Dual Immunofluorescence of γH2AX and 53BP1 in Human Peripheral Lymphocytes.

Double strand breaks (DSBs) are one of the most severe lesions that can occur in cell nuclei, and, if not repaired, they can lead to severe outcomes, including cancer. The cell is, therefore, provided with complex mechanisms to repair DSBs, and these pathways involve histone H2AX in its phosphorylated form at Ser-139 (namely γH2AX) and p53 binding protein 1 (53BP1). As both proteins can form foci at the sites of DSBs, identification of these markers is considered a suitable method to study both DSBs and their kinetics of repair. According to the molecular processes that lead to the formation of γH2AX and 53BP1 foci, it could be more useful to investigate their co-localization near the DSBs in order to set up an alternative approach that allows quantifying DSBs by the simultaneous detection of two DNA damage markers. Thus, this protocol aims to assess the genomic damage induced in human lymphocytes by the radiomimetic agent bleomycin through the presence of γH2AX and 53BP1 foci in a dual immunofluorescence. Using this methodology, we also delineated the variation in the number of γH2AX and 53BP1 foci over time, as a preliminary attempt to study the repair kinetics of bleomycin-induced DSBs.

Oxidative and DNA damage in obese patients undergoing bariatric surgery: A one-year follow-up study.

The pathogenesis of obesity and related comorbidities has long been associated with oxidative stress. The excess of adipose tissue contributes to the production of free radicals that sustain both a local and a systemic chronic inflammatory state, whereas its reduction can bring to an improvement in inflammation and oxidative stress. In our work, using the fluorescent lipid probe BODIPY® 581/591 C11 and the γH2AX foci assay, a well-known marker of DNA double strand breaks (DSB), we evaluated the extent of cell membrane oxidation and DNA damage in peripheral blood lymphocytes of normal weight (NW) controls and obese patients sampled before and after bariatric surgery. Compared to NW controls, we observed a marked increase in both the frequencies of oxidized cells or nuclei exhibiting phosphorylation of histone H2AX in preoperatory obese patients. After bariatric surgery, obese patients, resampled over one-year follow-up, improved oxidative damage and reduced the presence of DSB. In conclusion, the present study highlights the importance for obese patients undergoing bariatric surgery to also monitor these molecular markers during their postoperative follow-up.

Assessing the cytotoxic/genotoxic activity and estrogenic/antiestrogenic potential of essential oils from seven aromatic plants.

Alternative therapies with new drugs are needed because the clinical efficacy of conventional chemotherapy is often reduced due to collateral effects. Many natural products of plant origin, including essential oils (EOs) have proved to be effective in prevention and therapy of several diseases such as bacterial infections, chronic diseases and cancer. In the present study, we investigated some biological activities of EOs extracted from seven plants: Rosmarinus officinalis, Salvia somalensis, Thymus vulgaris, Achillea millefolium, Helichrysum italicum, Pistacia lentiscus, Myrtus communis. In particular, we evaluated the cytotoxic and genotoxic activity using the cytochalasin B-blocked micronucleus assay (CBMN) in human peripheral lymphocytes, cytotoxicity in a human ovarian carcinoma cell line (A2780), and the estrogenic/antiestrogenic activity using a yeast strain expressing the human estrogen receptor alpha (ERα). Our results show that most EOs can have a strong cytotoxic and a slight/moderate genotoxic effect on human peripheral lymphocytes, and also a pronounced cytotoxic effect in A2780 cells. In addition, some EOs seem to have a marked antiestrogenic activity that could potentially perturb the estrogen-dependent tissues.

Increased level of DNA damage in some organs of obese Zucker rats by γ-H2AX analysis.

In a recent study, we showed that lymphocytes of obese Italian children/adolescents displayed levels of double strand breaks (DSB), assayed as serine 139-phosphorylated histone H2AX (γ-H2AX), about eightfold higher than normal weight controls, and that 30% of this damage-generated micronuclei. These findings suggested that obese children could be at increased risk of obesity-mediated cancer later in life. We therefore aimed to assess the level of γ-H2AX in a genetic animal model of obesity (Zucker rat) to identify a genotoxic/carcinogenic risk in some organs. The DSB marker was studied in 3- to 4-week-old rats and in 9- to 13-week-old rats. Paraffin-embedded sections of heart, thyroid, liver, pancreas, lung, kidney, esophagus, and gut from the fa-/fa- (obese) and the fa+/fa- (lean) control animals were processed for immunohistochemistry detection of γ-H2AX. Pancreas (0.0624 ± 0.0195), lung (0.1197 ± 0.0217), esophagus (0.1230 ± 0.0351), kidney (0.1546 ± 0.0149), and gut (0.1724 ± 0.0352) of 9- to 13-week-old obese rats showed a higher proportion of γ-H2AX-positive nuclei, than their lean counterparts (0.0092 ± 0.0033, 0.0416 ± 0.0185, 0.0368 ± 0.0088, 0.0686 ± 0.0318, and 0.0703 ± 0.0239, respectively). No difference was seen in the 3- to 4-week-old age group with regard to obesity, indicating that the DNA damage increased with older age of the rats. We hypothesize that the organs of the obese animals showing high levels of DSB could represent target tissues for the development of obesity-related cancers. Environ. Mol. Mutagen. 58:477-484, 2017. © 2017 Wiley Periodicals, Inc.

Genomic instability and cellular stress in organ biopsies and peripheral blood lymphocytes from patients with colorectal cancer and predisposing pathologies.

Inflammatory bowel disease (IBD) and polyps, are common colorectal pathologies in western society and are risk factors for development of colorectal cancer (CRC). Genomic instability is a cancer hallmark and is connected to changes in chromosomal structure, often caused by double strand break formation (DSB), and aneuploidy. Cellular stress, may contribute to genomic instability. In colorectal biopsies and peripheral blood lymphocytes of patients with IBD, polyps and CRC, we evaluated 1) genomic instability using the γH2AX assay as marker of DSB and micronuclei in mononuclear lymphocytes kept under cytodieresis inhibition, and 2) cellular stress through expression and cellular localization of glutathione-S-transferase omega 1 (GSTO1). Colon biopsies showed γH2AX increase starting from polyps, while lymphocytes already from IBD. Micronuclei frequency began to rise in lymphocytes of subjects with polyps, suggesting a systemic genomic instability condition. Colorectal tissues lost GSTO1 expression but increased nuclear localization with pathology progression. Lymphocytes did not change GSTO1 expression and localization until CRC formation, where enzyme expression was increased. We propose that the growing genomic instability found in our patients is connected with the alteration of cellular environment. Evaluation of genomic damage and cellular stress in colorectal pathologies may facilitate prevention and management of CRC.

Transcriptional alterations of ET-1 axis and DNA damage in lung tissue of a rat obesity model.

Obesity has been implicated in the development of many cancers. This can lead to genome damage, especially in the form of double-strand break, the presence of which is now easily detected through nuclear phosphorylation of histone H2AX (γ-H2AX) focus assay. Recently, the endothelin (ET) axis has also been shown to have a role in the growth and progression of several tumors, including lung cancer. The aim of this study was to evaluate the ET-1 system transcriptional alterations and γ-H2AX in lung tissue of Zucker rats subdivided into obese (O, n=22) and controls (CO, n=18) rats: under either fasting conditions (CO(fc)-O(fc)) or acute hyperglycemia (CO(AH)-O(AH)). Significantly higher prepro-ET-1 (p=0.05) and ET-converting enzyme (ECE)-2 mRNA expression was observed in O with respect to CO. A significant positive association was observed between prepro-ET-1 and ET-A in the whole rat population (p=0.009) or in the obese group alone (p=0.007). The levels of γ-H2AX in O and in O(AH) rats were significantly higher (p=0.019) than in the corresponding CO and CO(AH) rats (p=0.038). The study shows an inappropriate secretion of ET-1 in O animals with a parallel DNA damage in their lungs, providing novel mechanisms by which ET receptor antagonist may exert organ protection.

High levels of γ-H2AX foci and cell membrane oxidation in adolescents with type 1 diabetes.

Oxidative stress caused by an excess of free radicals is implicated in the pathogenesis and development of type 1 diabetes mellitus (T1DM) and, in turn, it can lead to genome damage, especially in the form of DNA double-strand break (DSB). The DNA DSB is a potentially carcinogenic lesion for human cells. Thus, we aimed to evaluate whether the level of oxidative stress was increased in peripheral blood lymphocytes of a group of affected adolescents. In 35 T1DM adolescents and 19 healthy controls we assessed: (1) spontaneous and H2O2-induced oxidation of cell membrane using a fluorescence lipid probe; (2) spontaneous and LPS-induced expression of iNOS protein and indirect NO determination via cytofluorimetric analysis of O2(-); (3) immunofluorescent detection of the basal level of histone H2AX phosphorylation (γ-H2AX foci), a well-validated marker of DNA DSB. In T1DM, the frequencies of oxidized cells, both spontaneous and H2O2-induced (47.13±0.02) were significantly higher than in controls (35.90±0.03). Patients showed, in general, both a reduced iNOS expression and production of NO. Furthermore, the level of spontaneous nuclear damage, quantified as γ-H2AX foci, was markedly increased in T1DM adolescents (6.15±1.08% of γ-H2AX(+) cells; 8.72±2.14 γ-H2AXF/n; 9.26±2.37 γ-H2AXF/np), especially in females. In the present study, we confirmed the role that oxidative stress plays in the disease damaging lipids of cell membrane and, most importantly, causing genomic damage in circulating white blood cells of affected adolescents. This also indicates that oxidative stress can affect several tissues in the body. However, although the observed DNA damage is a clear indication that the proper DNA repair mechanisms are activated, the risk for young T1DM subjects of developing not only cardiovascular complications but also some type of cancer cannot be ruled out. In this view, females, probably due to hormonal imbalance typical of adolescence, might represent a more susceptible population.

Kinetics of nuclear phosphorylation (γ-H2AX) in human lymphocytes treated in vitro with UVB, bleomycin and mitomycin C.

After double-strand break induction, formation of γ-H2AX foci due to phosphorylation at Ser-139 of histone H2AX represents an early event of the DNA damage response (DDR). γ-H2AX foci are then rapidly dephosphorylated as signal for the subsequent recruitment of effector proteins. The induction and disappearance of the foci can be, therefore, used to monitor the functioning of the DDR machinery in a cell population exposed to genotoxic stress. Here, we investigated the time-course of γ-H2AX in unstimulated or cultured peripheral lymphocytes in vitro treated with UVB, bleomycin and mitomycin C (MMC). Once the mutagen exposure was performed, cells were harvested at different interval times from 0.5 to 5h. The results show that (i) in 20-h stimulated peripheral lymphocytes, UVB irradiation caused extensive and dose-dependent increases in nuclear phosphorylation, and disappearance of γ-H2AX foci progressed, proportionally to the UV fluence, with increasing the harvesting time; (ii) UVB-exposed G0 cells cultured for 20-h post-irradiation displayed low amounts of DNA phosphorylation, depicting a time-course in which the maximum effect was reached at 0.5h and dephosphorylation started after 1h; (iii) treatment of unstimulated lymphocytes with bleomycin sulphate induced an increase in nuclear phosphorylation of several folds higher than that of untreated cells, depicting kinetics comparable to those observed for UVB-exposed G1 cells; (iv) in stimulated cells, MMC caused a severe and dose-dependent high degree of H2AX phosphorylation together with a very slower kinetic of dephosphorylation with respect to the other experimental treatments. This study confirms the feasibility of the γ-H2AX focus assay as a genotoxic end-point and supports the view that the proposed type of analysis should be introduced in biomonitoring studies of human populations. This could also represent a feasible and useful tool in the screening and diagnosis of precancerous states or very early stages of other diseases.

Effects of spindle poisons in peripheral human lymphocytes by the in vitro cytokinesis-block micronucleus assay.

The search for micronuclei (MN) in binucleated cells is not always the best choice to recognize microtubule-perturbing agents, as they give rise to (micronucleated) mononucleated cells, mainly via mitotic slippage. We therefore treated peripheral lymphocytes with vincristine (VCR), nocodazole (NOC) and colcemid (COL): (i) to quantify the formation of MN in mononucleated cells and the occurrence of abnormal mitoses (c-anaphases, endoreduplicated or tetraploid metaphases); (ii) to investigate the role of cytokinesis inhibition in determining or modulating the cytogenetic effects induced by the spindle poisons (we used either cytochalasin B (cyt B) or latrunculin A, a cytokinesis inhibitor that acts differently as compared with cyt B); (iii) to assess the ploidy of cells bearing MN by fluorescence in situ hybridisation (FISH) analysis; and (iv) to evaluate the levels of the mitotic arrest deficient (MAD2) protein, that blocks the cell at the metaphase-anaphase transition, by immunoblotting. We observed the induction of numerous abnormal mitoses and tetraploid interphase nuclei, as well as of MN in mononucleated cells, a high percentage of which had a diploid complement. We also found that the effects were generally not dose but chemical dependent, where NOC was proven to be more effective than COL and VCR in inducing overall MN formation and, specifically, diploid micronucleated lymphocytes. Aneugens damaged cells to a greater extent in the presence of cytokinesis inhibitors rather than in their absence. MAD2 protein was expressed in controls to an extent reflecting the amount of lymphocytes which were initially in the G2/M transition phase. The same trend was seen in aneugen-treated cells where MAD2 levels decreased with increasing spindle poison concentration. Here, we demonstrate that micronucleated mononucleated cells and aberrant mitoses can be considered useful markers of exposure to aneugens-like spindle poisons causing preferentially, but not exclusively, mitotic slippage. Assessment of MAD2 levels can be used to confirm the cell-damaging activity of the compounds.

Nuclear damage in peripheral lymphocytes of obese and overweight Italian children as evaluated by the gamma-H2AX focus assay and micronucleus test.

Childhood obesity, often characterized by a chronic low-grade inflammation, has been associated with an increased risk of developing some types of cancer later in life. Nuclear γ-H2AX foci represent the first detectable response of cells to DNA tumorigenesis lesions, such as the double-strand breaks (DSBs). An excess of micronucleated peripheral lymphocytes was found in subjects with cancer or inflammation-based diseases. We set out to investigate the expression of genome damage, from DNA lesions to chromosome mutations (micronuclei), in overweight and obese children. Using the γ-H2AX focus assay and micronucleus (MN) test, we analyzed peripheral lymphocytes from 119 Italian children classified as normal weight (n=38), overweight (n=20), or obese (n=61). Cultures treated with bleomycin (BLM) were also set up for each child in both assays to check functioning of the apparatus that ensures DNA integrity. We measured serum TNF-α, IL-6, and C-reactive protein (CRP) as markers of inflammation. Overweight and obese children had significantly higher levels of H2AX phosphorylation (0.0191±0.0039 and 0.0274±0.0029 γ-H2AXF/n) and increased MN frequencies (2.30±0.25 and 2.45±0.22‰) than normal-weight children (0.0034±0.0006 γ-H2AXF/n, and 0.92±0.12‰ MN), while all subjects responded to BLM induction, irrespective of their weight status. The fold increase of spontaneous MN frequencies in overweight and obese subjects was 2.5 and 2.7, respectively, well below the corresponding increase in the γ-H2AX foci (5.6- and 8.0-fold, respectively). IL-6 and CRP mean values were significantly higher in obese and overweight children than in controls. Here, we demonstrated that peripheral cells of overweight and obese children showed increased levels of DSBs, which were not completely repaired as part of them has been converted into micronuclei. Characterization of childhood obesity inflammation could be implemented using molecular markers of genome damage.

Antiestrogenic and antigenotoxic activity of bee pollen from Cystus incanus and Salix alba as evaluated by the yeast estrogen screen and the micronucleus assay in human lymphocytes.

The estrogenic/antiestrogenic activity and the genotoxicity/antigenotoxicity of bee pollen from Salix alba L. and Cystus incanus L. and its derivative extracts in yeast and human cells was investigated. All samples showed a marked inhibitory effect on the activity of the natural estrogen 17 beta-estradiol (higher than 90% for extracts 2) and failed to cause estrogenic activity and chromosome damage. At least one preparation from each species showed a marked antigenotoxic effect against the action of the anticancer drugs mytomicin C, bleomycin, and vincristine. Bee pollens from C. incanus and S. alba were found to be neither genotoxic nor estrogenic as well as effective estrogen inhibitors, and able to reduce the chromosome damage induced by the three cancer drugs used, thus supporting their use as a safe food supplement and future chemoprotective/chemopreventive agents.

Protective effects of plicatin B on micronucleus induction in cultured human lymphocytes by different mutagens.

Among flavonoids, chalcones have been identified as interesting compounds having antioxidant, antimutagenic and antitumour properties. In this study we have evaluated the clastogenicity of plicatin B on human lymphocytes (whole blood and isolated lymphocytes) and its anticlastogenic activity, in the same cellular systems, using mitomycin C (MMC), radio-mimetic bleomycin (BL) and hydrogen peroxide (H2O2) as reference clastogens. Plicatin B per se resulted cytotoxic at high dose but non-clastogenic. The clastogenic effects induced by MMC and BL were significantly reduced (-33%) whereas with H2O2 the protective effect of plicatin B was observed (-62%) only at the greater H2O2 dose. The anticlastogen effects of plicatin B were effective when the chalcone was introduced in the culture, 1 h before the reference clastogens.

Licoflavone C attenuates the genotoxicity of cancer drugs in human peripheral lymphocytes.

Flavonoids exhibit a wide spectrum of biological activities that can lead to beneficial effects for human health. The search for cytotoxic, genotoxic and/or antimutagenic natural compounds is therefore of great relevance, especially in cancer chemotherapy. In view of this, we screened the potential genotoxicity/antigenotoxicty of licoflavone C (LFLC) - a naturally occurring prenyl-flavone extracted from Genista ephedroides - using the micronucleus (MN) assay on stimulated and cytochalasin B-blocked human lymphocytes. LFLC did not increase the spontaneous MN level up to 600 microM final concentration where a strong toxicity was seen to occur. We therefore performed an antigenotoxicity assay against the two mutagenic anticancer drugs, mitomycin C (MMC) and daunorubicin (DAU), using two non-toxic LFLC concentrations (0.1 microM and 1.0 microM). The MN frequencies induced by 0.025 microg/ml or 0.05 microg/ml DAU were significantly lowered by 45.4% or 46.6% and 41.8% or 44.8% at LFLC 0.1 and 1.0 microM, respectively. After treatment with 0.085 microg/ml or 0.17 microg/ml MMC, we detected a reduction in genotoxicity of 35.1% or 37.0% and of 38.0% or 35.8% at LFLC 0.1 and 1.0 microM, respectively. In conclusion, LFLC was proven to be protective toward the chromosome damage induced by DAU or MMC in cultured human peripheral lymphocytes.

No evidence of chromosome damage in children and adolescents with differentiated thyroid carcinoma after receiving 131I radiometabolic therapy, as evaluated by micronucleus assay and microarray analysis.

PURPOSE: As (131)I therapy, used to achieve ablation of thyroid gland remnant, can cause chromosome damage in cultured peripheral lymphocytes especially, we investigated whether administration of radioiodine may induce early genome damage in peripheral T lymphocytes of adolescents with differentiated thyroid carcinoma (DTC). METHODS: We studied 11 patients, aged 14.8 +/- 3.1 years, who assumed (131)I (range: 1.11-4.44 GBq) to ablate thyroid remnant. A blood sample for micronucleus assay and for evaluating expression of some genes involved in the DNA repair or the apoptosis pathways was obtained from each patient 1 h before (T(0)) and 24 (T(1)) and 48 h (T(2)) post-radioiodine administration. RESULTS: Compared to T(0), we did not find any difference in the number of micronucleated cells at both T(1) and T(2) in any subject. Nine out of 11 patients had altered expression levels in a majority of the DNA repair and apoptosis genes at T(1), which decreased at T(2). CONCLUSIONS: We demonstrated for the first time that peripheral cells of DTC children and adolescents who received (131)I at a mean dosage of 3.50 +/- 0.37 GBq did not show chromosome damage within 48 h from the end of radiometabolic therapy. This may be due to a prompt activation of the cell machinery that maintains the integrity of the genome to prevent harmful double-strand breaks from progressing to chromosome mutations, either by repairing the lesions or by eliminating the most seriously damaged cells via apoptosis.

Induction of chromatid-type aberrations in peripheral lymphocytes of hospital workers exposed to very low doses of radiation.

Radiological personnel represent workers exposed to low cumulative doses of radiation. As their surveillance is generally based on physical dosimetry, there is little or inconclusive information on biological effects due to radiation exposure at these doses. We aimed to explore the extent of chromosomal damage in circulating lymphocytes of hospital workers (technicians, nurses and physicians) chronically exposed to a very low level of radiation using conventional and molecular cytogenetic analyses (chromosome painting with chromosomes #2, #3 and #10 as probe cocktail). Compared with controls, exposed workers displayed a significant increase in the frequency of aberrant lymphocytes (1.26+/-0.11/100 cells versus 1.63+/-0.17/100 cells). In particular, exposed technicians showed significantly higher mean values than nurses or physicians (3.68+/-1.17/100 cells versus 1.36+/-0.18/100 cells and 1.36+/-0.09/100 cells, respectively). Interestingly, we found that the chromosomal damage was prevalently expressed as chromatid-type aberrations. Chromosome painting indicated that the frequency of chromosome rearrangements (CR; translocations and dicentrics pooled together) was approximately comparable between radiological workers and the control group. Moreover, we did not detect any significant difference due to radiation exposure when CR rates were considered separately for each of the three chromosomes in the probe cocktail.

Analysis of chromosome damage in circulating lymphocytes of radiological workers affected by thyroid nodules.

The aim of our study was to assess whether or not thyroid nodularity in combination with occupational exposure to low levels of ionising radiation would be correlated with chromosome damage in peripheral lymphocytes. Conventional chromosome-aberration analysis was performed on a group of 92 hospital workers with or without thyroid nodules. On the basis of measurements of their exposure levels, the workers were classified into a low (mean total level=0.03 mSv), medium (mean total level=1.04 mSv) or high (mean total level=8.60 mSv) exposure category. Our results indicate that among workers with thyroid nodules, the high-exposed workers showed significantly higher levels of both total (2.35+/-0.34 per 100 cells) and chromosome-type aberrations (1.46+/-0.20 per 100 cells) than medium-exposed (0.98+/-0.42 and 0.68+/-0.25 per 100 cells, respectively) or low-exposed workers (1.11+/-0.29 and 0.58+/-0.17 per 100 cells, respectively). Workers without thyroid nodules had comparable frequencies of chromosome aberrations among the three exposure categories. To our knowledge, this is the first study revealing a slight, but significant increase of chromosome damage in peripheral lymphocytes from hospital workers who developed thyroid nodules under conditions of occupational exposure to radiation well below the threshold limit for the workplace. The existence of a possible association between chromosome aberrations and development of thyroid nodularity will be discussed.

In vitro mutagenicity studies of the antiretrovirals AZT, Didanosine, and 3TC and a plant antiviral extract Secomet-V derived from the Trifollium species.

The plant extract Secomet-V has previously been shown by Kotwal et al. to have potent antiviral activity. It was tested for mutagenicity with the Ames gene mutation test in Salmonella and the chromosome damage (clastogenic) micronucleolus (MN) test in human lymphocytes. These tests predict long-term carcinogenesis activity of the agents tested. Secomet-V (with charcoal added) demonstrated weak clastogenic activity, but powerful mutagenic activity in the Ames test with the addition of exogenous metabolic activation. The mutagenic activity of the conventional antiretroviral drugs AZT, Didanosine (DID), and 3TC alone and in dual combinations was also assessed for the first time for Salmonella mutagenicity without any mutagenic effects. AZT, DID, and 3TC have also been tested for MN induction; DID and 3TC resulted negatively, whereas AZT was positive in a dose-related manner. The dual combinations of AZT and DID, 3TC and DID plus 3TC did not result in any additive or synergistic effect. Purification in the absence of charcoal results in a drastic reduction in extract mutagenicity, which is almost reduced completely by further ultrafiltration (cutoff <3,000 Da). This fraction, which is a mixture of molecules of less than 3,000 Da, still possesses the capability to induce sister chromatid exchanges in human lymphocytes. This could be due to residual mutagenicity or, more likely, to the slowdown of the DNA replication process. These findings open new possibilities for HIV therapy, because this antiviral activity of Secomet-V purified in the absence of charcoal and further filtered through a 3,000-Da filter is devoid of mutagenic activity and therefore safe for long-term use.