Aerobic exercise combined with antioxidative treatment does not counteract moderate- or mid-stage Alzheimer-like pathophysiology of APP/PS1 mice

Abstract

Aims: The present study evaluated the combined treatment effects of aerobic exercise and antioxidative stress on moderate-stage Alzheimer's disease (AD).

Methods: Ten-month-old APP/PS1 mice were given antioxidative treatment with acetylcysteine, along with aerobic exercise for 6 weeks. Spatial learning and memory were tested using the Morris water maze, and β-amyloid (Aβ) plaque deposits in the forebrain were quantified by Thioflavin-S staining. Levels of soluble Aβ1-42, β-secretase enzyme, ү-secretase enzyme, oxidative and antioxidant stress markers nitrotyrosine and peroxiredoxin-1, glial markers glial fibrillary acidic protein and ionized calcium-binding adaptor molecule 1, and synaptic protein synaptophysin in the hippocampus were all measured by western blotting and/or immunohistochemistry.

Results: APP/PS1 mice showed severe declines in spatial learning and memory compared with their wild-type littermates, which were not attenuated by aerobic exercise combined with antioxidative treatment. The pathologic analysis revealed that Aβ deposition and production, oxidative stress, glial inflammation, and synaptic loss were not mitigated in the brain of exercised APP/PS1 mice, compared with the sedentary APP/PS1 animals.

Conclusion: This study reveals that a combined treatment of aerobic exercise plus antioxidative stress does not counteract pathophysiology in the moderate- or mid-stages of AD.

Keywords: APP/PS1 mice; Aerobic exercise; Alzheimer's disease; Antioxidative treatment; Cognitive function; Pathology; β-amyloid.

Figure 1

Spatial learning and memory analysis of 11.5‐month‐old wild‐type (WT) and APP/PS1 mice with or without aerobic exercise and N‐acetyl‐L‐cysteine (NAC) combination treatment from 10 months of age. (A and B) APP/PS1 mice showed longer escape latency and higher swimming speed than WT mice during 4 days of Morris water maze training. Aerobic exercise and NAC combination treatment did not affect escape latency of both WT mice and APP/PS1 mice. Swimming speeds decreased in the aerobic exercise and NAC‐treated WT mice, but increased in the aerobic exercise and NAC‐treated APP/PS1 mice. (C) Tracings of the typical swim patterns on the 4th day. WT mice reached the hidden platform with small loops. In contrast, APP/PS1 mice, especially those with aerobic exercise and NAC combination treatment, swam randomly with most time spent in the outer portion of the pool before finding the hidden platform. (D and E) WT mice displayed a higher percentage of time spent in each quadrant and number of crossing the platform than APP/PS1 mice in the probe test on the 5th day. *P < 0.05, between genotype comparisons. Data represent means ± SEM from 7 mice per group.

Figure 2

Analysis of Aβ deposition and production in the brain of 11.5‐month‐old wild‐type and APP/PS1 mice with or without aerobic exercise and N‐acetyl‐L‐cysteine (NAC) combination treatment from 10 months of age. (A) Both APP/PS1 mice, with or without aerobic exercise and NAC combination treatment, showed Aβ plaque accumulation in the forebrain, revealed by Thioflavin‐S florescence staining. Scale bar = 1.5 mm. (B) Aerobic exercise and NAC combination therapy did not affect Aβ plaque load in the primary motor cortex (M1), secondary motor cortex (M2), primary somatosensory cortex (S1), visual cortex (V2), hippocampus (HC), and hypothalamus (HT) of APP/PS1 mice. Data represent mean ± SEM from 4 mice per group. (C and D) Western blotting and densitometry quantification revealed that β‐secretase, ү‐secretase, and Aβ1–42 expression increased in the hippocampus of APP/PS1 mice, but was not significantly changed following aerobic exercise and NAC combination therapy. Data represent mean ± SEM from 3 mice per group performed in triplicate. *P < 0.05, between genotype comparisons.

Figure 3

Analysis of oxidative stress in the hippocampus of 11.5‐month‐old wild‐type and APP/PS1 mice with or without aerobic exercise and N‐acetyl‐L‐cysteine (NAC) combination treatment from 10 months of age. (A and B) Western blotting and densitometry quantification revealed that the oxidative stress marker nitrotyrosine and the antioxidative marker Prdx‐1 increased in the hippocampus of APP/PS1 mice. Levels were not significantly changed after aerobic exercise and NAC combination therapy. Data represent mean ± SEM from 3 mice per group performed in triplicate. *P < 0.05, between genotype comparisons.

Figure 4

Analysis of synaptophysin (SYP) expression in the hippocampus of 11.5‐month‐old wild‐type (WT) and APP/PS1 mice with or without aerobic exercise and N‐acetyl‐L‐cysteine (NAC) combination treatment from 10 months of age. (A and B) Immunohistochemistry and mean integrated optical density (MIOD) analysis demonstrated that SYP immunoreactivity was decreased in APP/PS1 mice, and not affected by aerobic exercise and NAC combination. Scale bar = 500 μm. Data represent mean ± SEM from 4 mice per group. (C and D) Consistently, western blotting and densitometry quantification showed that the combination therapy did not change decreased SYP expression in the hippocampus of APP/PS1 mice, compared with WT mice. Data represent mean ± SEM from 3 mice per group performed in triplicate. *P < 0.05, between genotype comparisons.

Figure 5

Analysis of glial inflammation in the hippocampus of 11.5‐month‐old wild‐type (WT) and APP/PS1 mice with or without aerobic exercise and N‐acetyl‐L‐cysteine (NAC) combination treatment from 10 months of age. (A) The immunohistochemistry revealed that glial fibrillary acidic protein (GFAP)‐positive astrocytes (upper two panels) and Iba‐1‐positive microglia (lower two panels) were prominently activated in the hippocampus of APP/PS1 mice with or without the combination therapy, compared with WT littermates. Scale bar = 500 μm. (B) The quantification analysis revealed higher values of mean integrated optical density (MIOD) of GFAP and Iba‐1 in APP/PS1 mice, which was not affected by aerobic exercise and NAC combination. Data represent mean ± SEM from 4 mice per group. (C and D) Consistently, western blotting and densitometry quantification showed that the combination treatment did not affect upregulated expression of GFAP and Ibal‐1 in the hippocampus of APP/PS1 mice, compared with WT mice. Data represent mean ± SEM from 4 mice per group performed in triplicate. *P < 0.05, between genotype comparisons.