Distinct cellular sources of hepoxilin A₃ and leukotriene B₄ are used to coordinate bacterial-induced neutrophil transepithelial migration

Neutrophilic infiltration is a leading contributor to pathology in a number of pulmonary disease states, including cystic fibrosis. Hepoxilin A₃ (HXA₃) is a chemotactic eicosanoid shown to mediate the transepithelial passage of neutrophils in response to infection in several model systems and at multiple mucosal surfaces. Another well-known eicosanoid mediating general neutrophil chemotaxis is leukotriene B₄ (LTB₄)·. We sought to distinguish the roles of each eicosanoid in the context of infection of lung epithelial monolayers by Pseudomonas aeruginosa. Using human and mouse in vitro transwell model systems, we used a combination of biosynthetic inhibitors, receptor antagonists, as well as mutant sources of neutrophils to assess the contribution of each chemoattractant in driving neutrophil transepithelial migration. We found that following chemotaxis to epithelial-derived HXA₃ signals, neutrophil-derived LTB₄ is required to amplify the magnitude of neutrophil migration. LTB₄ signaling is not required for migration to HXA₃ signals, but LTB₄ generation by migrated neutrophils plays a significant role in augmenting the initial HXA₃-mediated migration. We conclude that HXA₃ and LTB₄ serve independent roles to collectively coordinate an effective neutrophilic transepithelial migratory response.