Role of mast cell leukotrienes in neutrophil recruitment and bacterial clearance in infectious peritonitis

Stimulated mast cells release a variety of chemotactic factors such as tumor necrosis factor α (TNF-α) and leukotriene B₄. Recent studies have shown that mast cell-derived TNF-α plays a critical role in host defense against Gram negative bacterial infections by the recruitment of neutrophils to the sites of infection. In the present study, we sought to investigate if mast cells release leukotriene (LT) B₄ in response to bacteria and, if so, to establish its in vivo relevance. We show that mast cells release significant amounts of LTB₄ and LTC₄ in response to exposure to FimH-expressing type 1 fimbriated Escherichia coli in vitro. To test the functional significance of mast cell-derived LTs during an E. coli infection in vivo, we examined the effect of a LT-synthesis inhibitor, A-63162, on bacterial clearance and neutrophil influx in an infectious peritonitis model in mast cell-deficient mice (WBB6F₁-W/W(v)) and their normal congenic control (WBB6F₁-+/+) mice. Our results show that a treatment with A-63162 reduced neutrophil influx and bacterial clearance in the peritoneal cavities of mast cell-sufficient but not -deficient mice. Thus, mast cell-derived LTs contribute to host defense by mediating early neutrophil influx and bacterial clearance at sites of infection.