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.

Study of acetylated histone h3k9 – an active chromatin mark – in chromosomes from adult and fetal human lymphocytes

Background: Incorrect epigenetic modifications of the human genome may result in epigenetic disorders, thus, highlighting the necessity of studying chromosome epigenetic patterns in human development. Aim of the study: A comparative analysis of acetylated histone H3K9 (AcH3K9) patterns in human metaphase chromosomes from the lymphocytes of adults and fetuses. Materials and methods: The immunocytochemical detection of AcH3K9 in the metaphase chromosomes from PHA-stimulated peripheral lymphocytes of 13 adults and cord blood lymphocytes of 10 fetuses at 20-22 weeks of gestation. Results: Both in the chromosomes of the adults and the fetuses, AcH3K9 accumulated in the R- and T-, but not G-bands and avoided the regions of pericentromeric heterochromatin of the chromosomes 1, 9 and 16. When comparing the adult and the fetal chromosomes, different levels of AcH3K9 were revealed in a few bands: 2q31, 5p13, 5p15 and 16p13 had higher level of Н3К9 acetylation in adults, in contrast to 9q13 which was hyperacetylated in fetuses. Conclusion: The АсН3К9 distribution in metaphase chromosomes is band-specific and is similar between the adults and the fetuses, excluding a few bands with different acetylation levels.

SIGNIFICANCE OF THE SPHINGOMYELIN CHANGES IN CORD BLOOD LYMPHOCYTES FOR THE ACTIVITY OF CENTRAL NERVOUS SYSTEM IN PRETERM NEWBORNS

Different neuropsychical pathologies are revealed in preterm infants during the subsequent stages of ontogenesis. Violation of the phospholipids composition of cell membranes is one of the essential pathogenetic mechanisms of the psychoneurological pathology.Objective:to study the content of phospholipid fractions of cord blood lymphocytes in preterm infants at different gestation terms.The spectrumof phospholipids was determined by thin layer chromatography in 39 healthy full-term newborns and in 65 preterm children (28-36 weeks). We revealed an increased content of sphingomyelin in cord blood lymphocytes in preterm infants. The highest rates were found in children with a gestation term of less than 32 weeks (p = 0.004 compared with full-term infants). Sphingomyelin, unlike other phospholipids of cell membranes, is concentrated mainly in the brain, which indicates its special role for CNS activity.Recently, there has been formed the idea on the importance of lipid components of fat globule membranes of breast milk for optimal neurological development of children. Given the changes in the sphingomyelin content in the cell membranes of preterm newborns and its important structural and functional role for CNS activity, we believe that special attention should be paid to its content in the formulas for preterm infants among standard components.