Hemoglobin adducts and micronucleus frequencies in mouse and rat after acrylamide or N-methylolacrylamide treatment

Internal exposure to heat-induced food contaminants in omnivores, vegans and strict raw food eaters: biomarkers of exposure to acrylamide (hemoglobin adducts, urinary mercapturic acids) and new insights on its endogenous formation

The urinary mercapturic acids N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA) are short-term biomarkers of exposure from acrylamide and its metabolite glycidamide, respectively. The medium-term exposure to acrylamide and glycidamide is monitored by the adducts N-(2-carbamoylethyl)-Val (AA-Val) and N-(2-carbamoyl-2-hydroxyethyl)-Val (GA-Val) in hemoglobin (Hb), respectively. Three questions were addressed by application of these biomarkers in two diet studies including 36 omnivores, 36 vegans and 16 strict raw food eaters (abstaining from any warmed or heated food for at least four months): first, what is the internal acrylamide exposure following a vegan or a raw food diet in comparison to that in omnivores? Second, did the exposure change between 2017 and 2021? And third, what is the stability over time of AAMA/GAMA excretion compared to that of AA-Val/GA-Val levels in Hb between both time points? Median urinary AAMA excretion per day in non-smoking omnivores, vegans and raw food eaters were 62.4, 85.4 and 15.4 µg/day, respectively; the corresponding median AA-Val levels were 27.7, 39.7 and 13.3 pmol/g Hb, respectively. Median levels in strict raw food eaters were about 25% (AAMA excretion) and 48% (AA-Val) of those in omnivores. In comparison to 2017, AAMA and GAMA excretion levels were hardly altered in 2021, however, levels of AA-Val and GA-Val in 2021 slightly increased. There was a weak correlation between AAMA excretion levels determined four years apart (rS = 0.30), and a moderate correlation between levels of AA-Val (rS = 0.55) in this timeframe. Our data in strict raw food eaters confirm a significant endogenous formation to acrylamide in a size range, which is-based on the levels of AA-Val-distinctly higher than reported previously based on levels of urinary AAMA excretion. The relatively lower AAMA excretion in raw food eaters likely represents a lower extent of glutathione conjugation due to missing hepatic first-pass metabolism in case of endogenous formation of acrylamide, which leads to a higher systemic exposure.

A biobased synthesized N-hydroxymethyl starch-amide for enhancing the wet and dry strength of paper products

The aim of this research was to develop a bio-based paper strength agent for the replacement of petroleum-based paper strength agents. Cationic starch was modified with 2-chloroacetamide in aqueous media. The modification reaction conditions were optimized based on the acetamide functional group incorporated into cationic starch. Further, modified cationic starch was dissolved in water and then reacted with formaldehyde to produce N-hydroxymethyl starch-amide. 1 % N-hydroxymethyl starch-amide was mixed with OCC pulp slurry before preparing the paper sheet for testing the physical properties. The wet tensile index, dry tensile index, and dry burst index of the N-hydroxymethyl starch-amide-treated paper increased 243 %, 36 %, and 38 %, respectively, compared to the control sample. In addition, comparative studies were done between N-hydroxymethyl starch-amide and commercial paper wet strength agent GPAM and PAE. The wet tensile index of 1 % N-hydroxymethyl starch-amide-treated tissue paper was similar to GPAM and PAE, and 2.5 times higher than the control sample.

Factors Influencing the Formation of Chemical-Hemoglobin Adducts

Hemoglobin (Hb) adducts have been used as biomarkers for the internal exposure to chemicals. Simultaneous exposure to chemicals that bond with the N-terminal valine of Hb to form adducts, such as glycidol, acrylamide, and glucose, may affect the formation of the individual Hb adducts. In this study, various factors influencing the formation of chemical–Hb adducts were analyzed using in vitro and in vivo systems. In the in vitro assays, the formation of glycidol– and acrylamide–Hb adducts was altered in the presence of glucose, serum albumin, and other chemicals. In contrast, in the in vivo experiments, glycidol– and acrylamide–Hb adduct formation was unchanged in mice exposed to glycidol and acrylamide. The interaction between glycidol and acrylamide with residues other than the N-terminal valine of Hb was analyzed using the protein thermal shift assay. Glycidol and acrylamide also interacted with amino acid residues other than the N-terminal valine of Hb. The presence of other blood components, such as amino acids, may affect the formation of chemical–Hb adducts. Further research is expected to elucidate the remaining unknown factors that affect the formation of chemical–Hb adducts.

Alterations of blood chemistry, hepatic and renal function, and blood cytometry in acrylamide-treated rats

Acrylamide is a vinyl monomer that is widely used for the synthesis of polyacrylamides, the treatment of drinking water, and as an additive in cosmetics. Acrylamide is also produced during the thermal processing of carbohydrate-rich foods. Although the potential toxic effects of acrylamide have been reported, few studies have evaluated biochemical parameters in blood. The present study investigated alterations of blood chemistry, hepatic function, and blood cytometry in acrylamide-treated rats. Thirty-two male Wistar rats were assigned to four experimental groups (n = 8/group): one control group received 0.3 ml of vehicle (saline solution), and the other three groups received acrylamide (25, 50, and 75 mg/kg, i.p., for 14 days). At the end of treatment, blood samples were collected to obtain serum, which was then processed using a Vitros250 device. For blood cytometry, the samples were processed in a Sysmex analyzer. The blood chemistry results showed that urea nitrogen, urea, and creatinine were elevated in the acrylamide-treated groups. Tests of hepatic function showed that total and direct bilirubins, transaminases, and alkaline phosphatase were also elevated compared with vehicle, whereas the levels of total proteins and albumin decreased. Blood cytometry showed that the levels of erythrocytes, hemoglobin, hematocrit, leukocytes, and platelets and mean cell volume decreased in the acrylamide-treated groups compared with vehicle. Overall, the present findings indicate that acrylamide causes deleterious effects on renal and hepatic physiology, producing dose-dependent alterations of blood chemistry and cytometry parameters in male Wistar rats.

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.

Hepatoprotective effect of Quercetin supplementation against Acrylamide-induced DNA damage in wistar rats

Background

Quercetin (QR), is a polyphenolic flavonoid compound which is found in large amounts in certain foods, and protects against oxidative stress. The current study was conducted to determine whether Quercetin can possibly exert hepatoprotective and antioxidant activity against acrylamide (ACR) induced toxicity in rats.

Methods

Four groups of Wistar rats consisting of six rats each: (i) control group; (ii) ACR treated group (50 mg/kg bw); (iii) QR group: rats were treated with QR (10 mg/kg bw); (iv) QR (10 mg/kg bw) was given i.p. for 5 days followed by ACR (50 mg/kg bw) on 5th day (single dose).

Results

ACR caused an elevation in 8-OH guanosine level and a reduction in Glutahione S-transferase (GST) activity. Administration of QR significantly protected liver tissue against hepatotoxic effect of acrylamide from amelioration of the marker enzyme (p < 0.05) and DNA damage (p < 0.01) as evident by comet assay and, besides some indices of histopathological alterations.

Conclusion

It is concluded that QR could protect the liver against DNA damage induced by ACR probably is thus capable of ameliorating ACR-induced changes in the rat livers.

Acrylamide-induced carcinogenicity in mouse lung involves mutagenicity: cII gene mutations in the lung of big blue mice exposed to acrylamide and glycidamide for up to 4 weeks

Potential health risks for humans from exposure to acrylamide (AA) and its epoxide metabolite glycidamide (GA) have garnered much attention lately because substantial amounts of AA are present in a variety of fried and baked starchy foods. AA is tumorigenic in rodents, and a large number of in vitro and in vivo studies indicate that AA is genotoxic. A recent cancer bioassay on AA demonstrated that the lung was one of the target organs for tumor induction in mice; however, the mutagenicity of AA in this tissue is unclear. Therefore, to investigate whether or not gene mutation is involved in the etiology of AA- or GA-induced mouse lung carcinogenicity, we screened for cII mutant frequency (MF) in lungs from male and female Big Blue (BB) mice administered 0, 1.4, and 7.0 mM AA or GA in drinking water for up to 4 weeks (19-111 mg/kg bw/days). Both doses of AA and GA produced significant increases in cII MFs, with the high doses producing responses 2.7-5.6-fold higher than the corresponding controls (P ≤ 0.05; control MFs = 17.2 ± 2.2 and 15.8 ± 3.5 × 10(-6) in males and females, respectively). Molecular analysis of the mutants from high doses indicated that AA and GA produced similar mutation spectra and that these spectra were significantly different from the spectra in control mice (P ≤ 0.01). The predominant types of mutations in the lung cII gene from AA- and GA-treated mice were A:T → T:A, and G:C → C:G transversions, and -1/+1 frameshifts at a homopolymeric run of Gs. The MFs and types of mutations induced by AA and GA in the lung are consistent with AA exerting its genotoxicity via metabolism to GA. These results suggest that AA is a mutagenic carcinogen in mouse lungs and therefore further studies on its potential health risk to humans are warranted. Environ. Mol. Mutagen. 56:446-456, 2015. © 2015 Wiley Periodicals, Inc.

A novel interaction mode between acrylamide and its specific antibody

Since the discovery of high-level acrylamide (Acr) contamination in food, extensive international studies have focused on its toxicity and detection. By using a novel antigen synthetic strategy, we have successfully obtained a specific antibody towards acrylamide (Acr-Ab). Herein, the Acr-Ab and its interactions with Acr were characterized. Enzyme-linked immunosorbent assay (ELISA) and dynamic light scattering (DLS) investigations revealed that the conformational structure of Acr-Ab was sensitive to buffers. It showed a satisfied immunoreactivity in phosphate buffered saline (PBS), but denatured in water. In natural state, Acr-Ab had a trend of getting aggregation through their complementarity determining regions (CDRs). Adding Acr leaded to their disassembling. While mixed with Acr, Acr-Ab exhibits not only a fast, high-specific, and reversible non covalent binding (by surface plasmon resonance, SPR), but also a covalent alkylation with Acr through cysteine and histidine residues on its surface, as demonstrated by high-performance liquid chromatography (HPLC). Neither of the two reactions involves conformational change in secondary or tertiary structures as shown in circular dichroism spectra (CD). These special properties of Acr-Ab and the entirely new interaction mode with Acr will extend our knowledge of Acr related biosystem and facilitate the development of new detection strategies for Acr.

Possible neoplastic effects of acrylamide on rat exocrine pancreas

We investigated whether the acrylamide formed during cooking carbohydrate-rich foods at high temperatures causes neoplastic changes in rat pancreas. Azaserine, which is an amino acid derivative that has the ability to initiate neoplastic changes in rat pancreas, was injected into 14-day-old male rats once a week for three weeks. Acrylamide was given to both azaserine-injected and non-injected rats at doses of 5 and 10 mg/kg/day in drinking water for 16 weeks after which tissue slides were prepared from the pancreata. Pancreas weights and body weights of rats treated with azaserine and acrylamide together increased significantly compared to the other groups. Moreover, the size, average diameter and volume of atypical acinar cell foci that developed in the pancreata of rats treated with azaserine and acrylamide together increased significantly compared to rats treated with either azaserine or acrylamide alone and control groups. Atypical acinar cell adenoma or adenocarcinoma was not observed in the pancreata of rats in any group.

Potato fiber protects the small intestinal wall against the toxic influence of acrylamide

OBJECTIVE

Acrylamide is a neurotoxic, genotoxic substance present in many commonly consumed food products and has been shown to have carcinogenic effects in rodents. The protective effects (if any) of potato fiber preparations, composed of cell wall material from potatoes, against the toxic influence of dietary acrylamide on the small intestinal wall were investigated.

METHODS

Male mice of the BALB/c strain were used in the study. Acrylamide was administered to the mice in their drinking water (0.5 mg/kg of body weight per day) and one of two types of potato fiber preparations (heated or raw potato fiber preparation) was added to their feed (2% addition to their feed). Histomorphometry of the small intestinal wall, hemoglobin adducts of acrylamide, animal weight, and feed and water consumption analyses were performed.

RESULTS

Acrylamide altered the morphology and histology of the small intestinal wall, decreasing proliferation, myenteron and submucosal thicknesses, villus length, fractal dimension, crypt depth, crypt number, and the small intestinal absorptive surface. Conversely, apoptosis, hemoglobin adduct levels, intensity of epithelium staining, enterocyte number, villus epithelial thickness, and crypt width and parameters associated with nerve ganglia were increased. The two potato fiber preparations that were used abolished the negative influences of acrylamide on the small intestinal wall and had no influence on the hemoglobin adduct levels of acrylamide.

CONCLUSION

The negative impact of acrylamide on the histologic structure, regeneration, and innervation of the small intestinal wall and the absorptive function of the small intestinal mucosa can be abolished by dietary potato fiber preparations.

The genotoxicity of acrylamide and glycidamide in big blue rats

Acrylamide (AA), a mutagen and rodent carcinogen, recently has been detected in fried and baked starchy foods, a finding that has prompted renewed interest in its potential for toxicity in humans. In the present study, we exposed Big Blue rats to the equivalent of approximately 5 and 10 mg/kg body weight/day of AA or its epoxide metabolite glycidamide (GA) via the drinking water, an AA treatment regimen comparable to those used to produce cancer in rats. After 2 months of dosing, the rats were euthanized and blood was taken for the micronucleus assay; spleens for the lymphocyte Hprt mutant assay; and liver, thyroid, bone marrow, testis (from males), and mammary gland (females) for the cII mutant assay. Neither AA nor GA increased the frequency of micronucleated reticulocytes. In contrast, both compounds produced small (approximately twofold to threefold above background) but significant increases in lymphocyte Hprt mutant frequency (MF, p < 0.05), with the increases having dose-related linear trends (p < 0.05 to p < 0.001). Neither compound increased the cII MF in testis, mammary gland (tumor target tissues), or liver (nontarget tissue), while both compounds induced weak positive increases in bone marrow (nontarget tissue) and thyroid (target tissue). Although the genotoxicity in tumor target tissue was weak, in combination with the responses in surrogate tissues, the results are consistent with AA being a gene mutagen in the rat via metabolism to GA.

A Voltammetric Biosensor Based on Glassy Carbon Electrodes Modified with Single-Walled Carbon Nanotubes/Hemoglobin for Detection of Acrylamide in Water Extracts from Potato Crisps

The presence of toxic acrylamide in a wide range of food products such as potato crisps, French fries or bread has been confirmed by Swedish scientists from Stockholm University. The neurotoxicity, possible carcinogenicity of this compound and its metabolites compels us to control them by quantitative and qualitative assays. Acrylamide forms adduct with hemoglobin (Hb) as a result of the reaction the -NH₂ group of the N-terminal valine with acrylamide. In this work we present the use of glassy carbon electrodes coated with single-walled carbon nanotubes (SWCNTs) and Hb for voltammetric detection of acrylamide in water solutions. The electrodes presented a very low detection limit (1.0×10^-9 M). The validation made in the matrix obtained by water extraction of potato crisps showed that the electrodes presented are suitable for the direct determination of acrylamide in food samples.

Approach for cancer risk estimation of acrylamide in food on the basis of animal cancer tests and in vivo dosimetry

The question about the contribution from acrylamide (AA) in food to the cancer risk in the general population has not yet had a satisfactory answer. One point of discussion is whether AA constitutes a cancer risk through its genotoxic metabolite, glycidamide (GA), or whether other mechanism(s) could be operating. Using a relative cancer risk model, an improvement of the cancer risk estimate for dietary AA can be obtained by estimation of the genotoxic contribution to the risk. One cornerstone in this model is the in vivo dose of the causative genotoxic agent. This paper presents an evaluation, according to this model, of published AA cancer tests on the basis of in vivo doses of GA in rats exposed in the cancer tests. The present status regarding data with importance for an improved estimation of the contribution from GA to the cancer risk of AA, such as in vivo doses measured in humans, is discussed.

Inhibition of acrylamide toxicity in mice by three dietary constituents

The inhibitory effects of three dietary constituents, tea polyphenols, resveratrol, and diallyl trisulfide, on acrylamide-biomacromolecule (liver DNA, protamine, and hemoglobin) adduct formation at human exposure level were studied by accelerator mass spectrometry. The results demonstrated that the three dietary constituents all significantly inhibited the formation of acrylamide adducts with liver DNA, whereas tea polyphenols and diallyl trisulfide reduced protamine and hemoglobin adducts, respectively. Further biochemical studies showed that acrylamide could significantly inactivate creatine kinase and glutathione S-transferase and deplete glutathione. When the inhibitors were cotreated with acrylamide, all of them could effectively recover the activities of creatine kinase. In addition, tea polyphenols and diallyl trisulfide could increase glutathione S-transferase activity remarkably. On the basis of these results, mechanisms of the effects are discussed. This study might provide a beneficial guide to people's diet for the purpose of reducing the harmful effect of acrylamide.

Using dietary exposure and physiologically based pharmacokinetic/pharmacodynamic modeling in human risk extrapolations for acrylamide toxicity

The discovery of acrylamide (AA) in many common cooked starchy foods has presented significant challenges to toxicologists, food scientists, and national regulatory and public health organizations because of the potential for producing neurotoxicity and cancer. This paper reviews some of the underlying experimental bases for AA toxicity and earlier risk assessments. Then, dietary exposure modeling is used to estimate probable AA intake in the U.S. population, and physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) modeling is used to integrate the findings of rodent neurotoxicity and cancer into estimates of risks from human AA exposure through the diet. The goal of these modeling techniques is to reduce the uncertainty inherent in extrapolating toxicological findings across species and dose by comparing common exposure biomarkers. PBPK/PD modeling estimated population-based lifetime excess cancer risks from average AA consumption in the diet in the range of 1-4 x 10 (-4); however, modeling did not support a link between dietary AA exposure and human neurotoxicity because marginal exposure ratios were 50-300 lower than in rodents. In addition, dietary exposure modeling suggests that because AA is found in so many common foods, even big changes in concentration for single foods or groups of foods would probably have a small impact on overall population-based intake and risk. These results suggest that a more holistic analysis of dietary cancer risks may be appropriate, by which potential risks from AA should be considered in conjunction with other risks and benefits from foods.

Differences in the frequency of micronucleated erythrocytes in humans in relation to consumption of fried carbohydrate-rich food

The aim of this study was to investigate if consumption of ordinary carbohydrate-rich food prepared in different ways has an impact on chromosome stability, i.e., on the formation of micronucleated young erythrocytes in humans. Twenty-four persons, divided into two groups, participated during 4 days in a semi-controlled food-consumption study. One group (low-heated-food-group, LowHF-group) consumed only food boiled in water (max 100 degrees C) and the other group (high-heated-food-group, HighHF-group) consumed preferentially strongly heated (fried) food. From each of the subjects, blood samples were drawn, before and after 4 days. The frequency (f) of micronucleated (MN) very young erythrocytes (transferrin-positive reticulocytes, Trf-Ret), fMNTrf-Ret, was determined, and the difference in the frequency, before and after the eating period, was calculated. The obtained mean differences for the two groups were compared. As an indicator of highly heated food the acrylamide (AA) content in part of the consumed foodstuffs was analysed by use of LC/MS-MS and the AA intake estimated. In the blood samples the hemoglobin-adduct levels from AA were analysed as a measure of the internal AA dose. The differences between the mean fMNTrf-Ret, before and after the eating period, were -0.15 per thousand for the LowHF-group and +0.17 per thousand for the HighHF-group, p<0.005 (t-test, one-tailed). The mean total AA intake in the HighHF-group during 4 days was estimated to about 3000+/-450microg per person. For the LowHF-group, the mean AA intake was low, 20+/-10microg per person. The lowest dose of AA that caused a significant increase of micronucleated erythrocytes in mice is more than a hundred times higher than the AA level in this study. Thus, it is unlikely that the exposure to AA is the major cause behind the observed difference. The answer is probably to be found in other compounds produced at the same time during heating of the food.

Novel voltammetric biosensor for determining acrylamide in food samples

Recent findings showing that acrylamide is formed in heat-treated foods rich in asparagine and reducing sugars such as glucose, have accelerated the needs for the development of new analytical methods to determine this potential human carcinogen. Acrylamide forms adduct with hemoglobin (Hb) as a result of the reaction with the alpha-NH2 group of N-terminal valine of Hb. This interaction is the basis of a new voltammetric biosensor to detect acrylamide. The biosensor was constructed using a carbon-paste electrode modified with hemoglobin (Hb), which contains four prosthetic groups of heme--Fe(III). Such an electrode displays a reversible reduction/oxidation process of Hb-Fe(III)/Hb-Fe(II). Interaction between Hb and acrylamide was observed through decreasing of the peak current of Hb-Fe(III) reduction. The electrodes presented a very low detection limit (1.2 x 10(-10)M). The validation made in the matrix obtained by water extraction of potato chips showed that the electrodes presented are suitable for the direct determination of acrylamide in food samples.

An absorption study of dietary administered acrylamide in swine

Acrylamide is a food toxicant suspected to be carcinogenic to humans. It is formed in the heat processing of carbohydrate-rich food. A current issue in food safety is whether acrylamide actually represents a risk for human health. At present, available information is insufficient to reach any conclusions. Inter alias, a still unclear matter is the fraction of acrylamide ingested by food that is absorbed and metabolized. This study compared the in vivo relative absorption of acrylamide formed in cooked food with that of the pure compound dissolved in drinking water using the pig (25 Italian Large White females) as the animal model. Acrylamide intakes of about 0.8 and 8 microg kg(-1) pig body wt day(-1) equal to one and ten times, respectively, the maximum average acrylamide daily intake for humans from the diet (expressed on a body wt basis) in industrialized countries, were chosen for the study. Adducts with the N-terminal valine of haemoglobin formed by acrylamide and its epoxide metabolite glycidamide, were used as exposure markers. Analyses were carried out by gas chromatography/mass spectrometry following in-house method validation. Both for the low and the high dose regimen, the glycidamide adduct levels in swine globins were lower of the limit of quantification of the method. As concerns acrylamide adducts, it was found that the relative absorption of acrylamide from feed and water was the same and that there is a direct proportionality between the adduct concentration and acrylamide intake.

Acrylamide: review of toxicity data and dose-response analyses for cancer and noncancer effects

Acrylamide (ACR) is used in the manufacture of polyacrylamides and has recently been shown to form when foods, typically containing certain nutrients, are cooked at normal cooking temperatures (e.g., frying, grilling or baking). The toxicity of ACR has been extensively investigated. The major findings of these studies indicate that ACR is neurotoxic in animals and humans, and it has been shown to be a reproductive toxicant in animal models and a rodent carcinogen. Several reviews of ACR toxicity have been conducted and ACR has been categorized as to its potential to be a human carcinogen in these reviews. Allowable levels based on the toxicity data concurrently available had been developed by the U.S. EPA. New data have been published since the U.S. EPA review in 1991. The purpose of this investigation was to review the toxicity data, identify any new relevant data, and select those data to be used in dose-response modeling. Proposed revised cancer and noncancer toxicity values were estimated using the newest U.S. EPA guidelines for cancer risk assessment and noncancer hazard assessment. Assessment of noncancer endpoints using benchmark models resulted in a reference dose (RfD) of 0.83 microg/kg/day based on reproductive effects, and 1.2 microg/kg/day based on neurotoxicity. Thyroid tumors in male and female rats were the only endpoint relevant to human health and were selected to estimate the point of departure (POD) using the multistage model. Because the mode of action of acrylamide in thyroid tumor formation is not known with certainty, both linear and nonlinear low-dose extrapolations were conducted under the assumption that glycidamide or ACR, respectively, were the active agent. Under the U.S. EPA guidelines (2005), when a chemical produces rodent tumors by a nonlinear or threshold mode of action, an RfD is calculated using the most relevant POD and application of uncertainty factors. The RfD was estimated to be 1.5 microg/kg/day based on the use of the area under the curve (AUC) for ACR hemoglobin adducts under the assumption that the parent, ACR, is the proximate carcinogen in rodents by a nonlinear mode of action. When the mode of action in assumed to be linear in the low-dose region, a risk-specific dose corresponding to a specified level of risk (e.g., 1 x 10-5) is estimated, and, in the case of ACR, was 9.5 x 10-2 microg ACR/kg/day based on the use of the AUC for glycidamide adduct data. However, it should be noted that although this review was intended to be comprehensive, it is not exhaustive, as new data are being published continuously.

Acrylamide, an in vivo thyroid carcinogenic agent, induces DNA damage in rat thyroid cell lines and primary cultures

Chronic treatment of rats with acrylamide induces various tumors among which thyroid tumors are the most frequent. The aim of the present study was to develop an in vitro model of acrylamide action on thyroid cells to allow the investigation of the mechanism of this tumorigenic action. The first part of the study considered as targets, characteristics of thyroid metabolism, which could explain the thyroid specificity of acrylamide action: the cAMP mitogenic effect and the important H2O2 generation by thyroid cells. However, acrylamide did not modulate H2O2 or cAMP generation in the thyroid cell models studied. No effect on thyroid cell proliferation was observed in the rat thyroid cell line FRTL5. On the other hand, as shown by the comet assay, acrylamide induced DNA damage, as the positive control H2O2 in the PC Cl3 and FRTL5 rat thyroid cell lines, as well as in thyroid cell primary cultures. The absence of effect of acrylamide on H2AX histone phosphorylation suggests that this effect does not reflect the induction of DNA double strand breaks. DNA damage leads to the generation of mutations. It is proposed that such mutations could play a role in the carcinogenic effect of acrylamide. The mechanism of this effect can now be studied in this in vitro model.

Acrylamide and Glycidamide: Approach towards Risk Assessment Based on Biomarker Guided Dosimetry of Genotoxic/Mutagenic Effects in Human Blood

Acrylamide (AA) is a carcinogen as demonstrated in animal experiments, but the relevance for the human situation is still unclear. AA and its metabolite glycidamide (GA) react with nucleophilic regions in biomolecules. However, whereas AA and GA react with proteins, DNA adducts are exclusively formed by GA under conditions simulating in vivo situations. For risk assessment it is of particular interest to elucidate whether AA or GA within the plasma concentration range resulting from food intake are "quenched" by preferential reaction with non-critical blood constituents or whether DNA in lymphocytes is damaged concomitantly under such conditions. To address this question dose- and time-dependent induction of hemoglobin (Hb) adducts as well as genotoxic and mutagenic effects by AA or GA were studied in human blood as a model system.

Adduction of biomacromolecules with acrylamide (AA) in mice at environmental dose levels studied by accelerator mass spectrometry

Since 2002, WHO has strongly called scientists to investigate intensively the toxicity and potential carcinogenicity of acrylamide (AA), because humans are widely exposed to AA via various foodstuffs. In this study we measured the biomacromolecule adducts of [2,3-(14)C]AA (0, 7.5 x 10(-2), 7.5 x 10(-1), 7.5, 9.3 x 10(1), 2.4 x 10(2) and 1.0 x 10(3)microg/kg b.w.) in adult male mice by ultrasensitive accelerator mass spectrometry (AMS) technique. The aim is to evaluate the potential molecular toxicity of AA at human relevant dose levels, particularly towards the sperm cells. Hemoglobin (Hb), serum albumin (SA), protamine, sperm DNA, tails and heads were isolated 24h post dosing and the adduct levels were measured by AMS, respectively. Good log/log linear dose-response correlations were established. Moreover, the correlation of AA-protamine adducts, AA-sperm DNA adducts, as well as AA-sperm head/tail adducts with AA-Hb or AA-SA adducts presented a linear log/log mode. In sperm, the formation of AA-protamine adducts were predominating to AA-DNA adducts. The adducts on sperm heads/tails might both influence the fertility efficacy.

Genotoxicity of acrylamide and its metabolite glycidamide administered in drinking water to male and female Big Blue mice

The recent discovery of acrylamide (AA), a probable human carcinogen, in a variety of fried and baked starchy foods has drawn attention to its genotoxicity and carcinogenicity. Evidence suggests that glycidamide (GA), the epoxide metabolite of AA, is responsible for the genotoxic effects of AA. To investigate the in vivo genotoxicity of AA, groups of male and female Big Blue (BB) mice were administered 0, 100, or 500 mg/l of AA or equimolar doses of GA, in drinking water, for 3-4 weeks. Micronucleated reticulocytes (MN-RETs) were assessed in peripheral blood within 24 hr of the last treatment, and lymphocyte Hprt and liver cII mutagenesis assays were conducted 21 days following the last treatment. Further, the types of cII mutations induced by AA and GA in the liver were determined by sequence analysis. The frequency of MN-RETs was increased 1.7-3.3-fold in males treated with the high doses of AA and GA (P < or = 0.05; control frequency = 0.28%). Both doses of AA and GA produced increased lymphocyte Hprt mutant frequencies (MFs), with the high doses producing responses 16-25-fold higher than that of the respective control (P < or = 0.01; control MFs = 1.5 +/- 0.3 x 10(-6) and 2.2 +/- 0.5 x 10(-6) in females and males, respectively). Also, the high doses of AA and GA produced significant 2-2.5-fold increases in liver cII MFs (P < or = 0.05; control MFs = 26.5 +/- 3.1 x 10(-6) and 28.4 +/- 4.5 x 10(-6)). Molecular analysis of the mutants indicated that AA and GA produced similar mutation spectra and that these spectra were significantly different from that of control mutants (P < or = 0.001). The predominant types of mutations in the liver cII gene from AA- and GA-treated mice were G:C-->T:A transversions and -1/+1 frameshifts in a homopolymeric run of Gs. The results indicate that both AA and GA are genotoxic in mice. The MFs and types of mutations induced by AA and GA in the liver are consistent with AA exerting its genotoxicity in BB mice via metabolism to GA.

Toxicokinetics of acrylamide and glycidamide in Fischer 344 rats

Acrylamide (AA) is a widely studied industrial chemical that is neurotoxic, mutagenic to somatic and germ cells, and carcinogenic in rodents. The recent discovery of AA at ppm levels in a wide variety of commonly consumed foods has energized research efforts worldwide to define toxic mechanisms, particularly toxicokinetics and bioavailability. This study compares the toxicokinetics of AA and its epoxide metabolite, glycidamide (GA), in serum and tissues of male and female F344 rats following acute exposure by intravenous, gavage, and dietary routes at 0.1 mg/kg AA or intravenous and gavage routes with an equimolar amount of GA. AA was rapidly absorbed after oral dosing, was widely distributed to tissues, was efficiently converted to GA, and produced increased levels of GA-DNA adducts in liver. GA was also rapidly absorbed, widely distributed to tissues, and produced increased liver DNA adduct levels. AA bioavailability after aqueous gavage was 60--98% and from the diet was 32--44%; however, first-pass metabolism or other kinetic change resulted in much higher internal exposures to GA (2- to 7-fold) when compared to the intravenous route. A similar effect on metabolism to GA following oral administration was previously observed under an identical exposure paradigm in mice. Furthermore, DNA adduct formation in rat liver showed the same proportionality with the respective GA AUC value as did mice in the previous study. These findings suggest that as the AA content in food is reduced, species-differences in GA formation and subsequent DNA adduct formation may be minimized. These findings provide additional information needed to assess genotoxic risks from the low levels of AA that are pervasive in the food supply.

The carcinogenicity of acrylamide

Acrylamide is carcinogenic to experimental mice and rats, causing tumors at multiple organ sites in both species when given in drinking water or by other means. In mice, acrylamide increases the incidence of alveologenic lung tumors and initiates skin tumors after dermal exposures. In two bioassays in rats, acrylamide administered in drinking water consistently induced peritesticular mesotheliomas, thyroid follicular cell tumors, and mammary gland tumors, as well as primary brain tumors when all such tumors were included in data analysis. In one of the rat bioassays, increased numbers of adrenal pheochromocytomas, adenomas of pituitary and clitoral glands, papillomas of the oral cavity, and adenocarcinomas of the uterus also occurred. In both humans and experimental animals, a significant fraction of ingested acrylamide is converted metabolically to the chemically reactive and genotoxic epoxide, glycidamide, which is likely to play an important role in the carcinogenicity of acrylamide. No studies on the carcinogenicity of glycidamide have been published, but bioassays of this compound are in progress. Epidemiologic studies of possible health effects from exposures to acrylamide have not produced consistent evidence of increased cancer risk, in either occupationally exposed workers or the general populations of several countries in which acrylamide is present in certain foods and beverages. A doubling of risk for pancreatic cancer was observed in the most highly exposed workers within the largest industrial cohort, but no consistent exposure-response relationships were identified. Retrospective re-analyses of previously conducted case-control studies of cancer incidence in several European populations have identified no causal relationship between consumption of foods or beverages that contain acrylamide and the incidence of cancers at various sites including kidney, large bowel, urinary bladder, oral cavity, pharynx, larynx, esophagus, breast, and ovary. These retrospective studies of cancer incidence in relation to acrylamide in food have limited power to detect increased cancer risks, and have been criticized on various grounds, but they do indicate that no major cancer risks are attributable to intake of acrylamide in Western diets.

Human exposure and internal dose assessments of acrylamide in food

This review provides a framework contributing to the risk assessment of acrylamide in food. It is based on the outcome of the ILSI Europe FOSIE process, a risk assessment framework for chemicals in foods and adds to the overall framework by focusing especially on exposure assessment and internal dose assessment of acrylamide in food. Since the finding that acrylamide is formed in food during heat processing and preparation of food, much effort has been (and still is being) put into understanding its mechanism of formation, on developing analytical methods and determination of levels in food, and on evaluation of its toxicity and potential toxicity and potential human health consequences. Although several exposure estimations have been proposed, a systematic review of key information relevant to exposure assessment is currently lacking. The European and North American branches of the International Life Sciences Institute, ILSI, discussed critical aspects of exposure assessment, parameters influencing the outcome of exposure assessment and summarised data relevant to the acrylamide exposure assessment to aid the risk characterisation process. This paper reviews the data on acrylamide levels in food including its formation and analytical methods, the determination of human consumption patterns, dietary intake of the general population, estimation of maximum intake levels and identification of groups of potentially high intakes. Possible options and consequences of mitigation efforts to reduce exposure are discussed. Furthermore the association of intake levels with biomarkers of exposure and internal dose, considering aspects of bioavailability, is reviewed, and a physiologically-based toxicokinetic (PBTK) model is described that provides a good description of the kinetics of acrylamide in the rat. Each of the sections concludes with a summary of remaining gaps and uncertainties.

Dose–response modeling of in vivo genotoxicity data for use in risk assessment: some approaches illustrated by an analysis of acrylamide

Methods for dose-response modeling of in vivo genotoxicity data are introduced and applied to a case study of acrylamide. Genetic toxicity results are typically summarized as being either positive or negative, with no further consideration of the dose-response patterns that can be estimated from such studies. This analysis explores the use of three modeling approaches: Poisson regression of counts of genetic effects per cell; dynamic modeling of the time-course of micronucleus production and loss as a function of exposure; and categorical regression of sets of genetic toxicity experiments, the results of which are recoded in terms of severities of response. Estimates derived from these models (benchmark doses and predictions of response rates for predetermined doses of interest) are then used to assess the relevance and role of the genetic toxicity results in a risk assessment. With respect to the acrylamide data base, the results suggest that the genetic damage studies do not appear to be consistent or congruent with the thyroid tumor endpoints observed in two long-term bioassays in rats. This suggests that acrylamide's mechanism of action with respect to production of such tumors may not be genotoxic, and that a cancer risk assessment that applied a linear, no-threshold approach to such endpoints might be inappropriate. Benchmark doses derived from the genetic toxicity data base do not appear to be the critical ones for acrylamide risk assessment. Dose metric and modeling issues associated with the proposed dose-response approach to evaluation of genetic toxicity data are explored, and it is recommended that further advancements of the methodology be developed and employed for optimal use of such data for risk assessment purposes.

DNA adduction and mutagenic properties of acrylamide

This review article summarizes our current knowledge on DNA damaging and mutagenic properties of acrylamide. Direct and indirect modes of interaction of acrylamide with DNA are discussed, and the resulting alkylating DNA adducts are highlighted. Emphasis is placed on glycidamide-DNA adducts generated via epoxidation of acrylamide presumably by cytochrome P4502E1. Dosimetry and mapping of acrylamide-induced DNA adducts in vitro and/or in vivo are described. Mutagenic potency and specificity of acrylamide in relation to its respective DNA adducts are discussed. Prospective views are provided on the potential applications of acrylamide-induced DNA adduct dosimetry/mapping and mutation frequency/spectrometry for biomonitoring purposes.

A comparison of genotoxicity between three common heterocyclic amines and acrylamide

Heterocyclic amines (HCAs), a group of genotoxic compounds formed during the heating of proteinaceous food items, have been known since the late 1970s. However, the genotoxic effect of these compounds in the low dose region has not yet been thoroughly studied. Here we used a sensitive flow cytometer-based micronucleus assay in mice to determine the frequency of micronucleated erythrocytes (fMPCE) of the three common HCAs, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), in the low dose region. We especially looked for any deviation from linearity of the dose-response curves. Male Balb/C mice were intra peritoneally injected with different doses of either PhIP (0-36 mg/kg b.w.), MeIQx (0-90 mg/kg b.w.) or IQ (0-40 mg/kg b.w.). In the case of PhIP, we found a significant dose-response relationship, while MeIQx and IQ did not display an increased fMPCE level. This flow cytometer method allows for determination of the DNA content of micronuclei. All three HCAs tested here yielded a low DNA content of micronuclei, indicating that they do not possess aneugenic effects. A comparison between the HCAs and acrylamide (AA), another heat induced genotoxic compound, revealed that the slope of the dose-response curve is about 10 times steeper for PhIP than AA. In spite of this, AA probably constitutes a higher human risk than HCAs since the intake is about a 100- to 1000-fold higher than the intake of HCAs.

DNA damage and DNA adduct formation in rat tissues following oral administration of acrylamide

Acrylamide is present as a contaminant in the human diet in heated food products. It has been found to be carcinogenic in laboratory rats and has been classified as probably carcinogenic in humans. In order to clarify the possible involvement of a primary genotoxic mechanism in acrylamide-induced carcinogenicity, both the presence of DNA damage, measured by the comet assay, and the formation of N7-(2-carbamoyl-2-hydroxyethyl)guanine (N7-GA-Gua) and N3-(2-carbamoyl-2-hydroxyethyl)adenine (N3-GA-Ade), derived from reaction of the active metabolite glycidamide (GA) with the DNA, analyzed by LC/MS/MS, were assessed in selected rat tissues. Rats were administered with single oral doses of acrylamide (18, 36 or 54 mg/kg body weight (b.w.) and the organs (blood leukocytes, brain, bone marrow, liver, testes and adrenals) were sampled at different times after treatment. Results from GA-induced DNA adduct measurements indicated a relatively even organ distribution of the adducts in brain, testes and liver. Organ-specificity in acrylamide carcinogenesis can therefore not be explained by a selective accumulation of GA-DNA adducts in the target organs, at least not after a single dose exposure. The DNA adduct profiles and half-lives were similar in the different organs; except that the N3-GA-Ade adduct was more rapidly removed from tissues than the N7-GA-Gua adduct. Increased extent of DNA migration, as measured by the in vivo rat comet assay, was found in brain and testes, and these specific results seem to be in accordance with the known organ-specificity in acrylamide carcinogenesis in rat. Only weak and transient DNA damage was recorded in the liver, bone marrow and adrenals. The DNA-damaging effect of the compound observed in the blood leukocytes could be a simple biomarker of acrylamide exposure and genotoxicity.

DNA adducts derived from administration of acrylamide and glycidamide to mice and rats

Acrylamide (AA) is an important industrial chemical that is neurotoxic, mutagenic to somatic and germ cells, and carcinogenic in chronic rodent bioassays. Recent findings of AA in many common starchy foods have sparked renewed interest in determining toxic mechanisms and in understanding the cancer, neurotoxicity, and reproductive risks from typical human exposures. Dosing mice and rats with AA (50 mg/kg) led to presence of glycidamide (GA) in serum and tissues. Furthermore, GA-derived DNA adducts of adenine and guanine were formed in all tissues examined, including both target tissues identified in rodent carcinogenicity bioassays and in non-target tissues. Dosing rats and mice with an equimolar amount of GA typically produced higher levels of DNA adducts than observed with AA. Kinetics of DNA adduct formation and accumulation were measured following oral administration of a single dose of AA (50 mg/kg) or from repeat dosing (1 mg/kg/day), respectively. The formation of these DNA adducts is consistent with previously reported mutagenicity of AA and GA in vitro, which involved reaction of GA with adenine and guanine bases. These results provide strong support for a genotoxic mechanism of AA carcinogenicity in rodents. The kinetic/biomarker approaches described here may represent a meaningful way to extrapolate cancer risks to actual human exposures from food, which are much lower.

Determination of acrylamide and glycidamide serum toxicokinetics in B6C3F1 mice using LC–ES/MS/MS

Acrylamide (AA) is a well-studied industrial toxicant; however, recent findings of AA at ppm levels in cooked starchy foods have refocused attention on the potential for neurotoxicity, germ cell mutagenicity, and carcinogenicity from AA. Oxidative metabolism of AA to glycidamide (GA) in experimental animals has previously been linked with many toxic effects of AA exposure. We report a new sensitive and selective analytical method, based on LC with electrospray tandem mass spectrometry, for the quantification of AA and GA in serum and its application to a preliminary toxicokinetic evaluation of AA and GA in adult B6C3F(1) mice following oral administration of AA.

Determination of haemoglobin adducts of acrylamide and glycidamide in smoking and non-smoking persons of the general population

Acrylamide (AA) is a food-borne toxicant suspected to be carcinogenic to humans. It is formed in the heating process of starch-containing food. Currently, there is a great discussion about the possible human health risks connected with the dietary uptake of acrylamide. Haemoglobin adducts of acrylamide and its oxidative metabolite glycidamide are both markers of biochemical effect. However, because glycidamide has a higher carcinogenic potency than acrylamide itself, the glycidamide adduct might mirror the genotoxicity better than acrylamide adducts. In order to gain more information about the human metabolism of acrylamide, we investigated a small group of persons for the effective internal doses of acrylamide and glycidamide using haemoglobin adducts as parameters of biochemical effect. The collective was subdivided into non-smokers (n=13) and smokers (n=16) by determining the smoking-specific acrylonitrile haemoglobin adduct (N-cyanoethylvaline, CEV). The mean values for the adducts of acrylamide (N-2-carbamoylethylvaline, AAVal) and glycidamide (N-(R,S)-2-hydroxy-2-carbamoylethylvaline, GAVal) in nonsmokers was 19 pmol/g globin AAVal (range 7-31 pmol/g globin) and 17 pmol/g globin GAVal (range 9-23 pmol/g globin). For smokers mean levels of AAVal were 80 pmol/g globin (range: 25-199 pmol/g globin) and those of GAVal were 53 pmol/g globin (range: 22-119 pmol/g globin). Metabolism to glycidamide turned out to be significantly more effective in non-smokers than in the higher exposed smokers. Compared with studies in rats, the metabolic conversion of acrylamide to glycidamide as measured by haemoglobin adducts seems to occur to a similar extent in humans as in rats. Risk estimations on acrylamide based on experimental data obtained in rats obviously did not overestimate the cancer risk for the general population. Furthermore, our results might indicate that the dose-response curve for acrylamide is not linear. This would be in line with the results of animal experiments on rodents.

The dose-response relationship at very low doses of acrylamide is linear in the flow cytometer-based mouse micronucleus assay

Acrylamide (AA) is genotoxic and has been classified as a probable human carcinogen. Human exposure to AA may be high by the consumption of starch-based food that has been treated at high temperature, e.g. potato chips and crisps. For risk assessment, extrapolation to the expected low doses to humans will be more reliable when data from low experimental doses can be used. We have registered the effects of a series of low doses in the sensitive flow cytometer-based micronucleus assay in mice, paying special attention to deviations from the expected linear dose-response function. Two experiments were performed with CBA mice, injected i.p. with different doses of AA. In one experiment the effects of 22 doses (two mice per dose) ranging from 0 to 100 mg/kg b.w. were studied. In the second experiment seven doses (five mice per dose) ranging from 0 to 30 mg/kg b.w. were used. In both experiments, a clear increase of the frequency of micronucleated erythrocytes was seen, already at the lowest doses used. The dose-response function was found to be linear with a tendency to have a steeper rise at the lowest doses. The low DNA content of the micronuclei indicated an absence of whole chromosomes, i.e. no aneugenic effect of AA.