Nitrogen dioxide-induced reactive oxygen intermediates production by human alveolar macrophages and peripheral blood...

Alveolar macrophages located on the alveolar surface have contact with air pollutants. We evaluated the dose-dependent effect of nitrogen dioxide exposure on the oxidative metabolism of alveolar macrophages and peripheral blood mononuclear cells by measuring the spontaneous and stimulated reactive oxygen intermediates production. Alveolar macrophages or peripheral blood mononuclear cells were placed on a polycarbonate membrane, which was in direct contact with the surface of a nutrient reservoir. The cells were exposed to nitrogen dioxide during different periods of time, varying between 30 and 120 min at concentrations ranging from 0.1 to 0.5 ppm. Exposure of alveolar macrophages to nitrogen dioxide for 30 min yielded a dose-dependent stimulation of reactive oxygen intermediates generation of 1.7- to 2.9-fold of control. An 120-min exposure to nitrogen dioxide at concentrations between 0.1 and 0.5 ppm resulted in a similar reactive oxygen intermediates production of about 1.9- to 2.2-fold of control at all concentrations tested. The nitrogen dioxide exposure to peripheral blood mononuclear cells yielded identical results. These experiments demonstrate that alveolar macrophages and peripheral blood mononuclear cells become activated by nitrogen dioxide and that concentrations up to 0.5 ppm nitrogen dioxide induce an increase in reactive oxygen intermediates production after 30 to 120 min exposure of the cells.