LPS-induced gene expression changes in phraryngeal epithelial cells
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE132019 | GEO | 2019/06/01
REPOSITORIES: GEO
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Project description:Four daily intraperitoneal injections of the Gram-negative bacterial endotoxin lipopolysaccharide (LPS) transiently protects the cerebral cortex against traumatic brain injury. Underlying mechanisms associated with this neuroprotection include increased neuronal production of anti-apoptotic and neurotrophic molecules, microglial-mediated displacement of inhibitory presynaptic terminals innervating the soma of cortical projection neurons, and synchronized firing of cortical projection neurons. The molecular mechanisms responsible for inducing this neuroprotection and microglial activation are unknown. A fundamental question is whether LPS enters the central nervous system (CNS) or mediates it actions on the luminal surface of brain endothelial cells. In this study, we demonstrate that LPS injected into the peritoneum does not enter the CNS or alter tight junctions of brain endothelial cells. However, LPS activation of vascular endothelial cells was substantiated by increased expression of activation markers (CD54 and CD105) and the LPS receptor, TLR4, on CD31-positive brain endothelial cells isolated by flow cytometry. Transcript analyses further revealed significant upregulation of Cxcl10, C3, Ccl2, Il1b, Cxcl2, and Cxcl1 in these activated endothelial cells, consistent with identification of MyD88 as a regulator of these transcripts by pathway analysis. Using conditional brain endothelial gene ablation strategies, we establish that MyD88-dependent endothelial TLR4 signaling and endothelial Cxcl10 expression are essential for LPS-induced neuroprotection and microglial activation. CXCL10 production by brain endothelial cells in response to circulating TLR ligands thus provides a pathway to directly or indirectly signal to CXCR3 on neurons and/or microglia. Targeting activation of brain endothelial receptors provides an attractive and practical approach for inducing transient neuroprotection.
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Project description:A cyanobacterial LPS antagonist prevents endotoxin shock and blocks sustained TLR4 stimulation required for cytokine expression. We report the identification and biologic characterization of an LPS-like molecule extracted from the cyanobacterium Oscillatoria Planktothrix FP1 (CyP).
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Project description:MicroRNAs regulated by lipopolysaccharide (LPS) target genes that contribute to the inflammatory phenotype. Here we showed that the protein kinase Akt1, which is activated by LPS, positively regulated miRNAs let-7e, miR-181c but negatively regulated miR-155 and miR-125b. In silico analyses and transfection studies revealed that let-7e repressed Toll-like receptor 4 (TLR4) whereas miR-155 repressed SOCS1, two proteins critical for LPS-driven TLR signalling, which regulate endotoxin sensitivity and tolerance. As a result, Akt1-/- macrophages exhibited increased responsiveness to LPS in culture and Akt1-/- mice did not develop endotoxin tolerance in vivo. Overexpression of let-7e and suppression of miR-155 in Akt1-/- macrophages restored sensitivity and tolerance to LPS in culture and in animals. These results indicate that Akt1 regulates the response of macrophages to LPS by controlling miRNA expression. The data deposited here contain the entire analysis of miRNA profile of Akt1+/+ and Akt1-/- thioglycollate elicited peritoneal macrophages following stimulation with LPS for 3 hours in culture.
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Project description:MicroRNAs regulated by lipopolysaccharide (LPS) target genes that contribute to the inflammatory phenotype. Here we showed that the protein kinase Akt1, which is activated by LPS, positively regulated miRNAs let-7e, miR-181c but negatively regulated miR-155 and miR-125b. In silico analyses and transfection studies revealed that let-7e repressed Toll-like receptor 4 (TLR4) whereas miR-155 repressed SOCS1, two proteins critical for LPS-driven TLR signalling, which regulate endotoxin sensitivity and tolerance. As a result, Akt1-/- macrophages exhibited increased responsiveness to LPS in culture and Akt1-/- mice did not develop endotoxin tolerance in vivo. Overexpression of let-7e and suppression of miR-155 in Akt1-/- macrophages restored sensitivity and tolerance to LPS in culture and in animals. These results indicate that Akt1 regulates the response of macrophages to LPS by controlling miRNA expression. The data deposited here contain the entire analysis of miRNA profile of Akt1+/+ and Akt1-/- thioglycollate elicited peritoneal macrophages following stimulation with LPS for 3 hours in culture. Thioglycollate elicited macrophages were cultured in complete DMEM medium, stimulated with LPS for 3 hours and RNA was extracted. Samples were analyzed using Taq-man PCR miRNA arrays (Dana Farber microarray Facility).
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Project description:Toll-like receptor 4 (TLR4) plays a pivotal role in the host response to lipopolysaccharide (LPS), a major cell wall component of Gram-negative bacteria. Here we elucidated whether the endocytic adaptor protein Disabled-2 (Dab2) that is abundantly expressed in the macrophages plays a role in LPS-stimulated TLR4 signaling and trafficking. Molecular analysis and transcriptome profiling of the RAW264.7 macrophage-like cells expressing short-hairpin RNA of Dab2 revealed that Dab2 mainly regulated LPS-stimulated TRIF-dependent, but not MyD88-dependent TLR4 signaling. Consequently, knockdown of Dab2 augmented TRIF-dependent interferon regulatory factor 3 activation and the expression for the subsets of inflammatory cytokines and interferon-inducible genes. We further delineated that Dab2 acted as a “clathrin sponge” and sequestered clathrin from TLR4/MD2 complex in the resting stage of macrophages. Clathrin was released from Dab2 and associated with TLR4 to facilitate the internalization of TLR4/MD2 complex together with the bound ligand from the cell surface upon LPS stimulation. Dab2 thereby functions as a negative immune regulator of TLR4 endocytosis and signaling, supporting a novel role of Dab2-associated regulatory circuit in the control of inflammatory response of macrophage to endotoxin.
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Project description:Lipid A (a hexaacylated 1,4 bis-phosphate) is a potent immune stimulant for TLR4/MD-2. Upon lipid A ligation, the TLR4/MD-2 complex dimerizes and initiates signal transduction. Historically, studies also suggested the existence of TLR4/MD-2-independent LPS signaling. Here we define the role of TLR4 and MD-2 in LPS signaling by using genome wide expression profiling in TLR4- and MD-2-deficient macrophages after stimulations with peptidoglycan-free LPS and synthetic E.coli lipid A. Of the 1,396 genes found significantly induced or repressed by any one of the treatments in the wildtype macrophages, none was present in the TLR4- or MD-2-deficient macrophages, confirming that the TLR4/MD-2 complex is the only receptor for endotoxin, and are both absolutely required for responses to LPS. Using a molecular genetics approach, we investigated the mechanism of TLR4/MD-2 activation by combining the known crystal structure of TLR4/MD-2 with computer modeling. We used lipid IVa, a defined lipid A mimetic to model the activation of mouse TLR4/MD2. The two phosphates on lipid A were predicted to interact extensively with the two positively charged patches mouse TLR4 according to our dimeric murine TLR4/MD-2/lipid IVa model. These two patches are composed of K263, R337, and K360 (Positive Patch 1), and K367 and R434 (Positive Patch 2). When either Positive Patch was abolished by mutagenesis into Ala, the responses to LPS and lipid A were almost abrogated. Thus, ionic interactions between the two phosphates on lipid A and the two positively charged patches on murine TLR4 appear to be essential for LPS receptor activation.
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