Fogliano C et al. (2026), Impact of Erbium and Gadolinium on Xenopus laev...

XB-ART-61791

Int J Mol Sci 2026 Mar 24;277:. doi: 10.3390/ijms27072920.

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Impact of Erbium and Gadolinium on Xenopus laevis Embryo Development: A Study of Rare Earth Element Toxicity.

Fogliano C, Di Marino S, Rusciano G, Vignola F, Petito A, Venditti P, Cretì P, Motta CM, Avallone B, Scudiero R, Carotenuto R.

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Rare earth elements (REE), such as gadolinium (Gd) and erbium (Er), are increasingly recognised as emerging environmental contaminants due to their widespread use in industrial processes, electronics, and medical imaging applications. Despite their extensive presence in aquatic ecosystems, little is known about their developmental toxicity. In this study, Xenopus laevis embryos were exposed to environmentally relevant concentrations of Gd and Er during critical early developmental stages. The assessed endpoints included survival, malformations, growth (body length), and heart rate. Both Gd and Er caused significant sublethal effects, including increased axial malformations, reduced growth, and altered cardiac activity. To explore potential mechanisms of toxicity, the expression patterns of key developmental genes (fgf8, bmp4, sox9, egr2, rax1, pax6) and pro-inflammatory cytokines (tnfα, il1β, p65) were analysed using Real-Time PCR. The results showed dysregulation of gene expression, indicating disruption to pathways involved in morphogenesis and neurodevelopment. Elevated reactive oxygen species levels suggested that oxidative stress was a contributing factor. Raman spectroscopy confirmed biochemical changes affecting proteins, lipids, and nucleic acids, providing evidence of cellular stress and metabolic imbalance. Overall, our findings demonstrate that even low-level exposure to Gd and Er can impair amphibian embryonic development and disturb molecular homeostasis. These results emphasise the ecological risks of REE pollution and highlight the importance of ongoing environmental monitoring and long-term toxicological research.

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Species referenced: Xenopus laevis
Genes referenced: abcb1 bmp4 egr2 fgf8 il1b pax6 rax rela sox9 tnf
GO keywords: inflammatory response [+]

Phenotypes: XLA.WT + ER(Fig. 2 DFH) [+]

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	Figure 1. Mortality (%), heart rate (beats/min) and growth retardation in Xenopus laevis embryos exposed to gadolinium (Gd) (A–C) or erbium (Er) (D–F) (n = 3 replicate experiments; 90 embryos/treatment). Different letters (a–c) indicate statistically significant differences among groups (p < 0.05; One-way ANOVA). Groups sharing the same letter are not significantly different.
	Figure 2. Representative images of morphological alterations observed in Xenopus laevis embryos exposed to gadolinium (Gd) (CEG) or erbium (Er) (DFH) relative to control embryos (A,B). Thin arrow: head deformities; arrow: altered pigmentation; thick arrow: oedema; dotted arrow: trunk bending; asterisk: gut abnormalities; bent arrow: eye deformities.
	Figure 3. Real-Time PCR of Xenopus laevis embryos exposed to gadolinium (Gd) and erbium (Er). (A,C) Regulatory genes of early embryonic development. (B,D) Genes involved in inflammatory responses and multidrug resistance. Two-Way ANOVA with the Bonferroni post hoc test. Data are expressed as mean SD; different letters (ad) indicate statistically significant differences among groups (p < 0.05). Groups sharing the same letter are not significantly different.
	Figure 4. Effect of Gd (A) and Er (B) on ROS production in Xenopus laevis embryos. Data, expressed as the Relative Fluorescent Units (RFU) per microgram of protein, are means ± SDs of two independent measures. n = 3. Different letters (a–c) indicate statistically significant differences among groups (p < 0.05; One-way ANOVA). Groups sharing the same letter are not significantly different.
	Figure 5. Mean spectrum (average of 10 signals) corresponding to the control sample. Labels indicate the main band assignment.
	Figure 6. Outcomes of PCA performed on treated samples. Score plot (a) and PC1 loading plot (b) obtained for Gd-treated samples. Score plot (c) and PC1 loading plot (d) obtained for Er-treated samples.