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-1 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 microM; 35.5% S.E. 7.3 at 0.1 microM and 37% S.E. 8.4 at 0.5 microM, 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 microM) 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.
Llewellyn-Jones
C G
CG
Lung Immunobiochemical Research Laboratory, General Hospital, Birmingham, UK.
Lomas
D A
DA
Carrell
R W
RW
Stockley
R A
RA
D003238:Connective Tissue / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D006720:Homozygote; D006801:Humans; D019272:Leukocyte Elastase / Q000037:antagonists & inhibitors; D009154:Mutation; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000378:metabolism*; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors; D010641:Phenotype; D000515:alpha 1-Antitrypsin / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology
D005353:Fibronectins; D000515:alpha 1-Antitrypsin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D010196:Pancreatic Elastase; D019272:Leukocyte Elastase