Rare earth element erbium induces hepatotoxicity in zebrafish

Rare earth elements (REEs) are collectively referred to as scandium, yttrium and 15 lanthanide metals in the periodic table. Due to their unique photoelectric and magnetic properties, they are widely used in permanent magnets, new energy and cutting-edge defense technologies. However, large-scale mining and utilization of REEs have led to a significant increase in their concentration in the environment. In the environment, these REEs are regarded as emerging contaminants (ECs). Erbium (Er), a rare earth element of the lanthanide series, is widely used in ceramics, optical fibers, and the nuclear industry. Currently, research on the ecotoxicity of erbium is limited, and its target organs of action remain unclear. In this study, zebrafish were used as experimental animals, and acute exposure experiments were conducted by exposing 72 hpf zebrafish larvae to different concentrations of erbium chloride solution to explore the ecotoxicity of erbium. The main research results are as follows: (1) Exposure to erbium causes abnormal liver development in zebrafish larvae and the liver area of the erbium-exposed group was smaller than that of the control group. (2) Erbium affects liver lipid metabolism, leading to lipid accumulation in the liver of zebrafish larvae, and increasing the contents of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC) and triglycerides (TG). (3) Exposure to erbium leads to an increase in ROS levels in the liver, and the upregulated expression of the sod1 and sod2 genes. (4) The Keap1/Nrf2 pathway inhibitor resveratrol can effectively alleviate liver lipid accumulation, reduce oxidative stress in the liver and alleviate the liver damage induced by erbium. This study discovered that erbium causes abnormal liver function in zebrafish larvae, suggesting that it might cause liver damage in zebrafish through the ROS-mediated Keap1/Nrf2 pathway. These findings contribute to a more comprehensive understanding of the impact of rare earth elements on the ecosystem and provide a scientific basis for related environmental protection policies.