An impaired intrinsic microglial clock system induces neuroinflammatory alterations in the early stage of amyloid precursor protein knock-in mouse brain

J Neuroinflammation. 2019 Aug 30;16(1):173. doi: 10.1186/s12974-019-1562-9.


Background: Disturbances in clock genes affect almost all patients with Alzheimer's disease (AD), as evidenced by their altered sleep/wake cycle, thermoregulation, and exacerbation of cognitive impairment. As microglia-mediated neuroinflammation proved to be a driver of AD rather than a result of the disease, in this study, we evaluated the relationship between clock gene disturbance and neuroinflammation in microglia and their contribution to the onset of AD.

Methods: In this study, the expression of clock genes and inflammatory-related genes was examined in MACS microglia isolated from 2-month-old amyloid precursor protein knock-in (APP-KI) and wild-type (WT) mice using cap analysis gene expression (CAGE) deep sequencing and RT-PCR. The effects of clock gene disturbance on neuroinflammation and relevant memory changes were examined in 2-month-old APP-KI and WT mice after injection with SR9009 (a synthetic agonist for REV-ERB). The microglia morphology was studied by staining, neuroinflammation was examined by Western blotting, and cognitive changes were examined by Y-maze and novel object recognition tests.

Results: CLOCK/BMAL1-driven transcriptional negative feedback loops were impaired in the microglia from 2-month-old APP-KI mice. Pro-inflammatory genes in microglia isolated from APP-KI mice were significantly higher than those isolated from WT mice at Zeitgeber time 14. The expression of pro-inflammatory genes was positively associated with NF-κB activation and negatively associated with the BMAL1 expression. SR9009 induced the activation of microglia, the increased expression of pro-inflammatory genes, and cognitive decline in 2-month-old APP-KI mice.

Conclusion: Clock gene disturbance in microglia is involved in the early onset of AD through the induction of chronic neuroinflammation, which may be a new target for preventing or slowing AD.

Keywords: APP-KI mice; Alzheimer’s disease; BMAL1; Clock genes; Microglia; Neuroinflammation.

MeSH terms

  • Amyloid beta-Protein Precursor / genetics
  • Amyloid beta-Protein Precursor / metabolism*
  • Animals
  • Brain / drug effects
  • Brain / metabolism*
  • CLOCK Proteins / antagonists & inhibitors
  • CLOCK Proteins / genetics
  • CLOCK Proteins / metabolism*
  • Gene Knock-In Techniques / methods*
  • Inflammation / genetics
  • Inflammation / metabolism
  • Inflammation Mediators / agonists
  • Inflammation Mediators / metabolism*
  • Locomotion / drug effects
  • Locomotion / physiology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Microglia / drug effects
  • Microglia / metabolism*
  • Pyrrolidines / toxicity
  • Thiophenes / toxicity


  • Amyloid beta-Protein Precursor
  • Inflammation Mediators
  • Pyrrolidines
  • SR9009
  • Thiophenes
  • CLOCK Proteins
  • Clock protein, mouse