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C Piccoli

Publications and source records attributed to C Piccoli.

34 records · Page 2Linked to original sources
PubMed1993

Gap junctional intercellular communication of primary and asbestos-associated malignant human mesothelial cells.

We examined gap junctional intercellular communication (GJIC) of primary human mesothelial cells and cell lines of asbestos-associated human pleural mesotheliomas, and the effect of asbestos and other mineral fibres on these cells. In homologous cultures, the GJIC capacity of six out of seven tumour cell lines was markedly less than for primary mesothelial cells. This defect in GJIC appeared not to be at the expression level of mRNA and protein of the gene encoding the 43 kDa gap junction protein. In heterologous cocultures of tumour cells and primary mesothelial cells, however, 80-90% of the tumour cell/normal cell contacts were functional. Exposure of primary mesothelial cells to TPA, a phorbol ester tumour promoter, resulted in marked inhibition of GJIC, being an action common to numerous tumour promoters. Such an effect though was not observed with the carcinogenic mesothelioma-inducing mineral fibres chrysotile and amosite, neither with glass wool. These results suggest that a permanent defect in GJIC capacity is a common feature of human mesothelioma cells, but how mineral fibres are involved in the process of mesotheliomagenesis is still unclear.

Asbestos↗
PubMed1993

Lack of correlation between the gap junctional communication capacity of human colon cancer cell lines and expression of the DCC gene, a homologue of a cell adhesion molecule (N-CAM).

In many human colorectal cancers, the DCC gene encoding for a homologue of the neural cell adhesion molecule (N-CAM) is found to be deleted. Previous work suggested that gap junctional intercellular communication (GJIC) might play an important role in carcinogenesis and could be regulated by the expression of cell adhesion molecules such as E-cadherin in some epithelial cell systems. In order to examine whether the deletion of the putative cell adhesion molecule DCC is related to the level of GJIC, which might, in turn, be important in human colorectal cancers, we compared levels of expression of the DCC gene with the GJIC capacity of a panel of human colorectal adenocarcinoma cell lines isolated from different stages of tumor progression. While the level of GJIC varied between the cell lines studied, we found no correlation between their communication capacity and DCC expression revealed by a reverse-transcriptase/polymerase chain reaction method. This lack of correlation suggests that DCC is not a crucial regulator of GJIC.

Adenocarcinoma↗
PubMed1991

Regulation of connexin 43-mediated gap junctional intercellular communication by Ca2+ in mouse epidermal cells is controlled by E-cadherin.

Gap junctional intercellular communication (GJIC) of cultured mouse epidermal cells is mediated by a gap junction protein, connexin 43, and is dependent on the calcium concentration in the medium, with higher GJIC in a high-calcium (1.2 mM) medium. In several mouse epidermal cell lines, we found a good correlation between the level of GJIC and that of immunohistochemical staining of E-cadherin, a calcium-dependent cell adhesion molecule, at cell-cell contact areas. The variant cell line P3/22 showed both low GJIC and E-cadherin protein expression in low- and high-Ca2+ media. P3/22 cells showed very low E-cadherin mRNA expression. To test directly whether E-cadherin is involved in the Ca(2+)-dependent regulation of GJIC, we transfected the E-cadherin expression vector into P3/22 cells and obtained several stable clones which expressed high levels of E-cadherin mRNA. All transfectants expressed E-cadherin molecules at cell-cell contact areas in a calcium-dependent manner. GJIC was also observed in these transfectants and was calcium dependent. These results suggest that Ca(2+)-dependent regulation of GJIC in mouse epidermal cells is directly controlled by a calcium-dependent cell adhesion molecule, E-cadherin. Furthermore, several lines of evidence suggest that GJIC control by E-cadherin involves posttranslational regulation (assembly and/or function) of the gap junction protein connexin 43.

Animals↗
PubMed1990

Effects on intercellular communication in human keratinocytes and liver-derived cells of polychlorinated biphenyl congeners with differing in vivo promotion activities.

Several purified polychlorinated biphenyl (PCB) congeners with differing toxicity/tumor promotional activities in rat liver in vivo were tested for their effects on gap-junctional intercellular communication (GJIC) in cell strains and lines derived from human liver and skin. This in vitro assay is being developed to detect various classes of tumor promoters. The 3-methylcholanthrene (MCA)-type cytochrome P450 inducer and hepatotoxic promoter 3,3',4,4'-tetrachlorobiphenyl was inactive in this assay for all of the cells tested, suggesting this promoter acts by other mechanisms. The phenobarbital-like enzyme inducer and less toxic promoter 2,2',4,4',5,5'-hexachlorobiphenyl inhibited GJIC in both liver and skin cells, whereas the 2,2',5,5'-tetrachlorobiphenyl congener, which does not act as a promoter in rat liver, inhibited GJIC only in the skin cell types and in one of the liver cell strains thought to be of bile duct origin. 2,3,4,4',5-Pentachlorobiphenyl, a mixed (phenobarbital plus MCA) inducer of cytochrome P450, inhibited GJIC in both liver and skin cells, suggesting that it may be a promoter in vivo. The results suggest that GJIC inhibition is a property of PCB congeners with phenobarbital-like enzyme induction capabilities, and that there exist some tissue/cell type differences in sensitivity to these congeners.

Carcinogens↗
PubMed1989

Gap-junctional intercellular communication in epidermal cell lines from selected stages of SENCAR mouse skin carcinogenesis.

Homologous and heterologous gap-junctional intercellular communication (IC) was characterized in a panel of cell lines derived from selected stages of SENCAR mouse skin carcinogenesis. This panel included a "carcinogen-altered" cell line, 3PC, obtained from Ca2+-resistant primary adult keratinocytes after exposure to dimethylbenz(a)anthracene as well as cell lines obtained from early and late-stage papillomas and a squamous cell carcinoma (CA3/7) generated during standard in vivo initiation/promotion protocols (dimethylbenz(a)anthracene/12-O-tetradecanoyl-phorbol-13-acetate). Also studied was a cell line (B66BA) obtained from a metastatic lesion following benzo(a)pyrene-induced skin tumorigenesis. Intercellular communication was measured in low-calcium (0.05 mM) medium by quantitation of cell-cell transfer of microinjected fluorescent dye Lucifer Yellow CH. Homologous IC ability diminished progressively from 68 dye-coupled cells per injection for 3PC cultures, to between 21 and 54 dye-coupled cells per injection for three papilloma-derived cell lines, to six and three dye-coupled cells per injection for CA3/7 and B66BA cells, respectively. To test communication of these cells with their normal counterparts, heterologous IC was examined in cocultures with primary adult keratinocytes. Under the conditions used, normal cells established functional communication channels with each cell line tested, showing no selectivity. These results suggest that progressive loss of homologous but not heterologous IC capacity accompanies neoplastic development in mouse skin carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Detection of non-genotoxic carcinogens in the BALB/c 3T3 cell transformation/mutation assay system.

We have employed BALB/c 3T3 cells in a simultaneous cell transformation and mutation assay protocol to see whether both genotoxic and non-genotoxic carcinogens can be identified. Three known mutagenic animal carcinogens tested positive for transforming activity: dimethylnitrosamine, methylcholanthrene and methylnitrosourea. In addition, we tested three non-mutagenic compounds--two human carcinogens, benzene and diethylstilbestrol, and the possible human carcinogen dichlorodiphenyltrichloroethane; all three displayed transforming activity. These results add to existing data supporting the validity of the BALB/c 3T3 cell transformation system as a reliable short-term in vitro test for carcinogens in general, and for non-genotoxic carcinogens in particular.

Animals↗
PubMed1987

Mutagenicity, sister chromatid exchange inducibility and in vitro cell transforming ability of particulates from Athens air.

Airborne particulates were collected over a period of twelve months by the use of Hi-Vol samplers in the basin of Athens, Greece. N-Hexane extracts were tested in a battery of in vitro tests for their ability to induce mutation in bacteria as well as mutation, sister chromatid exchange and morphological transformation in cultured mammalian cells. Positive results were found for mutagenicity with Salmonella strain TA98 in the Ames assay, for sister chromatid exchange induction in CHO cells and for transformation in BALB/c 3T3 cells in culture. They also showed weak non-dose-related induction of ouabain resistance in BALB/c 3T3 cells. The contribution of oxidizing and nitrating agents found in the Athens atmosphere, together with sunlight UV irradiation in the formation of direct acting mutagens and potential carcinogens from ambient polycyclic aromatic hydrocarbons, is suggested.

Air Pollutants↗
PubMed1987

Cell contact but not junctional communication (dye coupling) with biliary epithelial cells is required for hepatocytes to maintain differentiated functions.

Specific differentiated gene expression and the morphology of adult rat hepatocytes can be maintained for as long as 8 weeks in vitro only when they are cultured in the presence of biliary epithelial cells; when primary hepatocytes are cultured alone, they lose these functions within 2 to 3 days. We obtained evidence suggesting that contact between hepatocytes and biliary epithelial cells is necessary for maintaining hepatocyte functions. We examined whether junctional communication between and among hepatocytes and biliary epithelial cells is required for long-term maintenance of hepatocyte functions, using a dye-transfer method, in three co-cultures: (1) hepatocytes and biliary epithelial cells prepared from Sprague-Dawley rats; (2) hepatocytes from Sprague-Dawley rats and epithelial cells of the IAR 20 line, originally established from BDVI rats; and (3) hepatocytes from BDVI rats and IAR 20 epithelial cells. The established epithelial cell line (IAR 20) and early-passage cultures of biliary epithelial cells maintained hepatocyte-specific functions in culture for 40 and 70 days, respectively, but the latter induced more stable maintenance of albumin secretion. Hepatocytes cultured alone lost their characteristic morphology within 5 to 8 days, and almost no dye transfer was observed. In co-cultures, the capacity of biliary epithelial cells to communicate among themselves remained relatively high throughout the culture period, whereas hepatocytes showed almost no junctional communication at an early phase of culture and first began to communicate after 2 weeks, communication capacity increasing for at least the next 10 days of culture. The most notable finding was that there was no dye transfer between hepatocytes and biliary epithelial cells in any co-culture system. These results suggest that the maintenance of hepatocyte-specific functions requires intercellular contact but probably not gap-junctional communication between hepatocytes and biliary epithelial cells. This system is useful for studying heterotypic cell-cell interactions and the control of gene expression.

Albumins↗
PubMed1982

Benzo[a]pyrene metabolites: formation in rat liver cell-culture lines, binding to macromolecules, and mutagenesis in V79 hamster cells.

Benzo(a]pyrene was metabolized in liver cell lines derived from BC-IV and BD-IV rats which included several chemically-transformed lines (IAR-6-1; IAR-19; IAR-28), one spontaneous transformant (IAR-27) as well as one non-malignant line (IAR-20). Cultures were treated with tritiated benzo[a]pyrene over a 5-day period. The cells and medium were extracted with ethyl acetate and the distribution between organic-soluble and water-soluble metabolites determined. Organic-soluble metabolites consisting of dihydrodiols, phenols and quinones were determined by high-pressure liquid chromatography, and macromolecular binding of BP to each cell line was measured over a 24-h period. Comparisons between binding and overall metabolism were not directly proportional in these liver cell lines. However, there was a positive correlation for benzo[a]pyrene mutagenesis in the V-79 hamster cell assay with 8-azaguanine as a marker when the cell lines with the highest (IAR-20) and lowest (IAR-27) metabolic competence were used as activating cell layers.

Animals↗
PubMed1981

Mutagenicity assays of estrogenic hormones in mammalian cells.

In view of the extensive use of estrogenic hormones by the human population, either as therapeutic agents, or in the composition of contraceptive pills, it is important to investigate more thoroughly the adverse biological effects of synthetic hormones. Diethylstilbestrol, ethynylestradiol, estradiol-17beta and estrone were chosen for our experiments. Evidence of carcinogenicity in rodents has been reported for each of these compounds, but so far only few studies have been carried out in vitro. Because it has been shown that isolated liver cells in suspension are able efficiently to metabolize steroid hormones, we have tested these chemicals in V79 cells with a cell-mediated system using primary hepatocytes from male and female rats as the metabolic layer. The incubation in the presence of the chemical to be tested was carried out at concentrations ranging from 25 to 100 microM, for 48 h before plating the V79 cells to score for mutagenicity or toxicity. In the absence of hepatocytes, the 4 estrogenic hormones were very toxic, but not mutagenic. The co-cultivation of V79 cells with primary hepatocytes decreased the toxic effect induced by the sex hormones, except in the case of ethynylestradiol. However, no mutation, determined as 8-azaguanine- or ouabain-resistance, was induced under these conditions by any of the hormones tested. The lack of mutagenic activity of these hormones in our assay had been confirmed by the use of primary liver cells that originated from a rat treated with Aroclor, an inducer of drug-metabolizing enzymes.

Animals↗
PubMed1979

Critical importance of microsome concentration in mutagenesis assay with V79 Chinese hamster cells.

For optimum mutagensis in V79 Chinese hamster cells, the amount of liver postmitochondrial fraction in the assay was found to be of critical importance, depending on the chemicals being tested. Benzo[a]pyrene (BP) required lower (1-5%) concentrations of the liver 15 000 X g supernatant (S15) from methylcholanthrene pretreated rats for a maximum induction of cytotoxicity and mutagenicity, as determined by 8-azaguanine- and ouabain-resistance. A sharp peak of mutagenicity and cytotoxicity was induced by 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (7,8-diol BP) at a concentration of 1% of the S15 fraction. Little or no response was induced by these compounds with the S15 concentrations of more than 10%. Similarly, aflatoxin B1 induced a sharp peak of mutagenicity and cytotoxicity at a concentration of 2% of the liver S15 fraction from Aroclor-pretreated rats. Under the same condition, non-carcinogenic aflatoxin G2 did not induce cytotoxicity and mutagenicity. Analysis of BP metabolites by high-pressure liquid chromatography indicates that with the 30% S15 fraction, more than 80% of BP was metabolized during the first 15 min, while with the 2% S15 fraction, 7,8-diol BP increased continuously throughout the 120-min incubation period, suggesting a strong metabolic competition to rapidly remove BP and 7,8-diol BP with a high concentration of the S15. In contrast with these compounds, N-nitrosodimethylamine induced mutagenicity and cytotoxicity which increased linearly in proportion to the increasing amount of the S15 fraction from phenobarbitone- and Aroclor-pretreated rats. Various nitrosamines with different lipophilicity were examined at a high (30%) and low (2%) concentration of the S15 fraction from Aroclor-pretreated rats, in which ratios of mutation frequencies at 30% and 2% correlated inversely with lipophilicity of the compound. This result suggests that the lipid solubility of test compounds may be one factor which determines the concentration of post-mitochondrial supernatant for optimum mutagenesis.

Aflatoxins↗
PubMedDate not supplied

Regulation by the cAMP cascade of oxygen free radical balance in mammalian cells.

A study is presented of the effect of the cAMP cascade on oxygen metabolism in mammalian cell cultures. Serum-starvation of the cell cultures resulted in depression of the forward NADH-ubiquinone oxidoreductase activity of complex I, decreased content of glutathione, and enhancement of the cellular level of H2O2. Depressed transcription of cytosolic Cu/Zn-SOD 1, mitochondrial glutathione peroxidase and catalase was also observed. Activation of the cAMP cascade reversed the depression of the activity of complex I and the accumulation of H2O2. The effect of cAMP involved the cAMP-dependent protein kinase.

Animals↗