title: Ormeloxifene inhibits osteoclast differentiation in parallel to downregulating RANKL-induced ROS generation and suppressing the activation of ERK and JNK in murine RAW264.7 cells.
abstract: Ormeloxifene (Orm), a triphenylethylene compound, has been established as a selective estrogen receptor modulator (SERM) that suppresses the ovariectomy-induced bone resorption in rats. However, the precise mechanism underlying the bone-preserving action of Orm remains unclear. In this study, we evaluated the effect of Orm on osteoclast formation induced by receptor activator of nuclear factor κB ligand (RANKL) in the murine macrophage cell line RAW264.7. We also explored the mechanism of action of Orm by studying the RANKL-induced signaling pathways required for osteoclast differentiation. We found that Orm inhibited osteoclast formation from murine macrophage RAW264.7 cells induced by RANKL in a dose-dependent manner. Orm was able to abolish RANKL-induced reactive oxygen species (ROS) elevation and inhibited the transcriptional activation of two key RANKL-induced transcription factors namely activator protein-1 (AP-1) and NF-κB through mechanisms involving MAPKs. Activation of two MAPKs, i.e. ERK (MAPK1) and JNK (MAPK8), was alleviated by Orm effectively, which subsequently affected the activation of c-Jun and c-Fos, which are the essential components of the AP-1 transcription complex. Taken together, our results demonstrate that Orm potentially inhibits osteoclastogenesis by inhibiting ROS generation and thereby suppressing the activation of ERK1/2 (MAPK3/MAPK1) and JNK (MAPK8) and transcription factors (NF-κB and AP-1), which subsequently affect the regulation of osteoclastogenesis. These results provide a possible mechanism of action of Orm in regulating osteoclastogenesis, thereby supporting the beneficial bone-protective effects of this compound.
authors.affiliation: Division of Endocrinology, Central Drug Research Institute (CSIR), Lucknow, Uttar Pradesh 226001, India.
authors.forename: Geetika
authors.initials: G
authors.lastname: Kharkwal
authors.forename: Vishal
authors.initials: V
authors.lastname: Chandra
authors.forename: Iram
authors.initials: I
authors.lastname: Fatima
authors.forename: Anila
authors.initials: A
authors.lastname: Dwivedi
mesh_terms: D000818:Animals; D001578:Benzopyrans / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors*; D005786:Gene Expression Regulation / Q000187:drug effects; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects*; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D018808:Transcription Factor AP-1 / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D001578:Benzopyrans; D016328:NF-kappa B; D053245:RANK Ligand; D017382:Reactive Oxygen Species; D018808:Transcription Factor AP-1; C508548:ormeloxifene; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases