Biology subjects

Takuwa, H.

Publications and source records attributed to Takuwa, H..

10 recordsLinked to original sources

bioRxiv2026

In vivo brain temperature measurement using quantum dot imaging temperature sensors

Temperature regulation in the brain is essential for maintaining neuronal function and preventing thermally induced damage. Here, we report the development and in vivo application of quantum dots (QDs) to high-resolution thermometry in the mouse brain using two-photon excitation microscopy. These QDs, via the red-to-green photoluminescence (PL) intensity ratios, enabled stable temperature measurements in both normal and chronically hypo-perfused cerebral tissue. Our findings show that localized neuronal activity leads to transient heat generation, which is rapidly dissipated by cerebrovascular responses. In a chronic hypoperfusion model, impaired vascular function resulted in exaggerated and prolonged brain temperature elevations. This thermometry system provides unprecedented insight into the mechanisms of cerebral thermoregulation and highlights the importance of vascular cooling in protecting the brain from heat-induced stress, particularly in pathological conditions such as stroke.

bioengineering↗

bioRxiv2025

Pharmacological potentiation of Nav1.1 channels in interneurons mitigates tau depositions and neuronal death in a mouse model of neurodegenerative dementias

Epileptiform discharges and neuronal hyperexcitability are key pathophysiological features of Alzheimers disease and related tauopathies. We previously identified selective dynfuntion of parvalbumin-positive GABAergic interneurons (PV neurons), which regulate neural network excitability, in a tauopathy mouse model. However, the mechanistic link between PV neuron deficits, tau pathology, and neurodegeneration remains unclear. Here, we demonstrate that pharmacological enhancement of phasic PV neuron activity markedly attenuates tau accumulation and neuronal loss in a tauopathy mouse model. We developed DSR-143630, a novel activator of voltage-gated sodium channel Nav1.1, selectively expressed in PV neurons. Administration of DSR-143630 alleviated febrile seizures in Nav1.1 haploinsufficient mice and suppressed high-frequency oscillations (HFOs), an electrophysiological signature of hyperexcitability associated with cognitive impairments, in rTg4510 tau transgenic mice. Longitudinal tau PET and volumetric MRI demonstrated that DSR-143630 treatment from 4 to 11 months of age profoundly reduced age-dependent tau deposition and atrophy in the neocortex and hippocampus. Postmortem analyses further revealed decreased levels of phosphorylated tau, preservation of neuronal populations, and attenuated neuroinflammatory responses, including reactive gliosis. These findings establish PV neuron dysfunctions and consequent network hyperexcitability as key drivers of tau pathogenesis and highlight pharmacological Nav1.1 activation as a promising disease-modifying strategy for neurodegenerative tauopathies. One Sentence SummaryPharmacological potentiation of interneuronal activities attenuates aberrant network excitability, progressive tau deposition, and neurodegeneration.

neuroscience↗

bioRxiv2022

Distribution of intraperitoneally administered D2O in AQP4-knockout mouse brain after MCA occlusion

As the movement of water in the brain is known to be involved in neural activity and various brain pathologies, the ability to assess water dynamics in the brain will be important for the understanding of brain function and the diagnosis and treatment of brain diseases. Aquaporin-4 (AQP4) is a membrane channel protein that is highly expressed in brain astrocytes and is important for the movement of water molecules in the brain. In this study, we investigated the contribution of AQP4 to brain water dynamics by administering deuterium-labeled water (D2O) intraperitoneally to wild-type and AQP4 knockout (AQP4-ko) mice that had undergone surgical occlusion of the middle cerebral artery. Water dynamics in the infarct region and on either side of the anterior cerebral artery (ACA) was monitored with proton-density-weighted imaging (PDWI) performed on a 7T animal MRI. D2O caused a negative signal change quickly after administration. The AQP4-ko mice showed a delay of the time-to-minimum in both contralateral and ipsilateral ACA region compared to wild-type mice. Also, only the AQP4-ko mice showed a delay of the time-to-minimum in the ipsilateral ACA region compared to the contralateral side. In only the wild-type mice, the signal minimum in the ipsilateral ACA region was higher than that in the contralateral ACA region. In the infarct region, the signal attenuation was slower for the AQP4-ko mice in comparison to the wild-type mice. These results suggest that AQP4 loss affects water dynamics in the ACA region not only in the infarct region. Dynamic PDWI after D2O administration may be a useful tool for showing the effects of AQP4 in vivo. HighlightsO_LIThe measurement of brain water dynamics with D2O. C_LIO_LIIn vivo investigation of AQP4 loss and focal brain ischemia. C_LIO_LIAQP4 loss affects water dynamics in the ACA region not only in the infarct region. C_LI

physiology↗

bioRxiv2022

Genetically encoded sensors for analysing neurotransmission among synaptically-connected neurons

Anatomical connectome mapping in small areas of the nervous system as well as large-scale detection of neuronal activity patterns have been respectively achieved; however, it is still challenging to evaluate the functional connections among anatomically-connected neurons in a large-scale nervous system. We have developed a novel method to visualize neurotransmission named Split Protein HEmispheres for REconstitution (Sphere). By splitting a sensor into two fragments and expressing them in pre- and postsynaptic neurons separately, functional neurotransmitter sensors can be reconstituted only at the synapses between those neurons. We developed a Sphere-SF-iGluSnFR to measure glutamate levels, and further demonstrated that this system is functional in cultured cells, worms, and mouse brains. Moreover, this system is applicable to sensors other than glutamate, and colour variants have also been developed. This could allow for brain-wide imaging of functional synaptic transmission among particular neurons and identification of important neuronal circuits in the nervous system.

neuroscience↗

bioRxiv2020

Tracking tau fibrillogenesis and consequent primary phagocytosis of neurons mediated by microglia in a living tauopathy model

Fibrillary tau pathologies have been implicated in Alzheimers and allied neurodegenerative diseases, while mechanisms by which neurons bearing tau tangles die remain enigmatic. To address this issue, we pursued tau and related key pathologies macroscopically by PET and MRI and microscopically by intravital two-photon laser optics. Time-course macroscopic assays of tau transgenic mice demonstrated intimate associations of tau deposition and increase of an inflammatory microglial marker, translocator protein (TSPO), with regional brain atrophy. Longitudinal microscopy of these mice revealed a rapid turnover of tau lesions resulting from continuous generation of new tau aggregates followed by loss of neurons and their fibrillar contents. This technology also allowed the capturing of the disappearance of tangle-bearing neurons several days after being engulfed by activated microglia. Notably, a therapeutic TSPO ligand profoundly suppressed the mobility and phagocytotic activity of microglia and improved neuronal survival in this model, supporting the involvement of primary phagocytosis of viable neurons by microglia in tau-primed neuronal death. Finally, partial depletion of microglia revealed roles of immune factors, MFG-E8 and C1q, as eat-me signals for an immediate attraction of phagocytic microglia towards the elimination of tangle-loaded neurons.

neuroscience↗

bioRxiv2020

MRS-measured Glutamate versus GABA reflects excitatory versus inhibitory neural activities in awake mice

To assess if magnetic resonance spectroscopy (MRS)-measured Glutamate (Glu) and GABA reflect excitatory and inhibitory neural activities, respectively, we conducted MRS measurements along with two-photon mesoscopic imaging of calcium signals in excitatory and inhibitory neurons of living, unanesthetized mice. For monitoring stimulus-driven activations of a brain region, MRS signals and mesoscopic neural activities were measured during two consecutive sessions of 15-min prolonged sensory stimulations. In the first session, putative excitatory neuronal activities were increased, while inhibitory neuronal activities remained at the baseline level. In the second half, while excitatory neuronal activities remained elevated, inhibitory neuronal activities were significantly enhanced. We also assessed regional neurochemical and functional statuses related to spontaneous neural firing by measuring MRS signals and neuronal activities in a mouse model of Dravet syndrome under a resting condition. Mesoscopic assessments showed that activities of inhibitory neurons in the cortex were diminished relative to wild-type mice in contrast to spared activities of excitatory neurons. Consistent with these observations, the Dravet model exhibited lower concentrations of GABA than wild-type controls. Collectively, the current investigations demonstrate that the MRS-measured Glu and GABA can reflect spontaneous and stimulated activities of neurons producing and releasing these neurotransmitters in an awake condition.

neuroscience↗

bioRxiv2020

In vivo visualization of propagating α-synuclein pathologies in mouse and marmoset models by a bimodal imaging probe, C05-05

Deposition of -synuclein fibrils is implicated in Parkinsons disease (PD) and dementia with Lewy bodies (DLB), while in vivo detection of -synuclein pathologies in these illnesses has been challenging. Here, we have developed a small-molecule ligand, C05-05, for visualizing -synuclein deposits in the brains of living subjects. In vivo optical and positron emission tomography (PET) imaging of mouse and marmoset models demonstrated that C05-05 captured a dynamic propagation of fibrillogenesis along neural pathways followed by disruptions of these structures. High-affinity binding of 18F-C05-05 to -synuclein aggregates in human brain tissues was also proven by in vitro assays. Notably, PET-detectable 18F-C05-05 signals were intensified in the midbrains of PD and DLB patients as compared to healthy controls, providing the first demonstration of visualizing -synuclein pathologies in these illnesses. Collectively, we propose a new imaging technology offering neuropathology-based translational assessments of PD and allied disorders towards diagnostic and therapeutic research and development.

neuroscience↗

bioRxiv2020

Endothelial expression of human APP leads to cerebral amyloid angiopathy in mice

The deposition of amyloid {beta} (A{beta}) in blood vessels of the brain, known as cerebral amyloid angiopathy (CAA), is observed in more than 90% of Alzheimers disease (AD) patients. The presence of such CAA pathology is not as evident, however, in most mouse models of AD, thereby making it difficult to examine the contribution of CAA to the pathogenesis of AD. Since blood levels of soluble amyloid precursor protein (sAPP) in rodents are less than 1% of those in humans, we hypothesized that endothelial APP expression would be markedly lower in rodents, thus providing a reason for the poorly expressed CAA pathology. Here we generated mice that specifically express human APP770 in endothelial cells. These mice exhibited an age-dependent robust deposition of A{beta} in brain blood vessels but not in the parenchyma. Crossing these animals with APP knock-in mice led to an expanded CAA pathology as evidenced by increased amounts of amyloid accumulated in the cortical blood vessels. These results show that both neuronal and endothelial APP contribute cooperatively to vascular A{beta} deposition, and suggest that this mouse model will be useful for studying disease mechanisms underlying CAA and for developing novel AD therapeutics.

neuroscience↗

bioRxiv2020

Genetically targeted reporter imaging of deep neuronal network in the mammalian brain

Positron Emission Tomography (PET) allows biomolecular tracking, while PET monitoring of brain networks has been hampered by the lack of a suitable reporter. Here, we describe in vivo brain imaging that takes advantage of bacterial dihydrofolate reductase, ecDHFR, and its unique antagonist, TMP. In mice, peripheral administration of radiofluorinated and fluorescent TMP analogs enabled PET and intravital microscopy, respectively, of neuronal ecDHFR expressions. This technique is applicable to the visualization of neuronal ensemble activities elicited by chemogenetic manipulation in the mouse hippocampus. Notably, ecDHFR-PET offers mapping of neuronal projections in non-human primate brains, indicating the availability of ecDHFR-based tracking technologies for network monitoring. Finally, we demonstrate the utility of TMP analogs for PET assays of turnover and self-assembly of proteins tagged with ecDHFR mutants. Our findings may facilitate a broad spectrum of PET analyses of a mammalian brain circuit at molecular levels that were not previously applicable for technical reasons.

neuroscience↗

bioRxiv2019

Deschloroclozapine: a potent and selective chemogenetic actuator enables rapid neuronal and behavioral modulations in mice and monkeys

The chemogenetic technology Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) affords remotely reversible control of cellular signaling, neuronal activity and behavior. Although the combination of muscarinic-based DREADDs with clozapine-N-oxide (CNO) has been widely used, sluggish kinetics, metabolic liabilities, and potential off-target effects of CNO represent areas for improvement. Here we provide a new high affinity and selective agonist deschloroclozapine (DCZ) for muscarinic-based DREADDs. Positron emission tomography revealed that DCZ selectively bound to and occupied DREADDs in both mice and monkeys. Systemic delivery of low doses of DCZ (1 or 3 g/kg) enhanced neuronal activity via hM3Dq within minutes in mice and monkeys. Intramuscular injections of DCZ (100 g/kg) reversibly induced spatial working memory deficits in monkeys expressing hM4Di in the prefrontal cortex. DCZ represents the most potent, selective, metabolically stable and fast-acting DREADD agonist reported with utility in both mice and non-human primates for a variety of applications.

neuroscience↗