Carcinogenesis Advance Access published online on August 14, 2003
Carcinogenesis, doi:10.1093/carcin/bgg144
© 2003 by Oxford University Press
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CARCINOGENESIS
1 Institute of Public Health, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
* Corresponding author. E-mail: s.loft{at}pubhealth.ku.dk.
Received 27 May 2003
; revised 11 July 2003
; accepted 4 August 2003
Exposure to diesel exhaust particles (DEP) is suspected to contribute to lung cancer and cardiopulmonary diseases. In recent years generation of reactive oxygen species capable of inducing cellular oxidative stress has been in focus as one of the underlying mechanisms behind the genotoxic effects of particles. However, the role of the antioxidative defence system still needs to be clarified, especially in relation to low-dose DEP exposures. The aim of this study was to characterise the effects of short-term exposure to DEP in terms of DNA damage and expression of key response genes towards oxidative stress in lungs of mice. Mice were exposed by inhalation to 20 or 80 mg/m3 DEP inhaled as either a single dose, or four lower doses (5 and 20 mg/m3) inhaled on four consecutive days. Our results indicate that HO-1 mRNA expression in lung tissue was up-regulated after both types of DEP exposures, whereas OGG1 expression was only up-regulated after repeated exposures. The level of oxidative DNA damage in terms of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) was increased in the lung tissue after a single exposure, whereas increased levels of DNA strand breaks was observed in bronchoalveolar lavage cells after repeated DEP exposures. The levels of 8-oxodG and OGG1 mRNA level in lung tissue were mirror images. This suggest that after repeated exposures, up-regulation of DNA repair counteracts an increased rate of 8-oxodG formation leaving the steady state level of 8-oxodG in DNA unchanged. In conclusion, this study indicates that a single high dose of DEP generates 8-oxodG in lung tissue, whereas the same dose inhaled as four low-exposures may up-regulate the antioxidative defence system and protect against generation of 8-oxodG.
Diesel exhaust particles, DNA repair, gene expression, Oxidative DNA damage, heme oxygenase-1, inhalation, oxidative stress
Oxidative DNA damage and defence gene expression in the mouse lung after short-term exposure to diesel exhaust particles by inhalation
2 National Institute of Occupational Health, Lersø Parkallé 105, DK-2100 Copenhagen 
, Denmark
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