Lactic Acid Fermentation Is Required for NLRP3 Inflammasome Activation

Abstract

Activation of the Nod-like receptor 3 (NLRP3) inflammasome is important for activation of innate immune responses, but improper and excessive activation can cause inflammatory disease. We previously showed that glycolysis, a metabolic pathway that converts glucose into pyruvate, is essential for NLRP3 inflammasome activation in macrophages. Here, we investigated the role of metabolic pathways downstream glycolysis – lactic acid fermentation and pyruvate oxidation—in activation of the NLRP3 inflammasome. Using pharmacological or genetic approaches, we show that decreasing lactic acid fermentation by inhibiting lactate dehydrogenase reduced caspase-1 activation and IL-1β maturation in response to various NLRP3 inflammasome agonists such as nigericin, ATP, monosodium urate (MSU) crystals, or alum, indicating that lactic acid fermentation is required for NLRP3 inflammasome activation. Inhibition of lactate dehydrogenase with GSK2837808A reduced lactate production and activity of the NLRP3 inflammasome regulator, phosphorylated protein kinase R (PKR), but did not reduce the common trigger of NLRP3 inflammasome, potassium efflux, or reactive oxygen species (ROS) production. By contrast, decreasing the activity of pyruvate oxidation by depletion of either mitochondrial pyruvate carrier 2 (MPC2) or pyruvate dehydrogenase E1 subunit alpha 1 (PDHA1) enhanced NLRP3 inflammasome activation, suggesting that inhibition of mitochondrial pyruvate transport enhanced lactic acid fermentation. Moreover, treatment with GSK2837808A reduced MSU-mediated peritonitis in mice, a disease model used for studying the consequences of NLRP3 inflammasome activation. Our results suggest that lactic acid fermentation is important for NLRP3 inflammasome activation, while pyruvate oxidation is not. Thus, reprograming pyruvate metabolism in mitochondria and in the cytoplasm should be considered as a novel strategy for the treatment of NLRP3 inflammasome-associated diseases.

Interactions between NLRP3 inflammasome and glycolysis in macrophages: New insights into chronic inflammation pathogenesis

“…But the levels of NLRP3, ASC, pro-caspase-1 and pro-IL-1β did not change. 24 However, in other studies, increased lactate did not promote the activation of NLRP3 inflammasome. In macrophages and monocytes, exogenous lactate reduced TLR4-mediated induction of IL-1β, NLRP3, and pro-caspase-1; activation of nuclear factor κβ (NF-κB); release of IL-1β; and cleavage of caspase-1.…”

“…50 As the major negative regulator of autophagy, 60,61 mammalian target of rapamycin complex 1 (mTORC1) induces HK1 expression via phosphorylation of 4E-binding protein 1(4E-BP1), the eukaryotic translation initiation factor. 45,60,62 In line with Reduces the protein levels of mature IL-1β and active caspase-1 [24] Abbreviations: DET, deoxyelephantopin; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HIF-1a, hypoxia inducible factor-1α; HK, hexokinase; IL-18, interleukine-18; IL-1β, interleukine-1β; LBP, Lycium barbarum polysaccharide; NLRP3, Nod-like receptor protein 3; PK, pyruvate kinase; PKM, pyruvate kinase muscle isozyme.…”

“…22,23 NLRP3 specific ligands such as cholesterol crystals (CC), ATP, Lipopolysaccharidepore (LPS), forming toxins (nigericin) and monosodium urate (MSU) crystals, activate NLRP3 inflammasome. 21,24,25 It is often assumed that NLRP3 inflammasome activation in macrophage requires two steps: "priming" and "activation." The priming phase induces pro-IL-1β synthesis and NLRP3 upregulation., 26 while during the activation phase the oligomeric NLRP3 inflammasome complex assembles, thereby cleaving IL-1β and IL-18.…”

“…54 Lactate can induce phosphorylation of PKR, 47 promoting protein expression of PKR, induces the NLRP3 inflammasome-dependent IL-1β secretion in nigericin, ATP, monosodium urate (MSU) crystals, or alum stimulated BMDM and THP-1 cell. 24 The protein levels of mature IL-1β and active caspase-1 were reduced by using 2-DG or LDH inhibitor GSK2837808a, or by lactate dehydrogenase a (LDHA) specific small interfering RNA (siRNA). But the levels of NLRP3, ASC, pro-caspase-1 and pro-IL-1β did not change.…”

Participation of Acyl-Coenzyme A Synthetase FadD4 of Pseudomonas aeruginosa PAO1 in Acyclic Terpene/Fatty Acid Assimilation and Virulence by Lipid A Modification

“…The differential effects by LPS isolated from the fadD mutants could be explained in agreement to the roles that the IL-1 (IL-1α and IL-1β forms) plays in the regulation of immune response and inflammation, acting as an activator of T and B lymphocytes and natural killer cells, which require IL-1β for production of the anti-pathogen IFN-γ. In addition, differential induction of immune response may suggest the participation of different pathways such as the activation of the Nod-like receptor 3 (NLRP3) inflammasome, which is important for the activation of innate immune response to some DAMPs and PAMPs ( Behzadi et al, 2021b ; Lin et al, 2021 ).…”