Transcriptional expression analysis of ABC efflux transporters and xenobiotic-metabolizing enzymes in the Chinese rare minnow

Abstract

In the present study, the cDNA fragments of five ABC transporter genes (ABCB1, ABCB11, ABCC1, ABCC2, and ABCG2) in the rare minnow were cloned, and their tissue-specific expression patterns were evaluated across eight rare minnow tissues (liver, gill, intestine, kidney, spleen, brain, skin, and muscle). Furthermore, the transcriptional effects on these ABC transporter genes and five xenobiotic-metabolizing enzyme genes (CYP1A, GSTm, GSTp1, GCLC, and UGT1a) were determined in the rare minnow liver after 12 days of pyrene exposure. Basal expression analysis showed that the tissues with high expression of the ABC transporters included the liver, kidney, and intestine. Moreover, the most highly expressed of the ABC genes were ABCB1 and ABCC2 in all eight of the tissues tested. The ABCB11 gene was almost exclusively expressed in the liver of the rare minnow, whereas ABCC1 and ABCG2 showed weak expression in all eight tissues compared to ABCB1 and ABCC2. Our results provide the first thorough examination of the expression patterns of toxicologically relevant ABC transporters in the rare minnow and serve as a necessary basis for further studies of these ABC transporters in fish. Furthermore, synergistic up-regulation of CYP1A, GSTp1, GCLC, UGT1a, and ABCC2 was observed in the rare minnow liver following pyrene exposure, while GSTm, ABCB1, ABCB11, ABCC1, and ABCG2 were not significantly affected (p<0.05). The synergistic up-regulation of the xenobiotic-metabolizing enzymes and ABC transporters by pyrene suggests a possible involvement and cooperation of these genes in the detoxification process in rare minnows.