A Beta And Nmdar Activation Cause Mitochondrial Dysfunction Involving Er Calcium Release

Early cognitive deficits in Alzheimer's disease (AD) seem to be correlated to dysregulation of glutamate receptors evoked by amyloid-beta (A beta) peptide. A beta interference with the activity of N-methyl-D-aspartate receptors (NMDARs) may be a relevant factor for A beta-induced mitochondrial toxicity and neuronal dysfunction. To evaluate the role of mitochondria in NMDARs activation mediated by A beta, we followed in situ single-cell simultaneous measurement of cytosolic free Ca2+ (Ca-i(2+)) and mitochondrial membrane potential in primary cortical neurons. Our results show that direct exposure to A beta + NMDA largely increased Ca-i(2+) and induced immediate mitochondrial depolarization, compared with A beta or NMDA alone. Mitochondrial depolarization induced by rotenone strongly inhibited the rise in Ca-i(2+) evoked by A beta or NMDA, suggesting that mitochondria control Ca2+ entry through NMDARs. However, incubation with rotenone did not preclude mitochondrial Ca2+ (mitCa(2+)) retention in cells treated with A beta. A beta-induced Ca-i(2+) and mitCa(2+) rise were inhibited by ifenprodil, an antagonist of GluN2B-containing NMDARs. Exposure to A beta + NMDA further evoked a higher mitCa(2+) retention, which was ameliorated in GluN2B(-/-) cortical neurons, largely implicating the involvement of this NMDAR subunit. Moreover, pharmacologic inhibition of endoplasmic reticulum (ER) inositol-1,4,5-triphosphate receptor (IP3R) and mitCa(2+) uniporter (MCU) evidenced that A beta + NMDA-induced mitCa(2+) rise involves ER Ca2+ release through IP3R and mitochondrial entry by the MCU. Altogether, data highlight mitCa(2+) dyshomeostasis and subsequent dysfunction as mechanisms relevant for early neuronal dysfunction in AD linked to A beta-mediated GluN2B-composed NMDARs activation. (C) 2015 Elsevier Inc. All rights reserved.