Blood Flow Metab Research Articles

Venous Outflow and Parenchymal Hemorrhage: A Clogged Drain Problem?

Venous Outflow and Parenchymal Hemorrhage: A Clogged Drain Problem?

Stepwise disassembly of GABAergic synapses during pathogenic excitotoxicity.

SUMMARYGABAergic synaptic inhibition controls neuronal firing, excitability, and synaptic plasticity to regulate neuronal circuits. Following an acute excitotoxic insult, inhibitory synapses are eliminated, reducing synaptic inhibition, elevating circuit excitability, and contributing to the pathophysiology of brain injuries. However, mechanisms that drive inhibitory synapse disassembly and elimination are undefined. We find that inhibitory synapses are disassembled in a sequential manner following excitotoxicity: GABAARs undergo rapid nanoscale rearrangement and are dispersed from the synapse along with presynaptic active zone components, followed by the gradual removal of the gephyrin scaffold, prior to complete elimination of the presynaptic terminal. GABAAR nanoscale reorganization and synaptic declustering depends on calcineurin signaling, whereas disassembly of gephyrin relies on calpain activation, and blockade of both enzymes preserves inhibitory synapses after excitotoxic insult. Thus, inhibitory synapse disassembly occurs rapidly, with nanoscale precision, in a stepwise manner and most likely represents a critical step in the progression of hyperexcitability following excitotoxicity.

Anatomy embroiders function in Purkinje cells

The anatomy of the human cerebellar Purkinje cell, as captured by Ramón y Cajal in a drawing, inspired the spectacular cover embroidery by Lisa Stoneman (Roanoke College, Roanoke, VA, USA) in the October issue of The Lancet Neurology. 1 Mehta AR Abbott CM Chandran S Haley JE The Cajal Embroidery Project: celebrating neuroscience. Lancet Neurol. 2020; 19: 979 Summary Full Text Full Text PDF Scopus (6) Google Scholar Like contemporary confocal microscopy images do, this anatomical representation also raises fascinating questions about the function served by the complex array of dendrites in this cell type. Each Purkinje cell, in rodents, receives about 174 000 synaptic inputs from the parallel fibre axons of the far tinier cerebellar granule cells, along with a single powerful input from the climbing fibre arising from the inferior olivary nucleus. 2 Howarth C Gleeson P Attwell D Updated energy budgets for neural computation in the neocortex and cerebellum. J Cereb Blood Flow Metab. 2012; 32: 1222-1232 Crossref PubMed Scopus (337) Google Scholar Even though a large fraction of those synapses can become inactive with learning, 3 Isope P Barbour B Properties of unitary granule cell→Purkinje cell synapses in adult rat cerebellar slices. J Neurosci. 2002; 22: 9668-9678 Crossref PubMed Google Scholar it is remarkable that the information processed from such a large number of inputs, which are even more numerous in human beings, is ultimately channelled down a single inhibitory axon to the deep cerebellar nuclei, as denoted by the label a in Cajal's original 1894 drawing (appendix).

COVID-19 in a Hemorrhagic Neurovascular Disease, Cerebral Cavernous Malformation

COVID-19 in a Hemorrhagic Neurovascular Disease, Cerebral Cavernous Malformation

Temperature Management in Neurological and Neurosurgical Intensive Care Unit.

Temperature Management in Neurological and Neurosurgical Intensive Care Unit.

Imaging Acute Metabolic Changes in Patients with Mild Traumatic Brain Injury Using Hyperpolarized [1-13C]Pyruvate.

SummaryTraumatic brain injury (TBI) involves complex secondary injury processes following the primary injury. The secondary injury is often associated with rapid metabolic shifts and impaired brain function immediately after the initial tissue damage. Magnetic resonance spectroscopic imaging (MRSI) coupled with hyperpolarization of 13C-labeled substrates provides a unique opportunity to map the metabolic changes in the brain after traumatic injury in real-time without invasive procedures. In this report, we investigated two patients with acute mild TBI (Glasgow coma scale 15) but no anatomical brain injury or hemorrhage. Patients were imaged with hyperpolarized [1-13C]pyruvate MRSI 1 or 6 days after head trauma. Both patients showed significantly reduced bicarbonate (HCO3–) production, and one showed hyperintense lactate production at the injured sites. This study reports the feasibility of imaging altered metabolism using hyperpolarized pyruvate in patients with TBI, demonstrating the translatability and sensitivity of the technology to cerebral metabolic changes after mild TBI.

Lactate Attenuates Synaptic Transmission and Affects Brain Rhythms Featuring High Energy Expenditure.

SummaryLactate shuttled from blood, astrocytes, and/or oligodendrocytes may serve as the major glucose alternative in brain energy metabolism. However, its effectiveness in fueling neuronal information processing underlying complex cortex functions like perception and memory is unclear. We show that sole lactate disturbs electrical gamma and theta-gamma oscillations in hippocampal networks by either attenuation or neural bursts. Bursting is suppressed by elevating the glucose fraction in substrate supply. By contrast, lactate does not affect electrical sharp wave-ripple activity featuring lower energy use. Lactate increases the oxygen consumption during the network states, reflecting enhanced oxidative ATP synthesis in mitochondria. Finally, lactate attenuates synaptic transmission in excitatory pyramidal cells and fast-spiking, inhibitory interneurons by reduced neurotransmitter release from presynaptic terminals, whereas action potential generation in the axon is regular. In conclusion, sole lactate is less effective and potentially harmful during gamma-band rhythms by omitting obligatory ATP delivery through fast glycolysis at the synapse.

Interleukin 1 alpha administration is neuroprotective and neuro-restorative following experimental ischemic stroke

BackgroundStroke remains a leading cause of death and disability worldwide despite recent treatment breakthroughs. A primary event in stroke pathogenesis is the development of a potent and deleterious local and peripheral inflammatory response regulated by the pro-inflammatory cytokine interleukin-1 (IL-1). While the role of IL-1β (main released isoform) has been well studied in stroke, the role of the IL-1α isoform remains largely unknown. With increasing utilization of intravenous tissue plasminogen activator (t-PA) or thrombectomy to pharmacologically or mechanically remove ischemic stroke causing blood clots, respectively, there is interest in pairing successful cerebrovascular recanalization with neurotherapeutic pharmacological interventions (Fraser et al., J Cereb Blood Flow Metab 37:3531–3543, 2017; Hill et al., Lancet Neurol 11:942–950, 2012; Amaro et al., Stroke 47:2874–2876, 2016).MethodsTransient stroke was induced in mice via one of two methods. One group of mice were subjected to tandem ipsilateral common carotid artery and middle cerebral artery occlusion, while another group underwent the filament-based middle cerebral artery occlusion. We have recently developed an animal model of intra-arterial (IA) drug administration after recanalization (Maniskas et al., J Neurosci Met 240:22–27, 2015). Sub groups of the mice were treated with either saline or Il-1α, wherein the drug was administered either acutely (immediately after surgery) or subacutely (on the third day after stroke). This was followed by behavioral and histological analyses.ResultsWe now show in the above-mentioned mouse stroke models (transient tandem ipsilateral common carotid artery (CCA) and middle cerebral artery occlusion (MCA) occlusion, MCA suture occlusion) that IL-1α is neuroprotective when acutely given either intravenously (IV) or IA at low sub-pathologic doses. Furthermore, while IV administration induces transient hemodynamic side effects without affecting systemic markers of inflammation, IA delivery further improves overall outcomes while eliminating these side effects. Additionally, we show that delayed/subacute IV IL-1α administration ameliorates functional deficit and promotes neurorepair.ConclusionsTaken together, our present study suggests for the first time that IL-1α could, unexpectedly, be an effective ischemic stroke therapy with a broad therapeutic window.

About the Marty model of blood-brain barrier closure after its disruption using focused ultrasound

Many studies have demonstrated that pulsed ultrasound combined with circulating microbubbles can permeate the blood-brain barrier in a reversible manner. In 2012, our group demonstrated that the BBB remains permeable to small MRI contrast agents up to 24 h after ultrasound application and also that this duration was dependent on nanoparticle size. We derived a simple theoretical model explaining these observations (Marty et al 2012 J. Cereb. Blood Flow Metab. 32 1948–58). However, in this original paper the expression of the BBB closure time (t1/2) as a function of the size of delivered contrast agents (dH) could not be mathematically derived from the model but rather from a guessed function that is fit to the numerical solution of the model. In this context, the two numeric parameters of this fitting function could not be related to the other physical parameters of the model. Here, we present a formal solution, finding the same expression of t1/2 already published and linking t1/2 to relevant physical variables such as the molecular hydrodynamic diameter dH, the BBB closure rate k and the standard deviation of the initial BBB gap sizes distribution σ0.

Neurodegenerative Dementias: Improving Brain Health to Decrease Risk.

Neurodegenerative Dementias: Improving Brain Health to Decrease Risk.

Comment on " In Vivo [18F]GE-179 Brain Signal Does Not Show NMDA-Specific Modulation with Drug Challenges in Rodents and Nonhuman Primates".

Schoenberger and colleagues ( Schoenberger et al. ( 2018 ) ACS Chem. Neurosci. 9 , 298 - 305 ) recently reported attempts to demonstrate specific binding of the positron emission tomography (PET) radiotracer, [18F]GE-179, to NMDA receptors in both rats and Rhesus macaques. GE-179 did not work as expected in animal models; however, we disagree with the authors' conclusion that "the [18F]GE-179 signal seems to be largely nonspecific". It is extremely challenging to demonstrate specific binding for the use-dependent NMDA receptor intrachannel ligands such as [18F]GE-179 in animals via traditional blocking, due to its low availability of target sites ( Bmax'). Schoenberger and colleagues anesthetized rats and Rhesus monkeys using isoflurane, which has an inhibitory effect on NMDA receptor function and thus would be expected to further reduce the Bmax'. The extent of glutamate release achieved in the provocation experiments is uncertain, as is whether a significant increase in NMDA receptor channel opening can be expected under anesthesia. Prior data suggest that the uptake of disubstituted arylguanidine-based ligands such as GE-179 can be reduced by phencyclidine binding site antagonists, if injection is performed in the absence of ketamine and isoflurane anesthesia, e.g., with GE-179's antecedent, CNS 5161 ( Biegon et al. ( 2007 ) Synapse 61 , 577 - 586 ), and with GMOM ( van der Doef et al. ( 2016 ) J. Cereb. Blood Flow Metab. 36 , 1111 - 1121 ). However, the extent of nonspecific uptake remains uncertain.

Nociceptin/Orphanin FQ (N/OFQ) is neuroprotective in an ex vivo mouse model of cerebral ischaemia

Cerebral ischemia is a leading cause of death and disability in the UK with limited treatment options.1 The Nociceptin/Orphanin FQ (N/OFQ) receptor, NOP, and its endogenous ligand N/OFQ, are non-classical members of the opioid receptor family.2 Central activation of NOP results in general inhibition of neurotransmitter release, in particular glutamate,2 which contributes to cell death following cerebral ischemia. Activation of NOP by N/OFQ or other small molecule agonists would therefore be predicted to be neuroprotective. Here, we have assessed NOP expression in hippocampal and subcortical regions of the mouse brain by PCR and assessed the effects of activation in an ex vivo model of cerebral ischaemia. We used C57/BL6j neonatal mice, aged 6-9 days. For NOP expression studies, mRNA was extracted from hippocampal and subcortical regions using a tri-reagent methodology, and cDNA formed via reverse transcription. cDNA was probed for NOP relative to the house-keeper gene Beta-actin, using TaqMan probes via QPCR.3 To investigate the neuroprotective properties of NOP activation, an ex vivo model of cerebral ischemia was used where cortical brain slices were exposed to oxygen and glucose deprivation (OGD) to mimic ischemic damage, in the presence/absence of N/OFQ. Brain slices were immersed in artificial cerebral spinal fluid (aCSF) to recover from slicing prior to OGD exposure in the presence/absence of N/OFQ (1μM) for 40 minutes. Slices were incubated with 2% 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) to visualise infarcted tissue.4 Area of cell death including hippocampus and sub-cortex but excluding the outer cortex was measured using Imagej software 1.51. NOP receptor mRNA was expressed in both tissues with deltaCt, relative to Beta-actin of 10.52 ∗ 0.25 and 9.62 ∗ 0.65 in hippocampus and sub-cortex respectively (mean + SEM from 9 mice across 3 litters). Subcortical tissue expressed 1.87 fold more NOP than hippocampal tissue. In an acute model of cerebral ischaemia OGD increased the area of cell death from 25.92 ± 4.09% (in normoxic condition) to 66.02 ± 9.99% (Data are mean ± SEM from 12 neonatal mice, across 4 litters; p<0.01). Treatment with N/OFQ significantly (p<0.01) reduced this ischaemic damage to 39.47 ± 7.82%. The vehicle for N/OFQ, dH2O, was ineffective; 72.09 ± 11.87% compared to OGD control. These data show a neuroprotective role for NOP activation and suggest this pathway as a potential target in acute ischaemic stroke. Further studies, with more metabolically stable NOP agonists are underway and a series of in vivo experiments planned. BF is funded by a British Journal of Anaesthesia/Royal College of Anaesthetists PhD studentship. 1.Gibson, C.L and Bath, P.M. J. Cereb. Blood Flow Metab. 2016; 36: 487–491.2.Lambert, D.G. Nat. Rev. Drug Discov. 2008; 7: 694–710.3.McDonald, J., Leonard, A.D., Serrano-Gomez et al. Br. J. Anaesth. 2010; 104: 698–704.4.Zille, M., Farr, T.D., Przesdzing, I. et al . J. Cereb. Blood Flow Metab. 2012; 32: 213–231.

Possible mechanisms of diverse spaceflight effects on endothelial function in different vascular beds

Possible mechanisms of diverse spaceflight effects on endothelial function in different vascular beds

RNA Nanotherapeutics for the Amelioration of Astroglial Reactivity.

In response to injuries to the CNS, astrocytes enter a reactive state known as astrogliosis, which is believed to be deleterious in some contexts. Activated astrocytes overexpress intermediate filaments including glial fibrillary acidic protein (GFAP) and vimentin (Vim), resulting in entangled cells that inhibit neurite growth and functional recovery. Reactive astrocytes also secrete inflammatory molecules such as Lipocalin 2 (Lcn2), which perpetuate reactivity and adversely affect other cells of the CNS. Herein, we report proof-of-concept use of the packaging RNA (pRNA)-derived three-way junction (3WJ) motif as a platform for the delivery of siRNAs to downregulate such reactivity-associated genes. In vitro, siRNA-3WJs induced a significant knockdown of Gfap, Vim, and Lcn2 in a model of astroglial activation, with a concomitant reduction in protein expression. Knockdown of Lcn2 also led to reduced protein secretion from reactive astroglial cells, significantly impeding the perpetuation of inflammation in otherwise quiescent astrocytes. Intralesional injection of anti-Lcn2-3WJs in mice with contusion spinal cord injury led to knockdown of Lcn2 at mRNA and protein levels in vivo. Our results provide evidence for siRNA-3WJs as a promising platform for ameliorating astroglial reactivity, with significant potential for further functionalization and adaptation for therapeutic applications in the CNS.

DISTINCT ULTRASTRUCTURAL CHARACTERISTICS OF CAPILLARY BASAL LAMINA IN HUMAN AND MOUSE BRAINS: RELEVANCE TO MURINE MODELS OF NEUROVASCULAR DISEASE

Recent studies suggest that capillary dysfunction may be a source of neurodegeneration, stroke and cognitive decline (J Cereb Blood Flow Metab, 2016, 36:302; Neurobiol Aging, 2017, 50:107). Most neurovascular studies used mice to model human diseases. The morphologic changes in the capillary wall are less-well characterized in humans, especially in early or presymptomatic phases and in early onset diseases. Here we describe major differences in ultrastructure of capillary basal lamina (CBL) in humans (normal and diseased, <50 years) compared with mouse (young to middle age). Human autopsy brains without or with neurodegeneration, including Parkinson's disease, frontotemporal degeneration and amyotrophic lateral sclerosis, and mouse models of tauopathy were evaluated. Brain tissues were fixed in formaldehyde and/or glutaraldehyde and processed for electron microscopy (EM) or post-embedding immunogold EM. Antibodies to types I, III and IV collagen and to fibronectin were used. Mouse CBL is a thin and uniformly amorphous structure that is labeled with anti-type IV collagen in both normal mice and models of neurodegenerative disease at all ages. In contrast, the CBL in normal and diseased human brains has the amorphous BL, but also banded collagens. In addition, the BL frequently shows segmental splitting between endothelial and astrocytic sides of the BL. The split creates an expanded space that contains banded fibrils of type I and III collagen, but not type IV collagen. The expansion and splitting of BL increase with age and in diseased brains. The CBL in diseased human brains often extends into the pericapillary space. Anti-fibronectin co-localizes with collagens. These ultrastructural features are rarely observed in mice, but are detected in the youngest human brains studied. Human CBL has age- and disease-related alternations including split BL and accumulation of banded type I and III collagen fibrils associated with fibronectin. This BL “fibrosis” is rarely observed in mice brains. If these structural BL alterations are associated with capillary dysfunction, the lack of these changes in mice warrants caution about use of mouse models for neurovascular studies.

Isn't functional neuroimaging all about Ca2+ signaling in astrocytes?

Extensive research over the past decades about the multifaceted roles of brain astrocytes led to the suggestion that the signals observed with functional neuroimaging might primarily reflect astrocytic rather than neuronal activity. The basis for this paradigm-shifting concept was the evidence for an involvement of astrocytes in the control of local cerebral blood flow through intracellular Ca(2+) signaling. In this Neuro Forum, I discuss new important experimental findings obtained by Jego et al. (Jego P, Pacheco-Torres J, Araque A, Canals S. J Cereb Blood Flow Metab 34: 1599-1603, 2014) as well as other closely related studies published recently, prompting a dismissal of substantial astrocytic contribution in functional neuroimaging.

Essential Roles of Neutral Ceramidase and Sphingosine in Mitochondrial Dysfunction Due to Traumatic Brain Injury

In addition to immediate brain damage, traumatic brain injury (TBI) initiates a cascade of pathophysiological events producing secondary injury. The biochemical and cellular mechanisms that comprise secondary injury are not entirely understood. Herein, we report a substantial deregulation of cerebral sphingolipid metabolism in a mouse model of TBI. Sphingolipid profile analysis demonstrated increases in sphingomyelin species and sphingosine concurrently with up-regulation of intermediates of de novo sphingolipid biosynthesis in the brain. Investigation of intracellular sites of sphingosine accumulation revealed an elevation of sphingosine in mitochondria due to the activation of neutral ceramidase (NCDase) and the reduced activity of sphingosine kinase 2 (SphK2). The lack of change in gene expression suggested that post-translational mechanisms are responsible for the shift in the activities of both enzymes. Immunoprecipitation studies revealed that SphK2 is complexed with NCDase and cytochrome oxidase (COX) subunit 1 in mitochondria and that brain injury hindered SphK2 association with the complex. Functional studies showed that sphingosine accumulation resulted in a decreased activity of COX, a rate-limiting enzyme of the mitochondrial electron transport chain. Knocking down NCDase reduced sphingosine accumulation in mitochondria and preserved COX activity after the brain injury. Also, NCDase knockdown improved brain function recovery and lessened brain contusion volume after trauma. These studies highlight a novel mechanism of secondary TBI involving a disturbance of sphingolipid-metabolizing enzymes in mitochondria and suggest a critical role for mitochondrial sphingosine in promoting brain injury after trauma.

Lipopolysaccharide-induced cross-tolerance against renal ischemia–reperfusion injury is mediated by hypoxia-inducible factor-2α-regulated nitric oxide production

Although the protective effect of lipopolysaccharide (LPS) pretreatment on renal ischemia/reperfusion injury is known, a link to hypoxia-inducible factors (HIFs) has not been established. Here we show that LPS treatment led to HIF-2α accumulation in mouse kidneys and endothelial cells, a result of nuclear factor-κB activation. Inactivation of HIF-2α, rather than HIF-1α, completely negated LPS-mediated protection against renal ischemia/reperfusion injury. LPS-stimulated renoprotection was related to inducible/endothelial nitric oxide synthase (iNOS/eNOS) expression, increased production of nitric oxide, and enhanced postischemic microcirculatory recovery. All these effects were lost in HIF-2α knockout mice. Preischemic administration of a nitric oxide donor, rather than erythropoietin, restored the lost preconditioning effect of LPS in HIF-2α knockout mice. In vitro and in vivo studies demonstrated that HIF-2α in endothelial cells, rather than myeloid cells or hepatocytes, was responsible for the LPS-mediated effects. Thus, our results demonstrated that LPS preconditioning protected against renal ischemia/reperfusion injury by HIF-2α activation in endothelial cells that subsequently improved renal microvascular perfusion and reduced ischemic tubular damage.

Single-cell analysis of K562 cells: An imatinib-resistant subpopulation is adherent and has upregulated expression of BCR-ABL mRNA and protein

In chronic myeloid leukemia (CML) cells from different stages of maturation may have differential expression of BCR-ABL at both messenger RNA (mRNA) and protein level. However, the significance of such differential expression to clinical disease behavior is unknown. Using the CML-derived, BCR-ABL expressing cell line, K562, distinct plastic-adherent (K562/Adh) and nonadherent (K562/NonAdh) subpopulations were established and then analyzed both as single cells and as bulk cell populations. BCR-ABL mRNA was upregulated in K562/Adh compared with K562/NonAdh cells in both single cell and bulk population analyses (p < 0.0001). Similarly, phosphorylation of BCR protein was upregulated in K562/Adh, compared with K562/NonAdh cells (63.42% vs. 23.1%; p = 0.007), and these two K562 subpopulations were found to express significantly different microRNA species. Furthermore, treatment with the BCR-ABL tyrosine kinase inhibitor, imatinib, reduced cell viability more rapidly in K562/NonAdh compared with K562/Adh cells (p < 0.005) both at single and bulk cell levels. This discovery of an adherent subpopulation of K562 cells with increased BCR-ABL mRNA, increased phosphorylated BCR protein expression, differential microRNA expression, and increased imatinib resistance suggests that a similar subpopulation of cells can also mediate clinical resistance to imatinib during treatment of patients with CML.

On the use of fluorescence lifetime imaging and dihydroethidium to detect superoxide in intact animals and ex vivo tissues: A reassessment

Recently, D.J. Hall et al. reported that ethidium (E+) is formed as a major product of hydroethidine (HE) or dihydroethidium reaction with superoxide (O2−) in intact animals with low tissue oxygen levels (J. Cereb. Blood Flow Metab. 32:23–32, 2012). The authors concluded that measurement of E+ is an indicator of O2− formation in intact brains of animals. This finding is in stark contrast to previous reports using in vitro systems showing that 2-hydroxyethidium, not ethidium, is formed from the reaction between O2− and HE. Published in vivo results support the in vitro findings. In this study, we performed additional experiments in which HE oxidation products were monitored under different fluxes of O2−. Results from these experiments further reaffirm our earlier findings (H. Zhao et al., Free Radic. Biol. Med. 34:1359, 2003). We conclude that whether in vitro or in vivo, E+ measured by HPLC or by fluorescence lifetime imaging is not a diagnostic marker product for O2− reaction with HE.