Modulation Of Intracellular Calcium Homeostasis Research Articles

Taurine Regulation of Neuroendocrine Function.

Taurine (2-aminoethanesulfonic acid) is a sulfur-containing amino acid. It is one of the most abundant free amino acids in many excitable tissues, including the brain, skeletal and cardiac muscles. Physiological actions of taurine are widespread and include regulation of plasma glucose levels, bile acid conjugation, detoxification, membrane stabilization, blood pressure regulation, osmoregulation, neurotransmission, and modulation of mitochondria function and cellular calcium levels. Taurine plays an important role in modulating glutamate and GABA neurotransmission and prevents excitotoxicity in vitro primarily through modulation of intracellular calcium homeostasis. Taurine supplementation prevents age-dependent decline of cognitive functions. Because of the wide spread actions of taurine, its levels are highly regulated through enzymatic biosynthesis or dietary intake. Furthermore, depletion of endogenous or dietary supplementation of exogenous taurine have been shown to induce wide spread actions on multiple organs. Cysteine sulfonic acid decarboxylase (CSAD) was first identified in the liver and is thought to be the rate-limiting enzyme in taurine biosynthesis. CSAD mRNA is expressed in the brain in astrocytes. Homozygous knockout mice lacking CSAD (CSAD-KO) have very reduced taurine content and show severe functional histopathology in the visual system, skeletal system, heart, pancreas and brain. Conversely, dietary supplementation of taurine results in significant health benefits acting through the same organ systems. Fluctuation of taurine bioavailability lead to changes in the expression levels of taurine transporters in neuronal plasma membranes, endothelial cells forming the blood-brain barrier and proximal cells of the kidneys. Suggesting a highly regulated mechanism for maintaining taurine homeostasis and organ systems function. Here we show how alterations in taurine levels directly affect the function of one organ system and through functional interaction and compensatory adaptation; these effects extend to another organ systems with focus on the nervous system.

The role of vitamin D in male fertility: A focus on the testis.

In the last decade, vitamin D has emerged as a pleiotropic molecule with a multitude of autocrine, paracrine and endocrine functions, mediated by classical genomic as well as non-classical non-genomic actions, on multiple target organs and systems. The expression of vitamin D receptor and vitamin D metabolizing enzymes in male reproductive system, particularly in the testis, suggests the occurrence of vitamin D synthesis and regulation as well as function in the testis. The role of vitamin D in the modulation of testis functions, including hormone production and spermatogenesis, has been investigated in animals and humans. Experimental studies support a beneficial effect of vitamin D on male fertility, by modulating hormone production through genomic and non-genomic actions, and, particularly, by improving semen quality essentially through non-genomic actions. However, clinical studies in humans are controversial. Indeed, vitamin D seems to contribute to the modulation of the bioavailable rather than total testosterone. Moreover, although an increased prevalence or risk for testosterone deficiency was reported in men with vitamin D deficiencyin observational studies, the majority of interventional studies demonstrated the lack of effect of vitamin D supplementation on circulating levels of testosterone. The most consistent effect of vitamin D was reported on semen quality. Indeed, vitamin D was shown to be positively associated to sperm motility, and to exert direct actions on spermatozoa, including non-genomic driven modulation of intracellular calcium homeostasis and activation of molecular pathways involved in sperm motility, capacitation and acrosome reaction. The current review provides a summary of current knowledge on the role of vitamin D in male fertility, by reporting clinical and experimental studies in humans and animals addressing the relationship between vitamin D and testis function.

Liraglutide directly protects cardiomyocytes against reperfusion injury possibly via modulation of intracellular calcium homeostasis

BackgroundLiraglutide is glucagon-like peptide-1 receptor agonist for treating patients with type 2 diabetes mellitus. Our previous studies have demonstrated that liraglutide protects cardiac function through improving endothelial function in patients with acute myocardial infarction undergoing percutaneous coronary intervention. The present study will investigate whether liraglutide can perform direct protective effects on cardiomyocytes against reperfusion injury.MethodsIn vitro experiments were performed using H9C2 cells and neonatal rat ventricular cadiomyocytes undergoing simulative hypoxia/reoxygenation (H/R) induction. Cardiomyocytes apoptosis was detected by fluorescence TUNEL. Mitochondrial membrane potential (ΔΨm) and intracellular reactive oxygen species (ROS) was assessed by JC-1 and DHE, respectively. Fura-2/AM was used to measure intracellular Ca2+ concentration and calcium transient. Immunofluorescence staining was used to assess the expression level of sarcoplasmic reticulum Ca2+-ATPase (SERCA2a). In vivo experiments, myocardial apoptosis and expression of SERCA2a were detected by colorimetric TUNEL and by immunofluorescence staining, respectively.ResultsIn vitro liraglutide inhibited cardiomyotes apoptosis against H/R. ΔΨm of cardiomyocytes was higher in liraglutide group than H/R group. H/R increased ROS production in H9C2 cells which was attenuated by liraglutide. Liraglutide significantly lowered Ca2+ overload and improved calcium transient compared with H/R group. Immunofluorescence staining results showed liraglutide promoted SERCA2a expression which was decreased in H/R group. In ischemia/reperfusion rat hearts, apoptosis was significantly attenuated and SERCA2a expression was increased by liraglutide compared with H/R group.ConclusionsLiraglutide can directly protect cardiomyocytes against reperfusion injury which is possibly through modulation of intracellular calcium homeostasis.

Calcium Transport across Plasma Membrane in Early Stages of Chronic Kidney Disease – Impact of Vitamin D3 Supplementation

Mini review summarizes the results of studies focused on elucidating pathophysiological mechanisms of altered intracellular calcium homeostasis in the peripheral blood mononuclear cells of patients with early stages of chronic kidney disease. The basic mechanisms of calcium entry as well as those of its removal are impaired by the disease. These disturbances cause an increase concentration of free cytosolic calcium which can result in a change of broad range of cellular processes and expression patterns of various signaling molecules. Vitamin D3 supplementation is the standard treatment of frequent vitamin D3 insufficiency or deficiency in these patients. It can be assumed that vitamin D3 through the pleiotropic effects may participate in modulation of intracellular calcium homeostasis. Vitamin D3 supplementation resulted in a reduction of cytosolic free calcium affecting some of the transport systems involved in cell calcium entry as well as calcium exit. Normalization of the cytosolic free calcium concentration can have a beneficial effect on intracellular signaling. The mechanisms for regulating and controlling intracellular calcium homeostasis in chronic kidney disease patients are currently still under investigation.

Cardiomyocyte-specific p65 NF-κB deletion protects the injured heart by preservation of calcium handling

NF-κB is a well-known transcription factor that is intimately involved with inflammation and immunity. We have previously shown that NF-κB promotes inflammatory events and mediates adverse cardiac remodeling following ischemia reperfusion (I/R). Conversely, others have pointed to the beneficial influence of NF-κB in I/R injury related to its anti-apoptotic effects. Understanding the seemingly disparate influence of manipulating NF-κB is hindered, in part, by current approaches that only indirectly interfere with the function of its most transcriptionally active unit, p65 NF-κB. Mice were generated with cardiomyocyte-specific deletion of p65 NF-κB. Phenotypically, these mice and their hearts appeared normal. Basal and stimulated p65 expression were significantly reduced in whole hearts and completely ablated in isolated cardiomyocytes. When compared with wild-type mice, transgenic animals were protected from both global I/R by Langendorff as well as regional I/R by coronary ligation and release. The protected, transgenic hearts had less cytokine activity and decreased apoptosis. Furthermore, p65 ablation was associated with enhanced calcium reuptake by the sarcoplasmic reticulum. This influence on calcium handling was related to increased expression of phosphorylated phospholamban in conditional p65 null mice. In conclusion, cardiomyocyte-specific deletion of the most active, canonical NF-κB subunit affords cardioprotection to both global and regional I/R injury. The beneficial effects of NF-κB inhibition are related, in part, to modulation of intracellular calcium homeostasis.

Wnt3a a potent modulator of myogenic differentiation and muscle cell function

Previously we showed that conditioned media (CM) from MLO‐Y4 osteocytes accelerates myogenesis of C2C12 myoblasts. Here we examined molecular and functional events occurring when C2C12 cells were treated with one of the key factors released by osteocytes, Wnt3a; which induced a significant nuclear translocation of β‐catenin, a hallmark of canonical Wnt signaling. This pathway showed to play a crucial role in the enhancement of myogenic differentiation produced by both 10ng Wnt3a and 10% MLO‐Y4 CM. The potent effects of Wnt3a on stimulating the β‐catenin signaling pathway strongly correlated with changes in calcium oscillations. In addition, fully differentiated myotubes that were treated with Wnt3a displayed an enhanced sensitivity to caffeine. These data are consistent with the upregulation of a key myogenic regulatory factor (MRF), MyoD and some of the essential genes related to intracellular calcium homeostasis (i.e., IP3‐R1,3; Stim‐2; Camk2d; SERCA‐1,2). Our new findings suggest that Wnt3a works as a potent modulator of myogenic differentiation and muscle cell function. We propose that Wnt3a may be an important secreted factor from osteocytes that mediates bone to muscle signaling by modulation of intracellular calcium homeostasis leading to gene regulatory changes that stimulate myogenesis. Support: NIH RC2 AR058962 and Missouri Life Sciences Research Board to MB.

CD20-related signaling pathway is differently activated in normal and dystrophic circulating CD133(+) stem cells.

Among the heterogeneous population of circulating hematopoietic and endothelial progenitors, we identified a subpopulation of CD133(+) cells displaying myogenic properties. Unexpectedly, we observed the expression of the B-cell marker CD20 in blood-derived CD133(+) stem cells. The CD20 antigen plays a role in the modulation of intracellular calcium homeostasis through signaling pathways activation. Several observations suggest that an increase in intracellular calcium concentration ([Ca(2+)](i)) could be involved in the etiology of the Duchenne muscular dystrophy (DMD). Here, we show that a CD20-related signaling pathway able to induce an increase in [Ca(2+)](i) is differently activated after brain derived neurotrophic factor (BDNF) stimulation of normal and dystrophic blood-derived CD133(+) stem cells, supporting the assumption of a "CD20-related calcium impairment" affecting dystrophic cells. Presented findings represent the starting point toward the expansion of knowledge on pathways involved in the pathology of DMD and in the behavior of dystrophic blood-derived CD133(+) stem cells.

Toxic effects of metals: modulation of intracellular calcium homeostasis

Metals and metalloids with their organic derivatives are part of the environment occurring naturally or being introduced upon human activity (e.g. industry, agriculture or medicine). Even if they are useful for humans, these chemicals could be highly toxic (e.g. mercury, lead, arsenic, tin) acting as neurotoxins or carcinogens. Several human cases of metal derived intoxication have been documented resulting in health complications or ending with death. The mechanisms of toxicity are not well understood. Since calcium is a universal second messenger in all cell types it is a good candidate to investigate how changes in the intracellular calcium homeostasis are involved in metal(loid) toxicity. In this mini-overview the interaction of metallic species with channel proteins at the outer cell membrane, as well as with calcium release sides from the calcium stores and the impairment with calcium extrusion mechanism is discussed. Toxische Effekte von Metallen: Modulation der intrazellulären. Calcium-Homeostase Metalle und Metalloide, als auch ihre organischen Verbindungen, sind in der Umwelt weit verbreitet. Dabei sind sie teilweise natürlichen Ursprungs oder werden durch den Menschen geschaffen (industrielle Produktion, Einsatz in der Landwirtschaft oder in der Medizin). Trotz ihres weitgehenden Verwendung sind zumindest einige dieser Verbindungen ausgesprochen toxisch (z. B. Quecksilber-, Blei-, Arsen- oder Zinn-Verbindungen), insbesondere im Hinblick auf das Nervensystem. Deshalb ist es auch nicht überraschend, dass zahlreiche Fälle von Metallintoxikationen in der medizinischen Literatur beschrieben wurden. Nichtsdestotrotz sind die möglichen Mechanismen solcher Metallvergiftungen bis heute nicht vollständig verstanden. Da das intrazellulären Calcium ein universieller „Second Messanger”︁ in allen Zelltypen ist, haben wir untersucht, ob kurzfristige oder anhaltende Veränderungen der intrazellulären Calciumkonzentration durch die Metalle und Metalloide (oder ihrer Verbindungen) induziert werden. In dieser kurzen Übersicht beschreiben wir die Wirkungen verschiedener Metall- und Metalloid-Verbindungen auf Kanalproteine, den intrazellulären Calciumspeichern und den Calcium transportierenden Proteinen.

Modulation of intracellular calcium homeostasis by trimethyltin chloride in human tumour cells: Neuroblastoma SY5Y and cervix adenocarcinoma HeLa S3

Physiological modifications of intracellular Ca 2+ ([Ca 2+] i) levels trigger and/or regulate a diversity of cellular activities (e.g. neurotransmitter release, synaptic plasticity, muscular contraction, cell proliferation), while calcium overloads could result in cytotoxicity. Previously, we have shown that trimethyltin chloride (Me 3SnCl; TMT) modulates calcium homeostasis in cervix adenocarcinoma (HeLa S3) cells [Florea, A.-M., Dopp, E., Büsselberg, D., 2005. TMT induces elevated calcium transients in HeLa cells: types and levels of response. Cell Calcium 37, 252–258]. Here we compare [Ca 2+] i-changes induced by trimethyltin chloride in neuroblastoma SY5Y and HeLa S3 cells using calcium-sensitive dyes (fluo-4/AM (fluo-4) and rhod-2/AM (rhod-2)) and laser scanning microscopy (LSM). TMT-induced calcium elevations in neuroblastoma SY5Y as well as in HeLa S3 cells. [Ca 2+] i rose to a sustained plateau or to transient spikes. Overall, the detected averaged increase of the maximum calcium elevation were: 0.5 μM ∼125.6%; 5 μM ∼130.1%; 500 μM ∼145% in HeLa S3 cells and 0.5 μM ∼133.3%; 5 μM ∼136.1%; 500 μM ∼147.1% in neuroblastoma SY5Y cells. The calcium rise derived from internal stores did not significantly depend on the presence of calcium in the external solution: ∼109% (no calcium added) versus ∼117% (2 mM calcium; 5 μM TMT) in HeLa cells. This difference was similar in neuroblastoma SY5Y cells, were ∼127% versus ∼136% increase (5 μM TMT) were measured. Staining of calcium stores with rhod-2 showed a TMT-induced [Ca 2+] i-decrease in the stores followed by an increase of the calcium concentration in the nuclei of the two cell lines tested. Our results suggest that toxic effects in human tumour cells after exposure to trimethyltin compounds might be due to an elevation of [Ca 2+] i.

ST1926, a novel and orally active retinoid-related molecule inducing apoptosis in myeloid leukemia cells: modulation of intracellular calcium homeostasis

AbstractRetinoid-related molecules (RRMs) are derivatives of retinoic acid and promising antileukemic agents with a mechanism of action different from that of other common chemotherapeutics. Here, we describe a novel chemical series designed against the RRM prototype, CD437. This includes molecules with apoptotic effects in acute promyelocytic leukemia and other myelogenous leukemia cell lines, as well as ST2065, an RRM with antagonistic properties. The most interesting apoptotic agent is ST1926, a compound more powerful than CD437 in vitro and orally active in vivo on severe combined immunodeficiency (SCID) mice that received transplants of NB4 cells. ST1926 has the same mechanism of action of CD437, as indicated by the ability totrans-activate retinoic acid receptor γ, to induce the phosphorylation of p38 and JNK, and to down-regulate the expression of many genes negatively modulated by CD437. ST1926 causes an immediate increase in the cytosolic levels of calcium that are directly related to the apoptotic potential of the RRMs considered. The intracellular calcium elevation is predominantly the result of an inhibition of the mitochondrial calcium uptake. The phenomenon is blocked by the ST2065 antagonist, the intracellular calcium chelator BAPTA (1,2 bis (2-aminophenoxy) ethane-N, N, N′,N′-tetraacetic acid tetrakis (acetoxymethyl ester), and by high concentrations of calcium blockers of the dihydropyridine type, compounds that suppress ST1926-induced apoptosis.

The role of taurine in the central nervous system and the modulation of intracellular calcium homeostasis.

The effects of taurine in the mammalian nervous system are numerous and varied. There has been great difficulty in determining the specific targets of taurine action. The authors present a review of accepted taurine action and highlight recent discoveries regarding taurine and calcium homeostasis in neurons. In general there is a consensus that taurine is a powerful agent in regulating and reducing the intracellular calcium levels in neurons. After prolonged L-glutamate stimulation, neurons lose the ability to effectively regulate intracellular calcium. This condition can lead to acute swelling and lysis of the cell, or culminate in apoptosis. Under these conditions, significant amounts of taurine (mM range) are released from the excited neuron. This extracellular taurine acts to slow the influx of calcium into the cytosol through both transmembrane ion transporters and intracellular storage pools. Two specific targets of taurine action are discussed: Na(+)-Ca2+ exchangers, and metabotropic receptors mediating phospholipase-C.

Effect of aging on the mechanisms of PTH-induced calcium influx in rat intestinal cells.

We have investigated the effects of aging on parathyroid hormone (PTH) modulation of intracellular calcium homeostasis and their relationship to signal transduction pathways in isolated rat duodenal cells (enterocytes). PTH (10(-8)-10(-9) M) increased enterocyte (45)Ca(2+) influx and intracellular Ca(2+) concentration ([Ca(2+)](i)) to a greater extent (twofold and 50%, respectively) in aged (24 months) than in young (3 months) animals. The [Ca(2+)](i) response of old cells to the hormone was slower, lacking the early phase of changes in cytosolic Ca(2+). Ca(2+) influx induced by PTH was prevented by the protein kinase A antagonist Rp-cAMPS in both young and aged enterocytes, whereas neomycin and compound U73122, inhibitors of PLC-catalyzed phosphoinositide hydrolysis, abolished hormone-dependent Ca(2+) influx in young but had no effect on aged cells. Higher basal adenylyl cyclase (AC) activity and cAMP content were detected in old enterocytes. PTH increased the absolute levels of cAMP in aged cells and AC activity of microsomes isolated therefrom to a greater extent (>/= twofold) than in young enterocytes/membranes. In young cells, the hormone also induced a rapid and transient release of inositoltrisphosphate (IP(3)) and diacylglycerol (neomycin-sensitive) at 45 sec, and a delayed phase of DAG at 5 min (neomycin-insensitive). The early formation of IP(3) and DAG was blunted in aged animals. These results suggest that both the PLC and adenylyl cyclase cascades are involved in PTH stimulation of Ca(2+) influx in duodenal cells. During aging, however, only the cAMP pathway is operative, mediating a potentiation of the effects of the hormone. Additional studies are required to establish the relative role of PTH-dependent messenger systems in the regulation of intestinal calcium absorption and age-related abnormalities.

Role of eicosanoids in the ischemic and reperfused myocardium.

Eicosanoids represent a family of fatty acid derivatives which possess complex biological effects. The three major groups of products are synthesized from arachidonic acid via distinct enzyme complexes and include prostaglandins, leukotrienes and arachidonic acid oxidation products such as epoxides. While the exact sites of synthesis of eicosanoids still require to be determined, there is evidence that the heart has the ability to produce both cyclooxygenase and lipoxygenase derived products. In mammalian heart, activity of the third major pathway of arachidonic acid metabolism, the cytochrome P450-depen-dent monooxygenases, appears to be very low. Eicosanoids exert a myriad of actions on the cardiovascular system including the heart. For example, prostacyclin, produced by cyclooxygenase primarily in vascular endothelium, is generally considered to be a potent vasodilator. On the other hand, thromboxane A2, produced by the same enzyme primarily in platelets, exerts coronary constricting effects. The precise role of eicosanoids in the etiology of heart disease however, is still not fully understood. For example, in the ischemic and reperfused myocardium, both deleterious and beneficial effects of prostaglandins are proposed, a phenomenon which may be associated with the biphasic nature of the effects of these substances. The role of leukotrienes in myocardial ischemia and reperfusion is also complex although it is likely that a major function of these compounds is to provide a chemotactic signal for neutrophil recruitment in the ischemic zone. Initial studies with eicosatrienoic acid epoxides (epoxyeicosatrienoic acids; EETs) also reveal complex actions with respect to myocardial injury as well as modulation of intracellular calcium homeostasis. In this review we discuss the mechanisms and regulation of arachidonic acid metabolism particularly with respect to the heart and how alterations in the production of arachidonic acid metabolites can affect heart function in health and disease.

Lens epithelial cell response to isoforms of platelet-derived growth factor

It has been reported previously that platelet-derived growth factor (PDGF) may play an important role in the regulation of lens growth and differentiation. To evaluate PDGF-induced effects at the cellular level, we investigated the response of cultured bovine lens epithelial cells (BLEC) to PDGF-AB, -AA, and -BB isoforms at the cellular level. Stimulation of BLEC with PDGF isoforms showed no increase in cell proliferation under the culture conditions of this study. In contrast, measurement of cytosolic free calcium concentration ([Ca2+]i), which has been shown to be an important second messenger for controlling multiple cellular processes in the lens, revealed a dose-dependent rise in [Ca2+]i upon stimulation with PDGF-AB and -BB isoforms. PDGF-AA used in similar concentrations was not effective. Our data suggest that PDGF-AB and -BB may play a role in the regulation of cellular functions in BLEC via modulation of intracellular calcium homeostasis.

Lead perturbs epidermal growth factor (EGF) modulation of intracellular calcium metabolism and collagen synthesis in clonal rat osteoblastic (ROS 17/2.8) cells

EGF, a single-chain polypeptide growth factor important for many cellular functions including glycolysis and protein phosphorylation, is known to modulate calcium metabolism in several cell systems. EGF causes an increase in Ca 2+ influx and accumulation of inositol triphosphate and probably exhibits many, if not all, of its effects via the calcium messenger system. Lead is known to interact with and perturb normal calcium signaling pathways; therefore, the purpose of this work was to determine if lead perturbs EGF modulation of calcium metabolism in ROS 17/2.8 cells and if lead impairs collagen synthesis, which is controlled by EGF. To characterize 45Ca kinetics, cells were labelled with 45Ca (1.87 m m Ca) for 20 hr in the presence of 5 μ m Pb, 50 ng/ml EGF, or 5 μ m Pb and 50 ng/ml EGF. Kinetic parameters were determined from 45Ca efflux curves. Three kinetic compartments described the intracellular metabolism of 45Ca; 5 μ m Pb significantly altered the effect of EGF on intracellular calcium metabolism. Calcium distribution was shifted from the fast-exchanging, quantitatively small calcium pools S 1 and S 2 to the slow-exchanging, quantitatively large S 3. There was also a 50% increase in total cell calcium in cells treated with 5 μ m Pb and 50 ng/ml EGF over calcium in cells treated with 50 ng/ml EGF alone. Because EGF and phorbol 12-myristate 13-acetate (PMA) have similar effects on protein kinase C (PKC) and collagen metabolism, the transient effects of EGF and PMA on 45Ca and 210Pb were also characterized. EGF caused a rapid transient increase in efflux of both isotopes, which was further increased by the addition of PMA. In contrast, PMA pretreatment, which depletes PKC, significantly attenuated the latter effect of EGF, suggesting that downregulation by PKC of EGF-induced increases in 45Ca and 210Pb efflux. Moreover, collagen synthesis was decreased by lead, EGF, and PMA in a similar manner, further suggesting PKC as the common modulator of these effects. These data show that Pb impairs the normal modulation of intracellular calcium homeostasis and collagen synthesis by EGF. Furthermore, these results provide additional support to the postulate that an early and discrete effect of lead involves perturbation of the calcium messenger system at one or several loci.