Interaction of oxidative stress and neurotrauma in ALDH2 ^−/− mice causes significant and persistent behavioral and pro-inflammatory effects in a tractable model of mild traumatic brain injury

Abstract

Oxidative stress induced by lipid peroxidation products (LPP) accompanies aging and has been hypothesized to exacerbate the secondary cascade in traumatic brain injury (TBI). Increased oxidative stress is a contributor to loss of neural reserve that defines the ability to maintain healthy cognitive function despite the accumulation of neuropathology. ALDH2 ^−/− mice are unable to clear aldehyde LPP by mitochondrial aldehyde dehydrogenase-2 (Aldh2) detoxification and provide a model to study mild TBI (mTBI), therapeutic interventions, and underlying mechanisms. The ALDH2 ^−/− mouse model presents with elevated LPP-mediated protein modification, lowered levels of PSD-95, PGC1-α, and SOD-1, and mild cognitive deficits from 4 months of age. LPP scavengers are neuroprotective in vitro and in ALDH2 ^−/− mice restore cognitive performance. A single-hit, closed skull mTBI failed to elicit significant effects in WT mice; however, ALDH2 ^−/− mice showed a significant inflammatory cytokine surge in the ipsilateral hemisphere 24 h post-mTBI, and increased GFAP cleavage, a biomarker for TBI. Known neuroprotective agents, were able to reverse the effects of mTBI. This new preclinical model of mTBI, incorporating significant perturbations in behavior, inflammation, and clinically relevant biomarkers, allows mechanistic study of the interaction of LPP and neurotrauma in loss of neural reserve.

Graphical abstract

Highlights

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  ALDH2 ^−/− mice have elevated brain LPP adducts and mild cognitive impairment.

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  The effects of a “2nd hit” via LPS are exacerbated by LPP in vitro and in vivo.

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  ALDH2 ^−/− mice + mTBI show amplified/prolonged cognitive deficits and neuroinflammation.

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  This new preclinical model for mTBI supports a role for LPP in reduced neural reserve.