Genome-wide methylation changes upon Caco-2 cells exposure to undigested and digested titanium dioxide nanoparticles

Introduction: Titanium dioxide nanoparticles (TiO2NPs) are nanomaterials (NMs) with relevant properties for biomedicine and industry, which raise concerns about its effects on human health, particularly through ingestion. Moreover, digestion may modify NMs' properties, leading to unpredicted toxicity. Several studies found that exposure to NMs can lead to DNA methylation changes. DNA methylation regulates gene expression, playing a vital role in development, aging, and disease, with aberrant methylation linked to cancer and other health conditions. Aim: We aimed at identifying DNA methylation changes in intestinal cells exposed to three TiO2NPs (NM-102, NM-103 and NM-105), either digested or undigested. Their cellular effects were investigated by functional pathway and gene ontology (GO) analysis. Results: 48, 41, 55 differentially methylated genes (DMG) were identified after exposure to undigested NM-102, NM-103, NM-105; 71, 65, 55 DMG in the digested counterparts. Undigested TiO2NPs affected many G-proteins and adenylate cyclase related pathways (PKA, glucagon, GPER1, CREB1, ADORA2B), while the digested had lower impact. Cancer-related pathways were shared. Enriched molecular functions were mainly transcription-related; different biological processes were enriched if TiO2NPs were digested or not. Conclusions: TiO2NPs exposure causes DNA methylation changes that have a functional impact on intestinal cells, which differs with its physicochemical properties and digestion. NM-105 caused hypermethylation, unlike the other TiO2NPs. This study highlights DNA methylation relevance in assessing nanomaterials' toxicity.