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

Chronic 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 β(2)-integrin activation and function in neutrophilic firm adhesion to endothelium.

Human 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 β(2)-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 β(2)-integrins, antibodies against CD11b and CD18 were used in the adhesion assay and the expression pattern of CD11b was determined.

Human 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.

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

This 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.