Solid Xenon Carrier Based on α-Cyclodextrin: Properties, Preparation, and Application.

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.

Pharmacological torpor prolongs rat survival in lethal normobaric hypoxia.

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.

Long-term pharmacological torpor of rats with feedback-controlled drug administration.

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.

Comparison of natural and pharmacological hypothermia in animals: Determination of activation energy of metabolism.

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.

Transport of Ca2+ and Ca2+-Dependent Permeability Transition in the Liver and Heart Mitochondria of Rats with Different Tolerance to Acute Hypoxia.

The work examines the kinetic parameters of Ca2+ uptake via the mitochondrial calcium uniporter complex (MCUC) and the opening of the Ca2+-dependent permeability transition pore (MPT pore) in the liver and heart mitochondria of rats with high resistance (HR) and low resistance (LR) to acute hypoxia. We found that the rate of Ca2+ uptake by mitochondria of the liver and heart in HR rats is higher than that in LR rats, which is associated with a higher level of the channel-forming subunit MCU in liver mitochondria of HR rats and a lower content of the dominant-negative channel subunit MCUb in heart mitochondria of HR rats. It was shown that the liver mitochondria of HR rats are more resistant to the induction of the MPT pore than those of LR rats (the calcium retention capacity of liver mitochondria of HR rats was found to be 1.3 times greater than that of LR rats). These data correlate with the fact that the level of F0F1-ATP synthase, a possible structural element of the MPT pore, in the liver mitochondria of HR rats is lower than in LR rats. In heart mitochondria of rats of the two phenotypes, no statistically significant difference in the formation of the MPT pore was revealed. The paper discusses how changes in the expression of the MCUC subunits and the putative components of the MPT pore can affect Ca2+ homeostasis of mitochondria in animals with originally different tolerance to hypoxia and in hypoxia-induced tissue injury.

A pharmacological composition for induction of a reversible torpor-like state and hypothermia in rats.

AIMS: To initiate a state of artificial torpor we suggested a pharmacological multi-targeting strategy for simulation of the physiological pattern of natural hibernation including a significant reduction in heart rate, respiratory rate, body temperature and oxygen consumption as well as a decline in brain activity known as torpor. MATERIALS AND METHODS: We have developed a composition which initiates a pharmacologically induced torpor-like state (PITS-composition), made up of eight therapeutic agents, inert gas xenon and lipid emulsion served as a drug vehicle. KEY FINDINGS: After a single intravenous injection to rats, PITS-composition causes a rapid decline in heart rate followed by a steady decrease in body temperature from about 38.5 °C to 31.5 °C, at ambient temperature of 22 °C-23 °C. The hypothermic state may continue on average for 16-17 h with the subsequent spontaneous return of heart rate and body temperature to the initial values. In the open field test at torpor the motility, rearing and grooming were suppressed but 4-8 days later they were restored. SIGNIFICANCE: Suspended animation states, including natural hibernation or pharmacologically induced synthetic torpor are of special attention of medicine, since it may improve survival rate after cardiac arrest, brain hemorrhage and ischemia, and during long-term space traveling. The suggested here multi-targeting strategy made possible to develop the pharmacological composition able, after a single intravenous injection, to initiate long, stable and reversible hypothermia and torpor at room temperature. After the torpor, animals were able to spontaneously restore both physiological parameters, and behavioral reactions.

Thymulin, free or bound to PBCA nanoparticles, protects mice against chronic septic inflammation.

In the present work, we aimed to study the effects of free and polybutylcyanoacrylate nanoparticle-bound thymulin on immune cell activity in mice with chronic inflammation. NF-κB, MAPK, and PKC-θ signaling pathway activity was assessed, alongside Hsp72, Hsp90-α, and TLR4 expression and levels of apoptosis. In addition, plasma cytokines and blood and brain melatonin and serotonin levels were measured. In mice treated with gradually raised doses of lipopolysaccharide, significant increases in the activity of the signaling pathways tested, heat-shock protein and TLR4 expression, lymphocyte apoptosis, and plasma proinflammatory cytokine levels were noted. Moreover, we observed significantly heightened serotonin concentrations in the plasma and especially the brains of mice with inflammation. In contrast, melatonin levels were reduced in the tissues examined, particularly so in the brain. Treatment of these mice with thymulin alleviated fever, reduced apoptosis, increased splenic cell number, and decreased cytokine production, Hsp72, Hsp90, and TLR4 expression, and the activity of the signaling pathways examined. In addition, thymulin partially restored brain and blood serotonin and melatonin levels. Thus, thymulin suppressed the proinflammatory response in LPS-treated mice, indicating the potential of thymulin co-therapy in the treatment of sepsis. Nanoparticle-bound thymulin was more effective in several respects.

Antipsychotic inductors of brain hypothermia and torpor-like states: perspectives of application.

Hypothermia and hypometabolism (hypometabothermia) normally observed during natural hibernation and torpor, allow animals to protect their body and brain against the damaging effects of adverse environment. A similar state of hypothermia can be achieved under artificial conditions through physical cooling or pharmacological effects directed at suppression of metabolism and the processes of thermoregulation. In these conditions called torpor-like states, the mammalian ability to recover from stroke, heart attack, and traumatic injuries greatly increases. Therefore, the development of therapeutic methods for different pathologies is a matter of great concern. With the discovery of the antipsychotic drug chlorpromazine in the 1950s of the last century, the first attempts to create a pharmacologically induced state of hibernation for therapeutic purposes were made. That was the beginning of numerous studies in animals and the broad use of therapeutic hypothermia in medicine. Over the last years, many new agents have been discovered which were capable of lowering the body temperature and inhibiting the metabolism. The psychotropic agents occupy a significant place among them, which, in our opinion, is not sufficiently recognized in the contemporary literature. In this review, we summarized the latest achievements related to the ability of modern antipsychotics to target specific receptors in the brain, responsible for the initiation of hypometabothermia.

The seasonal peculiarities of force-frequency relationships in active ground squirrel Spermophilus undulatus ventricle.

The plasticity of calcium homeostasis is of crucial importance for the unique ability of the hibernators' heart to function under conditions of body temperature changing from 37 degrees C to near freezing point. However, the precise mechanism of calcium homeostasis regulation in these animals is largely unknown. Force-frequency relationship, as an indicator of participation of various sources of calcium (external and intracellular) in the activation of contraction, and post-rest potentiation as an index of the capacity of sarcoplasmic reticulum (intracellular calcium source) to store and release Ca(2+), were studied to analyse the role of different calcium-transporting systems in seasonal and temperature-induced changes in isometric twitch force of ground squirrel papillary muscles. The obtained results revealed significant functional differences during the annual cycle, which are indicative of an increased role of the sarcoplasmic reticulum in regulation of contractility in animals in transition to the hibernation period. Also, how myocardium during the hibernation period copes functionally with acute decreases in temperature was investigated.