Study on the AhR signaling pathway and phase II detoxification metabolic enzymes isoforms in scallop Chlamys farreri exposed to single and mixtures of PAHs

This study aimed to investigate the detoxification metabolism responses in scallop Chlamys farreri exposed to phenanthrene (PHE), chrysene (CHR), benzo[a]pyrene (B[a]P) and PHE + CHR + B[a]P for 15 days under laboratory conditions. The mRNA expression levels of AhR signaling pathway (AhR, HSP90, XAP2 and ARNT), detoxification system (phase I: CYP1A1 and CYP1B1; phase II: SULTs, UGT and GSTs) and ATP-binding cassette transporters (phase 0: ABCB1 and phase III: ABCC1, ABCG2) in digestive glands of scallops exposed to PHE (0.7, 2.1 mu g/L), CHR (0.7, 2.1 mu g/L), B[a]P (0.7, 2.1 mu g/L), and PHE + CHR + B[a]P (0.7 + 0.7 +0.7, 2.1 + 2.1 + 2.1 mu g/L) were detected. In present study, key genes (AhR, HSP90, XAP2 and ARNT) of the AhR signaling pathway can be significantly induced by pollutants, suggesting that the AhR/ARNT signaling pathway plays a role directly or indirectly. AhR, HSP90 and ARNT reached the maximum value on day 6, which can be preliminarily un-derstood as the synchronization of their functions. Besides, the results also indicated that different genes had specific response to different pollution exposure. CYP1B1, GST-2, GST-omega and GST-microsomal could be potional indexes to PHE, ARNT, GST-sigma 2 and GST-3 were sensitive to CHR exposure, HSP90, GST-theta and ABCG2 were considered as potional indexes to BaP while CYP1A1 and UGT were possible to be indexes for monitoring the mix exposure of these three PAHs. These findings in C. farreri suggested that phase II detoxification metabolic enzymes isoforms played an essential role in detoxification mechanisms and mRNA expression levels of specific SULTs, UGTs and GSTs were potentially to be ideal indexes in PAHs pollution research. In summary, this study provides more valuable information for the risk assessments of different rings of PAHs.