Ligation of selectin L and integrin CD11b/CD18 (Mac-1) induces release of gelatinase B (MMP-9) from human neutrophils

Abstract.

Objective and Design: To examine whether ligation of the adhesive receptors - selectin L and Mac-1 on the neutrophil surface could induce gelatinase B exocytosis.¶Materials: Neutrophils were isolated from fresh heparinized blood of human donors by Gradisol G centrifugation and hypotonic lysis of erythrocytes.¶Methods: Integrin CD11b/CD18 and selectin L mediated adhesive interaction of human neutrophils were mimicked by binding antibodies to these receptors on the surface of isolated leukocytes. Neutrophils (5 × 10⁶/ml) were incubated with antibodies against selectin L (40 μg/ml) and CD18 or CD11b (10 μg/ml). The secretion of gelatinase was examined by determination of enzyme activity and gelatin substrate zymography of cell supernatants.¶Results: Ligation of selectin L, CD18 and CD11b integrin subunits by monoclonal antibodies induced a rapid release of 24.6 ± 1.8% (p < 0.005), 24.0 ± 2.9% (p < 0.001) and 22.7 ± 2.0% (p < 0.005) of total neutrophil gelatinase, respectively as compared with 11.1 ± 1.6% in the control. These values were equivalent to N-formyl-methionylleucylphenylalanine (fMLP)-stimulated secretion of gelatinase. Under these experimental conditions there was no significant β-glucuronidase release from azurophilic granules. Gelatinase exocytosis elicited by selectin L and CD18 ligation was inhibited by 82.7 ± 10.1% and 49.3 ± 5.9%, respectively after preincubation of the neutrophils with 10 μM herbimycin A.¶Conclusions: Ligation of selectin L and integrin CD11b/CD18 provides stimulatory signals to neutrophils which induce secretion of gelatinase B that may facilitate their transmigration into sites of inflammation.