Triggered human neutrophils were able to maintain released elastase in an active form in the presence of purified alpha-lproteinase inhibitor (a-l-PI), serum or bronchoalveolar lavage fluid (BAL). The accumulation of free elastase activity was associated with a decrease in the ability of the a-l-PI to inhibit porcine pancreatic elastase, an increase in proteinase activity associated with a-2-mac*roglobulin, and the oxidation of a-l-PI to a molecule containing four methionine sulfoxide residues. Neutrophils used both hypochlorous acid and long-lived N-chloroamines to oxidize the a-l-PI, but hypochlorous acid was preferentially used for suppressing the activity of the antiproteinase over short distances whereas the N-chloroamines were effective even when the phagocytes and a-l-PI were physically separated. Sodium dodecyl sulfate-polyacryhamide gel electrophoresis of purified a-l-PI, serum, or BAL that had been incubated with triggered neutrophils revealed that the released neutrophil elastase was not complexed with the antiproteinase and that a portion of the a-l-PI had undergone proteolysis. These data suggest that the presence of free neutrophil elastase as well as inactive, oxidized,and proteolyzed a-l-PI in fluids recovered from inflammatory sites in vivo could be directly mediated by triggered neutrophils alone.

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Although the mesquite plant (Prosopis velutina) is not as widely distributed as some other allergenic species, its pollen can induce serious pollinosis in areas where it is localized. We previously isolated and characterized a peptidase from mesquite pollen with trypsin-like specificity (peptidase I mes ) (Matheson, N., Schmidt, J., and Travis, J. (1995) Am. J. Respir. Cell Mol. Biol. 12, 441-448). Now we have characterized a second enzyme with specificity for hydrophobic residues (mesquite pollen peptidase II mes ). This enzyme has a molecular mass near 92 kDa and activity that was not affected by reducing or chelating agents but was inhibited by specific synthetic serine proteinase inhibitors and the aminopeptidase inhibitor bestatin. However, it was not inhibited by human plasma proteinase inhibitors, nor did it inactivate any of those tested. The enzyme possessed amidolytic activity against p-nitroanilide substrates most effectively after alanine residues and also displayed aminopeptidase activity against non-p-nitroanilide peptides with a preference for phenylalanine. This specificity for hydrophobic amino acid residues was corroborated by inhibition studies with chloromethyl ketone and organophosphonate inhibitors. More interesting from a physiological point of view is that the bioactive peptides, angiotensins I and II and vasoactive intestinal peptide, were also hydrolyzed rapidly, indicating an ability of peptidase II mes to act also as an oligopeptidase. Because these bioactive peptides play a role in the inflammatory responses in allergic asthma, our data suggest that the purified mesquite pollen peptidase II mes may be involved in the degradation of neuro-and vasoactive peptides during pollen-initiated allergic reactions.Asthma is an allergic inflammation of the lungs which can occur after allergen sensitization. Such inflammatory responses are normally meant to defend against invading organisms or particulates or to effect tissue repair and are thus beneficial; however, in asthma, the response becomes exaggerated (perhaps because of a hereditary predisposition (1)), leading to adverse effects on the airways (2). Macrophages phagocytize the allergens introduced to the lungs by exposure to various environmental irritants such as dust, pollutants, and pollen, and process them to smaller fragments. As antigenpresenting cells, they then activate T-cells (3, 4) to stimulate B-cells to produce IgE. This immunoglobulin, when bound to a specific allergen, in turn, stimulates and activates several alveolar cell types to produce the many mediators of inflammation: histamine, prostaglandins, leukotrienes, cytokines, neutral proteases, active oxygen species, and chemoattractants (5). The interaction of these mediators leads to the pathology of asthma, including bronchoconstriction, hypertrophy of airway smooth muscle, vasodilation, submucosal edema, and mucus hypersecretion (6). Also, the mucociliary apparatus becomes dysfunctional, reducing the clearance of inhaled particulates. Epithelial cells lining the airwa...