Redefining the synergistic toxicity of nano-plastics and cadmium in earthworm coelomocytes: the mechanism of α-amylase molecular docking orientation and energy crisis

Nanoplastics (NPs) and cadmium (Cd), as ubiquitous environmental pollutants, are frequently detected in ecosystems, and their combined toxicity has received increasing attention. However, evidence and mechanisms regarding the cellular toxicity of NPs and Cd co-exposure in soil organisms remain insufficient. This study employed a multi-scale approach to investigate the toxic effects and mechanisms of NPs and Cd co-exposure on Eisenia fetida coelomocytes, and the structural changes of α-amylase. Results revealed that NPs-Cd co-exposure significantly reduced coelomocytes viability to 70.33 %, lower than Cd-alone exposure (78.41 %). Mechanically, compared to Cd exposure, co-exposure induced stronger reactive oxygen species (ROS) generation. NPs amplified Cd toxicity, leading to severe antioxidant system disruption, lipid peroxidation and mitochondrial dysfunction. At the molecular level, compared to Cd alone (74.03 %), NPs-Cd exposure induced lower α-amylase activity (66.33 %). Cd exposure caused protein skeleton damage, fluorescence sensitization, which were further exacerbated by NPs. Protein aggregation and docking simulation speculates that NPs-Cd cause greater toxicity in the form of protein corona. Linking NPs-Cd-induced oxidative stress with energy metabolism, this study highlighted the potential role of NPs as carriers in Cd accumulation. These findings highlight NPs' environmental risks and advance ecological risk assessment strategies for combined pollution.