Interleukin-18 induces apoptosis in human articular chondrocytes.
Elevated levels of the pro-inflammatory cytokine, interleukin-18 (IL-18) have recently been demonstrated in osteoarthritic cartilage. However, the effects of IL-18 on chondrocyte signalling and matrix biosynthesis are poorly understood. Therefore, the present study was undertaken to further characterize the impact of IL-18 on human articular chondrocyte in vitro. Human articular chondrocytes were stimulated with various concentrations of recombinant human IL-18 (1, 10, 100 ng/ml) for 0, 4, 8, 12, 24, 48, 72 h in vitro. The effects of IL-18 on the cartilage-specific matrix protein collagen type II, the cytoskeletal protein vinculin, the cell matrix signal transduction receptor beta-integrin, key signalling proteins of the MAPKinase pathway (such as SHC (Sarc Homology Collagen) and activated MAPKinase [ERK-1/-2]), the pro-inflammatory enzyme cyclo-oxygenase-2 (COX-2) and the apoptosis marker activated caspase-3 were evaluated by Western blot analysis and immunofluorescence labelling. Morphological features of IL-18 stimulated chondrocytes were estimated by transmission electron microscopy. IL-18 lead to inhibition of collagen type II-deposition, decreased beta-integrin receptor and vinculin synthesis, SHC and MAPKinase activation, increased COX-2 synthesis and activation of caspase-3 in chondrocytes in a time- and dose-dependent manner. Furthermore, chondrocytes treated with IL-18 exhibited typical morphological features of apoptosis as revealed by transmission electron microscopy. Taken together, the results of the present study underline key catabolic events mediated by IL-18 signalling in chondrocytes such as loss of cartilage-specific matrix and apoptosis. Inhibition of MAPKinase signalling is hypothesized to contribute to these features. Future therapeutics targeting IL-18 signalling pathways may be beneficial in rheumatoid arthritis and osteoarthritis therapy.
John
T
T
Department of Trauma and Reconstructive Surgery, Charité University Medical School, Campus Benjamin Franklin, Berlin, Germany. thilo.john@charite.de
Kohl
B
B
Mobasheri
A
A
Ertel
W
W
Shakibaei
M
M
D000368:Aged; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D048430:Cell Shape / Q000187:drug effects; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D024043:Collagen Type II / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D039641:Integrin beta Chains / Q000378:metabolism; D020382:Interleukin-18 / Q000378:metabolism* / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D013997:Time Factors; D016596:Vinculin / Q000378:metabolism
D024043:Collagen Type II; D005353:Fibronectins; D039641:Integrin beta Chains; D020382:Interleukin-18; D008565:Membrane Proteins; C488955:VCL protein, human; D016596:Vinculin; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3