Metabolic reprogramming of macrophages by PKM2 promotes IL-10 production via adenosine.

Macrophages play a crucial role in immune responses and undergo metabolic reprogramming to fulfill their functions. The tetramerization of the glycolytic enzyme pyruvate kinase M2 (PKM2) induces the production of the anti-inflammatory cytokine interleukin (IL)-10 in vivo, but the underlying mechanism remains elusive. Here, we report that PKM2 activation with the pharmacological agent TEPP-46 increases IL-10 production in LPS-activated macrophages by metabolic reprogramming, leading to the production and release of ATP from glycolysis.

4-Octyl Itaconate Alleviates Airway Eosinophilic Inflammation by Suppressing Chemokines and Eosinophil Development.

4-Octyl itaconate (4-OI) is a derivative of the Krebs cycle-derived metabolite itaconate and displays an array of antimicrobial and anti-inflammatory properties through modifying cysteine residues within protein targets. We have found that 4-OI significantly reduces the production of eosinophil-targeted chemokines in a variety of cell types, including M1 and M2 macrophages, Th2 cells, and A549 respiratory epithelial cells. Notably, the suppression of these chemokines in M1 macrophages was found to be NRF2-dependent.

The Circadian Clock Protein BMAL1 Acts as a Metabolic Sensor In Macrophages to Control the Production of Pro IL-1β.

The transcription factor BMAL1 is a clock protein that generates daily or circadian rhythms in physiological functions including the inflammatory response of macrophages. Intracellular metabolic pathways direct the macrophage inflammatory response, however whether the clock is impacting intracellular metabolism to direct this response is unclear. Specific metabolic reprogramming of macrophages controls the production of the potent pro-inflammatory cytokine IL-1β.

Targeting immunometabolism as an anti-inflammatory strategy.

The growing field of immunometabolism has taught us how metabolic cellular reactions and processes not only provide a means to generate ATP and biosynthetic precursors, but are also a way of controlling immunity and inflammation. Metabolic reprogramming of immune cells is essential for both inflammatory as well as anti-inflammatory responses. Four anti-inflammatory therapies, DMF, Metformin, Methotrexate and Rapamycin all work by affecting metabolism and/or regulating or mimicking endogenous metabolites with anti-inflammatory effects.

Caspase-11 promotes allergic airway inflammation.

Activated caspase-1 and caspase-11 induce inflammatory cell death in a process termed pyroptosis. Here we show that Prostaglandin E (PGE) inhibits caspase-11-dependent pyroptosis in murine and human macrophages. PGE suppreses caspase-11 expression in murine and human macrophages and in the airways of mice with allergic inflammation.

Pharmacological Activation of Pyruvate Kinase M2 Inhibits CD4 T Cell Pathogenicity and Suppresses Autoimmunity.

Pyruvate kinase (PK) catalyzes the conversion of phosphoenolpyruvate to pyruvate during glycolysis. The PK isoform PKM2 has additional roles in regulation of gene transcription and protein phosphorylation. PKM2 has been shown to control macrophage metabolic remodeling in inflammation, but its role in T cell biology is poorly understood.

Glutathione Transferase Omega-1 Regulates NLRP3 Inflammasome Activation through NEK7 Deglutathionylation.

The NLRP3 inflammasome is a cytosolic complex sensing phagocytosed material and various damage-associated molecular patterns, triggering production of the pro-inflammatory cytokines interleukin-1 beta (IL)-1β and IL-18 and promoting pyroptosis. Here, we characterize glutathione transferase omega 1-1 (GSTO1-1), a constitutive deglutathionylating enzyme, as a regulator of the NLRP3 inflammasome. Using a small molecule inhibitor of GSTO1-1 termed C1-27, endogenous GSTO1-1 knockdown, and GSTO1-1 mice, we report that GSTO1-1 is involved in NLRP3 inflammasome activation.

Specific Inhibition of the NLRP3 Inflammasome as an Antiinflammatory Strategy in Cystic Fibrosis.

Cystic fibrosis (CF) pulmonary disease is characterized by chronic infection with and sustained neutrophil-dominant inflammation. The lack of effective antiinflammatory therapies for people with CF (PWCF) represents a significant challenge. To identify altered immunometabolism in the CF neutrophil and investigate the feasibility of specific inhibition of the NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3) inflammasome as a CF antiinflammatory strategy .

Malonylation of GAPDH is an inflammatory signal in macrophages.

Macrophages undergo metabolic changes during activation that are coupled to functional responses. The gram negative bacterial product lipopolysaccharide (LPS) is especially potent at driving metabolic reprogramming, enhancing glycolysis and altering the Krebs cycle. Here we describe a role for the citrate-derived metabolite malonyl-CoA in the effect of LPS in macrophages.

Circadian clock protein BMAL1 regulates IL-1β in macrophages via NRF2.

A variety of innate immune responses and functions are dependent on time of day, and many inflammatory conditions are associated with dysfunctional molecular clocks within immune cells. However, the functional importance of these innate immune clocks has yet to be fully characterized. NRF2 plays a critical role in the innate immune system, limiting inflammation via reactive oxygen species (ROS) suppression and direct repression of the proinflammatory cytokines, IL-1β and IL-6.

Metabolic Modulation in Macrophage Effector Function.

Traditionally cellular respiration or metabolism has been viewed as catabolic and anabolic pathways generating energy and biosynthetic precursors required for growth and general cellular maintenance. However, growing literature provides evidence of a much broader role for metabolic reactions and processes in controlling immunological effector functions. Much of this research into immunometabolism has focused on macrophages, cells that are central in pro- as well as anti-inflammatory responses-responses that in turn are a direct result of metabolic reprogramming.

Pyruvate Kinase M2 Is Required for the Expression of the Immune Checkpoint PD-L1 in Immune Cells and Tumors.

Blocking interaction of the immune checkpoint receptor PD-1 with its ligand PD-L1 is associated with good clinical outcomes in a broad variety of malignancies. High levels of PD-L1 promote tumor growth by restraining CD8 T-cell responses against tumors. Limiting PD-L1 expression and function is therefore critical for allowing the development of antitumor immune responses and effective tumor clearance.

The Induction of Pro-IL-1β by Lipopolysaccharide Requires Endogenous Prostaglandin E Production.

PGE has been shown to increase the transcription of pro-IL-1β. However, recently it has been demonstrated that PGE can block the maturation of IL-1β by inhibiting the NLRP3 inflammasome in macrophages. These apparently conflicting results have led us to reexamine the effect of PGE on IL-1β production.

Pyruvate Kinase M2: A Potential Target for Regulating Inflammation.

Pyruvate kinase (PK) is the enzyme responsible for catalyzing the last step of glycolysis. Of the four PK isoforms expressed in mammalian cells, PKM2 has generated the most interest due to its impact on changes in cellular metabolism observed in cancer as well as in activated immune cells. As our understanding of dysregulated metabolism in cancer develops, and in light of the growing field of immunometabolism, intense efforts are in place to define the mechanism by which PKM2 regulates the metabolic profile of cancer as well as of immune cells.

A Common Variant in the Adaptor Mal Regulates Interferon Gamma Signaling.

Humans that are heterozygous for the common S180L polymorphism in the Toll-like receptor (TLR) adaptor Mal (encoded by TIRAP) are protected from a number of infectious diseases, including tuberculosis (TB), whereas those homozygous for the allele are at increased risk. The reason for this difference in susceptibility is not clear. We report that Mal has a TLR-independent role in interferon-gamma (IFN-γ) receptor signaling.

Cutting Edge: Mycobacterium tuberculosis Induces Aerobic Glycolysis in Human Alveolar Macrophages That Is Required for Control of Intracellular Bacillary Replication.

Recent advances in immunometabolism link metabolic changes in stimulated macrophages to production of IL-1β, a crucial cytokine in the innate immune response to Mycobacterium tuberculosis. To investigate this pathway in the host response to M. tuberculosis, we performed metabolic and functional studies on human alveolar macrophages, human monocyte-derived macrophages, and murine bone marrow-derived macrophages following infection with the bacillus in vitro.

Circadian control of innate immunity in macrophages by miR-155 targeting Bmal1.

The response to an innate immune challenge is conditioned by the time of day, but the molecular basis for this remains unclear. In myeloid cells, there is a temporal regulation to induction by lipopolysaccharide (LPS) of the proinflammatory microRNA miR-155 that correlates inversely with levels of BMAL1. BMAL1 in the myeloid lineage inhibits activation of NF-κB and miR-155 induction and protects mice from LPS-induced sepsis.

Pyruvate kinase M2 regulates Hif-1α activity and IL-1β induction and is a critical determinant of the warburg effect in LPS-activated macrophages.

Macrophages activated by the TLR4 agonist LPS undergo dramatic changes in their metabolic activity. We here show that LPS induces expression of the key metabolic regulator Pyruvate Kinase M2 (PKM2). Activation of PKM2 using two well-characterized small molecules, DASA-58 and TEPP-46, inhibited LPS-induced Hif-1α and IL-1β, as well as the expression of a range of other Hif-1α-dependent genes.

LPS induces the degradation of programmed cell death protein 4 (PDCD4) to release Twist2, activating c-Maf transcription to promote interleukin-10 production.

Programmed cell death protein 4 (PDCD4) is a tumor suppressor and has also been shown to suppress production of the immunomodulatory cytokine IL-10. The precise role of PDCD4 in IL-10 induction in macrophages is still not fully understood. Incubation of macrophages with inhibitors of PI3K and mTOR blocked LPS-stimulated PDCD4 degradation and expression of c-Maf and IL-10 production.

The Warburg effect then and now: from cancer to inflammatory diseases.

Inflammatory immune cells, when activated, display much the same metabolic profile as a glycolytic tumor cell. This involves a shift in metabolism away from oxidative phosphorylation towards aerobic glycolysis, a phenomenon known as the Warburg effect. The result of this change in macrophages is to rapidly provide ATP and metabolic intermediates for the biosynthesis of immune and inflammatory proteins.

Negative regulation of TLR4 via targeting of the proinflammatory tumor suppressor PDCD4 by the microRNA miR-21.

The tumor suppressor PDCD4 is a proinflammatory protein that promotes activation of the transcription factor NF-kappaB and suppresses interleukin 10 (IL-10). Here we found that mice deficient in PDCD4 were protected from lipopolysaccharide (LPS)-induced death. The induction of NF-kappaB and IL-6 by LPS required PDCD4, whereas LPS enhanced IL-10 induction in cells lacking PDCD4.

TAG, a splice variant of the adaptor TRAM, negatively regulates the adaptor MyD88-independent TLR4 pathway.

Toll-like receptor 4 (TLR4) signals the induction of transcription factor IRF3-dependent genes from the early endosome via the adaptor TRAM. Here we report a splice variant of TRAM, TAG ('TRAM adaptor with GOLD domain'), which has a Golgi dynamics domain coupled to TRAM's Toll-interleukin 1 receptor domain. After stimulation with lipopolysaccharide, TRAM and TAG localized to late endosomes positive for the GTPase Rab7a.

Glucocorticoids inhibit IRF3 phosphorylation in response to Toll-like receptor-3 and -4 by targeting TBK1 activation.

Phosphorylation of the transcription factor interferon regulatory factor 3 (IRF3) is essential for the induction of promoters which contain the interferon-stimulated response element (ISRE). IRF3 can be activated by Toll-like receptor 3 (TLR3) in response to the double-stranded RNA mimic poly(I-C) and by TLR4 in response to lipopolysaccharide (LPS). Here we have analyzed the effect of the glucocorticoid dexamethasone on this response.

NF-kappaB activation by the Toll-IL-1 receptor domain protein MyD88 adapter-like is regulated by caspase-1.

Toll-like receptors (TLRs)-2 and -4 are important proteins in innate immunity, recognizing microbial products and eliciting host defense responses. Both use the adapter proteins MyD88 and MyD88 adapter-like (Mal) to activate signaling pathways. Here we report that Mal but not MyD88 interacts with caspase-1, the enzyme that processes the precursors of the proinflammatory cytokines IL-1beta and IL-18.