Neuroprotective Effects of the Inert Gas Argon on Experimental Traumatic Brain Injury In Vivo with the Controlled Cortical Impact Model in Mice.

Fritz I Schneider,Ute Lindauer,Yu-Mi Ryang,Michael Stoffel,Sandro M Krieg

doi:10.3390/biology11020158

Fritz I Schneider, Ute Lindauer + Show 3 more

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https://doi.org/10.3390/biology11020158

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Abstract

Simple SummaryTraumatic brain injuries remain one of the leading causes of death in the western world and developing countries. There is an urgent need for causal therapies for such injuries. The noble gas argon has already shown promising results in in-vitro models. The influence of argon on the extent of damage after a craniocerebral trauma will be investigated in this study, in vivo, in mice. After the trauma, the animals were examined for neurological impairments and their brains were removed to detect brain edema and microscopically detectable alterations.Argon has shown neuroprotective effects after traumatic brain injury (TBI) and cerebral ischemia in vitro and in focal cerebral ischemia in vivo. The purpose of this study is to show whether argon beneficially impacts brain contusion volume (BCV) as the primary outcome parameter, as well as secondary outcome parameters, such as brain edema, intracranial pressure (ICP), neurological outcome, and cerebral blood flow (CBF) in an in-vivo model. Subjects were randomly assigned to either argon treatment or room air. After applying controlled cortical impact (CCI) onto the dura with 8 m/s (displacement 1 mm, impact duration 150 ms), treatment was administered by a recovery chamber with 25%, 50%, or 75% argon and the rest being oxygen for 4 h after trauma. Two control groups received room air for 15 min and 24 h, respectively. Neurological testing and ICP measurements were performed 24 h after trauma, and brains were removed to measure secondary brain damage. The primary outcome parameter, BCV, and the secondary outcome parameter, brain edema, were not significantly reduced by argon treatment at any concentration. There was a highly significant decrease in ICP at 50% argon (p = 0.001), and significant neurological improvement (beamwalk missteps) at 25% and 50% argon (p = 0.01; p = 0.049 respectively) compared to control.

Highlights

Secondary brain damage emerges as a result of ischemia, excitotoxic events, brain edema, rising intracranial pressure (ICP), blood-brain barrier leakage, low systemic blood pressure, and hypoxia over the course of minutes to days after trauma [1,2]
This study aims to examine argon in an in-vivo model of traumatic brain injury (TBI) and at determining the optimal length, concentration, and timing of posttraumatic argon treatment
Compared with the 24 h control group (19.4 ± 3.2 mm3), there was a mean growth of brain contusion volume (BCV) by 8.9 mm3 (85% of primary BCV) (p < 0.001) due to secondary brain damage

Summary

Introduction

Secondary brain damage emerges as a result of ischemia, excitotoxic events, brain edema, rising intracranial pressure (ICP), blood-brain barrier leakage, low systemic blood pressure, and hypoxia over the course of minutes to days after trauma [1,2]. Argon has shown significant reduction of neuronal cell death in vitro in mice after mechanical trauma and glucose/oxygen deprivation. Propidium iodide (PI) staining demonstrated a significant reduction in secondary damage, which was most pronounced at a concentration of 50% argon [3,4]. In-vivo studies showed protection against excitotoxic stress, i.e., NMDA-injections, and focal ischemia after middle cerebral artery occlusion (MCAO) in rats. In the case of NMDA injection, neuroprotectivity was demonstrated after one hour of treatment with 37.5% and 50% argon. In the MCAO experiments, a three-hour treatment with 50% argon significantly reduced cortical damage while increasing subcortical damage [4,5]. Other studies have found an increase in inflammatory mediators after argon treatment following in-vivo ischemia in rats [10]

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