An Exposure to the Oxidized DNA Enhances Both Instability of Genome and Survival in Cancer Cells

Background

Cell free DNA (cfDNA) circulates throughout the bloodstream of both healthy people and patients with various diseases and acts upon the cells. Response to cfDNA depends on concentrations and levels of the damage within cfDNA. Oxidized extracellular DNA acts as a stress signal and elicits an adaptive response.

Principal Findings

Here we show that oxidized extracellular DNA stimulates the survival of MCF-7 tumor cells. Importantly, in cells exposed to oxidized DNA, the suppression of cell death is accompanied by an increase in the markers of genome instability. Short-term exposure to oxidized DNA results in both single- and double strand DNA breaks. Longer treatments evoke a compensatory response that leads to a decrease in the levels of chromatin fragmentations across cell populations. Exposure to oxidized DNA leads to a decrease in the activity of NRF2 and an increase in the activity of NF-kB and STAT3. A model that describes the role of oxidized DNA released from apoptotic cells in tumor biology is proposed.

Conclusions/Significance

Survival of cells with an unstable genome may substantially augment progression of malignancy. Further studies of the effects of extracellular DNA on malignant and normal cells are warranted.     

92 Novel interpretation of the isotherms of multimodal ligands binding with DNA

The binding of ligands with DNA is a key moment in a whole range of cellular processes that provide not only the normal cell vital activity but also the development of some pathological processes. Depending on ligand type, structure of DNA adsorption centers, and physical–chemical conditions of the surrounding, the ligand may bind to DNA by several modes [1]. Particularly, adsorption isotherm of multimodal ligands binding to DNA in Scatchard’s coordinates has a concave shape with two brightly expressed linear areas in the region of small fillings. The analysis of such type of adsorption isotherm for determining of important binding parameters such as binding constant and number of adsorption centers (the part of DNA polymer with which one ligand molecule binds) presents difficulties. Practically in all cases, the analysis of such adsorption isotherm is carried out by linear parts of curves. Such analysis mode of experimental points is approximate method, since all registered of experimental points are roughly divided into two groups and they are treated by linear binding isotherm and therefore the binding parameters are determined. In the present work, the non-linear adsorption isotherm in Scatchard‘s coordinates is obtained which allowed, provided, the more precise treatment of all experimental points by unique curve which includes linear regions as well. Such mode of treatment of experimental points makes more precise the determination of not only binding constant and number of adsorption centers that correspond to the one ligand molecule binding, but also additional binding parameter – a proportion of adsorption centers of each binding to DNA type of multimodal ligand.     

Novel 3-hydroxy vinylboronates influence sphingolipid metabolism,cause apoptosis in Jurkat cells and prevent tumor development in nude mice

A series of novel 3-hydroxy vinylboronates which share structural similarities with sphingolipids were synthesized and tested in vitro and in vivo as anticancer agents. The molecules reduced cancer cell survival in vitro by influencing their sphingolipid metabolism. In a cancer model in nude mice the lead compound E7 prevented the development of tumor as long as the treatment period continued. Moreover, it delayed tumor growth after the treatment was finished.     

Novel monoamine oxidase inhibitors based on the privileged 2-imidazoline molecular framework

Series of structurally diverse 2-imidazoline derivatives have been synthesized by condensation of substituted aldehydes with ethylenediamine, Pd-catalyzed N-arylation of 2-imidazolines and by the formation of 1,2,4-oxadiazoles and benzoxazepines from 2-imidazoline-containing precursors. The 2-imidazoline derivatives were evaluated as potential inhibitors of human monoamine oxidase (MAO) A and B. Among the 2-imidazolines, good potency inhibitors were discovered with compound 9p (IC₅₀?=?0.012?µM) being the most potent MAO-B inhibitor, while compound 9d (IC₅₀?=?0.751?µM) was the most potent MAO-A inhibitor of the series. These potencies are in the same range as those of reference MAO inhibitors used in the clinic. Among 33 compounds evaluated, 13 exhibited IC₅₀ values in the submicromolar range for the inhibition of an MAO isoform. It is postulated that the imidazoline moieties of some of these inhibitors may be recognized by the imidazoline I₂-binding site of MAO. Good potency MAO inhibitors may be useful for the treatment of neuropsychiatric and neurodegenerative disorders such as depression and Parkinson’s disease, and future application for the treatment of prostate cancer, congestive heart failure and Alzheimer’s disease. In addition, high potency 2-imidazoline-derived MAO inhibitors may be used as potential probes for the imidazoline binding sites of the MAOs, as well as to determine alternative binding regions of imidazoline within the MAO active site.     

Purification and cytotoxic properties of Bacillus cereus hemolysin II

The hemolysin II from Bacillus cereus, HlyII, is a member of the beta-barrel pore-forming toxin family of secreted microbial proteins that includes the Staphylococcus aureus alpha-toxin. Compared with other proteins of the family, hemolysin II has 90 extra amino acids at its C-terminus. To examine more closely the cytotoxic and pore-forming properties of the protein, we have cloned and expressed it in Escherichia coli. We developed a purification procedure for the matured HlyII protein from both culture media and cell extracts using a combination of cation exchange and affinity chromatography together with gel-filtration. In both cases, the fully processed HlyII protein was purified as confirmed by N-terminal sequence analysis. The HlyII protein exhibits cytolytic activity of different extent on erythrocytes from various kinds of mammals. The results presented here show for the first time that two types of human cells are sensitive to HlyII action. In view of its broad cytotoxic activity as well as the ability to interact with artificial membranes, we assume that HlyII needs no specific receptor to bind to cell membranes.     

HNO induces DNA deletions in the yeast S. cerevisiae

HNO is genotoxic but its mechanism is not well understood. There are many possible mechanisms by which HNO can attack DNA. Since HNO is electrophilic, it may react with exocyclic amine groups on DNA bases and through a series of subsequent reactions form a deaminated product. Alternatively, HNO may induce radical chemistry through O(2)-dependent (or possibly O(2)-independent) chemistry. In cell free systems, experiments have shown that HNO does react with DNA, resulting in base oxidation and strand cleavage. In this study, we used a whole-cell system in the yeast Saccharomyces cerevisiae to study the mechanism of HNO induced DNA damage with Angeli's salt as HNO donor. The yeast DEL assay provided a measure of intrachromosomal recombination leading to DNA deletions. We also examined interchromosomal recombination leading to genomic rearrangements and used the canavanine (CAN) assay to study induction of forward point mutations. HNO was a potent inducer of DNA deletions and recombination but it was negative for induction of point mutations. This suggests that HNO causes DNA strand breaks rather than base damage. Genotoxicity was observed under aerobic and anaerobic conditions and NAC protected against HNO induced DNA deletions. Since HNO is genotoxic under anaerobic conditions, NAC probably protected against radicals generated by HNO independent of oxygen.     

Distribution and accumulation of PVM and PVY,PVX in infected potato plants

The ability of PVM, PVY and PVX viruses and their progeny to distribute themselves and accumulate in primary infected potato plants by mono‐ and mixed infections is analysed. It is shown, that the transport and accumulation of virus in inoculated potato plants depends on variety resistance, combination of viruses and sequence of their application.     

Probing the effect of morphology on lymphatic valve dynamic function

The lymphatic system is vital to the circulatory and immune systems, performing a range of important functions such as transport of interstitial fluid, fatty acid, and immune cells. Lymphatic vessels are composed of contractile walls and lymphatic valves, allowing them to pump lymph against adverse pressure gradients and to prevent backflow. Despite the importance of the lymphatic system, the contribution of mechanical and geometric changes of lymphatic valves and vessels in pathologies of lymphatic dysfunction, such as lymphedema, is not well understood. We develop a fully coupled fluid–solid, three-dimensional computational model to interrogate the various parameters thought to influence valve behavior and the consequences of these changes to overall lymphatic function. A lattice Boltzmann model is used to simulate the lymph, while a lattice spring model is used to model the mechanics of lymphatic valves. Lymphatic valve functions such as enabling lymph flow and preventing backflow under varied lymphatic valve geometries and mechanical properties are investigated to provide an understanding of the function of lymphatic vessels and valves. The simulations indicate that lymphatic valve function is optimized when valves are of low aspect ratio and bending stiffness, so long as these parameters are maintained at high enough values to allow for proper valve closing. This suggests that valve stiffening could have a profound effect on overall lymphatic pumping performance. Furthermore, dynamic valve simulations showed that this model captures the delayed response of lymphatic valves to dynamic flow conditions, which is an essential feature of valve operation. Thus, our model enhances our understanding of how lymphatic pathologies, specifically those exhibiting abnormal valve morphologies such as has been suggested to occur in cases of primary lymphedema, can lead to lymphatic dysfunctions.     

Studying hunting behaviour in the striped field mouse using data compression

We compare predatory behaviour towards a mobile insect in three species of small mammals: the granivorous striped field mouse, the insectivorous common shrew and the Norway rat (a generalist). The striped field mouse displays a surprisingly efficient hunting stereotype. We apply the data compression method (Ryabko et al. Theory Comput Syst 52:133–147, 2013) to compare the complexity of hunting behavioural patterns and to evaluate the flexibility of stereotypes and their succinctness. Norway rats demonstrated the highest level of complexity of hunting behaviour, with the highest proportion of ‘auxiliary’ and ‘noise’ elements and relatively low proportion of ‘key’ elements in their behaviours. The predominance of ‘key’ elements resulted in similarly low levels of complexity of hunting stereotypes in striped field mice and shrews. The similarity between hunting stereotypes of the insectivorous shrew and the granivorous striped field mouse enables us to argue about evolutionary roots of hunting behaviour in small mammals. We show that this method is a useful tool for comparing ethograms as ‘biological texts’.