[Effects of titanium dioxide nanoparticles and lipopolysaccharide on antioxidant function of liver tissues in mice]

To compare the effects of different sized titanium dioxide (titanium dioxide, TiO₂) on the antioxidant function of liver tissues in mice, and study the effect of TiO₂ nanoparticles on the susceptibility of lipopolysaccharide (LPS) on liver tissues.

Ninety 4-week-old clean-grade male ICR mice were divided into 18 groups, in which the mice were fed for different feed involving ordinary feed, nanometer TiO₂ feed which meant the feed including 1% (mass fraction) TiO₂ nanoparticles, and submicron TiO₂ feed which meant the feed including 1% (mass fraction) TiO₂ submicron particles. Respectively, they were fed for 1 month, 3 months and 6 months. On the second day after the feeding, respectively, 0 and 10 mg/kg LPS were given by gavage. The mice were harvested after 4 h and the body weight and liver weight for calculating the liver coefficient were recorded. Then the liver tissue homogenates were prepared for determining the antioxidant indexes including the total antioxidant capacity (T-AOC), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-PX), and malondialdehyde (MDA).

The change of body weight in mice was only discovered in group fed for 1 month, which showed significant decrease of body weight in treatment groups compared with control group. And there was no significant change of the liver coefficient in each group. Compared with control groups, nanometer TiO₂ groups and submicron TiO₂ group, the activity of T-AOC, T-SOD and MDA of nanometer TiO₂+LPS group and submicron TiO₂+LPS group in which the mice were fed for 1 month and 6 months increased in different degree. And another result was also existing. The MDA activity of liver in different sized treatment groups fed for 3 months decreased. Neither significant difference between the results of different sized TiO₂ treatment groups, nor significant difference among different sized TiO₂ groups and the control groups were observed.

Longterm peroral TiO₂ nanoparticles and TiO₂ submicron particles are more likely to cause damage to the liver in the growing mice, and the damage may be either reductive or oxidative. In addition, small sized TiO₂ can increase the susceptibility of mice liver to LPS and the susceptibility will increase with the increase of exposure time.