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.

scholarly journals Pro- and anti-inflammatory macrophages express a sub-type specific purinergic receptor profile

2021 ◽  
Author(s):  
J. Merz ◽  
A. Nettesheim ◽  
S. von Garlen ◽  
P. Albrecht ◽  
B. S. Saller ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Purinergic Receptors ◽  
Purinergic Receptor ◽  
Receptor Activation ◽  
Extracellular Nucleotides ◽  
M1 Macrophages ◽  
Murine Bone Marrow ◽  
Receptor Profile ◽  
Anti Inflammatory

AbstractExtracellular nucleotides act as danger signals that orchestrate inflammation by purinergic receptor activation. The expression pattern of different purinergic receptors may correlate with a pro- or anti-inflammatory phenotype. Macrophages function as pro-inflammatory M1 macrophages (M1) or anti-inflammatory M2 macrophages (M2). The present study found that murine bone marrow-derived macrophages express a unique purinergic receptor profile during in vitro polarization. As assessed by real-time polymerase chain reaction (PCR), Gαs-coupled P1 receptors A2A and A2B are upregulated in M1 and M2 compared to M0, but A2A 15 times higher in M1. The ionotropic P2 receptor P2X5 is selectively upregulated in M1- and M2-polarized macrophages. P2X7 is temporarily expressed in M1 macrophages. Metabotropic P2Y receptors showed a distinct expression profile in M1 and M2-polarized macrophages: Gαq coupled P2Y1 and P2Y6 are exclusively upregulated in M2, whereas Gαi P2Y13 and P2Y14 are overexpressed in M1. This consequently leads to functional differences between M1 and M2 in response to adenosine di-phosphate stimulation (ADP): In contrast to M1, M2 showed increased cytoplasmatic calcium after ADP stimulation. In the present study we show that bone marrow-derived macrophages express a unique repertoire of purinergic receptors. We show for the first time that the repertoire of purinergic receptors is highly flexible and quickly adapts upon pro- and anti-inflammatory macrophage differentiation with functional consequences to nucleotide stimulation.

scholarly journals P2Y2 purinergic receptor activation is essential for efficient hepatocyte proliferation in response to partial hepatectomy

2014 ◽  
Vol 307 (11) ◽  
pp. G1073-G1087 ◽  
Author(s):  
Bryan C. Tackett ◽  
Hongdan Sun ◽  
Yu Mei ◽  
Janielle P. Maynard ◽  
Sayuri Cheruvu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Partial Hepatectomy ◽  
Cell Cycle Progression ◽  
Purinergic Receptors ◽  
Purinergic Receptor ◽  
Receptor Activation ◽  
Hepatocyte Proliferation ◽  
Receptor Subtypes ◽  
Cycle Progression ◽  
The Impact

Extracellular nucleotides via activation of P2 purinergic receptors influence hepatocyte proliferation and liver regeneration in response to 70% partial hepatectomy (PH). Adult hepatocytes express multiple P2Y (G protein-coupled) and P2X (ligand-gated ion channels) purinergic receptor subtypes. However, the identity of key receptor subtype(s) important for efficient hepatocyte proliferation in regenerating livers remains unknown. To evaluate the impact of P2Y2 purinergic receptor-mediated signaling on hepatocyte proliferation in regenerating livers, wild-type (WT) and P2Y2 purinergic receptor knockout (P2Y2−/−) mice were subjected to 70% PH. Liver tissues were analyzed for activation of early events critical for hepatocyte priming and subsequent cell cycle progression. Our findings suggest that early activation of p42/44 ERK MAPK (5 min), early growth response-1 (Egr-1) and activator protein-1 (AP-1) DNA-binding activity (30 min), and subsequent hepatocyte proliferation (24–72 h) in response to 70% PH were impaired in P2Y2−/− mice. Interestingly, early induction of cytokines (TNF-α, IL-6) and cytokine-mediated signaling (NF-κB, STAT-3) were intact in P2Y2−/− remnant livers, uncovering the importance of cytokine-independent and nucleotide-dependent early priming events critical for subsequent hepatocyte proliferation in regenerating livers. Hepatocytes isolated from the WT and P2Y2−/− mice were treated with ATP or ATPγS for 5–120 min and 12–24 h. Extracellular ATP alone, via activation of P2Y2 purinergic receptors, was sufficient to induce ERK phosphorylation, Egr-1 protein expression, and key cyclins and cell cycle progression of hepatocytes in vitro. Collectively, these findings highlight the functional significance of P2Y2 purinergic receptor activation for efficient hepatocyte priming and proliferation in response to PH.

scholarly journals Purinoreceptors and ectonucleotidases control ATP-induced calcium waveforms and calcium-dependent responses in microglia

2021 ◽  
Author(s):  
Byeong Jae Chun ◽  
Surya Aryal ◽  
Bin Sun ◽  
Josh Bruno ◽  
Chris Richards ◽  
...  
Keyword(s):  
Purinergic Receptors ◽  
Cytokine Production ◽  
Purinergic Receptor ◽  
Receptor Activation ◽  
Receptor Expression ◽  
Microglia Cell ◽  
Calcium Dependent ◽  
Murine Microglia ◽  
Bv2 Microglia ◽  
And Migration

Adenosine triphosphate (ATP) drives microglia motility and cytokine production by activating P2X- and P2Y- class purinergic receptors with extracellular ATP and its metabolites. Purinergic receptor activation gives rise to diverse intracellular Ca2+ signals, or waveforms, that differ in amplitude, duration, and frequency. Whether and how these diverse waveforms influence microglia function is not well established. We developed a computational model trained with published primary murine microglia studies. We simulate how purinoreceptors influence Ca2+ signaling and migration and how purinoreceptor expression modifies these processes. Our simulation confirmed that P2 receptors encode the amplitude and duration of the ATP-induced calcium waveforms. Our simulations also implicate CD39, an ectonucleotidase that rapidly degrades ATP, as a regulator of purinergic receptor-induced Ca2+ responses. We, therefore, next evaluated how purinoreceptors and ectonucleotidase work in tandem. Our modeling results indicate that small transients are sufficient to promote motility, while large and sustained transients are needed for cytokine responses. Lastly, we predict how these phenotypical responses vary in a BV2 microglia cell line using published P2 receptor mRNA data to illustrate how our computer model can be extrapolated to diverse microglia subtypes. These findings provide important insights into how differences in purinergic receptor expression influence the microglial responses to ATP.

scholarly journals Adenine nucleotide control of coronary blood flow during exercise

2010 ◽  
Vol 299 (6) ◽  
pp. H1981-H1989 ◽  
Author(s):  
Mark W. Gorman ◽  
G. Alec Rooke ◽  
Margaret V. Savage ◽  
M. P. Suresh Jayasekara ◽  
Kenneth A. Jacobson ◽  
...  
Keyword(s):  
Blood Flow ◽  
Oxygen Consumption ◽  
Coronary Blood Flow ◽  
Negative Feedback ◽  
Oxygen Delivery ◽  
Myocardial Oxygen Consumption ◽  
Purinergic Receptors ◽  
Adenine Nucleotide ◽  
Purinergic Receptor ◽  
Receptor Activation

The adenine nucleotide hypothesis postulates that the ATP released from red blood cells is broken down to ADP and AMP in coronary capillaries and that ATP, ADP, and AMP act on purinergic receptors on the surface of capillary endothelial cells. Purinergic receptor activation initiates a retrograde conducted vasodilator signal to the upstream arteriole that controls coronary blood flow in a negative feedback manner. A previous study (M. Farias 3rd, M. W. Gorman, M. V. Savage, and E. O. Feigl, Am J Physiol Heart Circ Physiol 288: H1586–H1590, 2005) demonstrated that coronary venous plasma ATP concentration increased during exercise and correlated with coronary blood flow. The present experiments test the adenine nucleotide hypothesis by examining the balance between oxygen delivery (via coronary blood flow) and myocardial oxygen consumption during exercise before and after purinergic receptor blockade. Dogs ( n = 7) were chronically instrumented with catheters in the aorta and coronary sinus and a flow transducer around the circumflex coronary artery. During control treadmill exercise, myocardial oxygen consumption increased and the balance between oxygen delivery and myocardial oxygen consumption fell as indicated by a declining coronary venous oxygen tension. Blockade of P1 and P2Y1 purinergic receptors combined with inhibition of nitric oxide synthesis significantly decreased the balance between oxygen delivery and myocardial oxygen consumption compared with control. The results support the hypothesis that ATP and its breakdown products ADP and AMP are part of a negative feedback control mechanism that matches coronary blood flow to myocardial oxygen consumption at rest and during exercise.

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