Virginia Research Day 2021

Graduate Student Research Biomedical

07 Contribution of Mitochondrial Dysfunction in Astrocytic Reactivity Following Primary Blast Traumatic Brain Injury

Fernanda Guilhaume-Correa 1 Pamela J. VandeVord 2,3 Corresponding author: fergc92@vt.edu

1 Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, 2 Biomedical Engineering and Mechanics, Virginia Tech, 3 Salem Veterans Affairs Medical Center- Salem

Blast traumatic brain injury (bTBI) is a prevalent injury within military combat personnel and veterans due to their exposure to explosives with 80% of mild head injuries attributed to blast exposure. Military TBI often presents as a syndrome consisting of persistent, treatment resistant symptoms and treatments remain elusive and are limited to symptom management because the pathophysiology of symptoms is poorly understood. There is a critical knowledge gap in understanding the cellular and molecular response post blast exposure. Our goal is to identify unique injury mechanism responses in brain cells associated with blast wave energy. Within the central nervous system (CNS), a lot of cells contribute to the progressive dysfunction of the normal architecture and function of the brain. There is constant crosstalk between cells, as well as, cell-to- cell communication during a traumatic brain injury that still remains to be investigated. Particularly, astrocytes are very important to maintain a proper neuronal network functionality in the healthy and injured brain. It plays numerous important roles in the CNS by presenting vast amount of process extensions that are

radially arranged whereas most processes surround neurons helping with regulation of synaptogenesis, synaptic strength, neurotransmitters regulation as well as providing neurons with energetic and antioxidant precursors. In this study, we aimed to identify unique injury mechanisms in astrocytes after exposure to the mechanical injury. Precisely, we are looking at astrocytic mitochondrial changes post primary blast injury at an autonomous and non-autonomous model to then be able to determinate the importance of mitochondrial health to astrocytes activation. Therefore, we hypothesize that mechanical insult resulting from blast triggers astrocytes mitochondrial dynamics dysfunction which impart unique interconnected mitochondrial network as well as changes in the metabolic signature of astrocytes leading to its dysfunction which subsequently leads to an inadequate role to protect the neurons. Using a 2D in vitro blast model, primary rat astrocytes were exposed to an overpressure wave by using a high-rate fluid-filled device, which mimics

transmission of a shock-like wave intracranial profile. The peak overpressure was 17psi to correlate with mild injury outcomes observed in animal models. Following insult, samples were collected for analyses at 4 and 24 hours. We measured protein levels of two oxidative stress markers, NOX4 and SOD2. The membrane-permeant JC-1 dye was used to estimate mitochondrial health and DCFDA will be used for intracellular ROS detection. The results indicated a significant increase (p-value= 0.0079) in the expression of NOX4 between sham and blast at 24 hours. Changes of mitochondrial membrane potential was observed post exposure indicating a more hyperpolarized mitochondria. Further directions will aim on characterizing the pathophysiology of astrocytic mitochondrial dysfunction following primary blast injury using an in vivo blast model whereas samples will undergo magnetic bead cell separation which will provide data of non-autonomous astrocytic mitochondrial changes post primary blast injury.

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