title: Icariin induces osteoblast proliferation, differentiation and mineralization through estrogen receptor-mediated ERK and JNK signal activation.
abstract: Icariin, the main active flavonoid glucoside isolated from Herba epimedii (HEF), is an anabolic agent in bone that has been reported to prevent bone loss in ovariectomized rats and postmenopausal women. However, the molecular mechanism for this anabolic action of Icariin remain largely unknown. Here, we found that Icariin could promote MC3T3-E1 osteoblastic cell proliferation and reduce cell apoptosis, associated with increased mRNA levels of positive regulators of cell cycle gene Cyclin E and proliferating cell nuclear antigen (PCNA), decreaed mRNA level of negative regulator gene, Cyclin-dependent kinase 4 inhibitor B (Cdkn2B), and reduced caspase-3 activity. Icariin also enhanced MC3T3-E1 cell differentiation and mineralization demonstrated by increased the expression of differentiation markers, alkaline phosphatase (ALP) and collagen type I (Col I), and bone nodule formation via Alizarin red S staining. To characterize the underlying mechanisms, we examined the effect of Icariin on mitogen-activated protein kinase (MAPK) signaling. Icariin treatment rapidly induced extracellular signal-regulated kinase (ERK) and c-Jun N terminal kinase (JNK) activation but showed no effect on activation of p38 kinase. Furthermore, Icariin-mediated effects on osteoblasts were dramatically attenuated by treatment with specific inhibitors of MAPKs, U0126 (ERK inhibitor) and SP600125 (JNK inhibitor). Interestingly, treatment of osteoblasts with estrogen receptor antagonist ICI182780 attenuated Icariin-mediated effect of proliferation and mineralization, associated with suppression of ERK and JNK phosphorylation. These observations provide a potential mechanism of anabolic actions of Icariin involving ERK and JNK pathway by estrogen receptor.
authors.affiliation: Department of Endocrinology, Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China.
authors.forename: Lige
authors.initials: L
authors.lastname: Song
authors.forename: Jiashen
authors.initials: J
authors.lastname: Zhao
authors.forename: Xiuzhen
authors.initials: X
authors.lastname: Zhang
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhou
mesh_terms: D045930:Anabolic Agents / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002113:Calcification, Physiologic / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects*; D051381:Rats; D011960:Receptors, Estrogen / Q000378:metabolism*
chemical_list: D045930:Anabolic Agents; D005419:Flavonoids; D011960:Receptors, Estrogen; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; C056599:icariin
keywords: Estrogen receptor; Icariin; Mitogen-activated protein kinases; Osteoblasts; Osteoporosis