Disruption of the sleep-wake cycle and diurnal fluctuation of β-amyloid in mice with Alzheimer's disease pathology

Abstract

Aggregation of β-amyloid (Aβ) in the brain begins to occur years before the clinical onset of Alzheimer's disease (AD). Before Aβ aggregation, concentrations of extracellular soluble Aβ in the interstitial fluid (ISF) space of the brain, which are regulated by neuronal activity and the sleep-wake cycle, correlate with the amount of Aβ deposition in the brain seen later. The amount and quality of sleep decline with normal aging and to a greater extent in AD patients. How sleep quality as well as the diurnal fluctuation in Aβ change with age and Aβ aggregation is not well understood. We report a normal sleep-wake cycle and diurnal fluctuation in ISF Aβ in the brain of the APPswe/PS1δE9 mouse model of AD before Aβ plaque formation. After plaque formation, the sleep-wake cycle markedly deteriorated and diurnal fluctuation of ISF Aβ dissipated. As in mice, diurnal fluctuation of cerebrospinal fluid Aβ in young adult humans with presenilin mutations was also markedly attenuated after Aβ plaque formation. Virtual elimination of Aβ deposits in the mouse brain by active immunization with Aβ(42) normalized the sleep-wake cycle and the diurnal fluctuation of ISF Aβ. These data suggest that Aβ aggregation disrupts the sleep-wake cycle and diurnal fluctuation of Aβ. Sleep-wake behavior and diurnal fluctuation of Aβ in the central nervous system may be functional and biochemical indicators, respectively, of Aβ-associated pathology.

Figure 1

Chronological changes in sleep-wake patterns and diurnal fluctuations of interstitial fluid (ISF) amyloid beta (Aβ) in APPswe/PS1δE9 mice. (A–C, G–I) Diurnal changes of ISF Aβ_1-x in APPswe/PS1δE9 mice at 3, 6, 9 months across 2 days shown as % average of 2 days of absolute values of ISF Aβ_1-x in the hippocampus (A–C) and striatum (G–I). (D–F, J–L) Comparison of % average of 2 days of ISF Aβ_1-x between dark and light periods in the hippocampus (D–F) and striatum (J–L) of each age group (n = 6–8 per group; two tailed t-test). (M, N) Absolute levels of ISF Aβ_1-x in the hippocampus (M) and striatum (N) of 3, 6, and 9 month old APPswe/PS1δE9 mice (n = 6–8 per group; one-way ANOVA, followed by Tukey’s post hoc test). *P < 0.05; **P <0.01; ***P< 0.001. Values represent mean ± s.e.m.

Figure 2

Sleep-wake patterns in 3, 6, and 9 month old APPswe/PS1δE9 mice. (A–C) Sleep-wake patterns in 3, 6, and 9 month old APPswe/PS1δE9 mice across 2 days (2 light-dark periods) assessed as minutes awake per hour. (D–L) Chronological changes of minutes per hour spent in wakefulness, rapid eye movement (REM) sleep, and non-REM (NREM) sleep in 3, 6, and 9 month old APPswe/PS1δE9 mice and 9 month old wild-type littermates (B6C3). Analysis of a whole 24 hour period (D–F), analysis during light period (G–I), and analysis during dark period (J–L) (n = 6–8 per group; one-way ANOVA, Tukey’s post hoc test for multiple comparisons). *P < 0.05; **P<0.01; ***p < 0.001. Values represent mean ± s.e.m.

Figure 3

Attenuated diurnal fluctuation of CSF Aβ in mutation carriers in autosomal dominant Alzheimer’s disease (AD) families. (A–F) Diurnal fluctuation of CSF ISF Aβ40 and Aβ42 across 36 hours in no mutation carriers (mutation−; N=4) (A, D), mutation carriers who are PiB−(mutation+PiB−; N=4) (B, E) and mutation carriers who are PiB+ (mutation+PiB+; N=4) (C, F) as shown by cosinor curves. Cosinor analysis was used to assess diurnal patterns of CSF Aβ dynamics in each group and diurnal patterns were considered significant when amplitudes were different from zero (P < 0.05).

Figure 4

Aβ plaque deposition in the hippocampus and striatum in 9 month old phosphate buffered saline (PBS)-treated and Aβ₄₂-immunized APPswe/PS1δE9 mice. (A–D) Representative brain sections of the hippocampus (A, C) and striatum (B, D) of mice from each group stained with HJ 3.4 antibody to visualize Aβ immunoreactive plaques (Aβ-IR). (E, F) Amount of Aβ deposition in the PBS-treated mice and Aβ₄₂-vaccinated mice are shown with amount of Aβ deposition in six and nine month old APPswe/PS1δE9 mice in the hippocampus (E) and striatum (F) (n=5–6 in each group; two tailed t-test). ***P< 0.001. n.s. stands for not statistically significant. Values represent mean ± s.e.m. Scale bar in (A) represents 500µm.

Figure 5

Sleep-wake patterns and diurnal fluctuation of interstitial fluid (ISF) Aβ in 9 month old phosphate buffered saline (PBS)-treated and Aβ₄₂-immunized APPswe/PS1δE9 mice. (A, G) Sleep-wake patterns in 9 month old PBS-treated (A) and Aβ₄₂-immunized (G) APPswe/PS1δE9 mice across 2 days (2 light-dark periods) shown as minutes awake per hour. (D, J) Comparison of minutes awake per hour between the dark and light periods in each group (n = 5–6 per group; two tailed t-test). (B, H) Diurnal fluctuation of ISF Aβ_1-x in the hippocampus of 9 month old PBS-treated (B) and Aβ42-immunized (H) APPswe/PS1δE9 mice across 2 days presented as % average of absolute values of ISF Aβ_1-x(E, K) Comparison of % average of absolute values of ISF Aβ_1-x in the hippocampus between the dark and light periods (n = 5–6 per group; two tailed t-test). (C, I) Diurnal fluctuation of ISF Aβ_1-x in the striatum of 9 month old PBS-vaccinated (C) and Aβ₄₂-vaccinated (I) APPswe/PS1δE9 mice across 2 days. (F, L) Comparison of % average of absolute values of ISF Aβ_1-x in the striatum between the dark and light periods (n = 5–6 per group; two tailed t-test). *P < 0.05; ***p < 0.001. Values represent mean ± s.e.m.

Figure 6

Chronological changes in the amplitude of diurnal fluctuation of interstitial fluid (ISF) lactate in 3, 6, and 9 month old APPswe/PS1δE9 mice. (A–F) Diurnal fluctuation of ISF lactate in the hippocampus (A–C) and in the striatum (D–F). (G, H) Chronological changes in the amplitude of diurnal fluctuation in the hippocampus (G) and in the striatum (H) as measured by amplitude of cosinor analysis (n = 6 per group; one-way ANOVA after cosinor analysis for measurement of amplitude, Tukey’s post hoc test for multiple comparisons). *P < 0.05. Values represent mean ± s.e.m.

Figure 7

Chronological changes of absolute concentrations of interstitial fluid (ISF) Aβ42 and lactate in the hippocampus and striatum of mice and association between CSF Aβ42 and amyloid plaque deposition in humans. (A, D) Absolute levels of ISF Aβ_x-42 in the hippocampus (A) and in the striatum (D) of 3 and 9 month old APPswe/PS1δE9 mice (n = 5–6 per group; Mann-Whitney Test). (B, E) Absolute levels of ISF lactate in the hippocampus (B) and in the striatum (E) of 3, 6, and 9 month old APPswe/PS1δE9 mice (n = 6 per group; one-way ANOVA, Tukey’spost hoc test). (C) Comparison of absolute values of CSF Aβ42 in non-mutation carriers (NC), mutation carriers without amyloid plaque deposition (MC+PiB−), mutation carriers with amyloid plaque deposition (MC+PiB+) (n = 4 per group; Kruskal-Wallis test). (F) Correlation between absolute levels of CSF Aβ42 and amount of amyloid plaque deposition measured by mean cortical PiB binding potential (MCBP) (n = 12 paired measurement; Pearson’s correlation test). *P < 0.05; **P < 0.01. Values represent mean ± s.e.m.