Acute cigarette smoke exposure induces apoptosis of alveolar macrophages

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Abstract
Alveolar macrophages (AMs) may play a critical role in cigarette smoke (CS)-related pulmonary diseases. This study was designed to determine whether CS induces apoptosis of AMs. In in vitro studies, mouse, rat, and human AMs and human blood monocyte-derived macrophages cultured with aqueous whole CS extracts underwent apoptosis that was detected by light and electron microscopy and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling. The gas phase of CSE did not cause apoptosis. The CS-induced apoptosis was associated with increased oxidative stress, Bax protein accumulation, mitochondrial dysfunction, and mitochondrial cytochrome c release but was independent of p53, Fas, and caspase activation. This apoptosis was inhibited by antioxidants such as glutathione, ascorbic acid, and α-tocopherol. In in vivo studies where rats were exposed to the smoke from 10 cigarettes over 5 h in an exposure chamber, ∼3% of AMs obtained by bronchoalveolar lavage after 24 h showed apoptosis. These results suggest that acute CS exposure is capable of inducing apoptosis of AMs.