Ameloblastin and enamelin prevent osteoclast formation by suppressing RANKL expression via MAPK signaling pathway.
Ameloblastin (Ambn) and enamelin (Enam) play a pivotal role in enamel mineralization. Previous studies have demonstrated that these enamel-related gene products also affect bone growth and remodeling; however, the underlying mechanisms have not been elucidated. In the present study, we examined the effects of Ambn and Enam on the receptor activator of nuclear factor kappa-B ligand (RANKL) expression induced with 1,25-dihydroxyvitamin D3(1,25(OH)2D3) and dexamethasone (DEX) on mouse bone marrow stromal cell line ST2 cells. We then verified the effect of Ambn and Enam on osteoclastogenesis. We found that pretreatment with recombinant human Ambn (rhAmbn) and recombinant human Enam (rhEnam) remarkably suppressed RANKL mRNA and protein expression induced with 1,25(OH)2D3and DEX. Interestingly, rhAmbn and rhEnam attenuated the phosphorylation of mitogen-activated protein kinases (MAPK), including ERK1/2, JNK, and p38 in ST2 cells stimulated with 1,25(OH)2D3and DEX. Moreover, pretreatment with specific inhibitors of ERK1/2 and p38, but not JNK, blocked RANKL mRNA and protein expression. Cell co-culture results showed that rhAmbn and rhEnam downregulated mouse bone marrow cell differentiation into osteoclasts induced with 1,25(OH)2D3and DEX-stimulated ST2 cells. These results suggest that Ambn and Enam may indirectly suppress RANKL-induced osteoclastogenesis via downregulation of p38 and ERK1/2 MAPK signaling pathways in bone marrow stromal cells.
Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka, 803-8580, Japan; Division of Developmental Stomatognathic Function Science, Department of Health Promotion, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka, 803-8580, Japan.
Wichida
W
Chaweewannakorn
Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka, 803-8580, Japan.
Wataru
W
Ariyoshi
Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka, 803-8580, Japan.
Toshinori
T
Okinaga
Division of Developmental Stomatognathic Function Science, Department of Health Promotion, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka, 803-8580, Japan.
Kazumasa
K
Morikawa
Division of Developmental Stomatognathic Function Science, Department of Health Promotion, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka, 803-8580, Japan. Electronic address: katsura@kyu-dent.ac.jp.
Katsura
K
Saeki
Division of Developmental Stomatognathic Function Science, Department of Health Promotion, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka, 803-8580, Japan.
Kenshi
K
Maki
Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka, 803-8580, Japan. Electronic address: tatsujin@kyu-dent.ac.jp.
Tatsuji
T
Nishihara
D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002117:Calcitriol / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D002478:Cells, Cultured; D018920:Coculture Techniques; D003746:Dental Enamel Proteins / Q000235:genetics / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008297:Male; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D010010:Osteoclasts / Q000187:drug effects* / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014815:Vitamins / Q000494:pharmacology
C490889:AMBN protein, human; D003746:Dental Enamel Proteins; C550525:ENAM protein, human; D016326:Extracellular Matrix Proteins; D005938:Glucocorticoids; D053245:RANK Ligand; D011994:Recombinant Proteins; D014815:Vitamins; D003907:Dexamethasone; D002117:Calcitriol
Ameloblastin; Enamel-related gene products; Enamelin