Project description:Microglia are the resident mononuclear phagocytes of the CNS parenchyma and represent an initial line of defense against invading microorganisms. Microglia utilize Toll-like receptors (TLRs) for pathogen recognition and TLR2 specifically senses conserved motifs of gram-positive bacteria including lipoproteins, lipoteichoic acids, and peptidoglycan (PGN) leading to cytokine/chemokine production. Interestingly, primary microglia derived from TLR2 knockout (KO) mice over-expressed numerous IL-12 family members, including IL-12p40, IL-12p70, and IL-27 in response to intact S. aureus, but not the less structurally complex TLR2 ligands Pam3CSK4 or PGN. The ability of intact bacteria to augment IL-12 family member expression was specific for gram-positive organisms, since numerous gram-negative strains were unable to elicit exaggerated responses in TLR2 KO microglia. Inhibition of SYK or IRAK4 signaling did not impact heightened IL-12 family member production in S. aureus-treated TLR2 KO microglia, whereas PI3K, MAPK, and JNK inhibitors were all capable of restoring exaggerated cytokine expression to wild type levels. Additionally, elevated IL-12 production in TLR2 KO microglia was ablated by a TLR9 antagonist, suggesting that TLR9 drives IL-12 family member production following exposure to intact bacteria that remains unchecked in the absence of TLR2 signaling. Collectively, these findings indicate crosstalk between TLR2 and TLR9 pathways to regulate IL-12 family member production by microglia. The summation of TLR signals must be tightly controlled to ensure the timely cessation and/or fine tuning of cytokine signaling to avoid nonspecific bystander damage due to sustained IL-12 release.
Project description:Microglia are the resident mononuclear phagocytes of the CNS parenchyma and represent an initial line of defense against invading microorganisms. Microglia utilize Toll-like receptors (TLRs) for pathogen recognition and TLR2 specifically senses conserved motifs of gram-positive bacteria including lipoproteins, lipoteichoic acids, and peptidoglycan (PGN) leading to cytokine/chemokine production. Interestingly, primary microglia derived from TLR2 knockout (KO) mice over-expressed numerous IL-12 family members, including IL-12p40, IL-12p70, and IL-27 in response to intact S. aureus, but not the less structurally complex TLR2 ligands Pam3CSK4 or PGN. The ability of intact bacteria to augment IL-12 family member expression was specific for gram-positive organisms, since numerous gram-negative strains were unable to elicit exaggerated responses in TLR2 KO microglia. Inhibition of SYK or IRAK4 signaling did not impact heightened IL-12 family member production in S. aureus-treated TLR2 KO microglia, whereas PI3K, MAPK, and JNK inhibitors were all capable of restoring exaggerated cytokine expression to wild type levels. Additionally, elevated IL-12 production in TLR2 KO microglia was ablated by a TLR9 antagonist, suggesting that TLR9 drives IL-12 family member production following exposure to intact bacteria that remains unchecked in the absence of TLR2 signaling. Collectively, these findings indicate crosstalk between TLR2 and TLR9 pathways to regulate IL-12 family member production by microglia. The summation of TLR signals must be tightly controlled to ensure the timely cessation and/or fine tuning of cytokine signaling to avoid nonspecific bystander damage due to sustained IL-12 release. TLR2 KO mice were backcrossed with C57BL/6 animals for a minimum of eight generations prior to use in these studies. Age- and sex-matched C57BL/6 mice were used as wild type (WT) controls. Primary mixed glial cultures were prepared from the cerebral corticies of neonatal mice (2-4 days of age) and microglia were harvested using a differential shaking technique with a purity of >98%. A USA300 community-acquired methicillin-resistant S. aureus (CA-MRSA) clinical isolate recovered from a patient with a fatal brain abscess was used to stimulate the microglia isolates. Bacterial strains were heat-inactivated and used to stimulate microglia at 107 colony forming units (cfu)/well for 6 and 12 hours time points. Three replicates of each mouse type (WT, TLR2 KO) at both time points 6 and 12 hours were used for the microarray experiments. Data was only usable for 2 replicates of the KO-12 hr group.
Project description:To investigate the similarity of toll-like receptor tolerance in macrophages stimulated with different toll-like receptor ligands we stimulated naïve or tolerant macrophages with ligands for TLR4, TLR2, TLR3 and TLR9. The data identifies a core set of genes that are tolerised by all ligands and genes that show TLR specific patterns.
Project description:Cytokines of the interleukin 12 (IL-12) family are assembled combinatorially from shared alpha and beta subunits. A common theme is that human IL-12 family alpha subunits remain incompletely structured in isolation until they pair with a designate beta subunit. Accordingly, chaperones need to support and control specific assembly processes. Here, we site-specifically introduce photo-crosslinking amino acids into the IL-12 and IL-23 alpha subunits (IL-12alpha and IL-23alpha). This allows to stabilize transient chaperone:client complexes for mass spectrometry and reveals a large set of ER chaperones to interact with IL-12alpha and IL-23alpha. Among those, we focus on protein disulfide isomerase (PDI) family members and reveal IL-12 family subunits to be clients of several ill-characterized PDIs. We find that different PDIs show selectivity for different cysteines in IL-12alpha and IL-23alpha. Despite this, PDI binding generally stabilizes unassembled IL-12alpha and IL-23alpha against degradation. In contrast, alpha:beta assembly appears robust and only multiple simultaneous PDI depletions reduce IL-12 secretion. Our comprehensive analysis of the IL-12/IL-23 chaperone machinery reveals a hitherto uncharacterized role for several PDIs in this process. This extends our understanding of how cells accomplish the task of specific protein assembly reactions for signaling processes. Furthermore, our findings show that cytokine secretion can be modulated by targeting specific ER chaperones.
Project description:Toll like receptors (TLRs) sense microbial products and initiate adaptive immune responses by activating dendritic cells (DCs). Since pathogens may contain several agonists we asked whether different TLRs may synergize in DC activation. We report that in human and mouse DC TLR3 or TLR4 potently synergize with TLR7, TLR8 or TLR9 in the induction of selected cytokine genes. Upon synergistic stimulation, IL-12, IL-23 and Delta-4 are induced at levels 50-100 fold higher than those induced by optimal concentrations of single agonists, leading to enhanced and sustained TH1 polarizing capacity. Using microarray analysis we show that only 1.5% of the transcripts induced by single TLR agonists are synergistically regulated by combinations of TLR4 and TLR8 agonists.. These results identify a combinatorial code by which DCs discriminate pathogens and provide (suggest) a rationale to design adjuvants for TH1 responses. Series_overall_design: 3 untreated, 3 treated with LPS at 2h, 3 treated with LPS at 8h, 3 treated with R848 at 2h, 3 treated with R848 at 8h, 3 treated with LPS + R848 at 2h, 3 treated with LPS + R848 at 8h
Project description:Abnormal accumulation of aggregated proteins and sustained microglial activation are important contributors of neurodegenerative process in neurological diseases. Recent studies have shown that aggregation-prone proteins, such as a-synuclein, the protein implicated in Parkinson’s disease (PD), are released from neuronal cells and thus present in the extracellular fluid, pointing to the possible paracrine effects of these proteins on microglial immune responses. However, the mechanism underlying the disease-associated microglial activation and the role of neuronal proteins in this process remain unknown. Here, we show that extracellular a-synuclein released from neuronal cells is an endogenous ligand of toll-like receptor 2 (TLR2) and activates microglia, which in turn induces neurodegeneration. Interaction between neuron-released a-synuclein and TLR2 and subsequent activation of the TLR2 signaling were demonstrated comprehensively by using computational modeling of signaling network and by the experimental validation in TLR2-deficient microglia both in vitro and in vivo. In contrast to the neuron-released a-synuclein, recombinant a-synuclein proteins, including monomer, oligomer, fibril, or nitrated forms, were not able to interact or activate TLR2, suggesting that neuronal cells have a mechanism of enriching specific forms of a-synuclein capable of activating TLR2 during the process of releasing this protein. Taken together, the results suggest that both neuron-released extracellular a-synuclein and TLR2 might be novel therapeutic targets for modifying neuroinflammation in PD and related neurodegenerative diseases. We collected culture media from differentiated SH-SY5Y cells overexpressing either human a-synuclein (alpha-SCM) or beta-galactosidase (LZCM) and treat these media to primary rat microglia at the concentration of a-synuclein of 1.1M. Transcriptome analyses with microglial cells treated with either aSCM or LZCM at two different time points, 6 h and 24 h.
Project description:In this model, TLR2-TLR6 mediates MyD88 pathway gets activated, which activates IL-12 production and induces iNOS expression when the Macrophage is infected with Leishmania parasite. The early induction of IL-10 takes place which leads to the induction of NFIL3, HDAC3, and SHP-1. They inhibit IL-12 production and thus hamper IL-12 induced IFN-gamma mediated; Nitric oxide production. A key transcription factor NFAT5 connects IL-12 and IL-10 pathways. It upregulates IL-12 and downregulates IL-10. In this model, NFAT5 is downregulated which is also inhibiting IL-12.
Project description:To investigate Toll-like receptors (TLR) signaling in Chronic lymphocytic leukemia (CLL) cell lines, we analyzed HG-3, MEC-2 and PCL-12 CLL cell lines before and after TLR9 stimulation by RNA-sequencing followed by bioinformatic analyses and validation experiments.
Project description:Purpose: The goal of this study was to characterize the gingival oral barrier immunity of TLR9 ligand (CpG oligonucleotide) and TLR2/4 ligand (LPS)-treated mouse maxilla. Method: TLR9 ligand or TLR2/4 ligand was topically applied to the mouse palatal gingiva. Mouse palatal gingiva was harvested at 4 days after topical application. Gingival cells were harvested and subjected to 10X Genomix scRNA-seq. Cell Ranger processed data were analysed.
Project description:Interferon-induced transmembrane protein 3 (IFITM3) is a restriction factor that limits viral pathogenesis and exerts poorly understood immunoregulatory functions. Here, using human and mouse models, we demonstrate that IFITM3 promotes MyD88-dependent, TLR-mediated IL-6 production following exposure to cytomegalovirus (CMV). IFITM3 also restricts IL-6 production in response to influenza and SARS-CoV-2. In dendritic cells, IFITM3 binds to the reticulon 4 isoform Nogo-B and promotes its proteasomal degradation. We reveal that Nogo-B mediates TLR-dependent pro-inflammatory cytokine production and promotes viral pathogenesis in vivo, and in the case of TLR2 responses, this process involves alteration of TLR2 cellular localization. Nogo-B deletion abrogates inflammatory cytokine responses and associated disease in virus-infected IFITM3-deficient mice. Thus, we uncover Nogo-B as a driver of viral pathogenesis and highlight an immunoregulatory pathway in which IFITM3 fine-tunes the responsiveness of myeloid cells to viral stimulation.