Chinese Hamster Epithelial Liver Research Articles

Identification of Genotoxic Compounds in the Airborne Particulate Matter Endowed by Small Aerodynamic Diameter in the City of Catania (Italy)

Airborne particulate matter (PM) is one of the most important polluting factors in the atmosphere containing solid particles generated during the combustion processes. PM, due to the particle size, is easily inhaled and constitutes a potential hazard for the human health. We previously documented, using in vitro cell culture systems, cytogenetic damages caused by exposure to a non-fractionated PM in two different areas from the city of Catania (Sicily, Italy). In the present work, the PM was fractionated in six different sub-fractions, and the relative extractable organic matters (EOM) were analyzed in order to quantify the presence of Polycyclic Aromatic Hydrocarbons (PHAs), a well known class of genotoxic agents. More than 70% of the total EOM was found in the PM with aerodynamic diameters less than 3.5 microm (PM35), and about 60% of the total EOM was detected between PM0.14 and PM1.2. Also the large amount of all the analyzed PAHs were found between the PM0.14 and PM1.2. The obtained data indicates that the genotoxic effect previously shown on mammalian cells (Chinese hamster epithelial liver cells) should be due, in the large part, to the PM with smaller particle size, namely less than PM1.2.

Cytogenetic evaluation of extractable agents from airborne particulate matter generated in the city of Catania (Italy)

In order to document cytogenetic damage associated with air pollution and, possibly, with health effects in the city of Catania, Sicily (Italy), we analyzed the induction of chromosomal aberrations by extractable agents from airborne particulate matter in a Chinese hamster epithelial liver (CHEL) cells. These cells retain their metabolic competence to activate different classes of promutagens/procarcinogens into biologically active metabolites. Airborne particulate matter was obtained from two stationary samplers (stations I and II) in two areas endowed by an elevated car transit in the centre of Catania. The results obtained clearly indicated that airborne particulate matter from both stations I and II proved to be clastogens in CHEL cells but not in Chinese hamster ovary (CHO) cells without metabolic activation, indicating that airborne particulate mixtures need to be metabolically converted before exerting their genotoxic potential. On the basis of these results we can assert that the test system employed to identify the cytogenetic potential of airborne particulate matter is useful and profitable for environmental control, and helpful to plan specific actions aimed at reducing the hazards derived from exposure to polluted air.

Low molecular weight polyethylene glycol induces chromosome aberrations in Chinese hamster cells cultured in vitro.

The human population is widely exposed to polyethylene glycol (PEG) and its chemical derivatives, which are widely used as vehicles or co-solvents in many pharmaceutical and cosmetic preparations. However, PEG polymers of low molecular weight differ significantly from polymers of higher molecular weight in their physico-chemical properties, biological effects on cell permeability and their absorption and excretion, as well as their higher toxicity and possibly genotoxicity. In the present study we have analysed the induction of chromosome aberrations by the low molecular weight PEG polymers tetraethylene glycol (TEG), PEG 200 and PEG 400 in a Chinese hamster epithelial liver (CHEL) cell line, which retains sufficient metabolic capability to activate different promutagens and procarcinogens. The results indicate that in CHEL cells only TEG and PEG 200 are clastogenic. Parallel experiments performed in CHO cells in the presence and absence of rat liver S9 mix showed significant increases in chromosomal aberrations only in cultures treated with TEG in the presence of rat liver S9, indicating that low molecular weight polymers need to be activated to exert their genotoxic activity.

Evaluation of Genotoxic and Cytotoxic Properties of Pesticides Employed in Italian Agricultural Practices

In a program coordinated by the Italian Ministry of Works, we tested in vitro four pesticides widely employed in a developed agricultural region of central Italy. The four commercial agents were chosen on the basis of their diffusion in agricultural practice, knowledge of their active principle(s), and scant availability of data concerning their toxic and genotoxic activity. The agents were Cirtoxin, Decis, Tramat Combi (TC), and Lasso Micromix (LM). All substances were tested in three in vitro systems: Chinese hamster ovary (CHO) cells, a metabolically competent hamster cell line (Chinese hamster epithelial liver; CHEL), and root tips of Vicia faba (VF). The cytotoxic and genotoxic end points challenged were micronuclei and root tip length (RTL) in VF and mitotic index (MI), proliferation index (PI), cell survival (CS), cell growth (CG), cell cycle length (CCL), sister chromatid exchanges, chromosomal aberrations, and single-cell gel electrophoresis, or comet assay, in CHEL and CHO cells. Tested doses ranged from the field dose up to 200× the field dose to take into account accumulation effects. On the whole, tested agents appear to induce genotoxic damage only at subtoxic or toxic doses, indicating a low clastogenic risk. MI, PI, CS, CG, RTL, and CCL appear to be the less sensitive end points, showing no effects in the presence of a clear positive response in some or all of the other tests. Using cytogenetic tests, we obtained positive results for TC and LM treatments in CHO but not in CHEL cells. These data could be accounted for by postulating a detoxifying activity exerted by this cell line. However, cytogenetic end points appear to be more sensitive than those referring to cytotoxicity.

Structure-activity relationship in the induction of chromosomal aberrations and spindle disturbances in Chinese hamster epithelial liver cells by regioisomeric phenanthrene quinones.

Four regioisomeric phenanthrene (PH) quinones (Q) were investigated for their ability to induce chromosomal damage and spindle disturbances. PH 1,4-Q and PH 1,2-Q induced structural as well as numerical chromosomal aberrations, whereas the isomers PH 9,10-Q and PH 3,4-Q were virtually inactive in this respect, However, all four compounds enhanced the frequency of c-mitoses.

DT-Diaphorase Affects the Mutagenic Activity of Pyrene 1,6-Quinone in Chinese Hamster Epithelial Liver (CHEL) Cells

The mutagenic potential of pyrene 1,6-quinone (P 1,6-Q) has been studied in a wide range of in vitro genetic assays including the use of mammalian cell lines. P 1,6-Q has been shown to induce gene mutations and micronuclei in V79 cells, whereas, in Chinese hamster epithelial liver (CHEL) cells, a cell line which retains activities of various xenobiotic-metabolising enzymes, a non-specific pattern of structural and numerical chromosomal aberrations has been observed. In this study, we have evaluated the mutagenic activity of P 1,6-Q on V79 and CHEL cells both with and without dicoumarol, a potent inhibitor of DT-diaphorase. In V79 cells, dicoumarol (100μM) did not affect the mutagenic response, whereas in CHEL cells, the mutation frequency significantly increased. This suggests that DT-diaphorase, which is expressed in liver cells at high levels, has a possible role in the detoxification of P 1,6-Q to redox-stable hydroquinone.

Induction of chromosomal aberrations and spindle disturbances in Chinese hamster epithelial liver cells in culture by pyrene and benzo[a]pyrene quinones.

Regioisomers of pyrene and benzo[a]pyrene quinones were tested for their ability to induce structural and numerical aberrations and spindle disturbance in Chinese hamster epithelial liver (CHEL) cells in culture. All quinones tested were clastogenic. Pyrene-1,8-quinone (P-1,8-Q) and benzo[a]pyrene-3,6-quinone (BP-3,6-Q) induced strikingly high levels of triradials. In addition, dicentrics and ring chromosomes were very common in BP-3,6-Q-treated cultures. Isomers of these compounds, pyrene-1,6-quinone (P-1,6-Q) and benzo[a]pyrene-1,6-quinone (BP-1,6-Q), induced unobtrusive patterns of chromosomal aberrations. We suspect that the P-1,8-Q and BP-3,6-Q moieties bound to the DNA were still reactive, and formed crosslinks and/or underwent redox cycling leading to high local concentrations of reactive oxygen species. In addition, P-1,8-Q and BP-3,6-Q induced c-mitoses, hyperdiploidies and polyploidies, in particular endoreduplications. These effects were not seen with the other two test compounds, or they were only detected at the highest concentrations used, which were strongly cytotoxic (c-mitoses with P-1,6-Q, polyploidies with BP-1,6-Q).

Clastogenic effects of the dithiocarbamate fungicides thiram and ziram in Chinese hamster cell lines cultured in vitro

We report here the results obtained using the dithiocarbamate fungicides thiram and ziram to investigate the induction of chromosomal aberrations (CAs) in Chinese hamster ovary (CHO) cells both in the absence and presence of S9 metabolism, and in a Chinese hamster epithelial liver (CHEL) cells which retain metabolic competence to activate different classes of promutagens/procarcinogens. Both thiram and ziram proved to be strong chromosome breaking agents in the CHEL cells and CHO cells in the presence of S9 metabolism. These findings suggest that thiram and ziram require metabolic conversion to become genetically active, and corroborate the evidence that CHEL cells are suitable to activate and detect a broad spectrum of chemical procarcinogens including these two pesticides.

Application of an epithelial liver cell line, metabolically competent, for mutation studies of promutagens

Recently numerous attempts have been made to reduce the use of vertebrate animals in laboratory experiments to evaluate general and acute toxicity, mutagenesis and teratogenesis of new drugs or chemicals. One common approach is to use established, proliferating cell lines that preserve differentiated functions such as the competence to metabolize xenobiotics, To this end a continuous Chinese hamster epithelial liver cell line (CHEL cells) was established, cultured as used for mutagenesis studies. Structurally different promutagens, such as 7,12-dimethylbenz[ a]anthracene (7,12-DMBA), benzo[ a]-pyrene (B(a)P), aflatoxin B 1 (AB 1) and cyclophosphamide (CP), were used in order to check and validate the test system. anti-Chrysene-1,2-diol 3,4-epoxide (CDE) and mitomycin C (MMC) were taken as representatives of direct mutagens. The genetic change induced by the mutagens was quantified by measuring mutation frequencies at the HGPRT locus. Several parameters, such as mutant expression time for each chemical, cell density for selection of mutants and enzymatic characterization for HGPRT phenotype, were examined to establish the optimal assay conditions. All promutagens analyzed significantly affected either the cloning efficiency and/or the mutant frequency of CHEL cells after 24 h of exposure. In addition, various enzyme activities involved in the metabolism of the promutagens were determined in CHEL cells, under the experimental conditions of chemical exposure used in the mutagenesis assay. The enzyme were compared with those found in uninduced Chinese hamster liver.

High sensitivity of Chinese hamster epithelial liver cells to toxic analogues of purines

The resistance of Chinese hamster epithelial liver cells (CHEL) and Chinese hamster fibroblasts (V79) towards toxic purine analogues has been determined. The liver cells are more sensitive than fibroblasts to 6-thioguanine (6-TG), 8-azaguanine (8-AZ) and 2,6-diaminopurine (DAP). The hypoxanthine-guanine (HGPRT) and adenine phosphoribosyl transferase (APRT) activities of extracts of CHEL cells were lower than those of corresponding extracts of V79. The level of 5′-nucleotidase was about 5-fold higher in the epithelial cells. It appears that HGPRT and APRT activities of extracts of liver epithelial cells are masked or reduced by 5′-nucleotidase activity and other inhibitors. The significance of these findings is discussed.

Induction of sister-chromatid exchanges by procarcinogens in metabolically competent Chinese hamster epithelial liver cells

An epithelial cell strain has been established from the livers of male Chinese hamsters (CHEL cells). These cells, which proliferate in culture and retain their metabolic enzymatic activities during several subcultures, were used in a sister-chromatid exchange assay to evaluate the effectiveness of polycyclic aromatic hydrocarbons (PAHs), aflatoxin B 1 (AFB 1) and cyclophosphamide (CP). The results obtained demonstrate that CHEL cells are metabolically competent to activate different classes of procarcinogens into biologically active metabolites. Moreover, they showed a selective capacity to discriminate chemical carcinogens from noncarcinogens. Thus, the CHEL cell system appears to be a promising alternative to the short-term tests that include cell-free rodent liver homogenate to evaluate new promutagens and/or procarcinogens.

The uniqueness of habrobracon in experiments with chemical mutagens : Smith, Roger H., Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tenn. (U.S.A.)

The resistance of Chinese hamster epithelial liver cells (CHEL) and Chinese hamster fibroblasts (V79) towards toxic purine analogues has been determined. The liver cells are more sensitive than fibroblasts to 6-thioguanine (6-TG), 8-azaguanine (8-AZ) and 2,6-diaminopurine (DAP). The hypoxanthine-guanine (HGPRT) and adenine phosphoribosyl transferase (APRT) activities of extracts of CHEL cells were lower than those of corresponding extracts of V79. The level of 5′-nucleotidase was about 5-fold higher in the epithelial cells. It appears that HGPRT and APRT activities of extracts of liver epithelial cells are masked or reduced by 5′-nucleotidase activity and other inhibitors. The significance of these findings is discussed.