An early glycolysis burst in microglia regulates mitochondrial dysfunction in oligodendrocytes under neuroinflammation.

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.

Pro-resolution lipid mediator maresin-1 ameliorates inflammation, promotes neuroprotection, and prevents disease progression in experimental models of multiple sclerosis.

Multiple sclerosis (MS) is the most common inflammatory neurodegenerative disease in young adults, resulting in neurological defects and disability. The endogenous mechanisms to resolve inflammation are intact but become defective in patients, resulting in lack of resolution mediators and unresolved chronic inflammation. Docosahexaenoic acid (DHA) metabolism being impaired in MS, we hypothesize that supplementing its downstream metabolite maresin 1 (MaR1) will alleviate inflammation and demyelination in preclinical mouse model of MS; experimental allergic encephalomyelitis (EAE). Restoration of MaR1 by its exogenous administration in EAE mice propagated inflammatory resolution and had a protective effect on neurological deficits, prevented disease progression, and reduced disease severity by reducing immune cell infiltration (CD4+IL17+ and CD4+IFN-γ+) into the CNS. It significantly reduced the proinflammatory cytokine IL17 and promoted an anti-inflammatory response via IL10 and IL4. Neutralization of IL10 abolished the protective effect of MaR1 in EAE confirming IL10 is mediating MaR1 effect in EAE. Furthermore, it improved the pathophysiology and exerted neuroprotective effects by mitigating disease signs in EAE as evidenced by lower levels of NFL in the plasma of treated group compared to control and higher MBP expression in the brain from the MaR1 treated mice, decreased inflammatory infiltrates, and less demyelination and vacuolization in the spinal cord tissue sections of treated mice. SCENITH data confirmed that MaR1 maintains myelin by regulating oligodendrocyte metabolism. Also, it induces metabolic reprogramming in infiltrating CD4 cells and macrophages, which modulate their phenotype. Metabolic changes induced macrophages by MaR1 restores the impaired efferocytosis in EAE, promoting clearance of damaged myelin and dead cells; thereby lowering the disability with disease course. Overall, MaR1 supplementation has anti-inflammatory and neuroprotective effects in preclinical animal models and induces metabolic reprogramming in disease associated cell-types, promotes efferocytosis, implying that it could be a new therapeutic molecule in MS and other autoimmune diseases. Highlights: Inflammation is dysregulated in EAE due to impaired synthesis of DHA derived proresolving lipid mediator MaR1.Administration of the resolution agonist MaR1 propagates resolution processes and improves neurological outcome in RR model of EAE.MaR1 ameliorates clinical signs of EAE by attenuating pro-inflammatory cytokine IL17 mediated response and promoting anti-inflammatory response through IL10.MaR1 supplementation improves the pathophysiology in EAE and shows neuroprotection as indicated by the lower levels of NFL in the plasma and higher expression of MBP in the brain of treated mice.MaR1 induces metabolic reprogramming in disease-associated cell types.MaR1 promotes efferocytosis in EAE through metabolic reprogramming of macrophages. Significance: Inflammatory process is a protective response to several challenges like injury or infection. However, it must resolve over time to maintain tissue homeostasis. Impaired or delayed resolution leads to damaging effects, including chronic inflammation, tissue damage, and disease progression as occurs in multiple sclerosis (MS). We report that inflammation is dysregulated in preclinical animal model of MS, experimental autoimmune encephalomyelitis (EAE), partially due to impaired synthesis of proresolving lipid mediators. We show that the administration of the resolution agonist known as maresin 1 (MaR1) in EAE actively propagates resolution processes and improves neurological outcome. We conclude that MaR1 is a potential interventional candidate to attenuate dysregulated inflammation and to restore neurological deficits in EAE.

Immuno-Responsive Gene-1: A mitochondrial gene regulates pathogenic Th17 in CNS autoimmunity mouse model.

Pathogenic Th17 cells are crucial to CNS autoimmune diseases like multiple sclerosis (MS), though their control by endogenous mechanisms is unknown. RNAseq analysis of brain glial cells identified immuno-responsive gene 1 (Irg1), a mitochondrial-related enzyme-coding gene, as one of the highly upregulated gene under inflammatory conditions which were further validated in the spinal cord of animals with experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Moreover, Irg1 mRNA and protein levels in myeloid, CD4, and B cells were higher in the EAE group, raising questions about its function in CNS autoimmunity. We observed that Irg1 knockout (KO) mice exhibited severe EAE disease and greater mononuclear cell infiltration, including triple-positive CD4 cells expressing IL17a, GM-CSF, and IFNγ. Lack of Irg1 in macrophages led to higher levels of Class II expression and polarized myelin primed CD4 cells into pathogenic Th17 cells through the NLRP3/IL1ß axis. Our findings show that Irg1 in macrophages plays an important role in the formation of pathogenic Th17 cells, emphasizing its potential as a therapy for autoimmune diseases, including MS.