title: Brucella abortus Invasion of Osteocytes Modulates Connexin 43 and Integrin Expression and Induces Osteoclastogenesis via Receptor Activator of NF-κB Ligand and Tumor Necrosis Factor Alpha Secretion.
abstract: Osteoarticular brucellosis is the most common localization of human active disease. Osteocytes are the most abundant cells of bone. They secrete factors that regulate the differentiation of both osteoblasts and osteoclasts during bone remodeling. The aim of this study is to determine if Brucella abortus infection modifies osteocyte function. Our results indicate that B. abortus infection induced matrix metalloproteinase 2 (MMP-2), receptor activator for NF-κB ligand (RANKL), proinflammatory cytokines, and keratinocyte chemoattractant (KC) secretion by osteocytes. In addition, supernatants from B. abortus-infected osteocytes induced bone marrow-derived monocytes (BMM) to undergo osteoclastogenesis. Using neutralizing antibodies against tumor necrosis factor alpha (TNF-α) or osteoprotegerin (OPG), RANKL's decoy receptor, we determined that TNF-α and RANKL are involved in osteoclastogenesis induced by supernatants from B. abortus-infected osteocytes. Connexin 43 (Cx43) and the integrins E11/gp38, integrin-α, integrin-β, and CD44 are involved in cell-cell interactions necessary for osteocyte survival. B. abortus infection inhibited the expression of Cx43 but did not modify the expression of integrins. Yet the expression of both Cx43 and integrins was inhibited by supernatants from B. abortus-infected macrophages. B. abortus infection was not capable of inducing osteocyte apoptosis. However, supernatants from B. abortus-infected macrophages induced osteocyte apoptosis in a dose-dependent manner. Taken together, our results indicate that B. abortus infection could alter osteocyte function, contributing to bone damage.
authors.affiliation: Instituto de Inmunología, Genética y Metabolismo, Hospital de Clínicas José de San Martín, Facultad de Medicina, CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Ayelén Ivana
authors.initials: AI
authors.lastname: Pesce Viglietti
authors.affiliation: Instituto de Inmunología, Genética y Metabolismo, Hospital de Clínicas José de San Martín, Facultad de Medicina, CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Paula Constanza
authors.initials: PC
authors.lastname: Arriola Benitez
authors.affiliation: Instituto de Inmunología, Genética y Metabolismo, Hospital de Clínicas José de San Martín, Facultad de Medicina, CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: María Virginia
authors.initials: MV
authors.lastname: Gentilini
authors.affiliation: Instituto de Medicina Experimental, CONICET-Academia Nacional de Medicina, Buenos Aires, Argentina.
authors.forename: Lis Noelia
authors.initials: LN
authors.lastname: Velásquez
authors.affiliation: Instituto de Estudios Inmunológicos y Fisiopatológicos, CONICET-Universidad Nacional de La Plata, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, La Plata, Buenos Aires, Argentina.
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Fossati
authors.affiliation: Instituto de Inmunología, Genética y Metabolismo, Hospital de Clínicas José de San Martín, Facultad de Medicina, CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Guillermo Hernán
authors.initials: GH
authors.lastname: Giambartolomei
authors.affiliation: Instituto de Inmunología, Genética y Metabolismo, Hospital de Clínicas José de San Martín, Facultad de Medicina, CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina mdelpino@ffyb.uba.ar.
authors.forename: María Victoria
authors.initials: MV
authors.lastname: Delpino
mesh_terms: D000818:Animals; D017209:Apoptosis; D002003:Brucella abortus / Q000472:pathogenicity*; D002006:Brucellosis / Q000382:microbiology / Q000473:pathology; D002454:Cell Differentiation; D002460:Cell Line; D054360:Chemokine CXCL1 / Q000378:metabolism; D018031:Connexin 43 / Q000096:biosynthesis*; D016023:Integrins / Q000096:biosynthesis*; D008264:Macrophages / Q000382:microbiology; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D051379:Mice; D010010:Osteoclasts / Q000166:cytology; D010011:Osteocytes / Q000378:metabolism* / Q000382:microbiology; D053244:Osteoprotegerin / Q000276:immunology; D053245:RANK Ligand / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism*
chemical_list: D054360:Chemokine CXCL1; D018031:Connexin 43; C475895:Cxcl1 protein, mouse; C543076:GJA1 protein, mouse; D016023:Integrins; D053244:Osteoprotegerin; D053245:RANK Ligand; C505689:Tnfsf11 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D020778:Matrix Metalloproteinase 2; C522362:Mmp2 protein, mouse