title: Discoidin domain receptor 2 mediates the collagen II-dependent release of interleukin-6 in primary human chondrocytes.
abstract: We deciphered constituent parts of a signal transduction cascade that is initiated by collagen II and results in the release of various pro-inflammatory cytokines, including interleukin-6 (IL-6), in primary human chondrocytes. This cascade represents a feed-forward mechanism whereby cartilage matrix degradation is exacerbated by the mutually inducing effect of released collagen II fragments and pro-inflammatory cytokines. We previously proposed discoidin domain receptor 2 as a central mediator in this event. Since this cascade plays a prominent role in the pathogenesis of osteoarthritis, our study further investigates the hypothesis that discoidin domain receptor 2 is a candidate receptor for collagen II, and that transcription factor NFkappaB, lipid kinase PI3K, and the MAP kinases are constituent parts of this very signal transduction cascade. To accomplish this, we selectively knocked down the molecules of interest in primary human chondrocytes, induced the specified cascade by incubating primary human chondrocytes with collagen II, and observed the outcome, specifically the changes in interleukin-6 release. Knockdown was performed by siRNA-mediated gene silencing in the case of discoidin domain receptor 2 (DDR2) or by using specific inhibitors for the remainder of the molecules. Results indicated that discoidin domain receptor 2 mediates the collagen II-dependent release of interleukin-6 in primary human chondrocytes and that MAP kinases p38, JNK and ERK, as well as transcription factor NFkappaB, are integral components of intracellular collagen II signalling. Given the detrimental role of these molecules in osteoarthritis, our findings provide new targets for more specific therapeutics, which may have fewer side effects than those currently applied.
authors.affiliation: Institute for Clinical Chemistry, University of Cologne, Germany. andreas.klatt@uk-koeln.de
authors.forename: Andreas R
authors.initials: AR
authors.lastname: Klatt
authors.forename: Dagmar
authors.initials: D
authors.lastname: Zech
authors.forename: Gertrud
authors.initials: G
authors.lastname: Kühn
authors.forename: Brigitte
authors.initials: B
authors.lastname: Paul-Klausch
authors.forename: Gabriele
authors.initials: G
authors.lastname: Klinger
authors.forename: Joerg H
authors.initials: JH
authors.lastname: Renno
authors.forename: Joachim
authors.initials: J
authors.lastname: Schmidt
authors.forename: Gebhart
authors.initials: G
authors.lastname: Malchau
authors.forename: Klaus
authors.initials: K
authors.lastname: Wielckens
mesh_terms: D000704:Analysis of Variance; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism*; D024043:Collagen Type II / Q000494:pharmacology; D000070818:Discoidin Domain Receptors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D015850:Interleukin-6 / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D007719:Knee Joint; D016328:NF-kappa B / Q000378:metabolism; D020370:Osteoarthritis, Knee / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011975:Receptors, Mitogen / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D024043:Collagen Type II; D004791:Enzyme Inhibitors; D015850:Interleukin-6; D016328:NF-kappa B; D034741:RNA, Small Interfering; D011975:Receptors, Mitogen; D000070818:Discoidin Domain Receptors; D020794:Receptor Protein-Tyrosine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases