Downregulation of Calpain 1 Causes Neurotoxicity and Apoptosis in Primary Neurons Induced by A beta 25-35

Amyloid-peptides (A beta), which can aggregate oligomers or fibrils into neurons, play a critical role in Alzheimer's disease (AD). Calpain 1 (CAPN1) is one of the Ca2+ regulated proteases, involved in cell death, apoptosis, and motility. As an important signal transduction pathway, it has been reported to be closely related to muscle atrophy, myoblast fusion, diabetes mellitus, and neurodegenerative diseases, including Alzheimer's disease. Our previous study investigated the effect of CAPN1 RNAi on neurotoxicity and apoptosis in primary neurons induced by A beta 25-35. The primary neurons were cultured and separated into different groups pretreated with A beta 25-35 (10 mu M). Three groups were treated with CAPN1 shRNA, while one group was not. Along with CAPN1 shRNA, P25 (2 mu g/mL) and rapamycin (20 ng/mL) were added to the culture. The results showed that CAPN1 RNAi enhanced the formation of autophagosomes in cells, as observed by confocal microscopy. Parallelly, CAPN1 RNAi enhanced the cell viability, as observed by Cell Counting Kit-8 (CCK8) assay, and decreased the apoptotic rate, as observed by flow cytometry. In addition, CAPN1 RNAi decreased the mRNA level of CAPN1 and downregulated the expression levels of CDK5, GSK3 beta, and p-tau in primary neurons induced by A beta 25-35. All these results indicated the effect of CAPN1 RNAi against A beta-induced neurotoxicity. Our results suggested that CAPN1 RNAi exhibits a neuroprotective effect on the treatment of AD and provided a pharmacological basis for its clinical treatment.