Low particle concentrations of nanoplastics impair the gut health of medaka.

The environmental occurrence of nanoplastics (NPs) is now evident but their long-term impacts on organisms are unclear, limiting ecological and health risk assessment. We hypothesized that chronic exposure to low particle concentrations of NPs can result in gut-associated toxicity, and subsequently affect survival of fish. Japanese medaka Oryzias latipes were exposed to polystyrene NPs (diameter 100 nm; 0, 10, 10 ⁴ , and 10 ⁶ items/L) for 3 months, and histopathology, digestive and antioxidant enzymes, immunity, intestinal permeability, gut microbiota, and mortality were assessed. NP exposures caused intestinal lesions, and increased intestinal permeability of the gut. The trypsin, lipase, and chymotrypsin activities were increased, but the amylase activity was decreased. Oxidative damage was reflected by the decreased superoxide dismutase and alkaline phosphatase and increased malondialdehyde, catalase, and lysozyme. The integrated biomarkers response index values of all NP-exposed medaka were significantly increased compared to the control group. Moreover, NP exposures resulted in a decrease of diversity and changed the intestinal microbiota composition. Our results provide new evidence that long-term NPs exposure impaired the health of fish at extremely low particle concentrations, suggesting the need for long-term toxicological studies resembling environmental particle concentrations when assessing the risk of NPs.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 Elsevier B.V. All rights reserved.)