title: Regulation of osteoclastogenesis by gap junction communication.
abstract: Receptor activator of NF-kappaB ligand (RANKL) is crucial in osteoclastogenesis but signaling events involved in osteoclast differentiation are far from complete and other signals may play a role in osteoclastogenesis. A more direct pathway for cellular crosstalk is provided by gap junction intercellular channel, which allows adjacent cells to exchange second messengers, ions, and cellular metabolites. Here we have investigated the role of gap junction communication in osteoclastogenesis in mouse bone marrow cultures. Immunoreactive sites for the gap junction protein connexin 43 (Cx43) were detected in the marrow stromal cells and in mature osteoclasts. Carbenoxolone (CBX) functionally blocked gap junction communication as demonstrated by a scrape loading Lucifer Yellow dye transfer technique. CBX caused a dose-dependent inhibition (significant > or = 90 microM) of the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells formed in 7- to 8-day marrow cultures stimulated by parathyroid hormone (PTH; 10 nM) or forskolin (FSK; 1 microM). Furthermore, CBX (100 microM) significantly inhibited prostaglandin E2 (PGE2; 10 microM) and 1,25(OH)2-vitamin D3 stimulated osteoclast differentiation in the mouse bone marrow cultures. Consequently, quantitative real-time polymerase chain reaction (PCR) analysis demonstrated that CBX downregulated the expression of osteoclast phenotypic markers, but without having any significant effects on RANK, RANKL, and osteoprotegerin (OPG) mRNA expression. However, the results demonstrated that CBX significantly inhibits RANKL-stimulated (100 ng/ml) osteoclastogenesis in the mouse bone marrow cultures. Taken together, our results suggests that gap junctional diffusion of messenger molecules interacts with signaling pathways downstream RANKL in osteoclast differentiation. Further studies are required to define the precise mechanisms and molecular targets involved.
authors.affiliation: Department of Odontology, Division of Oral Cell Biology, Umeå University, SE 901 87, Umeå, Sweden.
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Matemba
authors.forename: Anita
authors.initials: A
authors.lastname: Lie
authors.forename: Maria
authors.initials: M
authors.lastname: Ransjö
mesh_terms: D000818:Animals; D001483:Base Sequence; D001862:Bone Resorption / Q000378:metabolism; D002117:Calcitriol / Q000494:pharmacology; D002229:Carbenoxolone / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002450:Cell Communication / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D015232:Dinoprostone / Q000494:pharmacology; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism*; D006023:Glycoproteins / Q000235:genetics; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D053244:Osteoprotegerin; D010281:Parathyroid Hormone / Q000494:pharmacology; D053245:RANK Ligand; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D002352:Carrier Proteins; D018031:Connexin 43; D018076:DNA, Complementary; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D053244:Osteoprotegerin; D010281:Parathyroid Hormone; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; D005576:Colforsin; D002117:Calcitriol; D015232:Dinoprostone; D002229:Carbenoxolone