Liver Damage in Ctenopharyngodon idellus Induced by Nanoplastics and Cadmium Exposure

Nanoplastics and cadmium often occur together in freshwater, but their combined effects on fish health are not well understood. In this study, we exposed grass carp, an important food fish, to these pollutants alone or in combination for 72 h to examine liver damage. The mixture caused much more severe liver injury—including cell death, darkening, and tissue breakdown—than either pollutant alone. It also weakened the fish’s immune system and natural antioxidant defenses more strongly. By analyzing gene activity, we found that co-exposure broadly disturbed the liver’s normal fat and hormone processing. Our results show that the two pollutants together create complex harmful effects that are not simply the sum of their individual actions. Nanoplastics (NPs) and heavy metal cadmium (Cd) are common co-existing pollutants in freshwater environments, but their combined toxic effects on the liver of herbivorous economic fish remain unclear. In this study, grass carp ( Ctenopharyngodon idella ) were exposed to polystyrene nanoplastics (PS-NPs, 100 nm) and/or Cd to investigate their individual and combined effects on hepatic toxicity. The results revealed that co-exposure interactively suppressed interleukin-10 ( IL-10 ) expression and heme oxygenase-1 ( HO-1 ) antioxidant response, and induced more severe hepatic necrosis, melanization, and fibrinoid necrosis, with the highest integrated biomarker response index and extensive disruption of lipid and steroid metabolism pathways. This study clarified the toxicological interaction of NPs and Cd on the liver of grass carp, and provided a theoretical basis for understanding the combined toxicity of NPs and heavy metal pollution in extreme contamination scenarios or accidental pollution events.