title: IFN-gamma prevents TNF-alpha-induced apoptosis in C2C12 myotubes through down-regulation of TNF-R2 and increased NF-kappaB activity.
abstract: Wasting of skeletal muscle (cachexia) is associated with a variety of chronic or inflammatory disorders and has long been recognized as a poor prognostic sign. It is currently accepted that the cytokine tumor necrosis factor alpha (TNF-alpha; cachectin) plays a key role in the development of this condition. TNF-alpha-induced apoptotic cell death represents a potential mechanism by which muscle wasting can occur. Evidence has accumulated that the cytokine interferon gamma (IFN-gamma) may act as a modulator of TNF-alpha signalling. Thus, the present study was designed to elucidate if TNF-alpha can directly induce apoptosis in differentiated myotubes, to assess the potential anti-apoptotic properties of IFN-gamma and to get insight into the signalling pathways implicated in the modulatory effects of IFN-gamma. Myoblasts of the murine cell line C2C12 were allowed to differentiate in a low serum containing media and myogenesis assessed by muscle specific protein expression. Non-proliferating, polynucleated, fully differentiated myotubes were obtained after seven days in differentiation media. Exposure of C2C12 myotubes to TNF-alpha for 48 h induced apoptosis characterized by enhanced caspase-3 activity, which resulted in poly(ADP-ribose) polymerase (PARP) cleavage and increased histone-associated-DNA fragmentation. These effects were fully reverted in the presence of IFN-gamma. This cytokine induced down-regulation of the subtype 2 of TNF-alpha receptors (TNF-R2), enhanced TNF-alpha-induced NF-kappaB translocation to the nucleus and binding to DNA and increased the immunoreactivity of the protein c-IAP1, a member of the inhibitor of apoptosis (IAP) gene family whose synthesis is stimulated by NF-kappaB at the transcriptional level. Together, these results demonstrate that TNF-alpha directly induces apoptosis in differentiated myotubes and suggest that the cytokine IFN-gamma, might represent a new immunoadjuvant therapeutic tool for managing cachexia.
authors.affiliation: Institut Universitari d'Investigacions en Ciències de la Salut/Departament de Biologia, Universitat de les Illes Balears, E-07122 Palma de Mallorca, Spain.
authors.forename: Laia
authors.initials: L
authors.lastname: Tolosa
authors.forename: Montse
authors.initials: M
authors.lastname: Morlá
authors.forename: Amanda
authors.initials: A
authors.lastname: Iglesias
authors.forename: Xavier
authors.initials: X
authors.lastname: Busquets
authors.forename: Jerònia
authors.initials: J
authors.lastname: Lladó
authors.forename: Gabriel
authors.initials: G
authors.lastname: Olmos
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D015536:Down-Regulation; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology / Q000502:physiology*; D051379:Mice; D024510:Muscle Development; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism*; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism*; D011994:Recombinant Proteins; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
chemical_list: D051034:Inhibitor of Apoptosis Proteins; D016328:NF-kappa B; D047889:Receptors, Tumor Necrosis Factor, Type II; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D011065:Poly(ADP-ribose) Polymerases; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases