| Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic contaminants arising from incomplete combustion or pyrolysis of organic material. Exposure to PAHs has been associated with a variety of toxicity, including developmental, immunological disorders, mutagenesis and carcinogenesis in aquatic organism. It is widely held that the understanding of the toxicity caused by PAHs requires the study of AHR and its downstream genes including the CYP450enzymes. The ATP-binding cassette (ABC) transporters together with phase â… and â…¡ detoxification enzymes have been considered as cellular detoxification system. To date, a number of these detoxification genes have been cloned and studied in fish. However, many studies have focused on several genes and enzymes, e.g. CYP1A, EROD and GST, whereas other biotransformation genes, especially the CYP2genes and the ABC transporter genes, are less studied. In this study, Chinese rare minnow (Gobiocypris rarus) was selected as a model fish to evaluate the effects of phase â… and â…¡ enzymes, and ABC transporters gene mRNA expression following different individual PAHs exposure. The major findings were summarized as follows:Partial cDNA sequences of CYP1B1, CYP1C1, CYP2Aa, CYP2Y3, CYP2K, GSTmã€GCLC, ABCB1, ABCB11, ABCC1, ABCC2and ABCG2were cloned from rare minnow. Sequence alignment and phylogenetic analysis revealed the predicted amino acid sequences of these genes share high homology with the corresponding sequences of mammalian and othe fish, except for CYP2s which showed high diverse among species. The expression profiles of these genes during the early stage as well as in different tissues of rare minnow were determined by real-time PCR, and showed similar results with other fish.BaP exposure caused severe developmental defects and high mortality in rare minnow. BaP significantly up-regulated three CYP1genes as well as the ABC transporters (ABCC1, ABCC2, ABCG2) in a dose-dependent manner. Simultaneous up-regulation of the CYP and ABC transporter genes suggests a possible involvement and cooperation in the detoxification process, and provides protection against BaP toxicity at the early life stage of rare minnow.Two low molecular weight PAHs (Phenanthrene and Anthracene) significantly up-regulated sevral detoxification genes expression in rare minnow liver, and CYP1A showed the highest induction. In addition, Phenanthrene significantly up-regulated sevral detoxification genes (CYP1A, GCLC, and CYP1B1) expression in rare minnow liver, gill, and intestine, and the induction pattern varied in these tissues.The strong induction of CYP2Y3mRNA level by BaP indicates that it may be a downstream gene of AhR, and fish CYP2s may also be potential biomarker to screen AHR agonist.Two high molecular weight PAHs (Pyrene and Benzo(a)pyrene) significantly induced the expression of CYP, GST, UGT, GCLC, and ABC transporter genes. Besides, BaP significantly up-regulated the expression of phase I and II enzymes, and ABC transporter genes in rare minnow liver, gill, and intestine. Simultaneous up-regulation of the biotransformation enzyme and transporter genes suggests there may be a coordinate regulation of phase I and II enzymes, and ABC transporters, and a possible involvement and cooperation in the detoxification process of PAHs. |
