Project description:We identified caspase-4/S1P/SREBP1 pathway that is activated in LPS-treated macrophages. To analyze the functions of caspase-4 and SREBP1 in gene expression in macrophages, we analyzed the effects of deletions of Casp4 and Srebf1 in bone marrow-derived macrophages by RNA-seq.
Project description:Macrophages exhibit a spectrum of activation states ranging from classical to alternative activation1. Alternatively activated macrophages are involved in diverse pathophysiological processes such as confining tissue parasites2, improving insulin sensitivity3 or promoting an immune tolerant microenvironment that facilitates tumour growth and metastasis4. Recently, the role of metabolism in the regulation of macrophage function has come into focus as both the classical and alternative activation programmes require specific regulated metabolic reprogramming5. While most of the studies regarding immunometabolism have focussed on the catabolic pathways activated to provide energy, little is known about the anabolic pathways mediating macrophage alternative activation. In this study, we show that the anabolic transcription factor sterol regulatory element binding protein 1 (SREBP1) is activated in response to the canonical Th2 cytokine interleukin 4 (IL-4) to trigger the de novo lipogenesis (DNL) programme, as a necessary step for macrophage alternative activation. Mechanistically, DNL consumes NADPH, partitioning it away from cellular antioxidant defences and raising ROS levels. ROS serves as a second messenger, signalling sufficient DNL, and promoting macrophage alternative activation. The pathophysiological relevance of this mechanism is validated by showing that SREBP1/DNL is essential for macrophage alternative activation in vivo in a helminth infection model.
Project description:Human macrophages secrete extracellular vesicles loaded with numerous immunoregulatory proteins. Here we employed high throughput quantitative proteomics to characterize the modulation of vesicle-mediated protein secretion during non-canonical caspase-4/5-dependent inflammasome activation. We show that human macrophages activate robust caspase-4- dependent extracellular vesicle secretion upon transfection of LPS, and this process is also partially dependent on NLRP-3 and caspase-5. Similar effect occurs with delivery of the LPS with E. coli-derived outer membrane vesicles. Moreover, sensitization of the macrophages through TLR4 prior to LPS transfection dramatically augments the EV-mediated protein secretion. Our data demonstrate that this process differs significantly from ATP-induced vesiculation, and is dependent on autocrine interferon signal associated with TLR4 activation. TLR4 activation preceding the non-canonical inflammasome activation significantly enhances vesicle-mediated secretion of inflammasome components caspase-1, ASC and lytic cell death effectors GSDMD, MLKL and NINJ1, suggesting that inflammatory EV transfer may exert paracrine effects in recipient cells. Moreover, using bioinformatic methods, we identify 15-deoxy-delta-12,14-prostaglandin J2 and parthenolide as inhibitors of caspase-4-mediated inflammation and vesicle secretion, indicating potential new therapeutic potential of these anti-inflammatory drugs.
Project description:The purpose of this study is to investigate how SREBP1a in macrophages regulates cellular function during muscle regeneration process after injury. We report that the systemic deletion of Srebf1, encoding SREBP1, and macrophage-specific deletion of Srebf1a, encoding SREBP1a, delays the resolution of inflammation, and impairs skeletal muscle regeneration after injury. Srebf1 deficiency impairs mitochondrial function of macrophages and suppresses the accumulation of reparative macrophages to the injured site.
Project description:Gut microbiota contributes to the regulation of host immune response and homeostasis. Bile acid (BA) derivatives from gut microbiota can affect the differentiation and function of the immune cells. However, it is incompletely clear for the regulation of BA metabolites in the macrophages. We here find that BA metabolites can regulate sensitivity of macrophages to LPS and or Gram-negative bacteria. BA derivatives could induce lncRNA57RIK expression through sphingosine-1-phosphate receptor 2 (S1PR2) in the macrophages of mice and humans, which play a critical role in Gram-negative bacteria mediated IL-1β maturation and pyroptosis of macrophages. This lncRNA57RIK could bind intracellular proteases caspase-4/11 with guanylate-binding protein 1 (GBP1) in the human and mice together to cause LPS mediated activation of caspase-4/11. Murine or human lncRNA57RIK knockout (KO) macrophages did not produce response(s) to LPS or gram negative bacteria. LncRNA57RIK KO mice had also reduced inflammatory responses to LPS or Salmonella typhimurium (S.T) infection. Taken together, gut microbiota derived BA metabolites mediated lncRNA57RIK is necessary for LPS induced caspase-4/11 activation.
Project description:To systematically understand how the circadian clock and the nutrient-driven rhythm integrate to regulate SREBP1 activity, we evaluated genome-wide the binding of SREBP1 to its targets along the day in wild-type (WT) C57BL/6mice. The recruitment of SREBP1 to the DNA showed a highly circadian behaviour, with a maximum during the fed status. However, the temporal expression of SREBP1 targets was not always synchronized with its binding. In particular, a different phase of expression was observed for SREBP1 target genes depending on their function, suggesting the involvement of other transcription factors in their regulation. The proper temporal expression pattern of these genes was dramatically changed in Bmal1KO mice upon time-restricted feeding, in spite of the rhythmic, although slightly delayed, binding of SREBP1. Our results show that besides the nutrient-driven regulation of SREBP1 nuclear translocation, a second layer of modulation of SREBP1 transcriptional activity exists and is strongly dependent from the circadian core clock. This system allows to fine tune the expression timing of SREBP1 target genes, thus helping to temporally separate the different physiological processes in which these genes are involved. 6 samples examined, 6 SREBP1 samples, as well as 6 Polr2b and 6 input samples from GEO series GSE35788 CycliX Consortium was a contributor to this submission.
Project description:Caspase-1 activation senses metabolic danger-associated molecular patterns and mediates the initiation of inflammation. Here, we reported that caspase-1 contributes to hyperlipidemia-induced modulation of vascular cell gene expression during early atherosclerosis in vivo. Our results demonstrate the therapeutic potential of caspase-1 inhibition in the treatment of cardiovascular diseases.
Project description:Caspase-1 activation senses metabolic danger-associated molecular patterns and mediates the initiation of inflammation. Here, we reported that caspase-1 contributes to hyperlipidemia-induced modulation of vascular cell gene expression during early atherosclerosis in vivo. Our results demonstrate the therapeutic potential of caspase-1 inhibition in the treatment of cardiovascular diseases. All mice were in a C57B/L6 strain background. Male wild-type mice, Apolipoprotein E (ApoE) gene knockout mice, and ApoE/Caspase-1 double gene deficient mice were fed with high fat diet for 3 weeks starting from 8 weeks to induce early dyslipidemia. At 11-week of age, aortas from these mice were used for microarray analysis. 5 biological replicates in each group.