Brucella lipopolysaccharides induce cyclooxygenase-2 expression in monocytic cells.

Human brucellosis is characterized by the presence of both acute inflammatory episodes and chronic inflammation with granuloma formation. On this basis, the proinflammatory effects of smooth lipopolysaccharide of Brucella (S-LPS) were addressed and compared to those of LPS from Escherichia coli. For this purpose, the induction of cyclooxygenase-2 (COX-2), the production of the chemokine monocyte chemoattractant protein-1 (MCP-1), and the activation of the nuclear factor kappa B (NF-kappa B) were studied. S-LPS was found to induce both COX-2 expression and MCP-1 production; however, the potency of E. coli LPS exceeded that of Brucella S-LPS by some orders of magnitude. However, at concentrations above 1 microg/ml, all of the LPS produced comparable effects, including their ability to activate the NF-kappa B system. These observations help explain the inflammatory events associated with Brucella infection and the ability of Brucella to produce monocyte recruitment and granuloma formation.