Intracellular magnesium level determines cell viability in the MPP⁺ model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder resulting from mitochondrial dysfunction in dopaminergic neurons. Mitochondria are believed to be responsible for cellular Mg²⁺ homeostasis. Mg²⁺ is indispensable for maintaining ordinal cellular functions, hence perturbation of the cellular Mg²⁺ homeostasis may be responsible for the disorders of physiological functions and diseases including PD. However, the changes in intracellular Mg²⁺ concentration ([Mg²⁺]_i) and the role of Mg²⁺ in PD have still been obscure. In this study, we investigated [Mg²⁺]_i and its effect on neurodegeneration in the 1-methyl-4-phenylpyridinium (MPP⁺) model of PD in differentiated PC12 cells. Application of MPP⁺ induced an increase in [Mg²⁺]_i immediately via two different pathways: Mg²⁺ release from mitochondria and Mg²⁺ influx across cell membrane, and the increased [Mg²⁺]_i sustained for more than 16h after MPP⁺ application. Suppression of Mg²⁺ influx decreased the viability of the cells exposed to MPP⁺. The cell viability correlated highly with [Mg²⁺]_i. In the PC12 cells with suppressed Mg²⁺ influx, ATP concentration decreased and the amount of reactive oxygen species (ROS) increased after an 8h exposure to MPP⁺. Our results indicate that the increase in [Mg²⁺]_i inhibited cellular ROS generation and maintained ATP production, which resulted in the protection from MPP⁺ toxicity.