Effects of Th1 and Th2 cells balance in pulmonary injury induced by nano titanium dioxide.

To explore the potential immunoregulatory mechanisms linking nano TiO₂ and pulmonary injury, Sprague Dawley rats were exposed by intra-tracheal instillation to nano TiO₂ with the individual doses of 0.5, 4.0 and 32 mg/kgb.w., micro TiO₂ with 32 mg/kgb.w. and 0.9% NaCl, respectively. The exposure was conducted twice a week, for four consecutive weeks. The results of lung histology demonstrated increased macrophages accumulation, extensive disruption of alveolar septa, slight alveolar thickness and expansion hyperemia. Mitochondria tumefaction organelles dissolution, endoplasmic reticulum expansion and the gap of nuclear broadening were shown. The changes of IFN-γ and IL-4 level showed no statistical difference. The mRNA expression of GATA-3 was up-regulated, whereas T-bet was significantly down-regulated. The protein expression of T-bet decreased and there were significant differences in nano 4 and 32 mg/kg groups. The imbalance of Th1/Th2 cytokines might be one of the mechanisms of immunotoxicity of respiratory system induced by nano TiO₂ particles.