Recombinant human secretory leukocyte-protease inhibitor: in vitro properties, and amelioration of human neutrophil elastase-induced emphysema and secretory cell metaplasia in the hamster.

Studies were undertaken to evaluate the in vitro properties of recombinant human secretory leukocyte-protease inhibitor (rSLPI) that had been made in Escherichia coli in an inactive form and refolded, and to determine whether emphysema and bronchial secretory cell metaplasia, induced in hamsters by intratracheal treatment with human neutrophil elastase (HNE), could be amelio-rated by prior intratracheal instillation of rSLPI. Chromatographic studies indicated that 3H-rSLPI formed a 1:1 complex with HNE. Blockage of the active site of HNE by a covalently bound tetrapeptide chloromethyl ketone reduced complex formation with 3H-rSLPI by more than 98%. Incubation of 3H-rSLPI-HNE complex with alpha 1-protease inhibitor for 3 hours at 37 degrees C decreased the amount of complex compared with incubation in the presence of bovine serum albumin (70% vs 27% dissociated). The calculated dissociation rate constant was 1.1 x 10(-4) sec-1, indicating a 1.8 hour dissociation half-life. Dissociated 3H-rSLPI retained its ability to recombine with HNE. rSLPI was as effective at inhibiting HNE released from stimulated neutrophils as 3H-rSLPI was at inhibiting purified HNE. Intratracheal pretreatment of hamsters with 3000 micrograms of rSLPI as long as 8 hours before the intratracheal instillation of 250 micrograms of HNE, resulted in significant protection against induction of emphysema and secretory cell metaplasia. One and 4 hours after instillation of rSLPI, 59% and 44%, respectively, of the initial functional activity was recovered in lung lavage supernatant, indicating a half-life of approximately 2 hours.(ABSTRACT TRUNCATED AT 250 WORDS)