title: Adenosine 5'-triphosphate, uridine 5'-triphosphate, bradykinin, and lysophosphatidic acid induce different patterns of calcium responses by human articular chondrocytes.
abstract: Small calcium-mobilizing inflammatory mediators have been implicated in joint pathology. Here we demonstrate that bradykinin, adenosine 5'-triphosphate, uridine 5'-triphosphate, and lysophosphatidic acid raise the intracellular calcium concentration ([Ca2+]i) in human articular chondrocytes. Heterologous cross-desensitization experiments showed that the uridine 5'-triphosphate response was abolished by prior treatment with adenosine 5'-triphosphate and, conversely, that the adenosine 5'-triphosphate response was abolished by prior treatment with uridine 5'-triphosphate; this indicated competition for the same receptor site, whereas bradykinin and lysophosphatidic acid did not compete with other ligands. Pretreatment with thapsigargin abolished ligand-mediated Ca2+ responses but not vice versa; this confirmed that Ca2+ release occurred from intracellular stores. Single-cell analysis of Fura-2 acetoxymethyl ester loaded chondrocytes showed mediator-dependent patterns of oscillatory Ca2+ changes in a subset of cells when challenged with submaximal concentrations of bradykinin, adenosine 5'-triphosphate, or uridine 5'-triphosphate in the presence of extracellular Ca2+. However, no oscillatory responses were seen after a challenge with lysophosphatidic acid. Therefore, although a number of different Ca2+-mobilizing ligands activate chondrocytes, the differences that occur in the temporal patterning of Ca2+ responses may result in unique mediator-dependent changes in cellular activity.
authors.affiliation: Department of Veterinary Medicine: Anatomy, Physiology, and Cell Biology, University of California at Davis, 95616, USA.
authors.forename: M
authors.initials: M
authors.lastname: Koolpe
authors.forename: J J
authors.initials: JJ
authors.lastname: Rodrigo
authors.forename: H P
authors.initials: HP
authors.lastname: Benton
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000819:agonists; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism; D019902:Chondrocytes / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D008024:Ligands; D008246:Lysophospholipids / Q000494:pharmacology*; D058913:Purinergic Agonists; D011956:Receptors, Cell Surface / Q000819:agonists; D011994:Recombinant Proteins / Q000494:pharmacology; D013110:Sphingosine / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology*
chemical_list: D002135:Calcium-Binding Proteins; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007375:Interleukin-1; D008024:Ligands; D008246:Lysophospholipids; D058913:Purinergic Agonists; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D019311:Staurosporine; D013110:Sphingosine; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2; D014544:Uridine Triphosphate