1. Force spectroscopy measurements show that cortical neurons exposed to excitotoxic agonists stiffen before showing evidence of bleb damage
- Author
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Catherine E. Morris, Shan Zou, Linda J. Johnston, Roderick Chisholm, Joseph S. Tauskela, and Geoff Mealing
- Subjects
n methyl dextro aspartic acid ,Time Factors ,Hydrostatic pressure ,lcsh:Medicine ,animal cell ,Microscopy, Atomic Force ,Sodium Channels ,Rats, Sprague-Dawley ,chemistry.chemical_compound ,myosin adenosine triphosphatase ,Blister ,calcium transport ,calcium ion ,rat ,lcsh:Science ,cell volume ,Cerebral Cortex ,Neurons ,Multidisciplinary ,Chemistry ,traumatic brain injury ,Glutamate receptor ,actin myosin interaction ,sodium transport ,sodium ion ,female ,Hypotonic Solutions ,bilayer membrane ,membrane damage ,hypotonic solution ,NMDA receptor ,bleb damage ,hydrostatic pressure ,osmosis ,Veratridine ,Neuron death ,excitotoxicity ,sodium channel ,Research Article ,medicine.medical_specialty ,spectroscopy ,water transport ,N-Methylaspartate ,water ,animal experiment ,Neurotoxins ,cell stiffening ,Glutamic Acid ,animal tissue ,medicine ,Animals ,Bleb (cell biology) ,nerve cell necrosis ,Sodium channel ,animal model ,Spectrum Analysis ,cell swelling ,lcsh:R ,positive feedback ,brain cell ,brain injury ,brain ischemia ,Elasticity ,Surgery ,Rats ,cell damage ,spectrin ,exposure ,Biophysics ,Tonicity ,lcsh:Q ,measurement ,atomic force microscopy based force spectroscopy - Abstract
In ischemic and traumatic brain injury, hyperactivated glutamate (N-methyl-D-aspartic acid, NMDA) and sodium (Nav) channels trigger excitotoxic neuron death. Na(+), Ca(++) and H2O influx into affected neurons elicits swelling (increased cell volume) and pathological blebbing (disassociation of the plasma membrane's bilayer from its spectrin-actomyosin matrix). Though usually conflated in injured tissue, cell swelling and blebbing are distinct processes. Around an injury core, salvageable neurons could be mildly swollen without yet having suffered the bleb-type membrane damage that, by rendering channels leaky and pumps dysfunctional, exacerbates the excitotoxic positive feedback spiral. Recognizing when neuronal inflation signifies non-lethal osmotic swelling versus blebbing should further efforts to salvage injury-penumbra neurons. To assess whether the mechanical properties of osmotically-swollen versus excitotoxically-blebbing neurons might be cytomechanically distinguishable, we measured cortical neuron elasticity (gauged via atomic force microscopy (AFM)-based force spectroscopy) upon brief exposure to hypotonicity or to excitotoxic agonists (glutamate and Nav channel activators, NMDA and veratridine). Though unperturbed by solution exchange per se, elasticity increased abruptly with hypotonicity, with NMDA and with veratridine. Neurons then invariably softened towards or below the pre-treatment level, sometimes starting before the washout. The initial channel-mediated stiffening bespeaks an abrupt elevation of hydrostatic pressure linked to NMDA or Nav channel-mediated ion/H2O fluxes, together with increased [Ca(++)]int-mediated submembrane actomyosin contractility. The subsequent softening to below-control levels is consistent with the onset of a lethal level of bleb damage. These findings indicate that dissection/identification of molecular events during the excitotoxic transition from stiff/swollen to soft/blebbing is warranted and should be feasible.
- Published
- 2013