The critical DNA damage by benzo(a)pyrene in lung tissues of smokers and approaches to preventing its formation

DNA modifications: Biomarkers for the exposome?

The concept of the exposome is the encompassing of all the environmental exposures, both exogenous and endogenous, across the life course. Many, if not all, of these exposures can result in the generation of reactive species, and/or the modulation of cellular processes, that can lead to a breadth of modifications of DNA, the nature of which may be used to infer their origin. Because of their role in cell function, such modifications have been associated with various major human diseases, including cancer, and so their assessment is crucial. Historically, most methods have been able to only measure one or a few DNA modifications at a time, limiting the information available. With the development of DNA adductomics, which aims to determine the totality of DNA modifications, a far more comprehensive picture of the DNA adduct burden can be gained. Importantly, DNA adductomics can facilitate a "top-down" investigative approach whereby patterns of adducts may be used to trace and identify the originating exposure source. This, together with other 'omic approaches, represents a major tool for unraveling the complexities of the exposome and hence allow a better a understanding of the environmental origins of disease.

Fine particulate matter PM2.5 and its constituent, hexavalent chromium induce acute cytotoxicity in human airway epithelial cells via inflammasome-mediated pyroptosis

PM2.5-induced airway injury contributes to an increased rate of respiratory morbidity. However, the relationship between PM2.5 toxicants and acute cytotoxic effects remains poorly understood. This study aimed to investigate the mechanisms of PM2.5- and its constituent-induced cytotoxicity in human airway epithelial cells. Exposure to PM2.5 resulted in dose-dependent cytotoxicity within 24 h. Among the PM2.5 constituents examined, Cr(VI) at the dose found in PM2.5 exhibited cytotoxic effects. Both PM2.5 and Cr(VI) cause necrosis while also upregulating the expression of proinflammatory cytokine transcripts. Interestingly, exposure to the conditioned PM, obtained from adsorption in the Cr(VI)-reducing agents, FeSO4 and EDTA, showed a decrease in cytotoxicity. Furthermore, PM2.5 mechanistically enhances programmed pyroptosis through the activation of NLRP3/caspase-1/Gasdermin D pathway and increase of IL-1β. These pyroptosis markers were reduced when exposure to conditioned PM. These findings provide a deeper understanding of mechanisms underlying PM2.5 and Cr(VI) in acute airway toxicity.

Cetuximab decorated redox sensitive D-alpha-tocopheryl- polyethyleneglycol-1000-succinate based nanoparticles for cabazitaxel delivery: Formulation, lung targeting and enhanced anti-cancer effects

This research work aims to fabricate cetuximab (CTX) decorated cabazitaxel (CBZ) loaded redox-sensitive D-alpha-tocopheryl-polyethyleneglycol-1000-succinate (TPGS-SS) nanoparticles (NPs) for epidermal growth factor receptor (EGFR)-targeted lung tumor therapy.The NPs were prepared using a dialysis bag diffusion method to produce, non-redox sensitive non targeted (TPGS-CBZ-NPs), redox-sensitive nontargeted (TPGS-SS-CBZ-NPs), and targeted redox-sensitive NPs (CTX-TPGS-SS-CBZ-NPs). Developed NPs were characterized for particle sizes, polydispersity, surface charge, surface morphologies, and entrapment efficiency. Moreover, additional in vitro studies have been conducted, including in vitro drug release, cytotoxicity, and cellular uptake studies.The particle size and charge over the surface were found to be in the range of 145.6 to 308.06 nm and -15 to -23 mV respectively. The IC50 values of CBZ clinical injection (Jevtana®), TPGS-CBZ-NPs, TPGS-SS-CBZ-NPs, and CTX-TPGS-SS-NPs were found to be 17.54 ± 3.58, 12.8 ± 2.45, 9.28 ± 1.13 and 4.013 ± 1.05 µg/ml, suggesting the 1.37, 1.89 and 4.37-folds respectively, enhancement of cytotoxicity as compared to CBZ clinical injection, demonstrating a significant augmentation in cytotoxicity. In addition, the in-vitro cellular uptake investigation showed that CTX-TPGS-SS-CMN6-NPs accumulated significantly compared to pure CMN6, TPGS-CMN6-NPs, and TPGS-SS-CMN6-NPs in the A549 cells. Furthermore, the targeting efficiency of developed NPs were analysed by ultrasound/photoacoustic and IVIS imaging.

Formononetin attenuates cigarette smoke-induced COPD in mice by suppressing inflammation, endoplasmic reticulum stress, and apoptosis in bronchial epithelial cells via AhR/CYP1A1 and AKT/mTOR signaling pathways

Chronic obstructive pulmonary disease (COPD) is a chronic, progressive, and lethal lung disease with few treatments. Formononetin (FMN) is a clinical preparation extract with extensive pharmacological actions. However, its effect on COPD remains unknown. This study aimed to explore the effect and underlying mechanisms of FMN on COPD. A mouse model of COPD was established by exposure to cigarette smoke (CS) for 24 weeks. In addition, bronchial epithelial BEAS-2B cells were treated with CS extract (CSE) for 24 h to explore the in vitro effect of FMN. FMN significantly improved lung function and attenuated pathological lung damage. FMN treatment reduced inflammatory cell infiltration and pro-inflammatory cytokines secretion. FMN also suppressed apoptosis by regulating apoptosis-associated proteins. Moreover, FMN relieved CS-induced endoplasmic reticulum (ER) stress in the mouse lungs. In BEAS-2B cells, FMN treatment reduced CSE-induced inflammation, ER stress, and apoptosis. Mechanistically, FMN downregulated the CS-activated AhR/CYP1A1 and AKT/mTOR signaling pathways in vivo and in vitro. FMN can attenuate CS-induced COPD in mice by suppressing inflammation, ER stress, and apoptosis in bronchial epithelial cells via the inhibition of AhR/CYP1A1 and AKT/mTOR signaling pathways, suggesting a new therapeutic potential for COPD treatment.

Toxicity Tolerance in the Carcinogenesis of Environmental Cadmium

Cadmium (Cd) is an environmental toxicant of worldwide public health significance. Diet is the main non-workplace Cd exposure source other than passive and active smoking. The intestinal absorption of Cd involves transporters for essential metals, notably iron and zinc. These transporters determine the Cd body burden because only a minuscule amount of Cd can be excreted each day. The International Agency for Research on Cancer listed Cd as a human lung carcinogen, but the current evidence suggests that the effects of Cd on cancer risk extend beyond the lung. A two-year bioassay demonstrated that Cd caused neoplasms in multiple tissues of mice. Also, several non-tumorigenic human cells transformed to malignant cells when they were exposed to a sublethal dose of Cd for a prolonged time. Cd does not directly damage DNA, but it influences gene expression through interactions with essential metals and various proteins. The present review highlights the epidemiological studies that connect an enhanced risk of various neoplastic diseases to chronic exposure to environmental Cd. Special emphasis is given to the impact of body iron stores on the absorption of Cd, and its implications for breast cancer prevention in highly susceptible groups of women. Resistance to cell death and other cancer phenotypes acquired during Cd-induced cancer cell transformation, under in vitro conditions, are briefly discussed. The potential role for the ZnT1 efflux transporter in the cellular acquisition of tolerance to Cd cytotoxicity is highlighted.

The activation of SIRT1 ameliorates BPDE-induced inflammatory damage in BEAS-2B cells via HMGB1/TLR4/NF-κB pathway

Benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), the metabolite of environmental pollutant benzo(a)pyrene (B(a)P) could induce pulmonary toxicity and inflammation. SIRT1, an NAD+ -dependent histone deacetylase, is known to regulate inflammation in the occurrence and development of various diseases, but its effects on BPDE-induced acute lung injury are still unknown. The present study aimed to explore the role of SIRT1 in BPDE-induced acute lung injury. Here, human bronchial epithelial (HBE) cells (BEAS-2B) cells were stimulated with BPDE at different concentrations (0.50, 0.75, and 1.00 μmol/L) for 24 h, we found that the levels of cytokines in the supernatant were increased and the expression of SIRT1 in cells was down-regulated, at the same time, BPDE stimulation up-regulated the protein expression of HMGB1, TLR4, and p-NF-κBp65 in BEAS-2B cells. Then the activator and inhibitor of SIRT1 were used before BPDE exposure, it was shown that the activation of SIRT1 significantly attenuated the levels of inflammatory cytokines and HMGB1, and reduced the expression of HMGB1, AC-HMGB1, TLR4, and p-NF-κBp65 protein; while these results were reversed by the inhibition of SIRT1. This study revealed that the SIRT1 activation may protect against BPDE-induced inflammatory damage in BEAS-2B cells by regulating the HMGB1/TLR4/NF-κB pathway.

Inhibition of RNF182 mediated by Bap promotes non-small cell lung cancer progression

Introduction

Ubiquitylation that mediated by ubiquitin ligases plays multiple roles not only in proteasome-mediated protein degradation but also in various cellular process including DNA repair, signal transduction and endocytosis. RING finger (RNF) proteins form the majority of these ubiquitin ligases. Recent studies have demonstrated the important roles of RNF finger proteins in tumorigenesis and tumor progression. Benzo[a]pyrene (BaP) is one of the most common environmental carcinogens causing lung cancer. The molecular mechanism of Bap carcinogenesis remains elusive. Considering the critical roles of RNF proteins in tumorigenesis and tumor progression, we speculate on whether Bap regulates RNF proteins resulting in carcinogenesis.

Methods

We used GEO analysis to identify the potential RING finger protein family member that contributes to Bap-induced NSCLC. We next used RT-qPCR, Western blot and ChIP assay to investigate the potential mechanism of Bap inhibits RNF182. BGS analyses were used to analyze the methylation level of RNF182.

Results

Here we reported that the carcinogen Bap suppresses the expression of ring finger protein 182 (RNF182) in non-small cell lung cancer (NSCLC) cells, which is mediated by abnormal hypermethylation in an AhR independent way and transcriptional regulation in an AhR dependent way. Furthermore, RNF182 exhibits low expression and hypermethylation in tumor tissues. RNF182 also significantly suppresses cell proliferation and induces cell cycle arrest in NSCLC cell lines.

Conclusion

These results demonstrated that Bap inhibits RNF182 expression to promote lung cancer tumorigenesis through activating AhR and promoting abnormal methylation.

Effect of polycyclic aromatic hydrocarbons on immunity

Nearly a quarter of the total number of deaths in the world are caused by unhealthy living or working environments. Therefore, we consider it significant to introduce the effect of a widely distributed component of air/water/food-source contaminants, polycyclic aromatic hydrocarbons (PAHs), on the human body, especially on immunity in this review. PAHs are a large class of organic compounds containing two or more benzene rings. PAH exposure could occur in most people through breath, smoke, food, and direct skin contact, resulting in both cellular immunosuppression and humoral immunosuppression. PAHs usually lead to the exacerbation of autoimmune diseases by regulating the balance of T helper cell 17 and regulatory T cells, and promoting type 2 immunity. However, the receptor of PAHs, aryl hydrocarbon receptor (AhR), appears to exhibit duality in the immune response, which seems to explain some seemingly opposite experimental results. In addition, PAH exposure was also able to exacerbate allergic reactions and regulate monocytes to a certain extent. The specific regulation mechanisms of immune system include the assistance of AhR, the activation of the CYP-ROS axis, the recruitment of intracellular calcium, and some epigenetic mechanisms. This review aims to summarize our current understanding on the impact of PAHs in the immune system and some related diseases such as cancer, autoimmune diseases (rheumatoid arthritis, type 1 diabetes, multiple sclerosis, and systemic lupus erythematosus), and allergic diseases (asthma and atopic dermatitis). Finally, we also propose future research directions for the prevention or treatment on environmental induced diseases.

New Insight into the Role of AhR in Lung Carcinogenesis

Lung cancer (LC), one of the most common malignant neoplasms, is the leading cause of high cancer mortality worldwide. Smoking is a risk factor for almost all histological types of LC. Benzo[a]pyrene (BaP), one of the main constituents of tobacco smoke, can cause cancer. It has been established that its toxic effects can develop in the following ways: genotoxic (formation of adducts with DNA) and non-genotoxic or epigenetic. The latter is less known, although it is known that BaP activates aryl hydrocarbon receptor (AhR), which regulate transcription of many target genes, including microRNAs, which can lead to initiation and enhancement of the malignant cell transformation. Recent studies are evaluating the role of AhR in the regulation of immune checkpoints, as cigarette smoke and BaP induce the AhR-regulated expression of PD-L1 (CD274) in lung epithelial cells in vitro and in vivo. In addition, kynurenine (a metabolite of tryptophan) has been found to stimulate the PD-1 (CD279) expression in cytotoxic T cells by activating AhR. Recent studies confirm great importance of AhR expressed in malignant cells for suppression of antitumor immunity. All this makes us rethink the role of AhR in lung carcinogenesis and investigate the mechanisms of its activation by exogenous and endogenous ligands. This review highlights the current understanding of the functional features of AhR and its role in the LC pathogenesis.

Sub-toxic events induced by truck speed-facilitated PM2.5 and its counteraction by epigallocatechin-3-gallate in A549 human lung cells

To distinguish the influences of fuel type and truck speed on chemical composition and sub-toxic effects of particulates (PM2.5) from engine emissions, biomarkers-interleukin-6 (IL-6), cytochrome P450 (CYP) 1A1, heme oxygenase (HO)-1, and NADPH-quinone oxidoreductase (NQO)-1-were studied in A549 human lung cells. Fuel type and truck speed preferentially affected the quantity and ion/polycyclic aromatic hydrocarbon (PAH) composition of PM2.5, respectively. Under idling operation, phenanthrene was the most abundant PAH. At high speed, more than 50% of the PAHs had high molecular weight (HMW), of which benzo[a]pyrene (B[a]P), benzo[ghi]perylene (B[ghi]P), and indeno[1,2,3-cd]pyrene (I[cd]P) were the main PAHs. B[a]P, B[ghi]P, and I[cd]P caused potent induction of IL-6, CYP1A1, and NQO-1, whereas phenanthrene mildly induced CYP1A1. Based on the PAH-mediated induction, the predicted increases in biomarkers were positively correlated with the measured increases. HMW-PAHs contribute to the biomarker induction by PM2.5, at high speed, which was reduced by co-exposure to epigallocatechin-3-gallate.

Indoor Secondary Pollutants Cannot Be Ignored: Third-Hand Smoke

Smoking has been recognized by the World Health Organization (WHO) as the fifth highest threat to humanity. Smoking, a leading disease promoter, is a major risk factor for non-communicable diseases (NCDs) such as cancer, cardiovascular disease, diabetes, and chronic respiratory diseases. NCDs account for 63% of all deaths worldwide. Passive smoking is also a health risk. Globally, more than a third of all people are regularly exposed to harmful smoke. Air pollution is a common global problem in which pollutants emitted into the atmosphere undergo a series of physical or chemical reactions to produce various oxidation products, which are often referred to as secondary pollutants. Secondary pollutants include ozone (O₃), sulfur trioxide (SO₃), nitrogen dioxide (NO₂), and respirable particulate matter (PM). It is worth mentioning that third-hand smoke (THS), formed by the reaction of nicotine with second-hand smoke (SHS) caused by indoor O₃ or nitrous acid (HONO), is a major indoor secondary pollutant that cannot be ignored. As a form of indoor air pollution that is relatively difficult to avoid, THS exists in any corner of the environment where smokers live. In this paper, we summarize the important research progress on the main components, detection, and toxicity of THS and look forward to future research directions. Scientific understanding of THS and its hazards will facilitate smoking bans in indoor and public places and raise public concern for how to prevent and remove THS.

Metabolic profiling of bisphenol A diglycidyl ether in vitro and in vivo

Bisphenol A diglycidyl ethers (BADGE) is one class of human-made chemicals, and it is one of the most widely used raw materials for epoxy resins. As an active compound, BADGE undergoes biotransformation in vitro and in vivo. However, there is a limited understanding of the biotransformation of BADGE and toxicity studies on transformation products. We conducted comprehensive research on the metabolic transformation of BADGE in vitro and in vivo. The results showed that 12 metabolites and 7 metabolites were identified in vitro and in vivo, respectively. Four biotransformation products, including M1 (hydrolysis), M3 (dehydroxylation), M10 (carboxylation), and M11 (glucose conjugation), can be found in both in vitro and in vivo samples. The main metabolic pathways were hydroxylation, carboxylation, cysteine (Cys) conjugation, and glucose conjugation. Besides, our results suggested the existence of metabolic differences in BADGE between species and gender. Further, we investigated toxicities of BADGE metabolites in-silico. Importantly, some hydrolysis (M1, M2), hydroxylation (M7), and oxidation (M8) products showed similar or even higher potential toxicity than BADGE depending on the endpoint. These results enrich the biotransformation profiles of BADGE and provide useful information for understanding its biotransformation in humans and a reference for the comprehensive assessment for human health risk.

Aryl Hydrocarbon Receptor in Oxidative Stress as a Double Agent and Its Biological and Therapeutic Significance

The aryl hydrocarbon receptor (AhR) has long been implicated in the induction of a battery of genes involved in the metabolism of xenobiotics and endogenous compounds. AhR is a ligand-activated transcription factor necessary for the launch of transcriptional responses important in health and disease. In past decades, evidence has accumulated that AhR is associated with the cellular response to oxidative stress, and this property of AhR must be taken into account during investigations into a mechanism of action of xenobiotics that is able to activate AhR or that is susceptible to metabolic activation by enzymes encoded by the genes that are under the control of AhR. In this review, we examine various mechanisms by which AhR takes part in the oxidative-stress response, including antioxidant and prooxidant enzymes and cytochrome P450. We also show that AhR, as a participant in the redox balance and as a modulator of redox signals, is being increasingly studied as a target for a new class of therapeutic compounds and as an explanation for the pathogenesis of some disorders.

Enzyme-Mediated Reactions of Phenolic Pollutants and Endogenous Metabolites as an Overlooked Metabolic Disruption Pathway

It is generally recognized that phenol-containing molecules mainly undergo phase II metabolic reactions, whereas glucuronide and sulfate are conjugated to form water-soluble products. Here, we report direct reactions of phenolic pollutants (triclosan, alkylphenol, bisphenol A [BPA], and its analogues) and some endogenous metabolites (vitamin E [VE] and estradiol) to generate new lipophilic ether products (e.g., BPA-O-VEs and alkylphenol-O-estradiol). A nontargeted screening strategy was used to identify the products in human liver microsome incubations, and the most abundant products (BPA-O-VEs) were confirmed via in vivo exposure in mice. BPA-O-VEs were frequently detected in sera from the general population at levels comparable to those of glucuronide/sulfate-conjugated BPA. Recombinant human cytochrome P450s were applied to find that CYP3A4 catalyzed the formation of these newly discovered ether metabolites by linking the VE hydroxyl group to the BPA phenolic ring, leading to the significantly reduced antioxidative activities of BPA-O-VEs compared to VEs. The effects of the reaction on the homeostasis of reacted biomolecules were finally assessed by in vitro assay and in vivo mice exposures. The generation of BPA-O-VEs decreased the VE concentrations and increased the reactive oxygen species generation after exposure to BPA at environmentally relevant concentrations. The identified reactions provided an overlooked metabolic disruption pathway for phenolic pollutants.

Can Exposure to Environmental Pollutants Be Associated with Less Effective Chemotherapy in Cancer Patients?

Since environmental pollutants are ubiquitous and many of them are resistant to degradation, we are exposed to many of them on a daily basis. Notably, these pollutants can have harmful effects on our health and be linked to the development of disease. Epidemiological evidence together with a better understanding of the mechanisms that link toxic substances with the development of diseases, suggest that exposure to some environmental pollutants can lead to an increased risk of developing cancer. Furthermore, several studies have raised the role of low-dose exposure to environmental pollutants in cancer progression. However, little is known about how these compounds influence the treatments given to cancer patients. In this work, we present a series of evidences suggesting that environmental pollutants such as bisphenol A (BPA), benzo[a]pyrene (BaP), persistent organic pollutants (POPs), aluminum chloride (AlCl₃), and airborne particulate matter may reduce the efficacy of some common chemotherapeutic drugs used in different types of cancer. We discuss the potential underlying molecular mechanisms that lead to the generation of this chemoresistance, such as apoptosis evasion, DNA damage repair, activation of pro-cancer signaling pathways, drug efflux and action of antioxidant enzymes, among others.

DNA damage, DNA repair and carcinogenicity: Tobacco smoke versus electronic cigarette aerosol

The allure of tobacco smoking is linked to the instant gratification provided by inhaled nicotine. Unfortunately, tobacco curing and burning generates many mutagens including more than 70 carcinogens. There are two types of mutagens and carcinogens in tobacco smoke (TS): direct DNA damaging carcinogens and procarcinogens, which require metabolic activation to become DNA damaging. Recent studies provide three new insights on TS-induced DNA damage. First, two major types of TS DNA damage are induced by direct carcinogen aldehydes, cyclic-1,N2-hydroxy-deoxyguanosine (γ-OH-PdG) and α-methyl-1, N2-γ-OH-PdG, rather than by the procarcinogens, polycyclic aromatic hydrocarbons and aromatic amines. Second, TS reduces DNA repair proteins and activity levels. TS aldehydes also prevent procarcinogen activation. Based on these findings, we propose that aldehydes are major sources of TS induce DNA damage and a driving force for carcinogenesis. E-cigarettes (E-cigs) are designed to deliver nicotine in an aerosol state, without burning tobacco. E-cigarette aerosols (ECAs) contain nicotine, propylene glycol and vegetable glycerin. ECAs induce O6-methyl-deoxyguanosines (O6-medG) and cyclic γ-hydroxy-1,N2--propano-dG (γ-OH-PdG) in mouse lung, heart and bladder tissues and causes a reduction of DNA repair proteins and activity in lungs. Nicotine and nicotine-derived nitrosamine ketone (NNK) induce the same types of DNA adducts and cause DNA repair inhibition in human cells. After long-term exposure, ECAs induce lung adenocarcinoma and bladder urothelial hyperplasia in mice. We propose that E-cig nicotine can be nitrosated in mouse and human cells becoming nitrosamines, thereby causing two carcinogenic effects, induction of DNA damage and inhibition of DNA repair, and that ECA is carcinogenic in mice. Thus, this article reviews the newest literature on DNA adducts and DNA repair inhibition induced by nicotine and ECAs in mice and cultured human cells, and provides insights into ECA carcinogenicity in mice.

Modifying effects of menthol against benzo(a)pyrene-induced forestomach carcinogenesis in female Swiss mice

Benzo(a)pyrene (BaP) is a polycyclic aromatic hydrocarbon widespread in the environment and closely associated to tobacco use, which is an important risk factor for highly incident stomach cancer. Menthol, a monoterpene extracted from Mentha genus species, has multiple biological properties, including anti-inflammatory and gastroprotective properties, but its effects on carcinogenesis are still to be fully understood. Thus, we evaluated the modifying effects of Ment against BaP-induced forestomach carcinogenesis. Female Swiss mice received BaP by intragastrical (i.g.) administration (50 mg/kg of body weight [b wt], 2×/week), from weeks 1-5 weeks. Concomitantly, mice received Menthol at 25 (Ment25) or 50 (Ment50) mg/kg b wt (i.g, 3×/week). Animals were euthanized at weeks 5 (n = 5 mice/group) or 30 (n = 10 mice/group). At week 5, both Ment doses reduced peripheral leukocyte blood genotoxicity 4 h after the last BaP administration, but only Ment50 attenuated this biomarker 8 h after the last BaP administration. In accordance to these findings, both Ment interventions attenuated BaP-induced increase in the percentage of H2A.X-positive forestomach epithelial cells. Moreover, Ment50 reduced cell proliferation and apoptosis (i.e., Ki-67 and caspase-3, respectively) in forestomach epithelium but exerted no significant effects on NFκB, and Nrf2 protein levels. At week 30, Ment50 reduced by ~55% the incidence of BaP-induced forestomach diffuse hyperplasia and multiplicity of forestomach tumors (squamous cell papillomas and carcinomas). Our findings indicate that Ment50, administered during initiation phase, attenuates forestomach carcinogenesis by reducing early genotoxicity, cell proliferation, and apoptosis induced by BaP.

Benzo[a]pyrene immunogenetics and immune archetype reprogramming of lung

Overexposure to carcinogenic precursor, benzo[a]pyrene [BaP], modulates the lung immune microenvironment. The present review seeks to elucidate novel pathways behind the tumor effect of BaP in the lungs, emphasizing immunomodulatory mediators and immune cells. In this review, BaP reprograms lung immune microenvironment through modulating transforming growth factor-beta (TGF-β), programmed cell death 1 (PD-1), cytotoxic T lymphocyte antigen-4 (CTLA-4), Interleukin 12 (IL-12), indoleamine 2,3 dioxygenase (IDO), forkhead box protein P3 (FOXP3) and interferon-gamma (IFN-γ) levels. Moreover, BaP modulated lung immune cellular architecture such as dendritic cells, T cells, Tregs, macrophages, neutrophils, and myeloid-derived suppressor cells (MDSCs). All mentioned changes in immune architecture and mediators lead to the induction of lung cancer.

Wood Smoke Extract Promotes Extracellular Matrix Remodeling in Normal Human Lung Fibroblasts

Wood smoke (WS) contains many harmful compounds, including polycyclic aromatic hydrocarbons (PAHs). WS induces inflammation in the airways and lungs and can lead to the development of various acute and chronic respiratory diseases. Pulmonary fibroblasts are the main cells involved in the remodeling of the extracellular matrix (ECM) during the WS-induced inflammatory response. Although fibroblasts remain in a low proliferation state under physiological conditions, they actively participate in ECM remodeling during the inflammatory response in pathophysiological states. Consequently, we used normal human lung fibroblasts (NHLFs) to assess the potential effects of the PAHs-containing wood smoke extract (WSE) on the growth rate, total collagen synthesis, and the expression levels of collagen I and III, matrix metalloproteinase (MMP)-1, MMP-2, MMP-9, tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, and the transforming growth factor (TGF)-β1. We also assessed MMPs activity. The results showed that WSE induced a trimodal behavior in the growth rate curves in NHLFs; the growth rate increased with 0.5-1 % WSE and decreased with 2.5% WSE, without causing cell damage; 5-20% WSE inhibited the growth and induced cell damage. After 3 hours of exposure, 2.5% WSE induced an increase in total collagen synthesis and upregulation of TGF-β1, collagen I and III, MMP-1, TIMP-1, and TIMP-2 expression. However, MMP-2 expression was downregulated and MMP-9 was not expressed. The gelatinase activity of MMP-2 was also increased. These results suggest that WSE affects the ECM remodeling in NHLFs and indicate the potential involvement of PAHs in this process.

Linking Coregulated Gene Modules with Polycyclic Aromatic Hydrocarbon-Related Cancer Risk in the 3D Human Bronchial Epithelium

Exposure to polycyclic aromatic hydrocarbons (PAHs) often occurs as complex chemical mixtures, which are linked to numerous adverse health outcomes in humans, with cancer as the greatest concern. The cancer risk associated with PAH exposures is commonly evaluated using the relative potency factor (RPF) approach, which estimates PAH mixture carcinogenic potential based on the sum of relative potency estimates of individual PAHs, compared to benzo[a]pyrene (BAP), a reference carcinogen. The present study evaluates molecular mechanisms related to PAH cancer risk through integration of transcriptomic and bioinformatic approaches in a 3D human bronchial epithelial cell model. Genes with significant differential expression from human bronchial epithelium exposed to PAHs were analyzed using a weighted gene coexpression network analysis (WGCNA) two-tiered approach: first to identify gene sets comodulated to RPF and second to link genes to a more comprehensive list of regulatory values, including inhalation-specific risk values. Over 3000 genes associated with processes of cell cycle regulation, inflammation, DNA damage, and cell adhesion processes were found to be comodulated with increasing RPF with pathways for cell cycle S phase and cytoskeleton actin identified as the most significantly enriched biological networks correlated to RPF. In addition, comodulated genes were linked to additional cancer-relevant risk values, including inhalation unit risks, oral cancer slope factors, and cancer hazard classifications from the World Health Organization's International Agency for Research on Cancer (IARC). These gene sets represent potential biomarkers that could be used to evaluate cancer risk associated with PAH mixtures. Among the values tested, RPF values and IARC categorizations shared the most similar responses in positively and negatively correlated gene modules. Together, we demonstrated a novel manner of integrating gene sets with chemical toxicity equivalence estimates through WGCNA to understand potential mechanisms.

Metabolomics study of fibroblasts damaged by UVB and BaP

We have recently shown that both UVB and BaP can induce the production of ROS, apoptosis and even cancer. However, the differences in the metabolic profiles of skin damaged by UVB, BaP or UVB combined with BaP have not been studied. Therefore, we examined the metabolic changes in the human foreskin fibroblast injured by UVB or BaP or the combination of the two, using ultra performance liquid chromatography (UPLC) coupled with quadrupole time-of-flight mass spectrometry (qTOF-MS). 24 metabolites were altered in the UVB damage group, 25 in the BaP damage group, and 33 in the UVB combined with BaP group. These alterations indicated that the metabolic mechanisms of HFF-1 cells treated with UVB or BaP are related to multiple main metabolites including glycerophosphocholine (PC), lactosylceramide (LacCer), guanidinosuccinic acid (GSA), glutathione(GSH), and lysophosphatidylcholine (LysoPC) and the main mechanisms involved glycerophospholipid and glutathione metabolism. Thus, our report provided useful insight into the underlying mechanisms of UVB and BaP damage to skin cells.

Lactic Acid Bacteria and Natural Product Complex Ameliorates Ovalbumin-Induced Airway Hyperresponsiveness in Mice

The incidence of respiratory diseases, such as asthma, has substantially increased in recent times owing to environmental changes, such as air pollution. Induction of a chronic inflammatory response begins with production of biologically active mediators from the airway epithelium, which attracts and recruits inflammatory cells into the lung airway. In our previous study, we confirmed that Lactobacillus casei HY2782 and Bifidobacterium animalis spp. lactis HY8002 could improve lung inflammation in the COPD animal model. In this study, we investigated the effect of the HY2782 complex against airway hyperresponsiveness by using an ovalbumin (OVA)-induced animal model. An orally administered HY2782 complex on OVA-induced allergic asthma in a BALB/c mouse model was used. The present results showed that the HY2782 complex suppressed total immunoglobulin E in serum and bronchoalveolar lavage fluid (BALF). The cytokine production profile in BALF and serum revealed that the HY2782 complex showed reduced levels of Th2 cytokines among immune factors released due to the elevated allergic response. Levels of inflammatory mediators in BALF, MCP-1, MIP-2, and CXCL-9 were decreased by oral administration of the HY2782 complex. Lower numbers of eosinophils and neutrophils in BALF suggested that inflammation was ameliorated by the HY2782 complex. Histological observation of lung sections also showed infiltration of fewer cells. From results, we suggested that the HY2782 complex effectively responds to improvement of the immune response and airway hypersensitivity reaction because of the anti-inflammatory effect of the Pueraria lobata root extract and antioxidant effect of HY2782.

Mechanisms of the synergistic lung tumorigenic effect of arsenic and benzo(a)pyrene combined- exposure

Humans are often exposed to mixtures of environmental pollutants especially environmental chemical carcinogens, representing a significant environmental health issue. However, our understanding on the carcinogenic effects and mechanisms of environmental carcinogen mixture exposures is limited and mostly relies on the findings from studying individual chemical carcinogens. Both arsenic and benzo(a)pyrene (BaP) are among the most common environmental carcinogens causing lung cancer and other types of cancer in humans. Millions of people are exposed to arsenic via consuming arsenic-contaminated drinking water and even more people are exposed to BaP via cigarette smoking and consuming BaP-contaminated food. Thus arsenic and BaP combined-exposure in humans is common. Previous epidemiology studies indicated that arsenic-exposed people who were cigarette smokers had significantly higher lung cancer risk than those who were non-smokers. Since BaP is one of the major carcinogens in cigarette smoke, it has been speculated that arsenic and BaP combined-exposure may play important roles in the increased lung cancer risk observed in arsenic-exposed cigarette smokers. In this review, we summarize important findings and inconsistencies about the co-carcinogenic effects and underlying mechanisms of arsenic and BaP combined-exposure and propose new areas for future studies. A clear understanding on the mechanism of co-carcinogenic effects of arsenic and BaP combined exposure may identify novel targets to more efficiently treat and prevent lung cancer resulting from arsenic and BaP combined-exposure.

Anticancer and immunomodulatory effect of rhaponticin on Benzo(a)Pyrene-induced lung carcinogenesis and induction of apoptosis in A549 cells

In worldwide, one of the most important cancer-related death is lung cancer. Also has the highest mortality rate between various cancer types. The count of lung cancer occurrence is increasing with an increased frequency by smoking. Proficient chemoprevention approaches are needed to prevent the occurrence of lung cancer. Therefore, the aim of this exploration is to determine the therapeutic impact on the immune modulatory effect of rhaponticin on lung tumorigenesis in vivo and in vitro cytotoxicity effect in A549 cells of human lung cancer. Lung cancer tumorigenesis in mice was challenged with benzo(a)pyrene (BaP) with 50 mg/kg bodyweight (b.wt) as oral administration for 6 weeks (two times/week). Rhaponticin were given orally 30 mg/kg b.wt (two times/week) in BaP induced mice from 12 weeks to 18 weeks. After treatment completes, the body weight was measured and then blood, lung tissue was collected for various parameters detection. The results evidenced that BaP induced mice decreased the bodyweight, increased lung weight, increased tumor markers (AHH, CEA and LDH), and increased the proinflammatory cytokines. The enzyme catalase, superoxide dismutase activity was decreased and increased lipid peroxidation in immune comprising cells compared with the control cells. Moreover, rhaponticin treatment improves in chemical assays and also the histopathological alteration of lung tissues. The present findings provide evidence about the therapeutic potentials of rhaponticin against BaP triggered lung tumorigenesis.

Developmental toxicity of cadmium in infants and children: a review

Several millions of people are exposed to cadmium worldwide due to natural and anthropogenic activities that led to their widespread distribution in the environment and have shown potential adverse effects on the kidneys, liver, heart and nervous system. Recently human and animal-based studies have been shown that In utero and early life exposure to cadmium can have serious health issues that are related to the risk of developmental disabilities and other outcomes in adulthood. Since, cadmium crosses the placental barrier and reaches easily to the fetus, even moderate or high-level exposure of this metal during pregnancy could be of serious health consequences which might be reflected either in the children’s early or later stages of life. Mortality from various diseases including cancer, cardiovascular, respiratory, kidney and neurological problems, correlation with In utero or early life exposure to cadmium has been found in epidemiological studies. Animal studies with strong evidence of various diseases mostly support for the human studies, as well as suggested a myriad mechanism by which cadmium can interfere with human health and development. More studies are needed to establish the mechanism of cadmium-induced toxicity with environmentally relevant doses in childhood and later life. In this review, we provide a comprehensive examination of the literature addressing potential long- term health issues with In utero and early life exposure to cadmium, as well as correlating with human and animal exposure studies.

Challenges associated with quantification of selected urinary biomarkers of exposure to tobacco products

Tobacco use, of which cigarette smoking is the most common, is a global health concern and is directly linked to over 7 million premature deaths annually. Measurement of the levels of tobacco-related biomarkers in biological matrices reflects human exposure to the chemicals in tobacco products. Nicotine, nicotine metabolites, anatabine, and anabasine are specific to tobacco and nicotine containing products. However, as nicotine and its metabolites are ubiquitous in the environment, background contamination during sample preparation can occur, making the quantification of target analytes challenging. The main purpose of the present study was to examine quality control measures needed in the determination of urinary nicotine, nicotine metabolites, anatabine, and anabasine. Urine samples (n = 75) and NIST standard reference materials SRM 3671 and SRM 3672 were analysed. A one-step extraction procedure using cold acetone was used in this study, which involved no additional clean up. The blank matrices investigated included synthetic urine prepared with HPLC-grade water, synthetic urine prepared with Milli-Q water, and bovine urine. By adopting strategies for minimizing the background levels, very low detection limits for all the target analytes ranging from 0.025 ng/mL for 3-hydroxycotinine to 0.634 ng/mL for nicotine, were achieved. Recoveries ranged between 67% and 118% with RSD values below 20%. Intra-day and inter-day precisions were in the range of 1.1-11.7% and 4.8-25.2%, respectively. The levels of all target analytes were higher in daily smokers than in non-smokers, with the largest difference observed for 3-hydroxycotinine. No difference was observed in the levels of target analytes between individuals who were former smokers, who never smoked or who were exposed to environmental tobacco smoke (ETS), except for total nicotine equivalents (TNE), which was significantly higher in non-smokers exposed to environmental tobacco smoke compared with study participants who never smoked. The results obtained from SRM 3671 and SRM 3672 could inform a potential certification of additional biomarkers of exposure to tobacco products in those standard reference materials.

Polycyclic Aromatic Hydrocarbons: Occurrence, Electroanalysis, Challenges, and Future Outlooks

The past several decades have seen increasing concern regarding the wide distribution of polycyclic aromatic hydrocarbons (PAHs) in environmental matrices. Primary toxicological data show PAHs' persistent characteristics and possible toxicity effects. Because of this pressing global issue, electroanalytical methods have been introduced. These methods are effective for PAH determination in environmental waters, even outclassing sophisticated analytical techniques such as chromatography, conventional spectrophotometry, fluorescence, and capillary electrophoresis. Herein, the literature published on PAHs is reviewed and discussed with special regard to PAH occurrence. Moreover, the recent developments in electrochemical sensors for PAH determination and the challenges and future outlooks in this field, are also presented.

Tinospora cordifolia and arabinogalactan exert chemopreventive action during benzo(a)pyrene-induced pulmonary carcinogenesis: studies on ultrastructural, molecular, and biochemical alterations

The aim of the present study was to unveil the chemopreventive potentials of aqueous Tinospora cordifolia stem extract and its active component viz. Arabinogalactan against Benzo(a)pyrene-induced pulmonary carcinogenesis. Animals were divided into six groups: (I) Control, (II) aqueous Tinospora cordifolia (200 mg/kg b.wt, p.o.), (III) arabinogalactan (7.5 mg/kg b.wt, p.o.), (IV) benzo(a)pyrene (50 mg/kg b.wt, i.p.) at second and fourth week of study, (V) benzo(a)pyrene + aqueous Tinospora cordifolia, and (VI) benzo(a)pyrene + arabinogalactan. The benzo(a)pyrene treatment resulted in severe alterations in the cellular arrangement and morphology of the alveolar tissue in benzo(a)pyrene group. However, benzo(a)pyrene + aqueous Tinospora cordifolia and benzo(a)pyrene + arabinogalactan groups revealed classical features of apoptosis including chromatin condensation and formation of apoptotic bodies. Furthermore, Fourier transform Infrared spectroscopy analysis showed disturbed phospholipid saturation and protein secondary structures in benzo(a)pyrene treated animals. Depletion in relative glycogen and enhancement in total nucleic acid content was observed in benzo(a)pyrene treated animals, and the same was found to be restored upon arabinogalactan and aqueous Tinospora cordifolia supplementation. Benzo(a)pyrene insult also upregulated the phase I carcinogen metabolizing enzymes and differentially modulated the phase II metabolizing enzymes during pulmonary carcinogenesis. Also, depleted (reduced glutathione) and increased lipid peroxidation levels were observed in benzo(a)pyrene treated animals, which was found to be normalized upon aqueous Tinospora cordifolia and arabinogalactan administration. Clastogenic damage inflicted by benzo(a)pyrene was also reversed in benzo(a)pyrene + aqueous Tinospora cordifolia and benzo(a)pyrene + arabinogalactan group. Thus, the present study infers that aqueous Tinospora cordifolia and arabinogalactan showed promising anticancer activity against lung tumorigenesis in terms of ultrastructural, biochemical, and biomolecular aspects.

Environmental pollutants and the immune response

Environmental pollution is one of the most serious challenges to health in the modern world. Pollutants alter immune responses and can provoke immunotoxicity. In this Review, we summarize the major environmental pollutants that are attracting wide-ranging concern and the molecular basis underlying their effects on the immune system. Xenobiotic receptors, including the aryl hydrocarbon receptor (AHR), sense and respond to a subset of environmental pollutants by activating the expression of detoxification enzymes to protect the body. However, chronic activation of the AHR leads to immunotoxicity. KEAP1-NRF2 is another important system that protects the body against environmental pollutants. KEAP1 is a sensor protein that detects environmental pollutants, leading to activation of the transcription factor NRF2. NRF2 protects the body from immunotoxicity by inducing the expression of genes involved in detoxification, antioxidant and anti-inflammatory activities. Intervening in these sensor-response systems could protect the body from the devastating immunotoxicity that can be induced by environmental pollutants.

Association between Metabolites and the Risk of Lung Cancer: A Systematic Literature Review and Meta-Analysis of Observational Studies

Globally, lung cancer is the most prevalent cancer type. However, screening and early detection is challenging. Previous studies have identified metabolites as promising lung cancer biomarkers. This systematic literature review and meta-analysis aimed to identify metabolites associated with lung cancer risk in observational studies. The literature search was performed in PubMed and EMBASE databases, up to 31 December 2019, for observational studies on the association between metabolites and lung cancer risk. Heterogeneity was assessed using the I² statistic and Cochran’s Q test. Meta-analyses were performed using either a fixed-effects or random-effects model, depending on study heterogeneity. Fifty-three studies with 297 metabolites were included. Most identified metabolites (252 metabolites) were reported in individual studies. Meta-analyses were conducted on 45 metabolites. Five metabolites (cotinine, creatinine riboside, N-acetylneuraminic acid, proline and r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene) and five metabolite groups (total 3-hydroxycotinine, total cotinine, total nicotine, total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (sum of concentrations of the metabolite and its glucuronides), and total nicotine equivalent (sum of total 3-hydroxycotinine, total cotinine and total nicotine)) were associated with higher lung cancer risk, while three others (folate, methionine and tryptophan) were associated with lower lung cancer risk. Significant heterogeneity was detected across most studies. These significant metabolites should be further evaluated as potential biomarkers for lung cancer.

Inhibition of UDP-glucuronosyltransferases (UGTs) by polycyclic aromatic hydrocarbons (PAHs) and hydroxy-PAHs (OH-PAHs)

Polycyclic aromatic hydrocarbons (PAHs) are known as one of the ubiquitous environmental pollutants caused by unavoidable combustion of by-products. Despite decades of research on adverse health effects towards humans, the effects of PAHs and their hydroxylated metabolites (OH-PAHs) on UDP-glucuronosyltransferases (UGTs) remain unclear. This study aimed to investigate inhibitory effects with structure-dependence of 14 PAHs and OH-PAHs towards the activity of 7 isoforms of UGTs using in vitro recombinant UGTs-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) as the probe reaction. PAHs and OH-PAHs showed inhibitory effects towards different UGT isoforms with different extents. For inhibition kinetics determination, 1-HONAP, 4-HOPHE, 9-HOPHE, and 1-HOPYR were utilized as the representative compounds, and UGT1A6, UGT1A9 and UGT2B7 were chosen as the three representative UGT isoforms. The inhibitory effects of 4-HOPHE, 9-HOPHE and 1-HOPYR on three above UGT isoforms were the same: UGT1A9>UGT1A6>UGT2B; for 1-HONAP, that is UGT1A6>UGT1A9>UGT2B. Molecular docking methods were utilized to find the activity cavity of UGT1A9 and UGT2B7 binding with 1-HONAP and 1-HOPYR. Hydrogen bonds and hydrophobic contacts were mainly contributors to their interactions. In vitro-in vivo extrapolation (IVIVE) showed that high in vivo inhibition possibility exists for the inhibition of OH-PAHs on UGTs. All the results provide a novel viewpoint for an explanation of the toxicity of PAHs and OH-PAHs.

Regulation of Wnt Singaling Pathway by Poly (ADP-Ribose) Glycohydrolase (PARG) Silencing Suppresses Lung Cancer in Mice Induced by Benzo(a)pyrene Inhalation Exposure

Benzo(a)pyrene (BaP) is a polycyclic aromatic hydrocarbon that specifically causes cancer and is widely distributed in the environment. Poly (ADP-ribosylation), as a key post-translational modification in BaP-induced carcinogenesis, is mainly catalyzed by poly (ADP-ribose) glycohydrolase (PARG) in eukaryotic organisms. Previously, it is found that PARG silencing can counteract BaP-induced carcinogenesis in vitro, but the mechanism remained unclear. In this study, we further examined this process in vivo by using heterozygous PARG knockout mice (PARG^+/−). Wild-type and PARG^+/− mice were individually treated with 0 or 10 μg/m³ BaP for 90 or 180 days by dynamic inhalation exposure. Pathological analysis of lung tissues showed that, with extended exposure time, carcinogenesis and injury in the lungs of WT mice was progressively worse; however, the injury was minimal and carcinogenesis was not detected in the lungs of PARG^+/− mice. These results indicate that PARG gene silencing protects mice against lung cancer induced by BaP inhalation exposure. Furthermore, as the exposure time was extended, the protein phosphorylation level was down-regulated in WT mice, but up-regulated in PARG^+/− mice. The relative expression of Wnt2b and Wnt5b mRNA in WT mice were significantly higher than those in the control group, but there was no significant difference in PARG^+/− mice. Meanwhile, the relative expression of Wnt2b and Wnt5b proteins, as assessed by immunohistochemistry and Western blot analysis, was significantly up-regulated by BaP in WT mice; while in PARG^+/− mice it was not statistically affected. Our work provides initial evidence that PARG silencing suppresses BaP induced lung cancer and stabilizes the expression of Wnt ligands, PARG gene and Wnt ligands may provide new options for the diagnosis and treatment of lung cancer.

Novel Insights reveal Anti-microbial Gene Regulation of Piglet Intestine Immune in response to Clostridium perfringens Infection

LncRNA play important roles in regulation of host immune and inflammation responses in defending bacterial infection. Clostridium perfringens (C. perfringens) type C is one of primary bacteria leading to piglet diarrhea and other intestinal inflammatory diseases. For the differences of host immune capacity, individuals usually show resistance and susceptibility to bacterial infection. However, whether and how lncRNAs involved in modulating host immune resistance have not been reported. We have investigated the expression patterns of ileum lncRNAs of 7-day-old piglets infected by C. perfringens type C through RNA sequencing. A total of 16 lncRNAs and 126 mRNAs were significantly differentially expressed in resistance (IR) and susceptibility (IS) groups. Many lncRNAs and mRNAs were identified to regulate resistance and susceptibility of piglets through immune related pathways. Five lncRNAs may have potential function on regulating the expressions of cytokines, these lncRNAs and cytokines work together to co-regulated piglet immune response to C. perfringens, affecting host resistance and susceptibility. These results provide valuable information for understanding the functions of lncRNA and mRNA in affecting piglet diarrhea resistance of defensing to C. perfringens type C, these lncRNAs and mRNAs may be used as the important biomarkers for decreasing C. perfringens spread and diseases in human and piglets.

Overexpression of Annexin A1 protects against benzo[a]pyrene‑induced bronchial epithelium injury

The incidence of asthma is increasing worldwide. Bronchial epithelium injury is common in asthma. The regulatory role of Annexin A1 (ANXA1) in bronchial epithelium injury is currently not well understood. The aim of the present study was to evaluate the role of ANXA1 on bronchial epithelium injury. The cell viability and levels of apoptosis were respectively tested by Cell Counting Kit-8 and flow cytometry. Reactive oxygen species (ROS) content and the activity of oxidative indicators were assessed by commercial kits. Enzyme linked immunosorbent assay was performed to detect the activity of active caspase-3. Reverse transcription-quantitative polymerase chain reaction and western blot assays were used to determine the expression levels of the target factors. The results demonstrated that ANXA1 improved the viability of benzo[a]pyrene (Bap)-treated bronchial epithelial cells. The Bap-induced oxidative stress was mitigated by the reduction in ROS generation, and the regulation of the activity of superoxide dismutase, glutathione peroxidases, malondialdehyde and lactic dehydrogenase. In addition, apoptosis was decreased by ANXA1 via the reduction of the expression of B-cell lymphoma 2 (Bcl-2), and the increase in the expression of Bcl-2-associated X protein and cyclin D1. Furthermore, the expression of phosphatase and tensin homolog (PTEN) and focal adhesion kinase (FAK) was rescued and the phosphorylation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) was depressed by ANXA1, when compared with the Bap group. SF1670 treatment reversed the anti-apoptotic effect of ANXA1. In conclusion, the results highlighted the protective effects of ANXA1 on bronchial epithelium injury, which most likely occurred via the PTEN/FAK/PI3K/Akt signaling pathway. Thus, the present study contributes to a potential therapeutic strategy for asthma patients.

Combined treatment with benzo[a]pyrene and 1α,25-dihydroxyvitamin D3 induces expression of plasminogen activator inhibitor 1 in monocyte/macrophage-derived cells

Benzo[a]pyrene (BaP) is an environmental pollutant found in cigarette smoke and is implicated as a causative agent of tobacco-related diseases, such as arteriosclerosis. In contrast, vitamin D signaling, which is principally mediated by conversion of vitamin D to the active form, 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], decreases cardiovascular disease risk. However, combined treatment with BaP and 1,25(OH)₂D₃ enhances BaP toxicity, including BaP-DNA adduct formation. We further investigated the cross-talk between BaP and 1,25(OH)₂D₃ signaling pathways, and found that combined treatment with these compounds induces mRNA and protein expression of plasminogen activator inhibitor 1 (PAI-1) in monocyte/macrophage-derived THP-1 and U937 cells. Protein synthesis inhibitor treatment did not inhibit induction of the PAI-1 gene (SERPINE1) in these cells. BaP plus 1,25(OH)₂D₃ induced differentiation markers, inhibited cellular proliferation, and induced apoptosis and oxidative stress in these cells. Reactive oxygen species scavenger treatment suppressed apoptosis but not SERPINE1 induction in cells treated with BaP plus 1,25(OH)₂D₃. Thus, combined treatment with BaP and 1,25(OH)₂D₃ induced SERPINE1 mRNA expression in these cells through a mechanism that does not require de novo protein synthesis or reactive oxygen species production. These findings suggest that induction of the proinflammatory factor PAI-1 plays a role in BaP toxicity. Interestingly, PAI-1 knockdown decreased expression of the cell surface antigen CD14, a monocytic differentiation marker, in THP-1 cells treated with BaP plus 1,25(OH)₂D₃. PAI-1 induction may also be related to a function of monocytes/macrophages in response to xenobiotic and vitamin D signaling.

Simultaneous detection of nucleotide excision repair events and apoptosis-induced DNA fragmentation in genotoxin-treated cells

Novel in vivo excision assays for monitoring the excised oligonucleotide products of nucleotide excision repair in UV-irradiated cells have provided unprecedented views of the kinetics and genomic distribution of repair events. However, an unresolved issue is the fate of the excised oligonucleotide products of repair and their mechanism of degradation. Based on our observation that decreases in excised oligonucleotide abundance coincide with the induction of apoptotic signaling in UV-irradiated cells, we considered the possibility that caspase-mediated apoptotic signaling contributes to excised oligonucleotide degradation or to a general inhibition of the excision repair system. However, genetic and pharmacological approaches to inhibit apoptotic signaling demonstrated that caspase-mediated apoptotic signaling does not affect excision repair or excised oligonucleotide stability. Nonetheless, our assay for detecting soluble DNAs produced by repair also revealed the production of larger DNAs following DNA damage induction that was dependent on caspase activation. We therefore further exploited the versatility of this assay by showing that soluble DNAs produced by both nucleotide excision repair and apoptotic signaling can be monitored simultaneously with a diverse set of DNA damaging agents. Thus, our in vivo excision repair assay provides a sensitive measure of both repair kinetics and apoptotic signaling in genotoxin-treated cells.

Interaction of Nucleotide Excision Repair Protein XPC-RAD23B with DNA Containing Benzo[a]pyrene-Derived Adduct and Apurinic/Apyrimidinic Site within a Cluster

The combined action of reactive metabolites of benzo[a]pyrene (B[a]P) and oxidative stress can lead to cluster-type DNA damage that includes both a bulky lesion and an apurinic/apyrimidinic (AP) site, which are repaired by the nucleotide and base excision repair mechanisms - NER and BER, respectively. Interaction of NER protein XPC-RAD23B providing primary damage recognition with DNA duplexes containing a B[a]P-derived residue linked to the exocyclic amino group of a guanine (BPDE-N(2)-dG) in the central position of one strand and AP site in different positions of the other strand was analyzed. It was found that XPC-RAD23B crosslinks to DNA containing (+)-trans-BPDE-N(2)-dG more effectively than to DNA containing cis-isomer, independently of the AP site position in the opposite strand; protein affinity to DNA containing one of the BPDE-N(2)-dG isomers depends on the AP site position in the opposite strand. The influence of XPC-RAD23B on hydrolysis of an AP site clustered with BPDE-N(2)-dG catalyzed by the apurinic/apyrimidinic endonuclease 1 (APE1) was examined. XPC-RAD23B was shown to stimulate the endonuclease and inhibit the 3'-5' exonuclease activity of APE1. These data demonstrate the possibility of cooperation of two proteins belonging to different DNA repair systems in the repair of cluster-type DNA damage.

Processing of the abasic sites clustered with the benzo[a]pyrene adducts by the base excision repair enzymes

The major enzyme in eukaryotic cells that catalyzes the cleavage of apurinic/apyrimidinic (AP or abasic) sites is AP endonuclease 1 (APE1) that cleaves the phosphodiester bond on the 5'-side of AP sites. We found that the efficiency of AP site cleavage by APE1 was affected by the benzo[a]pyrenyl-DNA adduct (BPDE-dG) in the opposite strand. AP sites directly opposite of the modified dG or shifted toward the 5' direction were hydrolyzed by APE1 with an efficiency moderately lower than the AP site in the control DNA duplex, whereas AP sites shifted toward the 3' direction were hydrolyzed significantly less efficiently. For all DNA structures except DNA with the AP site shifted by 3 nucleotides in the 3' direction (AP₊₃-BP-DNA), hydrolysis was more efficient in the case of (+)-trans-BPDE-dG. Using molecular dynamic simulation, we have shown that in the complex of APE1 with the AP₊₃-BP-DNA, the BP residue is located within the DNA bend induced by APE1 and contacts the amino acids in the enzyme catalytic center and the catalytic metal ion. The geometry of the APE1 active site is perturbed more significantly by the trans-isomer of BPDE-dG that intercalates into the APE1-DNA complex near the cleaved phosphodiester bond. The ability of DNA polymerases β (Polβ), λ and ι to catalyze gap-filling synthesis in cooperation with APE1 was also analyzed. Polβ was shown to inhibit the 3'→5' exonuclease activity of APE1 when both enzymes were added simultaneously and to insert the correct nucleotide into the gap arising after AP site hydrolysis. Therefore, further evidence for the functional cooperation of APE1 and Polβ in base excision repair was obtained.

Polycyclic aromatic hydrocarbons: from metabolism to lung cancer

Excessive exposure to polycyclic aromatic hydrocarbons (PAHs) often results in lung cancer, a disease with the highest cancer mortality in the United States. After entry into the lung, PAHs induce phase I metabolic enzymes such as cytochrome P450 (CYP) monooxygenases, i.e. CYP1A1/2 and 1B1, and phase II enzymes such as glutathione S-transferases, UDP glucuronyl transferases, NADPH quinone oxidoreductases (NQOs), aldo-keto reductases (AKRs), and epoxide hydrolases (EHs), via the aryl hydrocarbon receptor (AhR)-dependent and independent pathways. Humans can also be exposed to PAHs through diet, via consumption of charcoal broiled foods. Metabolism of PAHs through the CYP1A1/1B1/EH pathway, CYP peroxidase pathway, and AKR pathway leads to the formation of the active carcinogens diol-epoxides, radical cations, and o-quinones. These reactive metabolites produce DNA adducts, resulting in DNA mutations, alteration of gene expression profiles, and tumorigenesis. Mutations in xenobiotic metabolic enzymes, as well as polymorphisms of tumor suppressor genes (e.g. p53) and/or genes involved in gene expression (e.g. X-ray repair cross-complementing proteins), are associated with lung cancer susceptibility in human populations from different ethnicities, gender, and age groups. Although various metabolic activation/inactivation pathways, AhR signaling, and genetic susceptibilities contribute to lung cancer, the precise points at which PAHs induce tumor initiation remain unknown. The goal of this review is to provide a current state-of-the-science of the mechanisms of human lung carcinogenesis mediated by PAHs, the experimental approaches used to study this complex class of compounds, and future directions for research of these compounds.

Cigarette Smoking, BPDE-DNA Adducts, and Aberrant Promoter Methylations of Tumor Suppressor Genes (TSGs) in NSCLC from Chinese Population

Non-small cell lung cancer (NSCLC) is related to the genetic and epigenetic factors. The goal of this study was to determine association of cigarette smoking and BPDE-DNA adducts with promoter methylations of several genes in NSCLC. Methylation of the promoters of p16, RARβ, DAPK, MGMT, and TIMP-3 genes of tumor tissues from 199 lung cancer patients was analyzed with methylation-specific PCR (MSP), and BPDE-DNA adduct level in lung cancer tissue was obtained by ELISA. Level of BPDE-DNA adduct increased significantly in males, aged people (over 60 years), and smokers; however, no significant difference was found while comparing the BPDE-DNA adduct levels among different tumor types, locations, and stages. Cigarette smoking was also associated with increased BPDE-DNA adducts level (OR = 2.43, p > .05) and increased methylation level in at least 1 gene (OR = 5.22, p < .01), both in dose-response manner. Similarly, cigarette smoking also significantly increase the risk of p16 or DAPK methylation (OR = 3.02, p < .05 for p16, and 3.66, p < .05 for DAPK). The highest risk of BPDE-DNA adducts was detected among individuals with cigarette smoking for more than 40 pack-years (OR = 4.21, p < .01). Furthermore, the present study did not show that BPDE-DNA adducts are significantly associated with abnormal TSGs methylations in NSCLC, including SCC and AdO, respectively. Conclusively, cigarette smoking is significantly associated with the increase of BPDE-DNA adduct level, promoter hypermethylation of p16 and DAPK genes, while BPDE-DNA adduct was not significantly related to abnormal promoter hypermethylation in TSGs, suggesting that BPDE-DNA adducts and TSGs methylations play independent roles in NSCLC.

Implementation of modern therapy approaches and research for non-small cell lung cancer in Japan

The genetic backgrounds of the Japanese (or Asians) are, at least in part, different from those of Caucasians. It is necessary to recognize this difference to develop medicine that is both optimized and individualized. In particular, the consideration of ethnic differences is becoming increasingly important for lung cancer medicine. Japanese clinical practice guidelines indicate that some clinical biomarkers, such as epidermal growth factor receptor gene mutations, echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase fusion gene and uridine diphosphate glucuronosyltransferase genotypes should be determined in appropriate lung cancer patients. At the present time, tests for these biomarkers are covered by the Japanese national health-care programme, as is treatment with certain targeted drugs and cytotoxic agents. Therefore, most patients with lung cancer in Japan receive these tests as part of daily practice if their performance status and organ function are judged to be eligible. In addition, ethnic differences in bone marrow toxicity caused by cytotoxic drugs are reflected in treatment choice, and the requirements for the development of treatment modalities suitable for rare targeted populations are also increasing. To meet these requirements, many collaborative groups in Japan that have improved their infrastructure for investigator-initiated trials and conducted important activities need to provide further optimal treatment modalities for Japanese and Asian patients with lung cancer. Here, the characteristics of lung cancer in Japanese patients, general aspects of medical treatment and the care system in Japan, and representative studies on lung cancer in Japan are reviewed.

Laricitrin suppresses increased benzo(a)pyrene-induced lung tumor-associated monocyte-derived dendritic cell cancer progression

Benzo(a)pyrene (BaP) stimulates lung cancer cells, promoting monocyte-derived dendritic cells to secrete soluble factors, including heparin binding-epidermal growth factor and C-X-C motif chemokine 5. The secretions from monocyte-derived dendritic cells stimulate the progression of lung cancer cells, including the migration and invasion of cells. To the best of our knowledge, these secretions remain unknown, and require additional study. The present study identified that treatment with BaP-H1395-tumor-associated dendritic cell-conditioned medium had the most marked effect on cell migration and invasion. This result may be associated with the female gender, stage 2 adenocarcinoma or mutation of the proto-oncogene B-Raf (BRAF), according to the cell line background. Laricitrin, a dietary flavonoid derivative present in grapes and red wine, suppresses certain factors and decreases the progression of lung cancer cells that are promoted by BaP in the lung cancer tumor microenvironment. The results of the present study suggest that prolonged exposure to BaP exacerbates lung cancer, particularly in female lung cancer patients with the BRAF mutation, but that laricitrin may ameliorate this effect.

Error-Prone and Error-Free Translesion DNA Synthesis over Site-Specifically Created DNA Adducts of Aryl Hydrocarbons (3-Nitrobenzanthrone and 4-Aminobiphenyl)

Aryl hydrocarbons such as 3-nitrobenzanthrone (NBA), 4-aminobiphenyl (ABP), acetylaminofluorene (AAF), benzo(a)pyrene (BaP), and 1-nitropyrene (NP) form bulky DNA adducts when absorbed by mammalian cells. These chemicals are metabolically activated to reactive forms in mammalian cells and preferentially get attached covalently to the N² or C8 positions of guanine or the N⁶ position of adenine. The proportion of N² and C8 guanine adducts in DNA differs among chemicals. Although these adducts block DNA replication, cells have a mechanism allowing to continue replication by bypassing these adducts: translesion DNA synthesis (TLS). TLS is performed by translesion DNA polymerases—Pol η, κ, ι, and ζ and Rev1—in an error-free or error-prone manner. Regarding the NBA adducts, namely, 2-(2′-deoxyguanosin-N²-yl)-3-aminobenzanthrone (dG-N²-ABA) and N-(2′-deoxyguanosin-8-yl)-3-aminobenzanthrone (dG-C8-ABA), dG-N²-ABA is produced more often than dG-C8-ABA, whereas dG-C8-ABA blocks DNA replication more strongly than dG-N²-ABA. dG-N²-ABA allows for a less error-prone bypass than dG-C8-ABA does. Pol η and κ are stronger contributors to TLS over dG-C8-ABA, and Pol κ bypasses dG-C8-ABA in an error-prone manner. TLS efficiency and error-proneness are affected by the sequences surrounding the adduct, as demonstrated in our previous study on an ABP adduct, N-(2′-deoxyguanosine-8-yl)-4-aminobiphenyl (dG-C8-ABP). Elucidation of the general mechanisms determining efficiency, error-proneness, and the polymerases involved in TLS over various adducts is the next step in the research on TLS. These TLS studies will clarify the mechanisms underlying aryl hydrocarbon mutagenesis and carcinogenesis in more detail.