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Clin. Vaccine Immunol. doi:10.1128/CVI.00344-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Effects of lipopolysaccharide and Mannheimia haemolytica leukotoxin on bovine lung microvascular endothelial cells and alveolar epithelial cells

Department of Pathobiological Sciences, School of Veterinary Medicine, Department of Microbiology, School of Medicine, Department of Pediatrics, School of Medicine, University of Wisconsin-Madison, Madison, Wisconsin

^* To whom correspondence should be addressed. Email: mcclenahan{at}svm.vetmed.wisc.edu.

	Abstract

Bovine respiratory disease resulting from infection with Mannheimia hemolytica commonly results in extensive vascular leakage into the alveoli. M. hemolytica produces two substances, lipopolysaccharide (LPS) and leukotoxin (LKT), that are known to be important in inducing some of the pathological changes. In the present study, we examined bovine pulmonary epithelial cell (BPE) and bovine lung microvascular endothelial cell (BPMEC) monolayer permeability, as measured by trans –endothelial/-epithelial electrical resistance (TEER), after incubation with LPS, LKT, or LPS activated neutrophils. Endothelial cell monolayers exposed to LPS exhibited significant decreases in TEER that corresponded with increased levels of pro-inflammatory cytokines, apoptosis, and morphologic changes. In contrast, BPE cells exposed to LPS increased production of inflammatory cytokines, but displayed no changes in TEER, apoptosis, or visible morphologic changes. Both cells types appeared to express relatively equal levels of the LPS ligand, TLR-4. However, TEER in BPE cell monolayers was decreased when the cells were incubated with LPS activated neutrophils. Although incubation of BPE cells with LKT decreased TEER, this was not reduced by incubation of the LKT with a neutralizing antibody, and was reversed when the LKT was pre-incubated with the LPS neutralizing compound Polymyxin B. Because BPE cells did not express the LKT receptor CD11a/CD18, we infer that contaminating LPS was responsible for the decreased TEER. In conclusion, LPS triggered changes in endothelial cells that would be consistent with vascular leakage, but neither LPS nor LKT caused similar changes in epithelial cells, unless neutrophils were also present.