Introduction Titanium dioxide(TiO2) is frequently used as a whitening agent(E171). Although historically classified as "generally recognized as safe", the European Food Safety Authority (EFSA) suspended its food additive approval due to unresolved concerns(EFSA Panel, 2021), while China and the United States maintain permissible limits. E171 ranges between 200 and 300 nm in diameter while smaller nanoparticles are more likely to be absorbed by intestinal epithelial cells. Based on bioinformatics, we studied the molecular mechanism of the TiO2-induced intestinal damage process.
Methods Comparative Toxicogenomics Database (CTD) identified 160 colitis- and 258 colorectal cancer-associated genes modulated by TiO₂ and Cytoscape was used to make a PPI network diagram. Functional enrichment analysis (GO/KEGG) revealed key pathways, cross-validated with transcriptomic datasets from TiO₂-exposed enteritis (GSE92563) and colorectal tumor models (GSE109520). We screened the AOP-wiki database and constructed a new pathway network factors. Meanwhile, we used MECE and CT26 cells separately co-cultured with E171 and TiO2-10nm for 48h for gene sequencing to validate our predictive model.
Results In the intestinal inflammation model, TiO2 exposure initially activates the JNK and MAPK signaling pathways, causing changes in the cell membrane (invagination, endocytosis), cell death, inflammation, and hypoxia, leading to inflammatory bowel disease. For colorectal cancer, cytokines (Stat1, Pik3cd, Cxcr4, etc.) were activated, leading to extracellular matrix response and apoptosis, resulting in colorectal cancer and migration. Meanwhile, we analyzed the existing AOPs with high relevance to the intestinal damage mechanism of TiO2 (AOP392, AOP451, and AOP303) and constructed a new AOP. In cell sequencing, we also enriched the relevant pathways, which pointed to different factors in the two types of cells.
Conclusion We introduced these regulatory cascades as new MIE and KE into the AOP framework, outlining the precise mechanism by which TiO2 exposure induces colorectal damage and providing new evidence for food safety issues.
