Neutrophil adhesion to TNFα‐activated endothelial cells potentiates leukotrine B4production

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Abstract
Since adhesion of neutrophils (PMN) to endothelial cells may influence PMN activation responses, we examined whether adhesion of PMN to TNFα-activated human umbilical vein endothelial cells (HUVEC) stimulates leukotriene B4 (LTB4) production. Endothelial adhesivity towards PMN increased after HUVEC pretreatment with TNFα for 4 h. LTB4 production increased markedly in response to stimulation with arachidonic acid (20 μM) when PMN were added to the hyperadhesive HUVEC. In contrast, stimulation of PMN in suspension did not potentiate LTB4 production. LTB4 production persisted when PMN were applied to TNFα-pretreated HUVEC fixed with 1% paraformaldehyde excluding the possibility that metabolic activity of endothelium participates in this response. PMN adhesion to plastic and gelatin also enhanced LTB4 indicating that adhesion was critical event in inducing LTB4 production. We used monoclonal antibodies (mAb) to adhesion molecules on endothelial cells (i.e., endothelial leukocyte adhesion molecule-1 (ELAM-1) and intercellular adhesion molecule-1 (ICAM-1) or on PMN (CD18) to assess the role of PMN adhesion to the activated endothelium on LTB4 potentiation. Both anti-ELAM-1 mAb and anti-ICAM-1 mAb inhibitied PMN adhesion (by 55 and 41% respectively) as well as LTB4 production (by 65 and 50% respectively). Anti-CD18 mAB also reduced the adhesion (65%) and the LTB4 production (66%). Furthermore, combination of anti-ELAM-1 mAb (H18/7) and anti-ICAM-1 mAb (RR1/1) or of anti-ELAM-1 mAb (H18/7) and anti-CD 18 mAb (IB4) had an additive effect in inhibiting both PMN adhesion as well as LTB4 production. PMN adherence to immobolized recombinant soluble rELAM-1 or rlCAM-1 also increased LTB4 production, which was prevented with relevant mAbs. However, neither rELAM-1 nor rlCAM-1 stimulated LTB4 production of PMN in suspension. We conclude that PMN adhesion to TNFα-stimualted endothelial cells enhances LTB4 production by PMN, a response activated by binding of PMN to expressed endothelial cell surface adhesion molecules.

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