title: Inflammatory cytokines inhibit myogenic differentiation through activation of nuclear factor-kappaB.
abstract: Muscle wasting is often associated with chronic inflammation. Because tumor necrosis factor alpha (TNF-alpha) has been implicated as a major mediator of cachexia, its effects on C2C12 myocytes were examined. TNF-alpha activated nuclear factor-kappaB (NF-kappaB) and interfered with the expression of muscle proteins in differentiating myoblasts. Introduction of a mutant form of inhibitory protein kappaBalpha (IkappaBalpha) restored myogenic differentiation in myoblasts treated with TNF-alpha or interleukin 1beta. Conversely, activation of NF-kappaB by overexpression of IkappaB kinase was sufficient to block myogenesis, illustrating the causal link between NF-kappaB activation and inhibition of myogenic differentiation. The inhibitory effects of TNF-alpha on myogenic differentiation were reversible, indicating that the effects of the cytokine were not due to nonspecific toxicity. Treatment of differentiated myotubes with TNF-alpha did not result in a striking loss of muscle-specific proteins, which shows that myogenesis was selectively affected in the myoblast stage by TNF-alpha. An important finding was that NF-kappaB was activated to the same extent in differentiating and differentiated cells, illustrating that once myocytes have differentiated they become refractory to the effects of NF-kappaB activation. These results demonstrate that inflammatory cytokines may contribute to muscle wasting through the inhibition of myogenic differentiation via a NF-kappaB-dependent pathway.
authors.affiliation: Department of Pulmonology, Maastricht University, Maastricht, The Netherlands.
authors.forename: R C
authors.initials: RC
authors.lastname: Langen
authors.forename: A M
authors.initials: AM
authors.lastname: Schols
authors.forename: M C
authors.initials: MC
authors.lastname: Kelders
authors.forename: E F
authors.initials: EF
authors.lastname: Wouters
authors.forename: Y M
authors.initials: YM
authors.lastname: Janssen-Heininger
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D002100:Cachexia / Q000503:physiopathology; D016923:Cell Death; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology; D002460:Cell Line; D048429:Cell Size; D003402:Creatine Kinase / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015533:Transcriptional Activation; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D004268:DNA-Binding Proteins; D007375:Interleukin-1; D016328:NF-kappa B; D011993:Recombinant Fusion Proteins; D014409:Tumor Necrosis Factor-alpha; D003402:Creatine Kinase