Sub-chronic nanoplastic toxicity in Etroplus suratensis (Pisces, Cichilidae): Insights into tissue accumulation, stress and metabolic disruption.

Nanoplastics, as widespread and persistent pollutants, pose a significant threat to the health of organisms. In this study, the impacts of polystyrene nanoplastics on the euryhaline fish, pearl spot (Etroplus suratensis) were investigated. Pearl spot were exposed to 0, 0.2, 2, and 4 mg/L of PS NPs for 14 days and NP accumulation, as well as its impact of accumulation on biochemical and oxidative stress parameters and gene expression were examined. The NP accumulation pattern was different at different exposure concentrations. At 0.2 mg/L of NP exposure concentration, the accumulation order observed was gills ˃ liver ˃ muscle ˃ intestine ˃ brain ˃ spleen. However, at higher exposure concentrations (2 and 4 mg/L), the accumulation order changed to intestine ˃ liver ˃ gills ˃ muscle ˃ spleen ˃ brain. Moreover, the accumulation led to considerable variations in biochemical parameters. Glucose, total cholesterol, SGOT, SGPT, and ALP levels increased, while albumin, total protein, and A/G ratio decreased due to NP exposure. Additionally, the antioxidant levels including SOD, CAT, GPx, and TAC, were remarkably reduced. This could explain the higher levels of MDA and PC, as well as the reduced expression of NRF2 and P53 in the NP-exposed groups, indicating oxidative damage. The significant increases in cortisol levels and the up-regulation of HSP70 indicate that fish experience stress evoked by NP. The NP exposure reduced the IGF1 and CYP1A expression, indicating its potential to impair growth and xenobiotic metabolism. These findings indicate that NPs induce stress, biochemical changes, oxidative damage, inhibited growth, and metabolism disruption in fish. This study is the first to examine the environmentally relevant NPs concentrations on protein damage from oxidative stress, toxic metabolism, and the expression of NRF2, P53, IGF1, and CYP1A in a Cichlid fish.