Distribution of intraperitoneally administered deuterium-labeled water in aquaporin-4-knockout mouse brain after middle cerebral artery occlusion

IntroductionAs 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.MethodsIn 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 (MCA). 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.ResultsD2O caused a negative signal change quickly after administration. The AQP4-ko mice showed a delay of the time-to-minimum in both the contralateral and ipsilateral ACA regions 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.DiscussionThese 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

A liquid crystalline phase in spermidine-condensed DNA

Over a large range of salt and spermidine concentrations, short DNA fragments precipitated by spermidine (a polyamine) sediment in a pellet from a dilute isotropic supernatant. We report here that the DNA-condensed phase consists of a cholesteric liquid crystal in equilibrium with a more concentrated phase. These results are discussed according to Flory's theory for the ordering of rigid polymers. The liquid crystal described here corresponds to an ordering in the presence of attractive interactions, in contrast with classical liquid crystalline DNA. Polyamines are often used in vitro to study the functional properties of DNA. We suggest that the existence of a liquid crystalline state in spermidine-condensed DNA is relevant to these studies

DOCK2 is involved in the host genetics and biology of severe COVID-19

「コロナ制圧タスクフォース」COVID-19疾患感受性遺伝子DOCK2の重症化機序を解明 --アジア最大のバイオレポジトリーでCOVID-19の治療標的を発見--. 京都大学プレスリリース. 2022-08-10.Identifying the host genetic factors underlying severe COVID-19 is an emerging challenge. Here we conducted a genome-wide association study (GWAS) involving 2, 393 cases of COVID-19 in a cohort of Japanese individuals collected during the initial waves of the pandemic, with 3, 289 unaffected controls. We identified a variant on chromosome 5 at 5q35 (rs60200309-A), close to the dedicator of cytokinesis 2 gene (DOCK2), which was associated with severe COVID-19 in patients less than 65 years of age. This risk allele was prevalent in East Asian individuals but rare in Europeans, highlighting the value of genome-wide association studies in non-European populations. RNA-sequencing analysis of 473 bulk peripheral blood samples identified decreased expression of DOCK2 associated with the risk allele in these younger patients. DOCK2 expression was suppressed in patients with severe cases of COVID-19. Single-cell RNA-sequencing analysis (n = 61 individuals) identified cell-type-specific downregulation of DOCK2 and a COVID-19-specific decreasing effect of the risk allele on DOCK2 expression in non-classical monocytes. Immunohistochemistry of lung specimens from patients with severe COVID-19 pneumonia showed suppressed DOCK2 expression. Moreover, inhibition of DOCK2 function with CPYPP increased the severity of pneumonia in a Syrian hamster model of SARS-CoV-2 infection, characterized by weight loss, lung oedema, enhanced viral loads, impaired macrophage recruitment and dysregulated type I interferon responses. We conclude that DOCK2 has an important role in the host immune response to SARS-CoV-2 infection and the development of severe COVID-19, and could be further explored as a potential biomarker and/or therapeutic target

Neuronal dysfunction due to hyperexcitation under mild chronic cerebral hypoperfusion

Accumulations of tau protein aggregates are mechanistically implicated in Alzheimer’s disease and Parkinson\u27s disease, respectively. Several researchers have recently demonstrated that tau proteins can transfer between neurons in a manner dependent on neural activations. Therefore, continuous removal of tau protein released from activated neurons is important for homeostatic protection of neurons against tau-induced toxicities. In the present study, we investigated mechanisms and pathways involved in the clearance of tau assemblie from the brain using PBB3 as bimodal optical and radiological imaging agents for these aggregates. In optical imaging, neurons, glia cells and macrophages were also labeled with fluorescent protein expressed in these cells via an adeno-associated viral (AAV) vector. Longitudinal, multiscale measurements of the living mouse brains with macroscopic positron emission tomography (PET) and wide-field-of-view two-photon microscope have revealed that tau fibril injected into the brain parenchyma are transferred to the glymphatic system and subsequently to cerebral blood vessels, and this removal is mediated by astrocytes and immune cells such as perivascular macrophages. In addition, the animal PET and two-photon microscopic studies have indicated that mechanical blockade of the glymphatic flow by compression of the brain surface accelerates tau depositions in a tau transgenic model and induces neuronal alpha-synuclein accumulations in a wild-type mouse. These findings suggest that misfolded tau specie are excreted from neurons and are homeostatically cleared through the glymphatic and epidural lymphatic pathways in both normal physiological and diseased conditions, and deteriorations of these clearance processes lead to intraneuronal accumulations of fibrils composed of these proteins.日米

Age-dependent impairment of functional hyperemia is associated with amyloid accumulation in small arteries and arterioles in APP transgenic mouse somatosensory cortex

Objectives: In order to explore the causal relationship between cerebrovascular dysfunction and pathogenesis of Alzheimer\u27s disease, we performed a repeated longitudinal evaluation of CBF response to whisker stimulation and accumulation of amyloid in APP transgenic mouse somatosensory cortex.Methods: Long-term evaluation of CBF response and behavior activity was performed (Takuwa et al., 2010), every 2 to 4 weeks with laser-Doppler flowmetry (LDF) and an optical motion sensor, respectively in awake APP transgenic mice (3-27 months). Whisker stimulation was performed to provoke CBF response. On a separate date, amyloid and microvessels were fluorescently labeled with a compound X (newly-developed by our group) and sulforhodamine 101, respectively, and two-photon imaging (1024 by 1024 pixels) was performed with a z-step size of 4 µm (Fig. 1). Accumulation of vascular amyloid and tissue amyloid were evaluated separately. The thickness of the vascular amyloid was evaluated at several point along a particular vessel as the difference between the outer diameter of the vessel wall and the outer diameter of the amyloid. The fraction of the vessel covered by vascular amyloid was evaluated by measuring the length of non-amyloid spaces. The tissue amyloid was evaluated by calculating the area covered by labeled amyloid in the parechymal tissue.Results: We observed that evoked CBF age-dependently declined with age from 3 months (23%) to 27 months (5.5%), while animal locomotion and heart rate were preserved. Further detailed analysis suggested that the age-dependent decline of cerebrovascular functions increased dramatically after about 17 months (6.8% at minimum). On the other hand, the accumulation of amyloid was found to be detectable in the parenchyma tissue and the vessel wall of small arteries at 14 months. The accumulation of the tissue amyloid gradually increased and the vascular amyloid expanded from the arteries to arterioles between the ages from 14 to 19 months. The thickness of the vascular amyloid at 19 months was 60% higher than that at 14 months. The length of non-vascular-amyloid spaces at 19 months decreased to 82% of that at 14 months. The size of the tissue amyloid at 19 months increased by 70% relative to that at 14 months.Discussion: The results indicate that the impairment of CBF response is caused by i) age-dependent decline of the proteolytic activity and/or clearance of the parenchymal amyloid, and/or ii) direct toxic effects of the cerebral amyloid angiopathy at small arteries and arterioles on the cerebrovascular function. Reference: Takuwa H, Autio J, Nakayama H, Matsuura T, Obata T, Okada E, Masamoto K, Kanno I. (2010) Reproducibility and Variance of a Stimulation-Induced Hemodynamic Response in Barrel Cortex of Awake Behaving Mice. Brain Res. In pressBrain 201

Sensitive Period for the Recovery of the Response Rate of the Wind-Evoked Escape Behavior of Unilaterally Cercus-Ablated Crickets (Gryllus bimaculatus).

We examined the compensational recovery of the response rate (relative occurrence) of the wind-evoked escape behavior in unilaterally cercus-ablated crickets (Gryllus bimaculatus) and elucidated the existence of a sensitive period for such recovery by rearing the crickets under different conditions. In one experiment, each cricket was reared in an apparatus called a walking inducer (WI) to increase the sensory input to the remaining cercus, i.e., the self-generated wind caused by walking. In another experiment, each cricket was reared in a small plastic case separate from the outside atmosphere (wind-free: WF). In this rearing condition, the cricket did not experience self-generated wind as walking was prohibited. During the recovery period after the unilateral cercus ablation, the crickets were reared under either the WI or WF condition to investigate the role of the sensory inputs on the compensational recovery of the response rate. The compensational recovery of the response rate occurred only in the crickets reared under the WI condition during the early period after the ablation. In particular, WI rearing during the first three days after the ablation resulted in the largest compensational recovery in the response rate. In contrast, no compensational recovery was observed in the crickets reared under the WF condition during the first three days. These results suggest that a sensitive period exists in which sensory inputs from the remaining cercus affect the compensational recovery of the response rate more effectively than during other periods

Rearing under different conditions results in different functional recoveries of giant interneurons in unilaterally cercus-ablated crickets, Gryllus bimaculatus.

The effects of rearing conditions on the functional recovery of wind-sensitive giant interneurons (GIs) after unilateral cercal ablation were investigated in the cricket, Gryllus bimaculatus. Crickets were reared in a glass vials to prohibit free walking for 14 days after unilateral cercal ablation ("14-day vial" crickets). Other crickets were reared in an apparatus called a "walking inducer" (WI) to increase the walking distance during the same 14-day period ("14-day WI" crickets). In these crickets, the response properties of GIs 8-1, 9-1, 9-2, and 9-3 to air currents from various directions were investigated. From the intensity-response curves obtained, directionality curves expressed in terms of threshold velocity and response magnitude were made independently. To understand changes in the functional recovery of GIs more thoroughly, the directional characteristics of GIs in crickets 1 day after unilateral cercal ablation ("1-day free" crickets) were also compared. Between the 1-day free and 14-day vial crickets, all the GIs showed differences in both threshold velocity and response magnitude for some stimulus directions. Between the 14-day vial and 14-day WI crickets, differences in the threshold velocities of GIs 9-1, 9-2, and 9-3, and in the response magnitudes of GIs 8-1, 9-1, and 9-3 were detected. Because the rearing condition after unilateral cercal ablation largely affects the compensatory recovery in some parameters of wind-evoked escape behavior, such as relative occurrence and escape direction, we discuss the functional differences in GIs revealed here in relation to the roles of GIs in the neural system that controls escape behavior