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Alzheimer's disease (AD) is characterized by the deposition of aggregated amyloid-beta (Aβ), which triggers a cellular stress response called the unfolded protein response (UPR). The UPR signaling pathway is a cellular defense system for dealing with the accumulation of misfolded proteins but switches to apoptosis when endoplasmic reticulum (ER) stress is prolonged. ER stress is involved in neurodegenerative diseases including AD, but the molecular mechanisms of neuronal apoptosis and inflammation by Aβ-induced ER stress to exercise training are not fully understood. Here, we demonstrated that treadmill exercise (TE) prevented PS2 mutation-induced memory impairment and reduced Aβ-42 deposition through the inhibition of β-secretase (BACE-1) and its product, C-99 in cortex and/or hippocampus of aged PS2 mutant mice. We also found that TE down-regulated the expression of GRP78/Bip and PDI proteins and inhibited activation of PERK, eIF2α, ATF6α, sXBP1 and JNK-p38 MAPK as well as activation of CHOP, caspase-12 and caspase-3. Moreover, TE up-regulated the expression of Bcl-2 and down-regulated the expressions of Bax in the hippocampus of aged PS2 mutant mice. Finally, the generation of TNFα and IL-1α and the number of TUNEL-positive cells in the hippocampus of aged PS2 mutant mice was also prevented or decreased by TE. These results showed that TE suppressed the activation of UPR signaling pathways as well as inhibited the apoptotic pathways of the UPR and inflammatory response following Aβ-induced ER stress. Thus, therapeutic strategies that modulate Aβ-induced ER stress through TE could represent a promising approach for the prevention or treatment of AD.

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Accumulation of alpha-synuclein (α-Syn) is significantly correlated with the presence of progressive motor deficits, which is the main symptom of Parkinson's disease (PD). Although physical exercise reduces α-Syn levels, the molecular mechanisms by which physical exercise decreases α-Syn remain unclear. We hypothesized that treadmill exercise (TE) decreases α-Syn levels by improving mitochondrial function and promoting autophagy via the sirtuin-1 (SIRT1) signaling pathway in the chronic 1-methyl-1,2,3,6-tetrahydropyridine with probenecid (MPTP/P)-induced mouse model of PD. We found that TE reduces α-Syn levels, which subsequently ameliorates dopaminergic (DAergic) neuron loss and α-Syn-mediated apoptotic cell death. Most importantly, TE increases SIRT1 expression, which results in increased mitochondrial biogenesis and decreased oxidative stress by activating peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α). SIRT1 activation by TE also promotes autophagic clearance of α-Syn by inducing the activation of microtubule-associated protein 1 light chain 3 (LC3). Collectively, our results demonstrate that TE may reduce α-Syn levels by improving mitochondrial function and increasing autophagic flux, thereby ameliorating chronic MPTP/P-induced motor deficits in PD mice.