title: A single exposure to hyperbaric oxygen increases levels of circulating nucleosomes but does not induce mononuclear cell apoptosis in divers.
abstract: Recent reports that hyperbaric oxygenation (HBO2) induced apoptosis in T-cell lines raised concern about a possible immunosuppressive effect of HBO2. Nucleosomes, DNA fragments wrapped around a histone core, have been observed in the circulation in diseases with increased cell death such as sepsis. Our aim was to investigate, whether HBO2 increases circulating nucleosomes as a marker of cell death and induces apoptosis of peripheral blood mononuclear cells in vivo. After informed consent 29 healthy volunteers were exposed to a 30 minute dive at 2.8 atmospheres absolute in a pressure chamber under resting conditions, while breathing 100% oxygen. Samples were obtained before and 24 hours after exposure. Circulating nucleosomes were measured in serum. Caspase-3 activation, Bcl-2 expression and mRNA of Bcl-2, Bcl-xl and Bax were analyzed in mononuclear cell extracts. Nucleosomes were elevated markedly 24h after exposure (p<0.01), while caspase-3 was not activated significantly. mRNA levels of Bcl-2, Bcl-xl and Bax were not altered. In conclusion, while evidence of elevated levels of circulating nucleosomes was found, mononuclear cell apoptosis was not affected by a single exposure to hyperbaric oxygen.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University of Bonn Medical Center, Bonn, Germany.
authors.forename: S U
authors.initials: SU
authors.lastname: Weber
authors.forename: A
authors.initials: A
authors.lastname: Koch
authors.forename: U
authors.initials: U
authors.lastname: Siekmann
authors.forename: C
authors.initials: C
authors.lastname: Neitzel
authors.forename: F
authors.initials: F
authors.lastname: Stüber
authors.forename: A
authors.initials: A
authors.lastname: Hoeft
authors.forename: S
authors.initials: S
authors.lastname: Schröder
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000276:immunology / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D006931:Hyperbaric Oxygenation / Q000009:adverse effects*; D007963:Leukocytes, Mononuclear / Q000502:physiology*; D008297:Male; D009707:Nucleosomes / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D011446:Prospective Studies; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D055815:Young Adult; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D009707:Nucleosomes; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D053148:Caspase 3