Temporal Changes in Mitochondria-Centric Excitotoxic Responses Following Severe Penetrating Traumatic Brain Injury

Abstract

Background/Objectives: Traumatic brain injury (TBI) remains a significant and urgent medical concern for the US military. TBI triggers excitotoxic responses immediately, involving mitochondrial dysfunction characterized by loss of calcium (Ca2+) cycling, membrane damage and increased cell death. However, a comprehensive understanding of mitochondria-centric excitotoxic responses over time has yet to be fully demonstrated after severe TBI. The current study evaluated mitochondria-centric time course responses between 30 min and 2 weeks (seven time points) after penetrating TBI (pTBI). Methods: Anesthetized adult male Sprague-Dawley rats were subjected to either 10% unilateral pTBI or Sham craniectomy. Animals were euthanized at various time points, and mitochondria were isolated from the injury core. Results: Post-injury mitochondrial Ca2+ homeostasis was significantly compromised in pTBI compared to the Sham group. In parallel, mitochondrial membrane integrity markers, including cytochrome c (Cyt C) and voltage-dependent anion channel (VDAC), showed significant reduction over time post-pTBI. Apoptosis-responsive markers, such as glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and B-cell lymphoma 2 (Bcl-2), exhibited elevated responses over time post-pTBI. Conclusions: Our results demonstrate profound insights into elevated excitotoxic mitochondrial damage after severe TBI. This time course study uncovers novel mitochondrial targets involved in TBI excitotoxicity and offers mitigation opportunities to alleviate excitotoxic responses after penetrating TBI.

Keywords

• severe traumatic brain injury
• time course
• mitochondrial damage
• excitotoxicity
• calcium homeostasis
• cell death