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

Humans are exposed to phthalates released from plastics, cosmetics, or food on a daily basis. Phthalates have low acute liver toxicity, but their chronic exposures could induce molecular and cellular effects linked to adverse health outcomes, such as liver tumor promotion or chronic liver diseases. The alternation of gap junctional intercellular communication (GJIC) and MAPK-Erk1/2 pathways in liver progenitor or oval cells can disrupt liver tissue homeostatic mechanisms and affect the development and severity of these adverse outcomes. Our study with 20 different phthalates revealed their structurally dependent effects on liver GJIC and MAPK-Erk1/2 signaling in rat liver WB-F344 cell line with characteristics of liver oval cells. The phthalates with a medium-length side chain (3-6 C) were the most potent dysregulators of GJIC and activators of MAPK-Erk1/2. The effects occurred rapidly, suggesting the activation of non-genomic (non-transcriptional) mechanisms directly by the parental compounds. Short-chain phthalates (1-2 C) did not dysregulate GJIC even after longer exposures and did not activate MAPK-Erk1/2. Longer chain (≥7 C) phthalates, such as DEHP or DINP, moderately activated MAPK-Erk1/2, but inhibited GJIC only after prolonged exposures (>12 h), suggesting that GJIC dysregulation occurs via genomic mechanisms, or (bio)transformation. Overall, medium-chain phthalates rapidly affected the key tissue homeostatic mechanisms in the liver oval cell population via non-genomic pathways, which might contribute to the development of chronic liver toxicity and diseases.

• Keywords
• MAP-kinases Erk1/2 activation, gap junctional intercellular communication, gap junctions, hepatotoxicity, non-genomic mechanism, oval cells, phthalates, progenitor cells,
• MeSH
• Cell Line MeSH
• Liver cytology   drug effects   metabolism   MeSH
• Rats MeSH
• Phthalic Acids administration & dosage   chemistry   toxicity   MeSH
• MAP Kinase Signaling System drug effects   MeSH
• Gap Junctions drug effects   MeSH
• Cell Communication drug effects   MeSH
• Cell Survival drug effects   MeSH
• Dose-Response Relationship, Drug MeSH
• Structure-Activity Relationship MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Phthalic Acids MeSH

Changes in ecological and environmental factors lead to an increased occurrence of cyanobacterial water blooms, while secondary metabolites-producing cyanobacteria pose a threat to both environmental and human health. Apart from oral and dermal exposure, humans may be exposed via inhalation and/or swallowing of contaminated water and aerosols. Although many studies deal with liver toxicity, less information about the effects in the respiratory system is available. We investigated the effects of a prevalent cyanotoxin, microcystin-LR (MC-LR), using respiratory system-relevant human bronchial epithelial (HBE) cells. The expression of specific organic-anion-transporting polypeptides was evaluated, and the western blot analysis revealed the formation and accumulation of MC-LR protein adducts in exposed cells. However, MC-LR up to 20 μM neither caused significant cytotoxic effects according to multiple viability endpoints after 48-h exposure, nor reduced impedance (cell layer integrity) over 96 h. Time-dependent increase of putative MC-LR adducts with protein phosphatases was not associated with activation of mitogen-activated protein kinases ERK1/2 and p38 during 48-h exposure in HBE cells. Future studies addressing human health risks associated with inhalation of toxic cyanobacteria and cyanotoxins should focus on complex environmental samples of cyanobacterial blooms and alterations of additional non-cytotoxic endpoints while adopting more advanced in vitro models.

• Keywords
• 16HBE14o-, mitogen-activated protein kinase, HBE1, OATP, cytotoxicity, human bronchial epithelial cells, in vitro, microcystin-LR,
• MeSH
• Bronchi cytology   MeSH
• Cell Line MeSH
• Epithelial Cells drug effects   metabolism   MeSH
• Extracellular Signal-Regulated MAP Kinases metabolism   MeSH
• Humans MeSH
• Microcystins toxicity   MeSH
• p38 Mitogen-Activated Protein Kinases metabolism   MeSH
• Marine Toxins toxicity   MeSH
• Organic Anion Transporters genetics   MeSH
• Signal Transduction drug effects   MeSH
• Cell Survival drug effects   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• cyanoginosin LR MeSH Browser
• Extracellular Signal-Regulated MAP Kinases MeSH
• Microcystins MeSH
• p38 Mitogen-Activated Protein Kinases MeSH
• Marine Toxins MeSH
• Organic Anion Transporters MeSH