Biomarker responses in Corbicula fluminea to the presence of dioxin-like polychlorinated biphenyls and seasonal changes

Abstract

PCBs are potential genotoxicants and inductors of increased levels of ROS and oxidative stress in both humans and wildlife. In this study, biotransformation parameters and antioxidant (AO) enzymes were analyzed in the Asian clam, Corbicula fluminea, with respect to the presence of dioxin-like PCBs (dl-PCBs) in the environment. For this purpose, clams were collected from three localities with different environmental conditions. Sediments from each locality and clam tissues were analyzed for the presence of dl-PCBs. Biological responses included changes in the expression of fish CYP1A immunoreactive protein, changes in the activities of AO enzymes, SOD, CAT, GR and GPx, and the phase II biotransformation enzyme GST. Clams from the locality with the highest ΣWHO–TEQ values for sediment dl-PCBs had the highest ΣWHO–TEQ values for tissue dl-PCBs and the highest level of fish CYP1A immunoreactive protein expression. The correlations found between the concentrations of dl-PCBs and AO and GST activities revealed both concentration-dependent inhibitory and stimulatory effects. The activities of GPx, GR and GST were very sensitive to environmental xenobiotics, including dl-PCBs. The obtained results indicate that the activities of these enzymes were fine-tuned to provide optimized antioxidant responses. We also observed seasonal changes in GST and AO enzyme activities in Asian clam. The highest levels of activity were observed in spring as compared to summer or autumn. CDA, which was performed in order to classify the different clam populations, revealed a coordinated rearrangement of the clams’ metabolic components that were probably aimed at compensating for environmental fluctuations. The presented data reveal the sensitivity of C. fluminea to the presence of dl-PCBs in the environment and support the use of this clam as a sentinel species for biomonitoring studies.