Personalized approach in brain protection by hypothermia: individual changes in non-pathological and ischemia-related glutamate transport in brain nerve terminals.

Artem Pastukhov,Vitalii Maksymenko,Natalia Krisanova,Tatiana Borisova

doi:10.1186/s13167-016-0075-1

Artem Pastukhov, Vitalii Maksymenko + Show 2 more

Open Access

https://doi.org/10.1186/s13167-016-0075-1

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Journal: EPMA Journal	Publication Date: Dec 1, 2016
Citations: 13	License type: cc-by

Affiliation: Palladin Institute of Biochemistry

Abstract

BackgroundBoth deep and profound hypothermia are effectively applied in cardiac surgery of the aortic arch, when the reduction of cerebral circulation facilitates operations, and for the prevention of ischemic stroke consequences. Neurochemical discrimination of the effects of deep and profound hypothermia (27 and 17 °C, respectively) on non-pathological and pathological ischemia-related mechanisms of presynaptic glutamate transport with its potential contribution to predictive, preventive and personalized medicine (PPPM) was performed.MethodsExperiments were conducted using nerve terminals isolated from rat cortex (synaptosomes). Glutamate transport in synaptosomes was analyzed using radiolabel l-[14C]glutamate. Diameter of synaptosomes was assessed by dynamic light scattering.ResultsSynaptosomal transporter-mediated uptake and tonic release of l-[14C]glutamate (oppositely directed processes, dynamic balance of which determines the physiological extracellular level of the neurotransmitter) decreased in a different range in deep/profound hypothermia. As a result, hypothermia-induced changes in extracellular l-[14C]glutamate are not evident (in one half of animals it increased, and in other it decreased). A progressive decrease from deep to profound hypothermia was shown for pathological mechanisms of presynaptic glutamate transport, that is, transporter-mediated l-[14C]glutamate release (*) stimulated by depolarization of the plasma membrane and (**) during dissipation of the proton gradient of synaptic vesicles by the protonophore FCCP.ConclusionsTherefore, the direction of hypothermia-induced changes in extracellular glutamate is unpredictable in “healthy” nerve terminals and depends on hypothermia sensitivity of uptake vs. tonic release. In affected nerve terminals (e.g., in brain regions suffering from a reduction of blood circulation during cardiac surgery, and core and penumbra zones of the insult), pathological transporter-mediated glutamate release from nerve terminals decreases with progressive significance from deep to profound hypothermia, thereby underlying its potent neuroprotective action. So, alterations in extracellular glutamate during hypothermia can be unique for each patient. An extent of a decrease in pathological glutamate transporter reversal depends on the size of damaged brain zone in each incident. Therefore, test parameters and clinical criteria of neuromonitoring for the evaluation of individual hypothermia-induced effects should be developed and delivered in practice in PPPM.

Highlights

Both deep and profound hypothermia are effectively applied in cardiac surgery of the aortic arch, when the reduction of cerebral circulation facilitates operations, and for the prevention of ischemic stroke consequences
In affected nerve terminals, pathological transporter-mediated glutamate release from nerve terminals decreases with progressive significance from deep to profound hypothermia, thereby underlying its potent neuroprotective action
Rationale The majority of the experimental methods usually applied for the analysis of key characteristics of glutamatergic neurotransmission cannot be used in hypothermiarelated studies because they are temperature-sensitive per se

Summary

Introduction

Both deep and profound hypothermia are effectively applied in cardiac surgery of the aortic arch, when the reduction of cerebral circulation facilitates operations, and for the prevention of ischemic stroke consequences. Hypothermia is effectively practiced in cardiac surgery to facilitate operations on the aortic arch with the reduction of cerebral circulation. The optimal degree of hypothermia for circulatory arrest in aortic arch surgery has been intensively debated, and the concept of using hypothermia to diminish the oxygen consumption and metabolic requirements of hypoxic tissues is rather intuitive [1]. Multiple studies using animal models that have attempted to clarify the optimal temperature for hypothermic circulatory arrest have generally supported the use of deeper levels of hypothermia; influence of a range of temperatures on the brain functioning needs to be better assessed [1]. The mechanisms of the neuroprotective action of low temperatures during cardio surgery are a topical issue for medical practitioners

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