In vitro study of human alveolar macrophage and peripheral blood mononuclear cell reactive oxygen-intermediates release induced by sulfur dioxide at different concentrations.

Sulfur dioxide (SO2) is a major air pollutant in urban areas. Alveolar macrophages (AM) located on the alveolar surface are in direct contact with this inhaled gas. We evaluated the dose-dependent effect of SO2 exposure on the oxidative metabolism of AM and peripheral blood mononuclear cells (PBMNC) by measuring the spontaneous and stimulated reactive oxygen intermediates (ROI) release. AM or PBMNC were placed on a polycarbonate membrane, which was in direct contact with the surface of a nutrient reservoir. For exposure of the cells to SO2 a special chamber was employed, in which humidified standard air with 5% CO2 at 37 degrees C was mixed with SO2 at the desired concentration. Periods of time between 30 and 120 minutes and concentrations between 0.3 and 1.5 ppm SO2 were chosen for exposure. Thirty minutes exposure of AM to SO2 (0.3-1.5 ppm) yielded a dose-dependent stimulation of ROI release; 2.0- to 3.6-fold of control (r = 0.965, p < 0.005). An exposure of 120 minutes to SO2 resulted in a similar ROI production of about 2.5-fold at all tested concentrations. These experiments provide evidence that AM and PBMNC become activated by SO2 producing large amounts of ROI.