Comparison of Germ Cell Mutagenicity in Male CYP2E1-Null and Wild-Type Mice Treated with Acrylamide: Evidence Supporting a Glycidamide-Mediated Effect

Impacts of Acrylamide on testis and spermatozoa

Acrylamide (ACR) is an industrial chemical used to produce polyacrylamide, a synthetic polymer with a wide range of applications. Depending on the dosage, its presence in occupational and environmental sources poses potential health risks to humans and animals. ACR can be formed in starchy foods cooked at high temperatures. Its effects on human sperm are not well understood. Animal studies indicate that ACR induces toxicity in the male reproductive system through oxidative stress mechanisms. Exposure to ACR alters the normal structure of testicular tubules, leading to congestion, interstitial edema, degeneration of spermatogenic cells, formation of abnormal spermatid giant cells, and necrosis and apoptosis. It also disrupts the balance of important biomarkers such as malondialdehyde, nitric oxide, superoxide dismutase, catalase, and glutathione. ACR has a negative impact on mitochondrial function, antioxidant enzymes, ATP production, and sperm membrane integrity, resulting in decreased sperm quality. Furthermore, it interferes with the expression of steroidogenic genes associated with testosterone biosynthesis. This review explores the detrimental effects of ACR on sperm and testicular function and discusses the potential role of antioxidants in mitigating the adverse effects of ACR on male reproduction.

Inhibition of polyphenols on Maillard reaction products and their induction of related diseases: A comprehensive review

BACKGROUND

Food products undergo a pronounced Maillard reaction (MR) during the cooking process, leading to the generation of substantial quantities of Maillard reaction products (MRPs). Within this category, advanced glycation end products (AGEs), acrylamide (AA), and heterocyclic amines (HAs) have been implicated as potential risk factors associated with the development of diseases.

PURPOSE

To explore the effects of polyphenols, a class of bioactive compounds found in plants, on the inhibition of MRPs and related diseases. Previous research has mainly focused on their interactions with proteins and their effects on the gastrointestinal tract and other diseases, while fewer studies have examined their inhibitory effects on MRPs. The aim is to offer a scientific reference for future research investigating the inhibitory role of polyphenols in the MR.

METHODS

The databases PubMed, Embase, Web of Science and The Cochrane Library were searched for appropriate research.

RESULTS

Polyphenols have the potential to inhibit the formation of harmful MRPs and prevent related diseases. The inhibition of MRPs by polyphenols primarily occurs through the following mechanisms: trapping α-dicarbonyl compounds, scavenging free radicals, chelating metal ions, and preserving protein structure. Simultaneously, polyphenols exhibit the ability to impede the onset and progression of related diseases such as diabetes, atherosclerosis, cancer, and Alzheimer's disease through diverse pathways.

CONCLUSION

This review presents that inhibition of polyphenols on Maillard reaction products and their induction of related diseases. Further research is imperative to enhance our comprehension of additional pathways affected by polyphenols and to fully uncover their potential application value in inhibiting MRPs.

The role of additives on acrylamide formation in food products: a systematic review

Acrylamide (AA) is a toxic substance formed in many carbohydrate-rich food products, whose formation can be reduced by adding some additives. Furthermore, the type of food consumed determines the AA intake. According to the compiled information, the first route causing AA formation is the Maillard reaction. Some interventions, such as reducing AA precursors in raw materials, (i.e., asparagine), reducing sugars, or decreasing temperature and processing time can be applied to limit AA formation in food products. The L-asparaginase is more widely used in potato products. Also, coatings loaded with proteins, enzymes, and phenolic compounds are new techniques for reducing AA content. Enzymes have a reducing effect on AA formation by acting on asparagine; proteins by competing with amino acids to participate in Maillard, and phenolic compounds through their radical scavenging activity. On the other hand, some synthetic and natural additives increase the formation of AA. Due to the high exposure to AA and its toxic effects, it is essential to recognize suitable food additives to reduce the health risks for consumers. In this sense, this study focuses on different additives that are proven to be effective in the reduction or formation of AA in food products.

Acrylamide modulates the mouse epididymal proteome to drive alterations in the sperm small non-coding RNA profile and dysregulate embryo development

Paternal exposure to environmental stressors elicits distinct changes to the sperm sncRNA profile, modifications that have significant post-fertilization consequences. Despite this knowledge, there remains limited mechanistic understanding of how paternal exposures modify the sperm sncRNA landscape. Here, we report the acute sensitivity of the sperm sncRNA profile to the reproductive toxicant acrylamide. Furthermore, we trace the differential accumulation of acrylamide-responsive sncRNAs to coincide with sperm transit of the proximal (caput) segment of the epididymis, wherein acrylamide exposure alters the abundance of several transcription factors implicated in the expression of acrylamide-sensitive sncRNAs. We also identify extracellular vesicles secreted from the caput epithelium in relaying altered sncRNA profiles to maturing spermatozoa and dysregulated gene expression during early embryonic development following fertilization by acrylamide-exposed spermatozoa. These data provide mechanistic links to account for how environmental insults can alter the sperm epigenome and compromise the transcriptomic profile of early embryos.

Eruca sativa seed extract modulates oxidative stress and apoptosis and up-regulates the expression of Bcl-2 and Bax genes in acrylamide-induced testicular dysfunction in rats

Acrylamide (ACR) has been previously associated with male sexual dysfunction and infertility. Eruca sativa (L.) (arugula or rocket) have been widely used in traditional remedies in Mediterranean region and western Asia and was known for its strong aphrodisiac effect since Roman times. The current study was designed to investigate LC/MS analysis of total ethanol extract Eruca sativa (L.) and the efficiency and mechanism of action of Eruca sativa seed extract (ESS) in reducing hypogonadism induced by acrylamide in male rats. Male Wistar rats were divided into 6 groups (n = 7): control group, Eruca sativa seed extract (ESS) at doses of 100 and 200 mg\kg, acrylamide (ACR), ACR + ESS 100 mg/kg, and ACR + ESS 200 mg/kg. The animals received ACR at a dose of 10 mg/kg b.wt for 60 days. Sperm indices, testicular oxidative stress, testosterone hormone, and testicular histopathology and immunohistochemistry of PCNA and caspase-3 were investigated. Moreover, the expression level of testicular B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (Bax) genes was evaluated. In respect to the LC/MS of total ethanol extract Eruca sativa (L.) seed revealed tentative identification of 39 compounds, which belongs to different classes as sulphur-containing compounds, flavonoids, phenolic acid, and fatty acids. Administration of ESS extract (100, 200 mg/kg) improved semen quality, diminished lipid peroxidation, enhanced testicular antioxidant enzyme, restored serum testosterone level, and reduced testicular degeneration and Leydig cell death in the rats intoxicated with ACR. However, the effects of ESS at the dose of 200 mg/kg were similar to that of control group. Furthermore, ESS treatment significantly induced anti-apoptotic effect indicated by elevation of both Bcl-2 and Bax expressions. Nutriceutics of ESS extract protects testis against ACR-induced testicular toxicity via normalizing testicular steroidogenesis, keeping Leydig cells, and improving oxidative stress status.

Proteomic Dissection of the Impact of Environmental Exposures on Mouse Seminal Vesicle Function

Seminal vesicles are an integral part of the male reproductive accessory gland system. They produce a complex array of secretions containing bioactive constituents that support gamete function and promote reproductive success, with emerging evidence suggesting these secretions are influenced by our environment. Despite their significance, the biology of seminal vesicles remains poorly defined. Here, we complete the first proteomic assessment of mouse seminal vesicles and assess the impact of the reproductive toxicant acrylamide. Mice were administered acrylamide (25 mg/kg bw/day) or control daily for five consecutive days prior to collecting seminal vesicle tissue. A total of 5013 proteins were identified in the seminal vesicle proteome with bioinformatic analyses identifying cell proliferation, protein synthesis, cellular death, and survival pathways as prominent biological processes. Secreted proteins were among the most abundant, and several proteins are linked with seminal vesicle phenotypes. Analysis of the effect of acrylamide on the seminal vesicle proteome revealed 311 differentially regulated (FC ± 1.5, p ≤ 0.05, 205 up-regulated, 106 downregulated) proteins, orthogonally validated via immunoblotting and immunohistochemistry. Pathways that initiate protein synthesis to promote cellular survival were prominent among the dysregulated pathways, and rapamycin-insensitive companion of mTOR (RICTOR, p = 6.69E-07) was a top-ranked upstream driver. Oxidative stress was implicated as contributing to protein changes, with acrylamide causing an increase in 8-OHdG in seminal vesicle epithelial cells (fivefold increase, p = 0.016) and the surrounding smooth muscle layer (twofold increase, p = 0.043). Additionally, acrylamide treatment caused a reduction in seminal vesicle secretion weight (36% reduction, p = 0.009) and total protein content (25% reduction, p = 0.017). Together these findings support the interpretation that toxicant exposure influences male accessory gland physiology and highlights the need to consider the response of all male reproductive tract tissues when interpreting the impact of environmental stressors on male reproductive function.

Does the food processing contaminant acrylamide cause developmental neurotoxicity? A review and identification of knowledge gaps

There is a worldwide concern on adverse health effects of dietary exposure to acrylamide (AA) due to its presence in commonly consumed foods. AA is formed when carbohydrate rich foods containing asparagine and reducing sugars are prepared at high temperatures and low moisture conditions. Upon oral intake, AA is rapidly absorbed and distributed to all organs. AA is a known human neurotoxicant that can reach the developing foetus via placental transfer and breast milk. Although adverse neurodevelopmental effects have been observed after prenatal AA exposure in rodents, adverse effects of AA on the developing brain has so far not been studied in humans. However, epidemiological studies indicate that gestational exposure to AA impair foetal growth and AA exposure has been associated with reduced head circumference of the neonate. Thus, there is an urgent need for further research to elucidate whether pre- and perinatal AA exposure in humans might impair neurodevelopment and adversely affect neuronal function postnatally. Here, we review the literature with emphasis on the identification of critical knowledge gaps in relation to neurodevelopmental toxicity of AA and its mode of action and we suggest research strategies to close these gaps to better protect the unborn child.

Mutagenicity of acrylamide and glycidamide in human TP53 knock-in (Hupki) mouse embryo fibroblasts

Acrylamide is a suspected human carcinogen formed during high-temperature cooking of starch-rich foods. It is metabolised by cytochrome P450 2E1 to its reactive metabolite glycidamide, which forms pre-mutagenic DNA adducts. Using the human TP53 knock-in (Hupki) mouse embryo fibroblasts (HUFs) immortalisation assay (HIMA), acrylamide- and glycidamide-induced mutagenesis was studied in the tumour suppressor gene TP53. Selected immortalised HUF clones were also subjected to next-generation sequencing to determine mutations across the whole genome. The TP53-mutant frequency after glycidamide exposure (1.1 mM for 24 h, n = 198) was 9% compared with 0% in cultures treated with acrylamide [1.5 (n = 24) or 3 mM (n = 6) for 48 h] and untreated vehicle (water) controls (n = 36). Most glycidamide-induced mutations occurred at adenines with A > T/T > A and A > G/T > C mutations being the most common types. Mutations induced by glycidamide occurred at specific TP53 codons that have also been found to be mutated in human tumours (i.e., breast, ovary, colorectal, and lung) previously associated with acrylamide exposure. The spectrum of TP53 mutations was further reflected by the mutations detected by whole-genome sequencing (WGS) and a distinct WGS mutational signature was found in HUF clones treated with glycidamide that was again characterised by A > G/T > C and A > T/T > A mutations. The WGS mutational signature showed similarities with COSMIC mutational signatures SBS3 and 25 previously found in human tumours (e.g., breast and ovary), while the adenine component was similar to COSMIC SBS4 found mostly in smokers’ lung cancer. In contrast, in acrylamide-treated HUF clones, only culture-related background WGS mutational signatures were observed. In summary, the results of the present study suggest that glycidamide may be involved in the development of breast, ovarian, and lung cancer.

Using the comet assay and lysis conditions to characterize DNA lesions from the acrylamide metabolite glycidamide

The alkaline comet assay and a cell-free system were used to characterise DNA lesions induced by treatment with glycidamide (GA), a metabolite of the food contaminant acrylamide. DNA lesions induced by GA were sensitively detected when the formamidopyrimidine-DNA-glycosylase (Fpg) enzyme was included in the comet assay. We used LC-MS to characterise modified bases from GA-treated naked DNA with and without subsequent Fpg treatment. N7-GA-Guanine and N3-GA-Adenine aglycons were detected in the supernatant showing some depurination of adducted bases; treatment of naked DNA with Fpg revealed no further increase in the adduct yield nor occurrence of other adducted nucleobases. We treated human lymphocytes with GA and found large differences in DNA lesion levels detected with Fpg, depending on the duration and the pH of the lysis step. These lysis-dependent variations in GA-induced Fpg sensitive sites paralleled those observed after treatment of cells with methyl methane sulfonate (MMS). On the other hand, oxidative lesions (8-oxoGuanine) induced by a photoactive compound (Ro 12-9786) plus light, and also DNA strand breaks induced by X-rays, were detected largely independently of the lysis conditions. The results suggest that the GA-induced lesions are predominantly N7-GA-dG adducts slowly undergoing imidazole ring opening at pH 10 as in the standard lysis procedure; such structures are substrate for Fpg leading to strand breaks. The data suggest that the characteristic alkaline lysis dependence of some DNA lesions may be used to study specific types of DNA modifications. The comet assay is increasingly used in regulatory testing of chemicals; in this context, lysis-dependent variations represent a novel approach to obtain insight in the molecular nature of a genotoxic insult.

Dietary Acrylamide and the Risks of Developing Cancer: Facts to Ponder

Acrylamide (AA) is a water soluble white crystalline solid commonly used in industries. It was listed as an industrial chemical with potential carcinogenic properties. However to date, AA was used to produce polyacrylamide polymer, which was widely used as a coagulant in water treatment; additives during papermaking; grouting material for dams, tunnels, and other underground building constructions. AA in food could be formed during high-temperature cooking via several mechanisms, i.e., formation via acrylic acid which may be derived from the degradation of lipid, carbohydrates, or free amino acids; formation via the dehydration/decarboxylation of organic acids (malic acid, lactic acid, and citric acid); and direct formation from amino acids. The big debate is whether this compound is toxic to human beings or not. In the present review, we discuss the formation of AA in food products, its consumption, and possible link to the development of any cancers. We discuss the body enzymatic influence on AA and mechanism of action of AA on hormone, calcium signaling pathways, and cytoskeletal filaments. We also highlight the deleterious effects of AA on nervous system, reproductive system, immune system, and the liver. The present and future mitigation strategies are also discussed. The present review on AA may be beneficial for researchers, food industry, and also medical personnel.

Metabolomics analysis of serum from subjects after occupational exposure to acrylamide using UPLC-MS

Since occupational exposure to acrylamide (ACR) may cause nerve damage, sensitive biomarkers to evaluate the early effects of ACR on human health are needed. In the present study, we have compared a group of individuals with occupational exposure to ACR (contact group, n = 65) with a group of individuals with no exposure (non-contact group, n = 60). Serum metabolomics analysis of the contact and non-contact groups was carried out using ultra performance liquid chromatograph/time of flight mass spectrometry, combined with multivariate analysis, to identify potential metabolites. Serum biochemical indexes of the contact and non-contact groups were also determined using an automatic biochemistry analyzer. There was a clear separation between the contact group and the non-contact group; receiver operator characteristic curve analysis suggested that phytosphingosine, 4E,15Z-bilirubin IXa and tryptophan were the best metabolites to use as biomarkers. Liver function was also found to be abnormal in the contact group. Important, ACR-related, metabolic changes were seen in the contact group and new biomarkers for assessing the toxicity of ACR on the central nervous system have been proposed. This study will provide a sound basis for exploring the toxic mechanisms and metabolic pathways of ACR.

In Vivo acrylamide exposure may cause severe toxicity to mouse oocytes through its metabolite glycidamide

High acrylamide (ACR) content in heat-processed carbohydrate-rich foods, as well as roasted products such as coffee, almonds etc., has been found to be as a risk factor for carcinogenicity and genotoxicity by The World Health Organization. Glycidamide (GLY), the epoxide metabolite of ACR, is processed by the cytochrome P-450 enzyme system and has also been found to be a genotoxic agent. The aim of this study was to determine whether ACR and/or GLY have any detrimental effect on the meiotic cell division of oocytes. For this purpose, germinal vesicle-stage mouse oocytes were treated with 0, 100, 500, or 1000 μM ACR or 0, 25, or 250 μM GLY in vitro. In vivo experiments were performed after an intraperitoneal injection of 25 mg/kg/day ACR of female BALB/c mice for 7 days. The majority of in vitro ACR-treated oocytes reached the metaphase-II stage following 18 hours of incubation, which was not significantly different from the control group. Maturation of the oocytes derived from in vivo ACR-treated mice was impaired significantly. Oocytes, reaching the M-II stage in the in vivo ACR-treated group, were characterized by a decrease in meiotic spindle mass and an increase in chromosomal disruption. In vitro GLY treatment resulted in the degeneration of all oocytes, indicating that ACR toxicity on female germ cells may occur through its metabolite, GLY. Thus, ACR exposure must be considered, together with its metabolite GLY, when female fertility is concerned.

Therapeutic potential of quercetin against acrylamide induced toxicity in rats

Acrylamide (AA) is found in foods containing carbohydrates and proteins, where it is formed during the heating process. It is classified as neurotoxic and probably carcinogenic to humans. The present investigation was aimed to determine the lethal Dose (LD₅₀) of AA and to evaluate the protective effects of quercetin (QE) against AA induced adverse effects in rats. For the determination of LD₅₀, AA was administered orally at four different doses (46.4mg/kg, 100mg/kg, 215mg/kg and 464mg/kg) to experimental animals for seven days. After 7days LD₅₀ of AA was determined using graphical method of Miller and Tainter. Then AA was administered at 1/3rd dose of LD₅₀ (38.27mgkg^-1 body weight; p.o. for 10 days) followed by the therapy of QE (5, 10, 20 and 40mg kg^-1 orally), for 3 consecutive days for the determination of protective effect of QE against AA. The estimated LD₅₀ of AA was 114.81mg/kg with 95% confidence interval. Exposure to AA 1/3rd dose of LD₅₀ for 10days induced neurotoxicity which was confirmed by decreased acetylcholinesterase (AChE) activity. AA substantially increased lipid peroxidation (LPO), decreased the level of reduced glutathione (GSH) and antioxidant enzymes (SOD and CAT) in liver, kidney and brain. It also increased the activities of serum transaminases, urea, uric acid, creatinine, lipid profile, bilirubin in serum. Treatment with QE restored tissue and serological indices concomitantly towards normal levels. These results revealed that QE is able to significantly alleviate the toxicity induced by AA in rats.

Carcinogenicity of glycidamide in B6C3F1 mice and F344/N rats from a two-year drinking water exposure

Acrylamide is a contaminant in baked and fried starchy foods, roasted coffee, and cigarette smoke. Previously we reported that acrylamide is a multi-organ carcinogen in B6C3F1 mice and F344/N rats, and hypothesized that acrylamide is activated to an ultimate carcinogen through metabolism to the epoxide glycidamide. We have now examined the carcinogenic effects of glycidamide administered at 0, 0.0875, 0.175, 0.35 and 0.70 mM in drinking water to the same strains of rodents for two years. In male and female mice, there were significant increases in tumors of the Harderian gland, lung, forestomach, and skin. Female mice also had an increased incidence of tumors of the mammary gland and ovary. In male and female rats, there were significant increases in thyroid gland and oral cavity neoplasms and mononuclear cell leukemia. Male rats also had increases in tumors of the epididymis/testes and heart, while female rats demonstrated increases in tumors of the mammary gland, clitoral gland, and forestomach. A similar spectrum of tumors was obtained in mice and rats administered acrylamide. These data indicate that, under the conditions of these bioassays, acrylamide is efficiently metabolized to glycidamide and that the carcinogenic activity of acrylamide is due to its conversion into glycidamide.

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.

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.

Mouse spermatocytes express CYP2E1 and respond to acrylamide exposure

Metabolism of xenobiotics by cytochrome P450s (encoded by the CYP genes) often leads to bio-activation, producing reactive metabolites that interfere with cellular processes and cause DNA damage. In the testes, DNA damage induced by xenobiotics has been associated with impaired spermatogenesis and adverse effects on reproductive health. We previously reported that chronic exposure to the reproductive toxicant, acrylamide, produced high levels of DNA damage in spermatocytes of Swiss mice. CYP2E1 metabolises acrylamide to glycidamide, which, unlike acrylamide, readily forms adducts with DNA. Thus, to investigate the mechanisms of acrylamide toxicity in mouse male germ cells, we examined the expression of the CYP, CYP2E1, which metabolises acrylamide. Using Q-PCR and immunohistochemistry, we establish that CYP2E1 is expressed in germ cells, in particular in spermatocytes. Additionally, CYP2E1 gene expression was upregulated in these cells following in vitro acrylamide exposure (1 µM, 18 h). Spermatocytes were isolated and treated with 1 µM acrylamide or 0.5 µM glycidamide for 18 hours and the presence of DNA-adducts was investigated using the comet assay, modified to detect DNA-adducts. Both compounds produced significant levels of DNA damage in spermatocytes, with a greater response observed following glycidamide exposure. A modified comet assay indicated that direct adduction of DNA by glycidamide was a major source of DNA damage. Oxidative stress played a small role in eliciting this damage, as a relatively modest effect was found in a comet assay modified to detect oxidative adducts following glycidamide exposure, and glutathione levels remained unchanged following treatment with either compound. Our results indicate that the male germ line has the capacity to respond to xenobiotic exposure by inducing detoxifying enzymes, and the DNA damage elicited by acrylamide in male germ cells is likely due to the formation of glycidamide adducts.

The long-term effects of superovulation on fertility and sexual behavior of male offspring in mice

PURPOSE

To evaluate the long-term effects of superovulation on fertility and sexual behavior of male offspring in mice.

METHOD

The mice were superovaluted, and the fertility of male offspring (F1 generation and F2 generation) were evaluated in terms of the percentage of plugs and pregnancies, serum testosterone concentrations, and sperm motility. Furthermore, the sexual behavior of male offspring and sex ratio (F1 generation and F2 generation) were measured.

RESULTS

There were no significant differences in the percentage of plug and pregnancies, serum testosterone concentrations, sperm motilities and sex ratio between the offspring in naturally conceived group and superovulation groups (both F1 generation and F2 generation). The sperm hyperactivity at 90 min after incubation of F1 generation in naturally conceived group were higher than that of F1 generation in superovulation group, but the differences did not reach statistical significance. The offspring produced by superovaluted oocytes (both F1 generation and F2 generation) did not exhibit significant alterations in sexual behavior.

CONCLUSIONS

No significant alterations were found in fertility and sexual behavior of male offspring in mice produced by superovaluted oocytes compared with those of naturally conceived offspring.

Maternal acrylamide treatment reduces ovarian follicle number in newborn guinea pig offspring

Acrylamide is an industrial chemical which has toxic effects on reproduction. In this study, we investigated whether acrylamide administered prenatally can induce follicular atresia in the newborn guinea pig ovary. Another aim was to describe the localization of vimentin filaments and determine their participation in atresia. After prenatal acrylamide treatment, the pool of primordial and primary follicles was significantly reduced. The number of caspase 3 and TUNEL positive oocytes increased compared to the control group. There were no differences in Lamp1 (autophagy marker) staining. A vimentin immunosignal was present in the granulosa cells of primordial, primary and secondary follicles. Interestingly, in contrast to the control group, the oocytes from all follicles in the ACR-treated females were negative for vimentin. These data suggest that prenatal exposure to acrylamide reduced the number of ovarian follicles by inducing follicular atresia mediated by oocyte apoptosis. Acrylamide-induced apoptosis may be associated with destruction of vimentin filaments.

Ultra trace level determinations of acrylamide in surface and drinking water by GC-MS after derivatization with xanthydrol

A sensitive GC-MS method has been established for the determination of acrylamide in surface and drinking water based on derivatization with xanthydrol. Deuterated acrylamide (acrylamide-d3 ) was chosen as the internal standard for analyzing the water sample. The derivatization of acrylamide was performed directly in water, and the best reaction conditions (xanthydrol of 1.6 mM, HCl concentration of 0.05 M, reaction for 30 min at ambient temperature) were established by variation of parameters. Under the established conditions, the detection and quantification limits were 3.0 and 9.7 ng/L, respectively, and the interday RSD was less than 8% at concentrations of 20 and 100 ng/L.

Cytochrome P450 2E1: its clinical aspects and a brief perspective on the current research scenario

Research on Cytochrome P450 2E1 (CYP2E1), a key enzyme in alcohol metabolism has been very well documented in literature. Besides the involvement of CYP2E1 in alcohol metabolism as illustrated through the studies discussed in the chapter, recent studies have thrown light on several other aspects of CYP2E1 i.e. its extrahepatic expression, its involvement in several diseases and pathophysiological conditions; and CYP2E1 mediated carcinogenesis and modulation of drug efficacy. Studies involving these interesting facets of CYP2E1 have been discussed in the chapter focusing on the recent observations or ongoing studies illustrating the crucial role of CYP2E1 in disease development and drug metabolism.

Tumorigenicity of acrylamide and its metabolite glycidamide in the neonatal mouse bioassay

Acrylamide is a high-volume industrial chemical, a component of cigarette smoke, and a product formed in certain foods prepared at high temperatures. Previously, we compared the extent of DNA adduct formation and mutations in B6C3F(1) /Tk mice treated neonatally with acrylamide or glycidamide to obtain information concerning the mechanism of acrylamide genotoxicity. We have now examined the tumorigenicity of acrylamide and glycidamide in mice treated neonatally. Male B6C3F(1) mice were injected intraperitoneally on postnatal days 1, 8 and 15 with 0.0, 0.14 or 0.70 mmol acrylamide or glycidamide per kg body weight per day and the tumorigenicity was assessed after 1 year. Survival in each of the groups was >87%, there were no differences in body weights among the groups, and the only treatment-related neoplasms involved the liver. The incidence of combined hepatocellular adenoma or carcinoma was 3.8% in the control group, 8.3% in the 0.14 mmol acrylamide and glycidamide per kg body weight groups, 4.2% in the 0.70 mmol acrylamide per kg body weight group and 71.4% in the 0.70 mmol glycidamide per kg body weight group. Analysis of the hepatocellular tumors indicated that the increased incidence observed in mice administered 0.70 mmol glycidamide per kg body weight was associated with A → G and A → T mutations at codon 61 of H-ras. These results, combined with our previous data on DNA adduct formation and mutation induction, suggest that the carcinogenicity of acrylamide is dependent on its metabolism to glycidamide, a pathway that is deficient in neonatal mice.

Effect of acrylamide on some hormones and endocrine tissues in male rats

Acrylamide is oxidized by cytochrome P450 2E1 (CYP2E1) to its epoxide form, glycidamide, which is believed to be responsible for the mutagenic and carcinogenic activities. This study was carried out to investigate the early changes that may be related to the carcinogenic activity of acrylamide in thyroid, adrenal glands and testis in male rats. Forty adult Sprague Dawley male rats were divided equally into four groups, rats of Group I served as control, and rats of Groups II, III and IV were treated orally with acrylamide with doses 5, 10, 15 mg/kg/day body weight for 8 weeks. The results indicated that the plasma carcino embryonic antigen (CEA) and malondialdehyde (MDA) levels are higher, but free and total testosterone, triiodothyronine (T3) and thyroxine, or 3,5,3′,5′-tetraiodothyronine (T4) and corticosterone levels are lower in rats treated with acrylamide than that in control rats. This study provides evidence of endocrine disturbance to the testis, thyroid and adrenal glands, which are also the organs in which acrylamide has been shown to cause tumors in experimental animals.

Toxicological effects of acrylamide on the reproductive system of weaning male rats

It has been reported that acrylamide can be detected in starchy food treated by high temperature (120 °C). People could be exposed to acrylamide in factory, laboratory, or even in daily life via diet and drinking water. Recently, the toxicity of acrylamide receives more attention. In addition to the neurotoxicity in humans, other toxic effects of acrylamide are worth further investigation. In this study, we investigated whether acrylamide affected the male reproductive system using high-performance liquid chromatography. In this study, the reproductive toxicity of acrylamide was observed in 3-week-old weaning male Sprague-Dawley rats treated with acrylamide at various doses (0, 5, 15 or 30 mg/kg/day). The results showed that food availability and reproductive organ indexes of the weaning male rats decreased. Levels of follicle-stimulating hormone and testosterone in serum increased while luteinizing hormone in serum decreased. The histopathological lesions and abnormal sperms presented in weaning rats after acrylamide treatment. The results suggested that there is a toxicological effect of acrylamide on the reproductive system of weaning male rats. Based on the findings above, we suggested that more attention should be paid to the toxicological study of acrylamide on weaning male rats or human beings, rather than just on adult male animals.

Genotoxicity of acrylamide in vitro: Acrylamide is not metabolically activated in standard in vitro systems

The recent finding that acrylamide (AA), a genotoxic rodent carcinogen, is formed during the frying or baking of a variety of foods raises human health concerns. AA is known to be metabolized by cytochrome P450 2E1 (CYP2E1) to glycidamide (GA), which is responsible for AA's in vivo genotoxicity and probable carcinogenicity. In in-vitro mammalian cell tests, however, AA genotoxicity is not enhanced by rat liver S9 or a human liver microsomal fraction. In an attempt to demonstrate the in vitro expression of AA genotoxicity, we employed Salmonella strains and human cell lines that overexpress human CYP2E1. In the umu test, however, AA was not genotoxic in the CYP2E1-expressing Salmonella strain or its parental strain. Moreover, a transgenic human lymphoblastoid cell line overexpressing CYP2E1 (h2E1v2) and its parental cell line (AHH-1) both showed equally weak cytotoxic and genotoxic responses to high (>1 mM) AA concentrations. The DNA adduct N7-GA-Gua, which is detected in liver following AA treatment in vivo, was not substantially formed in the in vitro system. These results indicate that AA was not metabolically activated to GA in vitro. Thus, AA is not relevantly genotoxic in vitro, although its in vivo genotoxicity was clearly demonstrated.

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.

Mutagenicity of acrylamide and glycidamide in the testes of big blue mice

Acrylamide (AA) is an industrial chemical, a by-product of fried starchy foods, and a mutagen and rodent carcinogen. It can also cause damage during spermatogenesis. In this study, we investigated whether AA and its metabolite glycidamide (GA) induce mutagenic effects in the germ cells of male mice. Male Big Blue transgenic mice were administered 1.4 or 7.0mM of AA or GA in the drinking water for up to 4 weeks. Testicular cII mutant frequency (MF) was determined 3 weeks after the last treatment, and the types of the mutations in the cII gene were analyzed by DNA sequencing. The testes cII MFs in mice treated with either the low or high exposure concentrations of AA and GA were increased significantly. There was no significant difference in the cII MFs between AA and GA at the low exposure concentration. The mutation spectra in mice treated with AA (1.4mM) or GA (both 1.4 and 7.0mM) differed significantly from those of controls, but there were no significant differences in mutation patterns between AA and GA treatments. Comparison of the mutation spectra between testes and livers showed that the spectra differed significantly between the two tissues following treatment with AA or GA, whereas the mutation spectra in the two tissues from control mice were similar. These results suggest that AA possesses mutagenic effects on testes by virtue of its metabolism to GA, possibly targeting spermatogonial stem cells, but possibly via different pathways when compared mutations in liver.

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.

Exposure of the U.S. population to acrylamide in the National Health and Nutrition Examination Survey 2003-2004

BACKGROUND

The lifelong exposure of the population to acrylamide has raised concerns about the possible health effects of the chemical. Data on the extent of exposure to acrylamide and its primary metabolite, glycidamide, are needed to aid in the assessment of potential health effects.

OBJECTIVES

The aim of this study was to assess human exposure to acrylamide and glycidamide in the general U.S. population through the measurement of hemoglobin adducts of acrylamide (HbAA) and glycidamide (HbGA).

METHODS

HbAA and HbGA were measured in 7,166 subjects from the National Health and Nutrition Examination Survey. Stratified HbAA and HbGA data were reported by sex, age groups, race/ethnicity (Mexican American, non-Hispanic black, non-Hispanic white), and smoking status based on serum cotinine levels. Covariate-adjusted geometric means for each demographic group were calculated using multiple regression analysis.

RESULTS

HbAA and HbGA levels ranged from 3 to 910 and from 4 to 756 pmol/g hemoglobin, respectively, with smokers having the highest levels overall. Tobacco smoke exposure in nonsmokers had a small but significant effect on HbAA and HbGA levels. Adjusted geometric mean levels for children 311 years of age were higher than for adults >or= 60 years of age [mean (95% confidence interval): HbAA, 54.5 (49.1-51.5) and HbGA, 73.9 (71.3-76.6) vs. HbAA, 46.2 (44.3-48.2) and HbGA, 41.8 (38.7-45.2)]. Levels were highest in Mexican Americans [HbAA: 54.8 (51.9-57.8), HbGA: 57.9 (53.7-62.5)], whereas non-Hispanic blacks had the lowest HbGA levels [43.5 (41.1-45.9)].

CONCLUSIONS

U.S. population levels of acrylamide and glycidamide adducts are described. The high variability among individuals but modest differences between population subgroups suggest that sex, age, and race/ethnicity do not strongly affect acrylamide exposure. Adduct concentration data can be used to estimate relative exposure and to validate intake estimates.

Diet-induced obesity in male mice is associated with reduced fertility and potentiation of acrylamide-induced reproductive toxicity

The prevalence of human obesity and related chronic disorders such as diabetes, cardiovascular diseases, and cancer is rapidly increasing. Human studies have shown a direct relationship between obesity and infertility. The objective of the current work was to examine the effect of diet-induced obesity on male fertility and the effect of obesity on susceptibility to chemical-induced reproductive toxicity. From 5 to 30 wk of age, genetically intact male C57Bl/6J mice were fed a normal diet or one in which 60% of the kilocalories were from lard. Obese mice exhibited significant differences in the mRNA of several genes within the testes in comparison to lean males. Pparg was increased 2.2-fold, whereas Crem, Sh2b1, Dhh, Igf1, and Lepr were decreased 6.7, 1.4, 3.2, 1.6, and 7.2-fold, respectively. The fertility of male mice was compared through mating with control females. Acrylamide (AA)-induced reproductive toxicity was assessed in obese or lean males treated with water or 25 mg AA kg(-1) day(-1) via gavage for 5 days and then mated to control females. Percent body fat and weight were significantly increased in mice fed a high-fat vs. a normal diet. Obesity resulted in significant reduction in plugs and pregnancies of control females partnered with obese vs. lean males. Serum leptin and insulin levels were each approximately 5-fold higher in obese vs. age-matched lean mice. Sperm from obese males exhibited decreased motility and reduced hyperactivated progression vs. lean mice. Treatment with AA exacerbated male infertility of obese and lean mice; however, this effect was more pronounced in obese mice. Further, females partnered with AA-treated obese mice exhibited a further decrease in the percentage of live fetuses, whereas the percentage of resorptions increased. This work demonstrated that diet-induced obesity in mice caused a significant reduction in male fertility and exacerbated AA-induced reproductive toxicity and germ cell mutagenicity.

Human exposure to selected animal neurocarcinogens: a biomarker-based assessment and implications for brain tumor epidemiology

This review is based on the proceedings from the Second Lebow Conference, held in Chicago in 2007. The conference concentrated on developing a framework for innovative studies in the epidemiology of environmental exposures, focusing specifically on the potential relationship with brain tumors. Researchers with different perspectives, including toxicology, pharmacokinetics, and epidemiological exposure assessment, exchanged information and ideas on the use of biomarkers of exposure in molecular epidemiology studies and summarized the current knowledge on methods and approaches for biomarker-based exposure assessment. This report presents the state of science regarding biomarker-based exposure assessment of the four most common neurocarcinogens: acrylamide, 1,3-butadiene, N-nitroso compounds, and polycyclic aromatic hydrocarbons. Importantly, these chemicals are also carcinogenic in other organs; therefore, this discussion is useful for environmental epidemiologists studying all cancer types.