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MiRNA arrays for LPS-activated Akt1+/+ and Akt1-/- macrophages

ABSTRACT: 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.

ORGANISM(S): Rattus norvegicus Mus musculus Homo sapiens

PROVIDER: GSE17421 | GEO | 2009/08/21

SECONDARY ACCESSION(S): PRJNA118905

REPOSITORIES: GEO

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Project description:Background: The disruption of the circadian clock is associated with inflammatory and immunological disorders. BMAL2, a critical circadian protein, forms a dimer with CLOCK, activating transcription. Extracellular cold-inducible RNA-binding protein (eCIRP), released during sepsis, can induce macrophage endotoxin tolerance. We hypothesized that eCIRP modulates BMAL2 expression and promotes macrophage endotoxin tolerance through triggering receptor expressed on myeloid cells-1 (TREM-1). Methods: C57BL/6 wild-type (WT) male mice were subjected to sepsis by cecal ligation and puncture (CLP). Serum was collected 20 hours post-CLP to assess eCIRP levels. Peritoneal macrophages (PerM) and immortalized bone marrow-derived macrophages (iBMDMs) were seeded into plates and treated with recombinant mouse (rm) CIRP (eCIRP) at various doses. Induction of BMAL2 activation in iBMDM was performed by transfection of BMAL2 CRISPR activation plasmid. Circadian gene expression profiles in eCIRP-treated macrophages were determined by PCR array and confirmed by qPCR. Cytokine levels in the culture supernatants were assessed by ELISA. The interaction of BMAL2 in the PD-L1 promoter was determined by computational modeling and confirmed by the BIAcore assay. Results: PCR array screening of circadian clock genes in peritoneal macrophages treated with eCIRP revealed the elevated expression of BMAL2, CRY1, and PER2. eCIRP serum levels were increased in septic mice. In eCIRP-treated macrophages, TREM-1 deficiency prevented the upregulation of these circadian genes. Macrophages pre-treated with eCIRP exhibited reduced TNFá and IL-6 release upon LPS challenge, indicating macrophage endotoxin tolerance. In addition, eCIRP increased the expression of PD-L1, IL-10, and STAT3, markers of immune tolerance. Interestingly, TREM-1 deficiency reversed eCIRP-induced macrophage endotoxin tolerance. In macrophages, inducible BMAL2 expression correlated with increased PD-L1 expression. In septic human patients, blood monocytes exhibited increased expression of BMAL2 and PD-L1 in comparison to healthy subjects. Computational modeling and BIAcore assay identified a putative binding region of BMAL2 in the PD-L1 promoter, suggesting BMAL2 positively regulates PD-L1 expression in macrophages. Conclusion: eCIRP upregulates BMAL2 expression via TREM-1, leading to macrophage endotoxin tolerance in sepsis. Targeting eCIRP to maintain circadian rhythm may correct endotoxin tolerance and enhance host resistance to bacterial infection.

Project description:Toll-like receptor (TLR)-induced maturation of dendritic cells (DCs) leads to the production of proinflammatory cytokines as well as the upregulation of various molecules involved in T cell activation. These are believed to be the critical events that account for the induction of the adaptive immune response. Here, we have examined the role of micro-RNA-155 (miR-155) in DC function and the induction of immunity. Using a model where the transfer of self-antigen-pulsed, TLR-matured DCs can induce a functional CD8 T cell response and autoimmunity, we find that DCs lacking miR-155 have an impaired ability to break immune tolerance. Importantly, transfer of self- antigen-pulsed DCs overexpressing miR-155 was sufficient to break tolerance in the absence of TLR stimuli. Although these unstimulated DCs induced T cell function in vivo, there was no evidence for the upregulation of costimulatory ligands or cytokine secretion. Further analysis showed that miR-155 influenced the level of the phosphatase SHIP1 in DCs, and that the lack of SHIP1 in DCs was sufficient to break T cell tolerance in vivo, again in the absence of TLR induced DC maturation. Our study demonstrates that the overexpression of miR-155 in DCs is a critical event that is alone sufficient to break self tolerance and promote a CD8-mediated autoimmune response in vivo. This process is independent of the induction of conventional DC maturation markers, indicating that miR-155 regulation of SHIP represents a unique axis that regulates DC function in vivo. Dendritic cell culture: Bone marrow was flushed from tibias and femurs of mice with HBSS. Bone marrow cells were cultured at 2x106 cells/ml in 10 ml non-tissue culture treated dishes in RPMI 1640 containing 10% LPS-free FBS, Penicillin:streptomycin glutamine 2-mercaptoethanol (cRPMI), with 40ng/ml murine GM-CSF (Peprotech). On day 3 of cultures 10ml of fresh media was added also containing 40ng/ml GM-CSF. On days 6 and 8, 10ml of media was removed and centrifuged to collect cells, which were resuspended in 10ml fresh media containing GM-CSF and were added back to dishes. Non-adherent cells were isolated on day 9. DCs were plated in 24-well plates at 2x106 cells/ml in 1ml of cRPMI with or without the class B CpG ODN1826 (ACGT DNA Technologies corporation, Toronto, ON, Canada) at 10?M final concentration overnight. Array analysis of mi-RNA expression: BMDCs from WT mice were either stimulated with CpG or left in media alone overnight. Whole RNA was isolated using mirVana miRNA isolation kit following the manufacturers instructions. RNA samples were labeled and hybridized to Agilent mouse miRNA 8x15K arrays (Agilent). Data was generated from 8 individual samples (4 unstimulated and 4 CpG-treated).

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MiRNA arrays for LPS-activated Akt1+/+ and Akt1-/- macrophages

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