Genome-wide DNA methylation sequencing reveals the involvement of ferroptosis in hepatotoxicity induced by dietary exposure to food-grade titanium dioxide.

BACKGROUND: Following the announcement by the European Food Safety Authority that the food additive titanium dioxide (E 171) is unsafe for human consumption, and the subsequent ban by the European Commission, concerns have intensified over the potential risks E 171 poses to human vital organs. The liver is the main organ for food-grade nanoparticle metabolism. It is increasingly being found that epigenetic changes may play an important role in nanomaterial-induced hepatotoxicity. However, the profound effects of E 171 on the liver, especially at the epigenetic level, remain largely unknown. METHODS: Mice were exposed orally to human-relevant doses of two types of E 171 mixed in diet for 28 and/or 84 days. Conventional toxicology and global DNA methylation analyses were performed to assess E 171-induced hepatotoxicity and epigenetic changes. Whole genome bisulfite sequencing and further ferroptosis protein detection were used to reveal E 171-induced changes in liver methylation profiles and toxic mechanisms. RESULTS: Exposed to E 171 for 28 and/or 84 days resulted in reduced global DNA methylation and hydroxymethylation in the liver of mice. E 171 exposure for 84 days elicited inflammation and damage in the mouse liver, whereas 28-day exposure did not. Whole-genome DNA methylation sequencing disclosed substantial methylation alterations at the CG and non-CG sites of the liver DNA in mice exposed to E 171 for 84 days. Mechanistic analysis of the DNA methylation alterations indicated that ferroptosis contributed to the liver toxicity induced by E 171. E 171-induced DNA methylation changes triggered NCOA4-mediated ferritinophagy, attenuated the protein levels of GPX4, FTH1, and FTL in the liver, and thereby caused ferroptosis. CONCLUSIONS: Long-term oral exposure to E 171 triggers hepatotoxicity and induces methylation changes in both CG and non-CG sites of liver DNA. These epigenetic alterations activate ferroptosis in the liver through NCOA4-mediated ferritinophagy, highlighting the role of DNA methylation and ferroptosis in the potential toxicity caused by E 171 in vivo.

Maternal exposure to E 551 during pregnancy leads to genome-wide DNA methylation changes and metabolic disorders in the livers of pregnant mice and their fetuses.

The widespread use of nanoparticles in the food industry has raised concerns regarding their potential adverse effects on human health, particularly in vulnerable populations, including pregnant mothers and fetuses. However, studies evaluating the reproductive and developmental toxicity of food-grade nanomaterials are limited. This study investigated the potential risks of prenatal dietary exposure to food-grade silica nanoparticles (E 551) on maternal health and fetal growth using conventional toxicological and epigenetic methods. The results showed that prenatal exposure to a high-dose of E 551 induces fetal resorption. Moreover, E 551 significantly accumulates in maternal and fetal livers, triggering a hepatic inflammatory response. At the epigenetic level, global DNA methylation is markedly altered in the maternal and fetal livers. Genome-wide DNA methylation sequencing revealed affected mCG, mCHG, and mCHH methylation landscapes. Subsequent bioinformatic analysis of the differentially methylated genes suggests that E 551 poses a risk of inducing metabolic disorders in maternal and fetal livers. This is further evidenced by impaired glucose tolerance in pregnant mice and altered expression of key metabolism-related genes and proteins in maternal and fetal livers. Collectively, the results of this study highlighted the importance of epigenetics in characterizing the potential toxicity of maternal exposure to food-grade nanomaterials during pregnancy.