4-Hydroxynonenal mimics ozone-induced modulation of macrophage function ex vivo.

Ozone is a ubiquitous pollutant that can cause acute pulmonary inflammation, cellular injury and may contribute to the development or exacerbation 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 (HNE), a previously unidentified aldehyde product of ozone exposure, is formed in human subjects exposed to ozone, and whether the response of human alveolar macrophages (AM) following a 1-h exposure to 0.25 ppm ozone with moderate exercise could be mimicked by in vitro incubation of AM with HNE. Western analysis demonstrated increased HNE protein adducts in airway fluid and alveolar macrophages after ozone exposure. AM were examined for endotoxin (lipopolysaccharide [LPS])-stimulated interleukin-1 beta (IL-1 beta) release and expression of heat shock protein 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 after exposure, HSP72 levels decreased to below comparable air-exposed levels. Immediately after ozone exposure there was no effect on IL-1 beta release stimulated by LPS. However, IL-1 beta release stimulated by LPS was significantly inhibited 4 h after ozone exposure. By 18 h after ozone exposure, IL-1 beta release stimulated by LPS returned to normal. Incubation of human AM in vitro with HNE induced HSP72 and blocked LPS-stimulated IL-1 beta release possibly by inhibiting interleukin converting enzyme. Consequently, the in vitro results and demonstration of HNE protein adducts following ozone exposure are consistent with HNE being involved in this process in vivo and suggest that the cellular toxic effects of ozone could be a result of thiol reactive aldehydes produced by ozone.

Ozone-induced increases in substance P and 8-epi-prostaglandin F2 alpha in the airways of human subjects.

We are interested in the mechanisms of ozone-induced lung effects after short-term exposure and the relationship with subsequent pulmonary inflammation and disease. Our hypothesis is that ozone, as a powerful oxidant, will diminish the activity of neutral endopeptidase (NEP) in the airways of humans with resulting increased concentrations of neuropeptides such as substance P (SP). We have exposed seven (two women, five men) healthy, nonsmoking individuals (22 to 30 yr of age) to filtered air and ozone (0.25 ppm) for 1 h in an environmental chamber during heavy exercise. Bronchoscopy with airway lavage (AL) and bronchoalveolar lavage (BAL) was performed immediately after ozone exposure. The lavage samples were analyzed by enzyme immunoassay for SP and 8-epi-prostaglandin F2 alpha (8-epi-PGF2 alpha) (a marker for oxidative free radical reaction) and by radioimmunoassay for complement fragments. FEV1 had declined 12.4 +/- 1.9% (mean +/- SEM) as a result of ozone exposure. The AL concentration for SP and 8-epi-PGF2 alpha and BAL concentration of C3a after ozone exposure were significantly higher than after the filtered air exposure (P < 0.05). There was a significant correlation between SP and 8-epi-PGF2 alpha concentrations in the AL fluid (r2 = 0.89 and P < 0.05). There were no changes in C5a in either compartment or any of the mediators in the plasma samples. These results extend previous results from animal studies suggesting that ozone's mechanism of action is through an oxidative reaction resulting in a decreased activity of NEP in the airways with a subsequent increase in the concentration and activity of SP.