Effect of Sulfur Dioxide on Cytokine Production of Human Alveolar Macrophages in Vitro

Abstract

Tumor necrosis factor-αa, interleukin-1β, interleukin-6, and transforming growth factor-β are cytokines synthesized by alveolar macrophages. We investigated the effect of sulfur dioxide, a major air pollutant, on the production of these cytokines by alveolar macrophages. The cells were layered on a polycarbonate membrane and exposed for 30 min to 0.0, 1.0, 2.5, and 5.0 ppm sulfur dioxide at 37 °C and 100% air humidity. The cells were incubated for 24 h after exposure, thus allowing cytokine release. Cytotoxic effects of sulfur dioxide were evaluated by trypan blue exclusion. Cytokines were measured with enzyme-linked immunosorbent assays (i.e., tumor necrosis factor-α, interleukin-1β, and interleukin-6) or by use of a specific bioassay (i.e., transforming growth factor-β). The toxicity of sulfur dioxide for alveolar macrophages ranged from 3.1% to 9.5%. A 30-min exposure to sulfur dioxide induced a significant decrease in spontaneous and lipopolysaccharide-stimulated tumor necrosis factor-α (p < .001) and lipopolysaccharide-stimulated interleukin-1β release (p < .05). The release of interleukin-6 and transforming growth factor-β was not affected significantly by sulfur dioxide exposure. Our results demonstrated a functional impairment of alveolar macrophages after sulfur dioxide exposure (i.e., release of tumor necrosis factor-α and interleukin-1β). Neither spontaneous nor stimulated release of interleukin-6 and transforming growth factor-β were influenced by exposure to sulfur dioxide.