Published ahead of print on April 25, 2008, doi:10.1165/rcmb.2007-0295OC
© 2008 American Thoracic Society DOI: 10.1165/rcmb.2007-0295OC Distal Airways in Mice Exposed to Cigarette SmokeNrf2-Regulated Genes Are Increased in Clara CellsDivision of Pulmonary and Critical Care Medicine, 1 Department of Medicine, 2 Department of Cell Biology and Physiology, and 3 Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri; 4 Department of Pathology, Phoenix Children's Hospital, Phoenix, Arizona; and 5 First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan Correspondence and requests for reprints should be addressed to Tomoko Betsuyaku, M.D., First Department of Medicine, Hokkaido University School of Medicine, Kita-15, Nishi-7 Kita-Ku, Sapporo, Japan 060-8638. E-mail: bytomoko{at}med.hokudai.ac.jp Cigarette smoke (CS) is the main risk factor for chronic obstructive pulmonary disease (COPD). Terminal bronchioles are critical zones in the pathophysiology of COPD, but little is known about the cellular and molecular changes that occur in cells lining terminal bronchioles in response to CS. We subjected C57BL/6 mice to CS (6 d/wk, up to 6 mo), looked for morphologic changes lining the terminal bronchioles, and used laser capture microdissection to selectively isolate cells in terminal bronchioles to study gene expression. Morphologic and immunohistochemical analyses showed that Clara cell predominance remained despite 6 months of CS exposure. Since Clara cells have a role in protection against oxidative stress, we focused on the expression of antioxidant/detoxification genes using microarray analysis. Of the 35 antioxidant/detoxification genes with at least 2.5-fold increased expression in response to 6 months of CS exposure, 21 were NF-E2–related factor 2 (Nrf2)-regulated genes. Among these were cytochrome P450 1b1, glutathione reductase, thioredoxin reductase, and members of the glutathione S-transferase family, as well as Nrf2 itself. In vitro studies using immortalized murine Clara cells (C22) showed that CS induced the stabilization and nuclear translocation of Nrf2, which correlated with the induction of antioxidant and detoxification genes. Furthermore, decreasing Nrf2 expression by siRNA resulted in a corresponding decrease in CS-induced expression of several antioxidant and detoxification genes by C22 cells. These data suggest that the protective response by Clara cells to CS exposure is predominantly regulated by the transcription factor Nrf2.
Key Words: antioxidant • detoxifying enzymes • laser capture microdissection • oxidative stress
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