4-HYDROXYNONENAL MIMICS OZONE-INDUCED MODULATION OF MACROPHAGE FUNCTION EX-VIVO

Ozone is a ubiquitous pollutant that can cause acute pulmonary inflamm ation, cellular injury and may contribute to the development or exacer bation of chronic lung diseases. Despite much research, the effects of ozone on humans and potential cellular mechanisms of injury are still uncertain. However, ozone has been reported to increase the formation of aldehydes that could react with cellular proteins. Therefore, the purpose of these studies was to determine whether 4-hydroxynonenal (HN E), a previously unidentified aldehyde product of ozone exposure, is f ormed in human subjects exposed to ozone, and whether the response of human alveolar macrophages (AM) following a 1-h exposure to 0.25 ppm o zone with moderate exercise could be mimicked by in vitro incubation o f AM with HNE. Western analysis demonstrated increased HNE protein add ucts in airway fluid and alveolar macrophages after ozone exposure. AM were examined for endotoxin (lipopolysaccharide [LPS])-stimulated int erleukin-1 beta (IL-1 beta) release and expression of heat shock prote in 72 (HSP72). Immediately after ozone exposure there was no change in HSP72, but a 5-fold increase occurred 4 h after exposure. By 18 h aft er exposure, HSP72 levels decreased to below comparable air-exposed le vels. Immediately after ozone exposure there was no effect on IL-1 bet a release stimulated by LPS. However, IL-1 beta release stimulated by LPS was significantly inhibited 4 h after ozone exposure. By 18 h afte r ozone exposure, IL-1 beta release stimulated by LPS returned to norm al. Incubation of human AM in vitro with HNE induced HSP72 and blocked LPS-stimulated IL-1 beta release possibly by inhibiting interleukin c onverting enzyme. Consequently, the in vitro results and demonstration of HNE protein adducts following ozone exposure are consistent with H NE being involved in this process in vivo and suggest that the cellula r toxic effects of ozone could be a result of thiol reactive aldehydes produced by ozone.