miR-124 Regulates the Expression of BACE1 in the Hippocampus Under Chronic Cerebral Hypoperfusion.

Chronic cerebral hypoperfusion (CCH) is a high-risk factor of Alzheimer's disease (AD). MicroRNAs (miRNAs) are ideal mediators of hypoxic stress responses to facilitate cellular adaptation to long-term hypoxia. MiR-124 is a kind of nervous system-specific miRNAs, and one of its target genes is β-site amyloid precursor protein cleaving enzyme 1 (BACE1). In the present study, miR-124 was found to be inhibited all the time from early to late stage of cerebral hypoxia accompanying with the upregulation of BACE1 protein and overproduction of amyloid-β (Aβ) in the hippocampus from cerebral hypoperfusion rat models. Meanwhile, Aβ could further enhance the expression of BACE1 protein due to the inhibition of miR-124. Thus, miR-124 was the key factor in this hypoxia/Aβ-miR-124-BACE1-Aβ cycle. The activation of EPAC-Rap1 pathway was involved in the inhibition of miR-124 in hippocampus under hypoxia or Aβ insult. Our data suggest that, as an endogenous regulator of BACE1 protein, miR-124 may play a role in AD onset induced by CCH.