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Objectives <p>This study evaluated the acute toxicity and interaction patterns of chromium (Cr), zinc (Zn), and copper (Cu) in single and combined exposures in <i>Diaphanosoma celebensis</i>, and examined associated transcriptional responses of antioxidant defense-related genes.</p> Methods <p>Acute toxicity tests (48h) were conducted to determine LC<sub>50</sub> values for single metals and binary/ternary mixtures. Mixture toxicity was assessed using toxicity units (TU) and compared with concentration addition (CA) and independent action (IA) models. Gene expression was analyzed by qRT-PCR after exposure to sublethal concentrations (1/10 and 1/2 LC<sub>50</sub> or ΣTULC<sub>50</sub>).</p> Results <p>LC<sub>50</sub> values were 2.342&#xa0;mg/L for Cr, 2.256&#xa0;mg/L for Zn, and 0.286&#xa0;mg/L for Cu, indicating highest toxicity of Cu. Mixtures showed LC<sub>50</sub> values of 2.533&#xa0;mg/L (Cr–Zn), 5.414&#xa0;mg/L (Cr–Cu), 2.546&#xa0;mg/L (Zn–Cu), and 1.714&#xa0;mg/L (Cr–Zn–Cu). Based on the ΣTULC<sub>50</sub>, Cr–Zn and Cr–Zn–Cu exhibited additive effects, whereas Zn–Cu and Cr–Cu showed antagonistic interactions. Gene expression analysis showed that single-metal exposure upregulated <i>CuZn-SOD</i>, <i>catalase</i>, <i>Nrf</i>, and <i>GST-S</i>. Under mixture exposure, <i>Nrf</i> was consistently upregulated in all groups, whereas <i>GST-S</i> and <i>GST-mu</i> were most strongly induced in the antagonistic Cr–Cu and Zn–Cu mixtures, suggesting distinct detoxification responses depending on metal combination.</p> Conclusion <p>This study highlights that the toxicity of Cr, Zn, and Cu mixtures varies depending on metal combination, showing both additive and antagonistic interaction. The marked upregulation of <i>GST-S</i> and <i>GST-mu</i> in the antagonistic Cr–Cu and Zn–Cu mixtures suggests enhanced activation of glutathione-mediated detoxification pathways, although the underlying mechanisms require further investigation. Overall, these findings emphasize the importance of considering metal interactions and integrating molecular and organism-level endpoints in ecotoxicological assessment.</p>

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Single and combined effects to chromium, zinc, and copper in the brackish water flea Diaphanosoma celebensis

  • 期刊论文

  • 发表日期：

    2026年7月22日

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  • Hyesung Lee,
  • Je-Won Yoo,
  • Young-Mi Lee

摘要

Objectives

This study evaluated the acute toxicity and interaction patterns of chromium (Cr), zinc (Zn), and copper (Cu) in single and combined exposures in Diaphanosoma celebensis, and examined associated transcriptional responses of antioxidant defense-related genes.

Methods

Acute toxicity tests (48h) were conducted to determine LC50 values for single metals and binary/ternary mixtures. Mixture toxicity was assessed using toxicity units (TU) and compared with concentration addition (CA) and independent action (IA) models. Gene expression was analyzed by qRT-PCR after exposure to sublethal concentrations (1/10 and 1/2 LC50 or ΣTULC50).

Results

LC50 values were 2.342 mg/L for Cr, 2.256 mg/L for Zn, and 0.286 mg/L for Cu, indicating highest toxicity of Cu. Mixtures showed LC50 values of 2.533 mg/L (Cr–Zn), 5.414 mg/L (Cr–Cu), 2.546 mg/L (Zn–Cu), and 1.714 mg/L (Cr–Zn–Cu). Based on the ΣTULC50, Cr–Zn and Cr–Zn–Cu exhibited additive effects, whereas Zn–Cu and Cr–Cu showed antagonistic interactions. Gene expression analysis showed that single-metal exposure upregulated CuZn-SOD, catalase, Nrf, and GST-S. Under mixture exposure, Nrf was consistently upregulated in all groups, whereas GST-S and GST-mu were most strongly induced in the antagonistic Cr–Cu and Zn–Cu mixtures, suggesting distinct detoxification responses depending on metal combination.

Conclusion

This study highlights that the toxicity of Cr, Zn, and Cu mixtures varies depending on metal combination, showing both additive and antagonistic interaction. The marked upregulation of GST-S and GST-mu in the antagonistic Cr–Cu and Zn–Cu mixtures suggests enhanced activation of glutathione-mediated detoxification pathways, although the underlying mechanisms require further investigation. Overall, these findings emphasize the importance of considering metal interactions and integrating molecular and organism-level endpoints in ecotoxicological assessment.