title: Mitochondria and calcium flux as targets of neuroprotection caused by minocycline in cerebellar granule cells.
abstract: Minocycline, an antibiotic of the tetracycline family, has attracted considerable interest for its theoretical therapeutic applications in neurodegenerative diseases. However, the mechanism of action underlying its effect remains elusive. Here we have studied the effect of minocycline under excitotoxic conditions. Fluorescence and bioluminescence imaging studies in rat cerebellar granular neuron cultures using fura2/AM and mitochondria-targeted aequorin revealed that minocycline, at concentrations higher than those shown to block inflammation and inflammation-induced neuronal death, inhibited NMDA-induced cytosolic and mitochondrial rises in Ca(2+) concentrations in a reversible manner. Moreover, minocycline added in the course of NMDA stimulation decreased Ca(2+) intracellular levels, but not when induced by depolarization with a high K(+) medium. We also found that minocycline, at the same concentrations, partially depolarized mitochondria by about 5-30 mV, prevented mitochondrial Ca(2+) uptake under conditions of environmental stress, and abrogated NMDA-induced reactive oxygen species (ROS) formation. Consistently, minocycline also abrogates the rise in ROS induced by 75 microM Ca(2+) in isolated brain mitochondria. In search for the mechanism of mitochondrial depolarization, we found that minocycline markedly inhibited state 3 respiration of rat brain mitochondria, although distinctly increased oxygen uptake in state 4. Minocycline inhibited NADH-cytochrome c reductase and cytochrome c oxidase activities, whereas the activity of succinate-cytochrome c reductase was not modified, suggesting selective inhibition of complexes I and IV. Finally, minocycline affected activity of voltage-dependent anion channel (VDAC) as determined in the reconstituted system. Taken together, our results indicate that mitochondria are a critical factor in minocycline-mediated neuroprotection.
authors.affiliation: Neurofarmacología, Dpto Ciencias Médicas, Facultad de Medicina, UCLM, Albacete, Spain.
authors.forename: Eva Maria
authors.initials: EM
authors.lastname: Garcia-Martinez
authors.forename: Sara
authors.initials: S
authors.lastname: Sanz-Blasco
authors.forename: Andonis
authors.initials: A
authors.lastname: Karachitos
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Bandez
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Fernandez-Gomez
authors.forename: Sergio
authors.initials: S
authors.lastname: Perez-Alvarez
authors.forename: Raquel Maria Melero Fernandez
authors.initials: RM
authors.lastname: de Mera
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Jordan
authors.forename: Norberto
authors.initials: N
authors.lastname: Aguirre
authors.forename: Maria F
authors.initials: MF
authors.lastname: Galindo
authors.forename: Carlos
authors.initials: C
authors.lastname: Villalobos
authors.forename: Ana
authors.initials: A
authors.lastname: Navarro
authors.forename: Hanna
authors.initials: H
authors.lastname: Kmita
authors.forename: Joaquín
authors.initials: J
authors.lastname: Jordán
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000187:drug effects* / Q000378:metabolism; D008911:Minocycline / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D018696:Neuroprotective Agents; D008911:Minocycline; D002118:Calcium