Degree of neutrophil chemotaxis is dependent upon the chemoattractant and barrier

Stimulated neutrophil migration across lung endothelial and epithelial barriers is important in lung inflammatory processes. To better understand the interaction between chemoattractants, neutrophils, and endothelium and epithelium, we compared the ability of leukotriene B4 (LTB4), formylmethionylleucylphenylalanine (FMLP), and platelet-activating factor (PAF) to induce human neutrophil migration across 3-microns-pore filters alone and human umbilical vein endothelial (HUVE) cells and two different epithelial cell types, Madin-Darby canine kidney (MDCK) cells and human lung A549 cells, cultured in monolayers on these filters. LTB4, FMLP, and PAF induced neutrophil migration through naked filters, endothelial cells, and epithelial cells in a dose-related fashion. At optimal chemoattractant doses, LTB4, FMLP, and PAF induced relatively equivalent neutrophil migration through filters and endothelial and epithelial monolayers. However, the doses at which optimal neutrophil migration was observed to occur as well as the degree of neutrophil migration through the three barriers varied depending upon the chemoattractant. Based on dose-response experiments, the relative rank order of potency for the three chemoattractants was: LTB4 = FMLP greater than PAF for filter alone barrier; LTB4 greater than FMLP greater than PAF for HUVE cell barrier; and FMLP greater than LTB4 greater than PAF for MDCK and A549 epithelial cell barriers. Our data suggest that neutrophil chemotactic and subsequent lung inflammatory responses are interrelatedly influenced by both the quantity and type of chemoattractant present and the barrier through which the neutrophil must migrate.