Pyruvate’s blood glutamate scavenging activity contributes to the spectrum of its neuroprotective mechanisms in a rat model of stroke
Division of Anesthesiology and Critical Care, Soroka Medical Center, Ben-Gurion University of the Negev, 36 Hanoch Albek Str., Beer-Sheva, Israel 84833.European Journal of Neuroscience (Impact Factor: 3.18). 09/2011; 34(9):1432-41. DOI: 10.1111/j.1460-9568.2011.07864.x
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. Intravenous pyruvate at the low dose of 31.3 mg/kg did not demonstrate any neuroprotection. However, when combined with 0.6 mg/kg of GPT there was a similar neuroprotection observed as seen with pyruvate at 250 mg/kg. Animals treated with 1.69 g/kg glutamate had a worse neurological outcome and a larger extent of brain edema. The decrease in mortality, infarcted brain volume and edema, as well as the improved neurological outcome following MCAO, was correlated with a decrease in blood glutamate levels. We therefore suggest that the blood glutamate scavenging activity of GPT and pyruvate contributes to the spectrum of their neuroprotective mechanisms and may serve as a new neuroprotective strategy for the treatment of ischemic stroke.
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- "Neuroscientists have hypothesized that this phenomenon may be related to cerebral autoregulation failure coupled with catecholamine surges that may result in fatal malignant brain swelling. Glutamate surges are also likely a critical component driving this rapid cerebral edema, and evidence suggests that reducing the brain's concentration of glutamate can significantly reduce edema after TBI. Why this physiological response only occurs in a minority of athletes sustaining two temporally related head injuries is unknown. "
ABSTRACT: There has been a tremendous amount of interest focused on the topic of concussions over the past few decades. Neurosurgeons are frequently consulted to manage patients with mild traumatic brain injuries (mTBI) that have radiographic evidence of cerebral injury. These injuries share significant overlap with concussions, injuries that typically do not reveal radiographic evidence of structural injury, in the realms of epidemiology, pathophysiology, outcomes, and management. Further, neurosurgeons often manage patients with extracranial injuries that have concomitant concussions. In these cases, neurosurgeons are often the only "concussion experts" that patients encounter. The literature has been reviewed and data have been synthesized on the topic including sections on historical background, epidemiology, pathophysiology, diagnostic advances, clinical sequelae, and treatment suggestions, with neurosurgeons as the intended target audience. Neurosurgeons should have a fundamental knowledge of the scientific evidence that has developed regarding concussions and be prepared to guide patients with treatment plans.Surgical Neurology International 02/2012; 3(1):16. DOI:10.4103/2152-7806.92930 · 1.18 Impact Factor
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ABSTRACT: Blood glutamate scavengers have been shown to effectively reduce blood glutamate concentrations and improve neurological outcome after traumatic brain injury and stroke in rats. This study investigates the efficacy of blood glutamate scavengers oxaloacetate and pyruvate in the treatment of subarachnoid hemorrhage (SAH) in rats. Isotonic saline, 250 mg/kg oxaloacetate, or 125 mg/kg pyruvate was injected intravenously in 60 rats, 60 minutes after induction of SAH at a rate of 0.1 ml/100 g/min for 30 minutes. There were 20 additional rats that were used as a sham-operated group. Blood samples were collected at baseline and 90 minutes after SAH. Neurological performance was assessed at 24 h after SAH. In half of the rats, glutamate concentrations in the cerebrospinal fluid were measured 24 h after SAH. For the remaining half, the blood brain barrier permeability in the frontal and parieto-occipital lobes was measured 48 h after SAH. Blood glutamate levels were reduced in rats treated with oxaloacetate or pyruvate at 90 minutes after SAH (p < 0.001). Cerebrospinal fluid glutamate was reduced in rats treated with pyruvate (p < 0.05). Neurological performance was significantly improved in rats treated with oxaloacetate (p < 0.05) or pyruvate (p < 0.01). The breakdown of the blood brain barrier was reduced in the frontal lobe in rats treated with pyruvate (p < 0.05) and in the parieto-occipital lobes in rats treated with either pyruvate (p < 0.01) or oxaloacetate (p < 0.01). This study demonstrates the effectiveness of blood glutamate scavengers oxaloacetate and pyruvate as a therapeutic neuroprotective strategy in a rat model of SAH.Journal of the American Society for Experimental NeuroTherapeutics 06/2012; 9(3):649-57. DOI:10.1007/s13311-012-0129-6 · 5.05 Impact Factor
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ABSTRACT: We have recently reported on the efficacy of an NK1 tachykinin receptor antagonist in improving outcome following stroke, including reduced blood-brain barrier (BBB) disruption, reduced cerebral edema and improved functional outcome. The clinically approved stroke treatment, tissue plasminogen activator (tPA), has been associated with an increased risk of hemorrhage and death, if given at later time points. Accordingly, adjunctive therapies have been investigated to reduce the adverse effects of tPA and improve outcome. The aim of the present study was to characterize the effects of a combination of an NK1 tachykinin receptor antagonist with tPA, on BBB permeability and functional outcome following transient ischemic stroke in rats. Stroke was induced in male Sprague-Dawley rats using a reversible thread model of middle cerebral artery occlusion where occlusion was maintained for 2h, followed by reperfusion. Animals received either 25mg/kg of N-acetyl-l-tryptophan or 1mg/kg of tPA, either alone or in combination, or equal volume saline vehicle, intravenously at the time of reperfusion. Functional outcome was assessed by the rotarod, bilateral asymmetry test, modified neuroscore and open field tests. BBB permeability was assessed by Evans Blue extravasation. Combination therapy of an NK1 tachykinin receptor antagonist with tPA significantly reduced BBB permeability, functional deficits and the incidence of intracerebral hemorrhage and death. As such, combined tPA-NK1 tachykinin receptor antagonist treatment may represent a novel therapeutic intervention for the treatment of reperfusion injury in acute ischemic stroke.Neuroscience 06/2012; 220:1-10. DOI:10.1016/j.neuroscience.2012.06.047 · 3.36 Impact Factor
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