title: Aldo-keto reductase 1C2 is essential for 1-nitropyrene's but not for benzo[a]pyrene's induction of p53 phosphorylation and apoptosis.
abstract: It is reported that diesel exhaust particles contain more 1-nitropyrene (1-NP) than benzo[a]pyrene (B[a]P), both of which are potent carcinogenic compounds. In this study, we show that 1-NP is more potent in reducing cell viability than B[a]P, pyrene, nitrobenzene, and nitromethane. Aldo-keto reductases (AKRs) are enzymes which metabolize polycyclic aromatic hydrocarbons into active metabolites that form PAH-DNA-adducts causing mutagenesis of DNA. We found that the AKR1C2 inhibitor, ursodeoxycholic acid (UA), inhibited 1-NP-induced, but not B[a]P-induced, phosphorylation of p53 and cleavage of poly (ADP-ribose) polymerase (PARP). 1-NP-induced apoptosis was also suppressed by UA, as detected by Hoechst 33342 staining, flow cytometric analysis of subG0/G1 phase and annexin V binding to phosphatidylserine. The AKR1C1 and 1C4 inhibitor, 1,10-phenanthroline (Phen), inhibited the toxic effects of both 1-NP and B[a]P. In contrast, the AKR7A1 and 7A5 inhibitors, succinate and citrate, did not influence the toxic effects of 1-NP or B[a]P. In addition, several metabolic and signaling pathways were analyzed, these were used to compare the results of the toxic effect of AKRs on 1-NP and B[a]P. Through the application of kinase inhibitors, results indicated that p38-MAPK, but not ERK1/2 or JNK, was essential for mediating both 1-NP's and B[a]P's induction of the phosphorylation of p53 and cleavage of PARP. Neither ellipticine, a CYP1A1 inhibitor, nor 2,6-diisopropylphenol, a CYP1A2 and 2B1 inhibitor, blocked the toxic effects of 1-NP and B[a]P, which indicates that neither CYP1A1, 1A2, nor 2B1 is essential for the transformation of 1-NP and B[a], into toxic metabolites. AKR1C2 was constitutively expressed in HepG2 cells and was not regulated by 1-NP or B[a]P. In conclusion, this is the first report on AKRs' actions toward nitro-PAH in cells. The metabolic and signaling pathways for the toxic effects of both 1-NP and B[a]P are similar except that AKR1C2 plays differential role between them. The results provide valuable information for further investigations on AKRs.
authors.affiliation: Department of Biochemical Science and Technology, College of Life Sciences, National Chiayi University, Chiayi 600, Taiwan. jgjsu@mail.ncyu.edu.tw
authors.forename: Jyan-Gwo J
authors.initials: JG
authors.lastname: Su
authors.forename: Pei-Jyuan
authors.initials: PJ
authors.lastname: Liao
authors.forename: Min-Cong
authors.initials: MC
authors.lastname: Huang
authors.forename: Wen-Cheng
authors.initials: WC
authors.lastname: Chu
authors.forename: Shin-Chang
authors.initials: SC
authors.lastname: Lin
authors.forename: Yu-Jung
authors.initials: YJ
authors.lastname: Chang
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000449:Aldehyde Reductase; D000074408:Aldo-Keto Reductases; D017209:Apoptosis / Q000187:drug effects*; D001562:Benzimidazoles; D001564:Benzo(a)pyrene / Q000378:metabolism / Q000633:toxicity*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D005434:Flow Cytometry; D005456:Fluorescent Dyes; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D009153:Mutagens / Q000378:metabolism / Q000633:toxicity*; D010766:Phosphorylation / Q000187:drug effects; D010957:Plasmids / Q000187:drug effects / Q000235:genetics; D011084:Polycyclic Aromatic Hydrocarbons / Q000378:metabolism; D011721:Pyrenes / Q000378:metabolism / Q000633:toxicity*; D015398:Signal Transduction / Q000187:drug effects; D013778:Tetrazolium Salts; D013844:Thiazoles; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D001562:Benzimidazoles; D005456:Fluorescent Dyes; D007527:Isoenzymes; D009153:Mutagens; D011084:Polycyclic Aromatic Hydrocarbons; D011721:Pyrenes; D013778:Tetrazolium Salts; D013844:Thiazoles; D016159:Tumor Suppressor Protein p53; D001564:Benzo(a)pyrene; D000429:Alcohol Oxidoreductases; D000074408:Aldo-Keto Reductases; D000449:Aldehyde Reductase; D008156:Luciferases; C022616:thiazolyl blue; C017807:bisbenzimide ethoxide trihydrochloride; C032668:1-nitropyrene