title: Brucella abortus-activated microglia induce neuronal death through primary phagocytosis.
abstract: Inflammation has long been implicated as a contributor to pathogenesis in neurobrucellosis. Many of the associated neurocognitive symptoms of neurobrucellosis may be the result of neuronal dysfunction resulting from the inflammatory response induced by Brucella abortus infection in the central nervous system. In this manuscript, we describe an immune mechanism for inflammatory activation of microglia that leads to neuronal death upon B. abortus infection. B. abortus was unable to infect or harm primary cultures of mouse neurons. However, when neurons were co-cultured with microglia and infected with B. abortus significant neuronal loss occurred. This phenomenon was dependent on TLR2 activation by Brucella lipoproteins. Neuronal death was not due to apoptosis, but it was dependent on the microglial release of nitric oxide (NO). B. abortus infection stimulated microglial proliferation, phagocytic activity and engulfment of neurons. NO secreted by B. abortus-activated microglia induced neuronal exposure of the "eat-me" signal phosphatidylserine (PS). Blocking of PS-binding to protein milk fat globule epidermal growth factor-8 (MFG-E8) or microglial vitronectin receptor-MFG-E8 interaction was sufficient to prevent neuronal loss by inhibiting microglial phagocytosis without affecting their activation. Taken together, our results indicate that B. abortus is not directly toxic to neurons; rather, these cells become distressed and are killed by phagocytosis in the inflammatory surroundings generated by infected microglia. Neuronal loss induced by B. abortus-activated microglia may explain, in part, the neurological deficits observed during neurobrucellosis.
authors.affiliation: Instituto de Inmunología, Genética y Metabolismo (INIGEM), CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Rodríguez
authors.affiliation: Instituto de Inmunología, Genética y Metabolismo (INIGEM), CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: M Victoria
authors.initials: MV
authors.lastname: Delpino
authors.affiliation: Instituto de Inmunología, Genética y Metabolismo (INIGEM), CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: M Cruz
authors.initials: MC
authors.lastname: Miraglia
authors.affiliation: Department of Biochemistry and Immunology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte-Minas Gerais, Brazil.
authors.forename: Miriam M
authors.initials: MM
authors.lastname: Costa Franco
authors.affiliation: Instituto de Medicina Experimental (CONICET-Academia Nacional de Medicina), Buenos Aires, Argentina.
authors.forename: Paula
authors.initials: P
authors.lastname: Barrionuevo
authors.affiliation: Center for Nano Biotechnology Research and Department of Biological Sciences, Alabama State University, Montgomery, AL.
authors.forename: Vida A
authors.initials: VA
authors.lastname: Dennis
authors.affiliation: Department of Biochemistry and Immunology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte-Minas Gerais, Brazil.
authors.forename: Sergio C
authors.initials: SC
authors.lastname: Oliveira
authors.affiliation: Instituto de Inmunología, Genética y Metabolismo (INIGEM), CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Guillermo H
authors.identifier: 0000-0001-7441-5311
authors.initials: GH
authors.lastname: Giambartolomei
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000633:toxicity; D001425:Bacterial Outer Membrane Proteins / Q000633:toxicity; D002003:Brucella abortus / Q000472:pathogenicity*; D016923:Cell Death / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008074:Lipoproteins / Q000378:metabolism / Q000633:toxicity; D051379:Mice; D008807:Mice, Inbred BALB C; D008822:Mice, Transgenic; D017628:Microglia / Q000382:microbiology* / Q000502:physiology*; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000473:pathology*; D009569:Nitric Oxide / Q000378:metabolism; D010587:Phagocytosis / Q000502:physiology*; D016548:Prosencephalon / Q000166:cytology; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000172:deficiency / Q000235:genetics
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D008070:Lipopolysaccharides; D008074:Lipoproteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C097319:OMP19 protein, Brucella abortus; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D009569:Nitric Oxide
keywords: microglia activation; neurobrucellosis; neuroinflammation; neurotoxicity