title: Conjugated linoleic acid inhibits osteoclast differentiation of RAW264.7 cells by modulating RANKL signaling.
abstract: Bone destruction is a pathological hallmark of several chronic inflammatory diseases, including rheumatoid arthritis, periodontitis, and osteoporosis. Inflammation-induced bone loss of this sort results from increased numbers of bone-resorbing osteoclasts. Numerous studies have indicated that conjugated linoleic acid (CLA) positively influences calcium and bone metabolism. Gene-deletion studies have shown that receptor activator of nuclear factor-kappaB ligand (RANKL) is one of the critical mediators of osteoclastogenesis. In this report, we examine the ability of CLA to suppress RANKL signaling and osteoclastogenesis in RAW264.7 cells, a murine monocytic cell line. Treatment of these cells with RANKL activated nuclear factor-kappaB (NF-kappaB), and preexposure of the cells to CLA significantly suppressed RANKL-induced NF-kappaB activation, including phosphorylation of I-kappaBalpha, degradation of I-kappaBalpha, and nuclear translocation of p65. RANKL induced osteoclastogenesis in these monocytic cells, and CLA inhibited RANKL-induced tumor necrosis factor-alpha production and osteoclast differentiation, including osteoclast-specific genes such as tartrate-resistant acid phosphatase, cathepsin K, calcitonin receptor, and matrix metalloproteinase-9 expression and osteoclast-specific transcription factors such as c-Fos, nuclear factor of activated T-cells expression, and bone resorption pit formation. CLA also inhibited RANKL-induced activation of mitogen-activated protein kinase p38 but had little effect on c-Jun N-terminal kinase activation. Collectively, these data demonstrate for the first time that CLA inhibits osteoclastogenesis by modulating RANKL signaling. Thus, CLA may have important therapeutic implications for the treatment of bone diseases associated with enhanced bone resorption by excessive osteoclastogenesis.
authors.affiliation: Department of Medicine, Division of Clinical Immunology and Rheumatology, University of Texas Health Science Center at San Antonio, 78229-3900, USA.
authors.forename: Md Mizanur
authors.initials: MM
authors.lastname: Rahman
authors.forename: Arunabh
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Gabriel
authors.initials: G
authors.lastname: Fernandes
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001862:Bone Resorption / Q000378:metabolism; D002352:Carrier Proteins / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D007527:Isoenzymes / Q000378:metabolism; D044243:Linoleic Acids, Conjugated / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D015398:Signal Transduction; D000071681:Tartrate-Resistant Acid Phosphatase; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D005227:Fatty Acids; D007527:Isoenzymes; D044243:Linoleic Acids, Conjugated; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D020928:Mitogen-Activated Protein Kinases; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase