Chemo-attractant N-acetyl proline–glycine–proline induces CD11b/CD18-dependent neutrophil adhesion

BackgroundChronic inflammation in lung diseases contributes to lung tissue destruction leading to the formation of chemotactic collagen fragments such as N-acetylated proline–glycine–proline (N-ac-PGP). In the current study, we investigate whether N-ac-PGP influences β2-integrin activation and function in neutrophilic firm adhesion to endothelium.MethodsHuman polymorphonuclear leukocytes (PMNs) were isolated from fresh human blood. Subsequently, a transmigration assay was performed to evaluate the active migration of PMNs towards N-ac-PGP. Furthermore, the effect of the tripeptide on β2-integrin activation was assessed by performing the adhesion assay using fibrinogen as a ligand. To determine whether this effect was due to conformational change of β2-integrins, antibodies against CD11b and CD18 were used in the adhesion assay and the expression pattern of CD11b was determined.ResultsHuman neutrophils transmigrated through an endothelial cell layer in response to basolateral N-ac-PGP. N-ac-PGP induced also a neutrophil adherence to fibrinogen. Using functional blocking antibodies against CD11b and CD18, it was demonstrated that CD11b/CD18 (Mac-1) was responsible for the N-ac-PGP-induced firm adhesion of neutrophils to fibrinogen. Pertussis toxin decreased the Mac-1 activation indicating the involvement of G-proteins. N-ac-PGP most likely activated Mac-1 by initiating a conformational change, since the expression pattern of Mac-1 on the cell surface did not change significantly.ConclusionsChemo-attractant N-acetyl proline–glycine–proline induces CD11b/CD18-dependent neutrophil adhesion.General significanceThis is the first study to describe that the chemo-attractant N-ac-PGP also activates Mac-1 on the surface of neutrophils, which can additionally contribute to neutrophilic transmigration into the lung tissue during lung inflammation.

► We investigate the effect of N-ac-PGP on neutrophilic adhesion using fibrinogen.
► To determine the contribution of Mac-1 to neutrophilic adhesion, antibodies were used.
► We examine the effect of N-ac-PGP on the Mac-1 expression pattern.
► N-ac-PGP induces a conformational change of Mac-1 leading to neutrophilic adhesion.