Comparison Between Alkaline and Neutral Variants of Yeast Comet Assay

Extracts of medicinal plants with natural deep eutectic solvents: enhanced antimicrobial activity and low genotoxicity

Natural deep eutectic solvents (NADES) are a new alternative to toxic organic solvents. Their constituents are primary metabolites, non-toxic, biocompatible and sustainable. In this study four selected NADES were applied for the extraction of two medicinal plants: Sideritis scardica, and Plantago major as an alternative to water-alcohol mixtures, and the antimicrobial and genotoxic potential of the extracts were studied. The extraction efficiency was evaluated by measuring the extracted total phenolics, and total flavonoids. Best extraction results for total phenolics for the studied plants were obtained with choline chloride-glucose 5:2 plus 30% water; but surprisingly these extracts were inactive against all tested microorganisms. Extracts with citric acid-1,2-propanediol 1:4 and choline chloride-glycerol 1:2 showed good activity against S. pyogenes, E. coli, S. aureus, and C. albicans. Low genotoxicity and cytotoxicity were observed for all four NADES and the extracts with antimicrobial activity. Our results confirm the potential of NADESs for extraction of bioactive constituents of medicinal plants and further suggest that NADES can improve the effects of bioactive extracts. Further studies are needed to clarify the influence of the studied NADES on the bioactivity of dissolved substances, and the possibility to use such extracts in the pharmaceutical and food industry.

The small molecule drug CBL0137 increases the level of DNA damage and the efficacy of radiotherapy for glioblastoma

Glioblastoma (GBM) is an incurable brain tumor with inevitable recurrence. This is in part due to a highly malignant cancer stem cell (CSC) subpopulation of tumor cells that is particularly resistant to conventional treatments, including radiotherapy. Here we show that CBL0137, a small molecule anti-cancer agent, sensitizes GBM CSCs to radiotherapy. CBL0137 sequesters the FACT (facilitates chromatin transcription) complex to chromatin, resulting in cytotoxicity preferentially within tumor cells. We show that when combined with radiotherapy, CBL0137 inhibited GBM CSC growth and resulted in more DNA damage in the CSCs compared to irradiation or drug alone. Using an in vivo subcutaneous model, we showed that the frequency of GBM CSCs was reduced when tumors were pretreated with CBL0137 and then exposed to irradiation. Survival studies with orthotopic GBM models resulted in significantly extended survival for mice treated with combinatorial therapy. As GBM CSCs contribute to the inevitable recurrence in patients, targeting them is imperative. This work establishes a new treatment paradigm for GBM that sensitizes CSCs to irradiation and may ultimately reduce tumor recurrence.

Biological activity of quinazoline analogues and molecular modeling of their interactions with G-quadruplexes

BACKGROUND

Quinazolines 1 to 6, with an aromatic or aryl-vinyl substituent in position 2 are selected with the aim to compare their structures and biological activity. The selection includes a natural alkaloid, schizocommunin, and the synthetic 2-(2'-quinolyl)-3H-quinazolin-4-one, known to interact with guanine-quadruplex dependent enzymes, respectively telomerase and topoisomerase.

METHODS

Breast cancer cells of the MDA cell line have been used to study the bioactivity of the tested compounds by the method of Comet Assay and FACS analyses. We model observed effects assuming stacking interactions of studied heterocycles with a naked skeleton of G-quadruplex, consisting of guanine quartet layers and potassium ions. Interaction energies are computed using a dispersion corrected density functional theory method, and an electron-correlated molecular orbital theory method.

RESULTS

Selected compounds do not remarkably delay nor change the dynamics of cellular progression through the cell cycle phases, while changing significantly cell morphology. Our computational models quantify structural effects on heterocyclic G4-complex stabilization energies, which directly correlate with observed biological activity.

CONCLUSION

Our computational model of G-quadruplexes is an acceptable tool for the study of interaction energies of G-quadruplexes and heterocyclic ligands, predicting, and allowing design of novel structures.

GENERAL SIGNIFICANCE

Genotoxicity of quinazolin-4-one analogues on human breast cancer cells is not related to molecular metabolism but rather to their interference with G-quadruplex regulatory mechanisms. Computed stabilization energies of heterocyclic ligand complexes of G-quadruplexes might be useful in the prediction of novel telomerase / helicase, topoisomerase and NA polymerase dependent drugs.

Effects of selective serotonin reuptake inhibitors on DNA damage in patients with depression

BACKGROUND

The relationship between depression and increased oxidative stress is well known. DNA damage by oxidation factors is an important cause of the aging process in psychiatric disorders.

AIMS

Owing to the scarcity of human studies and high inconsistencies in studies of the effects of antidepressants on DNA damage, the current study was undertaken to investigate the effects of depression and its treatment on DNA damage.

METHODS

In a 15-week open-label study of citalopram (n = 25) and sertraline (n = 20), levels of DNA damage were measured by comet assay, proinflammatory (Interlukin-6 (IL-6)) and oxidative DNA damage (8-hydroxy-2'-deoxyguanosine (8-OHdG)) markers by ELISA, and gene expression of base excision repair enzymes (8-oxoguanine glycosylase (OGG1) and poly (ADP)-ribose polymerase-1 (PARP1)) by quantitative real-time polymerase chain reaction in healthy control patients (n = 14), with depression at the baseline and the same patients after week 15.

RESULTS

DNA damage, 8-OHdG, IL-6 and expression of PARP1 were elevated in patients with depression compared with the healthy controls (p < 0.001). Selective serotonin reuptake inhibitor (SSRI) therapy could significantly reduce the depression score (p < 0.01), DNA damage (p < 0.001), as well as 8-OHdG and IL-6 (p < 0.0001). Nevertheless, the expression of PARP1 and OGG1 showed no significant changes after treatment.

CONCLUSIONS

This is the first study on the effect of SSRIs on the DNA damage and some of the repair enzymes in depression. Based on the results, depression can cause increased DNA damage. This damage is followed by activation of compensatory mechanisms whereby the expression of DNA damage repair enzymes is elevated. Finally, the treatment of psychiatric disorder by antidepressants can lower the level of oxidative DNA damage.

Genotoxicity of gold nanoparticles functionalized with indolicidin towards Saccharomyces cerevisiae

The toxic effects of gold nanoparticles surface-functionalized with the antimicrobial peptide indolicidin (AuNPs-indolicidin) towards the yeast Saccharomyces cerevisiae, one of the major eukaryotic model organisms, have been evaluated. Growth and survival, genotoxicity, as measured by comet assay, and expression of the YCA1, an apoptosis indicating gene, following 72hr exposure of yeast to AuNPs-indolicidin, and to AuNPs and indolicidin alone have been examined. The gold nanoparticles exerted toxicity with DNA damage, accompanied by reactive oxygen species production (ROS), but they do not inhibit yeast growth and viability. Genotoxicity was less pronounced for surface-functionalized nanoparticles, showing that S. cerevisiae is quite resistant to the complex AuNPs-indolicidin. A progressive reduction of the genotoxic effect was observed along 72hr exposure, presumably due to the activation of DNA repair mechanisms. These findings suggest the occurrence of a physiological protective response of S. cerevisiae towards nanoparticles, thereby providing useful information to the assessment of the environmental impact of metal nanoparticles.

The effects of engineered nanoparticles on the cellular structure and growth of Saccharomyces cerevisiae

In order to study the effects of nanoparticles (NPs) with different physicochemical properties on cellular viability and structure, Saccharomyces cerevisiae were exposed to different concentrations of TiO2-NPs (1-3 nm), ZnO-NPs (<100 nm), CuO-NPs (<50 nm), their bulk forms, Ag-NPs (10 nm) and single-walled carbon nanotubes (SWCNTs). The GreenScreen assay was used to measure cyto- and genotoxicity, and transmission electron microscopy (TEM) used to assess ultrastructure. CuO-NPs were highly cytotoxic, reducing the cell density by 80% at 9 cm(2)/ml, and inducing lipid droplet formation. Cells exposed to Ag-NPs (19 cm(2)/ml) and TiO2-NPs (147 cm(2)/ml) contained dark deposits in intracellular vacuoles, the cell wall and vesicles, and reduced cell density (40 and 30%, respectively). ZnO-NPs (8 cm(2)/ml) caused an increase in the size of intracellular vacuoles, despite not being cytotoxic. SWCNTs did not cause cytotoxicity or significant alterations in ultrastructure, despite high oxidative potential. Two genotoxicity assays, GreenScreen and the comet assay, produced different results and the authors discuss the reasons for this discrepancy. Classical assays of toxicity may not be the most suitable for studying the effects of NPs in cellular systems, and the simultaneous assessment of other measures of the state of cells, such as TEM are highly recommended.

Application of comet assay for the assessment of DNA damage caused by chemical genotoxins in the dairy yeast Kluyveromyces lactis

Kluyveromyces lactis, also known as dairy yeast, has numerous applications in scientific research and practice. It has been approved as a GRAS (Generally Recognized As Safe) organism, a probiotic, a biotechnological producer of important enzymes at industrial scale and a bioremediator of waste water from the dairy industry. Despite these important practical applications the sensitivity of this organism to genotoxic substances has not yet been assessed. In order to evaluate the response of K. lactis cells to genotoxic agents we have applied several compounds with well-known cyto- and genotoxic activity. The method of comet assay (CA) widely used for the assessment of DNA damages is presented here with new special modifications appropriate for K. lactis cells. The comparison of the response of K. lactis to genotoxins with that of Saccharomyces cerevisiae showed that both yeasts, although considered close relatives, exhibit species-specific sensitivity toward the genotoxins examined.