Osthole-Mediated Cell Differentiation through Bone Morphogenetic Protein-2/p38 and Extracellular Signal-Regulated Kinase 1/2 Pathway in Human Osteoblast Cells

• Published in: The Journal of pharmacology and experimental therapeutics 2005-09, Vol.314 (3), p.1290-1299
• Main Authors: Kuo, Po-Lin, Hsu, Ya-Ling, Chang, Cheng-Hsiung, Chang, Jiunn-Kae
• Format: Article
• Language: English
• Subjects: Bone Morphogenetic Protein 2; Bone Morphogenetic Proteins - physiology; Cell Differentiation - drug effects; Cell Proliferation - drug effects; Cells, Cultured; Coumarins - pharmacology; DNA-Binding Proteins - physiology; Humans; MAP Kinase Signaling System - physiology; Mitogen-Activated Protein Kinase 1 - physiology; Mitogen-Activated Protein Kinase 3 - physiology; Osteoblasts - cytology; Osteoblasts - drug effects; Osteoporosis - drug therapy; Osteoporosis - etiology; p38 Mitogen-Activated Protein Kinases - physiology; RNA, Small Interfering - pharmacology; Smad Proteins; Smad1 Protein; Trans-Activators - physiology; Transforming Growth Factor beta - physiology
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.105.085092

The survival of osteoblast cells is one of the determinants of the development of osteoporosis in patients. Osthole (7-methoxy-8-isopentenoxycoumarin) is a coumarin derivative present in many medicinal plants. By means of alkaline phosphatase (ALP) activity, osteocalcin, osteopontin, and type I collagen, enzyme-linked immunosorbent assay, we have shown that osthole exhibits a significant induction of differentiation in two human osteoblast-like cell lines, MG-63 and hFOB. Induction of differentiation by osthole was associated with increased bone morphogenetic protein (BMP)-2 production and the activations of SMAD1/5/8 and p38 and extracellular signal-regulated kinase (ERK) 1/2 kinases. Addition of purified BMP-2 protein did not increase the up-regulation of ALP activity and osteocalcin by osthole, whereas the BMP-2 antagonist noggin blocked both osthole and BMP-2-mediated ALP activity enhancement, indicating that BMP-2 production is required in osthole-mediated osteoblast maturation. Pretreatment of osteoblast cells with noggin abrogated p38 activation but only partially decreased ERK1/2 activation, suggesting that BMP-2 signaling is required in p38 activation and is partially involved in ERK1/2 activation in osthole-treated osteoblast cells. Cotreatment of p38 inhibitor SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1 H -imidazole] or p38 small interfering RNA (siRNA) expression inhibited osthole-mediated activation of ALP but only slightly affected osteocalcin production. In contrast, the production of osteocalcin induced by osthole was inhibited by the mitogen-activated protein kinase kinase inhibitor PD98059 (2′-amino-3′-methoxyflavone) or by expression of an ERK2 siRNA. These data suggest that BMP-2/p38 pathway links to the early phase, whereas ERK1/2 pathway is associated with the later phase in osthole-mediated differentiation of osteoblast cells. In this study, we demonstrate that osthole is a promising agent for treating osteoporosis.