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Ca2+ Elevation (ca2+ + elevation)
Kinds of Ca2+ Elevation Selected AbstractsNonylphenol-induced cytosolic Ca2+ elevation and death in renal tubular cellsDRUG DEVELOPMENT RESEARCH, Issue 5 2009Jeng-Yu Tsai Abstract Nonylphenol is an environmental endocrine disrupter. The effect of nonylphenol on intracellular free Ca2+ levels ([Ca2+]i) and viability in Madin-Darby canine kidney (MDCK) cells was explored. Nonylphenol increased [Ca2+]i in a concentration-dependent manner (EC50,0.8,,M). Nonylphenol-induced Mn2+ entry demonstrated Ca2+ influx and removal of extracellular Ca2+ partly decreased the [Ca2+]i rise. The [Ca2+]i rise was inhibited by the protein kinase C activator, phorbol 13-myristate acetate (PMA) but not by L-type Ca2+ channel blockers. In Ca2+ -free medium, nonylphenol-induced [Ca2+]i rise was partly inhibited by pretreatment with 1,,M thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor). Conversely, nonylphenol pretreatment abolished thapsigargin-induced Ca2+ release. Nonylphenol-induced Ca2+ release was unaltered by inhibition of phospholipase C. At concentrations of 5,100,,M, nonylphenol killed cells in a concentration-dependent manner. The cytotoxic effect of 100,,M nonylphenol was not affected by preventing [Ca2+]i rises with BAPTA/AM. Collectively, this study shows that nonylphenol induced [Ca2+]i increase in MDCK cells via evoking Ca2+ entry through protein kinase C-regulated Ca2+ channels, and releasing Ca2+ from endoplasmic reticulum and other stores in a phospholipase C-independent manner. Nonylphenol also killed cells in a Ca2+ -independent fashion. Drug Dev Res, 2009. © 2009 Wiley-Liss, Inc. [source] Two distinct P2Y receptors are involved in purine- and pyrimidine-evoked Ca2+ elevation in mammalian brain astrocytic culturesDRUG DEVELOPMENT RESEARCH, Issue 1-2 2001Chiara Bolego Abstract ATP and 2-methyl-thio-ATP (2-Me-SATP) increase cytosolic calcium concentrations ([Ca2+]i) in rat striatal astrocytes (Centemeri et al. [1997] Br J Pharmacol 121:1700,1706). The aim of the present study was to: (1) characterize pyrimidine-induced [Ca2+]i increases in the same experimental system, and (2) try to identify the multiple P2Y receptor subtypes mediating Ca2+ mobilization. UDP and UTP triggered a concentration-dependent [Ca2+]i elevation (EC50s = 0.58 ,M ± 0.4 and 31 ,M ± 6, respectively). Pyrimidine-evoked [Ca2+]i elevation was solely due to mobilization from intracellular stores, because: (1) removing calcium from extracellular medium or (2) blocking its influx with Ni2+ did not modify UTP responses; (3) the store-depleting agent thapsigargin completely abolished UTP-evoked [Ca2+]i increments. Guanosine-5,-O-(2-thiodiphosphate) partially inhibited the UTP response, whereas pertussis toxin (PTx) had no effect. The phospholipase C inhibitor U-73122 significantly reduced the UTP-evoked [Ca2+]i rise. Computer-assisted analysis indicated that the UTP and UDP responses are mediated by a single receptor, while ATP and 2-Me-SATP interact with two distinct receptors. The selective P2Y1 receptor antagonist MRS2179 abolished the ATP higher potency component. Sequential challenges with the same nucleotides resulted in almost complete homologous desensitization. Pre-exposure to UTP lowered the subsequent responses to either ATP or 2-Me-SATP. Maximally active concentrations of UTP and ATP were not additive. In conclusion, [Ca2+]i elevation in astrocytes by purines and pyrimidines is mediated by two distinct P2Y receptors, likely the P2Y1 and P2Y6 subtypes. Drug Dev. Res. 52:122,132, 2001. © 2001 Wiley-Liss, Inc. [source] Role of intracellular Ca2+ and calmodulin/MAP kinase kinase/extracellular signal-regulated protein kinase signalling pathway in the mitogenic and antimitogenic effect of nitric oxide in glia- and neurone-derived cell linesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2006Antonella Meini Abstract To elucidate the mechanism of cell growth regulation by nitric oxide (NO) and the role played in it by Ca2+, we studied the relationship among intracellular Ca2+ concentration ([Ca2+]i), mitogen-activated protein kinases [extracellular signal-regulated protein kinase (ERK)] and proliferation in cell lines exposed to different levels of NO. Data showed that NO released by low [(z)-1-[2-aminiethyl]-N-[2-ammonioethyl]amino]diazen-1-ium-1,2diolate (DETA/NO) concentrations (10 µm) determined a gradual, moderate elevation in [Ca2+]i (46.8 ± 7.2% over controls) which paralleled activation of ERK and potentiation of cell division. Functionally blocking Ca2+ or inhibiting calmodulin or MAP kinase kinase activities prevented ERK activation and antagonized the mitogenic effect of NO. Experimental conditions favouring Ca2+ entry into cells led to increased [Ca2+]i (189.5 ± 4.8%), ERK activation and cell division. NO potentiated the Ca2+ elevation (358 ± 16.8%) and ERK activation leading to expression of p21Cip1 and inhibition of cell proliferation. Furthermore, functionally blocking Ca2+ down-regulated ERK activation and reversed the antiproliferative effect of NO. Both the mitogenic and antimitogenic responses induced by NO were mimicked by a cGMP analogue whereas they were completely antagonized by selective cGMP inhibitors. These results demonstrate for the first time that regulation of cell proliferation by low NO levels is cGMP dependent and occurs via the Ca2+/calmodulin/MAP kinase kinase/ERK pathway. In this effect the amplitude of Ca2+ signalling determines the specificity of the proliferative response to NO possibly by modulating the strength of ERK activation. In contrast to the low level, the high levels (50,300 µm) of DETA/NO negatively regulated cell proliferation via a Ca2+ -independent mechanism. [source] AMPA/kainate and NMDA-like glutamate receptors at the chromatophore neuromuscular junction of the squid: role in synaptic transmission and skin patterningEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003Pedro A. Lima Abstract Glutamate receptor types were examined at the chromatophore synapses of the squids Alloteuthis subulata and Loligo vulgaris, where nerve-induced muscle contraction causes chromatophore expansion. Immunoblotting with antibody raised against a squid AMPA receptor (sGluR) demonstrated that AMPA/kainate receptors are present in squid skin. Application of l -glutamate evoked chromatophore muscle contractions in both ventral and dorsal skins, while NMDA was only active on a subpopulation of dorsal chromatophores. In dorsal skin, neurotransmission was partly blocked by either AMPA/kainate receptor antagonists (CNQX and DNQX) or NMDA receptor antagonists (AP-5 and MK-801) or completely blocked by simultaneous application of both classes of antagonists. In isolated muscle fibres, ionophoretic application of l -glutamate evoked fast inward CNQX- and DNQX-sensitive currents with reversal potentials around +14 mV and a high conductance to Na+. In fibres from dorsal skin only, a slower outward glutamate-sensitive current appeared at positive holding potentials. At negative potentials, currents were potentiated by glycine or by removing external Mg2+ and were blocked by AP-5 and MK-801. Glutamate caused a fast, followed by a slow, transient increase in cytoplasmic Ca2+. The slow component was increased in amplitude and duration by glycine or by lowering external Mg2+ and decreased by AP-5 and MK-801. In cells from ventral skin, no ,NMDA-like responses' were detected. Thus, while AMPA/kainate receptors mediated fast excitatory synaptic transmission and rapid colour change over the whole skin, activation of both AMPA/kainate and NMDA-like receptors in a subpopulation of dorsal chromatophores prolonged the postsynaptically evoked Ca2+ elevation causing temporally extended colour displays with behavioural significance. [source] Brain-derived neurotrophic factor induces long-lasting Ca2+ -activated K+ currents in rat visual cortex neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2002Yoshito Mizoguchi Abstract Brain-derived neurotrophic factor (BDNF) increases postsynaptic intracellular Ca2+ and modulates synaptic transmission in various types of neurons. Ca2+ -activated K+ currents, opened mainly by intracellular Ca2+ elevation, contribute to hyperpolarization following action potentials and modulate synaptic transmission. We asked whether BDNF induces Ca2+ -activated K+ currents by postsynaptic elevation of intracellular Ca2+ in acutely dissociated visual cortex neurons of rats. Currents were analysed using the nystatin-perforated patch clamp technique and imaging of intracellular Ca2+ mobilization with fura-2. At a holding potential of ,50 mV, BDNF application (20 ng/mL) for 1,2 min induced an outward current (IBDNF-OUT; 80.0 ± 29.0 pA) lasting for more than 90 min without attenuation in every neuron tested. K252a (200 nm), an inhibitor of Trk receptor tyrosine kinase, and U73122 (3 ,m), a specific phospholipase C (PLC)-, inhibitor, suppressed IBDNF-OUT completely. IBDNF-OUT was both charybdotoxin- (600 nm) and apamin- (300 nm) sensitive, suggesting that this current was carried by Ca2+ -activated K+ channels. BAPTA-AM (150 ,m) gradually suppressed IBDNF-OUT. Fura-2 imaging revealed that a brief application of BDNF elicited a long-lasting elevation of intracellular Ca2+. These results show that BDNF induces long-lasting Ca2+ -activated K+ currents by sustained intracellular Ca2+ elevation in rat visual cortex neurons. While BDNF, likely acting through the Trk B receptor, was necessary for the induction of long-lasting Ca2+ -activated K+ currents via intracellular Ca2+ elevation, BDNF was not necessary for the maintenance of this current. [source] Differential induction of LTP and LTD is not determined solely by instantaneous calcium concentration: an essential involvement of a temporal factorEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2001Tomoyuki Mizuno Abstract Two opposite types of synaptic plasticity in the CA1 hippocampus, long-term potentiation (LTP) and long-term depression (LTD), require postsynaptic Ca2+ elevation. To explain these apparently contradictory phenomena, the current view assumes that a moderate postsynaptic increase in Ca2+ leads to LTD, whereas a large increase leads to LTP. No detailed study has so far been attempted to investigate whether the instantaneous Ca2+ elevation level differentially induces LTP or LTD. We therefore used low-frequency (1 Hz) stimulation of Schaffer collateral/commissural fibers in rat hippocampal slices, during a Mg2+ -free period, as the conditioning stimulus to investigate this. This allowed low-frequency afferent stimulation to cause a postsynaptic Ca2+ influx because the voltage-dependent block of N -methyl- d -aspartate (NMDA) receptor-channels by Mg2+ was removed. When delivered during the Mg2+ -free period, a single pulse, as well as 2,600 pulses, induced LTP that was occluded with tetanus-induced LTP. To decrease the Ca2+ influx, ,-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors were completely blocked by the addition of 10 µm 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) to the conditioning medium, in which 1 Hz afferent stimuli (1,600 pulses) induced less LTP and never induced LTD. To further reduce the Ca2+ influx, NMDA receptors were partially blocked with d -(,)-2-amino-5-phosphonopentanoic acid (d -AP5). A small number of 1 Hz stimuli, however, never induced LTD. Only when the conditioning stimuli exceeded 200 pulses was LTD induced. The present findings provide definitive evidence that protracted conditioning is a prerequisite for the induction of LTD. Thus, not only the amplitude but also the duration of postsynaptic Ca2+ elevation could be essential factors for differentially inducing LTP or LTD. [source] Mechanism of the persistent sodium current activator veratridine-evoked Ca2+ elevation: implication for epilepsyJOURNAL OF NEUROCHEMISTRY, Issue 3 2009Ádám Fekete Abstract Although the role of Na+ in several aspects of Ca2+ regulation has already been shown, the exact mechanism of intracellular Ca2+ concentration ([Ca2+]i) increase resulting from an enhancement in the persistent, non-inactivating Na+ current (INa,P), a decisive factor in certain forms of epilepsy, has yet to be resolved. Persistent Na+ current, evoked by veratridine, induced bursts of action potentials and sustained membrane depolarization with monophasic intracellular Na+ concentration ([Na+]i) and biphasic [Ca2+]i increase in CA1 pyramidal cells in acute hippocampal slices. The Ca2+ response was tetrodotoxin- and extracellular Ca2+ -dependent and ionotropic glutamate receptor-independent. The first phase of [Ca2+]i rise was the net result of Ca2+ influx through voltage-gated Ca2+ channels and mitochondrial Ca2+ sequestration. The robust second phase in addition involved reverse operation of the Na+,Ca2+ exchanger and mitochondrial Ca2+ release. We excluded contribution of the endoplasmic reticulum. These results demonstrate a complex interaction between persistent, non-inactivating Na+ current and [Ca2+]i regulation in CA1 pyramidal cells. The described cellular mechanisms are most likely part of the pathomechanism of certain forms of epilepsy that are associated with INa,P. Describing the magnitude, temporal pattern and sources of Ca2+ increase induced by INa,P may provide novel targets for antiepileptic drug therapy. [source] Effects of sphingosine-1-phosphate and sphingosylphosphorylcholine on intracellular Ca2+ and cell death in prostate cancer cell linesAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 4 2007A. C. M. Mulders Summary The sphingolipid metabolites sphingosine-1-phosphate (S1P) and sphingosylphosphorylcholine (SPC) can be involved in cellular growth and apoptosis, by both receptor-dependent and -independent mechanisms. We investigated the role of S1P and SPC in intracellular Ca2+ elevation, cell proliferation and cell death in DU 145 and PC3 hormone-refractory prostate cancer cell lines. S1P and SPC increased intracellular Ca2+ levels, most likely in a receptor-independent manner. Surprisingly, both S1P and SPC did not stimulate but rather reduced cell growth through induction of apoptosis. Therefore, antagonists targeted against S1P, SPC and their receptors do not appear to be promising new approaches in the treatment of hormone-refractory prostate cancer. [source] Biological properties of a specific G,q/11 inhibitor, YM-254890, on platelet functions and thrombus formation under high-shear stressBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2006Toshio Uemura 1The effects of YM-254890, a specific G,q/11 inhibitor, on platelet functions, thrombus formation under high-shear rate condition and femoral artery thrombosis in cynomolgus monkeys were investigated. 2YM-254890 concentration dependently inhibited ADP-induced intracellular Ca2+ elevation, with an IC50 value of 0.92±0.28 ,M. 3P-selectin expression induced by ADP or thrombin receptor agonist peptide (TRAP) was strongly inhibited by YM-254890, with IC50 values of 0.51±0.02 and 0.16±0.08 ,M, respectively. 4YM-254890 had no effect on the binding of fibrinogen to purified GPIIb/IIIa, but strongly inhibited binding to TRAP-stimulated washed platelets. 5YM-254890 completely inhibited platelet shape change induced by ADP, but not that induced by collagen, TRAP, arachidonic acid, U46619 or A23187. 6YM-254890 attenuated ADP-, collagen-, TRAP-, arachidonic acid- and U46619-induced platelet aggregation with IC50 values of <1 ,M, whereas it had no effect on phorbol 12-myristate 13-acetate-, ristocetin-, thapsigargin- or A23187-induced platelet aggregation. 7High-shear stress-induced platelet aggregation and platelet-rich thrombus formation on a collagen surface under high-shear flow conditions were concentration dependently inhibited by YM-254890. 8The antithrombotic effect of YM-254890 was evaluated in a model of cyclic flow reductions in the femoral artery of cynomolgus monkeys. The intravenous bolus injection of YM-254890 dose dependently inhibited recurrent thrombosis without affecting systemic blood pressure or prolonging template bleeding time. 9YM-254890 is a useful tool for investigating G,q/11 -coupled receptor signaling and the physiological roles of G,q/11. British Journal of Pharmacology (2006) 148, 61,69. doi:10.1038/sj.bjp.0706711 [source] CXCL10-induced cell death in neurons: role of calcium dysregulationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2006Yongjun Sui Abstract Chemokines play a key role in the regulation of central nervous system disease. CXCL10 over-expression has been observed in several neurodegenerative diseases, including multiple sclerosis, Alzheimer's disease and HIV-associated dementia. More recent studies by others and us have shown that CXCL10 elicits apoptosis in fetal neurons. The mechanism of CXCL10-mediated neurotoxicity, however, remains unclear. In this study, we provide evidence for the direct role of Ca2+ dysregulation in CXCL10-mediated apoptosis. We demonstrate that treatment of fetal neuronal cultures with exogenous CXCL10 produced elevations in intracellular Ca2+ and that this effect was modulated via the binding of CXCL10 to its cognate receptor, CXCR3. We further explored the association of intracellular Ca2+ elevations with the caspases that are involved in CXC10-induced neuronal apoptosis. Our data showed that increased Ca2+, which is available for uptake by the mitochondria, is associated with membrane permeabilization and cytochrome c release from this compartment. The released cytochrome c then activates the initiator active caspase-9. This initiator caspase sequentially activates the effector caspase-3, ultimately leading to apoptosis. This study identifies the temporal signaling cascade involved in CXCL10-mediated neuronal apoptosis and provides putative targets for pharmaceutical intervention of neurological disorders associated with CXCL10 up-regulation. [source] Glutamate-mediated astrocyte-to-neuron signalling in the rat dorsal hornTHE JOURNAL OF PHYSIOLOGY, Issue 5 2010Rita Bardoni By releasing neuroactive agents, including proinflammatory cytokines, prostaglandins and neurotrophins, microglia and astrocytes are proposed to be involved in nociceptive transmission, especially in conditions of persistent, pathological pain. The specific action on dorsal horn neurons of agents released from astrocytes, such as glutamate, has been, however, poorly investigated. By using patch-clamp and confocal microscope calcium imaging techniques in rat spinal cord slices, we monitored the activity of dorsal horn lamina II neurons following astrocyte activation. Results obtained revealed that stimuli that triggered Ca2+ elevations in astrocytes, such as the purinergic receptor agonist BzATP and low extracellular Ca2+, induce in lamina II neurons slow inward currents (SICs). Similarly to SICs triggered by astrocytic glutamate in neurons from other central nervous system regions, these currents (i) are insensitive to tetrodotoxin (TTX), (ii) are blocked by the NMDA receptor (NMDAR) antagonist d -AP5, (iii) lack an AMPA component, and (iv) have slow rise and decay times. Ca2+ imaging also revealed that astrocytic glutamate evokes NMDAR-mediated episodes of synchronous activity in groups of substantia gelatinosa neurons. Importantly, in a model of peripheral inflammation, the development of thermal hyperalgesia and mechanical allodynia was accompanied by a significant increase of spontaneous SICs in dorsal horn neurons. The NMDAR-mediated astrocyte-to-neuron signalling thus represents a novel pathway that may contribute to the control of central sensitization in pathological pain. [source] | |||||||||||||