Comparative toxicity of selected PAHs in rainbow trout hepatocytes: genotoxicity, oxidative stress and cytotoxicity

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants in aquatic ecosystems, which may have potentially toxic effects on organisms. In this study occurrence of DNA strand breaks, oxidative stress, and cytotoxicity were investigated in rainbow trout hepatocytes following in vitro exposure for 24 h to four PAHs (0.01–10 µM): naphthalene, fluoranthene, pyrene, and benzo[a]pyrene (B[a]P). The exposed hepatocytes were analyzed for DNA strand breaks using the comet assay and for antioxidant status by measuring intracellular glutathione (GSH) content using the fluorescent probe mBCl. The cytotoxicity of PAHs was assessed using the fluorescent probe CFDA-AM. The results showed that fluoranthene, pyrene, and B[a]P were genotoxic at all exposure concentrations, whereas naphthalene was genotoxic at concentrations ≥0.1 µM. All treatments reduced the intracellular concentrations of GSH for all four PAHs, except 10 µM of B[a]P, suggesting that some level of oxidative stress was present. The cytotoxic effect was observed for naphthalene at concentrations ≥0.1 µM and pyrene at all exposure concentrations, whereas fluoranthene and B[a]P were not cytotoxic at the tested concentrations. The study shows that low-molecular-weight PAHs may cause DNA strand breaks as high-molecular-weight PAHs do in fish tissue. In addition, two- to five-ring PAHs can induce oxidative stress and cytotoxicity.

KEYWORDS:

• Oncorhynchus mykiss
• hepatocytes
• polycyclic aromatic hydrocarbons (PAHs)
• DNA strand breaks
• oxidative stress
• cytotoxicity

Acknowledgements

The author thanks Prof. Ketil Hylland for advise in designing the experiments, Dr. Tor Fridrik Holth for technical advise during the experiments, Dr. Gunnar Brunborg for logistic support, and Mrs. Hildegunn Dahl for assistance in the preliminary experiments. Prof. Hylland and Dr. Holth provided critical inputs, which helped to improve the manuscript.

Disclosure statement

The author has no competing interests as defined by Drug and Chemical Toxicology, or other interests that might be perceived to influence the interpretation of the article. The author alone is responsible for the content and writing of the paper.

Additional information

Funding

This research was funded by the Faculty of Mathematics and Natural Sciences, University of Oslo.