Spleen injury and apoptotic pathway in mice caused by titanium dioxide nanoparticules

Nanoparticulate titanium dioxide (TiO2) has been demonstrated to decrease immunity of mice, but very little is known about the injury of spleen involved immunomodulation and its molecular mechanism. In order to understand the spleen injury induced by intraperitoneal injection of TiO2 nanoparticules (NPs) for consecutive 45 days, the spleen pathological changes, apoptosis, the expression levels of the apoptotic genes and their proteins, and oxidative stress in the mouse spleen were investigated. The results demonstrated that TiO2 NPs had obvious accumulation in the mouse spleen, leading to congestion and lymph nodule proliferation of spleen tissue, and splenocyte apoptosis. TiO2 NPs effectively activated caspase-3 and -9, decreased the Bcl-2 the levels of gene and protein, and increase the levels of Bax, and cytochrome c genes and their protein expression, promoted ROS accumulation. Taken together, this study indicated that TiO2 NPs-induced apoptosis in the mouse splenocyte via mitochondrial-mediated pathway. These findings provide strong evidence that the TiO2 NPs can induce the spleen pathological changes, apoptosis, leading to the reduction of immunity of mice.