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Aims: Although iron overload induces oxidative stress and brain mitochondrial dysfunction, and is associated with neurodegenerative diseases, brain mitochondrial iron uptake has not been investigated. We determined the role of mitochondrial calcium uniporter (MCU) in brain mitochondria as a major route for iron entry. We hypothesized that iron overload causes brain mitochondrial dysfunction, and that the MCU blocker prevents iron entry into mitochondria, thus attenuating mitochondrial dysfunction., Main Methods: Isolated brain mitochondria from male Wistar rats were used. Iron (Fe(2+) and Fe(3+)) at 0-286 μM were applied onto mitochondria at various incubation times (5-30 min), and the mitochondrial function was determined. Effects of MCU blocker (Ru-360) and iron chelator were studied., Key Findings: Both Fe(2+) and Fe(3+) entered brain mitochondria and caused mitochondrial swelling in a dose- and time-dependent manner, and caused mitochondrial depolarization and increased ROS production. However, Fe(2+) caused more severe mitochondrial dysfunction than Fe(3+). Although all drugs attenuated mitochondrial dysfunction caused by iron overload, only an MCU blocker could completely prevent ROS production and mitochondrial depolarization., Significance: Our findings indicated that iron overload caused brain mitochondrial dysfunction, and that an MCU blocker effectively prevented this impairment, suggesting that MCU could be the major portal for brain mitochondrial iron uptake., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Aims: Since variety in response to Ca(2+)-induced mitochondrial dysfunction in different neuronal mitochondrial populations is associated with the pathogenesis of several neurological diseases, we investigated the effects of Ca(2+) overload on synaptic (SM) and nonsynaptic mitochondrial (NM) dysfunction and probed the effects of cyclosporin A (CsA), 4'-chlorodiazepam (CDP) and Ru360 on relieving mitochondrial damage., Main Methods: SM and NM mitochondria were isolated from rats' brains (n=5/group) and treated with various concentrations (5, 10, 100, and 200 μM) of Ca(2+), with and without CsA (mPTP blocker), CDP (PBR/TSPO blocker) and Ru360 (MCU blocker) pretreatments. Mitochondrial function was determined by mitochondrial swelling, ROS production and mitochondrial membrane potential changes (ΔΨm)., Key Findings: At 200-μM Ca(2+), SM presented mitochondrial swelling to a greater extent than NM. At 100 and 200-μM Ca(2+), the ROS production of SM was higher than that of NM and ΔΨm dissipation of SM was also larger. CsA, CDP and Ru360 could reduce ROS production of SM and NM with exposure to 200-μM Ca(2+). However, only Ru360 could completely inhibit ROS generation in both SM and NM, whereas CsA and CDP could only partially reduce the ROS level in SM. Moreover, CsA and CDP pretreatments were not able to restore ΔΨm. However, Ru360 pretreatment could protect ΔΨm dissipation in both SM and NM, with complete protection observed only in NM., Significance: Our findings suggested that mitochondrial calcium uniporter is a possible major pathway for calcium uptake in both mitochondrial populations. However, SM might have additional pathways involved in the calcium uptake., (Copyright © 2012 Elsevier Inc. All rights reserved.)