Calcium Movements Research Articles

Assessment of Remineralization Capacity of Various Remineralizing Agents on Artificial Enamel Lesions Using Confocal Laser Scanning Microscope: An In Vitro Study

The present study aimed at evaluating the effectiveness of diverse remineralizing agents on artificial enamel lesion using confocal laser scanning microscope (CLSM). Totally 80 mandibular premolars which were single rooted were included. All teeth were suspended in a demineralizing solution to create artificial enamel lesions on the exposed enamel. The samples were separated randomly into four groups (20 each) depending on the application of the remineralizing agents as follows: group 1: control; group 2: calcium sucrose phosphate (CaSP); group 3: fluoride varnish; and group 4: casein phosphopeptides-amorphous calcium phosphate (CPP-ACP). The samples in individual group were treated with the corresponding remineralizing agent (except for the control group) two times a day for 14 days. The experimental and control groups were exposed to CLSM assessment to analyze the data of remineralization and demineralization. The mean depth of remineralization of fluoride varnish group was slightly more compared to other groups. The highest mean depth of remineralization was found in the fluoride varnish group (122.26 ± 0.28) followed by CaSP (110.58 ± 1.34), CPP-ACP (107.08 ± 0.48), and control (157.78 ± 0.46) groups. The different comparisons among the remineralization material groups showed a statistically significant difference (p < 0.05) in almost all groups except group 2 vs group 4. This study concluded that improved remineralization of artificial enamel lesion could be achieved with the fluoride varnish group when compared to the CaSP and CPP-ACP groups. Remineralization as a treatment technique has received a lot of consideration from clinicians. The process of remineralization and demineralization is considered an active process categorized by the movement of calcium and phosphate in and out of the enamel. Presently, the attention has changed toward increasing the resistance of the tooth by applying remineralizing agents topically, which has led to the notable fall in dental caries.

IL‐17 drives salivary gland dysfunction via inhibiting TRPC1‐mediated calcium movement in Sjögren’s syndrome

ObjectivesThis study aims to determine a role of interleukin‐17A (IL‐17) in salivary gland (SG) dysfunction and therapeutic effects of targeting IL‐17 in SG for treating autoimmune sialadenitis in primary Sjögren’s syndrome (pSS).MethodsSalivary IL‐17 levels and IL‐17‐secreting cells in labial glands of pSS patients were examined. Kinetic changes of IL‐17‐producing cells in SG from mice with experimental Sjögren’s syndrome (ESS) were analysed. To determine a role of IL‐17 in salivary secretion, IL‐17‐deficient mice and constructed chimeric mice with IL‐17 receptor C (IL‐17RC) deficiency in non‐hematopoietic and hematopoietic cells were examined for saliva flow rates during ESS development. Both human and murine primary SG epithelial cells were treated with IL‐17 for measuring cholinergic activation‐induced calcium movement. Moreover, SG functions were assessed in ESS mice with salivary retrograde cannulation of IL‐17 neutralisation antibodies.ResultsIncreased salivary IL‐17 levels were negatively correlated with saliva flow rates in pSS patients. Both IL‐17‐deficient mice and chimeric mice with non‐hematopoietic cell‐restricted IL‐17RC deficiency exhibited no obvious salivary reduction while chimeric mice with hematopoietic cell‐restricted IL‐17RC deficiency showed significantly decreased saliva secretion during ESS development. In SG epithelial cells, IL‐17 inhibited acetylcholine‐induced calcium movement and downregulated the expression of transient receptor potential canonical 1 via promoting Nfkbiz mRNA stabilisation. Moreover, local IL‐17 neutralisation in SG markedly attenuated hyposalivation and ameliorated tissue inflammation in ESS mice.ConclusionThese findings identify a novel function of IL‐17 in driving salivary dysfunction during pSS development and may provide a new therapeutic strategy for targeting SG dysfunction in pSS patients.

Evaluation of the diffusion of calcium hydroxide-based medicaments through the dentinal tubules and apical foramen: A mass spectrometry study.

Aims:This mass spectrometry study investigated the diffusion of hydroxyl and calcium ions from a calcium hydroxide intracanal medicament (Pulpdent®) when used alone or mixed in equal parts with a steroid–antibiotic paste (Ledermix®).Materials and Methods:The pH (using pH meter) and calcium ion concentration (using inductively coupled plasma-mass spectrometry) of the diffused medicaments were assessed using endodontically prepared human extracted teeth with either a sealed or a patent apex, at time intervals of 1, 3, 8, 24, and 168 h.Statistical Analysis:A one-way ANOVA was used to explore differences between and within groups, with Tukey–Kramer/Games–Howell posttests.Results:In both situations tested, Pulpdent® showed greater release of both calcium and hydroxyl ions than when mixed in equal parts with Ledermix®. Greater initial release of both ions occurred in roots with a patent apex, but by 1 week there was no significant difference between the two. If a 50:50 combination of Pulpdent® paste and Ledermix® paste is used, there is a lower release of calcium ions and hydroxyl ions than using Pulpdent® paste alone.Conclusion:With both Pulpdent® paste alone and Pulpdent® paste mixed equally with Ledermix® paste, the major pathway for movement of hydroxyl ions and calcium ions is diffusion through the dentine of the root, with the apex playing only a minor role.

Polyelectrolyte-calcium complexes as a pre-precursor induce biomimetic mineralization of collagen.

Polyelectrolytes such as polyaspartic acid (PAsp) are critical in biomimetic mineralization as stabilizers of amorphous calcium phosphate (ACP) precursors and as nucleation inhibitors similar to non-collagenous proteins (NCPs). Nevertheless, the application of polyelectrolyte-calcium complexes as a pre-precursor, such as PAsp-Ca complexes, in the mineralization of collagen is unexplored. Herein, we propose a polyelectrolyte-Ca complex pre-precursor (PCCP) process for collagen mineralization. By combining three-dimensional (3D) STORM, potential measurements, and cryogenic transmission electron microscopy with molecular dynamics simulations, we show that liquid-like electropositive PAsp-Ca complexes along with free calcium ions infiltrate electronegative collagen fibrils. The PAsp-Ca complexes are immobilized within the fibrils via chelation and hydrogen bonds, and outward movement of free calcium ions is prevented while phosphate and hydroxide are recruited through electrostatic attractions. Afterwards, ACP instantly forms and gradually crystallizes. The PCCP process not only unites two distinct crystallization pathways (classical (free Ca/P ions) and non-classical (polyelectrolyte-Ca complexes)), but also provides a novel strategy for rapid biomimetic mineralization of collagen.

Evaluation of the movement of calcium and boron supplied through the cutting surface of tomato node

Evaluation of the movement of calcium and boron supplied through the cutting surface of tomato node

Urinary calcium and gross movements levels among Hui nationality children in rural area of Ningxia with establised card household

Objective To investigate the urinary calcium and gross motor levels among Hui nationality children aged 3–6 years in rural Areas of Ningxia with establised card household, and to provide evidence for the improvement of urinary calcium and gross motor levels in this group. Methods Using convenient sampling method, 24 rural kindergartens in 8 poor counties in Ningxia were selected, and 358 registered Hui children were investigated and tested for urinary calcium and gross motor levels. Morning Urinary calcium was tested by using test kit. Gross Motor Development Test Scale version 3 (TGMD-3) was used to assess gross motor development in children. Results Calcium deficiency in boys and girls accounted for 23.6% and 38.6% respectively, the difference was statistically significant (χ 2 = 6.83, P 0.05). Conclusion Among those 3–6-year-old Hui children with established card household in Ningxia rural areas, uneven development of urine calcium and gross movements are noticed. There are a large proportion of children with calcium deficiency and gross movements development delay, active measures should be developed and be carrtied out. 【摘要】 目的 了解宁夏农村3~6岁建档立卡回族幼儿尿钙与粗大动作水平, 为该群体尿钙与粗大动作改善提供依据。 方法 采用方便抽样的方法, 抽取宁夏8个贫困县区农村幼儿园24所, 对其中358名建档立卡回族幼儿尿钙与粗大动作 水平进行调查测试。采用尿钙检测试剂盒, 测定幼儿当天留取的空腹晨尿;采用粗大肌肉动作发展测试量表第3版 (TG- MD-3)测试幼儿粗大动作指标。 结果 男、女童缺钙检出率分别为23.6%和38.6%, 差异有统计学意义 (χ 2 =6.83, P 0.05)。 结论 宁夏农村3~6岁建档立卡回族幼儿尿钙和粗大动作水平发展不均, 缺钙和粗大动作发展滞后人数较多, 应积极采取 措施加以改善。

Radiofrequency Fields and Calcium Movements Into and Out of Cells.

The recent rollout of 5G telecommunications systems has spawned a renewed call to re-examine the possibility of so-called "non-thermal" harmful effects of radiofrequency (RF) radiation. The possibility of calcium being affected by low-level RF has been the subject of research for nearly 50 years and there have been recent suggestions that voltage-gated calcium channels (VGCCs) are "extraordinarily sensitive" to ambient RF fields. This article examines the feasibility of particularly modulated RF coupling to gating mechanisms in VGCCs and also reviews studies from the literature from the last 50 years for consistency of outcome. We conclude that the currents induced by fields at the ICNIRP guideline limits are many orders of magnitude below those needed to affect gating, and there would need to be a biological mechanism for detection and rectification of the extremely-low-frequency (ELF) modulations, which has not been demonstrated. Overall, experimental studies have not validated that RF affects Ca2+ transport into or out of cells.

Chemical Biology Tools to Elucidate the Solution Conformation and Cellular Interactions of Cyclic Adenosine 5′‐Diphosphate Ribose

The movement of calcium ions (Ca2+) is intimately involved in regulating many physiological processes, and so there is great interest in the structure of molecules, especially second messengers, that regulate this flow. One such messenger is cyclic adenosine 5′‐diphosphate ribose (cADPR), which is suspected to play a role in Ca2+ release in cardiomyocytes. The speculated mechanism of action involves the binding of cADPR to FKBP12.6, releasing FKBP12.6 from RyR2 channels, through which Ca2+ enters the sarcoplasm from the sarcoplasmic reticulum during ventricular systole. Guided by the principle that structure determines function, we aim to advance the investigation of regulatory cADPR interactions by synthesizing and studying cADPR and its analogs using the combined tools of liquid chromatography‐mass spectrometry (LCMS) and nuclear magnetic resonance (NMR) spectroscopy. The endogenous cyclization of nicotinamide adenine dinucleotide (NAD+) to cADPR by CD38 is mimicked in vitro using ADP‐ribosylcyclase (ADP‐RC, sourced from Aplysia californica). The low substrate specificity of ADP‐RC conveniently permits the cyclization of various cADPR analogs. Kinetic assays were prompted by an observed feedback inhibition of ADP‐RC by nicotinamide (IC50 ~ 1mM), and performed using LCMS. Following synthesis and purification, NMR experimental data provided insight into favored structural conformations of cADPR (Saatori et al., 2018) Photoaffinity labeling (PAL) was aimed at identifying the cognate binding partners of cADPR, some of which have been previously described by Walseth et al. (1993). Conformational analyses of cADPR analogs revealed structural trends with correlations to the biological activity of the analogs.Support or Funding InformationDepartment of Chemistry, Saint John’s University

To Face or Not to Face: Relationship of IP3 Receptors and Mitochondria in Purkinje Fibers of Cerebellum

The cell bodies of Purkinje Cells are extremely rich in Endoplasmic Reticulum (ER) stacks associated with a semi-crystalline array of inositol- 1,4,5-trisphosphate receptor (IP3 receptor) (Katayama et al: EMBO Journal vol.15 no.18 pp.4844-4851, 1996). Calcium release from IP3 receptor is the major component of calcium movement in the cell bodies. The ER stacks are closely associated with the mitochondrial surfaces and we have explored their relative positions.Taking advantage Katayama's work, we have considered the question of whether the IP3 receptors are located on the mitochondrial-facing ER surface.We examined the thin section ultrastructure of rat cerebellar Purkinje cells fixed by perfusing via the carotid artery.The ER stacks show clear “periodically arranged small densities”, presumably IP3 receptors.

Role of Ribonucleotides in Improving Muscle Cell Function

Based on data present in literature about some beneficial effects of nucleotides in reducing inflammation, and on lacking information about the mechanisms underlying the cellular aspects of exercise, the aim of this study was to examine the effects of the administration of a mixture of nucleotides and nucleotide-ribose on energy metabolism and contractility in cultured skeletal muscle cells in presence or absence of caffeine-dependent hyper-contraction. C2C12 cells were treated with various nucleotides forms, named Ribodiet®, RIBOCARE® MIX 1, RIBOCARE® MIX 2, and RNA-Na. Cell viability, calcium, and magnesium movements and the main kinases involved in glucose uptake have been analyzed. The level of glycogen and the presence of lactate have been evaluated as well. Since some important findings were obtained, additional experiments analyzed the effects of the same nucleotide forms under severe exercise conditions in order to understand the correct human use of nucleotides as food supplements to better support the exercise effects. The results obtained show for the first time, a direct effect of nucleotides on energy metabolism and calcium/ magnesium movements during in vitro exercise simulation and provide useful indications to support muscle cells during exercise or during aging.

Ca(2+)N It Be Measured? Detection of Extramitochondrial Calcium Movement With High-Resolution FluoRespirometry

Our aim was to develop a method to detect extramitochondrial Ca2+ movement and O2 fluxes simultaneously. Using High-Resolution FluoRespirometry, we also tested whether mitochondrial permeability transition pore (mPTP) inhibition or anoxia affects the mitochondrial Ca2+ flux. Ca2+ movement evoked by CaCl2 or anoxia was assessed with CaGreen-5N dye using Blue-Fluorescence-Sensor in isolated liver mitochondria, liver homogenates and duodenal biopsies. Exogenous CaCl2 (50 µM) resulted in an abrupt elevation in CaGreen-5N fluorescence followed by a decrease (Ca2+ uptake) with simultaneous elevation in O2 consumption in liver preparations. This was followed by a rapid increase in the fluorescence signal, reaching a higher intensity (Ca2+ efflux) than that of the initial CaCl2-induced elevation. Chelation of Ca2+ with EGTA completely abolished the fluorescence of the indicator. After pre-incubation with cyclosporin A, a marked delay in Ca2+ movement was observed, not only in isolated liver mitochondria, but also in tissue homogenates. In all samples, the transition to anoxia resulted in immediate increase in the level of extramitochondrial Ca2+. The results demonstrate that the CaGreen-5N method is suitable to monitor simultaneous O2 and Ca2+ fluxes, and the opening of mPTP in various biological samples. In this system the duration of stimulated Ca2+ fluxes may provide a novel parameter to evaluate the efficacy of mPTP blocker compounds.

SOME CATIONS MOVEMENT IN CALCAREOUS SOIL COLUMNS UNDER EFFECT OF SALINE WATER MIXED WITH HUMIC ACID

A laboratory experiment was conducted to study the impact of humic acid with different levels of saline water on the movement of Sodium, Calcium and Magnesium, and the kinetics of Sodium adsorption ratio in calcareous soil with a texture clay loam using the mixing displacement techniques. The soil was taken from the surface layer (0-30 cm), air dried and passed through a 2 mm diameter sieve. It was filled in columns of polyethylene. A fixed column of water was placed above the surface of the soil column of different salinity water (0.72, 3.00, 5.00 and 7.00 dSm-1), in accordance with humic acid levels of 0.00, 0.25 and 0.50 g L -1. The process of washing and collecting leachate continued daily. The amount of Sodium, Calcium and Magnesium in the water filtered over time. The results showed that the amount of Sodium released increases with the levels of added humic acid and any levels of saline water used. The amount of Calcium and Magnesium released decreases with time and increases the added levels of the humic acid and any levels of saline water used. Diffusion equation is the best equation described the movement of salt.

Retention and release of nutrients from polyhalite to soil

AbstractRecent discoveries of polyhalite (K2SO4.MgSO4.2CaSO4.2H2O) in the UK provide an alternative to conventional fertilizer sources. This work investigated the interaction of polyhalite, commercially known as POLY4, with soil using leaching columns. Different physical forms of polyhalite (powder, crushed rock and granules) were compared to potassium chloride (KCl) for the movement of potassium, calcium, magnesium and sulphur (as sulphate) through the soil profile using 19.7 L of water, equivalent to 4,500 mm rainfall. The nutrients from polyhalite were found to be available at 30 cm depth, with calcium showing signs of interacting with the soil clay particles to release cationic nutrients. Polyhalite granules showed the greatest release of sulphate, magnesium and calcium as a proportion of the additional nutrient with 127%, 71% and 102%, respectively leached. For potassium, all forms of polyhalite had greater release than KCl (powder = 58%; granules = 86%; crushed rock = 57% and KCl 16%). Nutrients from polyhalite and those mobilized from soil interactions are present in soil solution indicating availability for plant growth.

Mechanisms underlying the effect of an oral antihyperglycaemic agent glyburide on calcium ion (Ca2+ ) movement and its related cytotoxicity in prostate cancer cells.

Glyburide is an agent commonly used to treat type 2 diabetes and also affects various physiological responses in different models. However, the effect of glyburide on Ca2+ movement and its related cytotoxicity in prostate cancer cells is unclear. This study examined whether glyburide altered Ca2+ signalling and viability in PC3 human prostate cancer cells and investigated those underlying mechanisms. Intracellular Ca2+ concentrations ([Ca2+ ]i ) in suspended cells were measured by using the fluorescent Ca2+ -sensitive dye fura-2. Cell viability was examined by WST-1 assay. Glyburide at concentrations of 100-1000μM induced [Ca2+ ]i rises. Ca2+ removal reduced the signal by approximately 60%. In Ca2+ -containing medium, glyburide-induced Ca2+ entry was inhibited by 60% by protein kinase C (PKC) activator (phorbol 12-myristate 13 acetate, PMA) and inhibitor (GF109203X), and modulators of store-operated Ca2+ channels (nifedipine, econazole and SKF96365). Furthermore, glyburide induced Mn2+ influx suggesting of Ca2+ entry. In Ca2+ -free medium, inhibition of phospholipase C (PLC) with U73122 significantly inhibited glyburide-induced [Ca2+ ]i rises. Treatment with the endoplasmic reticulum (ER) Ca2+ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished glyburide-evoked [Ca2+ ]i rises. Conversely, treatment with glyburide abolished BHQ-evoked [Ca2+ ]i rises. Glyburide at 100-500μM decreased cell viability, which was not reversed by pretreatment with the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Together, in PC3 cells, glyburide induced [Ca2+ ]i rises by Ca2+ entry via PKC-sensitive store-operated Ca2+ channels and Ca2+ release from the ER in a PLC-dependent manner. Glyburide also caused Ca2+ -independent cell death. This study suggests that glyburide could serve as a potential agent for treatment of prostate cancer.

Performance assessment of nanoparticulate lime to accelerate the downward movement of calcium in acid soil

AbstractCalcium in conventional lime (CL) moves downward extremely slowly into the soil in the short term. To monitor the effects of using nanoparticulate lime (NL) in low affordable doses and in large doses on accelerating the downward movement of Ca in a simulated plough layer profile (0–25 cm), we ran a column leaching experiment with an acid soil with NL applied into the top 5 cm. The experiment evaluated a reference treatment (0 NL), three low doses of NL (8, 40 and 80 kg ha−1 = 0.02×, 0.1×, and 0.2× the NL needed to raise soil pH to 6.0 in the top 5 cm: NLRpH‐6), and two large doses (400 and 800 kg ha−1 = 1× and 2× NLRpH‐6). Over the short term (70 days), NL accelerated the downward movement of Ca, likely by mass flow of nanoparticles down soil micro‐ and macropores. Applying NL to the top 5 cm at 40 and 80 kg ha−1 was effective at increasing the downward movement of Ca and the neutralization of soil acidity (in terms of pH) to 20 cm depth, as well as rectifying Al toxicity (in terms of exchangeable Al) to ≤ the critical limit to 10 cm. NL at 80 kg ha−1 was most economically justified in terms of rectifying Al toxicity throughout the profile. Therefore, NL may introduce new and alternative application strategy that allowing lower rates of lime to be used and thereby offset economic constraints posed by high application rates.

Antioxidant Effect of a Polyphenol-Rich Murtilla (Ugni molinaeTurcz.) Extract and Its Effect on the Regulation of Metabolism in Refrigerated Boar Sperm

The production of reactive oxygen species (ROS) in boar spermatozoa increases in refrigeration; this can have an impact on sperm quality and fertilization capacity. We evaluated the effect of polyphenol-rich aqueous extract of murtilla (Ugni molinae Turcz) on boar sperm stored at 17°C in order to reduce oxidative stress and improve sperm quality in the long term. Five experiments were performed: first, characterization of the polyphenol content from five genotypes of murtilla; second, determination of the genotype with the best antioxidant effect (MT-Ex); third, the antioxidant capacity on O2 − and lipid peroxidation; fourth, the influence of MT-Ex on motility, calcium movement, cAMP, and metabolic parameters; and fifth, analysis of long-term refrigeration. The average phenolic content was 344 ppm; gallic acid, catechin, quercetin, myricetin, and kaempferol were detected. All extracts evaluated presented a concentration-dependent antioxidant effect. MT-Ex reduces intracellular O2 −/peroxides but low lipid peroxidation. MT-Ex in nonstimulated ROS conditions reduces sperm motility, mitochondrial membrane potential, cAMP, and ATP, but the succinate dehydrogenase activity remained normal; also, we observed a reduction in calcium movement in in vitro sperm capacitation. The long-term analyses showed that MT-Ex improved sperm motility decay and reduced membrane damage and ROS at 168 h. Based on this study, we propose MT-Ex as a supplement in semen extenders.

Platelet Function in Experimental Models of Liver Cirrhosis

(1) Background: Platelet function is commonly altered in liver cirrhosis. In experimenta models of liver cirrhosis we have analyzed the mechanisms of this defective function. (2) Methods: Experiments were performed in a model of liver cirrhosis by bile duct-ligation in washed platelets by means of fluorescence spectroscopy with fura-2. (3) Results: We have found several alterations compatible with the existence of a hyperaggregatory state. These alterations are related to a defective platelet calcium handling, specifically to an enhanced intracellular calcium release evoked by thrombin and an increased amount of calcium stored in the intracellular organelles and are present before the appearance of ascites. Homocysteine plays a role in this enhanced platelet aggregation response, probably through an enhanced formation of reactive oxygen species, which is prevented by Folic acid pretreatment. Bile acids show a tendency to reduce calcium movements across platelet membranes which would reduce this hyperaggregatory state characterisitic of the non-ascitic phase of the disease. (4) Conclusions: In experimental models of liver cirrhosis, we have found platelet function alterations related to an increased calcium release secondary to an increased amount of calcium stored in the intracellular organelles. These alterations are related to a higher homocysteine sensitivity that induces an enhanced production of reactive oxygen species. Chronic treatment with folic acid eliminates those alterations, and it can be of interest to minimize risks associated with thrombotic events in cirrhosis.

Periplanetasin-4, a novel antimicrobial peptide from the cockroach, inhibits communications between mitochondria and vacuoles

Communications between various organelle-organelles play an essential role in cell survival. The cross-talk between mitochondria and vacuoles comes up with the vital roles of the intercompartmental process. In this study, we found a couple of cell death features, membrane damage, and apoptosis using antimicrobial peptide from American Cockroach. Periplanetasin-4 (LRHKVYGYCVLGP-NH2) is a 13-mer peptide derived from Periplaneta americana and exhibits phosphatidylserine exposure and caspase activation without DNA fragmentation. Apoptotic features without DNA damage provide evidence that this peptide did not interact with DNA directly and exhibited dysfunction of mitochondria and vacuoles. Superoxide radicals were generated from mitochondria and converted to hydrogen peroxide. Despite the enhancement of catalase and total glutathione contents, oxidative damage disrupted intracellular contents. Periplanetasin-4 induced cell death associated with the production of superoxide radicals, calcium uptake in mitochondria and disorder of vacuoles, such as increased permeability and alkalization. While calcium movement from vacuoles to the mitochondria occurred, the cross-talk with these organelles proceeded and the inherent functionality was impaired. To sum up, periplanetasin-4 stimulates superoxide signal along with undermining the mitochondrial functions and interfering in communication with vacuoles.

Vascular endothelial growth factor increases the function of calcium-impermeable AMPA receptor GluA2 subunit in astrocytes via activation of protein kinase C signaling pathway.

Astrocytic calcium signaling plays pivotal roles in the maintenance of neural functions and neurovascular coupling in the brain. Vascular endothelial growth factor (VEGF), an original biological substance of vessels, regulates the movement of calcium and potassium ions across neuronal membrane. In this study, we investigated whether and how VEGF regulates glutamate‐induced calcium influx in astrocytes. We used cultured astrocytes combined with living cell imaging to detect the calcium influx induced by glutamate. We found that VEGF quickly inhibited the glutamate/hypoxia‐induced calcium influx, which was blocked by an AMPA receptor antagonist CNQX, but not D‐AP5 or UBP310, NMDA and kainate receptor antagonist, respectively. VEGF increased phosphorylation of PKCα and AMPA receptor subunit GluA2 in astrocytes, and these effects were diminished by SU1498 or calphostin C, a PKC inhibitor. With the pHluorin assay, we observed that VEGF significantly increased membrane insertion and expression of GluA2, but not GluA1, in astrocytes. Moreover, siRNA‐produced knockdown of GluA2 expression in astrocytes reversed the inhibitory effect of VEGF on glutamate‐induced calcium influx. Together, our results suggest that VEGF reduces glutamate‐induced calcium influx in astrocytes via enhancing PKCα‐mediated GluA2 phosphorylation, which in turn promotes the membrane insertion and expression of GluA2 and causes AMPA receptors to switch from calcium‐permeable to calcium‐impermeable receptors, thereby inhibiting astrocytic calcium influx. The present study reveals that excitatory neurotransmitter glutamate‐mediated astrocytic calcium influx can be regulated by vascular biological factor via activation of AMPA receptor GluA2 subunit and uncovers a novel coupling mechanism between astrocytes and endothelial cells within the neurovascular unit.

Use of calcium channel blockers in cardiovascular disease

Calcium channel blockers (CCBs) are widely used agents in the management of a number of cardiovascular indications, including hypertension, angina and supraventricular tachycardias. By inhibiting the movement of calcium into the cytoplasm via transmembrane calcium channels, they reduce vascular and myocardial contractility, and modulate the activity of pacemaker cells. There are important differences between the different types of calcium channel blockers, and a sound understanding of their mechanism of action is required to promote their safe, effective use. This article briefly describes calcium channel pharmacology, the mechanism of action of CCBs and their place in the therapy of cardiovascular disease.