Sodium Pump Research Articles

Abstract 4136700: Sodium-Potassium Pump: Newly O-GlcNAc Protein Offering Potential Benefits in Hemorrhagic Shock situation

Hemorrhagic shock(HS) results from significant blood loss, leading to insufficient oxygen delivery, which causes metabolic changes and multi-organ dysfunction.The HS-related acute kidney injury developed by the patient are mainly due to alteration in Na/K ATPase.In previous O-GlcNAcylomic studies, we identified the Na/K ATPase as potentially O-GlcNAcylated.O-GlcNAcylation, a post-translational modification, plays a role in various cellular processes, such as cell survival and stress response.O-GlcNAcylation may have beneficial effect in shock situations. The objective of this study is to ascertain whether Na/K ATPase is O-GlcNAcylated and to elucidate its potential role during HS. Hemorrhagic shock was induced by an exsanguination of rats.They were then randomly treated or not with an O-GlcNAcase inhibitor, the NButGT(10mg/kg), to increase O-GlcNAc level.Blood pressure and heart rate were monitored throughout the experiment.Blood samples were collected for complete blood analysis, including biochemistry and gas measurements. kidneys were immediately frozen for histological and biochemical studies.To study the O-GlcNAcylation of Na/K ATPase an immunoprecipitation and Wheat Germ Agglutinin(WGA) based lectin affinity gel electrophoresis were used. HEK cells were treated with or without NButGT(100µM,6 hours) and/or ouabain(Na/K ATPase inhibitor) and a colorimetric kit was assessed to study O-GlcNAcylation impact on Na/K ATPase activity. O-GlcNAc levels increased by 2 folds in heart and kidney due to the NButGT treatment(p<0.05).Mean arterial pressure(MAP,p<0.01) and bicarbonate(p<0.01) are restored in treated group as kalemia(Sham:4.2 ± 0.1;HS:4.7±0.1;NButGT:4.3 ±0.1;mmol/L;p<0.05) and natremia(Sham:141.5±0.4;HS:139.8±0.5;NButGT:141.9 ±0.4; mmol/L;p<0.01).The study of the O-GlcNAcylation of the Na/K ATPase validated its O-GlcNAcylation.Histological analysis of the kidney showed that HS decreased Na/K ATPase expression, but treatment restored it(Sham:15.1±1.1;HS:10.3±0.6;NButGT:13.78±1.1;%area;p<0.05). An acute increase in O-GlcNAc levels through NButGT enhances Na/K ATPase activity. Increased O-GlcNAcylation during hemorrhagic shock restored MAP and reduced indicators of metabolic acidosis.Treatment with NButGT restored natremia and kalemia.This effect is linked to an increase in the expression and activity of Na/K ATPase.Our study is the first to confirm that Na/K ATPase is regulated by O-GlcNAcylation, particularly in terms of its localization and stability.

Upregulation of the sodium potassium pump current supresses ectopic activity after stem cell delivery in the human-based heart after myocardial infarction

Abstract Background Cell therapy is being explored to restore the damaged and intrinsically irreparable human heart. Whilst preclinical studies showed improvements in cardiac function after injury, they also highlighted a critical pro-arrhythmic window when delivered cells produce ectopy-induced ventricular tachycardia. Recent experiments investigating the cells in vivo maturation suggested upregulation of the inward rectifier potassium current (IK1) and knock-out of the funny current (If) and sodium calcium exchanger (INaCa) to supress the arrhythmias[1]. Purpose Whilst promising, such modifications may impact the cells’ calcium dynamics and ultimately, their efficacy. The goal of this study is to identify novel ionic targets that improve therapy safety whilst maintaining efficacy by employing the unique predictive capabilities of modelling and simulation. Methods For this, we used our established modelling and simulation framework of cell therapy in the chronically infarcted human heart with Purkinje, validated against experimental and clinical data from the action potential to the ECG. We incorporated experimentally observed gene expression of in vivo cell maturation[1] into our framework to reproduce human pluripotent stem cell-induced cardiomyocyte (hPSC-CM) electrophysiology at day 0 and day 14 after injection. To consider variability amongst experimentally reported hPSC-CMs, we also created a fast-beating hPSC-CM model by upregulating the SERCA pump current, If and INaCa. Results Our results showed that while day 0 hPSC-CMs did not cause spontaneous activity, day 14 hPSC-CMs produced ectopic beats in the ventricles every 1.5s. The rapid beating hPSC-CM phenotype at day 14 elicited tachycardia through spontaneous beating and intermittent re-entrant wavefronts (see Figure 1). Next, we demonstrated 65% upregulation of the sodium-potassium pump current (INaK) together with a 50% increase in IK1 and knock-out of If as a novel pathway to quiescence. Importantly, our simulations highlighted that compared to INaCa knock-out, an increase in INaK allowed for physiological calcium transients. Conclusion To conclude, in this work we have utilised modelling and simulation of the injured human heart to 1) capture pre-clinically observed arrhythmias after cell therapy and 2) identify INaK upregulation as a novel target to mitigate safety concerns, whilst preserving efficacy.

Brain-to-blood transport of fluorescein in vitro

Investigating blood-brain barrier (BBB) dysfunction has become a pre-clinical and clinical research focus as it accompanies many neurological disorders. Nevertheless, knowledge of how diagnostic BBB tracers cross the endothelium from blood-to-brain or vice versa often remains incomplete. In particular, brain-to-blood transport (efflux) may reduce tracer extravasation of intravascularly (i.v.) applied tracers. Conversely, impaired efflux could mimic phenotypic extravasation. Both processes would affect conclusions on BBB properties primarily attributed to blood-to-brain leakage. Here, we specifically investigated efflux of fluorescent BBB tracers, focusing on the most common non-toxic marker, sodium fluorescein, which is applicable in patients. We used acute neocortical slices from mice and applied fluorescein, sulforhodamine-B, rhodamine-123, FITC dextran to the artificial cerebrospinal fluid. Anionic low molecular weight (MW) fluorescein and sulforhodamine-B, but not ~ 10-fold larger FITC-dextran and cationic low MW rhodamine-123, showed efflux into the lumen of blood vessels. Our data suggest that fluorescein efflux depends on organic anion transporter polypeptides (Oatp) rather than P-glycoprotein. Furthermore, sodium-potassium ATPase inhibition and incomplete oxygen-glucose deprivation (OGD, 20% O2) reduced fluorescein efflux, while complete OGD (0% O2) abolished efflux. We provide evidence for active efflux of fluorescein in vitro. Impaired efflux of fluorescein could thus contribute to the frequently observed BBB dysfunction in neuropathologies in addition to blood-to-brain leakage.

Peripheral cranio-spinal nerve communication for trapezius muscle control using axonal profiling through immunostaining

Accessory nerve (CNXI) has been known to be the primary conduit for motor control of the trapezius, while the supplementary cervical nerves (C3 and C4) are responsible for processing sensory information from muscle. However, the lack of substantial direct evidence has led to these conclusions being regarded as mere speculation. This study used immunostaining (using antibodies against neurofilament 200 for all axons, choline acetyltransferase for cholinergic axons, tyrosine hydroxylase for sympathetic axons, and alpha 3 sodium potassium ATPase for proprioceptive afferent axons) of human samples to verify the functional contributions of nerves. Study highlights the pivotal role of C3 and C4 in regulating precise movements of trapezius, contributing to motor control, proprioceptive feedback, and sympathetic modulation. CNXI is composed primarily of somatic efferent fibers, with significant numbers of sympathetic or sensory fibers. Furthermore, C3-4 have both cholinergic and non-cholinergic axons, suggesting their involvement in proprioceptive feedback and somatic efferent functions. Although less common, mechanosensors such as nociceptive sensor and sympathetic fibers are also supplied by these cervical nerves. The study demonstrated that these nerves contain motor fibers and significant proprioceptive and sympathetic axons, challenging the long-held notion that CNXI are motor and upper spinal nerves are sensory.

Study on the antihypertensive mechanism of acupuncture at "Renying" (ST9) and "Zusanli" (ST36) via gastrin/cholecystokinin B receptors

To observe the effect of acupuncture on serum gastrin content and urinary sodium excretion in spontaneously hypertensive rat (SHR), so as to explore its potential mechanism in the treatment of hypertension. Thirty-two male SHRs were randomly divided into model, hydrochlorothiazide, acupuncture and sham acupuncture groups, with 8 rats in each group, and 8 male Wistar-kyoto rats were taken as the control group. Rats in the hydrochlorothiazide group received gavage of hydrochlorothiazide solution (10 mg·kg-1·d-1), once daily for 4 weeks. Acupuncture was applied to bilateral "Renying" (ST9) and "Zusanli" (ST36) or non-acupoint on both sides for rats in the acupuncture and sham acupuncture groups, with manual stimulation every 10 minutes for a total of 20 minutes, once a day for a total of 4 weeks. The systolic blood pressure of the tail-artery was measured before and 1, 2, 3, and 4 weeks after the intervention. HE staining was used to observe the pathological changes in renal tissue. Serum gastrin contents were detected using enzyme-linked immunosorbent assay (ELISA). Urinary sodium content was measured by atomic absorption spectrometry. The expression levels of cholecystokinin B receptor (CCKBR) and Na+/K+-ATPase proteins in renal tissue were detected by Western blot, and the mRNA expression levels of CCKBR and the α1 subunit of Na+/K+- ATPase (ATP1A1) were detected by fluorescence quantitative PCR. Compared with the control group, the systolic blood pressure of the tail artery in the model group were increased significantly before intervention and at the 1st, 2nd, 3rd and 4th weeks of intervention (P<0.05). Before intervention, the 24 h urine volume of the model, hydrochlorothiazide, acupuncture and sham acupuncture groups were decreased significantly (P<0.05). After intervention, the 24 h urine volume and urinary sodium excretion in the model group were significantly decreased (P<0.05)；the expression levels of CCKBR protein and mRNA in renal tissue were significantly decreased (P<0.05)；the expression levels of Na+/K+-ATPase protein and ATP1A1 mRNA were significantly increased (P<0.05)；the glomerulus was mildly congested with a small amount of lymphocyte infiltration. Compared with the model group, the systolic blood pressure of the tail artery in the hydrochlorothiazide and the acupuncture groups were decreased significantly at the 2nd, 3rd and 4th weeks of intervention (P<0.05)；the 24 h urine volume and urinary sodium excretion in the hydrochlorothiazide and the acupuncture groups were significantly increased (P<0.05)；the serum gastrin content and the expression levels of CCKBR protein and mRNA in renal tissue were significantly increased (P<0.05)；the expression levels of Na+/K+-ATPase protein and ATP1A1 mRNA were significantly decreased (P<0.05)；there were no obvious pathological changes in renal tissue. A small number of lymphocyte focal infiltration around blood vessels was observed in the kidney tissue of the sham acupuncture group. Acupuncture can significantly reduce the tail artery systolic blood pressure of SHR, which may be related to its effect in increasing serum gastrin content and CCKBR expression, inhibiting sodium pump reabsorption, thus promoting urinary sodium excretion.

The mayfly Neocloeon triangulifer senses decreasing oxygen availability (PO2) and responds by reducing ion uptake and altering gene expression.

Oxygen availability is central to the energetic budget of aquatic animals and may vary naturally and/or in response to anthropogenic activities. Yet, we know little about how oxygen availability is linked to fundamental processes such as ion transport in aquatic insects. We hypothesized and observed that ion (22Na and 35SO4) uptake would be significantly decreased at O2 partial pressures below the mean Pcrit (5.4 kPa) where metabolic rates (MO2) are compromised, and ATP production is limited. However, we were surprised to observe marked reductions in ion uptake at oxygen partial pressures well above the Pcrit, where MO2 was stable. For example, SO4 uptake decreased by 51% at 11.7kPa, and 82% at the Pcrit (5.4kPa) while Na uptake decreased by 19% at 11.7kPa, and 60% at the Pcrit. Nymphs held for longer time periods at reduced PO2 exhibited stronger reductions in ion uptake rates. Fluids from whole body homogenates exhibited a 29% decrease in osmolality in the most hypoxic condition. The differential expression of atypical guanylyl cyclase (gcy-88e) in response to changing PO2 conditions provides evidence for its potential role as an oxygen sensor. Several ion transport genes (e.g., chloride channel and sodium-potassium ATPase) and hypoxia-associated genes (e.g., ldh and egl-9) were also impacted by decreased oxygen availability. Together, our work suggests that N. triangulifer can sense decreased oxygen availability and perhaps conserves energy accordingly, even when MO2 is not impacted.

Palytoxin evokes reversible spreading depolarization in the locust CNS.

Spreading depolarization (SD) describes the near-complete depolarization of central nervous system (CNS) neural cells as a consequence of chemical, electrical, or metabolic perturbations. It is well established as the central mechanism underlying insect coma and various mammalian neurological dysfunctions. Despite significant progress in our understanding, the question remains: which cation channel, if any, generates SD in the CNS? Previously, we speculated that the sodium-potassium ATPase (NKA) might function as a large-conductance ion channel to initiate SD in insects, potentially mediated by a palytoxin (PLTX)-like endogenous activator. In the current study, we evaluate the effectiveness and properties of PLTX as an SD initiator in Locusta migratoria. Whereas bath-applied PLTX failed to ignite SD, direct injection into the neuropil triggered SD in 57% of the preparations. Notably, PLTX-induced SD onset was significantly more rapid compared with ouabain (OUA) injection and azide controls, though their electrophysiological features remained similar. Furthermore, PLTX-induced SD was recoverable and resulted in a greater frequency of repetitive SD events compared with ouabain. Surprisingly, prior PLTX treatment disrupted the onset and recovery of subsequent SD evoked by other means. PLTX injection could attenuate the amplitude and even completely inhibit the onset of azide-induced SD at higher doses. These results show that PLTX can trigger repetitive and reversible SD-like events in locusts and simultaneously interfere with anoxic SD occurrence. We suggest that the well-documented NKA pump conversion into an open nonselective cationic channel is a plausible mechanism of SD activation in the locust CNS, warranting additional investigations.NEW & NOTEWORTHY Spreading depolarization (SD) is a critical mechanism underlying central nervous system (CNS) shutdown and injury under stress, yet the initiating ion channel remains unknown. Here, we used the marine poison palytoxin (PLTX), which converts the sodium-potassium ATPase (NKA) into an open channel, to initiate SD in intact locust CNS. We show for the first time that PLTX-induced SD is rapid and recoverable in vivo, providing support that NKA conversion to a channel may be the SD-initiating mechanism.

Targeting the Sodium-Potassium Pump as a Therapeutic Strategy in Acute Myeloid Leukemia.

Tissue-specific differences in the expression of paralog genes, which are not essential in most cell types due to the buffering effect of the partner pair, can make for highly selective gene dependencies. To identify selective paralogous targets for acute myeloid leukemia (AML), we integrated the Cancer Dependency Map with numerous datasets characterizing protein-protein interactions, paralog relationships, and gene expression in cancer models. In this study, we identified ATP1B3 as a context-specific, paralog-related dependency in AML. ATP1B3, the β-subunit of the sodium-potassium pump (Na/K-ATP pump), interacts with the α-subunit ATP1A1 to form an essential complex for maintaining cellular homeostasis and membrane potential in all eukaryotic cells. When ATP1B3's paralog ATP1B1 is poorly expressed, elimination of ATP1B3 leads to the destabilization of the Na/K-ATP pump. ATP1B1 expression is regulated through epigenetic silencing in hematopoietic lineage cells through histone and DNA methylation in the promoter region. Loss of ATP1B3 in AML cells induced cell death in vitro and reduced leukemia burden in vivo, which could be rescued by stabilizing ATP1A1 through overexpression of ATP1B1. Thus, ATP1B3 is a potential therapeutic target for AML and other hematologic malignancies with low expression of ATP1B1. Significance: ATP1B3 is a lethal selective paralog dependency in acute myeloid leukemia that can be eliminated to destabilize the sodium-potassium pump, inducing cell death.

7342 Thyrotoxic Periodic Paralysis

Abstract Disclosure: G. Arora: None. Case presentation: A 40 year old male with no significant past medical history presented to the emergency department with diffuse body weakness for one day. On the night prior to admission, his thighs started getting sore which in a matter of a few hours, progressed to weakness involving his entire body. He was unable to flex his hips, shoulders, and neck. He was unable to get up or move without assistance. He was found to have an irregular heartbeat two weeks prior to admission and had undergone a thyroid ultrasound which showed inflammation of the thyroid gland. He was not started on any new medications. He endorsed fatigue, palpitations, neck swelling, and 45 lbs unintentional weight loss over 6 months. No fever, chills, vision changes, congestion, chest pain, shortness of breath, cough, tingling, numbness or weakness. He denied alcohol or drug use. Physical examination was notable for blood pressure 151/80 mm Hg, heart rate 120 bpm, enlarged thyroid gland tender to palpation, and muscle weakness (motor strength 3/5 in flexors and extensors of hips and knees). Labs were notable for K 2.3 (3.5 - 5.1 mmol/L), ALP 218 (32 - 91 U/L), TSH &amp;lt;0.010 (0.400 - 4.300 mcIU/mL), Free T4 3.5 (0.6 - 1.6 ng/dL), CK 608 (49 - 397 U/L). Urine toxicology was negative. MRI spine did not show any acute abnormality except for thyromegaly. He received potassium supplementation which led to symptomatic improvement and was admitted to medical floor. Further tests revealed: TSI 39.50 (&amp;lt;=0.54 IU/L), TSH receptor antibody 26 (&amp;lt;=1.75 IU/L), thyroid microsomal antibody 773.3 (0.0 - 9.0 IU/mL), anti-thyroglobulin antibody 4 (&amp;lt;4 IU/mL). Thyroid ultrasound showed an enlarged, heterogenous, hypervascular thyroid without any nodules. He was started on Propranolol and Propylthiouracil, which led to symptom resolution and he was discharged. Discussion: Thyrotoxic periodic paralysis (TPP) is a rare muscle disorder, belonging to the family of diseases called channelopathies. Thyroid hormone increases tissue responsiveness to beta-adrenergic stimulation, which increases Na-K ATPase activity on the skeletal muscle membrane driving potassium into cells. This leads to hyperpolarization of the muscle membrane and relative inexcitability of the muscle fibers, especially in the presence of a trigger such as provocation with exercise, fasting state or a high carbohydrate meal (insulin stimulates Na-K ATPase pump). Furthermore, more than 95% of TPP cases occur in males. This predominance is due to androgen-induced Na-K ATPase sensitization, more pronounced hyperinsulinemia, comparatively higher sympathetic and catecholamine-induced Na-K ATPase activity and higher muscle mass in males. Given the life-threatening association of severe hypokalemia, TPP should be considered in all patients presenting with acute painless muscle weakness. Presentation: 6/3/2024

Butyl benzyl phthalate induces neurotoxicity in Eisenia fetida: Mechanisms revealed by biochemical and metabolomic analyses

Phthalates, particularly butyl benzyl phthalate (BBP), are ubiquitous environmental contaminants with potential neurotoxic effects. However, their impact on soil organisms, especially earthworms (Eisenia fetida), remains poorly understood. The current study investigated the neurotoxic effects of BBP on Eisenia fetida in artificial and red soils using an integrated approach combining biochemical assays, metabolomics, and molecular docking. Earthworms were exposed to 0, 1, and 10 mg kg−1 BBP for 14 and 28 days. Biochemical assays revealed significant increases in oxidative stress markers and disruptions in neurotransmission-related enzyme activities. Metabolomic analysis of the cerebral ganglia identified alterations in energy metabolism, lipid metabolism, and neuroactive ligand-receptor interaction signaling pathways. Molecular docking studies corroborated these findings, showing strong interactions between BBP and essential neuronal proteins, particularly the sodium pump. The integration of these data suggests that BBP-induced neurotoxicity in Eisenia fetida is primarily mediated by calcium signaling pathway dysfunction and calcium homeostasis imbalance. Notably, neurotoxic effects were more pronounced in red soil than in artificial soil, highlighting the importance of considering soil type in ecotoxicological assessments. The current study provides novel insights into the mechanisms of BBP-induced neurotoxicity in soil invertebrates and underscores the potential ecological risks associated with phthalate contamination in agricultural environments.

Influence of Intraocular Pressure on the Expression and Activity of Sodium-Potassium Pumps in the Corneal Endothelium.

The corneal endothelium is responsible for pumping fluid out of the stroma in order to maintain corneal transparency, which depends in part on the expression and activity of sodium-potassium pumps. In this study, we evaluated how physiologic pressure and flow influence transcription, protein expression, and activity of Na+/K+-ATPase. Native and engineered corneal endothelia were cultured in a bioreactor in the presence of pressure and flow (hydrodynamic culture condition) or in a Petri dish (static culture condition). Transcription of ATP1A1 was assessed using qPCR, the expression of the α1 subunit of Na+/K+-ATPase was measured using Western blots and ELISA assays, and Na+/K+-ATPase activity was evaluated using an ATPase assay in the presence of ouabain. Results show that physiologic pressure and flow increase the transcription and the protein expression of Na+/K+-ATPase α1 in engineered corneal endothelia, while they remain stable in native corneal endothelia. Interestingly, the activity of Na+/K+-ATPase was increased in the presence of physiologic pressure and flow in both native and engineered corneal endothelia. These findings highlight the role of the in vivo environment on the functionality of the corneal endothelium.

Concept article: Antidepressant-induced destabilization in bipolar illness mediated by serotonin 3 receptor (5HT3).

Antidepressants used by patients with bipolar disorder have been associated with destabilization with an increase in mania, depression, and cycling. The most commonly proposed mechanism, that antidepressants 'overshoot' their antidepressant effect to create a manic or mixed state, is unlikely since antidepressants have actually been found to be ineffective in treating bipolar depression. Beginning with known bipolar-specific pathophysiologic abnormalities provides the greatest likelihood of insight. PubMed was queried with 'bipolar', 'sodium', 'intracellular sodium', 'serotonin 3', '5HT3', '5-hydroxytryptamine type 3 receptors', and 'antidepressant' either individually or in combination. Pathologic mood states (both mania and depression) are associated with increased intracellular sodium (Na) concentrations that depolarize the resting membrane potential to increase cellular excitability (mania) or cause depolarization block (depression). Stimulation of the serotonin (5HT) receptors depolarizes the post-synaptic neuron. Stimulation of 5HT3 may be of particular importance since it is coupled to a cation channel that directly depolarizes the membrane. These effects directly impact the physiology of patients with bipolar disorder to alter neuronal excitability in a fashion that worsens both mania and depression. The most consistently observed biological abnormality in individuals going through mania or bipolar depression involves a decline in Na pump activity, with consequent elevation of intracellular Na levels. Antidepressant treatment potentiates this, particularly by activation of 5HT3. This hypothesis can be tested by coadministering a 5HT3 antagonist (e.g., vortioxetine or ondansetron) to achieve blockade of that receptor while treating bipolar depression with a serotoninergic antidepressant.

Metformin protects against small intestine damage induced by diabetes and dunning's prostate cancer: A biochemical and histological study.

The oral biguanide metformin is used to treat type 2 diabetic mellitus (T2DM). Anti-cancer effects have been proven by metformin in different hormone-sensitive tumors, including breast, pancreatic, colon, and prostate cancer. Therefore, we investigated whether metformin could defend against small intestine damage in Dunning's prostate cancer. The study divided the six groups of male Copenhagen rats into the following categories: control, diabetic (D), cancer (C), diabetic + cancer (DC), cancer + metformin (CM), and diabetic + cancer + metformin (DCM). After sacrifice, the small intestines were removed to assess biochemical markers and histopathological evaluation. Biochemical evaluations showed that glutathione (reduced) levels and other enzyme activities related antioxidant systems, paraoxonase, sodium potassium ATPase, acetylcholinesterase activities were decreased. In contrast, lipid peroxidation, total oxidant status, reactive oxygen species, interleukin-1β, interleukin-6, tumor necrosis factor-α, sucrase, maltase, trypsin, myeloperoxidase, xanthine oxidase activities, protein carbonyl contents and sialic acid levels were raised in the damaged groups. Treatment with metformin restored all of this. The histological assessment revealed moderate to severe damage in the small intestine following processes D and C. According to the study's findings, metformin treatment led to a notable decline in histopathological damage in the C and DC. A slight lowering in inflammatory cells and an improvement in the damaged gland integrity in the small intestine were noted with metformin treatment.​ Metformin use protected the small intestinal tissue damage and decreased oxidative stress.

From Frog Muscle to Brain Neurons: Joys and Sorrows in Neuroscience.

One element, potassium, can be identified as the connecting link in the research of Czech neurophysiologist Prof. František Vyskočil. It accompanied him from the first student experiments on the frog muscle (Solandt effect) via sodium-potassium pump and quantum and non-quantum release of neurotransmitters (e.g. acetylcholine) to the most appreciated work on the reversible leakage of K+ from brain neurons during the Leao´s spreading cortical depression, often preceding migraine. He used a wide range of methods at the systemic, cellular and genetic levels. The electrophysiology and biochemistry of nerve-muscle contacts and synapses in the muscles and brain led to a range of interesting findings and discoveries on normal, denervated and hibernating laboratory mammals and in tissue cultures. Among others, he co-discovered the facilitating effects of catecholamines (adrenaline in particular) by end-plate synchronization of individual evoked quanta. This helps to understand the general effectiveness of nerve-muscle performance during actual stress. After the transition of the Czech Republic to capitalism, together with Dr. Josef Zicha from our Institute, he was an avid promoter of scientometry as an objective system of estimating a scientist´s success in basic research (journal Vesmír, 69: 644-645, 1990 in Czech).

Elucidating the redox-driven sodium pumping mechanism of the ancient Rnf complex

Elucidating the redox-driven sodium pumping mechanism of the ancient Rnf complex

The Na+/K+-ATPase generically enables deterministic bursting in class I neurons by shearing the spike-onset bifurcation structure.

Slow brain rhythms, for example during slow-wave sleep or pathological conditions like seizures and spreading depolarization, can be accompanied by oscillations in extracellular potassium concentration. Such slow brain rhythms typically have a lower frequency than tonic action-potential firing. They are assumed to arise from network-level mechanisms, involving synaptic interactions and delays, or from intrinsically bursting neurons. Neuronal burst generation is commonly attributed to ion channels with slow kinetics. Here, we explore an alternative mechanism generically available to all neurons with class I excitability. It is based on the interplay of fast-spiking voltage dynamics with a one-dimensional slow dynamics of the extracellular potassium concentration, mediated by the activity of the Na+/K+-ATPase. We use bifurcation analysis of the complete system as well as the slow-fast method to reveal that this coupling suffices to generate a hysteresis loop organized around a bistable region that emerges from a saddle-node loop bifurcation-a common feature of class I excitable neurons. Depending on the strength of the Na+/K+-ATPase, bursts are generated from pump-induced shearing the bifurcation structure, spiking is tonic, or cells are silenced via depolarization block. We suggest that transitions between these dynamics can result from disturbances in extracellular potassium regulation, such as glial malfunction or hypoxia affecting the Na+/K+-ATPase activity. The identified minimal mechanistic model outlining the sodium-potassium pump's generic contribution to burst dynamics can, therefore, contribute to a better mechanistic understanding of pathologies such as epilepsy syndromes and, potentially, inform therapeutic strategies.

Hydrogen-Bonding and Hydrophobic Interaction Networks as Structural Determinants of Microbial Rhodopsin Function.

Microbial pump rhodopsins are highly versatile light-driven membrane proteins that couple protein conformational dynamics with ion translocation across the cell membranes. Understanding how microbial pump rhodopsins use specific amino acid residues at key functional sites to control ion selectivity and ion pumping direction is of general interest for membrane transporters, and could guide site-directed mutagenesis for optogenetics applications. To enable direct comparisons between proteins with different sequences we implement, for the first time, a unique numbering scheme for the microbial pump rhodopsin residues, NS-mrho. We use NS-mrho to show that distinct microbial pump rhodopsins typically have hydrogen-bond networks that are less conserved than anticipated from the amino acid residue conservation, whereas their hydrophobic interaction networks are largely conserved. To illustrate the role of the hydrogen-bond networks as structural elements that determine the functionality of microbial pump rhodopsins, we performed experiments, atomic-level simulations, and hydrogen bond network analyses on GR, the outward proton pump from Gloeobacter violaceus, and KR2, the outward sodium pump from Krokinobacter eikastus. The experiments indicate that multiple mutations that recover KR2 amino acid residues in GR not only fail to convert it into a sodium pump, but completely inactivate GR by abolishing photoisomerization of the retinal chromophore. This observation could be attributed to the drastically altered hydrogen-bond interaction network identified with simulations and network analyses. Taken together, our findings suggest that functional specificity could be encoded in the collective hydrogen-bond network of microbial pump rhodopsins.

Lithium Ions as Modulators of Complex Biological Processes: The Conundrum of Multiple Targets, Responsiveness and Non-Responsiveness, and the Potential to Prevent or Correct Dysregulation of Systems during Aging and in Disease.

Lithium is one of the lightest elements on Earth and it has been in the environment since the formation of the galaxy. While a common element, it has not been found to be an essential element in biological processes, ranging from single cell organisms to Homo sapiens. Instead, at an early stage of evolution, organisms committed to a range of elements such as sodium, potassium, calcium, magnesium, zinc, and iron to serve essential functions. Such ions serve critical functions in ion channels, as co-factors in enzymes, as a cofactor in oxygen transport, in DNA replication, as a storage molecule in bone and liver, and in a variety of other roles in biological processes. While seemingly excluded from a major essential role in such processes, lithium ions appear to be able to modulate a variety of biological processes and "correct" deviation from normal activity, as a deficiency of lithium can have biological consequences. Lithium salts are found in low levels in many foods and water supplies, but the effectiveness of Li salts to affect biological systems came to recent prominence with the work of Cade, who reported that administrating Li salts calmed guinea pigs and was subsequently effective at relatively high doses to "normalize" a subset of patients with bipolar disorders. Because of its ability to modulate many biological pathways and processes (e.g., cyclic AMP, GSK-3beta, inositol metabolism, NaK ATPases, neuro processes and centers, immune-related events, respectively) both in vitro and in vivo and during development and adult life, Li salts have become both a useful tool to better understand the molecular regulation of such processes and to also provide insights into altered biological processes in vivo during aging and in disease states. While the range of targets for lithium action supports its possible role as a modulator of biological dysregulation, it presents a conundrum for researchers attempting to elucidate its specific primary target in different tissues in vivo. This review will discuss aspects of the state of knowledge regarding some of the systems that can be influenced, focusing on those involving neural and autoimmunity as examples, some of the mechanisms involved, examples of how Li salts can be used to study model systems, as well as suggesting areas where the use of Li salts could lead to additional insights into both disease mechanisms and natural processes at the molecular and cell levels. In addition, caveats regarding lithium doses used, the strengths and weaknesses of rodent models, the background genetics of the strain of mice or rats employed, and the sex of the animals or the cells used, are discussed. Low-dose lithium may have excellent potential, alone or in combination with other interventions to prevent or alleviate aging-associated conditions and disease progression.

IDENTIFICATION AND EXTRACTION PROCESS OF CARDIAC GLYCOSIDES FROM FOXGLOVE PLANTS

Foxglove (Digitalis spp.) is a plant known for its cardiac glycoside content, which has been used in medicine for centuries. Cardiac glycosides, such as digoxin and digitoxin, are the main components that have a therapeutic effect on the cardiovascular system. This research examines the cardiac glycoside content of various Digitalis species, with a focus on extraction methods, isolation and characteristics of these compounds. Methods used include high-performance liquid chromatography (HPLC), mass spectrometry (MS), and nuclear magnetic resonance (NMR). The analysis results showed that Digitalis purpurea and Digitalis lanata were the main sources of cardiac glycosides. Digoxin and digitoxin were isolated and identified as the main active components. Pharmacological studies show that this compound interacts with the sodium-potassium ATPase pump, which increases cardiac contractility and is used in the treatment of heart failure and arrhythmias. Cardiac glycosides from the foxglove plant play an important role in cardiovascular therapy. Further research is needed to develop more efficient extraction methods and understand the deeper mechanisms of action, as well as potential side effects associated with long-term use.

Dermatoprotective effect of Moringa oleifera leaf extract on sodium valproate-induced skin damage in rats

Valproic acid is an antiepileptic drug associated with skin-related issues like excessive hair growth, hair loss, and skin rashes. In contrast, Moringa oleifera, rich in nutrients and antioxidants, is gaining popularity worldwide for its medicinal properties. The protective properties of M. oleifera extract against skin-related side effects caused by valproic acid were investigated. Female rats were divided into control groups and experimental groups such as moringa, sodium valproate, and sodium valproate + moringa groups. A 70% ethanolic extract of moringa (0.3 g/kg/day) was given to moringa groups, and a single dose of sodium valproate (0.5 g/kg/day) was given to valproate groups for 15 days. In the skin samples, antioxidant parameters (such as glutathione, glutathione-S-transferase, superoxide dismutase, catalase, and total antioxidant capacity), as well as oxidant parameters representing oxidative stress (i.e. lipid peroxidation, sialic acid, nitric oxide, reactive oxygen species, and total oxidant capacity), were examined. Additionally, boron, hydroxyproline, sodium-potassium ATPase, and tissue factor values were determined. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was also carried out for protein analysis in the skin samples. The results showed that moringa could increase glutathione, total antioxidant capacity, sodium-potassium ATPase, and boron levels, while decreasing lipid peroxidation, sialic acid, nitric oxide, total oxidant capacity, reactive oxygen species, hydroxyproline, and tissue factor levels. These findings imply that moringa possesses the potential to mitigate dermatological side effects.