Dose metric evaluation of a cell-based bioassay for assessing the toxicity of metals to Dugong dugon: Effect of metal-media interactions on exposure concentrations

• Published in: Aquatic toxicology 2023-02, Vol.255, p.106394, Article 106394
• Main Authors: Bailey, David, Finlayson, Kimberly A., Dogruer, Gulsah, Bennett, William W., van de Merwe, Jason P.
• Format: Article
• Language: English
• Subjects: Animals; Biological Assay; Cadmium; Cadmium - metabolism; Cadmium - toxicity; Chromium; Cytotoxicity; Dugong - metabolism; In vitro bioassay; Metals - metabolism; Risk assessment; Trace Elements - metabolism; Water Pollutants, Chemical - toxicity
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2023.106394

•Cytotoxicity of Cr and Cd were assessed in dugong primary skin fibroblasts.•Interactions of Cr and Cd with media constituents were investigated.•Significant binding occurred between Cd and media constituents, but not Cr.•Cytotoxicity of Cd to dugong cells was underestimated by an order of magnitude.•A chemical risk assessment found Moreton Bay dugongs at high risk from Cd. Cell-based toxicity testing has emerged as a useful tool in (eco)toxicological research, allowing the ethical assessment of the effects of contaminants such as trace metals on marine megafauna. However, metal interactions with various dissolved ligands in the microplate environment may influence the effective exposure concentrations. Hence, the cells are not exposed to the nominal concentrations within the test system. This study aimed to establish and evaluate the effectiveness of cell-based bioassays for investigating the toxicity of selected metals in dugongs through the following objectives: (1) measure the cytotoxic potential of cadmium (Cd2+), and chromium (Cr6+) to dugong skin cell cultures, (2) investigate the interactions between media constituents and selected trace metals in cell-based bioassays, and (3) evaluate the risk to a free-ranging population of dugong based on effect values. Chromium was the most toxic of the metals tested (EC50 = 1.14 µM), followed by Cd (EC50 = 6.35 µM). Assessment of ultrafiltered (< 3 kDa) exposure media showed that 1% and 92.5% of Cr and Cd were associated with larger organic components of the media. Further, the binding of Cd to media constituents was calculated to underestimate Cd toxicity in cell-based assays by an order of magnitude. This understanding of metal partitioning in cell-based bioassays provides a more accurate method for assessing toxicity in cell-based bioassays. In addition, this study illustrated that dugong cells are more sensitive to Cr and Cd than other marine wildlife species. The chemical risk assessment found the dugong population in Moreton Bay to be at high risk from Cd exposure. [Display omitted]