Distinct differences in rates of oxygen consumption and ATP synthesis of regionally isolated non-synaptic mouse brain mitochondria

Brain mitochondrial dysfunction has been implicated in several neurodegenerative diseases. The distribution and efficiency of mitochondria display large heterogeneity throughout the regions of the brain. This may imply that the selective regional susceptibility of neurodegenerative diseases could be mediated through inherent differences in regional mitochondrial function. To investigate regional cerebral mitochondrial energetics, the rates of oxygen consumption and adenosine-5′-triphosphate (ATP) synthesis were assessed in isolated non-synaptic mitochondria of the cerebral cortex, hippocampus, and striatum of the male mouse brain. Oxygen consumption rates were assessed using a Seahorse XFe96 analyzer and ATP synthesis rates were determined by an online luciferin-luciferase coupled luminescence assay. Complex I- and complex II-driven respiration and ATP synthesis, were investigated by applying pyruvate in combination with malate, or succinate, as respiratory substrates, respectively. Hippocampal mitochondria exhibited the lowest basal and adenosine-5′-diphosphate (ADP)-stimulated rate of oxygen consumption when provided pyruvate and malate. However, hippocampal mitochondria also exhibited an increased proton leak and an elevated relative rate of oxygen consumption in response to the uncoupler carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), showing a large capacity for uncoupled respiration in the presence of pyruvate. When the complex II-linked substrate succinate was provided, striatal mitochondria exhibited the highest respiration and ATP synthesis rate, whereas hippocampal mitochondria had the lowest. However, the mitochondrial efficiency, determined as ATP produced/O₂ consumed, was similar between the three regions. This study reveals inherent differences in regional mitochondrial energetics and may serve as a tool for further investigations of regional mitochondrial function in relation to neurodegenerative diseases.     

基于功能磁共振成像的肝豆状核变性患者纹状体亚区损害及临床分析

目的基于功能磁共振成像分析肝豆状核变性（Wilson disease, WD）患者纹状体亚区神经功能损害及其与临床相关分析，探讨其神经心理学症状可能的致病机制。方法收集WD患者29例和健康志愿者30例，进行3.0 T磁共振功能磁共振成像及临床量表测试，采用mICA工具箱的group ICA功能将壳核和尾状核分成8个亚区，做全脑功能连接，提取功能连接异常区域的值与临床量表测试结果做相关性分析。结果与对照组相比，WD患者左侧尾状核中部与全脑未发现功能增强或减弱区域，余感兴趣区与全脑功能连接不同程度减弱。左侧尾状核前部（ROI5）-中扣带回功能连接值与简易智能状态量表（MMSE）值呈显著负相关（r=-0.47，P=0.009）；右侧尾状核前部（ROI6）-中扣带回功能连接值与MMSE值呈显著负相关（r=-0.46，P=0.011）；右侧尾状核中部（ROI8）-右侧岛叶功能连接值与MMSE值呈显著负相关（r=-0.38，P=0.041）。结论右侧尾状核前中部与背外侧前额叶功能连接减弱，双侧壳核前部与丘脑功能连接减弱，可能破坏皮质-纹状体-丘脑回路引起认知功能损害；参与记忆及动作相关认知的突显网络、默认模式网络的通路连接受阻则可能是WD患者认知障碍的神经病理机制。     

Integrated anatomical and physiological mapping of striatal afferent projections

The dorsomedial striatum, a key site of reward‐sensitive motor output, receives extensive afferent input from cortex, thalamus and midbrain. These projections are integrated by striatal microcircuits containing both spiny projection neurons and local circuit interneurons. To explore target cell specificity of these projections, we compared inputs onto D1‐dopamine receptor‐positive spiny neurons, parvalbumin‐positive fast‐spiking interneurons and somatostatin‐positive low‐threshold‐spiking interneurons, using cell type‐specific rabies virus tracing and optogenetic‐mediated projection neuron recruitment in mice. While the relative proportion of retrogradely labelled projection neurons was similar between target cell types, the convergence of inputs was systematically higher for projections onto fast‐spiking interneurons. Rabies virus is frequently used to assess cell‐specific anatomical connectivity but it is unclear how this correlates to synaptic connectivity and efficacy. To test this, we compared tracing data with target cell‐specific measures of synaptic efficacy for anterior cingulate cortex and parafascicular thalamic projections using novel quantitative optogenetic measures. We found that target‐specific patterns of convergence were extensively modified according to region of projection neuron origin and postsynaptic cell type. Furthermore, we observed significant divergence between cell type‐specific anatomical connectivity and measures of excitatory synaptic strength, particularly for low‐threshold‐spiking interneurons. Taken together, this suggests a basic uniform connectivity map for striatal afferent inputs upon which presynaptic–postsynaptic interactions impose substantial diversity of physiological connectivity.     

Cell therapy for Parkinson's disease: Why it doesn't work every time

The clinical experience with cell replacement therapy for advanced PD has yielded notable successes and failures. A recent autopsy case report of an individual that received implants of fetal dopamine neurons 16 years previously, but at no time experienced clinical benefit despite the best documented survival of grafted neurons and most extensive reinnervation of the striatum, raises sobering issues. With good reason, a great deal of effort in cell replacement science continues to focus on optimizing the cell source and implantation procedure. Here, we describe our preclinical studies in aged rats indicating that despite survival of large numbers of transplanted dopamine neurons and dense reinnervation of the striatum, synaptic connections between graft and host are markedly decreased and behavioral recovery is impaired. This leads us to the hypothesis that the variability in therapeutic response to dopamine neuron grafts may be less about the viability of transplanted neurons and more about the integrity of the aged, dopamine‐depleted striatum and its capacity for repair. Replacement of dopamine innervation only can be fully effective if the correct target is present. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.     

Reversible splenial lesion syndrome associated with SARS-CoV-2 infection in two children

BackgroundReversible splenial lesion syndrome (RESLES) is characterized by a temporary lesion in the splenium of the corpus callosum, emerging related to encephalitis, seizures, antiepileptic drug withdrawal, or metabolic disturbances. Among RESLES, mild encephalitis/encephalopathy with reversible splenial lesion (MERS) has been defined as a distinct clinicoradiologic syndrome associated with viral infections.Case presentationWe report two children with multisystem inflammatory syndrome-children related to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who developed RESLES during the disease course. Encephalopathy was the main central nervous system symptom. Both of the children showed a rapid recovery, and brain magnetic resonance imaging revealed complete resolution of the splenial lesion within 1 week.ConclusionThe complete resolution of the splenial lesion and rapid recovery from encephalopathy in RESLES associated with SARS CoV-2 were similar to observed in MERS.     

Ablation of striatal somatostatin interneurons affects MSN morphology and electrophysiological properties,and increases cocaine‐induced hyperlocomotion in mice

The striatum is mainly composed by medium spiny neurons (95 %) (MSNs). Although outnumbered, in other brain regions such as the hippocampus and the cortex, somatostatin interneurons (SSTi) are known to control and fine‐tune the activity of principal cells. This information is still fragmented for the striatum. Here, we questioned the striatal functional consequences of the selective ablation of SSTi in the striatum at the behavioural and cellular levels. We identified increased excitability coupled with decreased distal spine density in MSNs from SSTi‐ablated mice. Although the ethological behavioural analysis did not reveal differences between the groups, SSTi‐ablated mice were significantly more sensitive to the locomotor effects of cocaine without changes in motivation. This was accompanied by increased expression of the dopamine transporter (DAT) in the ventral striatum. Altogether, we show that SSTi are important players in the maintenance of MSN excitability and spine density impacting on mechanisms towards hyperdopaminergic states.     

The effect of chronic neuroglycopenia on resting state networks in GLUT1 syndrome across the lifespan

Glucose transporter type I deficiency syndrome (GLUT1DS) is an encephalopathic disorder due to a chronic insufficient transport of glucose into the brain. PET studies in GLUT1DS documented a widespread cortico‐thalamic hypometabolism and a signal increase in the basal ganglia, regardless of age and clinical phenotype. Herein, we captured the pattern of functional connectivity of distinct striatal, cortical, and cerebellar regions in GLUT1DS (10 children, eight adults) and in healthy controls (HC, 19 children, 17 adults) during rest. Additionally, we explored for regional connectivity differences in GLUT1 children versus adults and according to the clinical presentation. Compared to HC, GLUT1DS exhibited increase connectivity within the basal ganglia circuitries and between the striatal regions with the frontal cortex and cerebellum. The excessive connectivity was predominant in patients with movement disorders and in children compared to adults, suggesting a correlation with the clinical phenotype and age at fMRI study. Our findings highlight the primary role of the striatum in the GLUT1DS pathophysiology and confirm the dependency of symptoms to the patients' chronological age. Despite the reduced chronic glucose uptake, GLUT1DS exhibit increased connectivity changes in regions highly sensible to glycopenia. Our results may portrait the effect of neuroprotective brain strategy to overcome the chronic poor energy supply during vulnerable ages.