Alpha 1-proteinase inhibitor is a neutrophil chemoattractant after proteolytic inactivation by macrophage elastase

Structural transition of alpha 1-antitrypsin by a peptide sequentially similar to beta-strand s4A

Crystal structure studies have shown that cleaved and intact serpins differ essentially in the topology of beta-sheet A. This is five-stranded in the intact molecules and six-stranded after cleavage by insertion of strand s4A whose C-terminus has become free [Löbermann, H., Tokuoka, R., Deisenhofer, J. & Huber, R. (1984) J. Mol. Biol. 177, 531-556; Wright, T. H., Qian, H. X. & Huber, R. (1990) J. Mol. Biol. 213, 513-528]. The structural transition is accompanied by changes in spectral properties and an increase in thermal stability. We show here that an N alpha-acetyl-tetradecapeptide with the amino acid sequence of strand s4A, residues 345-358 of human alpha 1-antitrypsin, associates with intact alpha 1-antitrypsin and forms a stoichiometric complex with properties very similar to cleaved alpha 1-antitrypsin. Complex generation has the characteristics of a folding process.

Increased elastase secretion by peripheral blood monocytes in cystic fibrosis patients

Morbidity and mortality in cystic fibrosis (CF) is predominantly due to destruction of pulmonary tissue. The host immune response may, in part, play a pathogenic role in pulmonary destruction in these patients. To further understand host immune response in CF, we examined the state of activation of peripheral blood monocytes in CF. Baseline elastase activity was 2.2-fold greater in the CF monocytes than in controls. Pseudomonas aeruginosa mucoid exopolysaccharide (MEP) and high molecular weight polysaccharide (HMP) increased elastase activity in both control and CF monocytes, with a greater absolute increase in the CF monocytes. There was no difference in baseline or MEP-stimulated secretion of interleukin-1 (IL-1) or interleukin-6 (IL-6) between CF and control monocytes. Ibuprofen enhanced both MEP and HMP-stimulated elastase activity, whereas dexamethasone suppressed both baseline and stimulated elastase activity greater than 20% in both CF and control monocytes. These results suggest that circulating monocytes in CF are stimulated in vivo, resulting in a remarkably elevated elastase activity in vitro. Elevated elastase release by peripheral blood monocytes as they enter the lung in response to chemotactic stimuli may contribute to lung destruction in CF.

Chemoattractant activity of Staphylococcus aureus serine proteinase modified human plasma alpha-1-proteinase inhibitor

S. aureus serine proteinase inactivates human alpha-1-proteinase inhibitor (alpha-1-PI) by attacking a single peptide bond between Glu354 and Ala355 giving a modified inhibitor which is a tight complex of Mr = 4,000 and 48,000 fragments. In the present paper we show that this proteolytically inactivated alpha-1-PI is a potent chemotactic factor for human neutrophiles at a nanomolar concentration, and we discuss its potential involvement in the inflammatory reaction due to S. aureus infections.

In vivo catabolism of alpha 1-antichymotrypsin is mediated by the Serpin receptor which binds alpha 1-proteinase inhibitor, antithrombin III and heparin cofactor II

The in vivo catabolism of 125I-labeled alpha 1-antichymotrypsin was studied in our previously described mouse model. Native alpha 1-antichymotrypsin cleared with an apparent t1/2 of 85 min, but alpha 1-antichymotrypsin in complex with chymotrypsin or cathepsin G cleared with a t1/2 of 12 min. Clearance of the complex was blocked by a large molar excess of unlabeled complexes of proteinases with either alpha 1-antichymotrypsin or alpha 1-proteinase inhibitor. These studies indicate that the clearance of alpha 1-antichymotrypsin-proteinase complexes utilizes the same pathway as complexes with the homologous inhibitor alpha 1-proteinase inhibitor. Previous studies have demonstrated that this pathway is also responsible for the catabolism of two other serine proteinase inhibitors, antithrombin III and heparin cofactor II. This pathway is thus responsible for removing several proteinases involved in coagulation and inflammation from the circulation, thereby decreasing the likelihood of adventitious proteolysis.