Estrogen and glucocorticoid regulate osteoblast differentiation   through the   interaction of bone morphogenetic protein-2 and tumor necrosis   factor-alpha in   C2C12 cells.
Imbalanced functions between osteoclasts and osteoblasts are involved in inflammatory bone damage. The clinical effectiveness of blocking TNF-alpha in treatment of active rheumatoid arthritis established the significance of TNF-alpha in the pathogenesis. In the present study, we investigated the cellular mechanism by which estrogen and glucocorticoid interact in osteoblastic differentiation regulated by BMP and TNF-alpha using mouse myoblastic C2C12 cells. The expression of estrogen receptors, (ER)alpha and ERbeta, and glucocorticoid receptor (GCR) was significantly increased by BMP-2 treatment regardless of the presence of estradiol and dexamethasone. Estradiol, but not dexamethasone, enhanced BMP-induced Runx2 and osteocalcin expression in C2C12 cells. In addition, TNF-alpha suppressed BMP-2-induced Runx2 and osteocalcin expression, and estradiol and dexamethasone reversed the TNF-alpha effects on BMP-2-induced Runx2 expression. Dexamethasone also abolished osteocalcin expression induced by BMP-2. Interestingly, BMP-2-induced Smad1/5/8 phosphorylation and Id-1 promoter activity were enhanced by estradiol pretreatment. On the other hand, dexamethasone suppressed BMP-2-induced Smad1/5/8 activation. TNF-alpha-induced SAPK/JNK activity was suppressed by estradiol, while NFkappaB phosphorylation was inhibited by dexamethasone. Of note, the inhibitory effects of TNF- on BMP-2-induced Runx2 and osteocalcin expression were reversed by SAPK/JNK inhibition regardless of the presence of estradiol. The estradiol effects that enhance BMP-2-induced Runx2 and osteocalcin mRNA expression were restored by antagonizing ER, and moreover, membrane-impermeable estradiol-BSA failed to enhance the BMP-2-induced osteoblastic differentiation. Thus, estrogen and glucocorticoid are functionally involved in the process of osteoblast differentiation regulated by BMPs and TNF-alpha. BMP-2 increases the sensitivities of ERs and GCR, whereas estrogen and glucocorticoid differentially regulate BMP-Smad and TNF-alpha signaling.
Matsumoto
Yoshinori
Y
Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kitaku, Okayama 700-8558, Japan.
Otsuka
Fumio
F
Takano
Mariko
M
Mukai
Tomoyuki
T
Yamanaka
Ryutaro
R
Takeda
Masaya
M
Miyoshi
Tomoko
T
Inagaki
Kenichi
K
Sada
Ken-ei
KE
Makino
Hirofumi
H
D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D002478:Cells, Cultured; D004967:Estrogens / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D004967:Estrogens; D005938:Glucocorticoids; D011960:Receptors, Estrogen; D011965:Receptors, Glucocorticoid; D014409:Tumor Necrosis Factor-alpha; D015675:Osteocalcin