Granulocyte chemotaxis in the canine trachea: Inhibition by lipid mediator antagonists and systemic inhibitors

Inflammation of the airways contributes to the multicomponent disease known as asthma. The primary cells that infiltrate the airways in response to antigen exposure are PMNs and eosinophils, cells that can release cellular components, and damage the airways. We adapted a double-ballon endotracheal tube to study the cellular response to threede novo synthesized lipid mediators (LTB₄, PAF-acether and 15 HETE) found in respiratory fluids following antigen exposure.In random repeat challenges in groups of 7 dogs using mongrel dogs at 240 min following exposure to 10^–6 M agonists, the PMN content of the perfused fluid was 870±240, 1632±883, 515±395, and 1575±214 cells/ml/5 high power fields for vehicle, LTB₄, PAF, and 15 HETE respectively. Eosinophils that infiltrated the lumen at 240 min were 162±23, 608±287, 502±23, 115±14 cells/ml/5 HPF for vehicle, LTB₄, PAF, and 15 HETE respectively. Thus LTB₄ and PAF-acether significantly (p<0.05) increased eosinophils, and LTB₄ and 15 HETE increased PMNs (p<0.05). After determining the agonist response for the 3 agonists we included 2 specific antagonists in the perfusate. The LTB₄ antagonist U-75,302 10^–5 M, and the PAF antagonist L 652,731 10^–5 M in chambers containing LTB₄ and PAF-acether respectively blocked significantly the influx of PMNs and eosinophils compared to vehicle (p<0.01). Methylprednisolone 5 mg/kg i.m.-18 hrs blocked eosinophilia to PAF and LTB₄. Oral U-78,517F a Trolox amine lazaroid, active as an inhibitor of lipid peroxidation, 30 mg/kg-18 hrs significantly blocked eosinophilia to PAF-acether and LTB₄ directed chemotaxis compared to vehicle (p<0.05) but not 15 HETE. Specificity was shown for each antagonist since the PAF and LTB₄ antagonists did not block the opposite agonist. Use of this novelin vivo chemotaxis model allows the additional advantage of studying chemotaxis in living tissue.