Cytoskeleton Elements Contribute to Prion Peptide-Induced Endothelial Barrier Breakdown in a Blood-Brain Barrier In Vitro System.

The mechanisms involved in the interaction of PrP 106-126, a peptide corresponding to the prion protein amyloidogenic region, with the blood-brain barrier (BBB) were studied. PrP 106-126 treatment that was previously shown to impair BBB function, reduced cAMP levels in cultured brain endothelial cells, increased nitric oxide (NO) levels, and changed the activation mode of the small GTPases Rac1 (inactivation) and RhoA (activation). The latter are well established regulators of endothelial barrier properties that act via cytoskeletal elements.

Combined Treatment of an Amyotrophic Lateral Sclerosis Rat Model with Recombinant GOT1 and Oxaloacetic Acid: A Novel Neuroprotective Treatment.

Background/aim: The sporadic form of the disease affects the majority of amyotrophic lateral sclerosis (ALS) patients. The role of glutamate (Glu) excitotoxicity in ALS has been extensively documented and remains one of the prominent hypotheses of ALS pathogenesis. In light of this evidence, the availability of a method to remove excess Glu from brain and spinal cord extracellular fluids without the need to deliver drugs across the blood-brain barrier and with minimal or no adverse effects may provide a major therapeutic asset, which is the primary aim of this study.

Glutamate receptor antibodies directed against AMPA receptors subunit 3 peptide B (GluR3B) can be produced in DBA/2J mice, lower seizure threshold and induce abnormal behavior.

Objective: Anti-GluR3B antibodies (GluR3B Ab's), directed against peptide B/aa372-395 of GluR3 subunit of glutamate/AMPA receptors, are found in ∼35% of epilepsy patients, activate glutamate/AMPA receptors, evoke ion currents, kill neurons and damage the brain. We recently found that GluR3B Ab's also associate with neurological/psychiatric/behavioral abnormalities in epilepsy patients. Here we asked if GluR3B Ab's could be produced in DBA/2J mice, and also modulate seizure threshold and/or cause behavioral/motor impairments in these mice.

Glutamate receptor antibodies directed against AMPA receptors subunit 3 peptide B (GluR3B) associate with some cognitive/psychiatric/behavioral abnormalities in epilepsy patients.

Antibodies (Ab's) to glutamate receptors, directed specifically against AMPA receptors subunit 3 peptide B (i.e. GluR3 amino acids 372-395), named GluR3B Ab's, can by themselves activate GluR3-containing glutamate/AMPA receptors, evoke ion currents via the receptor's ion channel, kill neurons and damage the brain.

Blood glutamate scavenging as a novel neuroprotective treatment for paraoxon intoxication.

Organophosphate-induced brain damage is an irreversible neuronal injury, likely because there is no pharmacological treatment to prevent or block secondary damage processes. The presence of free glutamate (Glu) in the brain has a substantial role in the propagation and maintenance of organophosphate-induced seizures, thus contributing to the secondary brain damage. This report describes for the first time the ability of blood glutamate scavengers (BGS) oxaloacetic acid in combination with glutamate oxaloacetate transaminase to reduce the neuronal damage in an animal model of paraoxon (PO) intoxication.

Peptide derived from HIV-1 TAT protein destabilizes a monolayer of endothelial cells in an in vitro model of the blood-brain barrier and allows permeation of high molecular weight proteins.

Most chemotherapeutic agents are blood-brain barrier (BBB) impermeants. HIV-1-derived TAT protein variants contain a transmembrane domain, which may enable them to cross the BBB and reach the brain. Here we synthesized CAYGRKKRRQRRR, a peptide containing a cysteine moiety attached to the N terminus of the transmembrane domain (C-TAT peptide), and studied its effects in an in vitro BBB model, which we found to reflect penetration by a receptor-independent pathway.

Anatomical location of arterial and venous lines significantly affects motor performance in rats.

Several motor-function scales have been developed to assess neurological function in animal models of stroke, subarachnoid hemorrhage and closed head injury. We hypothesize that the location of arterial and venous catheters, even in the absence of brain injury, may impact rats' motor performance. Our study examined the effect of catheter location, rate of infection and the time required for catheter placement.

Relationship between glutamate, GOT and GPT levels in maternal and fetal blood: a potential mechanism for fetal neuroprotection.

Background: Excess glutamate in the brain is thought to be implicated in the pathophysiology of fetal anoxic brain injury, yet little is known about the mechanisms by which glutamate is regulated in the fetal brain. This study examines whether there are differences between maternal and fetal glutamate concentrations, and whether a correlation between them exists.

Methods: 10 ml of venous blood was extracted from 87 full-term (>37 weeks gestation) pregnant women in active labor.

Blood glutamate scavengers prolong the survival of rats and mice with brain-implanted gliomas.

L-Glutamate (Glu) plays a crucial role in the growth of malignant gliomas. We have established the feasibility of accelerating a naturally occurring brain to-blood Glu efflux by decreasing blood Glu levels with intravenous oxaloacetate, the respective Glu co-substrate of the blood resident enzyme humane glutamate–oxaloacetate transaminase(hGOT). We wished to demonstrate that blood Glu scavenging provides neuroprotection in the case of glioma.

Blood glutamate scavengers prolong the survival of rats and mice with brain-implanted gliomas.

L-Glutamate (Glu) plays a crucial role in the growth of malignant gliomas. We have established the feasibility of accelerating a naturally occurring brain to-blood Glu efflux by decreasing blood Glu levels with intravenous oxaloacetate, the respective Glu co-substrate of the blood resident enzyme humane glutamate-oxaloacetate transaminase (hGOT). We wished to demonstrate that blood Glu scavenging provides neuroprotection in the case of glioma.

Cell-free DNA as a marker for prediction of brain damage in traumatic brain injury in rats.

Traumatic brain injury (TBI) is a major cause of morbidity and mortality, and early predictors of neurological outcomes are of great clinical importance. Cell free DNA (CFD), a biomarker used for the diagnosis and monitoring of several diseases, has been implicated as a possible prognostic indicator after TBI. The purpose of this study was to determine the pattern and timing of CFD levels after TBI, and whether a relationship exists between the level of CFD and brain edema and neurological outcomes.

Effect of glutamate and blood glutamate scavengers oxaloacetate and pyruvate on neurological outcome and pathohistology of the hippocampus after traumatic brain injury in rats.

Background: Decreasing blood glutamate concentrations after traumatic brain injury accelerates brain-to-blood glutamate efflux, leading to improved neurologic outcomes. The authors hypothesize that treatment with blood glutamate scavengers should reduce neuronal cell loss, whereas administration of glutamate should worsen outcomes. The authors performed histologic studies of neuronal survival in the rat hippocampus after traumatic brain injury and treatment with blood glutamate scavengers.

Effect of estrogens on blood glutamate levels in relation to neurological outcome after TBI in male rats.

Purpose: Estrogen has been shown to possess neuroprotective properties both in vitro and in vivo. Traumatic brain injury (TBI) in ovulating females results in favorable neurological outcomes when compared to males with similar insults. The brain-to-blood glutamate gradient removes excess glutamate from brain extracellular fluids (ECF).

β2 adrenergic-mediated reduction of blood glutamate levels and improved neurological outcome after traumatic brain injury in rats.

Background: Isoflurane-anesthetized rats subjected to traumatic brain injury (TBI) show a transient reduction in blood L-glutamate levels. Having previously observed that isoproterenol produces a sustained decrease in blood glutamate levels in naive rats, we investigated the possible effects of nonselective and selective β1 and β2 adrenergic agonists and antagonists both on blood glutamate levels and on the neurological outcomes of rats subjected to TBI.

Methods: Rats received either 10 mL/kg of isotonic saline 1 hour after TBI, 50 µg/kg of isoproterenol pretreatment 30 minutes before TBI, 10 mg/kg of propranolol pretreatment 60 minutes before TBI, 10 mg/kg of metoprolol pretreatment 60 minutes before TBI, or 10 mg/kg of butaxamine pretreatment 40 minutes before TBI and 10 minutes before pretreatment with 50 µg/kg isoproterenol or 10 mg/kg of propranolol 60 minutes after TBI.

Pyruvate's blood glutamate scavenging activity contributes to the spectrum of its neuroprotective mechanisms in a rat model of stroke.

In previous studies, we have shown that by increasing the brain-to-blood glutamate efflux upon scavenging blood glutamate with either oxaloacetate or pyruvate, one achieves highly significant neuroprotection particularly in the context of traumatic brain injury. The current study examines, for the first time, how the blood glutamate scavenging properties of glutamate-pyruvate transaminase (GPT), alone or in combination with pyruvate, may contribute to the spectrum of its neuroprotective mechanisms and improve the outcome of rats exposed to brain ischemia, as they do after head trauma. Rats that were exposed to permanent middle cerebral artery occlusion (MCAO) and treated with intravenous 250 mg/kg pyruvate had a smaller volume of infarction and reduced brain edema, resulting in an improved neurological outcome and reduced mortality compared to control rats treated with saline.

Mechanisms of glutamate efflux at the blood-brain barrier: involvement of glial cells.

At high concentrations, glutamate (Glu) exerts potent neurotoxic properties, leading to irreversible brain damages found in numerous neurological disorders. The accepted notion that Glu homeostasis in brain interstitial fluid is maintained primarily through the activity of Glu transporters present on glial cells does not take into account the possible contribution of endothelial cells constituting the blood-brain barrier (BBB) to this process. Here, we present evidence for the presence of the Glu transporters, excitatory amino-acid transporters (EAATs) 1 to 3, in porcine brain endothelial cells (PBECs) and show their participation in Glu uptake into PBECs.

The effects of insulin, glucagon, glutamate, and glucose infusion on blood glutamate and plasma glucose levels in naive rats.

Background: Elevated levels of glutamate in brain fluids, in the context of several neurodegenerative conditions, are associated with a worsened neurological outcome. Because there is a clear relationship between brain glutamate levels and glutamate levels in the blood, and an association of the latter with stress, the purpose of this study was to investigate the effects of glucose, insulin, and glucagon on rat blood glutamate levels.

Methods: Rats received either 1 mL/100 g of rat body weight (BW) intravenous isotonic saline (control), 150 mg/1 mL/100 g BW intravenous glucose, 75 mg/1 mL/100 g BW intravenous glutamate, 50 g/100 g BW intraparitoneal glucagon, or 0.

Kainate postconditioning restores LTP in ischemic hippocampal CA1: onset-dependent second pathophysiological stress.

Postconditioning can be induced by a broad range of stimuli within minutes to days after an ischemic cerebral insult. A special form is elicited by pharmacological intervention called second pathophysiological stress. The present study aimed to evaluate the effects of low-dose (5 mg/kg) kainate postconditioning with onsets 0, 24 and 48 h after the ischemic insult on the hippocampal synaptic plasticity in a 2-vessel occlusion model in rat.

Claudin-5 expression in in vitro models of the blood-brain barrier.

Claudins are transmembrane proteins that form the backbone of the tight junctions (TJs) at the blood-brain barrier (BBB). TJs are cellular structures that physically obstruct the inter-endothelial space and restrict the paracellular diffusion of blood-borne substances from the peripheral circulation into the CNS. TJs are also dynamic structures that rapidly respond to external signals that produce changes in BBB permeability.

Cell-free DNA--a marker to predict ischemic brain damage in a rat stroke experimental model.

Background: The animal model of stroke that is most frequently used is a rat model of focal brain ischemia caused by middle cerebral artery occlusion (MCAO). Several studies have reported a link between levels of cell-free DNA (CFD) and neurologic outcome in human stroke. The purpose of this study was to assess brain injury and measure CFD levels in 2 models of MCAO in rats, and to determine whether brain injury correlates with CFD.

Morphological and neuro-behavioral parallels in the rat model of stroke.

Middle cerebral artery occlusion (MCAO) is widely used as a rat model of focal brain ischemia. Evaluation of brain damage often includes the morphological analysis of the injury area, MRI, and various scales which depend on functional tests, commonly known as neurological severity score (NSS). We determined the optimal number of NSS tests and assessed their capacity for non-invasive evaluation of brain ischemic injury in the rat MCAO model.

Determination of factors affecting glutamate concentrations in the whole blood of healthy human volunteers.

Background: Abnormally high concentrations of glutamate in brain fluids have been shown to be neurotoxic and correlate with a poor neurological outcome following traumatic brain injury (TBI). Since brain fluid glutamate can be reduced by scavenging blood glutamate, the purpose of this study was to investigate factors that may potentially influence levels of blood glutamate, glucose, and the enzymes glutamate-pyruvate transaminase (GPT) and glutamate-oxaloacetate transaminase (GOT) in healthy individuals.

Methods: Factors that were examined included age, gender, time of last meal or drink, and recent consumption of coffee.

The activation of β2-adrenergic receptors in naïve rats causes a reduction of blood glutamate levels: relevance to stress and neuroprotection.

This study examines the effects of the activation of β1 and β2-adrenergic receptors on glutamate homeostasis in the blood of naïve rats. Forty five male Sprague-Dawley rats were randomly assigned into one of seven treatment groups that were treated with various β-adrenergic receptor agonist and antagonist drugs. Blood glutamate levels were determined at t = 0, 30, 60, 90, and 120 min.

The effect of hyperthermia on blood glutamate levels.

Introduction: Glutamate neurotoxicity is determined by the balance between glutamate release within the brain and efflux of excess glutamate from the brain. Brain-to-blood efflux of glutamate is increased by decreasing the concentration of glutamate in blood. Little is known about the effect of hyperthermia on blood glutamate concentrations, and the effectiveness of blood glutamate-decreasing mechanisms in these conditions.