Evaluation of possible cytotoxic, genotoxic and epigenotoxic effects of titanium dioxide nanoparticles and possible protective effect of melatonin

Nanoparticles (NPs) are particles of matter that are between 1 to 100 nm in diameter. They are suggested to cause toxic effects in both humans and environment thorough different mechanisms. However, their toxicity profile may be different from the parent material. Titanium dioxide (TiO₂) NPs are widely used in cosmetic, pharmaceutical and food industries. As a white pigment, the use of TiO₂ is used in food coloring, industrial paints, clothing and UV filters has increased tremendously in recent years. Melatonin, on the other hand, is a well-known antioxidant and may prevent oxidative stress caused by a variety of different substances, including NPs. In the current study, we aimed to comparatively investigate the effects of normal-sized TiO₂ (220 nm) and nano-sized TiO₂ (21 nm) on cytopathology, cytotoxicity, oxidative damage (lipid peroxidation, protein oxidation and glutathione), genotoxicity (8-hydroxydeoxyguanosine), apoptosis (caspase 3, 8 and 9) and epigenetic alterations (global DNA methylation, H3 acetylation) on 3T3 fibroblast cells. In addition, the possible protective effects of melatonin, which is known to have strong antioxidant effects, against the toxicity of TiO₂ were also evaluated. Study groups were: a. the control group; b. melatonin group; c. TiO₂ group; d. nano-sized TiO₂ group; e. TiO₂ + melatonin group and f. nano-sized TiO₂ + melatonin group. We observed that both normal-sized and nano-sized TiO₂ NPs showed significant toxic effects. However, TiO₂ NPs caused higher DNA damage and global DNA methylation compared to normal-sized TiO₂ whereas normal-sized TiO₂ led to lower H3 acetylation vs. TiO₂ NPs. Melatonin showed partial protective effect against the toxicity caused by TiO₂ NPs.