Characterisation of the spatial distribution of metals and profile of metalloprotein complexes in a mouse model of repetitive mild traumatic brain injury.

Metal dyshomeostasis is a well-established consequence of neurodegenerative diseases and traumatic brain injury. While the significance of metals continues to be uncovered in many neurological disorders, their implication in repetitive mild traumatic brain injury remains uncharted. To address this gap, we characterised the spatial distribution of metal levels (iron, zinc and copper) using laser ablation-inductively coupled plasma-mass spectrometry, the profile of metal-binding proteins via size exclusion chromatography-inductively coupled plasma-mass spectrometry and the expression of the major iron storing protein ferritin via western blotting. Using a mouse model of repetitive mild traumatic brain injury, 3-month-old male and female C57Bl6 mice received one or five impacts (48 h apart). At 1-month following 5x TBI, iron and ferritin levels were significantly elevated in the contralateral cortex. There was a trend towards increased iron levels in the entire contralateral hemisphere and a reduction in contralateral cortical iron-binding proteins following 1x TBI. No major changes in zinc levels were seen in both hemispheres following 5x or 1x TBI, although there was a reduction in ipsilateral zinc-binding proteins following 5x TBI and a contralateral increase in zinc-binding proteins following 1x TBI. Copper levels were significantly increased in both hemispheres following 5x TBI, without changes in copper-binding proteins. This study shows for the first time that r-mTBI leads to metal dyshomeostasis, highlighting its potential involvement in promoting neurodegeneration which provides a rationale for examining the benefit of metal-targeting drugs, which have shown promising results in neurodegenerative conditions and single TBI, but have yet to be tested following r-mTBI.