Differential inflammatory activity across human abdominal aortic aneurysms reveals neutrophil-derived leukotriene B4 as a major chemotactic factor released from the intraluminal thrombus.

Development and progression of acquired abdominal aortic aneurysms (AAAs) have been associated with different inflammatory mediators. The aim of the present study was to elucidate the topology and the potential mechanisms linking the leukotriene pathway to human AAAs. Human aneurysmal lesions were obtained from 24 patients undergoing surgery, and the intraluminal thrombus was separated from the vascular wall. Histological examination revealed major expression of the leukotriene-producing enzymes 5-lipoxygenase and LTA(4) hydrolase, as well as the two receptors for leukotriene B(4) (BLT1R and BLT2R), corresponding to neutrophils in the luminal part of the thrombus. In contrast, in the vascular wall, the leukotriene pathway mainly localized in macrophage-rich adventitial areas. Furthermore, conditioned media of the intraluminal thrombus contained significantly higher concentrations of leukotriene B(4) than that derived from the vascular wall, which were significantly correlated to other neutrophil-derived mediators, such as elastase/alpha(1)-antitrypsin complexes, myeloperoxidase, and MMP9/NGAL complexes. Finally, the neutrophil-chemotactic activity of the conditioned media from the intraluminal thrombus exhibited major inhibition by antagonists of the leukotriene B(4) receptors. Taken together, these results indicate neutrophil-derived leukotriene B(4) as a major neutrophil chemotactic factor released from the intraluminal thrombus of human AAAs and suggest that targeting BLT receptors may represent a potential medical therapeutic strategy in the prevention of AAA progression in humans.