INTERLEUKIN-8 MEDIATES INTERLEUKIN-1-ALPHA-INDUCED NEUTROPHIL TRANSCELLULAR MIGRATION

Interleukin-1 alpha (IL-1 alpha) is a cytokine with a myriad of potent proinflammatory effects. Neutrophils are important immune effector cells in allergic and inflammatory lung diseases. We examined the effects of IL-1 alpha on human neutrophil migration across naked filters and human umbilical vein endothelial (HUVE) cell and type II-like pulmonary epithelial cell (A549) monolayers cultured on these filters. IL-1 alpha from 10(-13)) to 10(-9) M induced dose-dependent neutrophil migration through both HUVE and A549 cellular monolayers but not through naked filters, Neutrophil migration was consistently greater through A549 monolayers compared with HUVE monolayers. IL-1 alpha-induced neutrophil migration was also time dependent, and the kinetics of neutrophil migration through HUVE and A549 monolayers were similar. Significant migration through either monolayer was not observed until 2 h, and maximal migration occurred at 3 h through A549 and 5 h though HUVE cellular monolayers. Supernatants of IL-1 alpha (10(-11) M)-stimulated HUVE and A549 monolayers induced significantly more migration of neutrophils across naked filters than 10(-11) M IL-1 alpha itself, suggesting the release of soluble secondary chemotactic factor(s), Pretreatment of HUVE and A549 monolayers with actinomycin D inhibited both IL-1 alpha-induced production of soluble chemotactic factor(s) and transcellular migration by > 90 %. Supernatants from IL-1 alpha-treated HUVE and A549 cells contained significant concentrations of interleukin 8 (IL-8), and coincubation of these supernatants with anti-IL-8 inhibited approximately 50% of supernatant-induced chemotaxis. Coincubation of IL-1 alpha with anti-IL-8 during transmigration experiments also significantly inhibited neutrophil migration measured across cellular monolayers. Therefore, both endothelial and epithelial cells greatly facilitated IL-1 alpha-induced transcellular migration of neutrophils and this process was dependent upon IL-1 alpha-stimulated production of chemotactic factor(s), of which IL-8 was a major contributor, These data further support the active role of vascular endothelium and pulmonary epithelium in recruiting leukocytes to sites of inflammation through the release of secondary chemotactic factors.