title: Tumour necrosis factor activates the mitogen-activated protein kinases p38alpha and ERK in the synovial membrane in vivo.
abstract: Tumour necrosis factor (TNF) is considered to be a major factor in chronic synovial inflammation and is an inducer of mitogen-activated protein kinase (MAPK) signalling. In the present study we investigated the ability of TNF to activate MAPKs in the synovial membrane in vivo. We studied human TNF transgenic mice--an in vivo model of TNF-induced arthritis--to examine phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun amino terminal kinase (JNK) and p38MAPKalpha in the inflamed joints by means of immunoblot and immunohistochemistry. In addition, the effects of systemic blockade of TNF, IL-1 and receptor activator of nuclear factor-kappaB (RANK) ligand on the activation of MAPKs were assessed. In vivo, overexpression of TNF induced activation of p38MAPKalpha and ERK in the synovial membrane, whereas activation of JNK was less pronounced and rarely observed on immunohistochemical analysis. Activated p38MAPKalpha was predominantly found in synovial macrophages, whereas ERK activation was present in both synovial macrophages and fibroblasts. T and B lymphocytes did not exhibit major activation of any of the three MAPKs. Systemic blockade of TNF reduced activation of p38MAPKalpha and ERK, whereas inhibition of IL-1 only affected p38MAPKalpha and blockade of RANK ligand did not result in any decrease in MAPK activation in the synovial membrane. These data indicate that TNF preferentially activates p38MAPKalpha and ERK in synovial membrane exposed to TNF. This not only suggests that targeted inhibition of p38MAPKalpha and ERK is a feasible strategy for blocking TNF-mediated effects on joints, but it also shows that even currently available methods to block TNF effectively reduce activation of these two MAPKs.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine III, University of Vienna, Vienna, Austria.
authors.forename: Birgit
authors.initials: B
authors.lastname: Görtz
authors.forename: Silvia
authors.initials: S
authors.lastname: Hayer
authors.forename: Birgit
authors.initials: B
authors.lastname: Tuerck
authors.forename: Jochen
authors.initials: J
authors.lastname: Zwerina
authors.forename: Josef S
authors.initials: JS
authors.lastname: Smolen
authors.forename: Georg
authors.initials: G
authors.lastname: Schett
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001168:Arthritis / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005347:Fibroblasts / Q000201:enzymology; D006023:Glycoproteins / Q000627:therapeutic use; D006801:Humans; D000069285:Infliximab; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000037:antagonists & inhibitors; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008264:Macrophages / Q000201:enzymology; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D048308:Mitogen-Activated Protein Kinase 14 / Q000378:metabolism*; D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000627:therapeutic use; D018124:Receptors, Tumor Necrosis Factor / Q000627:therapeutic use; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012795:Sialoglycoproteins / Q000627:therapeutic use; D013583:Synovial Membrane / Q000201:enzymology*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*
chemical_list: D000911:Antibodies, Monoclonal; D018501:Antirheumatic Agents; D002352:Carrier Proteins; D006023:Glycoproteins; C507763:IL1RN protein, human; C507764:Il1rn protein, mouse; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D008562:Membrane Glycoproteins; D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; D011993:Recombinant Fusion Proteins; D012795:Sialoglycoproteins; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab; D048049:Extracellular Signal-Regulated MAP Kinases; D048308:Mitogen-Activated Protein Kinase 14; D048670:MAP Kinase Kinase 4