Behavioral deficits and neural damage of Caenorhabditis elegans induced by three rare earth elements

Rare earth elements (REEs) are widely used in industry, agriculture, medicine and daily life in recent years. However, environmental and health risks of REEs are still poorly understood. In this study, neurotoxicity of trichloride neodymium, praseodymium and scandium were evaluated using nematode Caenorhabditis elegans as the assay system. Median lethal concentrations (48 h) were 99.9, 157.2 and 106.4 mg/L for NdCl₃, PrCl₃ and ScCl₃, respectively. Sublethal dose (10-30 mg/L) of these trichloride salts significantly inhibited body length of nematodes. Three REEs resulted in significant declines in locomotor frequency of body bending, head thrashing and pharyngeal pumping. In addition, mean speed and wavelength of crawling movement were significantly reduced after chronic exposure. Using transgenic nematodes, we found NdCl₃, PrCl₃ and ScCl₃ resulted in loss of dendrite and soma of neurons, and induced down-expression of dat-1::GFP and unc-47::GFP. It indicates that REEs can lead to damage of dopaminergic and GABAergic neurons. Our data suggest that exposure to REEs may cause neurotoxicity of inducing behavioral deficits and neural damage. These findings provide useful information for understanding health risk of REE materials.