Cyclophosphamide activates ferroptosis-induced dysfunction of Leydig cells via SMAD2 pathway†.

Cyclophosphamide (CP) is a widely used chemotherapeutic drug and immunosuppressant in the clinic, and the hypoandrogenism caused by CP is receiving more attention. Some studies found that ferroptosis is a new mechanism of cell death closely related to chemotherapeutic drugs and plays a key role in regulating reproductive injuries. The purpose of this study is to explore ferroptosis' role in testicular Leydig cell dysfunction and molecular mechanisms relating to it. In this study, the level of ferroptosis in the mouse model of testicular Leydig cell dysfunction induced by CP was significantly increased and further affected testosterone synthesis. The ferroptosis inhibitors ferrostatin-1 (Fer-1) and iron chelator deferoxamine (DFO) can improve injury induced by CP. The results of immunohistochemistry showed that Fer-1 and DFO could improve the structural disorder of seminiferous tubules and the decrease of the number of Leydig cells in testicular tissue induced by CP. Immunofluorescence and western blot confirmed that Fer-1 and DFO could improve the expression of key enzymes in testosterone synthesis. The activation of SMAD family member 2 (Smad2)/cyclin-dependent kinase inhibitor 1A (Cdkn1a) pathway can improve the ferroptosis of Leydig cells induced by CP and protect the function of Leydig cells. By inhibiting the Smad2/Cdkn1a signal pathway, CP can regulate ferroptosis, resulting in testicular Leydig cell dysfunction. In this study, CP-induced hypoandrogenism is explained theoretically and a potential therapeutic strategy is provided.

Exosomes derived from BMSCs ameliorate cyclophosphamide-induced testosterone deficiency by enhancing the autophagy of Leydig cells via the AMPK-mTOR signaling pathway.

Cyclophosphamide-induced testosterone deficiency (CPTD) during the treatment of cancers and autoimmune disorders severely influences the quality of life of patients. Currently, several guidelines recommend patients suffering from CPTD receive testosterone replacement therapy (TRT). However, TRT has many disadvantages underscoring the requirement for alternative, nontoxic treatment strategies. We previously reported bone marrow mesenchymal stem cells-derived exosomes (BMSCs-exos) could alleviate cyclophosphamide (CP)-induced spermatogenesis dysfunction, highlighting their role in the treatment of male reproductive disorders. Therefore, we further investigated whether BMSCs-exos affect autophagy and testosterone synthesis in Leydig cells (LCs). Here, we examined the effects and probed the molecular mechanisms of BMSCs-exos on CPTD in vivo and in vitro by detecting the expression levels of genes and proteins related to autophagy and testosterone synthesis. Furthermore, the testosterone concentration in serum and cell-conditioned medium, and the photophosphorylation protein levels of adenosine monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) were measured. Our results suggest that BMSCs-exos could be absorbed by LCs through the blood-testis barrier in mice, promoting autophagy in LCs and improving the CP-induced low serum testosterone levels. BMSCs-exos inhibited cell death in CP-exposed LCs, regulated the AMPK-mTOR signaling pathway to promote autophagy in LCs, and then improved the low testosterone synthesis ability of CP-induced LCs. Moreover, the autophagy inhibitor, 3-methyladenine (3-MA), significantly reversed the therapeutic effects of BMSCs-exos. These findings suggest that BMSCs-exos promote LC autophagy by regulating the AMPK-mTOR signaling pathway, thereby ameliorating CPTD. This study provides novel evidence for the clinical improvement of CPTD using BMSCs-exos.

[Bone marrow mesenchymal stem cell-derived exosomes protect TM3 Leydig cells from cyclophosphamide-induced injury].

OBJECTIVE: To investigate the effect of exosomes derived from mouse bone marrow mesenchymal stem cells (BMSC) on the injury of TM3 Leydig cells induced by cyclophosphamide (CP). METHODS: The exosomes from BMSCs were extracted by ultrahigh speed centrifugation, and their particle size and morphology observed under the electron microscope, and their typical marker proteins examined by Western blot. The uptake of exosomes by TM3 Leydig cells was observed by co-culturing the exosomes with the TM3 cells. The viability and apoptosis rate of the TM3 cells in the normal control, CP-induction and CP+exosomes groups were detected using the CCK-8 method and flow cytometry respectively. ELISA was used to measure the testosterone (T) level in the cell supernatant, and Western blot adopted to determine the expression level of the steroidogenic acute regulatory (StAR) protein, a key enzyme related to T synthesis. RESULTS: The viability of the TM3 Leydig cells was markedly decreased and the apoptosis rate of the cells remarkably increased in the CP-induction group compared with that in the normal control, but both significantly restored after co-culture with exosomes (P < 0.01 and P < 0.05). The T level in the supernatant and the expression of the StAR protein in the cells were lower in the CP-induction than in the normal control group, but both dramatically increased in the CP+exosomes group (P < 0.01). CONCLUSION: Exosomes from BMSCs and protect TM3 Leydig cells from cyclophosphamide-induced injury and restore the level of testosterone secreted by the TM3 cells to a certain extent.