Cyclic compression-induced p38 activation and subsequent MMP13 expression requires Rho/ROCK activity in bovine cartilage explants.
OBJECTIVE
Excessive mechanical stress on the cartilage causes the degradation of the matrix, leading to the osteoarthritis (OA). Matrix metalloproteinases 13 (MMP13) is a major catalytic enzyme in OA and p38 plays an important role in its induction. However, precise pathway inducing p38 activation has not been elucidated. We hypothesized here that the small GTPase Rho and its effector ROCK might function in upper part of the mechanical stress-induced matrix degeneration pathway.


METHODS
Bovine metacarpal phalangeal articular cartilage explants were loaded with 1 MPa dynamic compression for 6 h with or without a ROCK specific inhibitor Y27632 or/and a p38 specific inhibitor SB202190. Then p38 phosphorylation and MMP13 expression were assessed by western blot or/and quantitative RT-PCR. Rho-activity was measured by pull-down assay using glutathione S-transferase fusion protein of Rho binding domain.


RESULTS
Cyclic compression caused Rho activation, p38 phosphorylation and MMP13 expression. Both Y27632 and SB202190 were found to block the mechanical stress-enhanced p38 phosphorylation and subsequent MMP13 expression.


CONCLUSIONS
The present results show that p38 phosphorylation and MMP13 expression are regulated by Rho/ROCK activation, and support the potential novel pathway that Rho/ROCK is in the upper part of the mechanical stress-induced matrix degeneration cascade in cartilage comprised of p38 and MMP13.
Department of Orthopaedic Surgery, Kinki University Faculty of Medicine, Osaka, Japan.
Koichi
K
Nakagawa
Takeshi
T
Teramura
Toshiyuki
T
Takehara
Yuta
Y
Onodera
Chiaki
C
Hamanishi
Masao
M
Akagi
Kanji
K
Fukuda
D000577:Amides / Q000494:pharmacology; D000818:Animals; D002356:Cartilage / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism*; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D013314:Stress, Mechanical; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000577:Amides; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011725:Pyridines; C108830:Y 27632; D054460:rho-Associated Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D053509:Matrix Metalloproteinase 13; D020741:rho GTP-Binding Proteins; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole