Pathogenic Th17 cells play crucial roles in CNS autoimmune diseases such as multiple sclerosis (MS), but their regulation by endogenous mechanisms remains unknown. Through RNA-seq analysis of primary brain glial cells, we identified immuno-responsive gene 1 (Irg1) as one of the highly upregulated gene under inflammatory conditions. Validation in the spinal cord of animals with experimental autoimmune encephalomyelitis (EAE), an MS model, confirmed elevated Irg1 levels in myeloid, CD4, and B cells in the EAE group raising the concern if Irg1 is detrimental or protective. Irg1 knockout (KO) mice exhibited severe EAE disease, increased mononuclear cell infiltration, and increased levels of triple-positive CD4+ T cells expressing IL17a, GM-CSF, and IFNγ. A lack of Irg1 in macrophages elevates Class II expression, promoting the polarization of myelin-primed CD4+ T cells into pathogenic Th17 cells via the NLRP3/IL-1β axis. Adoptive transfer in Rag-1 KO and single-cell RNA sequencing highlighted the crucial role of Irg1 in shaping pathogenic Th17 cells. Moreover, bone marrow chimeras revealed that immune cells lacking Irg1 maintained pathogenic and inflammatory phenotypes, suggesting its protective role in autoimmune diseases, including MS.

Multiple sclerosis (MS) is a prevalent inflammatory neurodegenerative disease in young people, causing neurological abnormalities and impairment. To investigate a novel therapeutic agent for MS, we observed the impact of maresin 1 (MaR1) on disease progression in a well-known, relapsing-remitting experimental autoimmune encephalomyelitis mouse model. Treatment with MaR1 accelerated inflammation resolution, reduced neurological impairment, and delayed disease development by reducing immune cell infiltration (CD4+IL-17+ and CD4+IFNγ+) into the central nervous system. Furthermore, MaR1 administration enhanced IL-10 production, primarily in macrophages and CD4+ cells. However, neutralizing IL-10 with an anti-IL-10 antibody eliminated the protective impact by MaR1 in relapsing-remitting experimental autoimmune encephalomyelitis model, implying the significance of IL-10 in MaR1 treatment. Metabolism has been recognized as a critical mediator of effector activity in many types of immune cells. In our investigation, MaR1 administration significantly repaired metabolic dysregulation in CD4+ cells, macrophages, and microglia in EAE mice. Furthermore, MaR1 treatment restored defective efferocytosis in treated macrophages and microglia. MaR1 also preserved myelin in EAE mice and regulated O4+ oligodendrocyte metabolism by reversing metabolic dysregulation via increased mitochondrial activity and decreased glycolysis. Overall, in a preclinical MS animal model, MaR1 therapy has anti-inflammatory and neuroprotective properties. It also induced metabolic reprogramming in disease-associated cell types, increased efferocytosis, and maintained myelination. Moreover, our data on patient-derived peripheral blood mononuclear cells substantiated the protective role of MaR1, expanding the therapeutic spectrum of specialized proresolving lipid mediators. Altogether, these findings suggest the potential of MaR1 as a novel therapeutic agent for MS and other autoimmune diseases.

Abstract Inflammation resolution is dysregulated in people affected with multiple sclerosis (MS) due to impaired metabolism of docosahexaenoic acid (DHA). We hypothesize that supplementing its downstream metabolite maresin 1 (MaR1) will alleviate inflammation and demyelination in a preclinical mouse model of MS; experimental allergic encephalomyelitis (EAE). Administration of the resolution agonist MaR1 mediated resolution and improved neurological outcome in the relapsing-remitting (RR) model of EAE. MaR1 induced metabolic changes in CD4, macrophages, microglia, and oligodendrocytes. It modulated the phenotype of disease-associated cell types by regulating their effector functions. It restored the impaired efferocytosis in EAE, promoting clearance of damaged myelin and dead cells; thereby lowering the disability with disease course. MaR1 is a potential interventional candidate to attenuate dysregulated inflammation to restore neurological deficits in EAE and other autoimmune diseases.

Abstract Multiple sclerosis (MS) is a condition characterized by inflammation and demyelination, primarily affecting individuals in their youth. Numerous studies have documented the buildup of dying cells and myelin debris in the CNS, leading to inflammation and disability. This suggests that enhancing the removal of cellular debris could be a promising approach to address disability and promote the restoration of myelin. Efferocytosis is a process in which phagocytes take in apoptotic cells and help maintain tissue balance by releasing anti-inflammatory cytokines. However, the relationship between efferocytosis and EAE pathogenesis is not well understood. Loss of Irg1 is expected to interfere with the efferocytosis process, causing a strong inflammatory environment in the CNS, which in turn impairs disease resolution. We observed that Irg1 knockout displayed more severe experimental autoimmune encephalomyelitis (EAE) disease compared to wild type. Further, macrophages lacking Irg1 showed upregulation in the levels of NLRP3, GSDMD,and IL1β, along with a decrease in the phagocytic activity. Also, it showed reduced expression of key efferocytosis genes such MerTk, CD206, and arginase 1, suggesting that a lack of Irg1 leads to a highly inflammatory environment, resulting in impaired efferocytosis. Our results indicate that directing interventions towards the Irg1 gene could surpass the constraints of existing drugs and open possibilities for novel techniques in the treatment of MS.

Multiple sclerosis (MS) is one of the most common inflammatory neurodegenerative diseases in young adults and causes neurological abnormalities and disability. We studied the effect of maresin 1 (MaR1) on the progression of disease in a relapsing-remitting form of experimental allergic encephalomyelitis (RR-EAE). Treatment with MaR1 in RR-EAE accelerated inflammation resolution, protected against neurological deficits, and delayed disease progression by decreasing immune cell infiltration (CD4+IL17+ and CD4+IFNγ+) into the CNS. Furthermore, the administration of MaR1 increased the production of IL-10, predominantly in macrophages and CD4+ cells. However, neutralizing IL-10 with an anti-IL-10 antibody abolished the protective effect of MaR1 on RR-EAE, suggesting that IL-10 plays a role in mediating the protective effect of MaR1 on EAE. Metabolism is rapidly becoming recognized as an important factor influencing the effector function of many immune cells. Using cutting-edge metabolic assays, our study revealed that compared with vehicle treatment, MaR1 treatment effectively restored the metabolic dysregulation observed in CD4+ cells, macrophages, and microglia in the treated group. Furthermore, MaR1 treatment reversed defective efferocytosis in EAE mice, which was potentially facilitated by the induction of metabolic alterations in macrophages and microglia. MaR1 treatment also protected myelin in the EAE group and regulated the metabolism of O4+ oligodendrocytes by restoring metabolic dysregulation through improved mitochondrial function and decreased glycolysis. Overall, in a preclinical MS animal model, MaR1 treatment produced anti-inflammatory and neuroprotective effects. It also triggered metabolic reprogramming in disease-associated cell types, accelerated efferocytosis, and preserved myelination. These data support that MaR1 has potential as a novel treatment agent for MS and other autoimmune diseases.

Metabolism and energy processes governing oligodendrocyte function during neuroinflammatory disease are of great interest. However, how varied cellular environments affect oligodendrocyte activity during neuroinflammation is unknown. We demonstrate that activated microglial energy metabolism controls oligodendrocyte mitochondrial respiration and activity. Lipopolysaccharide/interferon gamma promote glycolysis and decrease mitochondrial respiration and myelin protein synthesis in rat brain glial cells. Enriched microglia showed an early burst in glycolysis. In microglia-conditioned medium, oligodendrocytes did not respire and expressed less myelin. SCENITH revealed metabolic derangement in microglia and O4-positive oligodendrocytes in endotoxemia and experimental autoimmune encephalitogenic models. The early burst of glycolysis in microglia was mediated by PDPK1 and protein kinase B/AKT signaling. We found that microglia-produced NO and itaconate, a tricarboxylic acid bifurcated metabolite, reduced mitochondrial respiration in oligodendrocytes. During inflammation, we discovered a signaling pathway in microglia that could be used as a therapeutic target to restore mitochondrial function in oligodendrocytes and induce remyelination.