Biochemical screening of highly toxic aromatic contaminants in river sediment and comparison of sensitivity of biological model systems

Development and characterization of cell line from the gill tissue of Catla catla (Hamilton, 1822) for toxicological studies

Catla gill cell line (ICG) was established from gill tissue of Indian major carp (Catla catla), a freshwater fish cultivated in India. The cell line was maintained in Leibovitz's L-15 supplemented with 10% fetal bovine serum. These cells have been sub-cultured more than 55 passages over a period of 2 years. The ICG cell line consists predominantly of epithelial-like cells. The cells were able to grow at a wide range of temperatures from 24°C to 32°C with an optimum temperature of 28°C. The growth rate of gill cells increased as the fetal bovine serum (FBS) proportion increased from 2% to 20% at 28°C with optimum growth at the concentrations of 10% or 15% FBS. Amplification of mitochondrial gene 12s rRNA using primers specific to C. catla confirmed the origin of this cell line from C. catla. The cells were successfully cryopreserved and revived at passage numbers 25, 35, 45 and 55. The cytotoxicity of three metal salts (ZnCl(2), CuSO(4) and CdCl(2)) was assessed in ICG cell line using multiple endpoints such as MTT, Neutral Red assay, Alamar Blue assay and Coomassie Blue protein assay. Acute toxicity assay on fish were conducted by exposing C. catla for 96 h to three metal salts under static conditions. Statistical analysis revealed good correlation with r(2)=0.908-0.985 for all combinations between endpoints employed. Linear correlations between each in vitro EC(50) and the in vivo LC(50) data were highly significant.

Comparison of in vitro and in vivo acute toxicity assays in Etroplus suratensis (Bloch, 1790) and its three cell lines in relation to tannery effluent

Cell lines of Etroplus suratensis established in our laboratory were evaluated for their potential use as screening tools for the ecotoxicological assessment of tannery effluent. The cytotoxic effect of tannery effluent in three cell lines derived from eye, kidney and gill tissue of E. suratensis was assessed using multiple endpoints such as Neutral Red (NR) assay, Coomassie Blue (CB) protein assay and Alamar Blue (AB) assay. Acute toxicity tests on fish were conducted by exposing E. suratensis for 96 h to tannery effluent under static conditions. The toxic effect of tannery effluent on the survival of fish was found to be concentration and time dependent. The tannery effluent at the concentration of 15% caused 100% mortality at 96 h whereas the lower concentration (0.5%) caused 13.33% mortality. The cytotoxicity of tannery effluent was found to be similar in the three cell lines tested, independent of the toxic endpoints employed. EC(50) values, the effective concentration of tannery effluent resulting in 50% inhibition of cytotoxicity parameters after 48 h exposure to tannery effluent were calculated for eye, kidney and gill cell lines using NR uptake, AB and cell protein assays. Statistical analysis revealed good correlation with r(2)=0.95-0.99 for all combinations between endpoints employed. Linear correlations between each in vitro EC(50) and the in vivo LC(50) data, were highly significant p<0.001 with r(2)=0.977, 0.968 and 0.906 for AB(50), NR(50), and CB(50), respectively.

Comparative evaluation of the cytotoxicity sensitivity of six fish cell lines to four heavy metals in vitro

To establish the potential use of cell cultures as a simple and sensitive biological tool to detect environmental pollutants, six cell lines established from several fish species including GCF (grass carp fins), CIK (Ctenopharyngodon idellus kidney), EPC (epithelioma papulosum cyprini), CCO (channel catfish ovary), BB (brown bullhead caudal trunk) and FHM (fathead minnow muscle) were tested and compared for their cytotoxic sensitivity to four heavy metals: cadmium (Cd), chromium (Cr), zinc (Zn), and copper (Cu). Following a 24-h exposure to these metal salts at selected concentrations, test cells were characterized by morphology, viability and proliferation. Our results indicate that all these metal salts are cytotoxic to these fish cell lines, but at varied levels. Calculated inhibitory concentration (IC(50)) values revealed that the cytotoxicity of Cr and Cd was significantly more pronounced than that of the other two metal salts. Comparative analysis of these fish cell lines showed that C. idellus kidney (CIK) cells are the most sensitive cell line to copper, epithelioma papulosum cyprini (EPC) cells are more sensitive than other cells to Cr and Zn, while channel catfish ovary (CCO) cell line is the most sensitive one to Cd. In conclusion, CIK, EPC and CCO could potentially be sensitive bio-indicators for the initial monitoring and assessment of acute cytotoxicity of heavy metals in the aquatic environment.

Assessing the potential of fish cell lines as tools for the cytotoxicity testing of estuarine sediment aqueous elutriates

In the present study, we assess the potential of fish cell lines (CHSE, EPC and RTG-2) to be used as screening tools for the ecotoxicological assessment of estuarine sediments. The processing of sediment to a form suitable for in vitro exposure is an inherent problem when using cell cultures. The approach employed in this study was to prepare aqueous elutriate extracts from whole sediments, which were subsequently used to reconstitute powdered media. This procedure allowed the exposure of cell cultures to concentrations of up to and including 100% of the original aqueous sample. Cytotoxicity was assessed using multiple endpoint measurements. Cell viability was quantified using the neutral red and alamar blue colorimetric assays, which specifically assess lysosomal and mitochondrial function, respectively. In addition, the total protein content of the cells was measured using the coomassie blue assay. Initial tests were conducted to ensure that any resultant cytotoxicity was due to sample contaminants and not osmotic stress. In addition, elutriate samples were spiked with a model toxicant to verify the ability of the cell lines to detect and respond to bioavailable contaminants. Chemical analyses were conducted on sediments from all sampling sites to assist in interpreting any observed cytotoxicity. A differential response was observed for the cytotoxicity assays following exposure treatments, which emphasises the importance of employing multiple endpoints for the determination of toxicity. Of the three cell lines utilised in this study, RTG-2 cells were the most suitable for the testing of estuarine aqueous elutriate samples on the basis of tolerance to osmolality effects. Slight toxicity was observed following exposure to the aqueous elutriates tested in this study using RTG-2 cells and the alamar blue assay. In order to fully evaluate the overall sensitivity of this cell line, further research is warranted using an extensive range of test sites incorporating more polluted sediments.

In vitro cytotoxicity testing of three zinc metal salts using established fish cell lines

The utilisation of fish cell lines has proven to be a valuable, rapid and cost-effective tool in the ecotoxicological assessment of chemicals and environmental samples. The main objective of this study was to investigate the value of multiple endpoint measurements in evaluating the cytotoxicity of three divalent zinc salts in three established fish cell lines (EPC, CHSE and RTG-2) and the potential for their employment as effective screening tools for zinc contaminated environmental samples. A significant stimulatory effect was detected with the neutral red assay in EPC and RTG-2 cells exposed to the lower doses of some zinc compounds. Significant (p < or = 0.01) lactate dehydrogenase release was detectable only with the highest exposure concentration of ZnCl2. Toxicity ranking based on IC50 values calculated from the neutral red and coomassie blue assay data found that in general, ZnC2 was the most cytotoxic metal compound to the cell lines employed. Differential cell sensitivities were observed to be dependant on the particular compound tested and the endpoint employed. It was found that the use of light microscopy in the identification of cell morphological changes was a valuable adjunct in verifying the results of colorimetric tests. In conclusion, careful consideration should be given to study design and statistics applied and use of a battery style approach is recommended for toxicological screening studies.

Combinatorial bio/chemical analysis of dioxin and dioxin-like compounds in waste recycling, feed/food, humans/wildlife and the environment

The present review describes international activities using bioassays/biomarkers in combination with chemical analysis to measure the effects of dioxin and dioxin-like compounds (DLCs) in the environment. The above authors reviewed already the state-of-art bioanalytical detection methods (BDMs) for dioxins and DLCs [Environ Int (2001)]. The aim of this study will be to review applications of these bioassays/biomarkers to evaluate potential dioxins and DLCs. The present literature study lists relative potencies (REPs) of polyhalogenated dibenzo-p-dioxins and -furans (PXDD/Fs; X = Cl, Br, F), their thio analogues polychlorinated dibenzothiophenes (PCDTs) and thianthrens (PCTAs), polyhalogenated biphenyls (PXBs), polychlorinated naphthalenes (PCNs) and other Ah receptor agonists measured by several biodetectors (Tier 3 screening). The authors will discuss some examples of the applications of some of these biodetectors in biomonitoring programmes and recently occurred dioxin crisis in feed/food. The diagnosis of the biopotency of these pollutants in technical processes like thermally treated waste, waste water treatment, landfill leachate treatment, commercial PCB-mixtures, the release into the environment (soil, air and water) and the final intake into wildlife and humans will be reviewed.

Multi-bioassay approach for assessing the potency of complex mixtures of polycyclic aromatic hydrocarbons

The chick embryotoxicity screening test (CHEST) and the Salmonella/microsome bioassay were used to evaluate embryotoxic and mutagenic endpoints from crude coal tar (CT) and its fractionated polycyclic aromatic hydrocarbon (PAH) mixtures (designated as A, B, C, D and E). In the CHEST assay, CT and PAH mixtures were injected into the egg yolk. A dose-dependent increase in embryo mortality was observed for all fractions. The E fraction resulted in 47% embryo mortality at a dose of 0.125 mg/kg and was more toxic than CT. At a dose of 1 mg/kg, 85-100% embryonic deaths occurred in fractions C and D and these two fractions were more potent than fractions A and B. The main visual toxic manifestations were liver lesions, discoloration of the liver, and edema. Both CT and fractionated PAH mixtures were also tested in the Salmonella/microsome plate incorporation assay with Salmonella typhimurium strain TA98 and were evaluated with and without metabolic activation at five dose levels. In the presence of S9, the CT and fractions C, D and E induced a dose-dependent positive response. Results from the Salmonella/microsome assay were in good agreement with findings from the CHEST assay suggesting that these two bioassays in combination may facilitate the rapid detection and ranking of complex PAH mixtures.

A fish hepatoma cell line (PLHC-1) as a tool to study cytotoxicity and CYP1A induction properties of cellulose and wood chip extracts

Cytotoxicity and CYP1A induction properties of celluloses and wood chips were studied with a teleost liver cell line, PLHC-1. Cells were exposed to acetone extracts of celluloses produced using new bleaching techniques (elemental chlorine free, ECF; totally chlorine free, TCF) in two sulphate mills or without any bleaching (unbleached, UB) in a sulphite mill. In another set of exposures, celluloses (ECF and TCF bleached) and wood chips (from pine and birch) were collected from a sulphate mill, extracted with acetone, and the extracts used to treat the cells. After exposure, O-deethylation of 7-ethoxyresorufin (EROD, a measure of cytochrome P4501A (CYP1A) catalytic activity), and total protein content, a measure of cytotoxicity, were assayed. The presence of the CYP1A protein in the exposed cells was assessed by immunoblotting. The cellulose and wood chip extracts were able to cause both cytotoxicity and EROD induction in the PLHC-1 cells. In the exposures conducted with the material from three different mills, the celluloses made of birch were more cytotoxic and more potent inducers of EROD activity than were the celluloses of pine. Further, UB celluloses increased EROD activity and caused cytotoxicity at lower doses than material bleached with modern bleaching techniques. In the exposures made with material from one single mill, there were no clear trends between the celluloses made of pine or birch. Wood chips of pine, however, were more cytotoxic than wood chips of birch. Especially with pine wood chips, cytotoxicity interfered with the induction of EROD activity, thus complicating the evaluation of CYP1A induction. CYP1A protein content was not detected in cells exposed to extracts of celluloses or wood chips, possibly due to low amounts of protein available for the assay. Wood and pulp processing, like bleaching, may change the chemical composition of the raw material in a way that reduces the potency for biological effects of the final product, cellulose. This could explain why both UB celluloses and wood chips were more potent in the cells than ECF or TCF bleached celluloses. In this study the PLHC-1 cell line showed its potential for use in evaluating the biological activity existing in pulp and paper mill products and raw materials. The identity and source of the compounds that were able to affect the PLHC-1 cell line remain to be determined.