Gen Ohtsuki

Sporadic amyotrophic lateral sclerosis (ALS) is characterized by selective motor neuron vulnerability accompanied by prominent glial responses, yet their molecular heterogeneity and spatial organization in the human central nervous system and spinal cord remain incompletely defined. Here, we delineate ALS-associated glial states in situ by spatially resolved, single-cell proteomic profiling of postmortem human sporadic ALS and non-neurological control tissues across the motor cortex, spinal cord, and cerebellum. We identify subpopulations of astrocytes and microglia co-expressing both canonical ALS markers together with newly implicated ALS-associated proteins, including phosphorylated TDP-43, UBQLN2, TREM2, IL6ST, and glutaminase (GLS). These glial states are consistent with transcriptomic signatures characterized by TP53 and GLS upregulation, indicating convergence on senescence stress- and glutamine metabolism-related pathways. Notably, p53–GLS-associated profiles are selectively enriched in anatomically vulnerable regions in ALS, supporting region-specific glial metabolic alterations in human disease. Together, these findings provide insight into the metabolic alterations in ALS-affected human tissue and highlight the relevance of spatial context in shaping glial responses to neurodegeneration.

In this review, we synthesize recent conceptual and experimental advances in neuroscience, highlighting selected studies that delineate the roles of reactive microglia and astrocytes in the contexts of developmental inflammatory stress, neurodegenerative diseases, and cellular senescence. Since the characterization of disease-associated glial phenotypes in 2017, building on earlier pioneering discoveries, we focus here on disease-associated microglia (DAM) and disease-associated astrocyte (DAA) to reassess their contributions to glio-inflammation. It is now recognized that the stress-induced glial states are far from uniform; however, the ontogeny, molecular determinants, and functional consequences of this heterogeneity remain incompletely understood, particularly in psychiatric disorders, Alzheimer's disease, and amyotrophic lateral sclerosis. Accordingly, we compare the glial heterogeneity and its underlying mechanisms across translational mouse models and human neuropathology, considering their evolutionary and physiological contexts. While this review does not aim to be exhaustive, we propose an integrative framework that redefines glial stress responses through the combined lenses of inflammation, transcriptomics, mitochondrial dynamics, lipid metabolism, epigenomic regulation, and cellular senescence. Finally, we outline emerging frontiers for AI-enabled multi-omic physiological and pathological approaches, emphasizing their potential to illuminate glial state transitions and accelerate therapeutic discovery in the near future.

The functional alteration of microglia arises in brains exposed to external stress during early development. Pathophysiological findings of neurodevelopmental disorders such as schizophrenia and autism spectrum disorder suggest cerebellar functional deficits. However, the link between stress-induced microglia reactivity and cerebellar dysfunction is missing. Here, we investigate the developmental immune environment in translational mouse models that combine two risk factors: maternal infection and repeated social defeat stress (2HIT). We find the synergy of inflammatory stress insults, leading to microglial increase specifically in the cerebellum of both sexes. Microglial turnover correlates with the Purkinje neuron loss in 2HIT mice. Highly multiplexed imaging-mass-cytometry identifies a cell transition to TREM2(+) stress-associated microglia in the cerebellum. Single-cell-proteomic clustering reveals IL-6- and TGFβ-signaling association with microglial cell transitions. Reduced excitability of remaining Purkinje cells, cerebellum-involved brain-wide functional dysconnectivity, and behavioral abnormalities indicate cerebellar cognitive dysfunctions in 2HIT animals, which are ameliorated by both systemic and cerebellum-specific microglia replacement.

The functional alteration of microglia emerges in the brains exposed to extrinsic stress insults during early development. Pathophysiological findings of psychiatric disorders such as schizophrenia and autism implied a localized deficit of the cerebellum. However, the link between microglia reactivity and cerebellar dysfunction is missing. Here, we investigated the developmental immune environment of translational mouse models that combine two risk factors: maternal infection and repeated social defeat stress (i.e., 2HIT). We found synergy of inflammatory stress insults produced reactive microglia, specifically in the cerebellum in both sexes. The microglial proliferation correlated with the Purkinje neuron loss in 2HIT mice. Highly multiplexed imaging-mass-cytometry demonstrated a TREM2-positive population of stress-associated microglia in the cerebellum. Single-cell-proteomic clustering revealed IL-6- and TGFβ-signaling association with microglial cell transition. Purkinje cells reduced excitability, cerebellum-involved brain-wide functional dysconnectivity, and behavioral anomalies underpin the cerebellar cognitive dysfunctions in 2HIT animals, ameliorated by cerebellum-specific microglia replacement.

Immune cells play numerous roles in the host defense against the invasion of microorganisms and pathogens, which induces the release of inflammatory mediators (e.g., cytokines and chemokines). In the CNS, microglia is the major resident immune cell. Recent efforts have revealed the diversity of the cell types and the heterogeneity of their functions. The refinement of the synapse structure was a hallmark feature of the microglia, while they are also involved in the myelination and capillary dynamics. Another promising feature is the modulation of the synaptic transmission as synaptic plasticity and the intrinsic excitability of neurons as non-synaptic plasticity. Those modulations of physiological properties of neurons are considered induced by both transient and chronic exposures to inflammatory mediators, which cause behavioral disorders seen in mental illness. It is plausible for astrocytes and pericytes other than microglia and macrophage to induce the immune-triggered plasticity of neurons. However, current understanding has yet achieved to unveil what inflammatory mediators from what immune cells or glia induce a form of plasticity modulating pre-, post-synaptic functions and intrinsic excitability of neurons. It is still unclear what ion channels and intracellular signaling of what types of neurons in which brain regions of the CNS are involved. In this review, we introduce the ubiquitous modulation of the synaptic efficacy and the intrinsic excitability across the brain by immune cells and related inflammatory cytokines with the mechanism for induction. Specifically, we compare neuro-modulation mechanisms by microglia of the intrinsic excitability of cerebellar Purkinje neurons with cerebral pyramidal neurons, stressing the inverted directionality of the plasticity. We also discuss the suppression and augmentation of the extent of plasticity by inflammatory mediators, as the meta-plasticity by immunity. Lastly, we sum up forms of immune-triggered plasticity in the different brain regions with disease relevance. Together, brain immunity influences our cognition, sense, memory, and behaviorviaimmune-triggered plasticity.

Introduction: Prominently accountable for the upsurge of COVID‐19 cases as the world attempts to recover from the previous two waves, Omicron has further threatened the conventional therapeutic approaches. The lack of extensive research regarding Omicron has raised the need to establish correlations to understand this variant by structural comparisons. Here, we evaluate, correlate, and compare its genomic sequences through an immunoinformatic approach to understand its epidemiological characteristics and responses to existing drugs.Methods: We reconstructed the phylogenetic tree and compared the mutational spectrum. We analyzed the mutations that occurred in the Omicron variant and correlated how these mutations affect infectivity and pathogenicity. Then, we studied how mutations in the receptor‐binding domain affect its interaction with host factors through molecular docking. Finally, we evaluated the drug efficacy against the main protease of the Omicron through molecular docking and validated the docking results with molecular dynamics simulation.Results: Phylogenetic and mutational analysis revealed the Omicron variant is similar to the highly infectious B.1.620 variant, while mutations within the prominent proteins are hypothesized to alter its pathogenicity. Moreover, docking evaluations revealed significant differences in binding affinity with human receptors, angiotensin‐converting enzyme 2 and NRP1. Surprisingly, most of the tested drugs were proven to be effective. Nirmatrelvir, 13b, and Lopinavir displayed increased effectiveness against Omicron.Conclusion: Omicron variant may be originated from the highly infectious B.1.620 variant, while it was less pathogenic due to the mutations in the prominent proteins. Nirmatrelvir, 13b, and Lopinavir would be the most effective, compared to other promising drugs that were proven effective.

The cerebellum governs motor coordination and motor learning. Infection with external microorganisms, such as viruses, bacteria, and fungi, induces the release and production of inflammatory mediators, which drive acute cerebellar inflammation. The clinical observation of acute cerebellitis is associated with the emergence of cerebellar ataxia. In our animal model of the acute inflammation of the cerebellar cortex, animals did not show any ataxia but hyperexcitability in the cerebellar cortex and depression-like behaviors. In contrast, animal models with neurodegeneration of the cerebellar Purkinje cells and hypoexcitability of the neurons show cerebellar ataxia. The suppression of the Ca²⁺-activated K⁺ channels in vivo is associated with a type of ataxia. Therefore, there is a gap in our interpretation between the very early phase of cerebellar inflammation and the emergence of cerebellar ataxia. In this review, we discuss the hypothesized scenario concerning the emergence of cerebellar ataxia. First, compared with genetically induced cerebellar ataxias, we introduce infection and inflammation in the cerebellum via aberrant immunity and glial responses. Especially, we focus on infections with cytomegalovirus, influenza virus, dengue virus, and SARS-CoV-2, potential relevance to mitochondrial DNA, and autoimmunity in infection. Second, we review neurophysiological modulation (intrinsic excitability, excitatory, and inhibitory synaptic transmission) by inflammatory mediators and aberrant immunity. Next, we discuss the cerebellar circuit dysfunction (presumably, via maintaining the homeostatic property). Lastly, we propose the mechanism of the cerebellar ataxia and possible treatments for the ataxia in the cerebellar inflammation.

The vasculature system with a lymphatic function in the brain is manifested as meningeal lymphatic vessels and the glymphatic system, which drain waste products from cerebrospinal fluid (CSF) and produce interstitial fluid. Invasion of stimulated immune cells or inflammatory cytokines during the maturation is regarded as a sign of the disruption of brain functions through excessive immune stresses. However, it is unclear when the lymphatic system is functionally completed and in which parts of the organ the brain immunity is privileged ( i.e ., the blood-brain barrier is fully established). Here, we visualized the whole-head signal of gadolinium (Gd) contrast agents in mouse brains to investigate the CSF flow from the signals of Gd-contrast agents using magnetic resonance imaging (MRI) in the course of developmental stages. We found higher Gd-signals in the olfactory bulbs, prefrontal cortex, parietal surface regions of the neocortex along with dorsal meningeal lymphatic vessels, ventral midbrain, and a part of cerebellum, as well as in the basal brain regions, at the immature stage of postnatal (P) 4 weeks, compared to the P8-12 weeks. Our results suggest that the barrier of the vasculature system in mouse brains is still permeable until P1-month and small molecules can leak into the parenchyma.