Role of the mitochondrial calcium uniporter in Mg-free-induced epileptic hippocampal neuronal apoptosis.

Mitochondrial Ca overload is closely associated with seizure-induced neuronal damage. The mitochondrial calcium uniporter (MCU) plays a crucial role in regulating mitochondrial Ca homeostasis. However, the role of the MCU in seizure-induced neuronal damage remains elusive. In this study, the hippocampal neuronal culture (HNC) model of acquired epilepsy (AE) was used to investigate the role of the MCU in seizure-induced neuronal injury. We found an increase in mitochondrial Ca concentration in the HNC model of AE. The MCU inhibitor, Ru360, significantly reduced the rate of seizure-induced cell apoptosis and mitochondrial reactive oxygen species (ROS) production; whereas, the MCU agonist, spermine, exacerbated these processes. In addition, Ru360 significantly attenuated seizure-induced endoplasmic reticulum (ER) stress, which is characterized by the expression of glucose-regulated protein 78 (GRP78) and C/-EBP homologous protein (CHOP), while spermine had the opposite effect. We also found that pre-treatment with the mitochondria-targeted antioxidant, mitoquinone, decreased GRP78 and CHOP expression. Moreover, knockdown of CHOP using CHOP-specific small interfering RNA reduced neuronal seizure-induced apoptosis. Taken together, our data indicate that MCU inhibition has a neuroprotective effect against seizure-induced neuronal damage and that this mechanism may involve reduction of ROS-mediated ER stress.