Genotoxic Potential of Thymol on Honey Bee DNA in the Comet Assay

Thymol is a natural essential oil derived from the plant Thymus vulgaris L. It is known to be beneficial for human and animal health and has been used in beekeeping practice against Varroa mite for years. In this study, the genotoxic and antigenotoxic potential of thymol were evaluated on the honey bee (Apis mellifera L.) continuous cell line AmE-711 for the first time. Using the Comet assay, three increasing concentrations (10, 100, and 1000 µg/mL) of thymol were tested. Negative control (non-treated cells) and positive control (cells treated with 100 µM H₂O₂) were also included. The absence of thymol cytotoxicity was confirmed with the Trypan blue exclusion test. Thymol in the concentration of 10 µg/mL did not increase DNA damage in AmE-711 honey bee cells, while 100 and 1000 µg/mL concentrations showed genotoxic effects. For testing the antigenotoxic effect, all concentrations of thymol were mixed and incubated with H₂O₂. The antigenotoxic effect against was absent at all concentrations (10, 100, 1000 μg/mL) tested. Moreover, thymol enhanced the H₂O₂-induced DNA migration in the Comet assay. The obtained results indicate genotoxic effects of thymol on cultured honey bee cells suggesting its careful application in beekeeping practice to avoid possible negative effects on honey bees.

Oxidative Stress and DNA Damage in Peripheral Blood Mononuclear Cells from Normal, Obese, Prediabetic and Diabetic Persons Exposed to Thyroid Hormone In Vitro

Diabetes, a chronic group of medical disorders characterized byhyperglycemia, has become a global pandemic. Some hormones may influence the course and outcome of diabetes, especially if they potentiate the formation of reactive oxygen species (ROS). There is a close relationship between thyroid disorders and diabetes. The main objective of this investigation was to find out whether peripheral blood mononuclear cells (PBMCs) are more prone to DNA damage by triiodothyronine (T₃) (0.1, 1 and 10 μM) at various stages of progression through diabetes (obese, prediabetics, and type 2 diabetes mellitus—T2DM persons). In addition, some biochemical parameters of oxidative stress (catalase-CAT, thiobarbituric acid reactive substances—TBARS) and lactate dehydrogenase (LDH) were evaluated. PBMCs from prediabetic and diabetic patients exhibited increased sensitivity for T₃ regarding elevated level of DNA damage, inhibition of catalase, and increase of TBARS and LDH. PBMCs from obese patients reacted in the same manner, except for DNA damage. The results of this study should contribute to a better understanding of the role of thyroid hormones in the progression of T2DM.

The hCOMET project: International database comparison of results with the comet assay in human biomonitoring. Baseline frequency of DNA damage and effect of main confounders

The alkaline comet assay, or single cell gel electrophoresis, is one of the most popular methods for assessing DNA damage in human population. One of the open issues concerning this assay is the identification of those factors that can explain the large inter-individual and inter-laboratory variation. International collaborative initiatives such as the hCOMET project - a COST Action launched in 2016 - represent a valuable tool to meet this challenge. The aims of hCOMET were to establish reference values for the level of DNA damage in humans, to investigate the effect of host factors, lifestyle and exposure to genotoxic agents, and to compare different sources of assay variability. A database of 19,320 subjects was generated, pooling data from 105 studies run by 44 laboratories in 26 countries between 1999 and 2019. A mixed random effect log-linear model, in parallel with a classic meta-analysis, was applied to take into account the extensive heterogeneity of data, due to descriptor, specimen and protocol variability. As a result of this analysis interquartile intervals of DNA strand breaks (which includes alkali-labile sites) were reported for tail intensity, tail length, and tail moment (comet assay descriptors). A small variation by age was reported in some datasets, suggesting higher DNA damage in oldest age-classes, while no effect could be shown for sex or smoking habit, although the lack of data on heavy smokers has still to be considered. Finally, highly significant differences in DNA damage were found for most exposures investigated in specific studies. In conclusion, these data, which confirm that DNA damage measured by the comet assay is an excellent biomarker of exposure in several conditions, may contribute to improving the quality of study design and to the standardization of results of the comet assay in human populations.

Liver anatomy, intrahepatic vascular and biliary branching system of the mole rat (Spalax leucodon)

BACKGROUND

There are many studies on the morphology of the liver and its blood vessels in experimental animals, but such studies are lacking in the mole rat (Spalax leucodon). The aim of this paper was a detailed basic study on the topography, morphology, vascular and biliary branching systems of the liver in the mole rat.

MATERIALS AND METHODS

Coloured gelatine and mixture of coloured lead oxide and linseed oil were injection contrast masses used to obtain vascular and biliary branching pattern in the liver. It was revealed that the liver of the mole rat had five lobes (left, quadrate, right medial, right lateral and caudate lobes).

RESULTS

The left, undivided lobe was the largest lobe of the liver. The quadrate lobe was divided into two components by a deep notch. The gallbladder, of cylindrical shape, was present and attached to the quadrate lobe. The common bile duct was formed by the union of the left and right hepatic ducts. The pancreatic duct joined the common bile duct before it entered the duodenum. In the present study, only the right medial lobe and quadrate lobe always showed a single lobar artery, portal and hepatic veins. The left lobe showed four lobar arteries, portal and hepatic veins. The caudate lobe with its two processes and the right lateral and medial lobes had different arterial and portal blood supply as well as hepatic and biliary drainage of these lobes. The intrahepatic branches of the proper hepatic artery ran parallel to the branches of the common portal vein in the same lobes of the liver.

CONCLUSIONS

The results of this study are significant for comparative studies among different species of rodents and other experimental animals. Morphology, vasculature and biliary tract of the liver in the mole rat were similar to that of other experimental animals and identified differences may be related to the adaptation to the mode of life and diet of this rodent.

Methanol extracts of Teucrium arduini L. and Teucrium flavum L. induce protective effect against mitomycin C in human lymphocytes in vitro

The study was designed to evaluate antigenotoxic effect of methanol Teucrium arduini and Teucrium flavum extracts against mitomycin C (MMC)-induced chromosome and DNA damage in vitro. Cytokinesis-block micronucleus (CBMN) and comet assays were used to investigate effect of plant extracts in different concentrations (125, 250, 500 and 1000 µg/mL) on human peripheral blood lymphocytes (PBLs). The obtained results showed that the all tested concentrations of T. arduini and the highest concentration of T. flavum significantly reduced the MMC-induced micronucleus (MN) frequency in comparison to positive control (only MMC). There were significantly negative correlations between the extracts concentrations and MN frequencies (Pearson, r = -0.905, p = 0.0001 for T. arduini; r = -0.861, p = 0.0001 for T. flavum). The extracts of both plants further lowered the MMC-decreased nuclear division index (NDI) in a dose dependent-manner (Pearson, r = -0.837, p = 0.001 for T. arduini; r = -0.598, p = 0.040 for T. flavum), but significantly only in the highest concentration (1000 µg/mL). Comet assay showed that extracts reduced MMC-increased genetic damage index (GDI), significantly in the concentrations of 500 and 1000 μg/mL, in comparison with positive control. Based on our results, it can be concluded that methanol T. arduini and T. flavum extracts possess protective proapoptotic and antigenotoxic effect which is indication of their medicinal relevance and use in treatment.

Oxidative stress and DNA damage in peripheral blood mononuclear cells from normal, obese, prediabetic and diabetic persons exposed to adrenaline in vitro

Diabetes represents one of the major health concerns, especially in developed countries. Some hormones such as the stress hormone adrenaline can induce reactive oxygen species (ROS) and may worsen the diabetes. Therefore, the main aim of the investigation was to find out whether peripheral blood mononuclear cells (PBMCs) from normal persons have less DNA damage induced by adrenaline (0.1, 1 and 10 μM) in comparison to PBMCs from obese, prediabetic and diabetic patients. Also, the biochemical parameters of oxidative stress (TBARS, catalase) and lactate dehydrogenase were monitored. It was observed that higher concentrations of adrenaline (1 and 10 μM) induced DNA damage in the obese, prediabetic and diabetic groups. In healthy individuals only the highest concentration of adrenaline caused significant increase in the DNA damage. In summary, total comet score (TCS) comparison has shown significant differences between groups, and DNA damaging effects of adrenaline were most evident in diabetic patients. The results of the biochemical analysis also demonstrate that adrenaline exerts most obvious effects in diabetic individuals which is manifested as significant change of parameters of oxidative stress. In summary, the obtained results demonstrated that diabetics are more sensitive to genotoxic effects of adrenaline and this effect probably resulted from decreased antioxidative defence mechanisms in various stages of progression through diabetes. Therefore, these results could contribute to a better understanding of a role of endocrine factors to damage of cellular biomolecules which could be useful in finding novel therapeutic approaches and lifestyle changes with an aim to lower the possibility of diabetes complications.

Nepeta rtanjensis (Lamiaceae), a plant endemic to the Balkans: Phenolic composition, antioxidant activity, and in vitro antigenotoxic effects in triiodothyronine-induced DNA damage in human lymphocytes

The success of antioxidant therapy in hyperthyroidism implies that disease is mediated by oxidative stress, which is known as one of the causing agents of ageing, degenerative diseases, and cancer. The main objective of our study was to determine possible protective effects of methanolic extract of N. rtanjensis in triiodothyronine (T3)-induced DNA breaks of human lymphocytes under in vitro conditions, based upon plant antioxidant capacity related to its phytochemical profile, mainly its polyphenolic complex. The total phenolic and flavonoid content and the antioxidant activity using in vitro 1,1-dyphenyl-2- picrylhydrazyl reagent (DPPH) was determined in methanolic extracts of plant leaves and flowers. The phenolic compound content of 62.73±1.80mg of GaA/g, exhibited solid antioxidant activity (IC50= 112.59±0.95μg/ml). The antigenotoxic activity of 0.2, 0.5 and 1.0mg/ml N. rtanjensis methanol extracts mixture with 100µM of T3 was studied in human lymphocytes in vitro using the Comet assay. It is supposed that the antigenotoxicity of N. rtanjensis methanol extracts was caused by high presence of chlorogenic acid, rosmarinic acid and rutin, all known as efficient antioxidant bioactive compounds, which were determined by ultrahigh-pressure liquid chromatograph with MS/MS Mass Spectroscopy (UHPLC/-HESI-MS / MS).

Evaluation of the Antigenotoxic Effects of the Royal Sun Mushroom, Agaricus brasiliensis (Higher Basidiomycetes) in Human Lymphocytes Treated with Thymol in the Comet Assay

The aim of this investigation was to evaluate the possible protective activity of Agaricus brasiliensis (=A. blazei sensu Murrill) ethanol extract against thymol-induced DNA damage in human lymphocytes. Before we studied the possible interaction of thymol and A. brasiliensis extract, each component was tested in the comet assay. Thymol significantly increased DNA damage in human lymphocytes at higher concentrations (20, 50, 100, 150, and 200 µg/mL), whereas no genotoxic effect of A. brasiliensis ethanol extract was observed. In simultaneous treatment with thymol (200 µg/mL) and A. brasiliensis ethanol extract (50, 100, 150, and 200 µg/mL), the latter failed to reduce a thymol-induced DNA damaging effect regardless of the applied concentrations. To confirm that thymol induces DNA damage via reactive oxygen species, we performed cotreatment with quercetin. Cotreatment with quercetin (100 and 500 µmol/L) significantly reduced DNA damage caused by thymol (200 µg/mL), indicating that thymol exhibits genotoxicity mainly through induction of reactive oxygen species.

Premature centromere division of metaphase chromosomes in peripheral blood lymphocytes of Alzheimer's disease patients: relation to gender and age

Chromosomal alterations are a feature of both aging and Alzheimer's disease (AD). This study examined if premature centromere division (PCD), a chromosomal instability indicator increased in AD, is correlated with aging or, instead, represents a de novo chromosomal alteration due to accelerating aging in AD. PCD in peripheral blood lymphocytes was determined in sporadic AD patients and gender and age-matched unaffected controls. Metaphase nuclei were analyzed for chromosomes showing PCD, X chromosomes with PCD (PCD,X), and acrocentric chromosomes showing PCD. AD patients, regardless of age, demonstrated increased PCD on any chromosome and PCD on acrocentric chromosomes in both genders, whereas an increase in frequency of PCD,X was expressed only in women. This cytogenetic analysis suggests that PCD is a feature of AD, rather than an epiphenomenon of chronological aging, and may be useful as a physiological biomarker that can be used for disease diagnosis.

Premature centromere division of the X chromosome in neurons in Alzheimer's disease

Premature centromere division (PCD) represents a loss of control over the sequential separation and segregation of chromosome centromeres. Although first described in aging women, PCD on the X chromosome (PCD,X) is markedly elevated in peripheral blood lymphocytes of individuals suffering from Alzheimer disease (AD). The present study evaluated PCD,X, using a fluorescent in situ hybridization method, in interphase nuclei of frontal cerebral cortex neurons from sporadic AD patients and age-matched controls. The average frequency of PCD,X in AD patients (8.60 +/- 1.20%) was almost three times higher (p < 0.01) than in the control group (2.96 +/- 1.20). However, consistent with previous studies, no mitotic cells were found in neurons in either AD or control brain, suggesting an intrinsic inability of post-mitotic neurons to divide. In view of the fact that it has been well-documented that neurons in AD can re-enter into the cell division cycle, the findings presented here of increased PCD advance the hypothesis that deregulation of the cell cycle may contribute to neuronal degeneration and subsequent cognitive deficits in AD.

A study on the genotoxic effects of 8-Cl-cAMP on human lymphocytes in vitro

8-chloro-cyclic adenosine 3',5'-monophosphate (8-Cl-cAMP) is the most potent cAMP analogue that selectively inhibits a variety of cancer cell lines in vitro and tumors in vivo. Its action toward a variety of tumors, especially when coupled with other antitumor agents, have lead to phase I clinical investigations and recently phase II clinical investigations. Until today very little was done to evaluate its genotoxic potential. In order to evaluate its genotoxic potential we used the cytogenetic and cytokinesis block micronucleus assay in vitro on peripheral blood lymphocytes of healthy individuals. Using three concentrations (1 microM, 5 microM and 15 microM), 8-Cl-cAMP in normal human peripheral blood lymphocytes did not induce any cytogenetic aberrations of the structural type [chromatid breakage, isochromatid breakage and gaps], but did induce premature centromere separation (PCS) in all respective doses and increased the frequency of micronuclei (p <0.05) only in the highest dose (15 microM). Antiproliferative action of 8-Cl-cAMP was estimated by using the cytokinesis block nuclear division index (NDI). The results showed a decrease in the NDI of cells exposed to all doses of 8-Cl-cAMP when compared to control. Therefore, the overall results show a genotoxic potential of 8-Cl-cAMP in peripheral blood lymphocytes in vitro.

Analysis of premature centromere division (PCD) of the chromosome 18 in peripheral blood lymphocytes in Alzheimer disease patients

Premature centromere division (PCD) of the chromosome 18 was analyzed by using fluorescent in situ hybridization (FISH) on interphase peripheral blood lymphocytes isolated from six sporadic Alzheimer disease (AD) patients and six healthy elderly controls. Results of FISH analysis revealed that chromosome 18 expressed PCD in 5.18% interphase nuclei of AD patients, and in 2.59% interphase nuclei of age-matched controls (p<0.05). Our study also showed that hypoploidy and hyperploidy frequency for chromosome 18 exhibited a statistically significant increase in the AD group compared to the control one. The increase in spontaneous aneuploidy of chromosome 18 in AD patients which is correlated with PCD shows that deregulation of the time of centromere separation can be considered as a manifestation of chromosome instability leading to aneuploidy.

Sister chromatid exchange and micronuclei in human peripheral blood lymphocytes treated with thyroxine in vitro

Thyroid hormones enhance the metabolic rate and the aerobic metabolism favoring oxidative stress, which is accompanied by induction of damage to cellular macromolecules including the DNA. The aim of the present study was to investigate the ability of thyroxine to induce sister chromatid exchange and micronuclei, and to modulate cell-cycle kinetics in cultured human lymphocytes. Eight experimental concentrations of thyroxine were used, ranging from 2 x 10(-9) to 0.5 x 10(-4)M. Treatment with thyroxine increased the frequency of SCE per cell at the higher concentrations (1.5 x 10(-6), 0.5 x 10(-5), 1.5 x 10(-5) and 0.5 x 10(-4)M). On the other hand, there were no significant aneugenic and/or clastogenic effects observed in the cytokinesis-block micronucleus assay. The results show that thyroxine acted as a relatively weak clastogen compared with the positive control N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). In addition to the genotoxic effects, two high concentrations of thyroxine decreased the mitotic index and caused cell-cycle delay. In conclusion, thyroxine exhibited weak clastogenic effects only at high concentrations. Therefore, effects in humans might appear in cases of acute thyroxine overdose.

Mutagenic activity of estradiol evaluated by an in vitro micronucleus assay. Short communication

The objective of the present study was to evaluate possible genetic changes in cultured human lymphocytes treated with estradiol, using the cytokinesis block micronucleus assay. Eight experimental concentrations of estradiol were used (range from 10(-10) M to 0.7 x 10(-4) M). The obtained results indicate that estradiol exhibits aneugenic and/or clastogenic effects, expressed as increased frequency of micronucleated lymphocytes at two highest experimental concentrations used in this investigation. In addition to genotoxic effects, these concentrations decreased the cytokinesis block proliferation index (CBPI) and percentage of binucleated cells, indicating the cell cycle delay and possible cytotoxic effects. In conclusion, estradiol treatment might represent a human health risk, especially if overdosed or used for a prolonged period of time.

Analysis of sister-chromatid exchanges and micronuclei in cultured human lymphocytes treated with insulin

Insulin is an anabolic hormone that may facilitate development of malignant diseases in various susceptible tissues due to stimulation of mitotic divisions. In this work, an evaluation of mitogenic and genotoxic effects of human recombinant insulin has been performed in cultures of human peripheral blood lymphocytes. Genotoxic effects were studied by the following test systems: (1) in vitro SCE test, and (2) cytokinesis-blocked micronucleus assay. The obtained results indicate that insulin stimulates mitotic division at an optimal concentration of 10(-8) M. On the other hand, insulin has not exhibited genotoxic properties under experimental conditions in this investigation.

In vitro cytogenetic analysis of the effects of oxytocin on human peripheral blood lymphocytes

The purpose of this study was to determine possible genotoxic and cytotoxic (or mitogenic) effects of high concentrations of oxytocin, active component of Syntocinon in cultures of human peripheral blood lymphocytes. Two test systems were used: (1) analysis of numerical and structural chromosome aberrations, and (2) the in vitro sister chromatid exchange (SCE) test. On the basis of the results obtained it can be concluded that oxytocin does not express any genotoxical properties. Furthermore, the mitotic index did not change significantly.