Protective Efficacy of the Antioxidants Vitamin E and Trolox Against Microcystis aeruginosa and Microcystin-LR in Artemia franciscana Nauplii

Abstract

This study was undertaken to evaluate the protective efficacy of the antioxidants vitamin E and Trolox (a water-soluble vitamin E derivative) against the toxicity of microcystin-LR (MC-LR), Microcystis aeruginosa aqueous extract (CE), and a reference toxin, menadione sodium bisulfite (MSB), in Artemia franciscana nauplii. This was achieved by using the well-established brine shrimp bioassay. The experiment was conducted in 2 stages, with (1) 12-h mortality time course and (2) LC50 determination for 12- and 24-h exposures. Treatments consisted of MC-LR, CE, and MSB alone and with 4-h pretreatments of either vitamin E or Trolox. Sensitivity of A. franciscana nauplii with 24-h LC50 values of 11 (10.1–12.1) μg/ml for MSB and 9.5 (8.8–10.4) μg/ml for MC-LR were in general agreement with values reported for Artemia sp. Both antioxidant pretreatments resulted in significant reductions in mortality of approximately 50% at 9 h postexposure when challenged by either 40 μg/ml MC-LR or 20 μg/ml MSB. In contrast, the antioxidant pretreatments offered little to no protection from CE, suggesting that other uncharacterized bioactive compounds contributed to overall toxicity. The described bioassay is easily accessible, inexpensive, rapid, and complies with animal ethics guidelines of many countries, and thus provides a potential alternative to the mouse bioassay for the initial screening for chemoprotectants against MC-LR toxicity.

Acknowledgements

This study was funded by the Cooperative Research Centre for Water Quality and Treatment. The authors thank Associate Professor Glen Shaw (School of Public Health, Griffith University, Meadowbrook, Queensland, Australia) and Dr. Marc Seifert (Department of Natural Resources and Water, Brisbane, Queensland, Australia) for their valuable assistance in critically reviewing the draft of this article. The contributions of two anonymous reviewers are also acknowledged for enhancing the quality of this article.