Plasminogen activator inhibitor 2 (PAI-2) is not inactivated by exposure to oxidants which can be released from activated neutrophils

Purified recombinant human monocyte plasminogen activator inhibitor 2 (PAI-2) retained inhibitory activity after exposure to a number of oxidants, including hypochlorite anion (OCl-), chloramine-T (CT) and hydrogen peroxide (H2O2). Analysis of PAI-2 exposed to oxidants by gel filtration chromatography and SDS-PAGE indicated that although the protein could no longer be detected by silver staining, this was not due to fragmentation of the PAI-2 molecule. The sensitivity of a number of serine protease inhibitors (serpins), (eg. alpha 1 proteinase inhibitor (alpha 1PI) and plasminogen activator inhibitor 1 (PAI-1] to oxidative inactivation has been attributed to oxidation of reactive site methionine residues and/or tertiary structural modifications. The relevance of these phenomena and the potential for PAI-2 to be used as a therapeutic inhibitor of urokinase (uPA)-dependent proteolysis during inflammation and tumour metastasis is discussed.