Acrylonitrile-induced oxidative stress and oxidative DNA damage in male Sprague-Dawley rats

Cigarette Smoke-Induced Respiratory Response: Insights into Cellular Processes and Biomarkers

Cigarette smoke (CS) poses a significant risk factor for respiratory, vascular, and organ diseases owing to its high content of harmful chemicals and reactive oxygen species (ROS). These substances are known to induce oxidative stress, inflammation, apoptosis, and senescence due to their exposure to environmental pollutants and the presence of oxidative enzymes. The lung is particularly susceptible to oxidative stress. Persistent oxidative stress caused by chronic exposure to CS can lead to respiratory diseases such as chronic obstructive pulmonary disease (COPD), pulmonary fibrosis (PF), and lung cancer. Avoiding exposure to environmental pollutants, like cigarette smoke and air pollution, can help mitigate oxidative stress. A comprehensive understanding of oxidative stress and its impact on the lungs requires future research. This includes identifying strategies for preventing and treating lung diseases as well as investigating the underlying mechanisms behind oxidative stress. Thus, this review aims to investigate the cellular processes induced by CS, specifically inflammation, apoptosis, senescence, and their associated biomarkers. Furthermore, this review will delve into the alveolar response provoked by CS, emphasizing the roles of potential therapeutic target markers and strategies in inflammation and oxidative stress.

Low Level of Advanced Glycation End Products in Serum of Patients with Allergic Rhinitis and Chronic Epstein-Barr Virus Infection at Different Stages of Virus Persistence

Advanced glycation end products (AGEs) are formed in a nonenzymatic reaction of the reducing sugars with amino groups of proteins, lipids, and nucleic acids of different tissues and body fluids. A relatively small number of studies have been conducted on the role of AGEs in allergic inflammation. In this study, patients with allergic rhinitis (AR) were examined for the presence of Epstein-Barr virus and the content of fluorescent and nonfluorescent AGEs. We have also determined the level of a unique epitope (AGE10) which was recently identified in human serum using monoclonal antibodies against synthetic melibiose-derived AGE (MAGE). The levels of AGE10 determined with an immunoenzymatic method revealed no significant difference in the patients' blood with intermittent AR and chronic EBV persistence in the active and latent phases. It has been shown that there is a statistically significantly smaller amount of AGEs and pentosidine in groups of patients, both with and without viremia, than in healthy subjects. In turn, higher levels of immune complexes than of AGE10 were detected in the groups of patients, in contrast to the control group, which had lower levels of complexes than AGE10 concentration. In patients with active infection, there is even more complexes than of noncomplexed AGE10 antigen. The lower level of AGE in allergic rhinitis patient sera may also be due, besides complexes, to allergic inflammation continuously activating the cells, which effectively remove glycation products from the body.

Assessing cytochrome P450 function using genetically engineered mouse models

The ability to knock out and/or humanize different genes in experimental animals, globally or in cell- and tissue-specific patterns, has revolutionized scientific research in many areas. Genetically engineered mouse models, including knockout models, transgenic models, and humanized models, have played important roles in revealing the in vivo functions of various cytochrome P450 (CYP) enzymes. These functions are very diverse, ranging from the biotransformation of drugs and other xenobiotics, events that often dictate their pharmacokinetic or toxicokinetic properties and the associated therapeutic or adverse actions, to the metabolism of endogenous compounds, such as steroid hormones and other bioactive substances, that may determine susceptibility to many diseases, such as cancer and metabolic diseases. In this review, we provide a comprehensive list of Cyp-knockout, human CYP-transgenic, and CYP-humanized mouse models that target genes in the CYP1-4 gene families, and highlight their utility in assessing the in vivo metabolism, bioactivation, and toxicity of various xenobiotic compounds, including therapeutic agents and chemical carcinogens. We aim to showcase the advantages of utilizing these mouse models for in vivo drug metabolism and toxicology studies, and to encourage and facilitate greater utility of engineered mouse models to further improve our knowledge of the in vivo functions of various P450 enzymes, which is integral to our ability to develop safer and more effective therapeutics and to identify individuals predisposed to adverse drug reactions or environmental diseases.

Acrylonitrile induction of rodent neoplasia: Potential mechanism of action and relevance to humans

Acrylonitrile, an industrial chemical, is a multisite carcinogen in rats and mice, producing tumors in four tissues with barrier function, that is, brain, forestomach, Zymbal’s gland, and Harderian gland. To assess mechanism(s) of action (MoA) for induction of neoplasia and to evaluate whether the findings in rodents are indicative of human hazard, data on the potential key effects produced by acrylonitrile in the four rodent target tissues of carcinogenicity were evaluated. A notable finding was depletion of glutathione in various organs, including two target tissues, the brain, and forestomach, suggesting that this effect could be a critical initiating event. An additional combination of oxidative DNA damage and cytotoxic effects of acrylonitrile and its metabolites, cyanide, and 2-cyanoethylene oxide, could initiate pro-inflammatory signaling and sustained cell and tissue injury, leading to compensatory cell proliferation and neoplastic development. The in vivo DNA-binding and genotoxicity of acrylonitrile has been studied in several target tissues with no compelling positive results. Thus, while some mutagenic effects were reported in acrylonitrile-exposed rodents, data to determine whether this mutagenicity stems from direct DNA reactivity of acrylonitrile are insufficient. Accordingly, the induction of tumors in rodents is consistent primarily with a non-genotoxic MoA, although a contribution from weak mutagenicity cannot be ruled out. Mechanistic data to support conclusions regarding human hazard from acrylonitrile exposure is weak. Comparison of metabolism of acrylonitrile between rodents and humans provide little support for human hazard. Three of the tissues affected in bioassays (forestomach, Zymbal’s gland, and Harderian gland) are present only in rodents, while the brain is anatomically different between rodents and humans, diminishing relevance of tumor induction in these tissues to human hazard. Extensive epidemiological data has not revealed causation of human cancer by acrylonitrile.

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.

The role of the enzyme-modified comet assay in in vivo studies

The in vivo comet assay is an established genotoxicity test, with an OECD test guideline, but in its standard form it measures only DNA strand breaks. Including in the assay an additional step, in which the DNA is incubated with a lesion-specific enzyme, can provide important information about the nature of the DNA damage. Formamidopyrimidine DNA glycosylase, 8-oxoguanine DNA glycosylase or endonuclease III are commonly used in the in vitro genotoxicity test and in human biomonitoring to detect oxidised bases, but in vivo applications are rarer. A systematic literature search has identified a total of 60 papers that report such in vivo experiments, testing a variety of agents. In many cases, strand breaks were not seen, but significant levels of enzyme-sensitive sites were induced - indicating a mechanism of action involving oxidative stress. Compounds such as methyl methanesulfonate (MMS) or ethyl methanesulfonate (EMS) could be used as positive controls in both the standard and the enzyme-modified in vivo comet assays.

Airborne mammary carcinogens and breast cancer risk in the Sister Study

INTRODUCTION

Potentially carcinogenic hazardous air pollutants (air toxics) have been inconsistently associated with breast cancer. Whether metabolic factors modify these associations is unknown. We studied 29 non-metallic air toxics classified as mammary gland carcinogens in animal studies in relation to breast cancer risk.

METHODS

Participants included 49,718 women from the Sister Study. Census tract air toxic concentration estimates from the 2005 National Air Toxics Assessment were linked to enrollment residential addresses. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for individual air toxics were estimated using Cox regression. Body mass index (BMI) was considered a potential modifier. Relevant mixtures were identified using classification trees.

RESULTS

Over follow-up (average = 8.4 years), 2975 women were newly diagnosed with breast cancer (invasive or ductal carcinoma in situ). Several air toxics, including methylene chloride, polycyclic organic matter, propylene dichloride, and styrene, were associated with increased risk. Of these, methylene chloride was most consistently associated with risk across multiple analyses. It was associated with overall (HRquintile 4vs1 = 1.21 (95%CI = 1.07-1.38)) and estrogen receptor positive (ER+) invasive breast cancer (HRquintile 4vs1 = 1.28 (95%CI = 1.08-1.52)) in individual pollutant models, although no dose-response was observed. Associations were stronger among overweight/obese (vs. non-overweight/obese) women (p < 0.05) for six air toxics. The classification tree identified combinations of age, methylene chloride, BMI, and four other toxics (propylene dichloride, ethylene dibromide, ethylidene dichloride, styrene) related to overall breast cancer.

CONCLUSIONS

Some non-metallic air toxics, particularly methylene chloride, were associated with the hazard for overall and ER+ breast cancer. Overweight/obese women may be particularly susceptible to air toxics.

Hazardous air pollutants and telomere length in the Sister Study

BACKGROUND

Telomeres are vital for genomic integrity and telomere length has been linked to many adverse health outcomes. Some hazardous air pollutants, or air toxics, increase oxidative stress and inflammation, two possible determinants of shortened telomere length. No studies have examined air toxic-telomere length associations in a non-occupational setting.

METHODS

This study included 731 Sister Study participants (enrolled 2003-2007) who were randomly selected to assess telomere length in baseline blood samples. Multiplex qPCR was used to determine telomere to single copy gene (T/S) ratios. Census tract concentration estimates of 29 air toxics from the 2005 National Air Toxics Assessment were linked to baseline residential addresses. Air toxics were classified into tertile-based categories of the exposure. Multivariable linear regression was used to estimate β coefficients and 95% confidence intervals (CI) in single pollutant models. Multipollutant groups were identified with regression trees.

RESULTS

The average T/S ratio was 1.24. Benzidine (T3vsT1 β= -0.08; 95% CI: -0.14, -0.01) and 1,4-dioxane (T3vsT1 β= -0.06; 95% CI: -0.13, 0.00) in particular, as well as carbon tetrachloride, chloroprene, ethylene dibromide, and propylene dichloride, were associated with shorter relative telomere length. Benzidine (p=0.02) and 1,4-dioxane (p=0.06) demonstrated some evidence of a monotonic trend. The regression tree identified age, BMI, physical activity, ethylene oxide, acrylonitrile, ethylidene dichloride, propylene dichloride, and styrene in multipollutant groups related to telomere length.

CONCLUSIONS

In this first study of air toxics and telomere length in a non-occupational setting, several air toxics, particularly 1,4-dioxane and benzidine, were associated with shorter relative telomere length.

Acute and Chronic Exposure of Toluene Induces Genotoxicity in Different Regions of the Brain in Normal and Allergic Mouse Models

Toluene is a widely used industrial organic solvent and is ubiquitous in our environment. The neurobehavioral and neurotoxic effects of toluene are well recognized; however, its genotoxicity is still under discussion. Toluene biotransformation leads to the generation of reactive oxygen species that cause oxidative stress and DNA damages. Individuals with different immunogenetic backgrounds have different sensitivities to toxic chemical exposure. Previous studies have suggested that allergic stimulation may influence the threshold for toluene sensitivity due to the modulation of neurotrophin-related genes. Therefore, we aimed to investigate toluene-induced genotoxicity in different brain regions following acute and chronic exposure in vivo and to further examine whether allergic stimulation may influence the sensitivity to toluene-induced genotoxicity. In this present study, we found that exposure of toluene induced oxidative DNA damages resulting in genotoxicity in different brain regions including cortex, cerebellum, and hippocampus using comet assay. Higher genotoxicity induced by toluene was observed in the hippocampus of control mice compared to OVA-immunized mice. These results provide evidence that toluene-induced genotoxicity may contribute to its neurotoxicity in different immunogenetic individuals.

Neuroprotective role of 6-Gingerol-rich fraction of Zingiber officinale (Ginger) against acrylonitrile-induced neurotoxicity in male Wistar rats

Background Acrylonitrile (AN) is a neurotoxin that is widely used to manufacture synthetic fibres, plastics and beverage containers. Recently, we reported the ameliorative role of 6-gingerol-rich fraction from Zingiber officinale (Ginger, GRF) on the chlorpyrifos-induced toxicity in rats. Here, we investigated the protective role of GRF on AN-induced brain damage in male rats. Methods Male rats were orally treated with corn oil (2 mL/kg, control), AN (50 mg/kg, Group B), GRF (200 mg/kg, Group C), AN [50 mg/kg+GRF (100 mg/kg) Group D], AN [(50 mg/kg)+GRF (200 mg/kg) Group E] and AN [(50 mg/kg)+N-acetylcysteine (AC, 50 mg/kg) Group F] for 14 days. Then, we assessed the selected markers of oxidative damage, antioxidant status and inflammation in the brain of rats. Results The results indicated that GRF restored the AN-induced elevations of brain malondialdehyde (MDA), interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α) and Nitric Oxide (NO) levels. GRF also prevented the AN-induced depletion of brain glutathione (GSH) level and the activities of Glutathione S-transferase (GST), glutathione peroxidase (GPx) and superoxide dismutase (SOD) in rats (p<0.05). Furthermore, GRF prevented the AN-induced cerebral cortex lesion and increased brain immunohistochemical expressions of Caspases-9 and -3. Conclusions Our data suggest that GRF may be a potential therapeutic agent in the treatment of AN-induced model of brain damage.

Application of a series of biomarkers in Scallop Chlamys farreri to assess the toxic effects after exposure to a priority hazardous and noxious substance (HNS)-Acrylonitrile

The antioxidant enzymes and detoxification parameters responses of the scallop Chlamys farreri to different degree of acrylonitrile (AN) were investigated. Accordingly, the median lethal concentration (LC₅₀) at 96 h was 98.5 mg/L AN. Results from chronic toxicity test demonstrated that superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were stimulated in the highest two doses of AN (2.0 and 5.0 mg/L), but significantly inhibited in the highest concentration (5.0 mg/L) at the end of the exposure. The levels of DNA strand breaks, lipid peroxidation (LPO) and protein carbonyl (PC) contents showed damage effects exposed AN at the highest two doses. Additionally, AN significantly induced the enzymatic activity of glutathione-s-transferase (GST), related mRNA expression levels of P-glycoprotein (P-gp) and GST-pi; and no significant changes were found on CYP1A1 mRNA expression and ethoxyresorufin O-deethylase (EROD) activity. Our results indicated that P-gp and GST-pi mRNA expression in digestive glands of the scallop C. farreri may potentially be used in ecological risk assessment of hazardous and noxious substances (HNS) contamination of marine.

Investigating the association between urinary levels of acrylonitrile metabolite N-acetyl-S-(2-cyanoethyl)-L-cysteine and the oxidative stress product 8-hydroxydeoxyguanosine in adolescents and young adults

Acrylonitrile is a colorless volatile liquid mostly present in tobacco smoke. Acrylonitrile exposure has shown to increase oxidative stress in animal studies; however, there was no previous research in human epidemiology. In this study, 853 subjects were recruited from a cohort of Taiwanese adolescents and young adults to investigate the association between urinary concentrations of the acrylonitrile metabolite N-acetyl-S-(2-cyanoethyl)-L-cysteine (CEMA), the oxidative stress product 8-hydroxydeoxyguanosine (8-OHdG) and cardiovascular disease (CVD) risk factors. The geometric mean (SD) of CEMA and 8-OHdG concentrations were 4.67 (8.61) μg/L and 2.97 (2.14) μg/L, respectively. 10% elevated in CEMA (μg/L) was positively correlated with the change of 8-OHdG levels (μg/L) (β = 0.325, SE = 0.105, P = 0.002) in multiple linear regression analyses. The urinary CEMA was not related to other CVD risk factors. In subpopulation analyses, the association between CEMA and 8-OHdG was evident in all genders, adolescents, homeostasis model assessment of insulin resistance score ≥0.89, and environmental tobacco smokers. In this study, we observed that higher levels of CEMA levels were correlated with increased levels of 8-OHdG in this cohort. Future research on exposure to acrylonitrile and oxidative stress was warranted.

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.

Effects of acrylonitrile-induced oxidative stress on testicular apoptosis through activation of NF-κB signaling pathway in male sprague dawley rats

Acrylonitrile (ACN) treatment can induce testicular toxicity in Sprague-Dawley (SD) rats, with the toxicity potentially related to apoptosis, mediated by nuclear factor-κB (NF-κB). The present study investigated the potential role of NF-κB in the induction of apoptosis and testicular toxicity in ACN-treated rats. Adult male SD rats were randomly divided into 3 treatment groups: a control group (corn oil), an ACN group (50 mg/kg) in which ACN was administered by gavage, and an ACN and N-acetylcysteine (ACN+NAC) group. The rats were given NAC (300 mg/kg) 30 min prior to the administration of ACN, and ACN was administered by gavage for 90 days. The ACN treatment markedly increased malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activity in the testis. Glutathione (GSH) was significantly depleted in the ACN groups, and the effects of ACN were blocked by the anti-oxidant NAC. The ACN treatment also increased the expression of NF-κB (p65) and phosphorylated-IκB kinase (IKK)-α/β and decreased the expression of an inhibitor of NF-κB (IκB-α). The pretreatment with NAC significantly inhibited the activation of NF-κB. In addition, the expression of Bax increased after the ACN treatment, and the induction of Bax was abolished by NAC. Taken together, the data suggested that ACN-induced oxidative stress activated the NF-κB signaling pathway, which modulated the expression of Bax and contributed to testicular apoptosis.

À la recherche du temps perdu: Smoking and Genomic Imprinting

Tobacco smoking is the largest cause of preventable mortality and morbidity in the United States. Many of the pathological consequences of smoking result from mutations, but gene expression can also be modulated by genomic imprinting mediated by DNA methylation-so-called "epigenetic" regulation. Since genomic imprints, unlike gene mutations, can be reversed, it is of great interest what smoking-related imprints mean for smoking-related pathologies in smokers and their children, and the potential for imprint-targeted diagnostics and therapeutics.

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-1β, 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.

Toxicity of seven priority hazardous and noxious substances (HNSs) to marine organisms: Current status, knowledge gaps and recommendations for future research

Shipping industry and seaborne trade have rapidly increased over the last fifty years, mainly due to the continuous increasing demand for chemicals and fuels. Consequently, despite current regulations, the occurrence of accidental spills poses an important risk. Hazardous and noxious substances (HNSs) have been raising major concern among environmental managers and scientific community for their heterogeneity, hazardous potential towards aquatic organisms and associated social-economic impacts. A literature review on ecotoxicological hazards to aquatic organisms was conducted for seven HNSs: acrylonitrile, n-butyl acrylate, cyclohexylbenzene, hexane, isononanol, trichloroethylene and xylene. Information on the mechanisms of action of the selected HNS was also reviewed. The main purpose was to identify: i) knowledge gaps in need of being addressed in future research; and ii) a set of possible biomarkers suitable for ecotoxicological assessment and monitoring in both estuarine and marine systems. Main gaps found concern the scarcity of information available on ecotoxicological effects of HNS towards marine species and their poorly understood mode of action in wildlife. Differences were found between the sensitivity of freshwater and seawater organisms, so endpoints produced in the former may not be straightforwardly employed in evaluations for the marine environment. The relationship between sub-individual effects and higher level detrimental alterations (e.g. behavioural, morphological, reproductive effects and mortality) are not fully understood. In this context, a set of biomarkers associated to neurotoxicity, detoxification and anti-oxidant defences is suggested as potential indicators of toxic exposure/effects of HNS in marine organisms. Overall, to support the development of contingency plans and the establishment of environmental safety thresholds, it will be necessary to undertake targeted research on HNS ecotoxicity in the marine environment. Research should address these issues under more realistic exposure scenarios reflecting the prevailing spatial and temporal variability in ecological and environmental conditions.

ANTIOXIDANT CAPACITY OF WYOMING BIG SAGEBRUSH (ARTEMISIA TRIDENTATA SSP. WYOMINGENSIS) VARIES SPATIALLY AND IS NOT RELATED TO THE PRESENCE OF A SAGEBRUSH DIETARY SPECIALIST

Sagebrush (Artemisia spp.) in North America is an abundant native plant species that is ecologically and evolutionarily adapted to have a diverse array of biologically active chemicals. Several of these chemicals, specifically polyphenols, have antioxidant activity that may act as biomarkers of biotic or abiotic stress. This study investigated the spatial variation of antioxidant capacity, as well as the relationship between a mammalian herbivore and antioxidant capacity in Wyoming big sagebrush (Artemisia tridentata wyomingensis). We quantified and compared total polyphenols and antioxidant capacity of leaf extracts from sagebrush plants from different spatial scales and at different levels of browsing by a specialist mammalian herbivore, the pygmy rabbit (Brachylagus idahoensis). We found that antioxidant capacity of sagebrush extracts was positively correlated with total polyphenol content. Antioxidant capacity varied spatially within and among plants. Antioxidant capacity in sagebrush was not related to either browsing intensity or duration of association with rabbits. We propose that the patterns of antioxidant capacity observed in sagebrush may be a result of spatial variation in abiotic stress experienced by sagebrush. Antioxidants could therefore provide a biomarker of environmental stress for sagebrush that could aid in management and conservation of this plant in the threatened sagebrush steppe.

Changes in immunity parameters and blood cytokine concentrations after chronic nitrile acrylate intoxication

Experiments on outbred albino rats showed that chronic nitrile acrylate intoxication (60 days, 0.05 LD50 per day subcutaneously) led to reduction of T-dependent humoral immune response (T-independent humoral immune response was less affected); parameters cell immunity were suppressed to a greater extent than parameters of humoral immune reactions. Equal attenuation of the functions of Th1 and Th2 lymphocytes, decrease of the blood levels of immunoregulatory, pro- and anti-inflammatory cytokines (IFN-γ, IL-2, IL-4, IL-6, IL-10, IL-13), and decrease of acetyl cholinesterase activity in thymic and splenic T lymphocytes were observed.

Contribution of environment and genetics to pancreatic cancer susceptibility

Several risk factors have been identified as potential contributors to pancreatic cancer development, including environmental and lifestyle factors, such as smoking, drinking and diet, and medical conditions such as diabetes and pancreatitis, all of which generate oxidative stress and DNA damage. Oxidative stress status can be modified by environmental factors and also by an individual's unique genetic makeup. Here we examined the contribution of environment and genetics to an individual's level of oxidative stress, DNA damage and susceptibility to pancreatic cancer in a pilot study using three groups of subjects: a newly diagnosed pancreatic cancer group, a healthy genetically-unrelated control group living with the case subject, and a healthy genetically-related control group which does not reside with the subject. Oxidative stress and DNA damage was evaluated by measuring total antioxidant capacity, direct and oxidative DNA damage by Comet assay, and malondialdehyde levels. Direct DNA damage was significantly elevated in pancreatic cancer patients (age and sex adjusted mean ± standard error: 1.00 ± 0.05) versus both healthy unrelated and related controls (0.70 ± 0.06, p<0.001 and 0.82 ± 0.07, p = 0.046, respectively). Analysis of 22 selected SNPs in oxidative stress and DNA damage genes revealed that CYP2A6 L160H was associated with pancreatic cancer. In addition, DNA damage was found to be associated with TNFA -308G>A and ERCC4 R415Q polymorphisms. These results suggest that measurement of DNA damage, as well as select SNPs, may provide an important screening tool to identify individuals at risk for development of pancreatic cancer.

Simulation of a Hazardous and Noxious Substances (HNS) spill in the marine environment: lethal and sublethal effects of acrylonitrile to the European seabass

Despite the extensive maritime transportation of Hazardous and Noxious Substances (HNS), there is a current lack of knowledge on the effects posed by HNS spills on the marine biota. Among the HNS identified as priority, acrylonitrile was selected to conduct ecotoxicological assays. We assessed the acute and subletal effects of acrylonitrile in seabass, followed by a recovery phase to simulate the conditions of a spill incident. The work aimed at testing a broad range of biological responses induced by acrylonitrile. Sublethal exposure to the highest two doses increased the fish mortality rate (8.3% and 25% mortality in 0.75 and 2 mg L(-1) acrylonitrile concentrations), whereas no mortality were observed in control and 0.15 mg L(-1) treatments. Additionally, important alterations at sub-individual level were observed. Acrylonitrile significantly induced the activities of Catalase- CAT and Glutathione S-Transferase - GST; and the levels of DNA damage were significantly increased. Conversely, Superoxide Dismutase- SOD - activity was found to be significantly inhibited and no effects were found on Lipid Peroxidation- LPO and ethoxyresorufin O-deethylase - EROD - activity. Following a 7d recovery period, the levels of CAT, GST and EROD fell to levels at or below those in the control. In the 2 mg L(-1) group, SOD remained at the levels found during exposure phase. This study has gathered essential information on the acute and subletal toxicity of acrylonitrile to seabass. It also demonstrated that 7d recovery allowed a return of most endpoints to background levels. These data will be useful to assist relevant bodies in preparedness and response to HNS spills.

Differential response to acrylonitrile toxicity in rat primary astrocytes and microglia

Acrylonitrile (ACN) is a widely used chemical in the production of plastics, resins, nitriles, acrylic fibers, synthetic rubber and acrylamide. While acute high level exposures to ACN are known to be lethal, chronic low dose exposures causes glial cell tumors in rats. Recently, these glial tumors have been characterized as microglial in origin. While effects of ACN on astrocytes, the more numerous glial cell, have been investigated, the effects on microglia are unknown. This study was conducted to compare the responses of astrocytes and microglia to ACN treatment in vitro to address differential sensitivities and adaptive responses to this toxic chemical. Cell viability, ACN uptake, lipid peroxidation byproducts (F2-isoprostanes), glutathione (GSH) levels and expression of NF-E2-related factor 2 (Nrf2) were evaluated in primary rat microglia and astrocytes following ACN treatment. Results indicate that microglia are more sensitive to ACN than astrocytes, accumulating less ACN while demonstrating higher F2-isoprostane levels. GSH levels were up-regulated in both cell types, as a protective mechanism against ACN-induced oxidative stress, while Nrf2 levels were only induced in microglia. Our data suggest that microglia and astrocytes exhibit different sensitivities and responses to ACN, which are linked to the intracellular thiol status inherent to each of these cell types.

Alterations in brain structure and function in breast cancer survivors: effect of post-chemotherapy interval and relation to oxidative DNA damage

Neuroimaging studies have begun to uncover the neural substrates of cancer and treatment-related cognitive dysfunction, but the time course of these changes in the years following chemotherapy is unclear. This study analyzed multimodality 3T MRI scans to examine the structural and functional effects of chemotherapy and post-chemotherapy interval (PCI) in a cohort of breast cancer survivors (BCS; n = 24; PCI mean 6, range 3-10 y) relative to age- and education-matched healthy controls (HC; n = 23). Assessments included voxel-based morphometry for gray matter density (GMD) and fMRI for activation profile during a 3-back working memory task. The relationships between brain regions associated with PCI and neuropsychological performance, self-reported cognition, and oxidative and direct DNA damage as measured in peripheral lymphocytes were assessed in secondary analyses. PCI was positively associated with GMD and activation on fMRI in the right anterior frontal region (Brodmann Areas 9 and 10) independent of participant age. GMD in this region was also positively correlated with global neuropsychological function. Memory dysfunction, cognitive complaints, and oxidative DNA damages were increased in BCS compared with HC. Imaging results indicated lower fMRI activation in several regions in the BCS group. BCS also had lower GMD than HC in several regions, and in these regions, GMD was inversely related to oxidative DNA damage and learning and memory neuropsychological domain scores. This is the first study to show structural and functional effects of PCI and to relate oxidative DNA damage to brain alterations in BCS. The relationship between neuroimaging and cognitive function indicates the potential clinical relevance of these findings. The relationship with oxidative DNA damage provides a mechanistic clue warranting further investigation.

Role of neutrophils in acrylonitrile-induced gastric mucosal damage

Acrylonitrile (ACN) is a widely used intermediate in the manufacture of plastics, acrylic fibers, synthetic rubbers and resins that are used in a variety of products including food containers and medical devices. ACN is a possible human carcinogen and a documented animal carcinogen, with the stomach being an important target of its toxicity. ACN has been previously reported to require metabolic activation to reactive intermediates and finally to cyanide (CN⁻). The current study aimed at exploring the potential role of neutrophils in ACN-induced gastric damage in rats. Experimental neutropenia was attained by injecting rats with methotrexate. This significantly ameliorated gastric mucosal injury induced by ACN. This is evidenced by protection against the increase in gastric ulcer index, myeloperoxidase (MPO) activity and CN⁻ level. Also, neutropenia guarded against the decrease in prostaglandin E2 (PGE2), induction of oxidative stress and reduction of total nitrites and alleviated histopathological alterations in rat stomachs. These data indicate that neutrophil infiltration is, at least partly, involved in ACN-induced gastric damage in rats.

Oxidative stress and oxidative damage in chemical carcinogenesis. Toxicol Appl Pharmacol. 2011;254:86-99. [PMID: 21296097 DOI: 10.1016/j.taap.2009.11.028]

Reactive oxygen species (ROS) are induced through a variety of endogenous and exogenous sources. Overwhelming of antioxidant and DNA repair mechanisms in the cell by ROS may result in oxidative stress and oxidative damage to the cell. This resulting oxidative stress can damage critical cellular macromolecules and/or modulate gene expression pathways. Cancer induction by chemical and physical agents involves a multi-step process. This process includes multiple molecular and cellular events to transform a normal cell to a malignant neoplastic cell. Oxidative damage resulting from ROS generation can participate in all stages of the cancer process. An association of ROS generation and human cancer induction has been shown. It appears that oxidative stress may both cause as well as modify the cancer process. Recently association between polymorphisms in oxidative DNA repair genes and antioxidant genes (single nucleotide polymorphisms) and human cancer susceptibility has been shown.