α1-Antitrypsin Is Degraded and Non-Functional in Chronic Wounds But Intact and Functional in Acute Wounds: The Inhibitor Protects Fibronectin from Degradation by Chronic Wound Fluid Enzymes

Fluid obtained from chronic and acute wounds were examined for the presence of fibronectin, α1-antitrypsin, and proteinases capable of degrading both proteins. Immunoblot analysis of fluids from ten chronic wounds revealed that fibronectin and α1-antitrypsin were degraded in nine of ten samples. In contrast, both fibronectin and α1-antitrypsin were intact in acute wound fluids. The degradation of the inhibitor and fibronectin occurred in the same wound fluids, and these two events correlated perfectly. Chronic or acute wound fluid proteins were coupled to benzamidine Sepharose 6B beads and incubated with fibronectin or α1-antitrypsin. Chronic wound fluid proteins degraded fibronectin in the presence of ethylenediaminetetraacetate, leupeptin, cystatin, and pepstatin but not in the presence of phenylmethylsulfonyl fluoride. Acute wound fluids and normal human serum did not contain enzymes capable of degrading fibronectin. These data suggest that serine proteinases are responsible for fibronectin degradation in chronic wound fluids. Chronic wound fluids that contained degraded α1-antitrypsin also contain proteinases capable of degrading α1-antitrypsin from human serum. Acute wound fluids and normal human serum did not contain enzymes capable of degrading α1-antitrypsin. The inhibitor from acute wound fluids bound to one of its targets, trypsin. In contrast, the fragment(s) of α1-antitrypsin from chronic wound fluids did not bind trypsin. Chronic wounds associated with degraded fibronectin and the inhibitor contained ten- to forty-fold more elastase activity than acute wounds. The degradation of fibronectin by chronic wound fluid enzymes was inhibited by α1-antitrypsin in a dose-dependent manner. Collectively, these results demonstrate that there are enzymes in chronic wounds that perturb the function of α1-antitrypsin and allow fibronectin degradation by uninhibited serine proteinases.