APP and Alzheimer disease: Yang et al. (2014a) showed that exposure to SiNPs (15 nm; 10 μg/ml for 24 h) induced pathological signs of Alzheimer’s disease such as altered expression of amyloid precursor protein (APP) and neprilysin, enhanced phosphorylation of tau at Ser262 and Ser396, and activation of glycogen syntheses kinase (GSK)-3β in human SK-N-SH and mouse neuro2a neuroblastoma cells.