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Biochemistry Aug 2023The secondary metabolites of polypropanoids, methyleugenol (MEG), and estragole (EG), found in many herbs and spices, are commonly used as food flavoring agents and as...
The secondary metabolites of polypropanoids, methyleugenol (MEG), and estragole (EG), found in many herbs and spices, are commonly used as food flavoring agents and as ingredients in cosmetics. MEG and EG have been reported to cause hepatocarcinogenicity in rodents, human livers, and lung cells. The formation of -dG and -dA DNA adducts is primarily attributed to the carcinogenicity of these compounds. Therefore, these compounds have been classified as "possible human carcinogens" by the International Agency for Research on Cancer and "reasonably anticipated to be a human carcinogen" by the National Toxicology Program. Herein, we report the synthesis of the -MEG-dG and -EG-dG modified oligonucleotides to study the mutagenicity of these DNA adducts. Our studies show that -MEG-dG and -EG-dG could be bypassed by human translesion synthesis (TLS) polymerases hpolκ and hpolη in an error-free manner. The steady-state kinetics of dCTP incorporation by hpolκ across -MEG-dG and -EG-dG adducts show that the catalytic efficiencies (/) were ∼2.5- and ∼4.4-fold higher, respectively, compared to the unmodified dG template. A full-length primer extension assay demonstrates that hpolκ exhibits better catalytic efficiency than hpolη. Molecular modeling and dynamics studies capturing pre-insertion, insertion, and post-insertion steps reveal the structural features associated with the efficient bypass of the -MEG-dG adduct by hpolκ and indicate the reorientation of the adduct in the active site allowing the successful insertion of the incoming nucleotide. Together, these results suggest that though hpolκ and hpolη perform error-free TLS across MEG and EG during DNA replication, the observed carcinogenicity of these adducts could be attributed to the involvement of other low fidelity polymerases.
Topics: Humans; DNA Adducts; DNA-Directed DNA Polymerase; DNA Replication
PubMed: 37486230
DOI: 10.1021/acs.biochem.2c00663 -
Inflammation Aug 2023Inflammation is associated with the formation of reactive oxygen species (ROS) and the formation of lipid-derived compounds, such as isolevuglandins (IsoLGs),...
Inflammation is associated with the formation of reactive oxygen species (ROS) and the formation of lipid-derived compounds, such as isolevuglandins (IsoLGs), malondialdehyde, 4-hydroxy-nonenal, and 4-oxo-nonenal. The most reactive of these are the IsoLGs, which form covalent adducts with lysine residues and other cellular primary amines leading to changes in protein function, immunogenicity, and epigenetic alterations and have been shown to contribute to a number of inflammatory diseases. 2-Hydroxybenzylamine (2-HOBA) is a natural compound found in buckwheat seeds and reacts with all IsoLG adducts preventing adduct formation with proteins and DNA. Therefore, 2-HOBA is well positioned as an agent for the prevention of inflammatory-prone diseases. In this study, we examined the potential beneficial effects of 2-HOBA on oxidative stress and inflammatory biomarkers in two cohorts of healthy younger and older adults. We utilized the Olink targeted inflammation panel before and after an oral 15-day treatment regimen with 2-HOBA. We found significant relative changes in the plasma concentration of 15 immune proteins that may reflect the in vivo immune targets of 2-HOBA. Treatment of 2-HOBA resulted in significant increased levels of CCL19, IL-12β, IL-20Rα, and TNFβ, whereas levels of TWEAK significantly decreased. Ingenuity Pathway Analysis identified canonical pathways regulated by the differentially secreted cytokines, chemokines, and growth factors upon 2-HOBA treatment and further points to biofunctions related to the recruitment, attraction, and movement of different immune cell types. In conclusion, 2-HOBA significantly altered the protein biomarkers CCL19, IL-12β, IL-20Rα, TNFβ, and TWEAK, and these may be responsible for the protective effects of 2-HOBA against reactive electrophiles, such as IsoLGs, commonly expressed in conditions of excessive oxidative stress. 2-HOBA has a role as a IsoLG scavenger to proactively improve immune health in a variety of conditions.
Topics: Humans; Aged; Benzylamines; Amines; Inflammation; Proteins; Acetates
PubMed: 36935449
DOI: 10.1007/s10753-023-01801-w -
Chemico-biological Interactions Aug 2024It is established that organophosphorus pesticide (OPP) toxicity results from modification of amino acids in active sites of target proteins. OPPs can also modify...
It is established that organophosphorus pesticide (OPP) toxicity results from modification of amino acids in active sites of target proteins. OPPs can also modify unrelated target proteins such as histones and such covalent histone modifications can alter DNA-binding properties and lead to aberrant gene expression. In the present study, we report on non-enzymatic covalent modifications of calf thymus histones adducted to selected OPPs and organophosphate flame retardants (OPFRs) in vitro using a bottom-up proteomics method approach. Histones were not found to form detectable adducts with the two tested OPFRs but were avidly modified by a few of the seven OPPs that were tested in vitro. Dimethyl phosphate (or diethyl phosphate) adducts were identified on Tyr, Lys and Ser residues. Most of the dialkyl phosphate adducts were identified on Tyr residues. Methyl and ethyl modified histones were also detected. Eleven amino residues in histones showed non-enzymatic covalent methylation by exposure of dichlorvos and malathion. Our bottom-up proteomics approach showing histone-OPP adduct formation warrants future studies on the underlying mechanism of chronic illness from exposure to OPPs.
Topics: Histones; Organophosphorus Compounds; Animals; Pesticides; Cattle; Methylation; Malathion; Proteomics; Flame Retardants; Amino Acid Sequence; Dichlorvos
PubMed: 38844256
DOI: 10.1016/j.cbi.2024.111095 -
Journal of Neuroimmunology Jul 2024SUMO (small ubiquitin like modifier) conjugated proteins have emerged as an important post translational modifier of cellular function. SUMOylation modulates several... (Review)
Review
SUMO (small ubiquitin like modifier) conjugated proteins have emerged as an important post translational modifier of cellular function. SUMOylation modulates several cellular processes involved in transcriptional regulation of genes, protein-protein interactions and DNA damage and repair. Since abnormalities in SUMOylation has been observed in neoplastic and neurodegenerative disorders, the SUMO pathway has become an attractive site for targeting of new therapies to regulate SUMOylation and reduce disease burden. Conjugation of SUMO to their respective substrates is orchestrated by an enzymatic cascade involving three main enzymes, E1, activation enzyme, E2, conjugating enzyme and E3, a protein ligase. Each of these enzymes are therefore potential "druggable" sites for future therapeutics. SUMOylation is a well-known mechanism by which the innate immune response is regulated in response to viral infections and in the adaptive immune response to tumor immunity. We have shown that small molecules which inhibit the SUMO activation pathway are also capable of inhibiting autoimmune response. TAK981 which forms adducts with SUMO and anacardic acid which inhibits the E1 enzyme of the SUMO pathway were effective in preventing the development of experimental allergic encephalitis (EAE), a mouse model of multiple sclerosis. Anacardic acid and TAK981 inhibited activation of TH17 cells and reduced clinical and pathological injury in IL-17 mediated myelin oligodendrocyte glycoprotein (MOG) induced EAE. Ginkgolic acid, another known inhibitor of SUMO pathway, was also shown to be effective in reducing the severity of inflammatory arthropathies which is also IL-17 mediated. In addition, the increase in the transcription of myelin genes with TAK981 and anacardic acid improved remyelination in experimental models of demyelination. In the present review paper, we examine the mechanism of action of inhibitors of the SUMO pathway on regulating the immune response and the possibility of the use of these agents as therapeutics for MS.
Topics: Animals; Humans; Multiple Sclerosis; Sumoylation; Encephalomyelitis, Autoimmune, Experimental
PubMed: 38788318
DOI: 10.1016/j.jneuroim.2024.578371 -
Archives of Toxicology Dec 2023Aflatoxin B (AFB) is a highly hepatotoxic and carcinogenic mycotoxin produced by Aspergillus species. The compound is mainly metabolized in the liver and its metabolism...
Aflatoxin B (AFB) is a highly hepatotoxic and carcinogenic mycotoxin produced by Aspergillus species. The compound is mainly metabolized in the liver and its metabolism varies between species. The present study quantified relevant AFB- metabolites formed by mouse, rat, and human primary hepatocytes after treatment with 1 µM and 10 µM AFB. The use of liquid chromatographic separation coupled with tandem mass spectrometric detection enabled the selective and sensitive determination of phase I and phase II metabolites of AFB over incubation times of up to 24 h. The binding of AFB to macromolecules was also considered. The fastest metabolism of AFB was observed in mouse hepatocytes which formed aflatoxin P as a major metabolite and also its glucuronidated form, while AFP occurred only in traces in the other species. Aflatoxin M was formed in all species and was, together with aflatoxin Q and aflatoxicol, the main metabolite in human cells. Effective epoxidation led to high amounts of DNA adducts already 30 min post-treatment, especially in rat hepatocytes. Lower levels of DNA adducts and fast DNA repair were found in mouse hepatocytes. Also, protein adducts arising from reactive intermediates were formed rapidly in all three species. Detoxification via glutathione conjugation and subsequent formation of the N-acetylcysteine derivative appeared to be similar in mice and in rats and strongly differed from human hepatocytes which did not form these metabolites at all. The use of qualitative reference material of a multitude of metabolites and the comparison of hepatocyte metabolism in three species using advanced methods enabled considerations on toxification and detoxification mechanisms of AFB. In addition to glutathione conjugation, phase I metabolism is strongly involved in the detoxification of AFB.
Topics: Humans; Rats; Mice; Animals; Aflatoxin B1; Chromatography, High Pressure Liquid; DNA Adducts; Tandem Mass Spectrometry; DNA; Aflatoxins; Liver; Hepatocytes; Glutathione
PubMed: 37794256
DOI: 10.1007/s00204-023-03607-z -
The Journal of Physical Chemistry. B Dec 2023A DNA strand can encapsulate a silver molecule to create a nanoscale, aqueous stable chromophore. A protected cluster that strongly fluoresces can also be weakly...
A DNA strand can encapsulate a silver molecule to create a nanoscale, aqueous stable chromophore. A protected cluster that strongly fluoresces can also be weakly photolabile, and we describe the laser-driven photochemistry of the green fluorophore CACTCGT/Ag. The embedded cluster is selectively photoexcited at 490 nm and then bleached, and we describe how the efficiency, products, and route of this photochemical reaction are controlled by the DNA cage. With irradiation at 496.5 nm, the cluster absorption progressively drops to give a photodestruction quantum yield of 1.5 (±0.2) × 10, ∼10× less efficient than fluorescence. A new λ = 335 nm chromophore develops because the precursor with 4 Ag is converted into a group of clusters with 2 Ag - Ag, Ag, Ag, and Ag. The 4-7 Ag in this series are chemically distinct from the 2 Ag because they are selectively etched by iodide. This halide precipitates silver to favor only the smallest Ag cluster, but the larger clusters re-develop when the precipitated Ag ions are replenished. DNA-bound Ag decomposes because it is electronically excited and then reacts with oxygen. This two-step process may be state-specific because O quenches the red luminescence from Ag. However, the rate constant of 2.3 (±0.2) × 10 M s is relatively small, which suggests that the surrounding DNA matrix hinders O diffusion. On the basis of analogous photoproducts with methylene blue, we propose that a reactive oxygen species is produced and then oxidizes Ag to leave behind a loose Ag-DNA skeleton. These findings underscore the ability of DNA scaffolds to not only tune the spectra but also guide the reactions of their molecular silver adducts.
PubMed: 38054435
DOI: 10.1021/acs.jpcb.3c06358 -
Clinical & Translational Oncology :... Dec 2023The use of tobacco products is one of the established contributors toward the development and spread of oral cancer. Additionally, recent research has indicated oral... (Review)
Review
The use of tobacco products is one of the established contributors toward the development and spread of oral cancer. Additionally, recent research has indicated oral microbiome, infections with Human papilloma virus (HPV), Epstein-Barr virus (EBV), Candida as significant contributing factors to this disease along with lifestyle habits. Deregulation of cellular pathways envisaging metabolism, transcription, translation, and epigenetics caused by these risk factors either individually or in unison is manifold, resulting in the increased risk of oral cancer. Globally, this cancer continues to exist as one of the major causes of cancer-related mortalities; the numbers in the developing South Asian countries clearly indicate yearly escalation. This review encompasses the variety of genetic modifications, including adduct formation, mutation (duplication, deletion, and translocation), and epigenetic changes evident in oral squamous cell carcinoma (OSCC). In addition, it highlights the interference caused by tobacco products in Wnt signaling, PI3K/Akt/mTOR, JAK-STAT, and other important pathways. The information provided also ensures a comprehensive and critical revisit to non-tobacco-induced OSCC. Extensive literature survey and analysis has been conducted to generate the chromosome maps specifically highlighting OSCC-related mutations with the potential to act as spectacles for the early diagnosis and targeted treatment of this disease cancer.
Topics: Humans; Herpesvirus 4, Human; Epstein-Barr Virus Infections; Mouth Neoplasms; Carcinoma, Squamous Cell; Phosphatidylinositol 3-Kinases; Squamous Cell Carcinoma of Head and Neck; Head and Neck Neoplasms; Mutation
PubMed: 37058208
DOI: 10.1007/s12094-023-03192-8 -
Environmental Pollution (Barking, Essex... Oct 2023Aromatic amines (AAs) are polar organic chemicals with a wide environmental distribution originating from various sources, such as tobacco smoke, diesel exhaust, and...
Assessment of urinary aromatic amines in Brazilian pregnant women and association with DNA damage: Influence of genetic diversity, lifestyle, and environmental and socioeconomic factors.
Aromatic amines (AAs) are polar organic chemicals with a wide environmental distribution originating from various sources, such as tobacco smoke, diesel exhaust, and dermal absorption from textile products with azo dyes. The toxicity profile of AAs is directly related to the amino group's metabolic activation and the generation of the reactive intermediate, forming DNA adducts and potential carcinogenicity. Urinary levels of 8-hydroxy-2'-deoxyguanosine (8OHdG) are an important biomarker of DNA damage. Since AAs have been shown to cross the placental barrier, being a risk factor for adverse birth outcomes, prenatal exposure is a great public health concern. The present study aimed to measure the urinary levels of 58 AAs in Brazilian pregnant women (n = 300) and investigated the impact of this exposure on DNA damage by quantifying 8OHdG levels. The influence of tobacco smoke exposure and dermal absorption of AAs by clothes on urinary levels was also assessed. The results showed a 100% detection rate for eight AAs, two of them regulated by the European Union (2,6-dimethylaniline and 2,4-diaminotolune). Hundreds of AAs may be derived from aniline, which here showed a median of 1.38 ng/mL. Aniline also correlated positively with 2,6-dimethylaniline, p-aminophenol, and other AAs, suggesting exposure to multiple sources. The present findings suggest that both tobacco smoke and dermal contact with clothes containing azo dyes are potential sources that might strongly influence urinary levels of AAs in Brazilian pregnant women. A multiple regression linear model (R = 0.772) suggested that some regulated AAs (i.e., 2-naphthylamine and 4-aminobiphenyl), nicotine, smoke habit, age, and Brazilian region could induce DNA damage occurrence, increasing the levels of 8OHdG. Given the limited available data on human exposure to carcinogenic AAs, as well as the lack of toxicological information on those non-regulated, further studies focused on measuring their levels in human fluids and the potential exposure sources are clearly essential.
Topics: Pregnancy; Humans; Female; Tobacco Smoke Pollution; Pregnant Women; 8-Hydroxy-2'-Deoxyguanosine; Brazil; Placenta; Aniline Compounds; Amines; DNA Damage; Smoke; Azo Compounds; Life Style; Socioeconomic Factors; Genetic Variation
PubMed: 37572848
DOI: 10.1016/j.envpol.2023.122366 -
Journal of Fluorescence Nov 2023The presence of acylamide (AA) in large group of food products and its health hazards have been confirmed by scientists. In this study, a simple and innovative biosensor...
The presence of acylamide (AA) in large group of food products and its health hazards have been confirmed by scientists. In this study, a simple and innovative biosensor for AA determination was designed based on single-stranded DNA (ssDNA) with partial guanine and GelRed. The idea of this biosensor is based on the formation of AA-ssDNA adduct through the strong binding interaction between AA and guanine base of ssDNA, which subsequently inhibits the interaction of ssDNA and GelRed, leading to a weak fluorescence intensity. The binding interaction between AA and ssDNA was confirmed by UV-Vis absorption spectrometry and fluorescence intensity. Under optimum conditions, the designed biosensor exhibited excellent linear response in range of 0.01-95 mM, moreover it showed high selectivity toward AA. The limit of detection was 0.003 mM. This biosensor was successfully applied for the determination of AA in water extract of potato fries and coffee in the range of 0.05-100 mM with LOD of 0.01 mM and 0.05-95 mM with LOD of 0.004 mM, respectively.
PubMed: 37930599
DOI: 10.1007/s10895-023-03479-7 -
Proceedings of the National Academy of... May 2024DNA base damage is a major source of oncogenic mutations and disruption to gene expression. The stalling of RNA polymerase II (RNAP) at sites of DNA damage and the...
DNA base damage is a major source of oncogenic mutations and disruption to gene expression. The stalling of RNA polymerase II (RNAP) at sites of DNA damage and the subsequent triggering of repair processes have major roles in shaping the genome-wide distribution of mutations, clearing barriers to transcription, and minimizing the production of miscoded gene products. Despite its importance for genetic integrity, key mechanistic features of this transcription-coupled repair (TCR) process are controversial or unknown. Here, we exploited a well-powered in vivo mammalian model system to explore the mechanistic properties and parameters of TCR for alkylation damage at fine spatial resolution and with discrimination of the damaged DNA strand. For rigorous interpretation, a generalizable mathematical model of DNA damage and TCR was developed. Fitting experimental data to the model and simulation revealed that RNA polymerases frequently bypass lesions without triggering repair, indicating that small alkylation adducts are unlikely to be an efficient barrier to gene expression. Following a burst of damage, the efficiency of transcription-coupled repair gradually decays through gene bodies with implications for the occurrence and accurate inference of driver mutations in cancer. The reinitation of transcription from the repair site is not a general feature of transcription-coupled repair, and the observed data is consistent with reinitiation never taking place. Collectively, these results reveal how the directional but stochastic activity of TCR shapes the distribution of mutations following DNA damage.
Topics: DNA Repair; DNA Damage; Transcription, Genetic; RNA Polymerase II; Animals; Stochastic Processes; Mice; DNA; Humans; Alkylation; Mutation; Excision Repair
PubMed: 38717857
DOI: 10.1073/pnas.2403871121