P-104 Cytoprotective effect of melatonin in prepubertal Sertoli cells: role in cadmium-induced idiopathic male infertility

Abstract Study question Melatonin (MLT) is a cytoprotective agent holding potential to prevent cadmium (Cd) toxicity and its impact in testicular function and fertility. Summary answer MLT produced a potent cytoprotective effect in Sertoli cells (SCs) exposed to Cd-toxicity, reducing its H2O2 generation and reductive stress effects by modulation Nrf2 activity. What is known already MLT a hormonal substance exhibiting strong antioxidative and antiapoptotic properties, has been proved to hold great potential as cytoprotec tive agent in a range of tissues and cell models exposed to Cd toxicity, including the rat bone, ovaries, human MSC, and even mammalian testes. However, cellular and mechanistic aspects of this effect of MLT in testes remain poorly understood. Cd is a pro-oxidant heavy metal reported to interfere with testicular function and fertility. Both the toxicity of Cd and the cytoprotective function of MLT involve redox-dependent mechanisms with the activity of Nrf2 transcription factor as key player on the cellular stress response. Study design, size, duration Porcine pre-pubertal SCs were maintained at 37 °C in a 5% CO2 humidified atmosphere in the absence (unexposed-control group) or presence of 5 or 10µM CdCl2 (Sigma Chemical Co.) and/or 50nM MLT (Sigma-Aldrich) for 48h in HAMF12 (Euroclone) supplemented with 0.166nM retinoic acid (Sigma-Aldrich Co.) and 5/500ml of Insulin-Transferrin-Selenium (ITS) + Premix (Cat. No. 354352; Corning). Participants/materials, setting, methods After treatment the parameters investigated in the study were: a) SCs viability (MTT test); b) SCs functionality parameters AMH and inhibin B. (real-time PCR and ELISA analysis); c) Intracellular and extracellular ROS production ( with Amplex Red and DCFH-DA fluorescent probe respectively); d) Catalase enzyme activity (spectrophotometric assay procedure); e) Nrf2 and other transcription factors (by semi-quantitative microplate confocal microscopy analysis); f) Intracellular and extracellular levels of GSH and other thiols (by HPLC); g) c-Jun and ERK1/2 (Immunoblot). Main results and the role of chance MLT co-treatment significantly prevented the effects of Cd on cell viability and abnormal ROS production. The reduction of H2O2 efflux was very important and combined with an increased CAT activity that was demonstrated upon MLT treatment significantly in SCs exposed to 5μMCd. The co-treatment with MLT compared to Cd treatment, showed a trend toward a significant recovery of AMH and inhibin B gene expression and secretion levels, respectively, demonstrating the cytoprotective effect of MLT in SCs exposed to Cd toxicity at the functional level. In Cd-treated cells, MLT significantly reduced the expression and nuclear translocation of Nrf2 protein, and decreased GSTP induction. However, MLT reduced Cys uptake and stimulated GSH efflux when the cells were treated with 10 µM Cd, suggesting a specific role for the Nrf2-GSTP axis in the cytoprotective response to MLT of Cd-treated SCs. Finally MLT induced MAPK-ERK1-2 pathway and c-Jun transcription factor when the cells were treated with Cd. MLT is a cytoprotective agent in SCs exposed to Cd toxicity capable to restore cell viability and function. Its activity is associated with the modulation of Nrf2 and other stress response genes important in the control of thiols and H2O2 metabolism of SCs, including cJun and MAPKs. Limitations, reasons for caution Other ROS-scavenging genes other than CAT may have a role in the antioxidant response to MLT of SCs, such as superoxide dismutase, glutathione peroxidases, and peroxyredoxins that are worth investigating further. Wider implications of the findings The aspects that emerged from our study and, described for the first time in these cells, warrant further preclinical and clinical investigation holding potential in the treatment of Cd-induced testicular damage and fertility problems. Trial registration number Not applicable