Zakharova, Nadezhda M

Karanova M.V., Zakharova N.M.

This study continues our previous research aimed at investigating changes in the pools of amino acids in the myocardium of the ground squirrel during winter torpor. Neurochemical profiles of amino acids and the secondary metabolites (taurine, phosphoserine, and cysteic acid) were explored in the neocortex of the ground squirrel at different stages of torpor: in the beginning of torpor (2–3 days) and during prolonged torpor (9–10 days), as well as during short-term winter arousal (winter activity, euthermia). Reduced excitatory neurotransmitter levels (glutamate by 7% and 14%; aspartate by 25% and 52% in a coordinated manner and the increased level of GABA, the main transmission inhibitor (by 50% and 67%) were observed from the onset of the torpor entry and at the end of the torpor arousal, respectively. Alanine, which was formed in negligible amounts in the neocortex in the summer season, increased at the initial stage of hibernation and after multiday torpor bout (by 98% and 126%, respectively), indicating a partial switch to anaerobic glycolysis. Short-term interbout euthermia returned levels of these substances back to normal. The behavior of glutamate and aspartate, the anaplerotic substrates, that supported cycling of the tricarboxylic acid cycle during torpor and winter activity periods was like their responses in the myocardium, though differed quantitatively. The responses of the neuromodulators such as glycine, threonine, and lysine differed radically when compared to their responses in the myocardium. No changes in taurine and phosphoserine pools were detected, but the level of cysteic acid decreased compared to the summer control from 0.51 ± 0.06 μmol/g to 0.07 ± 0.01 μmol/g at the end of torpor, while during winter euthermia it became 2 times lower than the summer level. Our data suggest that metabolic pathways involving anaplerotic amino acids of the neocortex are more active than the myocardium during winter torpor, while the pools of neuromodulators that regulate inhibition processes, increase.

Teplova P.O., Komelina N.P., Lizorkina K.I., Zakharova N.M.

Previously, it has been shown that a series of physiological and biochemical changes occur in Yakutian long-tailed ground squirrels during autumn (the pre-hibernation period), involving the brain, heart, skeletal muscles, and other organs. This study was conducted to analyze the composition of peripheral blood cells obtained from Yakutian ground squirrels in autumn. For the first time, an increase in the total number of leukocytes, particularly granulocytes, and a decrease in the number of lymphocytes were observed when compared with samples obtained in summer; a leukogram shift from the lymphocytic to the granulocytic fraction was revealed. Significant increase in platelet counts and thrombocrit with preservation of the percentage ratio of mature and young cell fractions was shown. To date, information on the cellular components of blood during the autumn season when hibernators prepare for winter months of hibernation remains scarce. Nonetheless, the results of our study indicate that very significant adaptive changes occur in leukocytes and platelets of ground squirrels in this period. Possible causes of these changes are discussed.

Gritsyna Y.V., Popova S.S., Mikhailova G.Z., Bobyleva L.G., Udaltsov S.N., Morenkov O.S., Zakharova N.M., Vikhlyantsev I.M.

Changes in the content of heat shock protein 90 (HSP90) in m. soleus (contains mainly fibers expressing the “slow” isoform I MyHC) and m. gastrocnemius (contains mainly fibers expressing the “fast” isoforms II MyHC) of a true hibernant, the long-tailed ground squirrel (Urocitellus undulatus), during different periods of the annual cycle, summer activity (seasonal control), hypothermia/winter torpor, and winter (interbout) activity, were studied. It was found that despite the development of atrophic changes that were more pronounced in the “fast” m. gastrocnemius, the content of HSP90 in both muscles did not change throughout the hibernation period. The role of HSP90 in maintaining the stability of the titin giant sarcomeric protein molecules during the periods of the animal’s entry into and exit from hypothermia, when the activity of calpain proteases increased due to the increased content of Ca2+ in the cytosol of muscle cells, as well as during hypothermia, when the activity of calpains most likely was not completely inhibited, was discussed. During the winter/interbout activity, when there was an increased titin turnover in the striated ground squirrel muscles, a constant content of HSP90 was apparently necessary for the correct folding of newly synthesized titin molecules and their embedding into sarcomeres, as well as for the removal of improperly folded and old titin molecules/fragments, as well as other proteins. Thus, HSP90 proteostasis in skeletal muscles of the long-tailed ground squirrel could contribute to maintaining a stable level of titin and, possibly, other sarcomeric proteins during hibernation, which, in turn, would contribute to maintaining a highly ordered sarcomeric structure and the necessary level of contractile muscle activity in different phases of the hibernation–wakefulness cycle.

Prokhorov D.A., Kutyshenko V.P., Tarahovsky Y.S., Kukushkin N.I., Khrenov M.O., Kovtun A.L., Zakharova N.M.

The inert gas xenon (Xe) is increasingly used in medicine as a universal anesthetic, a regulator of cellular metabolism, and a broad-spectrum organoprotector. Commonly utilized Xe inhalation requires expensive equipment that is not universally available. Here we describe the production process and physical characteristics of a solid, highly stable xenon carrier based on α-cyclodextrin (α-CD), developed for oral administration. It was found, that the interaction of α-CD with Xe in an aqueous solution and elevated pressure leads to precipitation of the α-CD-Xe complex. We have discovered three new properties of the resulting complex that promote long-term storage and oral delivery of Xe. (i) At temperatures below 0 °C, the precipitated α-CD-Xe complex containing water is so stable that it allows the removal of water by vacuum freeze-drying (lyophilization). (ii). Lyophilized α-CD-Xe remains stable for months at room temperature. (iii) Upon contact with water, α-CD-Xe rapidly releases gaseous Xe. As revealed in the forced swim test, after oral administration of lyophilized α-CD-Xe to rats, the duration of swimming was significantly increased. The obtained data open up prospects for the development of drugs based on the lyophilized α-CD-Xe complex suitable for storage, transportation, and medical use, including outside the hospital.

Averin A.S., Zakharova N.M., Ignatiev D.A.

Karanova M.V., Zakharova N.M.

Muscular atrophy is not observed in hibernating animals during hibernation. The mechanisms of this phenomenon are unknown, however their fine regulation should be reflected in the status of free amino acids of skeletal muscles. In this study, the composition of free amino acids in skeletal muscles of the Yakut ground squirrel in winter hibernation at 0°C was explored. There was an increase in the content of alanine during hibernation that returned to the summer level during short-term awakening. Aspartic acid was found in the skeletal muscles of ground squirrels at the beginning of torpor, and it disappeared upon short-term awakening. The pools of glycine and taurine did not change at the beginning or the end of torpor. Pools of essential amino acids increased at the end of torpor, and with a short-term awakening they return to the initial level. The interrelated increase and decrease in the content of free amino acids indicated the absence of predominance of catabolism processes over anabolism.

Averin A.S., Zakharova N.M., Ignatiev D.A.

Abstract—The effects of a four-fold decrease in the concentration of Ca2+ in a perfusing medium under pronounced hypothermia at 20°C on the contractile responses of the papillary muscles of the right ventricle of a guinea pig, that is, the frequency–force dependence in the frequency range of 0.1–1.0 Hz and the effect of potentiation by a pause at stimulation frequencies of 0.3 and 0.8 Hz, were studied. It was shown that with a decrease in the concentration of extracellular Ca2+ there was a significant decrease in the contraction force of papillary muscles from 40 to 70%, reaching a maximum of 72 ± 3% at a frequency of 0.4 Hz; at the same time, the positive frequency–forcer dependence remained. The absolute values of the effect of potentiation by a pause decreased and the decrease was most pronounced at a lower stimulation frequency (79 ± 6% and 40 ± 19% at 0.3 and 0.8 Hz, respectively). Thus, it was shown that the predominant dependence of contraction on extracellular sources of Ca2+ in the myocardium of guinea pigs persisted under pronounced hypothermia; at the same time, an increase in the frequency of stimulation led to an increase in the content of Ca2+ in the sarcoplasmic reticulum.

Averin A.S., Zakharova N.M., Tarlachkov S.V.

While deep hypothermia is well known to lead to cardiac malfunction up to circulatory arrest, mild hypothermia can prevent hypoxic damage to the heart. Importantly, a large body of research on deep hypothermia was carried out on rats and mice whose myocardium is significantly different from the human. In the present work, we investigated the effect of deep hypothermia on rhythmoinotropic phenomena in the guinea pig (GP) whose myocardium is more alike the human. The force––frequency relationship (FFR), effect of post-rest potentiation, and frequency-dependent acceleration of relaxation (FDAR) were studied in GP right ventricular papillary muscles (PM) within a range of 0.1–3.0 Hz at temperatures of 30, 20 and 10°C. It was shown that a positive FFR, mediated mainly by the inward Ca2+ current through the L-type Ca2+ channel, persists when cooling to 10°C, suggesting that this mechanism retains its activity even under deep hypothermia. The effect of post-rest potentiation persists down to 20°C, while further cooling replaces potentiation by depression. This may indicate that at 10°C, the functioning of the sarcoplasmic reticulum is impaired, as manifested in the rest-induced inversion of the post-rest potentiation effect. The effect of frequency-dependent acceleration of the kinetics of muscular contraction also persists down to 20°C, supporting the suggestion that this effect in the GP myocardium relies on the sarcoplasmic reticulum. Thus, we found that among the studied frequency-dependent effects, there are those affected by deep hypothermia (post-rest potentiation effect, FDAR) and those resistant to this exposure (FFR), which may reflect the differences in thermal sensitivity of the underlying mechanisms of Ca2 + transport.

Mednikova Y.S., Voronkov D.N., Khudoerkov R.M., Pasikova N.V., Zakharova N.M.

Excitation mechanisms in the nervous system and neuronal–glial interactions involved in this process are described on the basis of published data and original findings. Two processes, passive and active, form excitation in the nervous system. The active type of excitation requires energy support and is associated with the regulation of the membrane properties of neurons, leading to generation of variable spontaneous pulses. Spike activity generated by the passive process is highly stable and results from transmembrane movement of Na+ and K+ ions along their concentration gradients. The passive type of excitation is due to glutamatergic contacts; the active type of excitation is due to a diffuse release of acetylcholine from cholinergic nuclei of the brain and attenuation of K+ membrane permeability. Energy supply of the active excitation process involves glia. Glial cells directly interact with brain vessels, accumulate glucose in the form of glycogen, realise glycolysis as the first step of energy metabolism, and regulate local cerebral blood flow coupled with M-cholinergic excitation of neurons. A steady decrease in the rate of the M-cholinergic process (in terms of concentration, temperature, or energy) leads to a rapid outflow of K+ ions from neurons, and removing K+ from the intercellular environment is also a function of glia.

Zakharova N.M., Tarahovsky Y.S., Komelina N.P., Khrenov M.O., Kovtun A.L.

Resistance to hypoxia is one of the most prominent features of natural hibernation and is expected to be present in the pharmacological torpor (PT) that simulates hibernation. We studied resistance to lethal hypoxia (3.5% oxygen content) in rats under PT. To initiate PT, we used the previously developed pharmacological composition (PC) which, after a single intravenous injection, can induce a daily decrease in Tb by 7 °C-8 °C at the environmental temperature of 22 °C-23 °C. Half-survival (median) time of rats in lethal hypoxia was found to increase from 5 ± 0.8 min in anesthetized control rats to 150 ± 12 min in rats injected with PC, which is a 30-fold increase. Behavioral tests after PT and hypoxia, including the traveling distance, the number of rearing and grooming episodes, revealed that animal responses are significantly restored within a week. It is assumed that the discovered unprecedented resistance of artificially torpid rats to lethal hypoxia may open up broad prospects for the therapeutic use of PT for preconditioning to various damaging factors, treatment of diseases, and extend the so-called "golden hour" for lifesaving interventions.

Zakharova N.M., Tarahovsky Y.S., Komelina N.P., Fadeeva I.S., Kovtun A.L.

The maintenance of pharmacological torpor and hypothermia (body temperature 28 °C - 33 °C) in rats for a week is presented. For this purpose, our laboratory has developed a device (BioFeedback-2) for the feed-back controlled multiple injections of small doses of a pharmacological composition that we created earlier. On the 7th day, the rat spontaneously come out of the pharmacological torpor, the body temperature returned to normal, and on the 8th day, the animal could consume food and water. The proposed approach for maintaining multi-day pharmacological torpor can be applied in medicine, as well as for protecting astronauts during long missions in space.

Лапин К.Н., Рыжков И.А., Захарова Н.М.

В комплексной химиотерапии опухолей часто применяют циклофосфамид, обладающий негативным действием на мужскую репродуктивную систему. К настоящему времени нет единой стратегии защиты от этого влияния, в том числе из-за отсутствия полной картины эффектов циклофосфамида на разных уровнях половой системы. Исследовано влияние циклофосфамида при однократном внутрибрюшинном введении в дозах 10 и 20 мг/кг в течение 5 дней на репродуктивную систему белых беспородных крыс-самцов. Проведен тест по изучению половой поведенческой реакции у самцов крыс. Показано, что циклофосфамид в дозах 10 и 20 мг/кг уменьшает количество «взбираний» на самку на 68 и 90 %, соответственно (p ≤ 0,05). Применение этого препарата в дозе 20 мг/кг сопровождается полным отсутствием интромиссий. Установлено, что после введения циклофосфамида в дозе 20 мг/кг уровень тестостерона и лютеинизирующего гормона в крови снижается на 71 и 74 % (p ≤ 0,05). Препарат в этой дозе вызывает уменьшение массы пениса, предстательной железы и семенных пузырьков на 12, 25 и 80 %, соответственно (p ≤ 0,05). После введения циклофосфамида в дозе 10 мг/кг при микроскопическом анализе половых клеток выявлено увеличение числа сперматозоидов с дефектами шейки и хвоста на 38 и 35 % (p ≤ 0,05.) Применение препарата в дозе 20 мг/кг вызывает возрастание количества сперматозоидов с дефектами головки, шейки и хвоста на 100, 63 и 75 %, соответственно (p ≤ 0,05).

Popova S., Ulanova A., Gritsyna Y., Salmov N., Rogachevsky V., Mikhailova G., Bobylev A., Bobyleva L., Yutskevich Y., Morenkov O., Zakharova N., Vikhlyantsev I.

Molecular mechanisms underlying muscle-mass retention during hibernation have been extensively discussed in recent years. This work tested the assumption that protein synthesis hyperactivation during interbout arousal of the long-tailed ground squirrel Urocitellus undulatus should be accompanied by increased calpain-1 activity in striated muscles. Calpain-1 is known to be autolysed and activated in parallel. Western blotting detected increased amounts of autolysed calpain-1 fragments in the heart (1.54-fold, p < 0.05) and m. longissimus dorsi (1.8-fold, p < 0.01) of ground squirrels during interbout arousal. The total protein synthesis rate determined by SUnSET declined 3.67-fold in the heart (p < 0.01) and 2.96-fold in m. longissimus dorsi (p < 0.01) during interbout arousal. The synthesis rates of calpain-1 substrates nebulin and titin in muscles did not differ during interbout arousal from those in active summer animals. A recovery of the volume of m. longissimus dorsi muscle fibres, a trend towards a heart-muscle mass increase and a restoration of the normal titin content (reduced in the muscles during hibernation) were observed. The results indicate that hyperactivation of calpain-1 in striated muscles of long-tailed ground squirrels during interbout arousal is accompanied by predominant synthesis of giant sarcomeric cytoskeleton proteins. These changes may contribute to muscle mass retention during hibernation.

Tarahovsky Y.S., Khrenov M.O., Kovtun A.L., Zakharova N.M.

The constancy of the activation energy of metabolism (E) for all living organisms is one of the most impressive, though controversial, statements of the modern metabolic theory of evolution. According to WBE-theory suggested by West, Brown, and Enquist, E should be in the range from −0.6 to −0.7 eV. However, there are many examples of significant deviations of E from the predictions of the theory. Now we have conducted a study of this value using rats in different types of pharmacological hypothermia: 1. Short-term (for several hours) hypothermia induced by anesthetic xylazine; 2. Daily torpor-like state induced by the pharmacological composition developed in our previous study. It has been found that in pharmacological daily hypothermia E = −0.56 ± 0.03 eV, which was close to that in daily heterotherms found in literature, E = −0.57 ± 0.04 eV. In short-term hypothermia E was substantially lower, E = −0.17 ± 0.071 eV. Our analysis revealed that in short-term hypothermia, changes in body temperature may lag behind changes in metabolic rate for a period Δt, affecting E. We propose an approach for estimating Δt and obtaining an adjusted E = −0.68 ± 0.17 eV, which corresponds to theoretical predictions. We assume that a similar consideration of Δt should be done when calculating E of daily heterotherms. We assume that in ectotherms, when the ambient temperature changes rapidly, changes in metabolic rate may lag behind changes in body temperature for a period (−) Δt, that should also be considered in E calculations. The proposed approach may contribute to the further development of the metabolic theory of evolution and may be useful in comparing artificial and natural hypothermia, as well as in studying the energy transformations in ecosystems.

Khunderyakova N.V., Zakharova N.M.

We studied energy metabolism in blood lymphocytes of Yakut ground squirrels Spermophilus undulatus in active state and during hibernation. Activities of succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH), marker enzymes of mitochondrial respiration and glycolysis, were measured by a cytobiochemical method based on quantitative assessment of a product of NBT reduction to diformazan in blood lymphocytes immobilized on glass. To measure SDH and LDH activities, cytobiochemical staining of immobilized cells was performed with succinate, lactate, and NAD. In the state of hibernation, SDH activity decreased by 3 times and LDH activity decreased by 10 times or more. These results suggest that the decrease in metabolic activity in lymphocytes of ground squirrels during hypothermia is associated with inhibition of glycolysis, rather than with mitochondrial energy supply.

Kurhaluk N., Tkaczenko H.

This literature review explores the impact of molecular, genetic, and environmental factors on the efficacy of targeted therapies in veterinary medicine. Relevant studies were identified through systematic searches of PubMed, Web of Science, Scopus, and ScienceDirect using keywords such as “species-specific treatment strategies”, “signalling pathways”, “epigenetic and paragenetic influences”, “targeted therapies”, “veterinary medicine”, “genetic variation”, and “free radicals and oxidative stress”. Inclusion criteria included studies focusing on species-specific therapeutic responses, genetic influences, and oxidative stress. To ensure that only the most recent and relevant evidence was included, only peer-reviewed publications from the last two decades were considered. Each study selected for analysis was critically appraised, with a particular emphasis on methodological quality, experimental design, and scientific contribution to the understanding of how environmental and biological factors influence therapeutic outcomes. A special emphasis was placed on studies that used a comparative, cross-species approach to assess variability in therapeutic responses and potential adverse effects. The review synthesises evidence on the role of epigenetic and paragenetic factors and highlights the importance of cross-species studies to understand how environmental and biological factors influence treatment outcomes. By highlighting genetic variation, oxidative stress, and individual species differences, the review argues for personalised and species-specific therapeutic approaches. The review emphasises that such an approach would improve veterinary care and inform future research aimed at optimising targeted therapies, ultimately leading to better animal health and treatment efficacy. A key contribution of the review is its emphasis on the need for more personalised treatment protocols that take into account individual genetic profiles and environmental factors; it also calls for a greater integration of cross-species studies.

Wang J., Jiang J., Hu H., Chen L.

Globally, the onset and progression of multiple human diseases are associated with mitochondrial dysfunction and dysregulation of Ca2+ uptake dynamics mediated by the mitochondrial calcium uniporter (MCU) complex, which plays a key role in mitochondrial dysfunction. Despite relevant studies, the underlying pathophysiological mechanisms have not yet been fully elucidated. This article provides an in-depth analysis of the current research status of the MCU complex, focusing on its molecular composition, regulatory mechanisms, and association with diseases. In addition, we conducted an in-depth analysis of the regulatory effects of agonists, inhibitors, and traditional Chinese medicine (TCM) monomers on the MCU complex and their application prospects in disease treatment. From the perspective of medicinal chemistry, we conducted an in-depth analysis of the structure–activity relationship between these small molecules and MCU and deduced potential pharmacophores and binding pockets. Simultaneously, key structural domains of the MCU complex in Homo sapiens were identified. We also studied the functional expression of the MCU complex in Drosophila, Zebrafish, and Caenorhabditis elegans. These analyses provide a basis for exploring potential treatment strategies targeting the MCU complex and provide strong support for the development of future precision medicine and treatments. The MCU complex exhibits varying behavior across different tissues and plays various roles in metabolic functions. It consists of six MCU subunits, an essential MCU regulator (EMRE), and solute carrier 25A23 (SLC25A23). They regulate processes, such as mitochondrial Ca2+ (mCa2+) uptake, mitochondrial adenosine triphosphate (ATP) production, calcium dynamics, oxidative stress (OS), and cell death. Regulation makes it a potential target for treating diseases, especially cardiovascular diseases, neurodegenerative diseases, inflammatory diseases, metabolic diseases, and tumors.

Karanova M.V., Gagarinsky E.L., Petrukhin O.V., Reshetnikov A.N.

The freshwater fish Perccottus glenii is of interest owing to its tolerance to a wide range of environmental temperatures; however, the details of the mechanisms of its low-temperature adaptation have been insufficiently studied. Our previous work has shown the involvement of secondary metabolites and amino acids in the compensatory responses to near-zero temperatures of skeletal muscles, brain, blood plasma, and liver of P. glenii. In the current study we report their compensatory responses in the heart. It has been shown that, at the beginning of hypobiosis (December), at a water temperature of 1°C, the level of taurine almost halves in comparison with summer concentration (9.70 ± 0.55 μmol/g wet weight), and it decreases further to 3.80 ± 0.25 μmol/g by the end of winter hypobiosis (beginning of April). Phosphoethanolamine was not detected in summer, but it appears in December (0.81 ± 0.07 μmol/g) and increases until the end of hibernation. Cysteic acid was also found only in December but its concentration decreased before the end of hypobiosis. The ratio of glutamate and alanine pools, the indicator of the metabolic contribution of aerobic and anaerobic energy, showed a slight decrease of glutamate during hypobiosis and increase of alanine. Amino acid responses suggest that oxidative phosphorylation and the tricarboxylic acid cycle are actively involved in the energy supply of the heart of P. glenii even at the end of hypobiosis.

Kokko A.P., Chowdhury R., Sherman K., Cerri M., Tinganelli W.

The idea of synthetic torpor, an artificial state resembling the hypo-metabolic state of torpor/hibernation, has recently gained significant scientific attention. Building on pioneering research demonstrating the protective effects of torpor against radiation in mammals, this mini-review aims to evaluate its scientific validity. We will explore the theoretical foundations, practical applications, and potential challenges linked to synthetic torpor. By critically examining the current knowledge, we aim to determine if synthetic torpor is a scientifically viable and achievable concept with broad implications for fields such as space exploration and healthcare.

Karanova M.V., Zakharovа N.M.

This study is a continuation of our previous research aimed at investigating changes in the pools of amino acids in the myocardium of the ground squirrel during winter torpor. Neurochemical profiles of amino acids and the secondary metabolites (taurine, phosphoserine, and cysteic acid) were explored in the neocortex of the ground squirrel at different stages of torpor: in the beginning of torpor (2–3 days) and during prolonged torpor (9–10 days), as well as during short-term winter arousal (winter activity, euthermia). Reduced excitatory neurotransmitter levels (glutamate by 7% and 14%; aspartate by 25% and 52% in a coordinated manner and the increased level of GABA, the main transmission inhibitor (by 50% and 67%) were observed from the onset of the torpor entry and at the end of the torpor arousal, respectively. Alanine, which was formed in negligible amounts in the neocortex in the summer season, increased at the initial stage of hibernation and after multiday torpor bout (by 98% and 126%, respectively), indicating a partial switch to anaerobic glycolysis. Short-term inter-bout euthermia returned levels of these substances back to normal. The behavior of glutamate and aspartate, the anaplerotic substrates, that supported cycling of the tricarboxylic acid cycle during torpor and winter activity periods was like their responses in the myocardium, though differed quantitatively. The responses of the neuromodulators such as glycine, threonine, and lysine differed radically when compared to their responses in the myocardium. No changes in taurine and phosphoserine pools were detected, but the level of cysteic acid decreased compared to the summer control from 0.51 ± 0.06 μmol/g to 0.07 ± 0.01 μmol/g at the end of torpor, while during winter euthermia it became 2 times lower than the summer level. Our data suggest that metabolic pathways, involving anaplerotic amino acids of the neocortex, are more active than the myocardium during winter torpor, while the pools of neuromodulators that regulate inhibition processes, increase.

Ilzorkina A.I., Belosludtseva N.V., Semenova A.A., Dubinin M.V., Belosludtsev K.N.

TRO19622 (olesoxime), a cholesterol-like cytoprotector, is an experimental drug developed as a potential treatment for a range of incurable degenerative diseases. Recent studies have shown that the main molecular targets of this compound in the cell are porins of the outer mitochondrial membrane, which play a crucial role in regulating the exchange of metabolites between mitochondria and the rest of the cell. Disruption of this channel activity may lead to mitochondrial dysfunction in healthy cells. In this study, key indicators of mitochondrial function and the viability of cells in cultures after incubation with TRO19622 were assessed. It was found that TRO19622 at 15–30 μM concentrations inhibits the coupled and uncoupled respiration rates in isolated mitochondria (state 3 rate and 3UDNP) with succinate as substrate, but does not affect the enzymatic activity of respiratory chain complexes I–IV. It was shown that TRO19622 at the studied doses has no effect on the rate of H2O2 formation in mitochondria and the calcium retention capacity index, which reflects the resistance of the organelles to the calcium-dependent nonspecific pore opening. Incubation of human skin fibroblasts and mammary adenocarcinoma cells (MCF-7) with 30 μM TRO19622 for 48 h has no impact on ROS production and cell viability. How TRO19622 works in the oxidative phosphorylation system and therapeutic prospects for using this mitochondrial-targeted agent are discussed.

Zakharova N.M., Tarahovsky Y.S., Khrenov M.O.

The temperature coefficients Q10 of heart rate (Q10HR) or oxygen consumption (Q10Ox) were analyzed during the arises from torpor of long-tailed ground squirrels Urocitellus undulatus, as well as during the rewarming of precooled adult rats and rat pups. The Q10Ox value was calculated using a standard equation, whereas for calculating Q10HR, the equation was empirically modified to track changes in this parameter over a wide range of body temperatures (Tb). It was found that during the initial period of rewarming from torpor, at Th ≤ 10 ℃, ground squirrels experienced a sharp increase in the temperature coefficients up to Q10HR = 40 – 50 and Q10Ox = 6 – 7. Even higher values of Q10HR 100 were found at the beginning of rewarming of rat pups, although they had a low level of Q10Ox = 1.2. Adult rats could not withstand cooling below 16 ℃ and demonstrated moderate variability of both Q10HR = 2.0 – 4.0 and Q10Ox = 2.0 – 2.2. During the restoration of normal Tb, the Q10HR in all animals approached the level ~2.0 predicted by the Van't Hoff-Arrhenius rule for chemical reactions in both living and inanimate nature. We assume that high values of Q10HR and Q10Ox, detected in the early period of ground squirrel’s arousal from hibernation, may reveal the functioning of adaptive processes aimed at accelerating body warming. Resistance to cooling and high Q10HR coefficient in the rat pups may indicate rudimentary adaptability to hibernation in the juvenile period of rats, as representatives of the order Rodentia, which also includes natural hibernators such as ground squirrels.

Fang L., Shen J., Wu Y., Tan Z.

Adenine is frequently utilized as a model medication for chronic renal disease. Adenine can affect organs other than the kidneys, including the heart and the intestine. The liver is a vital organ involved in the in vivo metabolism of adenine. Adenine may negatively impact liver function. Research indicated that adenine caused dysbiosis of the gut microbiota in mice. Investigations into the gut–liver axis have demonstrated a substantial association between drug-induced hepatic dysfunction and gut microbiota. Consequently, we delivered distinct dosages of adenine via gavage to mice to examine the correlation between adenine-induced liver impairment and gut microbiota dysbiosis. Mice were treated with low-dose adenine suspension (NLA), medium-dose adenine suspension (NMA), high-dose adenine suspension (NHA), and sterile water (NC) as a control. The results indicated that mice in the NLA, NMA, and NHA groups had decreased body weight and a reduction in liver index. Subsequent to adenine administration, the concentrations of AST, ALT, and LDH increased, whereas SDH levels decreased. As doses increased, liver function impairment and hepatic energy metabolism abnormalities aggravated. Adenine also damaged the colonic architecture in mice. Moreover, adenine modified the makeup and structure of the gut mucosal microbiota, enhancing specific bacterial genera and influencing the microbiota's energy metabolism-related functions. The results of our research established a correlation among certain bacteria, liver function injury, and hepatic energy metabolism. The gut mucosal microbiota was involved in adenine-induced liver injury and hepatic energy metabolism. These results can offer novel insights into the role of gut microbiota in drug-induced liver injury and provide specific guidelines for the modeling and therapeutic application of adenine.

Salucci S., Hitrec T., Piscitiello E., Occhinegro A., Alberti L., Taddei L., Burattini S., Luppi M., Tupone D., Amici R., Faenza I., Cerri M.

Torpor is a state used by several mammals to survive harsh winters and avoid predation, characterized by a drastic reduction in metabolic rate followed by a decrease in body temperature, heart rate, and many physiological variables. During torpor, all organs and systems must adapt to the new low-energy expenditure conditions to preserve physiological homeostasis. These adaptations may be exploited in a translational perspective in several fields. Recently, many features of torpor were shown to be mimicked in non-hibernators by the inhibition of neurons within the brainstem region of the Raphe Pallidus. The physiological resemblance of this artificial state, called synthetic torpor, with natural torpor has so far been described only in physiological terms, but no data have been shown regarding the induced morphological changes. Here, we show the first description of the ultrastructural changes in the liver, kidney, lung, skeletal muscle, and testis induced by a 6-hours inhibition of Raphe Pallidus neurons in a non-hibernating species, the rat.

Kulagina T.P., Vikhlyantsev I.M., Aripovsky A.V., Popova S.S., Gapeyev A.B.

Seasonal changes in the fatty acid composition in four skeletal muscles of the true hibernant Yakut long-tailed ground squirrel Urocitellus undulatus were studied. Measurements were taken on animals of four experimental groups: summer active, autumn active, winter dormant, and winter active. An increase in the total amount of fatty acids was found in winter in the quadriceps muscle of the thigh (m. vastus lateralis), the triceps muscle of the forearm (m. triceps), and the psoas muscle (m. psoas). In all muscles, including m. gastrocnemius, a decrease in the total amount of saturated fatty acids was observed in winter. An increase in the total amount of monounsaturated fatty acids in winter hibernating animals occurred in the quadriceps femoris muscle, triceps muscle of the forearm, and in the psoas muscle. In winter active animals, the total content of polyunsaturated fatty acids in the quadriceps femoris and psoas muscles increased. A significant decrease in palmitic acid content in sleeping and winter active ground squirrels compared to summer and autumn animals was found in all muscles studied. The amount of palmitoleic acid significantly increased in sleeping animals in the quadriceps femoris and psoas muscles. In the triceps muscle of the forearm. the amount of palmitoleic acid increased in autumn active and winter dormant individuals. The amount of oleic acid was increased in all muscles of winter hibernating animals relative to active autumn animals. The content of linoleic acid significantly increased in winter active ground squirrels in all muscles except the gastrocnemius. In the autumn period the amount of dihomo-gamma-linolenic acid also increased in all muscles, with a significant decrease in its content in winter sleeping and winter active animals to the level of summer (seasonal) control. The results obtained indicate that most changes in fatty acid composition have the same direction in all four studied skeletal muscles of the long-tailed ground squirrel. Possible roles of seasonal changes in fatty acid composition and the participation of fatty acids in biochemical processes in the muscle tissue of the long-tailed ground squirrel are discussed.

Weir K., Vega N., Busa V.F., Sajdak B., Kallestad L., Merriman D., Palczewski K., Carroll J., Blackshaw S.

AbstractTorpor encompasses diverse adaptations to extreme environmental stressors such as hibernation, aestivation, brumation, and daily torpor. Here we introduce StrokeofGenus, an analytic pipeline that identifies distinct transcriptomic states and shared gene expression patterns across studies, tissues, and species. We use StrokeofGenus to study multiple and diverse forms of torpor from publicly-available RNA-seq datasets that span eight species and two classes. We identify three transcriptionally distinct states during the cycle of heterothermia: euthermia, torpor, and interbout arousal. We also identify torpor-specific gene expression patterns that are shared both across tissues and between species with over three hundred million years of evolutionary divergence. We further demonstrate the general sharing of gene expression patterns in multiple forms of torpor, implying a common evolutionary origin for this process. Although here we apply StrokeofGenus to analysis of torpor, it can be used to interrogate any other complex physiological processes defined by transient transcriptomic states.

Xu J., Chen W., Hu H., Xie Z., Zhang D., Zhao J., Xiang J., Wei Q., Tidwell T., Girard O., Ma F., Li Z., Ren Y.

Hypobaric hypoxia causes altitude sickness and significantly affects human health. As of now, focusing on rats different proteomic and metabolic changes exposed to different hypoxic times at extreme altitude is blank. Our study integrated

Saha I., Bag N., Roy S., Ullah Z., Bardhan S., Karmakar P., Das S., Guo B.

Vassilopoulou E., Venter C., Roth-Walter F.

Malnutrition, which includes macro- and micronutrient deficiencies, is common in individuals with allergic dermatitis, food allergies, rhinitis, and asthma. Prolonged deficiencies of proteins, minerals, and vitamins promote Th2 inflammation, setting the stage for allergic sensitization. Consequently, malnutrition, which includes micronutrient deficiencies, fosters the development of allergies, while an adequate supply of micronutrients promotes immune cells with regulatory and tolerogenic phenotypes. As protein and micronutrient deficiencies mimic an infection, the body’s innate response limits access to these nutrients by reducing their dietary absorption. This review highlights our current understanding of the physiological functions of allergenic proteins, iron, and vitamin A, particularly regarding their reduced bioavailability under inflamed conditions, necessitating different dietary approaches to improve their absorption. Additionally, the role of most allergens as nutrient binders and their involvement in nutritional immunity will be briefly summarized. Their ability to bind nutrients and their close association with immune cells can trigger exaggerated immune responses and allergies in individuals with deficiencies. However, in nutrient-rich conditions, these allergens can also provide nutrients to immune cells and promote health.

Zakharova N.M., Tarahovsky Y.S., Khrenov M.O.

The temperature coefficients of heart rate (Q10 HR) or oxygen consumption (Q10 Ox) were analyzed upon arousal from natural hibernation in long-tailed ground squirrels Urocitellus undulatus and during the rewarming of artificially precooled adult rats and rat pups. The Q10 Ox value was calculated using a standard equation, whereas for calculating Q10 HR, the equation was empirically modified to track changes in this parameter over a wide range of body temperatures (T b). It was found that during the initial period of arousal from torpor, at T h ≤ 10°C, ground squirrels demonstrated a sharp increase in the temperature coefficients up to Q10 HR = 40–50 and Q10 Ox = 6–7. Even higher values of Q10 HR (>100) were recorded at the onset of rewarming of rat pups, although they had a low level of Q10 Ox (1.2). Adult rats could not tolerate cooling below 16°C and demonstrated a moderate variability of both Q10 HR = 2.0–4.0 and Q10 Ox = 2.0–2.2. During the recovery of normal T b, the Q10 HR values in all animals approximated to ~2.0, as predicted by the van’t Hoff–Arrhenius rule for chemical reactions in both living and inanimate nature. We assume that high values of Q10 HR and Q10 Ox, detected in the early period of ground squirrel’s arousal from hibernation, may indicate the functioning of adaptive processes aimed at accelerating body warming. Resistance to cooling and a high Q10 HR in rat pups may suggest the rudimentary adaptability to hibernation in the juvenile period of rats as representatives of the order Rodentia, which also includes such natural hibernators as ground squirrels.

Karanova M.V., Zakharova N.M.

The state of hibernation is characterized by an increased tolerance to long-term deep hypothermia, hypoxia, lack of food and water. At the same time, even a short-term reorganization of the adaptive mechanisms at low temperatures causes significant metabolic changes in animals, reflected in the amino acid profile. Metabolic changes in myocardial free amino acids during hibernation have not actually been studied, although the knowledge of these processes is important for deeper insight into the mechanisms of hibernation, relevant for clinical medicine. The aim of this work was to study the changes in the composition of myocardial free amino acids in a ground squirrel Urocitellus undulatus at different stages of hibernation. A negative interdependence of glutamic acid and alanine pools was revealed at different stages of torpor. The level of glutamic acid, as compared to the summer control (5.08 ± 0.44 µmol/g of wet weight), began to decline in the first (December) torpor bout, continued throughout prolonged torpor (down to 1.57 ± 0.14 µmol/g), and was accompanied by an increase in the alanine pool. During winter arousal, the glutamic acid pool rose above the summer level, while the alanine pool fell below that, with their total level remaining unchanged. Aspartic acid and glycine pools declined in parallel with the decrease in glutamate and aspartate pools, however, during winter arousal, glycine was not detected whatsoever. Given the involvement of glutamic acid and aspartate in anaplerotic reactions of the tricarboxylic acid (TCA) cycle and the reciprocal relationship of glutamic acid and alanine, it is concluded that the changes in the level of these metabolites at different stages of hibernation bouts reflect a gradual transition from aerobic (TCA cycle and oxidative phosphorylation) to anaerobic glycolysis, and vice versa during euthermia.

Rabeae H.M., Mahfouz S.S., Abdel-Aziz A.M., abdelLatif A.K., Hafez H.S.

Low temperatures and the lack of food during the winter lead the marsh frog Rana ridibunda and the grass frog Rana mascareniensis to hibernate in order to survive. The present study aimed to investigate the cytoarchitecture of brain sub-regions affected by the thermal cycle's fluctuations during the hibernation and activity period, besides the regional distribution quantitative expression of Na(+)/K(+)-ATPase and Pax6 transcriptional factor, the molecular gene expressions of some heat shock proteins, uncoupling protein, and metallothionein. The two frog species were isolated from the field during summer and hibernation time in winter. During hibernation it was notable the destitution of degenerated, pyknotic and vasogenic neurons in different brain areas with high rate nearby the pallium. The immunohistochemical expression of Na+/ K+-ATPase and Pax 6 is decreased during hibernation in different brain sub-regions in the two species suggesting their tendency for energy conservation strategy during hibernation. Additionally, RT-qPCR recorded the up regulation of a number of heat shock protein genes during hibernation with sharing increase between two species for hsp90 besides and the non-significant expression in summer and hibernation periods for hsp47 for both species. Moreover, uncoupling protein (ucp1and ucp2) and metallothionein genes in olfactory bulb were with significant up regulation during the hibernation suggesting that these proteins possibly have a protective effect against reactive oxygen species ROS. So, brain adaptations to low temperature play a crucial role in coordinating stress responses. The present study shed light on the importance of the olfactory bulb in the thermoregulation and sensation of temperature elevations during the hibernation period and defended by the expression of heat shock proteins and uncoupling proteins preventing the cellular damage and proteins misfolding. Neuronal energy production and regeneration activities among amphibians are markedly reduced with decreasing body temperature.

Andersen J.V., Schousboe A.

Salceda R.

The accurate function of the central nervous system (CNS) depends of the consonance of multiple genetic programs and external signals during the ontogenesis. A variety of molecules including neurotransmitters, have been implied in the regulation of proliferation, survival, and cell-fate of neurons and glial cells. Among these, neurotransmitters may play a central role since functional ligand-gated ionic channel receptors have been described before the establishment of synapses. This review argues on the function of glycine during development, and show evidence indicating it regulates morphogenetic events by means of their transporters and receptors, emphasizing the role of glycinergic activity in the balance of excitatory and inhibitory signals during development. Understanding the mechanisms involved in these processes would help us to know the etiology of cognitive dysfunctions and lead to improve brain repair strategies.

Karanova M.V., Zakharova N.M.

Muscular atrophy is not observed in hibernating animals during hibernation. The mechanisms of this phenomenon are unknown, however their fine regulation should be reflected in the status of free amino acids of skeletal muscles. In this study, the composition of free amino acids in skeletal muscles of the Yakut ground squirrel in winter hibernation at 0°C was explored. There was an increase in the content of alanine during hibernation that returned to the summer level during short-term awakening. Aspartic acid was found in the skeletal muscles of ground squirrels at the beginning of torpor, and it disappeared upon short-term awakening. The pools of glycine and taurine did not change at the beginning or the end of torpor. Pools of essential amino acids increased at the end of torpor, and with a short-term awakening they return to the initial level. The interrelated increase and decrease in the content of free amino acids indicated the absence of predominance of catabolism processes over anabolism.

Tseng E., Underwood J.G., Evans Hutzenbiler B.D., Trojahn S., Kingham B., Shevchenko O., Bernberg E., Vierra M., Robbins C.T., Jansen H.T., Kelley J.L.

Abstract Understanding hibernation in brown bears (Ursus arctos) can provide insight into some human diseases. During hibernation, brown bears experience periods of insulin resistance, physical inactivity, extreme bradycardia, obesity, and the absence of urine production. These states closely mimic aspects of human diseases such as type 2 diabetes, muscle atrophy, as well as renal and heart failure. The reversibility of these states from hibernation to active season enables the identification of mediators with possible therapeutic value for humans. Recent studies have identified genes and pathways that are differentially expressed between active and hibernation seasons in bears. However, little is known about the role of differential expression of gene isoforms on hibernation physiology. To identify both distinct and novel mRNA isoforms, full-length RNA-sequencing (Iso-Seq) was performed on adipose, skeletal muscle, and liver from three individual bears sampled during both active and hibernation seasons. The existing reference genome annotation was improved by combining it with the Iso-Seq data. Short-read RNA-sequencing data from six individuals were mapped to the new reference annotation to quantify differential isoform usage (DIU) between tissues and seasons. We identified differentially expressed isoforms in all three tissues, to varying degrees. Adipose had a high level of DIU with isoform switching, regardless of whether the genes were differentially expressed. Our analyses revealed that DIU, even in the absence of differential gene expression, is an important mechanism for modulating genes during hibernation. These findings demonstrate the value of isoform expression studies and will serve as the basis for deeper exploration into hibernation biology.

Ingelson-Filpula W.A., Storey K.B.

The winter months are challenging for many animal species, which often enter a state of dormancy or hypometabolism to “wait out” the cold weather, food scarcity, reduced daylight, and restricted mobility that can characterize the season. To survive, many species use metabolic rate depression (MRD) to suppress nonessential metabolic processes, conserving energy and limiting tissue atrophy particularly of skeletal and cardiac muscles. Mammalian hibernation is the best recognized example of winter MRD, but some turtle species spend the winter unable to breathe air and use MRD to survive with little or no oxygen (hypoxia/anoxia), and various frogs endure the freezing of about two-thirds of their total body water as extracellular ice. These winter survival strategies are highly effective, but create physiological and metabolic challenges that require specific biochemical adaptive strategies. Gene-related processes as well as epigenetic processes can lower the risk of atrophy during prolonged inactivity and limited nutrient stores, and DNA modifications, mRNA storage, and microRNA action are enacted to maintain and preserve muscle. This review article focuses on epigenetic controls on muscle metabolism that regulate MRD to avoid muscle atrophy and support winter survival in model species of hibernating mammals, anoxia-tolerant turtles and freeze-tolerant frogs. Such research may lead to human applications including muscle-wasting disorders such as sarcopenia, or other conditions of limited mobility.

Averin A.S., Zakharova N.M., Ignatiev D.A.

Abstract—The effects of a four-fold decrease in the concentration of Ca2+ in a perfusing medium under pronounced hypothermia at 20°C on the contractile responses of the papillary muscles of the right ventricle of a guinea pig, that is, the frequency–force dependence in the frequency range of 0.1–1.0 Hz and the effect of potentiation by a pause at stimulation frequencies of 0.3 and 0.8 Hz, were studied. It was shown that with a decrease in the concentration of extracellular Ca2+ there was a significant decrease in the contraction force of papillary muscles from 40 to 70%, reaching a maximum of 72 ± 3% at a frequency of 0.4 Hz; at the same time, the positive frequency–forcer dependence remained. The absolute values of the effect of potentiation by a pause decreased and the decrease was most pronounced at a lower stimulation frequency (79 ± 6% and 40 ± 19% at 0.3 and 0.8 Hz, respectively). Thus, it was shown that the predominant dependence of contraction on extracellular sources of Ca2+ in the myocardium of guinea pigs persisted under pronounced hypothermia; at the same time, an increase in the frequency of stimulation led to an increase in the content of Ca2+ in the sarcoplasmic reticulum.

Klichkhanov N.K., Nikitina E.R., Shihamirova Z.M., Astaeva M.D., Chalabov S.I., Krivchenko A.I.

The hibernation of small mammals is characterized by long torpor bouts alternating with short periods of arousal. During arousal, due to a significant increase in oxygen consumption, tissue perfusion, and the launch of thermogenesis in cells, a large amount of reactive oxygen species (ROS) and nitrogen (RNS) can be formed, which can trigger oxidative stress in cells. To estimate this possibility, we studied the intensity of free-radical processes in the red blood cells (RBCs) of little ground squirrels (LGS; Spermophilus pygmaeus) in the dynamics of arousal from hibernation. We found that in the torpid state, the degree of generation of ROS and RNS (8.3%, p&gt;0.09; 20.7%, p&lt;0.001, respectively), the degree of oxidative modification of membrane lipids and RBC proteins is at a low level (47%, p&lt;0.001; 82.7%, p&lt;0.001, respectively) compared to the summer control. At the same time, the activity of superoxide dismutase (SOD) and catalase (CAT) in RBC is significantly reduced (32.8%, p&lt;0.001; 22.2%, p&lt;0.001, respectively), but not the level of glutathione (GSH). In the torpid state, SOD is activated by exogenous GSH in concentration-dependent manner, which indicates reversible enzyme inhibition. During the arousal of ground squirrels, when the body temperature reaches 25°C, RBCs are exposed oxidative stress. This is confirmed by the maximum increase in the level of uric acid (25.4%, p&lt;0.001) in plasma, a marker of oxidative modification of lipids [thiobarbituric acid reactive substances (TBARS); 82%, p &lt; 0.001] and proteins (carbonyl groups; 499%, p &lt; 0.001) in RBC membranes, as well as the decrease in the level of GSH (19.7%, p &lt; 0.001) in erythrocytes relative to the torpid state and activity of SOD and CAT in erythrocytes to values at the Tb 20°C. After full recovery of body temperature, the level of GSH increases, the ratio of SOD/CAT is restored, which significantly reduces the degree of oxidative damage of lipids and proteins of RBC membranes. Thus, the oxidative stress detected at Tb 25°C was transient and physiologically regulated.

Andersen J.V., Markussen K.H., Jakobsen E., Schousboe A., Waagepetersen H.S., Rosenberg P.A., Aldana B.I.

Glutamate is the primary excitatory neurotransmitter of the brain. Cellular homeostasis of glutamate is of paramount importance for normal brain function and relies on an intricate metabolic collaboration between neurons and astrocytes. Glutamate is extensively recycled between neurons and astrocytes in a process known as the glutamate-glutamine cycle. The recycling of glutamate is closely linked to brain energy metabolism and is essential to sustain glutamatergic neurotransmission. However, a considerable amount of glutamate is also metabolized and serves as a metabolic hub connecting glucose and amino acid metabolism in both neurons and astrocytes. Disruptions in glutamate clearance, leading to neuronal overstimulation and excitotoxicity, have been implicated in several neurodegenerative diseases. Furthermore, the link between brain energy homeostasis and glutamate metabolism is gaining attention in several neurological conditions. In this review, we provide an overview of the dynamics of synaptic glutamate homeostasis and the underlying metabolic processes with a cellular focus on neurons and astrocytes. In particular, we review the recently discovered role of neuronal glutamate uptake in synaptic glutamate homeostasis and discuss current advances in cellular glutamate metabolism in the context of Alzheimer's disease and Huntington's disease. Understanding the intricate regulation of glutamate-dependent metabolic processes at the synapse will not only increase our insight into the metabolic mechanisms of glutamate homeostasis, but may reveal new metabolic targets to ameliorate neurodegeneration.

Utsunomiya K.S., da Silva L.J., Iwamoto J., Constantin R.P., Gilglioni E.H., Constantin J., Bracht A., Elferink R.P., Ishii-Iwamoto E.L.

In the present work, the multiple-indicator dilution (MID) technique was used to investigate the kinetic mechanisms by which nickel (Ni2+) affects the calcium (Ca2+) transport in intact rat liver. 45Ca2+ and extra- and intracellular space indicators were injected in livers perfused with 1 mM Ni2+, and the outflow profiles were analyzed by a mathematical model. For comparative purposes, the effects of norepinephrine were measured. The influence of Ni2+ on the cytosolic Ca2+ concentration ([Ca2+]c) in human hepatoma Huh7 cells and on liver glycogen catabolism, a biological response sensitive to cellular Ca2+, was also evaluated. The estimated transfer coefficients of 45Ca2+ transport indicated two mechanisms by which Ni2+ increases the [Ca2+]c in liver under steady-state conditions: (1) an increase in the net efflux of Ca2+ from intracellular Ca2+ stores due to a stimulus of Ca2+ efflux to the cytosolic space along with a diminution of Ca2+ re-entry into the cellular Ca2+ stores; (2) a decrease in Ca2+ efflux from the cytosolic space to vascular space, minimizing Ca2+ loss. Glycogen catabolism activated by Ni2+ was transient contrasting with the sustained activation induced by norepinephrine. Ni2+ caused a partial reduction in the norepinephrine-induced stimulation in the [Ca2+]c in Huh7 cells. Our data revealed that the kinetic parameters of Ca2+ transport modified by Ni2+ in intact liver are similar to those modified by norepinephrine in its first minutes of action, but the membrane receptors or Ca2+ transporters affected by Ni2+ seem to be distinct from those known to be modulated by norepinephrine.

Yushkov B.G.

Mashali M.A., Saad N.S., Canan B.D., Elnakish M.T., Milani-Nejad N., Chung J., Schultz E.J., Kiduko S.A., Huang A.W., Hare A.N., Peczkowski K.K., Fazlollahi F., Martin B.L., Murray J.D., Campbell C.M., et. al.

Heart failure (HF) is associated with highly significant morbidity, mortality, and health care costs. Despite the significant advances in therapies and prevention, HF remains associated with poor clinical outcomes. Understanding the contractile force and kinetic changes at the level of cardiac muscle during end-stage HF in consideration of underlying etiology would be beneficial in developing targeted therapies that can help improve cardiac performance.Investigate the impact of the primary etiology of HF (ischemic or non-ischemic) on left ventricular (LV) human myocardium force and kinetics of contraction and relaxation under near-physiological conditions.Contractile and kinetic parameters were assessed in LV intact trabeculae isolated from control non-failing (NF; n = 58) and end-stage failing ischemic (FI; n = 16) and non-ischemic (FNI; n = 38) human myocardium under baseline conditions, length-dependent activation, frequency-dependent activation, and response to the β-adrenergic stimulation. At baseline, there were no significant differences in contractile force between the three groups; however, kinetics were impaired in failing myocardium with significant slowing down of relaxation kinetics in FNI compared to NF myocardium. Length-dependent activation was preserved and virtually identical in all groups. Frequency-dependent activation was clearly seen in NF myocardium (positive force frequency relationship [FFR]), while significantly impaired in both FI and FNI myocardium (negative FFR). Likewise, β-adrenergic regulation of contraction was significantly impaired in both HF groups.End-stage failing myocardium exhibited impaired kinetics under baseline conditions as well as with the three contractile regulatory mechanisms. The pattern of these kinetic impairments in relation to NF myocardium was mainly impacted by etiology with a marked slowing down of kinetics in FNI myocardium. These findings suggest that not only force development, but also kinetics should be considered as a therapeutic target for improving cardiac performance and thus treatment of HF.

Averin A.S., Zakharova N.M., Tarlachkov S.V.

While deep hypothermia is well known to lead to cardiac malfunction up to circulatory arrest, mild hypothermia can prevent hypoxic damage to the heart. Importantly, a large body of research on deep hypothermia was carried out on rats and mice whose myocardium is significantly different from the human. In the present work, we investigated the effect of deep hypothermia on rhythmoinotropic phenomena in the guinea pig (GP) whose myocardium is more alike the human. The force––frequency relationship (FFR), effect of post-rest potentiation, and frequency-dependent acceleration of relaxation (FDAR) were studied in GP right ventricular papillary muscles (PM) within a range of 0.1–3.0 Hz at temperatures of 30, 20 and 10°C. It was shown that a positive FFR, mediated mainly by the inward Ca2+ current through the L-type Ca2+ channel, persists when cooling to 10°C, suggesting that this mechanism retains its activity even under deep hypothermia. The effect of post-rest potentiation persists down to 20°C, while further cooling replaces potentiation by depression. This may indicate that at 10°C, the functioning of the sarcoplasmic reticulum is impaired, as manifested in the rest-induced inversion of the post-rest potentiation effect. The effect of frequency-dependent acceleration of the kinetics of muscular contraction also persists down to 20°C, supporting the suggestion that this effect in the GP myocardium relies on the sarcoplasmic reticulum. Thus, we found that among the studied frequency-dependent effects, there are those affected by deep hypothermia (post-rest potentiation effect, FDAR) and those resistant to this exposure (FFR), which may reflect the differences in thermal sensitivity of the underlying mechanisms of Ca2 + transport.

Zakharova N.M., Tarahovsky Y.S., Komelina N.P., Khrenov M.O., Kovtun A.L.

Resistance to hypoxia is one of the most prominent features of natural hibernation and is expected to be present in the pharmacological torpor (PT) that simulates hibernation. We studied resistance to lethal hypoxia (3.5% oxygen content) in rats under PT. To initiate PT, we used the previously developed pharmacological composition (PC) which, after a single intravenous injection, can induce a daily decrease in Tb by 7 °C-8 °C at the environmental temperature of 22 °C-23 °C. Half-survival (median) time of rats in lethal hypoxia was found to increase from 5 ± 0.8 min in anesthetized control rats to 150 ± 12 min in rats injected with PC, which is a 30-fold increase. Behavioral tests after PT and hypoxia, including the traveling distance, the number of rearing and grooming episodes, revealed that animal responses are significantly restored within a week. It is assumed that the discovered unprecedented resistance of artificially torpid rats to lethal hypoxia may open up broad prospects for the therapeutic use of PT for preconditioning to various damaging factors, treatment of diseases, and extend the so-called "golden hour" for lifesaving interventions.