The role of the
antiproteases alpha 1-proteinase inhibitor (alpha 1PI) and
mucus proteinase inhibitor (MPI) in human lung
emphysema was investigated by measuring their amount and functional activity against
trypsin,
leukocyte elastase, and
pancreatic elastase in the bronchoalveolar lavage fluid (BALF). In addition,
leukocyte elastase was quantified in the lavage samples by measuring the concentration of the
elastase-alpha 1PI-complex. The study population consisted of 38 patients (5 nonsmokers, 8 former smokers, 25 smokers) with acquired
emphysema (i.e.,
emphysema which is not caused by alpha 1PI deficiency), and 44 individuals (16 nonsmokers, 8 former smokers, 20 smokers) without
emphysema. No differences were found between patients with and without
emphysema in the activities of alpha 1PI and MPI, or in the concentration of alpha 1PI. The concentration of MPI was significantly higher in the BALF of patients with
emphysema than in that of patients without
emphysema (p = 0.025). A significantly higher concentration of
elastase-alpha 1PI complex was found in patients with
emphysema than in those without
emphysema (p = 0.041). This finding could reflect the higher
proteinase burden to which patients with
emphysema are exposed. The increase of MPI in lavage fluid of patients with
emphysema seems to be the result of increased production in emphysematous lungs. However, it remains unclear why patients develop
emphysema while showing an increased content of MPI.