Biophysical Modeling of the Ionizing Radiation Influence on Cells Using the Stochastic (Monte Carlo) and Deterministic (Analytical) Approaches.

This review article describes our simplified biophysical model for the response of a group of cells to ionizing radiation. The model, which is a product of 10 years of studies, acts as (a) a comprehensive stochastic approach based on the Monte Carlo simulation with a probability tree and (b) the thereof derived detailed deterministic models describing the selected biophysical and radiobiological phenomena in an analytical manner. Specifically, the presented model describes effects such as the risk of neoplastic transformation of cells relative to the absorbed radiation dose, the dynamics of tumor development, the priming dose effect (also called the Raper-Yonezawa effect) based on the introduced adaptive response approach, and the bystander effect. The model is also modifiable depending on users' potential needs.

4-Methylpseudoproline analogues of cyclolinopeptide A: Synthesis, structural analysis and evaluation of their suppressive effects in selected immunological assays.

The synthesis of new analogues of cyclolinopeptide A (CLA) and their linear precursors modified with (R)- and (S)-4-methylpseudoproline in the Pro3-Pro4 fragment are presented. The peptides were tested in comparison with cyclosporine A (CsA) in concanavalin A (Con A) and pokeweed mitogen (PWM)-induced mouse splenocyte proliferation and in secondary humoral immune response in vitro to sheep erythrocytes (SRBC). Their effects on expression of selected signaling molecules in the Jurkat T cell line were also determined. In addition, the structural features of the peptides, applying nuclear magnetic resonance and circular dichroism, were analyzed. The results showed that only peptides 7 and 8 modified with (R)-4-methylpseudoproline residue (c(Leu1-Val2-(R)-(αMe)Ser(ΨPro)3-Pro4-Phe5-Phe6-Leu7-Ile8-Ile9) and c(Leu1-Val2-Pro3-(R)-(αMe)Ser(ΨPro)4-Phe5-Phe6-Leu7-Ile8-Ile9), respectively) strongly suppressed mitogen-induced splenocyte proliferation and the humoral immune response, with peptide 8 being more potent. Likewise, peptide 8 more strongly elevated expression of Fas, a proapoptotic signaling molecule in Jurkat cells. We postulate that the increased biological activity of peptide 8, compared to the parent molecule and other studied peptides, resulted from its more flexible structure, found on the basis of both CD and NMR studies. CD and NMR spectra showed that replacement of Pro3 by (R)-(αMe)Ser(¬Pro) caused much greater conformational changes than the same replacement of the Pro4 residue. Such a modification could lead to increased conformational freedom of peptide 8, resulting in a greater ability to adopt a more compact structure, better suited to its putative receptor. In conclusion, peptide 8 is a potent immune suppressor which may find application in controlling immune disorders.

Characterization of Fluorescein-Based Monoboronate Probe and Its Application to the Detection of Peroxynitrite in Endothelial Cells Treated with Doxorubicin.

Boronate probes have emerged recently as a versatile tool for the detection of reactive oxygen and nitrogen species. Here, we present the characterization of a fluorescein-based monoboronate probe, a 4-(pinacol boronate)benzyl derivative of fluorescein methyl ester (FBBE), that proved to be useful to detect peroxynitrite in cell culture experiments. The reactivity of FBBE toward peroxynitrite as well hypochlorite, hydrogen peroxide, and tyrosyl hydroperoxide was determined. Second-order rate constants of the reactions of FBBE with peroxynitrite, HOCl, and H2O2 at pH 7.4 were equal to (2.8 ± 0.2) × 10(5) M(-1) s(-1), (8.6 ± 0.5) × 10(3) M(-1) s(-1), and (0.96 ± 0.03) M(-1) s(-1), respectively. The presence of glutathione completely blocked the oxidation of the probe by HOCl and significantly inhibited its oxidation by H2O2 and tyrosyl hydroperoxide but not by peroxynitrite. The oxidative conversion of the probe was also studied in the systems generating singlet oxygen, superoxide radical anion, and nitric oxide in the presence and absence of glutathione. Spectroscopic characterization of FBBE and its oxidation product has been also performed. The differences in the reactivity pattern were supported by DFT quantum mechanical calculations. Finally, the FBBE probe was used to study the oxidative stress in endothelial cells (Ea.hy926) incubated with doxorubicin, a quinone anthracycline antibiotic. In endothelial cells pretreated with doxorubicin, FBBE was oxidized, and this effect was reversed by PEG-SOD and L-NAME but not by catalase.

Antithrombotic effects of pyridinium compounds formed from trigonelline upon coffee roasting.

Coffee may exert a preventive effect on arterial thrombosis. Trigonelline is one of the most abundant compounds in coffee that undergoes pyrolysis upon roasting of coffee beans. The aim of the present study was to identify pyridinium compounds formed upon trigonelline pyrolysis and coffee roasting and to investigate the effect of three of them, i.e., 1-methylpyridine and 1,3- and 1,4-dimethylpyridine, on experimentally induced arterial thrombosis in rats. 1,3- and 1,4-dimethylpyridine but not 1-methylpyridine inhibited arterial thrombus formation. 1,3-Dimethylpyridine inhibited platelet aggregation and reduced fibrin formation in platelet-rich plasma, whereas 1,4-dimethylpyridine increased the plasma level of 6-keto-PGF1α. 1,4-Dimethylpyridine slightly increased rat tissue plasminogen activator plasma activity. In summary, we demonstrated that pyridinium compounds display mild antithrombotic properties due to stimulation by prostacyclin release (1,4-dimethylpyridine) and inhibition of platelet aggregation (1,3-dimethylpyridine). Those pyridinium compounds may, to some extent, be responsible for the beneficial effects of coffee drinking.

Antioxidant action of SMe1EC2, the low-basicity derivative of the pyridoindole stobadine, in cell free chemical models and at cellular level.

The aim of the study was to evaluate the antioxidant action of SMe1EC2, the structural analogue of the hexahydropyridoindole antioxidant stobadine. The antiradical activity of SMe1EC2 was found to be higher when compared to stobadine, as determined both in cell-free model systems of AAPH-induced oxidation of dihydrorhodamine 123 and 2',7'-dichloro-dihydrofluorescein diacetate, and in the cellular system of stimulated macrophages RAW264.7. Analysis of proliferation of HUVEC and HUVEC-ST cells revealed absence of cytotoxic effect of SMe1EC2 at concentrations below 100 µM. The antioxidant activity of SMe1EC2, superior to the parent drug stobadine, is accounted for by both the higher intrinsic free radical scavenging action and by the better bioavailability of the low-basicity SMe1EC2 relative to the high-basicity stobadine.

Subadditive interactions between antioxidants in the protection against lipid peroxidation.

Synergistic interactions between antioxidants have been postulated but not proven. On the contrary, it has been reported that the antioxidant activity of mixtures of antioxidants can be lower than the sum of the antioxidant activities of individual components. We report that such a situation can be observed in 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-treated phosphatidylcholine liposomes in which lipid peroxidation was monitored by oxidation of 4,4-difluoro-5-(4-phenyl-1 3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid (C11-BODIPY581/591). Glutathione, present inside liposomes, and hydrophobic antioxidants, present in the lipid bilayer, protected against lipid peroxidation, but their simultaneous action was lower than the sum of individual contributions. A possible explanation for this effect is proposed.

The effects of superoxide dismutase knockout on the oxidative stress parameters and survival of mouse erythrocytes.

The erythrocytes of 12-month old Sod1 (-/-) mice showed an increased level of reactive oxygen species (ROS), as estimated by the degree of dihydroethidine and dihydrorhodamine oxidation, and the increased level of Heinz bodies. No indices of severe oxidative stress were found in the red blood cells and blood plasma of Sod1 (-/-) mice as judged from the lack of significant changes in the levels of erythrocyte and plasma glutathione, plasma protein thiol and carbonyl groups and thiobarbituric-acid reactive substances in the blood plasma. However, a decreased erythrocyte lifespan, increased reticulocyte count and splenomegaly were noted, indicating the importance of superoxide dismutase for maintaining erythrocyte viability. The levels of erythrocyte ROS and Heinz bodies and the reticulocyte count were indistinguishable in Sod1 (+/+) and Sod1 (+/-) mice, suggesting that a superoxide dismutase activity decrease to half of its normal value may be sufficient to secure the protective effects of the enzyme.