NCX1 Research Articles

Sodium-calcium exchanger-3 regulates pain “wind-up”: From human psychophysics to spinal mechanisms

SummaryRepeated application of noxious stimuli leads to a progressively increased pain perception; this temporal summation is enhanced in and predictive of clinical pain disorders. Its electrophysiological correlate is “wind-up,” in which dorsal horn spinal neurons increase their response to repeated nociceptor stimulation. To understand the genetic basis of temporal summation, we undertook a GWAS of wind-up in healthy human volunteers and found significant association with SLC8A3 encoding sodium-calcium exchanger type 3 (NCX3). NCX3 was expressed in mouse dorsal horn neurons, and mice lacking NCX3 showed normal, acute pain but hypersensitivity to the second phase of the formalin test and chronic constriction injury. Dorsal horn neurons lacking NCX3 showed increased intracellular calcium following repetitive stimulation, slowed calcium clearance, and increased wind-up. Moreover, virally mediated enhanced spinal expression of NCX3 reduced central sensitization. Our study highlights Ca2+ efflux as a pathway underlying temporal summation and persistent pain, which may be amenable to therapeutic targeting.

Preventing Axonal Sodium Overload or Mitochondrial Calcium Uptake Protects Axonal Mitochondria from Oxidative Stress-Induced Alterations.

In neuroinflammatory and neurodegenerative disorders such as multiple sclerosis, mitochondrial damage caused by oxidative stress is believed to contribute to neuroaxonal damage. Previously, we demonstrated that exposure to hydrogen peroxide (H2O2) alters mitochondrial morphology and motility in myelinated axons and that these changes initiate at the nodes of Ranvier, where numerous sodium channels are located. Therefore, we suggested that mitochondrial damage may lead to ATP deficit, thereby affecting the efficiency of the sodium-potassium ATPase and eventually leading to sodium overload in axons. The increased intra-axonal sodium may revert the axonal sodium-calcium exchangers and thus may lead to a pathological calcium overload in the axoplasm and mitochondria. Here, we used the explanted murine ventral spinal roots to investigate whether modulation of sodium or calcium influx may prevent mitochondrial alterations in myelinated axons during exogenous application of H2O2 inducing oxidative stress. For that, tetrodotoxin, an inhibitor of voltage-gated sodium ion channels, and ruthenium 360, an inhibitor of the mitochondrial calcium uniporter, were applied simultaneously with hydrogen peroxide to axons. Mitochondrial shape and motility were analyzed. We showed that inhibition of axonal sodium influx prevented oxidative stress-induced morphological changes (i.e., increase in circularity and area and decrease in length) and preserved mitochondrial membrane potential, which is crucial for ATP production. Blocking mitochondrial calcium uptake prevented decrease in mitochondrial motility and also preserved membrane potential. Our findings indicate that alterations of both mitochondrial morphology and motility in the contexts of oxidative stress can be counterbalanced by modulating intramitochondrial ion concentrations pharmacologically. Moreover, motile mitochondria show preserved membrane potentials, pointing to a close association between mitochondrial motility and functionality.

Regulation of APD and force by Na+/Ca2+ exchanger in hiPSC-cardiomyocytes

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): BMBF Introduction Human induced pluripotent stem cell-derived cardiomyocytes (HiPSC-CM) are an emerging, powerful tool to study human cardiac physiology, pharmacology and toxicology, to model cardiovascular diseases or even to use for cardiac repair. Understanding the similarities and differences between hiPSC-CM and adult human cardiomyocytes is critical for their use. Here we focus on sodium calcium exchanger (NCX) who plays a crucial role in the Ca2+-homeostasis in the mammalian heart. Importantly, alterations in NCX expression in human heart are associated with various cardiac pathologies such as heart failure or arrhythmias. In order to investigate whether hiPSC-CM could serve as model for adult human heart NCX we measured the properties of NCX in hiPSC-CM and human ventricular tissue. Rat ventricular tissue was used for comparison. Methods HiPSC-CM were differentiated from a healthy iPSC line and dissociated from engineered heart tissue (EHT). Adult human and rat cardiomyocytes were digested from ventricular samples. We measured NCX current by the whole-cell patch clamp technique at 37 °C. Standard sharp microelectrodes were used to record action potentials (AP). Contractile force in human and rat ventricular samples was measured isometrically. A video-optical contractility test system was used to measure force in EHT. SEA0400 (10 µM) was used to block NCX. Results NCX currents could be measured in every hiPSC-CM. The NCX current densities in hiPSC-CM were larger than in human ventricular cardiomyocytes (3.2±0.2 pA/pF n=28 vs. 1.3±0.2 pA/pF n=15, p<0.05), but lower than reported for rat left ventricular cardiomyocytes using the same protocol. SEA0400 shortened APD90 markedly in EHT (264.1±24.9 ms to 191±31.6 ms, n=4) and to a lesser extent in rat ventricular tissue (54.4±3.9 ms to 48.9±4.2 ms, n=7). Shortening in human left ventricular preparations was tiny (320±22.1 ms to 305.5±20.3 ms, n=6) and not different from time-matched controls (TMC). Resting membrane potential, action potential amplitude and upstroke velocity were not affected neither in EHT nor in left ventricular preparations (rat and human). Force was significantly increased by NCX block in rat ventricle (by 31±5.4%, n=18) and EHT (by 20.8±3.9%, n=4), but in human left ventricular preparations there was only a tendency to attenuate spontaneous run-down (-3.7±4.3% n=8 with SEA vs. -6.2±3.7% n=12 in TMC). Conclusion HiPSC-CM possess NCX in the physiological range. HiPSC-CM show NCX-effects on APD and force as predicted from rat ventricle and in full accordance with cardiac physiology. Lack of NCX effect in human adult ventricles that had been already reported previously needs further investigations.

Computational modeling identifies the cellular electromechanical effects of disrupted intracellular calcium handling in arrhythmogenic cardiomyopathy patients

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NWO - ZonMw (VIDI grant 016.176.340 to JL) Dutch Heart Foundation (ERA-CVD JTC2018 grant 2018T094; Dr. Dekker Program grant 2015T082 to JL) The Netherlands Cardio Vascular Research Initiative (CVON): the Dutch Heart Foundation, Dutch Federation of University Medical Center, the Netherlands Organization for Health Research and Development and the Royal Netherlands Academy of Sciences (CVON-eDETECT 2015-12 and CVON-PREDICT2 2018-30 to TvV). Background Patients with arrhythmogenic cardiomyopathy (ACM), an inherited progressive cardiac disease, mostly remain asymptomatic until the occurrence of life-threatening arrhythmias. Previous research identified disturbed calcium handling as a potential disease-initiating mechanism [1], but how this translates to arrhythmogenesis and cardiac mechanical dysfunction remains unknown. Purpose To characterize disturbed molecular regulators of intracellular calcium (Ca2+) handling in patients with ACM and predict their effects on action potential (AP), calcium transient (CaT) and tension development in both left and right ventricles (LV, RV) using a computer model of cellular electromechanics. Methods We performed gene expression (qPCR) and protein level (Western blot) analysis using LV and RV tissue samples obtained from 5 ACM patients who underwent heart transplant and 5 controls with no history of cardiac disease. Changes in protein levels were implemented in our recent human electromechanical cardiomyocyte computer model [2]. CaT, AP and tension traces were simulated and compared to control. Clinical data (age, sex, genetics, ECG, echocardiography) were related to the simulation outcome. Results Measured protein levels varied significantly between the 5 patients and between individual LV and RV samples. Exemplary results for one ACM patient are shown in the figure below. In the LV, AP duration was shorter than control (221ms vs. 255ms), CaT peak was increased (0.52µM vs. 0.39µM) but CaT amplitude was reduced due to increased diastolic Ca2+ (0.26µM vs. 0.060µM). Relaxation was also impaired, as shown by a longer CaT and tension duration (965ms vs. 640ms), and an increased diastolic tension (10mN vs. 4.8mN). In the RV, AP duration was shortened, and CaT and tension peak were lower than in the LV (0.37µM and 13.6mN). Diastolic levels were elevated compared to control, and CaT and tension development were prolonged. This can be related to the measured Ca2+ changes: in the LV, a lower activity of the sodium-calcium exchanger (NCX) (22% of control) and SERCA pump (52%) combined with an increased ryanodine receptor (RyR) activity (96%) may impair the extrusion of Ca2+, leading to accumulation of Ca2+ and increased diastolic Ca2+ levels. In the RV, milder changes in NCX (48% of control) and RyR (11%) may explain the larger Ca2+ extrusion, leading to lower CaT peak and diastolic levels. The patient showed a normal LV size, a severely dilated RV, as well as a poor LV fractional shortening suggesting increased ventricular stiffness, in line with the potential impaired relaxation shown by the simulations. Conclusion By integrating protein level data from ACM patients into a computational model of cellular electromechanics, we quantified the electromechanical effects of patient-specific Ca2+ handling changes. Future whole-heart extensions of this work have the potential to identify and understand proarrhythmic mechanisms in ACM patients.

Increase in Ca2+-Activated cAMP/PKA Signaling Prevents Hydroxychloroquine-Induced Bradycardia of the Cardiac Pacemaker

Bradycardia or tachycardia are known side effects of drugs that limit their clinical use. The heart pacemaker function which control the heart rate under normal conditions is determined by coupled clock system. Thus, interfering with specific clock mechanism will affect other clock mechanisms through changes in interconnected signaling and can lead to rhythm disturbance. However, upregulation of a different clock components can compensate for this change. We focus here on hydroxychloroquine (HCQ), which has been shown effective in treating COVID-19 patients, however its bradycardic side effect limits its clinical use. We aim to decipher the mechanisms underlying the effect of HCQ on pacemaker automaticity, to identify a potential drug that will eliminate the bradycardia. We used isolated rabbit sinoatrial node (SAN) cells, human-induced pluripotent stem cell–derived cardiomyocytes (hiPSC-CMs) and mouse SAN cells residing in SAN tissue. Further, we employed SAN cell computational model to suggest mechanistic insights of the effect of HCQ on pacemaker function. HCQ increased mean spontaneous beat interval and variability in all three models in parallel to slower intracellular kinetics. The computational model suggested that HCQ affects the pacemaker (funny) current (If), L-type Ca2+ current (ICa,L), transient outward potassium (Ito) and due to changes in Ca2+ kinetics, the sodium-calcium exchanger current (INCX). Co-application of 3’-isobutylmethylxanthine (IBMX) and HCQ prevented the increase in beat interval and variability in all three experimental models. The HCQ-induced increase in rabbit and mice SAN cell and hiPSC-CM spontaneous beat interval, can be prevented by a phosphodiester inhibitor that restores automaticity due to slower intracellular Ca2+ kinetics.

Age quadratically affects intestinal calcium and phosphorus transporter gene expression in broiler chickens.

This research aimed to evaluate the effects of age on growth, tibia development, and intestinal calcium (Ca) and phosphorus (P) transporter gene expressions in broiler chickens. A total of 224 male Arbor Acres broilers were fed with nutrient-adequate diets and reared in eight cages (28 broilers per cage). Eight broilers (one broiler per cage) were selected and killed at 5, 10, 15, 20, 25, 30, 35, and 40 days of age, respectively. Body weight continuously increased with age of broiler chickens from 5 to 40 days. The bone weight, ash weight, diameter, and length of the tibia also increased with broiler age. By contrast, the tibia ash, Ca, and P percentages quadratically changed with age (p<0.001), and the highest values of mineral contents were observed at 20, 25, and 25 days of age, respectively. The mRNA abundances of calcium-binding protein 28-kDa (CaBP-D28k), sodium-calcium exchanger 1 (NCX1), and plasma membrane ATPase 1b (PMCA1b) increased from 5 to 25 days and then decreased up to 40 days. Similar results were noted in the mRNA abundances of IIb sodium-phosphate cotransporter (NaPi-IIb), inorganic phosphate transporter 1 (PiT-1), inorganic phosphate transporter 2 (PiT-2), nuclear vitamin D receptor (nVDR), and membrane vitamin D receptor (mVDR). The mRNA abundances of Ca and P transporters and VDRs were the highest at 25 days of age. These data indicate that age quadratically affects intestinal Ca and P transporter gene expression and mineral absorption capacity in broiler chickens.

The Sodium-Calcium Exchanger Controls the Membrane Potential of AFT024: A Mesenchymal Stem Cell Hematopoietic Niche Forming Line.

The aim of this study was to characterize the functional expression of sodium-calcium exchangers on AFT024 cell line, a murine model of mesenchymal stem/stromal cells (MSCs) supporting human primitive hematopoiesis. All current-clamp and voltage-clamp experiments were performed using the perforated patch whole-cell recording technique with amphotericin B. The membrane potential of -14 mV shifted to -35 mV when lowering the external sodium concentration to 0.33 mM and an increase of cytosolic calcium concentration was observed. KB-R7943, a selective blocker of cardiac sodium-calcium exchangers, also named NCX1, induced a hyperpolarization at physiological sodium concentration while it blocked the hyperpolarization observed at low sodium concentration. This demonstrates for the first time the presence of the sodium-calcium exchangers in AFT024 cells and provides initial evidence that the membrane potential of these stromal cells is maintained depolarized by this exchanger. Lowering external sodium concentration and KB-R7943 had no effect on the membrane potential of 2018 cells, a nonhematopoietic-supportive cell line. Since NCX1 is differentially expressed in AFT024 cells as compared with nonhematopoietic supportive cells with more restricted differentiation potential, this study suggests a potential role of this sodium-calcium exchanger, in the differentiation process or hematopoietic support of MSCs.

Reducing Nav1.6 expression attenuates the pathogenesis of Alzheimer's disease by suppressing BACE1 transcription.

Aberrant increases in neuronal network excitability may contribute to cognitive deficits in Alzheimer's disease (AD). However, the mechanisms underlying hyperexcitability of neurons are not fully understood. Voltage‐gated sodium channels (VGSC or Nav), which are involved in the formation of excitable cell's action potential and can directly influence the excitability of neural networks, have been implicated in AD‐related abnormal neuronal hyperactivity and higher incidence of spontaneous non‐convulsive seizures. Here, we have shown that the reduction of VGSC α‐subunit Nav1.6 (by injecting adeno‐associated virus (AAV) with short hairpin RNA (shRNA) into the hippocampus) rescues cognitive impairments and attenuates synaptic deficits in APP/PS1 transgenic mice. Concurrently, amyloid plaques in the hippocampus and levels of soluble Aβ are significantly reduced. Interfering with Nav1.6 reduces the transcription level of β‐site APP‐cleaving enzyme 1 (BACE1), which is Aβ‐dependent. In the presence of Aβ oligomers, knockdown of Nav1.6 reduces intracellular calcium overload by suppressing reverse sodium–calcium exchange channel, consequently increasing inactive NFAT1 (the nuclear factor of activated T cells) levels and thus reducing BACE1 transcription. This mechanism leads to a reduction in the levels of Aβ in APP/PS1 transgenic mice, alleviates synaptic loss, improves learning and memory disorders in APP/PS1 mice after downregulating Nav1.6 in the hippocampus. Our study offers a new potential therapeutic strategy to counteract hippocampal hyperexcitability and subsequently rescue cognitive deficits in AD by selective blockade of Nav1.6 overexpression and/or hyperactivity.

Parallel kinase pathways stimulate actin polymerization at depolarized mitochondria

Mitochondrial damage (MtD) represents a dramatic change in cellular homeostasis, necessitating metabolic changes and stimulating mitophagy. One rapid response to MtD is a rapid peri-mitochondrial actin polymerization termed ADA (acute damage-induced actin). The activation mechanism for ADA is unknown. Here, we use mitochondrial depolarization or the complex I inhibitor metformin to induce ADA. We show that two parallel signaling pathways are required for ADA. In one pathway, increased cytosolic calcium in turn activates PKC-β, Rac, WAVE regulatory complex, and Arp2/3 complex. In the other pathway, a drop in cellular ATP in turn activates AMPK (through LKB1), Cdc42, and FMNL formins. We also identify putative guanine nucleotide exchange factors for Rac and Cdc42, Trio and Fgd1, respectively, whose phosphorylation states increase upon mitochondrial depolarization and whose suppression inhibits ADA. The depolarization-induced calcium increase is dependent on the mitochondrial sodium-calcium exchanger NCLX, suggesting initial mitochondrial calcium efflux. We also show that ADA inhibition results in enhanced mitochondrial shape changes upon mitochondrial depolarization, suggesting that ADA inhibits these shape changes. These depolarization-induced shape changes are not fragmentation but a circularization of the inner mitochondrial membrane, which is dependent on the inner mitochondrial membrane protease Oma1. ADA inhibition increases the proteolytic processing of an Oma1 substrate, the dynamin GTPase Opa1. These results show that ADA requires the combined action of the Arp2/3 complex and formin proteins to polymerize a network of actin filaments around mitochondria and that the ADA network inhibits the rapid mitochondrial shape changes that occur upon mitochondrial depolarization.

Dyspnea in Post-COVID Syndrome following Mild Acute COVID-19 Infections: Potential Causes and Consequences for a Therapeutic Approach.

Dyspnea, shortness of breath, and chest pain are frequent symptoms of post-COVID syndrome (PCS). These symptoms are unrelated to organ damage in most patients after mild acute COVID infection. Hyperventilation has been identified as a cause of exercise-induced dyspnea in PCS. Since there is a broad overlap in symptomatology with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), causes for dyspnea and potential consequences can be deduced by a stringent application of assumptions made for ME/CFS in our recent review papers. One of the first stimuli of respiration in exercise is caused by metabolic feedback via skeletal muscle afferents. Hyperventilation in PCS, which occurs early on during exercise, can arise from a combined disturbance of a poor skeletal muscle energetic situation and autonomic dysfunction (overshooting respiratory response), both found in ME/CFS. The exaggerated respiratory response aggravating dyspnea does not only limit the ability to exercise but further impairs the muscular energetic situation: one of the buffering mechanisms to respiratory alkalosis is a proton shift from intracellular to extracellular space via the sodium–proton-exchanger subtype 1 (NHE1), thereby loading cells with sodium. This adds to two other sodium loading mechanisms already operative, namely glycolytic metabolism (intracellular acidosis) and impaired Na+/K+ATPase activity. High intracellular sodium has unfavorable effects on mitochondrial calcium and metabolism via sodium–calcium-exchangers (NCX). Mitochondrial calcium overload by high intracellular sodium reversing the transport mode of NCX to import calcium is a key driver for fatigue and chronification. Prevention of hyperventilation has a therapeutic potential by keeping intracellular sodium below the threshold where calcium overload occurs.

Effects of Lithium and Selective Inhibitors of Sodium-Calcium Exchanger on Its Transport Currents in Neurons and HEK293 Cells

Effects of Lithium and Selective Inhibitors of Sodium-Calcium Exchanger on Its Transport Currents in Neurons and HEK293 Cells

Molecular Changes in the Cardiac RyR2 With Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT).

The cardiac ryanodine receptor Ca2+ release channel (RyR2) is inserted into the membrane of intracellular sarcoplasmic reticulum (SR) myocyte Ca2+ stores, where it releases the Ca2+ essential for contraction. Mutations in proteins involved in Ca2+ signaling can lead to catecholaminergic polymorphic ventricular tachycardia (CPVT). The most common cellular phenotype in CPVT is higher than normal cytoplasmic Ca2+ concentrations during diastole due to Ca2+ leak from the SR through mutant RyR2. Arrhythmias are triggered when the surface membrane sodium calcium exchanger (NCX) lowers cytoplasmic Ca2+ by importing 3 Na+ ions to extrude one Ca2+ ion. The Na+ influx leads to delayed after depolarizations (DADs) which trigger arrhythmia when reaching action potential threshold. Present therapies use drugs developed for different purposes that serendipitously reduce RyR2 Ca2+ leak, but can adversely effect systolic Ca2+ release and other target processes. Ideal drugs would specifically reverse the effect of individual mutations, without altering normal channel function. Such drugs will depend on the location of the mutation in the 4967-residue monomer and the effect of the mutation on local structure, and downstream effects on structures along the conformational pathway to the pore. Such atomic resolution information is only now becoming available. This perspective provides a summary of known or predicted structural changes associated with a handful of CPVT mutations. Known molecular changes associated with RyR opening are discussed, as well one study where minute molecular changes with a particular mutation have been tracked from the N-terminal mutation site to gating residues in the channel pore.

Pan-phylum genome-wide identification of sodium calcium exchangers reveal heterogeneous expansions and possible roles in nematode parasitism.

Calcium signaling is ubiquitous in nematode development from fertilization to cell specification to apoptosis. Calcium also regulates dauer entry in Caenorhabditis elegans, which corresponds to the infective stage of parasitic nematodes. In diverse parasites such as Trypanosoma cruzi and Toxoplasma gondii calcium has been shown to regulate host cell entry and egress, and perturbing calcium signaling represents a possible route to inhibit infection and parasitism in these species. Sodium calcium exchangers are considered the most important mechanism of calcium efflux, and our lab has previously characterized the sodium calcium exchanger gene family in C. elegans and studied the diversity of this family across a subset of specific nematode species. Here we build upon these data and explore sodium calcium exchangers across 108 species of nematodes. Our data reveal substantial differences in sodium calcium exchanger counts across the Phylum and detail expansions and contractions of specific exchanger subtypes within certain nematode clades. Finally, we also provide evidence for a role of sodium calcium exchangers in parasite activation by examining differentially expressed genes in non-activated versus activated infective stage larvae. Taken together our findings paint a heterogeneous picture of sodium calcium exchanger evolution across the Phylum Nematoda that may reflect unique adaptations to free-living and parasitic lifestyles.

Pathologically increased RyR2-Nav1.6 colocalization in db/db mouse model of diabetic cardiomyopathy

Diabetes affects more than 6% of the world population and can lead to diabetic cardiomyopathy (DCM), a condition characterized by left ventricular hypertrophy, heart failure (HF), and eventual sudden cardiac death. Linking structural remodeling with phenotype progression in DCM will enable early diagnosis and treatment, which is key for patient longevity. Previous studies have linked pathological increases in late sodium current, mediated by voltage-gated sodium channel subtype 1.6 (NaV1.6) localized near ryanodine receptor (RyR2) calcium release channels and sodium-calcium exchangers, to arrhythmogenic calcium release events in multiple cardiac disorders.

Cardioprotection in ischemia-reperfusion injury achieved by a single amino acid substitution of NCX1 (H165A)

We used genetically modified mice to test the hypothesis that pH regulation of the cardiac sodium calcium-exchanger (NCX1) contributes to ischemia/reperfusion (I/R) injury. NCX1 is the dominant calcium (Ca) efflux mechanism of cardiomyocytes and is strongly regulated by pH. During ischemia, when pH is lowered by anaerobic glycolysis, inhibition of NCX1 by acidosis may potentiate the Na overload imposed by Na/K pump failure and Na-H exchange. Upon reperfusion and restoration of normal pH, this high intracellular Na concentration drives the now functional NCX1 into reverse mode resulting in Ca overload.

Identification and characterization of the promoter and transcription factors regulating the expression of cerebral sodium/calcium exchanger 2 (NCX2) gene

The isoform 2 of sodium-calcium exchanger family (NCX2) is selectively expressed in neuronal and glial cells where it participates in Ca2+-clearance following neuronal depolarization, synaptic plasticity, hippocampal-dependent learning and memory consolidation processes. On the other hand, NCX2 is also involved in a neuroprotective effect following stroke. Despite the relevance of this antiporter under physiological and pathophysiological conditions, no studies have been reported on its genetic/epigenetic regulation. Therefore, we identified, cloned, and characterized a transcriptional regulatory region (R3) of rat Slc8a2 gene encoding for NCX2. In particular, R3 sequence displayed a promoter activity in PC12, SH-SY5Y and U87MG cell lines consistent with their endogenous NCX2 expression levels. On the other hand, R3 failed to induce detectable luciferase activity in BHK cell line that does not express NCX2 under control conditions. These data support the hypothesis that R3 represents the promoter region of NCX2. Moreover, among several conserved binding sequences for transcription factors identified by in-silico analysis, we evaluated the transcriptional regulation and the binding sites of Sp1, Sp4, NFkB1, GATA2 and CREB1 on R3 sequence by using site-direct mutagenesis and ChIP assays. In particular, transfection of Sp1, Sp4, and CREB1 enhanced both R3 promoter activity and NCX2 transcription in PC12 cell line. More important, CREB1 transfection also enhanced NCX2 protein levels and NCX reverse mode activity in PC12 cells. Altogether, these data suggested that: (i) the identified region contained the regulatory promoter of the antiporter; (ii) NCX2 might represent a downstream effector of transcription factors involved in synaptic plasticity and neuronal survival.

Hydrogeochemical characteristics and processes of groundwater in an over 2260 year irrigation district: A comparison between irrigated and nonirrigated areas

A comprehensive understanding of groundwater chemistry and its evolution in irrigation districts is essential for irrigation management. In this study, with emphasis on a comparison between irrigated and nonirrigated areas, the groundwater chemistry and hydrogeochemical processes of a typical irrigation district with an irrigation history of over 2260 years were studied to clarify the effects of long-term irrigation on groundwater quality. Based on 107 water samples collected from across the study area, a comprehensive analysis was conducted using multivariate statistics, stable isotope analysis, and hydrogeochemical modeling. The results showed that the variation range and average concentrations of almost all the ions in the irrigation district are much greater than those in the nonirrigated areas. The groundwater in the nonirrigated areas could be characterized by low TDS and HCO3 or HCO3·SO4 types, whereas the groundwater in the irrigation district could be characterized by complex water types and high TDS. Stable isotopes of hydrogen and oxygen indicated that the groundwater in the irrigation district experienced strong evaporation. The calculated groundwater residence time showed that it takes approximately 2180 years for the groundwater to flow through the irrigation district. Some old irrigation water was present, and it influenced the current groundwater chemistry in the study area. The processes forming the current groundwater chemistry in the irrigation district can be formulated as: mixing → evaporation → water–rock interaction. For mixing, the proportions of rainfall, irrigation water from the Jing River, and lateral recharge from the nonirrigated areas were found to be approximately 30%, 49%, and 21%, respectively. For evaporation, the ratio based on the TDS was 3.83 when comparing the groundwater in the irrigation district with the mixed water after evaporation. Hydrogeochemical modeling showed that the irrigation area is a potential carbon source. The dissolution of halite and gypsum, the precipitation of calcite and dolomite, CO2 degassing and Na-Ca exchange are the main chemical reactions in the geochemical evolution of groundwater. The lesson learned from this irrigation district is that long-term irrigation will lead to salinization and complexity of the groundwater. Hence, in the water resource management of irrigation districts, attention should not only be paid to the balance of water quantity, but also to the balance of salts and the hydrochemical evolution of groundwater.

An unexpected effect of risperidone reveals a nonlinear relationship between cytosolic Ca2+ and mitochondrial Ca2+ uptake.

Mitochondria actively contribute to cellular Ca2+ homeostasis. The molecular mechanisms of mitochondrial Ca2+ uptake and release are well characterized and are attributed to the multi-protein assembly of the mitochondrial Ca2+ uniporter complex (MCUC) and the mitochondrial sodium-calcium exchanger (NCLX), respectively. Hence, Ca2+ transfer from the endoplasmic reticulum (ER) and store-operated Ca2+ entry (SOCE) into the mitochondrial matrix has been quantitatively visualized on the subcellular level using targeted fluorescent biosensors. However, a correlation between the amplitude of cytosolic Ca2+ elevation with that in the mitochondrial matrix has not been investigated in detail so far. In the present study, we combined the Ca2+-mobilizing agonist histamine with the H1-receptor antagonist risperidone to establish a well-tunable experimental approach allowing the correlation between low, slow, high, and fast cytosolic and mitochondrial Ca2+ signals in response to inositol 1,4,5-trisphosphate (IP3)-triggered ER Ca2+ release. Our present data confirm a defined threshold in cytosolic Ca2+, which is necessary for the activation of mitochondrial Ca2+ uptake. Moreover, our data support the hypothesis of different modes of mitochondrial Ca2+ uptake depending on the source of the ion (i.e., ER vs SOCE).

Pathophysiology of heart and skeletal muscle during sepsis

The pathophysiological characteristics of sepsis in striated muscle tissues are the potential key to identifying the regulatory factors of sepsis and establishing a molecular basis for drug discovery. Arrhythmia is a major cause of septic death. The cardiac IKs channel is regulated by intracellular Ca2+, cAMP, and NO, which are increased during sepsis. Transgenic mice expressing cardiac IKs channel (IKs-TG mice) were significantly tolerant to a cecal slurry injection-induced sepsis in viability and cardiac anomalies. Our membrane proteomic analysis showed the interaction KCNQ1 interacts with Na-Ca exchanger (NCX1), which is involved in Ca2+ overload during sepsis, in isolated ventricular myocytes from IKs-TG mice. These suggest that the IKs channel participates in a compensatory response to sepsis, involving interaction between KCNQ1 and NCX1. Skeletal muscle is also a striated muscle tissue response to sepsis. Recent reports suggested muscular septic responses is a key to the high tolerance of sepsis in female. Cecal ligation and puncture-induced septic symptoms in Four Core Genotypes (FCGs) mice (XX gonadal males or females, and XY gonadal males or females) showed that XX female mice were significantly resistant among FCGs to septic death. Our RNA-seq analysis in skeletal muscle of septic FCGs revealed that four inflammation-related genes were overexpressed specifically in XX females. Our analysis of sepsis pathophysiology in cardiac and skeletal muscle has led to the detection of new molecular targets involved in sepsis symptoms.

The role of genome-scale leukocyte long noncoding RNA in identifying acute aortic dissection

Acute aortic dissection (AAD) is a disease with intima rupture and explosive inflammatory reaction. In this study, we detected the expression pattern of genome-scale leukocyte long noncoding RNAs (lncRNAs) in patients with AAD and explored the diagnostic efficacy and inflammatory mechanism. The expression levels of lncRNAs and mRNAs in 5 patients with AAD and 5 control cases were detected by microarray technology and were verified in 20 AAD cases and 10 control individuals. A total of 540 up- and 1078 down-regulated lncRNAs were significantly expressed between the two groups. Based on microarray analysis, confirmation through quantitative real-time polymerase chain reaction, and criteria for clinical relevance, three lncRNAs ENST00000430893.1, ENST00000536517.1, and ENST00000593848.1 were identified as potentially important diagnostic lncRNAs of AAD. Receiver operating characteristic curve (ROC curve) analysis showed that the area under curve (AUC) of ENST00000593848.1 was 0.790 (neutrophils, p &lt; 0.05) and 0.725 (monocytes, p &lt; 0.05). The corresponding target gene of ENST00000593848.1 was solute carrier family 8 member A1 (SLC8A1), which encodes a sodium calcium exchanger. Compared with transfection of no-load siRNA group, the Ca2+ levels, interleukin-6 (IL-6) levels, mRNA levels of extracellular regulated kinase (ERK) 1/2, and the activity of P-NF-κB p65 in THP-1 cells were increased after transfection of si-lncRNA (SILNC) (p &lt; 0.05). Together, these results indicate that the three different lncRNAs ENST00000430893.1, ENST00000536517.1, and ENST00000593848.1 may play an anti-inflammatory role in patients with AAD, and ENST00000593848.1 is a promising candidate to further explore as a potential diagnostic and prognostic factor as well as for developing novel therapeutic strategies.