Ficolin-A induces macrophage polarization to a novel pro-inflammatory phenotype distinct from classical M1.

BACKGROUND: Macrophages are key inflammatory immune cells that orchestrate the initiation and progression of autoimmune diseases. The characters of macrophage in diseases are determined by its phenotype in response to the local microenvironment. Ficolins have been confirmed as crucial contributors to autoimmune diseases, with Ficolin-2 being particularly elevated in patients with autoimmune diseases. However, whether Ficolin-A stimulates macrophage polarization is still poorly understood. METHODS: We investigated the transcriptomic expression profile of murine bone marrow-derived macrophages (BMDMs) stimulated with Ficolin-A using RNA-sequencing. To further confirm a distinct phenotype activated by Ficolin-A, quantitative RT-PCR and Luminex assay were performed in this study. Additionally, we assessed the activation of underlying cell signaling pathways triggered by Ficolin-A. Finally, the impact of Ficolin-A on macrophages were investigated in vivo through building Collagen-induced arthritis (CIA) and Dextran Sulfate Sodium Salt (DSS)-induced colitis mouse models with Fcna-/- mice. RESULTS: Ficolin-A activated macrophages into a pro-inflammatory phenotype distinct to LPS-, IFN-γ- and IFN-γ + LPS-induced phenotypes. The transcriptomic profile induced by Ficolin-A was primarily characterized by upregulation of interleukins, chemokines, iNOS, and Arginase 1, along with downregulation of CD86 and CD206, setting it apart from the M1 and M2 phenotypes. The activation effect of Ficolin-A on macrophages deteriorated the symptoms of CIA and DSS mouse models, and the deletion of Fcna significantly alleviated the severity of diseases in mice. CONCLUSION: Our work used transcriptomic analysis by RNA-Seq to investigate the impact of Ficolin-A on macrophage polarization. Our findings demonstrate that Ficolin-A induces a novel pro-inflammatory phenotype distinct to the phenotypes activated by LPS, IFN-γ and IFN-γ + LPS on macrophages.

Identification of a Small Molecule with Strong Anti-Inflammatory Activity in Experimental Autoimmune Encephalomyelitis and Sepsis through Blocking Gasdermin D Activation.

Pyroptosis is a key inflammatory form of cell death participating in the progression of many inflammatory diseases, such as experimental autoimmune encephalomyelitis (EAE) and sepsis. Identification of small molecules to inhibit pyroptosis is emerging as an attractive strategy. In this study, we performed a screening based on in silico docking of compounds on the reported Gasdermin D (GSDMD) three-dimensional structure and found C202-2729 demonstrated strong anti-inflammatory effects in both endotoxin shock and EAE mouse models. Oral administration of C202-2729 was capable of attenuating EAE disease severity significantly and has the comparable effects to teriflunomide, the first-line clinical drug of multiple sclerosis. We found C202-2729 remarkably suppressed macrophage and T cell-associated immune inflammation. Mechanistically, C202-2729 neither impact GSDMD cleavage nor the upstream inflammasome activation in mouse immortalized bone marrow-derived macrophages. However, C202-2729 exposure significantly repressed the IL-1ß secretion and cell pyroptosis. We found C202-2729 directly bonds to the N terminus of GSDMD and blocks the migration of the N-terminal GSDMD fragment to cell membrane, restraining the pore-forming and mature IL-1ß release. Collectively, our findings provide a new molecule with the potential for translational application in GSDMD-associated inflammatory diseases.

Pentoxifylline alleviates ischemic white matter injury through up-regulating Mertk-mediated myelin clearance.

BACKGROUND: Vascular dementia (VAD) is the second most common type of dementia lacking effective treatments. Pentoxifylline (PTX), a nonselective phosphodiesterase inhibitor, displays protective effects in multiple cerebral diseases. In this study, we aimed to investigate the therapeutic effects and potential mechanisms of PTX in VAD. METHODS: Bilateral common carotid artery stenosis (BCAS) mouse model was established to mimic VAD. Mouse behavior was tested by open field test, novel object recognition test, Y-maze and Morris water maze (MWM) tests. Histological staining, magnetic resonance imaging (MRI) and electron microscopy were used to define white matter integrity. The impact of PTX on microglia phagocytosis, peroxisome proliferator-activated receptors-γ (PPAR-γ) activation and Mer receptor tyrosine kinase (Mertk) expression was assessed by immunofluorescence, western blotting and flow cytometry with the application of microglia-specific Mertk knockout mice, Mertk inhibitor and PPAR-γ inhibitor. RESULTS: Here, we found that PTX treatment alleviated cognitive impairment in novel object recognition test, Y-maze and Morris water maze tests. Furthermore, PTX alleviated white matter injury in corpus callosum (CC) and internal capsule (IC) areas as shown by histological staining and MRI analysis. PTX-treatment group presented thicker myelin sheath than vehicle group by electron microscopy. Mechanistically, PTX facilitated microglial phagocytosis of myelin debris by up-regulating the expression of Mertk in BCAS model and primary cultured microglia. Importantly, microglia-specific Mertk knockout blocked the therapeutic effects of PTX in BCAS model. Moreover, Mertk expression was regulated by the nuclear translocation of PPAR-γ. Through modulating PPAR-γ, PTX enhanced Mertk expression. CONCLUSIONS: Collectively, our results demonstrated that PTX showed therapeutic potentials in VAD and alleviated ischemic white matter injury via modulating Mertk-mediated myelin clearance in microglia.

IL-37 Represses the Autoimmunity in Myasthenia Gravis via Directly Targeting Follicular Th and B Cells.

IL-37 is a newly identified immune-suppressive factor; however, the function, cellular sources, and mechanism of IL-37 in humoral immunity and Myasthenia gravis (MG) are still unclear. In this study, we found IL-37 were substantially downregulated in the serum and PBMCs of MG patients compared with healthy controls. The lower IL-37 was associated with severer disease (quantitative MG score) and higher follicular Th (Tfh)/Tfh17 and B cell numbers. Flow cytometry analysis revealed that IL-37 was mainly produced by CD4+ T cells without overlapping with Th1, Th17, and Tfh subsets in MG patients. Regulatory IL-37+ T cell rarely expressed Foxp3 and CD25 but produced numerous IL-4. Tfh and B cell expressed high levels of SIGIRR, the receptor of IL-37, in MG patients. Mechanically, IL-37 directly bond to SIGIRR, repressed the proliferation, cytokine production of Tfh and B cells, and the secretion of autoantibody via inhibition of STAT3 signaling in Tfh and B cells.

Rapamycin Ameliorates Experimental Autoimmune Encephalomyelitis by Suppressing the mTOR-STAT3 Pathway.

Rapamycin is a new immunosuppressant that has a primarily anti-inflammatory effect and selectively inhibits the activation of T helper (Th)-cell subsets. It is widely used to treat autoimmune disease. We studied the mechanism of rapamycin action against experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mice, a classic animal model of multiple sclerosis. Rapamycin significantly inhibited the development of EAE by decreasing both clinical scores and inflammatory cell infiltration into the spinal cord. Furthermore, rapamycin reversed EAE symptoms in mice showing the initial signs of paralysis. Rapamycin, is a mammalian target of rapamycin (mTOR) inhibitor. By measuring the downstream markers phospho-mTOR (p-mTOR)/mTOR and phospho-signal transducer and activator of transcription 3 (p-STAT3)/STAT3, we showed that rapamycin suppressed the mTOR-STAT3 pathway in EAE mice. The mTOR-STAT3 signaling pathway is important for Th1 and Th17 cell responses. We found that rapamycin-treated mice had reduced proportions of Th1 and Th17 cells, as well as lower mRNA expression for the transcription factors T-bet and RoRγt in EAE mouse splenocytes. To evaluate Th1 and Th17 cell function, we examined expression of their specific cytokines in the peripheral immune system and central nervous system. Rapamycin treatment reduced protein and mRNA levels of interferon (IFN)-γand interleukin (IL)-17 in splenocytes, and reduced IFN-γ and IL-17 mRNA levels in the spinal cords of EAE mice. These findings suggest that rapamycin treatment inhibits the mTOR-STAT3 pathway in EAE mice, thereby promoting immunosuppression. This study may provide new insight into the mechanism controlling rapamycin effects in multiple sclerosis.

LLDT-8 ameliorates experimental autoimmune encephalomyelitis by mediating macrophage functions in the priming stage.

Multiple sclerosis (MS) is an inflammatory demyelinating disease in the central nervous system caused by T cell activation mediated by peripheral macrophages, resulting in severe neurological deficits and disability. Due to the currently limited and expensive treatments for MS, we here introduce an economic Chinese medicine extract, (5R)-5-Hydroxytriptolide (LLDT-8), which shows low toxicity and high immunosuppressive activity. We used the widely accepted mouse model of MS, experimental autoimmune encephalomyelitis (EAE), to examine the immunosuppressive effect of LLDT-8 in vivo. Through the RNA-sequence analysis of peripheral macrophages in EAE mice, we discovered that LLDT-8 alleviates the symptoms of EAE by inhibiting the proinflammatory effect of macrophages, thereby blocking the activation and proliferation of T cells. In all, we found that LLDT-8 could be a potential treatment for MS.

Identification of D359-0396 as a novel inhibitor of the activation of NLRP3 inflammasome.

AIMS: Pyroptosis is a unique pro-inflammatory form of programmed cell death which plays a critical role in promoting the pathogenesis of multiple inflammatory and autoimmune diseases. However, the current drug that is capable of inhibition pyroptosis has not been translated successfully in the clinic, suggesting a requirement for drug screening in depth. METHODS: We screened more than 20,000 small molecules and found D359-0396 demonstrates a potent anti-pyroptosis and anti-inflammation effect in both mouse and human macrophage. In vivo, EAE (a mouse model of MS) and septic shock mouse model was used to investigate the protective effect of D359-0396. In vitro experiments we used LPS plus ATP/nigericin/MSU to induce pyroptosis in both mouse and human macrophage, and finally the anti-pyroptosis function of D359-0396 was assessed. RESULTS: Our findings show that D359-0396 is well-tolerated without remarkable disruption of homeostasis. Mechanistically, while D359-0396 is capable of inhibiting pyroptosis and IL-1ß release in macrophages, this process depends on the NLRP3-Casp1-GSDMD pathway rather than NF-κB, AIM2 or NLRC4 inflammasome signaling. Consistently, D359-0396 significantly suppresses the oligomerization of NLRP3, ASC, and the cleavage of GSDMD. In vivo, D359-0396 not only ameliorates the severity of EAE (a mouse model of MS), but also exhibits a better therapeutic effect than teriflunomide, the first-line drug of MS. Similarly, D359-0396 treatment also significantly protects mice from septic shock. CONCLUSION: Our study identified D359-0396 as a novel small-molecule with potential application in NLRP3-associated diseases.

Sirtuin 3 promotes microglia migration by upregulating CX3CR1.

We studied the role of Sirtuin 3 (SIRT3) in microglial cell migration in ischemic stroke. We used a middle cerebral artery occlusion (MCAO) model of focal ischemia. We then applied lentivirus-packaged SIRT3 overexpression and knock down in microglial N9 cells to investigate the underlying mechanism driving microglial cell migration. More microglial cells appeared in the ischemic lesion side after MCAO. The levels of SIRT3 were increased in macrophages, the main source of microglia, after ischemia. CX3CR1 levels were increased with SIRT3 overexpression. SIRT3 promoted microglial N9 cells migration by upregulating CX3CR1 in both normal and glucose deprived culture media. These effects were G protein-dependent. Our study for the first time shows that SIRT3 promotes microglia migration by upregulating CX3CR1.

Rapamycin and fingolimod modulate Treg/Th17 cells in experimental autoimmune encephalomyelitis by regulating the Akt-mTOR and MAPK/ERK pathways.

Rapamycin prevents experimental autoimmune encephalomyelitis (EAE) and activates the MAPK/ERK pathway in EAE. Thus, we hypothesized combining rapamycin and fingolimod treatments would have synergistic effects in EAE. We show that combination therapy ameliorated EAE and regulated spinal cord IL-17 and TGF-ß levels in EAE mice. Combination therapy also modulated IL-17 and TGF-ß concentration, RoRγt and Foxp3 mRNA levels, and Th17 cell and Treg frequencies in the spleen. Moreover, rapamycin decreased ps6k and increased pAkt and pERK, while combination therapy downregulated pAkt, ps6 k and pERK in EAE mice. Our findings provide insight into using this drug combination to treat EAE.

Fingolimod ameliorates the development of experimental autoimmune encephalomyelitis by inhibiting Akt-mTOR axis in mice.

Fingolimod is a new immunosuppressive agent approved by Food and Drug Administration (FDA) for treating multiple sclerosis (MS). It acts as a functional antagonist to downregulate the S1P1 receptor, which is known to signal through the Akt-mTOR pathway. We investigated the mechanism of fingolimod action in the classical animal model of MS: experimental autoimmune encephalomyelitis (EAE). Fingolimod treatment significantly reduced clinical scores and histopathology in this model, even when treatment was begun after the onset of pathology. The Akt-mTOR signaling pathway was shown to be activated in the EAE model, by measuring the abundance of downstream activation markers, pAkt and ps6k. And this pathway was inhibited when EAE mice were treated with fingolimod. Mice with EAE exhibited an increased frequency of Th1 cells in the spleen, with concomitant increases in the mRNA levels of Tbet and Ifng and increased IFN-γ production by activated splenocytes; the frequency of Treg cells, as well as mRNA levels of Foxp3 and Tgfb, was reduced, as was TGF-ß production by activated splenocytes. After treatment with fingolimod, these parameters were reversed, suggesting that fingolimod treatment inhibits the Akt-mTOR axis in EAE, which affects the differentiation and function of Th1 and Treg cells. These results provide an insight into the mechanism of action of fingolimod treatment and may provide new ideas for treating EAE and MS.

Metformin ameliorates the development of experimental autoimmune encephalomyelitis by regulating T helper 17 and regulatory T cells in mice.

Immoderate immunoreaction of antigen-specific Th17 and Treg cell dysfunction play critical roles in the pathogenesis of multiple sclerosis. We examined Th17/Treg immune responses and the underlying mechanisms in response to metformin in C57BL/6 mice with experimental autoimmune encephalomyelitis (EAE). Metformin reduced Th17 and increased Treg cell percentages along with the levels of associated cytokines. Molecules involved in cellular metabolism were altered in mice with EAE. Suppressed activation of mTOR and its downstream target, HIF-1α, likely mediated the protective effects of metformin. Our findings demonstrate that regulation of T cell metabolism represents a new therapeutic target for CNS autoimmune disorders.