title: Mouse hepatic oval cells require Met-dependent PI3K to impair TGF-β-induced oxidative stress and apoptosis.
abstract: We have previously shown that oval cells harboring a genetically inactivated Met tyrosine kinase (Met(-/-) oval cells) are more sensitive to TGF-β-induced apoptosis than cells expressing a functional Met (Met(flx/flx)), demonstrating that the HGF/Met axis plays a pivotal role in oval cell survival. Here, we have examined the mechanism behind this effect and have found that TGF-β induced a mitochondria-dependent apoptotic cell death in Met(flx/flx) and Met(-/-) oval cells, associated with a marked increase in levels of the BH3-only proteins Bim and Bmf. Bmf plays a key role during TGF-β-mediated apoptosis since knocking down of BMF significantly diminished the apoptotic response in Met(-/-) oval cells. TGF-β also induced oxidative stress accompanied by NADPH oxidase 4 (Nox4) mRNA up-regulation and decreased protein levels of antioxidant enzymes. Antioxidants inhibit both TGF-β-induced caspase 3 activity and Bmf up-regulation, revealing an oxidative stress-dependent Bmf regulation by TGF-β. Notably, oxidative stress-related events were strongly amplified in Met(-/-) oval cells, emphasizing the critical role of Met in promoting survival. Pharmacological inhibition of PI3K did impair HGF-driven protection from TGF-β-induced apoptosis and increased sensitivity of Met(flx/flx) oval cells to TGF-ß by enhancing oxidative stress, reaching apoptotic indices similar to those obtained in Met(-/-) oval cells. Interestingly, both PI3K inhibition and/or knockdown itself resulted in caspase-3 activation and loss of viability in Met(flx/flx) oval cells, whereas no effect was observed in Met(-/-) oval cells. Altogether, results presented here provide solid evidences that both paracrine and autocrine HGF/Met signaling requires PI3K to promote mouse hepatic oval cell survival against TGF-β-induced oxidative stress and apoptosis.
authors.affiliation: Dep Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, IdISSC, Madrid, Spain.
authors.forename: Adoración
authors.initials: A
authors.lastname: Martínez-Palacián
authors.forename: Gaelle
authors.initials: G
authors.lastname: del Castillo
authors.forename: Amileth
authors.initials: A
authors.lastname: Suárez-Causado
authors.forename: María
authors.initials: M
authors.lastname: García-Álvaro
authors.forename: Diego
authors.initials: D
authors.lastname: de Morena-Frutos
authors.forename: Margarita
authors.initials: M
authors.lastname: Fernández
authors.forename: Cesáreo
authors.initials: C
authors.lastname: Roncero
authors.forename: Isabel
authors.initials: I
authors.lastname: Fabregat
authors.forename: Blanca
authors.initials: B
authors.lastname: Herrera
authors.forename: Aránzazu
authors.initials: A
authors.lastname: Sánchez
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D005978:Glutathione / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000378:metabolism; D022781:Hepatocytes / Q000166:cytology*; D008564:Membrane Potentials; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D018384:Oxidative Stress; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010718:Phosphatidylserines / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D010718:Phosphatidylserines; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D016212:Transforming Growth Factor beta; D017228:Hepatocyte Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D019859:Proto-Oncogene Proteins c-met; C505409:Casp3 protein, mouse; D053148:Caspase 3; D005978:Glutathione