Rapid Neuronal Ultrastructure Disruption and Recovery during Spreading Depolarization-Induced Cytotoxic Edema.
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ABSTRACT:
SUBMITTER: Kirov SA
PROVIDER: S-EPMC7566686 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Cortical spreading depolarization is a metabolically costly phenomenon that affects the brain in both health and disease. Following severe stroke, subarachnoid hemorrhage, or traumatic brain injury, cortical spreading depolarization exacerbates tissue damage and enlarges infarct volumes. It is not known, however, whether spreading depolarization also occurs in the retina in vivo. We report now that spreading depolarization episodes are generated in the in vivo rat retina following retinal vessel occlusion produced by photothrombosis. The properties of retinal spreading depolarization are similar to those of cortical spreading depolarization. Retinal spreading depolarization waves propagate at a velocity of 3.0 ± 0.1 mm/min and are associated with a negative shift in direct current potential, a transient cessation of neuronal spiking, arteriole constriction, and a decrease in tissue O2 tension. The frequency of retinal spreading depolarization generation in vivo is reduced by administration of the NMDA antagonist MK-801 and the 5-HT(1D) agonist sumatriptan. Branch retinal vein occlusion is a leading cause of vision loss from vascular disease. Our results suggest that retinal spreading depolarization could contribute to retinal damage in acute retinal ischemia and demonstrate that pharmacological agents can reduce retinal spreading depolarization frequency after retinal vessel occlusion. Blocking retinal spreading depolarization generation may represent a therapeutic strategy for preserving vision in branch retinal vein occlusion patients.
| S-EPMC5012528 | biostudies-literature
Project description:The mechanisms underlying the complications of mild traumatic brain injury, including post-concussion syndrome, post-impact catastrophic death, and delayed neurodegeneration remain poorly understood. This limited pathophysiological understanding has hindered the development of diagnostic and prognostic biomarkers and has prevented the advancement of treatments for the sequelae of mild traumatic brain injury. We aimed to characterize the early electrophysiological and neurovascular alterations following repetitive mild traumatic brain injury and sought to identify new targets for the diagnosis and treatment of individuals at risk of severe post-impact complications. We combined behavioural, electrophysiological, molecular, and neuroimaging techniques in a rodent model of repetitive mild traumatic brain injury. In humans, we used dynamic contrast-enhanced MRI to quantify blood-brain barrier dysfunction after exposure to sport-related concussive mild traumatic brain injury. Rats could clearly be classified based on their susceptibility to neurological complications, including life-threatening outcomes, following repetitive injury. Susceptible animals showed greater neurological complications and had higher levels of blood-brain barrier dysfunction, transforming growth factor β (TGFβ) signalling, and neuroinflammation compared to resilient animals. Cortical spreading depolarizations were the most common electrophysiological events immediately following mild traumatic brain injury and were associated with longer recovery from impact. Triggering cortical spreading depolarizations in mild traumatic brain injured rats (but not in controls) induced blood-brain barrier dysfunction. Treatment with a selective TGFβ receptor inhibitor prevented blood-brain barrier opening and reduced injury complications. Consistent with the rodent model, blood-brain barrier dysfunction was found in a subset of human athletes following concussive mild traumatic brain injury. We provide evidence that cortical spreading depolarization, blood-brain barrier dysfunction, and pro-inflammatory TGFβ signalling are associated with severe, potentially life-threatening outcomes following repetitive mild traumatic brain injury. Diagnostic-coupled targeting of TGFβ signalling may be a novel strategy in treating mild traumatic brain injury.
| S-EPMC9246711 | biostudies-literature
Project description:Simultaneous changes in ion concentrations, glutamate, and cell volume together with exchange of matter between cell network and vasculature are ubiquitous in numerous brain pathologies. A complete understanding of pathological conditions as well as normal brain function, therefore, hinges on elucidating the molecular and cellular pathways involved in these mostly interdependent variations. In this paper, we develop the first computational framework that combines the Hodgkin-Huxley type spiking dynamics, dynamic ion concentrations and glutamate homeostasis, neuronal and astroglial volume changes, and ion exchange with vasculature into a comprehensive model to elucidate the role of glutamate uptake in the dynamics of spreading depolarization (SD)-the electrophysiological event underlying numerous pathologies including migraine, ischemic stroke, aneurysmal subarachnoid hemorrhage, intracerebral hematoma, and trauma. We are particularly interested in investigating the role of glutamate in the duration and termination of SD caused by K+ perfusion and oxygen-glucose deprivation. Our results demonstrate that glutamate signaling plays a key role in the dynamics of SD, and that impaired glutamate uptake leads to recovery failure of neurons from SD. We confirm predictions from our model experimentally by showing that inhibiting astrocytic glutamate uptake using TFB-TBOA nearly quadruples the duration of SD in layers 2-3 of visual cortical slices from juvenile rats. The model equations are either derived purely from first physical principles of electroneutrality, osmosis, and conservation of particles or a combination of these principles and known physiological facts. Accordingly, we claim that our approach can be used as a future guide to investigate the role of glutamate, ion concentrations, and dynamics cell volume in other brain pathologies and normal brain function.
| S-EPMC5655358 | biostudies-literature
Project description:ObjectiveSpreading depolarization (SD) is a transient self-propagating wave of neuronal and glial depolarization coupled with large membrane ionic changes and a subsequent depression of neuronal activity. Spreading depolarization in the cortex is implicated in migraine, stroke, and epilepsy. Conversely, spreading depolarization in the striatum, a brain structure deeply involved in motor control and in Parkinson's disease (PD) pathophysiology, has been poorly investigated.MethodsWe characterized the participation of glutamatergic and dopaminergic transmission in the induction of striatal spreading depolarization by using a novel approach combining optical imaging, measurements of endogenous DA levels, and pharmacological and molecular analyses.ResultsWe found that striatal spreading depolarization requires the concomitant activation of D1-like DA and N-methyl-d-aspartate receptors, and it is reduced in experimental PD. Chronic l-dopa treatment, inducing dyskinesia in the parkinsonian condition, increases the occurrence and speed of propagation of striatal spreading depolarization, which has a direct impact on one of the signaling pathways downstream from the activation of D1 receptors.ConclusionStriatal spreading depolarization might contribute to abnormal basal ganglia activity in the dyskinetic condition and represents a possible therapeutic target. © 2019 International Parkinson and Movement Disorder Society.
| S-EPMC8006568 | biostudies-literature
Project description:The present study aimed to perform an extensive, unbiased RNA sequencing (RNA-seq) analysis to identify biological pathways, as well as related diseases and functions, modified by SD in healthy brains. SDs were induced repetitively (2 hours, 30 min intervals) in healthy, female mice and monitored with intrinsic optical signal (IOS) imaging. SD induction was with either focal application of KCl in C57Bl/6 mice or with optogenetic stimulation in Thy1-ChR2-YFP mice. Two hours after onset of SD, total cortical RNA was extracted and subjected to Illumina paired-end RNA sequencing to identify differentially expressed genes (DEGs; fold change >1.25, p-value <0.05). We identified 101 significantly upregulated genes after KCl-induced SDs and 136 after optogenetic induction; of these 57 (31.7%) genes were in common.
2022-10-05 | GSE214623 | GEO
Project description:Spreading depolarization is assumed to be the mechanism of migraine with aura, which is accompanied by an initial predominant hyperaemic response followed by persistent vasoconstriction. Cerebral blood flow responses are impaired in patients and in experimental animals after spreading depolarization. Understanding the regulation of cortical blood vessels during and after spreading depolarization could help patients with migraine attacks, but our knowledge of these vascular mechanisms is still incomplete. Recent findings show that control of cerebral blood flow does not only occur at the arteriole level but also at capillaries. Pericytes are vascular mural cells that can constrict or relax around capillaries, mediating local cerebral blood flow control. They participate in the constriction observed during brain ischaemia and might be involved the disruption of the microcirculation during spreading depolarization. To further understand the regulation of cerebral blood flow in spreading depolarization, we examined penetrating arterioles and capillaries with respect to vascular branching order, pericyte location and pericyte calcium responses during somatosensory stimulation and spreading depolarization. Mice expressing a red fluorescent indicator and intravenous injections of FITC-dextran were used to visualize pericytes and vessels, respectively, under two-photon microscopy. By engineering a genetically encoded calcium indicator we could record calcium changes in both pericytes around capillaries and vascular smooth muscle cells around arterioles. We show that somatosensory stimulation evoked a decrease in cytosolic calcium in pericytes located on dilating capillaries, up to the second order capillaries. Furthermore, we show that prolonged vasoconstriction following spreading depolarization is strongest in first order capillaries, with a persistent increase in pericyte calcium. We suggest that the persistence of the 'spreading cortical oligaemia' in migraine could be caused by this constriction of cortical capillaries. After spreading depolarization, somatosensory stimulation no longer evoked changes in capillary diameter and pericyte calcium. Thus, calcium changes in pericytes located on first order capillaries may be a key determinant in local blood flow control and a novel vascular mechanism in migraine. We suggest that prevention or treatment of capillary constriction in migraine with aura, which is an independent risk factor for stroke, may be clinically useful.
| S-EPMC6022680 | biostudies-literature
Project description:Cortical spreading depression is associated with activation of NMDA receptors, which interact with the postsynaptic density protein 95 (PSD-95) that binds to nitric oxide synthase (nNOS). Here, we tested whether inhibition of the nNOS/PSD-95/NMDA receptor complex formation by anti-ischemic compound, UCCB01-144 (Tat- N-dimer) ameliorates the persistent effects of cortical spreading depression on cortical function. Using in vivo two-photon microscopy in somatosensory cortex in mice, we show that fluorescently labelled Tat- N-dimer readily crosses blood-brain barrier and accumulates in nerve cells during the first hour after i.v. injection. The Tat- N-dimer suppressed stimulation-evoked synaptic activity by 2-20%, while cortical blood flow and cerebral oxygen metabolic (CMRO2) responses were preserved. During cortical spreading depression, the Tat- N-dimer reduced the average amplitude of the negative shift in direct current potential by 33% (4.1 mV). Furthermore, the compound diminished the average depression of spontaneous electrocorticographic activity by 11% during first 40 min of post-cortical spreading depression recovery, but did not mitigate the suppressing effect of cortical spreading depression on cortical blood flow and CMRO2. We suggest that uncoupling of PSD-95 from NMDA receptors reduces overall neuronal excitability and the amplitude of the spreading depolarization wave. These findings may be of interest for understanding the neuroprotective effects of the nNOS/PSD-95 uncoupling in stroke.
| S-EPMC5435282 | biostudies-literature
Project description:The amyloid-beta peptide (Aβ) is thought to have prion-like properties promoting its spread throughout the brain in Alzheimer's disease (AD). However, the cellular mechanism(s) of this spread remains unclear. Here, we show an important role of intracellular Aβ in its prion-like spread. We demonstrate that an intracellular source of Aβ can induce amyloid plaques in vivo via hippocampal injection. We show that hippocampal injection of mouse AD brain homogenate not only induces plaques, but also damages interneurons and affects intracellular Aβ levels in synaptically connected brain areas, paralleling cellular changes seen in AD. Furthermore, in a primary neuron AD model, exposure of picomolar amounts of brain-derived Aβ leads to an apparent redistribution of Aβ from soma to processes and dystrophic neurites. We also observe that such neuritic dystrophies associate with plaque formation in AD-transgenic mice. Finally, using cellular models, we propose a mechanism for how intracellular accumulation of Aβ disturbs homeostatic control of Aβ levels and can contribute to the up to 10,000-fold increase of Aβ in the AD brain. Our data indicate an essential role for intracellular prion-like Aβ and its synaptic spread in the pathogenesis of AD.
| S-EPMC8423700 | biostudies-literature
Project description:RNAseq after cortical spreading depolarization (SD)
| PRJNA886413 | ENA
Project description:Spreading depolarization (SD) is a slow-moving wave of neuronal depolarization accompanied by a breakdown of ion concentration homeostasis, followed by long periods of neuronal silence (spreading depression), and is associated with several neurologic conditions. We developed multiscale (ions to tissue slice) computer models of SD in brain slices using the NEURON simulator: 36,000 neurons (two voltage-gated ion channels; three leak channels; three ion exchangers/pumps) in the extracellular space (ECS) of a slice (1 mm sides, varying thicknesses) with ion (K+, Cl-, Na+) and O2 diffusion and equilibration with a surrounding bath. Glia and neurons cleared K+ from the ECS via Na+/K+ pumps. SD propagated through the slices at realistic speeds of 2-4 mm/min, which increased by as much as 50% in models incorporating the effects of hypoxia or propionate. In both cases, the speedup was mediated principally by ECS shrinkage. Our model allows us to make testable predictions, including the following: (1) SD can be inhibited by enlarging ECS volume; (2) SD velocity will be greater in areas with greater neuronal density, total neuronal volume, or larger/more dendrites; (3) SD is all-or-none: initiating K+ bolus properties have little impact on SD speed; (4) Slice thickness influences SD because of relative hypoxia in the slice core, exacerbated by SD in a pathologic cycle; and (5) SD and high neuronal spike rates will be observed in the core of the slice. Cells in the periphery of the slice near an oxygenated bath will resist SD.
| S-EPMC9410770 | biostudies-literature