title: DNA damage and DNA damage response in human bronchial epithelial BEAS-2B cells following exposure to 2-nitrobenzanthrone and 3-nitrobenzanthrone: role in apoptosis.
abstract: Nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) are mutagenic and carcinogenic environmental pollutants found in diesel exhaust and on urban air pollution particles. In the present study, human bronchial epithelial BEAS-2B cells were exposed to 2-nitrobenzanthrone (2-NBA) and 3-nitrobenzanthrone (3-NBA). DNA damage responses were compared to those observed after exposure to 1-nitropyrene (1-NP) and benzo[a]pyrene (B[a]P). Examination by microscopy revealed that 3-NBA was the most potent toxic compound while weaker responses were observed with 1-NP and B[a]P. Most interestingly, 2-NBA did not induce cell death or any other stress-related responses. 3-NBA induced a typical apoptotic cell death judged by nuclear condensation and little plasma membrane damage as well as cleavage of caspase 3 and poly-(ADP-ribose) polymerase (PARP). Exposure to 3-NBA resulted in an accumulation of cells in S-phase, and further analysis by Western blotting, immunocytochemistry and flow cytometry revealed that 3-NBA induced a DNA damage response characterized by phosphorylation of ATM (ataxia-telangiectasia mutated), checkpoint kinase (Chk) 2/Chk1, H2AX and p53. The p53 inhibitor pifithrin-α inhibited 3-NBA-induced apoptosis while small effects were seen using pifithrin-μ, suggesting that 3-NBA-induced cell death is a result of transcriptional activation of p53. In conclusion, 3-NBA is a potent inducer of apoptosis, which seemed to be triggered by the DNA damage response. Furthermore, a change of the nitro-group to the second position (i.e. 2-NBA) dramatically changed the cellular reactivity of the compound.
authors.affiliation: Department of Air Pollution and Noise, Division of Environmental Medicine, Norwegian Institute of Public Health, N-0403 Oslo, Norway.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Oya
authors.forename: Johan
authors.initials: J
authors.lastname: Ovrevik
authors.forename: Volker M
authors.initials: VM
authors.lastname: Arlt
authors.forename: Eszter
authors.initials: E
authors.lastname: Nagy
authors.forename: David H
authors.initials: DH
authors.lastname: Phillips
authors.forename: Jørn A
authors.initials: JA
authors.lastname: Holme
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D064007:Ataxia Telangiectasia Mutated Proteins; D001551:Benz(a)Anthracenes / Q000737:chemistry / Q000633:toxicity*; D015153:Blotting, Western; D001980:Bronchi / Q000166:cytology*; D053148:Caspase 3 / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D048430:Cell Shape / Q000187:drug effects; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D018736:DNA Adducts / Q000378:metabolism; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D005434:Flow Cytometry; D006657:Histones / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008856:Microscopy, Fluorescence; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016196:S Phase / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D001551:Benz(a)Anthracenes; D018797:Cell Cycle Proteins; D018736:DNA Adducts; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D011065:Poly(ADP-ribose) Polymerases; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases; D053148:Caspase 3; C117220:3-nitrobenzanthrone