Effect of in Vitro Exposure to Ozone on Eicosanoid Metabolism and Phagocytic Activity of Human and Rabbit Neutrophils

Abstract

Neutrophil infiltration to sites of tissue injury occurs during an inflammatory response, and increased numbers of these cells within the pulmonary airspaces have been described in humans and laboratory animals following exposure to ozone (O₃), a potent irritant present in photochemical smog. This study examined the effects of O₃ on selected secretory and functional activities of human and rabbit neutrophils isolated from peripheral whole blood. Cells were exposed in vitro to 0, 0.1, 0.4, and 1.0 ppm O₃ for 2 h. Neutrophil-conditioned medium (NCM) was collected 2 h after exposure and analyzed for the presence of selected eicosanoids. In addition, the phagocytic activity of exposed neutrophils was evaluated by examination of the uptake of latex microspheres. Thromboxane B₂ (TxB₂) levels were significantly reduced in the NCM from both human and rabbit cells exposed at 1 ppm. The neutrophils from both species showed a significant increase in the production/release of prostaglandin E₂ with exposure to 1.0 ppm, while the human cells also exhibited a significant increase at 0.4 ppm. There were no significant O₃-related changes in levels of prostaglandin F_2α, 6-keto-prostaglandin F_1α, or leukotriene B₄. Rabbit neutrophils showed a significant increase in phagocytic uptake of latex spheres with exposure to 0.4 and 1.0 ppm O₃, whereas the human cells exhibited no change in such activity at any ozone concentration. This study suggests that continued exposure to a pulmonary irritant of neutrophils elicited during an inflammatory response may affect the subsequent activity of these cells. Furthermore, it provides additional data for assessing comparative ozone toxicity in different species.