A simple and rapid fluorescence in situ hybridization microwave protocol for reliable dicentric chromosome analysis

Cytokinesis Blocked Micronuclei Aberration Analysis

Cytokinesis blocked micronuclei (CBMN) assay is a rapid and sensitive analysis of chromosome aberrations and miss assortments during cell division. Genotoxic agent exposure produces DNA damage and chromosome fragments. Fragmented chromosomes without centromere failed to attach kinetochore which segregates a pair of homologous chromosomes to each daughter cells at cytokinesis, hence leading to form micronuclei. Chromosome or fragments of chromosome can also form micronuclei when they are not accurately sorted to daughter cells. Using cytochalasin B, an actin inhibitor, blocks cytokinesis of which completion leads serration appearance formed with two daughter cells while nuclei segregation is undergoing. As a result, one cell having two daughter nuclei, i.e., binucleated cell, is produced. By analyzing these binucleated cells, chromosome aberrations can be estimated as well as popular chromosome aberration analysis. Frequency of micronuclei formation predicts the testing agents' genotoxicity. By combining use with centromere-specific probes or DNA damage signal probes, the nature of genotoxicity of tested agents can be estimated.

Cytotoxicity and Mutagenicity of Narrowband UVB to Mammalian Cells

Phototherapy using narrowband ultraviolet-B (NB-UVB) has been shown to be more effective than conventional broadband UVB (BB-UVB) in treating a variety of skin diseases. To assess the difference in carcinogenic potential between NB-UVB and BB-UVB, we investigated the cytotoxicity via colony formation assay, genotoxicity via sister chromatid exchange (SCE) assay, mutagenicity via hypoxanthine phosphoribosyltransferase (HPRT) mutation assay, as well as cyclobutane pyrimidine dimer (CPD) formation and reactive oxygen species (ROS) generation in Chinese hamster ovary (CHO) and their NER mutant cells. The radiation dose required to reduce survival to 10% (D₁₀ value) demonstrated BB-UVB was 10 times more cytotoxic than NB-UVB, and revealed that NB-UVB also induces DNA damage repaired by nucleotide excision repair. We also found that BB-UVB more efficiently induced SCEs and HPRT mutations per absorbed energy dosage (J/m²) than NB-UVB. However, SCE and HPRT mutation frequencies were observed to rise in noncytotoxic dosages of NB-UVB exposure. BB-UVB and NB-UVB both produced a significant increase in CPD formation and ROS formation (p < 0.05); however, higher dosages were required for NB-UVB. These results suggest that NB-UVB is less cytotoxic and genotoxic than BB-UVB, but can still produce genotoxic effects even at noncytotoxic doses.

Ascorbic Acid 2-Glucoside Pretreatment Protects Cells from Ionizing Radiation, UVC, and Short Wavelength of UVB

Ascorbic acid 2-glucoside (AA2G), glucosylated ascorbic acid (AA), has superior properties for bioavailability and stability compared to AA. Although AA2G has shown radioprotective properties similar to AA, effects for UV light, especially UVC and UVB, are not studied. AA2G was tested for cytotoxicity and protective effects against ionizing radiation, UVC, and broadband and narrowband UVB in Chinese hamster ovary (CHO) cells and compared to AA and dimethyl sulfoxide (DMSO). Pretreatment with DMSO, AA, and AA2G showed comparative protective effects in CHO wild type and radiosensitive xrs5 cells for cell death against ionizing radiation with reducing the number of radiation-induced DNA damages. Pretreatment with AA and AA2G protected CHO wild type and UV sensitive UV135 cells from UVC and broadband UV, but not from narrowband UVB. DMSO showed no protective effects against tested UV. The UV filtration effects of AA and AA2G were analyzed with a spectrometer and spectroradiometer. AA and AA2G blocked UVC and reduced short wavelengths of UVB, but had no effect on wavelengths above 300nm. These results suggest that AA2G protects cells from radiation by acting as a radical scavenger to reduce initial DNA damage, as well as protecting cells from certain UVB wavelengths by filtration.

PNA Telomere and Centromere FISH Staining for Accurate Analysis of Radiation-Induced Chromosomal Aberrations

Dicentric and centric ring chromosomes are used for radiation-induced damage analysis and biodosimetry after radiation exposure. However, Giemsa stain-based cytogenetic analysis is labor-intense and time-consuming. Moreover, the disadvantage of Giemsa based chromosome analysis is a potential poor reproducibility when researchers are not fully trained for analysis. These problems come from analysis of morphological abnormality of chromosomal aberrations. Locus-specific FISH probes were used to overcome this problem. Centromere probes can visualize centromere locations and help identify dicentric chromosomes and centric rings. Telomere probes help to identify terminal deletion and telomere fusions. Probes were originally designed with a DNA probe but Peptide nucleic acid (PNA) probes took the place of DNA probes. This chapter introduces PNA telomere and centromere FISH staining and accurate analysis of chromosomal aberrations.

Modified PNA Telomere and Centromere FISH Protocols

Fluorescence in situ Hybridization (FISH) utilizes peptide nucleic acid (PNA) probes to identify specific DNA sequences. PNA probes have been effectively used to identify chromosome aberrations and have been shown to greatly aid in biodosimetery assays involved in identifying dicentrics. Traditional techniques have required the heat denaturing of the DNA in formamide followed by multiple hours at moderated temperatures to allow the probe to hybridize to its specific target. Over the past 30 years, advancements in both protocols and probes have made FISH a more reliable technique for both biological research and medical diagnostics, additionally the protocol has been shortened to several minutes. We will introduce two modified PNA FISH protocols, a rapid microwave-based approach and nonclassical hybridization protocol.

The Effect of Green and Black Tea Polyphenols on BRCA2 Deficient Chinese Hamster Cells by Synthetic Lethality through PARP Inhibition

Tea polyphenols are known antioxidants presenting health benefits due to their observed cellular activities. In this study, two tea polyphenols, epigallocatechin gallate, which is common in green tea, and theaflavin, which is common in black tea, were investigated for their PARP inhibitory activity and selective cytotoxicity to BRCA2 mutated cells. The observed cytotoxicity of these polyphenols to BRCA2 deficient cells is believed to be a result of PARP inhibition induced synthetic lethality. Chinese hamster V79 cells and their BRCA2 deficient mutant V-C8, and V-C8 with gene complemented cells were tested against epigallocatechin gallate and theaflavin. In addition, Chinese hamster ovary (CHO) wild-type cells and rad51D mutant 51D1 cells were used to further investigate the synthetic lethality of these molecules. The suspected PARP inhibitory activity of epigallocatechin and theaflavin was confirmed through in vitro and in vivo experiments. Epigallocatechin gallate showed a two-fold increase of cytotoxicity to V-C8 cells compared to V79 and gene complimented cells. Compared to CHO wild type cells, 51D1 cells also showed elevated cytotoxicity following treatment with epigallocatechin gallate. Theaflavin, however, showed a similar increase of cytotoxicity to VC8 compared to V79 and gene corrected cells, but did not show elevation of cytotoxicity towards rad51D mutant cells compared to CHO cells. Elevation of sister chromatid exchange formation was observed in both tea polyphenol treatments. Polyphenol treatment induced more micronuclei formation in BRCA2 deficient cells and rad51D deficient cells when compared against the respective wild type cells. In conclusion, tea polyphenols, epigallocatechin gallate, and theaflavin may present selective cytotoxicity to BRCA2 deficient cells through synthetic lethality induced by PARP inhibition.

Comparison of DNA damages in blood lymphocytes of indoor swimming pool lifeguards with non-lifeguards athletes

Chlorination has been used as a major disinfectant process for swimming pool water in many countries. The purpose of this study is to compare the DNA damage of the blood lymphocytes in indoor pool lifeguards with non-lifeguards athletes. We performed a study in which the participants were Gonabad's lifeguards. We chose 30 participants (15 male and 15 female) for each group. We collected vein blood samples from each participant in both exposed and control group. The lymphocytes were isolated from the whole blood by ficoll, and the cell viability was determined by the trypan blue. The alkaline Comet assay was also performed on lymphocytes in order to measure the DNA damage. All the parameters indicated that the DNA damage was significantly greater in lifeguards group than control group (p < 0.001). Also, the results revealed a statistically significant higher level of DNA damage in females as evident by an increase in the tail length (μm) [8.97 ± 4.21 for females as compared to 4.32 ± 1.33 for males (p = 0.001)], tail DNA (%) [4.18 ± 1.27 for females as compared to 3.14 ± 0.94 for males (p = 0.016)] and tail moment (μm) [0.68 ± 0.53 for females and 0.26 ± 0.14 for males (p = 0.010)]. There was also a significant positive correlation between DNA damage and the duration of work (P < 0.001).

Rapid detection of t(15;17)(q24;q21) in acute promyelocytic leukaemia by microwave-assisted fluorescence in situ hybridization

Acute promyelocytic leukaemia (APL) is a hematologic malignancy characterized by the rearrangement of the PML and RARα genes, mostly due to a reciprocal chromosomal translocation t(15;17)(q24;q21). A quick APL diagnosis is essential for starting a prompt suitable therapy. We describe a new rapid diagnostic laboratory approach to detect the PML-RARα rearrangement, which gives clear genetic results within 30 min of hybridization. It combines quick cell harvesting, fluorescence in situ hybridization performed with commercial DNA probe and microwave beams supplied by a domestic microwave oven. Copyright © 2015 John Wiley & Sons, Ltd.

Effects of microwaves (950 MHZ mobile phone) on morphometric and apoptotic changes of rabbit epididymis

The effect of mobile phone radiation on human reproduction system is still a matter of debate. In this study, 18 male rabbits were randomly divided into two experimental groups and one control group. Experimental groups received simulated microwaves with the frequency of 950 MHz and the output power of 3 and 6 watts for 2 weeks, 2 h a day. After a week of rest, the microscopic slides from the quada of the excised epididymis were prepared. Then, the diameter of epididymis, the height of epithelium and the number of apoptotic cells in epithelium in study groups were determined. The data were compared using spss software and one-way anova test. The epithelial height and diameter of the epididymis in 3 watt and 6 watt groups had a significant decrease compared to the control group (P < 0.001), while the testosterone level only in 6 watt group was significantly decreased compared to control group. The rate of apoptosis in the epithelial cells of the epididymis had a significant increase only in 6 watt group compared to the control group (P < 0.001). This study showed that the microwaves with the frequency of 950 MHz can have negative impacts on morphometric and apoptotic changes of rabbit epididymis.

Role of LET and chromatin structure on chromosomal inversion in CHO10B2 cells

Background

In this study we evaluated the effect of linear energy transfer (LET) and chromatin structure on the induction of chromosomal inversion. High LET radiation causes more complex DNA damage than low LET radiation; this “dirty” damage is more difficult to repair and may result in an increase in inversion formation. CHO10B2 cells synchronized in either G1 or M phase were exposed 0, 1, or 2 Gy of 5 mm Al and Cu filters at 200 kVp and 20 mA X-rays or 500 MeV/nucleon of initial energy and 200 keV/μ m Fe ion radiation. In order to increase the sensitivity of prior techniques used to study inversions, we modified the more traditional Giemsa plus fluorescence technique so that cells were only allowed to incorporate BrdU for a single cycle verses 2 cycles. The BrdU incorporated DNA strand was labeled using a BrdU antibody and an Alexa Fluor 488 probe. This modified technique allowed us to observe inversions smaller than 0.6 megabases (Mb).

Results

In this study we have shown that high LET radiation induces significantly more inversions in G1 cells than in M phase cells. Additionally, we have shown that the sizes of the induced inversions not only differ between Fe ion and X-rays, but also between G1 and M phase cells exposed to Fe ions.

Conclusion

We have effectively shown that both radiation quality and chromosome structure interact to alter not only the number of inversions induced, but also the size of the inversions.

Direct DNA and PNA probe binding to telomeric regions without classical in situ hybridization

BACKGROUND

Fluorescence in situ Hybridization (FISH) utilizes peptide nucleic acid (PNA) probes to identify specific DNA sequences. Traditional techniques have required the heat denaturing of the DNA in formamide followed by multiple hours at moderated temperatures to allow the probe to hybridize to its specific target. Over the past 30 years, advancements in both protocols and probes have made FISH a more reliable technique for both biological research and medical diagnostics, additionally the protocol has been shortened to several minutes. These PNA probes were designed to target and hybridize to both DNA and RNA, and PNA-protein interactions still remain unclear.

RESULTS

In this study we have shown that a telomeric single stranded specific PNA probe is able to bind to its target without heat denaturing of the DNA and without formamide. We have also identified a centromere specific probe, which was found to bind its target with only incubation with formamide.

CONCLUSIONS

Certain PNA probes are able to hybridize with their targets with minimal to no denaturing of the DNA itself. This limited denaturing preserves the chromosome structure and may lead to more effective and specific staining.