Figure 1.

The markers of oxidative stress are derived from different cells and cell compartments in the alveolar or bronchiolar wall. Neutrophilic granulocytes express myeloperoxidase (MPO) and eosinophilic granulocytes are endowed with eosinophilic peroxidase (EPO). Inducible nitric oxide synthase (iNOS) is expressed in the inflamatory cells and bronchial epithelium. 4-hydroxy-2-nonenal (4-HNE) and 3-nitrotyrosine can be detected in a variety of cell types. Hydrogen peroxide (H₂O₂), nitric oxide (NO), carbon monoxide (CO), and 8-isoprostane (8-iso) represent widely investigated markers in the exhaled air/exhaled breath condensate.