Pulmonary inflammation by ambient air particles is mediated by superoxide anion.

Lung inflammation is a key response to increased levels of particulate air pollution (PM); however, the cellular mechanisms leading to this response remain poorly understood. We have previously shown that oxidants are critical mediators of the inflammatory response elicited by inhalation of ambient air particles. Here we tested the possible role of a specific oxidant, superoxide anion, by using the membrane-permeable analog of superoxide dismutase, Mn(III) tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP). Adult Sprague-Dawley rats were instilled with either urban air particles (UAP) or saline. MnTBAP-treated rats received 10 mg/kg (ip) MnTBAP 2 h prior to exposure to UAP. Recruitment of inflammatory cells into bronchoalveolar lavage was evaluated 4 h after instillation. Rats exposed to UAP showed significant increases in the total cell number (8.9 ± 0.6× 106; sham: 5.1 ± 0.6 × 106, p < .02), the numbers of polymorphonuclear leukocytes (26 ± 4%; sham: 6 ± 1%, p < .0001), protein levels (1.2 ± 0.5 mg/ml,...