Nobutaka Hattori’s research while affiliated with Juntendo University and other places

Liquid‒liquid phase separation (LLPS) and the subsequent liquid‒solid transition are thought to be common aggregation mechanisms of neurodegeneration-associated proteins. α-Synuclein (α-syn), whose aggregation represents the major pathological hallmark of Parkinson’s disease, is reported to undergo LLPS, which accelerates oligomer and aggregate formation in vitro and in vivo ; however, the precise molecular events involved in the early stages of α-syn aggregation remain controversial. In the present study, α-syn aggregation was promoted by liquid droplets formed by ubiquilin-2 (UBQLN2) rather than directly by the LLPS of α-syn. During the liquid–gel/solid transition of UBQLN2 droplets, α-syn within the droplets was transformed into pathogenic fibrils both in vitro and within cells. The small compound SO286 inhibited both UBQLN2 self-interaction and α-syn–UBQLN2 interaction by binding to the STI1 region of UBQLN2, thereby impairing α-syn aggregation. These results indicate that UBQLN2 droplets catalyze α-syn fibril formation and suggest that small molecules that target fibrillation-catalyzing proteins may represent a promising strategy for the development of therapeutics against neurodegenerative diseases. Significance statement Although the fibril formation of α-synuclein is a major driver of Parkinson’s disease pathology, the mechanisms of its early stages remain unclear. Here, we demonstrated in vitro and in cells that ubiquilin-2 (UBQLN2) droplets, formed via liquid‒liquid phase separation, absorbed soluble α-synuclein and promoted the fibril formation of α-synuclein through their liquid–gel/solid transition. This result suggests a previously unrecognized role for UBQLN2 in catalyzing α-synuclein fibril formation via its own liquid‒liquid phase separation. Furthermore, a small molecule targeting the STI1 region of UBQLN2 inhibited both the liquid‒solid transition of UBQLN2 and the interaction between UBQLN2 and α-synuclein, thereby suppressing α-synuclein aggregation. These findings suggest a new approach for the development of therapeutic interventions for Parkinson’s disease.

The nervous system processes a vast amount of information, performing computations that underlie perception, cognition, and behavior. During development, neuronal guidance genes, which encode extracellular cues, their receptors, and downstream signal transducers, organize neural wiring to generate the complex architecture of the nervous system. It is now evident that many of these neuroguidance cues and their receptors are active during development and are also expressed in the adult nervous system. This suggests that neuronal guidance pathways are critical not only for neural wiring but also for ongoing function and maintenance of the mature nervous system. Supporting this view, these pathways continue to regulate synaptic connectivity, plasticity, and remodeling, and overall brain homeostasis throughout adulthood. Genetic and transcriptomic analyses have further revealed many neuronal guidance genes to be associated with a wide range of neurodegenerative and neuropsychiatric disorders. Although the precise mechanisms by which aberrant neuronal guidance signaling drives the pathogenesis of these diseases remain to be clarified, emerging evidence points to several common themes, including dysfunction in neurons, microglia, astrocytes, and endothelial cells, along with dysregulation of neuron-microglia-astrocyte, neuroimmune, and neurovascular interactions. In this review, we explore recent advances in understanding the molecular and cellular mechanisms by which aberrant neuronal guidance signaling contributes to disease pathogenesis through altered cell–cell interactions. For instance, recent studies have unveiled two distinct semaphorin-plexin signaling pathways that affect microglial activation and neuroinflammation. We discuss the challenges ahead, along with the therapeutic potentials of targeting neuronal guidance pathways for treating neurodegenerative diseases. Particular focus is placed on how neuronal guidance mechanisms control neuron-glia and neuroimmune interactions and modulate microglial function under physiological and pathological conditions. Specifically, we examine the crosstalk between neuronal guidance signaling and TREM2, a master regulator of microglial function, in the context of pathogenic protein aggregates. It is well-established that age is a major risk factor for neurodegeneration. Future research should address how aging and neuronal guidance signaling interact to influence an individual’s susceptibility to various late-onset neurological diseases and how the progression of these diseases could be therapeutically blocked by targeting neuronal guidance pathways.

Background Psychosis is known as one of the non-motor symptoms of Parkinson’ s disease (PD). Psychosis is typically associated with an increased burden regarding living activities in PD and thus constitutes a serious public health problem. Aims & Objectives We hypothesized that the visual hallucinations associated with PD would be predicted by neurodegeneration of specific regions. We consecutively enrolled 228 patients with PD between October 2016 and March 2021 at Juntendo University Hospital in Japan. Method All patients were assessed for motor function, cognition, mental state, and REM sleep-related events using the REM sleep behavior disorder (RBD) Single-Question Screen (RBD1Q), and for regional cerebral blood flow (rCBF) using N-isopropyl-p-123I-iodoamphetamine single photon emission tomography. Results The patients were divided into two groups: one with a history of visual hallucinations (Hal-PD; n = 119) and one without (nHal-PD; n = 109). Three factors were associated with Hal-PD: sex and scores on both the RBD1Q and Odor Stick Identification Test for Japanese (OSIT-J). In single photon emission tomography data, rCBF in the bilateral posterior cingulate (PC) and right cuneus were significantly lower in the Hal-PD than in the nHal-PD group. RBD1Q scores were associated with rCBF in the bilateral PC. Discussion & Conclusions Visual hallucinations were associated with rCBF in the bilateral PC and OSIT-J scores. Especially, rCBF in the left PC was an independent risk factor. RBD1Q scores were significantly associated with Hal-PD. RBD1Q scores may be an easy surrogate factor for visual hallucinations in settings where rCBF cannot be measured.

Recently, the role of T cells in the pathology of α-synuclein (αS)-mediated neurodegenerative disorders called synucleinopathies, including Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy, has attracted increasing attention. Although the existence of αS-specific T cells and the immunogenicity of the post-translationally modified αS fragment have been reported in PD and DLB, the key cellular subset associated with disease progression and its induction mechanism remain largely unknown. Peripheral blood mononuclear cells (PBMCs) from synucleinopathy patients and healthy controls were cultured in the presence of the αS peptide pools. Cytokine analysis using culture supernatants revealed that C-terminal αS peptides with a phosphorylated serine 129 residue (pS129), a feature of pathological αS aggregates, promoted the production of IL-17A, IL-17F, IL-22, IFN-γ and IL-13 in PD patients compared with that in controls. In pS129 peptide-reactive PD cases, Ki67 expression was increased in CD4 T cells but not in CD8 T cells, and intracellular cytokine staining assay revealed the existence of pS129 peptide-specific Th1 and Th17 cells. The pS129 peptide-specific Th17 responses, but not Th1 responses, demonstrated a positive correlation with the Movement Disorder Society-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) Part III scores. A similar correlation was observed for IL-17A levels in the culture supernatant of PBMCs from PD patients with disease duration < 10 years. Interestingly, enhanced Th17 responses to pS129 peptides were uniquely found in PD patients among the synucleinopathies, suggesting that Th17 responses are amplified by certain mechanisms in PD patients. To investigate such mechanisms, we analyzed Th17-inducible capacity of αS-exposed dendritic cells (DCs). In vitro stimulation with αS aggregates generated Th17-inducible DCs with IL-6 and IL-23 production through the signaling of TLR4 and spliced X-box binding protein-1 (XBP1s). In fact, the levels of IL-6 and IL-23 in plasma, and the XBP1s ratio in type 2 conventional DCs were increased in PD patients compared with those in controls. Here, we propose the importance of αS-specific Th17 responses in the progression of PD and the underlying mechanisms inducing Th17 responses. These findings may provide novel therapeutic strategies to prevent disease development through the suppression of TLR4-XBP1s-IL-23 signaling in DCs.

Background: Despite the effectiveness of immediate treatment, such as thrombolytic therapy, after a stroke, many patients are unable to benefit due to time restrictions. In an aging society, sarcopenia, a condition characterized by reduced muscle volume, is emerging as a significant issue, often contributing to poor recovery after stroke. Our study examined the role of mitochondria, which are abundant in muscle, and their migration during exercise in the context of stroke recovery. Methods: We used mice models to simulate chronic hypoperfusion and distal middle cerebral artery occlusion. We also conducted in vitro studies with rat primary cells, co-cultured with a nonlethal concentration of CoCl 2 and oxygen-glucose deprivation. Results: We found that 28 days post-hypoperfusion, there was a progression in white matter injury, including myelin loss, astroglial formation, and memory disorder. However, treadmill training protected against these damages. In cases of acute ischemia, training improved complications and reduced glial activation. We observed increased mitochondria in muscle and blood due to training, which migrated between tissues using platelets. In vitro analysis revealed that adding muscle mitochondria improved the survival of neurons, astrocytes, and oligodendrocytes. Most importantly, we found that mitochondrial transfusion from treadmill-trained mice platelet improved ischemic white matter injury and post-stroke complications. Conclusions: The study showed mitochondria as part of the secretome, essential for regulating cell interactions. It explored mitochondrial secretion, transfer between cells, and dynamics influencing ischemic tissue. The protective effects of remote ischemic preconditioning might be linked to muscle-derived mitochondria, a recent phenomenon. Unlike conventional platelet transfusion, mitochondria administration even from cryopreserved platelets shows brain protection effect. Therefore, this suggests that the advantage of this therapy is that mitochondria can be extracted from platelets that could not be used for transfusion and used for treatment. Our study suggests it could be a promising new treatment for reducing post-stroke complications and vascular dementia.

(Background): Stroke has become a leading cause of mortality and disability worldwide. However, except rehabilitation, there is no effective therapy during chronic phase after ischemic stroke. Interestingly, it has been reported that young cerebrospinal fluid (CSF) restores oligodendrogenesis and memory in aged mice. However, if specific components in CSF could contribute to functional recovery during chronic phase of ischemic stroke remains unclear. We tried to distinguish a specific microRNA in CSF and identify its potential therapeutic functions. (Method): Rats were subjected to permanent left middle cerebral artery occlusion (pMCAO). Brains and CSF were collected at 3, 7, 14, 28 days after pMCAO. MicroRNA in CSF was evaluated by microRNA Array. A specific microRNA was selected based on heatmap and volcano plot. IPA analysis was used to distinguish possibly related signaling pathways. Mimic/ inhibitor of this microRNA was applied respectively to primary cultured astrocytes and neurons soon after 3 hours’ oxygen glucose deprivation (OGD). Associated proteins were tested through western blot at 96 hours after OGD. In vivo, time course of pStat3 was assessed in peri-infarct cortical area. At 7 days after pMCAO, mimic of this microRNA was applied to CSF through Cisterna Magna. behavioral tests were assessed at 7, 14, 21, 28 days after pMCAO. At 28 days after pMCAO, brains were harvested for ischemia volume calculation and immunofluorescence. (Result): miR-204-5p was significantly upregulated in CSF at 7 days after pMCAO and selected as target microRNA. According to IPA analysis, miR-204-5p might be associated with Stat3 signaling pathway. Based on results of astrocyte culture, GFAP was significantly decreased by applying miR-204-5p mimic. Regarding neuron culture, pStat3, MAP2 showed a tendency to increase by applying miR-204-5p mimic. In vivo, pStat3 significantly increased at 3 days and began to decrease from 7 days after pMCAO. miR-204-5p mimic group showed a tendency of ameliorated functional dysfunction, smaller ischemia volume at 28 days after pMCAO. In peri-infarct area, compared with non-treatment group, GFAP was significantly decreased, and pStat3 showed tendency to increase in miR-204-5p mimic group. (Conclusion): Applying miR-204-5p mimic into CSF contributed to functional recovery via activating Stat3 signalling pathway and reducing astrocytosis, which might be a candidate of exosome or liposome preparation for future clinical trials.