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Okada Y, Sabirov RZ, Sato-Numata K, Numata T. Cell Death Induction and Protection by Activation of Ubiquitously Expressed Anion/Cation Channels. Part 1: Roles of VSOR/VRAC in Cell Volume Regulation, Release of Double-Edged Signals and Apoptotic/Necrotic Cell Death. Front Cell Dev Biol 2021; 8:614040. [PMID: 33511120 PMCID: PMC7835517 DOI: 10.3389/fcell.2020.614040] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 12/15/2020] [Indexed: 12/18/2022] Open
Abstract
Cell volume regulation (CVR) is essential for survival and functions of animal cells. Actually, normotonic cell shrinkage and swelling are coupled to apoptotic and necrotic cell death and thus called the apoptotic volume decrease (AVD) and the necrotic volume increase (NVI), respectively. A number of ubiquitously expressed anion and cation channels are involved not only in CVD but also in cell death induction. This series of review articles address the question how cell death is induced or protected with using ubiquitously expressed ion channels such as swelling-activated anion channels, acid-activated anion channels and several types of TRP cation channels including TRPM2 and TRPM7. The Part 1 focuses on the roles of the volume-sensitive outwardly rectifying anion channels (VSOR), also called the volume-regulated anion channel (VRAC), which is activated by cell swelling or reactive oxygen species (ROS) in a manner dependent on intracellular ATP. First we describe phenotypical properties, the molecular identity, and physical pore dimensions of VSOR/VRAC. Second, we highlight the roles of VSOR/VRAC in the release of organic signaling molecules, such as glutamate, glutathione, ATP and cGAMP, that play roles as double-edged swords in cell survival. Third, we discuss how VSOR/VRAC is involved in CVR and cell volume dysregulation as well as in the induction of or protection from apoptosis, necrosis and regulated necrosis under pathophysiological conditions.
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Affiliation(s)
- Yasunobu Okada
- National Institute for Physiological Sciences, Okazaki, Japan
- Department of Physiology, School of Medicine, Aichi Medical University, Nagakute, Japan
- Department of Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Ravshan Z. Sabirov
- Laboratory of Molecular Physiology, Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan
| | - Kaori Sato-Numata
- Japan Society for the Promotion of Science, Tokyo, Japan
- Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan
| | - Tomohiro Numata
- Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan
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Wang P, Jia J, Zhang D. Purinergic signalling in liver diseases: Pathological functions and therapeutic opportunities. JHEP Rep 2020; 2:100165. [PMID: 33103092 PMCID: PMC7575885 DOI: 10.1016/j.jhepr.2020.100165] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 06/24/2020] [Accepted: 07/22/2020] [Indexed: 12/12/2022] Open
Abstract
Extracellular nucleotides, including ATP, are essential regulators of liver function and serve as danger signals that trigger inflammation upon injury. Ectonucleotidases, which are expressed by liver-resident cells and recruited immune cells sequentially hydrolyse nucleotides to adenosine. The nucleotide/nucleoside balance orchestrates liver homeostasis, tissue repair, and functional restoration by regulating the crosstalk between liver-resident cells and recruited immune cells. In this review, we discuss our current knowledge on the role of purinergic signals in liver homeostasis, restriction of inflammation, stimulation of liver regeneration, modulation of fibrogenesis, and regulation of carcinogenesis. Moreover, we discuss potential targeted therapeutic strategies for liver diseases based on purinergic signals involving blockade of nucleotide receptors, enhancement of ectonucleoside triphosphate diphosphohydrolase activity, and activation of adenosine receptors.
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Key Words
- A1, adenosine receptor A1
- A2A, adenosine receptor A2A
- A2B, adenosine receptor A2B
- A3, adenosine receptor A3
- AIH, autoimmune hepatitis
- ALT, alanine aminotransferase
- APAP, acetaminophen
- APCP, α,β-methylene ADP
- Adenosine receptors
- BDL, bile duct ligation
- CCl4, carbon tetrachloride
- CD73, ecto-5ʹ-nucleotidase
- ConA, concanavalin A
- DCs, dendritic cells
- DMN, dimethylnitrosamine
- Ecto-5ʹ-nucleotidase
- Ectonucleoside triphosphate diphosphohydrolases 1
- HCC, hepatocellular carcinoma
- HFD, high-fat diet
- HGF, hepatocyte growth factor
- HSCs, hepatic stellate cells
- IFN, interferon
- IL-, interleukin-
- IPC, ischaemic preconditioning
- IR, ischaemia-reperfusion
- Liver
- MAPK, mitogen-activating protein kinase
- MCDD, methionine- and choline-deficient diet
- MHC, major histocompatibility complex
- NAFLD, non-alcoholic fatty liver disease
- NK, natural killer
- NKT, natural killer T
- NTPDases, ectonucleoside triphosphate diphosphohydrolases
- Nucleotide receptors
- P1, purinergic type 1
- P2, purinergic type 2
- PBC, primary biliary cholangitis
- PH, partial hepatectomy
- PKA, protein kinase A
- PPADS, pyridoxal-phosphate-6-azophenyl-2′,4′-disulphonate
- Purinergic signals
- ROS, reactive oxygen species
- TAA, thioacetamide
- TNF, tumour necrosis factor
- Tregs, regulatory T cells
- VEGF, vascular endothelial growth factor
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Affiliation(s)
- Ping Wang
- Liver Research Center, Beijing Friendship Hospital, Capital Medical University, Beijing Key Laboratory of Translational Medicine on Liver Cirrhosis & National Clinical Research Center for Digestive Diseases, Beijing 100050, China
| | - Jidong Jia
- Liver Research Center, Beijing Friendship Hospital, Capital Medical University, Beijing Key Laboratory of Translational Medicine on Liver Cirrhosis & National Clinical Research Center for Digestive Diseases, Beijing 100050, China
| | - Dong Zhang
- Experimental and Translational Research Center, Beijing Friendship Hospital, Capital Medical University, Beijing Key Laboratory of Tolerance Induction and Organ Protection in Transplantation & National Clinical Research Center for Digestive Diseases, Beijing 100050, China
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Hasan D, Satalin J, van der Zee P, Kollisch-Singule M, Blankman P, Shono A, Somhorst P, den Uil C, Meeder H, Kotani T, Nieman GF. Excessive Extracellular ATP Desensitizes P2Y2 and P2X4 ATP Receptors Provoking Surfactant Impairment Ending in Ventilation-Induced Lung Injury. Int J Mol Sci 2018; 19:ijms19041185. [PMID: 29652806 PMCID: PMC5979391 DOI: 10.3390/ijms19041185] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 04/08/2018] [Accepted: 04/10/2018] [Indexed: 12/16/2022] Open
Abstract
Stretching the alveolar epithelial type I (AT I) cells controls the intercellular signaling for the exocytosis of surfactant by the AT II cells through the extracellular release of adenosine triphosphate (ATP) (purinergic signaling). Extracellular ATP is cleared by extracellular ATPases, maintaining its homeostasis and enabling the lung to adapt the exocytosis of surfactant to the demand. Vigorous deformation of the AT I cells by high mechanical power ventilation causes a massive release of extracellular ATP beyond the clearance capacity of the extracellular ATPases. When extracellular ATP reaches levels >100 μM, the ATP receptors of the AT II cells become desensitized and surfactant impairment is initiated. The resulting alteration in viscoelastic properties and in alveolar opening and collapse time-constants leads to alveolar collapse and the redistribution of inspired air from the alveoli to the alveolar ducts, which become pathologically dilated. The collapsed alveoli connected to these dilated alveolar ducts are subject to a massive strain, exacerbating the ATP release. After reaching concentrations >300 μM extracellular ATP acts as a danger-associated molecular pattern, causing capillary leakage, alveolar space edema, and further deactivation of surfactant by serum proteins. Decreasing the tidal volume to 6 mL/kg or less at this stage cannot prevent further lung injury.
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Affiliation(s)
- Djo Hasan
- Mobile Intensive Care Unit Zuid-West Nederland, 3062 NW Rotterdam, The Netherlands.
- Department of Surgery, Erasmus MC, Erasmus Universiteit Rotterdam, 3015 CE Rotterdam, The Netherlands.
| | - Joshua Satalin
- Department of Surgery, Upstate Medical University, Syracuse, NY 13210, USA.
| | - Philip van der Zee
- Adult Intensive Care Unit, Erasmus MC, Erasmus Universiteit Rotterdam, 3015 CE Rotterdam, The Netherlands.
| | | | - Paul Blankman
- Department of Anesthesiology, Universitair Medisch Centrum Utrecht, 3584 CX Utrecht, The Netherlands.
| | - Atsuko Shono
- Department of Anesthesiology, Shimane University, Izumo, Shimane Prefecture 693-0021, Japan.
| | - Peter Somhorst
- Adult Intensive Care Unit, Erasmus MC, Erasmus Universiteit Rotterdam, 3015 CE Rotterdam, The Netherlands.
| | - Corstiaan den Uil
- Adult Intensive Care Unit, Erasmus MC, Erasmus Universiteit Rotterdam, 3015 CE Rotterdam, The Netherlands.
- Department of Cardiology, Erasmus MC, Erasmus Universiteit Rotterdam, 3062 PA Rotterdam, The Netherlands.
| | - Han Meeder
- Mobile Intensive Care Unit Zuid-West Nederland, 3062 NW Rotterdam, The Netherlands.
- Adult Intensive Care Unit, Erasmus MC, Erasmus Universiteit Rotterdam, 3015 CE Rotterdam, The Netherlands.
| | - Toru Kotani
- Department of Anesthesiology and Critical Care Medicine, Showa University, School of Medicine, Tokyo 142-8666, Japan.
| | - Gary F Nieman
- Department of Surgery, Upstate Medical University, Syracuse, NY 13210, USA.
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Leal Denis MF, Alvarez HA, Lauri N, Alvarez CL, Chara O, Schwarzbaum PJ. Dynamic Regulation of Cell Volume and Extracellular ATP of Human Erythrocytes. PLoS One 2016; 11:e0158305. [PMID: 27355484 PMCID: PMC4927150 DOI: 10.1371/journal.pone.0158305] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Accepted: 06/13/2016] [Indexed: 11/18/2022] Open
Abstract
Introduction The peptide mastoparan 7 (MST7) triggered in human erythrocytes (rbcs) the release of ATP and swelling. Since swelling is a well-known inducer of ATP release, and extracellular (ATPe), interacting with P (purinergic) receptors, can affect cell volume (Vr), we explored the dynamic regulation between Vr and ATPe. Methods and Treatments We made a quantitative assessment of MST7-dependent kinetics of Vr and of [ATPe], both in the absence and presence of blockers of ATP efflux, swelling and P receptors. Results In rbcs 10 μM MST7 promoted acute, strongly correlated changes in [ATPe] and Vr. Whereas MST7 induced increases of 10% in Vr and 190 nM in [ATPe], blocking swelling in a hyperosmotic medium + MST7 reduced [ATPe] by 40%. Pre-incubation of rbcs with 10 μM of either carbenoxolone or probenecid, two inhibitors of the ATP conduit pannexin 1, reduced [ATPe] by 40–50% and swelling by 40–60%, while in the presence of 80 U/mL apyrase, an ATPe scavenger, cell swelling was prevented. While exposure to 10 μM NF110, a blocker of ATP-P2X receptors mediating sodium influx, reduced [ATPe] by 48%, and swelling by 80%, incubation of cells in sodium free medium reduced swelling by 92%. Analysis and Discussion Results were analyzed by means of a mathematical model where ATPe kinetics and Vr kinetics were mutually regulated. Model dependent fit to experimental data showed that, upon MST7 exposure, ATP efflux required a fast 1960-fold increase of ATP permeability, mediated by two kinetically different conduits, both of which were activated by swelling and inactivated by time. Both experimental and theoretical results suggest that, following MST7 exposure, ATP is released via two conduits, one of which is mediated by pannexin 1. The accumulated ATPe activates P2X receptors, followed by sodium influx, resulting in cell swelling, which in turn further activates ATP release. Thus swelling and P2X receptors constitute essential components of a positive feedback loop underlying ATP-induced ATP release of rbcs.
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Affiliation(s)
- M. Florencia Leal Denis
- Instituto de Química y Fisicoquímica Biológicas “Prof. A. C. Paladini”, Universidad de Buenos Aires, CONICET, FFyB, Buenos Aires, Argentina
| | - H. Ariel Alvarez
- Instituto de Física de Líquidos y Sistemas Biológicos (IFLYSIB), CONICET, Universidad Nacional de La Plata (UNLP), La Plata, Argentina
| | - Natalia Lauri
- Instituto de Química y Fisicoquímica Biológicas “Prof. A. C. Paladini”, Universidad de Buenos Aires, CONICET, FFyB, Buenos Aires, Argentina
| | - Cora L. Alvarez
- Instituto de Química y Fisicoquímica Biológicas “Prof. A. C. Paladini”, Universidad de Buenos Aires, CONICET, FFyB, Buenos Aires, Argentina
| | - Osvaldo Chara
- Instituto de Física de Líquidos y Sistemas Biológicos (IFLYSIB), CONICET, Universidad Nacional de La Plata (UNLP), La Plata, Argentina
- Center for Information Services and High Performance Computing (ZIH), Technische Universität Dresden (TUD), Dresden, Germany
| | - Pablo J. Schwarzbaum
- Instituto de Química y Fisicoquímica Biológicas “Prof. A. C. Paladini”, Universidad de Buenos Aires, CONICET, FFyB, Buenos Aires, Argentina
- * E-mail:
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Abstract
Activation of ion channels and pores are essential steps during regulated cell death. Channels and pores participate in execution of apoptosis, necroptosis and other forms of caspase-independent cell death. Within the program of regulated cell death, these channels are strategically located. Ion channels can shrink cells and drive them towards apoptosis, resulting in silent, i.e. immunologically unrecognized cell death. Alternatively, activation of channels can induce cell swelling, disintegration of the cell membrane, and highly immunogenic necrotic cell death. The underlying cell death pathways are not strictly separated as identical stimuli may induce cell shrinkage and apoptosis when applied at low strength, but may also cause cell swelling at pronounced stimulation, resulting in regulated necrosis. Nevertheless, the precise role of ion channels during regulated cell death is far from being understood, as identical channels may support regulated death in some cell types, but may cause cell proliferation, cancer development, and metastasis in others. Along this line, the phospholipid scramblase and Cl(-)/nonselective channel anoctamin 6 (ANO6) shows interesting features, as it participates in apoptotic cell death during lower levels of activation, thereby inducing cell shrinkage. At strong activation, e.g. by stimulation of purinergic P2Y7 receptors, it participates in pore formation, causes massive membrane blebbing, cell swelling, and membrane disintegration. The LRRC8 proteins deserve much attention as they were found to have a major role in volume regulation, apoptotic cell shrinkage and resistance towards anticancer drugs.
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Affiliation(s)
- Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.
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Modulation of P2X4/P2X7/Pannexin-1 sensitivity to extracellular ATP via Ivermectin induces a non-apoptotic and inflammatory form of cancer cell death. Sci Rep 2015; 5:16222. [PMID: 26552848 PMCID: PMC4639773 DOI: 10.1038/srep16222] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 10/12/2015] [Indexed: 12/22/2022] Open
Abstract
Overexpression of P2X7 receptors correlates with tumor growth and metastasis. Yet, release of ATP is associated with immunogenic cancer cell death as well as inflammatory responses caused by necrotic cell death at sites of trauma or ischemia-reperfusion injury. Using an FDA-approved anti-parasitic agent Ivermectin as a prototype agent to allosterically modulate P2X4 receptors, we can switch the balance between the dual pro-survival and cytotoxic functions of purinergic signaling in breast cancer cells. This is mediated through augmented opening of the P2X4/P2X7-gated Pannexin-1 channels that drives a mixed apoptotic and necrotic mode of cell death associated with activation of caspase-1 and is consistent with pyroptosis. We show that cancer cell death is dependent on ATP release and death signals downstream of P2X7 receptors that can be reversed by inhibition of NADPH oxidases-generated ROS, Ca2+/Calmodulin-dependent protein kinase II (CaMKII) or mitochondrial permeability transition pore (MPTP). Ivermectin induces autophagy and release of ATP and HMGB1, key mediators of inflammation. Potentiated P2X4/P2X7 signaling can be further linked to the ATP rich tumor microenvironment providing a mechanistic explanation for the tumor selectivity of purinergic receptors modulation and its potential to be used as a platform for integrated cancer immunotherapy.
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Yang X, Zhu L, Lin J, Liu S, Luo H, Mao J, Nie S, Chen L, Wang L. Cisplatin activates volume-sensitive like chloride channels via purinergic receptor pathways in nasopharyngeal carcinoma cells. J Membr Biol 2014; 248:19-29. [PMID: 25236172 DOI: 10.1007/s00232-014-9724-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 08/16/2014] [Indexed: 12/31/2022]
Abstract
Cisplatin-based concomitant chemoradiotherapy is considered as the standard treatment for locally advanced nasopharyngeal carcinoma patients. However, the curative efficacy of cisplatin-based chemotherapy is limited because of the occurrence of cisplatin resistance. Some researches indicate that activating the volume-sensitive Cl(-) channel might be a new strategy for the reduction of cisplatin resistance. However, little is known about the activation pathway of the Cl(-) channels activated by cisplatin. In this study, the cisplatin-activated chloride current was investigated using the whole cell patch-clamp technique in the poorly differentiated nasopharyngeal carcinoma cells (CNE-2Z cells), and the activation pathway of the current was also discussed. The results showed that extracellular application of cisplatin activated a Cl(-) current, showing the properties of significant outward rectification, intracellular ATP dependency, and a selectivity sequence of I(-) > Br(-) > Cl(-) > gluconate, and being inhibited by the Cl(-) channel inhibitors tamoxifen and extracellular ATP. These characteristics are similar to those of the volume-sensitive Cl(-) current in CNE-2Z cells, indicating that cisplatin induces the Cl(-) current by activating the volume-sensitive like chloride channel. The cisplatin-activated current was blocked by suramin (a wide-spectrum purinergic antagonist) and RB2 (a relatively selective P2Y antagonist). In addition, the current was depressed by extracellular application of apyrase. The apoptotic volume decrease induced by cisplatin was also attenuated by RB2. P2Y receptors were expressed in CNE-2Z cells. These results suggest that cisplatin can induce a Cl(-) current by activating volume-sensitive like Cl(-) channels through the P2Y purinoceptor pathway.
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Affiliation(s)
- Xiaoya Yang
- Department of Physiology, College of Health Sciences, Guangzhou Medical University, Guangzhou, 510180, China
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Burnstock G, Vaughn B, Robson SC. Purinergic signalling in the liver in health and disease. Purinergic Signal 2014; 10:51-70. [PMID: 24271096 PMCID: PMC3944046 DOI: 10.1007/s11302-013-9398-8] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 10/24/2013] [Indexed: 12/18/2022] Open
Abstract
Purinergic signalling is involved in both the physiology and pathophysiology of the liver. Hepatocytes, Kupffer cells, vascular endothelial cells and smooth muscle cells, stellate cells and cholangiocytes all express purinoceptor subtypes activated by adenosine, adenosine 5'-triphosphate, adenosine diphosphate, uridine 5'-triphosphate or UDP. Purinoceptors mediate bile secretion, glycogen and lipid metabolism and indirectly release of insulin. Mechanical stress results in release of ATP from hepatocytes and Kupffer cells and ATP is also released as a cotransmitter with noradrenaline from sympathetic nerves supplying the liver. Ecto-nucleotidases play important roles in the signalling process. Changes in purinergic signalling occur in vascular injury, inflammation, insulin resistance, hepatic fibrosis, cirrhosis, diabetes, hepatitis, liver regeneration following injury or transplantation and cancer. Purinergic therapeutic strategies for the treatment of these pathologies are being explored.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK,
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Fausther M, Gonzales E, Dranoff JA. Role of purinergic P2X receptors in the control of liver homeostasis. ACTA ACUST UNITED AC 2012; 1:341-348. [PMID: 22662313 DOI: 10.1002/wmts.32] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
It is now accepted that extracellular ATP and other nucleotides are potent signaling molecules, akin to neurotransmitters, hormones and lipid mediators. In the liver, several clues support a significant role for extracellular ATP-induced signaling pathways in the control of tissue homeostasis. First, ATP and other nucleotides are physiologically detected in extracellular fluids within the liver, including sinusoidal blood and intraductular bile, in various mammalian species including human and rodents. Moreover, finely tuned mechanisms of ATP release by different liver cell types have been described, under physiological cellular changes. In addition, most hepatic cells constitutively express, at the membrane level, several ATP-metabolizing ectoenzymes and ATP-sensitive receptors that modulate and transduce these mediator signals respectively. Finally, hepatic cells also express numerous membrane transporters that actively contribute to purinergic salvage pathways. Once released in the extracellular medium, unmetabolised ATP molecules can bind to purinergic P2X and P2Y receptors, and subsequently trigger various intracellular signal transduction pathways collectively referred to as purinergic signaling. In the liver, purinergic signaling has been shown to regulate key basic cellular functions, such as glucose/lipid metabolism, protein synthesis and ionic secretion, and homeostatic processes, such as cell cycle, inflammatory response and immunity. Whilst the functional relevance of P2Y receptors in liver physiology has been well documented, limited information is available regarding the potential role of hepatic P2X receptors in the modulation of liver homeostasis.
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Affiliation(s)
- Michel Fausther
- Division of Gastroenterology & Hepatology, Department, of Internal Medicine, College of Medicine, University of Arkansas for, Medical Sciences, Little Rock, AR, USA
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Wormser C, Pore SA, Elperin AB, Silverman LN, Light DB. Potentiation of regulatory volume decrease by a p2-like receptor and arachidonic acid in american alligator erythrocytes. J Membr Biol 2011; 242:75-87. [PMID: 21728043 DOI: 10.1007/s00232-011-9377-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Accepted: 06/20/2011] [Indexed: 12/21/2022]
Abstract
This study examined the role of a P2 receptor and arachidonic acid (AA) in regulatory volume decrease (RVD) by American alligator red blood cells (RBCs). Osmotic fragility was determined optically, mean cell volume was measured by electronic sizing, and changes in intracellular Ca(2+) concentration were visualized using fluorescence microscopy. Gadolinium (50 μM), hexokinase (2.5 U/ml), and suramin (100 μM) increased osmotic fragility, blocked volume recovery after hypotonic shock, and prevented a rise in intracellular Ca(2+) that normally occurs during cell swelling. The P2X antagonists PPADS (50 μM) and TNP-ATP (10 μM) also increased fragility and inhibited volume recovery. In contrast, ATPγS (10 μM), α,β-methylene-ATP (50 μM) and Bz-ATP (50 μM) had the opposite effect, whereas 2-methylthio-ATP (50 μM) and UTP (10 μM) had no effect. In addition, the phospholipase A(2) (PLA(2)) inhibitors ONO-RS-082 (10 μM), chlorpromazine (10 μM), and isotetrandrine (10 μM) increased osmotic fragility and blocked volume recovery, whereas AA (10 μM) and its nonhydrolyzable analog eicosatetraynoic acid (ETYA, 10 μM) had the reverse effect. Further, AA (10 μM), but not ATPγS (10 μM), prevented the inhibitory effect of a low Ca(2+)-EGTA Ringer on RVD, whereas both AA (10 μM) and ATPγS (10 μM) caused cell shrinkage under isosmotic conditions. In conclusion, our results are consistent with the presence of a P2-like receptor whose activation stimulated RVD. In addition, AA also was important for volume recovery.
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Affiliation(s)
- Chloe Wormser
- Department of Biology, Lake Forest College, IL 60045, USA
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