Dermal exposure to nano-TiO₂ induced cardiovascular toxicity through oxidative stress, inflammation and apoptosis

Due to its excellent properties such as ultraviolet obscuration, chemical stability and small particle size, nano-titanium dioxide (nano-TiO₂) is widely used, particularly in sunblock products. The skin is therefore a chief route for exposure. Studies have found that oral or respiratory exposure to nano-TiO₂ has an adverse impact on the cardiovascular system. The relationship between dermal exposure to nano-TiO₂ and cardiovascular system toxicity, particularly the causative mechanisms, remain unclear. In this study, we used Balb/c mice to evaluate cardiovascular toxicity from nano-TiO₂ dermal exposure, and the underlying mechanisms associated with the human umbilical vein endothelial cells (HUVECs) were explored. Our results showed that nano-TiO₂ treatment resulted in an obvious increase in reactive oxygen species and 8-hydroxy-2'-deoxyguanosine, indicating the appearance of oxidative stress. Moreover, the levels of inflammatory biomarkers, such as immunoglobulin E, soluble intercellular adhesion molecule-1, interleukin-8, and hypersensitive C-reactive protein, also increased. Exposing HUVECs to nano-TiO₂ led to a decline in cell vitality, and an increase in caspase-3 levels, suggesting that nano-TiO₂ exposure caused cytotoxicity and even cell apoptosis. Interestingly, neutralizing oxidative stress by administering Vitamin E was shown to reduce the inflammatory response and cytotoxicity. Our findings suggest that nano-TiO₂ can injure the cardiovascular system via dermal exposure, and does this via oxidative stress-induced inflammation and cytotoxicity. Vitamin E treatment may be a strategy to mitigate the damage.