Targeted siRNA-mediated down-regulation of the expression of amyloid precursor and tau proteins implicated in Alzheimer's disease in neuroblastoma cell lines

Alzheimer's is a neurodegenerative disorder characterized by increased deposition of insoluble extracellular amyloid plaques in the brain with neurofibrillary tangles within the neurons.;Amyloid plaque formation or amyloidosis results from the deposition of amyloid beta-peptide produced from amyloid precursor protein (APP) by the proteolytic activity of alpha, beta and gamma-secretases. Tau pathology is characterized by excessive tau phosphorylation, reduced binding affinity of tau to microtubules, and the formation of aberrant tau aggregates known as neurofibrillary tangles (NET).;To determine the effect of beta-endorphin on the expression of APP, SK-N-SH neuroblastoma cells were treated with beta-endorphin and its effect was studied using RNA and protein analyses. In addition, siRNA-mediated down regulation of APP and tau protein was studied in SK-N-SH neuroblastoma cells and CHP-212 neuroblastoma cells, respectively. RT-PCR analysis indicated decreased levels of APP mRNA in beta-endorphin treated cells as well as the cells transfected with siRNA targeting APP. Western blot analysis showed a corresponding decrease in the expression of the protein in both treatments. Previously, propranolol was shown to decrease the expression of APP; forskolin on the other hand caused an increase in APP mRNA levels and corresponding increase in APP expression. Our results show an inhibition of APP expression both by beta-endorphin and siRNA targeting APP. It is likely that the elevated physiological release of beta-endorphin may have a beneficial effect in Alzheimer's patients.;CHP-212 transfected with &tgr; mRNA-directed siRNA at 50 and 100nM concentrations showed total degradation of &tgr; mRNA as determined by RT-PCR analysis. The above results demonstrate that expression of APP and &tgr; protein can be down-regulated/inhibited by siRNA mediated targeted degradation of their respective mRNAs.