In vitro evaluation of the role of platelet-activating factor and interleukin-8 in Mannheimia haemolytica-induced bovine pulmonary endothelial cell injury.
OBJECTIVE
To develop an in vitro model of the bovine alveolar-capillary interface and to evaluate the roles of interleukin-8 (IL-8) and platelet-activating factor (PAF) in neutrophil-mediated endothelial injury induced by infection with Mannheimia haemolytica.


METHODS
Cultured bovine pulmonary microvascular endothelial cells, freshly isolated bovine neutrophils, and monocyte-derived bovine macrophages.


METHODS
A coculture system was developed in which endothelial cells were grown to confluence in tissue culture inserts, neutrophils were added to the inserts, and macrophages were added to tissue culture wells. Mannheimia haemolytica-derived lipopolysaccharide (LPS) or supernatant was added to activate macrophages, and inhibitors of PAF or IL-8 were added to the insert. Endothelial cell cytotoxicity and permeability (ie, albumin leakage) and neutrophil activation (ie, adhesion, degranulation [lactoferrin expression], and superoxide production) were assessed.


RESULTS
The addition of M haemolytica-derived LPS to bovine macrophages in the coculture system resulted in significant increases in endothelial cell cytotoxicity and permeability and neutrophil degranulation and adhesion. Inhibition of IL-8 reduced endothelial cell permeability and neutrophil degranulation induced by exposure to M haemolytica-derived supernatant, whereas inhibition of PAF decreased superoxide release by neutrophils.


CONCLUSIONS
In vitro activation of bovine macrophages by M haemolytica-derived LPS resulted in neutrophil activation and neutrophil-mediated endothelial damage. Neutrophil-mediated endothelial injury and neutrophil degranulation were, at least in part, mediated by IL8, whereas PAF promoted superoxide release by neutrophils in this in vitro system designed to mimic the in vivo events that occur during the early stages of bovine pneumonic pasteurellosis.
McClenahan
David J
DJ
Department of Veterinary PathoBiology, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
Evanson
Oral A
OA
Weiss
Douglas J
DJ
D000818:Animals; D001381:Azepines / Q000494:pharmacology; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology* / Q000382:microbiology; D002448:Cell Adhesion / Q000276:immunology; D015550:Cell Degranulation / Q000276:immunology; D018920:Coculture Techniques / Q000662:veterinary; D004730:Endothelium, Vascular / Q000276:immunology* / Q000382:microbiology; D005260:Female; D016209:Interleukin-8 / Q000037:antagonists & inhibitors / Q000276:immunology*; D016676:Macrophages, Alveolar / Q000276:immunology / Q000382:microbiology; D016978:Mannheimia haemolytica / Q000276:immunology* / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology / Q000382:microbiology; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors / Q000276:immunology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D013481:Superoxides / Q000276:immunology; D014230:Triazoles / Q000494:pharmacology
D001381:Azepines; D016209:Interleukin-8; D010972:Platelet Activating Factor; D010975:Platelet Aggregation Inhibitors; D014230:Triazoles; C052518:WEB 2086; D013481:Superoxides