title: Hypoxia-induced generation of methane in mitochondria and eukaryotic cells: an alternative approach to methanogenesis.
abstract: OBJECTIVE
  Electrophilic methyl groups bound to positively charged nitrogen moieties may act as electron acceptors, and this mechanism could lead to the generation of methane from choline. The aims were to characterize the methanogenic potential of phosphatidylcholine metabolites, and to define the in vivo relevance of this pathway in hypoxia-induced cellular responses.
  
  
  METHODS
  The postulated reaction was investigated (1) in model chemical experiments, (2) in rat mitochondrial subfractions and (3) in bovine endothelial cell cultures under hypoxic conditions and in the presence of hydroxyl radical generation. The rate of methane formation was determined by gas chromatography with flame-ionisation detectors. The lucigenin-enhanced chemiluminescence assay was used to determine the reactive oxygen species-scavenging capacity of the choline metabolites.
  
  
  RESULTS
  Significant methane generation was demonstrated in all three series of experiments. Phosphatidylcholine metabolites with alcoholic moiety in the molecule (i.e. choline, N,N-dimethylethanolamine and N-methylethanolamine), inhibited oxygen radical production both in vitro and in vivo, and displayed an effectiveness proportional to the amount of methane generated and the number of methyl groups in the compounds.
  
  
  CONCLUSIONS
  Methane generation occurs in aerobic systems. Phosphatidylcholine metabolites containing both electron donor and acceptor groups may have a function to counteract intracellular oxygen radical production.
authors.affiliation: Cologne, Germany.
authors.forename: Miklós
authors.initials: M
authors.lastname: Ghyczy
authors.forename: Csilla
authors.initials: C
authors.lastname: Torday
authors.forename: József
authors.initials: J
authors.lastname: Kaszaki
authors.forename: Andrea
authors.initials: A
authors.lastname: Szabó
authors.forename: Miklós
authors.initials: M
authors.lastname: Czóbel
authors.forename: Mihály
authors.initials: M
authors.lastname: Boros
mesh_terms: D000818:Animals; D002417:Cattle; D015687:Cell Hypoxia / Q000187:drug effects; D002478:Cells, Cultured; D002794:Choline / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D004285:Dogs; D004579:Electron Transport / Q000187:drug effects; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D005057:Eukaryotic Cells / Q000187:drug effects / Q000378:metabolism*; D006098:Granulocytes / Q000187:drug effects / Q000378:metabolism; D008163:Luminescent Measurements; D008697:Methane / Q000096:biosynthesis*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D051381:Rats; D013367:Submitochondrial Particles / Q000187:drug effects / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D045304:Cytochromes c; D002794:Choline; D013755:Tetradecanoylphorbol Acetate; D008697:Methane