The aim of this work was to evaluate the ability of guinea pig alveolar epithelial type II cells to generate significant amounts of reactive oxygen species to inactivate alpha 1-proteinase inhibitor (alpha 1-PI). Inactivation of alpha 1-PI was evaluated by its inhibitory activity against porcine pancreatic elastase and was expressed as a percentage. The same experiments were performed in parallel with alveolar macrophages (AM) obtained from the same animals and with MRC-5 fibroblasts. Both type II cells and AM released significant amounts of hydrogen peroxide and superoxide, whereas the fibroblasts did not. Unstimulated type II cells (0.5 +/- 2%), AM (1.2 +/- 1.5%), and fibroblasts (0.5 +/- 0.5%) were unable to inactivate alpha 1-PI. Addition of phorbol myristate acetate did not increase their ability to inactivate alpha 1-PI. In contrast, type II cells (79.7 +/- 7%) and AM (80.1 +/- 8%) dramatically inactivated alpha 1-PI in the presence of myeloperoxidase (25 mU/ml), whereas fibroblasts did not. Addition of catalase to the reaction significantly prevented the inactivation of alpha 1-PI. Western blot analysis of alpha 1-PI did not reveal a significant proteolysis of alpha 1-PI, which supports the hypothesis that, in the presence of neutrophil-derived myeloperoxidase, type II cells may oxidatively inactivate alpha 1-PI.
No takes yet. Share an insight, caveat, or question.
Wallaert et al. (1993) studied this question.