Synergistic effect of vasoactive intestinal peptides on TNF-alpha-induced IL-6 synthesis in osteoblasts: amplification of p44/p42 MAP kinase activation.
We previously showed that tumor necrosis factor-alpha (TNF-alpha) stimulates synthesis of interleukin-6 (IL-6), a potent bone resorptive agent, via p44/p42 mitogen-activated protein (MAP) kinase and phosphatidylinositol 3-kinase/Akt in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of vasoactive intestinal peptide (VIP) on TNF-alpha-induced IL-6 synthesis in these cells. VIP, which by itself slightly stimulated IL-6 synthesis, synergistically enhanced the TNF-alpha-induced IL-6 synthesis in MC3T3-E1 cells. The synergistic effect of VIP on the TNF-alpha-induced IL-6 synthesis was concentration-dependent in the range between 1 and 70 nM. We previously reported that VIP stimulated cAMP production in MC3T3-E1 cells. Forskolin, a direct activator of adenylyl cyclase, or 8-bromoadenosine-3',5'-cyclic monophosphate (8bromo-cAMP), a plasma membrane-permeable cAMP analogue, markedly enhanced the TNF-alpha-induced IL-6 synthesis as well as VIP. VIP markedly up-regulated the TNF-alpha-induced p44/p42 MAP kinase phosphorylation. The Akt phosphorylation stimulated by TNF-alpha was only slightly affected by VIP. PD98059, a specific inhibitor of MEK1/2, significantly suppressed the enhancement of TNF-alpha-induced IL-6 synthesis by VIP. The synergistic effect of a combination of VIP and TNF-alpha on the phosphorylation of p44/p42 MAP kinase was diminished by H-89, an inhibitor of cAMP-dependent protein kinase. These results strongly suggest that VIP synergistically enhances TNF-alpha-stimulated IL-6 synthesis via up-regulating p44/p42 MAP kinase through the adenylyl cyclase-cAMP system in osteoblasts.
Natsume
Hideo
H
Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
Tokuda
Haruhiko
H
Mizutani
Jun
J
Adachi
Seiji
S
Matsushima-Nishiwaki
Rie
R
Minamitani
Chiho
C
Kato
Kenji
K
Kozawa
Osamu
O
Otsuka
Takanobu
T
D016475:3T3 Cells; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D004789:Enzyme Activation; D005419:Flavonoids / Q000494:pharmacology; D015850:Interleukin-6 / Q000096:biosynthesis*; D007546:Isoquinolines / Q000494:pharmacology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism / Q000494:pharmacology*
D005419:Flavonoids; D015850:Interleukin-6; D007546:Isoquinolines; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D014660:Vasoactive Intestinal Peptide; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one