Journal of Physiology-London最新文献

{"title":"Harnessing metabolic control for synaptic stability: REST/NRSF links glycolytic inhibition to excitatory neurotransmission.","authors":"Daniele Ferrante, Barbara Parisi, Antonella Marte, Dionisi Marianna, Cosimo Prestigio, Andrea Benzi, Santina Bruzzone, Fabio Benfenati, Franco Onofri, Pierluigi Valente, Pietro Baldelli","doi":"10.1113/JP288763","DOIUrl":"https://doi.org/10.1113/JP288763","url":null,"abstract":"<p><p>Under resting conditions most neuronal ATP is produced through mitochondrial oxidative phosphorylation, whereas glycolysis becomes more important during intense neuronal firing. Recent studies suggest that inhibiting glycolysis plays a key role in regulating seizure-related hyperactivity, with the epigenetic modulator REST/NRSF being activated when glycolysis inhibition lowers the NADH/NAD⁺ ratio. Our previous research has shown that REST/NRSF initiates homeostatic processes to counteract neuronal hyperactivity by regulating both firing and synaptic activities. However, the exact mechanism through which the metabolic activation of REST/NRSF controls neuronal excitability is still unknown. Here, we studied the role of REST/NRSF in the effects of glycolysis inhibition on hippocampal neuron activity. Treatment with 2-deoxy-d-glucose (2DG) decreased the NADH/NAD⁺ ratio, increased REST/NRSF expression, and promoted its nuclear translocation. Although GABAergic inhibitory inputs and the firing properties of both excitatory and inhibitory neurons were unaffected by 2DG, the amplitude of evoked EPSCs (eEPSCs) and miniature EPSCs (mEPSCs) was reduced in a REST/NRSF-dependent manner. This effect was associated with a REST/NRSF-dependent reduction in the size of GluA2-positive puncta and a decrease in GluA2 expression in the absence of changes in the density of excitatory synapses. These effects provide a mechanistic basis for the significant reduction in network firing and bursting activity observed when the hippocampal network was treated with 2DG. These findings highlight a role of the REST/NRSF-dependent pathway in the 2DG-mediated downregulation of excitatory inputs, a mechanism that contributes to neuronal network stability, strengthening the homeostatic defences against hyperactivity. KEY POINTS: Reducing glucose metabolism with 2-deoxy-d-glucose (2DG) lowers the cell's energy balance and increases the levels of a gene regulator called REST/NRSF. REST/NRSF then moves into the nucleus, where it controls the activity of genes linked to nerve cell communication. 2DG weakens the strength of signals between excitatory nerve cells, without affecting inhibitory signals or the basic ability of neurons to fire. This effect depends in part on REST/NRSF, which reduces the amount and size of GluA2-containing AMPA receptors at excitatory synapses, without altering the overall number of excitatory contacts. These findings suggest that blocking glucose metabolism activates a protective response that stabilizes brain networks, which could help control seizures in epilepsy.</p>","PeriodicalId":50088,"journal":{"name":"Journal of Physiology-London","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145276301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deciphering pro-arrhythmogenic mechanisms of EPAC in human atrial cardiomyocytes.","authors":"Arthur Boileve, Margaux Aize, Maximin Détrait, Laura Brard, Adrien Leboyer, Pierre-Antoine Dupont, Alexandre Lebrun, Vladimir Saplacan, Christophe Simard, Fabien Brette, Frank Lezoualc'h, Laurent Sallé","doi":"10.1113/JP288835","DOIUrl":"https://doi.org/10.1113/JP288835","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Exchange protein directly activated by cAMP (EPAC) 1 and EPAC2 are involved in electrophysiological modulation in ventricular cardiomyocytes. Their putative contribution in supra-ventricular arrhythmogenic processes has been suggested in animal models. However, nothing is known about the electrophysiological remodelling and the underlying signalling pathway regulated by EPACs in human atrial cardiomyocyte. Action potentials (AP) and K&lt;sup&gt;+&lt;/sup&gt; currents (I&lt;sub&gt;K&lt;/sub&gt;) were recorded with the patch-clamp technique in enzymatically freshly isolated human atrial cardiomyocytes. Acute EPAC activation with the EPAC agonist 8-(4-chlorophenylthio)-2'-O-methyl-cAMP acetoxymethyl ester (8-CPTAM; 10 µmol/l) lengthened APs by inhibition of the repolarizing K&lt;sup&gt;+&lt;/sup&gt; currents in myocytes obtained from sinus rhythm (SR) patients. The selective EPAC1 pharmacological blocker AM-001 (20 µmol/l) or the EPAC2 inhibitor ESI-05 (25 µmol/l) prevented the effect of 8-CPTAM on APs and I&lt;sub&gt;K&lt;/sub&gt;, indicating that both EPAC isoforms participate in this electrophysiological regulation. Mechanistically, the effects of EPAC1 and EPAC2 proteins on the inhibition of three major components of K&lt;sup&gt;+&lt;/sup&gt; currents, I&lt;sub&gt;to&lt;/sub&gt;, I&lt;sub&gt;KDR,&lt;/sub&gt; and I&lt;sub&gt;KUR&lt;/sub&gt;, were Ca&lt;sup&gt;2+&lt;/sup&gt;-independent but involved Ca&lt;sup&gt;2+&lt;/sup&gt;/calmodulin-dependent protein kinase II (CaMKII) and the AMP-activated protein kinase (AMPK)-nitric oxide synthase (NOS)-protein kinase G (PKG) axis. Interestingly, immunoblot analysis showed that EPAC1 but not EPAC2 was overexpressed in the atria of atrial fibrillation (AF) patients. Finally, the application of AM-001 consecutively to the 8-CPTAM treatment significantly corrected the EPAC-dependent downregulation of I&lt;sub&gt;K&lt;/sub&gt; in AF cardiomyocytes. Our results uncover that EPAC activation influences I&lt;sub&gt;K&lt;/sub&gt; by CaMKII and the AMPK-NOS-PKG signalling pathways in human atrial cardiomyocytes. Moreover, our findings suggest that EPAC1 over-activation in AF cardiomyocytes promotes the electrophysiological remodelling underlying the initiation of AF. KEY POINTS: Activation of exchange proteins directly activated by cAMP (EPAC) lengthens action potentials (AP) in human atrial cardiac myocytes. This AP duration increase is mediated by an inhibition of the repolarizing K&lt;sup&gt;+&lt;/sup&gt; current. Using EPAC1 and EPAC2 pharmacological inhibitors (AM-001 and ESI-05, respectively), we show that both EPAC1 and EPAC2 isoforms are involved in these electrophysiological effects. Mechanistically, EPAC-induced K&lt;sup&gt;+&lt;/sup&gt; current inhibition signalling involves both CaMKII and AMPK-NOS-PKG pathways. EPAC1 but not EPAC2 is overexpressed in atrial samples of patients with atrial fibrillation (AF). A selective pharmacological inhibitor of EPAC1, AM-001 prevents the downregulation of K&lt;sup&gt;+&lt;/sup&gt; current in cardiomyocytes from AF patients. Our results suggest that over-activation of EPAC1 and its signalling represent a cellular mechanism for atrial arry","PeriodicalId":50088,"journal":{"name":"Journal of Physiology-London","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145259802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nicotine influence on cerebrovascular and neurocognitive function with in utero electronic cigarette exposure.","authors":"Amber Mills, Deborah Corbin, Duaa Dakhallah, Paul D Chantler, I Mark Olfert","doi":"10.1113/JP289175","DOIUrl":"10.1113/JP289175","url":null,"abstract":"<p><p>Emerging studies find arteriolar dysfunction in offspring with in utero electronic-cigarette (Ecig) exposure, but the long-term effects on offspring's cerebrovascular and neurocognitive health are poorly understood. Ecigs provides a unique opportunity to directly evaluate the contributions of inhaled nicotine from the vehicle e-liquid, which was not possible with cigarettes. Moreover, many Ecigs have variable power settings, which can alter aerosol toxicity. We hypothesize that maternal vaping at different wattages will have variable effects on offspring cerebrovascular function and would be independent of nicotine. We used time-mated female Sprague-Dawley rats with Ecig exposure from gestation day (GD)2 to 21. We studied male and female offspring at 1, 3, 6 and 12 months of age, and found the magnitude of middle cerebral artery (MCA) impairment in offspring was greater at 30 W vs. 5 W, but that both conditions significantly impaired MCA function. Vascular dysfunction was evident with or without nicotine in the e-liquid, but nicotine exposure (50 mg/ml e-liquid) resulted in short-term memory deficits, evidence of neuronal damage, and increased astrocyte interaction with endothelial cells in 6- and 12-month-old offspring. We also observed altered expression of clock genes and antioxidant signalling pathways, along with a decrease in sirtuin-1 expression, a decreased ratio of beta-amyloid (Aβ) 42/40 protein expression, and an increase in NADPH oxidase 1, which are consistent with redox imbalance, neuroinflammation and advancing cellular senescence. These preclinical data provide evidence suggesting that in utero exposure to Ecigs from maternal vaping adversely affects the brain health of offspring in their adult life and that neurocognitive outcomes are worsened with exposure to nicotine. KEY POINTS: Cerebrovascular impairment in offspring with maternal electronic-cigarette (Ecig) exposure is dependent on the wattage of the Ecig device and not the presence of nicotine. While nicotine is not implicated in the aetiology of cerebrovascular impairment, it did contribute to neurocognitive deficits and the severity of neuronal damage. Offspring with Ecig exposure during pregnancy, regardless of wattage or nicotine presence, had decreased sirtuin 1 (SIRT1), elevated NADPH oxidase 1, and exhibited Alzheimer's like pathology. Rodent offspring with in utero exposure to Ecig exhibit long-lasting cerebrovascular and neurocognitive dysfunction into adult life, indicating the vaping during pregnancy is not harmless.</p>","PeriodicalId":50088,"journal":{"name":"Journal of Physiology-London","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145253401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ionic conductances driving tonic firing in Purkinje neurons of larval zebrafish.","authors":"Meha P Jadhav, Shivangi Verma, Vatsala Thirumalai","doi":"10.1113/JP286063","DOIUrl":"https://doi.org/10.1113/JP286063","url":null,"abstract":"<p><p>Purkinje neurons are critical for the functioning of the cerebellum, which is among the oldest and most conserved regions of the vertebrate brain. In mammals and in larval zebrafish, Purkinje neurons can generate tonic firing even when isolated from the network. Here we investigated the ionic basis of tonic firing in Purkinje neurons of larval zebrafish using voltage clamp for isolation of membrane currents along with pharmacology. We discovered that these neurons express L-type and P/Q-type high voltage-gated calcium currents, T-type low voltage-gated calcium currents and SK and BK-type calcium-dependent potassium currents. Among these, L-type calcium currents and SK-type calcium-dependent potassium currents were indispensable for tonic firing, while blocking T-type, P/Q-type and BK currents had little effect in comparison. We observed that action potentials were broadened when either L-type or SK channels were blocked. Based on these results, we propose that calcium entry via L-type calcium channels activates SK potassium channels leading to faster action potential repolarization, in turn aiding the removal of inactivation of sodium channels. This allows larval zebrafish Purkinje neurons to continue to fire tonically for sustained periods. In mammals also, tonic firing in Purkinje neurons is driven by calcium channels coupling to calcium-dependent potassium channels, yet the specific types of channels involved are different. We therefore suggest that coupling of calcium channels and calcium-dependent potassium channels could be a conserved mechanism for sustaining long bouts of high frequency firing. KEY POINTS: Tonic firing is an intrinsic property of Purkinje neurons in mammals and fish. These neurons express multiple types of voltage-gated conductances including L-type, T-type and P/Q-type calcium currents and SK- and BK-type calcium-dependent potassium currents. Blocking L-type calcium channels and SK-type calcium-dependent potassium channels resulted in spike broadening and reduced tonic firing. L-type calcium currents were activated during the repolarization of the spike. Based on this we conclude that calcium entry via L-type channels activates SK channels causing faster repolarization of the spike and therefore sustained tonic firing.</p>","PeriodicalId":50088,"journal":{"name":"Journal of Physiology-London","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145259838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reduced dietary intake induces body fluid hypotonicity via alterations in water and energy metabolism.","authors":"Hironori Watanabe, Tomoya Onodera, Yuma Kadokura, Kiyoshi Saito, Kei Nagashima","doi":"10.1113/JP288932","DOIUrl":"https://doi.org/10.1113/JP288932","url":null,"abstract":"<p><p>Maintenance of the body's fluid balance is essential for vital human functions. Although drinking water is widely recommended, the role of dietary intake in body fluids remains unclear. This study investigated whether overnight dietary restriction with adequate water consumption affects body water balance, its regulatory responses, and thermoregulatory and cognitive functions during exercise in a hot environment. Fifteen young adults experienced two conditions: sufficient meal intake (CON) and small dinner with skipped breakfast (RED), both with adequate controlled water consumption. Blood and urine samples, as well as indices of systemic circulation, thermoregulatory responses and cognitive functions, were obtained before, during and after a 60 min moderate-intensity treadmill exercise. RED induced lower serum osmolality and urine sodium excretion compared with CON (both P < 0.05), suggesting the development of body fluid hypotonicity with impaired urinary concentrating capacity. Water- and electrolyte-regulating hormone levels remained unchanged in RED (all P > 0.05). Systemic circulation and thermoregulatory responses (heart rate, blood pressure, skin blood flow and sweat rate) remained comparable between the conditions, leading to similar core body and skin surface temperature elevations (all P > 0.05). Moreover, cognitive performance (Go/No-Go, Stroop, reaction time and digit span tasks) was not changed in RED (all P > 0.05). Notably, RED increased oxygen uptake with a reduced respiratory quotient during exercise (both P < 0.05), indicating a metabolic shift toward lipid oxidation. These findings suggest that overnight dietary restriction induces body fluid hypotonicity with altered water and energy metabolism. KEY POINTS: Dietary intake provides substrates essential for water and osmotic balances, yet its role in maintaining hydration remains underexplored. This study assessed whether overnight dietary restriction (RED), with adequate water intake, induces dehydration and affects body functions during exercise in heat. RED induced body fluid hypotonicity, as evidenced by lower serum osmolality and sodium excretion, without changes in body weight or urine volume before and after exercise. RED led to reduced urinary concentrating capacity during exercise, which may reflect changes in the reabsorption of electrolytes and water in the renal tubules.</p>","PeriodicalId":50088,"journal":{"name":"Journal of Physiology-London","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145259708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mitochondrial Ca²⁺ uniporter haploinsufficiency leads to sexually dimorphic redox imbalance and metabolic remodelling in the mouse brain.","authors":"Jenna Gray, Girish Halemirle, Beatriz Ferrán, Hadyn Rose, Traci L Redwine, Sophia Pham, Bo Hagy, Atul Pranay, Jennifer Giorgione, Stacy A Hussong, Veronica Galvan, Kenneth Humphries, Holly Van Remmen, Mike Kinter, William E Sonntag, Pankaj K Singh, Carlos Manlio Díaz-García","doi":"10.1113/JP287618","DOIUrl":"https://doi.org/10.1113/JP287618","url":null,"abstract":"<p><p>The mitochondrial Ca²⁺ uniporter (MCU) links energy metabolism to cell excitability and signalling throughout the lifespan. However, whether neural metabolism responds to MCU impairments in a sex-specific manner has remained unknown, especially in models with partial MCU downregulation. Using hippocampal slices from adult heterozygous Mcu knock-out (hKO) mice, we observed sexually dimorphic changes in NAD(P)H autofluorescence dynamics following neuronal stimulation. In male mice, these signals were preserved despite decreased mitochondrial Ca²⁺ uptake, likely due to increased MDH2 levels and potentially other enzymes from the tricarboxylic acid cycle, the malate aspartate shuttle, and glycolysis. In contrast to males, neural tissue from female hKO mice showed delayed NAD(P)H production and limited NAD⁺ availability when compared to sex-matched controls, despite intact mitochondrial Ca²⁺ uptake. In addition, both male and female hKO mice exhibit decreased NADP⁺ levels and GSH/GSSG ratios (along with increased protein S-glutathionylation), indicating a weakened antioxidant capacity. Strikingly, markers of oxidative damage were also decreased (albeit more prominently in male mice), suggesting attenuated generation of reactive oxygen species. In addition, sex-specific changes in the hippocampal metabolome were manifested in hKO mice, along with a common decrease in spermidine levels. However, spermidine-dependent hypusination of eIF5A remained unaltered, suggesting further compensatory mechanisms at this age. In summary, our findings indicate that brain tissue can adapt to partial MCU deficits by salvaging most mitochondrial NADH production in active states, while compromising redox signalling and the polyamine pathway. The interplay between these molecular phenotypes likely impacts neurological conditions and potentially cognitive impairment with age. KEY POINTS: The inactivation of one Mcu allele (which encodes the mitochondrial Ca²⁺ uniporter) leads to altered neuronal excitability and attenuated mitochondrial Ca²⁺ elevations in active neurons from 6- to 12-months-old female and male mice, respectively. Tissue autofluorescence imaging reveals delayed mitochondrial NAD(P)H production in stimulated hippocampal tissue from female but not male heterozygous Mcu knockout mice. Mitochondrial Ca²⁺ uniporter haploinsufficiency is characterized by a sex-specific decrease in oxidative stress markers in the brain, despite a decline in NADP⁺ levels and the GSH/GSSG ratio in both male and female mice. Changes in the abundance of enzymes and polar metabolites in brain tissue reveal sexually dimorphic metabolic remodelling in the context of Mcu haploinsufficiency. Life-long downregulation of the mitochondrial Ca²⁺ uniporter results in decreased hippocampal spermidine levels in adult male and female mice.</p>","PeriodicalId":50088,"journal":{"name":"Journal of Physiology-London","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145259735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chloride channels in endothelial cells.","authors":"Alejandro Mata-Daboin, Tessa A C Garrud, Jonathan H Jaggar","doi":"10.1113/JP287608","DOIUrl":"https://doi.org/10.1113/JP287608","url":null,"abstract":"<p><p>Endothelial cells (ECs) line the lumen of blood and lymphatic vessels and form capillaries. ECs are exposed to a diverse array of physiological stimuli and regulate a multitude of functions, including contractility, blood coagulation, leukocyte recruitment, wound healing, angiogenesis and the blood-tissue exchange of gases, metabolites and macromolecules. Chloride (Cl^-) is the principal anion in ECs, with its intracellular concentration ([Cl^-]_i) regulated by pumps, transporters and channels. ECs express the Cl^- channel proteins transmembrane protein 16A (TMEM16A, ANO1), leucine-rich repeat (LRR)-containing 8 (LRRC8), CLCs and cystic fibrosis transmembrane conductance regulator (CFTR), which are plasma membrane proteins, and CLICs, which are located on intracellular organelles. Cl^- channels can regulate both the membrane potential and [Cl^-]_i of ECs to modulate physiological functions. Recent evidence indicates that intracellular Cl^- is a physiological second messenger that regulates the activity of WNK (i.e. with-no-lysine) kinases in ECs. Impaired functions of Cl^- channels in ECs have also been associated with diseases such as hypertension, atherosclerosis, cancer and lung oedema. This review discusses the current knowledge of individual Cl^- channel types that are expressed in ECs, as well as their signalling mechanisms, physiological functions and pathological relevance.</p>","PeriodicalId":50088,"journal":{"name":"Journal of Physiology-London","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145240152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhancement of hippocampal interneuron excitability by NMDA receptor positive allosteric modulation.","authors":"Hao Xing, Tue G Banke, Lu Zhang, Kuai Yu, Chad R Camp, Russell G Fritzemeier, Nicholas S Akins, Srinu Paladugu, Paul J Arcoria, Brian R Brady, Olga Prikhodko, Matthew J Kennedy, Dennis C Liotta, Hongjie Yuan, Stephen F Traynelis","doi":"10.1113/JP289774","DOIUrl":"https://doi.org/10.1113/JP289774","url":null,"abstract":"<p><p>N-Methyl-d-aspartate receptors (NMDARs) are known for their role in mediating a calcium-permeable, slow component of excitatory synaptic transmission. These receptors play important roles in multiple facets of brain functions, and their dysfunction has been implicated in neurological disease aetiology. Here, we describe the actions of a positive allosteric modulator (PAM), EU1622-240, on NMDARs within the hippocampal circuit. EU1622-240 is a pan-PAM that enhances the function of all GluN2 subunit-containing NMDARs with submicromolar potency, with the strongest effects on GluN2C- and GluN2D-containing NMDARs. Previously, we have shown that EU1622-240 enhances the maximal response, prolongs the response time course, enhances agonist potency and reduces single channel conductance. Using whole-cell patch-clamp recordings, we evaluated the effects of this PAM on both CA1 pyramidal cells and CA1 stratum radiatum interneurons in immature hippocampus. Although we observed potentiation of evoked NMDAR-mediated EPSCs on both CA1 pyramidal cells and interneurons, the PAM preferentially enhanced interneuron excitability owing to the expression of GluN2D in interneurons and increased the ratio of inhibition to excitation. This appears to result from cellular depolarization, increased spike firing and enhanced NMDAR-mediated current charge transfer in interneurons. In contrast, EU1622-240 did not detectably depolarize CA1 pyramidal cells in slices but did have modest effects when bicuculline was used to block GABAergic signalling. We also observed EU1622-240 enhancement of AMPA receptor synaptic signalling in a manner reminiscent of long-term potentiation. These data support the idea that EU1622-240 enhances interneuron function, with modest effects on the CA1 pyramidal cells, providing therapeutically beneficial effects in situations where interneuron output is diminished. KEY POINTS: EU1622-240 is a potent positive allosteric modulator of all GluN2-containing NMDA receptors. EU1622-240 is active at native receptors in acute brain slices, increasing NMDA receptor-mediated charge transfer onto both CA1 principal cells and interneurons. Despite its actions on principal cells, EU1622-240 appears to drive preferential enhancement of interneuron function within the hippocampal network. EU1622-240 is also capable of increasing calcium flow into cultured hippocampal neurons, in addition to influencing AMPA receptor-mediated EPSPs that occlude conventional theta-burst-driven long-term potentiation.</p>","PeriodicalId":50088,"journal":{"name":"Journal of Physiology-London","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145240130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Beat-to-beat QT interval variability as a tool to detect the underlying cellular mechanisms of arrhythmias.","authors":"Daisuke Sato, Bence Hegyi, Crystal M Ripplinger, Donald M Bers","doi":"10.1113/JP289051","DOIUrl":"https://doi.org/10.1113/JP289051","url":null,"abstract":"<p><p>Increased beat-to-beat QT interval variability (QTV) on the electrocardiogram (ECG) has been associated with arrhythmia risk and sudden cardiac death. However, the underlying mechanisms driving increased QTV are not fully understood. Our previous work showed that membrane voltage instability is a major contributor to QTV. In this study, we investigated how intracellular calcium (Ca²⁺) cycling instability is also a major contributor to QTV using a mathematical model of a ventricular myocyte that incorporates stochastic ion channel gating and detailed Ca²⁺ cycling. By independently modulating membrane voltage instability (via the L-type Ca²⁺ channel recovery time constant, τ_f) and intracellular Ca²⁺ cycling instability (via the steepness of the sarcoplasmic reticulum Ca²⁺ release-load relationship, u), we show that both voltage and Ca²⁺ instabilities significantly increase action potential duration (APD) variability, which contributes to QTV, even in the absence of overt arrhythmic patterns. Ca²⁺ transient variability increases with intracellular Ca²⁺ cycling instability, contributing to APD variability via Ca²⁺-sensitive currents, and consequently to QTV. Notably, APD variability/QTV significantly increases just before the onset of alternans, regardless of whether instability originates from voltage or Ca²⁺ dynamics. Thus, QTV may serve as a precursor to both voltage-driven and Ca²⁺-driven alternans. Furthermore, pharmacological interventions that selectively stabilize voltage vs. Ca²⁺ cycling may selectively reduce QTV. These findings suggest that QTV can help distinguish between arrhythmias caused by electrical dysfunction and those caused by Ca²⁺ cycling dysfunction. Therefore, QTV has potential as a non-invasive tool not only to identify individuals at risk but also to predict the specific type and underlying cause of arrhythmias. KEY POINTS: Both membrane voltage and intracellular Ca²⁺ cycling instabilities contribute to increased QTV, even without overt arrhythmic patterns. Ca²⁺ transient variability increases with intracellular Ca²⁺ cycling instability and independently contributes to QTV, regardless of voltage instability. QTV serves as a precursor to both electrical and Ca²⁺ alternans, highlighting its potential as an early non-invasive marker for arrhythmic events. The response of QTV to specific pharmacological interventions may differentiate between voltage-driven and Ca²⁺-driven instability, guiding personalized treatment strategies. The study suggests QTV as a promising tool for personalized arrhythmia risk assessment and mechanism-specific therapeutic strategies.</p>","PeriodicalId":50088,"journal":{"name":"Journal of Physiology-London","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145233964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Breast cancer cell-conditioned media inhibit growth and reduce basal and insulin-stimulated glucose uptake by inhibiting Rac1 activation in rat myotubes.","authors":"Mona Sadek Ali, Stine Bitsch-Olsen, Emma Frank, Scott Sebastian Birch Themsen, Edmund Battey, Mirela Perla, Steffen Henning Raun, Steven de Jong, Lykke Sylow","doi":"10.1113/JP288099","DOIUrl":"https://doi.org/10.1113/JP288099","url":null,"abstract":"<p><p>Metabolic disorders are common in women with breast cancer, raising mortality and recurrence rates, but their causes remain poorly understood. Given the importance of skeletal muscle metabolism in glucose homeostasis, we investigated the effect of breast cancer cell-conditioned media on insulin-stimulated glucose uptake in muscle. Rat L6 myotubes overexpressing myc-tagged GLUT4 were incubated with 40% conditioned media from tumourigenic MCF7 or BT474, or non-tumourigenic control MCF10A breast cells. Mass-spectrometry-based proteomics was applied to detect molecular rewiring in response to breast cancer in the muscle. Expression of myogenesis and inflammation markers, GLUT4 translocation, [³H]2-deoxyglucose uptake, and intramyocellular insulin signalling were determined. Breast cancer cell-conditioned media induced proteomic changes in pathways linked to sarcomere organisation, actin filament binding and vesicle trafficking. Myogenic differentiation was disrupted, marked by a 50% increase in Mki67 mRNA and trend (P = 0.087) towards reduced myosin heavy chain expression, as shown by immunofluorescence. Additionally, breast cancer cell-conditioned media activated inflammation via nuclear factor-κB and interleukin-6 signalling and reduced myotube width by 70% (P = 0.0524). Myotubes treated with breast cancer cell-conditioned media had a reduced basal and insulin-stimulated GLUT4 translocation and glucose uptake. Insulin signalling via the Rho GTPase Rac1 was reduced by 40%, while absolute Akt-TBC1D4 phosphorylation was unaffected. Conditioned media from MCF7 and BT474 breast cancer cells altered skeletal muscle proteome, induced inflammation, lowered growth markers, reduced glucose uptake, inhibited GLUT4 translocation and blocked insulin-stimulated Rac1 activation. These findings indicate that the rewiring of skeletal muscle could play a role in metabolic dysfunction in patients with breast cancer. KEY POINTS: Metabolic disorders in breast cancer increase mortality and cancer recurrence. Here, we show that incubation with breast cancer cell-conditioned media (CM) alters the proteome in rat skeletal muscle cells. In addition, breast cancer CM activates NF-κB and type 1 interferon pathways, inhibiting muscle growth. Moreover, breast cancer CM inhibits basal and insulin-mediated GLUT4 translocation and glucose uptake, likely by blocking insulin-stimulated Rac1, but not Akt-TBC1D4 activation. These results underscore a potential mechanistic link between breast cancer and metabolic disorders and suggest that skeletal muscle rewiring may play a role.</p>","PeriodicalId":50088,"journal":{"name":"Journal of Physiology-London","volume":" ","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145226350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}