Vol 10, No 4 (2016)

A number of mathematical, chemical, physical, and biological features of an array of natural oligopeptides were considered on the basis of the EROP-Moscow database. We show the substantial difference of these substances from polypeptide molecules of proteins according to their physicochemical characteristics. These characteristics may be critical for understanding the molecular mechanisms of the action of oligopeptides that lead to the development of physiological effects.

We compared the effects of the dipeptide carnosine on learning and the biochemical parameters in the brain of rats trained for defensive and food-procuring conditioned reflexes. In the first series, the animals were trained for active avoidance behavior; in the second series, the rats were trained for the food-procuring conditioned reflex in a modified shuttle box. After training, the hypothalamus and cortex were dissected and used for evaluation of lipid peroxidation processes and the levels of monoamine neurotransmitters. The activating effect of carnosine was observed during the entire training period of defensive training, whereas during training for the food-procuring reflex it was observed only in the first two sessions. In both training series, impairments of oxidative homeostasis were found in the brain; these were efficiently corrected with carnosine. This effect of carnosine may explain its positive influence on learning. Moreover, in both models, carnosine increased the contents of the main monoamine neurotransmitters in the hypothalamus. These data led us to the conclusion about high prospectivity of further studies of the carnosine modulatory effects in the nervous system.

Parkinson’s disease (PD) is a chronic neurodegenerative disease with a long period of asymptomatic progress, which occurs due to activation of mechanisms of neuroplasticity that support the degenerating nigrostriatal system of the brain. In the present study, we examined some compensatory mechanisms in the mouse brain for the first time using chronic models of preclinical and early clinical stages of PD that we developed. Using a model of the preclinical stage of PD, we found a compensatory increase in the number of monoenzymatic tyrosine hydroxylase-containing fibers in the striatum, whereas using a model of the early clinical stage of PD, an adaptive decrease in the rate of dopamine reuptake in the substantia nigra was revealed. These mechanisms of neuroplasticity may be considered as targets for the future development of new tools for neuroprotective therapy.

Brain-derived neurotrophic factor (BDNF) is involved in the formation of dependence on opiates. BDNF mRNA expression is altered during opiate dependence; however, the biological basis of this phenomenon has been insufficiently studied. At the posttranscriptional level, microRNAs may potentially regulate BDNF expression. Short non-coding microRNAs bind in a complementary manner, mostly to the 3'-noncoding area (3'-UTR) of mRNA and thus initiate degradation of a target by the RNA-induced silencing complex (RISC). In the present study, the potential contribution of microRNAs to the regulation of the BDNF mRNA expression was evaluated in the brain of rats with morphine dependence after spontaneous withdrawal. In order to form dependence in rats, morphine was injected twice a day in increasing doses of 10᾿00 mg/kg for 6 days. Expression of BDNF mRNA and microRNA, which may potentially regulate BDNF, was studied in brain regions 40 h after spontaneous morphine withdrawal using the real-time PCR method. Interaction of the Argonaute 2 protein (Ago-2), a component of RISC, with 3'-UTR BDNF mRNA was evaluated using RNA immunoprecipitation. We found that morphine withdrawal was followed by an increase in the BDNF exon I-containing mRNA in the frontal cortex and midbrain. In the frontal cortex, the increased BDNF mRNA level observed in abstinence was associated with a decrease in the miR-206 microRNA and Ago-2 bound to 3'-UTR BDNF mRNA contents. In the midbrain the abstinence condition was accompanied by a decrease in the miR-382 level, whereas Ago-2 binding to 3'-UTR BDNF mRNA remained unchanged. We believe that the weakening of miR-206-mediated degradation of BDNF mRNA may be responsible for the elevated BDNF expression in the frontal cortex in the conditions of morphine dependence.

We studied the dynamics of the intracellular concentration of calcium ions ([Ca²⁺]_i) and the influence of the endogenous cannabinoid N-arachidonoyldopamine (N-ADA) on disturbances of calcium homeostasis in cultured hippocampal neurons in the model of postischemic epileptogenesis (PE) in vitro, in accordance with a previously published method. It was found that 24 h after treatment with 20 μM glutamate, its application at a concentration of 50 μM results in a persistent increase in [Ca²⁺]_i whereas in neurons that were not previously subjected to glutamate treatment an increase in [Ca²⁺]_i after the application of 50 μM glutamate was reversible. The presence of N-ADA (5 μM) in the incubation medium both simultaneously with 20 μM glutamate exposure and for 24 h after it promoted recovery of the [Ca²⁺]_i level to the initial level. The results indicate that application of N-ADA promotes normalization of neuronal calcium homeostasis in a PE model in vitro.

Using the flow-cytometry method, we demonstrated the ability of alpha-tocopherol (alpha-T) at nano- and micromolar concentrations to recover the mitochondrial membrane potential (ΔΨm), which decreased after H₂O₂ treatment in PC12 neuronal line cells. Alterations in the ΔΨm in PC12 cells were evaluated using the fluorescent probe tetramethylrhodamine (TMRM). The higher cell-fluorescence intensity corresponded to a higher ΔΨm value. Treatment with H₂O₂ resulted in a decrease in the fluorescence intensity from 100% in the control to 43.2 ± 5.1% (p < 0.001). Long-term 18-h preincubation with 100 nM or 100 μM alpha-T increased the fluorescence intensity in PC12 cells from 43.2 ± 5.2% up to 88.4 ± 4.8 and 89.6 ± 6.5% of the control value, respectively (p < 0.01 according to the one-way analysis of variances). Alpha-T at both 100 nM and 100 μM concentrations significantly and with similar efficacy decreased the ratio of the proapoptotic protein Bax to the antiapoptotic protein Bcl-xL (Bax/Bcl-xL) in the control PC12 cells. However, we did not reveal any significant effect of H₂O₂ or preincubation with alpha-T on this ratio in PC12 lysates. Furthermore, H₂O₂ increased both the Bax and Bcl-xL levels in PC12 cells.