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Environmental Science & Technology Jul 2023Exposure to chemical pollution can induce genetic and epigenetic alterations, developmental changes, and reproductive disorders, leading to population declines in...
Exposure to chemical pollution can induce genetic and epigenetic alterations, developmental changes, and reproductive disorders, leading to population declines in polluted environments. These effects are triggered by chemical modifications of DNA nucleobases (DNA adducts) and epigenetic dysregulation. However, linking DNA adducts to the pollution load remains challenging, and the lack of evidence-based DNA adductome response to pollution hampers the development and application of DNA adducts as biomarkers for environmental health assessment. Here, we provide the first evidence for pollution effects on the DNA modifications in wild populations of Baltic sentinel species, the amphipod . A workflow based on high-resolution mass spectrometry to screen and characterize genomic DNA modifications was developed, and its applicability was demonstrated by profiling DNA modifications in the amphipods collected in areas with varying pollution loads. Then, the correlations between adducts and the contaminants level (polycyclic aromatic hydrocarbons (PAHs), trace metals, and pollution indices) in the sediments at the collection sites were evaluated. A total of 119 putative adducts were detected, and some (5-me-dC, N-me-dA, 8-oxo-dG, and dI) were structurally characterized. The DNA adductome profiles, including epigenetic modifications, differed between the animals collected in areas with high and low contaminant levels. Furthermore, the correlations between the adducts and PAHs were similar across the congeners, indicating possible additive effects. Also, high-mass adducts had significantly more positive correlations with PAHs than low-mass adducts. By contrast, correlations between the DNA adducts and trace metals were stronger and more variable than for PAHs, indicating metal-specific effects. These associations between DNA adducts and environmental contaminants provide a new venue for characterizing genome-wide exposure effects in wild populations and apply DNA modifications in the effect-based assessment of chemical pollution.
Topics: Animals; DNA Adducts; DNA; Environmental Pollution; Polycyclic Aromatic Hydrocarbons; Geologic Sediments
PubMed: 37341092
DOI: 10.1021/acs.est.3c00499 -
ACS Omega Oct 2023Stimuli-responsive ruthenium complexes - and -[Ru(Ctpy)(Cpyqu) OH] (- and -; Ctpy = 4'-decyloxy-2,2':6',2″-terpyridine and Cpyqu =...
Stimuli-responsive ruthenium complexes - and -[Ru(Ctpy)(Cpyqu) OH] (- and -; Ctpy = 4'-decyloxy-2,2':6',2″-terpyridine and Cpyqu = 2-[2'-(6'-decyloxy)-pyridyl]quinoline) were experimentally studied for adduct formation with a model DNA base. At 303 K, - exhibited 1:1 adduct formation with 9-ethylguanine (9-EtG) to yield -[Ru(Ctpy)(Cpyqu)(9-EtG)] (-). Rotation of the guanine ligand on the ruthenium center was sterically hindered by the presence of an adjacent quinoline moiety at 303 K. Results from H NMR measurements indicated that photoirradiation of a - solution caused photoisomerization to -, whereas heating of - caused ligand substitution to -. The distal isomer of the aqua complex, -, was observed to slowly revert to - at 303 K. In the presence of 9-EtG, - underwent thermal back-isomerization to - and adduct formation to -. Kinetic analysis of H NMR measurements showed that adduct formation between - and 9-EtG was 8-fold faster than that between - and 9-EtG. This difference may be attributed to intramolecular hydrogen bonding and steric repulsion between the aqua ligand and the pendant moiety of the bidentate ligand..
PubMed: 37841177
DOI: 10.1021/acsomega.3c05343 -
NAR Cancer Dec 2023The therapeutic efficacy of cisplatin and oxaliplatin depends on the balance between the DNA damage induction and the DNA damage response of tumor cells. Based on...
The therapeutic efficacy of cisplatin and oxaliplatin depends on the balance between the DNA damage induction and the DNA damage response of tumor cells. Based on clinical evidence, oxaliplatin is administered to cisplatin-unresponsive cancers, but the underlying molecular causes for this tumor specificity are not clear. Hence, stratification of patients based on DNA repair profiling is not sufficiently utilized for treatment selection. Using a combination of genetic, transcriptomics and imaging approaches, we identified factors that promote global genome nucleotide excision repair (GG-NER) of DNA-platinum adducts induced by oxaliplatin, but not by cisplatin. We show that oxaliplatin-DNA lesions are a poor substrate for GG-NER initiating factor XPC and that DDB2 and HMGA2 are required for efficient binding of XPC to oxaliplatin lesions and subsequent GG-NER initiation. Loss of DDB2 and HMGA2 therefore leads to hypersensitivity to oxaliplatin but not to cisplatin. As a result, low DDB2 levels in different colon cancer cells are associated with GG-NER deficiency and oxaliplatin hypersensitivity. Finally, we show that colon cancer patients with low DDB2 levels have a better prognosis after oxaliplatin treatment than patients with high DDB2 expression. We therefore propose that DDB2 is a promising predictive marker of oxaliplatin treatment efficiency in colon cancer.
PubMed: 38058548
DOI: 10.1093/narcan/zcad057 -
The Journal of Biological Chemistry Aug 2023The DNA adduct 6-oxo-MdG, (3-(2'-deoxy-β-D-erythro-pentofuranosyl)-6-oxo-pyrimido(1,2alpha)purin-10(3H)-one) is formed in the genome via oxidation of the...
The DNA adduct 6-oxo-MdG, (3-(2'-deoxy-β-D-erythro-pentofuranosyl)-6-oxo-pyrimido(1,2alpha)purin-10(3H)-one) is formed in the genome via oxidation of the peroxidation-derived adduct MdG. However, the effect of 6-oxo-MdG adducts on subsequent DNA replication is unclear. Here we investigated the ability of the human Y-family polymerase hPol η to bypass 6-oxo-MdG. Using steady-state kinetics and analysis of DNA extension products by liquid chromatography-tandem mass spectrometry, we found hPol η preferentially inserts a dAMP or dGMP nucleotide into primer-templates across from the 6-oxo-MdG adduct, with dGMP being slightly preferred. We also show primer-templates with a 3'-terminal dGMP or dAMP across from 6-oxo-MdG were extended to a greater degree than primers with a dCMP or dTMP across from the adduct. In addition, we explored the structural basis for bypass of 6-oxo-MdG by hPol η using X-ray crystallography of both an insertion-stage and an extension-stage complex. In the insertion-stage complex, we observed that the incoming dCTP opposite 6-oxo-MdG, although present during crystallization, was not present in the active site. We found the adduct does not interact with residues in the hPol η active site but rather forms stacking interactions with the base pair immediately 3' to the adduct. In the extension-stage complex, we observed the 3' hydroxyl group of the primer strand dGMP across from 6-oxo-MdG is not positioned correctly to form a phosphodiester bond with the incoming dCTP. Taken together, these results indicate 6-oxo-MdG forms a strong block to DNA replication by hPol η and provide a structural basis for its blocking ability.
Topics: Humans; DNA Adducts; DNA-Directed DNA Polymerase; DNA; DNA Replication
PubMed: 37468099
DOI: 10.1016/j.jbc.2023.105067 -
The Science of the Total Environment Jan 2024Benzo[a]pyrene (BaP) is a representative polycyclic aromatic hydrocarbon widely present in the environment. We previously reported that the aryl hydrocarbon receptor...
Benzo[a]pyrene (BaP) is a representative polycyclic aromatic hydrocarbon widely present in the environment. We previously reported that the aryl hydrocarbon receptor (AHR) mediates BaP-induced apoptosis and cardiac malformations in zebrafish embryos, but the underlying molecular mechanisms were unclear. Since BaP is a mutagenetic compound, we hypothesize that BaP induces apoptosis and heart defects via AHR-mediated DNA damage. In this study, zebrafish embryos were exposed to BaP at a concentration of 0.1 μM from 2 to 72 h post fertilization, either with or without inhibitors/agonists. AHR activity and levels of reactive oxygen species (ROS) were examined under a fluorescence microscope. mRNA expression levels were quantified by qPCR. DNA damage and apoptosis were detected by immunofluorescence. Our findings revealed that BaP exposure significantly increased BPDE-DNA adducts, mitochondrial damage, apoptosis and heart defects in zebrafish embryos. These effects were counteracted by inhibiting AHR/cyp1a1 using pharmaceutical inhibitors or genetic knockdown. Furthermore, we observed that spironolactone, an antagonist of nucleotide excision repair (NER), significantly enhanced BaP-induced BPDE-DNA adducts, mitochondrial damage, apoptosis and heart malformation rates. Conversely, SRT1720, a SIRT1 agonist, reduced the adverse effects of BaP. Supplementation with spironolactone also enhanced γ-H2AX signals in the heart of zebrafish embryos exposed to BaP. Additional experiments demonstrated that BaP suppressed the expression of SIRT1. We further established that AHR, when activated by BaP, directly inhibited SIRT1 transcription, leading to downregulation of XPC and XPA, which are essential NER genes involved in the recognition and verification steps of the NER process. Taken together, our results indicate that AHR mediates BaP-induced DNA damage in the heart of zebrafish embryos by inducing BPDE-DNA adduct formation via the AHR/Cyp1a1 signalling pathway, as well as suppressing NER via AHR-mediated inhibition of SIRT1.
Topics: Animals; DNA Adducts; Zebrafish; Cytochrome P-450 CYP1A1; Sirtuin 1; 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; Receptors, Aryl Hydrocarbon; Spironolactone; DNA Damage; Heart Defects, Congenital; Benzo(a)pyrene
PubMed: 37806592
DOI: 10.1016/j.scitotenv.2023.167636 -
The Journal of Physical Chemistry. B Oct 2023DNA is damaged through various exogenous sources (e.g., automobile exhaust, tobacco smoke, and processed foods), which can yield diverse C8-dG bulky aryl adducts....
DNA is damaged through various exogenous sources (e.g., automobile exhaust, tobacco smoke, and processed foods), which can yield diverse C8-dG bulky aryl adducts. Adducts are known to induce structural changes to DNA that can lead to various biological outcomes, ranging from cell death to diseases such as cancer. Unfortunately, the relationship between the chemical composition of the damaged product, the adducted DNA structure, and the biological consequences is not well understood, which limits the development of disease detection and prevention strategies. The present study uses density functional theory (DFT) calculations and quintuplicate 1 μs molecular dynamics (MD) simulations to characterize the structure of DNA containing 21 model C8-dG adducts that systematically differ in size (phenyl to pyrenyl), shape (α (2,3), β (3,4) fusion, or ring substitution), and nucleobase-aryl group linkage (N, O, and C-linked). DFT calculations reveal that the inherent structural features of the G nucleobase adducts are impacted by linker type and bulky moiety shape, but not size, with the conformational flexibility reducing with α-ring fusion and linker composition as N > O > C. These structural properties are maintained in nucleoside models, which also reveal an increased propensity for -to- rotation about the glycosidic bond with N < O < C linker type. Although these diverse chemical features do not influence the global structure of adducted DNA, the adducts differentially impact the conformation local to the adducted site, including the relative populations of structures with the bulky moiety in the major groove (B conformer) and intercalated (stacked) into the helix (S conformer). Specifically, while the smallest phenyl adducts favor the B conformation and the largest pyrenyl-derived adducts stabilize the S conformation, the B/S ratio decreases with an increase in ring size and N > O > C linker composition. The shape and size (length) of the adduct can further finetune the B/S ratio, with β-fused naphthyl or α-fused phenanthryl N-linked adducts and O or C-linked adducts containing ring substitution increasing the prevalence of the S adducted DNA conformation. Overall, this work uncovers the significant effect of bulky moiety size and linker type, as well as the lesser impact of aryl group shape, on adducted DNA structure, which suggests differential replication and repair outcomes, and thereby represents an important step toward rationalizing connections between the structure and biological consequences of diverse DNA adducts.
Topics: Molecular Dynamics Simulation; Guanine; DNA Adducts; DNA; Nucleic Acid Conformation
PubMed: 37831812
DOI: 10.1021/acs.jpcb.3c04864 -
BMC Cancer Jan 2024KRAS is the undisputed champion of oncogenes, and despite its prominent role in oncogenesis as mutated gene, KRAS mutation appears infrequent in gliomas. Nevertheless,...
BACKGROUND
KRAS is the undisputed champion of oncogenes, and despite its prominent role in oncogenesis as mutated gene, KRAS mutation appears infrequent in gliomas. Nevertheless, gliomas are considered KRAS-driven cancers due to its essential role in mouse malignant gliomagenesis. Glioblastoma is the most lethal primary brain tumor, often associated with disturbed RAS signaling. For newly diagnosed GBM, the current standard therapy is alkylating agent chemotherapy combined with radiotherapy. Cisplatin is one of the most effective anticancer drugs and is used as a first-line treatment for a wide spectrum of solid tumors (including medulloblastoma and neuroblastoma) and many studies are currently focused on new delivery modalities of effective cisplatin in glioblastoma. Its mechanism of action is mainly based on DNA damage, inducing the formation of DNA adducts, triggering a series of signal-transduction pathways, leading to cell-cycle arrest, DNA repair and apoptosis.
METHODS
Long-term cultures of human glioblastoma, U87MG and U251MG, were either treated with cis-diamminedichloroplatinum (cisplatin, CDDP) and/or MEK-inhibitor PD98059. Cytotoxic responses were assessed by cell viability (MTT), protein expression (Western Blot), cell cycle (PI staining) and apoptosis (TUNEL) assays. Further, gain-of-function experiments were performed with cells over-expressing mutated hypervariable region (HVR) KRAS plasmids.
RESULTS
Here, we studied platinum-based chemosensitivity of long-term cultures of human glioblastoma from the perspective of KRAS expression, by using CDDP and MEK-inhibitor. Endogenous high KRAS expression was assessed at transcriptional (qPCR) and translational levels (WB) in a panel of primary and long-term glioblastoma cultures. Firstly, we measured immediate cellular adjustment through direct regulation of protein concentration of K-Ras4B in response to cisplatin treatment. We found increased endogenous protein abundance and involvement of the effector pathway RAF/MEK/ERK mitogen-activated protein kinase (MAPK) cascade. Moreover, as many MEK inhibitors are currently being clinically evaluated for the treatment of high-grade glioma, so we concomitantly tested the effect of the potent and selective non-ATP-competitive MEK1/2 inhibitor (PD98059) on cisplatin-induced chemosensitivity in these cells. Cell-cycle phase distribution was examined using flow cytometry showing a significant cell-cycle arrest in both cultures at different percentage, which is modulated by MEK inhibition. Cisplatin-induced cytotoxicity increased sub-G1 percentage and modulates G2/M checkpoint regulators cyclins D1 and A. Moreover, ectopic expression of a constitutively active KRAS rescued CDDP-induced apoptosis and different HVR point mutations (particularly Ala 185) reverted this phenotype.
CONCLUSION
These findings warrant further studies of clinical applications of MEK1/2 inhibitors and KRAS as 'actionable target' of cisplatin-based chemotherapy for glioblastoma.
Topics: Humans; Antineoplastic Agents; Cell Line, Tumor; Cisplatin; Glioblastoma; Mitogen-Activated Protein Kinase Kinases; Platinum; Protein Kinase Inhibitors; Proto-Oncogene Proteins p21(ras)
PubMed: 38225605
DOI: 10.1186/s12885-023-11758-6 -
Archives of Toxicology Jun 2024Dietary exposure to N-nitrosamines has recently been assessed by the European Food Safety Authority (EFSA) to result in margins of exposure that are conceived to...
Dietary exposure to N-nitrosamines has recently been assessed by the European Food Safety Authority (EFSA) to result in margins of exposure that are conceived to indicate concern with respect to human health risk. However, evidence from more than half a century of international research shows that N-nitroso compounds (NOC) can also be formed endogenously. In this commentary of the Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG), the complex metabolic and physiological biokinetics network of nitrate, nitrite and reactive nitrogen species is discussed with emphasis on its influence on endogenous NOC formation. Pioneering approaches to monitor endogenous NOC have been based on steady-state levels of N-nitrosodimethylamine (NDMA) in human blood and on DNA adduct levels in blood cells. Further NOC have not been considered yet to a comparable extent, although their generation from endogenous or exogenous precursors is to be expected. The evidence available to date indicates that endogenous NDMA exposure could exceed dietary exposure by about 2-3 orders of magnitude. These findings require consolidation by refined toxicokinetics and DNA adduct monitoring data to achieve a credible and comprehensive human health risk assessment.
Topics: Humans; Risk Assessment; Nitrosamines; Dietary Exposure; Dimethylnitrosamine; DNA Adducts; Food Contamination; Food Safety; Animals; Nitrites; Nitrates; Reactive Nitrogen Species
PubMed: 38573336
DOI: 10.1007/s00204-024-03726-1 -
Toxicological Sciences : An Official... Mar 2024Increasing environmental genotoxic chemicals have been shown to induce epigenetic alterations. However, the interaction between genetics and epigenetics in chemical...
Increasing environmental genotoxic chemicals have been shown to induce epigenetic alterations. However, the interaction between genetics and epigenetics in chemical carcinogenesis is still not fully understood. Here, we constructed an in vitro human lung carcinogenesis model (16HBE-T) by treating human bronchial epithelial cells with a typical significant carcinogen benzo(a)pyrene (BaP). We identified a novel circular RNA, circ0087385, which was overexpressed in 16HBE-T and human lung cancer cell lines, as well as in lung cancer tissues and serum exosomes from lung cancer patients. The upregulated circ0087385 after exposure to BaP promoted DNA damage in the early stage of chemical carcinogenesis and affected the cell cycle, proliferation, and apoptosis of the malignantly transformed cells. Overexpression of circ0087385 enhanced the expression of cytochrome P450 1A1 (CYP1A1), which is crucial for metabolically activating BaP. Interfering with circ0087385 or CYP1A1 reduced the levels of ultimate carcinogen benzo(a)pyrene diol epoxide (BPDE) and BPDE-DNA adducts. Interfering with CYP1A1 partially reversed the DNA damage induced by high expression of circ0087385, as well as decreased the level of BPDE and BPDE-DNA adducts. These findings provide novel insights into the interaction between epigenetics and genetics in chemical carcinogenesis which are crucial for understanding the epigenetic and genetic toxicity of chemicals.
Topics: Humans; Cytochrome P-450 CYP1A1; DNA Adducts; 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; Lung Neoplasms; Benzo(a)pyrene; DNA Damage; Carcinogens; Carcinogenesis
PubMed: 38310363
DOI: 10.1093/toxsci/kfae017 -
Journal of Environmental Science and... 2024Hexavalent chromium (Cr(VI)) is a well-known occupational and environmental human carcinogen. The cellular effect of Cr(VI) is complex and often nonspecific due to its... (Review)
Review
Hexavalent chromium (Cr(VI)) is a well-known occupational and environmental human carcinogen. The cellular effect of Cr(VI) is complex and often nonspecific due to its ability to modulate multiple cellular targets. The toxicity of Cr(VI) is strongly linked to the generation of reactive oxygen species (ROS) during its reduction process. ROS can cause oxidation of cellular macromolecules, such as proteins, lipids, and DNA, thereby altering their functions. A major genotoxic effect of Cr(VI) that contributes to carcinogenesis is the formation of DNA adducts, which can lead to DNA damage. Modulations of cellular signaling pathways and epigenetics may also contribute to the carcinogenic effects of Cr(VI). Cr(VI) has a major impact on many aspects of mitochondrial biology, including oxidative phosphorylation, mitophagy, and mitochondrial biogenesis. These effects have the potential to alter the trajectory of Cr(VI)-induced carcinogenic process. This perspective article summarizes current understandings of the effect of Cr(VI) on mitochondria and discusses the future directions of research in this area, particularly with regard to carcinogenesis.
Topics: Chromium; Mitochondria; Humans; Carcinogenesis; Reactive Oxygen Species; Carcinogens; DNA Damage; Animals; Carcinogens, Environmental
PubMed: 38230947
DOI: 10.1080/26896583.2024.2301899