Multiomics Analyses Reveal the Central Role of Pentose Phosphate Pathway in Resident Thymic Macrophages to Cope with Efferocytosis-Associated Stress
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE203543 | GEO | 2022/06/02
REPOSITORIES: GEO
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Project description:Tissue-resident macrophages (TRMs) are heterogeneous cell populations found throughout the body. Depending on their location, they perform diverse functions maintaining tissue homeostasis and providing immune surveillance. To survive and function within, TRMs adapt metabolically to the distinct microenvironments. However, little is known about the metabolic signatures of TRMs. The thymus provides a nurturing milieu for developing thymocytes yet efficiently removes those that failed the selection, relying on the TRMs – resident thymic macrophages (TMφs). This study harnesses multiomics analyses to characterize TMφs and unveils their unique metabolic features. We find that the pentose phosphate pathway (PPP) is preferentially activated in TMφs, responding to the reduction-oxidation demands associated with the efferocytosis of dying thymocytes. The blockade of PPP in Mφs leads to decreased efferocytosis, which can be rescued by ROS scavengers. Our study reveals the key role of PPP in TMφs and underscores the importance of metabolic adaptation in supporting Mφ efferocytosis.
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Project description:Apoptotic cell clearance (efferocytosis), a process essential for organismal homeostasis, is performed by phagocytes that inhabit a wide range of environments, including physiologic hypoxia. Here, we find macrophages, the predominant tissue-resident phagocyte, display enhanced efferocytosis under chronic hypoxia, characterized by increased internalization and accelerated degradation of apoptotic cells. Analysis of mRNA and protein programs revealed that chronic hypoxia induces two distinct but complimentary states in macrophages. The first, ‘primed’ state consists of concomitant induction of transcriptional and translational programs broadly associated with metabolism in apoptotic cell-naïve macrophages that persist during efferocytosis. The second, ‘poised’ state consists of transcription, but not translation, of phagocyte function programs in apoptotic cell-naïve macrophages that are subsequently translated during efferocytosis. We discovered that one such primed state consists of the efficient flux of glucose into a noncanonical pentose phosphate pathway (PPP) loop, whereby PPP-derived intermediates cycle back through the PPP to enhance production of NADPH. Mechanistically, we found that PPP-derived NADPH directly supports enhanced efferocytosis under chronic hypoxia via its role in phagolysosomal maturation, while simultaneously maintaining cellular redox homeostasis. Thus, macrophages adapt to chronic hypoxia by adopting states that both support cell fitness and ensure ability to rapidly and safely perform essential homeostatic functions.
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Project description:Metabolic pathways are now considered as intrinsic virulence attributes of pathogenic bacteria and hence represent potential targets for anti-bacterial strategies. Here, we addressed the role of the pentose phosphate pathway (PPP) and its connections with other metabolic pathways in the pathophysiology of Francisella novicida. We have previously shown that this intracellular bacterial pathogen used gluconeogenesis to metabolize host-derived nutrients in the cytosolic compartment of infected macrophages. Francisella species, which lacks the oxidative branch of the PPP, are equipped with all the genes of the non-oxidative branch (i.e. tktA, tal, rpiA and rpe, encoding transketolase, transaldolase, ribose-phosphate isomerase and ribulose phosphate epimerase, respectively). The involvement of the PPP in the early stage of intracellular life cycle of F. novicida was first demonstrated with the study of PPP inactivation mutants. Indeed, inactivation of tktA, rpiA or rpe genes, severely impaired intramacrophagic multiplication during the first 24–hours. However, time-lapse video microscopy demonstrated that rpiA and rpe mutants were able to resume late intracellular bacterial multiplication. To get further insight into the links between the PPP and other metabolic networks of the bacterium, we next performed a thorough proteo-metabolomic analysis of these mutants. We show that the PPP constitutes a major bacterial metabolic hub with multiple connections with glycolysis, tricarboxylic acid cycle and other metabolic pathways, such as fatty acid degradation and sulfur metabolism. Hence, our study highlights how, by its multiple connections with other metabolic pathways, PPP is instrumental to Francisella pathogenesis and growth in its intracellular niche.
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2016-08-18 | GSE74439 | GEO
Project description:Metabolic reprogramming has emerged as a crucial regulator of immune cell activation but how systemic metabolism influences immune cell metabolism and function remains to be investigated. To investigate the effect of dyslipidemia on immune cell metabolism, we performed in-depth transcriptional, metabolic and functional characterization of macrophages isolated from hypercholesterolemic mice. Systemic metabolic changes in such mice alter cellular macrophage metabolism and attenuate inflammatory macrophage responses. In addition to diminished maximal mitochondrial respiration, hypercholesterolemia reduces the LPS-mediated induction of the pentose phosphate pathway (PPP) and the Nrf2-mediated oxidative stress response. Our observation that suppression of the PPP diminishes LPS-induced cytokine secretion supports the notion that this pathway contributes to inflammatory macrophage responses. Overall, this study reveals that systemic and cellular metabolism are strongly interconnected, together dictating macrophage phenotype and function.
2018-10-31 | GSE107412 | GEO
Project description:Non-oxidative pentose phosphate pathway (PPP) is a crucial gatekeeper of glucose catabolism in metabolic tissues. However, its role in regulatory T cells (Tregs) remains unknown. Here we report deleting transketolase (TKT), an indispensable enzyme of non-oxidative PPP, in Tregs caused a fatal auto-immune disease in mice. TKT deletion impaired suppressive capability without disturbing Treg cell number. Mechanistically, TKT deficiency caused Treg metabolic remodeling with decreased glucose catabolism, activated fatty acid and amino acid catabolism and uncontrolled oxidative phosphorylation. Moreover, excessive ammonia from deregulated amino acid catabolism impaired mitochondrial fitness while reduced α-ketoglutarate/succinate ratio led to DNA hypermethylation, limiting functional gene expression and suppressive activity of TKT-deficient Tregs. Therefore, our study identifies non-oxidative PPP as a new pathway for controlling Treg function.
2022-03-31 | GSE172047 | GEO
Project description:Non-oxidative pentose phosphate pathway (PPP) is a crucial gatekeeper of glucose catabolism in metabolic tissues. However, its role in regulatory T cells (Tregs) remains unknown. Here we report deleting transketolase (TKT), an indispensable enzyme of non-oxidative PPP, in Tregs caused a fatal auto-immune disease in mice. TKT deletion impaired suppressive capability without disturbing Treg cell number. Mechanistically, TKT deficiency caused Treg metabolic remodeling with decreased glucose catabolism, activated fatty acid and amino acid catabolism and uncontrolled oxidative phosphorylation. Moreover, excessive ammonia from deregulated amino acid catabolism impaired mitochondrial fitness while reduced α-ketoglutarate/succinate ratio led to DNA hypermethylation, limiting functional gene expression and suppressive activity of TKT-deficient Tregs. Therefore, our study identifies non-oxidative PPP as a new pathway for controlling Treg function.
2022-03-31 | GSE171675 | GEO
Project description:In this study, the distribution and regulation of periplasmic and cytoplasmic carbon fluxes in Gluconobacter oxydans 621H with glucose were studied by 13C-based metabolic flux analysis (13C-MFA) in combination with transcriptomics and enzyme assays. For 13C-MFA, cells were cultivated with specifically 13C-labeled glucose and intracellular metabolites were analyzed for their labeling pattern by LC-MS. In growth phase I, 90% of the glucose was oxidized periplasmatically to gluconate and partially further oxidized to 2-ketogluconate. Of the glucose taken up by the cells, 9% was phosphorylated to glucose 6-phosphate, whereas 91% was oxidized by cytoplasmic glucose dehydrogenase to gluconate. Additional gluconate was taken up into the cells by transport. Of the cytoplasmic gluconate, 70% was oxidized to 5-ketogluconate and 30% was phosphorylated to 6-phosphogluconate. In growth phase II, 87% of gluconate was oxidized to 2-ketogluconate in the periplasm and 13% was taken up by the cells and almost completely converted to 6-phosphogluconate. Since G. oxydans lacks phosphofructokinase, glucose 6-phosphate can only be metabolized via the oxidative pentose phosphate pathway (PPP) or the Entner-Doudoroff pathway (EDP). 13C-MFA showed that 6-phosphogluconate is catabolized primarily via the oxidative PPP in both phase I and II (62% and 93%) and demonstrated a cyclic carbon flux through the oxidative PPP. The transcriptome comparison revealed an increased expression of PPP genes in growth phase II, which was supported by enzyme activity measurements and correlated with the increased PPP flux in phase II. Moreover, genes possibly related to a general stress response displayed increased expression in growth phase II. The transcriptome comparisons of G. oxydans growth phase II vs. growth phase I were repeated independently three times in biological replicates resulting in 3 hybridizations as termed by sample 1 to 3.
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Project description:Oxygen fluctuation during tissue remodeling imposes a major metabolic challenge in human tumors. Stem-like tumor cells in glioblastomas are believed to possess extraordinary metabolic flexibility, enabling them to initiate growth even under non-permissive conditions. To identify adaptive response mechanism, we compared the effects of acute and chronic hypoxia versus oxygenation on stem-like glioblastoma (GS) cells. GS cell lines were established and propagated either under normoxia (21% O2) or hypoxia (1% O2) and subsequently exposed to acute normoxia or hypoxia, respectively. Gene expression profiling revealed that acute hypoxia predominantly induced metabolic pathways and cell cycle arrest, whereas chronic hypoxia activated neurodevelopmental processes. In particular, we found increased expression of glycolytic enzymes, especially of the preparatory phase of glycolysis, under acute hypoxia, whereas pentose phosphate pathway (PPP) enzymes were downregulated. The opposite was found for acute oxygenation of hypoxic GS cells. Findings were confirmed by qPCR and immunoblot analyses. Despite downregulation by hypoxia, expression of PPP enzymes is increased in GBMs compared to normal brain, whereas expression of hypoxia-inducible enzymes of the parallel preparatory phase of glycolysis is decreased. Immunohistochemistry revealed strong staining for PPP enzymes in the bulk of GBM tissue, especially in highly proliferative areas, but not in pseudopalisading (hypoxic) cells. Glycolytic enzymes displayed an inverse pattern. Mass spectrometric analysis using [1,2-13C2]-D-glucose showed reduced glucose flux through the PPP under hypoxia in favor of flux through glycolysis. Acute and chronic hypoxia increased cell migration but reduced proliferation, whereas normoxia had opposite effects. Our findings extend Warburg’s observations by showing that in most tumor cells the PPP, which supplies metabolites for biomass production, is favored over the parallel preparatory phase of glycolysis, but is suppressed under acute severe hypoxia, causing a switch to direct glycolysis to protect against hypoxic stress.
2020-12-31 | GSE45117 | GEO
Project description:The Pentose Phosphate Pathway (PPP), a metabolic offshoot of the glycolytic pathway, provides protective metabolites and molecules essential for cell redox balance and survival. Transketolase (TKT) is the critical enzyme that controls the extent of “traffic flow” through the PPP. Here, we explored the role of TKT in maintaining the health of the human retina. We found that Müller cells were the primary retinal cell type expressing TKT in the human retina. We further explored the role of TKT in human Müller cells by knocking down its expression in primary cultured Müller cells (huPMCs), isolated from the human retina (11 human donors in total), under lightinduced oxidative stress. TKT knockdown and light stress reduced TKT enzymatic activities and the overall metabolic activities of huPMCs with no detectable cell death. TKT knockdown restrained the PPP traffic flow, reduced the expression of NAD(P)H Quinone Dehydrogenase 1 (NQO1) and impaired the antioxidative response of NRF2 to light stress. TKT knockdown also inhibited overall glucose intake, reduced expression of Dihydrolipoamide dehydrogenase (DLD) and impaired the energy supply of huPMCs. In summary, Müller cell-mediated TKT activity plays a critical protective role in the stressed retina. Knockdown of TKT disrupted the PPP and impaired overall glucose utilisation by huPMCs and rendered huPMCs more vulnerable to light stress by impairing energy supply and antioxidative NRF2 responses.
2022-06-26 | GSE198554 | GEO