RNA interference-mediated silencing of BACE and APP attenuates the isoflurane-induced caspase activation

Background: beta-Amyloid protein (A beta) has been shown to potentiate the caspase-3 activation induced by the commonly used inhalation anesthetic isoflurane. However, it is unknown whether reduction in A beta levels can attenuate the isoflurane-induced caspase-3 activation. We therefore set out to determine the effects of RNA interference-mediated silencing of amyloid precursor protein (APP) and beta-site APP-cleaving enzyme (BACE) on the levels of A beta and the isoflurane-induced caspase-3 activation. Methods: H4 human neuroglioma cells stably transfected to express full-length human APP (H4-APP cells) were treated with small interference RNAs (siRNAs) targeted at silencing BACE and APP for 48 hours. The cells were then treated with 2% isoflurane for six hours. The levels of BACE, APP, and caspase-3 were determined using Western blot analysis. Sandwich Enzyme-linked immunosorbent assay (ELISA) was used to determine the extracellular A beta levels in the conditioned cell culture media. Results: Here we show for the first time that treatment with BACE and APP siRNAs can decrease levels of BACE, full-length APP, and APP c-terminal fragments. Moreover, the treatment attenuates the A beta levels and the isoflurane-induced caspase-3 activation. These results further suggest a potential role of A beta in the isoflurane-induced caspase-3 activation such that the reduction in A beta levels attenuates the isoflurane-induced caspase-3 activation. Conclusion: These findings will lead to more studies which aim at illustrating the underlying mechanism by which isoflurane and other anesthetics may affect Alzheimer's disease neuropathogenesis.