The Toxic Effect of Lithium Ion on Neurons (PC12 cells) and A[beta]^sub 42^ Molecules

In this study, the neurotoxicity of Li ion and its effect on the morphologies of A[beta]^sub 42^ molecules were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, fluorescence (FL), atomic force microscopy (AFM), and circular dichroism (CD) spectroscopy. MTT assays show that Li ion with a dosage level lower than 50 mg/l did not show detectable cytotoxicity on pheochromocytoma (PC12) cells whereas a dosage level higher than 100 mg/l resulted in significant cytotoxicity. The interaction between A[beta]^sub 42^ and Li ion occurs, and the quenching effect of Li ion on the fluorescence emission of A[Beta]^sub 42^ is found to be concentration dependent, suggesting that Li ion can bind to the A[beta]^sub 42^ molecules. CD results suggest that a more incompact conformation state will be adopted upon the interaction between A[beta]^sub 42^ and Li ion. According to AFM images, Li ion could induce the formation of the fibrils after incubation for 3 or 5 days. The formation of the oligomer and fibrils originates from the strong interactions between A[beta]^sub 42^ and Li ion. Li ion could accelerate the random coil A[beta]^sub 42^ monomers aggregating into the [beta]-sheet fibrils, which would induce the neurotoxic effect.[PUBLICATION ABSTRACT]