Inhibition of the mitochondrial calcium uniporter inhibits Aβ-induced apoptosis by reducing reactive oxygen species-mediated endoplasmic reticulum stress in cultured microglia

Amyloid-beta (A beta) has been shown to induce microglial apoptosis, which is itself sensitive to disturbed mitochondrial calcium (Ca2+) homeostasis. The mitochondrial calcium uniporter (MCU) plays an important regulatory role in mitochondrial Ca2+ homeostasis, but its role in A beta-induced microglia apoptosis is unknown. In this study, we found increased mitochondrial Ca2+ concentration in A beta-treated primary microglia and BV-2 cells; also, the MCU inhibitor Ru360 significantly attenuated A beta-induced microglial apoptosis, whereas the MCU activator spermine augmented it. In addition, Ru360 significantly attenuated A beta-induced mitochondrial reactive oxygen species (ROS) production, as well as endoplasmic reticulum (ER) stress characterized by glucose-regulated protein 78 (GRP78) and C/-EBP homologous protein (CHOP) expression. Spermine, however, exerted the opposite effects on mitochondrial ROS production and ER stress. We also found that mitochondria-targeted antioxidant (Mito-TEMPO) treatment decreased GRP78 and CHOP expression in A beta-treated microglia. Moreover, blocking endogenous CHOP expression using a CHOP small interfering RNA (siRNA) attenuated A beta-induced cell death. Altogether, our data suggested that 1) inhibition of MCU exerts a neuroprotective effect on A beta-induced microglia apoptosis, and 2) that the underlying mechanism may be related to reducing mitochondrial ROS-mediated ER stress. (C) 2017 Elsevier B.V. All rights reserved.