Project description:Itaconate is produced by inflammatory macrophages and negatively feedbacks on inflammation. It is synthesized by aconitate decarboxylase 1 (ACOD1) from cis-aconitate, a metabolite of the tricarboxylic acid cycle. Here, we studied the role of ACOD1 in the inflammatory response of microglia, the resident macrophage-like cells of the brain. Similarly to macrophages, ACOD1 deficient microglia displayed a stronger inflammatory response to lipopolysaccharide (LPS) compared to their wild type counterparts. ACOD1 deficiency reprogramed arginine metabolism by enhancing argininosuccinate synthesis in the expense of polyamine synthesis in an ACLY-dependent manner. These findings provide new insights in the immunometabolic role of ACOD1 in inflammatory microglia.
Project description:TPL2 (MAP3K8) is a central signaling node in the inflammatory response of peripheral immune cells. We find that TPL2 kinase activity modulates microglial cytokine release and is required for microglia-mediated neuron death in vitro. In acute in vivo neuroinflammation settings, TPL2 kinase activity regulates cytokine levels and activation states of microglia. In a tauopathy model of chronic neurodegeneration, loss of TPL2 kinase activity reduces neuroinflammation and rescues synapse loss, brain volume loss, and behavioral deficits. Single-cell RNAseq analysis indicates protection in the tauopathy model was associated with reductions in activated microglia subpopulations as well as infiltrating peripheral immune cells. Overall, using various models, we find that TPL2 kinase activity promotes multiple harmful consequences of microglial activation in the brain including cytokine release, iNOS induction, astrocyte activation, and immune cell infiltration. Consequently, inhibiting TPL2 kinase activity could represent a potential therapeutic strategy in neurodegenerative conditions.
Project description:Metabolic reprogramming is a hallmark of the immune cells in response to inflammatory stimuli. This metabolic process involves a switch from oxidative phosphorylation (OXPHOS)to glycolysis, or alterations in other metabolic pathways. However, most of the experimental findings have been acquired in murine immune cells and little is known about the metabolic reprogramming of human microglia. In this study, we investigated the transcriptomic and metabolic profiles of mouse and iPSC-derived human microglia challenged with the TLR4 agonist LPS. We found that both species displayed a metabolic shift and an overall increased glycolytic gene signature in response to LPS treatment. The metabolic reprogramming was characterized by the upregulation of hexokinases in mouse microglia and phosphofructokinases in human microglia. This study provides the first direct comparison of energy metabolism between mouse and human microglia, highlighting the species-specific pathways involved in immunometabolism and the importance of considering these differences in translational research.
Project description:Although microglial have an essential role in host defense in the brain, the abnormal activation of microglia can lead to devastating outcomes, such as neuroinflammation and neurodegeneration. Emerging evidence increasingly supports that FTY720 (fingolimod), an FDA-approved drug has beneficial effects in the CNS on brain cells and more recently immunosuppressive activities in microglia via modulation of the S1P1 receptor. However, the exact molecular aspects of FTY720 contribution in microglia remain largely unaddressed. To understand the molecular mechanisms underlying the roles of FTY720 in microglia, we performed gene expression profiling in resting, FTY720, LPS and LPS+FTY720 challenged primary microglial cells (PM) isolated from 3-day-old ICR mice and we identified FTY720 target genes and co-regulated modules that were critical in inflammation. By examining RNA-sequencing and binding motif datasets from FTY720 suppressed LPS-induced inflammatory mediators, we also identified unexpected relationships between the inducible transcription factors (TFs), motif strength, and transcription of key inflammatory mediators. Furthermore, we show that FTY720 controls important inflammatory genes targets by modulating STAT1, and IRF8 level at their promoter site. Our unprecedented findings demonstrate that FTY720 could be a useful therapeutic application for neuroinflammatory diseases associated with microglia activation as well as provide a rich resource and framework for future analyses of FTY720 on microglia interaction.
Project description:Microglia become activated by disturbances in the homeostasis of their local microenvironment. While there are varying degrees of microglia activation, a pro-inflammatory reactive state induced by exposure to stimuli like LPS and IFN-γ. In this study, we identified a total of 5497 proteins in whole cell proteome and 4938 proteins for secretome of activated BV-2 mouse microglia cell line with LPS or IFN-γ using improved shotgun proteomic approach. From the differentially expressed proteins in stimulated microglia, we were able to classify pathways related immune-inflammatory response or metabolism. Moreover, we performed longitudinal quantification of secreted proteins during the detrimental activation of microglia which releases neurotoxic molecules mediated neuronal cell loss in the brain region.
Project description:Microglia are phagocytic cells that survey the brain and perform neuroprotective functions in response to tissue damage, but their activating receptors are largely unknown. Triggering receptor expressed on myeloid cells 2 (TREM2) is a microglial immunoreceptor whose loss-of-function mutations in humans cause presenile dementia, while genetic variants are associated with increased risk of neurodegenerative diseases. In myeloid cells, TREM2 has been involved in the regulation of phagocytosis, cell proliferation and inflammatory responses in vitro. However, it is unknown how TREM2 contributes to microglia function in vivo. Here, we identify a critical role for TREM2 in the activation and function of microglia during cuprizone (CPZ)-induced demyelination. TREM2-deficient (TREM2(-/-)) mice had defective clearance of myelin debris and more axonal pathology, resulting in impaired clinical performances compared to wild-type (WT) mice. TREM2(-/-) microglia proliferated less in areas of demyelination and were less activated, displaying a more resting morphology and decreased expression of the activation markers MHC II and inducible nitric oxide synthase as compared to WT. Mechanistically, gene expression and ultrastructural analysis of microglia suggested a defect in myelin degradation and phagosome processing during CPZ intoxication in TREM2(-/-) microglia. These findings place TREM2 as a key regulator of microglia activation in vivo in response to tissue damage. Two STAGE (6weeks 12 weeks),
Project description:Trained immunity and immune tolerance have been identified as long-term response patterns of the innate immune system. The causes of these opposing reactions remain elusive. Here we report about differential inflammatory responses of microglial cells derived from neonatal mouse brain to increasing doses of the endotoxin LPS. Prolonged priming with ultra-low LPS doses provokes trained immunity, i.e. increased production of pro-inflammatory mediators in comparison to the unprimed control. In contrast, priming with high doses of LPS induces immune tolerance implying decreased production of inflammatory mediators and pronounced release of anti-inflammatory cytokines. Investigation of the signaling processes and cell functions involved in these memory-like immune responses reveals essential role of phosphoinositide 3-kinase γ (PI3Kγ), one of the phosphoinositide 3-kinase species highly expressed in innate immune cells. Together, our data suggest profound influence of preceding contacts with pathogens on the immune response of microglia. The impact of these interactions – trained immunity or immune tolerance - appears to be shaped by pathogen dose.
Project description:Siponimod (Mayzent®), a sphingosine 1-phosphate receptor (S1PR) modulator which prevents lymphocyte egress from lymphoid tissues, is approved for the treatment of relapsing-remitting- and active secondary progressive multiple sclerosis. It can cross the blood-brain-barrier (BBB) and selectively binds to S1PR1 and S1PR5 expressed by several cell populations of the central nervous system (CNS) including microglia. To investigate wether Siponimod modulates the genetic signature of inflammed microglia, we performed a transcriptome analyses of primary rat microglial cells stimulated with LPS and With or Without Siponimod.
Project description:Expression of Itgax (encoding the CD11c surface protein) and Spp1 (encoding OPN) have been associated with activated microglia that can develop in healthy brains and some neuroinflammatory disorders. Here, we show that OPN production in the brain is confined to a small CD11c+ microglial subset that differentiates from CD11c- precursors in perinatal life after uptake of apoptotic neurons. Our analysis suggests that co-expression of OPN and CD11c genes marks a microglial subset that is expressed at birth and persists into late adult life, independent of environmental activation stimuli. Definition of OPN-producing CD11c+ microglia as a functional microglial subset provides new insight into microglial differentiation in health and disease.