DNA damage response and apoptosis induced by hyperthermia in human umbilical cord blood lymphocytes

Melatonin as a regulator of apoptosis in leukaemia: molecular mechanism and therapeutic perspectives

Leukaemia is a dangerous malignancy that causes thousands of deaths every year throughout the world. The rate of morbidity and mortality is significant despite many advancements in therapy strategies for affected individuals. Most antitumour medications used now in clinical oncology use apoptotic signalling pathways to induce cancer cell death. Accumulated data have shown a direct correlation between inducing apoptosis in cancer cells with higher tumour regression and survival. Until now, the efficacy of melatonin as a powerful antitumour agent has been firmly established. A change in melatonin concentrations has been reported in multiple tumours such as endometrial, hematopoietic, and breast cancers. Findings show that melatonin's anticancer properties, such as its prooxidation function and ability to promote apoptosis, indicate the possibility of utilizing this natural substance as a promising agent in innovative cancer therapy approaches. Melatonin stimulates cell apoptosis via the regulation of many apoptosis facilitators, including mitochondria, cytochrome c, Bcl-2, production of reactive oxygen species, and apoptosis receptors. This paper aimed to further assess the anticancer effects of melatonin through the apoptotic pathway, considering the role that cellular apoptosis plays in the pathogenesis of cancer. The effect of melatonin may mean that it is appropriate for use as an adjuvant, along with other therapeutic approaches such as radiotherapy and chemotherapy.

Classifier Spot Count Optimization of Automated Fluorescent Slide Scanning System

Purpose: Ionizing radiation induced foci (IRIF) known also as DNA repair foci represent the most sensitive endpoint for assessing DNA double strand breaks (DSB). IRIF are usually visualized and enumerated with the aid of fluorescence microscopy using antibodies to γH2AX and 53BP1. Although several approaches and software packages were developed for the quantification of IRIF, not one of them was commonly accepted and inter-laboratory variability in the outputs was reported. In this study, the sensitization of Metafer software to counting also small appearing IRIF was validated.

Materials and Methods: Human lymphocytes were γ-irradiated at a dose of 2 Gy. The cells were fixed at 0.5, 1, 2, and 18 hours post-irradiation, permeabilized and IRIF were immunostained using appropriate antibodies. Cell images were acquired with the automatic Metafer system. Radiation-induced γH2AX and 53BP1 foci were enumerated using either manual counting (JCountPro program) or the Metafer software (after its classifier optimization has been done) and compared. The statistical analysis was performed using One-way ANOVA.

Results: The enumeration of 53BP1, γH2AX foci manually by JCountPro did not statistically significantly differ from the automatic one performed with the optimized Metafer classifier. A detailed step-by-step protocol of this successful optimization is described in this study.

Conclusions: We concluded that the Metafer software after the optimization was efficient in objectively enumerating IRIF, having a potential for usage in clinics and molecular epidemiology.

Imaging flow cytometry and fluorescence microscopy in assessing radiation response in lymphocytes from umbilical cord blood and cancer patients

DNA double strand breaks (DSB) induced by ionizing radiation (IR) are usually measured using γH2AX/53BP1 DNA repair foci, that is considered to be the most sensitive assay for DSB analysis. While fluorescence microscopy (FM) is the gold standard for this analysis, imaging flow cytometry (IFC) may offer number of advantages such as lack of the fluorescence background, higher number of cells analyzed, and higher sensitivity in detection of DNA damage induced by IR at low doses. Along with appearance of γH2AX foci, the variable fraction of the cells exhibits homogeneously stained γH2AX signal resulting in so-called γH2AX pan-staining, which is believed to appear at early stages of apoptosis. Here, we investigated incidence of γH2AX pan-staining at different time points after irradiation with γ-rays using IFC and compared the obtained data with the data from FM. Appearance of γH2AX pan-staining during the apoptotic process was further analyzed by fluorescence-activated cell sorting (FACS) of cells at different stages of apoptosis and subsequent immunofluorescence analysis. Our results show that IFC was able to reveal dose dependence of pan-staining, while FM failed to detect all pan-staining cells. Moreover, we found that γH2AX pan-staining could be induced by therapeutic, but not low doses of γ-rays and correlate well with percentage of apoptotic cells was analyzed using flow cytometric Annexin-V/7-AAD assay. Further investigations showed that γH2AX pan-staining is formed in the early phases of apoptosis and remains until later stages of apoptotic process. Apoptotic DNA fragmentation as detected with comet assay using FM correlated with the percentage of live and late apoptotic/necrotic cells as analyzed by flow cytometry. Lastly, we successfully tested IFC for detection of γH2AX pan-staining and γH2AX/53BP1 DNA repair foci in lymphocyte of breast cancer patients after radiotherapy, which may be useful for assessing individual radiosensitivity in a clinically relevant cohort of patients.

Evaluation of Calyculin A Effect on γH2AX/53BP1 Focus Formation and Apoptosis in Human Umbilical Cord Blood Lymphocytes

Dephosphorylation inhibitor calyculin A (cal A) has been reported to inhibit the disappearance of radiation-induced γH2AX DNA repair foci in human lymphocytes. However, other studies reported no change in the kinetics of γH2AX focus induction and loss in irradiated cells. While apoptosis might interplay with the kinetics of focus formation, it was not followed in irradiated cells along with DNA repair foci. Thus, to validate plausible explanations for significant variability in outputs of these studies, we evaluated the effect of cal A (1 and 10 nM) on γH2AX/53BP1 DNA repair foci and apoptosis in irradiated (1, 5, 10, and 100 cGy) human umbilical cord blood lymphocytes (UCBL) using automated fluorescence microscopy and annexin V-FITC/propidium iodide assay/γH2AX pan-staining, respectively. No effect of cal A on γH2AX and colocalized γH2AX/53BP1 foci induced by low doses (≤10 cGy) of γ-rays was observed. Moreover, 10 nM cal A treatment decreased the number of all types of DNA repair foci induced by 100 cGy irradiation. 10 nM cal A treatment induced apoptosis already at 2 h of treatment, independently from the delivered dose. Apoptosis was also detected in UCBL treated with lower cal A concentration, 1 nM, at longer cell incubation, 20 and 44 h. Our data suggest that apoptosis triggered by cal A in UCBL may underlie the failure of cal A to maintain radiation-induced γH2AX foci. All DSB molecular markers used in this study responded linearly to low-dose irradiation. Therefore, their combination may represent a strong biodosimetry tool for estimation of radiation response to low doses. Assessment of colocalized γH2AX/53BP1 improved the threshold of low dose detection.

The Biocompatibility of Wireless Power Charging System on Human Neural Cells

The progress in technology and science leads to the invention and use of many electrical devices in the daily lives of humans. In addition to that, people have been easily exposed to increased newly generated artificial electromagnetic waves. Exponential use of modern electronic devices has automatically led to increase in electromagnetic wave exposure. Therefore, we constructed the prototype of wireless power charging system to study the biocompatibility of electromagnetic field (EMF) generated by this system on various human cell lines. There are many studies indicating the negative bio-effect of EMF on various types of cells, such as induction of apoptosis. From the other point of view, these effects could rather be beneficial in the way, that they could eliminate the progress of various diseases or disorders. For that reason, we compared the impact of EMF (87 kHz, 0.3–1.2 mT, 30 min) on human normal as well as cancer cell lines based on morphological and cellular level. Our results suggested that EMF generated by wireless power charging systems does not have any detrimental effect on cell morphology, viability and cytoskeletal structures of human neural cells.