Low dose assessment of the carcinogenicity of furan in male F344/N Nctr rats in a 2-year gavage study

Hepatotoxicity of oral exposure to 2-methyl-4-nitroaniline: toxicity prediction and in vivo evaluation

2-Methyl-4-nitroaniline (MNA), an intermediate in the synthesis of azo dyes, is widely distributed in various environmental media and organisms. Although there is speculation regarding MNA's potential to be hepatotoxic, the underlying mechanisms of its hepatotoxicity and its definitive diagnostic process remain largely unexplored. In this research. In the present study, we initially predicted the toxicity and possible toxic effect pathways of MNA using ProTox-II, and found that MNA binds to the PPARγ receptor (binding energy －6.118 kcal/mol) with a potential PPARγ agonist effect. Subsequently, in vivo exposure evaluation was conducted on Wistar rats to assess the impact of MNA after a 90-day exposure period, by detecting serum biochemical indexes, hematological indexes, urinary indexes, inflammatory factors, liver histopathological observations and liver tissue PPARγ mRNA expression. The results showed that MNA causes liver function abnormalities, liver histopathological changes and inflammatory response, along with a pronounced increase in PPARγ mRNA levels. This study suggests that the hepatotoxic mechanism of MNA may be related to its possible upregulation of PPARγ expression, increased liver dysfunction and inflammatory responses. Based on these results, the benchmark dose lower limit (BMDL) of 1.503 mg/kg for male Wistar rats was also established, providing a vital benchmark for determining the safety threshold of MNA. Our data highlight the hepatotoxic mechanism of MNA and contribute to a better understanding of its potential etiological diagnosis.

Dietary lipoic acid alleviates autism-like behavior induced by acrylamide in adolescent mice: the potential involvement of the gut-brain axis

Consuming fried foods has been associated with an increased susceptibility to mental health disorders. Nevertheless, the impact of alpha-lipoic acid (α-LA, LA) on fried food-induced autism-like behavior remains unclear. This study aimed to explore how LA affects autism-related behavior and cognitive deficits caused by acrylamide in mice, a representative food hazard found in fried foods. This improvement was accomplished by enhanced synaptic plasticity, increased neurotrophin expression, elevated calcium-binding protein D28k, and restored serotonin. Additionally, LA substantially influenced the abundance of bacteria linked to autism and depression, simultaneously boosted short-chain fatty acid (SCFA) levels in fecal samples, and induced changes in serum amino acid concentrations. In summary, these findings suggested that exposure to acrylamide in adolescent mice could induce the development of social disorders in adulthood. LA showed promise as a nutritional intervention strategy to tackle emotional disorders during adolescence.

The importance of preclinical models in cholangiocarcinoma

Cholangiocarcinoma (CCA) is an adenocarcinoma of the hepatobiliary system with a grim prognosis. Incidence is rising globally and surgery is currently the only curative treatment, but is only available for patients who are fit and diagnosed in an early-stage of disease progression. Great importance has been placed on developing preclinical models to help further our understanding of CCA and potential treatments to improve therapeutic outcomes. Preclinical models of varying complexity and cost have been established, ranging from more simplistic in vitro 2D CCA cell lines in culture, to more complex in vivo genetically engineered mouse models. Currently there is no single model that faithfully recaptures the complexities of human CCA and the in vivo tumour microenvironment. Instead a multi-model approach should be used when designing preclinical trials to study CCA and potential therapies.

Comparative genomic analysis of Fischer F344 rat livers exposed for 90 days to 3-methylfuran or its parental compound furan

Furan is a naturally forming compound found in heat-processed foods such as coffee, canned meats, and jarred baby food. It is concurrently found with analogues including 2-methylfuran (2-MF) and 3-methylfuran (3-MF), and toxicity studies demonstrate all are potent liver toxins. Toxicity studies found 3-MF is more toxic than either furan, or 2-MF. The present analysis assesses the transcriptional response in liver samples taken from male Fischer (F344) rats exposed to furan or 3-MF from 0 to 2.0 and 0-1.0 mg/kg bw/day, respectively, for 90 days. Transcriptional analyses found decreased liver function and fatty acid metabolism are common responses to both furan and 3-MF exposure. Furan liver injury promotes a ductular reaction through Hippo and TGFB signalling, which combined with increased immune response results in ameliorating perturbed bile acid homeostasis in treated rats. Failure to activate these pathways in 3-MF exposed rats and decreased p53 activity leads to cholestasis, and increased toxicity. Finally, BMD analysis indicate many of the most sensitive pathways affected by furan and 3-MF exposure relate to metabolism - malate dehydrogenase and glucose metabolism with BMDLs of 0.03 and 0.01 mg/kg bw/day for furan and 3-MF exposure, respectively, which agrees with BMDLs previously reported for apical and microarray data.

Adverse outcome pathway exploration of furan-induced liver fibrosis in rats: Genotoxicity pathway or oxidative stress pathway through CYP2E1 activation?

Furan is a widespread endogenous contaminant in heat-processed foods that can accumulate rapidly in the food chain and has been widely detected in foods, such as wheat, bread, coffee, canned meat products, and baby food. Dietary exposure to this chemical may bring health risk. Furan is classified as a possible category 2B human carcinogen by the International Agency for Research on Cancer, with the liver as its primary target organ. Hepatic fibrosis is the most important nontumoral harmful effect of furan and also an important event in the carcinogenesis of furan. Although the specific mechanism of furan-induced liver fibrosis is still unclear, it may involve oxidative stress and genetic toxicity, in which the activation of cytochrome P450 2E1 (CYP2E1) may be the key event. Thus, we conducted a study using an integrating multi-endpoint genotoxicity platform in 120-day in vivo subchronic toxicity test in rats. Results showed that the rats with activated CYP2E1 exhibited DNA double-strand breaks in D4, gene mutations in D60, and increased expression of reactive oxygen species and nuclear factor erythroid 2-related factor 2 in D120. Necrosis, apoptosis, hepatic stellate cell activation, and fibrosis also occurred in the liver, suggesting that furan can independently affect liver fibrosis through oxidative stress and genotoxicity pathways. Point of Departure (PoD) was obtained by benchmark-dose (BMD) method to establish health-based guidance values. The human equivalent dose of PoD derived from BMDL05 was 2.26 μg/kg bw/d. The findings laid a foundation for the safety evaluation and risk assessment of furan and provided data for the further construction and improvement of the adverse outcome pathway network in liver fibrosis.

Assessment of the oxidative damage and apoptotic pathway related to furan cytotoxicity in cultured mouse Leydig cells

Research on heat-induced food contamination is being given more attention as a result of the health risks that have been publicly revealed in recent years. Furan is known as a colorless, combustible, heterocyclic aromatic organic molecule and is formed when food products are processed and stored. It has been established that furan, which is inevitably ingested, has a deleterious impact on human health and causes toxicity. Furan is known to have adverse effects on the immune system, neurological system, skin, liver, kidney, and fat tissue. Infertility caused by furan is a result of its damaging effects on several tissues and organs as well as the reproductive system. Although studies on the adverse effects of furan on the male reproductive system have been performed, there is no study revealing apoptosis in Leydig cells at the gene level. In this study, TM3 mouse Leydig cells were exposed to 250- and 2,500-μM concentrations of furan for 24 h. The findings demonstrated that furan decreased cell viability and antioxidant enzyme activity while increasing lipid peroxidation, reactive oxygen species, and apoptotic cell rates. Furan also increased the expression of the important apoptotic genes Casp3 and Trp53 while decreasing the expression of another pro-apoptotic gene, Bcl2, and antioxidant genes Sod1, Gpx1, and Cat. In conclusion, these results imply that furan may cause loss of cell function in mouse Leydig cells responsible for testosterone biosynthesis by impairing the efficiency of the antioxidant system, possibly by inducing cytotoxicity, oxidative stress, and apoptosis.

Review on Furan as a Food Processing Contaminant: Identifying Research Progress and Technical Challenges for Future Research

A wide range of food processing contaminants (FPCs) are usually formed while thermal processing of food products. Furan is a highly volatile compound among FPCs and could be formed in a variety of thermally processed foods. Therefore, identification of possible reasons of furan occurrence in different thermally processed foods, identification of the most consequential sources of furan exposure, factors impacting its formation, and its detection by specific analytical approaches are necessary to indicate gaps and challenges for future research findings. Furthermore, controlling furan formation in processed foods on a factory scale is also challenging, and research advancements are still ongoing in this context. Meanwhile, understanding adverse effects of furan on human health on a molecular level is necessary to gain insights into human risk assessment.

A comprehensive review of furan in foods: From dietary exposures and in vivo metabolism to mitigation measures

Furan is a thermal food processing contaminant that is ubiquitous in various food products such as coffee, canned and jarred foods, and cereals. A comprehensive summary of research progress on furan is presented in this review, including discussion of (i) formation pathways, (ii) occurrence and dietary exposures, (iii) analytical techniques, (iv) toxicities, (v) metabolism and metabolites, (vi) risk assessment, (vii) potential biomarkers, and (viii) mitigation measures. Dietary exposure to furan varies among different countries and age groups. Furan acts through various toxicological pathways mediated by its primary metabolite, cis-2-butene-1,4-dial (BDA). BDA can readily react with glutathione, amino acids, biogenic amines, or nucleotides to form corresponding metabolites, some of which have been proposed as potential biomarkers of exposure to furan. Present risk assessment of furan mainly employed the margin of exposure approach. Given the widespread occurrence of furan in foods and its harmful health effects, mitigating furan levels in foods or exploring potential dietary supplements to protect against furan toxicity is necessary for the benefit of food safety and public health.

Furan Metabolites Are Elevated in Users of Various Tobacco Products and Cannabis

Humans are exposed to furan, a toxicant and possible human carcinogen, through multiple sources including diet and tobacco smoke. The urinary metabolites of furan are derived from the reaction of its toxic metabolite with protein nucleophiles and are biomarkers of exposure and potential harm. An established isotopic dilution liquid-chromatography mass spectrometry method was used to measure these biomarkers in urine from users of e-cigarettes, cannabis, and/or combustible tobacco with/without reduced nicotine levels. Amounts of furan mercapturic acid metabolites were higher in these individuals relative to nonsmokers, indicating that they may be at risk for potential furan-derived toxicities.

Comprehensive analysis of the general toxicity, genotoxicity, and carcinogenicity of 3-acetyl-2,5-dimethylfuran in male gpt delta rats

The safety of flavoring agents has been evaluated according to classification by chemical structure and using a decision tree approach. The genotoxic potential found in some flavoring agents has highlighted the importance of efficient toxicity studies. We performed a comprehensive toxicity analysis using reporter gene transgenic rats to assess the safety of 3-acetyl-2,5-dimethylfuran (ADF), a flavoring agent exhibiting genotoxic potential in silico and in vitro assays. Male F344 gpt delta rats were given 0, 30, or 300 mg/kg body weight/day ADF by gavage for 13 weeks. In serum biochemistry analyses, triglyceride, total cholesterol, phospholipid, and total protein levels and albumin/globulin ratios were significantly altered in the 30 and 300 mg/kg groups. Histopathologically, nasal cavity toxicity and hepatocellular hypertrophy were observed in the 300 mg/kg group. In the livers of 300 mg/kg group, a significant increase in gpt mutant frequencies were observed along with ADF-specific DNA adduct formation. The number and area of glutathione S-transferase placental form-positive foci were significantly increased in the same group. Thus, ADF affected nasal cavity, liver, and lipid metabolism and showed genotoxicity and possible carcinogenicity in the liver. Overall, our comprehensive toxicity study using gpt delta rats provided insights into the safety evaluation of ADF.

Food-Borne Chemical Carcinogens and the Evidence for Human Cancer Risk

Commonly consumed foods and beverages can contain chemicals with reported carcinogenic activity in rodent models. Moreover, exposures to some of these substances have been associated with increased cancer risks in humans. Food-borne carcinogens span a range of chemical classes and can arise from natural or anthropogenic sources, as well as form endogenously. Important considerations include the mechanism(s) of action (MoA), their relevance to human biology, and the level of exposure in diet. The MoAs of carcinogens have been classified as either DNA-reactive (genotoxic), involving covalent reaction with nuclear DNA, or epigenetic, involving molecular and cellular effects other than DNA reactivity. Carcinogens are generally present in food at low levels, resulting in low daily intakes, although there are some exceptions. Carcinogens of the DNA-reactive type produce effects at lower dosages than epigenetic carcinogens. Several food-related DNA-reactive carcinogens, including aflatoxins, aristolochic acid, benzene, benzo[a]pyrene and ethylene oxide, are recognized by the International Agency for Research on Cancer (IARC) as causes of human cancer. Of the epigenetic type, the only carcinogen considered to be associated with increased cancer in humans, although not from low-level food exposure, is dioxin (TCDD). Thus, DNA-reactive carcinogens in food represent a much greater risk than epigenetic carcinogens.

Selecting an Appropriate Experimental Animal Model for Cholangiocarcinoma Research

Cholangiocarcinoma (CCA) is a highly aggressive biliary tree malignancy with intrahepatic and extra-hepatic subtypes that differ in molecular pathogeneses, epidemiology, clinical manifestations, treatment, and prognosis. The overall prognosis and patient survival remains poor because of lack of early diagnosis and effective treatments. Preclinical in vivo studies have become increasingly paramount as they are helpful not only for the study of the fundamental molecular mechanisms of CCA but also for developing novel and effective therapeutic approaches of this fatal cancer. Recent advancements in cell and molecular biology have made it possible to mimic the pathogenicity of human CCA in chemical-mechanical, infection-induced inflammatory, implantation, and genetically engineered animal models. This review is intended to help investigators understand the particular strengths and weaknesses of the currently used in vivo animal models of human CCA and their related modeling techniques to aid in the selection of the one that is the best for their research needs.

Hazard Ratio and Hazard Index as Preliminary Estimators Associated to the Presence of Furans and Alkylfurans in Belgian Foodstuffs

This paper provides an estimation of the hazard related to the presence of furan and five alkyl furans (2- and 3-methylfuran, 2-ethylfuran, 2,5- and 2,3-dimethylfuran) in foodstuffs available in the Belgian market. To achieve this objective, a specific sampling plan was designed to ensure that the samples collected (n = 1003) represent the diversity of the Belgian food chain. Herein, the concepts of the Hazard Ratio of a sample (HRs) and the Hazard Index of a sample (HIs) were introduced to primarily characterize the hazard related to the co-occurrence of these compounds. The HRs was measured as the ratio of the potential daily exposure to a substance (expressed in mg/Kg of food) to both the 10% reference dose level for chronic effects (expressed in mg/(kg b.w*day)) and the human standard weight (expressed in kg). Whereas the HIs is the sum of the HRs of compounds that affect the same target organ/system, a hazard index greater than one indicates a highly contaminated matrix that could induce a hazard. It is an alarm indicating that additional attention should be given to this matrix. This may involve additional analyses to confirm the high level, to identify sources, etc. It is also an alarm for the risk assessor to be very careful with flagged matrices and to avoid combination with other matrices. The HIs highlight a relatively low concern for all foods analyzed (HI median < 1.0) with a relatively higher suspected hazard for coffee drinks (HI median = 0.068, HI max = 0.57). This preliminary estimation of the potential hazard suggests that coffee beverages should be examined in more detail in a full risk assessment and that coffee consumption should be taken with caution given the levels of furan and alkylfurans reported in this study.

Toxicity, genotoxicity, and carcinogenicity of 2-methylfuran in a 90-day comprehensive toxicity study in gpt delta rats

2-Methylfuran (2-MF) exists naturally in foods and is used as a flavoring agent. Furan, the core structure of 2-MF, possesses hepatocarcinogenicity in rodents. Accumulation of toxicological information on furan derivatives is needed to elucidate their carcinogenic mode of action. In the current study, we examined the comprehensive toxicological studies of 2-MF using gpt delta rats. 2-MF was intragastrically administered to groups of 10 male and 10 female Sprague-Dawley gpt delta rats at a dose of 0, 1.2, 6, or 30 mg/kg/day for 13 weeks. Effects of 2-MF on the hepatobiliary system including an increase in serum alkaline phosphatase were observed in the 6 and 30 mg/kg groups, and cholangiofibrosis was found in the 30 mg/kg group. The no observed adverse effect level was set at 1.2 mg/kg/day for both sexes and 1.14 mg/kg/day was determined as the benchmark dose low. The acceptable daily intake was calculated to be 11.4 μg/kg/day. Increases in the number and areas of glutathione S-transferase placental form-positive foci in the 30 mg/kg group were apparent, suggesting the hepatocarcinogenicity of 2-MF in rats. By contrast, the lack of increase in in vivo mutagenicity in the liver implied that 2-MF hepatocarcinogenesis may not involve genotoxic mechanisms.

Glycidamide and cis-2-butene-1,4-dial (BDA) as potential carcinogens and promoters of liver cancer - An in vitro study

Acrylamide and furan are environmental and food contaminants that are metabolized by cytochrome P450 2E1 (CYP2E1), giving rise to glycidamide and cis-2-butene-1,4-dial (BDA) metabolites, respectively. Both glycidamide and BDA are electrophilic species that react with nucleophilic groups, being able to introduce mutations in DNA and perform epigenetic remodeling. However, whereas these carcinogens are primarily metabolized in the liver, the carcinogenic potential of acrylamide and furan in this organ is still controversial, based on findings from experimental animal studies. With the ultimate goal of providing further insights into this issue, we explored in vitro, using a hepatocyte cell line and a hepatocellular carcinoma cell line, the putative effect of these metabolites as carcinogens and cancer promoters. Molecular alterations were investigated in cells that survive glycidamide and BDA toxicity. We observed that those cells express CD133 stemness marker, present a high proliferative capacity and display an adjusted expression profile of genes encoding enzymes involved in oxidative stress control, such as GCL-C, GSTP1, GSTA3 and CAT. These molecular changes seem to be underlined, at least in part, by epigenetic remodeling involving histone deacetylases (HDACs). Although more studies are needed, here we present more insights towards the carcinogenic capacity of glycidamide and BDA and also point out their effect in favoring hepatocellular carcinoma progression.

The role of endogenous versus exogenous sources in the exposome of putative genotoxins and consequences for risk assessment

The "totality" of the human exposure is conceived to encompass life-associated endogenous and exogenous aggregate exposures. Process-related contaminants (PRCs) are not only formed in foods by heat processing, but also occur endogenously in the organism as physiological components of energy metabolism, potentially also generated by the human microbiome. To arrive at a comprehensive risk assessment, it is necessary to understand the contribution of in vivo background occurrence as compared to the ingestion from exogenous sources. Hence, this review provides an overview of the knowledge on the contribution of endogenous exposure to the overall exposure to putative genotoxic food contaminants, namely ethanol, acetaldehyde, formaldehyde, acrylamide, acrolein, α,β-unsaturated alkenals, glycation compounds, N-nitroso compounds, ethylene oxide, furans, 2- and 3-MCPD, and glycidyl esters. The evidence discussed herein allows to conclude that endogenous formation of some contaminants appears to contribute substantially to the exposome. This is of critical importance for risk assessment in the cases where endogenous exposure is suspected to outweigh the exogenous one (e.g. formaldehyde and acrolein).

Discovery of Novel Tubulin Polymerization Inhibitors by Utilizing 3D-QSAR, Molecular Docking and Molecular Dynamics Simulation

Tubulin is a potential therapeutic target for cancer. Compounds inhibit the polymerization of tubulin or promote the polymerization of tubulin to interfere with the mitotic process of cells, resulting in...

Red-Fleshed Apple Anthocyanin Extract Reduces Furan Content in Ground Coffee, Maillard Model System, and Not-from-Concentrate Apple Juice

Furan is a volatile and carcinogenic heterocyclic chemical compound that occurs in a wide range of thermally processed food. It can be induced during food-preparing processes by high temperatures and UV-C light. In the present study, the degradation of furan content in ground coffee, Maillard model system, and not-from-concentrate (NFC) apple juice by red-fleshed apple anthocyanin extract (RAAE) was studied. The results demonstrated that RAAEs had different degrees of degradation of furan content in coffee powder, and the RAAE from ‘XJ3’ had the most significant effect, with a reduction rate of up to 20%. Moreover, by adding RAAE to the Maillard model system, we found the amounts of furan were significantly reduced. At the same time, RAAE from ‘XJ3’ could observably reduce the content of furan in pasteurized NFC juice, with ‘Fuli’ NFC juice furan content decreasing the most, which was 68%. Taken together, our study demonstrated that the use of RAAE could be a feasible way to reduce furan content in ground coffee, Maillard model system, and NFC apple juice.

Oxidative Stress, Mutations and Chromosomal Aberrations Induced by In Vitro and In Vivo Exposure to Furan

Furan is a volatile compound that is formed in foods during thermal processing. It is classified as a possible human carcinogen by international authorities based on sufficient evidence of carcinogenicity from studies in experimental animals. Although a vast number of studies both in vitro and in vivo have been performed to investigate furan genotoxicity, the results are inconsistent, and its carcinogenic mode of action remains to be clarified. Here, we address the mutagenic and clastogenic activity of furan and its prime reactive metabolite cis-2 butene-1,4-dial (BDA) in mammalian cells in culture and in mouse animal models in a search for DNA lesions responsible of these effects. To this aim, Fanconi anemia-derived human cell lines defective in the repair of DNA inter-strand crosslinks (ICLs) and Ogg1-/- mice defective in the removal of 8-hydroxyguanine from DNA, were used. We show that both furan and BDA present a weak (if any) mutagenic activity but are clear inducers of clastogenic damage. ICLs are strongly indicated as key lesions for chromosomal damage whereas oxidized base lesions are unlikely to play a critical role.

Formation of furan in baby food products: Identification and technical challenges

Furan is generally produced during thermal processing of various foods including baked, fried, and roasted food items such as cereal products, coffee, canned, and jarred prepared foods as well as in baby foods. Furan is a toxic and carcinogenic compound to humans and may be a vital hazard to infants and babies. Furan could be formed in foods through thermal degradation of carbohydrates, dissociation of amino acids, and oxidation of polyunsaturated fatty acids. The detection of furan in food products is difficult due to its high volatility and low molecular weight. Headspace solid-phase microextraction coupled with gas chromatography/mass spectrometer (GC/MS) is generally used for analysis of furan in food samples. The risk assessment of furan can be characterized using margin of exposure approach (MOE). Conventional strategies including cooking in open vessels, reheating of commercially processed foods with stirring, and physical removal using vacuum treatment have remained unsuccessful for the removal of furan due to the complex production mechanisms and possible precursors of furan. The innovative food-processing technologies such as high-pressure processing (HPP), high-pressure thermal sterilization (HPTS), and Ohmic heating have been adapted for the reduction of furan levels in baby foods. But in recent years, only HPP has gained interest due to successful reduction of furan because of its nonthermal mechanism. HPP-treated baby food products are commercially available from different food companies. This review summarizes the mechanism involved in the formation of furan in foods, its toxicity, and identification in infant foods and presents a solution for limiting its formation, occurrence, and retention using novel strategies.

Developing models of cholangiocarcinoma to close the translational gap in cancer research

Introduction: Cholangiocarcinoma (CCA) is an aggressive primary liver malignancy with abysmal prognosis and increasing global incidence. Individuals afflicted with CCA often remain asymptomatic until late stages of disease, resulting in very limited possibilities for therapeutic intervention. The emergence of numerous preclinical models in vitro and in vivo has expanded the tool kit for CCA researchers; nonetheless, how these tools can be best applied to understand CCA biology and accelerate drug development requires further scrutiny.Areas covered: The paper reviews the literature on animal and organoid models of CCA (available through PubMed between September 2020 and January 2021) and examines their investigational role in CCA therapeutics. Finally, the potential of these systems for screening therapeutics to improve CCA patient outcomes is illuminated.Expert Opinion: The expansion of CCA models has yielded a diverse and interesting tool kit for preclinical research. However, investigators should consider which tools are best suited to answer key preclinical questions for real progress. A combination of advanced in vitro cell systems and in vivo testing will be necessary to accelerate translational medicine in cholangiocarcinoma.

Urinary metabolites of furan in waterpipe tobacco smokers compared to non-smokers in home settings in the US

OBJECTIVES

Determine uptake of furan, a potential human carcinogen, in waterpipe tobacco (WPT) smokers in home settings.

METHODS

We analysed data from a US convenience sample of 50 exclusive WPT smokers, mean age 25.3 years, and 25 non-smokers, mean age 25.5 years. For WPT smokers, data were collected at a home visit by research assistants during which participants smoked one WPT head of one brand for a mean of 33.1 min in their homes. Research assistants provided and prepared a WP for participants by weighing and loading 10 g of WPT in the WP head. At the completion of the smoking session, research assistants measured the remaining WPT. Cotinine and six furan metabolites were quantified in first morning urine samples provided on 2 consecutive days for non-smokers, and on the morning of a WPT smoking session and on the following morning for smokers.

RESULTS

WPT smokers consumed a mean of 2.99 g WPT. In WPT smokers, urinary cotinine levels increased significantly 26.1 times the following morning; however, urinary metabolites of furan did not increase significantly. Compared to non-smokers, 2 furan metabolites, N-acetyl-S-[1-(5-acetylamino-5-carboxylpentyl)-1H-pyrrol-3-yl]-L-cysteine and N-acetyl-S-[1-(5-amino-5-carboxypentyl)-1H-pyrrol-3-yl]-L-cysteine sulfoxide, were significantly higher in WPT smokers in pre and in post WPT smoking levels.

CONCLUSIONS

To enable a more rigorous assessment of furan exposure from WPT smoking, future research should determine furan concentrations in WPT smoke, quantify furan metabolites from users of various WPT brands; and extend the investigation to social settings where WPT smoking is habitually practiced.

Evaluation of 5-day In Vivo Rat Liver and Kidney With High-throughput Transcriptomics for Estimating Benchmark Doses of Apical Outcomes

A 5-day in vivo rat model was evaluated as an approach to estimate chemical exposures that may pose minimal risk by comparing benchmark dose (BMD) values for transcriptional changes in the liver and kidney to BMD values for toxicological endpoints from traditional toxicity studies. Eighteen chemicals, most having been tested by the National Toxicology Program in 2-year bioassays, were evaluated. Some of these chemicals are potent hepatotoxicants (eg, DE71, PFOA, and furan) in rodents, some exhibit toxicity but have minimal hepatic effects (eg, acrylamide and α,β-thujone), and some exhibit little overt toxicity (eg, ginseng and milk thistle extract) based on traditional toxicological evaluations. Male Sprague Dawley rats were exposed once daily for 5 consecutive days by oral gavage to 8-10 dose levels for each chemical. Liver and kidney were collected 24 h after the final exposure and total RNA was assayed using high-throughput transcriptomics (HTT) with the rat S1500+ platform. HTT data were analyzed using BMD Express 2 to determine transcriptional gene set BMD values. BMDS was used to determine BMD values for histopathological effects from chronic or subchronic toxicity studies. For many of the chemicals, the lowest transcriptional BMDs from the 5-day assays were within a factor of 5 of the lowest histopathological BMDs from the toxicity studies. These data suggest that using HTT in a 5-day in vivo rat model provides reasonable estimates of BMD values for traditional apical endpoints. This approach may be useful to prioritize chemicals for further testing while providing actionable data in a timely and cost-effective manner.

A review on furan: Formation, analysis, occurrence, carcinogenicity, genotoxicity and reduction methods

Furan (C₄H₄O) is a volatile, heterocyclic and carcinogenic heterocyclic chemical compound occurring in a wide range of thermally processed foods. Several studies have been conducted to analyze the formation conditions, triggering furan formation via model systems. Furan can be encountered via various pathways including thermal degradation, oxidation of polyunsaturated fatty acids, thermal rearrangement of carbohydrates in the presence of amino acids, thermal degradation of certain amino acids. Furan has been proven to cause cancer in experimental animal models and classified as a possible human carcinogen by International agency for research on cancer based on sufficient evidences. Thus, different strategies should be developed to reduce furan contents in commercially available food stuffs while food processing. This review summarizes some current evidences of furan formation from different precursors, analytical methods for its detection, and its toxicity that might lead to carcinogenicity and genotoxicity with human risk assessment. In addition, furan occurrence in different thermally processed foods entailed by several recent studies as well as furan mitigation strategies during food processing have also been illustrated in this review.

Dietary exposure to furan of the Austrian population

In the period from 2007 to 2017 furan levels of foods were analysed by the Austrian Agency for Health and Food Safety. Based on these analytical data and the Austrian consumption data the dietary exposure of children and adults to furan was estimated by using a deterministic approach. For the adult population the mean and 95^th percentile dietary exposures to furan were estimated at 0.31 µg/kg bodyweight per day and at 0.72 µg/kg bodyweight per day, respectively. The mean dietary exposure of children was estimated at 0.18 µg/kg bodyweight per day and is thus only about half as high as for Austrian adults. At the 95^th percentile the dietary exposure of children was estimated at 0.49 µg/kg bodyweight per day. The main contributor to the total dietary exposure for adults is coffee followed by convenience products and for children the main contributors are grain products as well as convenience products, bread and snacks. Based on the BMDL₁₀ of 0.064 mg/kg bodyweight per day for the development of cholangiofibrosis, the MOE-calculation revealed that the current levels of dietary exposure to furan are of concern for Austrian adult high consumers. The MOE-calculation, based on the BMDL₁₀ of 1.31 mg/kg bodyweight per day for the development of hepatocellular adenomas, indicated a health concern for Austrian children and adults.

Inhaled Furan Selectively Damages Club Cells in Lungs of A/J Mice

Furan, a possible human carcinogen, is a product of incomplete combustion and is present in cigarette smoke, engine exhaust, and processed food. Oral administration induces liver toxicity and carcinogenesis in F344 rats and B6C3F1 mice. To assess possible adverse effects from inhalation, A/J mice were nose-only exposed for 3 hours to furan (0, 30, 75, 150, 300, or 600 ppmv) and euthanized after 24 hours, 48 hours, or 1 week. Histopathology evaluation revealed bronchiolar club cell necrosis (diffuse, marked) with airway denudation following exposure to 300 and 600 ppmv furan with evidence of club cell regeneration and partial repair after 1 week. Initial signs of hepatotoxicity were observed in the 150 ppmv furan-exposed group. Acute necrosis and mineralization were observed in livers at 24 and 48 hours with hepatocyte regeneration by 1-week postexposure in mice exposed to 300 and 600 ppmv furan; the 300 ppmv exposed group had multifocal mineralization that evoked a mild granulomatous response. Measurement of urinary furan metabolites confirmed that the mice metabolized furan to the toxic intermediate, cis-2-butene-1,4-dial. These observations indicate that inhaled furan is toxic to lungs with club cells as the target as well as liver.

Towards a dietary-exposome assessment of chemicals in food: An update on the chronic health risks for the European consumer

An informed opinion to a hugely important question, whether the food on the Europeans' plate is safe to eat, is provided. Today, the Europeans face food-borne health risks from non-communicable diseases induced by excess body weight, outbreaks caused by pathogens, antimicrobial resistance and exposures to chemical contaminants. In this review, these risks are first put in an order of importance. Then, not only potentially injurious dietary chemicals are discussed but also beneficial factors of the food. This review can be regarded as an attempt towards a dietary-exposome evaluation of the chemicals, the average European adult consumers could chronically expose to during their life-times. Risk ranking reveals that currently the European adults are chronically exposed to a mixture of potentially genotoxic-carcinogenic contaminants, particularly food process contaminants, at the potential risk levels. Furthermore, several of the contaminants whose dietary exposures pose risks appear to be carcinogens operating with a genotoxic mode of action targeting the liver. This suggests that combined health risks from the exposure to a mixture of the chemical contaminants poses a greater potential risk than the risks assessed for single compounds. Over 100 European-level risk assessments are examined. Finally, the importance of a diversified and balanced diet is emphasized.

Animal models of cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive biliary tract malignancy with a poor overall prognosis. There is a critical need to develop effective targeted therapies for the treatment of this lethal disease. In an effort to address this challenge, preclinical in vivo studies have become paramount in understanding CCA carcinogenesis, progression, and therapy. Various CCA animal models exist including carcinogen-based models in which animals develop CCA after exposure to a carcinogen, genetically engineered mouse models in which genetic changes are induced in mice leading to CCA, murine syngeneic orthotopic models, as well as xenograft tumors derived from xenotransplantation of CCA cells, organoids, and patient-derived tissue. Each type has distinct advantages as well as shortcomings. In the ideal animal model of CCA, the tumor arises from the biliary tract in an immunocompetent host with a species-matched tumor microenvironment. Such a model would also be time-efficient, recapitulate the genetic and histopathological features of human CCA, and predict therapeutic response in humans. Recently developed biliary tract transduction and orthotopic syngeneic transplant mouse models encompass several of these elements. Herein, we review the different animal models of CCA, their advantages and deficiencies, as well as features which mimic human CCA.

Differential susceptibility of kidneys and livers to proliferative processes and transcriptional level of the genes encoding desmin, vimentin, connexin 43, and nestin in rats exposed to furan

In this study, we aimed to assess the differential toxic impact, induced by furan exposure, on the liver and kidney tissues by estimating reactive oxygen species (ROS) level, total antioxidant capacity (TAC), oxidative damage, and the tissue injury markers in a male rat model. To explain such impacts, 20 rats were assigned into two groups: a control group, where rats were administered corn oil as a vehicle, and a furan-administered group, where furan was orally administered to rats at a dose of 16 mg/kg b wt/day (five days per week over eight weeks). The transcriptional levels of intermediate filament proteins (desmin, vimentin, nestin, and connexin 43) were assessed by using quantitative real-time polymerase chain reaction (PCR), and the cell proliferation markers (proliferating cell nuclear antigen [PCNA] and proliferation-associated nuclear antigen [Ki-67]) were recognized by immunohistochemical analysis. Furthermore, the ultrastructural changes of liver and kidney were monitored using electron microscopy. Our findings showed that furan exposure could induce hepatic and renal damage to different extents. Furan can increase the ROS content, oxidative damage indices, and liver tissue injury indices but not kidney injury indices. Furthermore, it decreases the TAC in the serum of exposed rats. In addition, furan exposure was associated with changes in the mRNA expression pattern of intermediate filament proteins in both kidney and liver tissues. Moreover, furan enhances the expression of PCNA and Ki-67 in the liver tissues but not in the kidney tissues. The ultrastructure evaluation revealed the incidence of glomerular podocyte degeneration and hepatocyte injury. These results conclusively demonstrate that the deleterious effects of furan are caused by promoting fibrosis and hepatocyte proliferation in liver tissues and triggering podocyte injury in the kidney tissues.

Thermal processing food-related toxicants: a review

Heterocyclic aromatic amines, acrylamide, 5-hydroxymethylfurfural, furan, polycyclic aromatic hydrocarbons, nitrosamines, acrolein, chloropropanols and chloroesters are generated toxicants formed in some foodstuffs, mainly starchy and protein-rich food during thermal treatment such as frying, roasting and baking. The formation of these chemical compounds is associated with development of aromas, colors and flavors. One of the challenges facing the food industry today is to minimize these toxicants without adversely affecting the positive attributes of thermal processing. To achieve this objective, it is essential to have a detailed understanding of the mechanism of formation of these toxicants in processed foods. All reviewed toxicants in that paper are classified as probable, possible or potential human carcinogens and have been proven to be carcinogenic in animal studies. The purpose of that review is to summarize some of the most frequent occurring heat-generated food toxicants during conventional heating, their metabolism and carcinogenicity. Moreover, conventional and microwave heating were also compared as two different heat treatment methods, especially how they change food chemical composition and which thermal food toxicants are formed during specific method.

Spirulina platensis attenuates furan reprotoxicity by regulating oxidative stress, inflammation, and apoptosis in testis of rats

Furan is a common food contaminant and environmental pollutant. Spirulina platensis (SP) is a blue-green algae extensively used as therapeutic and health supplements. This study aimed to explore the probable beneficial role of SP against the influence of furan on reproductive system of male rats. Adult male rats were divided into control, vehicle control, SP (300 mg/kg bwt/ day, 7 days), furan (16 mg/kg bwt/ day,30 day), SP/furan, furan/SP and furan+SP groups. Hematology, sperm count, sperm morphology, serum testosterone (TES), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and estradiol (E2) levels, reduced glutathione (GSH), malondialdehyde (MDA), testicular enzymes, and pro inflammatory cytokines were estimated. In addition, histopathology of testis and seminal vesicles and apoptosis were evaluated. Anaemia, leukocytosis, and reduced gonadosomatic index were observed in the furan treated group. TES, LH, FSH, E2, and GSH were significantly decreased following furan treatment. MDA, testicular enzymes, and pro inflammatory cytokines were significantly incremented in testis of furan treated rats. Furan induced apoptic changes in testis. SP significantly counteracted furan reprotoxic impacts, particularly at co-exposure. Conclusively, these findings verified that SP could be candidate therapy against furan reprotoxic impacts.

Exposure assessment of process-related contaminants in food by biomarker monitoring

Exposure assessment is a fundamental part of the risk assessment paradigm, but can often present a number of challenges and uncertainties. This is especially the case for process contaminants formed during the processing, e.g. heating of food, since they are in part highly reactive and/or volatile, thus making exposure assessment by analysing contents in food unreliable. New approaches are therefore required to accurately assess consumer exposure and thus better inform the risk assessment. Such novel approaches may include the use of biomarkers, physiologically based kinetic (PBK) modelling-facilitated reverse dosimetry, and/or duplicate diet studies. This review focuses on the state of the art with respect to the use of biomarkers of exposure for the process contaminants acrylamide, 3-MCPD esters, glycidyl esters, furan and acrolein. From the overview presented, it becomes clear that the field of assessing human exposure to process-related contaminants in food by biomarker monitoring is promising and strongly developing. The current state of the art as well as the existing data gaps and challenges for the future were defined. They include (1) using PBK modelling and duplicate diet studies to establish, preferably in humans, correlations between external exposure and biomarkers; (2) elucidation of the possible endogenous formation of the process-related contaminants and the resulting biomarker levels; (3) the influence of inter-individual variations and how to include that in the biomarker-based exposure predictions; (4) the correction for confounding factors; (5) the value of the different biomarkers in relation to exposure scenario's and risk assessment, and (6) the possibilities of novel methodologies. In spite of these challenges it can be concluded that biomarker-based exposure assessment provides a unique opportunity to more accurately assess consumer exposure to process-related contaminants in food and thus to better inform risk assessment.

Risks for public health related to the presence of furan and methylfurans in food

The European Commission asked EFSA for a scientific evaluation on the risk to human health of the presence of furan and methylfurans (2-methylfuran, 3-methylfuran and 2,5-dimethylfuran) in food. They are formed in foods during thermal processing and can co-occur. Furans are produced from several precursors such as ascorbic acid, amino acids, carbohydrates, unsaturated fatty acids and carotenoids, and are found in a variety of foods including coffee and canned and jarred foods. Regarding furan occurrence, 17,056 analytical results were used in the evaluation. No occurrence data were received on methylfurans. The highest exposures to furan were estimated for infants, mainly from ready-to-eat meals. Grains and grain-based products contribute most for toddlers, other children and adolescents. In adults, elderly and very elderly, coffee is the main contributor to dietary exposure. Furan is absorbed from the gastrointestinal tract and is found in highest amounts in the liver. It has a short half-life and is metabolised by cytochrome P450 2E1 (CYP2E1) to the reactive metabolite, cis-but-2-ene-1,4-dialdehyde (BDA). BDA can bind covalently to amino acids, proteins and DNA. Furan is hepatotoxic in rats and mice with cholangiofibrosis in rats and hepatocellular adenomas/carcinomas in mice being the most prominent effects. There is limited evidence of chromosomal damage in vivo and a lack of understanding of the underlying mechanism. Clear evidence for indirect mechanisms involved in carcinogenesis include oxidative stress, gene expression alterations, epigenetic changes, inflammation and increased cell proliferation. The CONTAM Panel used a margin of exposure (MOE) approach for the risk characterisation using as a reference point a benchmark dose lower confidence limit for a benchmark response of 10% of 0.064 mg/kg body weight (bw) per day for the incidence of cholangiofibrosis in the rat. The calculated MOEs indicate a health concern. This conclusion was supported by the calculated MOEs for the neoplastic effects.

Scientific opinion of Flavouring Group Evaluation 502 (FGE.502): grill flavour 'Grillin' 5078'

The EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF Panel) was requested to deliver a scientific opinion on the implication for human health of the product Grillin' 5078 [FL-no: 21.003] in the Flavouring Group Evaluation 502, according to Regulation (EC) No 1331/2008 and Regulation (EC) No 1334/2008 of the European Parliament and of the Council. The product is derived from heat-treated high oleic sunflower oil and intended to be used as a food flavouring with charbroiled or grilled aroma in a wide variety of food categories either in liquid or powder form. Information on manufacturing and compositional data was considered adequate to show the reproducibility of the production process. However, the Panel noted that a considerable amount of the non-volatile fraction of the product could not be identified. The chronic dietary exposure to the substance estimated using the Added Portions Exposure Technique (APET) was calculated to be 60 mg/person per day for a 60-kg adult and 37.8 mg/person per day for a 15-kg child. The data submitted for evaluating the genotoxic potential of the flavouring was considered insufficient. There are still 12 substances in the flavouring for which the evaluation of genotoxic potential is pending. No toxicity studies have been provided on the final product itself. Only information on a number of constituents of the flavouring and data on toxicity of several thermally treated fats and oils were provided by the applicant. However, the Panel considered the time-temperature conditions that were applied in the preparation of the substances tested as not comparable to those applied in the course of the production of the flavouring. The Panel concluded that on the basis of the data provided by the applicant the safety of Grillin' 5078 cannot be established.

Scientific Opinion of Flavouring Group Evaluation 500 (FGE.500): rum ether

The Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids of the European Food Safety Authority was requested to deliver a scientific opinion on the implications for human health of the flavouring rum ether [FL-no: 21.001] in the Flavouring Group Evaluation 500 (FGE.500), according to Regulation (EC) No 1331/2008 and Regulation (EC) No 1334/2008 of the European Parliament and of the Council. Rum ether is a complex mixture of volatile substances obtained by distillation of the reaction products of pyroligneous acid and ethyl alcohol under oxidative conditions in the presence of manganese dioxide and sulfuric acid. A total of 84 volatile constituents have been reported by the applicant. It is a colourless liquid with a rum-like odour and flavour. Its major uses are in the food categories beverages, confectionery and baked goods. The Panel decided to apply a congeneric group-based approach. The 84 reported constituents were allocated to 12 congeneric groups, based on structural and metabolic similarity. For eight of the congeneric groups, the Panel concluded that there is no safety concern at the intended conditions of use. However, the Panel concluded that substances in congeneric group 1 (ethanol and acetaldehyde) and congeneric group 12 (furan) are carcinogenic and genotoxic. The Panel also identified genotoxicity concerns for substances in congeneric group 3 (3-pentene-2-one). The exposure for congeneric group 10 (ethers of various structures) was above the Threshold of Toxicological Concern (TTC) applicable for this group, but a point of departure or health based guidance value that covers all the substances in this group could not be identified. The Panel concluded that according to the overall strategy for the risk assessment of flavouring substances, the presence of genotoxic substances as process-derived constituents of rum ether is of safety concern.