Preliminary investigations have shown that cigarette smoking is associated with an increase in the iron (Fe) content of alveolar macrophages (AM). They also show that Fe, which has been newly internalized by AM via transferrin, is largely transferred to ferritin within 24 hours after its internalization. Ferritin- associated Fe may be released and serve as a potential source of metabolically active Fe. It is hypothesized that AM associated Fe may promote hydroxyl radical (OH.) mediated damage of pulmonary epithelial cells, enhancing the movement of proteases from the alveolar space to the interstitium where they produce the elastin degradation that is of central importance in the pathogenesis of emphysema. The first goal will be to further characterize the contents of Fe and Fe binding proteins in the lower respiratory tract. The ferritin content of AM will be determined and the potential for AM to release their ferritin- associated Fe will be assessed in the presence of ascorbic acid or superoxide anion. The quantities of lactoferrin that are bound to AM or present in bronchoalveolar fluid will be determined, as Fe bound to this protein may also participate in OH. production by AM. The second goal will be define how AM-associated Fe may promote oxidative damage to membranes in an in vitro model using the resealed erythrocyte membrane vesicle (EMV) as a target and the AM as a generator of reactive oxygen species. Oxidant production by AM will be assessed under the conditions used to study EMV damage, to correlate the release of 14C- sucrose from resealed EMV with the Fe content and oxidant production of AM. Peroxidation of erythrocyte membrane lipids will be measured and correlated with the extent of EMV damage which is reflected by the release of 14C-sucrose. The concentration of Fe and anti-oxidants inside and outside the AM will be modulated and alterations in the AM's ability to injure the EMV target will be assessed. Thirdly, alveolar epithelial permeability will be studied in isolated-perfused hamster lungs to relate the biochemical observations made in the EMV model to oxidant damage that may occur in the lung in vivo. The alveolar clearance of 14C-sucrose and 70,000 dalton, 125I-dextran (an index of alveolar epithelial permeability) will be determined in the presence of oxidants produced by non-cellular generating systems or by AM. The alterations in epithelial permeability that occur in the presence of oxidants will be correlated with the generation of lipid peroxidation products in the lung. The influence of Fe on oxidant-mediated damage to the alveolar epithelium will also be assessed in isolated-perfused hamster lungs.
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