Sarm1 Regulates Circadian Rhythm Disorder in Alzheimer's Disease in Mice

Background: Sarm1 (Sterile alpha and TIR motif-containing 1) is a key protein that regulates neurodegenerative pathologies. Alzheimer's disease (AD) is highly associated with neurodegenerative lesions and biorhythmic disturbances. Objective: This study aims to decipher the role of Sarm1 in AD-induced circadian rhythm disturbances and AD progression. Methods: Open field and water maze tests were used to assess the cognitive function of mice. Thioflavin-S staining was used to assess amyloid-beta (A beta) plaque deposition in the hippocampus and cortex. Rhythmic waveform of home cage activity and temperature was recorded to evaluate circadian rhythm. Expression of clock molecules including Bmal1 and Per2 in the hippocampus were analyzed using western blot and real-time PCR. Further, HT22 cells with Sam1 knockout were treated with A beta(31-35) treatment to initiate circadian rhythm disorder in the cellular level to assess the changes in Bmal1 and Per2. Results: Our data suggested that Sarm1 deficiency rescued cognitive disorder, decreased A beta plaque deposition in the hippocampus and cortex, inhibited astrocyte activation, improved circadian rhythm, altered clock molecule expression in the cortex and hippocampus in APP/PS1 mice. Conclusion: Sarm1 attenuates circadian rhythm disturbances and reduces AD progression. These data support the potential use of Sarm1 as a therapeutic target to improve circadian rhythm to impede AD progression.