Tau folding and cytotoxicity of neuroblastoma cells in the presence of manganese oxide nanoparticles: Biophysical, molecular dynamics, cellular, and molecular studies.

Manganese oxide nanoparticles (Mn2O3 NPs) have been widely used in the medical and biological applications. However, few studies have been undertaken to investigate the cytotoxicity of Mn2O3 NPs against nervous system. Herein, we studied the toxicity of Mn2O3 NPs against tau protein and neuroblastoma cells (SH-SY5Y) in vitro. Circular dichroism (CD) spectroscopy, fluorescence spectroscopy, molecular docking, and molecular dynamic studies were used to explore the conformational changes of protein. The cell-based experiments, such as viability, activation of caspases-3/9, apoptosis, and gene (Bax and Bcl-2) expression assays were performed in vitro. Spectroscopic methods and molecular dynamic studies revealed that Mn2O3 NPs can fold the structure of tau toward a more packed structure. The Mn2O3 NPs also decreased the cell viability in a dose-dependent manner. Indeed, caspase-3 and caspase-9 activation, Bax/Bcl-2 ratio elevation and apoptosis induction were observed after exposure of SH-SY5Y to Mn2O3 NPs. In conclusion, tau folding and cytotoxicity against SH-SY5Y cells may be involved in adverse effects induced by Mn2O3 NPs.