Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences

This work demonstrates the antiferroptotic and cytotoxic effects of 2-aminomethyl phenothiazine (PTZ-NH2), and its alkyl derivative (PTZ-capryl) and mitochondria-targeted triphenylphosphonium conjugate (PTZ-TPP) on BT-474 cells, as well as their effects on isolated rat liver mitochondria. It was found that all studied compounds at 0.5 and 1 μM concentrations have a protective effect in the erastin-induced ferroptosis model. This effect of the tested compounds may be associated with the elimination of ROS overproduction in erastin-treated cells. The antioxidant effect of the compounds was also demonstrated on isolated rat liver mitochondria. At the same time, high concentrations of PTZ-NH2 had a cytotoxic effect on BT-474 cells (IC50=55 μM), and it was significantly enhanced in the case of PTZ-TPP (IC50=15 μM), which is possibly due to the mitochondrial targeting of PTZ-TPP. In contrast, the alkyl derivative did not exhibit cytotoxic action up to a maximum concentration of 100 μM, which allows it to be recommended as a promising antiferroptotic agent with a wide therapeutic window. The current findings discuss the possible mechanisms of inhibitory action of the tested compounds on ferroptotic cell death.

The aim of this study was to evaluate the kinetic parameters of the oxidation of some 3-aminopyridine-2(1H)-ones by hydrogen peroxide catalyzed by horseradish peroxidase and the affinity of horseradish peroxidase to these compounds. It has been shown that the oxidation of 3-aminopyridine-2(1H)-ones follows kinetics of the pseudo-first order. A hyperbolic decrease in the observed reaction rate constant (kobs) was also found with an increase in the initial concentration of 3-aminopyridine-2(1H)-ones. The dependence of kobs on the concentration of the enzyme was linear, suggesting competitive inhibition of oxidation by the reaction product. It was found that an increase in the polarity of the substituent in the fourth position leads to an increase in the rate of oxidation of pyridinones. Vmax/Km values were also higher for compounds carrying polar substituents in the fourth position. This kinetic parameter (Vmax/Km) reflects the substrate specificity of the enzyme. The data we obtained clarify the mechanisms of interaction between horseradish peroxidase and 3-aminopyridinones and suggest that 3-aminopyridinones can be used to develop sensitive methods for the detection of hydrogen peroxide and modification of immune enzyme analysis techniques.

Knowledge of the nature of intermolecular interactions and the amino-acid residues that provide them makes it possible to purposefully change the stability of intermolecular complexes. This study, using nickase Nt.BspD6I as an example, demonstrated the effect of hydrophobic interactions on a protein’s ability to oligomerize and the need for chemical and geometric complementarity of interface surfaces in the formation of stable homocomplexes.

The use of ionizing radiation at an ultra-high dose rate (≥40 Gy/s), which is called FLASH irradiation, contributes to the preservation of healthy tissues with a level of tumor control comparable to that of irradiation at a standard dose rate. This review summarizes the current knowledge obtained in studies of irradiation of tumor and normal cell lines and animals, including tumor carriers, in conventional and FLASH modes. For comparison, data on FLASH irradiation with photons, electrons, and protons, as well as ions of helium and carbon, are also provided. The biophysical, molecular biological, and immunological aspects of FLASH exposure necessary for understanding radiation-induced processes in cells and tissues in order to improve tumor radiotherapy are discussed.

The effect of high-energy (660 MeV) proton irradiation at the phasotron accelerator in FLASH mode (80 Gy/s) compared with the standard proton exposure power of 3.0 Gy/min was studied. When irradiated in two modes at doses of 1.0 and 1.5 Gy, the induction of cytogenetic damage in bone marrow cells and the state of lymphoid organs (thymus and spleen) were evaluated; survival under total in vivo irradiation of mice was analyzed at doses of 7.0 and 8.0 Gy. The growth rate of a model tumor under ex vivo irradiation was determined at doses of 40 and 60 Gy. It has been shown that irradiation of animals in the FLASH mode at a dose of 1.5 Gy protected the proliferative activity of the spleen and also led to a decrease in cytogenetic damage in bone marrow erythrocytes according to the micronucleus test compared with the standard irradiation mode at a dose of 1.5 Gy, that is, a milder effect of the FLASH mode dose was observed. However, irradiation of mice in FLASH mode at high doses (7.0 and 8.0 Gy) led to earlier death of animals compared to the standard irradiation regime. A tumor node formed with further growth only after FLASH irradiation of a suspension of Ehrlich ascites carcinoma at a dose of 40 Gy; in all other groups a tumor was not formed.

The effects of uridine and its monophosphoryl derivative on the level of the main biochemical markers of myocardial damage in the blood and on the electrical activity of the heart were investigated in a rat model of cardiomyopathy induced by isoprenaline. It was shown that administration of isoprenaline (150 mg/kg, subcutaneously) caused an increase in the activity of serum enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT), leading to an elevated AST/ALT ratio (De Ritis ratio), and enhanced activity of lactate dehydrogenase in blood lymphocytes, which confirms the development of myocardial damage in experimental animals. ECG analysis revealed prolongation of the RR, P-R, QT, and QTc intervals and the QRS complex, indicating that the duration of both depolarization and repolarization phases increased relative to the duration of the cardiac cycle in rats with isoprenaline-induced myocardial damage. Preliminary administration of uridine and uridine-5'-monophosphate to experimental animals at a dose of 30 mg/kg equally effectively prevented an increase in the enzymatic activity of AST and the De Ritis ratio, led to a decrease in the duration of P-R, QRS, QT, and QTc intervals, and partially normalized the metabolic activity of rat blood lymphocytes. These findings suggest that uridine and uridine-5'-monophosphate have a similar protective effect on the contractile function of cardiomyocytes and can be considered as agents for metabolic therapy in the treatment of ischemic heart disease.

Studies of the phenomenology of the effect of synchronization of heart rate fluctuations in a person at rest with variations of the geomagnetic field in the range of 3–40 min periods have been continued. During 2012–2023, 508 experiments (lasting 100–120 min each) were conducted to monitor minute heart rate indicators in three practically healthy women (55, 45 and 30 years old). Individual experimental samples comprised 328, 113, and 67 records, respectively. It was shown that for each of the three volunteers, in about 60% of the experiments, the wavelet spectrum of heart rates turned out to be very close to the spectrum of synchronous variations of at least one of the horizontal components of the geomagnetic field (X or Y). As well, within the studied frequency range of 3–40 min, three sub-ranges were identified in which the degree of synchronicity of oscillation occurrence was maximum: 3.5 min, 10–12 min, and 33–36 min. It can be concluded that the effect of biogeosynchronization apparently did not occur uniformly over the entire range of 3–40 min, but mainly in these sub-ranges.

Detecting environmental changes/novelty is of basic importance for adaptive behavior. By comparing the current context with the previous one, living organisms can make predictions and adjust their actions. The mechanisms and structures of the brain involved in the function of comparison have not yet been sufficiently elucidated. The available studies emphasize the special contribution of the hippocampus to the process of comparison; it is indicated that the identification of novelty is carried out by hippocampal neurons through the mechanisms of match/mismatch, or misalignment. Here, we provide information about existing hypotheses of how these mechanisms occur, which other brain structures are involved in detecting inconsistencies, how they are related to the hippocampus, and what processes contribute to this. In particular, it is assumed that it is not novelty in itself, but only novelty that contrasts with previously acquired experience that initiates the process of misalignment. The arguments that the theta rhythm plays a crucial role in the functioning of the hippocampus as a comparator are analyzed. Theta oscillations caused by the appearance of a new signal or a change in a situation mediate the mechanism of temporal coordination of structures involved in the comparison function. In comparison, the theta rhythm functions as an active filter: it participates in the selection and transmission of a new signal to the registration system in the hippocampus. An increase in theta oscillations and their coherence in the brain structures processing new information serves as a signal of misalignment, facilitating a change in behavior strategy. In addition to theta rhythm, gamma oscillations are also involved in comparison: during the generation of theta rhythm in the prefrontal cortex, the temporary coincidence of gamma oscillations in other areas of the brain with a certain phase of the theta cycle can perform the function of comparison during the memorization process. A deep understanding of the mechanisms of comparator function and its disorders can help in the treatment of pathologies such as schizophrenia, Alzheimer’s disease, and temporal lobe epilepsy.

TRO19622 (olesoxime, a cholesterol-like cytoprotector) is an experimental drug developed for the potential therapy of a number of incurable degenerative diseases. The main molecular target of this compound in the cell is the porin proteins of the outer mitochondrial membrane, which play a key role in regulating the exchange of metabolites between mitochondria and the rest of the cell. Violations of the activity of these channels can cause the development of mitochondrial dysfunction in healthy cells. This paper evaluates the main indicators of mitochondrial functions and the cell viability index in cultures after their incubation with TRO19622. It was found that TRO19622 at concentrations of 15–30 μM inhibited the rates of phosphorylating and uncoupled respiration of isolated mitochondria (states 3 and 3UDNP) with succinate as a substrate, but did not affect the enzymatic activity of complexes I–IV of the respiratory chain. It was shown that TRO19622 in the studied doses did not affect the rate of H2O2 formation in mitochondria and the parameter of calcium capacity, reflecting the resistance of organelles to the opening of a calcium-dependent nonspecific pore. Incubation of human skin fibroblasts and breast adenocarcinoma cells (MCF-7) with 30 μM TRO19622 for 48 h had no effect on the production of reactive oxygen species and cell viability. The mechanisms of action of TRO19622 on the oxidative phosphorylation system and the prospects of using this mitochondrial-directed therapeutic agent are discussed.

The effectiveness of 1H-NMR-based metabolomic analysis for the detection of metabolic changes during carcinogenesis was assessed based on a comparison of the quantitative composition of metabolites in the blood plasma of healthy rats and rats that receiving M-1 sarcoma grafts. Plasma was collected from the rats under study on day 12 and day 36 after sarcoma transplantation to identify metabolites associated with tumor development. Analysis of the NMR spectra using multivariate statistical methods showed differences in the composition of metabolites for the groups of animals under study as soon as on day 12 after sarcoma transplantation; on day 36 the differences were significant. Twenty three metabolites were quantified. On day 12, only the lactate and allantoin levels were significantly different between the groups, while on day 36, the levels of nine metabolites were different between the two groups. All of the identified metabolites are involved in cancer metabolism, which makes 1H-NMR spectroscopy a promising method for cancer diagnosis.

Regulation of the cardiovascular system in hypothermia and after its exposure is one of the important and urgent issues of biomedical research. This is due both to the severe consequences of hypothermia and to the potential benefits of its use for medical purposes. Adrenergic regulation is key for the normal functioning of the cardiovascular system. There are three groups of adrenergic receptors, α1, α2, and β, which are expressed in different proportions in the myocardium and blood vessels. Activation of each of the subtypes of adrenoreceptors can cause multidirectional effects, which are largely modified at low temperatures. The effectiveness of β-adrenergic stimulation decreases and can even act unidirectionally with hypothermia, leading to disorders in the work of the myocardium. The severity of the effects of α1-adrenoagonists in the heart and blood vessels also decreases; however, sensitivity to stimulation of α1a receptors in blood vessels may increase. Activation of this type of receptor has a cardioprotective effect. Activation of α2-adrenergic receptors also causes a wide range of cardioprotective effects. At the same time, there is evidence of direct inotropic and vascular effects mediated by this type of receptor. There is some evidence of an increase in these effects in hypothermia. The present review considers the current state of research on the effects of stimulation of certain types of adrenoreceptors in normal and hypothermic conditions. The mechanisms of physiological effects and the prospects for their further research are discussed.

This review is devoted to modern concepts of paraptosis as one of the types of regulated cell death, in comparison with other types of cell death. Paraptosis is a form of cell death caused by stress of the endoplasmic reticulum (ER), accompanied by the accumulation of damaged or incorrectly folded proteins in it, extensive nonautophagic vacuolation of the cisterns of the endoplasmic reticulum and, in some cases, mitochondria, with subsequent damage to the mitochondria and cytoskeleton and cell death. Knowledge about the molecular mechanisms of paraptosis is of interest for the treatment of cancer diseases resistant to apoptosis-inducing agents.