CONICET | Buscador de Institutos y Recursos Humanos

Abstract: Inhalation ofcontaminated aerosols is one of the most common forms for human infection by Brucella abortus. Together with epithelialand endothelial cells, fibroblasts are an important component of the alveolar respiratorybarrier. While the interaction of Brucellawith human lung epithelial cells has been studied, its interaction withhuman lung fibroblasts remains unknown. In this work, we investigated the abilityof B. abortus 2308 to infect andinduce inflammatory mediators in a cell line of normalhuman lung fibroblasts (MRC-5). The cells were infected for 2 h and then incubatedwith gentamicin to kill extracellular bacteria (time 0 p.i.). At 2, 24 and 48 hp.i., cells were lysed to determine CFU of intracellular bacteria, and culturesupernatants were collected at 48 h p.i. to measure cytokines. Results showed thatB. abortus infects and replicates in lungfibroblasts and that its survival depends on a functional virB operon. The infection induced the secretion of interleukin-8(IL-8) (p˂0.0001), which secretion was mediated by p38MAPK and NF-κB pathways, and monocyte chemotactic protein 1 (MCP-1) (p˂0.0001), which secretiondepended on p38 MAPK, NF-κB and PI3K pathways.The cytokine secretion did not depend on bacterial viability since heat-killed B. abortus and B. abortus lipopolysaccharide were also able to induce IL-6, IL-8and MCP-1 secretion. In addition, the secretion of IL-6 and MCP-1 by fibroblastsincreased significantly upon stimulation with conditioned medium (CM) from B. abortus-infected macrophages ascompared to stimulation with CM from non-infected cells. These results suggest thathuman lung fibroblasts respond to B.abortus infection producing chemokines either directly or by stimulation withsoluble factors secreted by infected macrophages.