The long-term effects of intermittent theta burst stimulation on Alzheimer's disease-type pathologies in APP/PS1 mice

Intermittent theta burst stimulation (iTBS), an emerging and highly efficient paradigm of repetitive transcranial magnetic stimulation (rTMS), has been demonstrated to mitigate cognitive impairment in Alzheimer's disease. Previous clinical studies have shown that the cognitive improvement of iTBS could last several weeks after treatment. Nonetheless, it is largely uncertain how the long-term effects of iTBS treatment are sustained. To investigate whether iTBS has a long-term effect on AD-type pathologies, 6-month-old APP/PS1 mice are administrated with 30 consecutive days of iTBS treatment. After a 2-month interval, morphological alterations in the brain are examined by immunohistochemistry and immunofluorescence staining, while levels of associated proteins are assessed by Western blot at the age of 9 months. We find that iTBS treatment significantly diminishes Aβ burden in the cerebral cortex and hippocampus of APP/PS1 mice. Moreover, we observe that iTBS treatment inhibits the expression of BACE1 and elevates the level of IDE, suggesting that the reduction of Aβ load could be attributed to the inhibition of Aβ production and facilitation of Aβ degradation. Furthermore, iTBS treatment attenuates neuroinflammation, neuronal apoptosis, and synaptic loss in APP/PS1 mice. Collectively, these data indicate that 1 month of iTBS treatment ameliorates pathologies in the brain of AD mice for at least 2 months. We provide the novel evidence that iTBS may exert after-effects on AD-type pathologies via inhibition of Aβ production and facilitation of Aβ degradation.