Mitogen-activated protein (MAP) kinases are involved in interleukin-1 (IL-1)-induced IL-6 synthesis in osteoblasts: modulation not of p38 MAP kinase, but of p42/p44 MAP kinase by IL-1-activated protein kinase C.
We previously reported that interleukin-1alpha (IL-1alpha)-induced activation of protein kinase C (PKC) via phosphatidylcholine-specific phospholipase C (PC-PLC) limits IL-6 synthesis induced by IL-1alpha itself in osteoblast-like MC3T3-E1 cells. In the present study, we further investigated the mechanism behind IL-1alpha-induced IL-6 synthesis in MC3T3-E1 cells. IL-1alpha time-dependently stimulated the phosphorylation of both p42/p44 mitogen-activated protein (MAP) kinase and p38 MAP kinase. PD98059, a specific inhibitor of the upstream kinase that activates p42/p44 MAP kinase, inhibited the IL-1alpha-induced IL-6 synthesis as well as the phosphorylation of p42/p44 MAP kinase induced by IL-1alpha. SB203580, a specific inhibitor of p38 MAP kinase, also reduced both the phosphorylation of p38 MAP kinase and the IL-6 synthesis. 1-Oleoyl-2-acetylglycerol, an activator of PKC, suppressed the IL-1alpha-induced IL-6 synthesis. Calphostin C, a specific inhibitor of PKC, or D-609, a specific inhibitor of PC-PLC, significantly enhanced the IL-1alpha-induced phosphorylation of p42/p44 MAP kinase without affecting the phosphorylation of p38 MAP kinase. The phosphorylation of p42/p44 MAP kinase by IL-1alpha was markedly increased in PKC-down-regulated MC3T3-E1 cells. Neither 12-O-tetradecanoylphorbol-13-acetate, known to be an activator of PKC, nor 1-oleoyl-2-acetylglycerol affected the phosphorylation of p38 MAP kinase induced by IL-1alpha. These results strongly suggest that IL-1alpha-induced IL-6 synthesis is mediated via activations of both p42/p44 MAP kinase and p38 MAP kinase in osteoblasts, and that PKC activated by IL-1alpha itself negatively regulates IL-6 synthesis at a point upstream from p42/p44 MAP kinase.
Miwa
M
M
Department of Internal Medicine, Gifu Social Insurance Hospital, Kani, Japan.
Kozawa
O
O
Tokuda
H
H
Uematsu
T
T
D000818:Animals; D000831:Animals, Newborn; D001952:Bridged-Ring Compounds / Q000494:pharmacology; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000096:biosynthesis; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009281:Naphthalenes / Q000494:pharmacology; D009636:Norbornanes; D010006:Osteoblasts / Q000201:enzymology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013859:Thiocarbamates; D013871:Thiones / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
D001952:Bridged-Ring Compounds; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D007375:Interleukin-1; D015850:Interleukin-6; D009281:Naphthalenes; D009636:Norbornanes; D011725:Pyridines; D013859:Thiocarbamates; D013871:Thiones; C046498:tricyclodecane-9-yl-xanthogenate; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one