Effects of Pasteurella haemolytica leukotoxin and lipopolysaccharide on histamine, prostanoid, and leukotriene release by bovine lung parenchyma in vitro.

OBJECTIVE: To identify the effect of Pasteurella haemolytica lipopolysaccharide (LPS) and leukotoxin (LKT) on spontaneous and calcium ionophore-induced histamine and inflammatory mediator release from isolated bovine lung parenchyma. SAMPLE POPULATION: Lungs from 8 healthy cattle. PROCEDURE: Isolated bovine lung parenchyma was incubated in vitro for 2 hours with LKT or LPS, and spontaneous and induced release of inflammatory mediators was determined.
RESULTS: LKT and LPS increased spontaneous release of histamine and leukotriene B4. In addition, incubation with LPS increased spontaneous release of prostaglandin E2. Moreover, a differential effect of the 2 toxins on calcium ionophore-induced inflammatory mediator release was observed. LKT specifically primed isolated lung parenchyma to release leukotriene B4 and thromboxane B2 in response to calcium ionophore, whereas LPS did not alter the profile of prostanoids released by bovine lung tissue exposed to calcium ionophore.
CONCLUSIONS: Pasteurella haemolytica toxins have a direct effect on bovine lung parenchyma, causing release of inflammatory mediators, which contribute to response to infection. Furthermore, bacterial toxins (LKT in this study) may sensitize tissues to the effects of other irritant stimuli, amplifying the inflammatory response.