ABSTRACTOsteoarticular complications are common in human brucellosis, but the pathogenic mechanisms involved are largely unknown. Since matrix metalloproteinases (MMPs) are involved in joint and bone damage in inflammatory and infectious diseases, we investigated the production of MMPs by human osteoblasts and monocytes, either uponBrucella abortusinfection or upon reciprocal stimulation with factors produced by each infected cell type.B. abortusinfection of the normal human osteoblastic cell line hFOB 1.19 triggered a significant release of MMP-2, which was mediated in part by granulocyte-macrophage colony-stimulating factor (GM-CSF) acting on these same cells. Supernatants from infected osteoblasts exhibited increased levels of monocyte chemoattractant protein 1 and induced the migration of human monocytes (THP-1 cell line). Infection withB. abortusinduced a high MMP-9 secretion in monocytes, which was also induced by heat-killedB. abortusand by the Omp19 lipoprotein fromB. abortus. These effects were mediated by Toll-like receptor 2 and by the action of tumor necrosis factor alpha (TNF-α) produced by these same cells. Supernatants fromB. abortus-infected monocytes induced MMP-2 secretion in uninfected osteoblasts, and this effect was mediated by TNF-α. Similarly, supernatants from infected osteoblasts induced MMP-9 secretion in uninfected monocytes. This effect was mediated by GM-CSF, which induced TNF-α production by monocytes, which in turn induced MMP-9 in these cells. These results suggest that MMPs could be potentially involved in the tissue damage observed in osteoarticular brucellosis.
Serum levels of tumor necrosis factor alpha in patients treated with granulocyte-macrophage colony-stimulating factor [letter; comment]
