Nano-TiO2 Reduces Testosterone Production in Primary Cultured Leydig Cells from Rat Testis Through the Cyclic Adenosine Phosphate/Cyclic Guanosine Phosphate/Epidermal Growth Factor Receptor/Matrix Metalloproteinase Signaling Pathway

Abstract

Nano-titanium dioxide (nano-TiO2) has been shown to inhibit testosterone synthesis in male mice or rats; however, the mechanisms underlying these effects have yet to be elucidated. In this study, we investigated whether the inhibition of testosterone synthesis by nano-TiO2 on Leydig cells (LCs) was related to the dysfunction of the cAMP/CGMP/EGFR/MMP signaling pathway in primary cultures of LCs prepared from rat testis exposed to nano-TiO2. We found that the early apoptotic rate of LCs increased by 4.34 and 4.94 times, respectively, after exposure to 20 g/mL and 40 g/mL nano-TiO2 ; we also found that NO increased by 1.1 and 2.86 times, respectively. ROS increased by times of 0.71, 3.15 and 3.43; RNS increased by 0.62, 1.34 and 1.14 times; and SOD activity decreased by 18.3%, 28.16%, and 67.6%, respectively, when the concentration of nano-TiO2 was 10, 20 and 40 g/mL. These results indicated that nano-TiO2 treatment resulted caused damage to the LCs, including an imbalance of oxidation and antioxidation. Following nano-TiO2 treatment, the cAMP content had decreased by 48%, 48% and 47.6%; cGMP content had decreased by 18.7%, 52.2% and 56.7%; the levels of ATP in the LCs had decreased by 15.15%, 45.75% and 66.67%; the expression of HCGR protein had decreased by 26.7%, 45.07% and 74.64%; the expression of LHR protein had decreased by 18.3%, 28.16% and 67.6%; and the levels of T had decreased by 34.48%, 46.62% and 44.12%. Collectively, our results indicated that the inhibition of testosterone production by nano-TiO2 is related to the dysfunction of the cAMP/CGMP/EGFR/MMP signaling pathway.