Acrylonitrile's genotoxicity profile: mutagenicity in search of an underlying molecular mechanism.

Acrylonitrile (ACN) is a known rodent and possible human carcinogen. There have also been concerns as to it causing adverse reproductive health effects. Numerous genotoxicity studies at the somatic level in a variety of test systems have demonstrated ACN's mutagenicity; its potential to induce mutations in germ cells has also been evaluated. ACN is metabolized to reactive intermediates capable of forming adducts with macromolecules including DNA, a necessary first step in establishing a direct mutagenic mode of action (MOA) for its carcinogenicity. The mutagenicity of ACN has been well demonstrated, however, numerous studies have found no evidence for the capacity of ACN to induce direct DNA lesions that initiate the mutagenic process. Although ACN and its oxidative metabolite (2-cyanoethylene oxide or CNEO) have been shown to bind in vitro with isolated DNA and associated proteins, usually under non-physiological conditions, studies in mammalian cells or in vivo have provided little specification as to an ACN-DNA reaction. Only one early study in rats has shown an ACN/CNEO DNA adduct in liver, a non-target tissue for its carcinogenicity in the rat. By contrast, numerous studies have shown that ACN can act indirectly to induce at least one DNA adduct by forming reactive oxygen species (ROS) in vivo, but it has not been definitively shown that the resulting DNA damage is causative for the induction of mutations. Genotoxicity studies for ACN in somatic and germinal cells are summarized and critically reviewed. Significant data gaps have been identified for bringing together the massive data base that provides the basis of ACN's current genotoxicity profile.

Acrylonitrile butadiene styrene microplastics aggravate the threat of decabromodiphenyl ethane to Eisenia fetida: Bioaccumulation, tissue damage, and transcriptional responses.

Little is known about how brominated flame retardants (NBFRs) and microplastics (MPs) co-pollution influences soil organisms. Here, we investigated the impacts of acrylonitrile butadiene styrene (ABS)-MPs in soil on the 28-d dynamic bioaccumulation, tissue damage, and transcriptional responses of decabromodiphenyl ethane (DBDPE) in Eisenia fetida by simulating different pollution scenarios (10 mg kg-1 DBDPE, 10 mg kg-1 DBDPE accompanied by 0.1 % ABS-MPs, and 10 mg kg-1 DBDPE accompanied by 0.1 % ABS-resin). The results show ABS resin did not influence DBDPE bioaccumulation or distribution, but ABS-MPs, particularly 74-187 µm size of MPs, prolonged DBDPE equilibrium time and significantly promoted DBDPE bioaccumulation in tissue (1.76-2.38 folds) and epidermis (2.72-3.34 folds). However, ABS-MPs and ABS-resin reduced DBDPE concentrations of intestines by 22.2-30.6 % and 37.3 %, respectively. DBDPE-MPs caused more serious epidermis and intestines damages than DBDPE. Additionally, compared to the control, DBDPE significantly up-regulated 1957 genes and down-regulated 2203 genes; meanwhile, DBDPE-MPs up-regulated 1475 genes and down-regulated 2231 genes. DBDPE and DBDPE-MPs both regulated lysosome, phagosome, and apoptosis as the top 3 enriched pathways, while DBDPE-MPs specifically regulated signaling pathways and compound metabolism. This study demonstrated that the presence of ABS-MPs aggravated the biotoxicity of DBDPE, providing scientific information for assessing the ecological risks of MPs and additives from e-waste in soil.

Quantitative risk assessment of respiratory exposure to acrylonitrile vapor in petrochemical industry by U.S. Environmental Protection Agency method: a cross-sectional study.

Acrylonitrile is a potential carcinogen for humans, and exposure to this substance can cause adverse effects for workers. This study aimed to carcinogenic and health risk assessment of acrylonitrile vapor exposure in exposed personnel of a petrochemical complex. This crosssectional study was performed in 2019 in a petrochemical complex. In this study, to sample and determine acrylonitrile's respiratory exposure, the method provided by the National Institute of Occupational Safety and Health (NIOSH 1601) was used, and a total of 45 inhaled air samples were sampled from men workers, aged 39.43 ± 9.37 years. All subjects' mean exposure to acrylonitrile vapors was 71.1 ± 122.8 µg/m3. Also, the mean exposure index among all subjects was 0.02 ± 0.034. The non-carcinogenic risk assessment results showed that the mean Hazard quotient index was 4.04 ± 6.93. The mean lifetime cancer risk index was also 2.1 × 10-3 ± 3.5 × 10-3 and was in the definite risk range. Considering that both carcinogenicity and health indicators of exposure to acrylonitrile in the studied petrochemical complex are more than the recommended limits, the necessary engineering and management measures to control and manage the risk to an acceptable level are essential to improving the worker's health.

Study of urinary mercapturic acids as biomarkers of human acrylonitrile exposure.

Exposure to the vinyl monomer acrylonitrile (AN) is primarily occupational. AN is also found in cigarette smoke. AN can be detoxified to form N-acetyl-S-(2-cyanoethyl)-cysteine (CEMA) or activated to 2-cyanoethylene oxide (CEO) and detoxified to form N-acetyl-S-(1-cyano-2-hydroxyethyl)-cysteine (CHEMA) and N-acetyl-S-(2-hydroxyethyl)-cysteine (HEMA). These urinary mercapturic acids (MAs) are considered to be potential biomarkers of AN exposure. This study assessed personal AN exposure, urinary MAs (CEMA, CHEMA, and HEMA), and cotinine (a biomarker of cigarette smoke) in 80 AN-exposed and 23 non-exposed factory workers from urine samples provided before and after work shifts. Unambiguous linear correlations were observed between levels of urinary CEMA and CHEMA with personal AN exposures, indicating their potential as chemically-specific biomarkers for AN exposures. AN exposure was the dominant factor in MA formation for AN-exposed workers, whereas urinary cotinine used as a biomarker showed that cigarette smoke exposure was the primary factor for non-exposed workers. The CHEMA/CEMA and (CHEMA+HEMA)/CEMA ratios in this human study differ from those in similar studies of AN-treated rats and mice in literature, suggesting a possible dose- and species-dependent effect in AN metabolic activation and detoxification.

Evaluation of Pulmonary Effects of 3-D Printer Emissions From Acrylonitrile Butadiene Styrene Using an Air-Liquid Interface Model of Primary Normal Human-Derived Bronchial Epithelial Cells.

This study investigated the inhalation toxicity of the emissions from 3-D printing with acrylonitrile butadiene styrene (ABS) filament using an air-liquid interface (ALI) in vitro model. Primary normal human-derived bronchial epithelial cells (NHBEs) were exposed to ABS filament emissions in an ALI for 4 hours. The mean and mode diameters of ABS emitted particles in the medium were 175 ± 24 and 153 ± 15 nm, respectively. The average particle deposition per surface area of the epithelium was 2.29 × 107 ± 1.47 × 107 particle/cm2, equivalent to an estimated average particle mass of 0.144 ± 0.042 µg/cm2. Results showed exposure of NHBEs to ABS emissions did not significantly affect epithelium integrity, ciliation, mucus production, nor induce cytotoxicity. At 24 hours after the exposure, significant increases in the pro-inflammatory markers IL-12p70, IL-13, IL-15, IFN-γ, TNF-α, IL-17A, VEGF, MCP-1, and MIP-1α were noted in the basolateral cell culture medium of ABS-exposed cells compared to non-exposed chamber control cells. Results obtained from this study correspond with those from our previous in vivo studies, indicating that the increase in inflammatory mediators occur without associated membrane damage. The combination of the exposure chamber and the ALI-based model is promising for assessing 3-D printer emission-induced toxicity.

Acrylonitrile exposure triggers ovarian inflammation and decreases oocyte quality probably via mitochondrial dysfunction induced apoptosis in mice.

Acrylonitrile is an organic chemical synthetic monomer that is widely used in food packaging and manufacturing. Animal studies have reported that acrylonitrile is carcinogenic and toxic, but the effects on the female reproductive function in mammals are unknown. In the present study, we report that acrylonitrile treatment affects ovarian homeostasis in mice, resulting in impaired follicular development. Follicles in acrylonitrile-exposed mice exhibited high levels of inflammation and apoptosis, and acrylonitrile treatment interfered with oocyte development. Transcriptomics analysis showed that acrylonitrile altered the expression of oocyte genes related to apoptosis, oxidative stress, endoplasmic reticulum stress, and autophagy. Further molecular tests revealed that acrylonitrile induced early apoptosis, DNA damage, elevated levels of reactive oxygen species, endoplasmic reticulum abnormalities, and lysosomal aggregation. We also observed disruption of mitochondrial structure and distribution and depolarization of membrane potential. Finally, acrylonitrile treatment in female mice decreased the number and weight of offspring. Altogether, these findings suggest that acrylonitrile impairs the stability of the ovarian internal environment, which in turn affects oocyte development and reduces the number of offspring.

Acute acrylonitrile exposure inhibits endogenous H2S biosynthesis in rat brain and liver: The role of CBS/3-MPST-H2S pathway in its astrocytic toxicity.

Hydrogen sulfide (H2S) as the third gasotransmitter molecule serves various biological regulatory roles in health and disease. Acrylonitrile (AN) is a common occupational toxicant and environmental pollutant, causing brain and liver damage in mammals. The biotransformation of AN is dependent-upon reduced glutathione (GSH), cysteine and other sulfur-containing compounds. However, the effects of AN on the endogenous H2S biosynthesis pathway have yet to be determined. Herein, we demonstrated that a single exposure to AN (at 25, 50, or 75 mg/kg for 1, 6 or 24 h) decreased the endogenous H2S content and H2S-producing capacity in a dose-dependent manner, both in the cerebral cortex and liver of rats in vivo. In addition, the inhibitory effects of AN (1, 2.5, 5, 10 mM for 12 h) on the H2S content and/or the expression of H2S-producing enzymes were also found both in primary rat astrocytes and rat liver cell line (BRL cells). Impairment in the H2S biosynthesis pathway was also assessed in primary rat astrocytes treated with AN. It was found that inhibition of the cystathionine-ß-synthase (CBS)/3-mercaptopyruvate sulfurtransferase (3-MPST)-H2S pathway with the CBS inhibitor or 3-MPST-targeted siRNA significantly increased the AN-induced (5 mM for 12 h) cytotoxicity in astrocytes. In turn, CBS activation or 3-MPST overexpression as well as exogenous NaHS supplementation significantly attenuated AN-induced cytotoxicity. Taken together, endogenous H2S biosynthesis pathway was disrupted in rats acutely exposed to AN, which contributes to acute AN neurotoxicity in primary rat astrocytes.

Acrylonitrile induced cell cycle arrest and apoptosis by promoting the formation of reactive oxygen species in human choriocarcinoma cells.

Acrylonitrile (AN), which is widely utilized in the manufacture of plastics, acrylamide, acrylic fibers, and resins, is also one of main components of cigarette smoke (CS). In this study, we examined the effects of AN on the cell viability and apoptosis of JEG-3 and BeWo human choriocarcinoma cancer cell lines. A cell viability assay confirmed that AN decreased the cell proliferation of JEG-3 and BeWo cells in a dose-dependent manner. Additionally, Western blot assay revealed that protein expression of cyclin D and cyclin E decreased, while protein expression of p21 and p27 increased in response to AN treatment for 48 hr. The changes in reactive oxygen species (ROS) levels in JEG-3 and BeWo cells exposed to AN were also measured by a dichlorofluorescein diacetate (DCFH-DA) assay, which revealed that ROS levels increased in response to AN treatment for 48 hr. Moreover, western blot assay confirmed that AN treatment of JEG-3 and BeWo cells for 4 hr promoted the expression of phosphorylated eukaryotic initiation factor 2 alpha protein (p-eIF2α), C/EBP homologous protein (CHOP) and caspase 12, which are known to be involved in ROS-mediated endoplasmic reticulum stress (ER-stress)-related apoptosis. Overall, the protein expression of p53 and Bax (a pro-apoptosis marker) increased, while the expression of Bcl-xl (an anti-apoptotic marker) decreased and the number of apoptotic cells increased in response to AN treatment for 48 hr. Taken together, these results suggest that AN has the potential to induce apoptosis of JEG-3 and BeWo human choriocarcinoma cancer cells by activating ROS.

Analysis of DNA Adducts and Mutagenic Potency and Specificity in Rats Exposed to Acrylonitrile.

Acrylonitrile (ACN), which is a widely used industrial chemical, induces cancers in multiple organs/tissues of rats by unresolved mechanisms. For this report, evidence for ACN-induced direct/indirect DNA damage and mutagenesis was investigated by assessing the ability of ACN, or its reactive metabolite, 2-cyanoethylene oxide (CEO), to bind to DNA in vitro, to form select DNA adducts [N7-(2'-oxoethyl)guanine, N2,3-ethenoguanine, 1,N6-ethenodeoxyadenosine, and 3,N4-ethenodeoxycytidine] in vitro and/or in vivo, and to perturb the frequency and spectra of mutations in the hypoxanthine-guanine phosphoribosyltransferase (Hprt) gene in rats exposed to ACN in drinking water. Adducts and frequencies and spectra of Hprt mutations were analyzed using published methods. Treatment of DNA from human TK6 lymphoblastoid cells with [2,3-14C]-CEO produced dose-dependent binding of 14C-CEO equivalents, and treatment of DNA from control rat brain/liver with CEO induced dose-related formation of N7-(2'-oxoethyl)guanine. No etheno-DNA adducts were detected in target tissues (brain and forestomach) or nontarget tissues (liver and spleen) in rats exposed to 0, 3, 10, 33, 100, or 300 ppm ACN for up to 105 days or to 0 or 500 ppm ACN for ∼15 months; whereas N7-(2'-oxoethyl)guanine was consistently measured at nonsignificant concentrations near the assay detection limit only in liver of animals exposed to 300 or 500 ppm ACN for ≥2 weeks. Significant dose-related increases in Hprt mutant frequencies occurred in T-lymphocytes from spleens of rats exposed to 33-500 ppm ACN for 4 weeks. Comparisons of "mutagenic potency estimates" for control rats versus rats exposed to 500 ppm ACN for 4 weeks to analogous data from rats/mice treated at a similar age with N-ethyl-N-nitrosourea or 1,3-butadiene suggest that ACN has relatively limited mutagenic effects in rats. Considerable overlap between the sites and types of mutations in ACN-exposed rats and butadiene-exposed rats/mice, but not controls, provides evidence that the carcinogenicity of these epoxide-forming chemicals involves corresponding mutagenic mechanisms.

Analysis of Biomarkers of DNA Damage and Mutagenicity in Mice Exposed to Acrylonitrile.

Acrylonitrile (ACN), which is a widely used industrial chemical, induces cancers in the mouse via unresolved mechanisms. For this report, complementary and previously described methods were used to assess in vivo genotoxicity and/or mutagenicity of ACN in several mouse models, including (i) female mice devoid of cytochrome P450 2E1 (CYP2E1), which yields the epoxide intermediate cyanoethylene oxide (CEO), (ii) male lacZ transgenic mice, and (iii) female (wild-type) B6C3F1 mice. Exposures of wild-type mice and CYP2E1-null mice to ACN at 0, 2.5 (wild-type mice only), 10, 20, or 60 (CYP2E1-null mice only) mg/kg body weight by gavage for 6 weeks (5 days/week) produced no elevations in the frequencies of micronucleated erythrocytes, but induced significant dose-dependent increases in DNA damage, detected by the alkaline (pH >13) Comet assay, in one target tissue (forestomach) and one nontarget tissue (liver) of wild-type mice only. ACN exposures by gavage also caused significant dose-related elevations in the frequencies of mutations in the hypoxanthine-guanine phosphoribosyltransferase (Hprt) reporter gene of T-lymphocytes from spleens of wild-type mice; however, Hprt mutant frequencies were significantly increased in CYP2E1-null mice only at a high dose of ACN (60 mg/kg) that is lethal to wild-type mice. Similarly, drinking water exposures of lacZ transgenic mice to 0, 100, 500, or 750 ppm ACN for 4 weeks caused significant dose-dependent elevations in Hprt mutant frequencies in splenic T-cells; however, these ACN exposures did not increase the frequency of lacZ transgene mutations above spontaneous background levels in several tissues from the same animals. Together, the Comet assay and Hprt mutant frequency data from these studies indicate that oxidative metabolism of ACN by CYP2E1 to CEO is central to the induction of the majority of DNA damage and mutations in ACN-exposed mice, but ACN itself also may contribute to the carcinogenic modes of action via mechanisms involving direct and/or indirect DNA reactivity.

Extended Mortality Follow-up of a Cohort of 25,460 Workers Exposed to Acrylonitrile.

We extended the mortality follow-up of a cohort of 25,460 workers employed at 8 acrylonitrile (AN)-producing facilities in the United States by 21 years. Using 8,124 deaths and 1,023,922 person-years of follow-up, we evaluated the relationship between occupational AN exposure and death. Standardized mortality ratios (SMRs) based on deaths through December 31, 2011, were calculated. Work histories and monitoring data were used to develop quantitative estimates of AN exposure. Hazard ratios were estimated by Cox proportional hazards regression. All-cause mortality and death from total cancer were less than expected compared with the US population. We observed an excess of death due to mesothelioma (SMR = 2.24, 95% confidence interval (CI): 1.39, 3.42); no other SMRs were elevated overall. Cox regression analyses revealed an elevated risk of lung and bronchial cancer (n = 808 deaths; for >12.1 ppm-year vs. unexposed, hazard ratio (HR) = 1.43, 95% CI: 1.13, 1.81; P for trend = 0.05), lagged 10 years, that was robust in sensitivity analyses adjusted for smoking and co-exposures including asbestos. Death resulting from bladder cancer (for >2.56 ppm vs. unexposed, lagged 10-year HR = 2.96, 95% CI: 1.38, 6.34; P for trend = 0.02) and pneumonitis (for >3.12 ppm-year vs. unexposed, HR = 4.73, 95% CI: 1.42, 15.76; P for trend = 0.007) was also associated with AN exposure. We provide additional evidence of an association between AN exposure and lung cancer, as well as possible increased risk for death due to bladder cancer and pneumonitis.

Activation of autophagic flux and the Nrf2/ARE signaling pathway by hydrogen sulfide protects against acrylonitrile-induced neurotoxicity in primary rat astrocytes.

Hydrogen sulfide (H2S), the third gasotransmitter, has been shown to act as a neuroprotective factor in numerous pathological processes; however, its underlying mechanism(s) of action remain unclear. It is widely accepted that activation of moderate autophagy and the Nrf2/ARE signaling pathway play important roles in the biological self-defense systems. In the present study, we investigated whether exogenous H2S protects against the cytotoxicity of acrylonitrile (AN), a neurotoxin, in primary rat astrocytes. We found that pretreatment for 1 h with sodium hydrosulfide (NaHS), a donor of H2S (200-800 µM), significantly attenuated the AN-induced decrease in cell viability, increase in lactate dehydrogenase release and morphological changes. Furthermore, NaHS significantly attenuated AN-induced oxidative stress by reducing reactive oxygen species (ROS) levels and increasing glutathione (GSH) concentration. Moreover, NaHS activated the autophagic flux, detectable as a change in autophagy-related proteins (Beclin-1, Atg5 and p62), the formation of acidic vesicular organelles and LC3B aggregation, confirmed by adenoviral expression of mRFP-GFP-LC3. Additionally, NaHS stimulated translocation of Nrf2 into the nucleus and increased expression of heme oxygenase-1 and γ-glutamylcysteine synthetase, downstream targets of Nrf2. Notably, the autophagy inhibitor 3-methyladenine and Beclin-1, or Nrf2-targeted siRNA, significantly attenuated the neuroprotective effects of NaHS against AN-induced neurotoxicity. In conclusion, we identified a crucial role of  autophagy and the Nrf2/ARE signaling pathway in H2S-mediated neuroprotection against AN-induced toxicity in primary rat astrocytes. Our findings provide novel insights into the mechanisms of H2S-mediated neuroprotection, and suggest that H2S-based donors may serve as potential new candidate drugs to treat AN-induced neurotoxicity.

Protective effects of apigenin against acrylonitrile-induced subchronic sperm injury in rats.

This study aimed to investigate the protective effects of apigenin (AP), a flavonoid found in plants, against acrylonitrile (ACN)-induced subchronic sperm and testes injury in rats. Male Sprague-Dawley rats were randomly divided into four groups: a control group (corn oil), an ACN group (ACN 50 mg kg-1), an ACN + AP1 group (ACN + AP 234 mg kg-1), and an ACN + AP2 group (ACN + AP 468 mg kg-1). The ACN + AP group received AP by gavage after treatment with 50 mg kg-1 ACN for 30 min, whereas the rats in the control group were given an equivalent volume of corn oil. The gavage was conducted 6 days per week for 12 weeks. The results showed that AP increased the sperm concentration, motility, and mitochondrial membrane potential (MMP) (P < 0.05), which were reduced by ACN. Conversely, reactive oxygen species (ROS) and malondialdehyde (MDA) were significantly decreased by AP (P < 0.05). AP improved the damage of the ultrastructure of sperm caused by ACN. AP reduced the pathological injuries and spermatogenic cell apoptosis caused by ACN in rat testes. AP also increased glutathione peroxidase activity and decreased MDA content. In conclusion, AP reduces ACN-induced decreasing sperm quality by inhibition of inflammation and oxidative stress.

Preconditioning of endoplasmic reticulum stress protects against acrylonitrile-induced cytotoxicity in primary rat astrocytes: The role of autophagy.

This study explored the protective effects of endoplasmic reticulum (ER) stress preconditioning induced by 2-deoxy-d-glucose (2-DG) or oxidized dithiothreitol (DTTox) on acrylonitrile (AN)-induced cytotocity in primary rat astrocytes. Cells were pretreated with 2-DG or DTTox for different times at various concentration. Next, astrocytes were treated with 2.5mM AN for an additional 12h. Cell viability and cytotoxicity were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction and lactate dehydrogenase (LDH) leakage, respectively. Reactive oxygen species (ROS) and mitochondrial membrane potential (ΔΨm) were determined. Expression of glucose-regulated protein 78 (GRP78), phosphorylated-eukaryotic translation initiation factor 2α (p-eIF2α), microtubule-associated protein light chain 3 (LC3), P62, and Beclin1 were used to assess autophagy. In addition, 3-methyadenine (3-MA), an autophagy-specific inhibitor, was used to assess the role of autophagy in ER stress preconditioning-induced protection against AN cytotoxicity. The results showed that AN alone significantly decreased astrocytic viability and enhanced cytotoxicity. Compared to the AN-alone group, preconditioning with 2-DG or DTTox significantly increased cell viability and reduced cytotoxicity to indistinguishable levels. Decreased ROS generation and increased ΔΨm were also inherent to ER stress preconditioning with these compounds. Furthermore, autophagy was activated by both 2-DG and DTTox. Blockage of autophagy attenuated the protection afforded by 2-DG or DTTox preconditioning in AN-treated astrocytes. These results establish that ER stress preconditioning affords cellular protection against AN, and that activation of autophagy mediates the cytoprotection. Modulation of ER stress and resultant activation of autophagy may be a novel target for to ameliorate AN toxicity.

Short-term health effects in the general population following a major train accident with acrylonitrile in Belgium.

BACKGROUND: Following a train derailment, several tons of acrylonitrile (ACN) exploded, inflamed and part of the ACN ended up in the sewage system of the village of Wetteren. More than 2000 residents living in the close vicinity of the accident and along the sewage system were evacuated. A human biomonitoring study of the adduct N-2-cyanoethylvaline (CEV) was carried out days 14-21 after the accident. OBJECTIVES: (1) To describe the short-term health effects that were reported by the evacuated residents following the train accident, and (2) to explore the association between the CEV concentrations, extrapolated at the time of the accident, and the self-reported short-term health effects. METHODS: Short-term health effects were reported in a questionnaire (n=191). An omnibus test of independence was used to investigate the association between the CEV concentrations and the symptoms. Dose-response relationships were quantified by Generalized Additive Models (GAMs). RESULTS: The most frequently reported symptoms were local symptoms of irritation. In non-smokers, dose-dependency was observed between the CEV levels and the self-reporting of irritation (p=0.007) and nausea (p=0.007). Almost all non-smokers with CEV concentrations above 100pmol/g globin reported irritation symptoms. Both absence and presence of symptoms was reported by non-smokers with CEV concentrations below the reference value and up to 10 times the reference value. Residents who visited the emergency services reported more symptoms. This trend was seen for the whole range of CEV concentrations, and thus independently of the dose. DISCUSSION AND CONCLUSION: The present study is one of the first to relate exposure levels to a chemical released during a chemical incident to short-term (self-reported) health effects. A dose-response relation was observed between the CEV concentrations and the reporting of short-term health effects in the non-smokers. Overall, the value of self-reported symptoms to assess exposure showed to be limited. The results of this study confirm that a critical view should be taken when considering self-reported health complaints and that ideally biomarkers are monitored to allow an objective assessment of exposure.

Protective effects of antioxidants on acrylonitrile-induced oxidative stress in female F344 rats.

The induction of oxidative stress and damage appears to be involved in acrylonitrile induction of brain astrocytomas in rat. The present study examined the effects of dietary antioxidant supplementation on acrylonitrile-induced oxidative stress and oxidative damage in rats in vivo. To assess the effects of antioxidants on biomarkers of acrylonitrile-induced oxidative stress, female F344 rats were provided with diets containing vitamin E (0.05%), green tea polyphenols (GTP, 0.4%), N-acetyl cysteine (NAC, 0.3%), sodium selenite (0.1mg/kg), and taurine (10g/kg) for 7 days, and then co-administered with 0 and 100 ppm acrylonitrile in drinking water for 28 days. Significant increase in oxidative DNA damage in brain, evidenced by elevated 8OHdG levels, was seen in acrylonitrile-exposed rats. Supplementation with vitamin E, GTP, and NAC reduced acrylonitrile-induced oxidative DNA damage in brain while no protective effects were seen with the selenium or taurine supplementation. Acrylonitrile increased oxidative DNA damage, measured by the fpg-modified alkaline Comet assay in rat WBCs, which was reduced by supplementation of Vitamin E, GTP, NAC, selenium, and taurine. In addition to stimulation of oxidative DNA damage, acrylonitrile triggered induction of pro-inflammatory cytokines Tnfα, Il-1ß, and Ccl2, and the growth stimulatory cyclin D1 and cyclin D2 genes, which were effectively down-regulated with antioxidant treatment. Antioxidant treatment also was able to stimulate the pro-apoptotic genes Bad, Bax, and FasL and DNA repair genes Xrcc6 and Gadd45α. The results of this study support the involvement of oxidative stress in the development of acrylonitrile-induced astrocytomas and suggest that antioxidants block acrylonitrile-mediated damage through mechanisms that may involve in the suppression of inflammatory responses, inhibition of cell proliferation and stimulation of apoptosis. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1808-1818, 2016.

Differential protection of pre- versus post-treatment with curcumin, Trolox, and N-acetylcysteine against acrylonitrile-induced cytotoxicity in primary rat astrocytes.

OBJECTIVE: This study was designed to examine the differential protection of pre- versus post-treatment with three different antioxidants, curcumin (CUR), Trolox, and N-acetylcysteine (NAC), on acrylonitrile (AN)-induced cytotoxicity in primary rat astrocytes. METHODS: Primary astrocyte cultures were treated with CUR, Trolox and NAC for 4h prior to, or following 24h treatment with AN (2.5mM). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH) release, lipid peroxidation, glutathione, reactive oxygen species (ROS) and mitochondrial membrane potential were measured to evaluate protection associated with the three antioxidants. Knockdown of Nrf2 expression by liposome transfection with siRNA was used to confirm the role of Nrf2 activation in the protection associated with the three antioxidants. RESULTS: Compared with AN treatment alone, pre-treatment with CUR at either concentration significantly increased cell viability and mitochondrial membrane potential, and reduced glutathione levels; lipid peroxidation and ROS production were significantly decreased as well. NAC also showed significant efficacy in attenuating AN-induced toxicity at higher concentration. However, pre-treatment with Trolox failed to ameliorate the AN-induced toxicity. When post-treatment with Trolox, this antioxidant led to significant protective effects at both concentrations, while CUR and NAC were efficacious only at the higher concentrations. Knockdown of Nrf2 only abolished the protective effects of CUR pre-treatment on AN-induced cytotoxicity, while the protective effects of NAC and Trolox pre-treatment groups showed no differences between the Nrf2-knockdown and non-knockdown treatments. CONCLUSIONS: The selected antioxidants exert differential cellular protection when administered prior or subsequent to AN-induced cytotoxic events in decreasing cellular viability, antioxidative capacity and mitochondrial function, enhanced cytotoxicity and ROS production. These results suggest that antioxidants should be carefully chosen for their efficacy in preventing or diminishing oxidative damage caused by AN. The differential effect of pre- and post-treatment may be attributed to activation of the Nrf2 signaling pathway.

In vivo comet assay of acrylonitrile, 9-aminoacridine hydrochloride monohydrate and ethanol in rats.

As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the in vivo rat alkaline comet assay, we examined the ability of acrylonitrile, 9-aminoacridine hydrochloride monohydrate (9-AA), and ethanol to induce DNA damage in the liver and glandular stomach of male rats. Acrylonitrile is a genotoxic carcinogen, 9-AA is a genotoxic non-carcinogen, and ethanol is a non-genotoxic carcinogen. Positive results were obtained in the liver cells of male rats treated with known genotoxic compounds, acrylonitrile and 9-AA.

Mortality among chemical plant workers exposed to acrylonitrile: 2011 follow-up.

OBJECTIVES: To update a cohort study of chemical workers and reevaluate lung cancer mortality in relation to acrylonitrile (AN) exposure. METHODS: Subjects were 2096 workers employed during 1955 to 2011. We identified 474 deaths through 2011, and quantitatively estimated worker exposures to AN. Analyses included national and county-based standardized mortality ratios and relative risk regression of internal cohort rates. RESULTS: We found no statistically significant excess mortality risks associated with Lima employment for any cause of death category, including lung cancer and other cancer sites implicated in previous studies. CONCLUSIONS: This update provides no evidence that exposure to AN at levels experienced by Lima workers is associated with an increased risk of lung cancer mortality, as suggested in original study. Earlier reported bladder cancer risks decreased to a much lower, not statistically significant level.