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IRF-8/miR-451a regulates M-MDSC differentiation via the AMPK/mTOR signal pathway during lupus development.

ABSTRACT: Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease. Myeloid-derived suppressor cells (MDSCs) have been found to be involved in the regulation of SLE development. However, little is known about the association between MDSC subsets and the factors that draw MDSCs into abnormal expansion. This study found that the percentage of M-MDSCs increased in mice with pristane-induced lupus. Toll-like receptor (TLR)7 signal activation and high interferon-α (IFN-α) level promoted M-MDSC differentiation in vitro. Moreover, both AMP-activated protein kinase (AMPK) agonist metformin and two mammalian targets of rapamycin (mTOR) inhibitors (INK128 and rapamycin) inhibited the percentage of M-MDSCs in lupus mice as well as in the TLR7- and IFN-α-induced bone marrow (BM) differentiation into MDSCs in vitro. In terms of mechanism, whole-genome transcriptome profiling was performed by RNA sequencing, revealing that the expression of the transcription factor IRF-8 was higher in M-MDSCs isolated from pristane-induced lupus mice, compared with control mice. IRF-8 was identified to be crucial for TLR7- and IFN-α-induced BM differentiation into MDSCs in vitro. Furthermore, interferon (IFN) regulatory factor8 (IRF-8) was targeted by miR-451a in M-MDSC differentiation. Of note, metformin-modified M-MDSCs could relieve lupus symptoms in pristane-induced lupus mice. The findings revealed a novel mechanism linking IRF-8/miR-451a to M-MDSC differentiation via the AMPK/mTOR signal pathway during lupus development. This study might provide an important reference for SLE therapy by targeting M-MDSCs.

SUBMITTER: Shi G

PROVIDER: S-EPMC8289825 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The mammalian target of rapamycin (mTOR) signal controls innate and adaptive immune response in multiple immunoregulatory contexts. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid cells of potent immunosuppressive capacity. In this study, we aimed to investigate the role of MDSCs in the protection of acute kidney injury (AKI) and the regulation of mTOR signal on MDSC's protective role in this context. In mice AKI model, rapamycin administration was associated with improved renal function, restored histological damage and decreased CD4+ and CD8+ T-cell infiltration in kidney tissue. MDSCs, especially CD11b+Ly6G+Ly6Clow G-MDSCs were recruited to the injured kidney following the interaction of CXCL1, CXCL2 and their receptor CXCR2 after inhibiting mTOR signal with rapamycin treatment. The adoptive transfer of rapamycin-treated MDSCs into the mice with AKI significantly improved the renal function, ameliorated histologic damages and limited the infiltration of T cells in kidney tissue. In addition, the expression of pro-inflammatory cytokines IL-1? and IFN-? mRNA was downregulated while the expression of TGF-?1 and Foxp3 mRNA was upregulated in kidney tissue after transferring rapamycin-treated MDSCs. Adoptive transfer of rapamycin-treated MDSCs also downregulated the serum levels of IL-1?, IL-6 and IFN-? and upregulated the serum levels of TGF-?1 compared with the IR group and PBS-treated MDSC group. In in vitro study, inhibiting mTOR signal regulated the induction of MDSC towards the CD11b+Ly6G+Ly6Clow G-MDSC subset. The ability to suppress T-cell proliferation of both bone marrow-derived CD11b+Ly6G+Ly6Clow G-MDSCs and CD11b+Ly6G-Ly6Chigh M-MDSCs was enhanced by mTOR signal inhibition via upregulating the expression of Arginase-1 and iNOS. Accordingly, both G-MDSCs and M-MDSCs presented downregulated runx1 gene expression after rapamycin treatment. Taken together, our results demonstrated that MDSCs ameliorated AKI and the protective effect was enhanced by mTOR signal inhibition via promoting MDSCs recruitment, regulating the induction of MDSCs and strengthening their immunosuppressive activity.

Project description:BACKGROUND:Toll-like receptor 4 (TLR4) is well known for activating the innate immune system; however, it is also highly expressed in adaptive immune cells, such as CD4+ T-helper 17 (Th17) cells, which play a key role in multiple sclerosis (MS) pathology. However, the function and governing mechanism of TLR4 in Th17 remain unclear. METHODS:The changes of TLR4 in CD4+ T cells from MS patients and experimental autoimmune encephalomyelitis (EAE) mice were tested. TLR4-deficient (TLR4-/-) naïve T cells were induced in vitro and transferred into Rag1-/- mice to measure Th17 differentiation and EAE pathology. DNA sequence analyses combining with deletion fragments and mutation analyses, chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift assay (EMSA) were used to explore the mechanism of TLR4 signaling pathway in regulating Th17 differentiation. RESULTS:The levels of TLR4 were increased in CD4+ Th17 cells both from MS patients and EAE mice, as well as during Th17 differentiation in vitro. TLR4-/- CD4+ naïve T cells inhibited their differentiation into Th17, and transfer of TLR4-/- CD4+ naïve T cells into Rag1-/- mice was defective in promoting EAE, characterized by less demyelination and Th17 infiltration in the spinal cord. TLR4 signal enhanced Th17 differentiation by activating RelA, downregulating the expression of miR-30a, a negative regulator of Th17 differentiation. Inhibition of RelA activity increased miR-30a level, but decreased Th17 differentiation rate. Furthermore, RelA directly regulated the expression of miR-30a via specific binding to a conserved element of miR-30a gene. CONCLUSIONS:TLR4-/- CD4+ naïve T cells are inadequate in differentiating to Th17 cells both in vitro and in vivo. TLR4-RelA-miR-30a signal pathway regulates Th17 differentiation via direct binding of RelA to the regulatory element of miR-30a gene. Our results indicate modulating TLR4-RelA-miR-30a signal in Th17 may be a therapeutic target for Th17-mediated neurodegeneration in neuroinflammatory diseases.

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IRF-8/miR-451a regulates M-MDSC differentiation via the AMPK/mTOR signal pathway during lupus development.

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