COMPARISON OF THE EFFECTS OF METHOXYSUCCINYL-ALA-ALA-PRO-VAL-CHLOROMETHYL KETONE-INHIBITED NEUTROPHIL ELASTASE WITH THE EFFECTS OF ITS NATURALLY-OCCURRING MUTATIONALLY INACTIVATED HOMOLOG (HBP) ON FIBROBLASTS AND MONOCYTES INVITRO

The mature neutrophils in the circulation contain, besides the different proteases known for a long time, a recently discovered proteolytically inactive elastase homologue (HBP/CAP37/azurocidin). This homologue, which we have named HBP due to its strong affinity to heparin, is a chemoattractant for monocytes and has been shown to induce reversible detachment and contraction when added to monolayers of endothelial cells or fibroblasts. HBP may therefore play a pivotal role in leukocyte migration in response to inflammation. In this report a comparison of CH3O-Suc-Ala-Ala-Pro-Val-CH2Cl-inhibited elastase with HBP, its naturally occurring homologue selectively mutated in active serine and histidine, reveals that homotypic aggregation of monocytes and contraction of fibroblasts is specific for HBP. HBP induces thrombospondin secretion from monocytes four times as efficiently as the inhibited elastase, and the same molecule was found unable to compete for a specific saturable binding of HBP to monocytes with an apparent K(D) of 3 x 10(-8)M.