The multifunctional promyelocytic leukemia protein (PML) is involved in the regulation of various cellular processes in both physiological and pathological conditions. Specifically, PML is one of the inositol-1,4,5-trisphosphate receptors (IP3Rs) activity regulators and can influence Ca2+ transport from the endoplasmic reticulum (ER) to mitochondria. In this work, the effects of PML knockout on calcium homeostasis in the cytosol, ER, and mitochondria of HeLa cells were studied upon stimulation with histamine, which induces Ca2+ mobilization from the ER via IP3Rs. We utilized calcium indicators with different subcellular localizations, including synthetic dyes Fura-2 (cytosolic), Xrhod-5F (mitochondrial), and protein sensor R-CEPIAer (ER), as well as mitochondrial potential-sensitive probes Rh123 and TMRM. Our results show that PML knockout induced changes in HeLa cell and mitochondrial morphology, slightly decreased basal and integral Ca2+ levels, enhanced mitochondrial Ca2+ uptake from the cytoplasm, and maintained residual mitochondrial potential after depolarization. Additionally, it reduced the Ca2+ pool in ER membranes not associated with histamine receptor activation and, consequently, IP3Rs. These findings suggest that changes in calcium ion transport due to PML knockout in HeLa cells affect mitochondrial activity.

Hydrogen sulfide (H2S), which under physiological conditions exists in cells mainly in the form of the HS– anion, is considered as a gaseous transmitter of inter- and intracellular signals along with nitrogen monoxide and carbon monoxide. Analysis of the dynamics of H2S content in living cells is impossible without the creation of sensitive and specific probes. The group of K.H. Ahn synthesized several acedan-based compounds, which in the presence of H2S attached a sulfhydryl group, forming fluorescent carbocyclic compounds. According to the spectral characteristics and reaction rate with H2S, the optimal substance was P3, which forms the carbocyclic compound csP3 with the same large Stokes shift as P3 (approx. 130 nm) and has a brighter fluorescence. In this work, we tested the suitability of csP3 for recording changes in H2S in solutions simulating the minimum salt composition of the intracellular medium, as well as in cells of primary neuronal culture from the rat cerebral cortex. It was found that the fluorescence intensity of csP3, which was formed when Na2S (H2S donor, 100 and 300 µM) was added to the P3 solution, differed for solutions corresponding in salt composition to the extracellular medium and cytosol. In both cases, fluorescence increased in the presence of bicarbonate (NaHCO3, 10 mM). A decrease in the polarity of solutions due to the addition of dimethyl sulfoxide (30

Актуальность. При исследованиях внутриклеточного сигналинга и межнейрональной передачи сигнала в мозге в норме и при патологии все большее применение находят трансгенные животные, экспрессирующие в нейронах флуоресцентный Са2+-сенсор. Вместе с тем, пока недостаточно исследовано, насколько изменения кальциевого гомеостаза в интактном мозге соотносятся с гораздо более подробно изученными изменениями этого важнейшего параметра в нейроглиальных культурах, служащих модельными системами живого мозга. Целью работы было на модели ишемического инсульта выяснить в какой степени изменения внутриклеточной концентрации Са2+ ([Ca2+]) в мозге трансгенной мыши, измеренные с помощью флуоресцентного белкового сенсора GCaMP6f, соотносятся с изменениями [Ca2+] в первичных нейроглиальных культурах из кортекса этих животных. Методы. Методом широкопольной оптической нейровизуализации (ШОН) измерены изменения концентрации свободного Са2+ в цитозоле нейронов ([Ca2+]c) головного мозга мышей. Измерения проводили перед и после фотоиндуцированного инсульта в сенсомоторной зоне коры. Изменения [Ca2+]c отслеживали по флуоресценции GCaMP6f, экспрессируемого в нейронах кортекса. На первичных нейроглиальных культурах из коры головного мозга мышей той же линии проверено влияние эксайтотоксических доз глутамата (Glu) на [Ca2+]c и на изменения средней концентрации свободного Са2+ в цито- и нуклеоплазме ([Ca2+]i). Измерения [Ca2+]i выполнены методом флуоресцентной микроскопии с использованием синтетических Са2+- индикаторов Fura-2 и Fura-FF. В культивируемых нейронах дополнительно к измерениям кальциевого гомеостаза выполнены измерения внутриклеточного рН (pHi), митохондриального потенциала (ΔΨm) и эндогенной флуоресценции NADH. Результаты. Фотоиндуцированная ишемия вызывает сильный рост [Ca2+]c в зоне облучения ~1,1 мм2 (n=9). В течение сутокобласть высокой [Ca2+]c расширяется до ~6 мм2, но к 7-м сут практически возвращается к размерам необратимого повреждения. В нейроглиальных культурах из коры головного мозга мышей этой же линии кинетика изменений [Ca2+]c, индуцированных Glu, напоминает кинетику [Ca2+]i, однако [Ca2+]c имеет значительно меньшую амплитуду при развитии отсроченной кальциевой дисрегуляции (ОКД). Сопоставление изменений [Ca2+] и pHi показывает, что различия могут быть обусловлены тушением флуоресценции GCaMP6f при закислении цитозоля в результате эксайтотоксического действия Glu. Заключение. Сопоставление сигналов экспрессируемого нейронами Са2+-сенсора GCaMP6f в мозге и синтетических Са2+-индикаторов в первичных нейроглиальных культурах, полученных из животных той же линии, показывает, что феномен ОКД, впервые обнаруженный в культурах, вероятно, реализуется и в нейронах целого мозга при инсульте. Вместе с тем, необходимо учитывать, что относительные изменения [Ca2+]c на разных стадиях развития ишемического повреждения и последующего восстановления мозга после фотоиндуцированного инсульта, могут быть искажены за счет влияния pHi на флуоресценцию белкового сенсора. Relevance. In studies of brain intracellular and intercellular signaling in normal and pathological conditions, transgenic animals expressing a fluorescent Ca2+ sensor in neurons are increasingly used. Calcium homeostasis was studied in detail in primary neuroglial cultures, which serve as model systems of the living brain. But how change in calcium homeostasis during ischemic conditions in the intact brain correlate with experiments on cell cultures has been poorly studied so far. The aim of this work was to compare ischemia-driven changes in the intracellular concentration of Ca2+ ([Ca2+]) in vivo and in vitro: in the brain of transgenic mice, using the GCaMP6f fluorescent protein sensor, and in the neuroglial cell culture, obtained from the cortex of these animals. Methods. Changes in the cytosolic concentration of free Ca2+ ([Ca2+]c) in the neurons was measured by wide-field optical imaging (WFOI). Measurements were taken before and after photothrombotic stroke performed in the sensorimotor cortex. Changes in [Ca2+]c were monitored by the fluorescence of GCaMP6f expressed in cortical neurons. In primary neuroglial cultures from the cerebral cortex glutamate (Glu) in excitotoxic doses was used to model ischemic injury. Measurements of averaged Ca2+ concentration in the cyto- and nucleoplasm ([Ca2+]i) were carried out by fluorescence microscopy using synthetic Ca2+ indicators Fura-2 and Fura-FF. In addition, measurements of intracellular pH (pHi) and mitochondrial potential (ΔΨm) were carried out in vitro. Results. Photothrombotic stroke caused a strong increase in [Ca2+]c in the illuminated zone ~1.1 mm2 (n=9). During the 24 hours, the area with high [Ca2+]c expands to ~6 mm2, but by the 7th day it almost returns to the size of the primary damage. In neuroglial cultures from the cerebral cortex of the same mice strain, the [Ca2+]c kinetics measured by GCaMP6f resembles the [Ca2+]i kinetics, but [Ca2+]c has a significantly lower amplitude during the development of delayed calcium deregulation (DCD). Comparison of changes in [Ca2+]i and pHi shows that the differences may be due to the quenching of GCaMP6f fluorescence due to cytosol acidification as a result of the excitotoxic Glu action. Conclusion. Comparison of measurements by the genetically-encoded GCaMP6f Ca2+ sensor in vivo and by the synthetic Ca2+ indicators in primary neuroglial cultures shows that the DCD phenomenon, first discovered in cultures, is probably realized in intact brain neurons in stroke. It should be taken into account that the relative changes in [Ca2+]c can be distorted due to the effect of pHi on the fluorescence of the protein sensor at different stages of ischemia development and subsequent brain recovery after a photothrombotic stroke.

Brain injury is accompanied by neuroinflammation, accumulation of extracellular glutamate and mitochondrial dysfunction, all of which cause neuronal death. The aim of this study was to investigate the impact of these mechanisms on neuronal death. Patients from the neurosurgical intensive care unit suffering aneurysmal subarachnoid hemorrhage (SAH) were recruited retrospectively from a respective database. In vitro experiments were performed in rat cortex homogenate, primary dissociated neuronal cultures, B35 and NG108-15 cell lines. We employed methods including high resolution respirometry, electron spin resonance, fluorescent microscopy, kinetic determination of enzymatic activities and immunocytochemistry. We found that elevated levels of extracellular glutamate and nitric oxide (NO) metabolites correlated with poor clinical outcome in patients with SAH. In experiments using neuronal cultures we showed that the 2-oxoglutarate dehydrogenase complex (OGDHC), a key enzyme of the glutamate-dependent segment of the tricarboxylic acid (TCA) cycle, is more susceptible to the inhibition by NO than mitochondrial respiration. Inhibition of OGDHC by NO or by succinyl phosphonate (SP), a highly specific OGDHC inhibitor, caused accumulation of extracellular glutamate and neuronal death. Extracellular nitrite did not substantially contribute to this NO action. Reactivation of OGDHC by its cofactor thiamine (TH) reduced extracellular glutamate levels, Ca2+ influx into neurons and cell death rate. Salutary effect of TH against glutamate toxicity was confirmed in three different cell lines. Our data suggest that the loss of control over extracellular glutamate, as described here, rather than commonly assumed impaired energy metabolism, is the critical pathological manifestation of insufficient OGDHC activity, leading to neuronal death.

The effect of high concentrations of glutamate (Glu) on primary cultures of neurons from the rat brain led to a strong depolarization of mitochondria, which developed synchronously with a secondary increase in the intracellular free Ca 2+ concentration (delayed calcium deregulation, DCD). Simultaneously with measurements of the intracellular free Ca 2+ concentration ([Ca 2+ ] i ), pH was measured in the mitochondrial matrix (pH m ) and cytosol (pH c ) of neurons when exposed to a toxic dose of Glu (100 µM). For this purpose, pH-sensitive green fluorescent protein mtYFP in mitochondria and pH-sensitive red fluorescent protein mKate in cytosol were expressed in primary cultures from the hippocampus of newborn rats. The resulting neuronal culture was loaded with the Ca 2+ indicator Fura-FF; [Ca 2+ ] i , pH m and pH c were simultaneously measured in those neurons that expressed both mtYFP and mKate. It was found that during the first phase of the [Ca 2+ ] i response to Glu, when partial depolarization of mitochondria was observed, there was an increase in the pH gradient between the mitochondrial matrix and the cytosol (ΔpH), which compensated for the decrease in the electrical component of the mitochondrial potential (∆Ψ m ), thereby maintaining the constancy of the electrochemical potential of mitochondria. The development of DCD led to an abrupt decrease in ∆Ψ m and ΔpH in the soma of neurons; however, a complete collapse of ΔpH was not observed. This may mean that DCD was not caused by a nonspecific megapore in the inner mitochondrial membrane (mPTP), as is commonly believed. Alternatively, part of the mitochondria in the soma of neurons could retain the barrier properties of the inner membrane and did not form mPTP even with the development of DCD and reaching a high [Ca 2+ ] i plateau.

Lipopolysaccharide (LPS), a fragment of the bacterial cell wall, specifically interacting with protein complexes on the cell surface, can induce the production of pro-inflammatory and apoptotic signaling molecules, leading to the damage and death of brain cells. Similar effects have been noted in stroke and traumatic brain injury, when the leading factor of death is glutamate (Glu) excitotoxicity too. But being an amphiphilic molecule with a significant hydrophobic moiety and a large hydrophilic region, LPS can also non-specifically bind to the plasma membrane, altering its properties. In the present work, we studied the effect of LPS from Escherichia coli alone and in combination with the hyperstimulation of Glu-receptors on the functional state of mitochondria and Ca 2+ homeostasis, oxygen consumption and the cell survival in primary cultures from the rats brain cerebellum and cortex. In both types of cultures, LPS (0.1–10 μg/ml) did not change the intracellular free Ca 2+ concentration ([Ca 2+ ] i ) in resting neurons but slowed down the median of the decrease in [Ca 2+ ] i on 14% and recovery of the mitochondrial potential (ΔΨm) after Glu removal. LPS did not affect the basal oxygen consumption rate (OCR) of cortical neurons; however, it did decrease the acute OCR during Glu and LPS coapplication. Evaluation of the cell culture survival using vital dyes and the MTT assay showed that LPS (10 μg/ml) and Glu (33 μM) reduced jointly and separately the proportion of live cortical neurons, but there was no synergism or additive action. LPS-effects was dependent on the type of culture, that may be related to both the properties of neurons and the different ratio between neurons and glial cells in cultures. The rapid manifestation of these effects may be the consequence of the direct effect of LPS on the rheological properties of the cell membrane.

Мастер-класс ВЫБОР СТРАТЕГИИ НАЧАЛЬНОЙ ШКОЛЫ В УСЛОВИЯХ ВЫСОКОЙ НЕВРОТИЗАЦИИ ГОРОДСКИХ ДЕТЕЙ Частная школа Кукувайя, Москва, Россия Руководители -Мудрова Евгения Борисовна, Святловская Евгения Александровна (в рамках секции 3 "Мышление и сознание") Королёва А.В.ВЫБОР СТРАТЕГИИ НАЧАЛЬНОЙ ШКОЛЫ В УСЛОВИЯХ ВЫСОКОЙ НЕВРОТИЗАЦИИ ГОРОДСКИХ ДЕТЕЙ ВЗГЛЯД ОСТЕОПАТА.КОГДА НАБЛЮДЕНИЕ И ПОМОЩЬ ВРАЧА-ОСТЕОПАТА СТАНОВИТСЯ НЕОБХОДИМОЙ ЧАСТЬЮ УЧЕБНОГО ПРОЦЕССА.Korolyeva A.V. WHAT STRATEGY TO CHOOSE FOR PRIMARY SCHOOL

Background: Disorders of mitochondrial Ca2+ homeostasis play a key role in the glutamate excitotoxicity of brain neurons. DS16570511 (DS) is a new penetrating inhibitor of mitochondrial Ca2+ uniporter complex (MCUC). The paper examines the effects of DS on the cultivated cortical neurons and isolated mitochondria of the rat brain. Methods: The functions of neurons and mitochondria were examined using fluorescence microscopy, XF24 microplate-based.ell respirometry, ion-selective microelectrodes, spectrophotometry, and polarographic technique. Results: At the doses of 30 and 45 mu M, DS reliably slowed down the onset of glutamate-induced delayed calcium deregulation of neurons and suppressed their death. 30 mu M DS caused hyperpolarization of mitochondria of resting neurons, and 45 mu M DS temporarily depolarized neuronal mitochondria. It was also demonstrated that 30-60 mu M DS stimulated cellular respiration. DS was shown to suppress Ca2+ uptake by isolated brain mitochondria. In addition, DS inhibited ADP-stimulated mitochondrial respiration and ADP-induced decrease in the mitochondrial membrane potential. It was found that DS inhibited the activity of complex II of the respiratory chain. In the presence of Ca2+, high DS concentrations caused a collapse of the mitochondrial membrane potential. Conclusions: The data obtained indicate that, in addition to the inhibition of MCUC, DS affects the main energy-transducing functions of mitochondria. General significance: The using DS as a tool for studying MCUC and its functional role in neuronal cells should be done with care, bearing in mind multiple effects of DS, a proper evaluation of which would require multivariate analysis.

The study of human neurons and their interaction with neurochemicals is difficult due to the inability to collect primary biomaterial. However, recent advances in the cultivation of human stem cells, methods for their neuronal differentiation and chimeric fluorescent calcium indicators have allowed the creation of model systems in vitro. In this paper we report on the development of a method to obtain human neurons with the GCaMP6s calcium indicator, based on a human iPSC line with the TetON-NGN2 transgene complex. The protocol we developed allows us quickly, conveniently and efficiently obtain significant amounts of human neurons suitable for the study of various neurochemicals and their effects on specific neurophysiological activity, which can be easily registered using fluorescence microscopy. In the neurons we obtained, glutamate (Glu) induces rises in [Ca2+]i which are caused by ionotropic receptors for Glu, predominantly of the NMDA-type. Taken together, these facts allow us to consider the model we have created to be a useful and successful development of this technology.

Neural activity depends on the maintenance of ionic and osmotic homeostasis. Under these conditions, the cell volume must be regulated to maintain optimal neural function. A disturbance in the neuronal volume regulation often occurs in pathological conditions such as glutamate excitotoxicity. The cell volume, mechanical properties, and actin cytoskeleton structure are tightly connected to achieve the cell homeostasis. Here, we studied the effects of glutamate-induced excitotoxicity, external osmotic pressure, and inhibition of actin polymerization on the viscoelastic properties and volume of neurons. Atomic force microscopy was used to map the viscoelastic properties of neurons in time-series experiments to observe the dynamical changes and a possible recovery. The data obtained on cultured rat cortical neurons were compared with the data obtained on rat fibroblasts. The neurons were found to be more responsive to the osmotic challenges but less sensitive to the inhibition of actin polymerization than fibroblasts. The alterations of the viscoelastic properties caused by glutamate excitotoxicity were similar to those induced by the hypoosmotic stress, but, in contrast to the latter, they did not recover after the glutamate removal. These data were consistent with the dynamic volume changes estimated using ratiometric fluorescent dyes. The recovery after the glutamate-induced excitotoxicity was slow or absent because of a steady increase in intracellular calcium and sodium concentrations. The viscoelastic parameters and their changes were related to such parameters as the actin cortex stiffness, tension, and cytoplasmic viscosity.

Exposure of cultured neurons to high concentrations of Glu leads to a strong depolarization of mitochondria, which develops synchronously with the secondary rise in the intracellular Ca2+ concentration (delayed calcium deregulation, DCD). In this study, using the primary culture of rat cerebellar neurons, we investigated the mechanism of neuronal sensitization, which manifests itself in the reduction of latent periods of DCD during repeated exposures to Glu. It was shown that the most likely cause of sensitization is the inability of mitochondria to maintain a high transmembrane potential (ΔΨm) as a result of an increase in the proton conductivity of the internal mitochondrial membrane, but not the opening of the mitochondrial permeability transition pore in the inner mitochondrial membrane. Mitochondrial dysfunction reduces the production of ATP, leading to the inability of neurons to quickly restore the concentration of Na+, ATP, and NADH in the intervals between successive Glu administrations. One of the reasons that aggravate the dysfunction of mitochondria and contribute to the sensitization of neurons to the repeated action of Glu is Ca2+ accumulated in the mitochondria during the first glutamate impact.

The MTT assay based on the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium in the cell cytoplasm to a strongly light absorbing formazan is among the most commonly used methods for determination of cell viability and activity of NAD-dependent oxidoreductases. In the present study, the effects of MTT (0.1 mg/ml) on mitochondrial potential (ΔΨm), intracellular NADH, and respiration of cultured rat cerebellum neurons and isolated rat liver mitochondria were investigated. MTT caused rapid quenching of NADH autofluorescence, fluorescence of MitoTracker Green (MTG) and ΔΨm-sensitive probes Rh123 (rhodamine 123) and TMRM (tetramethylrhodamine methyl ester). The Rh123 signal, unlike that of NADH, MTG, and TMRM, increased in the nucleoplasm after 5-10 min, and this was accompanied by the formation of opaque aggregates of formazan in the cytoplasm and neurites. Increase in the Rh123 signal indicated diffusion of the probe from mitochondria to cytosol and nucleus due to ΔΨm decrease. Inhibition of complex I of the respiratory chain decreased the rate of formazan formation, while inhibition of complex IV increased it. Inhibition of complex III and ATP-synthase affected only insignificantly the rate of formazan formation. Inhibition of glycolysis by 2-deoxy-D-glucose blocked the MTT reduction, whereas pyruvate increased the rate of formazan formation in a concentration-dependent manner. MTT reduced the rate of oxygen consumption by cultured neurons to the value observed when respiratory chain complexes I and III were simultaneously blocked, and it suppressed respiration of isolated mitochondria if substrates oxidized by NAD-dependent dehydrogenases were used. These results demonstrate that formazan formation in cultured rat cerebellum neurons occurs primarily in mitochondria. The initial rate of formazan formation may serve as an indicator of complex I activity and pyruvate transport rate.

For the first time, simultaneous monitoring of changes in the concentration of cytosolic ATP ([ATP]c), pH (pHc), and intracellular free Ca2+ concentration ([Ca2+]i) of the individual neurons challenged with toxic glutamate (Glu) concentrations was performed. To this end, the ATP-sensor AT1.03, which binds to ATP and therefore enhances the efficiency of resonance energy transfer between blue fluorescent protein (energy donor) and yellow-green fluorescent protein (energy acceptor), was expressed in cultured hippocampal neurons isolated from 1–2-day-old rat pups. Excitation of fluorescence in the acceptor protein allowed monitoring changes in pHc. Cells were loaded with fluorescent low-affinity Ca2+ indicators Fura-FF or X-rhod-FF to register [Ca2+]i. It was shown that Glu (20 μM, glycine 10 μM, Mg2+-free) produced a rapid acidification of the cytosol and decrease in [ATP]c. An approximately linear relationship (r 2 = 0.56) between the rate of [ATP]c decline and latency of glutamate-induced delayed calcium deregulation (DCD) was observed: higher rate of [ATP]c decrease corresponded to shorter DCD latency period. DCD began with a decrease in [ATP]c of as much as 15.9%. In the phase of high [Ca2+]i, the plateau of [ATP]c dropped to 10.4% compared to [ATP]c in resting neurons (100%). In the presence of the Na+/K+-ATPase inhibitor ouabain (0.5 mM), glutamate-induced reduction in [ATP]c in the phase of the high [Ca2+]i plateau was only 36.6%. Changes in [ATP]c, [Ca2+]i, mitochondrial potential, and pHc in calcium-free or sodium-free buffers, as well as in the presence of the inhibitor of Na+/K+-ATPase ouabain, led us to suggest that in addition to increase in proton conductivity and decline in [ATP]c, one of the triggering factors of DCD might be a reversion of the neuronal plasma membrane Na+/Ca2+ exchange.