Leukotriene D 4 activates β 2 -integrin adhesion in human polymorphonuclear leukocytes

We examined the functional role and mechanisms by which activation of cysteinyl leukotriene-1 receptor (cysLT 1 R) regulates β 2 -integrin adhesion to intercellular adhesion molecule (ICAM)-1 in human polymorphonuclear leukocytes (PMNs) in vitro . Human peripheral blood PMNs and eosinophils were isolated separately from the same mildly atopic donors. Surface expression of cysLT 1 R was identified both in PMNs and in eosinophils by immunofluorescence analysis. Total cysLT 1 R protein was substantially greater in eosinophils than in PMNs as determined by Western blot analysis. However, leukotriene D 4 (LTD 4 ) upregulated β 2 -integrin adhesion of PMNs to ICAM-1 with high efficacy in a time- and concentration-dependent manner. Upregulated β 2 -integrin adhesion of PMNs was related temporally and quantitatively to phosphorylation of 85-kDa cytosolic group IVa phospholipase A2 (gIVaPLA2). Augmented LTD 4 -induced adhesion was blocked significantly by montelukast, a cysLT 1 R antagonist. Trifluoromethylketone (a gIVaPLA2 inhibitor) blocked β 2 -integrin adhesion caused by LTD 4 activation, as did anti-CD18 monoclonal antibody directed against β 2 -integrin on the PMN surface. Our data demonstrate that LTD 4 causes phosphorylation of gIVaPLA2 and upregulation of β 2 -integrin adhesion to ICAM-1 or ICAM-1 surrogate through cysLT 1 R activation. Activation of gIVaPLA2 is a critical step through which β 2 -integrin adhesion is upregulated by the cysLT 1 R expressed on the surface membrane of human PMN.