Neutrophil elastase associated with alveolar macrophages from older volunteers

We focused on the role of neutrophil elastase (NE) in alveolar macrophages (AMs), and evaluated the esterolytic activity using an NE-sensitive substrate, methoxysuccinyl-alanyl-alanyl-prolyl-valyl paranitroanilide (MEOSAAPVNA) in AMs from 36 older healthy volunteers (61 ± 2 yr mean age ± standard error) and examined the relationship to chronic effects of cigarette smoking and also to the presence of low attenuation areas (LAAs) on the computed tomographic (CT) scans. The AMs from the subjects with LAAS showed significantly higher activity than those from the current smokers without LAA (1.16 ± 0.40 versus 0.34 ± 0.07 nM, respectively, p < 0.05). Although the study of inhibitory profile revealed that the esterolytic activity could not be attributed to NE alone, the NE activity seemed to dominate in AMs at least from some who had higher esterolytic activity. We then examined the releasability of NE from cultured AMS in 10 subjects. The immunologic NE complex with alpha 1-protease inhibitor (α₁-PI) was released significantly higher in the LAA(+) group than in the LAA(-) group (17.4 ± 6.5 versus 1.8 ± 0.6 μg/L, respectively, p < 0.05). These data suggest that NE in AMs may play a role in the development of emphysematous changes in susceptible smokers.