title: Differences in mitochondrial function in homogenated samples from healthy and epileptic specific brain tissues revealed by high-resolution respirometry.
abstract: Mitochondrial dysfunction and oxidative stress are strongly implicated in neurodegenerative diseases and epilepsy. Strikingly, neurodegenerative diseases show regional specificity in vulnerability and follow distinct patterns of neuronal loss. A challenge is to understand, why mitochondria fail in particular brain regions under specific pathological conditions. A potential explanation could be provided by regional or cellular specificity of mitochondrial function. We applied high-resolution respirometry to analyze the integrated Complex I- and II (CI and CII)-linked respiration, the activity of Complex IV, and the combined CI&II-linked oxidative phosphorylation (OXPHOS)- and electron-transfer system (ETS)-capacity in microsamples obtained from distinct regions of the mouse brain. We compared different approaches to assess mitochondrial density and suggest flux control ratios as a valid method to normalize respiration to mitochondrial density. This approach revealed significant differences of CI- and CII-linked OXPHOS capacity and coupling control between motor cortex, striatum, hippocampus and pons of naïve mice. CI-linked respiration was highest in motor cortex, while CII-linked respiration predominated in the striatum. To investigate if this method could also determine differences in normal and disease states within the same brain region, we compared hippocampal homogenates in a chronic epilepsy model. Three weeks after stereotaxic injection of kainate, there was a down-regulation of CI- and upregulation of CII-linked respiration in the resulting epileptic ipsilateral hippocampus compared to the contralateral one. In summary, respirometric OXPHOS analysis provides a very sensitive diagnostic approach using small amounts of distinct brain tissues. In a single assay, information is obtained on numerous OXPHOS parameters as indicators of tissue-specific mitochondrial performance.
authors.affiliation: Dept. Pharmacology, Medical University Innsbruck, Peter-Mayr-Str. 1a, 6020 Innsbruck, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Burtscher
authors.affiliation: Dept. Pharmacology, Medical University Innsbruck, Peter-Mayr-Str. 1a, 6020 Innsbruck, Austria.
authors.forename: Luca
authors.initials: L
authors.lastname: Zangrandi
authors.affiliation: Dept. Pharmacology, Medical University Innsbruck, Peter-Mayr-Str. 1a, 6020 Innsbruck, Austria. Electronic address: Schwarzer.Christoph@i-med.ac.at.
authors.forename: Christoph
authors.initials: C
authors.lastname: Schwarzer
authors.affiliation: D. Swarovski Research Laboratory, Department of Visceral, Transplant and Thoracic Surgery, Medical University Innsbruck, Anichstr. 35, 6020 Innsbruck, Austria; OROBOROS INSTRUMENTS, Schöpfstr. 18, 6020 Innsbruck, Austria. Electronic address: Erich.Gnaiger@i-med.ac.at.
authors.forename: Erich
authors.initials: E
authors.lastname: Gnaiger
mesh_terms: D000818:Animals; D001921:Brain / Q000473:pathology* / Q000502:physiology*; D019069:Cell Respiration; D004195:Disease Models, Animal; D004827:Epilepsy / Q000473:pathology*; D008297:Male; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism*; D010085:Oxidative Phosphorylation
keywords: Brain regions; Epilepsy; Mitochondria; Neurodegeneration; Respirometry