Proline-rich tyrosine kinase 2 and Src kinase signaling transduce monosodium urate crystal-induced nitric oxide production and matrix metalloproteinase 3 expression in chondrocytes.
OBJECTIVE
Articular deposition of monosodium urate monohydrate (MSU) crystals may promote cartilage and bone erosion. Therefore, the aim of this study was to determine how MSU crystals stimulate chondrocytes.


METHODS
Nitric oxide (NO) release, and expression of inducible nitric oxide synthase (iNOS) and matrix metalloproteinase 3 (MMP-3) were assessed in cultured chondrocytes treated with MSU. MSU-induced functional signaling by specific protein kinases (p38, Src, and the focal adhesion kinase [FAK] family members proline-rich tyrosine kinase 2 [Pyk-2] and FAK) was also examined using selective pharmacologic inhibitors and transfection of kinase mutants.


RESULTS
MSU induced MMP-3 and iNOS expression and NO release in chondrocytes in a p38-dependent manner that did not require interleukin-1 (IL-1), as demonstrated by using IL-1 receptor antagonist. MSU induced rapid tyrosine phosphorylation of Pyk-2 and FAK, their adaptor protein paxillin, and interacting kinase c-Src. Pyk-2 and c-Src signaling both mediated p38 MAPK activation in response to MSU. Pyk-2 and c-Src signaling played a major role in transducing MSU-induced NO production and MMP-3 expression. But, despite the observed FAK phosphorylation, a selective pharmacologic FAK inhibitor and a FAK dominant-negative mutant both failed to block MSU-induced NO release or MMP-3 expression in parallel experiments.


CONCLUSIONS
In chondrocytes, MSU crystals activate a signaling kinase cascade typically employed by adhesion receptors that involves upstream Src and FAK family activation and downstream p38 activation. In this cascade, Pyk-2, Src, and p38 kinases transduce MSU-induced NO production and MMP-3 expression. Our results identify Pyk-2 and c-Src as novel sites for potential therapeutic intervention in cartilage degradation in chronic gout.
Liu
Ru
R
VA Medical Center and University of California, San Diego, CA 92161, USA.
Lioté
Frédéric
F
Rose
David M
DM
Merz
Denise
D
Terkeltaub
Robert
R
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000201:enzymology*; D003460:Crystallization; D051418:Focal Adhesion Kinase 2; D051416:Focal Adhesion Protein-Tyrosine Kinases; D015971:Gene Expression Regulation, Enzymologic; D019278:Matrix Metalloproteinase 3 / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014527:Uric Acid / Q000737:chemistry / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases; D019061:src-Family Kinases / Q000378:metabolism*
D014527:Uric Acid; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019061:src-Family Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D019278:Matrix Metalloproteinase 3