Cardiorespiratory toxicity of environmentally relevant zinc oxide nanoparticles in the freshwater fish Catostomus commersonii

Abstract

The inhalation of zinc oxide engineered nanomaterials (ENMs) has been linked to cardiorespiratory dysfunction in mammalian models but the effects of aquatic ENM exposure on fish have not been fully investigated. Nano-zinc oxide (nZnO) is widely used in consumer products such as sunscreens and can make its way into aquatic ecosystems from domestic and commercial wastewater. This study examined the impact of an environmentally relevant nZnO formulation on cardiorespiratory function and energy metabolism in the white sucker (Catostomus commersonii), a freshwater teleost fish. Evidence of oxidative and cellular stress was present in gill tissue, including increases in malondialdehyde levels, heat shock protein (HSP) expression, and caspase 3/7 activity. Gill Na⁺/K⁺-ATPase activity was also higher by approximately three-fold in nZnO-treated fish, likely in response to increased epithelial permeability or structural remodeling. Despite evidence of toxicity in gill, plasma cortisol and lactate levels did not change in animals exposed to 1.0 mg L⁻¹ nZnO. White suckers also exhibited a 35% decrease in heart rate during nZnO exposure, with no significant changes in resting oxygen consumption or tissue energy stores. Our results suggest that tissue damage or cellular stress resulting from nZnO exposure activates gill neuroepithelial cells, triggering a whole-animal hypoxic response. An increase in parasympathetic nervous signaling will decrease heart rate and may reduce energy demand, even in the face of an environmental toxicant. We have shown that acute exposure to nZnO is toxic to white suckers and that ENMs have the potential to negatively impact cardiorespiratory function in adult fish.

• Biochemistry
• environmental toxicology
• exposure
• mechanistic toxicology
• nanotoxicology

Acknowledgements

The authors would like to thank Ms. Maria Thistle for statistical advice, Mr. Wayne Anderson for assistance with animal collection and care, and Mr. James Ehrman for assistance with ENM characterization.

Declaration of interest

The study was funded by a Natural Science and Engineering Research Council of Canada Discovery grants (T. J. M., S. C.) and a New Brunswick Health Research Foundation Operating grant to T. J. M. The author Christopher Anthony Dieni was supported by a Margaret and Wallace McCain Postdoctoral Fellowship, and K. M. A. B. and N. I. C. were funded by Universitas and Goodridge Summer Undergraduate Research Scholarships, respectively. The authors declare no conflict of interest related to the work presented.