Highlights of the eighth international conference on carcinogenic/mutagenic N-substituted aryl compounds

The role of SOD2 and NOS2 genes in the molecular aspect of bladder cancer pathophysiology

Bladder cancer (BC) is a severe health problem of the genitourinary system and is characterised by a high risk of recurrence. According to the recent GLOBOCAN report, bladder cancer accounts for 3% of diagnosed cancers in the world, taking 10th place on the list of the most common cancers. Despite numerous studies, the full mechanism of BC development remains unknown. Nevertheless, precious results suggest a crucial role of oxidative stress in the development of BC. Therefore, this study explores whether the c. 47 C > T (rs4880)-SOD2, (c. 1823 C > T (rs2297518) and g.-1026 C > A (rs2779249)-NOS2(iNOS) polymorphisms are associated with BC occurrence and whether the bladder carcinogenesis induces changes in SOD2 and NOS2 expression and methylation status in peripheral blood mononuclear cells (PBMCs). In this aim, the TaqMan SNP genotyping assay, TaqMan Gene Expression Assay, and methylation-sensitive high-resolution melting techniques were used to genotype profiling and evaluate the expression of the genes and the methylation status of their promoters, respectively. Our findings confirm that heterozygote of the g.-1026 C > A SNP was associated with a decreased risk of BC. Moreover, we detected that BC development influenced the expression level and methylation status of the promoter region of investigated genes in PBMCs. Concluding, our results confirmed that oxidative stress, especially NOS2 polymorphisms and changes in the expression and methylation of the promoters of SOD2 and NOS2 are involved in the cancer transformation initiation of the cell urinary bladder.

Recent Advances in Chemodosimeters Designed for Amines

The analysis of amines has long been a very important task in science, industry, and healthcare. To date, this task has been accomplished by using expensive and time-consuming methods. Colorimetric and fluorescent chemodosimeters enable the fast, accurate, and sensitive analysis of various species with inexpensive instruments or the naked eye. Accordingly, the studies on these probes have gained great momentum in the last 20 years. In this review, amine chemodosimeters developed in the last 10 years were investigated. The investigated chemodosimeters are metal-free structures based on small organic compounds. The strategies for the detection, differentiation, and quantification of amines were discussed by considering the reaction types.

Regulatory Components of Oxidative Stress and Inflammation and Their Complex Interplay in Carcinogenesis

Cancer progression is closely linked to oxidative stress (OS) inflammation. OS is caused by an imbalance between the amount of reactive oxygen species produced and antioxidants present in the body. Excess ROS either oxidizes biomolecules or activates the signaling cascade, resulting in inflammation. Immune cells secrete cytokines and chemokines when inflammation is activated. These signaling molecules attract a wide range of immune cells to the site of infection or oxidative stress. Similarly, increased ROS production by immune cells at the inflamed site causes oxidative stress in the affected area. A review on the role of oxidative stress and inflammation in cancer-related literature was conducted to obtain data. All of the information gathered was focused on the current state of oxidative stress and inflammation in various cancers. After gathering all relevant information, a narrative review was created to provide a detailed note on oxidative stress and inflammation in cancer. Proliferation, differentiation, angiogenesis, migration, invasion, metabolic changes, and evasion of programmed cell death are all aided by OS and inflammation in cancer. Imbalance between reactive oxygen species (ROS) and antioxidants lead to oxidative stress that damages macromolecules (nucleic acids, lipids and proteins). It causes breakdown of the biological signaling cascade. Prolonged oxidative stress causes inflammation by activating transcription factors (NF-κB, p53, HIF-1α, PPAR-γ, Nrf2, AP-1) that alter the expression of many other genes and proteins, including growth factors, tumor-suppressor genes, oncogenes, and pro-inflammatory cytokines, resulting in cancer cell survival. The present review article examines the complex relationship between OS and inflammation in certain types of cancer (colorectal, breast, lung, bladder, and gastric cancer).

Chronic Arsenic Exposure Upregulates the Expression of Basal Transcriptional Factors and Increases Invasiveness of the Non-Muscle Invasive Papillary Bladder Cancer Line RT4

The bladder is a target organ for inorganic arsenic, a carcinogen and common environmental contaminant found in soil and water. Urothelial carcinoma (UC) is the most common type of bladder cancer (BC) that develops into papillary or non-papillary tumors. Papillary tumors are mostly non-muscle invasive (NMIUC), easier treated, and have a better prognosis. Urothelial carcinoma can be molecularly sub-typed as luminal or basal, with papillary tumors generally falling into the luminal category and basal tumors exclusively forming muscle invasive urothelial carcinomas (MIUC). It is unclear why some UCs develop more aggressive basal phenotypes. We hypothesized that chronic arsenic exposure of a papillary luminal bladder cancer would lead to the development of basal characteristics and increase in invasiveness. We treated the human papillary bladder cancer cell line RT4 with 1 µM arsenite (As³⁺) for twenty passages. Throughout the study, key luminal and basal gene/protein markers in the exposed cells were evaluated and at passage twenty, the cells were injected into athymic mice to evaluate tumor histology and measure protein markers using immunohistochemistry. Our data indicates that chronic As³⁺- treatment altered cellular morphology and decreased several luminal markers in cell culture. The histology of the tumors generated from the As³⁺-exposed cells was similar to the parent (non-treated) however, they appeared to be more invasive in the liver and displayed elevated levels of some basal markers. Our study demonstrates that chronic As³⁺ exposure is able to convert a non-invasive papillary bladder cancer to an invasive form that acquires some basal characteristics.

Oxidative stress parameters as biomarkers of bladder cancer development and progression

The epidemiological studies confirm that the overproduction of free radical is an important factor of cancer induction as well as development, and loss of antioxidant systems efficiency is associated with an increased risk of carcinogenesis. While bladder cancer is the fourth most common type of cancer all over the world, there is little evidence of the advancing changes in oxidative/nitrative stress during the progression of bladder cancer. Our study aimed to investigate the plasma levels of typical markers of oxidative/nitrative stress depending on the clinical classification of bladder cancer differentiation and infiltration degree. We examined 40 patients with newly diagnosed bladder cancer and 20 healthy volunteers as a control group. We analysed the plasma levels of protein carbonyls, thiol groups, 3-nitrotyrosine, lipid peroxidation, as well as non-enzymatic plasma antioxidant capacity using DPPH^· and ABTS^·+ radicals. We confirmed that all analysed biomarkers are higher in enrolled BC patients than in healthy subjects. Furthermore, our findings demonstrate a positive correlation between the degree of bladder cancer progression and the level of oxidative stress, but no correlation in the case of NT-3. Based on obtained results, we might conclude that during carcinogenesis of the bladder increased oxidative damage of biomolecules is manifested. This indicates the participation of oxidative stress in the development of bladder cancer, and it is important the ensure the proper antioxidant protection.

The Interplay between Oxidative Stress, Inflammation and Angiogenesis in Bladder Cancer Development

In 2018, 550,000 people were diagnosed with bladder cancer (BC), of which nearly 200,000 people died. Moreover, men are 4 times more likely than women to be diagnosed with BC. The risk factors include exposure to environmental and occupational chemicals, especially tobacco smoke, benzidine and genetic factors. Despite numerous studies, the molecular basis of BC development remains unclear. A growing body of evidence suggests that inflammation, oxidant-antioxidant imbalance and angiogenesis disorders may play a significant role in the development and progression of bladder cancer. The patients with bladder cancer were characterised by an increased level of reactive oxygen species (ROS), the products of lipid peroxidation, proinflammatory cytokines and proangiogenic factors as compared to controls. Furthermore, it was shown that polymorphisms localised in genes associated with these pathways may modulate the risk of BC. Interestingly, ROS overproduction may induce the production of proinflammatory cytokines, which finally activated angiogenesis. Moreover, the available literature shows that both inflammation and oxidative stress may lead to activation of angiogenesis and tumour progression in BC patients.

Reaction of Aniline with Singlet Oxygen (O21Δg)

Dissolved organic matter (DOM) acts as an effective photochemical sensitizer that produces the singlet delta state of molecular oxygen (O₂¹Δ_g), a powerful oxidizer that removes aniline from aqueous solutions. However, the exact mode of this reaction, the p- to o-iminobenzoquinone ratio, and the selectivity of one over the other remain largely speculative. This contribution resolves these uncertainties. We report, for the first time, a comprehensive mechanistic and kinetic account of the oxidation of aniline with the singlet delta oxygen using B3LYP and M06 functionals in both gas and aqueous phases. Reaction mechanisms have been mapped out at E, H, and G scales. The 1,4-cycloaddition of O₂¹Δ_g to aniline forms a 1,4-peroxide intermediate (M1), which isomerizes via a closed-shell mechanism to generate a p-iminobenzoquinone molecule. On the other hand, the O₂¹Δ_g ene-type reaction forms an o-iminobenzoquinone product when the hydroperoxyl bond breaks, splitting hydroxyl from the 1,2-hydroperoxide (M3) moiety. The gas-phase model predicts the formation of both p- and o-iminobenzoquinones. In the latter model, the M1 adduct displays the selectivity of up to 96%. A water-solvation model predicts that M1 decomposes further, forming only p-iminobenzoquinone with a rate constant of k = 1.85 × 10⁹ (L/(mol s)) at T = 313 K. These results corroborate the recent experimental findings of product concentration profile in which p-iminobenzoquinonine represents the only detected product.

Curcumin reverses benzidine-induced epithelial-mesenchymal transition via suppression of ERK5/AP-1 in SV-40 immortalized human urothelial cells

Overexposure to benzidine has been manifested as an important cause of bladder cancer. However, the molecular mechanism of benzidine-induced malignancy is still insufficiently interpreted. Epithelial-mesenchymal transition (EMT) is a crucial pathophysiological process in embryonic development as well as initiation and development of epithelium-originated malignant tumors. The role of extracellular regulated protein kinase 5 (ERK5) in benzidine-meditated bladder cancer development has not been explored. In the present study, we explored the role of ERK5/AP-1 pathway in benzidine-induced EMT in human normal urothelial cells and the intervention effect of curcumin on bezidine-induced EMT. We found that benzidine-induced EMT in SV-40 immortalized human urothelial cells (SV-HUC-1) at low concentrations. We detected that ERK5/AP-1 pathway was notably activated. Specific ERK5 inhibitor, XMD8-92 was applied to determine the role of ERK5 in benzidine-induced EMT. Results indicated that XMD8-92 reversed the EMT process. Furthermore, curcumin effectively attenuated benzidine-induced urocystic EMT by suppressing ERK5/AP-1 pathway. In conclusion, the present study revealed the positive role of ERK5/AP-1 in benzidine-provoked urocystic EMT and the curcumin promising use in bladder cancer prevention and intervention via ERK5/AP-1 pathway.

A knowledge-based expert rule system for predicting mutagenicity (Ames test) of aromatic amines and azo compounds

Cancer is one of the main causes of death in Western countries, and a major issue for human health. Prolonged exposure to a number of chemicals was observed to be one of the primary causes of cancer in occupationally exposed persons. Thus, the development of tools for identifying hazardous chemicals and the increase of mechanistic understanding of their toxicity is a major goal for scientific research. We constructed a new knowledge-based expert system accounting the effect of different substituents for the prediction of mutagenicity (Ames test) of aromatic amines, a class of compounds of major concern because of their widespread application in industry. The herein presented model implements a series of user-defined structural rules extracted from a database of 616 primary aromatic amines, with their Ames test outcomes, aimed at identifying mutagenic and non-mutagenic chemicals. The chemical rationale behind such rules is discussed. Besides assessing the model's ability to correctly classify aromatic amines, its predictivity was further evaluated on a second database of 354 azo dyes, another class of chemicals of major concern, whose toxicity has been predicted on the basis of the toxicity of aromatic amines potentially generated from the metabolic reduction of the azo bond. Good performance in classification on both the amine (MCC, Matthews Correlation Coefficient=0.743) and the azo dye (MCC=0.584) datasets confirmed the predictive power of the model, and its suitability for use on a wide range of chemicals. Finally, the model was compared with a series of well-known mutagenicity predicting software. The good performance of our model compared with other mutagenicity models, especially in predicting azo dyes, confirmed the usefulness of this expert system as a reliable support to in vitro mutagenicity assays for screening and prioritization purposes. The model has been fully implemented as a KNIME workflow and is freely available for downstream users.

Functional POR A503V is associated with the risk of bladder cancer in a Chinese population

Human cytochrome P450 oxidoreductase (POR) plays important roles in the metabolism of exogenous carcinogens and endogenous sterol hormones. However, few studies have explored the association between POR variants and the risk of bladder cancer. In this study, we first sequenced all 16 POR exons among 50 randomly selected controls, and found three variants, rs1135612, rs1057868 (A503V) and rs2228104, which were then assessed the relation to risk of bladder cancer in a case-control study of 1,050 bladder cancer cases and 1,404 cancer-free controls in a Chinese population. People with A503V TT genotype have a decreased risk of bladder cancer in a recessive model (TT vs. CC/CT, OR = 0.73, 95% CI = 0.57–0.93), which was more pronounced among elderly male, non-smoking, subjects. Especially, A503V TT genotype showed a protective effect in the invasive tumor stage. Functional analysis revealed that A503V activity decreased in cytochrome c reduction (50.5 units/mg vs. 135.4 units/mg), mitomycin C clearance (38.3% vs. 96.8%), and mitomycin C-induced colony formation (78.0 vs 34.3 colonies per dish). The results suggested that POR A503V might decrease the risk of bladder cancer by reducing its metabolic activity, and should be a potential biomarker for predicting the susceptibility to human bladder cancer.

Benzidine induces epithelial-mesenchymal transition in human uroepithelial cells through ERK1/2 pathway

Prolonged benzidine exposure is a known cause of urothelial carcinoma (UC). Benzidine-induced epithelial-to-mesenchymal transition (EMT) is critically involved in cell malignant transformation. The role of ERK1/2 in regulating benzidine-triggered EMT has not been investigated. This study was to investigate the regulatory role of ERK1/2 in benzidine-induced EMT. By using wound healing and transwell chamber migration assays, we found that benzidine could increase SV-HUC-1 cells invasion activity, western blotting and Immunofluorescence showed that the expression levels of Snail, β-catenin, Vimentin, and MMP-2 were significantly increased, while, the expression levels of E-cadherin, ZO-1 were decreased. To further demonstrate the mechanism in this process, we found that the phosphorylation of ERK1/2, p38, JNK and AP-1 proteins were significantly enhanced compared to the control group (*P < 0.05). Afterward, treated with MAPK pathways inhibitors, only ERK inhibitor（U0126）could reduce the expression of EMT markers in SV-HUC-1 cells, but not p38 and JNK inhibitor（SB203580, SP600125）, which indicated that benzidine induces the epithelial-mesenchymal transition in human uroepithelial cells through ERK1/2 pathway. Taken together, findings from this study could provide into the molecular mechanisms by which benzidine exerts its bladder-cancer-promoting effect as well as its target intervention.

Malachite green interacts with the membrane skeletal protein, spectrin

Energy minimized complex of MG with the self association domain of spectrin.

Molecular recognition of malachite green by hemoglobin and their specific interactions: insights from in silico docking and molecular spectroscopy

Malachite green is an organic compound that can be widely used as a dyestuff for various materials; it has also emerged as a controversial agent in aquaculture. Since malachite green is proven to be carcinogenic and mutagenic, it may become a hazard to public health. For this reason, it is urgently required to analyze this controversial dye in more detail. In our current research, the interaction between malachite green and hemoglobin under physiological conditions was investigated by the methods of molecular modeling, fluorescence spectroscopy, circular dichroism (CD) as well as hydrophobic ANS displacement experiments. From the molecular docking, the central cavity of hemoglobin was assigned to possess high-affinity for malachite green, this result was corroborated by time-resolved fluorescence and hydrophobic ANS probe results. The recognition mechanism was found to be of static type, or rather the hemoglobin-malachite green complex formation occurred via noncovalent interactions such as π-π interactions, hydrogen bonds and hydrophobic interactions with an association constant of 10(4) M(-1). Moreover, the results also show that the spatial structure of the biopolymer was changed in the presence of malachite green with a decrease of the α-helix and increase of the β-sheet, turn and random coil suggesting protein damage, as derived from far-UV CD and three-dimensional fluorescence. Results of this work will help to further comprehend the molecular recognition of malachite green by the receptor protein and the possible toxicological profiles of other compounds, which are the metabolites and ramifications of malachite green.

Potential toxicity and affinity of triphenylmethane dye malachite green to lysozyme

Malachite green is a triphenylmethane dye that is used extensively in many industrial and aquacultural processes, generating environmental concerns and health problems to human being. In this contribution, the complexation between lysozyme and malachite green was verified by means of computer-aided molecular modeling, steady state and time-resolved fluorescence, and circular dichroism (CD) approaches. The precise binding patch of malachite green in lysozyme has been identified from molecular modeling and ANS displacement, Trp-62, Trp-63, and Trp-108 residues of lysozyme were earmarked to possess high-affinity for this dye, the principal forces in the lysozyme-malachite green adduct are hydrophobic and π-π interactions. Steady state fluorescence proclaimed the complex of malachite green with lysozyme yields quenching through static type, which substantiates time-resolved fluorescence measurements that lysozyme-malachite green conjugation formation has an affinity of 10(3)M(-1). Moreover, via molecular modeling and also CD data, we can safely arrive at a conclusion that the polypeptide chain of lysozyme partially destabilized upon complexation with malachite green. The data emerged here will help to further understand the toxicological action of malachite green in human body.

Synergistic action of azoreductase and laccase leads to maximal decolourization and detoxification of model dye-containing wastewaters

The azoreductase PpAzoR from Pseudomonas putida shows a broader specificity for decolourization of azo dyes than CotA-laccase from Bacillus subtilis. However, the final products of PpAzoR activity exhibited in most cases a 2 to 3-fold higher toxicity than intact dyes themselves. We show that addition of CotA-laccase to PpAzoR reaction mixtures lead to a significant drop in the final toxicity. A sequential enzymatic process was validated through the use of 18 representative azo dyes and three model wastewaters that mimic real dye-containing effluents. A heterologous Escherichia coli strain was successfully constructed co-expressing the genes coding for both PpAzoR and CotA. Whole-cell assays of recombinant strain for the treatment of model dye wastewater resulted in decolourization levels above 80% and detoxification levels up to 50%. The high attributes of this strain, make it a promising candidate for the biological treatment of industrial dye containing effluents.

Analysis of heterocyclic aromatic amines in foods by gas chromatography–mass spectrometry as their tert.-butyldimethylsilyl derivatives

A derivatization method for the analysis of 12 heterocyclic aromatic amines (HAs) in food, by gas chromatography-electron impact mass spectrometry, was developed. The amines are derivatized in a one-step reaction with N-methyl-N-(tert.-butyldimethylsilyl)trifluoroacetamide. The derivatives are characterized by easy-to-interpret mass spectra due to the prominent ion [M-57]+ by loss of a tert.-butyldimethylsilyl group, allowing quantification in the selected-ion monitoring mode at the picogram level. The effect of temperature, time, and reagents on the formation of the derivatives was monitored in detail. Quality parameters were evaluated in the optimum working conditions. This derivatization method is not applicable to the pyridoimidazoles Glu-P-1 and Glu-P-2 and to the beta-carboline harman due to incompletely derivatization. The instability of the imidazolquinoline and imidazoquinoxaline derivatives, requiring their injection on the same working day, is a further drawback. This simple, rapid and accurate derivatization procedure is suitable for routine analysis, as illustrated by the analysis of some common foods.