Human CYP2E1 mediates the formation of glycidamide from acrylamide

Dietary Exposure to Acrylamide Has Negative Effects on the Gastrointestinal Tract: A Review

Changing eating habits and an increase in consumption of thermally processed products have increased the risk of the harmful impact of chemical substances in food on consumer health. A 2002 report by the Swedish National Food Administration and scientists at Stockholm University on the formation of acrylamide in food products during frying, baking and grilling contributed to an increase in scientific interest in the subject. Acrylamide is a product of Maillard's reaction, which is a non-enzymatic chemical reaction between reducing sugars and amino acids that takes place during thermal processing. The research conducted over the past 20 years has shown that consumption of acrylamide-containing products leads to disorders in human and animal organisms. The gastrointestinal tract is a complex regulatory system that determines the transport, grinding, and mixing of food, secretion of digestive juices, blood flow, growth and differentiation of tissues, and their protection. As the main route of acrylamide absorption from food, it is directly exposed to the harmful effects of acrylamide and its metabolite-glycidamide. Despite numerous studies on the effect of acrylamide on the digestive tract, no comprehensive analysis of the impact of this compound on the morphology, innervation, and secretory functions of the digestive system has been made so far. Acrylamide present in food products modifies the intestine morphology and the activity of intestinal enzymes, disrupts enteric nervous system function, affects the gut microbiome, and increases apoptosis, leading to gastrointestinal tract dysfunction. It has also been demonstrated that it interacts with other substances in food in the intestines, which increases its toxicity. This paper summarises the current knowledge of the impact of acrylamide on the gastrointestinal tract, including the enteric nervous system, and refers to strategies aimed at reducing its toxic effect.

Food emulsifiers increase toxicity of food contaminants in three human GI tract cell lines

Food products simultaneously containing both food contaminants and emulsifiers are common in baked products, coffee and chocolate. Little is known regarding how food contaminants and emulsifiers interact and alter toxicity. Recent studies have shown that while emulsifiers themselves have little toxicity, they could cause changes in the gut microenvironment and lead to issues such as increased uptake of allergens. This study examined toxic effect of two common process contaminants acrylamide (AA) and benzo [a]pyrene (BAP) combined with food emulsifiers polyoxyethylene sorbitan monooleate (TW) or glycerol monostearate (G). In liver cell line HepG2 and gastrointestinal cell lines HIEC6 and Caco-2, toxicities of AA and BAP were increased by TW but not by G as indicated by decrease in IC50 values. Addition of TW also exacerbated gene expression changes caused by AA or BAP. Cellular uptake and cell membrane permeability were enhanced by TW but not by G, but tight junction proteins of Caco-2 monolayer was impacted by both emulsifiers. These results suggested that TW could increase toxicity of AA and BAP through increasing cell permeability thus chemical uptake and potentially through other interactions. The study is to draw the attention of regulators on the potential synergistic interaction of co-occurring chemicals in food.

Eugenol alleviates acrylamide-induced rat testicular toxicity by modulating AMPK/p-AKT/mTOR signaling pathway and blood-testis barrier remodeling

This study aimed to investigate the effects of eugenol treatment on reproductive parameters in acrylamide (ACR)-intoxicated rats. The study evaluated alterations in relative testes and epididymides weights, sperm quality, serum hormonal status, seminal plasma amino acids, testicular cell energy and phospholipids content, oxidative and nitrosative stress parameters, adenosine monophosphate-activated protein kinase/ phosphoinositide 3-kinase/phosphor-protein kinase B/mammalian target of rapamycin (AMPK/PI3K/p-AKT/mTOR) signaling pathway, blood-testis barrier (BTB) remodeling markers, testicular autophagy and apoptotic markers, as well as histopathological alterations in testicular tissues. The results revealed that eugenol treatment demonstrated a significant improvement in sperm quality parameters, with increased sperm cell concentration, progressive motility live sperm, and a reduction in abnormal sperm, compared to the ACR-intoxicated group. Furthermore, eugenol administration increased the levels of seminal plasma amino acids in a dose-dependent manner. In addition, eugenol treatment dose-dependently improved testicular oxidative/nitrosative stress biomarkers by increasing oxidized and reduced glutathione levels and reducing malondialdehyde and nitric oxide contents as compared to ACRgroup. However, eugenol treatment at a high dose restored the expression of AMPK, PI3K, and mTOR genes, to levels comparable to the control group, while significantly increasing p-AKT content compared to the ACRgroup. In conclusion, the obtained findings suggest the potential of eugenol as a therapeutic agent in mitigating ACR-induced detrimental effects on the male reproductive system via amelioration of ROS-mediated autophagy, apoptosis, AMPK/p-AKT/mTOR signaling pathways and BTB remodeling.

Reconstructing hepatic metabolic profile and glutathione-mediated metabolic fate of acrylamide

The toxicity of acrylamide (AA) has continuously attracted wide concerns as its extensive presence from both environmental and dietary sources. However, its hepatic metabolic transformation and metabolic fate still remain unclear. This study aims to unravel the metabolic profile and glutathione (GSH) mediated metabolic fate of AA in liver of rats under the dose-dependent exposure. We found that exposure to AA dose-dependently alters the binding of AA and GSH and the generation of mercapturic acid adducts, while liver as a target tissue bears the metabolic transformation of AA via regulating GSH synthesis and consumption pathways, in which glutamine synthase (GSS), cytochrome P450 2E1 (CYP2E1), and glutathione S-transferase P1 (GSTP1) play a key role. In response to high- and low-dose exposures to AA, there were significant differences in liver of rats, including the changes in GSH and cysteine (CYS) activities and the conversion ratio of AA to glycidamide (GA), and liver can affect the transformation of AA by regulating the GSH-mediated metabolic pathway. Low-dose exposure to AA activates GSH synthesis pathway in liver and upregulates GSS activity and CYS content with no change in γ-glutamyl transpeptidase 1 (GGT1) activity. High-dose exposure to AA activates the detoxification pathway of GSH and increases GSH consumption by upregulating GSTP1 activity. In addition, molecular docking results showed that most of the metabolic molecules transformed by AA and GA other than themselves can closely bind to GSTP1, GSS, GGT1, N-acetyltransferase 8, and dimethyl sulfide dehydrogenase 1. The binding of AA-GSH and GA-GSH to GSTP1 and CYP2E1 enzymes determine the tendentiousness between toxicity and detoxification of AA, which exerts a prospective avenue for targeting protective role of hepatic enzymes against in vivo toxicity of AA.

Mechanisms of action of coffee bioactive compounds - a key to unveil the coffee paradox

The knowledge of the relationship between the chemical structure of food components with their mechanisms of action is crucial for the understanding of diet health benefits. This review relates the chemical variability present in coffee beverages with the mechanisms involved in key physiological events, supporting coffee as a polyvalent functional food. Coffee intake has been related with several health-promoting properties such as neuroprotective (caffeine, chlorogenic acids and melanoidins), anti-inflammatory (caffeine, chlorogenic acids, melanoidins, diterpenes), microbiota modulation (polysaccharides, melanoidins, chlorogenic acids), immunostimulatory (polysaccharides), antidiabetic (trigonelline, chlorogenic acids), antihypertensive (chlorogenic acids) and hypocholesterolemic (polysaccharides, chlorogenic acids, lipids). Nevertheless, caffeine and diterpenes are coffee components with ambivalent effects on health. Additionally, a large range of potentially harmful compounds, including acrylamide, hydroxymethylfurfural, furan, and advanced glycation end products, are formed during the roasting of coffee and are present in the beverages. However, coffee beverages are part of the daily human dietary healthy habits, configuring a coffee paradox.

Dynamic assessment of the relationship between oxidative stress and apoptotic pathway in embryonic fibroblast cells exposed to glycidamide: possible protective role of hesperidin

Worldwide research is being conducted to determine the level of acrylamide (ACR) that humans are exposed to from food and environmental sources. Glycidamide (GA) is an important epoxide metabolite of ACR, and its cytotoxicity is stronger than ACR. In this study, it was aimed to elucidate the effects and underlying mechanisms of GA on the induction of apoptosis in embryonic fibroblast cells. The toxicogenomic profile of GA was studied in terms of both apoptotic and oxidative stress. Embryonic fibroblast cells were exposed to GA (1 and 1000 µM) in the presence and absence of hesperidin (Hes) (20 µM) or vitamin C (VitC) (50 µM) for 24 h. Cell viability, cytotoxicity, lipid peroxidation, hydroxyl radicals, hydrogen peroxide, antioxidant enzyme levels and gene expressions, apoptotic, and oxidative stress-related gene expressions were measured in embryonic fibroblast cells. The results showed that GA induced cytotoxicity and diminished the expression levels of apoptotic genes. Furthermore, GA increased the levels of oxidative stress markers and significantly changed the oxidative stress-related gene expression. It has been determined that antioxidant molecules are considerably suppressed in GA-induced toxicity at both gene and enzyme levels. In addition to these results, when VitC, which is known to have strong antioxidant properties in eliminating the toxic effects of GA, is taken as reference, it has been proven that Hes has stronger antioxidant properties compared to VitC. Finally, GA-induced apoptosis in embryonic fibroblast cells is associated with nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent oxidative stress and Hes has antioxidant properties with strong effects.

Metabolomics strategy comprehensively unveils the effect of catechins intervention on the biomarkers of exposure to acrylamide and biomarkers of cardiometabolic risk

Polyphenolic antioxidants have been suggested to control the generation of acrylamide during thermal reactions. However, their role in protecting against the toxicity of acrylamide and the mechanism of action regarding profile alteration of biomarkers and metabolome remains unclear. A total of 65 adults were randomized into tea polyphenols (TP) and control groups and served with potato chips, which corresponded to an intake level of 12.6 μg/kg·bw of acrylamide, followed by capsules containing 200 mg, 100 mg or 50 mg TP, or equivalent placebo. Moreover, nontargeted urinary metabolomics analysis in acrylamide exposed rats was conducted using ultra-high performance liquid chromatography linked with a quadrupole-orbitrap high-resolution mass spectrometry. Our results showed that supplementation with catechins promoted the excretion of N-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-l-cysteine in both humans and rats. We also found that epigallocatechin gallate (EGCG) or epicatechin (EC) intervention attenuated the ratio of hemoglobin adduct of glycidamide to hemoglobin adduct of acrylamide in rat blood. Metabolomics analysis revealed that EGCG/EC intervention regulated the differential expressed metabolites, including l-glutamic acid, 2-oxoglutarate, citric acid, and cysteinylglycine. Kyoto Encyclopedia of Genes and Genomes pathway analysis further showed acrylamide-induced metabolic disorders were improved after EGCG/EC supplementation by glycolipid metabolism (alanine, aspartate and glutamate metabolism, and d-Glutamine and d-glutamate metabolism) and energy metabolism (tricarboxylic acid cycle). Notably, the supplement use of EGCG prevented the cardiometabolic risk after exposure to acrylamide by mediating the phenylalanine and hippuric acid in phenylalanine metabolism. Here we showed the beneficial effect of catechins as major polyphenolic antioxidant ingredients on the toxicity of acrylamide by the changes in biomarkers from metabolic profile analysis based on human and animal studies. These findings shed light into the catechins as natural polyphenolic antioxidants that could be a therapeutic ingredient for preventing acrylamide-induced cardiometabolic toxicity.

Time Trends of Acrylamide Exposure in Europe: Combined Analysis of Published Reports and Current HBM4EU Studies

More than 20 years ago, acrylamide was added to the list of potential carcinogens found in many common dietary products and tobacco smoke. Consequently, human biomonitoring studies investigating exposure to acrylamide in the form of adducts in blood and metabolites in urine have been performed to obtain data on the actual burden in different populations of the world and in Europe. Recognizing the related health risk, the European Commission responded with measures to curb the acrylamide content in food products. In 2017, a trans-European human biomonitoring project (HBM4EU) was started with the aim to investigate exposure to several chemicals, including acrylamide. Here we set out to provide a combined analysis of previous and current European acrylamide biomonitoring study results by harmonizing and integrating different data sources, including HBM4EU aligned studies, with the aim to resolve overall and current time trends of acrylamide exposure in Europe. Data from 10 European countries were included in the analysis, comprising more than 5500 individual samples (3214 children and teenagers, 2293 adults). We utilized linear models as well as a non-linear fit and breakpoint analysis to investigate trends in temporal acrylamide exposure as well as descriptive statistics and statistical tests to validate findings. Our results indicate an overall increase in acrylamide exposure between the years 2001 and 2017. Studies with samples collected after 2018 focusing on adults do not indicate increasing exposure but show declining values. Regional differences appear to affect absolute values, but not the overall time-trend of exposure. As benchmark levels for acrylamide content in food have been adopted in Europe in 2018, our results may imply the effects of these measures, but only indicated for adults, as corresponding data are still missing for children.

Trends of Exposure to Acrylamide as Measured by Urinary Biomarkers Levels within the HBM4EU Biomonitoring Aligned Studies (2000–2021)

Acrylamide, a substance potentially carcinogenic in humans, represents a very prevalent contaminant in food and is also contained in tobacco smoke. Occupational exposure to higher concentrations of acrylamide was shown to induce neurotoxicity in humans. To minimize related risks for public health, it is vital to obtain data on the actual level of exposure in differently affected segments of the population. To achieve this aim, acrylamide has been added to the list of substances of concern to be investigated in the HBM4EU project, a European initiative to obtain biomonitoring data for a number of pollutants highly relevant for public health. This report summarizes the results obtained for acrylamide, with a focus on time-trends and recent exposure levels, obtained by HBM4EU as well as by associated studies in a total of seven European countries. Mean biomarker levels were compared by sampling year and time-trends were analyzed using linear regression models and an adequate statistical test. An increasing trend of acrylamide biomarker concentrations was found in children for the years 2014–2017, while in adults an overall increase in exposure was found to be not significant for the time period of observation (2000–2021). For smokers, represented by two studies and sampling for, over a total three years, no clear tendency was observed. In conclusion, samples from European countries indicate that average acrylamide exposure still exceeds suggested benchmark levels and may be of specific concern in children. More research is required to confirm trends of declining values observed in most recent years.

Developmental neurotoxicity of acrylamide and its metabolite glycidamide in a human mixed culture of neurons and astrocytes undergoing differentiation in concentrations relevant for human exposure

Neural stem cells (NSCs) derived from human induced pluripotent stem cells were used to investigate effects of exposure to the food contaminant acrylamide (AA) and its main metabolite glycidamide (GA) on key neurodevelopmental processes. Diet is an important source of human AA exposure for pregnant women, and AA is known to pass the placenta and the newborn may also be exposed through breast feeding after birth. The NSCs were exposed to AA and GA (1 ×10^-8 - 3 ×10^-3 M) under 7 days of proliferation and up to 28 days of differentiation towards a mixed culture of neurons and astrocytes. Effects on cell viability was measured using Alamar Blue™ cell viability assay, alterations in gene expression were assessed using real time PCR and RNA sequencing, and protein levels were quantified using immunocytochemistry and high content imaging. Effects of AA and GA on neurodevelopmental processes were evaluated using endpoints linked to common key events identified in the existing developmental neurotoxicity adverse outcome pathways (AOPs). Our results suggest that AA and GA at low concentrations (1 ×10^-7 - 1 ×10^-8 M) increased cell viability and markers of proliferation both in proliferating NSCs (7 days) and in maturing neurons after 14-28 days of differentiation. IC₅₀ for cell death of AA and GA was 5.2 × 10^-3 M and 5.8 × 10^-4 M, respectively, showing about ten times higher potency for GA. Increased expression of brain derived neurotrophic factor (BDNF) concomitant with decreased synaptogenesis were observed for GA exposure (10^-7 M) only at later differentiation stages, and an increased number of astrocytes (up to 3-fold) at 14 and 21 days of differentiation. Also, AA exposure gave tendency towards decreased differentiation (increased percent Nestin positive cells). After 28 days, neurite branch points and number of neurites per neuron measured by microtubule-associated protein 2 (Map2) staining decreased, while the same neurite features measured by βIII-Tubulin increased, indicating perturbation of neuronal differentiation and maturation.

Comprehensive profile of DNA adducts as both tissue and urinary biomarkers of exposure to acrylamide and chemo-preventive effect of catechins in rats

Two representative DNA adducts from acrylamide exposure, N7-(2-carbamoyl-2-hydroxyethyl) guanine (N7-GA-Gua) and N3-(2-carbamoyl-2-hydroxyethyl) adenine (N3-GA-Ade), are important long-term exposure biomarkers for evaluating genotoxicity of acrylamide. Catechins as natural antioxidants present in tea possess multiple health benefits, and may also have the potential to protect against acrylamide-induced DNA damage. The current study developed an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method for simultaneous analysis of N7-GA-Gua and N3-GA-Ade in tissues and urine. The validated UHPLC-MS/MS method showed high sensitivity, with limit of detection and limit of quantification ranging 0.2-0.8 and 0.5-1.5 ng/mL, respectively, and achieved qualified precision (RSD<14.0%) and spiking recovery (87.2%-110.0%) with elution within 6 min, which was suitable for the analysis of the two DNA adducts in different matrices. The levels of N7-GA-Gua and N3-GA-Ade ranged 0.9-11.9 and 0.6-3.5 μg/g creatinine in human urine samples, respectively. To investigate the interventional effects of catechins on the two DNA adducts from acrylamide exposure, rats were supplemented with three types of catechins (tea polyphenols, epigallocatechin gallate, and epicatechin) 30 min before administration with acrylamide. Our results showed that catechins effectively inhibited the formation of DNA adducts from acrylamide exposure in both urine and tissues of rats. Among three catechins, epicatechin performed the best inhibitory effect. The current study provided evidence for the chemo-preventive effect of catechins, indicating that dietary supplement of catechins may contribute to health protection against exposure to acrylamide.

Characterization of primary glutathione conjugates with acrylamide and glycidamide: Toxicokinetic studies in Sprague Dawley rats treated with acrylamide

Acrylamide (AA) is classified as a probable human carcinogen and is ubiquitous in foods processed at high temperatures. The carcinogenicity of AA has been attributed to its active metabolite, glycidamide (GA). Both AA and GA can spontaneously or enzymatically conjugate with glutathione (GSH) to form their corresponding GSH conjugates. Profiling AA-glutathione conjugate (AA-GSH) and GA-glutathione conjugates (2 isomers: GA2-GSH and GA3-GSH) in serum would better illustrate AA detoxification compared with urinary metabolite analysis. However, the lack of AA-, GA2, and GA3-GSH study remains a critical data gap. Our study aimed to investigate the toxicokinetics of AA-, GA2-and GA3-GSH in Sprague Dawley rats treated with 0.1 mg/kg, 1.0 mg/kg, or 5.0 mg/kg AA. Blood samples were collected for LC-MS/MS analysis of the GSH conjugate products. Within 24 h of treatment, we observed rapid formation, elimination, and linear kinetics of AA-, GA2-and GA3-GSH. The ∑GA-GSH AUC/AA-GSH AUC ratios were 0.14-0.29, similar to ∑GA/AA AUC in serum but different from ∑GA/AA-derived urinary mercapturic acids in rodents. Our analysis of AA- and GA-GSHs values represents direct detoxification of AA and GA in vivo. This study advances our understanding of sex and inter-species differences in AA detoxification and may refine the existing kinetic models for a more relevant risk extrapolation.

Long-term acrylamide exposure exacerbates brain and lung pathology in a mouse malaria model

The consumption of dietary acrylamide (ACR), a carcinogen, results in the dysfunction of various organs and the immune system. However, the impact of ACR exposure on the progression of infectious diseases is unknown. This study investigated the effect of ACR on the progression of malaria infection using a mouse model of malaria. C57BL/6 mice were continuously treated with ACR at a dose of 20 mg/kg bodyweight/day for six weeks (long-term exposure) or phosphate-buffered saline (PBS). Next, the mice were infected with the rodent malaria parasite, Plasmodium berghei NK65 (PbNK). Parasitemia and survival rate were analyzed in the different treatment groups. Magnetic resonance imaging (MRI) and histopathological analyses were performed to evaluate the effect of ACR exposure on the morphology of various organs. Long-term ACR exposure exacerbated PbNK-induced multiorgan dysfunction. MRI and histopathological analysis revealed signs of encephalomeningitis and acute respiratory distress syndrome in the PbNK-infected long-term ACR exposure mice, which decreased the survival rate of mice, but not in the PbNK-infected long-term PBS exposure group. These findings enhance our understanding of the impact of ACR on the progression of infectious diseases, such as malaria.

Mitochondrial, lysosomal and DNA damages induced by acrylamide attenuate by ellagic acid in human lymphocyte

Acrylamide (AA), is an important contaminant formed during food processing under high temperature. Due to its potential neurotoxicity, reproductive toxicity, hepatotoxicity, immunotoxicity, genotoxicity and carcinogenicity effects, this food contaminant has been recognized as a human health concern. Previous studies showed that acrylamide-induced toxicity is associated with active metabolite of acrylamide by cytochrome P450 enzyme, oxidative stress, mitochondrial dysfunction and DNA damage. In the current study, we investigated the role of oxidative stress in acrylamide's genotoxicity and therapeutic potential role of ellagic acid (EA) in human lymphocytes. Human lymphocytes were simultaneously treated with different concentrations of EA (10, 25 and 50 μM) and acrylamide (50 μM) for 4 h at 37°C. After 4 hours of incubation, the toxicity parameters such cytotoxicity, ROS formation, oxidized/reduced glutathione (GSH/GSSG) content, malondialdehyde (MDA) level, lysosomal membrane integrity, mitochondria membrane potential (ΔΨm) collapse and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were analyzed using biochemical and flow cytometry evaluations. It has been found that acrylamide (50 μM) significantly increased cytotoxicity, ROS formation, GSH oxidation, lipid peroxidation, MMP collapse, lysosomal and DNA damage in human lymphocytes. On the other hand, cotreatment with EA (25 and 50 μM) inhibited AA-induced oxidative stress which subsequently led to decreasing of the cytotoxicity, GSH oxidation, lipid peroxidation, MMP collapse, lysosomal and DNA damage. Together, these results suggest that probably the co-exposure of EA with foods containing acrylamide could decrease mitochondrial, lysosomal and DNA damages, and oxidative stress induced by acrylamide in human body.

Acrylamide and its metabolite induce neurotoxicity via modulation of protein kinase C and AMP-activated protein kinase pathways

Acrylamide is known as a neurotoxicant found in commonly consumed food as well as in human body. However, the underlying mechanisms involved in neurotoxicity by acrylamide and its metabolite, glycidamide remain largely unknown. In this study, we have examined the interplay between CYP2E1, AMPK, ERK and PKC in acrylamide-induced neurotoxicity associated with autophagy in PC12 cells. Acrylamide-induced cell death was mediated by CYP2E1 expression and the activation of ERK, PKC-ɑ and PKC-δ, whereas AMPK knockdown exacerbated the acrylamide-induced neurotoxic effects. PKC-ɑ, but not PKC-δ, plays an upstream regulator of ERK and AMPK. Moreover, AMPK activation suppressed ERK, and CYP2E1 and AMPK bilaterally inhibit each other. Furthermore, acrylamide increased autophagy with impaired autophagic flux, evidenced by the increased beclin-1, LC3-II and p62 protein. Acrylamide-induced neuronal death was ameliorated by 3-methyladenine, an autophagy inhibitor, whereas neuronal death was exacerbated by chloroquine, a lysosomal inhibitor. Interestingly, PKC-δ siRNA, but not PKC-ɑ siRNA, dramatically reduced acrylamide-induced beclin-1 and LC3-II levels, whereas AMPK siRNA further increased beclin-1, LC3-II and p62 protein levels. Glycidamide, a major metabolite, mimicked acrylamide only with a higher potency. Taken together, acrylamide- and glycidamide-induced neurotoxicity may involve cytotoxic autophagy, which is mediated by interplay between PKCs and AMPK pathways.

Method Validation of Acrylamide in Dried Blood Spot by Liquid Chromatography-tandem Mass Spectrometry

BACKGROUND AND OBJECTIVE

Acrylamide (AA) is a carcinogenic substance that is easily found in working environment, food, contaminated air and tobacco smoke. This substance can be distributed rapidly through all body compartments. The aim of this study is to get the method for determining acrylamide in dried blood spot.

MATERIALS AND METHODS

Dried blood spot was used as the bio-sampling method and was optimized and validated by using propranolol as the internal standard. The sample was prepared using a protein precipitation technique optimized. Reversed-phase chromatography with Acquity® UPLC BEH C18 column (1.7, 2.1× 100 mm) was used for compound separation.

RESULTS

Optimized analytical condition for this substance was eluted with the flow rate of 0.20 mL/min under a gradient of the mobile phase of 0.1% formic acid in water and acetonitrile within 3 min. Triple quadrupole mass spectrometry with electrospray ionization (ESI) in positive mode was used as quantification analysis. The Multiple Reaction Monitoring (MRM) was set at m/z 71.99>55.23 (m/z) for acrylamide and 260.2>116.2 (m/z) for propranolol. The range of concentration was linear within 2.5-100 μg mL-1.

CONCLUSION

All the validation parameters were fulfilled the criteria in US FDA Guideline for Bioanalytical Method Validation 2018.

Revisiting the evidence for genotoxicity of acrylamide (AA), key to risk assessment of dietary AA exposure

The weight of evidence pro/contra classifying the process-related food contaminant (PRC) acrylamide (AA) as a genotoxic carcinogen is reviewed. Current dietary AA exposure estimates reflect margins of exposure (MOEs) < 500. Several arguments support the view that AA may not act as a genotoxic carcinogen, especially not at consumer-relevant exposure levels: Biotransformation of AA into genotoxic glycidamide (GA) in primary rat hepatocytes is markedly slower than detoxifying coupling to glutathione (GS). Repeated feeding of rats with AA containing foods, bringing about uptake of 100 µg/kg/day of AA, resulted in dose x time-related buildup of AA-hemoglobin (Hb) adducts, whereas GA-Hb adducts remained within the background. Since hepatic oxidative biotransformation of AA into GA was proven by simultaneous urinary mercapturic acid monitoring it can be concluded that at this nutritional intake level any GA formed in the liver from AA is quantitatively coupled to GS to be excreted as mercapturic acid in urine. In an oral single dose–response study in rats, AA induced DNA N⁷-GA-Gua adducts dose-dependently in the high dose range (> 100 µg/kg b w). At variance, in the dose range below 100 µg/kg b.w. down to levels of average consumers exposure, DNA N⁷ -Gua lesions were found only sporadically, without dose dependence, and at levels close to the lower bound of similar human background DNA N⁷-Gua lesions. No DNA damage was detected by the comet assay within this low dose range. GA is a very weak mutagen, known to predominantly induce DNA N⁷-GA-Gua adducts, especially in the lower dose range. There is consensus that DNA N⁷-GA-Gua adducts exhibit rather low mutagenic potency. The low mutagenic potential of GA has further been evidenced by comparison to preactivated forms of other process-related contaminants, such as N-Nitroso compounds or polycyclic aromatic hydrocarbons, potent food borne mutagens/carcinogens. Toxicogenomic studies provide no evidence supporting a genotoxic mode of action (MOA), rather indicate effects on calcium signalling and cytoskeletal functions in rodent target organs. Rodent carcinogenicity studies show induction of strain- and species-specific neoplasms, with MOAs not considered likely predictive for human cancer risk. In summary, the overall evidence clearly argues for a nongenotoxic/nonmutagenic MOA underlying the neoplastic effects of AA in rodents. In consequence, a tolerable intake level (TDI) may be defined, guided by mechanistic elucidation of key adverse effects and supported by biomarker-based dosimetry in experimental systems and humans.

Glycidamide Promotes the Growth and Migratory Ability of Prostate Cancer Cells by Changing the Protein Expression of Cell Cycle Regulators and Epithelial-to-Mesenchymal Transition (EMT)-Associated Proteins with Prognostic Relevance

Acrylamide (AA) and glycidamide (GA) can be produced in carbohydrate-rich food when heated at a high temperature, which can induce a malignant transformation. It has been demonstrated that GA is more mutagenic than AA. It has been shown that the proliferation rate of some cancer cells are increased by treatment with GA; however, the exact genes that are induced by GA in most cancer cells are not clear. In the present study, we demonstrated that GA promotes the growth of prostate cancer cells through induced protein expression of the cell cycle regulator. In addition, we also found that GA promoted the migratory ability of prostate cancer cells through induced epithelial-to-mesenchymal transition (EMT)-associated protein expression. In order to understand the potential prognostic relevance of GA-mediated regulators of the cell cycle and EMT, we present a three-gene signature to evaluate the prognosis of prostate cancer patients. Further investigations suggested that the three-gene signature (CDK4, TWIST1 and SNAI2) predicted the chances of survival better than any of the three genes alone for the first time. In conclusion, we suggested that the three-gene signature model can act as marker of GA exposure. Hence, this multi-gene panel may serve as a promising outcome predictor and potential therapeutic target in prostate cancer patients.

Feasibility of using urinary N7-(2-carbamoyl-2-hydroxyethyl) Guanine as a biomarker for acrylamide exposed workers

Acrylamide (AA), a probable human carcinogen, is a widely-used industrial chemical but is also present in tobacco smoke and carbohydrate-rich foods processed at high temperatures. AA is metabolized to glycidamide (GA) to cause the formation of DNA adducts. N7-(2-carbamoyl-2-hydroxyethyl) guanine (N7-GAG), the most abundant DNA adduct induced by GA, was recently detected in urine of smokers and non-smokers. In this study, we assessed the variability of AA exposure and biomarkers of AA exposure in urine samples repeatedly collected from AA-exposed workers and explored the half-life of N7-GAG. A total of 8 AA-exposed workers and 36 non-exposed workers were recruited. Pre-shift and post-shift urine samples were collected from the exposed group in parallel with personal sampling for eight consecutive days and from the control group on day 1 of the study. Urinary N7-GAG and the mercapturic acids of AA and GA, namely N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-(R,S)-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA) were analyzed using on-line solid phase extraction-liquid chromatography-electrospray ionization/tandem mass spectrometry methods. We found that N7-GAG levels in urine were significantly higher in exposed workers than in controls and that N7-GAG level correlated positively with AAMA and GAMA levels. Results from this study showed that AAMA and GAMA possibly remain the more preferred biomarkers of AA exposure and that N7-GAG levels could be elevated by occupational exposures to AA and serve as a biomarker of AA-induced genotoxicity for epidemiological studies.

Exposure to acrylamide and the risk of cardiovascular diseases in the National Health and Nutrition Examination Survey 2003-2006

BACKGROUND

Long-term exposure to acrylamide (AA) from diet sources may induce oxidative stress and chronic inflammation. However, the association between AA exposure and the prevalence of cardiovascular diseases (CVD) remains unclear.

OBJECTIVES

We aimed to examine the association between blood exposure levels of AA biomarkers and the prevalence of main types of CVD in a general population of US adults.

METHODS

We analyzed the associations between AA hemoglobin biomarkers [hemoglobin adducts of acrylamide (HbAA) and glycidamide (HbGA), sum of HbAA and HbGA (HbAA+HbGA), and ratio of HbGA to HbAA (HbGA:HbAA)] and self-reported diagnosis of CVD in 8290 adults (≥20 years of age) from the National Health and Nutrition Examination Survey (NHANES) 2003-2006. Multivariable logistic regression models were employed for estimating the associations in three groups classified by the combination of smoking status and serum cotinine levels.

RESULTS

In people exposed to environmental tobacco smoke (n = 4670), HbGA, HbAA+HbGA, and HbGA:HbAA were significantly and inversely associated with the prevalence of total CVD (p < 0.0001, p = 0.0155, and p = 0.0014 for trend, respectively) after adjusting for various covariates. The odd ratios (ORs) for total CVD in the highest quartiles of HbGA, HbAA+HbGA, and HbGA:HbAA were 0.311 [95% confidence interval (CI): 0.193-0.500], 0.664 (95% CI: 0.485-0.911), and 0.495 (95% CI: 0.326-0.752) when compared with the individual lowest quartiles. In active smokers (n = 2432), HbAA was positively associated with CVD risk (p = 0.0088 for trend), while HbGA:HbAA was inversely related to total CVD (p = 0.0137 for trend). However, no significant associations of any AA hemoglobin biomarker with total and individual CVD prevalence were observed in the nonsmoking group (n = 1188).

CONCLUSIONS

AA hemoglobin biomarkers are significantly associated with CVD in the active smoking group and the group exposed to environmental tobacco smoke but not in the nonsmoking group. Further prospective studies should clarify the causal relationship between HbAA and HbGA and the prevalence of CVD.

Toxicological Implications of Mitochondrial Localization of CYP2E1

Cytochrome P450 2E1 (CYP2E1) metabolizes an extensive array of pollutants, drugs, and other small molecules, often resulting in bioactivation to reactive metabolites. Therefore, it is unsurprising that it has been the subject of decades of research publications and reviews. However, while CYP2E1 has historically been studied in the endoplasmic reticulum (erCYP2E1), active CYP2E1 is also present in mitochondria (mtCYP2E1). Relatively few studies have specifically focused on mtCYP2E1, but there is growing interest in this form of the enzyme as a driver in toxicological mechanisms given its activity and location. Many previous studies have linked total CYP2E1 to conditions that involve mitochondrial dysfunction (fasting, diabetes, non-alcoholic steatohepatitis, and obesity). Furthermore, a large number of reactive metabolites that are formed by CYP2E1 through metabolism of drugs and pollutants have been demonstrated to cause mitochondrial dysfunction. Finally, there appears to be significant inter-individual variability in targeting to the mitochondria, which could constitute a source of variability in individual response to exposures. This review discusses those outcomes, the biochemical properties and toxicological consequences of mtCYP2E1, and highlights important knowledge gaps and future directions. Overall, we feel that this exciting area of research is rich with new and important questions about the relationship between mtCYP2E1, mitochondrial dysfunction, and pathology.

DNA adduct identification using gold-aptamer nanoprobes

The optical and physico-chemical properties of gold nanoparticles (AuNPs) have prompted new and improved approaches which have greatly evolved the fields of biosensing and molecular detection. In this study, the authors took advantage of AuNPs' ease of modification and functionalised it with selected DNA aptamers using a salt aging method to produce gold-aptamer nanoprobes. After characterisation, these nanoprobes were subsequently used for biomolecular detection of glycidamide (GA)-guanine (Gua) adducts generated in vitro. The results are based on differences in nanoprobe stabilisation against salt-induced aggregation, similar to the non-cross-linking method developed by Baptista for discrimination of specific sequences. Alkylated Guas were efficiently discriminated from deoxyguanosine and GA in solution. Despite this, a clear identification of DNA adducts derived from genomic DNA alkylation has proven to be a more challenging task.

The genetic consequences of paternal acrylamide exposure and potential for amelioration

Acrylamide is a toxin that humans are readily exposed to due to its formation in many carbohydrate rich foods cooked at high temperatures. Acrylamide is carcinogenic, neurotoxic and causes reproductive toxicity when high levels of exposure are reached in mice and rats. Acrylamide induced effects on fertility occur predominantly in males. Acrylamide exerts its reproductive toxicity via its metabolite glycidamide, a product which is only formed via the cytochrome P450 detoxifying enzyme CYP2E1. Glycidamide is highly reactive and forms adducts with DNA. Chronic low dose acrylamide exposure in mice relevant to human exposure levels results in significantly increased levels of DNA damage in terms of glycidamide adducts in spermatocytes, the specific germ cell stage where Cyp2e1 is expressed. Since cells in the later stages of spermatogenesis are unable to undergo DNA repair, and this level of acrylamide exposure causes no reduction in fertility, there is potential for this damage to persist until sperm maturation and fertilisation. Cyp2e1 is also present within epididymal cells, allowing for transiting spermatozoa to be exposed to glycidamide. This could have consequences for future generations in terms of predisposition to diseases such as cancer, with growing indications that paternal DNA damage can be propagated across multiple generations. Since glycidamide is the major contributor to DNA damage, a mechanism for preventing these effects is inhibiting the function of Cyp2e1. Resveratrol is an example of an inhibitor of Cyp2e1 which has shown success in reducing damage caused by acrylamide treatment in mice.

Protection of cyanidin-3-glucoside against oxidative stress induced by acrylamide in human MDA-MB-231 cells

Acrylamide (AA) occurs in many cooked starchy foods and has caused widespread concern as a possible carcinogen. In the present study, we investigate the intervention of AA toxicity in MDA-MB-231 cells pretreated with cyanidin-3-glucoside (Cy-3-glu). Compared to the cells treated with AA, Cy-3-glu significantly inhibited AA-induced cytotoxicity, reduced reactive oxygen species (ROS) generation, recovered glutathione (GSH) depletion and decreased the activities of glutathione peroxidase (GPx) and glutathione S-transferase (GST). Moreover, the expression of GPx1, GSTP1 and gamma-glutamyl cysteine synthase (γ-GCS) were enhanced, and cytochrome P450 2E1 (CYP2E1) expression was inhibited by the pretreatment of Cy-3-glu. Cy-3-glu presents the protective role against oxidative stress induced by AA in MDA-MB-231 cells.

The modifying effect of CYP2E1, GST, and mEH genotypes on the formation of hemoglobin adducts of acrylamide and glycidamide in workers exposed to acrylamide

This study assesses the association of acrylamide (AA) and glycidamide (GA) hemoglobin adducts (AAVal and GAVal) and their ratios with genetic polymorphisms of the metabolic enzymes cytochrome P450 2E1 (CYP2E1), exon 3 and 4 of microsomal epoxide hydrolase (mEH3 and mEH4), glutathione transferase theta (GSTT1), and mu (GSTM1) or/and the combinations of these polymorphisms, involved in the activation and detoxification of AA in humans. Fifty-one AA-exposed workers and 34 controls were recruited and provided a post-shift blood sample. AAVal and GAVal were determined simultaneously using isotope-dilution liquid chromatography-electronspray ionization/tandem mass spectrometry (LC-ESI-MS/MS). Genetic polymorphisms of CYP2E1, mEH3 and 4, GSTT1, and GSTM1 were also analyzed. Our results reveal that the GAVal/AAVal ratio, potentially reflecting the proportion of AA metabolized to GA, ranged from 0.13 to 0.45 with a mean at 0.27. Multivariate regression analysis demonstrates that the joint effect of CYP2E1, GSTM1, and mEH4 genotypes was significantly associated with AAVal and GAVal levels after adjustment for AA exposures. These results suggest that mEH4 and the combined genotypes of CYP2E1, GSTM1 and mEH4 may be associated with the formation of AAVal and GAVal. Further studies may be needed to shed light on the roles that phase I and II enzymes play in AA metabolism.

Hemoglobin adducts as a measure of variations in exposure to acrylamide in food and comparison to questionnaire data

Measurement of haemoglobin (Hb) adducts from acrylamide (AA) and its metabolite glycidamide (GA) is a possibility to improve the exposure assessment in epidemiological studies of AA intake from food. This study aims to clarify the reliability of Hb-adduct measurement from individual single samples for exposure assessment of dietary AA intake. The intra-individual variations of AA- and GA-adduct levels measured in blood samples collected over 20 months from 13 non-smokers were up to 2-fold and 4-fold, respectively. The corresponding interindividual variations observed between 68 non-smokers, with large differences in AA intake, were 6-fold and 8-fold, respectively. The intra-individual variation of the GA-to-AA-adduct level ratio was up to 3-fold, compared to 11-fold between individuals (n = 68). From AA-adduct levels the average AA daily intake (n = 68) was calculated and compared to that estimated from dietary history methodology: 0.52 and 0.67 μg/kg body weight and day, respectively. At an individual level the measures showed low association (Rs = 0.39).

CONCLUSIONS

Dietary AA is the dominating source to measured AA-adduct levels and corresponding inter- and intra-individual variations in non-smokers. Measurements from single individual samples are useful for calculation of average AA intake and its variation in a cohort, and for identification of individuals only from extreme intake groups.

Analysis of hemoglobin adducts from acrylamide, glycidamide, and ethylene oxide in paired mother/cord blood samples from Denmark

The knowledge about fetal exposure to acrylamide/glycidamide from the maternal exposure through food is limited. Acrylamide, glycidamide, and ethylene oxide are electrophiles and form adducts with hemoglobin (Hb), which could be used for in vivo dose measurement. In this study, a method for analysis of Hb adducts by liquid chromatography-mass spectrometry, the adduct FIRE procedure, was applied to measurements of adducts from these compounds in maternal blood samples (n = 87) and umbilical cord blood samples (n = 219). The adduct levels from the three compounds, acrylamide, glycidamide, and ethylene oxide, were increased in tobacco smokers. Highly significant correlations were found between cord and maternal blood with regard to measured adduct levels of the three compounds. The mean cord/maternal hemoglobin adduct level ratios were 0.48 (range 0.27-0.86) for acrylamide, 0.38 (range 0.20-0.73) for glycidamide, and 0.43 (range 0.17-1.34) for ethylene oxide. In vitro studies with acrylamide and glycidamide showed a lower (0.38-0.48) rate of adduct formation with Hb in cord blood than with Hb in maternal blood, which is compatible with the structural differences in fetal and adult Hb. Together, these results indicate a similar life span of fetal and maternal erythrocytes. The results showed that the in vivo dose in fetal and maternal blood is about the same and that the placenta gives negligible protection of the fetus to exposure from the investigated compounds. A trend of higher levels of the measured adducts in cord blood with gestational age was observed, which may reflect the gestational age-related change of the cord blood Hb composition toward a higher content of adult Hb. The results suggest that the Hb adduct levels measured in cord blood reflect the exposure to the fetus during the third trimester. The evaluation of the new analytical method showed that it is suitable for monitoring of background exposures of the investigated electrophilic compounds in large population studies.

Modification of major plasma proteins by acrylamide and glycidamide: Preliminary screening by nano liquid chromatography with tandem mass spectrometry

Environmental and food-borne acrylamide is a suspected carcinogen in humans and is associated with several cancer types. Its biological metabolite, glycidamide, is also harmful to human health. The presence of acrylamide in the living environment makes this toxic chemical an important public health issue. Acrylamide and glycidamide bind with proteins to form protein adducts in metabolic processes. These metabolic adducts can be considered environmental modifications of proteins. This study used a simple proteomic strategy to identify acrylamide and glycidamide adducts bound in major plasma proteins. After simple sample preparation, new protein modifications by acrylamide and glycidamide were identified using nano LC combined with quadruple time-of-flight (Q-TOF) mass spectrometry. This method required only 10 μL of human plasma sample for protein modification survey. Hopefully, this strategy can help to discover protein-acrylamide (or glycidamide) adducts that are biomarkers of human exposure to high-dose acrylamide. These biomarkers may also elucidate the metabolic pathways of acrylamide and glycidamide.

In vivo doses of acrylamide and glycidamide in humans after intake of acrylamide-rich food

For assessment of cancer risk from acrylamide (AA) exposure through food, the relation between intake from food in humans and the in vivo doses (area under the concentration-time curve, AUC) of AA (AUC-AA) and of its genotoxic metabolite glycidamide (GA) (AUC-GA) is used as a basis for extrapolation between exposure levels and between species. In this study, AA-rich foods were given to nonsmokers: a high intake of 11 μg AA/kg body weight (bw) and day for 4 days or an extra (medium) intake of 2.5 μg AA/kg bw and day for a month. Hemoglobin (Hb)-adduct levels from AA and GA, measured in blood samples donated before and after exposures, were used for calculation of AUC-AA and AUC-GA using reaction rate constants for the adduct formation measured in vitro. Both AA- and GA-adduct levels increased about twofold after the periods with enhanced intake. AUC for the high and medium groups, respectively, in nanomolar hours per microgram AA per kilogram bw, was for AA 212 and 120 and for GA 49 and 21. The AA intake in the high group was better controlled and used for comparisons with other data. The AUCs per exposure dose obtained in the present human study (high group) are in agreement with those previously obtained at 10(2) times higher exposure levels in humans. Furthermore, the values of AUC-AA and AUC-GA are five and two times higher, respectively, than the corresponding values for F344 rats exposed to AA at levels as in published cancer bioassays.

Food contaminant acrylamide increases expression of Cox-2 and nitric oxide synthase in breast epithelial cells

Acrylamide has been discovered in foods cooked at high temperature. A potentially harmful effect of this dietary component has been suggested by data indicating its association with increased breast cancer. This study investigated the potential effects of acrylamide in nontumorigenic breast cells by assessing expression levels of inducible nitric oxide synthase (iNOS) and cycloogenase-2 (Cox-2) and NOS activity, which are known to be early molecular changes in disease formation. Treatment of cells with acrylamide increased levels of iNOS (both expression and activity) and Cox-2. Its potent metabolite, glycidamide, also induced both iNOS and Cox-2, with induction of iNOS occurring at a lower concentration. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), another food-borne carcinogen, was found to induce Cox-2 expression. Combining acrylamide with PhIP did not result in a further increase. These studies suggest that further research is needed to determine the role of carcinogens formed from cooking foods in inducing early molecular changes associated with breast cancer.