Mitochondrial Dynamics Alteration in Astrocytes Following Primary Blast-Induced Traumatic Brain Injury

Mild blast-induced traumatic brain injury (bTBI) is a modality of injury that has been of major concern considering a large number of military personnel exposed to the blast wave from explosives. bTBI results from the propagation of high-pressure static blast forces and their subsequent energy transmission within brain tissue. Current literature presents a neuro-centric approach to the role of mitochondria dynamics dysfunction in bTBI; however, changes in astrocyte-specific mitochondrial dynamics have not been characterized. As a result of fission and fusion, the mitochondrial structure is constantly altering shape to respond to physiological stimuli or stress insults by adapting structure and function, which are intimately connected. Dysregulation of the protein regulator of mitochondrial fission, DRP1, and upregulation in the phosphorylation of DRP1 at the serine 616 site is reported to play a crucial role in astrocytic mitochondrial dysfunction, favoring fission over fusion post-TBI. Astrocytic mitochondria are starting to be recognized to play an essential role in overall brain metabolism, synaptic transmission, and neuron protection. Mitochondria are vulnerable to injury insults leading to the worsening of mitochondrial fission and increased mitochondrial fragmentation. In this study, a combination of in vitro and in vivo bTBI models were used to examine the effect of blast on astrocytic mitochondrial dynamics. Acute differential remodeling of the astrocytic mitochondrial network was observed, accompanied by an acute (4hr) and sub-acute (7 days) activation of the GTP-protein DRP1. Further, results showed a time-dependent reactive astrocyte phenotype transition in the rat hippocampus. This discovery can lead to innovative therapeutics targets to help prevent secondary injury cascades that involve mitochondria dysfunction.