Phagocytosis of the protozoon Tetrahymena pyriformis as an endpoint in the estimation of cocaine salt and cocaine freebase toxicity

Genotoxicity, oxidative stress, and inflammatory response induced by crack-cocaine: relevance to carcinogenesis

Crack-cocaine is a cocaine by-product widely consumed by general population in developing countries. The drug is low cost and is associated with more intense effects when compared to other illicit drugs. Genotoxicity, oxidative stress, and inflammatory response are considered crucial events in carcinogenesis, since they actively participate in the multistep process. The purpose of this paper was to provide a mini review regarding the relationship between carcinogenesis and genotoxicity, oxidative stress, and inflammation induced by crack-cocaine. The present study was conducted on search of the scientific literature from the published studies available in PubMed, MEDLINE, Scopus, and Google Scholar for all kind of articles (all publications to November 2020) using the following key words: crack-cocaine, DNA damage, genotoxicity, cellular death, cytotoxicity, mutation, oxidative stress, inflammation, and mutagenicity. The results showed that published papers available were almost all in vivo test system being conducted in humans or rodents. Crack-cocaine was able to induce genotoxicity and oxidative stress in mammalian cells. However, the role of inflammatory response after exposure to crack-cocaine was not conclusive so far. In summary, this study is consistent with the notion that crack-cocaine is a chemical carcinogen as a result of genotoxicity and oxidative stress induced in mammalian and non-mammalian cells.

Toxicogenomic evaluation of chemically induced chromosomal imbalance using DNA image analysis

The study of carcinogenic potential of a variety of chemical agents such as food additives and drugs of abuse via the application of various in vitro methodologies constitutes the first step for the evaluation of their toxicogenomic profile. Considering the chromosomal theories of carcinogenesis, where it is stated that aneuploidy and chromosomal imbalance (instability) are among the main causes of carcinogenesis, chemicals capable to induce such changes in the cells could be considered as potential carcinogens. Chromosomal imbalance and aneuploidy directly affect the overall DNA content of the exposed cell as well as other cellular morpho- and densitometric features. These features can be measured by means of computerized DNA image analysis technologies and include DNA content (DNA Index), Proliferation Index, Ploidy Balance, Degree of Aneuploidy, Skewness and Kurtosis. Considering the enormous number of untested chemicals and drugs of abuse that follow non-genotoxic mechanisms of carcinogenesis, the establishment of a reliable technology for the estimation of chemically induced chromosomal imbalance is of particular importance in toxicogenomic studies. In the present article and based on our previously published work, we highlight the advantages of the applications of DNA image analysis technology in an easy-to-use experimental model for the evaluation of the potential risk of various chemicals. The use of this technology for the detection of chemically induced chromosomal instability will contribute to the development of safer regulatory directives concerning the use of chemicals in food and pharmaceutical industry, as well as in the clarification of mechanisms of action of drugs of abuse.

DNA content alterations in Tetrahymena pyriformis macronucleus after exposure to food preservatives sodium nitrate and sodium benzoate

The toxicity, in terms of changes in the DNA content, of two food preservatives, sodium nitrate and sodium benzoate was studied on the protozoan Tetrahymena pyriformis using DNA image analysis technology. For this purpose, selected doses of both food additives were administered for 2 h to protozoa cultures and DNA image analysis of T. pyriformis nuclei was performed. The analysis was based on the measurement of the Mean Optical Density which represents the cellular DNA content. The results have shown that after exposure of the protozoan cultures to doses equivalent to ADI, a statistically significant increase in the macronuclear DNA content compared to the unexposed control samples was observed. The observed increase in the macronuclear DNA content is indicative of the stimulation of the mitotic process and the observed increase in MOD, accompanied by a stimulation of the protozoan proliferation activity is in consistence with this assumption. Since alterations at the DNA level such as DNA content and uncontrolled mitogenic stimulation have been linked with chemical carcinogenesis, the results of the present study add information on the toxicogenomic profile of the selected chemicals and may potentially lead to reconsideration of the excessive use of nitrates aiming to protect public health.

Effect of cocaine and crack on the ploidy status of Tetrahymena pyriformis: a study using DNA image analysis

The effect of cocaine and crack on the ploidy status of Feulgen-stained Tetrahymena pyriformis macronuclei using computerized DNA image analysis system was tested. For this purpose, selected doses of 5, 10 and 20 μg (per mL culture) of both drugs were administered for 2, 5 and 20 h to protozoa cultures and DNA image analysis of T. pyriformis nuclei was performed. The analysis was based on the measurement of the following parameters: Ploidy Balance (PB), Degree of Aneuploidy (DA), skewness and kurtosis. The results have shown a positive effect of both cocaine and crack on PB and on DA of T. pyriformis macronuclei. In particular, our results reveal that the aneugenic effect (which is expressed as a decrease in PB and an increase in DA) of cocaine on T. pyriformis macronuclei follows a dose-dependent manner, while crack induces aneuploidy in a dose-independent manner. Changes in the PB and DA values would induce a disturbance in the cellular density and heterogeneity of chromatin and the increase in skewness and kurtosis values after exposure of T. pyriformis to both drugs, did confirm this hypothesis. These observations were further correlated with alterations in the chromosomal segregation and with damage in mitotic spindle microtubules observed previously. In this study the impact of cocaine and crack on genomic instability and carcinogenesis was further supported and T. pyriformis can be proposed as a model organism to test the nuclear ploidy status after exposure to harmful chemicals and drugs.

DNA content of Tetrahymena pyriformis as a biomarker for different toxic agents

The toxicity of different substances was studied on the protozoan Tetrahymena pyriformis, using as an endpoint the DNA content of the macronucleus. Substances from various chemical classes were administered to the Tetrahymena cultures and then the DNA content of the protozoan macronuclei was measured by means of Image Analysis System. The increase in the DNA content of the nuclei is indicative of the stimulation of the mitotic process. Since mitogenic stimuli can substantially alter susceptibility to chemical carcinogenesis, the results of such experiments, which are cheap and easy to run, may contribute to the investigation of the toxic action of several substances on cellular level.

Automated image analysis to improve bead ingestion toxicity test counts in the protozoan Tetrahymena pyriformis

AIMS

To improve bead ingestion counts in Tetrahymena pyriformis by automated image analysis as an alternative to direct-counts.

METHODS AND RESULTS

Fluorescent latex beads were added to T. pyriformis cultures for ingestion tests. The number of beads ingested by 25 cells was counted directly by epifluorescence microscopy and compared with similar data from image analysis. anova indicated that counts were not significantly different (P < 0.05). The image analysis particularly provided advantages in terms of speed.

CONCLUSIONS

The image analysis is superior to direct beads counting in T. pyriformis particularly in terms of speed of analysis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The image analysis method is very rapid and will allow many more toxicological analyses to be undertaken with less operator error.

Morphological and physiological changes in Tetrahymena pyriformis for the in vitro cytotoxicity assessment of Triton X-100

Non-ionic surfactants such as Triton X-100 have been widely used in industrial processing and in cleaning products for almost 50 years, being effective and economic emulsifying, wetting agents, dispersants and solubilizers. Cleaning products containing these surfactants are disposed of mainly by discharge into wastewater, which receives biological treatment in wastewater treatment systems. However, surface-active agents interact with eukaryotic cell membranes leading to biological damage at high concentrations. Tetrahymena pyriformis was used here as model organism to assess the effects of Triton X-100 through a series of in vitro cytotoxicity tests. Growth rates and morphological changes were, by their simplicity and reproducibility, the simplest toxicological assays. Cytoskeleton analysis seemed to be related with phagocytosis rate. Viability was evaluated by two different tests. Calcein AM/EthD-1 was used to assess T. pyriformis membrane damage during the 48-h experiment. The colorimetric MTT assay proved to be highly sensitive even at very short periods of Triton X-100 exposure. Tests performed in this study included simple and fast bioassays that provide overall information on the morphological and physiological state of cells exposed to different non-lytic and lytic concentrations of Triton X-100.

DNA toxicity of cocaine hydrochloride and cocaine freebase by means of DNA image analysis on Tetrahymena pyriformis

An assay for computerized scoring of the DNA content of the protozoan Tetrahymena pyriformis has been used for the detection of toxic responses to cocaine, since DNA is responsible for the replication of the genetic material and also reflects closely the number of chromosomes in the nucleus. Thus, doubling of the number of chromosomes in a cell will also correspond to doubling of the DNA content and of the nuclear volume. Two chemical forms of cocaine were used, cocaine hydrochloride and cocaine freebase (crack), at two doses of 1 and 2 mg per 100 ml of protozoan culture, respectively. Image analysis of the protozoan nucleus patterns revealed a rapid stimulating effect on the DNA content for both cocaine hydrochloride and freebase after 1 h of incubation. However, after 2 h of treatment a reduction, although not statistically significant, of the DNA content of the protozoan was observed. These observations were further correlated with the phagocytic activity of the protozoan cultures. This paper provides some possible explanations of the toxic effects of cocaine on this particular cell model.