Haanes, Kristian A

Hansen, Mette R

Hede, Susanne E

Krabbe, Simon

Novak, Ivana

Tokushima University Institutional Repository

ATP and other nucleotides/sides have now beenrecognized as important extracellular signaling mole-cules in many biological systems (1). In epithelia,ATP signaling is thought to regulate fluid transport,and exocrine glands are one of the first epitheliawhere the effect of ATP on ion channels and Ca2+signaling was observed (2, 3). Nevertheless, manysteps in ATP signaling, also known as purinergicsignaling, remain to be clarified. This includes thequestions of where and how ATP is released, whichpurinergic receptors are stimulated and where andhow ATP is hydrolyzed by ecto-nucleotidases. Ingeneral, our studies aim to understand the role ofpurinergic signaling in communication between pan-creatic acini and ducts. We have established thatpancreatic acini release ATP and nucleotidases (4,5) possibly from zymogen granules and we proposethat pancreatic ducts are important sites for puriner-gic signaling, where the effect on specific receptorsis translated into epithelial cell responses. Therefore,our recent studies focused on determining expres-sion and effect of purinergic and adenosine recep-tors and their effect on Ca2+ and Cl- transport.For our studies we used freshly isolated rat pan-creatic ducts and human duct cell lines often usedfor ion transport studies -PANC-1, Capan -1 andCFPAC-1. Investigation of the expression of pro-teins of interest included RT-PCR and Western blotanalysis. Functionally, we monitored intracellularCa2+ and Cl- responses using Fura-2 and MQAE andelectrophysiological responses.Pancreatic ducts (rat and human) possess a num-ber of purinergic P2 receptors from both the P2Yand P2X families. Human pancreatic duct cell linesexpress P2Y1, P2Y2, P2Y4, P2Y6 and P2Y11-14 re-ceptors, as well as the P2X1, P2X2, P2X4, P2X5,P2X6 and P2X7 receptors (6). Responses in intra-cellular Ca2+ signals to certain agonists (UTP, BzATPand ivermectin) shows that at least P2Y2, P2Y4,P2X4 and P2X7 receptors are functional. Our lateststudy shows that these purinergic receptors mayalso regulate pancreatic Ca2+ transport, a processthat involves the Na+/Ca2+ exchanger and a numberof Ca2+-handling proteins, which both rodent andhuman pancreatic ducts express (7). Pancreaticducts (rat and human) also express four types ofadenosine receptors (A1, A2A, A2B and A3), though A2types are most abundant (8). Functionally, using in-tracellular Ca2+ and Cl- measurements and electro-physiology we have determined that the A2A recep-tors regulate the cystic fibrosis transmembrane con-ductance regulator (CFTR) Cl- channels. Further-more, these receptors are localized to the luminalmembranes of pancreatic ducts. Taken together, thepurinergic signaling plays an important role in regu-lation of exocrine function of the pancreas. P2 re-ceptors affect Ca2+ signaling and homeostasis, Ca2+regulated Cl- and K+ channels (9) and adenosine re-ceptors can affect CFTR and thus secretion.EXPANDED ABSTRACTExtracellular purinergic signaling in pancreasIvana Novak, Kristian A Haanes, Mette R Hansen, Simon Krabbe, andSusanne E HedeDepartment of Biology, August Krogh Building, University of Copenhagen, Copenhagen, DenmarkKeywords : pancreas, purinergic receptors, adenosine receptors, CFTR, calcium transportJ. Med. Invest. 56 Suppl. : 355-356, December, 2009Received for publication October 28, 2009 ; accepted November4, 2009.Address correspondence and reprint requests to Prof. IvanaNovak, Molecular and Integrative Physiology, Department ofBiology, August Krogh Building, Univesitetsparken 13, Univer-sity of Copenhagen, DK-2100 Copenhagen, Denmark andFax : +45-3532-1567.The Journal of Medical Investigation Vol. 56 Supplement 2009355ACKNOWLEDGEMENTSOur studies were supported by the Danish Sci-ence Research Council, the Carlsberg Foundationand the Lundbeck Foundations.REFERENCES1. Burnstock G : Purinergic signalling and disor-ders of the central nervous system. Nat RevDrug Discov 7 : 575-590, 20082. Gallacher DV : Are there purinergic receptorson parotid acinar cells? Nature 296 : 83-86,19823. Novak I : ATP as a signaling molecule-the exo-crine focus. News Physiol Sci 18 : 12-17, 20034. Srensen CE, Novak I : Visualization of ATP re-lease in pancreatic acini in response to cholin-ergic stimulus. Use of fluorescent probes andconfocal microscopy. J Biol Chem 276 : 32925-32932, 20015. Yegutkin GG, Samburski SS, Jalkalen S, NovakI : ATP-consuming and ATP-generating en-zymes secreted by pancreas. J Biol Chem 281 :29441-29447, 20066. Hansen MR, Krabbe S, Novak I : Purinergic re-ceptors and calcium signalling in human pan-creatic duct cell lines. Cell Physiol Biochem22 : 157-168, 20087. Hansen MR, Krabbe S, Ankorina-Stark I,Novak I : Purinergic receptors stimulate Ca2+transport in pancreatic ducts : Role of Na+/Ca2+exchanger and other Ca2+ binding and trans-porting proteins. Cell Physiol Biochem 23 :387-396, 20088. Novak I, Hede SE, Hansen MR : Adenosinereceptors in rat and human pancreatic ductsstimulate chloride transport. Pflugers Arch 456 :437-447, 20079. Novak I : Purinergic receptors in the endocrineand exocrine pancreas. Purinergic Signal 4 :237-253, 2008I. Novak, et al. Purinergic signaling in pancreas356

Extracellular purinergic signaling in pancreas

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Extracellular purinergic signaling in pancreas

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