Research ReportChronic mild sleep restriction accentuates contextual memory impairments, and accumulations of cortical Aβ and pTau in a mouse model of Alzheimer's disease

- Sleep restriction causes an increase in circulating corticosterone in 3xTg mice.
- Sleep restriction causes deficits in contextual and cued memory in 3xTg mice.
- Aβ and pTau levels increased in the cortex of sleep restricted 3xTg mice.
- Aβ and pTau and circulating corticosterone are significantly positively correlated.

Age-associated dysregulation of sleep can be worsened by Alzheimer′s disease (AD). AD and sleep restriction both impair cognition, yet it is unknown if mild chronic sleep restriction modifies the proteopathic processes involved in AD. The goal of this work was to test the hypothesis that sleep restriction worsens memory impairments, and amyloid β-peptide (Aβ) and pTau accumulations in the brain in a mouse model of AD, with a focus on a role for circulating glucocorticoids (GC). Male 3xTgAD mice were subjected to sleep restriction (SR) for 6 h/day for 6 weeks using the modified multiple platform technique, and behavioral (Morris water maze, fear conditioning, open field) and biochemical (immunoblot) outcomes were compared to mice undergoing daily cage transfers (large cage control; LCC) as well as control mice that remained in their home cage (control; CTL). At one week, both LCC and SR mice displayed significant elevations in plasma corticosterone compared to CTL (p<0.002). By four weeks, SR mice displayed a two-fold increase in circulating corticosterone levels compared to CTL. Behavioral data indicated deficits in contextual and cued memory in SR mice that were not present for LCC or CTL (p<0.04). Both Aβ and pTau levels increased in the cortex of SR mice compared to CTL and LCC; however these changes were not noted in the hippocampus. Significant positive correlations between cortical Aβ and pTau levels and circulating corticosterone indicate a potential role for GCs in mediating behavioral and biochemical changes observed after sleep restriction in a mouse model of AD.