Toxicology Letters 174 (2007) 10–17 Available online at www.sciencedirect.com Dynamic changes of XPA, XPC, XPF, XPG and ERCC1 protein expression and their correlations with levels of DNA damage in human bronchial epithelia cells exposed to benzo[a]pyrene Jin Yang, Xiaoyong Liu, Piye Niu, Yunfeng Zou, Zhiyong Gong, Jing Yuan, Tangchun Wu ∗ Department of Occupational and Environmental Health and Ministry of Education Key Lab for Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Hangkong Road 13, 430030 Wuhan, China Received 11 June 2007; received in revised form 5 August 2007; accepted 7 August 2007 Available online 11 August 2007 Abstract Benzo[a]pyrene (BaP) is a ubiquitously distributed environmental pollutant known to cause DNA damage, which may be repaired through nucleotide excision repair (NER). However, little is known about dynamic changes in levels of DNA damage and their correlations with levels of NER proteins in cells exposed to BaP. In a series of experiments using the human bronchial epithelia cells (16HBE) exposed to different concentrations of BaP for different times, we measured dynamic changes in levels of DNA damage and expression of NER subunit xeroderma pigmentosum (XP) groups A, C, F, G (XPA, XPC, XPF, XPG) and excision repair cross-complementing 1 (ERCC1), and analyzed their possible correlations. We found that in vitro exposure to BaP reduced cell viability in a dose-dependent manner ranging from 2 to 64 M and increased DNA damage in a dose- and time-dependent manner. Our results showed that levels of these NER proteins significantly increased and peaked at 12th or 24th, 8th or 12th and 4th or 8th hours in cells exposed to 2, 8 and 16 M BaP, respectively. ERCC1 expression increased by 2.4-, 4.2- and 19.3-fold for exposure to 2, 8 and 16 M BaP, respectively, compared with control group. Moreover, levels of ERCC1 in cells exposed 16 M BaP significantly higher than those in 2 and 8 M BaP from 2nd to 48th hours. In addition, there was a significant positive correlation between Olive tail moments and relative ratios of ERCC1 in cells exposed to BaP. Our results suggested ERCC1 may be an important limiting factor for NER, but the mechanisms underlying this observation needs further investigation. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Benzo[a]pyrene; Nucleotide excision repair; Human bronchial epithelia cells 1. Introduction Polycyclic aromatic hydrocarbons (PAHs) are a class of stable organic molecules. They are ubiquitous envi- ∗ Corresponding author. Tel.: +86 27 8369 2347; fax: +86 27 8369 2560. E-mail address: wut@mails.tjmu.edu.cn (T. Wu). ronmental pollutants and are produced as a consequence of the incomplete combustion of organic materials. Benzo[a]pyrene (BaP) is a main member of PAHs, which is a potent carcinogen as tested in many different ani- mal models (Tokiwa et al., 1993). BaP is metabolized by cytochrome P450 enzymes to mutagenic derivatives that can form DNA adduct and cause DNA damage. It is this property that is generally believed to account for the tumorigenic activity of BaP (Hecht et al., 1993). 0378-4274/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.toxlet.2007.08.004