Leukotriene B4-induced changes in vascular permeability are mediated by neutrophil release of heparin-binding protein (HBP/CAP37/azurocidin).

In humans, heparin-binding protein (HBP) and the potent chemotactic lipid leukotriene B(4) (LTB(4)) are important mediators of innate immune responses. Here we show that human neutrophils (PMNs) challenged with LTB(4) (30 s to 5 min) release HBP as determined by Western blot analysis. This response peaks at 100 nM of agonist and is mediated by the BLT1 receptor. Protein phosphatase-1 (30 microM) and wortmannin (0.5 microM) block the LTB(4)-mediated HBP release from PMNs, which suggests involvement of the 1-phosphatidylinositol 3-kinase intracellular pathway during degranulation. Furthermore, postsecretory supernatants from LTB(4)-stimulated PMNs induce intracellular calcium mobilization in endothelial cells in vitro and increase in vascular permeability in vivo, as assessed in a mouse model of pleurisy. Selective removal of HBP from the supernatant significantly reduces these activities attributing a key role to HBP in the LTB(4)-induced change in vascular permeability. This lipid-protein axis could offer novel opportunities for pharmacological intervention in key steps of the vascular response to inflammation.