Repetitive Mild Traumatic Brain Injury Causes Neuronal Damage in the APP/PS1 Mouse Model of Alzheimer's Disease Without an Enduring Impact on Amyloid Pathology, Sleep, or Epileptiform Activity.

Traumatic brain injury (TBI) is a known risk factor for Alzheimer's disease and related neurodegenerative diseases. Sleep disturbances and epileptiform abnormalities can appear after TBI and may contribute to the development of neuropathology. In this study, we characterized sleep, epileptiform activity, and neuropathology after repetitive mild traumatic brain injury (rmTBI) in a mouse model of Alzheimer's disease. We used the Closed Head Impact Model of Engineered Rotational Acceleration to deliver rmTBI or sham (control) treatment to 6-month-old APP/PS1 mice (N = 19). One month post-injury, we implanted electroencephalogram and electromyographic electrodes, recorded for 72 h, and then collected brain tissue and blood plasma. Our assessment of sleep architecture showed that time spent in vigilance state was not affected by the rmTBI 1 month post-injury; however, power spectra analysis showed a shift toward higher frequencies in the rmTBI group during non-rapid eye movement sleep. Epileptiform activity did not differ between sham and rmTBI. Compared with sham controls, the rmTBI group showed higher neurofilament light (NF-L), but not glial fibrillary acidic protein in blood plasma and no change in Aβ pathology. These results indicate sustained neurological injury in the APP/PS1 mice 1 month after rmTBI without affecting amyloid deposition in the brain. Our study suggests that rmTBI can induce neural injury without causing enduring sleep disruption, seizures, and exacerbation of amyloidosis in the APP/PS1 mouse model.