Effects of K+-induced depolarization and purinergic receptor activation on elemental content in insulin-producing RINm5F-cells.

1995 ◽  
Vol 19 (1) ◽  
pp. 25-34 ◽  
Author(s):  
E Pålsgård
Keyword(s):  
Purinergic Receptor ◽  
Receptor Activation ◽  
Elemental Content ◽  
Rinm5f Cells

scholarly journals TRPM4 Channels Couple Purinergic Receptor Mechanoactivation and Myogenic Tone Development in Cerebral Parenchymal Arterioles

2014 ◽  
Vol 34 (10) ◽  
pp. 1706-1714 ◽  
Author(s):  
Yao Li ◽  
Rachael L Baylie ◽  
Matthew J Tavares ◽  
Joseph E Brayden
Keyword(s):  
Transient Receptor Potential ◽  
Purinergic Receptor ◽  
Critical Role ◽  
Receptor Potential ◽  
Transient Receptor Potential Channel ◽  
Receptor Activation ◽  
Myogenic Tone ◽  
Pial Arteries ◽  
Myogenic Regulation

Cerebral parenchymal arterioles (PAs) have a critical role in assuring appropriate blood flow and perfusion pressure within the brain. They are unique in contrast to upstream pial arteries, as defined by their critical roles in neurovascular coupling, distinct sensitivities to chemical stimulants, and enhanced myogenic tone development. The objective of the present study was to reveal some of the unique mechanisms of myogenic tone regulation in the cerebral microcirculation. Here, we report that in vivo suppression of TRPM4 (transient receptor potential) channel expression, or inhibition of TRPM4 channels with 9-phenanthrol substantially reduced myogenic tone of isolated PAs, supporting a key role of TRPM4 channels in PA myogenic tone development. Further, downregulation of TRPM4 channels inhibited vasoconstriction induced by the specific P2Y4 and P2Y6 receptor ligands (UTP γS and UDP) by 37% and 42%, respectively. In addition, 9-phenanthrol substantially attenuated purinergic ligand-induced membrane depolarization and constriction of PAs, and inhibited ligand-evoked TRPM4 channel activation in isolated PA myocytes. In concert with our previous work showing the essential contributions of P2Y4 and P2Y6 receptors to myogenic regulation of PAs, the current results point to TRPM4 channels as an important link between mechanosensitive P2Y receptor activation and myogenic constriction of cerebral PAs.

scholarly journals Simulation of P2X-mediated calcium signaling in microglia

2018 ◽  
Author(s):  
Ben Chun ◽  
Bradley D. Stewart ◽  
Darin Vaughan ◽  
Adam D. Bachstetter ◽  
Peter M. Kekenes-Huskey
Keyword(s):  
Computational Model ◽  
Purinergic Receptor ◽  
Receptor Activation ◽  
Quantitative Model ◽  
Published Data ◽  
Transcriptional Responses ◽  
Extracellular Adenosine ◽  
Wide Range ◽  
Intracellular Ca

AbstractMicroglia function is orchestrated through highly-coupled signaling pathways that depend on calcium (Ca2+). In response to extracellular adenosine triphosphate (ATP), transient increases in intracellular Ca2+ driven through the activation of purinergic receptors, P2X and P2Y, are sufficient to promote cytokine synthesis and potentially their release. While steps comprising the pathways bridging purinergic receptor activation with transcriptional responses have been probed in great detail, a quantitative model for how these steps collectively control cytokine production has not been established. Here we developed a minimal computational model that quantitatively links extracellular stimulation of two prominent ionotropic puriner-gic receptors, P2X4 and P2X7, with the graded production of a gene product, namely the tumor necrosis factor α (TNFα) cytokine. In addition to Ca2+ handling mechanisms common to eukaryotic cells, our model includes microglia-specific processes including ATP-dependent P2X4 and P2X7 activation, activation of NFAT transcription factors, and TNFα production. Parameters for this model were optimized to reproduce published data for these processes, where available. With this model, we determined the propensity for TNFα production in microglia, subject to a wide range of ATP exposure amplitudes, frequencies and durations that the cells could encounter in vivo. Furthermore, we have investigated the extent to which modulation of the signal transduction pathways influence TNFα production. Our key findings are that TNFα production via P2X4 is maximized at low ATP when subject to high frequency ATP stimulation, whereas P2X7 contributes most significantly at millimolar ATPranges. Given that Ca2+ homeostasis in microglia is profoundly important to its function, this computational model provides a quantitative framework to explore hypotheses pertaining to microglial physiology.

Abstract 340: Recombinant Soluble Apyrase Inhibits Vascular Smooth Muscle Cell Migration

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Oluwaseun Adeola ◽  
Yan Ji ◽  
Phillip Fish ◽  
Tammy Strawn ◽  
Gary A Weisman ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Cell Migration ◽  
Endothelial Cell ◽  
Purinergic Receptor ◽  
Neointimal Hyperplasia ◽  
Receptor Activation ◽  
Vehicle Control ◽  
Extracellular Nucleotides ◽  
Lower Chamber ◽  
Upper Chamber

Background: Purinergic receptor activation by extracellular nucleotides is involved in thrombosis and neointimal hyperplasia that accompany atherosclerosis and postangioplasty restenosis. Human apyrases [ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDases)] are membrane bound enzymes that hydrolyze extracellular nucleotides, thereby inhibiting purinergic receptor activation. CD39, the first identified human apyrase, is constitutively expressed on endothelial cell (EC) and vascular smooth muscle cell (VSMC) surfaces. APT102, a recombinant soluble form of CD39L3, has been shown to reduce platelet activation through its ADPase activity, but its effects on VSMC and EC function are yet to be established. We tested the hypothesis that APT102 will inhibit migration of VSMCs and ECs. Methods: We studied cell migration using a modified Boyden chamber assay in which 5x10 4 cells suspended in 0.2% FBS/DMEMF12 were added to the upper chamber of transwells separated from the lower chamber medium by a microporous membrane through which VSMCs and ECs can migrate. APT102 (100 nM) or vehicle control was added to the upper chamber; lower chamber contained 2.5% FBS/DMEMF12 and either ATP (10 μM) or vehicle control. Transwells were incubated at 37 0 C for 6 h, after which cells that migrated through pores and adhered to the lower chamber side of the membrane were fixed, stained and counted. Results: ATP (10μM) significantly enhanced migration of both VSMCs and ECs. APT102 significantly inhibited VSMC migration and completely abrogated the pro-migratory effect of ATP. In contrast, APT102 had no inhibitory effect on EC migration, either spontaneous or ATP-enhanced. Conclusion: APT102 inhibits VSMC but not EC migration. These results suggest that pharmacological targeting of extracellular nucleotides may provide a safe and effective therapeutic strategy to inhibit neointimal hyperplasia and restenosis after angioplasty, without delaying endothelial cell recovery, which is a significant limitation of drug-eluting stents. Further studies are needed to clarify the mechanism(s) underlying the differential effect of extracellular nucleotide degradation by APT102 on VSMC and EC migration.

Adenosine nucleotides in bile

1996 ◽  
Vol 270 (2) ◽  
pp. G246-G252 ◽  
Author(s):  
R. S. Chari ◽  
S. M. Schutz ◽  
J. E. Haebig ◽  
G. H. Shimokura ◽  
P. B. Cotton ◽  
...  
Keyword(s):  
Purinergic Receptors ◽  
Purinergic Receptor ◽  
Receptor Activation ◽  
Hepatoma Cells ◽  
Human Bile ◽  
Nucleotide Release ◽  
Cholangiocarcinoma Cell ◽  
Adenosine Nucleotides ◽  
Vitro Model

Activation of purinergic receptors by ATP stimulates Cl- efflux in biliary epithelial cells. To determine whether purinergic agonists are present under physiological conditions, we have assayed mammalian bile for nucleotides and assessed whether hepatoma and cholangiocarcinoma cell lines are capable of nucleotide release. Bile samples were collected from human, rat, and pig donors and assayed for nucleotide concentrations by luminometry. ATP, ADP, and AMP were present in bile from each species, and the average total nucleotide concentration in human bile was 5.21 +/- 0.91 microM (n = 16). In an in vitro model of HTC rat hepatoma cells or Mz-ChA-1 cholangiocarcinoma cells on a superfused column, nucleotides were present in the effluent from each cell type. Addition of alpha, beta-methyleneadenosine 5'-diphosphate (50 microM) to inhibit 5'-nucleotidase activity increased AMP concentrations two- to threefold. Exposure to forskolin (100 microM) or ionomycin (2 microM) stimulated nucleotide release from cholangiocarcinoma but not hepatoma cells. These studies indicate that adenosine nucleotides are present in bile in concentrations sufficient to activate purinergic receptors. Purinergic receptor activation by local nucleotide release might constitute an autocrine and/or paracrine mechanism for modulation of biliary secretion.

ATP induces contraction of cultured brain capillary pericytes, via activation of P2Y type purinergic receptors

2020 ◽  
Author(s):  
Sofie Hørlyck ◽  
Changsi Cai ◽  
Hans C Helms ◽  
Martin Lauritzen ◽  
Birger Brodin
Keyword(s):  
Intracellular Calcium ◽  
Purinergic Receptors ◽  
Calcium Release ◽  
Purinergic Receptor ◽  
Cytosolic Calcium ◽  
Receptor Activation ◽  
Confocal Imaging ◽  
Inositol Triphosphate ◽  
Brain Capillary

Brain capillary pericytes have been suggested to play a role in the regulation of cerebral blood-flow under physiological and pathophysiological conditions. ATP has been shown to cause constriction of capillaries under ischemic conditions and suggested to be involved in the "no-reflow" phenomenon. In order to investigate the effects of extracellular ATP on pericyte cell contraction, we studied purinergic receptor activation of cultured bovine brain capillary pericytes. We measured [Ca2+]i-responses to purinergic agonists with the fluorescent indicators fura-2 and Cal-520 and estimated contraction of pericytes as relative change in cell area, using real-time confocal imaging. Addition of ATP caused an increase in cytosolic calcium and contraction of the brain capillary pericytes, both reversible and inhibited by a purinergic receptor antagonist PPADS. Furthermore, we demonstrated that ATP-induced contraction could be eliminated by intracellular calcium-chelation with BAPTA, indicating that the contraction was mediated via purinergic P2 -type receptor-mediated [Ca2+]i-signaling. ATP stimulation induced inositol triphosphate signaling, consistent with the notion of P2Y receptor activation. Receptor profiling studies demonstrated presence of P2Y1 and P2Y2 receptors, using ATP, UTP, ADP and the subtype specific agonists MRS2365 (P2Y1) and 2-thio-UTP (P2Y2)). Addition of specific P2X agonists only caused a [Ca2+]i increase at high concentrations, attributed to activation of inositol triphosphate signaling. Our results suggest that contraction of brain capillary pericytes in vitro by activation of P2Y type purinergic receptors is caused by intracellular calcium release. This adds more mechanistic understanding to the role of pericytes in vessel constriction, and points towards P2Y receptors as potential therapeutic targets.

Mechanical strain-induced Ca2+waves are propagated via ATP release and purinergic receptor activation

2000 ◽  
Vol 279 (2) ◽  
pp. C295-C307 ◽  
Author(s):  
H. Sauer ◽  
J. Hescheler ◽  
M. Wartenberg
Keyword(s):  
Gap Junctions ◽  
Purinergic Receptor ◽  
Mechanical Strain ◽  
Atp Release ◽  
Anion Channel ◽  
Receptor Activation ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Junctional Coupling ◽  
Intracellular Ca

Mechanical strain applied to prostate cancer cells induced an intracellular Ca2+ (Cai 2+) wave spreading with a velocity of 15 μm/s. Cai 2+ waves were not dependent on extracellular Ca2+ and membrane potential because propagation was unaffected in high-K+ and Ca2+-free solution. Waves did not depend on the cytoskeleton or gap junctions because cytochalasin B and nocodazole, which disrupt microfilaments and microtubules, respectively, and 1-heptanol, which uncouples gap junctions, were without effects. Fluorescence recovery after photobleaching experiments revealed an absence of gap junctional coupling. Cai 2+ waves were inhibited by the purinergic receptor antagonists basilen blue and suramin; by pretreatment with ATP, UTP, ADP, UDP, 2-methylthio-ATP, and benzoylbenzoyl-ATP; after depletion of ATP by 2-deoxyglucose; and after ATP scavenging by apyrase. Waves were abolished by the anion channel inhibitors 5-nitro-2-(3-phenylpropylamino)benzoic acid, tamoxifen, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid, niflumic acid, and gadolinium. ATP release following strain was significantly inhibited by anion channel blockers. Hence, ATP is secreted via mechanosensitive anion channels and activates purinergic receptors on the same cell or neighboring cells in an autocrine and paracrine manner, thus leading to Cai 2+ wave propagation.

scholarly journals SPINK9 Stimulates Metalloprotease/EGFR–Dependent Keratinocyte Migration via Purinergic Receptor Activation

2014 ◽  
Vol 134 (6) ◽  
pp. 1645-1654 ◽  
Author(s):  
Maria Sperrhacke ◽  
Jan Fischer ◽  
Zhihong Wu ◽  
Sarah Klünder ◽  
Radislav Sedlacek ◽  
...  
Keyword(s):  
Purinergic Receptor ◽  
Receptor Activation ◽  
Keratinocyte Migration

Effect of purinergic receptor activation on Na+-K+ pump activity, excitability, and function in depolarized skeletal muscle

2010 ◽  
Vol 298 (6) ◽  
pp. C1438-C1444 ◽  
Author(s):  
Martin Broch-Lips ◽  
Thomas Holm Pedersen ◽  
Ole Bækgaard Nielsen
Keyword(s):  
Skeletal Muscle ◽  
Purinergic Receptor ◽  
Purinergic Signaling ◽  
Receptor Activation ◽  
Control Force ◽  
Fourfold Increase ◽  
Pump Activity ◽  
Force Recovery ◽  
And Function ◽  
Muscle Excitability

Activity-induced elevation of extracellular purines and pyrimidines has been associated with autocrine and paracrine signaling in many tissues. Here we investigate the effect of purinergic signaling for the excitability and contractility of depolarized skeletal muscle. Muscle excitability was experimentally depressed by elevating the extracellular K+ from 4 to 10 mM, which reduced the tetanic force to 24 ± 2% of the force at 4 mM K+. Upon addition of 1 mM ATP, however, the force recovered to 65 ± 8% of the control force ( P < 0.001, n = 5). A similar recovery was seen with ADP, but not with UTP or adenosine. The ATP-induced force recovery could be inhibited by P2Y1 receptor antagonists (3 μM SCH-202676 or 1 μM MRS-2500). A fourfold increase in M-wave area demonstrated that the ATP-induced force recovery was associated with restoration of muscle excitability ( P < 0.05, n = 4). Experiments using 86Rb+ as a tracer for K+ showed that ATP also induced a twofold increase in the activity of muscle Na+-K+ pumps. The force recovery and the stimulation of the Na+-K+ pump activity by ATP were inhibited by 50 μM of the phospholipase C inhibitor U-73122. It is concluded that purinergic signaling can increase the Na+-K+ pump activity and improve force and excitability of depolarized skeletal muscles. This novel purinergic regulation may be important for the maintenance of muscle excitability during intense exercise, where the extracellular K+ can increase substantially.

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