Involvement of stress-activated protein kinase/c-Jun N-terminal kinase in endothelin-1-induced heat shock protein 27 in osteoblasts.
OBJECTIVE
We have reported that endothelin-1 (ET-1) activates p38 mitogen-activated protein (MAP) kinase through protein kinase C in osteoblast-like MC3T3-E1 cells, and that p38 MAP kinase plays a role in the ET-1-induced heat shock protein 27 (HSP27). Recently, we found that stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) is activated by ET-1 in these cells. In the present study, we have investigated the involvement of SAPK/JNK in ET-1-induced HSP27 in MC3T3-E1 cells.


METHODS
The concentration of HSP27 in soluble extracts of the cells, the expression of mRNA for HSP27, and the phosphorylation of SAPK/JNK were determined by an enzyme immunoassay, Northern blot analysis, and Western blot analysis respectively.


RESULTS
SP600125, a specific inhibitor of SAPK/JNK, markedly reduced ET-1-stimulated HSP27 accumulation. The inhibitory effect of SP600125 was dose dependent in the range between 1 and 50 microM. SP600125 reduced the ET-1-increased level of HSP27 mRNA. Calphostin C and Go 6976, inhibitors of protein kinase C, reduced the ET-1-induced phosphorylation of SAPK/JNK. 12-O-Tetradecanoylphorbol-13-acetate, a direct activator of protein kinase C, induced SAPK/JNK phosphorylation, which was suppressed by SP600125. A combination of SP600125 and p38 MAP kinase inhibitor such as SB203580 and PD169316 additively reduced the ET-1-stimulated accumulation of HSP27.


CONCLUSIONS
These results strongly suggest that JNK plays a part in ET-1-induced HSP27 in addition to p38 MAP kinase in osteoblasts.
Tokuda
H
H
Department of Internal Medicine, Chubu National Hospital, National Institute for Longevity Sciences, Obu, Aichi 474-8511, Japan.
Niwa
M
M
Ito
H
H
Oiso
Y
Y
Kato
K
K
Kozawa
O
O
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D015152:Blotting, Northern; D015153:Blotting, Western; D002227:Carbazoles / Q000494:pharmacology; D019332:Endothelin-1 / Q000378:metabolism*; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins; D007124:Immunoenzyme Techniques; D007211:Indoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018832:Molecular Chaperones; D009281:Naphthalenes / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010006:Osteoblasts / Q000201:enzymology / Q000378:metabolism*; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
D000873:Anthracenes; D002227:Carbazoles; D019332:Endothelin-1; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D006360:Heat-Shock Proteins; C486113:Hsbp1 protein, mouse; D007211:Indoles; D018832:Molecular Chaperones; D009281:Naphthalenes; D009363:Neoplasm Proteins; D012333:RNA, Messenger; C081021:Go 6976; C432165:pyrazolanthrone; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate