Evaluation of the cytotoxicity of 10 chemicals in human and rat hepatocytes and in cell lines: Correlation between in vitro data and human lethal concentration

Thallium Toxicity and its Interference with Potassium Pathways Tested on Various Cell Lines

Thallium (Tl) is a highly toxic heavy metal whose mechanism of toxicity is still not completely understood. The aim of this study was to test Tl cytotoxicity on several cell lines of different tissue origin in order to clarify specific Tl toxicity to a particular organ. In addition, possible interference of Tl with cell potassium (K) transport was examined. Human keratinocytes (HaCaT), human hepatocellular carcinoma (HepG2), porcine kidney epithelial cells (PK15), human neuroblastoma (SH-SY5Y) and Chinese hamster lung fibroblast cells (V79) were treated with thallium (I) acetate in a wide concentration range (3.9-500 µg/mL) for 24 h, 48 and 72 h. To assess competitive interaction between Tl and K, the cells were treated with four Tl concentrations close to IC50 (15.63, 31.25, 62.50, 125 µg/mL) in combination with/or without potassium (I) acetate (500 µg/mL). The cells' morphology was monitored, and cytotoxic effect was assessed by 3-(4, 5-dimethylthiazole-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) test. The most sensitive to Tl exposure were SH-SY5Y cells, while HepG2 were the most resistant. The combined exposure to thallium (I) acetate and potassium (I) acetate for every cell line, except V79 cells, resulted in higher cell viability compared to thallium (I) acetate alone. The results of our study indicate that cell sensitivity to Tl treatment is largely affected by tissue culture origin, its function, and Na+/K+-ATPase activity.

Occurrence of Iodophenols in Aquatic Environments and the Deiodination of Organic Iodine with Ferrate(VI)

Toxic and odorous iodophenols are commonly identified as disinfection by-products (DBPs) in drinking water. Herein, ng/L levels of iodophenols were identified in river water, wastewater treatment plant effluent, and medical wastewater, with the simultaneous identification of μg/L to mg/L levels of iodide (I^-) and total organic iodine (TOI). Oxidation experiment suggested that the I^-, TOI, and iodophenols could be oxidized by ferrate [Fe(VI)], and more than 97% of TOI had been transformed into stable and nontoxic IO₃^-. Fe(VI) initially cleaved the C-I bond of iodophenols and led to the deiodination of iodophenols. The resulted I^- was swiftly oxidized into HOI and IO₃^-, with the intermediate phenolic products be further oxidized into lower molecular weight products. The Gibbs free energy change (ΔG) of the overall reaction was negative, indicating that the deiodination of iodophenols by Fe(VI) was spontaneous. In the disinfection of iodine-containing river water, ng/L levels of iodophenols and chloro-iodophenols formed in the reaction with NaClO/NH₂Cl, while Fe(VI) preoxidation was effective for inhibiting the formation of iodinated DBPs. Fe(VI) exhibited multiple functions for oxidizing organic iodine, abating their acute toxicity/cytotoxicity and controlling the formation of iodinated DBPs for the treatment of iodide/organic iodine-containing waters.

Assessment of intracellular accumulation of cadmium and thallium

The aim of the study was to develop fast and accurate method for assessment of intracellular level of cadmium (Cd) and thallium (Tl), and to establish accumulation of the metals in the cells. HepG2 cells were treated with Cd or Tl (1.0 or 10.0 mg/L; 24 h) and level of Cd or Tl was assessed. ICP-MS was applied and the method was optimized and validated. Correlation coefficient (R²) for Cd was 0.9999 with intercept 0.0732 while for Tl was 1.00009 with intercept -0.1497, and limit of detection (LOD) for Cd was 0.020 μg/L and for Tl 0.097 μg/L. Both metals, Cd and Tl, accumulate in the cells in concentration-dependent manner. However, higher uptake of Cd in comparison to Tl was observed. Cells treated with the same concentration of the metal (1.0 mg/L) accumulated 10.0% of Cd and 1.0% of Tl. Higher uptake of Cd than Tl can explain higher toxicity of Cd toward HepG2 cells. Obtained results imply to the importance of monitoring the level of metals in the cells in order to connect changes at the molecular level with exposure to specific metal.

MEIC Evaluation of Acute Systemic Toxicity

Results from tests on the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) reference chemicals 31–50 in 67 different in vitro toxicity assays are presented in this paper as a prerequisite to in vitro/in vivo comparisons for all MEIC in vitro toxicity data in forthcoming papers, i.e. the final MEIC evaluation of the relevance of the tests. With the aim of increasing knowledge about the relative significance of some in vitro methodological factors, the strategies and methods of the preceding parts in the MEIC series (Parts II and III) were again employed to enable comparative cytotoxicity analysis of the new in vitro results presented in this paper. A principal components analysis (PCA) of the results from tests of the 20 chemicals in 67 assays demonstrated a dominating first component describing as much as 74% of the variance in the toxicity data, indicating a similar ranking of the cytotoxicities of the chemicals in most of the tests. The influence on the general variability of the results of a few, key methodological factors was also evaluated by using linear regression comparisons of the results of all pairs of methods available in the study, i.e. methods which were similar in all respects except for the factor being analysed. Results from this “random probe” analysis were: a) the cytotoxicities of 11 of the 20 chemicals increased considerably with exposure time (> 10 times over 4–168 hours); b) in general, human cell line toxicity was well predicted by cytotoxicity in animal cells; c) prediction of human cell line toxicity by most ecotoxicological tests was only fairly good; d) 14 comparisons of similar assays with different cell lines showed similar toxicities (mean R2 = 0.83); e) nine comparisons of similar assays employing different primary cultures and cell lines shared similar toxicities (mean R2 = 0.71); and f) 16 comparisons of similar assays with different growth/viability endpoints showed similar toxicities (mean R2 = 0.71). Results b, d, e and f must contribute to the PCA-documented high general similarity of the in vitro toxicity data. Results a and c, together with factors which were not analysed, such as different protocols and inter-laboratory variability of tests, could explain the 26% dissimilarity. To provide background information to the planned final MEIC evaluation of the relevance of the 61 methods in which all 50 chemicals have been tested, an additional PCA was made of the 50 chemical-61 assay in vitro database (from Parts II and III and the present paper). This supplementary PCA demonstrated an 80% similarity of results. Compared with the previous analysis of the tests of the first 30 MEIC reference chemicals (MEIC Part III), the present analysis of the tests of the last 20 MEIC chemicals indicates a somewhat higher variation in the results. Correspondingly, some deviating endpoint measurements and cell line responses were demonstrated by the pairwise comparisons in the present study. As a result, the analysis revealed a high correlation (R2 = 0.73) between the average human cell line toxicity and the results from a new protein denaturation test. These preliminary results suggest that intracellular protein denaturation may be a frequently occurring mechanism in basal cytotoxicity.

MEIC Evaluation of Acute Systemic Toxicity

Results from tests on the first 30 MEIC reference chemicals in 16 different systems are presented as a prerequisite to the subsequent in vitro/in vivo comparisons of acute toxicity data, i.e. the final MEIC evaluation of all test results of the study. The study is a supplement to the previously published results from 68 methods (including methods 45B and 46B [old numbers]) used to test the same set of chemicals. The strategies and methods of the preceding paper were employed to enable a comparative cytotoxicity analysis of the results from these 68 methods and from the 16 new methods to be made. Principal components analysis (PCA) of 82 assays demonstrated a dominating first component which described as much as 83% of the variance in the toxicity data. This remarkable similarity of all toxicity data was the main finding of the present study, and confirmed the results of the previous study with a less-extensive database. Also, the influence on the general variability of results of several key methodological factors was evaluated by analysis of selected sets of data, including linear regression of the results of pairs of methods, which were similar in all respects except for the factor under analysis. This analysis of the same 82 assays as before also confirmed previous results from the 68 assay database: a) the toxicities of a third of the chemicals increased considerably with exposure time; b) in general, cytotoxicity for human cells was well predicted by cytotoxicity tests with animal cells; c) this prediction was poor for two chemicals, i.e. digoxin and malathion; d) prediction of human cytotoxicity by ecotoxicological tests was only fairly good; e) 25 comparisons of similar assays employing different cell lines showed strikingly similar toxicities (mean R2 = 0.86); f) 22 comparisons of similar pairs of assays employing different primary cultures and cell lines also revealed similar toxicities (mean R2 = 0.79); and g) 15 comparisons of similar assays with different growth/viability endpoint measurements demonstrated strikingly similar toxicities (mean R2 = 0.89). Results b, e, f and g must be the main causes of the general similarity of results, while results a, c and d, together with other factors, could explain the 20% dissimilarity. These findings support the basal cytotoxicity concept and may assist in guiding and refining in vitro toxicity testing in the future.

Effects of gamma radiation treatment on three different medicinal plants: Microbial limit test, total phenolic content, in vitro cytotoxicity effect and antioxidant assay

BACKGROUND AND AIM

The aim of this study is to evaluate the effects of gamma radiation treatment on three medicinal plants, namely Euodia malayana, Gnetum gnemon and Khaya senegalensis at two different forms; methanol leaf extracts and dried leaves respectively.

EXPERIMENTAL PROCEDURE

The microbial limit test (MLT) studies indicated the suitable dosage of minimum and maximum gamma irradiation for leaf extracts as well as dried leaves of all the tested medicinal plants. Quantitative analysis of total phenolic content (TPC) analysis is based on calorimetric measurements determined using the Folin-Ciocalteu reagent with gallic acid (GA) used as the reference. In vitro cytotoxicity assay by using fibroblast (L929) cell lines was performed on each plant to determine the toxicity effect which sodium dodecyl sulfate (SDS) as the positive control. DPPH (2,2-diphenyl-1-picryl-hydrazyl) assay was conducted by using vitamin C and GA as the positive controls to determine the antioxidant property of each plant.

RESULTS AND CONCLUSION

The MLT analysis indicated that the suitable dosage gamma irradiation for leaf extracts was 6-12 kGy and dried leaves were 9-13 kGy. The amount of GA concentration in each plant increased significantly from 30-51 mg GAE g^-1 before treatment to 57-103 mg GAE g^-1 after treatment with gamma radiation. This showed no significant effect of in vitro cytotoxicity activity before and after treatment with gamma irradiation in this study. Effective concentration (EC₅₀) values of Khaya senegalensis plant reduced significantly (P ≤ 0.005) from 44.510 μg/ml before treatment to 24.691 μg/ml after treatment with gamma radiation, which indicate an increase of free radical scavenging activity.

Testing Wound-healing Activity in T15 Fibroblast Cultures: A Morphometric Analysis

The purpose was to evaluate the use of mouse T15 fibroblast cell cultures for the investigation of wound-healing activity. In order to investigate their mechanisms of action, the effects of drugs with wound-healing activities were compared by using morphometric analyses by microscopy after cell staining. A number of parameters were used to evaluate the effects of titrated extracts from Centella asiatica and dexpanthenol (drugs that have been used in medical practice for their wound-healing activities) on cultured mouse T15 fibroblasts. These parameters were: the total number of cells; the number of T15 cells in mitosis; the percentages of fusiform, polygonal, round and vacuole-containing cells; and the number of intracellular collagen granules. The results indicate that these two drugs exhibit wound-healing activities by activating fibroblast cells, and have cytoprotective effects, although their mechanisms of action on mouse T15 fibroblasts were different. On the basis of our findings, mouse T15 fibroblast cell cultures seem to be useful for the pharmacological screening of compounds with wound-healing activity.

Biocompatibility of a new PD solution for Japan, Reguneal™, measured as in vitro proliferation of fibroblasts

BACKGROUND

The aim of this study was to investigate in vitro biocompatibility of Reguneal™, a new bicarbonate containing peritoneal dialysis fluid (PDF) for Japan, and compare it with other PDFs available in that country.

METHODS

We assessed basal cytotoxicity using in vitro proliferation of cultured fibroblasts, L-929, determining the quantity of living cells by the uptake of Neutral Red. Levels of ten glucose degradation products (GDPs) were measured by a validated ultrahigh-performance liquid chromatography method in combination with an ultraviolet detector. We compared inhibition of fibroblast cell growth between brands of PDF, adjusting for dextrose and GDP concentrations using random-effects mixed models.

RESULTS

The results demonstrate that cytotoxicity of Reguneal™ is comparable to a sterile-filtered control and is less cytotoxic than most of the other PDFs, most of which significantly inhibited cell growth. As a "class effect", increasing dextrose and GDP concentrations were non-significantly but positively associated with cytotoxicity. As a "brand effect", these relationships varied widely between brands, and some PDFs had significant residual effects on basal cytotoxicity through mechanisms that were unassociated with either dextrose or GDP concentration.

CONCLUSION

Our study suggests that Reguneal™ is a biocompatible PDF. The results of our study also highlight that dextrose and GDPs are important for biocompatibility, but alone are not a complete surrogate. The results of our study need to be confirmed in other tissue culture models, and should lead to further research on determinants of biocompatibility and the effect of such PDFs on clinical outcomes.

Environmental Toxin Screening Using Human-Derived 3D Bioengineered Liver and Cardiac Organoids

INTRODUCTION

Environmental toxins, such as lead and other heavy metals, pesticides, and other compounds, represent a significant health concern within the USA and around the world. Even in the twenty-first century, a plethora of cities and towns in the U.S. have suffered from exposures to lead in drinking water or other heavy metals in food or the earth, while there is a high possibility of further places to suffer such exposures in the near future.

METHODS

We employed bioengineered 3D human liver and cardiac organoids to screen a panel of environmental toxins (lead, mercury, thallium, and glyphosate), and charted the response of the organoids to these compounds. Liver and cardiac organoids were exposed to lead (10 µM-10 mM), mercury (200 nM-200 µM), thallium (10 nM-10 µM), or glyphosate (25 µM-25 mM) for a duration of 48 h. The impacts of toxin exposure were then assessed by LIVE/DEAD viability and cytotoxicity staining, measuring ATP activity and determining IC50 values, and determining changes in cardiac organoid beating activity.

RESULTS

As expected, all of the toxins induced toxicity in the organoids. Both ATP and LIVE/DEAD assays showed toxicity in both liver and cardiac organoids. In particular, thallium was the most toxic, with IC50 values of 13.5 and 1.35 µM in liver and cardiac organoids, respectively. Conversely, glyphosate was the least toxic of the four compounds, with IC50 values of 10.53 and 10.85 mM in liver and cardiac organoids, respectively. Additionally, toxins had a negative influence on cardiac organoid beating activity as well. Thallium resulting in the most significant decreases in beating rate, followed by mercury, then glyphosate, and finally, lead. These results suggest that the 3D organoids have significant utility to be deployed in additional toxicity screening applications, and future development of treatments to mitigate exposures.

CONCLUSION

3D organoids have significant utility to be deployed in additional toxicity screening applications, such as future development of treatments to mitigate exposures, drug screening, and environmental toxin detection.

Bioaccumulation and biotransformation of the beta-blocker propranolol in multigenerational exposure to Daphnia magna

Multigenerational bioaccumulation and biotransformation activity and short-term kinetics (e.g., uptake and depuration) of propranolol in Daphnia magna were investigated at environmental concentration. The body burden and the major metabolite, desisopropyl propranolol (DIP), of propranolol were quantified using LC-MS/MS at the end of each generation after exposure for 11 generations. The accumulation of propranolol in D. magna at an environmental concentration of 0.2 μg/L was not much different between the parent (F0) and the eleventh filial (F10) generation. However, at 28 μg/L, its accumulation was 1.6 times higher-up to 18.9 μg/g-in the F10 generation relative to the F0. In contrast to propranolol, DIP intensity gradually increased from F0 to F10 at 0.2 μg/L, reflecting an increase in detoxification load and biotransformation performance; no increasing trend was observed at 28 μg/L. The bioaccumulation factor (BAF) showed higher values with a lower concentration and longer period of exposure. The average values of the BAF for 21 days of long-term exposure in successive 11 generations were 440.4 ± 119.7 and 1026.5 ± 208.6 L/kg for 28 μg/L and 0.2 μg/L, respectively. These are comparable to the BAF of 192 for the short-term 72-h exposure at 28 μg/L in the parent generation. It is also recommended that future studies for pharmaceutical ingredients be conducted on drug-drug interaction and structural characteristics on the prediction of biotransformation activity and bioaccumulation rate.

Cytotoxicity evaluation of large cyanobacterial strain set using selected human and murine in vitro cell models

The production of cytotoxic molecules interfering with mammalian cells is extensively reported in cyanobacteria. These compounds may have a use in pharmacological applications; however, their potential toxicity needs to be considered. We performed cytotoxicity tests of crude cyanobacterial extracts in six cell models in order to address the frequency of cyanobacterial cytotoxicity to human cells and the level of specificity to a particular cell line. A set of more than 100 cyanobacterial crude extracts isolated from soil habitats (mainly genera Nostoc and Tolypothrix) was tested by MTT test for in vitro toxicity on the hepatic and non-hepatic human cell lines HepG2 and HeLa, and three cell systems of rodent origin: Yac-1, Sp-2 and Balb/c 3T3 fibroblasts. Furthermore, a subset of the extracts was assessed for cytotoxicity against primary cultures of human hepatocytes as a model for evaluating potential hepatotoxicity. Roughly one third of cyanobacterial extracts caused cytotoxic effects (i.e. viability<75%) on human cell lines. Despite the sensitivity differences, high correlation coefficients among the inhibition values were obtained for particular cell systems. This suggests a prevailing general cytotoxic effect of extracts and their constituents. The non-transformed immortalized fibroblasts (Balb/c 3T3) and hepatic cancer line HepG2 exhibited good correlations with primary cultures of human hepatocytes. The presence of cytotoxic fractions in strongly cytotoxic extracts was confirmed by an activity-guided HPLC fractionation, and it was demonstrated that cyanobacterial cytotoxicity is caused by a mixture of components with similar hydrophobic/hydrophilic properties. The data presented here could be used in further research into in vitro testing based on human models for the toxicological monitoring of complex cyanobacterial samples.

Evaluation of differential cytotoxic effects of the oil spill dispersant Corexit 9500

AIMS

The British Petroleum (BP) oil spill has raised several ecological and health concerns. As the first response, BP used a chemical dispersant, Corexit-9500, to disperse the crude oil in the Gulf of Mexico to limit shoreline contamination problems. Nevertheless, portions of this oil/Corexit mixture reached the shoreline and still remain in various Gulf shore environments. The use of Corexit itself has become a significant concern since its impacts on human health and environment is unclear.

MAIN METHODS

In this study, in vitro cytotoxic effects of Corexit were evaluated using different mammalian cells.

KEY FINDINGS

Under serum free conditions, the LC50 value for Corexit in BL16/BL6 cell was 16 ppm, in 1321N1 cell was 33 ppm, in H19-7 cell was 70 ppm, in HEK293 was 93 ppm, and in HK-2 cell was 95 ppm. With regard to the mechanisms of cytotoxicity, we hypothesize that Corexit can possibly induce cytotoxicity in mammalian cells by altering the intracellular oxidative balance and inhibiting mitochondrial functions. Corexit induced increased reactive oxygen species and lipid peroxide levels; also, it depleted glutathione content and altered catalase activity in H19-7 cells. In addition, there was mitochondrial complex-I inhibition and increase in the pro-apoptotic factors including caspase-3 and BAX expression.

SIGNIFICANCE

The experimental results show changes in intracellular oxidative radicals leading to mitochondrial dysfunctions and apoptosis in Corexit treatments, possibly contributing to cell death. Our findings raise concerns about using large volumes of Corexit, a potential environmental toxin, in sensitive ocean environments.

Genetic toxicology of thallium: a review

This review summarizes the current knowledge about the general toxicity of thallium (Tl) and its environmental sources, with special emphasis placed on its potential mutagenic, genotoxic, and cytotoxic effects on both eukaryotic and prokaryotic cells. Tl is a nonessential heavy metal that poses environmental and occupational threats as well as therapeutic hazards because of its use in medicine. It is found in two oxidation states, thallous (Tl(+)) and thallic (Tl(3+)), both of which are considered highly toxic to human beings and domestic and wild organisms. Many Tl compounds are colorless, odorless and tasteless, and these characteristics, combined with the high toxicity of TI compounds, have led to their use as poisons. Because of its similarity to potassium ions (K(+)), plants and mammals readily absorb Tl(+) through the skin and digestive and respiratory systems. In mammals, it can cross the placental, hematoencephalic, and gonadal barriers. Inside cells, Tl can accumulate and interfere with the metabolism of potassium and other metal cations, mimicking or inhibiting their action. The effects of Tl on genetic material have not yet been thoroughly explored, and few existing studies have focused exclusively on Tl(+). Both in vivo and in vitro studies indicate that Tl compounds can have a weak mutagenic effect, but no definitive effect on the induction of primary DNA damage or chromosomal damage has been shown. These studies have demonstrated that Tl compounds are highly toxic and lead to changes in cell-cycle progression.

An integrated in vitro approach for toxicity testing of airborne contaminants

While it is possible to establish the chemical composition of air pollutants through conventional air sampling and analytical techniques, such data do not provide direct measures of toxicity and the potential mechanisms that induce adverse effects. The aim of this study was to optimize in vitro methods for toxicity testing of airborne contaminants. An integrated approach was designed in which appropriate exposure techniques were developed. A diversified range of in vitro assays using multiple human cell systems were implemented. Direct exposure of cells to airborne contaminants was developed by culturing cells on porous membranes in conjunction with a horizontal diffusion chamber system. Concentration-response curves were generated allowing the measurement of toxicity endpoints. Regression analysis indicated a significant correlation between in vitro and published in vivo toxicity data for the majority of selected chemical contaminants. Airborne IC50 values were calculated for selected volatile organic compounds (xylene, 5350 +/- 328 ppm > toluene, 10,500 +/- 527 ppm) and gaseous contaminants (NO2, 11 +/- 3.54 ppm > SO2, 48 +/- 2.83 ppm and > NH3, 199 +/- 1.41 ppm). Results of this study indicate the significant potential of in vitro methods as an advanced technology for toxicity assessment of airborne contaminants.

In vitro cytotoxicity of selected chemicals commonly produced during fire combustion using human cell lines

Fire combustion products contain a broad range of chemicals, which have a multitude of possible toxic interactions in humans. The aim of this study was to evaluate the cytotoxicity of selected substances commonly produced during fire combustion. A range of human cell lines and cultures including: skin fibroblasts, HepG2 (liver derived), and A549 (lung derived cells) were used to represent different human target organs. The colorimetric MTS assay (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) was used to detect the cytotoxic effects of selected substances including: acetic acid, ammonia, formaldehyde, hydrobromic acid, hydrochloric acid, hydrofluoric acid, potassium cyanide, sodium fluoride, sodium nitrite, sodium sulphide, and sulphurous acid. In this study, the NOAEC (No Observable Adverse Effect Concentration), IC(10) (10% inhibitory concentration), IC50 (50% inhibitory concentration), and TLC (Total Lethal Concentration) values were determined. The ratio between in vitro IC50 to in vivo human toxicity data (Lowest Lethal Dose-LDLo and Lowest Lethal Concentration--LCLo) was also established. Results indicated a strong relationship between IC50 values on the cell types used: fibroblast and A549 (R2: 0.92), A549 and HepG2 (R2: 0.72), fibroblast and HepG2 (R2: 0.69). Good correlation was obtained between the IC50 against LDLo and LCLo when an appropriate adjustment factor was implemented. Results of this study indicated that in vitro methods could be a potential technique for assessing the toxicity of fire combustion products.

Comparison of basal cytotoxicity data between mammalian and fish cell lines: A literature survey

During the last 20 years, in vitro assays with fish cells have been used in ecotoxicology for testing chemicals, effluents and in toxicity identification evaluations (TIE) studies. Due to the good correlation found between the in vitro data and the in vivo fish data in ranking chemical toxicity, they have been proposed as an alternative to acute fish bioassays for toxicity screening of chemicals. Nevertheless, they are recognized to be less sensitive when compared with in vivo fish bioassays. Fish cells have slower cell cycles than mammalian cells, so it was suggested that mammalian cells could be more sensitive than fish cells for testing chemicals. However, as fish cells offer some advantages over mammalian cells, mainly related to their ease of handling, some authors found them preferable to use for routine testing. The present study was undertaken to analyze whether mammalian cell lines are more, less, or equally sensitive, compared to fish cells lines. To this end, basal cytotoxicity data from a literature survey of mammalian and fish cell lines have been compared. There was a good linear correlation of IC50 values (r = 0.915) between fish and mammalian cells for a set of 51 chemicals after 24-h of treatment. The correlation coefficient of IC50 values (r = 0.888) decreased when 24-h treated mammalian cells were correlated against 48-h treated fish cell lines. For the dataset selected for this study, fish and mammalian cells showed a similar sensitivity for most of the chemicals after being treated for 24 h. We conclude that fish and mammalian cells can equally well predict the basal toxicity of the set of chemicals used in this study, and that increased exposure periods did not increase the correlation between midpoint toxicities nor sensitivities for any of the cell lines used. The more practical handling of fish cells favors their recommendation as a better alternative for replacing fish bioassay than mammalian cells.

Comparison of alamar blue and MTT assays for high through-put screening

The performance of alamar blue and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) cell viability assays in a high through-put format were compared. A total of 117 drugs chosen for their wide range of therapeutic areas were screened at 10 microM using both assays in human hepatoma cell line HepG2. Except for terfenadine and astemizole, which performed consistently in both assays, the alamar blue assay was slightly more sensitive than the MTT assay for most compounds. The MTT assay was less sensitive detecting an effect for daunorubicin and trifluoperazine. Seven drugs, astemizole, daunorubicin, ellipticine, fluphenazine, terfenadine, thioridazine and trifluoperazine, had percent viability results of 55% or less in the alamar blue assay at the single point screen. These were re-tested in both assays for reconfirmation of cytotoxicity and determination of the EC50 values. Except for daunorubicin, the EC50 values were comparable in both assays. Based on these results and the Z'-factor assessment of assay quality, both assays provided useful information to identify in vitro cytotoxic drugs at early stages of drug candidate selection. However, careful interpretation of data is warranted due to the possibility of false positive or negative results caused by inducers and/or inhibitors of metabolic enzymes that are responsible for transformation of cell toxicity end points, as we demonstrated using dicumarol.

A comparison of murine and human alveolar macrophage responses to urban particulate matter

There is increasing evidence linking mortality, increased asthma morbidity, and other respiratory disorders to increases in fine airborne particulate matter (PM) concentrations. However, there are only limited data dealing with the biological mechanisms that ultimately lead to the reported health effects. Rodents are frequently used as an animal model to help elucidate the mechanisms of toxicity that may provide clues for the understanding of PM toxicity in humans; however, the relationships between murine and human PM toxicity have not been established. PM is known to target the pulmonary epithelium and resident alveolar macrophages (AM). PM can initiate cytotoxic effects on the AM including apoptosis and necrosis, depending on the particle concentration, which may be central to the pathological effects just described. This study examined AM apoptosis and necrosis initiated by PM in AM from humans and BALB/c mice in an in vitro exposure model. Freshly isolated AM from human volunteers were incubated with seven different residual fractions of PM1648 derived from organic solvent extractions, high-temperature heating and acid digestions that change the surface characteristics of the original PM. These results were compared to the analogous murine experiments. The results suggested that, at the same concentration of PM, the trend of toxicity and the posttreatment effects observed in BALB/c and human AM have a similar pattern. Altering the surface chemistry by removal of one or more PM components, such as through the various treatments conducted in this study, is sufficient to alter PM bioactivity in both human and murine AM in a similar manner. In addition, the human and murine models were compared with regard to in vitro cytotoxicity using PM(2.5) particles. The cytotoxic PM(2.5) effects were identical in both human and mouse models. Regression analysis revealed that the BALB/c mouse is a suitable model for PM cytotoxicity of AM as it is a good predictive model for the human AM responses.

Effects of human pharmaceuticals on cytotoxicity, EROD activity and ROS production in fish hepatocytes

Pharmaceuticals are found in the aquatic environment but their potential effects on non-target species like fish remain unknown. This in vitro study is a first approach in the toxicity assessment of human drugs on fish. Nine pharmaceuticals were tested on two fish hepatocyte models: primary cultures of rainbow trout hepatocytes (PRTH) and PLHC-1 fish cell line. Cell viability, interaction with cytochrome P450 1A (CYP1A) enzyme and oxidative stress were assessed by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrasodium bromide tetrazolium (MTT), 7-ethoxyresorufin-o-deethylase (EROD) and dichlorofluorescein (DCFH-DA) assays, respectively. The tested drugs were clofibrate (CF), fenofibrate (FF), carbamazepine (CBZ), fluoxetine (FX), diclofenac (DiCF), propranolol (POH), sulfamethoxazole (SFX), amoxicillin (AMX) and gadolinium chloride (GdCl(3)). All substances were cytotoxic, except AMX at concentration up to 500 microM. The calculated MTT EC(50) values ranged from 2 microM (CF) to 651 microM (CBZ) in PLHC-1, and from 53 microM (FF) to 962 microM (GdCl(3)) in PRTH. CF, FF, and FX were the most cytotoxic drugs and induced oxidative stress before being cytotoxic. Compared to hepatocytes from human and dog, fish hepatocytes seemed to be more susceptible to the peroxisome proliferators (PPs) CF and FF. In PLHC-1 cells none of the tested drugs induced the EROD activity whereas POH appeared as a weak EROD inducer in PRTH. Moreover, in PRTH, SFX, DiCF, CBZ and to a lesser extend, FF and CF inhibited the basal EROD activity at clearly sublethal concentrations which may be of concern at the biological and chemical levels in a multipollution context.

Characterisation of some cytotoxic endpoints using rat liver and HepG2 spheroids as in vitro models and their application in hepatotoxicity studies. II. Spheroid cell spreading inhibition as a new cytotoxic marker

Cells in liver spheroids and Hep G2 spheroids transferred from gyrotatory culture conditions and maintained in normal static culture conditions will spread out at the edges. Based on this observation, we developed a new test called the Spheroid Cell Spreading Inhibition Test (SCSIT) to screen hepatic cytotoxicity of xenobiotics and determine the spheroid cell spreading inhibition concentration (SCSIC) of test chemicals. Four model hepatoxicants, D-galactosamine, propranolol, diclofenac, and paracetamol, were studied with SCSIT in both rat liver and HepG2 spheroids. Both liver and HepG2 spheroids were prepared under gyrotatory culture conditions and used at 6 days in vitro. The results showed that all four hepatotoxicants tested inhibited cell spreading in liver spheroids (D-galactosamine at 20 mM, propranolol at 125 microM, diclofenac at 500 microM, and paracetamol at 25 mM) and HepG2 spheroids (D-galactosamine at 16 mM, propranolol at 125 microM, diclofenac at 500 microM, and paracetamol at 25 mM). The SCSIT results agreed with the conventional cytotoxic indicators, release of LDH and/or gamma-GT and the inhibition of glucose secretion from rat liver spheroids. In conclusion, this study, for the first time, described the biological characteristics of liver and HepG2 spheroid cell spreading and demonstrates its application in hepatic cytotoxicity studies. This method may be used in testing in vitro "acute" toxicity, comparing relative cytotoxicity and generating reference concentrations for subsequent studies. Therefore, SCSIT could be a useful tool for screening hepatotoxicity relevant to preclinical lead optimization and compound library screening.

Evaluation of the Cytotoxic Effects of MEIC Chemicals 31–50 on Primary Culture of Rat Hepatocytes and Hepatic and Non-hepatic Cell Lines

The cytotoxicities of 20 chemicals (numbers 31–50) from the Multicenter Evaluation of In Vitro Cytotoxicity (MEIC) programme were assessed with a primary culture of rat hepatocytes and with two hepatic cell lines (Hep G2 and FaO) and one non-hepatic cell line (3T3). The cytotoxicities of the chemicals were evaluated by using the MTT test after the cells had been exposed to the chemicals for 24 hours. For a better evaluation of results, dose–response curves were mathematically linearised and cytotoxicity was expressed as IC50 values and IC10 values (the concentration causing 50% and 10% loss of cell viability, respectively). We found that all the compounds showed similar acute basal cytotoxicity in all four cellular systems (regardless of whether the cells were, or were not, metabolically competent or were or were not of human origin). When these results were used to predicit human toxicity in terms of a mathematical parameter (prediction error [PE]), we found that all four systems gave similar predictions of human toxicity. The best cytotoxicity parameter included in the PE calculation was the IC50/10, because of an underestimation of human toxicity by in vitro systems. However, when PEs were calculated for rodent toxicity, better results were obtained. Data from the literature obtained by using other experimental models for predicting human toxicity were analysed according to the same criteria. We conclude that cellular systems are better predictive tools for human toxicity than are prokaryotic cells or whole-organism models.