Modulation of benzo[a]pyrene-DNA adduct formation by CYP1 inducer and inhibitor

Benzo[a]pyrene exposure prevents high fat diet-induced obesity in the 4T1 model of mammary carcinoma

Tumor metastasis is the main cause of death in triple-negative breast cancer (TNBC) patients. TNBC is the most aggressive subtype of breast cancer lacking the expression of estrogen, progesterone, and human epidermal growth factor 2 receptors, thereby rendering it insensitive to targeted therapies. It has been well-established that excess adiposity contributes to the progression of TNBC; however, due to the aggressive nature of this breast cancer subtype, it is imperative to determine how multiple factors can contribute to progression. Therefore, we aimed to investigate if exposure to an environmental carcinogen could impact a pre-existing obesity-promoted cancer. We utilized a spontaneous lung metastatic mouse model where 4T1 breast tumor cells are injected into the mammary gland of BALB/c mice. Feeding a high fat diet (HFD) in this model has been shown to promote tumor growth and metastasis. Herein, we tested the effects of both a HFD and benzo(a)pyrene (B[a]P) exposure. Our results indicate that diet and B[a]P had no tumor promotional interaction. However, unexpectedly, our findings reveal an inhibitory effect of B[a]P on body weight, adipose tissue deposition, and tumor volume at time of sacrifice specifically under HFD conditions.

High Expression of AhR and Environmental Pollution as AhR-Linked Ligands Impact on Oncogenic Signaling Pathways in Western Patients with Gastric Cancer-A Pilot Study

The vast majority of gastric cancer (GC) cases are adenocarcinomas including intestinal and diffuse GC. The incidence of diffuse GC, often associated with poor overall survival, has constantly increased in Western countries. Epidemiological studies have reported increased mortality from GC after occupational exposure to pro-carcinogens that are metabolically activated by cytochrome P450 enzymes through aryl hydrocarbon receptor (AhR). However, little is known about the role of AhR and environmental AhR ligands in diffuse GC as compared to intestinal GC in Western patients. In a cohort of 29, we demonstrated a significant increase in AhR protein and mRNA expression levels in GCs independently of their subtypes and clinical parameters. AhR and RHOA mRNA expression were correlated in diffuse GC. Further, our study aimed to characterize in GC how AhR and the AhR-related genes cytochrome P450 1A1 (CYP1A1) and P450 1B1 (CYP1B1) affect the mRNA expression of a panel of genes involved in cancer development and progression. In diffuse GC, CYP1A1 expression correlated with genes involved in IGF signaling, epithelial-mesenchymal transition (Vimentin), and migration (MMP2). Using the poorly differentiated KATO III epithelial cell line, two well-known AhR pollutant ligands, namely 2-3-7-8 tetrachlorodibenzo-p-dioxin (TCDD) and benzo[a]pyrene (BaP), strongly increased the expression of CYP1A1 and Interleukin1β (IL1B), and to a lesser extend UGT1, NQO1, and AhR Repressor (AhRR). Moreover, the increased expression of CYP1B1 was seen in diffuse GC, and IHC staining indicated that CYP1B1 is mainly expressed in stromal cells. TCDD treatment increased CYP1B1 expression in KATO III cells, although at lower levels as compared to CYP1A1. In intestinal GC, CYP1B1 expression is inversely correlated with several cancer-related genes such as IDO1, a gene involved in the early steps of tryptophan metabolism that contributes to the endogenous AhR ligand kynurenine expression. Altogether, our data provide evidence for a major role of AhR in GC, as an environmental xenobiotic receptor, through different mechanisms and pathways in diffuse and intestinal GC. Our results support the continued efforts to clarify the identity of exogenous AhR ligands in diffuse GC in order to define new therapeutic strategies.

Low-Penetrance Susceptibility Variants in Colorectal Cancer-Current Outlook in the Field

Colorectal cancer (CRC) is one of the most frequent and mortality-causing neoplasia, with various distributions between populations. Strong hereditary predispositions are the causatives of a small percentage of CRC, and most cases have no transparent genetic background. This is a vast arena for exploring cancer low-susceptibility genetic variants. Nonetheless, the research that has been conducted to date has failed to deliver consistent conclusions and often features conflicting messages, causing chaos in this field. Therefore, we decided to organize the existing knowledge on this topic. We screened the PubMed and Google Scholar databases. We drew up markers by gene locus gathered by hallmark: oncogenes, tumor suppressor genes, genes involved in DNA damage repair, genes involved in metabolic pathways, genes involved in methylation, genes that modify the colonic microenvironment, and genes involved in the immune response. Low-penetration genetic variants increasing the risk of cancer are often population-specific, hence the urgent need for large-scale testing. Such endeavors can be successful only when financial decision-makers are united with social educators, medical specialists, genetic consultants, and the scientific community. Countries' policies should prioritize research on this subject regardless of cost because it is the best investment. In this review, we listed potential low-penetrance CRC susceptibility alleles whose role remains to be established.

Dose-related Mutagenic and Clastogenic Effects of Benzo[b]fluoranthene in Mouse Somatic Tissues Detected by Duplex Sequencing and the Micronucleus Assay

Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants that originate from the incomplete combustion of organic materials. We investigated the clastogenicity and mutagenicity of benzo[ b ]fluoranthene (BbF), one of 16 priority PAHs, in MutaMouse males after a 28-day oral exposure. BbF causes robust dose-dependent increases in micronucleus frequency in peripheral blood, indicative of chromosome damage. Duplex Sequencing (DS), an error-corrected sequencing technology, reveals that BbF induces dose-dependent increases in mutation frequencies in bone marrow (BM) and liver. Mutagenicity is increased in intergenic relative to genic regions, suggesting a role for transcription-coupled repair of BbF-induced DNA damage. At higher doses, the maximum mutagenic response to BbF is higher in liver, which has a lower mitotic index but higher metabolic capacity than BM; however, mutagenic potency is comparable between the two tissues. BbF induces primarily C:G>A:T mutations, followed by C:G>T:A and C:G>G:C, indicating that BbF metabolites mainly target guanines and cytosines. The mutation spectrum of BbF correlates with cancer mutational signatures associated with tobacco exposure, supporting its contribution to the carcinogenicity of combustion-derived PAHs in humans. Overall, BbF's mutagenic effects are similar to benzo[ a ]pyrene, a well-studied mutagenic PAH. Our work showcases the utility of DS for effective mutagenicity assessment of environmental pollutants.

Synopsis

We used Duplex Sequencing to study the mutagenicity of benzo[ b ]fluoranthene across the mouse genome. Dose-dependent changes in mutation frequency and spectrum quantify its role in PAH-induced carcinogenicity.

High-throughput characterization of functional variants highlights heterogeneity and polygenicity underlying lung cancer susceptibility

Genome-wide association studies (GWASs) have identified numerous lung cancer risk-associated loci. However, decoding molecular mechanisms of these associations is challenging since most of these genetic variants are non-protein-coding with unknown function. Here, we implemented massively parallel reporter assays (MPRAs) to simultaneously measure the allelic transcriptional activity of risk-associated variants. We tested 2,245 variants at 42 loci from 3 recent GWASs in East Asian and European populations in the context of two major lung cancer histological types and exposure to benzo(a)pyrene. This MPRA approach identified one or more variants (median 11 variants) with significant effects on transcriptional activity at 88% of GWAS loci. Multimodal integration of lung-specific epigenomic data demonstrated that 63% of the loci harbored multiple potentially functional variants in linkage disequilibrium. While 22% of the significant variants showed allelic effects in both A549 (adenocarcinoma) and H520 (squamous cell carcinoma) cell lines, a subset of the functional variants displayed a significant cell-type interaction. Transcription factor analyses nominated potential regulators of the functional variants, including those with cell-type-specific expression and those predicted to bind multiple potentially functional variants across the GWAS loci. Linking functional variants to target genes based on four complementary approaches identified candidate susceptibility genes, including those affecting lung cancer cell growth. CRISPR interference of the top functional variant at 20q13.33 validated variant-to-gene connections, including RTEL1, SOX18, and ARFRP1. Our data provide a comprehensive functional analysis of lung cancer GWAS loci and help elucidate the molecular basis of heterogeneity and polygenicity underlying lung cancer susceptibility.

Metformin alleviates benzo[a]pyrene-induced alveolar injury by inhibiting necroptosis and protecting AT2 cells

Exposure to benzo[a]pyrene (B[a]P) has been linked to lung injury and carcinogenesis. Airway epithelial cells express the B[a]P receptor AHR, so B[a]P is considered to mainly target airway epithelial cells, whereas its potential impact on alveolar cells remains inadequately explored. Metformin, a first-line drug for diabetes, has been shown to exert anti-inflammatory and tissue repair-promoting effects under various injurious conditions. Here, we explored the effect of chronic B[a]P exposure on alveolar cells and the impact of metformin on B[a]P-induced lung injury by examining the various parameters including lung histopathology, inflammation, fibrosis, and related signal pathway activation. MLKL knockout (Mlkl-/-) and AT2-lineage tracing mice (SftpcCre-ERT2;LSL-tdTomatoflox+/-) were used to delineate the role of necroptosis in B[a]P-induced alveolar epithelial injury and repair. Mice receiving weekly administration of B[a]P for 6 weeks developed a significant alveolar damaging phenotype associated with pulmonary inflammation, fibrosis, and activation of the necroptotic cell death pathway. These effects were significantly relieved in MLKL null mice. Furthermore, metformin treatment, which were found to promote AMPK phosphorylation and inhibit RIPK3, as well as MLKL phosphorylation, also significantly alleviated B[a]P-induced necroptosis and lung injury phenotype. However, the protective efficacy of metformin was rendered much less effective in Mlkl null mice or by blocking the necroptotic pathway with RIPK3 inhibitor. Our findings unravel a potential protective efficacy of metformin in mitigating the detrimental effects of B[a]P exposure on lung health by inhibiting necroptosis and protecting AT2 cells.

Differential eigengene network analysis reveals benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin consensus regulatory network in human liver cell line HepG2

Aryl hydrocarbon receptor (AHR) is one of the main mediators of the toxic effects of benzo[a]pyrene (BaP) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, a vast number of BaP- and TCDD-affected genes may suggest a more complex transcriptional regulatory network driving common adverse effects of these two chemicals. Unlike TCDD, BaP is rapidly metabolized in the liver, yielding products with a questionable ability to bind and activate AHR. In this study, we used transcriptomics data from the BaP- and TCCD-exposed human liver cell line HepG2, and performed differential eigengene network analysis to understand the correlation among genes and to untangle the common regulatory mechanism in the action of BaP and TCDD. The genes were grouped into 11 meta-modules with an overall preservation of 0.72 and were also segregated into three consensus time clusters: 12, 24, and 48 h. The analysis showed that the consensus genes in each time cluster were either directly regulated by the AHR or the AHR-TF interactions. Some TFs form a direct physical interaction with AHR such as ESR1, FOXA1, and E2F1, whereas others, including CTCF, RXRA, FOXO1, CEBPA, CEBPB, and TP53 show an indirect interaction with AHR. The analysis of biological processes (BPs) identified unique and common BPs in BaP and TCDD samples, with DNA damage response detected in all three time points. In summary, we identified a consensus transcriptional regulatory network common for BaP and TCDD consisting of direct AHR targets and AHR-TF targets. This analysis sheds new light on the common mechanism of action of a genotoxic (BaP) and non-genotoxic (TCDD) chemical in liver cells.

Unveiling the Latest Breakthroughs: A Comprehensive Review of the Therapeutic Activity and Safety Profile of Aloe vera

The use of herbal drugs as alternative and complementary medicine has increased in popularity, raising concerns about their safety profile. Aloe vera, a plant with diverse therapeutic properties, has been extensively used for centuries. This review aims to assess the therapeutic activity and safety profile of Aloe vera. A comprehensive literature search was conducted to gather relevant information from various biomedical databases. The chemical composition, mechanism of action, and therapeutic activities of Aloe vera were analyzed. Aloe vera contains numerous active components such as vitamins, enzymes, minerals, sugars, lignin, saponins, and anthraquinones. Its mechanisms of action involve collagen synthesis, anti-inflammatory effects, immune modulation, laxative properties, and antiviral activity. Aloe vera has demonstrated potential therapeutic benefits in wound healing, diabetes management, liver and kidney protection, and glycemic control. However, it is essential to consider potential side effects, such as skin irritation and allergic reactions. This review provides evidence-based information to improve patient safety and promote informed decisions regarding the use of Aloe vera as a therapeutic agent.

Genotoxicity and the stability of N-nitrosomorpholine activity following UVA irradiation

This study investigated N-nitrosomorpholine (NMOR) genotoxicity following UVA irradiation without metabolic activation. Following UVA irradiation, the photo treated NMOR (irradiated NMOR) was directly mutagenic, without UVA or metabolic activation, in the Ames test. The activity was relatively stable, and approximately 79% of the activity remained after 10 days of storage at 37 °C, 4 °C, or -20 °C. Micronuclei (MN) formation was observed in HaCaT cells after treatment with irradiated NMOR without metabolic activation. The action spectrum of MN formation in response to NMOR irradiation followed the NMOR absorption curve. In vivo, MN formation was observed in the peripheral blood reticulocytes of mice injected with irradiated NMOR under the inhibition of cytochrome P450-mediated metabolism of NMOR. Volatile NMOR may attach to environmental materials and be irradiated with environmental UVA light. Photoactivated NMOR-attached air pollutants could float in the air and fall onto the human body, leading to genotoxicity induced by the irradiated NMOR.

Assessment of the performance of the Ames MPF™ assay: A multicenter collaborative study with six coded chemicals

The Ames MPF™ is a miniaturized, microplate fluctuation format of the Ames test. It is a standardized, commercially available product which can be used to assess mutagenicity in Salmonella and E. coli strains in 384-well plates using a color change-based readout. Several peer-reviewed comparisons of the Ames MPF™ to the Ames test in Petri dishes confirmed its suitability to evaluate the mutagenic potential of a variety of test items. An international multicenter study involving seven laboratories tested six coded chemicals with this assay using five bacterial strains, as recommended by the OECD test guideline 471. The data generated by the participating laboratories was in excellent agreement (93%), and the similarity of their dose response curves, as analyzed with sophisticated statistical approaches further confirmed the suitability of the Ames MPF™ assay as an alternative to the Ames test on agar plates, but with advantages with respect to significantly reduced amount of test substance and S9 requirements, speed, hands-on time and, potentially automation.

DNA damage resulting from human endocrine disrupting chemical exposure: Genotoxicity, detection and dietary phytochemical intervention

In recent years, exposure to endocrine disrupting chemicals (EDCs) has posed an increasing threat to human health. EDCs are major risk factors in the occurrence and development of many diseases. Continuous DNA damage triggers severe pathogenic consequences, such as cancer. Beyond their effects on the endocrine system, EDCs genotoxicity is also worthy of attention, owing to the high accessibility and bioavailability of EDCs. This review investigates and summarizes nearly a decade of DNA damage studies on EDC exposure, including DNA damage mechanisms, detection methods, population marker analysis, and the application of dietary phytochemicals. The aims of this review are (1) to systematically summarize the genotoxic effects of environmental EDCs (2) to comprehensively summarize cutting-edge measurement methods, thus providing analytical solutions for studies on EDC exposure; and (3) to highlight critical data on the detoxification and repair effects of dietary phytochemicals. Dietary phytochemicals decrease genotoxicity by playing a major role in the detoxification system, and show potential therapeutic effects on human diseases caused by EDC exposure. This review may support research on environmental toxicology and alternative chemo-prevention for human EDC exposure.

BPDE-DNA adduct formation and alterations of mRNA, protein, and DNA methylation of CYP1A1, GSTP1, and GSTM1 induced by benzo[a]pyrene and the intervention of aspirin in mice

Benzo[a]pyrene (B[a]P), one typical environmental pollutant, the toxicity mechanisms, and potential prevention remain perplexing. Available evidence suggests cytochrome P450 1A1 (CYP1A1) and glutathione S-transferases (GSTs) metabolize B[a]P, resulting in metabolic activation and detoxification of B[a]P. This study aimed to reveal the impact of B[a]P exposure on trans-7,8-diol-anti-9,10-epoxide DNA (BPDE-DNA) adduct formation, level of CYP1A1, glutathione S-transferase pi (GSTP1) and glutathione S-transferase mu1 (GSTM1) mRNA, protein and DNA methylation in mice, and the potential prevention of aspirin (ASP). This study firstly determined the BPDE-DNA adduct formation in an acute toxicity test of a large dose in mice induced by B[a]P, which subsequently detected CYP1A1, GSTP1, and GSTM1 at levels of mRNA, protein, and DNA methylation in the organs of mice in a subacute toxicity test at appropriate doses and the potential prevention of ASP, using the methods of real-time quantitative PCR (QPCR), western blotting, and real-time methylation-specific PCR (MSP), respectively. The results verified that B[a]P induced the formation of BPDE-DNA adduct in all the organs of mice in an acute toxicity test, and the order of concentration of which was lung > kidney > liver > brain. In a subacute toxicity test, following B[a]P treatment, mice showed a dose-dependent slowdown in body weight gain and abnormalities in behavioral and cognitive function and which were alleviated by ASP co-treatment. Compared to the controls, following B[a]P treatment, CYP1A1 was significantly induced in all organs in mice at mRNA level (P < 0.05), was suppressed in the lung and cerebrum of mice at protein level, and inhibited at DNA methylation level in the liver, lung, and cerebrum, whereas GSTP1 and GSTM1 at mRNA, protein, and DNA methylation levels showed organ-specific changes in mice following B[a]P treatment, which was generally alleviated by ASP intervention. In conclusion, B[a]P induced BPDE-DNA adduct formation in all organs in mice and altered the mRNA, protein, and DNA methylation levels in CYP1A1, GSTP1, and GSTM1 in an organ-dependent pattern, which could be related to the organ toxicity and mechanism of B[a]P. ASP intervention may be an effective measure to prevent B[a]P toxicity. The findings provide scientific evidence for further study on the organ toxicity and mechanisms of B[a]P.

The aryl hydrocarbon receptor (AhR) activation mediates benzo(a)pyrene-induced overexpression of AQP3 and Notch1 in HaCaT cells

The aim of this study was twofold: (1) evaluate the effect of benzo[a]pyrene (BaP) on expression levels of AQP3 and Notch1 genes in HaCaT cells exposed "in vitro" and (2) investigate the possible biological role of assessed genes by bioinformatics methods. Cells were exposed to increasing concentrations of BaP (0.0-4.0 μM) for 1-4 days. After treatments, cell viability and expression levels of AhR, CYP1A1, AQP3, and Notch1 genes were evaluated. The possible biological role of assessed genes was evaluated using bioinformatics tools. Low cytotoxicity in HaCaT cells dosed with BaP was detected. A significant overexpression (p < .05) of CYP1A1, AQP3, and Notch1 was found in exposed HaCaT cells. The gene expression upregulation was dependent on AhR activation. The bioinformatics analysis showed that these genes were enriched in related cancer signaling pathways. The findings suggest that AQP3 and Notch1 are upregulated by AhR activation in HaCaT cells exposed to BaP.

Hornerin mediates phosphorylation of the polo-box domain in Plk1 by Chk1 to induce death in mitosis

The centrosome assembles a bipolar spindle for faithful chromosome segregation during mitosis. To prevent the inheritance of DNA damage, the DNA damage response (DDR) triggers programmed spindle multipolarity and concomitant death in mitosis through a poorly understood mechanism. We identified hornerin, which forms a complex with checkpoint kinase 1 (Chk1) and polo-like kinase 1 (Plk1) to mediate phosphorylation at the polo-box domain (PBD) of Plk1, as the link between the DDR and death in mitosis. We demonstrate that hornerin mediates DDR-induced precocious centriole disengagement through a dichotomous mechanism that includes sequestration of Sgo1 and Plk1 in the cytoplasm through phosphorylation of the PBD in Plk1 by Chk1. Phosphorylation of the PBD in Plk1 abolishes the interaction with Sgo1 and phosphorylation-dependent Sgo1 translocation to the centrosome, leading to precocious centriole disengagement and spindle multipolarity. Mechanistically, hornerin traps phosphorylated Plk1 in the cytoplasm. Furthermore, PBD phosphorylation inactivates Plk1 and disrupts Cep192::Aurora A::Plk1 complex translocation to the centrosome and concurrent centrosome maturation. Remarkably, hornerin depletion leads to chemoresistance against DNA damaging agents by attenuating DDR-induced death in mitosis. These results reveal how the DDR eradicates mitotic cells harboring DNA damage to ensure genome integrity during cell division.

Evaluation of the Impact of BaP Exposure on the Gut Microbiota and Allergic Responses in an OVA-Sensitized Mouse Model

BACKGROUND

Exposure to environmental pollutants, including benzo[a]pyrene (BaP), has been implicated in allergic diseases and intestinal microbiota homeostasis, but the environment-microbiota-immunity triangular relationship and to what extent BaP-induced remodeling of the gut microbiota contributes to intestinal allergic inflammation remain to be established.

OBJECTIVES

We investigated the impact of BaP on intestinal allergic inflammation and examined the relationship between this effect and gut microbiota dysbiosis. We explored the potential ability of intestinal bacteria to degrade BaP and alleviate cytotoxicity as a detoxification strategy to counteract the effects of BaP exposure.

METHODS

We combined microbiome shotgun metagenomics with animal histological and intestinal allergic inflammatory responses to assess the effects of BaP (50μg/mouse per day) in a 23-d toxicity test in antigen-induced allergic female mice. In addition, genome annotation, quantitative analysis of BaP, and in vitro cytotoxicity-tests using CaCo-2 cells were conducted to infer the role of intestinal bacteria in BaP detoxification.

RESULTS

BaP exposure impacted the taxonomic composition and the functional potential of the gut microbiota and aggravated antigen-induced intestinal allergic inflammatory responses. The level of inflammatory cytokines correlated with the abundance of specific bacterial taxa, including Lachnospiraceae bacterium 28-4 and Alistipes inops. We identified 614 bacteria harboring genes implicated in the degradation of BaP, and 4 of these bacterial strains were shown to significantly reduce the cytotoxicity of BaP to CaCo-2 cells in vitro.

DISCUSSION

Using allergic female mice as a model, we investigated the relationship between BaP, microbiota, and host immune reactions, highlighting the role of gut bacteria in BaP-aggravated allergic reactions. Our findings offer novel insight toward establishing the causal relationship between BaP exposure and the occurrence of allergic disorders. Identifying gut bacteria that degrade BaP may provide new strategies for ameliorating BaP cytotoxicity. https://doi.org/10.1289/EHP11874.

Benzo[a]pyrene induces NLRP1 expression and promotes prolonged inflammasome signaling

Benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon in the air, triggers pulmonary inflammation. This study focused on BaP-induced inflammation in the alveolar epithelium. A549 cells were stimulated with BaP for four days. BaP treatment markedly increased NLRP1 expression but slightly decreased NLRP3. Furthermore, aryl hydrocarbon receptor (AhR) knockdown displayed no increase in BaP-induced NLRP1 expression. Similar results were also observed by blocking reactive oxygen species (ROS), which is mediated through AhR, suggesting that the AhR-ROS axis operates in BaP-induced NLRP1 expression. p53 involvement in ROS-mediated NLRP1 induction has also been implied. When we confirmed inflammasome activation in cells treated with BaP for four days, while BaP transiently activated NLRP3, it predominantly activated the NLRP1 inflammasome. These findings have led to the conclusion that BaP could be a potential ligand for the NLRP1 inflammasome persistently observed in the lung epithelium. Our study may provide additional evidence for the sustained pulmonary inflammation caused by environmental air pollution.

Protective Effects of Piceatannol on DNA Damage in Benzo[a]pyrene-Induced Human Colon Epithelial Cells

Evidence shows that the dietary intake of polycyclic aromatic hydrocarbons (PAHs) from food processing induces the cellular DNA damage response and leads to the development of colorectal cancer (CRC). Therefore, protecting from cellular DNA damage might be an effective strategy in preventing CRC. Benzo[a]pyrene (B[a]P) was used as a CRC initiator in the present study. Compared with other stilbenoids, piceatannol (PIC) showed the most effective inhibition of B[a]P-induced cytochrome P450 1B1 (CYP1B1) protein expression in NCM460 normal human colon epithelial cells. PIC treatment alleviated DNA migration and enhanced the expression of DNA-repair-related proteins, including histone 2AX (H2AX), checkpoint kinase 1 (Chk1), and p53, in B[a]P-induced NCM460 cells. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, flow cytometry, and enzyme-linked immunosorbent assay (ELISA) revealed that PIC exerted antioxidative effects on NCM460 cells by increasing the glutathione (GSH) content and scavenging the excess intracellular reactive oxygen species (ROS) induced by B[a]P. Furthermore, PIC suppressed B[a]P-induced CYP1B1 protein expression and stimulated miR-27b-3p expression. The upregulation of phase II detoxification enzymes, such as nicotinamide adenine dinucleotide phosphate (NADPH) and quinone oxidoreductase 1 (NQO1), and the antioxidative enzyme, heme oxygenase 1 (HO-1), via the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway was observed in the PIC-treated group. Our results suggest that PIC is a potential CRC-blocking agent due to its ability to alleviate DNA damage, decrease intracellular ROS production, modulate the metabolism and detoxification of B[a]P, and activate the Nrf2 signaling pathway in B[a]P-induced NCM460 cells.

Quantification and Mapping of Alkylation in the Human Genome Reveal Single Nucleotide Resolution Precursors of Mutational Signatures

Chemical modifications to DNA bases, including DNA adducts arising from reactions with electrophilic chemicals, are well-known to impact cell growth, miscode during replication, and influence disease etiology. However, knowledge of how genomic sequences and structures influence the accumulation of alkylated DNA bases is not broadly characterized with high resolution, nor have these patterns been linked with overall quantities of modified bases in the genome. For benzo(a) pyrene (BaP), a ubiquitous environmental carcinogen, we developed a single-nucleotide resolution damage sequencing method to map in a human lung cell line the main mutagenic adduct arising from BaP. Furthermore, we combined this analysis with quantitative mass spectrometry to evaluate the dose-response profile of adduct formation. By comparing damage abundance with DNase hypersensitive sites, transcription levels, and other genome annotation data, we found that although overall adduct levels rose with increasing chemical exposure concentration, genomic distribution patterns consistently correlated with chromatin state and transcriptional status. Moreover, due to the single nucleotide resolution characteristics of this DNA damage map, we could determine preferred DNA triad sequence contexts for alkylation accumulation, revealing a characteristic DNA damage signature. This new BaP damage signature had a profile highly similar to mutational signatures identified previously in lung cancer genomes from smokers. Thus, these data provide insight on how genomic features shape the accumulation of alkylation products in the genome and predictive strategies for linking single-nucleotide resolution in vitro damage maps with human cancer mutations.

Benzo(a)pyrene and Cerium Dioxide Nanoparticles in Co-Exposure Impair Human Trophoblast Cell Stress Signaling

Human placenta is a multifunctional interface between maternal and fetal blood. Studying the impact of pollutants on this organ is crucial because many xenobiotics in maternal blood can accumulate in placental cells or pass into the fetal circulation. Benzo(a)pyrene (BaP) and cerium dioxide nanoparticles (CeO2 NP), which share the same emission sources, are found in ambient air pollution and also in maternal blood. The aim of the study was to depict the main signaling pathways modulated after exposure to BaP or CeO2 NP vs. co-exposure on both chorionic villi explants and villous cytotrophoblasts isolated from human term placenta. At nontoxic doses of pollutants, BaP is bioactivated by AhR xenobiotic metabolizing enzymes, leading to DNA damage with an increase in γ-H2AX, the stabilization of stress transcription factor p53, and the induction of its target p21. These effects are reproduced in co-exposure with CeO2 NP, except for the increase in γ-H2AX, which suggests a modulation of the genotoxic effect of BaP by CeO2 NP. Moreover, CeO2 NP in individual and co-exposure lead to a decrease in Prx-SO3, suggesting an antioxidant effect. This study is the first to identify the signaling pathways modulated after co-exposure to these two pollutants, which are common in the environment.

Association of xenobiotic-metabolizing genes polymorphisms with cervical cancer risk in the Tunisian population

BACKGROUND

Host genetic characteristics and environmental factors interactions may play a crucial role in cervical carcinogenesis. We investigated the impact of functional genetic variants of four xenobiotic-metabolizing genes (AhR, CYP1A1, GSTM1, and GSTT1) on cervical cancer development in Tunisian women.

METHODS

The AhR gene polymorphism was analyzed using the tetra-primer ARMS-PCR, whereas the CYP1A1 polymorphism genotypes were identified by PCR-RFLP. A multiplex ligation-dependent polymerase chain reaction approach was applied for the analysis of GSTM1 and GSTT1 polymorphisms.

RESULTS

The homozygous A/A genotype of the AhR gene (rs2066853) and the heterozygous T/C genotype of the CYP1A1 SNP (CYP1A1-MspI) appeared to be associated with an increased risk of cervical tumorigenesis (OR^a = 2.81; OR^a = 5.52, respectively). Furthermore, a significantly increased risk of cervical cancer was associated with the GSTT1 null genotype (OR^a = 2.65). However, the null GSTM1 genotype showed any significant association with the risk of cervical cancer compared to the wild genotype (OR^a = 1.18; p = 0.784). Considering the combined effect, we noted a significantly higher association with cancer risk for individuals with at least two high-risk genotypes of CYP1A1/GSTT1 (OR^a = 4.2), individuals with at least two high-risk genotypes of CYP1A1/GSTT1/AhR (OR^a = 11.3) and individuals with at least two high-risk genotypes of CYP1A1/GSTM1/GSTT1/AhR exploitation low-risk genotype as a reference.

CONCLUSION

This study indicated that the single-gene contribution and the combined effect of xenobiotic-metabolizing gene polymorphisms (AhR, CYP1A1-MspI, GSTM1, and GSTT1) may have a considerable association with increased cervical cancer risk.

Investigation of 2-phenylimidazo[1,2-a]quinolines as potential antiproliferative agents

Background: It has been demonstrated that the lead compound 2-phenylimidazo[1,2-a]quinoline 1a selectively inhibits CYP1 enzymes. Additionally, CYP1 inhibition has been linked to inducing antiproliferative effects in various breast cancer cell lines as well as relieving drug resistance caused by CYP1 upregulation. Materials & methods: Herein, 54 novel analogs of 2-phenylimidazo[1,2-a]quinoline 1a have been synthesized with varied substitution on the phenyl and imidazole rings. Antiproliferative testing was conducted using ³H thymidine uptake assays. Results: 2-Phenylimidazo[1,2-a]quinoline 1a and phenyl-substituted analogs 1c (3-OMe), 1n (2,3-napthalene) displayed excellent anti-proliferative activities, demonstrating their potency against cancer cell lines for the first time. Molecular modeling suggested that 1c and 1n bind similarly to 1a in the CYP1 binding site.

Derivation of metabolic point of departure using high-throughput in vitro metabolomics: investigating the importance of sampling time points on benchmark concentration values in the HepaRG cell line

Amongst omics technologies, metabolomics should have particular value in regulatory toxicology as the measurement of the molecular phenotype is the closest to traditional apical endpoints, whilst offering mechanistic insights into the biological perturbations. Despite this, the application of untargeted metabolomics for point-of-departure (POD) derivation via benchmark concentration (BMC) modelling is still a relatively unexplored area. In this study, a high-throughput workflow was applied to derive PODs associated with a chemical exposure by measuring the intracellular metabolome of the HepaRG cell line following treatment with one of four chemicals (aflatoxin B₁, benzo[a]pyrene, cyclosporin A, or rotenone), each at seven concentrations (aflatoxin B₁, benzo[a]pyrene, cyclosporin A: from 0.2048 μM to 50 μM; rotenone: from 0.04096 to 10 μM) and five sampling time points (2, 6, 12, 24 and 48 h). The study explored three approaches to derive PODs using benchmark concentration modelling applied to single features in the metabolomics datasets or annotated metabolites or lipids: (1) the 1st rank-ordered unannotated feature, (2) the 1st rank-ordered putatively annotated feature (using a recently developed HepaRG-specific library of polar metabolites and lipids), and (3) 25th rank-ordered feature, demonstrating that for three out of four chemical datasets all of these approaches led to relatively consistent BMC values, varying less than tenfold across the methods. In addition, using the 1st rank-ordered unannotated feature it was possible to investigate temporal trends in the datasets, which were shown to be chemical specific. Furthermore, a possible integration of metabolomics-driven POD derivation with the liver steatosis adverse outcome pathway (AOP) was demonstrated. The study highlights that advances in technologies enable application of in vitro metabolomics at scale; however, greater confidence in metabolite identification is required to ensure PODs are mechanistically anchored.

Influences of polycyclic aromatic hydrocarbon on the epigenome toxicity and its applicability in human health risk assessment

The existence of polycyclic aromatic hydrocarbons (PAHs) in ambient air is an escalating concern worldwide because of their ability to cause cancer and induce permanent changes in the genetic material. Growing evidence implies that during early life-sensitive stages, the risk of progression of acute and chronic diseases depends on epigenetic changes initiated by the influence of environmental cues. Several reports deciphered the relationship between exposure to environmental chemicals and epigenetics, and have known toxicants that alter the epigenetic states. Amongst PAHs, benzo[a]pyrene (B[a]P) is accepted as a group 1 cancer-causing agent by the International Agency for the Research on Cancer (IARC). B[a]P is a well-studied pro-carcinogen that is metabolically activated by the aryl hydrocarbon receptor (AhR)/cytochrome P450 pathway. Cytochrome P450 plays a pivotal role in the stimulation step, which is essential for DNA adduct formation. Accruing evidence suggests that epigenetic alterations assume a fundamental part in PAH-promoted carcinogenesis. This interaction between PAHs and epigenetic factors results in an altered profile of these marks, globally and locus-specific. Some of the epigenetic changes due to exposure to PAHs lead to increased disease susceptibility and progression. It is well understood that exposure to environmental carcinogens, such as PAH triggers disease pathways through changes in the genome. Several evidence reported due to the epigenome-wide association studies, that early life adverse environmental events may trigger widespread and persistent variations in transcriptional profiling. Moreover, these variations respond to DNA damage and/or a consequence of epigenetic modifications that need further investigation. Growing evidence has associated PAHs with epigenetic variations involving alterations in DNA methylation, histone modification, and micro RNA (miRNA) regulation. Epigenetic alterations to PAH exposure were related to chronic diseases, such as pulmonary disease, cardiovascular disease, endocrine disruptor, nervous system disorder, and cancer. This hormetic response gives a novel perception concerning the toxicity of PAHs and the biological reaction that may be a distinct reliance on exposure. This review sheds light on understanding the latest evidence about how PAHs can alter epigenetic patterns and human health. In conclusion, as several epigenetic change mechanisms remain unclear yet, further analyses derived from PAHs exposure must be performed to find new targets and disease biomarkers. In spite of the current limitations, numerous evidence supports the perception that epigenetics grips substantial potential for advancing our knowledge about the molecular mechanisms of environmental toxicants, also for predicting health-associated risks due to environmental circumstances exposure and individual susceptibility.

Characterization of benzo[a]pyrene and colchicine based on an in vivo repeat-dosing multi-endpoint genotoxicity quantitative assessment platform

Two prototypical genotoxicants, benzo[a]pyrene (B[a]P) and colchicine (COL), were selected as model compounds to deduce their quantitative genotoxic dose–response relationship at low doses in a multi-endpoint genotoxicity assessment platform. Male Sprague-Dawley rats were treated with B[a]P (2.5–80 mg/kg bw/day) and COL (0.125–2 mg/kg bw/day) daily for 28 days. The parameters included were as follows: comet assay in the peripheral blood and liver, Pig-a gene mutation assay in the peripheral blood, and micronucleus test in the peripheral blood and bone marrow. A significant increase was observed in Pig-a mutant frequency in peripheral blood for B[a]P (started at 40 mg/kg bw/day on Day 14, started at 20 mg/kg bw/day on Day 28), whereas no statistical difference for COL was observed. Micronucleus frequency in reticulocytes of the peripheral blood and bone marrow increased significantly for B[a]P (80 mg/kg bw/day on Day 4, started at 20 mg/kg bw/day on Days 14 and 28 in the blood; started at 20 mg/kg bw/day on Day 28 in the bone marrow) and COL (started at 2 mg/kg bw/day on Day 14, 1 mg/kg bw/day on Day 28 in the blood; started at 1 mg/kg bw/day on Day 28 in the bone marrow). No statistical variation was found in indexes of comet assay at all time points for B[a]P and COL in the peripheral blood and liver. The dose–response relationships of Pig-a and micronucleus test data were analyzed for possible point of departures using three quantitative approaches, i.e., the benchmark dose, breakpoint dose, and no observed genotoxic effect level. The practical thresholds of the genotoxicity of B[a]P and COL estimated in this study were 0.122 and 0.0431 mg/kg bw/day, respectively, and our results also provided distinct genotoxic mode of action of the two chemicals.

Impact of benzo[a]pyrene with other pollutants induce the molecular alternation in the biological system: Existence, detection, and remediation methods

The exposure of benzo [a]pyrene (BaP) in recent times is rather unavoidable than ever before. BaP emissions are sourced majorly from anthropogenic rather than natural provenance from wildfires and volcanic eruptions. A major under-looked source is via the consumption of foods that are deep-fried, grilled, and charcoal smoked foods (meats in particular). BaP being a component of poly aromatic hydrocarbons has been classified as a Group I carcinogenic agent, which has been shown to cause both systemic and localized effects in animal models as well as in humans; has been known to cause various forms of cancer, accelerate neurological disorders, invoke DNA and cellular damage due to the generation of reactive oxygen species and involve in multi-generational phenotypic and genotypic defects. BaP's short and accumulated exposure has been shown in disrupting the fertility of gamete cells. In this review, we have discussed an in-depth and capacious run-through of the various origins of BaP, its economic distribution and its impact as well as toxicological effects on the environment and human health. It also deals with a mechanism as a single compound and its ability to synergize with other chemicals/materials, novel sensitive detection methods, and remediation approaches held in the environment.

Benzo[a]pyrene-Environmental Occurrence, Human Exposure, and Mechanisms of Toxicity

Benzo[a]pyrene (B[a]P) is the main representative of polycyclic aromatic hydrocarbons (PAHs), and has been repeatedly found in the air, surface water, soil, and sediments. It is present in cigarette smoke as well as in food products, especially when smoked and grilled. Human exposure to B[a]P is therefore common. Research shows growing evidence concerning toxic effects induced by this substance. This xenobiotic is metabolized by cytochrome P450 (CYP P450) to carcinogenic metabolite: 7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE), which creates DNA adducts, causing mutations and malignant transformations. Moreover, B[a]P is epigenotoxic, neurotoxic, and teratogenic, and exhibits pro-oxidative potential and causes impairment of animals' fertility. CYP P450 is strongly involved in B[a]P metabolism, and it is simultaneously expressed as a result of the association of B[a]P with aromatic hydrocarbon receptor (AhR), playing an essential role in the cancerogenic potential of various xenobiotics. In turn, polymorphism of CYP P450 genes determines the sensitivity of the organism to B[a]P. It was also observed that B[a]P facilitates the multiplication of viruses, which may be an additional problem with the widespread COVID-19 pandemic. Based on publications mainly from 2017 to 2022, this paper presents the occurrence of B[a]P in various environmental compartments and human surroundings, shows the exposure of humans to this substance, and describes the mechanisms of its toxicity.

An insight on microbial degradation of benzo[a]pyrene: current status and advances in research

Benzo[a]pyrene (BaP) is a high molecular weight polycyclic aromatic hydrocarbon produced as a result of incomplete combustion of organic substances. Over the years, the release of BaP in the atmosphere has increased rapidly, risking human lives. BaP can form bonds with DNA leading to the formation of DNA adducts thereby causing cancer. Therefore addressing the problem of its removal from the environment is quite pertinent though it calls for a very cumbersome and tedious process owing to its recalcitrant nature. To resolve such issues many efforts have been made to develop physical and chemical technologies of BaP degradation which have neither been cost-effective nor eco-friendly. Microbial degradation of BaP, on the other hand, has gained much attention due to added advantage of the high level of microbial diversity enabling great potential to degrade the substance without impairing environmental sustainability. Microorganisms produce enzymes like oxygenases, hydrolases and cytochrome P450 that enable BaP degradation. However, microbial degradation of BaP is restricted due to several factors related to its bio-availability and soil properties. Technologies like bio-augmentation and bio-stimulation have served to enhance the degradation rate of BaP. Besides, advanced technologies such as omics and nano-technology have opened new doors for a better future of microbial degradation of BaP and related compounds.

Alterations of DNA methylation and mRNA levels of CYP1A1, GSTP1, and GSTM1 in human bronchial epithelial cells induced by benzo[a]pyrene

Benzo[a]pyrene (B[a]P) is a known human carcinogen and plays a major function in the initiation of lung cancer at its first proximity. However, the underlying molecular mechanisms are less well understood. In this study, we investigated the impact of B[a]P treatment on the DNA methylation and mRNA levels of CYP1A1, GSTP1, and GSTM1 in human bronchial epithelial cells (16HBEs), and provide scientific evidence for the mechanism study on the carcinogenesis of B[a]P. We treated 16HBEs with DMSO or concentrations of B[a]P at 1, 2, and 5 mmol/L for 24 h, observed the morphological changes, determined the cell viability, DNA methylation, and mRNA levels of CYP1A1, GSTP1, and GSTM1. Compared to the DMSO controls, B[a]P treatment had significantly increased the neoplastic cell number and cell viability in 16HBEs at all three doses (1, 2, and 5 mmol/L), and had significantly reduced the CYP1A1 and GSTP1 DNA promoter methylation levels. Following B[a]P treatment, the GSTM1 promoter methylation level in 16HBEs was profoundly reduced at low dose group compared to the DMSO controls, yet it was significantly increased at both middle and high dose groups. The mRNA levels of CYP1A1, GSTP1, and GSTM1 were significantly decreased in 16HBEs following B[a]P treatment at all three doses. The findings demonstrate that B[a]P promoted cell proliferation in 16HBEs, which was possibly related to the altered DNA methylations and the inhibited mRNA levels in CYP1A1, GSTP1, and GSTM1.

Effects of benzo[a]pyrene exposure on black rockfish (Sebastes schlegelii): EROD activity, CYP1A protein, and immunohistochemical and histopathological alterations

Cytochrome P450 1A (CYP1A) is the major phase I of metabolic enzyme that plays essential roles in the detoxification of drugs and biotransformation of environmental pollutants. This study investigated CYP1A enzyme induction using EROD activity, CYP1A protein levels, and immunohistochemistry, along with histopathology of the liver, gills, kidneys, and intestine from the black rockfish, Sebastes schlegelii, exposed to benzo[a]pyrene (B[a]P). S. schlegelii has high risks of ingestion of sediment and absorption of heavy crude oil after accidental oil spills in Korea. This study thus exposed fish to B[a]P at 2, 20, and 200 μg/g body weight. EROD activity and CYP1A protein levels in hepatic microsomes had a positive correlation with the concentration of B[a]P (2-200 μg/g); in particular, exposure to 200 μg/g of B[a]P resulted in a 4- and 6-fold increase in hepatic EROD activity and CYP1A protein level, respectively. Hyperplasia of primary lamellar epithelium and atrophy of renal tubules were observed in the gills and kidney, respectively, following exposure to B[a]P at 200 μg/g. In contrast, severe histological alteration was not seen in intestinal tissues. Immunohistochemical analysis of the distribution of cellular CYP1A in four tissues showed strong immunostaining in the cytoplasm and nuclear membranes of the liver against B[a]P at 200 μg/g. Polycyclic aromatic hydrocarbons (PAHs), such as B[a]P, cause adverse histological changes in tissues of fish and provide evidence that PAH metabolism is inducible in fish liver, leading to increased CYP1A induction. Furthermore, the CYP1A induction in specific tissues might assist in monitoring and field assessment of marine ecosystems.

Transcription profiles in BEAS-2B cells exposed to organic extracts from particulate emissions produced by a port-fuel injection vehicle, fueled with conventional fossil gasoline and gasoline-ethanol blend

Emissions from road traffic are among the major contributors to air pollution worldwide and represent a serious environmental health risk. Although traffic-related pollution has been most commonly associated with diesel engines, increasing evidence suggests that gasoline engines also produce a considerable amount of potentially hazardous particulate matter (PM). The primary objective of this study was to compare the intrinsic toxic properties of the organic components of PM, generated by a conventional gasoline engine fueled with neat gasoline (E0), or gasoline-ethanol blend (15 % ethanol, v/v, E15). Our results showed that while E15 has produced, compared to gasoline and per kg of fuel, comparable particle mass (μg PM/kg fuel) and slightly more particles by number, the organic extract from the particulate matter produced by E15 contained a larger amount of harmful polycyclic aromatic hydrocarbons (PAHs), as determined by the chemical analysis. To examine the toxicity, we monitored genome-wide gene expression changes in human lung BEAS-2B cells, exposed for 4 h and 24 h to a subtoxic dose of each PM extract. After 4 h exposure, numerous dysregulated genes and processes such as oxidative stress, lipid and steroid metabolism, PPARα signaling and immune response, were found to be common for both extract treatments. On the other hand, 24 h exposure resulted in more distinctive gene expression patterns. Although we identified several common modulated processes indicating the metabolism of PAHs and activation of aryl hydrocarbon receptor (AhR), E15 specifically dysregulated a variety of other genes and pathways related to cancer promotion and progression. Overall, our findings suggest that the ethanol addition to gasoline changed the intrinsic properties of PM emissions and increased the PAH content in PM organic extract, thus contributing to a more extensive toxic response particularly after 24 h exposure in BEAS-2B cells.

Dysregulations of long non-coding RNAs - The emerging "lnc" in environmental carcinogenesis

Long non-coding RNAs (lncRNAs) refer to a class of RNA molecules that are more than 200 nucleotides in length and usually lack protein-coding capacity. LncRNAs play important roles in regulating gene expression as well as many aspects of normal physiological processes. Dysregulations of lncRNA expressions and functions are considered to be critically involved in the development and progression of many diseases especially cancer. The lncRNA research in the field of cancer biology over the past decade reveals that a large number of lncRNAs are dysregulated in various types of cancer and that dysregulated lncRNAs may play important roles in cancer initiation, metastasis and therapeutic responses. Metal carcinogens and other common environmental carcinogens such as polycyclic aromatic hydrocarbons, fine particular matters, cigarette smoke, ultraviolet and ionizing radiation are important cancer etiology factors. However, the mechanisms of how metal carcinogens and other common environmental carcinogen exposures initiate cancer and promote cancer progression remain largely unknown. Accumulating evidence show that exposure to metal carcinogens and other common environmental carcinogens dysregulate lncRNA expression in various model systems, which may offer novel mechanistic insights for environmental carcinogenesis. This review will first provide a brief introduction about lncRNA biology and the mechanisms of lncRNA functions, followed by summarizing and discussing recent studies about lncRNA dysregulation by metal carcinogen and other common environment carcinogen exposures and the potential roles of dysregulated lncRNAs in environmental carcinogenesis. A perspective for future studies in this emerging and important field is also presented.

DNA adduct formation and reduced EIF4A3expression contributes to benzo[a]pyrene-induced DNA damage in human bronchial epithelial BEAS-2B cells

Benzo[a]pyrene(B[a]P) is a known human carcinogen. The ability of B[a]P to form stable DNA adducts has been repeatedly demonstrated. However, the relationship between DNA adduct formation and cell damage and its underlying molecular mechanisms are less well understood. In this study, we determined the cytotoxicity of benzo[a]pyrenediolepoxide, a metabolite of B[a]P, in human bronchial epithelial cells (BEAS-2B). The formation of BPDE-DNA adducts was quantified using a dot blot. DNA damage resulting from the formation of BPDE-DNA adducts was detected by chromatin immuneprecipitation sequencing (ChIP-Seq), with minor modifications, using specific antibodies against BPDE. In total, 1846 differentially expressed gene loci were detected between the treatment and control groups. The distribution of the BPDE-bound regions indicated that BPDE could covalently bind with both coding and non-coding regions to cause DNA damage. However, the majority of binding occurred at protein-coding genes. Furthermore, among the BPDE-bound genes, we found 16 protein-coding genes related to DNA damage repair. We explored the response to BPDE exposure at the transcriptional level using qRT-PCR and observed a strong inhibition of EIF4A3. We then established an EIF4A3 overexpression cell model and performed comet assays, which revealed that the levels of DNA damage in EIF4A3-overexpressing cells were lower than those in normal cells following BPDE exposure. This suggests that the BPDE-DNA adduct-induced reduction in EIF4A3 expression contributed to the DNA damage induced by BPDE exposure in BEAS-2B cells. These novel findings indicate that ChIP-Seq combined with BPDE specific antibody may be used for exploring the underlying mechanism of DNA adduct-induced genomic damage.

A review on analysis methods, source identification, and cancer risk evaluation of atmospheric polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) have gained attention because of their environmental persistence and effects on ecosystems, animals, and human health. They are mutagenic, carcinogenic, and teratogenic. The review provides background knowledge about their sources, metabolism, temporal variations, and size distribution in atmospheric particulate matter. The review article briefly discusses the analytical methods suitable for the extraction, characterization, and quantification of nonpolar and polar PAHs, addressing the challenges. Herein, we discussed the molecular diagnostic ratios (DRs), stable carbon isotopic analysis (SCIA), and receptor models, with much emphasis on the positive matrix factorization (PMF) model, for apportioning PAH sources. Among which, DRs and PCA identified as the most widely employed method, but their accuracy for PAH source identification has received global criticism. Therefore, the review recommends compound-specific isotopic analysis (CSIA) and PMF as the best alternative methods to provide detailed qualitative and quantitative source analysis. The compound-specific isotopic signatures are not affected by environmental degradation and are considered promising for apportioning PAH sources. However, isotopic fractions of co-eluted compounds like polar PAHs and aliphatic hydrocarbons make the PAHs isotopic fractions interpretation difficult. The interference of unresolved complex mixtures is a limitation to the application of CSIA for PAH source apportionment. Hence, for CSIA to further support PAH source apportionment, fast and cost-effective purification techniques with no isotopic fractionation effects are highly desirable. The present review explains the concept of stable carbon isotopic analysis (SCIA) relevant to PAH source analysis, identifying the techniques suitable for sample extract purification. We demonstrate how the source apportioned PAHs can be applied in assessing the health risk of PAHs using the incremental lifetime cancer risk (ILCR) model, and in doing so, we identify the key factors that could undermine the accuracy of the ILCR and research gaps that need further investigation.

Cigarette smoking enhances the metabolic activation of the polycyclic aromatic hydrocarbon phenanthrene in humans

Although it is well established that human cytochrome P450 1 family enzymes are induced by cigarette smoking through activation of the Ah receptor, it is not known whether this leads to increased metabolic activation or detoxification of carcinogenic polycyclic aromatic hydrocarbons (PAH), which are present in cigarette smoke and the general environment. We gave oral doses of deuterated phenanthrene ([D10]Phe), a non-carcinogenic surrogate of carcinogenic PAH such as benzo[a]pyrene, to smokers (N = 170, 1 or 10 μg doses) and non-smokers (N = 57, 1 μg dose). Bioactivation products (dihydrodiol and tetraol) and detoxification products (phenols) of [D10]Phe were determined in 6-h urine to obtain a comprehensive metabolic profile. Cigarette smoking increased the bioactivation of [D10]Phe and decreased its detoxification resulting in significantly different metabolic patterns between smokers and non-smokers (P < 0.01), consistent with increased cancer risk in smokers. The Phe bioactivation ratios ([D10]PheT/total [D9]OHPhe) were significantly higher (2.3 (P < 0.01) to 4.8 (P < 0.001) fold) in smokers than non-smokers. With solid human in vivo evidence, our results for the first time demonstrate that cigarette smoking enhances the metabolic activation of Phe, structurally representative of carcinogenic PAH, in humans, strongly supporting their causal role in cancers caused by smoking. The results suggest potential new methods for identifying smokers who could be at particularly high risk for cancer.

CYP1B1 as a therapeutic target in cardio-oncology

Cardiovascular complications have been frequently reported in cancer patients and survivors, mainly because of various cardiotoxic cancer treatments. Despite the known cardiovascular toxic effects of these treatments, they are still clinically used because of their effectiveness as anti-cancer agents. In this review, we discuss the growing body of evidence suggesting that inhibition of the cytochrome P450 1B1 enzyme (CYP1B1) can be a promising therapeutic strategy that has the potential to prevent cancer treatment-induced cardiovascular complications without reducing their anti-cancer effects. CYP1B1 is an extrahepatic enzyme that is expressed in cardiovascular tissues and overexpressed in different types of cancers. A growing body of evidence is demonstrating a detrimental role of CYP1B1 in both cardiovascular diseases and cancer, via perturbed metabolism of endogenous compounds, production of carcinogenic metabolites, DNA adduct formation, and generation of reactive oxygen species (ROS). Several chemotherapeutic agents have been shown to induce CYP1B1 in cardiovascular and cancer cells, possibly via activating the Aryl hydrocarbon Receptor (AhR), ROS generation, and inflammatory cytokines. Induction of CYP1B1 is detrimental in many ways. First, it can induce or exacerbate cancer treatment-induced cardiovascular complications. Second, it may lead to significant chemo/radio-resistance, undermining both the safety and effectiveness of cancer treatments. Therefore, numerous preclinical studies demonstrate that inhibition of CYP1B1 protects against chemotherapy-induced cardiotoxicity and prevents chemo- and radio-resistance. Most of these studies have utilized phytochemicals to inhibit CYP1B1. Since phytochemicals have multiple targets, future studies are needed to discern the specific contribution of CYP1B1 to the cardioprotective and chemo/radio-sensitizing effects of these phytochemicals.

Chemopreventive effect of galangin against benzo(a)pyrene-induced stomach tumorigenesis through modulating aryl hydrocarbon receptor in Swiss albino mice

The present study was aimed to evaluate the chemopreventive potential of galangin against benzo(a)pyrene (BaP)-induced stomach carcinogenesis in Swiss albino mice. Stomach cancer was induced in experimental mice using BaP oral administration. The mice were treated with galangin (10 mg/kg b.wt.) before and during BaP administration. Oral administration of galangin at a dose of 10 mg/kg b.wt. significantly (p < 0.05) prevented the tumor incidence, tumor volume in the experimental animals. Further, galangin pretreatment prevents BaP-induced lipid peroxidation and restores BaP-mediated loss of cellular antioxidants status. It has also been found that galangin prevents BaP-induced activation of phase I detoxification enzymes. Furthermore, galangin pretreatment prevented the BaP-induced overexpression of cytochrome P450s isoform genes (CYP1A1, CYP1B1), aryl hydrocarbon receptor system (AhR, ARNT), transcriptional activators (CBP/p300, NF-kB), tumor growth factors, proto-oncogenes, invasion markers (TGFB, SRC-1, MYC, iNOS, MMP2, MMP9) and Phase II metabolic isoenzyme genes (GST) in the stomach tissue homogenate when compared to the control groups. The western blot results confirm that galangin (10 mg/kg. b.wt.) treatment significantly prevented the BaP-mediated expression of ArR, ARNT, and CYP1A1 proteins in the mouse stomach tissue. Therefore, the present results confirm that galangin prevents BaP-induced stomach carcinogenesis probably through modulating ArR and ARNT expression in the experimental mice.

Xenobiotic metabolism and transport in Caenorhabditis elegans

Caenorhabditis elegans has emerged as a major model in biomedical and environmental toxicology. Numerous papers on toxicology and pharmacology in C. elegans have been published, and this species has now been adopted by investigators in academic toxicology, pharmacology, and drug discovery labs. C. elegans has also attracted the interest of governmental regulatory agencies charged with evaluating the safety of chemicals. However, a major, fundamental aspect of toxicological science remains underdeveloped in C. elegans: xenobiotic metabolism and transport processes that are critical to understanding toxicokinetics and toxicodynamics, and extrapolation to other species. The aim of this review was to initially briefly describe the history and trajectory of the use of C. elegans in toxicological and pharmacological studies. Subsequently, physical barriers to chemical uptake and the role of the worm microbiome in xenobiotic transformation were described. Then a review of what is and is not known regarding the classic Phase I, Phase II, and Phase III processes was performed. In addition, the following were discussed (1) regulation of xenobiotic metabolism; (2) review of published toxicokinetics for specific chemicals; and (3) genetic diversity of these processes in C. elegans. Finally, worm xenobiotic transport and metabolism was placed in an evolutionary context; key areas for future research highlighted; and implications for extrapolating C. elegans toxicity results to other species discussed.

Pinocembrin attenuates benzo(a)pyrene-induced CYP1A1 expression through multiple pathways: An in vitro and in vivo study

Benzo(a)pyrene [B(a)P], which is a carcinogen, is a substance most typically known in cigarette smoke and considered as an important intermediary of lung cancer. The enzyme CYP1A1 is crucial for the metabolic conversion of B(a)P into the intermediates that induce carcinogenesis. Stimulation of the aryl hydrocarbon receptor, which is regulated by B(a)P, is thought to induce numerous signaling cascades. Interruption in the mitogen-activated protein kinase (MAPK) pathway causes changes in cellular processes and may alter the AhR pathway. The aim of this investigation is to examine the potential ability of a flavonoid pinocembrin (PCB) to alleviate B(a)P toxicity and analyze the underlying molecular mechanisms. We found that PCB inhibited DNA adduct formation by attenuating CYP1A1 expression through the suppression of the AhR/Src/ERK pathways. PCB mitigated the B(a)P-stimulated DNA damage, inhibited Src and ERK1/2 expression, decreased CYP1A1 expression, and reduced the B(a)P-induced stimulation of NF-κB and MAPK signaling in lung epithelial cells. Finally, the activity of CYP1A1 and Src in lung tissues from mice supplemented with PCB was noticeably decreased and lower than that in lung tissues from mice supplemented with B(a)P alone. Collectively, these data suggest that PCB may alleviate the toxic effects of PAHs, which are important environmental pollutants.

Sperm quality assessment in Ficopomatus enigmaticus (Fauvel, 1923): Effects of selected organic and inorganic chemicals across salinity levels

Contamination by organic and inorganic compounds remains one of the most complex problems in both brackish and marine environments, causing potential implications for the reproductive success and survival of several broadcast spawners. Ficopomatus enigmaticus is a tubeworm polychaete that has previously been used as a model organism for ecotoxicological analysis, due to its sensitivity and ecological relevance. In the present study, the effects of five trace elements (zinc, copper, cadmium, arsenic and lead), one surfactant (sodium dodecyl sulfate, SDS) and one polycyclic aromatic hydrocarbon (benzo(a)pyrene, B(a)P) on the sperm quality of F. enigmaticus were investigated. Sperm suspensions were exposed in vitro to different concentrations of each selected contaminant under four salinity conditions (10, 20, 30, 35). Possible adverse effects on sperm function were assessed by measuring oxidative stress, membrane integrity, viability and DNA damage. Sperm quality impairments induced by organic contaminants were more evident than those induced by inorganic compounds. SDS exerted the largest effect on sperm. In addition, F. enigmaticus sperm showed high tolerance to salinity variation, supporting the wide use of this species as a promising model organism for ecotoxicological assays. Easy and rapid methods on polychaete spermatozoids were shown to be effective as integrated sperm quality parameters or as an alternative analysis for early assessment of marine and brackish water pollution.

Postlabeling/PAGE Method for Detection of DNA Adducts

In DNA adduct analysis, the ³²P-postlabeling technique is a powerful tool due to its high detection sensitivity. It is performed by enzymatic digestion of DNA samples, enrichment of the adduct nucleotides, and then 5'-labeling with ³²P. This method is particularly useful for detection of bulky adducts. An additional advantage is that only a small amount of DNA is required for detecting DNA adducts. This chapter describes the experimental procedure for separation and detection of DNA adducts by polyacrylamide gel electrophoresis, which is an attractive method for visually assessing differences in adduct formation between samples.

Development and Application of TK6-derived Cells Expressing Human Cytochrome P450s for Genotoxicity Testing

Metabolism plays a key role in chemical genotoxicity; however, most mammalian cells used for in vitro genotoxicity testing lack effective metabolizing enzymes. We recently developed a battery of TK6-derived cell lines that individually overexpress 1 of 8 cytochrome P450s (CYP1A1, 1A2, 1B1, 2A6, 2B6, 2C9, 2C19, and 3A4) using a lentiviral expression system. The increased expression and metabolic function of each individual CYP in each established cell line were confirmed using real-time PCR, Western blotting, and mass spectrometry analysis; the parental TK6 cells and empty vector (EV) transduced cells had negligible CYP levels. Subsequently, we evaluated these cell lines using 2 prototypical polyaromatic hydrocarbon mutagens, 7,12-dimethylbenz[a]anthracene (DMBA) and benzo[a]pyrene (B[a]P), that require metabolic activation to exert their genotoxicity. DMBA-induced cytotoxicity, phosphorylation of histone H2A.X, and micronucleus formation were significantly increased in TK6 cells with CYP1A1, 1B1, 2B6, and 2C19 expression as compared with EV controls. B[a]P significantly increased cytotoxicity, DNA damage, and chromosomal damage in TK6 cells overexpressing CYP1A1 and 1B1 when compared with EV controls. B[a]P also induced micronucleus formation in TK6 cells expressing CYP1A2. These results suggest that our CYP-expressing TK6 cell system can be used to detect the genotoxicity of compounds requiring metabolic transformation.

Zebrafish CYP1A expression in transgenic Caenorhabditis elegans protects from exposures to benzo[a]pyrene and a complex polycyclic aromatic hydrocarbon mixture

Polycyclic aromatic hydrocarbons (PAHs) are environmental toxicants primarily produced during incomplete combustion; some are carcinogens. PAHs can be safely metabolized or, paradoxically, bioactivated via specific cytochrome P450 (CYP) enzymes to more reactive metabolites, some of which can damage DNA and proteins. Among the CYP isoforms implicated in PAH metabolism, CYP1A enzymes have been reported to both sensitize and protect from PAH toxicity. To clarify the role of CYP1A in PAH toxicity, we generated transgenic Caenorhabditis elegans that express CYP1A at a basal (but not inducible) level. Because this species does not normally express any CYP1 family enzyme, this approach permitted a test of the role of basally expressed CYP1A in PAH toxicity. We exposed C. elegans at different life stages to either the PAH benzo[a]pyrene (BaP) alone, or a real-world mixture dominated by PAHs extracted from the sediment of a highly contaminated site on the Elizabeth River (VA, USA). This site, the former Atlantic Wood Industries, was declared a Superfund site due to coal tar creosote contamination that caused very high levels (in the [mg/mL] range) of high molecular weight PAHs within the sediments. We demonstrate that CYP1A protects against BaP-induced growth delay, reproductive toxicity, and reduction of steady state ATP levels. Lack of sensitivity of a DNA repair (Nucleotide Excision Repair)-deficient strain suggested that CYP1A did not produce significant levels of DNA-reactive metabolites from BaP. The protective effects of CYP1A in Elizabeth River sediment extract (ERSE)-exposed nematodes were less pronounced than those seen in BaP-exposed nematodes; CYP1A expression protected against ERSE-induced reduction of steady-state ATP levels, but not other outcomes of exposure to sediment extracts. Overall, we find that in C. elegans, a basal level of CYP1A activity is protective against the examined PAH exposures.

Modulatory Effects of Silymarin on Benzo[a]pyrene-Induced Hepatotoxicity

Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon, is a group 1 carcinogen that introduces mutagenic DNA adducts into the genome. In this study, we investigated the molecular mechanisms underlying the involvement of silymarin in the reduction of DNA adduct formation by B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE), induced by B[a]P. B[a]P exhibited toxicity in HepG2 cells, whereas co-treatment of the cells with B[a]P and silymarin reduced the formation of BPDE-DNA adducts, thereby increasing cell viability. Determination of the level of major B[a]P metabolites in the treated cells showed that BPDE levels were reduced by silymarin. Nuclear factor erythroid 2-related factor 2 (Nrf2) and pregnane X receptor (PXR) were found to be involved in the activation of detoxifying genes against B[a]P-mediated toxicity. Silymarin did not increase the expression of these major transcription factors, but greatly facilitated their nuclear translocation. In this manner, treatment of HepG2 cells with silymarin modulated detoxification enzymes through NRF2 and PXR to eliminate B[a]P metabolites. Knockdown of Nrf2 abolished the preventive effect of silymarin on BPDE-DNA adduct formation, indicating that activation of the Nrf2 pathway plays a key role in preventing B[a]P-induced genotoxicity. Our results suggest that silymarin has anti-genotoxic effects, as it prevents BPDE-DNA adduct formation by modulating the Nrf2 and PXR signaling pathways.

Enhanced DNA adduct formation by benzo[a]pyrene in human liver cells lacking cytochrome P450 oxidoreductase

Diet is a major source of human exposure to polycyclic aromatic hydrocarbons (PAHs), of which benzo[a]pyrene (BaP) is the most commonly studied and measured. BaP has been considered to exert its genotoxic effects after metabolic activation by cytochrome P450 (CYP) enzymes whose activity can be modulated by cytochrome P450 oxidoreductase (POR), the electron donor to CYP enzymes. Previous studies showed that BaP-DNA adduct formation was greater in the livers of Hepatic Reductase Null (HRN) mice, in which POR is deleted specifically in hepatocytes, than in wild-type (WT) mice. In the present study we used human hepatoma HepG2 cells carrying a knockout (KO) in the POR gene as a human in vitro model that can mimic the HRN mouse model. Treatment to BaP for up to 48 h caused similar cytotoxicity in POR KO and WT HepG2 cells. However, levels of BaP activation (i.e. BaP-7,8-dihydrodiol formation) were higher in POR KO HepG2 cells than in WT HepG2 cells after 48 h. This also resulted in substantially higher BaP-DNA adduct formation in POR KO HepG2 cells indicating that BaP metabolism is delayed in POR KO HepG2 cells thereby prolonging the effective exposure of cells to unmetabolized BaP. As was seen in the HRN mouse model, these results suggest that cytochrome b₅, another component of the mixed-function oxidase system, which can also serve as electron donor to CYP enzymes along with NADH:cytochrome b₅ redutase, contributes to the bioactivation of BaP in POR KO HepG2 cells. Collectively, these findings indicate that CYPs play a more important role in BaP detoxication as opposed to activation.

The Multifarious Link between Cytochrome P450s and Cancer

Cancer is a leading cause of death worldwide. Cytochrome P450s (P450s) play an important role in the metabolism of endogenous as well as exogenous substances, especially drugs. Moreover, many P450s can serve as targets for disease therapy. Increasing reports of epidemiological, diagnostic, and clinical research indicate that P450s are enzymes that play a major part in the formation of cancer, prevention, and metastasis. The purposes of this review are to shed light on the current state of knowledge about the cancer molecular mechanism involving P450s and to summarize the link between the cancer effects and the participation of P450s.

Introduction and Perspectives of DNA Electrophoresis

Gel electrophoresis of DNA is one of the most frequently used techniques in molecular biology. Typically, it is used in the following: the analysis of in vitro reactions and purification of DNA fragments, analysis of PCR reactions, characterization of enzymes involved in DNA reactions, and sequencing. With some ingenuity gel electrophoresis of DNA is also used for the analysis of cellular biochemical reactions. For example, DNA breaks that accumulate in cells are analyzed by the comet assay and pulsed-field gel electrophoresis (PFGE). Furthermore, DNA replication intermediates are analyzed with two-dimensional (2D) gel electrophoresis. Moreover, several new methods for analyzing various chromosomal functions in cells have been developed. In this chapter, a brief introduction to these is given.

Biomarkers of Exposure and Effect in the Lungs of Smokers, Nonsmokers, and Electronic Cigarette Users

BACKGROUND

Nicotine-containing electronic cigarette (e-cig) use has become widespread. However, understanding the biological impact of e-cigs compared with smoking on the lung is needed. There are major gaps in knowledge for chronic effects and for an etiology to recent acute lung toxicity leading to death among vapers.

METHODS

We conducted bronchoscopies in a cross-sectional study of 73 subjects (42 never-smokers, 15 e-cig users, and 16 smokers). Using bronchoalveolar lavage and brushings, we examined lung inflammation by cell counts, cytokines, genome-wide gene expression, and DNA methylation.

RESULTS

There were statistically significant differences among never-smokers, e-cig users, and smokers for inflammatory cell counts and cytokines (FDR q < 0.1). The e-cig users had values intermediate between smokers and never-smokers, with levels for most of the biomarkers more similar to never-smokers. For differential gene expression and DNA methylation, e-cig users also more like never-smokers; many of these genes corresponded to smoking-related pathways, including those for xenobiotic metabolism, aryl hydrocarbon receptor signaling, and oxidative stress. Differentially methylated genes were correlated with changes in gene expression, providing evidence for biological effects of the methylation associations.

CONCLUSIONS

These data indicate that e-cigs are associated with less toxicity than cigarettes for smoking-related pathways. What is unknown may be unique effects for e-cigs not measured herein, and a comparison of smokers completely switching to e-cigs compared with former smokers. Clinical trials for smokers switching to e-cigs who undergo serial bronchoscopy and larger cross-sectional studies of former smokers with and without e-cig use, and for e-cigs who relapse back to smoking, are needed.

IMPACT

These data can be used for product regulation and for informing tobacco users considering or using e-cigs. What is unknown may be unique effects for e-cigs not measured herein, and clinical trials with serial bronchoscopy underway can demonstrate a direct relationship for changes in lung biomarkers.