Type 2 diabetes mellitus (DM2) is a widespread metabolic disorder that results in podocyte damage and diabetic nephropathy. Previous studies demonstrated that TRPC6 channels play a pivotal role in podocyte function and their dysregulation is associated with development of different kidney diseases including nephropathy. It was assumed that activation of TRPC6 channels leads directly to the Ca ²⁺ influx into cells. Another Ca ²⁺ influx pathway, a store-operated Ca ²⁺ entry (SOCE) via ORAI channels, was also shown to be disturbed during the diabetes development. Here, using single channel patch clamp technique, we demonstrated that non-selective cationic TRPC6 channels are sensitive to the Ca ²⁺ store depletion in human podocyte cell line Ab8/13 and in freshly isolated rat glomerular podocytes. Ca ²⁺ imaging indicated the involvement of ORAI and sodium-calcium exchanger (NCX) in Ca ²⁺ entry induced upon store depletion. Ca ²⁺ inflow by NCX is a result of pronounced TRPC6-mediated Na ⁺ influx leading moreover to the membrane depolarization and ORAI suppression. In rats fed a high-fat diet combined with a low-dose streptozotocin injection, which leads to DM2 development, we observed the reduction of SOCE in rat glomerular podocytes. This was accompanied by a reorganization of store-operated Ca ²⁺ influx such that TRPC6 channels lost their sensitivity to Ca ²⁺ store depletion and ORAI-mediated Ca2+ entry is suppressed in TRPC6-independent manner. Altogether our data provide new insights into the mechanism of SOCE organization in podocytes in the norm and in pathology, which should be taken into account in the pharmacological treatment of the early stages of diabetic nephropathy.
The gating mechanism of acid-sensitive ion channels (ASICs) remains unclear, despite the availability of atomic-scale structures in various functional states. The collapse of the acidic pocket and structural changes in the low-palm region are assumed to trigger activation. For the acidic pocket, protonation of some residues can minimize repulsion in the collapsed conformation. The relationship between low-palm rearrangements and gating is unknown. In this work, we performed a Monte Carlo energy optimization of known ASIC1a structures and determined the residue–residue interactions in different functional states. For rearrangements in the acidic pocket, our results are consistent with previously proposed mechanisms, although significant complexity was revealed for the residue–residue interactions. The data support the proposal of a gating mechanism in the low-palm region, in which residues E80 and E417 share a proton to activate the channel.
Fourteen hexane-soluble polyphenolic secondary metabolites were previously isolated as individual compounds from Empetrum nigrum L. and identified as three bibenzyls, four 9,10-dihydrophenanthrenes, two chalcones, four dihydrochalcones and one flavanone. In this study, the mass-spectra and retention indexes (RI) of compounds 1-14 without prior derivatization were obtained and the resulting fragmentation pathways rationalized in accordance with literary data and the compounds structures. Preliminary differences in metabolite composition were assessed by comparative profiling using GC-MS chromatography combined with multivariate data analysis for a limited amount of E. nigrum n-hexane extracts obtained from plants growing in three different geographic locations. To characterize antioxidant capacity of isolated compounds 1-14 we used our well-established model based on reactive oxygen species (ROS) production by activated human platelets and showed that most of the examined polyphenols act as antioxidants by inhibition of ROS production.
The pharmacology of acid-sensitive ion channels (ASICs) is diverse, but potent and selective modulators, for instance for ASIC2a, are still lacking. In the present work we studied the effect of five 2-aminobenzimidazole derivatives on native ASICs in rat brain neurons and recombinant receptors expressed in CHO cells using the whole-cell patch clamp method. 2-aminobenzimidazole selectively potentiated ASIC3. Compound Ru-1355 strongly enhanced responses of ASIC2a and caused moderate potentiation of native ASICs and heteromeric ASIC1a/ASIC2a. The most active compound, Ru-1199, caused the strongest potentiation of ASIC2a, but also potentiated native ASICs, ASIC1a and ASIC3. The potentiating effects depended on the pH and was most pronounced with intermediate acidifications. In the presence of high concentrations of Ru-1355 and Ru-1199, the ASIC2a responses were biphasic, the initial transient currents were followed by slow component. These slow additional currents were weakly sensitive to the acid-sensitive ion channels pore blocker diminazene. We also found that sustained currents mediated by ASIC2a and ASIC3 are less sensitive to diminazene than the peak currents. Different sensitivities of peak and sustained components to the pore-blocking drug suggest that they are mediated by different open states. We propose that the main mechanism of action of 2-aminobenzimidazole derivatives is potentiation of the open state with slow kinetics of activation and desensitization.
Oxygen breathing at elevated partial pressures (PO 2 ’s) at or more than 3 atmospheres absolute (ATA) causes a reduction in brain γ-aminobutyric acid (GABA) levels that impacts the development of central nervous system oxygen toxicity (CNS-OT). Drugs that increase brain GABA content delay the onset of CNS-OT, but it is unknown if oxidant damage is lessened because brain tissue PO 2 remains elevated during hyperbaric oxygen (HBO 2 ) exposures. Experiments were performed in rats and mice to measure brain GABA levels with or without GABA transporter inhibitors (GATs) and its influence on cerebral blood flow, oxidant damage, and aspects of mitochondrial quality control signaling (mitophagy and biogenesis). In rats pretreated with tiagabine (GAT1 inhibitor), the tachycardia, secondary rise in mean arterial blood pressure, and cerebral hyperemia were prevented during HBO 2 at 5 and 6 ATA. Tiagabine and the nonselective GAT inhibitor nipecotic acid similarly extended HBO 2 seizure latencies. In mice pretreated with tiagabine and exposed to HBO 2 at 5 ATA, nuclear and mitochondrial DNA oxidation and astrocytosis was attenuated in the cerebellum and hippocampus. Less oxidant injury in these regions was accompanied by reduced conjugated microtubule-associated protein 1A/1B-light chain 3 (LC3-II), an index of mitophagy, and phosphorylated cAMP response element binding protein (pCREB), an initiator of mitochondrial biogenesis. We conclude that GABA prevents cerebral hyperemia and delays neuroexcitation under extreme HBO 2 , limiting oxidant damage in the cerebellum and hippocampus, and likely lowering mitophagy flux and initiation of pCREB-initiated mitochondrial biogenesis.
Maternal hyperhomocysteinemia causes the disruption of placental blood flow and can lead to serious disturbances in the formation of the offspring’s brain. In the present study, the effects of prenatal hyperhomocysteinemia (PHHC) on the neuronal migration, neural tissue maturation, and the expression of signaling molecules in the rat fetal brain were described. Maternal hyperhomocysteinemia was induced in female rats by per os administration of 0.15% aqueous methionine solution in the period of days 4–21 of pregnancy. Behavioral tests revealed a delay in PHHC male pups maturing. Ultrastructure of both cortical and hippocampus tissue demonstrated the features of the developmental delay. PHHC was shown to disturb both generation and radial migration of neuroblasts into the cortical plate. Elevated Bdnf expression, together with changes in proBDNF/mBDNF balance, might affect neuronal cell viability, positioning, and maturation in PHHC pups. Reduced Kdr gene expression and the content of SEMA3E might lead to impaired brain development. In the brain tissue of E20 PHHC fetuses, the content of the procaspase-8 was decreased, and the activity level of the caspase-3 was increased; this may indicate the development of apoptosis. PHHC disturbs the mechanisms of early brain development leading to a delay in brain tissue maturation and formation of the motor reaction of pups.
The review examines the impact of the COVID-19 pandemic on the prevalence, manifestation, as well as the possibility of preventing and treating behavioral (non-chemical) addictions. Particular attention is paid to various manifestations of Internet addiction (IA): gaming, gambling, cybersexual and food addiction (FA). During the pandemic, Internet use increased significantly, leading to an increase in IA, mainly due to gaming, which correlated with the level of psychosocial problems. The increase in gambling occurred mainly in individuals with addiction or risk groups, while in the population the frequency of gambling decreased or did not change. Immediately after the start of the COVID-19 pandemic, the number of requests to porn sites increased dramatically, suggesting an increase in cybersex addiction. However, longitudinal studies in adolescents show a slight decrease in the interest in pornography in boys, and an increase from an initially low level in girls. The proportion of eating disorders and FA significantly increased. An increase in FA was associated with depression, anxiety, and also in obese individuals. In the era of COVID-19 prevention practices and general remedial activity should take into account the needs of the general population, emphasizing the importance of self-regulating and balanced lifestyles with moderate and sensible Internet use during the pandemic.
SARS-CoV-2 infection may cause such complications as post-COVID-19 syndrome, which includes chronic fatigue, myalgia, arthralgia, as well as a variety of neurological manifestations, e.g., neuropathy of small fibers, hearing and vestibular dysfunction, and cognitive impairment. This clinical case describes a 41-year-old patient suffering from post-COVID-19 syndrome and chronic fatigue syndrome. A detailed examination was performed, including an in-depth study of peripheral and central hearing and vestibular functions, as well as small nerve fibers length and density in the skin and cornea of the eye. Contrary to expectations, no peripheral nervous system dysfunction was detected, despite the presence of dizziness and gait instability in the patient. Hearing tests (gap detection test and dichotic test) showed central auditory processing disorders. The evaluated lesion in the processing of temporal and verbal auditory information can be a significant factor contributing to additional overload of the neural activity and leading to chronic fatigue when performing daily activities in patients with CFS and post-COVID-19 complications.
Microbiota are known to play an important role in gastrointestinal physiology and pathophysiology. Microbiota and their metabolites can affect gut motility, neural regulation and the enteric endocrine systems and immune systems of the gut. The use of fermented/hydrolyzed products may be a promising new avenue for stimulating gastrointestinal motility. The purpose of this study was to investigate the effect of lactobacillus metabolites (PP), produced using a U.S.-patented fermentation method, on rat colon motility in vitro. The distal colon was incised from newborn male Wistar rats. A sensitive tensometric method for the study of colon contractions was used. The [Ca2+]i in colon tissue was registered using a computerized ratiometric system for an intracellular ion content assay (Intracellular Imaging and Photometry System, Intracellular imaging, Inc. Cincinnati, OH, USA). The cumulative addition of PP induced contraction with sigmoid dose responses with ED50 = 0.13 ± 0.02% (n = 4), where 10% PP was accepted as a maximal dose. This contraction was accompanied by an increase in the concentration of [Ca2+]i. It was shown that introducing Lactobacillus metabolites produced using a U.S.-patented fermentation method quickly stimulates dose-dependent colon contractions and an increase in intracellular calcium. The direct application of PP via enema to the colon could stimulate colon motility and suppress pathogenic microbiota, owing to the antagonistic property of PP on pathogens.
This literature review presents the role of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO), as well as arginine, the enzyme substrate, in the disease of metabolic syndrome and COVID-19 (SARS-CoV-2 virus). Metabolic syndrome is a combination of obesity, insulin resistance, hyperglycemia, dyslipidemia and hypertension. It has been shown that in elderly people, patients with obesity, metabolic syndrome, type 2 diabetes mellitus (DM2), and patients with COVID-19, endothelial dysfunction (ED) and vascular endothelial activation are detected. ED is the main cause of a number of pathological conditions during the development of COVID-19 and earlier in patients with metabolic syndrome, while a sharp drop in the level of nitric oxide (NO) is detected due to a decrease in the expression and activity of eNO synthase and enzyme depletion, which leads to a violation of the integrity of bloodvessels, that is, to vasoconstrictive, inflammatory and thrombotic conditions, followed by ischemia of organs and edema of tissues. It should be noted that metabolic syndrome, DM2, hypertension and obesity, in particular, are age-related diseases, and it is known that blood glucose levels increase with age, which reduces the bioavailability of NO in endothelial cells. Defects in the metabolism of NO cause dysfunction in the pulmonary blood vessels, the level of NO decreases, which leads to impaired lung function and coagulopathy. The review presents possible mechanisms of these disorders associated with ED, the release of eNO synthase, changes in phosphorylation and regulation of enzyme activity, as well as insulin resistance. A modern view of the role of the polymorphism of the eNO synthase gene in the development of these pathologies is presented. To increase the level of endothelial NO, drugs are offered that regulate the bioavailability of NO. These include arginine, agonist NO – minoxidil, steroid hormones, statins, metformin. However, further research and clinical trials are needed to develop treatment strategies that increase NO levels in the endothelium.
Urolithiasis is a common multifactorial disease characterized by a high recurrence rate. This review is devoted to the urine pH as one of the main factors determining its lithogenic properties. It affects the excretion of lithogenic substances and stone formation inhibitors, the solubility, and the crystallization of substances involved in stone formation. The urine pH significantly affects the solubility of uric acid in urine, which decreases at a pH < 5.5. This explains the high incidence of uric acid concretions in patients with metabolic syndrome. Their insulin resistance leads to a decrease in the excretion of ammonium ions in the proximal tubules, leading to persistent urine acidification. The activity of many transport processes involved in the processing of calcium, citrates and phosphates is sensitive to changes in systemic or local pH. The data on the effect of urine pH on the solubility of calcium oxalate remain contradictory. At the same time, there is no doubt about the determining role of urine pH in the excretion of citrate, the most important stone formation inhibitor. The alkaline urine pH promotes the formation of concretions containing calcium phosphates. In conditions of constantly elevated urine pH in patients with persistent urease-producing urinary tract infection, a rapid growth of "infectious" concretions occurs. The review summarizes information on the causes of the decrease and increase in the urine pH, as well as the possibilities of medicinal and non-medicinal methods of modifying the urine pH during the prevention of stone formation recurrence.
The present study aimed to explore the consequences of a single exposure to a social defeat on dopamine release in the rat nucleus accumbens measured with a fast-scan cyclic voltammetry. We found that 24 h after a social defeat, accumbal dopamine responses, evoked by a high frequency electrical stimulation of the ventral tegmental area, were more profound in socially defeated rats in comparison with non-defeated control animals. The enhanced dopamine release was associated with the prolonged immobility time in the forced swim test. The use of the dopamine depletion protocol revealed no alteration in the reduction and recovery of the amplitude of dopamine release following social defeat stress. However, administration of dopamine D2 receptor antagonist, raclopride (2 mg/kg, i.p.), resulted in significant increase of the electrically evoked dopamine release in both groups of animals, nevertheless exhibiting less manifested effect in the defeated rats comparing to control animals. Taken together, our data demonstrated profound alterations in the dopamine transmission in the association with depressive-like behavior following a single exposure to stressful environment. These voltammetric findings pointed to a promising path for the identification of neurobiological mechanisms underlying stress-promoted behavioral abnormalities.
Maternal hyperhomocysteinemia (HCY) is a common pregnancy complication caused by high levels of the homocysteine in maternal and fetal blood, which leads to the alterations of the cognitive functions, including learning and memory. In the present study, we investigated the mechanisms of these alterations in a rat model of maternal HCY. The behavioral tests confirmed the memory impairments in young and adult rats following the prenatal HCY exposure. Field potential recordings in hippocampal slices demonstrated that the long-term potentiation (LTP) was significantly reduced in HCY rats. The whole-cell patch-clamp recordings in hippocampal slices demonstrated that the magnitude of NMDA receptor-mediated currents did not change while their desensitization decreased in HCY rats. No significant alterations of glutamate receptor subunit expression except GluN1 were detected in the hippocampus of HCY rats using the quantitative real-time PCR and Western blot methods. The immunofluorescence microscopy revealed that the number of synaptopodin-positive spines is reduced, while the analysis of the ultrastructure of hippocampus using the electron microscopy revealed the indications of delayed hippocampal maturation in young HCY rats. Thus, the obtained results suggest that maternal HCY disturbs the maturation of hippocampus during the first month of life, which disrupts LTP formation and causes memory impairments.
Low-frequency electrical stimulation is used to treat some drug-resistant forms of epilepsy. Despite the effectiveness of the method in suppressing seizures, there is a considerable risk of side effects. An optogenetic approach allows the targeting of specific populations of neurons, which can increase the effectiveness and safety of low-frequency stimulation. In our study, we tested the efficacy of the suppression of ictal activity in entorhinal cortex slices in a 4-aminopyridine model with three variants of low-frequency light stimulation (LFLS): (1) activation of excitatory and inhibitory neurons (on Thy1-ChR2-YFP mice), (2) activation of inhibitory interneurons only (on PV-Cre mice after virus injection with channelrhodopsin2 gene), and (3) hyperpolarization of excitatory neurons (on Wistar rats after virus injection with archaerhodopsin gene). Only in the first variant did simultaneous LFLS of excitatory and inhibitory neurons replace ictal activity with interictal activity. We suggest that LFLS caused changes in the concentration gradients of K+ and Na+ cations across the neuron membrane, which activated Na-K pumping. According to the mathematical modeling, the increase in Na-K pump activity in neurons induced by LFLS led to an antiepileptic effect. Thus, a less specific and generalized optogenetic effect on entorhinal cortex neurons was more effective in suppressing ictal activity in the 4-aminopyridine model.
The facilitated activity of N-methyl-D-aspartate receptors (NMDARs) in the central and peripheral nervous systems promotes neuropathic pain. Amitriptyline (ATL) and desipramine (DES) are tricyclic antidepressants (TCAs) whose anti-NMDAR properties contribute to their analgetic effects. At therapeutic concentrations <1 µM, these medicines inhibit NMDARs by enhancing their calcium-dependent desensitization (CDD). Li+, which suppresses the sodium–calcium exchanger (NCX) and enhances NMDAR CDD, also exhibits analgesia. Here, the effects of different [Li+]s on TCA inhibition of currents through native NMDARs in rat cortical neurons recorded by the patch-clamp technique were investigated. We demonstrated that the therapeutic [Li+]s of 0.5–1 mM cause an increase in ATL and DES IC50s of ~10 folds and ~4 folds, respectively, for the Ca2+-dependent NMDAR inhibition. The Ca2+-resistant component of NMDAR inhibition by TCAs, the open-channel block, was not affected by Li+. In agreement, clomipramine providing exclusively the NMDAR open-channel block is not sensitive to Li+. This Ca2+-dependent interplay between Li+, ATL, and DES could be determined by their competition for the same molecular target. Thus, submillimolar [Li+]s may weaken ATL and DES effects during combined therapy. The data suggest that Li+, ATL, and DES can enhance NMDAR CDD through NCX inhibition. This ability implies a drug–drug or ion–drug interaction when these medicines are used together therapeutically.
One of the most unusual features of the avian magnetic compass is its sensitivity to weak oscillating magnetic fields (OMF) in the radiofrequency range. This effect, observed earlier in numerous experiments in European robins Erithacus rubecula and garden warblers Sylvia borin, is usually associated with the radical-pair magnetoreception in the eye, which is the mainstream biophysical model of the avian magnetic compass. We studied the effect of OMF on the orientation behavior of a long-distance migrant, the pied flycatcher Ficedula hypoleuca. The OMF with an amplitude of 190 nT disoriented pied flycatchers, similarly to the species studied earlier. However, the application of OMP with an amplitude of 17 nT did not lead to disorientation in pied flycatchers when tested in round arenas: the birds showed their correct season-specific migratory direction. This finding is in stark contrast with previous results, obtained in garden warblers at exactly the same place and under the same conditions: garden warblers were disoriented by OMF which was an order of magnitude weaker. Moreover, the threshold of sensitivity to OMF amplitude in pied flycatchers is found to be higher than that in both species previously studied, the European robin and the garden warbler. We discuss the variable sensitivity of avian compass to OMF in the context of migration ecology of two long-distance African migrants, the pied flycatcher and garden warbler, and the short-distance migrant, the European robin. Significance statement Birds are known to use a magnetic compass to determine the proper direction of their flight during seasonal migrations. Many previous experiments demonstrated that operation of this compass is disrupted by weak oscillating magnetic fields (OMF) in the radiofrequency range. Among the two bird species studied so far, a long-distance migrant, garden warbler, is more sensitive to OMF than a short-distance migrant, European robin. This might be a result of finer tuning of the magnetic compass of long-distance migrants, making it less robust to perturbations. In our experiments, however, the magnetic compass of another long-distance migrant, pied flycatcher, remained operational under OMF even stronger than that which disrupted magnetic orientation of European robins. This unexpected result demonstrates high variability of navigational systems of birds and raises questions about their adaptation to behavioral patterns of birds on their migration routes.
The Phaeophyceae (brown algae) essentially contribute to biotopes of cold and temperate seas. Their thalli are rich in biologically active natural products which are strongly and universally dominated with phlorotannins – polyphenols of complex and diverse structure based on multiple differently arranged phloroglucinol units. These electron-rich compounds are strong antioxidants with antimicrobial, anti-inflammatory and neuroprotective activities. In the algal cells phlorotannins can either accumulate in cytoplasm or can be secreted into the cell wall (CW) with subsequent covalent binding to the alginate network. The biological activities of easily extractable intracellular phlorotannins were comprehensively characterized, whereas the properties of the CW-bound polyphenol fraction are still mostly unknown. Recently, we identified dibenzodioxin bonding as the principal structural feature of the CW-bound phlorotannins of fucoid algae, whereas soluble intracellular phlorotannins relied on aryl- and ether bonds. However, profiles of biological activity associated with these structural differences are still unknown. Therefore, here, to the best of our knowledge, for the first time, we address the antioxidant, cytotoxic, neuroprotective, and antibacterial properties of the CW-bound phlorotannin fractions isolated from two representatives of the order Fucales - Fucus vesiculosus and Pelvetia canaliculata. The CW-bound phlorotannins appeared to be softer antioxidants, stronger antibacterial agents and were featured with essentially less cytotoxicity in comparison to the intracellular fraction. However, the neuroprotective effects of both sub-cellular phlorotannin fractions of F. vesiculosus and P. canaliculata were essentially similar. Thus, due to their lower cytotoxicity, CW-bound phlorotannins can be considered as promising antioxidants and neuroprotectors.
Global warming implies the risk of a changing oxygen regime in the seas and oceans of our planet. The mitochondrial complex of nuclear erythrocytes of cartilaginous fish, as the energy basis of blood cells, has repeatedly encountered such climatic fluctuations throughout their evolutionary history. In this regard, the features of the adaptive strategy of the erythrocyte mitochondrial complex in the thornback ray (Raja clavata L.) are of interest from the evolutionary and ecological points of view. The rate of oxygen consumption in resuspended (Ht = 25–30%) erythrocytes taken from the Black Sea thornback ray in saline was studied by the polarographic method. A high “basal” rate of respiration in the erythrocytes of the thornback ray was shown, which ranged from 10.5 to 21.6 pmol O2 min−1·106 cells. The addition of substrates of the mitochondrial respiration activators glutamate, maleate, and succinate to the erythrocyte suspension caused a 2–6-fold increase in the respiratory activity of thornback ray erythrocytes. In cases where the rate of respiration of erythrocytes was high, protonophore–dinitrophenol caused an inhibition of the activity of mitochondrial respiration. At low respiration rates of erythrocytes, its effect was opposite and caused a stimulation of mitochondrial respiration. Oligomycin caused a significant inhibition of the respiratory activity of the red blood cell suspension of the thornback ray. This suppression of cell respiration was enhanced under conditions of exposure to the permeabilization of erythrocytes with digitonin. This can be recommended as one of the ways to block the respiratory activity of erythrocytes in cartilaginous fish. Another way of effectively blocking the respiration of the mitochondrial complex of the thornback ray’s erythrocytes was the effect of the blockers rotenone and sodium azide. The peculiarity of the mitochondria of the erythrocytes of the thornback ray was the absence of the complete inhibition of respiration by sodium azide (NaN3), which is characteristic of the mitochondria of other fish species. Our data on the activation of the “respiration” of erythrocytes in fish indicate that the potential capabilities of cold-blooded and warm-blooded vertebrates have rather similar characteristics. This may indicate the initial “laying” of the architecture of the inner membrane to support the energy potential of the mitochondria of the cell.
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