Single-cell RNA sequencing explores the mechanisms underlying the protective effects of myeloid cell-specific Pkm gene knockout in ALF-modeling mice
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ABSTRACT: Acute liver failure (ALF) has an extremely high mortality rate and lacks effective treatment. Previous studies have shown that targeting macrophage pyruvate kinase isoenzyme type M2 (PKM2) may be a new approach for ALF treatment, but the exact mechanism remains to be elucidated. In this project, based on Single-cell RNA-sequencing (scRNA-seq), Pkm myeloid selective knockout (PL) mice and wild-type (WT) mice were used to establish ALF model, analyze the single-cell transcriptomic features of liver tissues of WT mice during ALF pathology, and screen for the differentially expressed genes in liver tissues of PL mice. Potential molecular pathways of PKM2 regulation of ALF in macrophages were explored by bioinformatics analysis and validated by molecular biology methods. Result shows that, up-regulated genes in macrophages and neutrophils in mouse liver tissues during ALF were mainly enriched in multiple programmed death, such as pyroptosis, apoptosis and necroptosis, and immune-inflammation pathways. The down-regulated genes in PL mouse liver macrophages and neutrophils were mostly enriched in the above pathways. Among them, Pkm knockdown significantly down-regulated the expression of key genes of NOD-like signaling pathway, such as NLRP3, IL-1β and IL-18, inhibited hepatic macrophage pyroptosis and attenuated ALF. This study will help to elucidate the molecular mechanism of PKM2 regulating macrophage inflammatory response involved in ALF, suggesting that PKM2 may be a potential therapeutic target for ALF, and providing a theoretical basis for further research on new methods of targeting PKM2 in the treatment of ALF.
Project description:Pyruvate kinase M2 (PKM2), the rate-limiting enzyme of glycolysis, plays a critical role in macrophage activation and a broad spectrum of chronic liver diseases. However, whether PKM2 contributes to the pathogenesis of acute liver injury (ALI) remains largely unexplored. By bioinformatic screening and analysis of ALI liver, we found that PKM2 was significantly upregulated in the liver tissues of ALI patients and mice. Immunofluorescence staining further demonstrated that PKM2 was markedly upregulated in macrophages during ALI progression. Notably, macrophage PKM2 depletion effectively alleviated acetaminophen (APAP)- and lipopolysaccharide/D-galactosamine (LPS/D-GalN)-induced ALI, as demonstrated by ameliorated immune cells infiltration, pro-inflammatory mediators, and hepatocellular cell death. PKM2-deficient macrophages showed M2 anti-inflammatory polarization in vivo and in vitro. Furthermore, PKM2 deletion limited HIF-1α signaling and aerobic glycolysis of macrophages, which thereby attenuated macrophage pro-inflammatory activation and hepatocyte injury. Pharmacological PKM2 antagonist efficiently ameliorated liver injury and prolonged the survival of mice in APAP-induced ALI model. Our study highlights the pivotal role of macrophage PKM2 in advancing ALI, and therapeutic targeting of PKM2 may serve as a novel strategy to combat ALI.
Project description:Alternative splicing of the Pkm gene product generates the PKM1 and PKM2 isoforms of pyruvate kinase, and PKM2 expression is closely linked to embryogenesis, tissue regeneration, and cancer. To interrogate the functional requirement for PKM2 during development and tissue homeostasis, we generated germline PKM2 null mice (Pkm2-/-). Unexpectedly, despite being the primary isoform expressed in most wild-type adult tissues, we found that Pkm2-/- mice are viable and fertile. Thus, PKM2 is not required for embryonic or postnatal development. Loss of PKM2 leads to compensatory expression of PKM1 in the tissues that normally express PKM2. Strikingly, PKM2 loss leads to spontaneous development of hepatocellular carcinoma (HCC) with high penetrance that is accompanied by progressive changes in systemic metabolism characterized by altered systemic glucose homeostasis, inflammation, and hepatic steatosis. Therefore, in addition to its role in cancer metabolism, PKM2 plays a role in controlling systemic metabolic homeostasis and inflammation, thereby preventing HCC by a non-cell-autonomous mechanism. RNA was isolated from flash frozen ground whole liver tissue of 35 week old PKM2 KO and WT mice. Three independent mice from each condition were used as biological replicates.
Project description:Nonalcoholic steatohepatitis (NASH) might soon become the leading cause of end-stage liver disease worldwide with limited treatment options. Liver fibrosis, driven by chronic inflammation and hepatic stellate cells (HSCs) activation, critically determines morbidity and mortality in patients with NASH. Pyruvate kinase M2 (PKM2) is involved in immune activation and inflammatory liver diseases; however, its role and therapeutic potential in NASH fibrosis remain largely unexplored. By bioinformatic screening and analysis of human and murine NASH livers, we found that PKM2 was specifically upregulated in non-parenchymal cells (NPCs) in fibrotic NASH livers, especially in macrophages. Macrophage-specific Pkm2 knockout (Pkm2fl/flLysMCre) significantly ameliorated hepatic inflammation and fibrosis severity in three distinct NASH models induced by methionine–choline-deficient (MCD) diet, high-fat high-cholesterol (HFHC) diet and western diet plus weekly carbon tetrachloride injection (WD/CCl4). Single-cell transcriptomic analysis indicated that deletion of PKM2 in macrophage reduced profibrotic Ly6Chigh macrophage infiltration. Mechanistically, PKM2-dependent glycolysis promotes NLRP3 activation in proinflammatory macrophages, thus inducing HSCs activation and fibrogenesis. Pharmacological PKM2 agonist efficiently attenuated the profibrotic crosstalk between macrophages and HSCs in vitro and in vivo. Translationally, ablation of PKM2 in NPCs by cholesterol-conjugated heteroduplex oligonucleotides, a novel oligonucleotide drug that preferentially accumulated in the liver, dose-dependently reversed NASH fibrosis without observable hepatotoxicity. Our study highlights the pivotal role of macrophage PKM2 in advancing NASH fibrogenesis. Therapeutic modulation of PKM2 in a macrophage-specific or liver-specific fashion may serve as a novel strategy to combat NASH fibrosis.
Project description:Alternative splicing of the Pkm gene product generates the PKM1 and PKM2 isoforms of pyruvate kinase, and PKM2 expression is closely linked to embryogenesis, tissue regeneration, and cancer. To interrogate the functional requirement for PKM2 during development and tissue homeostasis, we generated germline PKM2 null mice (Pkm2-/-). Unexpectedly, despite being the primary isoform expressed in most wild-type adult tissues, we found that Pkm2-/- mice are viable and fertile. Thus, PKM2 is not required for embryonic or postnatal development. Loss of PKM2 leads to compensatory expression of PKM1 in the tissues that normally express PKM2. Strikingly, PKM2 loss leads to spontaneous development of hepatocellular carcinoma (HCC) with high penetrance that is accompanied by progressive changes in systemic metabolism characterized by altered systemic glucose homeostasis, inflammation, and hepatic steatosis. Therefore, in addition to its role in cancer metabolism, PKM2 plays a role in controlling systemic metabolic homeostasis and inflammation, thereby preventing HCC by a non-cell-autonomous mechanism.
Project description:This study demonstrated that ARID1A loss markedly promotes lung tumorigenesis in genetic mice models. RNA sequencing reveals significant enrichment of the glycolytic pathway in ARID1A-deficient tumors, which is characterized by the upregulation of PGAM1, PKM2, and PGK1. Besides, ARID1A depletion increases chromatin accessibility and enhances the binding ability of Hif-1a to the promoter regions of Pgam1, Pkm, and Pgk1. In patients with lung cancer, ARID1A status is negatively correlated with mRNA level of PGAM1, PKM, and PGK1.
Project description:During myocardial infarction (MI), energy production decreases as hypoxia inhibits oxidative metabolism. Our lab has identified an ischemia-regulated alternative splicing event of the glycolytic enzyme pyruvate kinase (muscle, PKM), reducing PKM1 expression and increasing PKM2 expression. We hypothesized the upregulation of PKM2 aids in energy production to maintain heart function after MI. We utilized high-throughput sequencing to evaluate altered gene expression and identify pathways that may be regulated by PKM2.
Project description:Pneumococcal pneumonia is a leading cause of death and a major source of human morbidity. The initial immune response plays a central role in determining the course and outcome of pneumococcal disease. We combine bacterial titer measurements from mice infected with Streptococcus pneumoniae with mathematical modeling to investigate the coordination of immune responses and the effects of initial inoculum on outcome. To evaluate the contributions of individual components, we systematically build a mathematical model from three subsystems that describe the succession of defensive cells in the lung: resident alveolar macrophages, neutrophils and monocyte-derived macrophages. The alveolar macrophage response, which can be modeled by a single differential equation, can by itself rapidly clear small initial numbers of pneumococci. Extending the model to include the neutrophil response required additional equations for recruitment cytokines and host cell status and damage. With these dynamics, two outcomes can be predicted: bacterial clearance or sustained bacterial growth. Finally, a model including monocyte-derived macrophage recruitment by neutrophils suggests that sustained bacterial growth is possible even in their presence. Our model quantifies the contributions of cytotoxicity and immune-mediated damage in pneumococcal pathogenesis.
Project description:Aplastic anaemia (AA) is a disease that shows complex pathogenesis involving multiple immune factors. While immunosuppressive therapies such as cyclosporine can effectively control AA, they may be ineffective in certain patients or those with relapse. Therefore, new treatments are needed. Among the targets for these treatments, the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway regulates inflammatory cytokines and immune activation. Ruxolitinib, a JAK1/2 inhibitor, reduces T-cell activation and the associated inflammatory response and improves AA disease status in mice. However, its mechanism of action is unclear; thus, further research is needed before its clinical use. We previously showed increased pyroptosis in patients with severe AA (SAA) and that macrophage pyroptosis is an important factor in immune activation. The current study investigated the interaction of ruxolitinib with macrophages and whether the drug could treat SAA by improving pyroptosis levels. We induced differentiation of the THP-1 human monocyte cell line into macrophages in vitro and then induced pyroptosis. After constructing a macrophage pyroptosis model, treatment with different concentrations of ruxolitinib was administered. The results showed that ruxolitinib reduced the levels of pyroptosis and inflammatory-related factors. A mouse model of SAA was validated. In conclusion, ruxolitinib may treatment affects SAA by reducing the level of macrophage pyroptosis.
Project description:Macrophages are involved in the pathophysiology of many diseases as critical cells of the innate immune system. Pyroptosis is a form of macrophage death that induces cytokinesis of phagocytic substances in the macrophages, thereby defending against infection. Dimethyl itaconate (DI) is an analog of itaconic acid with anti-inflammatory effects. However, the effect of dimethyl itaconate on macrophage pyroptosis has not been elucidated clearly. Thus, the present study aimed to analyze the effect of DI treatment on a macrophage pyroptosis model (Lipopolysaccharide, LPS+Adenosine Triphosphate, ATP). The results showed that 0.25 mM DI ameliorated macrophage pyroptosis and downregulated interleukin (IL)-1β expression. Then, real-time quantitative polymerase chain reaction (RT-qPCR) was used to confirm the result of RNA-sequencing of the upregulated oxidative stress-related genes (Gclc and Gss) and downregulated inflammation-related genes (IL-12β and IL-1β). In addition, Gene Ontology (GO) enrichment analysis showed that differential genes were associated with transcript levels and DNA replication. Kyoto encyclopedia of genes and genomes (KEGG) enrichment showed that signaling pathways, such as tumor necrosis factor (TNF), Jak, Toll-like receptor and IL-17, were altered after DI treatment. N-acetyl-L-cysteine (NAC) reversed the DI effect on the LPS+ATP-induced macrophage pyroptosis and upregulated the IL-1β expression. Oxidative stress-related protein Nrf2 is involved in the DI regulation of macrophage pyroptosis. Taken together, these findings suggested that DI alleviates the pyroptosis of macrophages through oxidative stress.
Project description:T cells stimulated in the absence of CD28 costimulation are functionally anergic, characterized by reduced glucose metabolism and ability to produce effector cytokines. Surprisingly, previous studies have shown relatively few CD28-specific changes in gene transcription upon costimulation. Using mice expressing mutations in the CD28 cytoplasmic tail, we show a major effect of CD28 costimulation is alternative splicing of numerous genes including the glycolytic enzyme pyruvate kinase (Pkm), which is preferentially spliced from Pkm1 to Pkm2 upon stimulation. PKM2 is dispensable for T cell activation, but necessary for CD8+ T cells to utilize aerobic glycolysis, produce effector cytokines, and provide anti-tumor immunity. Mechanistically, CD28 regulates expression of the Cap-Binding Complex adaptor protein ARS2, which binds Pkm splicing factors and facilitates their interaction with the elongating transcript. Data suggest a major function of CD28 costimulation is control of RNA biogenesis in support of T cell transcriptome remodeling and acquisition of effector function.