title: IL-6 protects against hyperoxia-induced mitochondrial damage via Bcl-2-induced Bak interactions with mitofusins.
abstract: Overexpression of IL-6 markedly diminishes hyperoxic lung injury, hyperoxia-induced cell death, and DNA fragmentation, and enhances Bcl-2 expression. We hypothesized that changes in the interactions between Bcl-2 family members play an important role in the IL-6-mediated protective response to oxidative stress. Consistent with this hypothesis, we found that IL-6 induced Bcl-2 expression, both in vivo and in vitro, disrupted interactions between proapoptotic and antiapoptotic factors, and suppressed H(2)O(2)-induced loss of mitochondrial membrane potential in vitro. In addition, IL-6 overexpression in mice protects against hyperoxia-induced lung mitochondrial damage. The overexpression of Bcl-2 in vivo prolonged the survival of mice exposed to hyperoxia and inhibited alveolar capillary protein leakage. In addition, apoptosis-associated DNA fragmentation was substantially reduced in these animals. This IL-6-mediated protection was lost when Bcl-2 was silenced, demonstrating that Bcl-2 is an essential mediator of IL-6 cytoprotection. Finally, Bcl-2 blocked the dissociation of Bak from mitofusin protein (Mfn) 2, and inhibited the interaction between Bak and Mfn1. Taken together, our results suggest that IL-6 induces Bcl-2 expression to perform cytoprotective functions in response to oxygen toxicity, and that this effect is mediated by alterations in the interactions between Bak and Mfns.
authors.affiliation: Pulmonary Critical Care Unit, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Bulfinch 148, Boston, MA 02114, USA. abwaxman@partners.org.
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Waxman
authors.forename: Narasaiah
authors.initials: N
authors.lastname: Kolliputi
mesh_terms: D055371:Acute Lung Injury / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006801:Humans; D018496:Hyperoxia / Q000188:drug therapy* / Q000503:physiopathology; D015850:Interleukin-6 / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D015227:Lipid Peroxidation / Q000187:drug effects; D008168:Lung / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D010100:Oxygen / Q000633:toxicity*; D025941:Protein Interaction Mapping; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C494772:BAK1 protein, human; C494773:Bak1 protein, mouse; C508600:IL6 protein, human; D015850:Interleukin-6; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D050998:bcl-2 Homologous Antagonist-Killer Protein; D020558:GTP Phosphohydrolases; C470018:MFN2 protein, human; C488750:Mfn1 protein, mouse; C488751:Mfn2 protein, mouse; C470017:Mfn1 protein, human; D010100:Oxygen