International Journal of Nanomedicine (Sep 2018)
Suppression of testosterone production by nanoparticulate TiO2 is associated with ERK1/2-PKA-PKC signaling pathways in rat primary cultured Leydig cells
Abstract
Lingjuan Li,1 Xu Mu,1 Lingqun Ye,1 Yuguan Ze,1 Fashui Hong2–5 1Department of Biochemistry and Molecular Biology, School of Basic Medical and Biological Sciences, Soochow University, Suzhou 215123, China; 2Jiangsu Collaborative Innovation Center of Regional Modern Agriculture and Environmental Protection, Huaiyin Normal University, Huai’an 223300, China; 3Jiangsu Key Laboratory for Food Safety and Nutritional Function Evaluation, Huaiyin Normal University, Huai’an 223300, China; 4Jiangsu Key Laboratory for Eco-Agricultural Biotechnology Around Hongze Lake, Huaiyin Normal University, Huai’an 223300, China; 5School of Life Sciences, Huaiyin Normal University, Huai’an 223300, China Background: Nanoparticulate titanium dioxide (nano-TiO2) enters the body through various routes and causes organ damage. Exposure to nano-TiO2 is reported to cause testicular injury in mice or rats and decrease testosterone synthesis, sperm number, and motility. Importantly, nano-TiO2 suppresses testosterone production by Leydig cells (LCs) and impairs the reproductive capacity of animals. Methods: In an attempt to establish the molecular mechanisms underlying the inhibitory effect of nano-TiO2 on testosterone synthesis, primary cultured rat LCs were exposed to varying concentrations of nano-TiO2 (0, 10, 20, and 40 µg/mL) for 24 hours, and alterations in cell viability, cell injury, testosterone production, testosterone-related factors (StAR, 3βHSD, P450scc, SR-BI, and DAX1), and signaling molecules (ERK1/2, PKA, and PKC) were investigated. Results: The data show that nano-TiO2 crosses the membrane into the cytoplasm or nucleus, triggering cellular vacuolization and nuclear condensation. LC viability decreased in a time-dependent manner at the same nano-TiO2 concentration, nano-TiO2 treatment (10, 20, and 40 µg/mL) decreased MMP (36.13%, 45.26%, and 79.63%), testosterone levels (11.40% and 44.93%), StAR (14.7%, 44.11%, and 72.05%), 3βHSD (26.56%, 50%, and 79.69%), pERK1/2 (27.83%, 63.61%, and 78.89%), PKA (47.26%, 70.54%, and 85.61%), PKC (30%, 50%, and 71%), SR-BI (16.41%, 41.79%, and 67.16%), and P450scc (39.41%, 55.26%, and 86.84%), and upregulated DAX1 (1.31-, 1.63-, and 3.18-fold) in primary cultured rat LCs. Conclusion: Our collective findings indicated that nano-TiO2-mediated suppression of testosterone in LCs was associated with regulation of ERK1/2–PKA–PKC signaling pathways. Keywords: nanoparticulate titanium dioxide, primary cultured rat Leydig cells, mitochondrial injury, testosterone, ERK1/2–PKA–PKC signaling pathways
