LTB4 Activates the MAP Kinase Pathway in Endothelial Cells to Cause Long‐Lasting Neutrophil Tethering, MCP ‐1 and NO Releases

ABSTRACT Leukotriene B 4 (LTB 4 ), a potent chemotactic and immune‐modulating eicosanoid, signals via two receptors (BLT 1 and BLT 2 ), leading to rapid but transient migratory, adhesive and secretory responses in phagocytes. Previously, we reported that BLT 1 is the predominating BLT in human umbilical vein endothelial cells (HUVEC). However, little is known about how ligation of these receptors affects adhesive and secretory endothelial responses over time. Here, we demonstrate that in HUVEC, LTB 4 dose‐dependently and stereospecifically causes a biphasic tethering of neutrophils, where the second phase is robust, similar to that induced by lipopolysaccharide, and persists for 3–8 h. LTB 4 also causes up‐regulation of E‐selectin, ICAM‐1 and VCAM‐1 and release of MCP‐1 and nitric oxide (but not of IL‐8 or HMGB1). These responses appeared to be mediated via BLT 1 and BLT 2 as judged by BLT 1 shRNA gene silencing and/or treatment with BLT 1 and BLT 2 specific antagonists prior to LTB 4 activation of HUVEC. Moreover, LTB 4 responses used primarily the MAP kinase/Erk pathway. Our findings suggest a new role for LTB 4 not only in early but also in late vascular inflammatory responses.