Search Results (94)

This study was performed to elucidate the mechanism underpinning the nodal swelling induced by equinatoxin II (EqtII), a cation-selective pore-forming toxin derived from the sea anemone Actinia equina. Experiments were conducted using frog myelinated nerve fibers as a model system. Application of EqtII led to an approximately two-fold increase in the nodal volume of myelinated axons, but only when extracellular Ca²⁺ was present. Replacing extracellular Cl⁻ with isethionate had no measurable effect on this response, whereas substitution of NaCl with either sucrose or LiCl, an established Na⁺/Ca²⁺ exchanger (NCX) inhibitor, abolished the swelling. The persistence of the effect in the presence of tetrodotoxin indicates that voltage-gated Na⁺ channels are not involved in the underlying mechanism. Our data suggest that Ca²⁺ influx through EqtII-induced membrane pores raises intracellular Ca²⁺ levels, thereby stimulating the NCX in its forward-operating mode. This process promotes Ca²⁺ extrusion in exchange for Na⁺ entry. The resulting accumulation of intracellular Na⁺ increases osmotic pressure within the axon, leading to water influx and nodal swelling. Full article

Soil salinity remains a major constraint to rice productivity, particularly during early developmental stages when plants are highly sensitive to osmotic and ionic stress. In this study, we evaluated 201 genetically diverse rice genotypes from the 3K Rice Diversity Panel to investigate stage-specific mechanisms of salinity tolerance and develop machine learning-based predictive models for rapid phenotypic screening. Morphological and physiological traits were measured under control and saline conditions at germination and early seedling stages to derive Stress Tolerance Indices (STIs). The average membership function value (AMFV), calculated from multi-trait STI profiles, effectively captured variation in salinity responses and enabled classification of genotypes into five tolerance categories. Genome-wide association analysis using high-density SNP markers identified 36 significant marker–trait associations, including potentially novel SNPs on chromosomes 1 and 12. Several loci co-localized with candidate genes (LTR1, LGF1, OsCPS4, OsNCX7, and OsNHX4), while functional SNPs within genes (OsDRP2C, RLCK168, and OsMed37_2) and non-synonymous variants (qSVII11.1 and qSNaK3.1) further supported their candidacy in salinity tolerance. Mining favourable SNPs of causal genes identified superior multilocus combinations consistent with STI-based phenotypic patterns, with genotype 91-382 emerging as the strongest performer, exhibiting enhanced Na⁺ exclusion, K⁺ retention, and biomass resilience across developmental stages. To address multicollinearity among STI traits, we applied cross-validated LASSO (germination) and Elastic Net (early seedling) models, achieving high predictive accuracy and revealing a developmental shift from biomass-driven tolerance at germination to ion-regulatory processes at the seedling stage. Independent validation showed strong agreement between predicted and observed AMFVs. By integrating physiological indices, GWAS-derived SNP signals, and regularized machine learning approaches, this study provides a robust framework for identifying elite donors and accelerating breeding for salt-tolerant rice. Full article

Cardiac Ca²⁺ handling is critical for excitation–contraction coupling (ECC), with the ryanodine receptor type 2 (RyR2) serving as the key sarcoplasmic reticulum (SR) Ca²⁺ release channel in cardiomyocytes. The dysfunction of RyR2 is linked to fatal cardiac arrhythmias, including heart failure (HF) and catecholaminergic polymorphic ventricular tachycardia (CPVT). This review aims to elucidate the structural basis of RyR2, its core role in cardiac ECC and Ca²⁺ homeostasis, and the regulatory mechanisms of key modulators on its activity. By integrating recent high-resolution cryo-EM structural analyses with molecular and cellular studies on RyR2 regulation, as well as clinical evidence of RyR2 mutations in arrhythmogenic heart diseases, we provide a comprehensive overview of the field. Cryo-EM has unraveled RyR2’s gating mechanisms, ligand-binding sites, and structural features. Functionally, RyR2 mediates calcium-induced calcium release (CICR) and maintains Ca²⁺ homeostasis through coordination with SERCA2a and NCX. Key modulators (CaM, FKBP12.6, and PKA/CaMKII) and disease-linked mutations regulate RyR2 activity through distinct pathways, with defective RyR2 leading to store-overload-induced Ca²⁺ release (SOICR) and arrhythmias. Furthermore, reactive oxygen species (ROS) can induce RyR2 oxidation, establishing a pathological Ca²⁺ leak-ROS cycle in heart disease. In conclusion, RyR2 is a pivotal sensor of myocardial function, with its structural and regulatory mechanisms now well-characterized by recent studies. However, the effects of numerous RyR2 mutations remain unclear, and deeper mechanistic insights will lay a key foundation for developing novel therapies against RyR2-related cardiac diseases. Full article

The present study investigated the effects of fermented Chinese herbal (FCH) compounds on the egg production, egg shell quality, and egg yolk cholesterol of laying hens. A total of 1260 Hy-Line pink laying hens, 34 weeks old, were randomly divided into three groups, with six replicates per group and 70 hens per replicate, as follows: the control group (CON group) was fed a diet without FCH compounds, and the 2% FCH group and the 3% FCH group were fed a diet supplemented with 2% FCH and 3% FCH, respectively. The results show that the FCH compound significantly increased the laying rate compared to the CON group (p < 0.05). Analyses of the serum biochemical indices showed that supplementation with FCH compound significantly decreased the levels of total cholesterol (TC), total triglyceride (TG), high-density lipoprotein cholesterol (HLDL-c), low-density lipoprotein cholesterol (LDL-c), very-low-density lipoprotein cholesterol (VLVL-c), aspartate transaminase (AST), and alanine aminotransferase (ALT) (p < 0.05) and increased the serum total bile acids, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and 17-β-Estradiol (E2) levels (p < 0.05). The FCH group significantly increased the activity of superoxide dismutase (SOD) and total antioxidant capacity and decreased malondialdehyde (MDA) levels in the liver and uterus compared to the CON (p < 0.05). FCH supplementation was also associated with improved egg quality, seen through factors including enhanced yolk color, albumen height, Haugh unit score, eggshell strength, and thickness and reduced egg breaking rate and TC and TG contents in egg yolk. The gene expression analyses showed that FCH supplementation significantly increased the calcium metabolism-related gene expression (CaBP-D_28k, NCX, VDR, CYP₂₇B₁, OPN, PMCA, CA₂) in duodenum, kidney, and uterus tissues compared to the CON group (p < 0.05). FCH significantly repressed FAS and HMGCR mRNA expression and enhanced CYP7A1 mRNA expression in the liver (p < 0.05). These results indicate that diet supplementation with FCH compounds may improve egg quality by regulating reproductive hormones, lipid metabolism, and calcium metabolism. Full article

Background/Objectives: Macrophages with the M2 phenotype are an immune population with great relevance for tumor development. We have previously demonstrated that mesenchymal stromal cells (MSCs) from cervical cancer (CeCa-MSCs) enhance the immunomodulatory activity of CeCa cells on T lymphocytes; however, the effect of these cells on the ability of tumor cells to polarize macrophages had not been evaluated to date. Methods: To address this, we set out to analyze the effect of normal cervix (NCx) and CeCa-MSCs interacting with CeCa tumor cells (TCs) to polarize macrophages in a coculture system. Results: Our results show that macrophages from TC/NCx-MSC cocultures decreased CD163 expression. In turn, we observed that macrophages from TC/CeCa-MSC cocultures, in contrast to those in the presence of TCs/NCx-MSCs, increased the intracellular production of IDO, IL-4, and IL-10; decreased T lymphocyte proliferation; and increased the presence of soluble IL-10. Interestingly, coculture in the presence of TCs/NCx-MSCs decreased the capacity of macrophages to generate regulatory T lymphocyte populations, as well as their phagocytic capacity, and increased IL-6 secretion, unlike the coculture of macrophages in the presence of TCs/CeCa-MSCs. Our results show that TCs/CeCa-MSCs in cocultures, unlike TCs/NCx-MSCs, have a greater capacity to polarize macrophages to an M2 phenotype and that such macrophages have a greater immunosuppressive potential. Conclusions: This in vitro study suggests that intracellular communication between MSCs and tumor cells in CeCa may promote tumor growth through the polarization of macrophages with increased immunosuppressive activity. Full article

Na⁺/Ca²⁺ exchangers (NCXs) are membrane transporters crucial for calcium homeostasis in excitable tissues, particularly in the central nervous system. Growing evidence indicates that NCX dysfunction contributes to calcium overload and neuronal damage in several neurological conditions. Thus, pharmacological modulation of NCX isoforms (NCX1, NCX2, and NCX3) has emerged as a potential therapeutic strategy for disorders such as stroke, multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Alzheimer’s disease (AD), and Parkinson’s disease (PD). However, the identification of selective modulators directed at specific NCX isoforms, or even different splice variants, remains challenging and limits their clinical validation. This Review aims to provide an updated overview of small-molecule NCX modulators, described over the last two decades. Chemical structures, mechanisms of action, and isoform specificity are discussed, along with the most commonly used biological assays for their functional evaluation. Full article

Hyperinsulinemia refers to an elevated level of circulating insulin (80 and 100 µU/mL), often leading to metabolic disorders such as obesity, insulin resistance, and type 2 diabetes (T2D). There is no precise and universally accepted definition of hyperinsulinemia and insulin resistance. The literature in the field remains unclear regarding whether insulin resistance precedes the development of hyperinsulinemia. Recently, a new hypothesis has been proposed suggesting that chronic hyperinsulinemia precedes and causes insulin resistance. The causes of the initiation of hyperinsulinemia, insulin resistance, and type 2 diabetes are multifactorial. Thus, it is not easy to define in general. Recent work demonstrates that the main prediabetic factor leading to insulin resistance is chronic hyperinsulinemia. However, recent work in the literature proposes that relatively long-term hyperinsulinemia does precede insulin resistance and already promotes cardiovascular remodeling. This later may lead to the development of vascular diseases such as hypertension. Thus, defining hyperinsulinemia and insulin resistance, as well as their signaling pathways implicated in the development of type 2 diabetes (T2D), needs to be clarified. Full article

Background and Objectives: Brain natriuretic peptide (NT-proBNP) is a biomarker widely used in diagnosing and monitoring heart failure. Its impact on electrolyte homeostasis is known, particularly for sodium. However, its relationship with serum calcium remains unclear. This retrospective observational study aimed to investigate the longitudinal association between NT-proBNP and serum calcium levels in a cohort of hospitalized patients with the goal of determining whether NT-proBNP could have a direct or indirect impact on calcium metabolism. Materials and Methods: We included 688 patients with 1022 repeated measurements of NT-proBNP and serum calcium collected during hospitalization from March 2022 to February 2025. Linear mixed models (LMMs) were employed to analyze longitudinal associations, adjusting for age, eGFR, estimated plasma volume status (ePVs), CRP, potassium, and albumin. Results: Baseline analysis revealed a negative correlation between NT-proBNP and serum calcium (r = −0.23, p < 0.001). Univariate LMM demonstrated a significant negative association (β = −1.3 × 10⁻⁵, p < 0.001), which remained significant in multivariate analysis (β = −6.9 × 10⁻⁶, p = 0.01), accounting for intrasubject variability. This suggests that as NT-proBNP increases, serum calcium levels decrease within individual patients, independent of confounders. This study’s findings indicate that NT-proBNP may influence calcium excretion, possibly through mechanisms involving the sodium–calcium exchanger (NCX) in renal tubules, similar to its effects on sodium homeostasis. Conclusions: This is the first study to evaluate the longitudinal impact of NT-proBNP on serum calcium, highlighting a potential clinical relevance in patients with cardiac dysfunction. Limitations include a retrospective design and a lack of urine calcium data. Further research is warranted to validate these findings and elucidate the underlying mechanisms. Full article

The vegetal alkaloid toxin veratridine (VTD) is a selective voltage-gated Na⁺ (Na_V) channel activator, widely used as a pharmacological tool in vascular physiology. We have previously shown that Na_V channels, expressed in arteries, contribute to vascular tone in mouse mesenteric arteries (MAs). Here, we aimed to better characterize the mechanisms of action of VTD using mouse cecocolic arteries (CAs), a model of resistance artery. Using wire myography, we found that VTD induced vasorelaxation in mouse CAs. This VTD-induced relaxation was insensitive to prazosin, an α1-adrenergic receptor antagonist, but abolished by atropine, a muscarinic receptor antagonist. Indeed, VTD–vasorelaxant effect was totally inhibited by the Na_V channel blocker tetrodotoxin (0.3 µM), the NO synthase inhibitor L-NNA (20 µM), and low extracellular Na⁺ concentration (14.9 mM) and was partially blocked by the NCX1 antagonist SEA0400 (45.4% at 1 µM). Thus, we assumed that the VTD-induced vasorelaxation in CAs was due to acetylcholine release by parasympathetic neurons, which induced NO synthase activation mediated by the NCX1-Ca²⁺ entry mode in endothelial cells (ECs). We demonstrated NCX1 expression in ECs by RT-qPCR and immunohisto- and western immunolabelling. VTD did not induce an increase in intracellular Ca²⁺ ([Ca²⁺]i), while SEA0400 partially blocked acetylcholine-triggered [Ca²⁺]i elevations in Mile Sven 1 ECs. Altogether, these results illustrate that VTD activates Na_V channels in parasympathetic neurons and then vasorelaxation in resistance arteries, which could explain arterial hypotension after VTD intoxication. Full article

Background: Ischemic-reperfusion damage of cardiomyocytes due to myocardial infarction (MI) often leads to the death of an individual. Premenopausal women have been observed to have a significantly lower risk of cardiovascular disease (CVD) than men of the same age. In menopausal women, this trend is significantly reversed, and the risk of CVD increases up to 10-fold. Estrogens affect the development and function of the heart muscle, and as they decrease, the risk and poor prognosis of CVD increase. This study is focused on the effects of estrogen supplementation on morbidity, vitality, and NCX1 expression after MI on a model system. Methods: In this study, female Sprague Dawley rats (n = 58), which were divided into three experimental groups (NN—control group, non-supplemented; OVX-N—ovariectomized, non-supplemented; OVX-S—ovariectomized, supplemented), received left thoracotomy in the fourth intercostal space. The left anterior descendent coronary artery was ligated 2 mm from its origin with an 8.0 suture. An immunohistological analysis as well as an RT-PCR analysis of NCX1 expression were performed. Results: A higher survival rate was recorded in the OVX-N group (86%) in comparison with the OVX-S group (53%) (p < 0.05). In addition, higher NCX1 expression 7 days/14 days after MI in the OVX-S group in comparison with the NN and OVX-N (p < 0.001 and p < 0.05) groups was recorded. Seven days after MI, a significantly higher expression (p < 0.005) of mRNA NCX1 in the OVX-N group was also recorded in comparison with the NN group. Conclusions: This study provides a comprehensive description of the effect of estrogen supplementation on NCX1 expression and overall vitality in ovariectomized rats that survived MI. Full article

Previous studies have observed alterations in excitation–contraction (EC) coupling during end-stage heart failure that include action potential and calcium (Ca²⁺) transient prolongation and a reduction of the Ca²⁺ transient amplitude. Underlying these phenomena are the downregulation of potassium (K⁺) currents, downregulation of the sarcoplasmic reticulum Ca²⁺ ATPase (SERCA), increase Ca²⁺ sensitivity of the ryanodine receptor, and the upregulation of the sodium–calcium (Na⁼-Ca²⁺) exchanger. However, in human heart failure (HF), debate continues about the relative contributions of the changes in calcium handling vs. the changes in the membrane currents. To understand the consequences of the above changes, they are incorporated into a computational human ventricular myocyte HF model that can explore the contributions of the spontaneous Ca²⁺ release from the sarcoplasmic reticulum (SR). The reduction of transient outward K⁺ current (I_to) is the main membrane current contributor to the decrease in RyR2 open probability and L-type calcium channel (LCC) density which emphasizes its importance to phase 1 of the action potential (AP) shape and duration (APD). During current-clamp conditions, RyR2 hyperphosphorylation exhibits the least amount of Ca²⁺ release from the SR into the cytosol and SR Ca²⁺ fractional release during a dynamic slow–rapid–slow (0.5–2.5–0.5 Hz) pacing, but it displays the most abundant and more lasting Ca²⁺ sparks two-fold longer than a normal cell. On the other hand, under voltage-clamp conditions, HF by decreased SERCA and upregulated I_NCX show the least SR Ca²⁺ uptake and EC coupling gain, as compared to HF by hyperphosphorylated RyR2s. Overall, this study demonstrates that the (a) combined effect of SERCA and NCX, and the (b) RyR2 dysfunction, along with the downregulation of the cardiomyocyte’s potassium currents, could substantially contribute to Ca²⁺ mishandling at the spark level that leads to heart failure. Full article

The effects of enhanced late I_Na, a persistent component of the Na⁺ channel current, on the intracellular ion dynamics and the automaticity of the pulmonary vein cardiomyocytes were studied with fluorescent microscopy. Anemonia viridis toxin II (ATX- II), an enhancer of late I_Na, caused increases in the basal Na⁺ and Ca²⁺ concentrations, increases in the number of Ca²⁺ sparks and Ca²⁺ waves, and the generation of repetitive Ca²⁺ transients. These phenomena were inhibited by eleclazine, a blocker of the late I_Na; SEA0400, an inhibitor of the Na⁺/Ca²⁺ exchanger (NCX); H89, a protein kinase A (PKA) inhibitor; and KN-93, a Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) inhibitor. These results suggest that enhancement of late I_Na in the pulmonary vein cardiomyocytes causes disturbance of the intracellular ion environment through activation of the NCX and Ca²⁺-dependent enzymes. Such mechanisms are probably involved in the ectopic electrical activity of the pulmonary vein myocardium. Full article

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that lacks effective treatment strategies to halt or delay its progression. The homeostasis of Ca²⁺ ions is crucial for ensuring optimal cellular functions and survival, especially for neuronal cells. In the context of PD, the systems regulating cellular Ca²⁺ are compromised, leading to Ca²⁺-dependent synaptic dysfunction, impaired neuronal plasticity, and ultimately, neuronal loss. Recent research efforts directed toward understanding the pathology of PD have yielded significant insights, particularly highlighting the close relationship between Ca²⁺ dysregulation, neuroinflammation, and neurodegeneration. However, the precise mechanisms driving the selective loss of dopaminergic neurons in PD remain elusive. The disruption of Ca²⁺ homeostasis is a key factor, engaging various neurodegenerative and neuroinflammatory pathways and affecting intracellular organelles that store Ca²⁺. Specifically, impaired functioning of mitochondria, lysosomes, and the endoplasmic reticulum (ER) in Ca²⁺ metabolism is believed to contribute to the disease’s pathophysiology. The Na+-Ca²⁺ exchanger (NCX) is considered an important key regulator of Ca²⁺ homeostasis in various cell types, including neurons, astrocytes, and microglia. Alterations in NCX activity are associated with neurodegenerative processes in different models of PD. In this review, we will explore the role of Ca²⁺ dysregulation and neuroinflammation as primary drivers of PD-related neurodegeneration, with an emphasis on the pivotal role of NCX in the pathology of PD. Consequently, NCXs and their interplay with intracellular organelles may emerge as potentially pivotal players in the mechanisms underlying PD neurodegeneration, providing a promising avenue for therapeutic intervention aimed at halting neurodegeneration. Full article

Consecutive interactions of 3Na⁺ or 1Ca²⁺ with the Na⁺/Ca²⁺ exchanger (NCX) result in an alternative exposure (access) of the cytosolic and extracellular vestibules to opposite sides of the membrane, where ion-induced transitions between the outward-facing (OF) and inward-facing (IF) conformational states drive a transport cycle. Here, we investigate sub-state populations of apo and ion-bound species in the OF and IF states by analyzing detergent-solubilized and nanodisc-reconstituted preparations of NCX_Mj with ¹⁹F-NMR. The ¹⁹F probe was covalently attached to the cysteine residues at entry locations of the cytosolic and extracellular vestibules. Multiple sub-states of apo and ion-bound species were observed in nanodisc-reconstituted (but not in detergent-solubilized) NCX_Mj, meaning that the lipid-membrane environment preconditions multiple sub-state populations toward the OF/IF swapping. Most importantly, ion-induced sub-state redistributions occur within each major (OF or IF) state, where sub-state interconversions may precondition the OF/IF swapping. In contrast with large changes in population redistributions, the sum of sub-state populations within each inherent state (OF or IF) remains nearly unchanged upon ion addition. The present findings allow the further elucidation of structure–dynamic modules underlying ion-induced conformational changes that determine a functional asymmetry of ion access/translocation at opposite sides of the membrane and ion transport rates concurring physiological demands. Full article

The peripheral nervous system can encounter alterations due to exposure to some of the most commonly used anticancer drugs (platinum drugs, taxanes, vinca alkaloids, proteasome inhibitors, thalidomide), the so-called chemotherapy-induced peripheral neurotoxicity (CIPN). CIPN can be long-lasting or even permanent, and it is detrimental for the quality of life of cancer survivors, being associated with persistent disturbances such as sensory loss and neuropathic pain at limb extremities due to a mostly sensory axonal polyneuropathy/neuronopathy. In the state of the art, there is no efficacious preventive/curative treatment for this condition. Among the reasons for this unmet clinical and scientific need, there is an uncomplete knowledge of the pathogenetic mechanisms. Ion channels and transporters are pivotal elements in both the central and peripheral nervous system, and there is a growing body of literature suggesting that they might play a role in CIPN development. In this review, we first describe the biophysical properties of these targets and then report existing data for the involvement of ion channels and transporters in CIPN, thus paving the way for new approaches/druggable targets to cure and/or prevent CIPN. Full article