Environmentally relevant lanthanum chloride exposure induces hepatic steatosis in zebrafish larvae via PPARα-dependent ApoB suppression

Lanthanum (La), the second most produced rare earth element, is detected in various environmental and human samples. Epidemiological studies have reported a strong association between La exposure and liver injury. However, the effects of early La exposure on liver development and underlying mechanisms remain limited. Here, we evaluate the hepatotoxicity of LaCl₃ at environmentally relevant concentrations using zebrafish larvae. Embryonic LaCl₃ exposure causes concentration-dependent hepatic steatosis, which cannot be reversed after exposure cessation. Metabolomic profiling reveals that very-low-density lipoprotein (VLDL) and its multiple downstream metabolites are consistently downregulated upon LaCl₃ treatment, together with increased triglycerides (TG) level, indicating impaired TG-VLDL biosynthesis. In addition, transcriptomics suggest that genes related to the PPARα signaling pathway are significantly downregulated, especially those involved in TG-VLDL biosynthesis (mttp and all apob subtypes). Further studies show that LaCl₃ can inhibit the transcriptional regulatory activity of PPARα. The upregulation of the PPARα signaling pathway corresponding genes of ppara, mttp, and apob effectively rescues LaCl₃-induced liver impairments. Subsequently, a subcellular localization assay finds that increased ApoB degradation in the endoplasmic reticulum contributes to LaCl₃-triggered lipid droplet accumulation. Overall, our findings fill critical research gaps regarding LaCl₃-induced hepatotoxicity and provide important evidence for the environmental risk assessment of La.