Figure 7.

Schematic diagram for the suppression of testosterone production by TiO2-NPs associated with ROS-MAPK(ERK1/2)-StAR signaling pathway. Acute oral exposure to high doses of TiO₂ NPs in male rats would lead to the production of ROS and further activation of MAPK (ERK1/2) by ROS. ERK and StAR regulate each other, and interference with the expression of ERK1/2 will lead to the inability of StAR to transport cholesterol to the mitochondria normally, resulting in the inhibition of testosterone synthesis in the testis. (“↑” activation, “‡” inactivation, “P” phosphorylation)