Conversion Of Microglia Research Articles

The Dectin-1 Receptor Signaling Pathway Mediates the Remyelination Effect of Lentinan through Suppression of Neuroinflammation and Conversion of Microglia.

Demyelinating diseases such as multiple sclerosis (MS) are chronic inflammatory autoimmune diseases and involve demyelination and axonal degeneration. Microglia rapidly respond to changes in the environment by altering morphotype and function during the progressive disease stage. Although substantial progress has been made in the drug development for MS, treatment of the progressive forms of the disease remains unsatisfactory. There is great interest in identifying novel agents for treating MS. Lentinus edodes is a traditional food, which can improve physiological function. Lentinan (LNT), a type of polysaccharide extracted from mushroom Lentinus edodes, is an anti-inflammatory and immunomodulatory agent. Here, we studied the remyelination effects of LNT and its therapeutic target in regulating the functions of neuroinflammation. We found that LNT enhanced remyelination and rescued motor deficiency by regulating dectin-1 receptor to inhibit neuroinflammation and microglial cell transformation. LNT promoted the conversion of microglial cells from the M1 status induced by LPS to the M2 status, enhanced the anti-inflammatory markers IL-10 and BDNF, inhibited inflammatory markers TNF-α and IL-1β, and downregulated the microglia activation and oligodendrocyte and astrocyte proliferation by modulating dectin-1. If we injected the dectin-1-specific inhibitor laminarin (Lam), the remyelination effects induced by LNT were completely abolished. Thus, these results suggest that LNT is a novel and potential therapeutic agent that can rescue MS neuroimmune imbalance and remyelination through a dectin-1 receptor-dependent mechanism.

Astragaloside IV protects neurons from microglia-mediated cell damage through promoting microglia polarization.

Astragaloside IV (AST-IV) is a major active ingredient of astragalus, with a neuroprotective effect. The current study is aimed to investigate the impact of AST-IV on the M1/M2 microglial activation in response to lipopolysaccharide (LPS) stimulation, how AST-IV attenuated microglia-mediated neuronal damage, and the molecular mechanisms underlying AST-IV's protection of neurons against microglia-mediated neuronal damage. Our results showed that AST-IV partially protected microglia from death evoked by LPS and downregulated the release of pro-inflammatory (M1) mediators including interleukin (IL)-1β, IL-6, tumour necrosis factor α (TNF-α) and nitric oxide, as well as the expression of Toll-like receptors 4 (TLR4), MyD88, and nuclear factor κB (NF-κB) of these cells. In contrast, AST-IV elevated the production of anti-inflammatory cytokine IL-10 and expression of arginase 1, an M2 marker of microglia, whose conditioned medium promoted PC12 neurons survival. These results indicate that AST-IV exerts an anti-inflammatory effect on microglia, possibly through inhibiting TLR4/NF-κB signalling pathways, and protects neurons from microglia-mediated cell death through conversion of microglia from inflammatory M1 to an anti-inflammatory M2 phenotype.

Erratum: Sall1 is a transcriptional regulator defining microglia identity and function.

Microglia are the resident macrophages of the central nervous system (CNS). Gene expression profiling has identified Sall1, which encodes a transcriptional regulator, as a microglial signature gene. We found that Sall1 was expressed by microglia but not by other members of the mononuclear phagocyte system or by other CNS-resident cells. Using Sall1 for microglia-specific gene targeting, we found that the cytokine receptor CSF1R was involved in the maintenance of adult microglia and that the receptor for the cytokine TGF-β suppressed activation of microglia. We then used the microglia-specific expression of Sall1 to inducibly inactivate the murine Sall1 locus in vivo, which resulted in the conversion of microglia from resting tissue macrophages into inflammatory phagocytes, leading to altered neurogenesis and disturbed tissue homeostasis. Collectively, our results show that transcriptional regulation by Sall1 maintains microglial identity and physiological properties in the CNS and allows microglia-specific manipulation in vivo.

Sall1 is a transcriptional regulator defining microglia identity and function.

Microglia are the resident macrophages of the central nervous system (CNS). Gene expression profiling has identified Sall1, which encodes a transcriptional regulator, as a microglial signature gene. We found that Sall1 was expressed by microglia but not by other members of the mononuclear phagocyte system or by other CNS-resident cells. Using Sall1 for microglia-specific gene targeting, we found that the cytokine receptor CSF1R was involved in the maintenance of adult microglia and that the receptor for the cytokine TGF-β suppressed activation of microglia. We then used the microglia-specific expression of Sall1 to inducibly inactivate the murine Sall1 locus in vivo, which resulted in the conversion of microglia from resting tissue macrophages into inflammatory phagocytes, leading to altered neurogenesis and disturbed tissue homeostasis. Collectively, our results show that transcriptional regulation by Sall1 maintains microglial identity and physiological properties in the CNS and allows microglia-specific manipulation in vivo.

Safflower Yellow regulates microglial polarization and inhibits inflammatory response in LPS-stimulated Bv2 cells.

Activated microglia, especially polarized M1 cells, produce pro-inflammatory cytokines and free radicals, thereby contributing directly to neuroinflammation and various brain disorders. Given that excessive or chronic neuroinflammation within the central nervous system (CNS) exacerbates neuronal damage, molecules that modulate neuroinflammation are candidates as neuroprotective agents. In this study, we provide evidence that Safflor yellow (SY), the main active component in the traditional Chinese medicine safflower, modulates inflammatory responses by acting directly on BV2 microglia. LPS stimulated BV2 cells to upregulate expression of TLR4-Myd88 and MAPK-NF-κB signaling pathways and to release IL-1β, IL-6, TNF-α, and COX-2. However, SY treatment inhibited expression of TLR4-Myd88 and p-38/p-JNK-NF-κB, downregulated expression of iNOS, CD16/32, and IL-12, and upregulated CD206 and IL-10. In conclusion, our results demonstrate that SY exerts an anti-inflammatory effect on BV2 microglia, possibly through TLR-4/p-38/p-JNK/NF-κB signaling pathways and the conversion of microglia from inflammatory M1 to an anti-inflammatory M2 phenotype.

O002 A novel function of interferon beta in promoting the generation of anti-inflammatory M2-like microglia in vitro and in vivo

IntroductionIFNβ is an approved therapeutic option for the treatment of the autoimmune multiple sclerosis (MS). The molecular mechanisms underlying the effects of IFNβ in MS ant its animal model experimental autoimmune encephalomyelitis (EAE) are not fully understood and especially the effects of IFNβ in the CNS cells are largely unknown. In this study, we identified a novel mechanism for the beneficial effect of IFNβ in MS/EAE through the conversion of microglia (MG) from pro-inflammatory M1-like MG to anti-inflammatory M2-like MG. MethodsFor in vitro study: Neonatal MG were generated and activated with LPS (1μg/ml) in the presence or absence of IFNβ (1000U/ml) for 3h and 6h. Cells were then harvested and subjected to RNA extraction, followed by Q-PCR for IL-1β, IL-12p40, IL-23p19, TNFα and IL-10. To measure secreted cytokine production, the supernatants from cells treated with LPS in the presence or absence of IFNβ for 24h were collected and subjected to ELISA. To determine the effect of IFNβ-treated MG on Th1 and Th17 activation, MG matured with LPS in the presence or absence of IFNβ were co-cultured with T cells purified from spleens of 2D2 mice for 3days. The production of IFNγ and IL-17 was measured by both intracellular staining and ELISA.For in vivo study: Mice (n=12) were immunized with MOG35-55 and administrated with either IFNβ (10,000U/ml, n=6) or vehicle (n=6) every other day starting from day 5 after immunization. Clinical scores were recorded at day 15. Spinal cords and brains from EAE mice were subjected to Iba-1 immunostaining or RNA extraction, followed by Q-PCR for Arginase-1, YM-1 and IL-10 expression. ResultsOur results show that the expression and production of proinflammatory M1-type cytokines, such as IL-1β, IL-12p40, IL-23 and TNFα were inhibited by IFNβ and the production of anti-inflammatory M2 cytokine IL-10 was enhanced by IFNβ in LPS-stimulated primary MG. Through this phenotype switch, IFNβ-treated MG suppressed Th1 and Th17 activation leading to the downregulation of IFNγ and IL-17 production. In vivo, IFNβ-treated EAE mice exhibit lower clinical scores, reduced Iba-1 expression, and increased expression of the M2 markers, arginase, YM-1 and IL-10 in the CNS. ConclusionTaken altogether, our results demonstrate for the first time that IFNβ favors the generation of MG2 leading to the secretion of the anti-inflammatory cytokine IL-10 and reduced expression of the pro-inflammatory cytokines, IL-12, IL-23, IFNγ and IL-17 that provides a novel molecular mechanism for the beneficial effect of IFNβ in MS/EAE.

IFNβ promotes the conversion of pro-inflammatory M1-like into anti-inflammatory M2-like microglia (171.14)

Abstract IFNβ is an approved therapeutic option for the treatment of certain autoimmune diseases such as MS/EAE. However, the molecular mechanisms underlying the effects of IFNβ in MS/EAE are not fully understood. In this study, we identified a novel mechanism for the beneficial effect of IFNβ in MS/EAE through the conversion of microglia (MG) from pro-inflammatory M1-like (MG1) to anti-inflammatory M2-like (MG2). Our results show that IFNβ inhibits expression and production of proinflammatory M1-type cytokines, such as IL-12p40, IL-23 and TNFα and promotes the anti-inflammatory M2 cytokine IL-10 in LPS-stimulated primary MG. In addition, IFNβ treatment also enhanced the expression of specific M2 makers, such as arginase and YM-1. Through this phenotype switch, IFNβ-treated MG suppressed Th1 and Th17 activation leading to the downregulation of IFNγ and IL-17. In vivo, IFNβ-treated EAE mice exhibit lower clinical scores, reduced Iba-1, IFNγ and IL-17 expression, and increased expression of the M2 markers, arginase, YM-1 and IL-10 in the CNS. Taken altogether, our results demonstrate that IFNβ favors the generation of MG2 leading to the secretion of the anti-inflammatory cytokine IL-10 and reduced expression of the pro-inflammatory cytokines, IL-12, IL-23, IFNγ and IL-17 in vitro and in vivo.