title: Octacalcium phosphate crystals directly stimulate expression of inducible nitric oxide synthase through p38 and JNK mitogen-activated protein kinases in articular chondrocytes.
abstract: Basic calcium phosphate (BCP) crystals, including hydroxyapatite, octacalcium phosphate (OCP) and carbonate-apatite, have been associated with severe osteoarthritis and several degenerative arthropathies. Most studies have considered the chondrocyte to be a bystander in the pathogenesis of calcium crystal deposition disease, assuming that synovial cell cytokines were the only triggers of chondrocyte activation. In the present study we identified direct activation of articular chondrocytes by OCP crystals, which are the BCP crystals with the greatest potential for inducing inflammation. OCP crystals induced nitric oxide (NO) production and inducible nitric oxide synthase (NOS) mRNA expression by isolated articular chondrocytes and cartilage fragments, in a dose-dependent manner and with variations over time. OCP crystals also induced IL-1beta mRNA expression. Using pharmacological and cytokine inhibitors, we observed that OCP crystals induced NO production and inducible NOS mRNA activation were regulated at both the transcriptional and the translational levels; were independent from IL-1beta gene activation; and involved p38 and c-Jun amino-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) pathways, as further confirmed by OCP crystal-induced p38 and JNK MAPK phosphorylation. Taken together, our data suggest that the transcriptional inducible NOS response to OCP crystals involved both the p38 and the JNK MAPK pathways, probably under the control of activator protein-1. NO, a major mediator of cartilage degradation, can be directly produced by BCP crystals in chondrocytes. Together with synovial activation, this direct mechanism may be important in the pathogenesis of destructive arthropathies triggered by microcrystals.
authors.affiliation: INSERM U606, Centre Viggo Petersen, Hôpital Lariboisière, Paris, France. korng.ea@free.fr
authors.forename: Hang-Korng
authors.initials: HK
authors.lastname: Ea
authors.forename: Benjamin
authors.initials: B
authors.lastname: Uzan
authors.forename: Christian
authors.initials: C
authors.lastname: Rey
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lioté
mesh_terms: D000818:Animals; D002130:Calcium Phosphates / Q000494:pharmacology*; D002358:Cartilage, Articular / Q000166:cytology*; D002417:Cattle; D002478:Cells, Cultured / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D019902:Chondrocytes / Q000187:drug effects* / Q000201:enzymology; D003460:Crystallization; D004790:Enzyme Induction / Q000187:drug effects; D005419:Flavonoids / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007375:Interleukin-1 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000502:physiology; D048056:Mitogen-Activated Protein Kinase 9 / Q000037:antagonists & inhibitors / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D009924:Organ Culture Techniques; D014176:Protein Biosynthesis / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D002130:Calcium Phosphates; D005419:Flavonoids; D007093:Imidazoles; D007375:Interleukin-1; D011725:Pyridines; D012333:RNA, Messenger; C022045:octacalcium phosphate; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D048056:Mitogen-Activated Protein Kinase 9; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D019331:NG-Nitroarginine Methyl Ester