Correction: Bischoff et al. The Effects of the Food Additive Titanium Dioxide (E171) on Tumor Formation and Gene Expression in the Colon of a Transgenic Mouse Model for Colorectal Cancer. Nanomaterials 2022, 12, 1256.

In the published publication [...].

Reply to Kaminski, N.E.; Cohen, S.M. Comment on "Bischoff et al. The Effects of the Food Additive Titanium Dioxide (E171) on Tumor Formation and Gene Expression in the Colon of a Transgenic Mouse Model for Colorectal Cancer. Nanomaterials 2022, 12, 1256".

We appreciate the interest in our article describing transcriptome changes in a transgenic mouse model carrying an APC gene mutation and would like to reply to the reader [...].

The Effects of the Food Additive Titanium Dioxide (E171) on Tumor Formation and Gene Expression in the Colon of a Transgenic Mouse Model for Colorectal Cancer.

Titanium dioxide (TiO2) is present in many different food products as the food additive E171, which is currently scrutinized due to its potential adverse effects, including the stimulation of tumor formation in the gastrointestinal tract. We developed a transgenic mouse model to examine the effects of E171 on colorectal cancer (CRC), using the Cre-LoxP system to create an Apc-gene-knockout model which spontaneously develops colorectal tumors. A pilot study showed that E171 exposed mice developed colorectal adenocarcinomas, which were accompanied by enhanced hyperplasia in epithelial cells, lymphatic nodules at the base of the polyps, and increased tumor size. In the main study, tumor formation was studied following the exposure to 5 mg/kgbw/day of E171 for 9 weeks (Phase I). E171 exposure showed a statistically nonsignificant increase in the number of colorectal tumors in these transgenic mice, as well as a statistically nonsignificant increase in the average number of mice with tumors. Gene expression changes in the colon were analyzed after exposure to 1, 2, and 5 mg/kgbw/day of E171 for 2, 7, 14, and 21 days (Phase II). Whole-genome mRNA analysis revealed the modulation of genes in pathways involved in the regulation of gene expression, cell cycle, post-translational modification, nuclear receptor signaling, and circadian rhythm. The processes associated with these genes might be involved in the enhanced tumor formation and suggest that E171 may contribute to tumor formation and progression by modulation of events related to inflammation, activation of immune responses, cell cycle, and cancer signaling.

Oxidative stress in pancreatic alpha and beta cells as a selection criterion for biocompatible biomaterials.

The clinical success rate of islet transplantation, namely independence from insulin injections, is limited by factors that lead to graft failure, including inflammation, acute ischemia, acute phase response, and insufficient vascularization. The ischemia and insufficient vascularization both lead to high levels of oxidative stress, which are further aggravated by islet encapsulation, inflammation, and undesirable cell-biomaterial interactions. To identify biomaterials that would not further increase damaging oxidative stress levels and that are also suitable for manufacturing a beta cell encapsulation device, we studied five clinically approved polymers for their effect on oxidative stress and islet (alpha and beta cell) function. We found that 300 poly(ethylene oxide terephthalate) 55/poly(butylene terephthalate) 45 (PEOT/PBT300) was more resistant to breakage and more elastic than other biomaterials, which is important for its immunoprotective function. In addition, it did not induce oxidative stress or reduce viability in the MIN6 beta cell line, and even promoted protective endogenous antioxidant expression over 7 days. Importantly, PEOT/PBT300 is one of the biomaterials we studied that did not interfere with insulin secretion in human islets.

Transcriptome changes in undifferentiated Caco-2 cells exposed to food-grade titanium dioxide (E171): contribution of the nano- and micro- sized particles.

The food additive titanium dioxide (TiO2), or E171, is a white food colorant. Recent studies showed after E171 ingestion a significantly increased number of colorectal tumours in a colorectal cancer mouse model as well as inflammatory responses and dysregulation of the immune system in the intestine of rats. In the mouse colon, E171 induced gene expression changes related to oxidative stress, impairment of the immune system, activation of signalling and cancer-related processes. E171 comprises nanoparticles (NPs) and microparticles (MPs). Previous in vitro studies showed that E171, NPs and MPs induced oxidative stress responses, DNA damage and micronuclei formation. This study aimed to investigate the relative contribution of the NPs and MPs to effects of E171 at the transcriptome level in undifferentiated Caco-2 cells by genome wide microarray analysis. The results showed that E171, NPs, and MPs induce gene expression changes related to signalling, inflammation, immune system, transport and cancer. At the pathway level, metabolism of proteins with the insulin processing pathway and haemostasis were specific to E171 exposure. The gene expression changes associated with the immune system and inflammation induced by E171, MPs, and NPs suggest the creation of a favourable environment for colon cancer development.

Transcriptomics analysis reveals new insights in E171-induced molecular alterations in a mouse model of colon cancer.

Titanium dioxide as a food additive (E171) has been demonstrated to facilitate growth of chemically induced colorectal tumours in vivo and induce transcriptomic changes suggestive of an immune system impairment and cancer development. The present study aimed to investigate the molecular mechanisms behind the tumour stimulatory effects of E171 in combination with azoxymethane (AOM)/dextran sodium sulphate (DSS) and compare these results to a recent study performed under the same conditions with E171 only. BALB/c mice underwent exposure to 5 mg/kgbw/day of E171 by gavage for 2, 7, 14, and 21 days. Whole genome mRNA microarray analyses on the distal colon were performed. The results show that E171 induced a downregulation of genes involved in the innate and adaptive immune system, suggesting impairment of this system. In addition, over time, signalling genes involved in colorectal cancer and other types of cancers were modulated. In relation to cancer development, effects potentially associated with oxidative stress were observed through modulation of genes related to antioxidant production. E171 affected genes involved in biotransformation of xenobiotics which can form reactive intermediates resulting in toxicological effects. These transcriptomics data reflect the early biological responses induced by E171 which precede tumour formation in an AOM/DSS mouse model.

Time course gene expression data in colon of mice after exposure to food-grade E171.

We investigated gene expression responses in BALB/c mice exposed by gavage to 5 mg/kg bw/day of E171 for 2, 7, 14 and 21 days. Food additive E171 (titanium dioxide) has been shown to induce oxidative stress and DNA damage in vitro as well as facilitating growth of colorectal tumours in vivo. Full genome expression changes of the colon of mice were investigated by using Agilent SurePrint G3 mouse Gene exp 60kv2 microarrays slides. The data presented in this DiB include all differentially expressed for each time point with EntrezGeneID, gene symbols, gene names and Log2FC as well as genes included in pathways after over-representation analysis in ConsensusPathDataBase. The functions of these genes in relation to the colon were described in our associated article (Proquin et al., 2017 in press) [1]. Raw and normalized gene expression data are available through NCBI GEO (GEO accession: GSE92563).

Gene expression profiling in colon of mice exposed to food additive titanium dioxide (E171).

Dietary factors that may influence the risks of colorectal cancer, including specific supplements, are under investigation. Previous studies showed the capacity of food additive titanium dioxide (E171) to induce DNA damage in vitro and facilitate growth of colorectal tumours in vivo. This study aimed to investigate the molecular mechanisms behind these effects after E171 exposure. BALB/c mice were exposed by gavage to 5 mg/kgbw/day of E171 for 2, 7, 14, and 21 days. Transcriptome changes were studied by whole genome mRNA microarray analysis on the mice's distal colons. In addition, histopathological changes as well as a proliferation marker were analysed. The results showed significant gene expression changes in the olfactory/GPCR receptor family, oxidative stress, the immune system and of cancer related genes. Transcriptome analysis also identified genes that thus far have not been included in known biological pathways and can induce functional changes by interacting with other genes involved in different biological pathways. Histopathological analysis showed alteration and disruption in the normal structure of crypts inducing a hyperplastic epithelium. At cell proliferation level, no consistent increase over time was observed. These results may offer a mechanistic framework for the enhanced tumour growth after ingestion of E171 in BALB/c mice.

Omics for prediction of environmental health effects: Blood leukocyte-based cross-omic profiling reliably predicts diseases associated with tobacco smoking.

The utility of blood-based omic profiles for linking environmental exposures to their potential health effects was evaluated in 649 individuals, drawn from the general population, in relation to tobacco smoking, an exposure with well-characterised health effects. Using disease connectivity analysis, we found that the combination of smoking-modified, genome-wide gene (including miRNA) expression and DNA methylation profiles predicts with remarkable reliability most diseases and conditions independently known to be causally associated with smoking (indicative estimates of sensitivity and positive predictive value 94% and 84%, respectively). Bioinformatics analysis reveals the importance of a small number of smoking-modified, master-regulatory genes and suggest a central role for altered ubiquitination. The smoking-induced gene expression profiles overlap significantly with profiles present in blood cells of patients with lung cancer or coronary heart disease, diseases strongly associated with tobacco smoking. These results provide proof-of-principle support to the suggestion that omic profiling in peripheral blood has the potential of identifying early, disease-related perturbations caused by toxic exposures and may be a useful tool in hazard and risk assessment.

Interindividual variation in gene expression responses and metabolite formation in acetaminophen-exposed primary human hepatocytes.

Acetaminophen (APAP) is a readily available over-the-counter drug and is one of the most commonly used analgesics/antipyretics worldwide. Large interindividual variation in susceptibility toward APAP-induced liver failure has been reported. However, the exact underlying factors causing this variability in susceptibility are still largely unknown. The aim of this study was to better understand this variability in response to APAP by evaluating interindividual differences in gene expression changes and APAP metabolite formation in primary human hepatocytes (PHH) from several donors (n = 5) exposed in vitro to a non-toxic to toxic APAP dose range. To evaluate interindividual variation, gene expression data/levels of metabolites were plotted against APAP dose/donor. The correlation in APAP dose response between donors was calculated by comparing data points from one donor to the data points of all other donors using a Pearson-based correlation analysis. From that, a correlation score/donor for each gene/metabolite was defined, representing the similarity of the omics response to APAP in PHH of a particular donor to all other donors. The top 1 % highest variable genes were selected for further evaluation using gene set overrepresentation analysis. The biological processes in which the genes with high interindividual variation in expression were involved include liver regeneration, inflammatory responses, mitochondrial stress responses, hepatocarcinogenesis, cell cycle, and drug efficacy. Additionally, the interindividual variation in the expression of these genes could be associated with the variability in expression levels of hydroxyl/methoxy-APAP and C8H13O5N-APAP-glucuronide. The before-mentioned metabolites or their derivatives have also been reported in blood of humans exposed to therapeutic APAP doses. Possibly these findings can contribute to elucidating the causative factors of interindividual susceptibility toward APAP.

diXa: a data infrastructure for chemical safety assessment.

MOTIVATION: The field of toxicogenomics (the application of '-omics' technologies to risk assessment of compound toxicities) has expanded in the last decade, partly driven by new legislation, aimed at reducing animal testing in chemical risk assessment but mainly as a result of a paradigm change in toxicology towards the use and integration of genome wide data. Many research groups worldwide have generated large amounts of such toxicogenomics data. However, there is no centralized repository for archiving and making these data and associated tools for their analysis easily available. RESULTS: The Data Infrastructure for Chemical Safety Assessment (diXa) is a robust and sustainable infrastructure storing toxicogenomics data. A central data warehouse is connected to a portal with links to chemical information and molecular and phenotype data. diXa is publicly available through a user-friendly web interface. New data can be readily deposited into diXa using guidelines and templates available online. Analysis descriptions and tools for interrogating the data are available via the diXa portal. AVAILABILITY AND IMPLEMENTATION: http://www.dixa-fp7.eu CONTACT: d.hendrickx@maastrichtuniversity.nl; info@dixa-fp7.eu SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Interindividual variation in response to xenobiotic exposure established in precision-cut human liver slices.

Large differences in toxicity responses occur within the human population. In this study we evaluate whether interindividual variation in baseline enzyme activity (EA)/gene expression (GE) levels in liver predispose for the variation in toxicity responses by assessing dose-response relationships for several prototypical hepatotoxicants. Baseline levels of cytochrome-P450 (CYP) GE/EA were measured in precision-cut human liver slices. Slices (n=4-5/compound) were exposed to a dose-range of acetaminophen, aflatoxin B1, benzo(α) pyrene or 2-nitrofluorene. Interindividual variation in induced genotoxicity (COMET-assay and CDKN1A/p21 GE) and cytotoxicity (lactate dehydrogenase-leakage), combined with NQO1- and GSTM1-induced GE-responses for oxidative stress and GE-responses of several CYPs was evaluated. The benchmark dose-approach was applied as a tool to model exposure responses on an individual level. Variation in baseline CYP levels, both GE and EA, can explain variation in compound exposure-responses on an individual level. Network analyses enable the definition of key parameters influencing interindividual variation after compound exposure. For 2-nitrofluorene, this analysis suggests involvement of CYP1B1 in the metabolism of this compound, which represents a novel finding. In this study, GSTM1 which is known to be highly polymorphic within the human population, but so far could not be linked to toxicity in acetaminophen-poisoned patients, is suggested to cause interindividual variability in acetaminophen-metabolism, dependent on the individual's gene expression-responses of CYP-enzymes. This study demonstrates that using interindividual variation within network modelling provides a source for the definition of essential and even new parameters involved in compound-related metabolism. This information might enable ways to make more quantitative estimates of human risks.

Evaluation of database-derived pathway development for enabling biomarker discovery for hepatotoxicity.

Current testing models for predicting drug-induced liver injury are inadequate, as they basically under-report human health risks. We present here an approach towards developing pathways based on hepatotoxicity-associated gene groups derived from two types of publicly accessible hepatotoxicity databases, in order to develop drug-induced liver injury biomarker profiles. One human liver 'omics-based and four text-mining-based databases were explored for hepatotoxicity-associated gene lists. Over-representation analysis of these gene lists with a hepatotoxicant-exposed primary human hepatocytes data set showed that human liver 'omics gene lists performed better than text-mining gene lists and the results of the latter differed strongly between databases. However, both types of databases contained gene lists demonstrating biomarker potential. Visualizing those in pathway format may aid in interpreting the biomolecular background. We conclude that exploiting existing and openly accessible databases in a dedicated manner seems promising in providing venues for translational research in toxicology and biomarker development.

'Omics analysis of low dose acetaminophen intake demonstrates novel response pathways in humans.

Acetaminophen is the primary cause of acute liver toxicity in Europe/USA, which led the FDA to reconsider recommendations concerning safe acetaminophen dosage/use. Unfortunately, the current tests for liver toxicity are no ideal predictive markers for liver injury, i.e. they only measure acetaminophen exposure after profound liver toxicity has already occurred. Furthermore, these tests do not provide mechanistic information. Here, 'omics techniques (global analysis of metabolomic/gene-expression responses) may provide additional insight. To better understand acetaminophen-induced responses at low doses, we evaluated the effects of (sub-)therapeutic acetaminophen doses on metabolite formation and global gene-expression changes (including, for the first time, full-genome human miRNA expression changes) in blood/urine samples from healthy human volunteers. Many known and several new acetaminophen-metabolites were detected, in particular in relation to hepatotoxicity-linked, oxidative metabolism of acetaminophen. Transcriptomic changes indicated immune-modulating effects (2g dose) and oxidative stress responses (4g dose). For the first time, effects of acetaminophen on full-genome human miRNA expression have been considered and confirmed the findings on mRNA level. 'Omics techniques outperformed clinical chemistry tests and revealed novel response pathways to acetaminophen in humans. Although no definitive conclusion about potential immunotoxic effects of acetaminophen can be drawn from this study, there are clear indications that the immune system is triggered even after intake of low doses of acetaminophen. Also, oxidative stress-related gene responses, similar to those seen after high dose acetaminophen exposure, suggest the occurrence of possible pre-toxic effects of therapeutic acetaminophen doses. Possibly, these effects are related to dose-dependent increases in levels of hepatotoxicity-related metabolites.

Evidence of female-specific glial deficits in the hippocampus in a mouse model of prenatal stress.

Prenatal stress (PS) has been associated with an increased incidence of numerous neuropsychiatric disorders, including depression, anxiety, schizophrenia, and autism. To determine the effects of PS on hippocampal-dependent behaviour hippocampal morphology, we examined behavioural responses and hippocampal cytoarchitecture of a maternal restraint stress paradigm of PS in C57BL6 mice. Female offspring only showed a reduction in hippocampal glial count in the pyramidal layer following PS. Additionally, only PS females showed increased depressive-like behaviour with cognitive deficits predominantly in female offspring when compared to males. This data provides evidence for functional female-specific glial deficits within the hippocampus as a consequence of PS.