title: Cyclo-oxygenase 2 expression impairs serum-withdrawal-induced apoptosis in liver cells.
abstract: We have investigated the mechanism of COX-2 (cyclo-oxygenase 2)-dependent inhibition of apoptosis in liver, a key pathway underlying proliferative actions of COX-2 in liver cancers, cirrhosis, chronic hepatitis C infection and regeneration after partial hepatectomy. Stable expression of COX-2 in CHL (Chang liver) cells induced proliferation, with an increase in the proportion of cells in S-phase, but no other significant changes in cell-cycle distribution. This was associated with a marked inhibition of the apoptotic response to serum deprivation, an effect mimicked by treating empty-vector-transfected control cells (CHL-V cells) with prostaglandin E2 and prevented in COX-2-expressing cells (CHL-C cells) treated with selective inhibitors of COX-2. Serum-deprived CHL-V cells displayed several indicators of activation of intrinsic apoptosis: caspases 9 and 3 activated within 6 h and caspase 8 within 18 h, Bax expression was induced, cytochrome c was released to the cytosol, and PARP-1 [poly(ADP-ribose) polymerase 1] cleavage was evident in nuclei. COX-2 expression blocked these events, concomitant with reduced expression of p53 and promotion of Akt phosphorylation, the latter indicating activation of survival pathways. CHL cells were resistant to stimulation of the extrinsic pathway with anti-Fas antibody. Moreover, in vivo expression of GFP (green fluorescent protein)-labelled COX-2 in mice by hydrodynamics-based transient transfection conferred resistance to caspase 3 activation and apoptosis induced by stimulation of Fas.
authors.affiliation: Centro de Investigaciones Biológicas (CSIC), Centro Nacional de Investigaciones Cardiovasculares, Melchor Fernández Almagro 3, 28029 Madrid, Spain.
authors.forename: Amalia
authors.initials: A
authors.lastname: Fernández-Martínez
authors.forename: Belén
authors.initials: B
authors.lastname: Mollá
authors.forename: Rafael
authors.initials: R
authors.lastname: Mayoral
authors.forename: Lisardo
authors.initials: L
authors.lastname: Boscá
authors.forename: Marta
authors.initials: M
authors.lastname: Casado
authors.forename: Paloma
authors.initials: P
authors.lastname: Martín-Sanz
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D015415:Biomarkers / Q000378:metabolism; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D022781:Hepatocytes / Q000201:enzymology*; D006801:Humans; D016196:S Phase / Q000502:physiology
chemical_list: D015415:Biomarkers; D051546:Cyclooxygenase 2