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CNS-endogenous TLR7 and TLR9 induce different immune responses and effects on experimental autoimmune encephalomyelitis

ABSTRACT: Innate receptors, including Toll like receptors (TLRs), are implicated in pathogenesis of CNS inflammatory diseases such as multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). TLR response to pathogens or endogenous signals includes production of immunoregulatory mediators. One of these, interferon (IFN)β, a Type I IFN, plays a protective role in MS and EAE. We have previously shown that intrathecal administration of selected TLR ligands induced IFNβ and infiltration of blood-derived myeloid cells into the CNS, and suppressed EAE in mice. We have now extended these studies to evaluate a potential therapeutic role for CNS-endogenous TLR7 and TLR9. Intrathecal application of Imiquimod (TLR7 ligand) or CpG oligonucleotide (TLR9 ligand) into CNS of otherwise unmanipulated mice induced IFNβ expression, with greater magnitude in response to CpG. CNS extraparenchymal CD45+ cells were identified as source of IFNβ. Intrathecal CpG induced infiltration of monocytes, neutrophils, CD4+ T cells and NK cells whereas Imiquimod did not recruit blood-derived CD45+ cells. CpG, but not Imiquimod, had a beneficial effect on EAE, when given at time of disease onset. This therapeutic effect of CpG on EAE was not seen in mice lacking the Type I IFN receptor. In mice with EAE treated with CpG, the proportion of monocytes was significantly increased in the CNS. Infiltrating cells were predominantly localized to spinal cord meninges and demyelination was significantly reduced compared to non-treated mice with EAE. Our findings show that TLR7 and TLR9 signaling induce distinct inflammatory responses in the CNS with different outcome in EAE and point to recruitment of blood-derived cells and IFNβ induction as possible mechanistic links between TLR9 stimulation and amelioration of EAE. The protective role of TLR9 signaling in the CNS may have application in treatment of diseases such as MS.

ORGANISM(S): Mus musculus

PROVIDER: GSE172083 | GEO | 2021/04/15

REPOSITORIES: GEO

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Project description:IFNβ, an effective therapy against relapsing-remitting (RR) multiple sclerosis (MS) is naturally secreted during the innate immune response against viral pathogens. The objective of this study was to characterize the immunomodulatory mechanisms of IFNβ targeting innate immune response and their effects on DC-mediated regulation of T-cell differentiation. We found that IFNβ−1a in-vitro treatment of human monocyte-derived dendritic cells (DCs) induced the expression of TLR7 and the members of its downstream signaling pathway, including myeloid differentiation factor 88 (MyD88), IL-1R-associated kinase (IRAK)4, and TNF receptor-associated factor (TRAF)6, while it inhibited the expression of IL-1R. Using siRNA TLR7 gene silencing, we confirmed that IFNβ-1a-induced changes in MyD88, IRAK4 and IL-1R expression were dependent on TLR7. TLR7 expression was also necessary for the IFNβ-1a-induced inhibition of IL-1β and IL-23, and the induction of IL-27 secretion by DCs. Supernatant (SN) transfer experiments confirmed that IFNβ-1a-induced changes in DCs’ cytokine secretion inhibit Th17 cell differentiation as evidenced by the inhibition of retinoic acid-related orphan nuclear hormone receptor C (RORC) and IL-17A gene expression and IL-17A secretion. Our study has identified a novel therapeutic mechanism of IFNβ−1a, that selectively targets the autoimmune response in MS. Overall design: Gene expression changes induced by IFNβ−1a were tested using Affymetrix Human Genome U133 (HG-U133) arrays (Affymetrix) that contain 45,000 probe sets representing 39,000 transcripts derived from approximately 33,000 human genes. 107 PBMCs per condition derived from 15 CIS patients were stimulated with plate-immobilized αCD3 (1 μg/ml) and αCD28 (5 μg/ml) mAb (BD Biosciences) in the absence or presence of IFNβ-1a (1000 U/ml) (EMD Serono Inc) for 24 h in serum-free medium (Gibco). Cells were harvested and the total RNA was isolated using a Rneasy kit (Quiagen). Arrays were hybridized for 16 hours at 45oC in the GeneChip® Hybridization Oven 640 (Affymetrix). The arrays were washed and stained with R-phycoerythrin streptavidin in the GeneChip® Fluidics Station 400 (Affymetrix). The arrays were scanned with a Hewlett Packard GeneArray Scanner. Affymetrix GeneChip® Microarray Suite 5.0 software was used for washing, scanning and basic analysis.

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CNS-endogenous TLR7 and TLR9 induce different immune responses and effects on experimental autoimmune encephalomyelitis

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