Air pollution is the leading cause of lung cancer after tobacco smoking, contributing to 20% of all lung cancer deaths. Increased risk associated with living near trafficked roads, occupational exposure to diesel exhaust, indoor coal combustion and cigarette smoking, suggest that combustion components in ambient fine particulate matter (PM2.5), such as polycyclic aromatic hydrocarbons (PAHs), may be central drivers of lung cancer. Activation of the aryl hydrocarbon receptor (AhR) induces expression of xenobiotic-metabolizing enzymes (XMEs) and increase PAH metabolism, formation of reactive metabolites, oxidative stress, DNA damage and mutagenesis. Lung cancer tissues from smokers and workers exposed to high combustion PM levels contain mutagenic signatures derived from PAHs. However, recent findings suggest that ambient air PM2.5 exposure primarily induces lung cancer development through tumor promotion of cells harboring naturally acquired oncogenic mutations, thus lacking typical PAH-induced mutations. On this background, we discuss the role of AhR and PAHs in lung cancer development caused by air pollution focusing on the tumor promoting properties including metabolism, immune system, cell proliferation and survival, tumor microenvironment, cell-to-cell communication, tumor growth and metastasis. We suggest that the dichotomy in lung cancer patterns observed between smoking and outdoor air PM2.5 represent the two ends of a dose-response continuum of combustion PM exposure, where tumor promotion in the peripheral lung appears to be the driving factor at the relatively low-dose exposures from ambient air PM2.5, whereas genotoxicity in the central airways becomes increasingly more important at the higher combustion PM levels encountered through smoking and occupational exposure.

• Keywords
• Air pollution, Carcinogenesis, Diesel exhaust, Genotoxicity, Inflammation, Occupational exposure, Smoking, Tumor metastasis, Tumor microenvironment, Tumor promotion,
• MeSH
• Air Pollutants * toxicity   MeSH
• Humans MeSH
• Environmental Monitoring MeSH
• Tumor Microenvironment MeSH
• Lung Neoplasms * chemically induced   genetics   MeSH
• Particulate Matter toxicity   MeSH
• Polycyclic Aromatic Hydrocarbons * toxicity   MeSH
• Receptors, Aryl Hydrocarbon genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• Air Pollutants * MeSH
• Particulate Matter MeSH
• Polycyclic Aromatic Hydrocarbons * MeSH
• Receptors, Aryl Hydrocarbon MeSH

Dysregulation of gap junction intercellular communication (GJIC) is recognized as one of the key hallmarks for identifying non-genotoxic carcinogens (NGTxC). Currently, there is a demand for in vitro assays addressing the gap junction hallmark, which would have the potential to eventually become an integral part of an integrated approach to the testing and assessment (IATA) of NGTxC. The scrape loading-dye transfer (SL-DT) technique is a simple assay for the functional evaluation of GJIC in various in vitro cultured mammalian cells and represents an interesting candidate assay. Out of the various techniques for evaluating GJIC, the SL-DT assay has been used frequently to assess the effects of various chemicals on GJIC in toxicological and tumor promotion research. In this review, we systematically searched the existing literature to gather papers assessing GJIC using the SL-DT assay in a rat liver epithelial cell line, WB-F344, after treating with chemicals, especially environmental and food toxicants, drugs, reproductive-, cardio- and neuro-toxicants and chemical tumor promoters. We discuss findings derived from the SL-DT assay with the known knowledge about the tumor-promoting activity and carcinogenicity of the assessed chemicals to evaluate the predictive capacity of the SL-DT assay in terms of its sensitivity, specificity and accuracy for identifying carcinogens. These data represent important information with respect to the applicability of the SL-DT assay for the testing of NGTxC within the IATA framework.

• Keywords
• carcinogenesis, carcinogens, gap junction intercellular communication, scrape loading-dye transfer,
• MeSH
• Coloring Agents metabolism   MeSH
• Biological Assay methods   MeSH
• Cell Line MeSH
• Microscopy, Fluorescence methods   MeSH
• Liver pathology   MeSH
• Carcinogens MeSH
• Rats MeSH
• Cells, Cultured MeSH
• Gap Junctions metabolism   MeSH
• Cell Communication drug effects   physiology   MeSH
• Carcinogenicity Tests methods   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Coloring Agents MeSH
• Carcinogens MeSH

Inhalation exposures to polycyclic aromatic hydrocarbons (PAHs) have been associated with various adverse health effects, including chronic lung diseases and cancer. Using human bronchial epithelial cell line HBE1, we investigated the effects of structurally different PAHs on tissue homeostatic processes, namely gap junctional intercellular communication (GJIC) and MAPKs activity. Rapid (<1 h) and sustained (up to 24 h) inhibition of GJIC was induced by low/middle molecular weight (MW) PAHs, particularly by those with a bay- or bay-like region (1- and 9-methylanthracene, fluoranthene), but also by fluorene and pyrene. In contrast, linear low MW (anthracene, 2-methylanthracene) or higher MW (chrysene) PAHs did not affect GJIC. Fluoranthene, 1- and 9-methylanthracene induced strong and sustained activation of MAPK ERK1/2, whereas MAPK p38 was activated rather nonspecifically by all tested PAHs. Low/middle MW PAHs can disrupt tissue homeostasis in human airway epithelium via structure-dependent nongenotoxic mechanisms, which can contribute to their human health hazards.

• Keywords
• Gap junctional intercellular communication, Human bronchial epithelial cell line, Methylated anthracenes, Mitogen-activated protein kinases, Nongenotoxic mechanisms, Polycyclic aromatic hydrocarbons,
• MeSH
• Bronchi cytology   MeSH
• Cell Line MeSH
• Epithelial Cells drug effects   physiology   MeSH
• Humans MeSH
• Gap Junctions drug effects   MeSH
• Cell Communication drug effects   MeSH
• Mitogen-Activated Protein Kinases metabolism   MeSH
• Polycyclic Aromatic Hydrocarbons toxicity   MeSH
• Cell Survival drug effects   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Mitogen-Activated Protein Kinases MeSH
• Polycyclic Aromatic Hydrocarbons MeSH

UNLABELLED: Dysregulation of gap junctional intercellular communication (GJIC) has been associated with different pathologies, including cancer; however, molecular mechanisms regulating GJIC are not fully understood. Mitogen Activated Protein Kinase (MAPK)-dependent mechanisms of GJIC-dysregulation have been well-established, however recent discoveries have implicated phosphatidylcholine-specific phospholipase C (PC-PLC) in the regulation of GJIC. What is not known is how prevalent these two signaling mechanisms are in toxicant/toxin-induced dysregulation of GJIC, and do toxicants/toxins work through either signaling mechanisms or both, or through alternative signaling mechanisms. Different chemical toxicants were used to assess whether they dysregulate GJIC via MEK or PC-PLC, or both Mek and PC-PLC, or through other signaling pathways, using a pluripotent rat liver epithelial oval-cell line, WB-F344. Epidermal growth factor, 12-O-tetradecanoylphorbol-13-acetate, thrombin receptor activating peptide-6 and lindane regulated GJIC through a MEK1/2-dependent mechanism that was independent of PC-PLC; whereas PAHs, DDT, PCB 153, dicumylperoxide and perfluorodecanoic acid inhibited GJIC through PC-PLC independent of Mek. Dysregulation of GJIC by perfluorooctanoic acid and R59022 required both MEK1/2 and PC-PLC; while benzoylperoxide, arachidonic acid, 18β-glycyrrhetinic acid, perfluorooctane sulfonic acid, 1-monolaurin, pentachlorophenol and alachlor required neither MEK1/2 nor PC-PLC. Resveratrol prevented dysregulation of GJIC by toxicants that acted either through MEK1/2 or PC-PLC. Except for alachlor, resveratrol did not prevent dysregulation of GJIC by toxicants that worked through PC-PLC-independent and MEK1/2-independent pathways, which indicated at least two other, yet unidentified, pathways that are involved in the regulation of GJIC. IN CONCLUSION: the dysregulation of GJIC is a contributing factor to the cancer process; however the underlying mechanisms by which gap junction channels are closed by toxicants vary. Thus, accurate assessments of risk posed by toxic agents, and the role of dietary phytochemicals play in preventing or reversing the effects of these agents must take into account the specific mechanisms involved in the cancer process.

• MeSH
• Principal Component Analysis MeSH
• Cell Line MeSH
• Butadienes pharmacology   MeSH
• Phosphatidylcholines metabolism   MeSH
• Type C Phospholipases metabolism   MeSH
• Rats MeSH
• Gap Junctions drug effects   metabolism   MeSH
• Nitriles pharmacology   MeSH
• Norbornanes MeSH
• Rats, Inbred F344 MeSH
• Bridged-Ring Compounds pharmacology   MeSH
• Resveratrol MeSH
• Stilbenes pharmacology   MeSH
• Thiocarbamates MeSH
• Thiones pharmacology   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• Butadienes MeSH
• Phosphatidylcholines MeSH
• Type C Phospholipases MeSH
• Nitriles MeSH
• Norbornanes MeSH
• phosphatidylcholine-specific phospholipase C MeSH Browser
• Bridged-Ring Compounds MeSH
• Resveratrol MeSH
• Stilbenes MeSH
• Thiocarbamates MeSH
• Thiones MeSH
• tricyclodecane-9-yl-xanthogenate MeSH Browser
• U 0126 MeSH Browser

BACKGROUND: Recently, we used cell-free assays to demonstrate the toxic effects of complex mixtures of organic extracts from urban air particles (PM2.5) collected in four localities of the Czech Republic (Ostrava-Bartovice, Ostrava-Poruba, Karvina and Trebon) which differed in the extent and sources of air pollution. To obtain further insight into the biological mechanisms of action of the extractable organic matter (EOM) from ambient air particles, human embryonic lung fibroblasts (HEL12469) were treated with the same four EOMs to assess changes in the genome-wide expression profiles compared to DMSO treated controls. METHOD: For this purpose, HEL cells were incubated with subtoxic EOM concentrations of 10, 30, and 60 μg EOM/ml for 24 hours and global gene expression changes were analyzed using human whole genome microarrays (Illumina). The expression of selected genes was verified by quantitative real-time PCR. RESULTS: Dose-dependent increases in the number of significantly deregulated transcripts as well as dose-response relationships in the levels of individual transcripts were observed. The transcriptomic data did not differ substantially between the localities, suggesting that the air pollution originating mainly from various sources may have similar biological effects. This was further confirmed by the analysis of deregulated pathways and by identification of the most contributing gene modulations. The number of significantly deregulated KEGG pathways, as identified by Goeman's global test, varied, depending on the locality, between 12 to 29. The Metabolism of xenobiotics by cytochrome P450 exhibited the strongest upregulation in all 4 localities and CYP1B1 had a major contribution to the upregulation of this pathway. Other important deregulated pathways in all 4 localities were ABC transporters (involved in the translocation of exogenous and endogenous metabolites across membranes and DNA repair), the Wnt and TGF-β signaling pathways (associated particularly with tumor promotion and progression), Steroid hormone biosynthesis (involved in the endocrine-disrupting activity of chemicals), and Glycerolipid metabolism (pathways involving the lipids with a glycerol backbone including lipid signaling molecules). CONCLUSION: The microarray data suggested a prominent role of activation of aryl hydrocarbon receptor-dependent gene expression.

• MeSH
• Gene Expression drug effects   MeSH
• Fibroblasts cytology   drug effects   physiology   MeSH
• Air Pollutants chemistry   metabolism   pharmacology   MeSH
• Humans MeSH
• Microarray Analysis MeSH
• Organic Chemicals chemistry   metabolism   pharmacology   MeSH
• Oxidation-Reduction MeSH
• Particulate Matter chemistry   metabolism   pharmacology   MeSH
• Lung cytology   MeSH
• Gene Expression Profiling MeSH
• Dose-Response Relationship, Drug MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Czech Republic MeSH
• Names of Substances
• Air Pollutants MeSH
• Organic Chemicals MeSH
• Particulate Matter MeSH

Toxicity and liver tumor promotion of cyanotoxins microcystins have been extensively studied. However, recent studies document that other metabolites present in the complex cyanobacterial water blooms may also have adverse health effects. In this study we used rat liver epithelial stem-like cells (WB-F344) to examine the effects of cyanobacterial extracts on two established markers of tumor promotion, inhibition of gap-junctional intercellular communication (GJIC) and activation of mitogen-activated protein kinases (MAPKs) - ERK1/2. Extracts of cyanobacteria (laboratory cultures of Microcystis aeruginosa and Aphanizomenon flos-aquae and water blooms dominated by these species) inhibited GJIC and activated MAPKs in a dose-dependent manner (effective concentrations ranging 0.5-5mgd.w./mL). Effects were independent of the microcystin content and the strongest responses were elicited by the extracts of Aphanizomenon sp. Neither pure microcystin-LR nor cylindrospermopsin inhibited GJIC or activated MAPKs. Modulations of GJIC and MAPKs appeared to be specific to cyanobacterial extracts since extracts from green alga Chlamydomonas reinhardtii, heterotrophic bacterium Klebsiella terrigena, and isolated bacterial lipopolysaccharides had no comparable effects. Our study provides the first evidence on the existence of unknown cyanobacterial toxic metabolites that affect in vitro biomarkers of tumor promotion, i.e. inhibition of GJIC and activation of MAPKs.

• MeSH
• Enzyme Activation drug effects   MeSH
• Alkaloids MeSH
• Aphanizomenon chemistry   isolation & purification   MeSH
• Bacterial Toxins MeSH
• Cell Line MeSH
• Time Factors MeSH
• Extracellular Signal-Regulated MAP Kinases metabolism   MeSH
• Phosphorylation drug effects   MeSH
• Carcinogens chemistry   toxicity   MeSH
• Complex Mixtures chemistry   toxicity   MeSH
• Rats MeSH
• Gap Junctions drug effects   MeSH
• Cell Communication drug effects   MeSH
• Microcystis chemistry   isolation & purification   MeSH
• Microcystins analysis   toxicity   MeSH
• Mitogen-Activated Protein Kinases metabolism   MeSH
• Cyanobacteria chemistry   isolation & purification   MeSH
• Fresh Water microbiology   MeSH
• Cyanobacteria Toxins MeSH
• Uracil analogs & derivatives   toxicity   MeSH
• Dose-Response Relationship, Drug MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Comparative Study MeSH
• Geographicals
• Czech Republic MeSH
• Names of Substances
• Alkaloids MeSH
• Bacterial Toxins MeSH
• cylindrospermopsin MeSH Browser
• Extracellular Signal-Regulated MAP Kinases MeSH
• Carcinogens MeSH
• Complex Mixtures MeSH
• Microcystins MeSH
• Mitogen-Activated Protein Kinases MeSH
• Cyanobacteria Toxins MeSH
• Uracil MeSH