Gadolinium impairs male steroidogenesis: In vivo and in vitro evidence.

The increasing use of gadolinium (Gd) in industrial and medical fields made it a hazardous environmental pollutant. Once ingested through water and/or food, Gd may potentially have toxic effects on all body districts. However, the effects of Gd on testicular function have been little explored. In the present study, adult male rats were allowed to drink GdCl3 or Gd2O3 (10-20-40 mg/Kg b.w.) for 4 weeks. Following Gd treatment, a significant decrease in steroidogenic-related protein (StAR, 3β-HSD, 17β-HSD, and 5α-Red) expressions, T and DHT levels, and spermatozoa concentration were observed. To clarify the cellular mechanisms underlying Gd-induced damage, we exposed mouse Leydig (TM3) cells to increasing concentrations (5-1000 µM) of GdCl3 or Gd2O3 for 24 h. The in vitro results showed a dose-dependent decrease in cell viability and confirmed that both Gd forms inhibited steroidogenesis-related protein expressions. Steroidogenesis is a multistep process taking place in mitochondria and endoplasmic reticulum, and Mitochondria-Associated Endoplasmic Reticulum Membranes (MAMs) play a key role. We found a decrease in MMP as well as in mitochondrial biogenesis (PGC1-α, NRF1, TFAM), fusion (MFN2), fission (DRP1) and MAMs (ATAD3, SOAT1, FACL4) marker expressions. The Gd-caused oxidative stress, as suggested by the increase in TBARS levels in GdCl3- or Gd2O3-treated TM3 cells, increased autophagy and apoptosis by inhibiting the Akt pathway. In conclusion, our study highlights for the first time the adverse effects, and the underlying intracellular mechanisms, of orally administred Gd on the testicular function, laying the foundation for further research to understand its impact on male fertility.