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.

Beta vulgaris L. beetroot protects against iron-induced liver injury by restoring antioxidant pathways and regulating cellular functions.

Beta vulgaris L. is a root vegetable that is consumed mainly as a food additive. This study aimed to describe the protective effect of B. vulgaris on Fe2+-mediated oxidative liver damage through in vitro, ex vivo, and in silico studies to establish a strong rationale for its protective effect. To induce oxidative damage, we incubated the livers of healthy male rats with 0.1 mM FeSO4 to induce oxidative injury and coincubated them with an aqueous extract of B. vulgaris root (BVFE) (15-240 µg/mL). Induction of liver damage significantly (p < .05) decreased the levels of GSH, SOD, CAT, and ENTPDase activities, with a corresponding increase in MDA and NO levels and Na+/K+ ATPase, G6 Pase, and F-1,6-BPase enzyme activities. BVFE treatment (p < .05) reduced these levels and activities to almost normal levels, with the most prominent effects observed at 240 µg/mL BVFE. An HPLC investigation revealed sixteen compounds in BVFE, with quercetin being the most abundant. Chlorogenic acid and iso-orientation showed the highest binding affinities for G6 Pase and Na+/K + ATPase, respectively. These findings suggest that B. vulgaris can protect against Fe2+-mediated liver damage by suppressing oxidative stress and cholinergic and purinergic activities while regulating gluconeogenesis. Overall, the hepatoprotective activity of this extract might be driven by the synergistic effect of the identified compounds and their probable interactions with target proteins.

Role of Na+-K+ ATPase Alterations in the Development of Heart Failure.

Na+-K+ ATPase is an integral component of cardiac sarcolemma and consists of three major subunits, namely the α-subunit with three isoforms (α1, α2, and α3), ß-subunit with two isoforms (ß1 and ß2) and γ-subunit (phospholemman). This enzyme has been demonstrated to transport three Na and two K ions to generate a trans-membrane gradient, maintain cation homeostasis in cardiomyocytes and participate in regulating contractile force development. Na+-K+ ATPase serves as a receptor for both exogenous and endogenous cardiotonic glycosides and steroids, and a signal transducer for modifying myocardial metabolism as well as cellular survival and death. In addition, Na+-K+ ATPase is regulated by different hormones through the phosphorylation/dephosphorylation of phospholemman, which is tightly bound to this enzyme. The activity of Na+-K+ ATPase has been reported to be increased, unaltered and depressed in failing hearts depending upon the type and stage of heart failure as well as the association/disassociation of phospholemman and binding with endogenous cardiotonic steroids, namely endogenous ouabain and marinobufagenin. Increased Na+-K+ ATPase activity in association with a depressed level of intracellular Na+ in failing hearts is considered to decrease intracellular Ca2+ and serve as an adaptive mechanism for maintaining cardiac function. The slight to moderate depression of Na+-K+ ATPase by cardiac glycosides in association with an increased level of Na+ in cardiomyocytes is known to produce beneficial effects in failing hearts. On the other hand, markedly reduced Na+-K+ ATPase activity associated with an increased level of intracellular Na+ in failing hearts has been demonstrated to result in an intracellular Ca2+ overload, the occurrence of cardiac arrhythmias and depression in cardiac function during the development of heart failure. Furthermore, the status of Na+-K+ ATPase activity in heart failure is determined by changes in isoform subunits of the enzyme, the development of oxidative stress, intracellular Ca2+-overload, protease activation, the activity of inflammatory cytokines and sarcolemmal lipid composition. Evidence has been presented to show that marked alterations in myocardial cations cannot be explained exclusively on the basis of sarcolemma alterations, as other Ca2+ channels, cation transporters and exchangers may be involved in this event. A marked reduction in Na+-K+ ATPase activity due to a shift in its isoform subunits in association with intracellular Ca2+-overload, cardiac energy depletion, increased membrane permeability, Ca2+-handling abnormalities and damage to myocardial ultrastructure appear to be involved in the progression of heart failure.

[Study on the antihypertensive mechanism of acupuncture at "Renying" (ST9) and "Zusanli" (ST36) via gastrin/cholecystokinin B receptors]. / åŸºäºŽèƒƒæ³Œç´ /èƒ†å›Šæ”¶ç¼©ç´ B受体探讨针刺"人迎""足三里"的降压机制.

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Update on a brain-penetrant cardiac glycoside that can lower cellular prion protein levels in human and guinea pig paradigms.

Lowering the levels of the cellular prion protein (PrPC) is widely considered a promising strategy for the treatment of prion diseases. Building on work that established immediate spatial proximity of PrPC and Na+, K+-ATPases (NKAs) in the brain, we recently showed that PrPC levels can be reduced by targeting NKAs with their natural cardiac glycoside (CG) inhibitors. We then introduced C4'-dehydro-oleandrin as a CG with improved pharmacological properties for this indication, showing that it reduced PrPC levels by 84% in immortalized human cells that had been differentiated to acquire neural or astrocytic characteristics. Here we report that our lead compound caused cell surface PrPC levels to drop also in other human cell models, even when the analyses of whole cell lysates suggested otherwise. Because mice are refractory to CGs, we explored guinea pigs as an alternative rodent model for the preclinical evaluation of C4'-dehydro-oleandrin. We found that guinea pig cell lines, primary cells, and brain slices were responsive to our lead compound, albeit it at 30-fold higher concentrations than human cells. Of potential significance for other PrPC lowering approaches, we observed that cells attempted to compensate for the loss of cell surface PrPC levels by increasing the expression of the prion gene, requiring daily administration of C4'-dehydro-oleandrin for a sustained PrPC lowering effect. Regrettably, when administered systemically in vivo, the levels of C4'-dehydro-oleandrin that reached the guinea pig brain remained insufficient for the PrPC lowering effect to manifest. A more suitable preclinical model is still needed to determine if C4'-dehydro-oleandrin can offer a cost-effective complementary strategy for pushing PrPC levels below a threshold required for long-term prion disease survival.

Hepatocyte Growth Factor Modulates Corneal Endothelial Wound Healing In Vitro.

In this study, we assessed the impact of hepatocyte growth factor (HGF) on corneal endothelial cells (CECs), finding that HGF concentrations of 100-250 ng/mL significantly increased CEC proliferation by 30%, migration by 32% and improved survival under oxidative stress by 28% compared to untreated controls (p < 0.05). The primary objective was to identify non-fibrotic pharmacological strategies to enhance corneal endothelial regeneration, addressing a critical need in conditions like Fuchs' endothelial dystrophy (FED), where donor tissue is scarce. To confirm the endothelial nature of the cultured CECs, Na+/K+-ATPase immunohistochemistry was performed. Proliferation rates were determined through BrdU incorporation assays, while cell migration was assessed via scratch assays. Cell viability was evaluated under normal and oxidative stress conditions using WST-1 assays. To ensure that HGF treatment did not trigger epithelial-mesenchymal transition, which could lead to undesirable fibrotic changes, α-SMA staining was conducted. These comprehensive methodologies provided robust data on the effects of HGF, confirming its potential as a therapeutic agent for corneal endothelial repair without inducing harmful EMT, as indicated by the absence of α-SMA expression. These findings suggest that HGF holds therapeutic promise for enhancing corneal endothelial repair, warranting further investigation in in vivo models to confirm its clinical applicability.

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.

Influence of Anticholinesterase Drugs on Activity and Properties of Na+,K+-ATPase in Rat Erythrocytes under Stress Caused by Intense Physical Exercise.

We studied the effect of intramuscular injection of physostigmine and neostigmine on Na+,K+-ATPase activity in erythrocytes of rats subjected to intense physical exercise. Both anticholinesterase drugs had a significant effect on the development of the stress response, which was expressed in a decrease in the manifestation of its individual components such as the concentration of ascorbic acid in the adrenal glands, stress-related erythrocyte polycythemia, and LPO indicators. Anticholinesterase drugs reverse the stress-induced decrease in Na+,K+-ATPase activity, as well as changes in its magnesium-dependent properties. There were no changes in the activity of the studied enzyme in the erythrocyte ghosts. We associate the observed differences with the correction of the functions of the cholinergic components of the hypothalamic-pituitary-adrenal axis leading to the development of a hypoergic type stress reaction.

Vascular smooth muscle BK channels limit ouabain-induced vasocontraction: Dual role of the Na/K-ATPase as a hub for Src-kinase and the Na/Ca-exchanger.

Large-conductance, calcium-activated potassium channels (BK channels) and the Na/K-ATPase are expressed universally in vascular smooth muscle. The Na/K-ATPase may act via changes in the intracellular Ca2+ concentration mediated by the Na/Ca exchanger (NCX) and via Src kinase. Both pathways are known to regulate BK channels. Whether BK channels functionally interact in vascular smooth muscle cells with the Na/K-ATPase remains to be elucidated. Thus, this study addressed the hypothesis that BK channels limit ouabain-induced vasocontraction. Rat mesenteric arteries were studied using isometric myography, FURA-2 fluorimetry and proximity ligation assay. The BK channel blocker iberiotoxin potentiated methoxamine-induced contractions. The cardiotonic steroid, ouabain (10-5 M), induced a contractile effect of IBTX at basal tension prior to methoxamine administration and enhanced the pro-contractile effect of IBTX on methoxamine-induced contractions. These facilitating effects of ouabain were prevented by the inhibition of either NCX or Src kinase. Furthermore, inhibition of NCX or Src kinase reduced the BK channel-mediated negative feedback regulation of arterial contraction. The effects of NCX and Src kinase inhibition were independent of each other. Co-localization of the Na/K-ATPase and the BK channel was evident. Our data suggest that BK channels limit ouabain-induced vasocontraction by a dual mechanism involving the NCX and Src kinase signaling. The data propose that the NCX and the Src kinase pathways, mediating the ouabain-induced activation of the BK channel, act in an independent manner.

A case of alternating hemiplegia in 2-month-old children with nystagmus as the first symptom: A case report.

RATIONALE: This case report delves into the rare neurological condition known as alternating hemiplegia of childhood (AHC), focusing on its clinical manifestations, diagnostic approaches, and treatment options. AHC typically presents in infants under the age of 18 months with intermittent episodes of hemiplegia, often triggered by stressors such as environmental changes, bathing, or emotional stress. Recognizing the clinical features of AHC is crucial for early identification and intervention. PATIENT CONCERNS: The paper presents a case of a 2-month-old child with nystagmus as the initial symptom, followed by limb movement disorder in the left upper limb and weakness in the right limbs. The child's condition did not improve with treatment at an external hospital, highlighting the complexity of the disease and the need for specialized care. DIAGNOSES: After a comprehensive review of the patient's medical history, physical examination, and imaging studies, the child was diagnosed with AHC. The diagnosis was confirmed through video electroencephalogram and whole-exome gene detection, which revealed a de novo mutation in the ATP1A3 gene, identified as pathogenic according to the American College of Medical Genetics and Genomics guidelines. INTERVENTIONS: The child was admitted to Peking University First Hospital and treated with levetiracetam and flunarizine oral administration. These medications were chosen for their efficacy in managing the symptoms of AHC, particularly the hemiplegic episodes. OUTCOMES: Post-treatment, the child experienced a reduction in the frequency and intensity of hemiplegic attacks compared to the initial stage. However, the child still exhibited paroxysmal symptoms and abnormal eye movements, and developmental milestones were delayed, indicating the need for ongoing care and monitoring. LESSONS: This case underscores the importance of early recognition and prompt intervention in managing children with AHC. The varied clinical presentations of AHC necessitate vigilance for early differential diagnosis. Although AHC is currently incurable, appropriate treatment can mitigate the impact of complications and improve the long-term quality of life for affected children, facilitating better societal integration.

Bufalin CaCO3 Nanoparticles Triggered Pyroptosis through Calcium Overload via Na+/Ca2+ Exchanger Reverse for Cancer Immunotherapy.

Bufalin is a promising active ingredient in traditional Chinese medicine but has shown limited anticancer applications due to its toxicity. Here, we report BCNPs@gel, a bufalin-containing CaCO3 nanoparticle hydrogel, for enhancing cancer treatment through inducing cellular pyroptosis. Under the tumor microenvironment's low pH conditions, bufalin and Ca2+ are released from the delivery system. Bufalin serves as a direct anticancer drug and a Na+/K+-ATPase inhibitor by forcing the Na+/Ca2+ exchanger to reverse its function, which transfers Ca2+ into cytoplasm and ultimately causes Ca2+ overload-triggered pyroptosis. Meanwhile, we found that bufalin can upregulate PD-L1 in tumor cells. In combination with the PD-1 antibody, the delivery system showed a greater performance during the cancer treatment. BCNPs@gel enhances antitumor efficiency, reduces systemic side effects, extends antitumor mechanism of bufalin, and provides new strategies for inducing pyroptosis and calcium overload in cancer immunotherapy via Na+/K+-ATPase inhibitor. This work provides an application model for numerous other traditional Chinese medicine ingredients.

The natural compound periplogenin suppresses the growth of prostate carcinoma cells by directly targeting ATP1A1.

Natural compounds constitute a major resource for the development of medicines for multiple diseases. While many natural compounds show strong biological activity, the mechanisms that confer clinical benefits are often elusive and have been attributed to multiple pathways. Periplogenin (PPG), a natural compound isolated from Cortex periplocae, exhibits strong anti-tumor activities in several human cancer cell lines. However, its molecular mode of action remained unclear. In this study, we leveraged a forward genetic screening approach in DU145 prostate cancer cells to uncover the molecular target of PPG using chemical mutagenesis. Next generation sequencing revealed that a single amino acid substitution at amino acid 804 in ATP1A1 (ATPase Na + /K + Transporting Subunit Alpha 1) confers resistance to the cytotoxic activity of PPG. Mechanistically, ATP1A1 T804 forms a hydrogen bond with PPG which is abolished by the T804A substitution in ATP1A1, resulting in resistance to PPG treatment in vitro. Importantly, in vivo, PPG strongly suppressed tumor development in a DU145 xenograft model whereas DU145 xenograft tumors carrying a ATP1A1-T804A mutation were largely unaffected by the treatment. These findings demonstrate that PPG suppresses the growth of DU145 prostate cancer cells in vitro and in vivo by directly binding to ATP1A1 and highlight the power of our unbiased forward genetic screening approach to uncover direct drug target structures at single amino acid resolution.

Tannic acid: A possible therapeutic agent for hypermethioninemia-induced neurochemical changes in young rats.

This study explores the therapeutic benefits of tannic acid (TnA) in an experimental protocol of chronic hypermethioninemia in rats. Rats were categorized into four groups: Group I - control, Group II - TnA 30 mg/kg, Group III - methionine (Met) 0.2-0.4 g/kg + methionine sulfoxide (MS) 0.05-0.1 g/kg, Group IV - TnA/Met + MS. Saline was administered by subcutaneous pathway into groups I and II twice daily from postnatal day 6 (P6) to P28, whereas those in groups III and IV received Met + MS. From P28 to P35, groups II and IV received TnA orally. Animals from group III presented cognitive and memory impairment assessed through object recognition and Y-maze tests (p < 0.05). Elevated levels of reactive species, lipid peroxidation, and nitrites followed by a decline in sulfhydryl content, catalase activity, and superoxide dismutase activity were observed in animals treated with Met + MS (p < 0.05). However, TnA treatment reversed all these effects (p < 0.05). In group III, there was an increase in acetylcholinesterase activity and IL-6 levels, coupled with a reduction in Na+/K+-ATPase activity (p < 0.05). TnA was able to protect against these effects (p < 0.05). The gene expression of catalase, brain-derived neurotrophic factor, and nuclear factor erythroid 2-related factor 2 was decreased in the hippocampus and striatum from group III (p < 0.05). TnA reversed almost all of these alterations (p < 0.05). These findings suggest that TnA is a therapeutic target for patients with hypermethioninemia.

Sodium chloride in the tumor microenvironment enhances T cell metabolic fitness and cytotoxicity.

The efficacy of antitumor immunity is associated with the metabolic state of cytotoxic T cells, which is sensitive to the tumor microenvironment. Whether ionic signals affect adaptive antitumor immune responses is unclear. In the present study, we show that there is an enrichment of sodium in solid tumors from patients with breast cancer. Sodium chloride (NaCl) enhances the activation state and effector functions of human CD8+ T cells, which is associated with enhanced metabolic fitness. These NaCl-induced effects translate into increased tumor cell killing in vitro and in vivo. Mechanistically, NaCl-induced changes in CD8+ T cells are linked to sodium-induced upregulation of Na+/K+-ATPase activity, followed by membrane hyperpolarization, which magnifies the electromotive force for T cell receptor (TCR)-induced calcium influx and downstream TCR signaling. We therefore propose that NaCl is a positive regulator of acute antitumor immunity that might be modulated for ex vivo conditioning of therapeutic T cells, such as CAR T cells.

Gill ionocyte remodeling mediates blood pH regulation in rockfish (Sebastes diploproa) exposed to environmentally relevant hypercapnia.

Marine fishes excrete excess H+ using basolateral Na+-K+-ATPase (NKA) and apical Na+/H+ exchanger 3 (NHE3) in gill ionocytes. However, the mechanisms that regulate H+ excretion during exposure to environmentally relevant hypercapnia (ERH) remain poorly understood. Here, we explored transcriptomic, proteomic, and cellular responses in gills of juvenile splitnose rockfish (Sebastes diploproa) exposed to 3 days of ERH conditions (pH ∼7.5, ∼1,600 µatm Pco2). Blood pH was fully regulated at ∼7.75 despite a lack of significant changes in gill 1) mRNAs coding for proteins involved in blood acid-base regulation, 2) total NKA and NHE3 protein abundance, and 3) ionocyte density. However, ERH-exposed rockfish demonstrated increased NKA and NHE3 abundance on the ionocyte plasma membrane coupled with wider apical membranes and greater extension of apical microvilli. The observed gill ionocyte remodeling is consistent with enhanced H+ excretion that maintains blood pH homeostasis during exposure to ERH and does not necessitate changes at the expression or translation levels. These mechanisms of phenotypic plasticity may allow fishes to regulate blood pH during environmentally relevant acid-base challenges and thus have important implications for both understanding how organisms respond to climate change and for selecting appropriate metrics to evaluate its impact on marine ecosystems.NEW & NOTEWORTHY Splitnose rockfish exposed to environmentally relevant hypercapnia utilize existing proteins (rather than generate additional machinery) to maintain homeostasis.

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.

Simplified Method for Kinetic and Thermodynamic Screening of Cardiotonic Steroids through the K+-Dependent Phosphatase Activity of Na+/K+-ATPase with Chromogenic pNPP Substrate.

The antitumor effect of cardiotonic steroids (CTS) has stimulated the search for new methods to evaluate both kinetic and thermodynamic aspects of their binding to Na+/K+-ATPase (IUBMB Enzyme Nomenclature). We propose a real-time assay based on a chromogenic substrate for phosphatase activity (pNPPase activity), using only two concentrations with an inhibitory progression curve, to obtain the association rate (kon ), dissociation rate (koff ), and equilibrium (Ki ) constants of CTS for the structure-kinetics relationship in drug screening. We show that changing conditions (from ATPase to pNPPase activity) resulted in an increase of Ki of the cardenolides digitoxigenin, essentially due to a reduction of kon In contrast, the Ki of the structurally related bufadienolide bufalin increased much less due to the reduction of its koff partially compensating the decrease of its kon When evaluating the kinetics of 15 natural and semisynthetic CTS, we observed that both kon and koff correlated with Ki (Spearman test), suggesting that differences in potency depend on variations of both kon and koff A rhamnose in C3 of the steroidal nucleus enhanced the inhibitory potency by a reduction of koff rather than an increase of kon Raising the temperature did not alter the koff of digitoxin, generating a ΔH‡ (koff ) of -10.4 ± 4.3 kJ/mol, suggesting a complex dissociation mechanism. Based on a simple and inexpensive methodology, we determined the values of kon , koff , and Ki of the CTS and provided original kinetics and thermodynamics differences between CTS that could help the design of new compounds. SIGNIFICANCE STATEMENT: This study describes a fast, simple, and cost-effective method for the measurement of phosphatase pNPPase activity enabling structure-kinetics relationships of Na+/K+-ATPase inhibitors, which are important compounds due to their antitumor effect and endogenous role. Using 15 compounds, some of them original, this study was able to delineate the kinetics and/or thermodynamics differences due to the type of sugar and lactone ring present in the steroid structure.

COMPARATIVE ANALYSIS OF MEMORY AND BEHAVIORAL CHANGES AFTER RADON-CONTAINED MINERAL WATER INHALATION THERAPY IN AGED RATS.

This research article elucidates the pivotal role of radiopharmacy in the contemporary landscape, underscoring its potential therapeutic efficacy in addressing symptoms associated with aged-related neurocognitive processes. Clinical trials, characterized by the judicious application of modest radiation doses, exemplified by low-dose radon, have yielded affirmative outcomes in the amelioration of aged, related symptoms. MATERIAL AND METHODS: The study was conducted on an animal model. The effect of low doses of radon on cognitive processes is being studied by inhalation of randomized mineral water. Changes in the clinical picture were studied using behavioral tests, namely the Barnes maze tests. At the cellular level, radon-contained water inhalation causes different changes: in the fraction of synaptic membranes (determined by Na, K-ATPase activity), aged, related changes by telomerase activity and oxidative stress level changes. RESULTS: Our studies show that age-related changes in brain tissue are less noticeable after radon inhalation, namely, the concentration of amyloid plaques decreases in a group of aged rats after radon therapy. A significant improvement in cognitive function was observed after radon inhalation in aged rats. CONCLUSION: The results show that exposure to radon-containing mineral water leads to improved spatial perception, potentially improving age-related cognitive functions not only at the level of neurocognitive tests, but also changes at the level of cellular functioning.

Familial hemiplegic migraine.

Hemiplegic migraine consists of attacks of migraine with aura that includes reversible motor weakness. It is classified as familial or sporadic depending on the involvement or not of a first or second degree relative. The most described subtypes of familial hemiplegic migraine include FHM1, FHM2, and FHM3. These have been demonstrated to have a mutation in either CACNA1A, ATP1A2 or SCN1A, which encode different subunits of channels, involving P/Q-type calcium channel, Na/K pump and Na channel, respectively, located in neurons and glial cells. Mutations localized in different genes are defined as "other loci." Patients with a known mutation can have different genetic penetrance, and may present a more complex and disabling phenotype that develops earlier in life. The clinical manifestations can be similar in the three mutations, including neurologic comorbidities other than muscular weakness, such as episodes of loss of consciousness, epilepsy, gait or limb ataxia or movement disorders, among others. Treatment includes antiepileptics such as lamotrigine, valproate or topiramate, calcium blockers such as flunarizine or verapamil and acetazolamide.

Uncovering key steps in FGF12 cellular release reveals a common mechanism for unconventional FGF protein secretion.

FGF12 belongs to a subfamily of FGF proteins called FGF homologous factors (FHFs), which until recently were thought to be non-signaling intracellular proteins. Our recent studies have shown that although they lack a conventional signal peptide for secretion, they can reach the extracellular space, especially under stress conditions. Here, we unraveled that the long "a" isoform of FGF12 is secreted in a pathway involving the A1 subunit of Na(+)/K(+) ATPase (ATP1A1), Tec kinase and lipids such as phosphatidylinositol and phosphatidylserine. Further, we showed that the short "b" isoform of FGF12, which binds ATP1A1 and phosphatidylserine less efficiently, is not secreted from cells. We also indicated regions in the FGF12a protein sequence that are crucial for its secretion, including N-terminal fragment and specific residues, and proposed that liquid-liquid phase separation may be important in this process. Our results strongly suggest that the mechanism of this process is very similar for all unconventionally secreted FGF proteins.