Repeated impacts induce acute neurobehavioral and molecular deficits in a mouse model of traumatic brain injury

Redox stress is a significant contributor to the molecular dysfunction associated with traumatic brain injury (TBI). Each of the canonical molecular biomarkers of TBI, including GFAP and UCHL1, demonstrate a clear relationship with redox stress via protein oxidation and enzymatic inhibition. Additionally, several markers of redox stress have demonstrated utility in assessing preclinical and clinical TBI, including F2-isoprostanes, generated from the oxidation of arachidonic acid. Thus, we investigated the role of urinary 8-isoprostane as a biomarker for delineating between sham and impacted mice. In this study, male and female mice (n = 19) subjected to five daily impacts using a repeated impact acceleration (rIA) model were evaluated against sham mice for neurological deficits. Impacted mice exhibited behavioral deficits, with increases in righting reflex (RR) times (p < 0.0001), and time-course increases in modified neurological severity scores (mNSS) (p < 0.01). Urine collected immediately following (day 5) and 72 h post-rIA (day 8) revealed time-course increases in 8-isoprostane levels (p < 0.05). Tissue-based protein expression for several markers of molecular dysfunction was assessed using immunoblotting in a two stage discovery based strategy, for which GFAP expression significantly differed with respect to treatment (p < 0.0001) and sex (p < 0.01). Pooled, unadjusted analysis identified a significant relationship between GFAP and urinary 8-isoprostane levels at day 8 (R² = 0.75; p < 0.0001) with a non-significant, attenuated within-group relationship (R² = 0.08; p > 0.05). Overall, these results suggest repeated impacts using a preclinical TBI mouse model induce acute neurobehavioral deficits, assessed via RR and mNSS, and molecular deficits, including increases in GFAP and urinary 8-isoprostane.