Mitocentricity.

Worldwide, interest in mitochondria is constantly growing, as evidenced by scientific statistics, and studies of the functioning of these organelles are becoming more prevalent than studies of other cellular structures. In this analytical review, mitochondria are conditionally placed in a certain cellular center, which is responsible for both energy production and other non-energetic functions, without which the existence of not only the eukaryotic cell itself, but also the entire organism is impossible. Taking into account the high multifunctionality of mitochondria, such a fundamentally new scheme of cell functioning organization, including mitochondrial management of processes that determine cell survival and death, may be justified. Considering that this issue is dedicated to the memory of V. P. Skulachev, who can be called mitocentric, due to the history of his scientific activity almost entirely aimed at studying mitochondria, this work examines those aspects of mitochondrial functioning that were directly or indirectly the focus of attention of this outstanding scientist. We list all possible known mitochondrial functions, including membrane potential generation, synthesis of Fe-S clusters, steroid hormones, heme, fatty acids, and CO2. Special attention is paid to the participation of mitochondria in the formation and transport of water, as a powerful biochemical cellular and mitochondrial regulator. The history of research on reactive oxygen species that generate mitochondria is subject to significant analysis. In the section "Mitochondria in the center of death", special emphasis is placed on the analysis of what role and how mitochondria can play and determine the program of death of an organism (phenoptosis) and the contribution made to these studies by V. P. Skulachev.

Beta-Hydroxybutyrate Mitigates Sensorimotor and Cognitive Impairments in a Photothrombosis-Induced Ischemic Stroke in Mice.

The consequences of stroke include cognitive deficits and sensorimotor disturbances, which are largely related to mitochondrial impairments in the brain. In this work, we have shown that the mimetic of the ketogenic diet beta-hydroxybutyrate (ßHB) can improve neurological brain function in stroke. At 3 weeks after photothrombotic stroke, mice receiving ßHB with drinking water before and after surgery recovered faster in terms of sensorimotor functions assessed by the string test and static rods and cognitive functions assessed by the Morris water maze. At the same time, the ßHB-treated mice had lower expression of some markers of astrocyte activation and inflammation (Gfap, Il-1b, Tnf). We hypothesize that long-term administration of ßHB promotes the activation of the nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) pathway, which leads to increased expression of antioxidant genes targeting mitochondria and genes involved in signaling pathways necessary for the maintenance of synaptic plasticity. ßHB partially maintained mitochondrial DNA (mtDNA) integrity during the first days after photothrombosis. However, in the following three weeks, the number of mtDNA damages increased in all experimental groups, which coincided with a decrease in Ogg1 expression, which plays an important role in mtDNA repair. Thus, we can assume that ßHB is not only an important metabolite that provides additional energy to brain tissue during recovery from stroke under conditions of mitochondrial damage but also an important signaling molecule that supports neuronal plasticity and reduces neuroinflammation.

Sex-Specific Effects of Estradiol and Progesterone in Ischemic Kidney Injury.

The positive effects of female sex hormones, particularly estradiol and progesterone, have been observed in treatment of various pathologies. Acute kidney injury (AKI) is a common condition in hospitalized patients in which the molecular mechanisms of hormone action are poorly characterized. In this study, we investigated the influence of estradiol and progesterone on renal cells during ischemic injury. We performed both in vivo experiments on female and male rats and in vitro experiments on renal tubular cells (RTCs) obtained from the kidneys of intact animals of different sexes. Since mitochondria play an important role in the pathogenesis of AKI, we analyzed the properties of individual mitochondria in renal cells, including the area, roundness, mitochondrial membrane potential, and mitochondrial permeability transition pore (mPTP) opening time. We found that pre-treatment with progesterone or estradiol attenuated the severity of ischemia/reperfusion (I/R)-induced AKI in female rats, whereas in male rats, these hormones exacerbated renal dysfunction. We demonstrated that the mPTP opening time was higher in RTCs from female rats than that in those from male rats, which may be one of the reasons for the higher tolerance of females to ischemic injury. In RTCs from the kidneys of male rats, progesterone caused mitochondrial fragmentation, which can be associated with reduced cell viability. Thus, therapy with progesterone or estradiol displays quite different effects depending on sex, and could be only effective against ischemic AKI in females.

Anti-Inflammatory Effect of Synaptamide in Ischemic Acute Kidney Injury and the Role of G-Protein-Coupled Receptor 110.

The development of drugs for the treatment of acute kidney injury (AKI) that could suppress the excessive inflammatory response in damaged kidneys is an important clinical challenge. Recently, synaptamide (N-docosahexaenoylethanolamine) has been shown to exert anti-inflammatory and neurogenic properties. The aim of this study was to investigate the anti-inflammatory effect of synaptamide in ischemic AKI. For this purpose, we analyzed the expression of inflammatory mediators and the infiltration of different leukocyte populations into the kidney after injury, evaluated the expression of the putative synaptamide receptor G-protein-coupled receptor 110 (GPR110), and isolated a population of CD11b/c+ cells mainly representing neutrophils and macrophages using cell sorting. We also evaluated the severity of AKI during synaptamide therapy and the serum metabolic profile. We demonstrated that synaptamide reduced the level of pro-inflammatory interleukins and the expression of integrin CD11a in kidney tissue after injury. We found that the administration of synaptamide increased the expression of its receptor GPR110 in both total kidney tissue and renal CD11b/c+ cells that was associated with the reduced production of pro-inflammatory interleukins in these cells. Thus, we demonstrated that synaptamide therapy mitigates the inflammatory response in kidney tissue during ischemic AKI, which can be achieved through GPR110 signaling in neutrophils and a reduction in these cells' pro-inflammatory interleukin production.

Biomarkers of the End-Stage Renal Disease Progression: Beyond the GFR.

Chronic kidney disease can progress to the end-stage renal disease (ESRD) characterized by a high risk of morbidity and mortality. ESRD requires immediate therapy or even dialysis or kidney transplantation, therefore, its timely diagnostics is critical for many patients. ESRD is associated with pathological changes, such as inflammation, fibrosis, endocrine disorders, and epigenetic changes in various cells, which could serve as ESRD markers. The review summarizes information on conventional and new ESRD biomarkers that can be assessed in kidney tissue, blood, and urine. Some biomarkers are specific to a particular pathology, while others are more universal. Here, we suggest several universal inflammatory, fibrotic, hormonal, and epigenetic markers indicative of severe deterioration of renal function and ESRD progression for improvement of ESRD diagnostics.

Mitochondrial Network: Electric Cable and More.

Mitochondria in a cell can unite and organize complex, extended structures that occupy the entire cellular volume, providing an equal supply with energy in the form of ATP synthesized in mitochondria. In accordance with the chemiosmotic concept, the oxidation energy of respiratory substrates is largely stored in the form of an electrical potential difference on the inner membrane of mitochondria. The theory of the functioning of extended mitochondrial structures as intracellular electrical wires suggests that mitochondria provide the fastest delivery of electrical energy through the cellular volume, followed by the use of this energy for the synthesis of ATP, thereby accelerating the process of ATP delivery compared to the rather slow diffusion of ATP in the cell. This analytical review gives the history of the cable theory, lists unsolved critical problems, describes the restructuring of the mitochondrial network and the role of oxidative stress in this process. In addition to the already proven functioning of extended mitochondrial structures as electrical cables, a number of additional functions are proposed, in particular, the hypothesis is put forth that mitochondrial networks maintain the redox potential in the cellular volume, which may vary depending on the physiological state, as a result of changes in the three-dimensional organization of the mitochondrial network (fragmentation/fission-fusion). A number of pathologies accompanied by a violation of the redox status and the participation of mitochondria in them are considered.

Noncoupled Mitochondrial Respiration as Therapeutic Approach for the Treatment of Metabolic Diseases: Focus on Transgenic Animal Models.

Mitochondrial dysfunction contributes to numerous chronic diseases, and mitochondria are targets for various toxins and xenobiotics. Therefore, the development of drugs or therapeutic strategies targeting mitochondria is an important task in modern medicine. It is well known that the primary, although not the sole, function of mitochondria is ATP generation, which is achieved by coupled respiration. However, a high membrane potential can lead to uncontrolled reactive oxygen species (ROS) production and associated dysfunction. For over 50 years, scientists have been studying various synthetic uncouplers, and for more than 30 years, uncoupling proteins that are responsible for uncoupled respiration in mitochondria. Additionally, the proteins of the mitochondrial alternative respiratory pathway exist in plant mitochondria, allowing noncoupled respiration, in which electron flow is not associated with membrane potential formation. Over the past two decades, advances in genetic engineering have facilitated the creation of various cellular and animal models that simulate the effects of uncoupled and noncoupled respiration in different tissues under various disease conditions. In this review, we summarize and discuss the findings obtained from these transgenic models. We focus on the advantages and limitations of transgenic organisms, the observed physiological and biochemical changes, and the therapeutic potential of uncoupled and noncoupled respiration.

Ketogenic Diet and Ketone Bodies against Ischemic Injury: Targets, Mechanisms, and Therapeutic Potential.

The ketogenic diet (KD) has been used as a treatment for epilepsy since the 1920s, and its role in the prevention of many other diseases is now being considered. In recent years, there has been an intensive investigation on using the KD as a therapeutic approach to treat acute pathologies, including ischemic ones. However, contradictory data are observed for the effects of the KD on various organs after ischemic injury. In this review, we provide the first systematic analysis of studies conducted from 1980 to 2022 investigating the effects and main mechanisms of the KD and its mimetics on ischemia-reperfusion injury of the brain, heart, kidneys, liver, gut, and eyes. Our analysis demonstrated a high diversity of both the composition of the used KD and the protocols for the treatment of animals, which could be the reason for contradictory effects in different studies. It can be concluded that a true KD or its mimetics, such as ß-hydroxybutyrate, can be considered as positive exposure, protecting the organ from ischemia and its negative consequences, whereas the shift to a rather similar high-calorie or high-fat diet leads to the opposite effect.

Pilot Study of Cytoprotective Mechanisms of Selenium Nanorods (SeNrs) under Ischemia-like Conditions on Cortical Astrocytes.

The cytoprotective properties of the trace element selenium, its nanoparticles, and selenium nanocomplexes with active compounds are shown using a number of models. To date, some molecular mechanisms of the protective effect of spherical selenium nanoparticles under the action of ischemia/reoxygenation on brain cells have been studied. Among other things, the dependence of the effectiveness of the neuroprotective properties of nanoselenium on its diameter, pathways, and efficiency of penetration into astrocytes was established. In general, most research in the field of nanomedicine is focused on the preparation and study of spherical nanoparticles of various origins due to the ease of their preparation; in addition, spherical nanoparticles have a large specific surface area. However, obtaining and studying the mechanisms of action of nanoparticles of a new form are of great interest since nanorods, having all the positive properties of spherical nanoparticles, will also have a number of advantages. Using the laser ablation method, we managed to obtain and characterize selenium nanorods (SeNrs) with a length of 1 µm and a diameter of 100 nm. Using fluorescence microscopy and inhibitory analysis, we were able to show that selenium nanorods cause the generation of Ca2+ signals in cortical astrocytes in an acute experiment through the mobilization of Ca2+ ions from the thapsigargin-sensitive pool of the endoplasmic reticulum. Chronic use of SeNrs leads to a change in the expression pattern of genes encoding proteins that regulate cell fate and protect astrocytes from ischemia-like conditions and reoxygenation through the inhibition of a global increase in the concentration of cytosolic calcium ([Ca2+]i). An important component of the cytoprotective effect of SeNrs during ischemia/reoxygenation is the induction of reactive A2-type astrogliosis in astrocytes, leading to an increase in both baseline and ischemia/reoxygenation-induced phosphoinositide 3-kinase (PI3K) activity and suppression of necrosis and apoptosis. The key components of this cytoprotective action of SeNrs are the actin-dependent process of endocytosis of nanoparticles into cells and activation of the Ca2+ signaling system of astrocytes.

Cerium Oxide Nanoparticles Protect Cortical Astrocytes from Oxygen-Glucose Deprivation through Activation of the Ca2+ Signaling System.

Most of the works aimed at studying the cytoprotective properties of nanocerium are usually focused on the mechanisms of regulation of the redox status in cells while the complex effects of nanocerium on calcium homeostasis, the expression of pro-apoptotic and protective proteins are generally overlooked. There is a problem of a strong dependence of the effects of cerium oxide nanoparticles on their size, method of preparation and origin, which significantly limits their use in medicine. In this study, using the methods of molecular biology, immunocytochemistry, fluorescence microscopy and inhibitory analysis, the cytoprotective effect of cerium oxide nanoparticles obtained by laser ablation on cultured astrocytes of the cerebral cortex under oxygen-glucose deprivation (OGD) and reoxygenation (ischemia-like conditions) are shown. The concentration effects of cerium oxide nanoparticles on ROS production by astrocytes in an acute experiment and the effects of cell pre-incubation with nanocerium on ROS production under OGD conditions were studied. The dose dependence for nanocerium protection of cortical astrocytes from a global increase in calcium ions during oxygen-glucose deprivation and cell death were demonstrated. The concentration range of cerium oxide nanoparticles at which they have a pro-oxidant effect on cells has been identified. The effect of nanocerium concentrations on astrocyte preconditioning, accompanied by increased expression of protective proteins and limited ROS production induced by oxygen-glucose deprivation, has been investigated. In particular, a correlation was found between an increase in the concentration of cytosolic calcium under the action of nanocerium and the suppression of cell death. As a result, the positive and negative effects of nanocerium under oxygen-glucose deprivation and reoxygenation in astrocytes were revealed at the molecular level. Nanocerium was found to act as a "double-edged sword" and to have a strictly defined concentration therapeutic "window".

Anti-Inflammatory Properties of Metformin During Cultivation of Primary Rat Astrocytes in a Medium with High Glucose Concentration.

Investigation of the relationship between inflammation and energy metabolism is important for understanding biology of chronic noncommunicable diseases. Use of metformin, a drug for treatment of diabetes, is considered as a promising direction for treatment of neurodegenerative diseases and other neuropathologies with an inflammatory component. Astrocytes play an important role in the regulation of energy metabolism and neuroinflammation; therefore, we studied the effect of metformin on the cellular responses of primary rat astrocytes cultured in a medium with high glucose concentration (22.5 mM, 48-h incubation). Lipopolysaccharide (LPS) was used to stimulate inflammation. The effects of metformin were assessed by monitoring changes in the expression of proinflammatory cytokines and synthesis of oxylipins, assayed with ultra-high-performance liquid chromatography and tandem mass spectrometry (UPLC-MS/MS). Changes at the intracellular level were assessed by analyzing phosphorylation of ERK kinase and transcription factor STAT3, as well as enzymes mediating oxylipin synthesis, cyclooxygenase 1 and 2 (COX). It was found that, independent on glucose concentration, metformin reduced the LPS-stimulated release of cytokines IL-1ß and IL-6, decreased activity of the transcription factor STAT3, ERK kinase, synthesis of the derivatives of the cyclooxygenase branch of metabolism of oxylipins and anandamide, and did not affect formation of ROS. The study of energy phenotype of the cells showed that metformin activated glycolysis and inhibited mitochondrial respiration and oxidative phosphorylation, independent on LPS stimulation and cell cultivation at high glucose concentration. Thus, it has been shown that metformin exhibits anti-inflammatory effects, and its effect on the synthesis of cytokines, prostaglandins, and other lipid mediators could determine beneficial effects of metformin in models of neuropathology.

Size-Dependent Cytoprotective Effects of Selenium Nanoparticles during Oxygen-Glucose Deprivation in Brain Cortical Cells.

It is known that selenium nanoparticles (SeNPs) obtained on their basis have a pleiotropic effect, inducing the process of apoptosis in tumor cells, on the one hand, and protecting healthy tissue cells from death under stress, on the other hand. It has been established that SeNPs protect brain cells from ischemia/reoxygenation through activation of the Ca2+ signaling system of astrocytes and reactive astrogliosis. At the same time, for a number of particles, the limitations of their use, associated with their size, are shown. The use of nanoparticles with a diameter of less than 10 nm leads to their short life-time in the bloodstream and rapid removal by the liver. Nanoparticles larger than 200 nm activate the complement system and are also quickly removed from the blood. The effects of different-sized SeNPs on brain cells have hardly been studied. Using the laser ablation method, we obtained SeNPs of various diameters: 50 nm, 100 nm, and 400 nm. Using fluorescence microscopy, vitality tests, PCR analysis, and immunocytochemistry, it was shown that all three types of the different-sized SeNPs have a cytoprotective effect on brain cortex cells under conditions of oxygen-glucose deprivation (OGD) and reoxygenation (R), suppressing the processes of necrotic death and inhibiting different efficiency processes of apoptosis. All of the studied SeNPs activate the Ca2+ signaling system of astrocytes, while simultaneously inducing different types of Ca2+ signals. SeNPs sized at 50 nm- induce Ca2+ responses of astrocytes in the form of a gradual irreversible increase in the concentration of cytosolic Ca2+ ([Ca2+]i), 100 nm-sized SeNPs induce stable Ca2+ oscillations without increasing the base level of [Ca2+]i, and 400 nm-sized SeNPs cause mixed patterns of Ca2+ signals. Such differences in the level of astrocyte Ca2+ signaling can explain the different cytoprotective efficacy of SeNPs, which is expressed in the expression of protective proteins and the activation of reactive astrogliosis. In terms of the cytoprotective efficiency under OGD/R conditions, different-sized SeNPs can be arranged in descending order: 100 nm-sized > 400 nm-sized > 50 nm-sized.

Neuronal Calcium Sensor-1 Protects Cortical Neurons from Hyperexcitation and Ca2+ Overload during Ischemia by Protecting the Population of GABAergic Neurons.

A defection of blood circulation in the brain leads to ischemia, damage, and the death of nerve cells. It is known that individual populations of GABAergic neurons are the least resistant to the damaging factors of ischemia and therefore they die first of all, which leads to impaired inhibition in neuronal networks. To date, the neuroprotective properties of a number of calcium-binding proteins (calbindin, calretinin, and parvalbumin), which are markers of GABAergic neurons, are known. Neuronal calcium sensor-1 (NCS-1) is a signaling protein that is expressed in all types of neurons and is involved in the regulation of neurotransmission. The role of NCS-1 in the protection of neurons and especially their individual populations from ischemia and hyperexcitation has not been practically studied. In this work, using the methods of fluorescence microscopy, vitality tests, immunocytochemistry, and PCR analysis, the molecular mechanisms of the protective action of NCS-1 in ischemia/reoxygenation and hyperammonemia were established. Since NCS-1 is most expressed in GABAergic neurons, the knockdown of this protein with siRNA led to the most pronounced consequences in GABAergic neurons. The knockdown of NCS-1 (NCS-1-KD) suppressed the basic expression of protective proteins without significantly reducing cell viability. However, ischemia-like conditions (oxygen-glucose deprivation, OGD) and subsequent 24-h reoxygenation led to a more massive activation of apoptosis and necrosis in neurons with NCS-1-KD, compared to control cells. The mass death of NCS-1-KD cells during OGD and hyperammonemia has been associated with the induction of a more pronounced network hyperexcitation symptom, especially in the population of GABAergic neurons, leading to a global increase in cytosolic calcium ([Ca2+]i). The symptom of hyperexcitation of neurons with NCS-1-KD correlated with a decrease in the level of expression of the calcium-binding protein-parvalbumin. This was accompanied by an increase in the expression of excitatory ionotropic glutamate receptors, N-methyl-D-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (NMDAR and AMPAR) against the background of suppression of the expression of glutamate decarboxylase (synthesis of γ-aminobutyric acid).

Protective Effect of D-Panthenol in Rhabdomyolysis-Induced Acute Kidney Injury.

We investigated the nephroprotective effect of D-panthenol in rhabdomyolysis-induced acute kidney injury (AKI). Adult male Wistar rats were injected with 50% glycerol solution to induce rhabdomyolysis. Animals with rhabdomyolysis were injected with D-panthenol (200 mg/kg) for 7 days. On day 8, we examined AKI markers, renal histology, antioxidant capacity, and protein glutathionylation in kidneys to uncover mechanisms of D-panthenol effects. Rhabdomyolysis kidneys were shown to have pathomorphological alterations (mononuclear infiltration, dilatation of tubules, and hyaline casts in Henle's loops and collecting ducts). Activities of skeletal muscle damage markers (creatine kinase and lactate dehydrogenase) increased, myoglobinuria was observed, and creatinine, BUN, and pantetheinase activity in serum and urine rose. Signs of oxidative stress in the kidney tissue of rhabdomyolysis rats, increased levels of lipid peroxidation products, and activities of antioxidant enzymes (SOD, catalase, and glutathione peroxidase) were all alleviated by administration of D-panthenol. Its application improved kidney morphology and decreased AKI markers. Mechanisms of D-panthenol's beneficial effects were associated with an increase in total coenzyme A levels, activity of Krebs cycle enzymes, and attenuation of protein glutathionylation. D-Panthenol protects kidneys from rhabdomyolysis-induced AKI through antioxidant effects, normalization of mitochondrial metabolism, and modulation of glutathione-dependent signaling.

Gut Microbiota as a Source of Uremic Toxins.

Uremic retention solutes are the compounds that accumulate in the blood when kidney excretory function is impaired. Some of these compounds are toxic at high concentrations and are usually known as "uremic toxins". The cumulative detrimental effect of uremic toxins results in numerous health problems and eventually mortality during acute or chronic uremia, especially in end-stage renal disease. More than 100 different solutes increase during uremia; however, the exact origin for most of them is still debatable. There are three main sources for such compounds: exogenous ones are consumed with food, whereas endogenous ones are produced by the host metabolism or by symbiotic microbiota metabolism. In this article, we identify uremic retention solutes presumably of gut microbiota origin. We used database analysis to obtain data on the enzymatic reactions in bacteria and human organisms that potentially yield uremic retention solutes and hence to determine what toxins could be synthesized in bacteria residing in the human gut. We selected biochemical pathways resulting in uremic retention solutes synthesis related to specific bacterial strains and revealed links between toxin concentration in uremia and the proportion of different bacteria species which can synthesize the toxin. The detected bacterial species essential for the synthesis of uremic retention solutes were then verified using the Human Microbiome Project database. Moreover, we defined the relative abundance of human toxin-generating enzymes as well as the possibility of the synthesis of a particular toxin by the human metabolism. Our study presents a novel bioinformatics approach for the elucidation of the origin of both uremic retention solutes and uremic toxins and for searching for the most likely human microbiome producers of toxins that can be targeted and used for the therapy of adverse consequences of uremia.

Calorie Restriction Provides Kidney Ischemic Tolerance in Senescence-Accelerated OXYS Rats.

Kidney diseases belong to a group of pathologies, which are most common among elderly people. With age, even outwardly healthy organisms start to exhibit some age-related changes in the renal tissue, which reduce the filtration function of kidneys and increase the susceptibility to injury. The therapy of acute kidney injury (AKI) is aggravated by the absence of targeted pharmacotherapies thus yielding high mortality of patients with AKI. In this study, we analyzed the protective effects of calorie restriction (CR) against ischemic AKI in senescence-accelerated OXYS rats. We observed that CR afforded OXYS rats with significant nephroprotection. To uncover molecular mechanisms of CR beneficial effects, we assessed the levels of anti- and proapoptotic proteins of the Bcl-2 family, COX IV, GAPDH, and mitochondrial deacetylase SIRT-3, as well as alterations in total protein acetylation and carbonylation, mitochondrial dynamics (OPA1, Fis1, Drp1) and kidney regeneration pathways (PCNA, GDF11). The activation of autophagy and mitophagy was analyzed by LC3 II/LC3 I ratio, beclin-1, PINK-1, and total mitochondrial protein ubiquitination. Among all considered protective pathways, the improvement of mitochondrial functioning may be suggested as one of the possible mechanisms for beneficial effects of CR.

Age-Related Decline in Nrf2/ARE Signaling Is Associated with the Mitochondrial DNA Damage and Cognitive Impairments.

In this research, we compared the cognitive parameters of 2-, 7-, and 15-month-old mice, changes in mitochondrial DNA (mtDNA) integrity and expression of genes involved in the nuclear erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) signaling pathway. We showed an age-related decrease in the Nfe2l2 expression in the cerebral cortex, not in the hippocampus. At the same time, we find an increase in the mtDNA copy number in the cerebral cortex, despite the lack of an increase in gene expression, which is involved in the mitochondrial biogenesis regulation. We suppose that increase in mtDNA content is associated with mitophagy downregulation. We supposed that mitophagy downregulation may be associated with an age-related increase in the mtDNA damage. In the hippocampus, we found a decrease in the Bdnf expression, which is involved in the pathways, which play an essential role in regulating long-term memory formation. We showed a deficit of working and reference memory in 15-month-old-mice in the water Morris maze, and a decrease in the exploratory behavior in the open field test. Cognitive impairments in 15-month-old mice correlated with a decrease in Bdnf expression in the hippocampus, Nfe2l2 expression, and an increase in the number of mtDNA damage in the cerebral cortex. Thus, these signaling pathways may be perspective targets for pharmacological intervention to maintain mitochondrial quality control, neuronal plasticity, and prevent the development of age-related cognitive impairment.

Age-Associated Loss in Renal Nestin-Positive Progenitor Cells.

The decrease in the number of resident progenitor cells with age was shown for several organs. Such a loss is associated with a decline in regenerative capacity and a greater vulnerability of organs to injury. However, experiments evaluating the number of progenitor cells in the kidney during aging have not been performed until recently. Our study tried to address the change in the number of renal progenitor cells with age. Experiments were carried out on young and old transgenic nestin-green fluorescent protein (GFP) reporter mice, since nestin is suggested to be one of the markers of progenitor cells. We found that nestin+ cells in kidney tissue were located in the putative niches of resident renal progenitor cells. Evaluation of the amount of nestin+ cells in the kidneys of different ages revealed a multifold decrease in the levels of nestin+ cells in old mice. In vitro experiments on primary cultures of renal tubular cells showed that all cells including nestin+ cells from old mice had a lower proliferation rate. Moreover, the resistance to damaging factors was reduced in cells obtained from old mice. Our data indicate the loss of resident progenitor cells in kidneys and a decrease in renal cells proliferative capacity with aging.

Is the Mitochondrial Membrane Potential (∆Ψ) Correctly Assessed? Intracellular and Intramitochondrial Modifications of the ∆Ψ Probe, Rhodamine 123.

The mitochondrial membrane potential (∆Ψ) is the driving force providing the electrical component of the total transmembrane potential of hydrogen ions generated by proton pumps, which is utilized by the ATP synthase. The role of ∆Ψ is not limited to its role in bioenergetics since it takes part in other important intracellular processes, which leads to the mandatory requirement of the homeostasis of ∆Ψ. Conventionally, ∆Ψ in living cells is estimated by the fluorescence of probes such as rhodamine 123, tetramethylrodamine, etc. However, when assessing the fluorescence, the possibility of the intracellular/intramitochondrial modification of the rhodamine molecule is not taken into account. Such changes were revealed in this work, in which a comparison of normal (astrocytic) and tumor (glioma) cells was conducted. Fluorescent microscopy, flow cytometry, and mass spectrometry revealed significant modifications of rhodamine molecules developing over time, which were prevented by amiodarone apparently due to blocking the release of xenobiotics from the cell and their transformation with the participation of cytochrome P450. Obviously, an important role in these processes is played by the increased retention of rhodamines in tumor cells. Our data require careful evaluation of mitochondrial ∆Ψ potential based on the assessment of the fluorescence of the mitochondrial probe.

Human Multipotent Mesenchymal Stromal Cell-Derived Extracellular Vesicles Enhance Neuroregeneration in a Rat Model of Sciatic Nerve Crush Injury.

Peripheral nerve injury remains a serious problem for medicine, with no effective method of treatment at the moment. The most prominent example of this problem is neonatal brachial plexus palsy, which results from the stretching of the brachial plexus nerves in the birth or perinatal period. Multipotent mesenchymal cells (MSCs) and the extracellular vesicles (EVs) they produce are known to have a marked neuroprotective effect in central nervous system injuries. We suggested that the use of MSCs-derived EVs may be an effective approach to the regeneration of peripheral nerves after injury. Sciatic nerve injury was modeled in rats via crushing, and then a gel containing MSCs-EVs was applied to the injured area. After 15 and 30 days, a histological, physiological, and functional assessment of nerve, dorsal root ganglia (DRG), and innervated muscles' recovery was performed. Transplantation of EVs to the area of sciatic nerve injury significantly reduced muscle atrophy as compared to the control group. Functional recovery of the innervated muscles, as measured by the extensor postural thrust test, was revealed 30 days after the surgery. We associate the obtained results with EVs-induced neuroprotective mechanisms, which were expressed in a decrease in apoptotic neuronal death and an increase in regeneration-associated proteins NF-200 and GAP-43, as well as in DRG and damaged nerve. We suggest that the therapeutic scheme we used is efficient for the treatment of acute peripheral nervous system injuries and can be transferred to the clinics. However, additional studies are required for a more detailed analysis of neuroprotection mechanisms.