title: Mitochondrial redox and pH signaling occurs in axonal and synaptic organelle clusters.
abstract: Redox switches are important mediators in neoplastic, cardiovascular and neurological disorders. We recently identified spontaneous redox signals in neurons at the single mitochondrion level where transients of glutathione oxidation go along with shortening and re-elongation of the organelle. We now have developed advanced image and signal-processing methods to re-assess and extend previously obtained data. Here we analyze redox and pH signals of entire mitochondrial populations. In total, we quantified the effects of 628 redox and pH events in 1797 mitochondria from intercostal axons and neuromuscular synapses using optical sensors (mito-Grx1-roGFP2; mito-SypHer). We show that neuronal mitochondria can undergo multiple redox cycles exhibiting markedly different signal characteristics compared to single redox events. Redox and pH events occur more often in mitochondrial clusters (medium cluster size: 34.1 ± 4.8 μm(2)). Local clusters possess higher mitochondrial densities than the rest of the axon, suggesting morphological and functional inter-mitochondrial coupling. We find that cluster formation is redox sensitive and can be blocked by the antioxidant MitoQ. In a nerve crush paradigm, mitochondrial clusters form sequentially adjacent to the lesion site and oxidation spreads between mitochondria. Our methodology combines optical bioenergetics and advanced signal processing and allows quantitative assessment of entire mitochondrial populations.
authors.affiliation: Department of Neuroradiology, University of Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.
authors.forename: Michael O
authors.initials: MO
authors.lastname: Breckwoldt
authors.affiliation: Cardiovascular Research Center, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, USA.
authors.forename: Antonis A
authors.initials: AA
authors.lastname: Armoundas
authors.affiliation: Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, MD, USA.|Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD, USA.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Aon
authors.affiliation: Department of Neuroradiology, University of Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bendszus
authors.affiliation: Division of Cardiology, Department of Medicine, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: O'Rourke
authors.affiliation: Institute of Crop Science and Resource Conservation (INRES), University of Bonn, Friedrich-Ebert-Allee 144, 53113 Bonn, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Schwarzländer
authors.affiliation: Division of Redox Regulation, German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
authors.forename: Tobias P
authors.initials: TP
authors.lastname: Dick
authors.affiliation: Department of Neuroradiology, University of Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.|Cardiovascular Research Center, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, USA.
authors.forename: Felix T
authors.initials: FT
authors.lastname: Kurz
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D015388:Organelles / Q000378:metabolism*; D010084:Oxidation-Reduction; D015398:Signal Transduction; D013569:Synapses / Q000378:metabolism*