CXCL7 aggravates the pathological manifestations of neuromyelitis optica spectrum disorder by enhancing the inflammatory infiltration of neutrophils, macrophages and microglia.

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory demyelinating disease of the central nervous system (CNS). Our previous study indicated that neutrophil-related chemokine CXCL7 is elevated in the cerebrospinal fluid (CSF) of NMOSD patients. To study the potential function of CXCL7 during NMOSD, we measured the chemokines level in CSF of follow-up patients, and established three NMOSD mouse models by injecting aquaporin4 (AQP4)-IgG. Astrocytes loss, inflammatory infiltration, and myelin sheath damage were detected by western blot or immunofluorescence analysis. We found CXCL7 was significantly increased in the serum and CSF of model mice, and exogenous CXCL7 caused serious astrocyte injury, obvious microglia activation, and increased infiltration of neutrophils and macrophages, resulting in secondary demyelination. Consistently, knocking down the CXCL7 reversed the loss of AQP4, and attenuated the inflammatory response. Collectively, our data indicates that CXCL7 aggravates NMOSD-like pathological damage to astrocytes and myelin sheath mainly via promoting neuroinflammatory response.

Mitofusin 2 confers the suppression of microglial activation by cannabidiol: Insights from in vitro and in vivo models.

Currently, there is increasing attention on the regulatory effects of cannabidiol (CBD) on the inflammatory response and the immune system. However, the mechanisms have not yet been completely revealed. Mitofusin 2 (Mfn2) is a mitochondrial fusion protein involved in the inflammatory response. Here, we investigated whether Mfn2 confers the anti-inflammatory effects of CBD. We found that treatment with CBD decreased the levels of tumor necrosis factor α, interleukin 6, inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and ionized calcium-binding adaptor molecule-1 (Iba1) in lipopolysaccharide (LPS)-challenged microglia. CBD also significantly suppressed the increase in reactive oxygen species (ROS) and the decline of mitochondrial membrane potential in BV-2 cells subjected to LPS. Interestingly, CBD treatment increased the expression of Mfn2, while knockdown of Mfn2 blocked the effect of CBD. By contrast, overexpression of Mfn2 reversed the increase in the levels of iNOS, COX-2, and Iba1 induced by Mfn2 small interfering RNA. In mice challenged with LPS, we found that CBD ameliorated the anxiety responses and cognitive deficits, increased the level of Mfn2, and decreased the expression of Iba1. Since neuro-inflammation and microglial activation are the common events that are observed in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis, we treated EAE mice with CBD. Mice that received CBD showed amelioration of clinical signs, reduced inflammatory response, and increased myelin basic protein level. Most importantly, the adeno-associated virus delivery of short hairpin RNA against Mfn2 reversed the protective effects of CBD. Altogether, these results indicate that Mfn2 is an essential immunomodulator conferring the anti-inflammatory effects of CBD. Our results also shed new light on the mechanisms underlying the protective effects of CBD against inflammatory diseases including multiple sclerosis.

IRAK-M suppresses the activation of microglial NLRP3 inflammasome and GSDMD-mediated pyroptosis through inhibiting IRAK1 phosphorylation during experimental autoimmune encephalomyelitis.

The activation of the NOD-like receptor family pyrin domain-containing protein 3 (NLRP3) inflammasome triggers pyroptosis proinflammatory cell death in experimental autoimmune encephalomyelitis (EAE). However, the underlying mechanisms of the inflammatory processes of microglia in EAE remain unclear. Our previous studies suggested that interleukin-1 receptor-associated kinase (IRAK)-M down-regulates the toll-like receptor 4/interleukin-1 receptor signaling pathway. Here, we used IRAK-M knockout (IRAK-M-/-) mice and their microglia to dissect the role of IRAK-M in EAE. We found that deletion of IRAK-M increased the incidence rate and exacerbated the clinical symptoms in EAE mice. We then found that IRAK-M deficiency promoted the activation of microglia, activated NLRP3 inflammasomes, and enhanced GSDMD-mediated pyroptosis in the microglia of EAE. In contrast, over-expression of IRAK-M exerted inhibitory effects on neuroinflammation, NLRP3 activation, and pyroptosis. Moreover, IRAK-M deficiency enhanced the phosphorylation of IRAK1, while IRAK-M over-expression downregulated the level of phosphorylated IRAK1. Finally, we found upregulated binding of IRAK1 and TNF receptor-associated factor 6 (TRAF6) in IRAK-M-/- EAE mice compared to WT mice, which was blocked in AAVIRAK-M EAE mice. Our study reveals a complex signaling network of IRAK-M, which negatively regulates microglial NLRP3 inflammasomes and pyroptosis by inhibiting IRAK1 phosphorylation during EAE. These findings suggest a potential target for the novel therapeutic approaches of multiple sclerosis (MS)/EAE and NLRP3-related inflammatory diseases.

Single-nucleus RNA sequencing unveils critical regulators in various hippocampal neurons for anti-N-methyl-D-aspartate receptor encephalitis.

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a neuropsychiatric disease with variable clinical manifestations caused by NMDAR autoantibody. The underlying molecular underpinnings of this disease are rarely characterized on a genomic scale. Anti-NMDAR encephalitis mainly affects the hippocampus, however, its effect on gene expression in hippocampal neurons is unclear at present. Here, we construct the active and passive immunization mouse models of anti-NMDAR encephalitis, and use single-nucleus RNA sequencing to investigate the diverse expression profile of neuronal populations isolated from different hippocampal regions. Dramatic changes in cell proportions and differentially expressed genes were observed in excitatory neurons of the dentate gyrus (DG) subregion. In addition, we found that ATP metabolism and biosynthetic regulators related genes in excitatory neurons of DG subregion were significantly affected. Kcnq1ot1 in inhibitory neurons and Meg3 in interneurons also changed. Notably, the latter two molecules exhibited opposite changes in different models. Therefore, the above genes were used as potential targets for further research on the pathological process of anti-NMDAR encephalitis. These data involve various hippocampal neurons, which delineate a framework for understanding the hippocampal neuronal circuit and the potential molecular mechanisms of anti-NMDAR encephalitis.

The CSF Levels of Neutrophil-Related Chemokines in Patients with Neuromyelitis Optica.

Pathologic findings showed that neutrophils played an important role in the pathogenesis of NMO. This study aims to investigate the CSF levels of neutrophil-related chemokines in NMO. CXCL1, CXCL5, and CXCL7 were measured in 95 patients with NMO, 15 patients with MS, 18 patients with GFAP astrocytopathy, and 16 controls. The CSF level of CXCL1, CXCL5, and CXCL7 was significantly elevated in the NMO group but not correlated with the patient clinical severity. Besides, the CSF CXCL1, CXCL5, and CXCL7 could act as biomarkers to distinguish NMO from MS with good reliability, especially the CXCL7.