title: Differential regulation of IL-6 and TNF-alpha via calcineurin in human skeletal muscle cells.
abstract: Interleukin-6 increases in skeletal muscle during exercise, and evidence points to Ca2+ as an initiator of IL-6 production. However, the signalling pathway whereby this occurs is unknown. One candidate for Ca2+ -mediated IL-6 induction is calcineurin, an activator of NF-AT. Here we investigated whether skeletal myocytes produce IL-6 in a Ca2+/calcineurin-dependent manner, and whether TNF-alpha, an inducer of IL-6, is affected by these stimuli. Human skeletal muscle cell cultures were stimulated with ionomycin time-and dose-dependently to elevate intracellular Ca2+ levels, with or without addition of cyclosporin A (CSA); a calcineurin inhibitor. mRNA was extracted from myocytes and analysed for IL-6 and TNF-alpha gene expression. IL-6 mRNA increased time- and dose-dependently with ionomycin stimulation, an effect that was blunted by approximately 75% in the presence of CSA. In contrast, TNF-alpha gene expression was decreased by approximately 70% in response to ionomycin treatment, but increased in response to addition of CSA. These data demonstrate that IL-6 and TNF-alpha are regulated differentially in skeletal muscle cells in response to a Ca2+ stimulus. Blocking the calcineurin pathway resulted in inhibition of the IL-6 response to ionomycin, whereas TNF-alpha increased by addition of CSA, further indicating a differential regulation of IL-6 and TNF-alpha in human skeletal myocytes.
authors.affiliation: Centre of Inflammation and Metabolism, Department of Infectious Diseases and the Copenhagen Muscle Research Centre, Faculty of Health Sciences, University Hospital of Copenhagen, Tagensvej 20, 2200 Copenhagen N, Denmark. ckeller@inflammation-metabolism.dk
authors.forename: Charlotte
authors.initials: C
authors.lastname: Keller
authors.forename: Ylva
authors.initials: Y
authors.lastname: Hellsten
authors.forename: Adam
authors.initials: A
authors.lastname: Steensberg
authors.forename: Bente Klarlund
authors.initials: BK
authors.lastname: Pedersen
mesh_terms: D019703:Calcineurin / Q000378:metabolism*; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics*; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*
chemical_list: D015850:Interleukin-6; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D015759:Ionomycin; D016572:Cyclosporine; C120817:calcineurin phosphatase; D019703:Calcineurin; D010744:Phosphoric Monoester Hydrolases