p38 MAPK-mediated signals are required for inducing osteoclast differentiation but not for osteoclast function.
Receptor activator of nuclear factor-kappaB ligand (RANKL)-induced signals play critical roles in osteoclast differentiation and function. SB203580, an inhibitor of p38 MAPK, blocked osteoclast formation induced by 1alpha,25-dihydroxyvitamin D(3) and prostaglandin E(2) in cocultures of mouse osteoblasts and bone marrow cells. Nevertheless, SB203580 showed no inhibitory effect on RANKL expression in osteoblasts treated with 1alpha,25-dihydroxyvitamin D(3) and prostaglandin E(2). RANKL-induced osteoclastogenesis in bone marrow cultures was inhibited by SB203580, suggesting a direct effect of SB203580 on osteoclast precursors, but not on osteoblasts, in osteoclast differentiation. However, SB203580 inhibited neither the survival nor dentine-resorption activity of osteoclasts induced by RANKL. Lipopolysaccharide (LPS), IL-1, and TNFalpha all stimulated the survival of osteoclasts, which was not inhibited by SB203580. Phosphorylation of p38 MAPK was induced by RANKL, IL-1, TNFalpha, and LPS in osteoclast precursors but not in osteoclasts. LPS stimulated phosphorylation of MAPK kinase 3/6 and ATF2, upstream and downstream signals of p38 MAPK, respectively, in osteoclast precursors but not in osteoclasts. Nevertheless, LPS induced degradation of IkappaB and phosphorylation of ERK in osteoclasts as well as in osteoclast precursors. These results suggest that osteoclast function is induced through a mechanism independent of p38 MAPK-mediated signaling.
Institute for Oral Science, Department of Biochemistry, Matsumoto Dental University, 1780 Gobara, Hirooka, Shiojiri, Nagano 399-0781, Japan.
Xiaotong
X
Li
Nobuyuki
N
Udagawa
Kanami
K
Itoh
Koji
K
Suda
Yoshiyuki
Y
Murase
Tatsuji
T
Nishihara
Tatsuo
T
Suda
Naoyuki
N
Takahashi
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology; D002352:Carrier Proteins / Q000494:pharmacology; D002454:Cell Differentiation; D015232:Dinoprostone / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins / Q000494:pharmacology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D010010:Osteoclasts / Q000502:physiology*; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D048051:p38 Mitogen-Activated Protein Kinases
D002352:Carrier Proteins; D007093:Imidazoles; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D011725:Pyridines; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002117:Calcitriol; D015232:Dinoprostone; C093642:SB 203580