Pasteurella haemolytica leukotoxin and endotoxin induced cytokine gene expression in bovine alveolar macrophages requires NF-kappa B activation and calcium elevation

In bovine alveolar macrophages (BAMs), exposure to leukotoxin (Lkt) and end otoxin (LPS) from Pasteurella haemolytica results in expression of inflamma tory cytokine genes and intracellular calcium ([Ca2+](i)) elevation. Leukot oxin from P. haemolytica interacts only with leukocytes and platelets from ruminant species. Upregulation of cytokine genes in different cells by LPS involves activation of the transcription factor NF-kappa B (NF-kappa B), re sulting in its translocation from the cytoplasm to the nucleus. Using immun ocytochemical staining and confocal imaging, we studied whether NF-kappa B activation represents a common mechanism for the expression of multiple cyt okine genes in BAMs (Lkt-susceptible cells) stimulated with Lkt and LPS. Bo vine pulmonary artery endothelial cells and porcine alveolar macrophages we re used as nonsusceptible cells. The role of Ca2+ and tyrosine kinases in N F-kappa B activation and inflammatory cytokine gene expression was studied, since an inhibitor of tyrosine kinases attenuates LPS-induced [Ca2+], elev ation in BAMs. The results are summarized as follows: (a) Lkt induced NF-ka ppa B activation and [Ca2+], elevation only in BAMs, while LPS effects were demonstrable in all cell types; (b) chelation of [Ca2+](i) blocked NF-kapp a B activation and IL-1 beta, TNF alpha, and IL-8 mRNA expression; and (c) tyrosine kinase inhibitor herbimycin A blocked expression of all three cyto kine genes in BAMs stimulated with Lkt, while only the expression of IL-1 b eta was blocked in BAMs stimulated with LPS. We conclude that cytokine gene expression in BAMs requires NF-kappa B activation and [Ca2+](i) elevation, and Lkt effects exhibit cell type- and species specificity. (C) 1999 Acade mic Press.