THE EFFECT OF THE Z-MUTATION ON THE ABILITY OF ALPHA(1)-ANTITRYPSIN TO PREVENT NEUTROPHIL-MEDIATED TISSUE-DAMAGE

Recent studies have shown that alpha(1)-antitrypsin (alpha(1)-AT) from Z antitrypsin deficiency subjects has a slightly lower association rate constant with neutrophil elastase (NE) than (alpha(1)-AT from normal subjects, although it is unknown whether this is of clinical importance. We have purified alpha(1)-AT from a normal(M alpha(1)-AT) and from a deficient (Z alpha(1)-AT) subject and have confirmed that the association rate constants for NE are different (5.28; S.E. 0.06 10(7) M(-1) s(-1) and 1.2; S.E. 0.2 10(7) M-l s(-1) respectively). We have assessed the ability of both of these proteins to inhibit neutrophil mediated fibronectin (FN) degradation in vitro. Both proteins inhibited FN degradation in a dose dependant manner although Z alpha(1)-AT was less effective than M alpha(1)-AT at equivalent concentrations of active inhibitor (P < 0.05). Inhibition by M alpha(1)-AT was 28.5% S.E. 3.9 at 0.01 mu M; 35.5% S.E. 7.3 at 0.1 mu M and 37% S.E. 8.4 at 0.5 mu M, whereas inhibition by Z alpha(1)-AT was 9.25% S.E. 3.9; 19.25% S.E. 7.7 and 21.2% S.E. 9.7, respectively. When the time course of inhibition of FN degradation was studied the difference (although less at 1.0 mu M) became greater over the 3 h period of the assay. These results suggest that Z alpha(1)-AT is less able than the M phenotype to inhibit connective tissue degradation by neutrophils at equivalent concentrations. This is probably due to the lower association rate constant although the reduced stability of the Z molecule may play a role. The differences, together with the reduced plasma concentration, may accentuate the susceptibility of deficient subjects to the development of emphysema.