Increased NF-κB signalling up-regulates BACE1 expression and its therapeutic potential in Alzheimer's disease

Elevated levels of beta-site APP cleaving enzyme 1 (BACE1) were found in the brain of some sporadic Alzheimer's disease (AD) patients; however, the underlying mechanism is unknown. BACE1 cleaves beta-amyloid precursor protein (APP) to generate amyloid beta protein (A beta), a central component of neuritic plaques in AD brains. Nuclear factor-kappa B (NF-kappa B) signalling plays an important role in gene regulation and is implicated in inflammation, oxidative stress and apoptosis. In this report we found that both BACE1 and NF-kappa B p65 levels were significantly increased in the brains of AD patients. Two functional NF-kappa B-binding elements were identified in the human BACE1 promoter region. We found that NF-kappa B p65 expression resulted in increased BACE1 promoter activity and BACE1 transcription, while disruption of NF-kappa B p65 decreased BACE1 gene expression in p65 knockout (RelA-knockout) cells. In addition, NF-kappa B p65 expression leads to up-regulated beta-secretase cleavage and A beta production, while non-steroidal anti-inflammatory drugs (NSAIDs) inhibited BACE1 transcriptional activation induced by strong NF-kappa B activator tumour necrosis factor-alpha (TNF-alpha). Taken together, our results clearly demonstrate that NF-kappa B signalling facilitates BACE1 gene expression and APP processing, and increased BACE1 expression mediated by NF-kappa B signalling in the brain could be one of the novel molecular mechanisms underlying the development of AD in some sporadic cases. Furthermore, NSAIDs could block the inflammation-induced BACE1 transcription and A beta production. Our study suggests that inhibition of NF-kappa B-mediated BACE1 expression may be a valuable drug target for AD therapy.