MLKL Modulates Necroptosis and Neuroinflammation in a Mouse Model of MS

Abstract

MLKL not only plays an important role in necroptosis but also regulates many diseases through non-necrotizing apoptotic function. Many studies have shown that MLKL plays an important role in neuroinflammation, degenerative diseases, and infectious diseases. Multiple sclerosis is an immune-mediated neurodegenerative disease characterized mainly by inflammatory demyelinating lesions of the central nervous system (CNS). At present, few studies have investigated the role of MLKL in regulating necroptosis and neuroinflammation in MS. We aimed to explore the role of MLKL in regulating necroptosis and neuroinflammation and to further elucidate the regulatory mechanisms in a mouse model of MS. An experimental autoimmune encephalomyelitis (EAE) MS mouse model was established, and the mice were divided into two groups (the EAE + NSA group and the EAE group). The two groups of mice were injected with the MLKL inhibitor necrosulfonamide(NSA) or control solution at the same time. We measured the severity of disease using a clinical EAE scoring system. HE staining and LFB staining of the spinal cord were used to observe the infiltration of CNS inflammatory cells and myelination in the two groups of mice. Western blotting was performed to assess the expression of proteins in the NLRP3/caspase-1/GSDMD pathway, the MyD88/NF-κB pathway and the RIPK3/MLKL pathway. Immunofluorescence experiments were performed to observe changes in microglia, astroglia, oligodendrocytes, and related factors. Finally, we analyzed the changes in inflammation in both groups via an ELISA. Blockade of MLKL alleviates clinical symptoms, demyelination and inflammatory cell infiltration in EAE mice. Furthermore, it increased the number of oligodendrocytes, protected axons, decreased the number of activated astrocytes and microglia and reduced inflammation. MLKL inhibitors may ameliorate necroptosis through the RIPK3/MLKL pathway. Blockade of MLKL may exert therapeutic effects by inhibiting the activation of the NLRP3/caspase-1/GSDMD pathway and the MyD88/NF-κB pathway in EAE mice. Blocking MLKL plays a therapeutic role in EAE not only through regulating necroptosis via the RIPK3/MLKL pathway but also through regulating neuroinflammation via the NLRP3/caspase-1/GSDMD pathway and the MyD88/NF-κB pathway.

Keywords: Experimental autoimmune encephalomyelitis (EAE); Mixed lineage kinase domain-like protein(MLKL); Multiple sclerosis (MS); MyD88/NF-κB signaling pathway; NLRP3/caspase-1/GSDMD pathway; Necroptosis; Necrosulfonamide (NSA); RIPK3/MLKL signaling pathway.