Study Of Ca2 Research Articles

Nanotechnology‐Fortified Manipulation of Cell Ca2+ Signaling

The manipulation of cytosolic Ca2+ concentration ([Ca2+]i) plays a crucial role in the study of Ca2+ signaling and the therapy of its affected diseases. Nanotechnology enables the development of nanotransducers for targeted, non‐invasive, highly spatiotemporal, and on‐demand [Ca2+]i regulation by responding to external energy fields to activate Ca2+ channels, in situ deliver Ca2+, or release the payload of chemical modulators. As considerable strides have been made in Ca2+ signaling‐related fundamental research and applications in recent years, in this article, it is tried to present a thorough review of nanotransducer‐based [Ca2+]i manipulation, from the working principle to specific applications. Focusing on the design rationale and constructions of nanotransducers, the interactions between nanotransducers and Ca2+ channels are highlighted, as well as the downstream effectors of Ca2+ signaling pathways, followed by their representative biomedical applications in disease treatment and neuromodulation. Moreover, despite the enormous progress made to date, nanotransducer‐regulated Ca2+ signaling still confronts obstacles, and several scientific issues urgently need to be resolved. Thus, to provide brief and valid instructions for the development of nanotransducers for the regulation of Ca2+ signaling, proposals on how to improve the nanotransducer‐based [Ca2+]i manipulation as well as future challenges and prospects are discussed.

The Participation of Ca2+ Channels in Epilepsy: A Bibliometric Analysis of the Scientific Literature in Latin America.

Bibliometric analysis allows us to quantify and evaluate scientific activity, and it has become increasingly important in all areas of scientific literature. Thanks to these analyses, we can infer where science should put greater efforts into elucidating the underlying mechanisms of diseases that have yet to be fully described or investigated. This paper delves into published articles related to the involvement of calcium (Ca2+) channels in epilepsy, which is a condition with a high prevalence in Latin America. We followed the scientific publication on SCOPUS and analyzed the impact of publications from Latin America in the field of epilepsy and the study of Ca2+ channels. We identified the countries with the largest number of publications and found that 68% of them were experimental (animal models), while 32% were clinical. We also identified the main journals, growth over time, and citation numbers. We found a total of 226 works produced by Latin American countries from 1976 to 2022. The countries that have contributed the most to the topic are Brazil, Mexico, and Argentina, with occasional collaborations between them to make contributions to the study of epilepsy and Ca2+ channels. Additionally, we found that the journal with the most citations is Nature Genetics. The number of authors per article ranges from 1 to 242, and neuroscience journals are the preferred target for researchers, with a predilection for publishing original articles, although 26% of the publications are review articles.

Studies of Ca2+-activated contractility using skinned cryosections of human ventricular papillary muscle samples from frozen storage of discarded clinical specimens collected in biorepository

Studies of Ca2+-activated contractility using skinned cryosections of human ventricular papillary muscle samples from frozen storage of discarded clinical specimens collected in biorepository

Modelling the pathology and treatment of cardiac fibrosis in vascularised atrial and ventricular cardiac microtissues.

Recent advances in human cardiac 3D approaches have yielded progressively more complex and physiologically relevant culture systems. However, their application in the study of complex pathological processes, such as inflammation and fibrosis, and their utility as models for drug development have been thus far limited. In this work, we report the development of chamber-specific, vascularised human induced pluripotent stem cell-derived cardiac microtissues, which allow for the multi-parametric assessment of cardiac fibrosis. We demonstrate the generation of a robust vascular system in the microtissues composed of endothelial cells, fibroblasts and atrial or ventricular cardiomyocytes that exhibit gene expression signatures, architectural, and electrophysiological resemblance to in vivo-derived anatomical cardiac tissues. Following pro-fibrotic stimulation using TGFβ, cardiac microtissues recapitulated hallmarks of cardiac fibrosis, including myofibroblast activation and collagen deposition. A study of Ca2+ dynamics in fibrotic microtissues using optical mapping revealed prolonged Ca2+ decay, reflecting cardiomyocyte dysfunction, which is linked to the severity of fibrosis. This phenotype could be reversed by TGFβ receptor inhibition or by using the BET bromodomain inhibitor, JQ1. In conclusion, we present a novel methodology for the generation of chamber-specific cardiac microtissues that is highly scalable and allows for the multi-parametric assessment of cardiac remodelling and pharmacological screening.

Neuronal activity regulates Matrin 3 abundance and function in a calcium-dependent manner through calpain-mediated cleavage and calmodulin binding

RNA-binding protein (RBP) dysfunction is a fundamental hallmark of amyotrophic lateral sclerosis (ALS) and related neuromuscular disorders. Abnormal neuronal excitability is also a conserved feature in ALS patients and disease models, yet little is known about how activity-dependent processes regulate RBP levels and functions. Mutations in the gene encoding the RBP Matrin 3 (MATR3) cause familial disease, and MATR3 pathology has also been observed in sporadic ALS, suggesting a key role for MATR3 in disease pathogenesis. Here, we show that glutamatergic activity drives MATR3 degradation through an NMDA receptor-, Ca2+-, and calpain-dependent mechanism. The most common pathogenic MATR3 mutation renders it resistant to calpain degradation, suggesting a link between activity-dependent MATR3 regulation and disease. We also demonstrate that Ca2+ regulates MATR3 through a nondegradative process involving the binding of Ca2+/calmodulin to MATR3 and inhibition of its RNA-binding ability. These findings indicate that neuronal activity impacts both the abundance and function of MATR3, underscoring the effect of activity on RBPs and providing a foundation for further study of Ca2+-coupled regulation of RBPs implicated in ALS and related neurological diseases.

Calcium Signaling in Trauma: Increased Intracellular Calcium Flux in the Severely Injured

IntroductionThe pathogenesis of organ dysfunction following traumatic injury involves endothelial barrier disruption, and plasma from severely injured patients increases endothelial permeability in vitro. Many endothelial cell (EC) functions entail changes in intracellular calcium (Ca2+) concentrations, and multiple inflammatory mediators have been shown to induce EC barrier disruption in a Ca2+ dependent manner. However, study of Ca2+ signaling in trauma remains limited. Our objective was to investigate the role of intracellular Ca2+ signaling in trauma pathology. We hypothesized that ex vivo plasma from injured patients would induce intracellular EC Ca2+ flux and do so to a greater magnitude in more severely injured patients.MethodsBlood was collected from injured patients at a single, urban Level I Trauma Center. Patients were categorized by minimal injury without shock (Group 1: ISS<15 + base excess >‐6mEq/L; n=3) and severe injury with shock (Group 2: ISS>15 + base excess <‐6mEq/L; n=4). Human cerebral microvascular endothelial cells were grown on culture inserts and pre‐incubated with Fluo‐4 Ca2+ indicator. Plasma was diluted to concentrations previously used for in vitro permeability assays and flowed over EC’s under physiologic conditions for five minutes. Confocal microscopy was used to visualize and quantify intracellular Ca2+ flux. Thrombin was used as a positive control for inducing Ca2+ flux. We used Prism software to calculate areas under curves (AUC) and unpaired t‐tests to compare group means.ResultsCompared to Group 1 plasma, Group 2 induced greater calcium flux, which was sustained for a longer period of time, corresponding to greater AUC for total intracellular calcium flux (P<0.05, Figure).ConclusionsEx vivo plasma from more severely injured trauma patients increases intracellular Ca2+ flux in EC’s. These data suggest Ca2+signaling may play a role in trauma‐induced endotheliopathy and present as a therapeutic target. Our study lays the groundwork for additional investigation to elucidate sources of Ca2+ in this setting as well as identify plasma mediators of both Ca2+ flux and endothelial permeability.

Multiphoton Imaging of Ca2+ Instability in Acute Myocardial Slices from a RyR2R2474S Murine Model of Catecholaminergic Polymorphic Ventricular Tachycardia.

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is a familial stress-induced arrhythmia syndrome, mostly caused by mutations in Ryanodine receptor 2 (RyR2), the sarcoplasmic reticulum (SR) Ca2+ release channel in cardiomyocytes. Pathogenetic mutations lead to gain of function in the channel, causing arrhythmias by promoting diastolic spontaneous Ca2+ release (SCR) from the SR and delayed afterdepolarizations. While the study of Ca2+ dynamics in single cells from murine CPVT models has increased our understanding of the disease pathogenesis, questions remain on the mechanisms triggering the lethal arrhythmias at tissue level. Here, we combined subcellular analysis of Ca2+ signals in isolated cardiomyocytes and in acute thick ventricular slices of RyR2R2474S knock-in mice, electrically paced at different rates (1–5 Hz), to identify arrhythmogenic Ca2+ dynamics, from the sub- to the multicellular perspective. In both models, RyR2R2474S cardiomyocytes had increased propensity to develop SCR upon adrenergic stimulation, which manifested, in the slices, with Ca2+ alternans and synchronous Ca2+ release events in neighboring cardiomyocytes. Analysis of Ca2+ dynamics in multiple cells in the tissue suggests that SCRs beget SCRs in contiguous cells, overcoming the protective electrotonic myocardial coupling, and potentially generating arrhythmia triggering foci. We suggest that intercellular interactions may underscore arrhythmic propensity in CPVT hearts with ‘leaky’ RyR2.

Study of calcium profile in neuronal cells with respect to temperature and influx due to potential activity

Calcium is a critically important second messenger in the nervous system. It enters through voltage-gated Ca2+ channels and regulates the release of the synaptic transmitter. This mechanism is monitored by calcium diffusion, buffering mechanism and calcium influx into the cytoplasm. The study of Ca2+ dynamics is interesting because the concentration of Ca2+ shows highly complex spatial-temporal behavior. There are many controls on the cytoplasmic Ca2+ concentration. First, it is heavily buffered (i.e., bound) by large proteins and second control is that of the variable diffusion coefficient. The diffusion coefficient is directly proportional to the temperature and inversely proportional to the viscosity. In this paper, the one-dimensional steady-state case with boundary conditions has been studied to understand the Ca2+ distribution in neuronal cells incorporating diffusion of calcium, point source, excess buffer approximation (EBA), an influx due to the calcium current. Moreover, the dependency of Ca2+ concentration based on the variable diffusion coefficient is studied. The finite element method (FEM) has been employed to obtain the solutions.

Optogenetic Interneuron Stimulation and Calcium Imaging in Astrocytes.

In brain networks, neurons are constantly involved in a dynamic interaction with the other cell populations and, particularly, with astrocytes, the most abundant glial cells in the brain. Astrocytes respond to neurotransmitters with Ca2+ elevations which represent a key event in the modulation of local brain circuits played by these glial cells. Due to technical limitations, the study of Ca2+ signal dynamics in astrocytes has focused for decades almost exclusively on somatic and perisomatic regions. Accordingly, Ca2+ signal in astrocytic fine protrusions, which are in close contact with the synapse, has been poorly investigated. Over the last years, the diffusion of novel tools such as the viral vector gene delivery of genetically encoded Ca2+ indicators (GECI), the optogenetics, and multiphoton laser scanning microscopy has boosted significantly our capability to study astrocytic Ca2+ signals in the different subcellular compartments. Here we report a protocol that combines these techniques to study astrocyte Ca2+ signaling in response to somatostatin (SST)-expressing interneurons, one of the main classes of GABAergic inhibitory interneurons.

Ca2+ dynamics in zebrafish morphogenesis.

Intracellular calcium ion (Ca2+) signaling is heavily involved in development, as illustrated by the use of a number of Ca2+ indicators. However, continuous Ca2+ patterns during morphogenesis have not yet been studied using fluorescence resonance energy transfer to track the Ca2+ sensor. In the present study, we monitored Ca2+ levels during zebrafish morphogenesis and differentiation with yellow cameleon, YC2.12. Our results show not only clear changes in Ca2+ levels but also continuous Ca2+ patterns at 24 hpf and later periods for the first time. Serial Ca2+dynamics during early pharyngula period (Prim-5-20; 24–33 hpf) was successfully observed with cameleon, which have not reported anywhere yet. In fact, high Ca2+ level occurred concurrently with hindbrain development in segmentation and pharyngula periods. Ca2+ patterns in the late gastrula through segmentation periods which were obtained with cameleon, were similar to those obtained previously with other Ca2+sensor. Our results suggested that the use of various Ca2+ sensors may lead to novel findings in studies of Ca2+ dynamics. We hope that these results will prove valuable for further research in Ca2+ signaling.

Calcium Transient Registration in Response to Single Stimulation and During Train of Pulses in Mouse Neuromuscular Junction

Calcium (Ca2+) is a key ion involved in transmitter release in chemical synapses. Optical recording of fluorescence changes of Ca2+ indicators is one of the most frequently used methods to measure intracellular Ca2+ dynamics. This technique is based on use of Ca2+-binding fluorescent dyes which change their emission intensity after binding to Ca2+. The most crucial step in this type of experiments is loading of Ca2+ dye. In this paper, we present the method of Ca2+-sensitive dye loading to mammalian nerve endings through the stump of the nerve. We represent Ca2+ transient registered parameters in response to a single motor nerve stimulus. The study of Ca2+ dynamics during high frequency stimulation close to real pattern of synaptic transmission allows us to understand such fundamental process as synaptic plasticity. We describe the results obtained during the registration of Ca2+ transient caused by the rhythmic motor nerve stimulation. Intracellular level of Ca2+ estimated by the amplitude of Ca2+ transient rises with the increase of stimulation frequency. The amplitude of Ca2+ transient decreases after blocking of voltage dependent Ca2+ channels by cadmium. The obtained data showed that detected increase of fluorescence intensity is induced by Ca2+ influx through the voltage-gated Ca2+ channels to the nerve ending during an action potential. This dye-loading method is suitable for registration of presynaptic Ca2+ dynamics under both single nerve stimulus and rhythmic activity.

Fast interaction between AMPA and NMDA receptors by intracellular calcium

Suppression of NMDA receptor (NMDAR)-mediated currents by intracellular Ca2+ has been described as a negative feedback loop in NMDAR modulation. In the time scale of tenths of milliseconds the depth of the suppression does not depend on the Ca2+ source. It may be caused by Ca2+ influx through voltage-gated calcium channels, NMDAR channels or release from intracellular stores. However, NMDARs are often co-expressed in synapses with Ca2+-permeable AMPA receptors (AMPARs). Due to significant differences in activation kinetics between these two types of glutamate receptors (GluRs), Ca2+ entry through AMPARs precedes full activation of NMDARs, and therefore, might have an impact on the amplitude of NMDAR-mediated currents. The study of Ca2+-mediated crosstalk between AMPAR and NMDAR in native synapses is challenging due to high NMDAR Ca2+ permeability. Therefore, recombinant Ca2+-permeable AMPAR and Ca2+-impermeable NMDAR mutant channels were co-expressed in HEK 293 cells to examine their interaction. An AMPAR-mediated increase in intracellular Ca2+ concentration ([Ca2+]i) reversibly reduced the size of NMDAR-mediated whole-cell currents. The time course of the NMDAR channel inactivation and recovery from inactivation followed the time course of the [Ca2+]i transient. When brief (1ms) pulses of glutamate were applied to outside-out patches, the degree of NMDAR inactivation increased with the increase in charge carried by the currents through co-activated AMPARs. However, AMPAR-mediated NMDAR inactivation was abolished in the presence of intracellular fast Ca2+ buffer BAPTA or in Ca2+-free extracellular solution. We conclude that Ca2+ entering through AMPARs inactivates co-localized NMDARs in the time range of excitatory postsynaptic currents.

Study of Ca2+-ATPase Activity and Solubility in the Whole Kuruma Prawn (Marsupenaeus japonicus) Meat During Heating: Based on the Kinetics Analysis of Myofibril Protein Thermal Denaturation

Protein denaturation is considered to be the main cause of physicochemical changes in prawns during heating. However, no studies have been analyzed the kinetics of protein denaturation and the relationship between the degree of denaturation and chemical changes. Therefore, we investigated the changes in Ca2+-ATPase activity, protein solubility, and total sulfhydryl content of whole prawn meat during heating by determining the thermal denaturation kinetics of the proteins. Activation energies (E a ) for the denaturation of myosin (183.2 kJ/mol) and actin (178.8 kJ/mol) were obtained by non-isothermal differential scanning calorimetry analysis. Using the kinetic parameters, the distribution of protein denaturation was predicted in whole prawns under arbitrary heating conditions. The results revealed an uneven distribution of the protein denaturation in prawns that was dependent on the heating conditions. Ca2+-ATPase activity decreased with increasing heating times at 51 or 85 °C and was strongly related to the average degree of protein denaturation. The results of protein solubility analysis suggested that hydrogen bonds, hydrophobic interactions, and ionic bonds changed with protein denaturation. The number of ionic bonds was reduced, while hydrogen content was enhanced at both temperatures. Hydrophobic interactions increased gradually at 51 °C (p 0.05). Our results indicate that the extent of protein solubility is significantly correlated with the average degree of protein denaturation during the heating process.

TRPV4 Channel Cooperativity in the Resistance Vasculature

TRPV4 Channel Cooperativity in the Resistance Vasculature

Cognitive Function and Calcium. Ca2+-dependent regulatory mechanism of circadian clock oscillation and its relevance to neuronal function

Circadian clock generates a variety of biological rhythms such as sleep/wake cycles and blood hormone rhythms. The circadian clock also bolsters daily mental activities. In fact, abnormalities of the circadian rhythms are found in several neurological disorders. The circadian clock has two important functions: (i) a cell-autonomous oscillatory function and (ii) a phase-adjusting function that synchronizes the clock oscillation with environmental cycling conditions such as light/dark cycle. Behavioral rhythms are controlled by the central clock in hypothalamic suprachiasmatic nucleus (SCN). The central clock orchestrates peripheral clocks in the other tissues via neuronal connection and/or actions of humoral factors. The molecular mechanism of the cell-autonomous clock is based on transcriptional feedback regulation of clock genes by their encoded products. Ca2+ is essential for not only the light response of the clock but also the cell autonomous oscillation mechanism. This article provides an overview of recent progress in studies of Ca2+-dependent regulatory mechanism of the molecular clockwork.

Characterization of the Photophysical, Thermodynamic and Structural Properties of the Terbium(III)-KChIP3 Complex

KChIP3 (K+ channel interacting protein 3) is a calcium binding protein and active modulator of Kv4 channels in neuronal cells as well as a novel Ca2+ regulated transcriptional modulator. KChIP3(calsenilin) may also be involved in Alzheimer's disease through prevention of presenilin-2 fragmentation. Many of the KChIP3 interactions with its binding partners (Kv4, calmodulin, DNA, and drugs) have been shown to be dependent on calcium. Therefore, understanding the structural changes induced by Ca2+ is of utmost relevance to elucidating the mechanism of calcium signal transduction. Here, we show that the fluorescence emission and excitation spectra of the calcium luminescent analog Tb3+ is enhanced upon binding to the EF-hand of KChIP3, likely due to a mechanism of energy transfer between Phe/Trp and Tb3+. We also observe that unlike Tb3+ bound calmodulin, the luminescence lifetime of terbium bound to KChIP3 decays as a complex multiexponential (τaverage ∼ 1.8 ms) and is sensitive to the protein structure and drug (NS5806) binding. Using isothermal calorimetry we have determined that Tb3+ binds at least to four binding sites (Kd ∼ 2.2 μM) and is able to displace bound Ca2+ through an entropically driven mechanism (ΔH ∼ 3 kcal/mol). Secondary structural analysis of KChIP3 using far-UV CD spectroscopy shows that binding of Tb3+ induces the formation of an intermediate structure with less alpha helical content than that induced by Ca2+. However, using the hydrophobic probe 1,8-ANS we show that the structural changes induced by Tb3+ are large enough to expose a hydrophobic surface on KChIP3 identical to Ca2+ bound protein. Similarly to Ca2+, terbium binding also induces the dimerization of KChIP3. Overall, these results support the use of Tb3+ as an alternative fluorescent label in the study of Ca2+ induced structural changes in KChIP3.

New insights into the regulation of synaptic plasticity from an unexpected place: Hippocampal area CA2

The search for molecules that restrict synaptic plasticity in the brain has focused primarily on sensory systems during early postnatal development, as critical periods for inducing plasticity in sensory regions are easily defined. The recent discovery that Schaffer collateral inputs to hippocampal area CA2 do not readily support canonical activity-dependent long-term potentiation (LTP) serves as a reminder that the capacity for synaptic modification is also regulated anatomically across different brain regions. Hippocampal CA2 shares features with other similarly "LTP-resistant" brain areas in that many of the genes linked to synaptic function and the associated proteins known to restrict synaptic plasticity are expressed there. Add to this a rich complement of receptors and signaling molecules permissive for induction of atypical forms of synaptic potentiation, and area CA2 becomes an ideal model system for studying specific modulators of brain plasticity. Additionally, recent evidence suggests that hippocampal CA2 is instrumental for certain forms of learning, memory, and social behavior, but the links between CA2-enriched molecules and putative CA2-dependent behaviors are only just beginning to be made. In this review, we offer a detailed look at what is currently known about the synaptic plasticity in this important, yet largely overlooked component of the hippocampus and consider how the study of CA2 may provide clues to understanding the molecular signals critical to the modulation of synaptic function in different brain regions and across different stages of development.

Studying Signal Transduction in Single Dendritic Spines

Many forms of synaptic plasticity are triggered by biochemical signaling that occurs in small postsynaptic compartments called dendritic spines, each of which typically houses the postsynaptic terminal associated with a single glutamatergic synapse. Recent advances in optical techniques allow investigators to monitor biochemical signaling in single dendritic spines and thus reveal the signaling mechanisms that link synaptic activity and the induction of synaptic plasticity. This is mostly in the study of Ca2+-dependent forms of synaptic plasticity for which many of the steps between Ca2+ influx and changes to the synapse are now known. This article introduces the new techniques used to investigate signaling in single dendritic spines and the neurobiological insights that they have produced.

Decoding Neurodevelopment: Findings on Environmental Exposures and Synaptic Plasticity

What makes one person different from the next? In large part it’s that our individual brains are wired a bit differently; each neuron in each person’s brain has a different set of synapses connecting to a different set of neurons. When we’re born, most of the major functional subregions of the brain and their interconnections are in place, but various experiences and environmental exposures affect which synaptic connections become stronger and which become weaker. Different areas of the brain have this synaptic plasticity—or ability to grow stronger or weaker connections—at different time periods, and the timing of these “critical periods” is tightly regulated. Thermogram showing hormone receptors in the hippocampus of an infant. Exposures to certain neurotoxic agents during critical periods of synaptic plasticity may set the stage for developmental disorders. © Explorer/Photo Researchers, Inc. The field of neurobiology is humming with new findings on the intricate workings that orchestrate this process, too many to describe in one story. But of special interest are key discoveries by investigators at the National Institute of Environmental Health Sciences (NIEHS) about some of the basic mechanisms involved in synaptic plasticity, and work by other investigators that explores the hypothesis that environmental toxicants that disrupt synaptic plasticity at critical periods play a role in disorders that have roots in early brain development, such as autism spectrum disorders (ASDs), attention deficit/hyperactivity disorder, and schizophrenia.1,2

Calcium imaging of living astrocytes in the mouse spinal cord following sensory stimulation.

Astrocytic Ca2+ dynamics have been extensively studied in ex vivo models; however, the recent development of two-photon microscopy and astrocyte-specific labeling has allowed the study of Ca2+ signaling in living central nervous system. Ca2+ waves in astrocytes have been described in cultured cells and slice preparations, but evidence for astrocytic activation during sensory activity is lacking. There are currently few methods to image living spinal cord: breathing and heart-beating artifacts have impeded the widespread application of this technique. We here imaged the living spinal cord by two-photon microscopy in C57BL6/J mice. Through pressurized injection, we specifically loaded spinal astrocytes using the red fluorescent dye sulforhodamine 101 (SR101) and imaged astrocytic Ca2+ levels with Oregon-Green BAPTA-1 (OGB). Then, we studied astrocytic Ca2+ levels at rest and after right electrical hind paw stimulation. Sensory stimulation significantly increased astrocytic Ca2+ levels within the superficial dorsal horn of the spinal cord compared to rest. In conclusion, in vivo morphofunctional imaging of living astrocytes in spinal cord revealed that astrocytes actively participate to sensory stimulation.