Figure 14.

Schematic representation of nanoparticulate TiO₂-mediated inhibition of testosterone production via the ERK1/2–PKA–PKC signaling pathway. Taken together, data from the current study suggest that nano-TiO₂ enters the cytoplasm and nuclei of LCs, causing structural damage and decreased cell activity and testosterone generation or secretion. Furthermore, suppression of testosterone production in LCs by nano-TiO₂ may be associated with dysfunction of ERK1/2–PKA–PKC signaling pathways, with downregulation of StAR, P450scc, 3βHSD, SR-BI, PKA, PKC, and pERK/1/2 and upregulation of DAX1. The complex dynamic pathway of nano-TiO₂-mediated inhibition of testosterone synthesis or secretion in LCs requires further investigation.