating mitochondrial content through activation of autophagy and inhibition of mitochondrial protein translation. During the transition from inflammation to immunosuppression, Metformin mimics the metabolic reprogramming of myeloid cells induced by ZEB1. Mechanistically, in immunosuppression, ZEB1 inhibits amino acid uptake, leading to downregulation of mTORC1 signalling and a decrease in mitochondrial translation in macrophages. These results identify ZEB1 as a driver of myeloid cell metabolic plasticity, suggesting that targeting its expression and function could serve as a strategy to modulate dysregulated inflammation and immunosuppression.

DOI: https://doi.org/10.1038/s41467-023-42277-4
Sci Adv. 2023 Nov 17. 9(46): eadi2414

Salvage therapy expands highly cytotoxic and metabolically fit resilient CD8+ T cells via ME1 up-regulation.

Joanina K Gicobi, Zhiming Mao, Grace DeFranco, Jacob B Hirdler, Ying Li, Vianca V Vianzon, Emilia R Dellacecca, Michelle A Hsu, Whitney Barham, Yiyi Yan, Aaron S Mansfield, Yi Lin, Xiaosheng Wu, Taro Hitosugi, Dawn Owen, Michael P Grams, Jacob J Orme, Fabrice Lucien, Hu Zeng, Sean S Park, Haidong Dong.

Patients with advanced cancers who either do not experience initial response to or progress while on immune checkpoint inhibitors (ICIs) receive salvage radiotherapy to reduce tumor burden and tumor-related symptoms. Occasionally, some patients experience substantial global tumor regression with a rebound of cytotoxic CD8+ T cells. We have termed the rebound of cytotoxic CD8+ T cells in response to salvage therapy as T cell resilience and examined the underlying mechanisms of resilience. Resilient T cells are enriched for CX3CR1+ CD8+ T cells with low mitochondrial membrane potential, accumulate less reactive oxygen species (ROS), and express more malic enzyme 1 (ME1). ME1 overexpression enhanced the cytotoxicity and expansion of effector CD8+ T cells partially via the type I interferon pathway. ME1 also increased mitochondrial respiration while maintaining the redox state balance. ME1 increased the cytotoxicity of peripheral lymphocytes from patients with advanced cancers. Thus, preserved resilient T cells in patients rebound after salvage therapy and ME1 enhances their resiliency.

DOI: https://doi.org/10.1126/sciadv.adi2414
Immunity. 2023 Nov 14. pii: S1074-7613(23)00455-7. [Epub ahead of print]56(11): 2459-2461

SMPDL3A links cholesterol metabolism to the cGAS-STING pathway.

Heegwon Shin, Hachung Chung.

Liver X receptor (LXR), well known for its role in cholesterol metabolism, also has anti-inflammatory properties. In this issue of Immunity, Hou et al. demonstrate that LXR signaling induces SMPDL3A, a cGAMP-degrading enzyme that restricts cGAS-cGAMP-STING innate immune signaling, providing a mechanistic link between lipid metabolism and inflammation.

DOI: https://doi.org/10.1016/j.immuni.2023.10.015
EMBO Rep. 2023 Nov 15. e57164

Trained immunity induced by high-salt diet impedes stroke recovery.

Tze-Yen Lin, Danye Jiang, Wan-Ru Chen, Jhih Syuan Lin, Xin-Yu Zhang, Chih-Hung Chen, Chia-Lang Hsu, Liang-Chuan Lai, Ping-Hung Chen, Kai-Chien Yang, Lauren H Sansing, Che-Feng Chang.

  A high-salt diet (HSD) elicits sustained sterile inflammation and worsens tissue injury. However, how this occurs after stroke, a leading cause of morbidity and mortality, remains unknown. Here, we report that HSD impairs long-term brain recovery after intracerebral hemorrhage, a severe form of stroke, despite salt withdrawal prior to the injury. Mechanistically, HSD induces innate immune priming and training in hematopoietic stem and progenitor cells (HSPCs) by downregulation of NR4a family and mitochondrial oxidative phosphorylation. This training compromises alternative activation of monocyte-derived macrophages (MDMs) without altering the initial inflammatory responses of the stroke brain. Healthy mice transplanted with bone marrow from HSD-fed mice retain signatures of reduced MDM reparative functions, further confirming a persistent form of innate immune memory that originates in the bone marrow. Loss of NR4a1 in macrophages recapitulates HSD-induced negative impacts on stroke outcomes while gain of NR4a1 enables stroke recovery in HSD animals. Together, we provide the first evidence that links HSD-induced innate immune memory to the acquisition of persistent dysregulated inflammatory responses and unveils NR4a1 as a potential therapeutic target.

Keywords:  high-salt diet; intracerebral hemorrhage; macrophages; nr4a1; trained immunity

DOI:  https://doi.org/10.15252/embr.202357164
bioRxiv. 2023 Nov 03. pii: 2023.11.01.565193. [Epub ahead of print]

One-carbon unit supplementation fuels tumor-infiltrating T cells and augments checkpoint blockade.

Xincheng Xu, Zihong Chen, Caroline R Bartman, Xi Xing, Kellen Olszewski, Joshua D Rabinowitz.

Nucleotides perform important metabolic functions, carrying energy and feeding nucleic acid synthesis. Here, we use isotope tracing-mass spectrometry to quantitate the contributions to purine nucleotides of salvage versus de novo synthesis. We further explore the impact of augmenting a key precursor for purine synthesis, one-carbon (1C) units. We show that tumors and tumor-infiltrating T cells (relative to splenic T cells) synthesize purines de novo . Purine synthesis requires two 1C units, which come from serine catabolism and circulating formate. Shortage of 1C units is a potential bottleneck for anti-tumor immunity. Elevating circulating formate drives its usage by tumor-infiltrating T cells. Orally administered methanol functions as a formate pro-drug, with deuteration enabling control of formate-production kinetics. In MC38 tumors, safe doses of methanol raise formate levels and augment anti-PD-1 checkpoint blockade, tripling durable regressions. Thus, 1C deficiency can gate antitumor immunity and this metabolic checkpoint can be overcome with pharmacological 1C supplementation.
Statement of significance: Checkpoint blockade has revolutionized cancer therapy. Durable tumor control, however, is achieved in only a minority of patients. We show that the efficacy of anti-PD-1 blockade can be enhanced by metabolic supplementation with one-carbon donors. Such donors support nucleotide synthesis in tumor-infiltrating T cells and merit future clinical evaluation.

DOI: https://doi.org/10.1101/2023.11.01.565193
bioRxiv. 2023 Nov 05. pii: 2023.11.04.565656. [Epub ahead of print]

Myeloid Drp1 Deficiency Limits Revascularization in Ischemic Muscles via Inflammatory Macrophage Polarization and Metabolic Reprograming.

Shikha Yadav, Vijay Ganta, Varadarajan Sudhahar, Dipankar Ash, Sheela Nagarkoti, Archita Das, Margorzata McMenamin, Stephanie Kelley, Tohru Fukai, Masuko Ushio-Fukai.

In the preclinical model of peripheral arterial disease (PAD), M2-like anti-inflammatory macrophage polarization and angiogenesis are required for revascularization. The regulation of cell metabolism and inflammation in macrophages is tightly linked to mitochondrial dynamics. Drp1, a mitochondrial fission protein, has shown context-dependent macrophage phenotypes with both pro- and anti-inflammatory characteristics. However, the role of macrophage Drp1 in reparative neovascularization remains unexplored. Here we show that Drp1 expression was significantly increased in F4/80+ macrophages within ischemic muscle at day 3 following hindlimb ischemia (HLI), an animal model of PAD. Myeloid-specific Drp1 -/- mice exhibited reduced limb perfusion recovery, angiogenesis and muscle regeneration after HLI. These effects were concomitant with enhancement of pro-inflammatory M1-like macrophages, p-NFkB, and TNFα levels, while showing reduction in anti-inflammatory M2-like macrophages and p-AMPK in ischemic muscle of myeloid Drp1 -/- mice. In vitro, Drp1 -/- macrophages under hypoxia serum starvation (HSS), an in vitro PAD model, demonstrated enhanced glycolysis via reducing p-AMPK as well as mitochondrial dysfunction and excessive mitochondrial ROS, resulting in increased M1-gene and reduced M2-gene expression. Conditioned media from HSS-treated Drp1 -/- macrophages exhibited increased secretion of pro-inflammatory cytokines and suppressed angiogenic responses in cultured endothelial cells. Thus, Drp1 deficiency in macrophages under ischemia drives inflammatory metabolic reprogramming and macrophage polarization, thereby limiting revascularization in experimental PAD.

DOI: https://doi.org/10.1101/2023.11.04.565656
Adv Sci (Weinh). 2023 Nov 15. e2303489

Branched-Chain Amino Acid Accumulation Fuels the Senescence-Associated Secretory Phenotype.

Yaosi Liang, Christopher Pan, Tao Yin, Lu Wang, Xia Gao, Ergang Wang, Holly Quang, De Huang, Lianmei Tan, Kun Xiang, Yu Wang, Peter B Alexander, Qi-Jing Li, Tso-Pang Yao, Zhao Zhang, Xiao-Fan Wang.

  The essential branched-chain amino acids (BCAAs) leucine, isoleucine, and valine play critical roles in protein synthesis and energy metabolism. Despite their widespread use as nutritional supplements, BCAAs' full effects on mammalian physiology remain uncertain due to the complexities of BCAA metabolic regulation. Here a novel mechanism linking intrinsic alterations in BCAA metabolism is identified to cellular senescence and the senescence-associated secretory phenotype (SASP), both of which contribute to organismal aging and inflammation-related diseases. Altered BCAA metabolism driving the SASP is mediated by robust activation of the BCAA transporters Solute Carrier Family 6 Members 14 and 15 as well as downregulation of the catabolic enzyme BCAA transaminase 1 during onset of cellular senescence, leading to highly elevated intracellular BCAA levels in senescent cells. This, in turn, activates the mammalian target of rapamycin complex 1 (mTORC1) to establish the full SASP program. Transgenic Drosophila models further indicate that orthologous BCAA regulators are involved in the induction of cellular senescence and age-related phenotypes in flies, suggesting evolutionary conservation of this metabolic pathway during aging. Finally, experimentally blocking BCAA accumulation attenuates the inflammatory response in a mouse senescence model, highlighting the therapeutic potential of modulating BCAA metabolism for the treatment of age-related and inflammatory diseases.

Keywords:  BCAA; SASP; age-related inflammation; mTORC1; senescence

DOI:  https://doi.org/10.1002/advs.202303489
Phytomedicine. 2023 Oct 31. pii: S0944-7113(23)00534-2. [Epub ahead of print]123 155175

Chicoric acid ameliorates sepsis-induced cardiomyopathy via regulating macrophage metabolism reprogramming.

Hai-Jian Sun, Guan-Li Zheng, Zi-Chao Wang, Yao Liu, Neng Bao, Ping-Xi Xiao, Qing-Bo Lu, Ji-Ru Zhang.

   BACKGROUND: Sepsis-related cardiac dysfunction is believed to be a primary cause of high morbidity and mortality. Metabolic reprogramming is closely linked to NLRP3 inflammasome activation and dysregulated glycolysis in activated macrophages, leading to inflammatory responses in septic cardiomyopathy. Succinate dehydrogenase (SDH) and succinate play critical roles in the progression of metabolic reprogramming in macrophages. Inhibition of SDH may be postulated as an effective strategy to attenuate macrophage activation and sepsis-induced cardiac injury.
PURPOSE: This investigation was designed to examine the role of potential compounds that target SDH in septic cardiomyopathy and the underlying mechanisms involved.
METHODS/RESULTS: From a small molecule pool containing about 179 phenolic compounds, we found that chicoric acid (CA) had the strongest ability to inhibit SDH activity in macrophages. Lipopolysaccharide (LPS) exposure stimulated SDH activity, succinate accumulation and superoxide anion production, promoted mitochondrial dysfunction, and induced the expression of hypoxia-inducible factor-1α (HIF-1α) in macrophages, while CA ameliorated these changes. CA pretreatment reduced glycolysis by elevating the NAD+/NADH ratio in activated macrophages. In addition, CA promoted the dissociation of K(lysine) acetyltransferase 2A (KAT2A) from α-tubulin, and thus reducing α-tubulin acetylation, a critical event in the assembly and activation of NLRP3 inflammasome. Overexpression of KAT2A neutralized the effects of CA, indicating that CA inactivated NLRP3 inflammasome in a specific manner that depended on KAT2A inhibition. Importantly, CA protected the heart against endotoxin insult and improved sepsis-induced cardiac mitochondrial structure and function disruption. Collectively, CA downregulated HIF-1α expression via SDH inactivation and glycolysis downregulation in macrophages, leading to NLRP3 inflammasome inactivation and the improvement of sepsis-induced myocardial injury.
CONCLUSION: These results highlight the therapeutic role of CA in the resolution of sepsis-induced cardiac inflammation.

Keywords:  Cardiac injury; Chicoric acid; Lipopolysaccharides; Macrophages; NLRP3; Sepsis

DOI:  https://doi.org/10.1016/j.phymed.2023.155175
bioRxiv. 2023 Oct 25. pii: 2023.10.23.563587. [Epub ahead of print]

Lipin-1 restrains macrophage lipid synthesis to promote inflammation resolution.

Temitayo T Bamgbose, Robert M Schilke, Oluwakemi O Igiehon, Ebubechukwu H Nkadi, David Custis, Sushma Bharrhan, Benjamin Schwarz, Eric Bohrnsen, Catharine M Bosio, Rona S Scott, Arif Yurdagul, Brian N Finck, Matthew D Woolard.

Macrophages are critical to maintaining and restoring tissue homeostasis during inflammation. The lipid metabolic state of macrophages influences their function, but a deeper understanding of how lipid metabolism is regulated in pro-resolving macrophage responses is needed. Lipin-1 is a phosphatidic acid phosphatase with a transcriptional coregulatory activity (TC) that regulates lipid metabolism. We previously demonstrated that lipin-1 supports pro-resolving macrophage responses, and here, myeloid-associated lipin-1 is required for inflammation resolution, yet how lipin-1-regulated cellular mechanisms promote macrophage pro-resolution responses is unknown. We demonstrated that the loss of lipin-1 in macrophages led to increased free fatty acid, neutral lipid, and ceramide content and increased phosphorylation of acetyl-CoA carboxylase. The inhibition of the first step of lipid synthesis and transport of citrate from the mitochondria in macrophages reduced lipid content and restored efferocytosis and inflammation resolution in lipin-1 m KO macrophages and mice. Our findings suggest macrophage-associated lipin-1 restrains lipid synthesis, promoting pro-resolving macrophage function in response to pro-resolving stimuli.
Teaser: Lipin 1 blockade of lipid biosynthesis inducing mitochondrial citrate export promotes efferocytosis and inflammation resolution.

DOI: https://doi.org/10.1101/2023.10.23.563587
Cancer Metab. 2023 Nov 13. 11(1): 22

Autofluorescence imaging of endogenous metabolic cofactors in response to cytokine stimulation of classically activated macrophages.

Shelby N Bess, Matthew J Igoe, Abby C Denison, Timothy J Muldoon.

   BACKGROUND: Macrophages are one of the most prevalent subsets of immune cells within the tumor microenvironment and perform a range of functions depending on the cytokines and chemokines released by surrounding cells and tissues. Recent research has revealed that macrophages can exhibit a spectrum of phenotypes, making them highly plastic due to their ability to alter their physiology in response to environmental cues. Recent advances in examining heterogeneous macrophage populations include optical metabolic imaging, such as fluorescence lifetime imaging (FLIM), and multiphoton microscopy. However, the method of detection for these systems is reliant upon the coenzymes NAD(P)H and FAD, which can be affected by factors other than cytoplasmic metabolic changes. In this study, we seek to validate these optical measures of metabolism by comparing optical results to more standard methods of evaluating cellular metabolism, such as extracellular flux assays and the presence of metabolic intermediates.
METHODS: Here, we used autofluorescence imaging of endogenous metabolic co-factors via multiphoton microscopy and FLIM in conjunction with oxygen consumption rate and extracellular acidification rate through Seahorse extracellular flux assays to detect changes in cellular metabolism in quiescent and classically activated macrophages in response to cytokine stimulation.
RESULTS: Based on our Seahorse XFP flux analysis, M0 and M1 macrophages exhibit comparable trends in oxygen consumption rate (OCR) and extracellular acidification rate (ECAR). Autofluorescence imaging of M0 and M1 macrophages was not only able to show acute changes in the optical redox ratio from pre-differentiation (0 hours) to 72 hours post-cytokine differentiation (M0: 0.320 to 0.258 and M1: 0.316 to 0.386), mean NADH lifetime (M0: 1.272 ns to 1.379 ns and M1: 1.265 ns to 1.206 ns), and A1/A2 ratio (M0: 3.452 to ~ 4 and M1: 3.537 to 4.529) but could also detect heterogeneity within each macrophage population.
CONCLUSIONS: Overall, the findings of this study suggest that autofluorescence metabolic imaging could be a reliable technique for longitudinal tracking of immune cell metabolism during activation post-cytokine stimulation.

Keywords:  Autofluorescence imaging; Lactate; Macrophage; Metabolism; NADH; Seahorse extracellular flux; Succinate

DOI:  https://doi.org/10.1186/s40170-023-00325-z
J Immunol. 2023 Nov 13. pii: ji2200756. [Epub ahead of print]

Plasma Cell Differentiation, Antibody Quality, and Initial Germinal Center B Cell Population Depend on Glucose Influx Rate.

Shawna K Brookens, Sung Hoon Cho, Yeeun Paik, Kaylor Meyer, Ariel L Raybuck, Chloe Park, Dalton L Greenwood, Jeffrey C Rathmell, Mark R Boothby.

Serum Ab concentrations, selection for higher affinity BCRs, and generation of higher Ab affinities are important elements of immune response optimization and functions of germinal center (GC) reactions. B cell proliferation requires nutrients to support the anabolism inherent in clonal expansion. Glucose usage by mouse GC B cells has been reported to contribute little to their energy needs, with questions raised as to whether glucose uptake or glycolysis increases in GC B cells compared with their naive precursors. Indeed, metabolism can be highly flexible, such that supply shortage along one pathway may be compensated by increased flux on others. We now show that reduction of the glucose transporter GLUT1 in mice after establishment of a preimmune B cell repertoire, even after initiation of the GC B cell gene expression program, decreased initial GC B cell population numbers, affinity maturation, and plasma cell outputs. Glucose oxidation was heightened in GC B cells, but this hexose flowed more into the pentose phosphate pathway, whose activity was important in controlling reactive oxygen species (ROS) and Ab-secreting cell production. In modeling how glucose usage by B cells promotes the Ab response, the control of ROS appeared insufficient. Surprisingly, the combination of galactose, which mitigated ROS, with provision of mannose, an efficient precursor to glycosylation, supported robust production of and normal Ab secretion by Ab-secreting cells under glucose-free conditions. Collectively, the findings indicate that GCs depend on normal glucose influx, especially in plasma cell production, but reveal an unexpected metabolic flexibility in hexose requirements.

DOI: https://doi.org/10.4049/jimmunol.2200756
Nutrients. 2023 Nov 06. pii: 4697. [Epub ahead of print]15(21):

1,25-Dihydroxyvitamin D3 Provides Benefits in Vitiligo Based on Modulation of CD8+ T Cell Glycolysis and Function.

Yujia Wei, Tingmei Wang, Xiaoqi Nie, Zeqi Shi, Zhong Liu, Ying Zeng, Ronghua Pan, Ri Zhang, Yunhua Deng, Dong Li.

  Vitiligo is a common autoimmune skin disease caused by autoreactive CD8+ T cells. The diverse effects of 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] on immune cell metabolism and proliferation have made it an interesting candidate as a supporting therapeutic option in various autoimmune diseases. This study aimed to elucidate the immunomodulatory effects of 1,25(OH)₂D₃ in vitiligo. Cross-sectional relationships between serum 1,25(OH)₂D₃ levels and disease characteristics were investigated in 327 patients with vitiligo. The immunomodulatory and therapeutic effects of 1,25(OH)₂D₃ were then investigated in vivo and in vitro, respectively. We found that 1,25(OH)₂D₃ deficiency was associated with hyperactivity of CD8+ T cells in the vitiligo cohort. In addition, 1,25(OH)₂D₃ suppressed glycolysis by activating the AMP-activated protein kinase (AMPK) signaling pathway, thereby inhibiting the proliferation, cytotoxicity and aberrant activation of CD8+ T cells. Finally, the in vivo administration of 1,25(OH)₂D₃ to melanocyte-associated vitiligo (MAV) mice reduced the infiltration and function of CD8+ T cells and promoted repigmentation. In conclusion, 1,25(OH)₂D₃ may serve as an essential biomarker of the progression and severity of vitiligo. The modulation of autoreactive CD8+ T cell function and glycolysis by 1,25(OH)₂D₃ may be a novel approach for treating vitiligo.

Keywords:  CD8+ T cells; glycolysis; vitamin D; vitiligo

DOI:  https://doi.org/10.3390/nu15214697
Mol Biol Cell. 2023 Nov 16. mbcE23010009

Label-free single-cell live imaging reveals fast metabolic switch in T lymphocytes.

Noémie Paillon, Thi Phuong Lien Ung, Stéphanie Dogniaux, Chiara Stringari, Claire Hivroz.

T cell activation induces a metabolic switch generating energy for proliferation, survival, and functions. We used non-invasive label-free two-photon fluorescence lifetime microscopy (2P-FLIM) to map the spatial and temporal dynamics of the metabolic NAD(P)H co-enzyme during T lymphocyte activation. This provides a readout of the OXPHOS and glycolysis rates at a single cell level. Analyzes were performed in the CD4+ leukemic T cell line Jurkat, and in human CD4+ primary T cells. Cells were activated on glass surfaces coated with activating antibodies mimicking immune synapse formation. Comparing the fraction of bound NAD(P)H between resting and activated T cells, we show that T cell activation induces a rapid switch toward glycolysis. This occurs after 10 minutes and remains stable for one hour. Three-dimensional analyzes revealed that the intracellular distribution of fraction of bound NAD(P)H increases at the immune synapse in activated cells. Finally, we show that fraction of bound NAD(P)H tends to negatively correlate with spreading of activated T cells, suggesting a link between actin remodeling and metabolic changes. This study highlights that 2P-FLIM measurement of fraction of bound NAD(P)H is well suited to follow a fast metabolic switch in 3D, in single T lymphocytes with subcellular resolution.

DOI: https://doi.org/10.1091/mbc.E23-01-0009
J Transl Med. 2023 Nov 15. 21(1): 815

Macrophage metabolism, phenotype, function, and therapy in hepatocellular carcinoma (HCC).

Jingquan Huang, Qiulin Wu, David A Geller, Yihe Yan.

  The pivotal role of the tumor microenvironment (TME) in the initiation and advancement of hepatocellular carcinoma (HCC) is widely acknowledged, as it fosters the proliferation and metastasis of HCC cells. Within the intricate TME of HCC, tumor-associated macrophages (TAMs) represent a significant constituent of non-malignant cells. TAMs engage in direct communication with cancer cells in HCC, while also exerting influence on other immune cells to adopt a tumor-supportive phenotype that facilitates tumor progression. Among the multifaceted mechanisms at play, the metabolic reprogramming of both tumor cells and macrophages leads to phenotypic alterations and functional modifications in macrophages. This comprehensive review elucidates the intricate interplay between cellular metabolism and macrophage phenotype/polarization, while also providing an overview of the associated signaling molecules and potential therapeutic strategies for HCC.

Keywords:  Function; Hepatocellular carcinoma; Macrophage; Metabolism; Phenotype; Tumor microenvironment

DOI:  https://doi.org/10.1186/s12967-023-04716-0
Front Immunol. 2023 ;14 1282653

IFN-γ lowers tumor growth by increasing glycolysis and lactate production in a nitric oxide-dependent manner: implications for cancer immunotherapy.

Avik Chattopadhyay, Sirisha Jagdish, Aagosh Kishor Karhale, Nikita S Ramteke, Arsha Zaib, Dipankar Nandi.

   Introduction: Interferon-gamma (IFN-γ), the sole member of the type-II interferon family, is well known to protect the host from infectious diseases as well as mount anti-tumor responses. The amounts of IFN-γ in the tumor microenvironment determine the host responses against tumors; however, several tumors employ evasive strategies by responding to low IFN-γ signaling.
Methods: In this study, the response of various tumor cell lines to IFN-γ was studied in vitro.
Results: IFN-γ-activation increases glycolytic flux and reduces mitochondrial function in a nitric oxide (NO)- and reactive oxygen species (ROS)-dependent manner in the H6 hepatoma tumor cell line. The higher glycolysis further fueled NO and ROS production, indicating a reciprocal regulation. These processes are accompanied by Hypoxia inducing factor (HIF)-1α stabilization and HIF-1α-dependent augmentation of the glycolytic flux. The IFN-γ enhancement of lactate production also occurred in other NO-producing cell lines: RAW 264.7 monocyte/macrophage and Renca renal adenocarcinoma. However, two other tumor cell lines, CT26 colon carcinoma and B16F10 melanoma, did not produce NO and lactate upon IFN-γ-activation. HIF-1α stabilization upon IFN-γ-activation led to lower cell growth of B16F10 but not CT26 cells. Importantly, the IFN-γ-activation of both CT26 and B16F10 cells demonstrated significant cellular growth reduction upon metabolic rewiring by exogenous administration of potassium lactate.
Discussion: Clinical studies have shown the crucial roles of IFN-γ for successful cancer immunotherapies involving checkpoint inhibitors and chimeric antigen receptor T cells. The positive implications of this study on the metabolic modulation of IFN-γ activation on heterogeneous tumor cells are discussed.

Keywords:  HIF-1 alpha; interferon-gamma; lactate; nitric oxide; tumor

DOI:  https://doi.org/10.3389/fimmu.2023.1282653
Cell Host Microbe. 2023 Nov 08. pii: S1931-3128(23)00420-1. [Epub ahead of print]

Fiber-deficient diet inhibits colitis through the regulation of the niche and metabolism of a gut pathobiont.

Peter Kuffa, Joseph M Pickard, Austin Campbell, Misa Yamashita, Sadie R Schaus, Eric C Martens, Thomas M Schmidt, Naohiro Inohara, Gabriel Núñez, Roberta Caruso.

  Exclusive enteral nutrition (EEN) with fiber-free diets is an effective steroid-sparing treatment to induce clinical remission in children with Crohn's disease (CD). However, the mechanism underlying the beneficial effects of EEN remains obscure. Using a model of microbiota-dependent colitis with the hallmarks of CD, we find that the administration of a fiber-free diet prevents the development of colitis and inhibits intestinal inflammation in colitic animals. Remarkably, fiber-free diet alters the intestinal localization of Mucispirillum schaedleri, a mucus-dwelling pathobiont, which is required for triggering disease. Mechanistically, the absence of dietary fiber reduces nutrient availability and impairs the dissimilatory nitrate reduction to ammonia (DNRA) metabolic pathway of Mucispirillum, leading to its exclusion from the mucus layer and disease remission. Thus, appropriate localization of the specific pathobiont in the mucus layer is critical for disease development, which is disrupted by fiber exclusion. These results suggest strategies to treat CD by targeting the intestinal niche and metabolism of disease-causing microbes.

Keywords:  Crohn’s disease; Mucispirillum schaedleri; Ruminococcus torques; dissimilatory nitrate reduction to ammonia; exclusive enteral nutrition; fiber-free diet; mucus-dwelling pathobiont

DOI:  https://doi.org/10.1016/j.chom.2023.10.016
iScience. 2023 Nov 17. 26(11): 108188

Metabolic predictors of response to immune checkpoint blockade therapy.

Ofir Shorer, Keren Yizhak.

  Metabolism of immune cells in the tumor microenvironment (TME) plays a critical role in cancer patient response to immune checkpoint inhibitors (ICI). Yet, a metabolic characterization of immune cells in the TME of patients treated with ICI is lacking. To bridge this gap we performed a semi-supervised analysis of ∼1700 metabolic genes using single-cell RNA-seq data of > 1 million immune cells from ∼230 samples of cancer patients treated with ICI. When clustering cells based on their metabolic gene expression, we found that similar immunological cellular states are found in different metabolic states. Most importantly, we found metabolic states that are significantly associated with patient response. We then built a metabolic predictor based on a dozen gene signature, which significantly differentiates between responding and non-responding patients across different cancer types (AUC = 0.8-0.92). Taken together, our results demonstrate the power of metabolism in predicting patient response to ICI.

Keywords:  Cancer; Human metabolism; Immunology

DOI:  https://doi.org/10.1016/j.isci.2023.108188
Fish Shellfish Immunol. 2023 Nov 15. pii: S1050-4648(23)00700-3. [Epub ahead of print] 109214

Butyrate induces STAT3/HIF-1α/IL-22 signaling via GPCR and HDAC3 inhibition to activate autophagy in head kidney macrophages from turbot (Scophthalmus maximus L.).

Jinjin Zhang, Wentao Wang, Shufei Liang, Xueqi Zhou, Rokeya Sultana Rekha, Gudmundur H Gudmundsson, Peter Bergman, Qinghui Ai, Kangsen Mai, Min Wan.

  As one of short-chain fatty acids, butyrate is an important metabolite of dietary fiber by the fermentation of gut commensals. Our recent study uncovered that butyrate promoted IL-22 production in fish macrophages to augment the host defense. In the current study, we further explored the underlying signaling pathways in butyrate-induced IL-22 production in fish macrophages. Our results showed that butyrate augmented the IL-22 expression in head kidney macrophages (HKMs) of turbot through binding to G-protein receptor 41 (GPR41) and GPR43. Moreover, histone deacetylase 3 (HDAC3) inhibition apparently up-regulated the butyrate-enhanced IL-22 generation, indicating HDACs were engaged in butyrate-regulated IL-22 secretion. In addition, butyrate triggered the STAT3/HIF-1α signaling to elevate the IL-22 expression in HKMs. Importantly, the evidence in vitro and in vivo was provided that butyrate activated autophagy in fish macrophages via IL-22 signaling, which contributing to the elimination of invading bacteria. In conclusion, we clarified in the current study that butyrate induced STAT3/HIF-1α/IL-22 signaling pathway via GPCR binding and HDAC3 inhibition in fish macrophages to activate autophagy that was involved in pathogen clearance in fish macrophages.

Keywords:  Autophagy; Butyrate; GPCRs; HDAC3; IL-22; STATS

DOI:  https://doi.org/10.1016/j.fsi.2023.109214
Free Radic Biol Med. 2023 Nov 09. pii: S0891-5849(23)01094-8. [Epub ahead of print]

A critical role for host-derived cystathionine-β-synthase, in Staphylococcus aureus-induced udder infection.

Shaodong Fu, Bo Yang, Yabin Gao, Yawei Qiu, Naiyan Sun, Zhi Li, Shiyuan Feng, Yuanyuan Xu, Jinqiu Zhang, Zhenhua Luo, Xiangan Han, Jinfeng Miao.

  Cystathionine-β-synthase (CBS) catalyzes the first step of the transsulfuration pathway. The role of host-derived CBS in Staphylococcus aureus (S. aureus)-induced udder infection remains elusive. Herein, we report that S. aureus infection enhances the expression of CBS in mammary epithelial cells in vitro and in vivo. A negative correlation is present between the expression of CBS and inflammation after employing a pharmacological inhibitor/agonist of CBS. In addition, CBS achieves a fine balance between eliciting sufficient protective innate immunity and preventing excessive damage to cells and tissues preserving the integrity of the blood-milk barrier (BMB). CBS/H2S reduces bacterial load by promoting the generation of antibacterial substances (ROS, RNS) and inhibiting apoptosis, as opposed to relying solely on intense inflammatory reactions. Conversely, H2S donor alleviate inflammation via S-sulfhydrating HuR. Finally, CBS/H2S promotes the expression of Abcb1b, which in turn strengthens the integrity of the BMB. The study described herein demonstrates the importance of CBS in regulating the mammary immune response to S. aureus. Increased CBS in udder tissue modulates excessive inflammation, which suggests a novel target for drug development in the battle against S. aureus and other infections.

Keywords:  Blood–milk barrier; Cystathionine-β-synthase; Staphylococcus aureus; Udder infection

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.11.001
Biol Sex Differ. 2023 Nov 14. 14(1): 85

Sex-based differences in natural killer T cell-mediated protection against diet-induced steatohepatitis in Balb/c mice.

Carlos Cuño-Gómiz, Estefanía de Gregorio, Anna Tutusaus, Patricia Rider, Nuria Andrés-Sánchez, Anna Colell, Albert Morales, Montserrat Marí.

   BACKGROUND: Metabolic dysfunction-associated steatotic liver disease (MASLD) is prevalent in Western countries, evolving into metabolic dysfunction-associated steatohepatitis (MASH) with a sexual dimorphism. Fertile women exhibit lower MASLD risk than men, which diminishes post-menopause. While NKT-cell involvement in steatohepatitis is debated, discrepancies may stem from varied mouse strains used, predominantly C57BL6/J with Th1-dominant responses. Exploration of steatohepatitis, encompassing both genders, using Balb/c background, with Th2-dominant immune response, and CD1d-deficient mice in the Balb/c background (lacking Type I and Type II NKT cells) can clarify gender disparities and NKT-cell influence on MASH progression.
METHODS: A high fat and choline-deficient (HFCD) diet was used in male and female mice, Balb/c mice or CD1d-/- mice in the Balb/c background that exhibit a Th2-dominant immune response. Liver fibrosis and inflammatory gene expression were measured by qPCR, and histology assessment. NKT cells, T cells, macrophages and neutrophils were assessed by flow cytometry.
RESULTS: Female mice displayed milder steatohepatitis after 6 weeks of HFCD, showing reduced liver damage, inflammation, and fibrosis compared to males. Male Balb/c mice exhibited NKT-cell protection against steatohepatitis whereas CD1d-/- males on HFCD presented decreased hepatoprotection, increased liver fibrosis, inflammation, neutrophilic infiltration, and inflammatory macrophages. In contrast, the NKT-cell role was negligible in early steatohepatitis development in both female mice, as fibrosis and inflammation were similar despite augmented liver damage in CD1d-/- females. Relevant, hepatic type I NKT levels in female Balb/c mice were significantly lower than in male.
CONCLUSIONS: NKT cells exert a protective role against experimental steatohepatitis as HFCD-treated CD1d-/- males had more severe fibrosis and inflammation than male Balb/c mice. In females, the HFCD-induced hepatocellular damage and the immune response are less affected by NKT cells on early steatohepatitis progression, underscoring sex-specific NKT-cell influence in MASH development.

Keywords:  CD1d; Hepatic NKT cells; Inflammation; Liver; Metabolic dysfunction-associated steatohepatitis (MASH); Metabolic dysfunction-associated steatotic liver disease (MASLD); Non-alcoholic fatty liver disease (NAFLD); Non-alcoholic steatohepatitis (NASH); Sex differences

DOI:  https://doi.org/10.1186/s13293-023-00569-w
Sci Rep. 2023 Nov 17. 13(1): 20138

Anti-inflammatory reprogramming of microglia cells by metabolic modulators to counteract neurodegeneration; a new role for Ranolazine.

Ilaria Piano, Arianna Votta, Patrizia Colucci, Francesca Corsi, Sara Vitolo, Chiara Cerri, Dario Puppi, Michele Lai, José Fernando Maya-Vetencourt, Massimiliano Leigheb, Chiara Gabellini, Elisabetta Ferraro.

Microglia chronic activation is a hallmark of several neurodegenerative diseases, including the retinal ones, possibly contributing to their etiopathogenesis. However, some microglia sub-populations have anti-inflammatory and neuroprotective functions, thus making arduous deciphering the role of these cells in neurodegeneration. Since it has been proposed that functionally different microglia subsets also rely on different metabolic routes, we hypothesized that modulating microglia metabolism might be a tool to enhance their anti-inflammatory features. This would have a preventive and therapeutic potential in counteracting neurodegenerative diseases. For this purpose, we tested various molecules known to act on cell metabolism, and we revealed the anti-inflammatory effect of the FDA-approved piperazine derivative Ranolazine on microglia cells, while confirming the one of the flavonoids Quercetin and Naringenin, both in vitro and in vivo. We also demonstrated the synergistic anti-inflammatory effect of Quercetin and Idebenone, and the ability of Ranolazine, Quercetin and Naringenin to counteract the neurotoxic effect of LPS-activated microglia on 661W neuronal cells. Overall, these data suggest that using the selected molecules -also in combination therapies- might represent a valuable approach to reduce inflammation and neurodegeneration while avoiding long term side effects of corticosteroids.

DOI: https://doi.org/10.1038/s41598-023-47540-8
BMB Rep. 2023 Nov 14. pii: 6039. [Epub ahead of print]

Glucosamine increases macrophage lipid accumulation by regulating the mammalian target of rapamycin signaling pathway.

Sang-Min Kim, Dong Yeol Kim, Jiwon Park, Young-Ah Moon, Inn-Oc Han.

Elevation of blood glucose is associated with increased risk of atherosclerosis development. Data from the current study showed that glucosamine (GlcN), a normal glucose metabolite of the hexosamine biosynthetic pathway (HBP), promoted lipid accumulation in RAW264.7 macrophage cells. Oleic acid- and lipopolysaccharide (LPS)-induced lipid accumulation was further enhanced by GlcN in RAW264.7 cells, although the rate of fatty acid uptake was not significantly changed. GlcN increased acetyl CoA carboxylase (ACC), fatty acid synthase (FAS), scavenger receptor class A, liver X receptor and sterol regulatory element-binding protein-1c (SREBP-1c) mRNA expression, and conversely, suppressed ATP-binding cassette transporter A1 (ABCA-1) and ABCG-1 expression. Additionally, GlcN promoted O-GlcNAcylation of nuclear SREBP-1 but did not affect its DNA binding activity. GlcN stimulated phosphorylation of mammalian target of rapamycin (mTOR) and S6 kinase. The mTOR inhibitor, rapamycin, suppressed GlcN-induced lipid accumulation in RAW264.7 cells. The GlcN-mediated increase in ACC and FAS mRNA was suppressed, while the decrease in ABCA-1 and ABCG-1 by GlcN was not significantly altered by rapamycin. Our collective results highlight the importance of the mTOR signaling pathway in GlcN-induced macrophage lipid accumulation and further support a potential link between mTOR and HBP signaling in lipogenesis.
J Hepatol. 2023 Nov 15. pii: S0168-8278(23)05271-6. [Epub ahead of print]

Adipose tissue macrophage dysfunction is associated with a breach of vascular integrity in NASH.

Markus Boesch, Andreas Lindhorst, Rita Feio-Azevedo, Paola Brescia, Alessandra Silvestri, Matthias Lannoo, Ellen Deleus, Joris Jaekers, Halit Topal, Baki Topal, Tessa Ostyn, Marie Wallays, Lena Smets, Lukas Van Melkebeke, Anetta Härtlova, Tania Roskams, Pierre Bedossa, Jef Verbeek, Olivier Govaere, Sven Francque, Alejandro Sifrim, Thierry Voet, Maria Rescigno, Martin Gericke, Hannelie Korf, Schalk van der Merwe.

   BACKGROUND & AIMS: Non-alcoholic fatty liver disease (NAFLD) is reaching epidemic proportions, fueled by the obesity pandemic. In NAFLD, monocytes infiltrate visceral adipose tissue that promote local and hepatic inflammation. It however remains unclear what drives inflammation and how the immune landscape in adipose tissue differs across the NAFLD severity spectrum. We aimed to assimilate the adipose tissue macrophage (ATM) heterogeneity in a NAFLD cohort.
METHODS: Visceral adipose tissue macrophages from lean and obese patients stratified into NAFLD phenotypes underwent single-cell RNA sequencing. Adipose tissue vascular integrity and breaching was assessed on protein level for targets of interest via immunohistochemistry and immunofluorescence.
RESULTS: We discovered multiple ATM populations, including resident vasculature-associated macrophages (ResVAMs) and distinct metabolically active macrophages (MMacs). Using trajectory analysis, we show that ResVAMs and MMacs replenish from a common transitional macrophage subtype (TransMac) and during NASH, MMacs are not effectively replenished by TransMac precursors. We postulate an accessory role for MMac and ResVAMs in protecting the adipose tissue vascular barrier, since they both interact with endothelial cells and localize around the vasculature. Across the NAFLD severity spectrum however, both these subsets become altered and this coincided with an adipose tissue vasculature breach characterized by albumin extravasation into the perivascular tissue.
CONCLUSIONS: NAFLD-related macrophage dysfunction coincide with a loss of adipose tissue vascular integrity providing a strong plausible mechanism by which tissue inflammation is perpetuated in adipose tissue and downstream in the liver.
IMPACT AND IMPLICATIONS: Our study describe for the first time the myeloid cell landscape in human visceral adipose tissue at single cell level within a cohort of well-characterised NAFLD patients. We report unique NASH-specific transcriptional changes within metabolically active macrophages (MMacs) and resident vasculature-associated macrophages (ResVAM) and we demonstrate their spatial location surrounding the vasculature. These dysfunctional transcriptional macrophage states, coincided with the loss of adipose tissue vascular integrity, providing a strong plausible mechanism by which tissue inflammation is perpetuated in adipose tissue and downstream in the liver. Our study provide a theoretical basis for new therapeutic strategies to be directed towards reinstating ResVAM and MMac endogenous metabolic and homeostatic and cytoprotective mechanisms including their function to protect the vascular integrity and barrier.

Keywords:  Non-alcoholic fatty liver disease; adipose tissue; macrophages; single-cell RNA sequencing

DOI:  https://doi.org/10.1016/j.jhep.2023.10.039
Immune Netw. 2023 Oct;23(5): e40

Glucocorticoids Impair the 7α-Hydroxycholesterol-Enhanced Innate Immune Response.

Yonghae Son, Bo-Young Kim, Miran Kim, Jaesung Kim, Ryuk Jun Kwon, Koanhoi Kim.

  Glucocorticoids suppress the vascular inflammation that occurs under hypercholesterolemia, as demonstrated in an animal model fed a high-cholesterol diet. However, the molecular mechanisms underlying these beneficial effects remain poorly understood. Because cholesterol is oxidized to form cholesterol oxides (oxysterols) that are capable of inducing inflammation, we investigated whether glucocorticoids affect the immune responses evoked by 7α-hydroxycholesterol (7αOHChol). The treatment of human THP-1 monocytic cells with dexamethasone (Dex) and prednisolone (Pdn) downregulated the expression of pattern recognition receptors (PRRs), such as TLR6 and CD14, and diminished 7αOHChol-enhanced response to FSL-1, a TLR2/6 ligand, and lipopolysaccharide, which interacts with CD14 to initiate immune responses, as determined by the reduced secretion of IL-23 and CCL2, respectively. Glucocorticoids weakened the 7αOHChol-induced production of CCL2 and CCR5 ligands, which was accompanied by decreased migration of monocytic cells and CCR5-expressing Jurkat T cells. Treatment with Dex or Pdn also reduced the phosphorylation of the Akt-1 Src, ERK1/2, and p65 subunits. These results indicate that both Dex and Pdn impair the expression of PRRs and their downstream products, chemokine production, and phosphorylation of signaling molecules. Collectively, glucocorticoids suppress the innate immune response and activation of monocytic cells to an inflammatory phenotype enhanced or induced by 7αOHChol, which may contribute to the anti-inflammatory effects in hypercholesterolemic conditions.

Keywords:  7α-Hydroxycholesterol; GlucocorticoidsMonocytes/macrophages; Inflammation; Pattern recognition receptors

DOI:  https://doi.org/10.4110/in.2023.23.e40
Am J Physiol Cell Physiol. 2023 Nov 13.

Caveolin-1 forms a complex with P2X7 receptor and tunes P2X7-mediated ATP signaling in mouse bone marrow-derived macrophages.

Yuuki Sawai, Yoshiaki Suzuki, Masataka Asagiri, Shigeaki Hida, Rubii Kondo, Gerald W Zamponi, Wayne R Giles, Yuji Imaizumi, Hisao Yamamura.

  The ionotropic purinergic P2X7 receptor responds to extracellular ATP and can trigger pro-inflammatory immune signaling in macrophages. Caveolin-1 (Cav-1) is known to modulate functions of macrophages and innate immunity. However, it is unknown how Cav-1 modulates P2X7 receptor activity in macrophages. We herein examined P2X7 receptor activity and macrophage functions using bone marrow-derived macrophages (BMDMs) from wild-type (WT) and Cav-1 knockout (KO) mice. ATP (1 mM) application caused biphasic increase in cytosolic [Ca2+] and sustained decrease in cytosolic [K+]. A specific P2X7 receptor blocker, A-740003, inhibited the maintained cytosolic [Ca2+] increase and cytosolic [K+] decrease. Total internal reflection fluorescent imaging and proximity ligation assays revealed a novel molecular complex formation between P2X7 receptors and Cav-1 in WT BMDMs that were stimulated with lipopolysaccharides. This molecular coupling was increased by ATP application. Specifically, the ATP-induced Ca2+ influx and K+ efflux through P2X7 receptors were increased in Cav-1 KO BMDMs, even though the total and surface protein levels of P2X7 receptors in WT and Cav-1 KO BMDMs were unchanged. Cell-impermeable dye (TO-PRO3) uptake analysis revealed that macro-pore formation of P2X7 receptors was enhanced in Cav-1 KO BMDMs. Cav-1 KO BMDMs increased ATP-induced IL-1b secretion, reactive oxygen species production, Gasdermin D (GSDMD) cleavage, and lactate dehydrogenase release indicating pyroptosis. A-740003 completely prevented ATP-induced pyroptosis. In combination, these data sets show that Cav-1 has a negative effect on P2X7 receptor activity in BMDMs and that Cav-1 in macrophages may contribute to finely tuned immune responses by preventing excessive IL-1b secretion and pyroptosis.

Keywords:  ATP; P2X7; calcium channel; caveolin-1; macrophage

DOI:  https://doi.org/10.1152/ajpcell.00303.2023
Brain Behav Immun. 2023 Nov 14. pii: S0889-1591(23)00343-4. [Epub ahead of print]

Gonadal hormones impart male-biased behavioral vulnerabilities to immune activation via microglial mitochondrial function.

Evan A Bordt, Haley A Moya, Young Chan Jo, Caitlin T Ravichandran, Izabella M Bankowski, Alexis M Ceasrine, Christopher J McDougle, William A Carlezon, Staci D Bilbo.

There is a strong male bias in the prevalence of many neurodevelopmental disorders such as autism spectrum disorder. However, the mechanisms underlying this sex bias remain elusive. Infection during the perinatal period is associated with an increased risk of neurodevelopmental disorder development. Here, we used a mouse model of early-life immune activation that reliably induces deficits in social behaviors only in males. We demonstrate that male-biased alterations in social behavior are dependent upon microglial immune signaling and are coupled to alterations in mitochondrial morphology, gene expression, and function specifically within microglia, the innate immune cells of the brain. Additionally, we show that this behavioral and microglial mitochondrial vulnerability to early-life immune activation is programmed by the male-typical perinatal gonadal hormone surge. These findings demonstrate that social behavior in males over the lifespan are regulated by microglia-specific mechanisms that are shaped by events that occur in early development.

DOI: https://doi.org/10.1016/j.bbi.2023.11.010
Nutrients. 2023 Oct 27. pii: 4574. [Epub ahead of print]15(21):

Intermittent Fasting Attenuates Metabolic-Dysfunction-Associated Steatohepatitis by Enhancing the Hepatic Autophagy-Lysosome Pathway.

Kyung Eun Kim, Hyun Joo Shin, Yeajin Ju, Youngae Jung, Hyeong Seok An, So Jeong Lee, Eun Ae Jeong, Jaewoong Lee, Geum-Sook Hwang, Gu Seob Roh.

  An intermittent fasting (IF) regimen has been shown to protect against metabolic dysfunction-associated steatohepatitis (MASH). However, the precise mechanism remains unclear. Here, we explored how IF reduced hepatic lipid accumulation, inflammation, and fibrosis in mice with MASH. The mice were fed a high-fat diet (HFD) for 30 weeks and either continued on the HFD or were subjected to IF for the final 22 weeks. IF reduced body weight, insulin resistance, and hepatic lipid accumulation in HFD-fed mice. Lipidome analysis revealed that IF modified HFD-induced hepatic lipid composition. In particular, HFD-induced impaired autophagic flux was reversed by IF. The decreased hepatic lysosome-associated membrane protein 1 level in HFD-fed mice was upregulated in HFD+IF-fed mice. However, increased hepatic lysosomal acid lipase protein levels in HFD-fed mice were reduced by IF. IF attenuated HFD-induced hepatic inflammation and galectin-3-positive Kupffer cells. In addition to the increases in hepatic hydroxyproline and lumican levels, lipocalin-2-mediated signaling was reversed in HFD-fed mice by IF. Taken together, our findings indicate that the enhancement of the autophagy-lysosomal pathway may be a critical mechanism of MASH reduction by IF.

Keywords:  autophagy; intermittent fasting; lysosome; non-alcoholic steatohepatitis

DOI:  https://doi.org/10.3390/nu15214574