title: NFkappaB-mediated upregulation of bcl-xl restrains TRAIL-mediated apoptosis in murine viral hepatitis.
abstract: Inhibition of NFkappaB enhances the susceptibility of cancer to TRAIL-mediated apoptosis and is suggested as a strategy for cancer therapy. Because the role of NFkappaB in TRAIL-mediated apoptosis of hepatocytes is unknown, we investigated the influence of NFkappaB-inhibition in death ligand-mediated apoptosis in hepatitis. Adenoviral hepatitis resulted in upregulation of NFkappaB-activity, which could be inhibited by expression of IkappaBalpha-superrepressor. We treated mice after the onset of adenoviral hepatitis with adenoviruses expressing FasL (AdFasL), TRAIL (AdTRAIL), or GFP (AdGFP). In contrast to apoptosis induced by AdFasL, NFkappaB inhibition strongly enhanced AdTRAIL-mediated apoptosis of hepatocytes. Expression of IkappaBalpha inhibits adenoviral infection-mediated overexpression of bcl-xl, providing a molecular mechanism for TRAIL sensitization. In agreement with this hypothesis, downregulation of bcl-xl by siRNA enhanced susceptibility of hepatocytes to TRAIL, but not to FasL-mediated apoptosis, resulting in TRAIL-mediated severe liver damage after AdTRAIL application. Our data demonstrate that inhibition of NFkappaB in adenoviral hepatitis strongly sensitizes hepatocytes to TRAIL-mediated apoptosis. Bcl-xl, in contrast to bcl-2 and c-FLIP, is strongly upregulated after viral infection and represents an essential NFkappaB-dependent survival factor against TRAIL-mediated apoptosis. In conclusion, inhibition of NFkappaB or bcl-xl during TRAIL therapy may harbor a risk of liver damage in patients with viral hepatitis.
authors.affiliation: Department of Gastroenterology, Hepatology and Endocrinology, Medizinische Hochschule Hannover, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Zender
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hütker
authors.forename: Bettina
authors.initials: B
authors.lastname: Mundt
authors.forename: Morlen
authors.initials: M
authors.lastname: Waltemathe
authors.forename: Christian
authors.initials: C
authors.lastname: Klein
authors.forename: Christian
authors.initials: C
authors.lastname: Trautwein
authors.forename: Nisar P
authors.initials: NP
authors.lastname: Malek
authors.forename: Michael Peter
authors.initials: MP
authors.lastname: Manns
authors.forename: Florian
authors.initials: F
authors.lastname: Kühnel
authors.forename: Stefan
authors.initials: S
authors.lastname: Kubicka
mesh_terms: D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D002460:Cell Line; D053222:Fas Ligand Protein; D006524:Hepatitis, Viral, Animal / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D015854:Up-Regulation; D051020:bcl-X Protein
chemical_list: D051017:Apoptosis Regulatory Proteins; C494811:BCL2L1 protein, human; C494812:Bcl2l1 protein, mouse; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; C505654:Tnfsf10 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D051020:bcl-X Protein