Involvement of the β ₂-integrin CD18 in apoptosis signal transduction in human neutrophils

Abstract:

Objective and design: To examine the hypothesis that an accelerated rate of neutrophil apoptosis occurs following β ₂-integrin activation, and further investigate the signal transduction pathways involved.¶Material: Human polymorphonuclear neutrophils.¶Treatment: Neutrophils were challenged with pansorbins coated with antibodies towards the β ₂-integrin subunit CD18 in a proportion of 1:100 with or without the inhibitors diphenylene iodonium (10 M), cytochalasin B (5 μg/ml), genistein (10 nM), herbimycin A (10 M) and Z-VAD-FMK (10 μM).¶Methods: Measurement of phosphatidylserine exposure and DNA fragmentation in flow cytometry and assessment of H₂O₂-production through spectrofluorometry. The results were analysed using Mann Whitney U test and Kruskal Wallis.¶Results: Pansorbins coated with antibodies to CD18 induce apoptosis in neutrophils (p<0.01), and activate the production of reactive oxygen species (p<0.01). Pre-treatment with the inhibitors have no effect on anti-CD18 induced apoptosis.¶Conclusion: Anti-CD18 pansorbins induce apoptosis in neutrophils through an alternative pathway not involving reactive oxygen species and independent of tyrosine phosphorylation, cytoskeletal reorganisation and caspases.¶