Iron release and oxidative DNA damage in splenic toxicity of aniline

Comparative γ-H2AX analysis for assessment of the genotoxicity of six aromatic amines implicated in bladder cancer in human urothelial cell line

Recently, it was reported that ten cases of bladder cancer occurred among employees, who handled several kinds of aromatic amines, at a Japanese chemical plant. The common aromatic amines were identified as ortho-toluidine, para-toluidine, aniline, ortho-chloroaniline, ortho-anisidine, and 2,4-dimethylaniline. All of these aromatic amines, except ortho-chloroaniline, have been found to be carcinogenic in animals and/or humans. Genotoxic events are known to be crucial steps in the initiation of cancer; information on the genotoxicity of these aromatic amines is insufficient and consistent results have not been obtained. In this study, we examined the genotoxicity of the six different aromatic amines associated with bladder cancer by assessing phosphorylated histone H2AX (γ-H2AX) in a cultured human urothelial cell line, 1T1. We showed that all six aromatic amines generated γ-H2AX. In addition, the γ-H2AX-inducing potential of these six aromatic amines was distinctly different; ortho-chloroaniline and 2,4-dimethylaniline showed particularly high potential, followed by ortho-toluidine, ortho-anisidine, para-toluidine ≒ aniline. The findings of this study may provide important information for the risk assessment of chemicals and for interpreting epidemiological studies on occupational bladder cancer.

Molecular Mechanism of Aniline Induced Spleen Toxicity and Neuron Toxicity in Experimental Rat Exposure: A Review

Aniline exposure leads to neuron and spleen toxicity specifically and makes diverse neurological effects and sar-coma that is defined by splenomegaly, hyperplasia, and fibrosis and tumors formation at the end. However, the molecular mechanism(s) of aniline-induced spleen toxicity is not understood well, previous studies have represented that aniline expo-sure results in iron overload and initiation of oxidative/nitrosative disorder stress and oxidative damage to proteins, lipids and DNA subsequently, in the spleen. Elevated expression of cyclins, cyclin-dependent kinases (CDKs) and phosphorylation of pRB protein along with increases in A, B and CDK1 as a cell cycle regulatory proteins cyclins, and reduce in CDK inhibitors (p21 and p27) could be critical in cell cycle regulation, which contributes to tumorigenic response after aniline exposure. Aniline-induced splenic toxicity is corre-lated to oxidative DNA damage and initiation of DNA glycosylases expression (OGG1, NEIL1/2, NTH1, APE1 and PNK) for removal of oxidative DNA lesions in rat. Oxidative stress causes transcriptional up-regulation of fibrogenic/inflammatory factors (cytokines, IL-1, IL-6 and TNF-α) via induction of nuclear factor-kappa B, AP-1 and redox-sensitive transcription factors, in aniline treated-rats. The upstream signalling events as phosphorylation of IκB kinases (IKKα and IKKβ) and mito-gen-activated protein kinases (MAPKs) could potentially be the causes of activation of NF-κB and AP-1. All of these events could initiate a fibrogenic and/or tumorigenic response in the spleen. The spleen toxicity of aniline is studied more and the different mechanisms are suggested. This review summarizes those events following aniline exposure that induce spleen tox-icity and neurotoxicity.

Assessment of the mutagenic potential of para-chloroaniline and aniline in the liver, spleen, and bone marrow of Big Blue® rats with micronuclei analysis in peripheral blood

Splenic tumors have been reported in rat cancer bioassays with para-chloroaniline (PCA) and aniline. Development of these tumors is hypothesized to be due to hematotoxicity via the formation of methemoglobin (MetHb) and not direct DNA reactivity. To evaluate the mode of action (MOA) for tumor formation a transgenic rodent (TGR) in vivo gene mutation assay in Big Blue® TgF344 rats was performed with parallel micronuclei analysis in peripheral blood. Male rats were gavaged daily for 28 d to 0.5, 15, and 60 mg/kg PCA and 100 mg/kg aniline, the base molecular structure of PCA. On test day 10, the 60 mg/kg PCA dose was reduced to 30 mg/kg due to toxicity. On test day 4 and 29 peripheral blood micronucleus analysis was performed and on test day 29 clinical chemistry, hematology, and MetHb measurements were taken. At study termination, on test day 31, spleen, bone marrow, and liver (control tissue) were analyzed for cII transgene mutant frequency (MF). Repeat gavage exposure to PCA and aniline for 28 d did not produce an increase in cII transgene MF in analyzed tissues. An increase in micronuclei was seen at both time points at ≥15 mg/kg PCA and 100 mg/kg aniline. At the same dose levels, significant reductions in red blood cells, increases in absolute reticulocytes (ABRET), and increased levels of MetHb were observed. Together these results support that generation of micronuclei and tumorigenicity following exposure to PCA and aniline is due to compensatory mechanisms (e.g. increased cellular turnover) and not direct DNA reactivity. Environ. Mol. Mutagen. 59:785-797, 2018. © 2018 Wiley Periodicals, Inc.

Contribution of poly(ADP-ribose)polymerase-1 activation and apoptosis in trichloroethene-mediated autoimmunity

Trichloroethene (TCE), a common environmental toxicant and widely used industrial solvent, has been implicated in the development of various autoimmune diseases (ADs). Although oxidative stress has been involved in TCE-mediated autoimmunity, the molecular mechanisms remain to be fully elucidated. These studies were, therefore, aimed to further explore the contribution of oxidative stress to TCE-mediated autoimmune response by specifically assessing the role of oxidative DNA damage, its repair enzyme poly(ADP-ribose)polymerase-1 (PARP-1) and apoptosis. To achieve this, groups of female MRL +/+ mice were treated with TCE, TCE plus N-acetylcysteine (NAC) or NAC alone (TCE, 10 mmol/kg, i.p., every 4th day; NAC, 250 mg/kg/day in drinking water) for 6 weeks. TCE treatment led to significantly higher levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the livers compared to controls, suggesting increased oxidative DNA damage. TCE-induced DNA damage was associated with significant activation of PARP-1 and increases in caspase-3, cleaved caspase-8 and -9, and alterations in Bcl-2 and Bax in the livers. Moreover, the TCE-mediated alterations corresponded with remarkable increases in the serum anti-ssDNA antibodies. Interestingly, NAC supplementation not only attenuated elevated 8-OHdG, PARP-1, caspase-3, cleaved caspase-9, and Bax, but also the TCE-mediated autoimmune response supported by significantly reduced serum anti-ssDNA antibodies. These results suggest that TCE-induced activation of PARP-1 followed by increased apoptosis presents a novel mechanism in TCE-associated autoimmune response and could potentially lead to development of targeted preventive and/or therapeutic strategies.

Altered miRNA expression in aniline-mediated cell cycle progression in rat spleen

Aniline exposure is associated with toxicity to the spleen, however, early molecular events in aniline-induced cell cycle progression in the spleen remain unknown. MicroRNAs (miRNAs) have been implicated in tumor development by modulating key cell cycle regulators and controlling cell proliferation. This study was, therefore, undertaken on the expression of miRNAs, regulation of cyclins and cyclin-dependent kinases (CDKs) in an experimental condition that precedes a tumorigenic response. Male SD rats were treated with aniline (1 mmol/kg/day by gavage) for 7 days, and expression of miRNAs, cyclins and CDKs in rat spleens were analyzed. Microarray and/or qPCR analyses showed that aniline exposure led to significantly decreased miRNA expression of let-7a, miR-24, miR-34c, miR-100, miR-125b, and greatly increased miR-181a. The aberrant expression of miRNAs was associated with significantly increased protein expression of cyclins A, B1, D3 and E. Furthermore, remarkably enhanced expression of CDKs like CDK1, CDK2, CDK4, CDK6, especially p-CDK1 and p-CDK2 as well as alternations in the expression of pRB, p27, and CDC25A in the spleens of aniline-treated rats was also observed. The data suggest that aniline exposure leads to aberrant expression of miRNAs in the spleen which could be important in the regulation of cell cycle proteins. Our findings, thus, provide new insight into the role of miRNAs in cell cycle progression, which may contribute to aniline-induced tumorigenic response in the spleen.

Iron carbide nanoparticles: an innovative nanoplatform for biomedical applications

Iron carbide nanoparticles (ICNPs) are nano-intermetallic compounds that consist of iron and carbon. Benefiting from the magnetic and chemical activity of iron, and/or mechanical strength and chemical inertness of carbon, they have been widely applied in energetic and biomedical-related fields. Particularly in biomedicine, ICNPs have shown high colloidal stability and good performance in magnetic-dependent diagnosis and therapies such as magnetic resonance imaging (MRI) and magnetic hyperthermia (MH), due to their high magnetization and moderate coercivity. The carbon content protects ICNPs from oxidation and corrosion (ion release), which prolongs their life time and reduces their toxicity in physiological environments, and endows nanoparticles (NPs) with high performance in carbon-relevant theranostics as well. On this basis, ICNPs have great promise in multi-modal imaging or imaging-guided tumor-selective therapy to realize precise diagnoses with mild side effects. This paper aims to cover the state of the art applications of ICNPs in biomedicine, primarily including MRI, MH, magnetic targeting (MT), magnetic separation (MS), photothermal therapy (PTT) and photoacoustic tomography (PAT). The biocompatibility of ICNPs is also addressed.

Palladium-Catalyzed Arylation of Fluoroalkylamines

We report the synthesis of fluorinated anilines by palladium-catalyzed coupling of fluoroalkylamines with aryl bromides and aryl chlorides. The products of these reactions are valuable because anilines typically require the presence of an electron-withdrawing substituent on nitrogen to suppress aerobic or metabolic oxidation, and the fluoroalkyl groups have steric properties and polarity distinct from those of more common electron-withdrawing amide and sulfonamide units. The fluoroalkylaniline products are unstable under typical conditions for C-N coupling reactions (heat and strong base). However, the reactions conducted with the weaker base KOPh, which has rarely been used in cross-coupling to form C-N bonds, occurred in high yield in the presence of a catalyst derived from commercially available AdBippyPhos and [Pd(allyl)Cl]2. Under these conditions, the reactions occur with low catalyst loadings (<0.50 mol % for most substrates) and tolerate the presence of various functional groups that react with the strong bases that are typically used in Pd-catalyzed C-N cross-coupling reactions of aryl halides. The resting state of the catalyst is the phenoxide complex, (BippyPhosPd(Ar)OPh); due to the electron-withdrawing property of the fluoroalkyl substituent, the turnover-limiting step of the reaction is reductive elimination to form the C-N bond.

Induction of base excision repair enzymes NTH1 and APE1 in rat spleen following aniline exposure

Mechanisms by which aniline exposure elicits splenotoxicity, especially a tumorigenic response, are not well-understood. Earlier, we have shown that aniline exposure leads to oxidative DNA damage and up-regulation of OGG1 and NEIL1/2 DNA glycosylases in rat spleen. However, the contribution of endonuclease III homolog 1 (NTH1) and apurinic/apyrimidinic endonuclease 1 (APE1) in the repair of aniline-induced oxidative DNA damage in the spleen is not known. This study was, therefore, focused on examining whether NTH1 and APE1 contribute to the repair of oxidative DNA lesions in the spleen, in an experimental condition preceding tumorigenesis. To achieve this, male SD rats were subchronically exposed to aniline (0.5 mmol/kg/day via drinking water for 30 days), while controls received drinking water only. By quantitating the cleavage products, the activities of NTH1 and APE1 were assayed using substrates containing thymine glycol (Tg) and tetrahydrofuran, respectively. Aniline treatment led to significant increases in NTH1- and APE1-mediated BER activity in the nuclear extracts of spleen of aniline-treated rats compared to the controls. NTH1 and APE1 mRNA expression in the spleen showed 2.9- and 3.2-fold increases, respectively, in aniline-treated rats compared to the controls. Likewise, Western blot analysis showed that protein expression of NTH1 and APE1 in the nuclear extracts of spleen from aniline-treated rats was 1.9- and 2.7-fold higher than the controls, respectively. Immunohistochemistry indicated that aniline treatment also led to stronger immunoreactivity for both NTH1 and APE1 in the spleens, confined to the red pulp areas. These results, thus, show that aniline exposure is associated with induction of NTH1 and APE1 in the spleen. The increased repair activity of NTH1 and APE1 could be an important mechanism for the removal of oxidative DNA lesions. These findings thus identify a novel mechanism through which NTH1 and APE1 may regulate the repair of oxidative DNA damage in aniline-induced splenic toxicity.

Induced expression of cytochrome P450 1A and NAD(P)H:quinone oxidoreductase determined at mRNA, protein, and enzyme activity levels in rats exposed to the carcinogenic azo dye 1-phenylazo-2-naphthol (Sudan I)

Sudan I (1-phenylazo-2-hydroxynaphthol) is a suspected human carcinogen causing tumors in the livers and urinary bladders of rats, mice, and rabbits. Here, we investigated for the first time the influence of Sudan I exposure on the expression of several biotransformation enzymes in the livers, kidneys, and lungs of rats concomitantly at the mRNA and protein levels and assayed their enzymatic activities. We also studied its effect on the formation of Sudan I-derived DNA adducts in vitro. Sudan I increased the total amounts of cytochrome P450 (P450) in all organs tested. Western blots using antibodies raised against various P450s, NADPH:P450 reductase, and NAD(P)H:quinone oxidoreductase 1 (NQO1) showed that the expression of P450 1A1 and NQO1 was induced in the liver, kidney, and lung of rats treated with Sudan I. The higher protein levels correlated with increased enzyme activities of P450 1A1/2 and NQO1. Furthermore, 9.9-, 5.9-, and 2.8-fold increases in the formation of Sudan I oxidative metabolites catalyzed by microsomes isolated from the liver, kidney, and lung, respectively, of rats treated with Sudan I were found. The relative amounts of P450 1A and NQO1 mRNA, measured by real-time polymerase chain reaction (RT-PCR) analysis, demonstrated that Sudan I induced the expression of P450 1A1 and NQO1 mRNA in the liver, kidney, and lung, and of P450 1A2 mRNA in kidney and lung. Finally, microsomes isolated from livers, kidneys, and lungs of Sudan I exposed rats more effectively catalyzed the formation of Sudan I-DNA adducts than microsomes from organs of control rats. This was attributable to the higher P450 1A1 expression. Because P450 1A1 is playing a major role in the bioactivation of Sudan I in rat and human systems, its induction by Sudan I may have a profound effect on cancer risk by this azo dye. In addition, the induction of P450 1A1/2 and NQO1 enzymes can influence individual human susceptibility to other environmental carcinogens and have an effect on cancer risk.

Evaluation of impact of exposure of Sudan azo dyes and their metabolites on human intestinal bacteria

Sudan azo dyes are banned for food usage in most countries, but they are illegally used to maintain or enhance the color of food products due to low cost, bright staining, and wide availability of the dyes. In this report, we examined the toxic effects of these azo dyes and their potential reduction metabolites on 11 prevalent human intestinal bacterial strains. Among the tested bacteria, cell growth of 2, 3, 5, 5, and 1 strains was inhibited by Sudan I, II, III, IV, and Para Red, respectively. At the tested concentration of 100 μM, Sudan I and II inhibited growth of Clostridium perfringens and Lactobacillus rhamnosus with decrease of growth rates from 14 to 47%. Sudan II also affected growth of Enterococcus faecalis. Growth of Bifidobacterium catenulatum, C. perfringens, E. faecalis, Escherichia coli, and Peptostreptococcus magnus was affected by Sudan III and IV with decrease in growth rates from 11 to 67%. C. perfringens was the only strain in which growth was affected by Para Red with 47 and 26% growth decreases at 6 and 10 h, respectively. 1-Amino-2-naphthol, a common metabolite of the dyes, was capable of inhibiting growth of most of the tested bacteria with inhibition rates from 8 to 46%. However, the other metabolites of the dyes had no effect on growth of the bacterial strains. The dyes and their metabolites had less effect on cell viability than on cell growth of the tested bacterial strains. Clostridium indolis and Clostridium ramosum were the only two strains with about a 10 % decrease in cell viability in the presence of Sudan azo dyes. The present results suggested that Sudan azo dyes and their metabolites potentially affect the human intestinal bacterial ecology by selectively inhibiting some bacterial species, which may have an adverse effect on human health.

A sensitive and selective enzyme-linked immunosorbent assay for the analysis of Para red in foods

Para red is a synthetic dye and a potential genotoxic carcinogen. A hapten mimicking Para red structure was synthesized by introducing a carboxyl to the naphthol part of Para red and coupled to carrier protein to form an immunogen for the production of specific antibodies. A sensitive and selective enzyme-linked immunosorbent assay (ELISA) was developed for the detection of Para red in food samples. The limit of detection and inhibition half-maximum concentrations of Para red in phosphate buffered saline with 10% methanol were 0.06 and 2.2 ng mL(-1), respectively. Cross-reactivity values of the ELISA with the tested compounds including Sudan red I, II, III, IV, and G, sunset yellow, 2-naphthol, and 4-nitroaniline were ≤0.2%. This assay was used to determine Para red in tomato sauce, chilli sauce, chilli powder and sausage samples after ultrasonic extraction, cleanup and concentration steps. The average recoveries, repeatability (intraday extractions and analysis), and intra-laboratory reproducibility (interday extractions and analysis) were in the range 90-108%, 4-12% and 8-17%, respectively. This assay was compared to a high-performance liquid chromatographic method for 28 samples, displaying a good correlation (R(2) = 0.95). Para red residues in 53 real world samples determined by ELISA were below the limit of detection.

Aniline-induced nitrosative stress in rat spleen: proteomic identification of nitrated proteins

Aniline exposure is associated with toxicity to the spleen which is characterized by splenomegaly, hyperplasia, fibrosis, and a variety of sarcomas on chronic exposure in rats. However, mechanisms by which aniline elicits splenotoxic responses are not well understood. Earlier we have shown that aniline exposure leads to increased nitration of proteins in the spleen. However, nitrated proteins remain to be characterized. Therefore, in the current study using proteomic approaches, we focused on characterizing the nitrated proteins in the spleen of aniline-exposed rats. Aniline exposure led to increased tyrosine nitration of proteins, as determined by 2D Western blotting with anti-3-nitrotyrosine specific antibody, compared to the controls. The analyzed nitrated proteins were found in the molecular weight range of 27.7 to 123.6kDa. A total of 37 nitrated proteins were identified in aniline-treated and control spleens. Among them, 25 were found only in aniline-treated rats, 11 were present in both aniline-treated and control rats, while one was found in controls only. The nitrated proteins identified mainly represent skeletal proteins, chaperones, ferric iron transporter, enzymes, nucleic acids binding protein, and signaling and protein synthesis pathways. Furthermore, aniline exposure led to significantly increased iNOS mRNA and protein expression in the spleen, suggesting its role in increased reactive nitrogen species formation and contribution to increased nitrated proteins. The identified nitrated proteins provide a global map to further investigate alterations in their structural and functional properties, which will lead to a better understanding of the role of protein nitration in aniline-mediated splenic toxicity.

Induction of NEIL1 and NEIL2 DNA glycosylases in aniline-induced splenic toxicity

The mechanisms by which aniline exposure elicits splenotoxic response, especially the tumorigenic response, are not well-understood. Earlier, we have shown that aniline-induced oxidative stress is associated with increased oxidative DNA damage in rat spleen. The base excision repair (BER) pathway is the major mechanism for the repair of oxidative DNA base lesions, and we have shown an up-regulation of 8-oxoguanine glycosylase 1 (OGG1), a specific DNA glycosylase involved in the removal of 8-hydroxy-2'-deoxyguanosine (8-OHdG) adducts, following aniline exposure. Nei-like DNA glycosylases (NEIL1/2) belong to a family of BER proteins that are distinct from other DNA glycosylases, including OGG1. However, contribution of NEIL1/2 in the repair of aniline-induced oxidative DNA damage in the spleen is not known. This study was, therefore, focused on evaluating if NEILs also contribute to the repair of oxidative DNA lesions in the spleen following aniline exposure. To achieve that, male SD rats were subchronically exposed to aniline (0.5 mmol/kg/day via drinking water for 30 days), while controls received drinking water only. The BER activity of NEIL1/2 was assayed using a bubble structure substrate containing 5-OHU (preferred substrates for NEIL1 and NEIL2) and by quantitating the cleavage products. Aniline treatment led to a 1.25-fold increase in the NEIL1/2-associated BER activity in the nuclear extracts of spleen compared to the controls. Real-time PCR analysis for NEIL1 and NEIL2 mRNA expression in the spleen revealed 2.7- and 3.9-fold increases, respectively, in aniline-treated rats compared to controls. Likewise, Western blot analysis showed that protein expression of NEIL1 and NEIL2 in the nuclear extract of spleens from aniline-treated rats was 2.0- and 3.8-fold higher than controls, respectively. Aniline treatment also led to stronger immunoreactivity for NEIL1 and NEIL2 in the spleens, confined to the red pulp areas. These studies, thus, show that aniline-induced oxidative stress is associated with an induction of NEIL1/2. The increased NIEL-mediated BER activity is another indication of aniline-induced oxidative damage in the spleen and could constitute another important mechanism of removal of oxidative DNA lesions, especially in transcribed DNA following aniline insult.

Towards a unifying, systems biology understanding of large-scale cellular death and destruction caused by poorly liganded iron: Parkinson's, Huntington's, Alzheimer's, prions, bactericides, chemical toxicology and others as examples

Exposure to a variety of toxins and/or infectious agents leads to disease, degeneration and death, often characterised by circumstances in which cells or tissues do not merely die and cease to function but may be more or less entirely obliterated. It is then legitimate to ask the question as to whether, despite the many kinds of agent involved, there may be at least some unifying mechanisms of such cell death and destruction. I summarise the evidence that in a great many cases, one underlying mechanism, providing major stresses of this type, entails continuing and autocatalytic production (based on positive feedback mechanisms) of hydroxyl radicals via Fenton chemistry involving poorly liganded iron, leading to cell death via apoptosis (probably including via pathways induced by changes in the NF-κB system). While every pathway is in some sense connected to every other one, I highlight the literature evidence suggesting that the degenerative effects of many diseases and toxicological insults converge on iron dysregulation. This highlights specifically the role of iron metabolism, and the detailed speciation of iron, in chemical and other toxicology, and has significant implications for the use of iron chelating substances (probably in partnership with appropriate anti-oxidants) as nutritional or therapeutic agents in inhibiting both the progression of these mainly degenerative diseases and the sequelae of both chronic and acute toxin exposure. The complexity of biochemical networks, especially those involving autocatalytic behaviour and positive feedbacks, means that multiple interventions (e.g. of iron chelators plus antioxidants) are likely to prove most effective. A variety of systems biology approaches, that I summarise, can predict both the mechanisms involved in these cell death pathways and the optimal sites of action for nutritional or pharmacological interventions.

Up-regulation of heme oxygenase-1 in rat spleen after aniline exposure

The splenic toxicity of aniline is characterized by vascular congestion, hyperplasia, fibrosis, and the development of a variety of sarcomas in rats. However, the underlying mechanisms by which aniline elicits splenotoxic response are not well understood. Previously we have shown that aniline exposure causes oxidative damage to the spleen. To further explore the oxidative mechanism of aniline toxicity, we evaluated the potential contribution of heme oxygenase-1 (HO-1), which catalyzes heme degradation and releases free iron. Male SD rats were given 1 mmol/kg/day aniline in water by gavage for 1, 4, or 7 days, and respective controls received water only. Aniline exposure led to significant increases in HO-1 mRNA expression in the spleen (2-and 2.4-fold at days 4 and 7, respectively) with corresponding increases in protein expression, as confirmed by ELISA and Western blot analysis. Furthermore, immunohistochemical assessment of spleen showed stronger immunostaining for HO-1 in the spleens of rats treated for 7 days, confined mainly to the red pulp areas. No changes were observed in mRNA and protein levels of HO-1 after 1 day exposure. The increase in HO-1 expression was associated with increases in total iron (2.4-and 2.7-fold), free iron (1.9-and 3.5-fold), and ferritin levels (1.9-and 2.1-fold) at 4 and 7 days of aniline exposure. Our data suggest that HO-1 up-regulation in aniline-induced splenic toxicity could be a contributing pro-oxidant mechanism, mediated through iron release, and leading to oxidative damage.

Decolorization of water and oil-soluble azo dyes by Lactobacillus acidophilus and Lactobacillus fermentum

The capability of Lactobacillus acidophilus and Lactobacillus fermentum to degrade azo dyes was investigated. The bacteria were incubated under anaerobic conditions in the presence of 6 microg/ml Methyl Red, Ponceau BS, Orange G, Amaranth, Orange II, and Direct Blue 15; 5 microg/ml Sudan I and II; or 1.5 microg/ml Sudan III and IV in deMann-Rogosa-Sharpe broth at 37 degrees C for 36 h, and reduction of the dyes was monitored. Both bacteria were capable of degrading all of the water-soluble azo dyes to some extent. They were also able to completely reduce the oil-soluble diazo dyes Sudan III and IV but were unable to reduce the oil-soluble monoazo dyes Sudan I and II to any significant degree in the concentrations studied. Growth of the bacteria was not significantly affected by the presence of the Sudan azo dyes. Metabolites of the bacterial degradation of Sudan III and IV were isolated and identified by liquid chromatography electrospray ionization tandem mass spectrometry analyses and compared with authentic standards. Aniline and o-toluidine (2-methylaniline), both potentially carcinogenic aromatic amines, were metabolites of Sudan III and IV, respectively.

Sudan azo dyes and Para Red degradation by prevalent bacteria of the human gastrointestinal tract

Sudan azo dyes have genotoxic effects and ingestion of food products contaminated with Sudan I, II, III, IV, and Para Red could lead to exposure in the human gastrointestinal tract. In this study, we examined thirty-five prevalent species of human intestinal bacteria to evaluate their capacity to degrade Sudan dyes and Para Red. Among these tested bacterial strains, 23, 13, 33, 30, and 29 out of 35 species tested were able to reduce Sudan I, II, III, IV, and Para Red, respectively, to some extent. Bifidobacterium infantis, Clostridium indolis, Enterococcus faecalis, Lactobacillus rhamnosus, and Ruminococcus obeum were able to reduce completely all four tested Sudan dyes and Para Red. Escherichia coli and Peptostreptococcus magnus were the only two strains that were not able to reduce any of the tested Sudan dyes and Para Red to any significant extent. Metabolites of the reduction of the tested Sudan dyes and Para Red by E. faecalis were isolated and identified by HPLC and LC/ESI-MS analyses and compared with authentic standards. Thus it appears that the ability to reduce Sudan dyes and Para Red except Sudan II is common among bacteria in the human colon.

Oxidative DNA damage and its repair in rat spleen following subchronic exposure to aniline

The mechanisms by which aniline exposure elicits splenotoxic response, especially the tumorigenic response, are not well-understood. Splenotoxicity of aniline is associated with iron overload and generation of reactive oxygen species (ROS) which can cause oxidative damage to DNA, proteins and lipids (oxidative stress). 8-Hydroxy-2'-deoxyguanosine (8-OHdG) is one of the most abundant oxidative DNA lesions resulting from ROS, and 8-oxoguanine glycosylase 1 (OGG1), a specific DNA glycosylase/lyase enzyme, plays a key role in the removal of 8-OHdG adducts. This study focused on examining DNA damage (8-OHdG) and repair (OGG1) in the spleen in an experimental condition preceding a tumorigenic response. To achieve that, male Sprague-Dawley rats were subchronically exposed to aniline (0.5 mmol/kg/day via drinking water for 30 days), while controls received drinking water only. Aniline treatment led to a significant increase in splenic oxidative DNA damage, manifested as a 2.8-fold increase in 8-OHdG levels. DNA repair activity, measured as OGG1 base excision repair (BER) activity, increased by approximately 1.3 fold in the nuclear protein extracts (NE) and approximately 1.2 fold in the mitochondrial protein extracts (ME) of spleens from aniline-treated rats as compared to the controls. Real-time PCR analysis for OGG1 mRNA expression in the spleen revealed a 2-fold increase in expression in aniline-treated rats than the controls. Likewise, OGG1 protein expression in the NEs of spleens from aniline-treated rats was approximately 1.5 fold higher, whereas in the MEs it was approximately 1.3 fold higher than the controls. Aniline treatment also led to stronger immunostaining for both 8-OHdG and OGG1 in the spleens, confined to the red pulp areas. It is thus evident from our studies that aniline-induced oxidative stress is associated with increased oxidative DNA damage. The BER pathway was also activated, but not enough to prevent the accumulation of oxidative DNA damage (8-OHdG). Accumulation of mutagenic oxidative DNA lesions in the spleen following exposure to aniline could play a critical role in the tumorigenic process.

Activation of oxidative stress-responsive signaling pathways in early splenotoxic response of aniline

Aniline exposure causes toxicity to the spleen, which leads to a variety of sarcomas, and fibrosis appears to be an important preneoplastic lesion. However, early molecular mechanisms in aniline-induced toxicity to the spleen are not known. Previously, we have shown that aniline exposure results in iron overload and induction of oxidative stress in the spleen, which can cause transcriptional upregulation of fibrogenic/inflammatory cytokines via activation of oxidative stress (OS)-responsive signaling pathways. To test this mechanism, male SD rats were treated with aniline (1mmol/kg/day via gavage) for 7 days, an experimental condition that precedes the appearance of fibrosis. Significant increases in both NF-kappaB and AP-1 binding activity was observed in the nuclear extracts of splenocytes from aniline-treated rats as determined by ELISAs, and supported by Western blot data showing increases in p-IkappaBalpha, p-p65 and p-c-Jun. To understand the upstream signaling events which could account for the activation of NF-kappaB and AP-1, phosphorylation patterns of IkappaB kinases (IKKalpha and IKKbeta) and mitogen-activated protein kinases (MAPKs) were pursued. Our data showed remarkable increases in both p-IKKalpha and p-IKKbeta in the splenocytes from aniline-treated rats, suggesting their role in the phosphorylation of both IkappaBalpha and p65 subunits. Furthermore, aniline exposure led to activation of all three classes of MAPKs, as evident from increased phosphorylation of extracellular-signal-regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK1/2) and p38 MAPKs, which could potentially contribute to the observed activation of both AP-1 and NF-kappaB. Activation of upstream signaling molecules was also associated with simultaneous increases in gene transcription of cytokines IL-1, IL-6 and TNF-alpha. The observed sequence of events following aniline exposure could initiate a fibrogenic and/or tumorigenic response in the spleen.

Activation of transcription factor AP-1 and mitogen-activated protein kinases in aniline-induced splenic toxicity

Signaling mechanisms in aniline-induced fibrogenic and/or tumorigenic response in the spleen are not known. Previous studies have shown that aniline exposure leads to iron accumulation and oxidative stress in the spleen, which may cause activation of redox-sensitive transcription factors and regulate the transcription of genes involved in fibrosis and/or tumorigenesis. To test this, male SD rats were treated with 0.5 mmol/kg/day aniline via drinking water for 30 days, and activation of transcription factor AP-1 was determined in the splenocyte nuclear extracts (NEs). AP-1 DNA-binding activity in the NEs of freshly isolated splenocytes from aniline-treated rats increased in comparison to the controls, as determined by electrophoretic mobility shift assay (EMSA). AP-1 binding was also determined in the NEs of cultured splenocytes (2 h and 24 h), which showed even a greater increase in binding activity at 2 h. The specificity of AP-1 binding for relevant DNA motifs was confirmed by competition EMSA and by supershift EMSA using antibodies specific to c-Jun and c-Fos. To further explore the signaling mechanisms in the AP-1 activation, phosphorylation patterns of mitogen-activated protein kinases (MAPKs) were pursued. Aniline exposure induced increases in the phosphorylation of the three classes of MAPKs: extracellular-signal-regulated kinase (ERK 1/2), c-Jun N-terminal kinase (JNK 1/2), and p38 MAPKs. Furthermore, TGF-beta1 mRNA expression showed a 3-fold increase in the spleens of aniline-treated rats. These observations suggest a strong association among MAPK phosphorylation, AP-1 activation, and enhanced TGF-beta1 gene expression. The observed sequence of events subsequent to aniline exposure could regulate genes that lead to fibrogenic and/or tumorigenic response in the spleen.